Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33397 Publications

Gesamte Wertschöpfungskette im Blick

Gutzmer, J.; Klossek, A.
Das Helmholtz-Institut Freiberg für Ressourcentechnologie wurde am 29. August 2011 gegründet und wird gemeinsam durch das Helmholtz-Zentrum Dresden-Rossendorf und die TU Bergakademie Freiberg aufgebaut. Das Institut hat das Ziel, innovative Technologien für die Wirtschaft zu entwickeln, um mineralische und metallhaltige Rohstoffe effizienter bereitzustellen und zu nutzen sowie umweltverträglich zu recyceln.
Mit Grundlagen- und anwendungsorientierter interdisziplinärer Forschung, bei der alle Stufen der Rohstoff-Wertschöpfungskette vernetzt werden, wird eine strategische Lücke zwischen der bergbaulichen Kompetenz bei der Gewinnung und dem Knowhow von Rohstoffanwendungen in der deutschen aber auch in der europäischen Forschung geschlossen. Das Institut positioniert sich damit als nationales Kompetenzzentrum für die Erforschung, die Entwicklung und die Innovation von Technologien, die strategisch wichtige mineralische sowie insbesondere metallhaltige Rohstoffe bereitstellen.
Keywords: Helmholtz Institut Freiberg
  • Resource (2012)2, 25-28

Permalink: https://www.hzdr.de/publications/Publ-17688
Publ.-Id: 17688


A multiple sulfur and organic carbon isotope record from non-conglomeratic sedimentary rocks of the Mesoarchean Witwatersrand Supergroup, South Africa

Guy, B. M.; Ono, S.; Gutzmer, J.; Kaufman, A. J.; Lin, Y.; Fogel, M. L.; Beukes, N. J.
sulfur isotope ratios (36S/34S/33S/32S) and organic carbon isotope ratios (13C/12C) were measured from 198 non-conglomeratic sedimentary samples that were collected from five deep diamond drill-cores that cover the majority of the ca. 2.96–2.82 Ga Witwatersrand Supergroup. 13Corg, 34Spy and 33Spy values of the sample set range from
−44.3 to
−21.9‰,
−3.7 to +16.5‰ and
−4.0 to +1.9‰, respectively.
These geochemical data vary relative to depositional facies (proximal marine, distal marine and fluvialdominated) and tectonic setting (trailing margin and foreland basin).
In the trailing margin setting of the ∼2.96 Ga Hospital Hill Subgroup, the proximal marine depofacies is characterized by relatively high organic carbon contents (up to 0.9 wt.%) and 13Corg values around −28‰, in contrast to the distal marine depofacies that yields low organic carbon contents (0.01 wt.%) and high 13Corg values (up to −22‰). Both depofacies yield low sulfur contents (0.02 wt.‰), a narrow range of 34S values (∼+3 ±2‰) and positive 33S values (up to +1.9‰). This data is consistent with photoautotrophic carbon fixation in shallow marine environments and limited organic carbon production/preservation in deeper water settings due to longer transport distances and effective biological degradation (e.g., Fe-reducing microbes). Positive 33S values imply that sulfur was largely derived from a photochemical elemental sulfur reservoir. In the foreland basin tectonic setting of the ∼2.94 Ga Government and ∼2.92 Ga Jeppestown subgroups, shelf deposits associated with fluvial braidplain depofacies are characterized by 13C-depleted organic carbon (∼−44 to −38‰), relatively high sulfur contents (0.2–1.3 wt.%), variable 34S values (−3.7 to +16.5‰) and small negative 33S values (∼−0.4‰). These data suggest that the microbial community in the fluvial-dominated depofacies may have consisted of photoautotrophs, methanogens, anaerobic methanotrophs and sulfate reducers. Sulfate was derived from a variety of sources that include photochemical, crustal and marine sulfur reservoirs.
The occurrence of three regionally persistent diamictite deposits in the Government Subgroup coincides with the onset of compressional tectonics and development of pyritic shales with highly 13Cdepleted organic carbon, suggesting that an increase in continental sulfur flux and methane oxidation may have triggered the Mesoarchean glaciations (drawdown of H2 and CH4). However, the link between large 33S anomalies (−4.0 to +1.2‰) and diamictite suggests low levels of atmospheric oxygen and minimal dilution of photochemical signatures.
Keywords: Diagenetic pyrite, Mesoarchean, Sulfur mass-independent fractionation, Witwatersrand Supergroup, Anaerobic methanotrophy, Diamictite

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Permalink: https://www.hzdr.de/publications/Publ-17687
Publ.-Id: 17687


The value of adaptive mineral processing based on spatially varying ore fabric parameters

van den Boogaart, K. G.; Weißflog, C.; Gutzmer, J.
We show that adapting the mineral processing to the local ore fabric (mineralogy and microstructure) can substantially improve the profitability of the mine, however, only a proper geomathematical methodology using conditional expectations of profits rather than direct measurements can avoid losses. Based on geometallurgical exploration data and processing models potential gain and actual gain of this approach can be quantified before exploitation commences. Rules for optimal decisions, estimators for the gain of this approach from exploration data, and a method to compute the optimal geometallurgical sampling density are presented.
Keywords: Geometallurgy, adaptive mineral processing, geostatistics
  • Open Access Logo Contribution to proceedings
    IAMG 2011 conference, 05.-09.09.2011, Salzburg, Österreich
    Mathematical Geosciences at the Crossroads of Theory and Practice - Proceedings IAMG 2011 conference, 978-3-200-02566-0, 609-621

Permalink: https://www.hzdr.de/publications/Publ-17686
Publ.-Id: 17686


The compositional meaning of the dection limit

van den Boogaart, K. G.; Tolosana-Delgado, R.; Bren, M.
In compositional data analysis a value below detection limit (BDL) is typically modeled as the definitive information that the actual value is below some fixed value - the detection limit (see e.g. Palarea-Albaladejo et. al (2007, 2008)). Analytical chemistry (Heinrichs and Herrmann (1990); Fletcher (1981); Kellner et al. (2004)) however has a different view on measured concentrations. The measured concentration Cm is not the true concentration cm of the measurant but a quantity computed from an observable quantity Om through a calibration equation. This has serious consequences for the interpretation and statistical analysis of below detection limit observations in the context of compositional data analysis.
Keywords: BDL, detection limit, compositional data analysis
  • Open Access Logo Contribution to proceedings
    4th International Workshop on Compositional Data Analysis (2011), 09.-13.05.2011, Sant Feliu de Guíxols, Espania
    Proceedings of the 4th International Workshop on Compositional Data Analysis (2011)

Permalink: https://www.hzdr.de/publications/Publ-17685
Publ.-Id: 17685


Kontaktlose Durchflussmessung in Metallschmelzen

Buchenau, D.; Gerbeth, G.; Priede, J.
Control of the flow rate of liquid metals is required in a number of technological processes such as the cooling of nuclear reactors, transmutation systems and the dosing and casting of liquid metals. Electromagnetic flow meters play an important role in the diagnostics and automatic control of such processes. For example, the electromagnetic control of casting processes can be used to improve the quality of products by reducing their brittleness and increasing durability at high production efficiency, especially for complex shape components. A number of different electromagnetic flow meter designs have been developed starting from the end of the forties of the last century. One such flow meter - the magnetic flywheel, which is described in the textbook of Shercliff uses the electromagnetic force exerted by the flow on a close magnet. Commercial electromagnetic flow meters are typically based on the flow-induced electrical voltage measurements by electrodes in direct contact to the melt in a steady magnetic field. In view of the typical problems coming along with applications at liquid metal flows such as high temperatures, interfacial effects and corrosion, the main disadvantage of this type of flow meter is the electrical contact to the liquid metal, which is necessary to measure the electric potential difference. Therefore, contactless operating measurement techniques are very attractive for liquid metal applications.
Keywords: Contactless electromagnetic flow meter, liquid metal, phase shift, rotational frequency
  • Technisches Messen 79(2012)9, 389-393

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Permalink: https://www.hzdr.de/publications/Publ-17684
Publ.-Id: 17684


Linear Models with Compositions in R

Tolosana-Delgado, R.; van den Boogaart, K. G.
This chapter contains sections titled:

Introduction

The Illustration Data Set

Explanatory Binary Variable

Explanatory Categorical Variable

Explanatory Continuous Variable

Explanatory Composition

Conclusions

Acknowledgement

References
Keywords: linear models with compositions in R - checking intrinsic relations between (sets of) variables;explanatory variables, categorical variables - analysis of the variance (ANOVA), or analysis of the covariance (ANCOVA);classical concept of linear combination - meaningless on the simplex
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buccianti: Compositional Data Analysis: Theory and Applications, Chichester, UK: John Wiley & Sons, Ltd, 2011, 9780470711354
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buccianti: Compositional Data Analysis: Theory and Applications, Chichester, UK: John Wiley & Sons, Ltd, 2011, 9781119975462-1
    DOI: 10.1002/9781119976462

Permalink: https://www.hzdr.de/publications/Publ-17683
Publ.-Id: 17683


Geostatistics for Compositions

Tolosana-Delgado, R.; van den Boogaart, K. G.; Pawlowsky-Glahn, V.
This chapter contains sections titled:

Introduction

A Brief Summary of Geostatistics

Cokriging of Regionalised Compositions

Structural Analysis of Regionalised Composition

Dealing with Zeros: Replacement Strategies and Simplicial Indicator Cokriging

Application

Conclusions

Acknowledgements

References
Keywords: geostatistics for compositions - any multivariate geostatistical data set, compositional in nature;geostatistics, collection of techniques - and tools, analysing regionalised data sets;problems of geostatistics
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buccianti: Compositional Data Analysis: Theory and Applications, Chichester: John Wiley & Sons, Ltd, 2011, 9781119976462-1
    DOI: 10.1002/9781119976462
  • Book chapter
    Vera Pawlowsky-Glahn, Antonella Buchianti: Compositional Data Analysis: Theory and Applications, Chichester: John Wiley & Sons, Ltd, 2011, 9780470711354, 73-86

Permalink: https://www.hzdr.de/publications/Publ-17682
Publ.-Id: 17682


Influence of low (radio)metal concentrations on bacterial growth using calorimetric metabolic monitoring

Hassan Obeid, M.; Geissler, A.; Solioz, M.; Fahmy, K.; Oertel, J.
Introduction: The transition of industrially caused metal contaminations into the food chain constitutes a serious risk for the environment and human health. It is particularly a major challenge to develop ecotoxicological biomonitors that provide a physical readout based on measurable metabolic effects rather than extrapolating risks from restricted physical and chemical environmental parameters that account for neither bioavailability nor metabolic responses to toxicity.

Objectives: We have studied bacterial growth by measuring metabolic heat using state ofthe art microcalorimetry to observe the effects of low doses of heavy (radio)metals on three different bacterial strains. Escherichia coli and Lactococcus lactis were used as genetically well defined test organisms and Peanibacillus sp. JG-TB8 as a natural isolate recovered from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Germany).

Material and Methods: Liquid cultures of Escherichia coli, Lactococcus lactis and Peanibacillus sp. JG-TB8 were exposed to micromolar concentrations of europium(III), copper(II) and uranium(VI) salts and the metabolic heat release was measured as a function of time and temperature using a thermal activity monitor (TAM-III, TA-instruments).

Results: Reproducible effects of europium and copper on the time dependent heat release are observed already at concentration of 10 µM. In contrast to europium and copper, for which the inhibitory action scales with concentration, uranium influences bacterial growth in a more complicated manner which strongly depends on temperature and pH, probably as a consequence of its different speciations. In contrast to conventional optical monitoring of cell growth, much more subtle effects, such as consecutive exponential growth phases can be distinguished.

Conclusions: The results demonstrate that microcalorimetric monitoring is an extremely sensitive tool to investigate the influence of low heavy metal and radionuclide concentrations on the metabolic activity of microorganisms. The bacterial growth rates were determined with high accuracy continuously in real time. The proven long-term stability will also allow the monitoring of higher living organisms (e.g. C. elegans).
Keywords: microcalorimetry metal stress
  • Contribution to proceedings
    Jahrestagungder Deutschen Gesellschaft für Biophysik, 23.-26.09.2012, Göttingen, Deutschland
  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2013, Göttingen, Germany

Permalink: https://www.hzdr.de/publications/Publ-17681
Publ.-Id: 17681


Comment on “A Conditional Dependence Adjusted Weights of Evidence Model” by Minfeng Deng in Natural Resources Research 18(2009), 249–258

Schaeben, H.; van den Boogaart, K. G.
without abstract

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Permalink: https://www.hzdr.de/publications/Publ-17680
Publ.-Id: 17680


Membrane nanodiscs: a platform for the structural and functional characterization of a bacterial PIB-type ATPase

Fischermeier, E.; Sayed, A.; Oertel, J.; Fahmy, K.
Introduction:
Reconstitution of membrane proteins in a native-like lipidic environment is vital for the determination of their structural and functional properties. Nanodics (NDs) constitute such an environment by providing a planar nanoscale phospholipid bilayer bounded by a ring of two membrane scaffolding proteins (MSP). NDs are advantageous over liposomes and bicelles as they exhibit less scatter, are soluble and of defined size and can integrate membrane proteins as single molecules that are accessible from both sides. Here we show that NDs can be utilized to study the mechanism of PIB-type ATPases, a protein family pumping transition metals, e.g. copper, across biological membranes. Moreover, we explore the potential of ND for proposed single molecule structural studies using X-FEL radiation.

Objectives:
We want to explore the use of NDs as a biochemical platform for spectroscopic, biochemical and ultimately single molecule structural studies of membrane proteins, as for example the allosteric coupling between copper transport and ATP-hydrolysis in the PIB-type ATPase CopA from L. pneumophila.

Materials and Methods:
CopA and MSP1 were affinity-purified following recombinant expression in E. coli. Nanodiscs were reconstituted from a MSP : lipid : CopA (1:60:0.1) cholate-mixture after detergent removal and characterized by dynamic light scattering, AFM, CD spectroscopy and X-ray diffraction using X-FEL radiation.

Results:
MSP1 was purified and NDs were prepared with different lipid moieties. Thorough analyses by natural and magnetic CD as well as dynamic light scattering show a well defined and stable composition of NDs of an average diameter of 10nm. Preliminary x-ray diffraction data from NDs have been recorded using the X-FEL at SLAC, (USA).
After successfull purification of CopA from L. pneumophila, enzyme activity was tested by ATPase assays and spectroscopic techniques, followed by reconstitution into NDs for further biophysical investigation.

Conclusions: NDs provide a suitable platform for structural and functional studies of integral membrane proteins in a native-like lipidic environment. They offer the potential to apply functional assays under identical conditions as envisaged advanced x-ray diffraction experiments using pulsed r-ray sources. Here, we have established the functional reconstitution of the bacterial heavy-metal pump CopA into NDs to study structure–function relationships.
Keywords: membrane proteins copper transport X-FEL
  • Contribution to proceedings
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2012, Göttingen, Deutschland
  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2013, Göttingen, Grmany

Permalink: https://www.hzdr.de/publications/Publ-17679
Publ.-Id: 17679


Spectroscopic characterization of transition metal complexes with quercetin in aqueous solutions

Attia, E.; Fahmy, K.
Introduction: Flavonoids are ubiquitous polyphenolic compounds in fruits and vegetables, also referred as Vitamin P, which participate and redox reactions and influence the bioavailability of metals. Quercetin, one of the most abundant dietary flavonoids, has been shown to form a copper complex that binds to DNA and can cause strand cleavage.

Objectives: We want to determine the binding site of transition metals in flavonoids examplified for quercetin. The photreactivity of such complexes and their potential effect on DNA structure is investigated.

Material and methods: Quercetin (3,3’,4’,5,7pentahydroxylflavone) was purchased from SIGMA, salmon testes genomic DNA was from CALBIOCHEM. IR spectra of quercetin films were recorded by attenuated total reflectance (ATR) using a VECTOR 22 FTIR Spectrophotometer (BRUKER). CD spectra were measured with a JASCO 800 instrument.

Results:
The formation of copper–quercetin complexes was observed by the red shift of the quercetin absorption. Zn2+ showed low affinity in the mM range, whereas copper formed complexes already at nM concentratrions. In contrast to Zn, Cu2+ strongly quenches quercetin fluorescence, probably as a result of different ligand to metal charge transfer efficiencies. To address the complexation mode, IR-spectra were recorded from quercetin film is solution. The addition of transition metals affects a band at 1590 cm-1, typical of carbonyl stretching, suggesting that under our experimental conditions, coordination involves the C=O in position 4. Preliminary experiments show structural affects of the interaction of the complex with DNA.

Conclusions:
Copper-Quercetin complexes were synthesized in different solvents and the complex is stable under both aerobic and anaerobic conditions. The carbonyl at C4 of quercetin is the binding site for Cu2+ and affects photooxidative behaviour of the complex. Using ATR-technique highly hydrophbic flavonoids can be studied under fully hydrated conditions.
Keywords: infrared spectroscopy flavonoids
  • Poster
    Jahrestagung der Deutschen Gesellschaft für Biophysik, 23.-26.09.2013, Göttingen, Germany

Permalink: https://www.hzdr.de/publications/Publ-17678
Publ.-Id: 17678


Interpretation of a compositional time series

Tolosana-Delgado, R.; van den Boogaart, K. G.
Common methods for multivariate time series analysis use linear operations, from the definition of a time-lagged covariance/correlation to the prediction of new outcomes. However, when the time series response is a composition (a vector of positive components showing the relative importance of a set of parts in a total, like percentages and proportions), then linear operations are afflicted of several problems. For instance, it has been long recognised that (auto/cross-)correlations between raw percentages are spurious, more dependent on which other components are being considered than on any natural link between the components of interest. Also, a long-term forecast of a composition in models with a linear trend will ultimately predict negative components.
In general terms, compositional data should not be treated in a raw scale, but after a log-ratio transformation (Aitchison, 1986: The statistical analysis of compositional data. Chapman and Hill). This is so because the information conveyed by a compositional data is relative, as stated in their definition. The principle of working in coordinates allows to apply any sort of multivariate analysis to a log-ratio transformed composition, as long as this transformation is invertible. This principle is of full application to time series analysis.
We will discuss how results (both auto/cross-correlation functions and predictions) can be back-transformed, viewed and interpreted in a meaningful way. One view is to use the exhaustive set of all possible pairwise log-ratios, which allows to express the results into D(D􀀀1)=2 separate, interpretable sets of one-dimensional models showing the behaviour of each possible pairwise log-ratios. Another view is the interpretation of estimated coefficients or correlations back-transformed in terms of compositions. These two views are compatible and complementary. These issues are illustrated with time series of seasonal precipitation patterns at different rain gauges of the USA. In this data set, the proportion of annual precipitation falling in winter, spring, summer and autumn is considered a 4-component time series. Three invertible log-ratios are defined for calculations, balancing rainfall in autumn vs. winter, in summer vs. spring, and in autumnwinter vs. springsummer. Results suggest a 2-year correlation range, and certain oscillatory behaviour in the last balance, which does not occur in the other two.
Keywords: Aitchison Simplex, compositional data analysis
  • Open Access Logo Contribution to proceedings
    European Geosciences Union General Assembly 2012, 22.-27.04.2012, Wien, Österreich
    Geophysical Research Abstracts Vol. 14, EGU2012-8233: EGU General Assembly

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Permalink: https://www.hzdr.de/publications/Publ-17676
Publ.-Id: 17676


Analyzing Compositional Data with R

van den Boogaart, K. G.; Tolosana-Delgado, R.
Data describing amounts of components of specimens are compositional if the size of each specimen is constant, or irrelevant. Ideally compositional data is given by relative portions summing up to 1 or 100%. But more often compositional data appear disguised in several ways: different components might be reported in different physical units, different cases might sum up to different totals, and almost never all relevant components are reported. Nevertheless, the constraints of constant sum and relative meaning of the portions have important implications for their statistical analysis, contradicting the typical assumptions of usual uni- and multivariate statistical methods, and thus rendering their direct application spurious. A comprehensive statistical methodology, based on a vector space structure of the mathematical simplex, has only been developed very recently and several software packages are now available to treat compositional data within it. The book is at the same time a textbook on compositional data analysis from a modern perspective and a sort of manual on the R package “compositions”: both R and “compositions” are available for download as free software.
Keywords: Compositional Data Analysis, Aitchison Geometry
  • Book (Authorship)
    Heidelberg: Springer, 2013
    258 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17675
Publ.-Id: 17675


The Research Group of Economic Geology at the TU Bergakademie Freiberg and the Helmholtz Institute Freiberg for Resource Technology (HIF)

Birtel, S.; Sandmann, D.; Seifert, T.; Gutzmer, J.
Das Poster stellt die Themengebiete der Lagerstättenlehre der TUBAF und des HIF's und seine Rolle in der Forschungslandschaft dar
  • Poster
    EODI meeting, 30.-31.08.2012, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-17674
Publ.-Id: 17674


Flow measurements in a continuous casting model using a low temperature liquid metal

Timmel, K.; Röder, M.; Eckert, S.; Gerbeth, G.
This paper describes experimental investigations of flow structures and related transport processes in the continuous casting mould under the influence of an external DC magnetic field at laboratory scale. Experimental results will be presented here which have been obtained using a physical model (mini-LIMMCAST) operating with the low melting point alloy GaInSn. The Ultrasound-Doppler-Velocimetry (UDV) was applied for measurements of the flow pattern in the mould. An array of ten transducers was attached to the narrow mould side, measuring the horizontal velocities in the the region around the liquid metal jet. Further, with two sensors on the mould top, vertical velocities were recorded successively in the whole mould width.
Keywords: continuous steel casting, liquid metal model, electromagnetic brake (EMBr)
  • Lecture (Conference)
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland
  • Contribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Deutschland, 71-74

Permalink: https://www.hzdr.de/publications/Publ-17673
Publ.-Id: 17673


Bayes spaces: use of improper distributions and exponential families

Egozcue, J. J.; Pawlowsky-Glahn, V.; Tolosana-Delgado, R.; Ortego, M. I.; van den Boogaart, K. G.
Bayes spaces are vector spaces of sigma-additive positive measures. Proportional measures are considered equivalent and can be represented by densities with respect to a fixed dominating measure. The addition in these spaces is perturbation. It corresponds to Bayes theorem, which appears as a linear operation. Bayes spaces, with continuous dominating measures, contain finite and infinite measures. Finite measures are equivalent to probability measures. Infinite measures include what in Bayesian statistics are called improper priors and non-integrable likelihood functions, justifying the use of such improper densities in Bayes theorem. Many concepts of probability theory can be handled in a natural way in the context of Bayes spaces. Particularly, an exponential family of probability densities appears as a cone contained in an affine subspace of the Bayes space. The framework of Bayes spaces allows an easy handling of exponential families and their extensions to improper distributions. Furthermore, the vector space structure of Bayes spaces allows the definition of derivatives of densities. In Bayesian statistics, these derivatives are a new tool to examine sensitivity of posterior distributions with respect to both observed data and prior changes.
Keywords: Simplex, Aitchison geometry, Derivative, Sensitivity
  • Revista de la Real Academia de Ciencias Exactas, Fisicas y Naturales. Serie A. Matematicas (2012)
    DOI: 10.1007/s13398-012-0082-6

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Permalink: https://www.hzdr.de/publications/Publ-17672
Publ.-Id: 17672


Mineral potential mapping using Cox-type regression for marked point processes

van den Boogaart, K. G.; Schaeben, H.
Mineral potential mapping infers the chance of finding a deposit at a location from geological covariables. Usual methods, like weights of evidence, fit a model for the occurrence probability of a deposit in a pixel to a dataset of pixels, where the all geological covariables and presence or absence of the deposit is known.

We propose a new more flexible approach, viewing the locations of deposits as an inhomogeneous marked point process. This allows to model intensity rather than probability. The local occurrence probability is computed from the fitted model. The variation of log intensity is described by a linear model in the covariables like in a Cox-regression model for survival analysis. Applied to similar data the approach gives results similar to the classical approaches.

However it additionally allows for the inclusion of continues covariables, the use of information on smaller uneconomical mineralisation zones as additional information for the model fit by introducing mark distributions, inclusion of incompletely explored areas by reweighting with the probability of finding, and the use of samples rather than complete maps for the region without deposit
using the spatial character of point processes.
Keywords: Weights of Evidence, Mining Exploration, Instationary Point Processes
  • Contribution to proceedings
    34th International Geological Congress, 05.-10.08.2012, Brisbane, Australia
    Proceedings of the 34th International Geological Congress, Canberra: australian Geoscience Council

Permalink: https://www.hzdr.de/publications/Publ-17671
Publ.-Id: 17671


The Sensitivity to Axial Alignment of a Flow Driven by a Travelling Magnetic Field

Pal, J.; Cramer, A.; Gerbeth, G.; Koal, K.; Tschisgale, S.; Siller, J.
The present study, both experimentally and by numerical simulation, concerns the sensitivity of a flow that is driven by a travelling magnetic field (TMF) with respect to a stepwise applied mismatch between the axes of the TMF and of the cylindrical liquid metal column. The TMF is generated by six equidistantly arranged cylindrical coils powered with an AC current having a phase shift of 60° between them. Because the flow induced by a TMF is basically of a torus type, vertical velocity components are representative for the motion in the meridional plane. Ultrasound Doppler Velocimetry (UDV) was applied to acquire the velocity component along the beam axis in the centre of the liquid metal column and at various azimuthal positions for a fixed radial coordinate. The measurements are compared to the flow data gained by large eddy simulations. Computations were based on the usual approximations to simplify the magnetohydrodynamic equations, which are low frequency and low induction, and on an analytical expression for the Lorentz force considering the shift between the fluid volume and the field. The results show that even a small shift between the axes may result in a distinct three-dimensional constituent of the flow structure which changes completely the usually assumed axisymmetric torus-type flow.
Keywords: fluid flows; magnetic fields; TMF; stirring; flow measurements
  • Journal of Iron and Steel Research International 19(2012)1-1, 557-560
  • Lecture (Conference)
    7th International Conference on Electromagnetic Processing of Materials (EPM2012), 22.-26.10.2012, Bejing, China

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Permalink: https://www.hzdr.de/publications/Publ-17670
Publ.-Id: 17670


Cloud Computing and Big Data in German Research Institutes

Konrad, U.
Supercomputing and Big Data expand the spectrum of scientific studies, since they provide access to the understanding of phenomena of highest complexity in the area of the theories and models as well as for the analysis of experimental data. Since 2008 Cloud Computing has become another buzzword after Web 2.0. In the commercial area Cloud Computing hast already achieved an enormous significance. This plenary speech describes the fundamentals and the actual status of Big Data and Cloud Computing in the area of research in Europe.
Keywords: Information Technology, Supercomputing, Cloud Computing, Big Data
  • Invited lecture (Conferences)
    The 1st International Workshop for Young Scientists “Intelligent Technologies for Information Processing and Management”, 17.-19.07.2012, Ufa, Russia

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Permalink: https://www.hzdr.de/publications/Publ-17669
Publ.-Id: 17669


Spectroscopic and Quantum Chemical Study of the Curium(III) and Europium(III) Citrate Speciation in Biological Systems

Heller, A.; Barkleit, A.; Foerstendorf, H.; Tsushima, S.; Heim, K.; Bernhard, G.
Heavy metals, particularly radionuclides, represent a serious health risk to humans in case of incorpo-ration. For the understanding of their (radio-) toxicity, distribution, deposition and elimination, it is crucial to investigate their aqueous speciation and molecular transport mechanisms in biosystems. Unfortunately, only little is known about the behavior of artificial, radioactive trivalent actinides (An(III)) and naturally occurring, nonradioactive lanthanides (Ln(III)) in the human organism. Nevertheless, quite recently, we showed that citrate complexes are the dominant binding form of An(III) and Ln(III) in human urine at pH < 6. Hence, an accurate prediction of the speciation of these elements in the presence of citrate is crucial for the understanding of the impact on the metabolism of the human or-ganism and the corresponding health risks.
Therefore, we studied the complexation of Cm(III) and Eu(III), as representatives of An(III) and Ln(III), respectively, in aqueous citrate solution over a wide pH range using a combined approach of Time-Resolved Laser-induced Fluorescence Spectroscopy (TRLFS), Fourier-Transform Infrared Spectroscopy with Attenuated Total Reflection (ATR FT IR) and density functional theory (DFT) calculations.
With TRLFS, four citrate complexes were identified for both Cm(III) and Eu(III), which are MHCit0, M(HCitH)HCit 2-, M(HCit)2 3-, and M(Cit)2 5-. Furthermore, the stability constants were determined. Additionally, there were also indications for the formation of MCit- complexes.
With ATR FT IR and DFT, structural details of the EuHCit and EuCit- complexes were obtained. The combination of both methods gave clear evidence for the deprotonation of the hydroxyl group of the citrate ion in the EuCit- complex, what also revealed that the complexation of the Eu 3+ ion takes place not only through the carboxylate groups, like in EuCit0, but additionally via the hydroxylate group. In both EuCit0 and EuCit- the carboxylate binding mode is predominantly mono-dentate.
Under very low metal to citrate ratio that is typical for human body fluids, the Cm(III) and Eu(III) speciation was found to be strongly pH-dependent. The Cm(III) and Eu(III) citrate complexes domi-nant in human urine at pH < 6 were identified to be Cm(HCitH)HCit2- and a mixture of Eu(HCitH)HCit 2- and EuHCit0. The results specify our previous in vitro study using natural human urine samples and point out the importance of low molecular weight ligands for An(III) and Ln(III) complexation in body fluids and other biological systems.
Keywords: actinides, lanthanides, speciation, spectroscopy, biofluids, citrate
  • Contribution to proceedings
    Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland
    Abstract book
  • Lecture (Conference)
    Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17668
Publ.-Id: 17668


Reaktionsaufklärung und Einzelkanalstudien am Beispiel der Oxidation von Isobutan zu tert-Butyl-Hydroperoxid

Willms, T.; Kryk, H.; Hampel, U.
Die Aufgaben des Arbeitspaketes 2.5 des Projektes „Energieeffiziente chemische Mehrphasenprozesse“ werden kurz vorgestellt. Nach der Vorstellung der am HZDR zur Reaktionsaufklärung verfügbaren apparativen Ausstattung wird das Potential der Energieeffizienzverbesserung der Oxidation von Isobutan mit Sauerstoff zu tert.-Butylhydroperoxid angesichts der Technologie mikrostrukturierter Reaktoren evaluiert. Ein vereinfachter Mechanismus der Reaktion wird angegeben. Darauf aufbauend wird das weitere Vorgehen zur Reaktionsaufklärung im Rahmen des Projekts skizziert, sowie die Verknüpfungen des Arbeitspaketes 2.5 mit anderen Arbeitspaketen aufgezeigt.
  • Lecture (others)
    Offizielles Kick-off-Meeting zur Helmholtz-Energie-Allianz "Energieeffiziente chemische Mehrphasenprozesse", 30.07.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17667
Publ.-Id: 17667


Extreme High-Rate Capable Timing Resistive Plate Chambers with Ceramic Electrodes

Garcia, L. A.; Kaspar, M.; Kämpfer, B.; Kotte, R.; Naumann, L.; Peschke, R.; Stach, D.; Wendisch, C.; Wüstenfeld, J.
The future Compressed Baryonic Matter experiment to be built at the Facility for Antiproton and Ion Research in Darmstadt, Germany, will create the highest particle densities ever created in a laboratory. One of its components, the Time-of-Flight Wall, will be comprised of Resistive Plate Chambers. The high particle fluxes expected at the most inner region, close to the beam pipe, have led to the research of new low-resistive materials to be used as electrodes. Si3N4/SiC composites are a very good candidate for this function. Their bulk resistivity, in the order of 109–1010 Ω cm, allows for increased rate capabilities up to 106 s−1 cm−2. In this report, the properties of these new materials will be discussed. Also, the performance of resistive plate chambers with ceramic electrodes under irradiation in electron and proton beams will be presented.

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Permalink: https://www.hzdr.de/publications/Publ-17665
Publ.-Id: 17665


Implementation of specific-heat and NMR experiments in the 1500 ms long-pulse magnet at the Hochfeld-Magnetlabor Dresden

Weickert, F.; Meier, B.; Zherlitsyn, S.; Herrmannsdörfer, T.; Daou, R.; Nicklas, M.; Haase, J.; Steglich, F.; Wosnitza, J.
We report on the design and successful testing (up to 55 T) of a 60 T long-pulse (LP) magnet with a pulse duration of 1500 ms at the Hochfeld-Magnetlabor Dresden. This magnet has the capability of producing magnetic fields with time and homogeneity characteristics suitable to host specific-heat and nuclear magnetic resonance (NMR) experiments. We describe the development of a specific-heat probe for this magnet, which uses the quasi-adiabatic heat-pulse method and enables magnetocaloric-effect measurements. Furthermore, we report the implementation of a NMR setup, consisting of home-built probe and spectrometer. Both experimental devices were tested successfully in the LP magnet up to 31 and 44 T, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-17664
Publ.-Id: 17664


Ultrasonic flow measurements in a downscaled water mockup of a large scale precession driven dynamo experiment

Gundrum, T.; Stefani, F.; Ma, C.; Sun, Y.; Giesecke, A.; Albrecht, T.; Gerbeth, G.
The DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN) is planned to become a platform both for large scale experiments related to geo- and astrophysics as well as for experiments on thermo-hydraulic and safety aspects of liquid metal applications in energy related technologies. The most ambitious project in the framework of DRESDYN is a homogeneous hydromagnetic dynamo driven solely by precession. The detailed knowledge of the flow structure in the precessing cylindrical vessel is of key importance for the prediction of the dynamo action. In this paper we present UDV measurements of the velocity field in a 1:6 downscaled water mock-up.
Keywords: Ultrasound Doppler Velocimetry, Precession, Dynamo
  • Open Access Logo Contribution to proceedings
    8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 19.-21.09.2012, Dresden, Germany
    Proceedings of the 8th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Dresden: HZDR, 23-26

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Permalink: https://www.hzdr.de/publications/Publ-17663
Publ.-Id: 17663


Fermi-surface evolution in Yb-substituted CeCoIn5

Polyakov, A.; Ignatchik, O.; Bergk, B.; Götze, K.; Bianchi, A. D.; Blackburn, S.; Prevost, B.; Seyfarth, G.; Coté, M.; Hurt, D.; Capan, C.; Fisk, Z.; Goodrich, R. G.; Sheikin, I.; Richter, M.; Wosnitza, J.
We report results of systematic de Haas–van Alphen (dHvA) studies on Ce1−xYbxCoIn5 single crystals with varyingYb concentration. For x = 0.1, the well-known Fermi surfaces and the heavy effective masses of CeCoIn5 (x = 0) have changed only slightly.We start to observe changes of the Fermi-surface topology at x = 0.2 leading to a drastic reconstruction above x = 0.55. At these concentrations, the effective masses are reduced considerably to values between 0.7 and 2.6 free electron masses. For both YbCoIn5 and CeCoIn5, the angular-resolved dHvA frequencies can be very well described by conventional density-functional theory calculations. Projection of the Bloch states onto atomic Yb-4f orbitals yields a 4f occupation of 13.7 electrons, in agreement with previous experimental results indicating an intermediate Yb valence of +2.3.

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Permalink: https://www.hzdr.de/publications/Publ-17662
Publ.-Id: 17662


Critical fields and growth rates of the Tayler instability as probed by a columnar gallium experiment

Rüdiger, G.; Gellert, M.; Schultz, M.; Strassmeier, K. G.; Stefani, F.; Gundrum, T.; Seilmayer, M.; Gerbeth, G.
Many astrophysical phenomena (such as the slow rotation of neutron stars or the rigid rotation of the solar core) can be explained by the action of the Tayler instability of toroidal magnetic fields in the radiative zones of stars. In order to place the theory of this instability on a safe fundament, it has been realized in a laboratory experiment measuring the critical field strength, the growth rates, as well as the shape of the supercritical modes. A strong electrical current flows through a liquid metal confined in a resting columnar container with an insulating outer cylinder. As the very small magnetic Prandtl number of the gallium–indium–tin alloy does not influence the critical Hartmann number of the field amplitudes, the electric currents for marginal instability can also be computed with direct numerical simulations. The results of this theoretical concept are confirmed by the experiment. Also the predicted growth rates on the order of minutes for the nonaxisymmetric perturbations are certified by the measurements. That they do not directly depend on the size of the experiment is shown as a consequence of the weakness of the applied fields and the absence of rotation.
Keywords: magnetohydrodynamics (MHD) – stars: magnetic field – stars: rotation

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Publ.-Id: 17661


Identification of hexanuclear Actinide(IV) carboxylates with Thorium, Uranium and Neptunium by EXAFS spectroscopy

Hennig, C.; Takao, S.; Takao, K.; Weiss, S.; Kraus, W.; Emmerling, F.; Meyer, M.; Scheinost, A. C.
Hydrated actinide(IV) ions undergo hydrolysis and further polymerization and precipitation with increasing pH. The resulting amorphous and partly crystalline oxydydroxides AnOn(OH)4−2nxH2O can usually be observed as colloids above the An(IV) solubility limit. The aging process of such colloids results in crystalline AnO2. The presence of carboxylates in the solution prevents the occurrence of such colloids by formation of polynuclear complexes through a competing reaction between hydrolysis and ligation. The majority of recently described carboxylates reveals a hexanuclear core of [An6(μ3-O)4(μ3-OH)4]12+ terminated by 12 carboxylate ligands. We found that the An(IV) carboxylate solution species remain often preserved in crystalline state. The An(IV) carboxylates show An-An distances which are ~ 0.03 Å shorter than the An-An distances in AnO2 like colloids. The difference in the distances could be used to identify such species in solution.
Keywords: EXAFS, Actinides, Carboxylates

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Permalink: https://www.hzdr.de/publications/Publ-17660
Publ.-Id: 17660


Experimental Investigations on Vertical Pipe Flow Using Ultrafast Electron-Beam X-Ray Tomography

Banowski, M.; Lucas, D.; Hoppe, D.; Barthel, F.; Szalinski, L.; Sprewitz, U.; Beyer, M.; Hampel, U.
This presentation introduces into the tomography measurement system and the vertical pipe test facility for liquid-gas experiments at TOPFLOW. The reconstruction and data evaluation algorithms are discussed shortly. Some results of two-phase upward flow experimental series for air-water and steam-water flow regimes are showed with qualitative and quantitative data. Finally limits and errors of this measurement technique are presented.
Keywords: two-phase, measuring technique, X-ray, tomography, pipe flow, bubble
  • Lecture (Conference)
    10th Multiphase Flow Conference: Simulation, Experiment and Application, 13.-14.06.2012, Dresden, Deutschland
  • Contribution to proceedings
    10th Multiphase Flow Conference: Simulation, Experiment and Application, 13.-14.06.2012, Dresden, Deutschland
    CD-ROM

Permalink: https://www.hzdr.de/publications/Publ-17659
Publ.-Id: 17659


High temperature diffusion processes at the metal/slag interface

Bogusz, A.; Masset, P. J.
The interface metal/molten oxide is of interest for several high temperature processes (metallurgy, gasification…). The exchange reactions occurring at the interface between the metal and the molten slag are complex and up to date not well understood. More generally, this is of importance for the understanding of the exchange reaction kinetics between one metallic compound (solid or liquid) and an ionic one (slag). This work proposes a theoretical approach which takes into account the effect of speciation in the slag on the diffusion process of the species in the two phases and the redox reaction occurring within the vicinity of the interface. The systems investigated consist of Fe and CaO-SiO2 without convection. The concentration profiles of silicon and iron oxide in both parts were calculated. The effect of impurities present in metal phase such as sulphur in the molten slag was investigated. This provides a basis of comprehensive approach for the purification of metal and a better understanding of processes at metal/oxide interface.
Keywords: Diffusion, Mass exchange, Electrochemical reactions, Metal/slag interface

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Permalink: https://www.hzdr.de/publications/Publ-17658
Publ.-Id: 17658


CFD-Modellierung von unterkühltem Sieden: Kopplung des Wandsiedemodells mit einem Populationsbilanz-modell und Vergleich mit DEBORA-Experimenten

Krepper, E.; Rzehak, R.
Unterkühltes Sieden spielt auf Grund seines hohen Wärmeübertragungsvermögens in vielen industriellen Anwendungen zur Energieerzeugung eine große Rolle. Überschreitet der Wärmestrom einen kritischen Wert, so kann die rasch ansteigende Temperatur zu Zerstörungen führen. Der Nachweis der Wirkung von Auslegungsverbesserungen auf den in jedem Fall sicher zu vermeidenden kritischen Wärmestrom erfordert aufwendige Experimente. Der Ersatz oder zumindest die Unterstützung durch numerische Simulationen ist daher von hohem Interesse.
Der Vortrag gibt eine Einordnung der Rolle von Siedevorgängen in der Kerntechnik und beschreibt den aktuellen Stand der CFD-Modellierung. Sehr aussichtsreich ist die auf dem Euler/Euler-Verfahren beruhende Beschreibung der Mehrphasenströmung. Im Institut für Fluiddynamik gibt es langjährige Erfahrungen bei der Modellierung der Impuls- und Massenaustauschbeziehungen. Wichtig für die Modellierung dieser Schließungsmodelle ist die genaue Kenntnis der Phasengrenzfläche. Der Vortrag beschreibt hierfür die Anwendung des Populationsbilanzmodells, das die Simulation der Blasengrößenverteilung ermöglicht. Kürzlich wurde diese Ansatz mit dem Wandsiedemodell gekoppelt und in den CFD Code CFX implementiert. Das Potential dieses Ansatzes wird anhand des Vergleichs mit an der französischen Versuchsanlage DEBORA durchgeführten Siedeexperimenten gezeigt. Weiterer Entwicklungsbedarf wird aufgezeigt.
Die Arbeiten sind Teil eines großen Verbundprojektes, das vom BMBF unter dem Programm „Energie 2020+“ gefördert, durch HZDR koordiniert wird und in dem 8 weitere Partner (Universitäten, Forschungszentren, Industriepartner) mitarbeiten
Keywords: CFD, boiling, CHF, population balance, DEBORA
  • Lecture (others)
    Institutsseminar, 12.07.2012, Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17657
Publ.-Id: 17657


Population balance model for the CFD simulation of adiabatic and diabatic two phase gas liquid flows

Krepper, E.; Lucas, D.
A generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework was developed in close cooperation of ANSYS-CFX and Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and implemented into CFX. By simulating a poly-dispersed gas-liquid two-phase flow, the mass exchanged between bubble size classes by bubble coalescence and bubble fragmentation as well as the momentum exchange due to bubble size dependent bubble forces have to be considered. In a vertical pipe flow particularly the radial separation phenomenon of small and large bubbles, which was proven to be a key phenomenon for the establishment of the corresponding flow regime, is well described by this approach. Recently the approach was extended considering bubble shrinking or growing by condensation or evaporation. Size dependent bubble forces can at least be represented roughly assigning the size groups to few different dispersed gaseous phases having different velocity fields.
The derived model has been validated against experimental data from the TOPFLOW test facility at the HZDR. Numerous tests investigating air-water flow at 0.25 MPa and steam-water flow at stem pressures between 1-6.5 MPa and sub-cooling temperatures from 2 to 17 K in vertical pipes having a length up to 8 m and a diameter up to 200 mm were performed. The wire-mesh technology measuring local gas volume fractions, bubble size distributions and velocities of gas and liquid phases at different distances from the gas injection was applied.
For air/water flow the shift of the gas volume fraction profile from a wall peak to core peak could be reproduced. For steam water flow by varying the gas nozzle diameter the initial bubble size was influenced and the effect of the bubble size on the condensation rate could be shown. Due to the drop of hydrostatic pressure along the pipe, the saturation temperature falls towards the upper pipe end and for some tests in the upper part re-evaporation was reproduced.
Weaknesses in this approach can be attributed to the characterization of bubble coalescence and bubble fragmentation, which must be further investigated. A further topic is bubble induced turbulence.
Keywords: CFD, two-phase-flow, population balance, inhomogeneous MUSIG, air-water flow, steam-water flow
  • Contribution to proceedings
    9th International Conference on CFD in the Minerals and Process Industries, CSIRO, 10.-12.12.2012, Melbourne, Australien
  • Invited lecture (Conferences)
    9th International Conference on CFD in the Minerals and Process Industries, CSIRO, 10.-12.12.2012, Melbourne, Australien

Permalink: https://www.hzdr.de/publications/Publ-17656
Publ.-Id: 17656


CFD model of wall boiling including a population balance model

Krepper, E.; Rzehak, R.; Lifante, C.; Frank, T.
In this work the present capabilities of CFD for wall boiling are investigated. The computational model is based on the Euler / Euler two-phase flow description with heat flux partitioning. In the framework of interpenetrating continua the exchange of momentum, mass and energy between the phases are essential. The description of the interfacial morphology plays an important role. In the actual work a population balance model for the description of the gaseous phase considering bubble coalescence, bubble fragmentation and bubble size changes caused by condensation of evaporation is applied. The wall boiling model is coupled with the population balance model.
For the demonstration, DEBORA tests (Garnier, 2001) were used. In the DEBORA tests in a vertical tube Dichlorodi¬fluoromethane (R12) was heated from the side walls. Radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size were measured.
The results show the potential of this model approach which is able to describe the observed bubble size increase after leaving the wall as well as the change of gas volume fraction profile from wall to core peaking with increasing inlet temperature.
Keywords: CFD, two phase flow, wall boiling, population balance model, experiments, model validation
  • Contribution to proceedings
    CFD4NRS-4, The Experimental Validation and Application of CFD and CMFD Codes in Nuclear Reactor Technology, 10.-12.09.2012, Daejeon, Südkorea
    CFD model of wall boiling including a population balance model

Permalink: https://www.hzdr.de/publications/Publ-17655
Publ.-Id: 17655


Observations of transport processes in dense material as challenge for PET imaging procedures and image reconstruction methods

Kulenkampff, J.; Lippmann-Pipke, J.; Zakhnini, A.; Pietrzyk, U.
Understanding transport processes in soils and rocks is crucial for geosciences. These processes are simulated with sophisticated models. However, complex structure, inhomogeneous composition and randomness still produce unsatisfactory predictions. Experimental data is needed for calibration and validation of the model codes and parameters.
PET, as method for spatiotemporal quantitative observation of tracer propagation with unrivaled sensitivity and selectivity, is first choice for providing these data sets during transport experiments. During a decade of research we established “GeoPET” as profitable laboratory method in geosciences, with convincing results.
However, compared to medical imaging, high material density and extended observation periods cause some challenges: We have to consider strong attenuation, a high scatter fraction and interferences from high energy gamma-emissions typical for long living radionuclides, like I-124, Co-58 and Na-22. Consequently, we have to handle images that are prone to artefacts and blurring. These deficiencies are presumably exacerbated by the inhomogeneous sensitivity of our ClearPET-scanner in combination with a disadvantageous normalization method of the applied osmaposl-reconstruction algorithm from the STIR-library (Thielemans et al. 2012).
In order to identify causes of these deficiencies and to improve the methods for correction and reconstruction, we conducted OpenGATE-Monte-Carlo-simulations (Jan et al. 2011, Zakhnini et al. submitted) of our experiments, with according results of experiment and simulation. From the simulation we are able to track the fate of each event, including scattering and detection process. These simulations resulted in some practical advices for the energy window and detector geometry, and the development of an efficient scatter correction method. More involved enhancements suggested from these simulations are additional detectors for Compton-scattering, other detector geometries, and development or application of more robust reconstruction methods.
Keywords: PET, Monte-Carlo-Simulation, flow experiments, imaging
  • Lecture (Conference)
    2012 Workshop “Tomography, data processing and image reconstruction for medicine and engineering”, 10.-12.09.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17654
Publ.-Id: 17654


REE-Lagerstätten in der NW-Mongolei

Kempe, U.; Möckel, R.
Seltenerdlagerstättenmineralisationen im Nordwesten der Mongolei werden vorgestellt. Dabei wurden neben den Gehalten von SEE, Y, Zr, Nb und Ta auch genetische Aspekte untersucht. Zu den untersuchten Objekten gehören die Lagerstätten und Vorkommen von Khalzan Buregte, Shar Tolgoi und Ulaan Tolgoi. Die eingesetzten Untersuchungsmethoden umfassten u.a. Durchlicht- und Rasterelektronenmikroskopie sowie Röntgenphasenanalyse und geochemische Gesamtgesteinsanalysen der Hauptkomponenten, der Seltenen Erden und Yttrium.

Die Ergebnisse zeigen, dass die primären, magmatischen Gehalte von Zr, Nb und der SEE sub-ökonomisches Niveau erreichen. Hydrothermale, postmagmatische Ereignisse führten jedoch zu einer deutlichen Anreicherung von Zr, Nb, besonders der Schweren SEE und Y. Für die Lagerstätte von Khalzan-Buregte besteht eine klare wirtschaftliche Perspektive wenn die logistischen Probleme und die Aufgaben in der Erzaufbereitung gelöst werden können. Mögliche Bedeutungen der anderen untersuchten Gebiete (für Shar Tolgoi SEE, für Ulaan Tolgoi Nb und Ta) werden diskutiert.
Keywords: rare earth elements, Mongolia, Khalzan Buregte
  • Lecture (Conference)
    BGR Statusseminar, 10.05.2012, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17653
Publ.-Id: 17653


Positron annihilation at planar defects in oxides

Kuriplach, J.; Melikhova, O.; Cizek, J.; Prochazka, I.; Brauer, G.; Anwand, W.
Planar defects may exhibit free volumes which, in principle, are detectable using positron annihilation spectroscopy. In this contribution, we present a preliminary theoretical study of positron trapping at stacking faults in zinc oxide and at a grain boundary in zirconia. In particular, we calculate the positron lifetime and positron binding energy to such defects. In the case of the grain boundary in zirconia, the influence of the yttrium segregation on the GB structure and positron characteristics is also examined. Calculated structural and positron characteristics are critically compared with experimental and other calculated data.
Keywords: zinc oxide, stacking fault, zirconia, grain boundary, planar defects, positron trapping

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Permalink: https://www.hzdr.de/publications/Publ-17652
Publ.-Id: 17652


PT-symmetric quantum state discrimination

Bender, C.; Brody, D.; Caldeira, J.; Günther, U.; Meister, B.; Samsonov, B.
Suppose that a system is known to be in one of two quantum states. If these states are not orthogonal, then the requirement of unitarity forbids the possibility of determining with one measurement which state the system is in. However, because a non-Hermitian PT-symmetric Hamiltonian determines the inner product that is appropriate for the Hilbert space of physical states, it is always possible to choose this inner product so that the two states are orthogonal. Thus, it is possible to perform a simulated quantum state discrimination with a single measurement in which a perfect state discrimination is realized probabilistically.
Keywords: PT quantum mechanics, non-Hermitian Hamiltonian, quantum state discrimination

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Permalink: https://www.hzdr.de/publications/Publ-17651
Publ.-Id: 17651


Hydrogen-induced plastic deformation in ZnO

Lukac, F.; Cizek, J.; Vlcek, M.; Prochazka, I.; Anwand, W.; Brauer, G.; Traeger, F.; Rogalla, D.; Becker, H.-W.
In the present work hydrothermally grown ZnO single crystals covered with Pd over-layer were electrochemically loaded with hydrogen and the influence of hydrogen on ZnO microstructure was investigated by positron annihilation spectroscopy (PAS). Nuclear reaction analysis (NRA) was employed for determination of depth profile of hydrogen concentration in the sample. NRA measurements confirmed that a substantial amount of hydrogen was introduced into ZnO by electrochemical charging. The bulk hydrogen concentration in ZnO determined by NRA agrees well with the concentration estimated from the transported charge using the Faraday’s law. Moreover, a subsurface region with enhanced hydrogen concentration was found in the loaded crystals. Slow positron implantation spectroscopy (SPIS) investigations of hydrogen-loaded crystal revealed enhanced concentration of defects in the subsurface region. This testifies hydrogen-induced plastic deformation of the loaded crystal. Absorbed hydrogen causes a significant lattice expansion. At low hydrogen concentrations this expansion is accommodated by elastic straining, but at higher concentrations hydrogen-induced stress exceeds the yield stress in ZnO and plastic deformation of the loaded crystal takes place. Enhanced hydrogen concentration detected in the subsurface region by NRA is, therefore, due to excess hydrogen trapped at open volume defects introduced by plastic deformation. Moreover, it was found that hydrogeninduced plastic deformation in the subsurface layer leads to typical surface modification: formation of hexagonal shape pyramids on the surface due to hydrogen-induced slip in the [0001] direction.
Keywords: zinc oxide; hydrogen; plastic deformation; nuclear reaction analysis
  • Contribution to proceedings
    International Workshop on Positron Studies of Defects 2011 (PSD-11), 28.08.-02.09.2011, Delft, Netherlands
    Physics Procedia 35: ELSEVIER, 128-133

Permalink: https://www.hzdr.de/publications/Publ-17650
Publ.-Id: 17650


Radiolabelling of engineered nanoparticles – different strategies for Ag0-NP, TiO2-NP and MWCNT.

Franke, K.; Hildebrand, H.; Schymura, S.; Cydzik, I.; Simonelli, F.; Bulgheroni, A.; Holzwarth, U.; Kozempel, J.; Gibson, N.
Radioactive tracers provide a simple and effective tool for transport studies of nanoparticulate materials within environmental samples at laboratory scale. Compared to classical approaches radiolabelling of nanoparticles (NP) offers advantages in sensitivity and selectivity together with the possibility of in-situ imaging of transport phenomena. Particularly with regard to quantitative evaluation for transport studies radiotracers allow an easy differentiation between the elemental/nanoparticulate background concentration and the NP-derived input into an environmental sample. The limiting factor of the use of radiotracers is the possible alteration of experimentally relevant physical/chemical properties of the NP due to the radiolabelling and also the stable binding of the tracer on the NP. Depending on the experimental needs (half-life, decay-mode/radiation), different labelling methods are available.
The study aims at the comparison/evaluation of radiolabelling methods for Ag0-NP, TiO2-NP and MWCNT:

(1) direct activation of NP due to cyclotron irradiation:
- Ag0-NP: 107Ag(p,3n)105Cd --> 105Ag / 107Ag(p,p2n)105Ag
- TiO2-NP: 48Ti(p,n)48V
- MWCNT: 12C(p,3d)7Be

(2) self-diffusion of radioisotopes:
- Ag0-NP: 105,110mAg
- TiO2-NP: 44,45Ti

(3) radioiodination
- MWCNT: 125,131I

(4) recoil labelling:
- Ag0-NP: 7Li(p,n)7Be
- TiO2-NP: 7Li(p,n)7Be
- MWCNT: 7Li(p,n)7Be

The direct irradiation and the recoil labelling were carried out at a Scanditronix MC40 cyclotron [1, 2], self-diffusion experiments were carried by means of a Cyclone® 18/9 (IBA molecular) [3]. The methods were tested with respect to labelling yield, achievable activity concentration, pH-dependent stability of the labelling and the influence on NP-properties. Data thus obtained enable an appropriate selection of radiolabelling methods for different experimental applications.

References
[1] Abbas K, Cydzik I, Del Torchio R, Farina M, Forti E, Gibson N, Holzwarth U, Simonelli F, Kreyling W (2010) J Nanopart Res 12:2435–2443.
[2] Holzwarth U, Bulgheroni A, Gibson N, Kozempel J, Cotogno G, Abbas K, Simonelli F, Cydzik I (2012) J Nanopart Res 14:880
[3] Hildebrand H and Franke K (2012) J Nanopart Res submitted.
  • Lecture (Conference)
    International Conference on Nuclear and Radiochemistry (NRC-8), 16.-21.09.2012, Como, Italia

Permalink: https://www.hzdr.de/publications/Publ-17649
Publ.-Id: 17649


Cyclotron produced 45Ti – production, purification and yields

Franke, K.; Hildebrand, H.; Mansel, A.
Studies of the environmental fate of nanoparticulate TiO2 require suitable tools for tracing the nanoparticles in complex environments and media. A promising method is the isotopic radiolabelling of the TiO2-nanoparticles with 44Ti (T1/2 = 47.3 a) or 45Ti (T1/2 = 3.08 h). Due to the different decay modes and half-lives, different experimental setups are accessible with these radioisotopes. The presented work is focused on the production and purification of the short –lived positron-emitting radionuclide 45Ti (n.c.a.).
For this purpose, we used the nuclear reaction 45Sc(p,n)45Ti [1]. The irradiation was done at a COSTIS target station mounted at a 2 m beam transfer line of a Cyclone® 18/9 (IBA molecular). The mono-isotopic natural scandium allowed an easy target design. A scandium foil (thickness: 100 µm) was put together with an energy-degrading foil into a disk-like sample holder and was then transferred into the COSTIS target station. The irradiation was carried out with 12 MeV protons and a current of 20 µA for 20 min – 30 min.
Radionuclide separation and purification was done by means of ion exchange chromatography [2] or liquid-liquid extraction [3]. Both methods were compared. Higher yields and better purification results were obtained with liquid-liquid extraction. The yield of the liquid-liquid extraction was about 75 % - 80 %, n.c.a. 45Ti stock solution (1 M HCl) had a activity concentration of up to 120 MBq/mL.

References
[1] McGee T, Rao CL, Saha GB, Yaffe L (1970) Nucl Phys A150:11-29.
[2] Vâvere AL, Laforest R, Welch MJ (2005) Nucl Med Biol 32:117-122.
[3] Sevastinov YG (1974) J Radioanal Chem 21:247-257.
  • Poster
    International Conference on Nuclear and Radiochemistry (NRC-8), 16.-21.09.2012, Como, Italy

Permalink: https://www.hzdr.de/publications/Publ-17648
Publ.-Id: 17648


Inelastic scattering of fast neutrons from excited states in 56Fe

Schwengner, R.; Beyer, R.; Junghans, A.; Massarczyk, R. Keywords: Inelastic neutron scattering; photoneutron source nELBE; fast neutrons; time-of-flight; gamma-ray spectroscopy; excited states, scattering cross sections
  • Lecture (others)
    Seminar, 14.03.2012, Geel, Belgien

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Permalink: https://www.hzdr.de/publications/Publ-17647
Publ.-Id: 17647


CFD Simulation of DEBORA boiling experiments

Rzehak, R.; Krepper, E.
In this work we investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler / Euler two-phase flow description with heat flux partitioning. This kind of modeling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using Dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, bubble size and liquid temperature as well as axial profiles of wall temperature.
After reviewing the theoretical and experimental basis of correlations used in the CFX model, used for the calculations, we give a careful assessment of the necessary recalibrations to describe the DEBORA tests. The basic CFX model is validated by a detailed comparison to the experimental data for two selected test cases. Simulations with a single set of calibrated parameters are found to give reasonable quantitative agreement with the data for several tests within a certain range of conditions and reproduce the observed tendencies correctly. Several model refinements are then presented each of which is designed to improve one of the remaining deviations between simulation and measurements. Specifically we consider a homogeneous MUSIG model for the bubble size, modified bubble forces, a wall function for turbulent boiling flow and a partial slip boundary condition for the liquid phase. Finally, needs for further model developments are identified and promising directions discussed.
Keywords: Subcooled flow boiling; Computational fluid dynamics simulation; Heat flux partitioning; Two-fluid model

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Publ.-Id: 17646


BI-Annual Report 2009/10 Rossendorf Beamline at ESRF (ROBL-CRG)

Scheinost, A. C.; Baehtz, C.; (Editors)
The Rossendorf Beamline (ROBL) - located at BM20 of the European Synchrotron Radiation Facility (ESRF) in Grenoble, France - is in operation since 1998. This 7th report covers the period from January 2009 to December 2010. In these two years, 67 peer- reviewed papers have been published based on experiments done at the beamline, more than in any biannual period before. Six highlight reports have been selected for this report to demonstrate the scientific strength and diversity of the experiments performed on the two end-stations of the beamline, dedicated to Radiochemistry (RCH) and Materials Research (MRH).


The beamtime was more heavily overbooked than ever before, with an acceptance rate of only 25% experiments. We would like to thank our external proposal review members, Prof. Andre Maes (KU Leuven, Belgium), Prof. Laurent Charlet (UJF Grenoble, France), Dr. Andreas Leinweber (MPI Metallforschung, Stuttgart, Germany), Prof. David Rafaja (TU Bergakademie Freiberg, Germany), Prof. Dirk Meyer (TU Dresden, Germany), who evaluated the inhouse proposals in a thorough manner, thereby ensuring that beamtime was distributed according to scientific merit.


The period was not only characterized by very successful science, but also by intense work on the optics upgrade. In spring 2009, a workshop was held at ROBL, assembling beamline experts from German, Spanish and Swiss synchrotrons, to evaluate the best setup for the new optics. These suggestions was used to prepare the call for tender published in July 2009. From the tender acceptance in November 2009 on, a series of design review meetings and factory acceptance tests followed. Already in July 2010, the first piece of equipment was delivered, the new double-crystal, double-multilayer monochromator. The disassembly of the old optics components started end of July, 2011, followed by the installation of the new components. As of December 2011, the new optics have seen the first test beam and thorough hot commissioning will be continued until May 2012, since the ESRF shuts down for a major upgrade from December 2011 to April 2012. We expect that we will be ready for user operation from June 2012 on, with a better beamline than ever.


The beamline staff would like to thank all partners, research groups and organizations who supported the beamline during the last 24 months. Special thanks to the FZD management, the CRG office of the ESRF with Axel Kaprolat as liaison officer and Eric Dettona as lead technician, and to the ESRF safety group members, Paul Berkvens, Patrick Colomp and Yann Pira.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-003 2011

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Permalink: https://www.hzdr.de/publications/Publ-17645
Publ.-Id: 17645


Developments to radioimmunotherapy in the context of radiopharmaceutical and oncological developments

Steinbach, J.
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Seminarvortrag Paul Scherrer Institut, 25.05.2012, Villingen, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-17644
Publ.-Id: 17644


Radiotracers for the Cholinergic System

Steinbach, J.
kein Abstract verfügbar
  • Invited lecture (Conferences)
    30th International Symposium "Radioactive Isotopes in Clinical Medicine and Research", 11.-14.01.2012, Bad Hofgastein, Österreich

Permalink: https://www.hzdr.de/publications/Publ-17643
Publ.-Id: 17643


Magnetic resonance imaging: from fundamentals to perfusion quantification

Bos, A.
kein Abstract verfügbar
  • Lecture (Conference)
    2. Dresdner Workshop, Molecular Imaging in Life Science, 20.06.2012, Dresden-Rossendorf, D

Permalink: https://www.hzdr.de/publications/Publ-17642
Publ.-Id: 17642


Multimodality Molecular imaging in small animals from nanoscale to mikroscale

Bergmann, R.
kein Abstract verfügbar
  • Lecture (Conference)
    2. Dresdner Workshop, Molecular Imaging in Life Science, 20.06.2012, Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17641
Publ.-Id: 17641


Quantitative PET: Prerequisites and Pitfalls

van den Hoff, J.
kein Abstract verfügbar
  • Lecture (Conference)
    Dresdner Workshop, Molecular Imaging in Life Science, 20.06.2012, Dresden-Rossendorf, D

Permalink: https://www.hzdr.de/publications/Publ-17640
Publ.-Id: 17640


Quantitation of tumour biology using nanoScan PET/CT and nanoScan PET/MRI in mouse models

Bergmann, R.
Abstract nicht verfügbar
  • Invited lecture (Conferences)
    World Congress of Molecular Imaging, 05.-08.09.2012, Dublin, Ireland

Permalink: https://www.hzdr.de/publications/Publ-17639
Publ.-Id: 17639


Hydrodynamics and Bubble Wake Modelling of Three-Phase Semifluidized Beds

Schubert, M.; Larachi, F.
Three-phase fluidized beds are widely encountered in the chemical, petrochemical, and biochemical industry. Traditionally, they have been employed for hydrogenation and hydrodesulfurization of heavy oil and petroleum residuum in hydrotreating and upgrading processes, for the Fischer-Tropsch synthesis, for coal liquefaction and gasification, but also for bio-oxidation processes for wastewater treatment and for the production of pharmaceuticals. However, the field of application is widespread, including also physical processing such as filtration, particle collection, air cooling, and (de)humidification, as well as three-phase transport.
The most common operation mode is the cocurrent gas and liquid upflow fluidized bed system with liquid as the continuous phase. The semifluidization phenomenon is rather characterized by a combination of a fluidized bed and a fixed bed in series in a single containing column built by expansion of the fluidized bed and then compressing the solid particles against a porous retaining grid at the top that constrains the bed. A semifluidized bed is claimed to overcome some drawbacks of fluidized beds such as solids backmixing, attrition of particles, and erosion of surfaces, and is characterized by uniform bed temperature profiles and flow distribution which may not be as easily achievable as in the case of fixed beds.
For full hydrodynamic characterization of the semifluidized bed all phase holdups in both sections must be known. While the total pressure drop of the semifluidized bed was reasonably well predicted by ad hoc model equations proposed for each section, so far individual holdups were not directly measured for the fixed bed section (Chern et al. 1984). The gas holdup in the upper fixed bed section was only calculated on the basis of the pressure drop measurements and on using separate flow model equations. Furthermore, knowledge about the porosity is required which was proposed to take a constant value. While this assumption is valid for isolated packed beds, it is not evident that it holds in a semifluidized system, especially for industrial porous catalyst particles.
  • Poster
    19th International Congress of Chemical and Process Engineering CHISA 2010 and the 7th European Congress of Chemical Engineering (ECCE-7), 28.08.-01.09.2010, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-17638
Publ.-Id: 17638


Molecular imaging in pharmaceutical research

Bergmann, R.
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Workshop “Molecular Imaging”, Universität Izmir, 14.05.2012, Izmir, Turkey

Permalink: https://www.hzdr.de/publications/Publ-17637
Publ.-Id: 17637


Optical Imaging in Physiology and Pharmaceutical Research

Bergmann, R.
kein Abstract verfügbar
  • Invited lecture (Conferences)
    Workshop “Optical Imaging", Universität Rijeka, 14.-15.03.2012, Rijeka, Kroatia

Permalink: https://www.hzdr.de/publications/Publ-17636
Publ.-Id: 17636


Structural analysis of the aqueous (UO2)2CO3(OH)3−-complex – A combined approach using ATR FT-IR spectroscopy and DFT calculations

Gückel, K.; Tsushima, S.; Foerstendorf, H.; Rossberg, A.
The migration behavior of heavy metal contaminants like actinyl ions (UO22+) in ground water aqui-fers is mainly controlled by sorption processes at water-mineral interfaces. Sorption and therewith the retardation of uranium in the environment depends predominately on its aqueous speciation.

From our recent spectroscopic study, the formation of a dimeric uranyl carbonate hydroxo complex on the surface of gibbsite was derived [1]. The found interatomic distances and coordination numbers for the surface complex are in line with the results of Szabo et al. [2] for the mixture of aqueous (UO2)2CO3(OH)3−-complexes. However, an unequivocal verification of the molecular structure is still lacking. According to previous investigations [2, 3] and predicted aqueous speciation of uranium(VI), a uranyl carbonate hydroxo complex is predominant over a broad pH range. Under near neutral pH conditions, similar to those of natural waters, the (UO2)2CO3(OH)3−-complex is the dominating species over a wide concentration range. Maya et al. [3] determined the stability constant (−log β= 18.63 ± 0.08) and measured the Raman spectrum [4] of the complex. The stoichiometry of this complex and the coordination geometry of the uranyl ion was discussed by means of four possible structures [2] of which the preferred structure.
Up to date, no vibrational spectra of the aqueous complex are available in the literature potentially providing further structural information particularly about the configuration of the carbonate ion. We prepared the dimeric complex under well defined atmospheric conditions and recorded IR spectra. In combination with DFT calculations, the assignment of the spectroscopic data to the respective isomer is accomplished.

1. K. Gückel, A.R., V. Brendler, H. Foerstendorf, Chemical Geology, 2012. under revision.
2. Szabo, Z., H. Moll, and I. Grenthe, Structure and dynamics in the complex ion (UO2)(2)(CO3)(OH)(3)(-). Journal of the Chemical Society-Dalton Transactions, 2000(18): p. 3158-3161.
3. Maya, L., HYDROLYSIS AND CARBONATE COMPLEXATION OF DIOXOURANIUM(VI) IN THE NEUTRAL-PH RANGE AT 25-DEGREES-C. Inorganic Chemistry, 1982. 21(7): p. 2895-2898.
4. Maya, L. and G.M. Begun, A RAMAN-SPECTROSCOPY STUDY OF HYDROXO AND CARBONATO SPECIES OF THE URANYL(VI) ION. Journal of Inorganic & Nuclear Chemistry, 1981. 43(11): p. 2827-2832.
  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland, 05.-07.11.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17635
Publ.-Id: 17635


Gas-Liquid Saturation Distribution in Tubular Metallic Foam Reactors using Gamma-Ray Computer Tomography

Mohammed, I.; Lange, R.; Bieberle, A.; Schubert, M.
Multiphase catalytic reactor are commonly used in many industrial process, the application of these reactors is of increasing important in petrochemical and other industries. Presently structured packing elements have been suggested for various multiphase reactors alternative of random packing. Metallic foam which used as gas filter, heat exchanger with their extremely higher porosity (85-90%) resulting in low pressure drop, higher surface area which are attractive points for multiphase reactor, moreover the continuous structured network and the void structure enable the fluid to flow in all direction that give intercontacting between the cells which is missing in monolith type, this phenomena need properly understanding due to the complex nature of the interaction between gas, liquid and solid make one of the major challenge is achieving proper distribution since malditribution can decreasing reactor selectivity to desired product and underutilization of the catalysis.
Hydrodynamic study particularly of gas-liquid flow distribution in foam are scarcer, Calvo et al studied liquid radial spreading in rectangular column packed with sheet of metallic foam operating in single phases liquid trickle flow in counter-current, unfortunately no study address the liquid saturation which is the ratio of the liquid volume to the bed voidage which is essential to prediction the effective liquid velocity within the packing which is in turn related to heat and mass transfer.
Since the two phase flow in metallic foam is difficult to visualize and characterize duo to opaque system and the need for application work at different flow condition, therefore we present work apply gamma ray computer tomography developed in HZDR with higher resolution based on novel detector technology to measured liquid saturation and investigate liquid distribution in cylindrical column packed with metallic foam in down flow gas and liquid to investigated the effect of foam density (ppi) pore per inch and operation condition (gas and liquid flow rate),the result will qualitative evaluation of gas/liquid distribution uniformly in metallic foam which will use to quantify the phase maldistrbutione at flow condition specify for commercial reactor operation and at flow rates bracketing such condition.
  • Poster
    8th European Congress of Chemical Engineering, 25.-29.09.2011, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17634
Publ.-Id: 17634


Visualization of multiphase flows using wire-mesh sensor technology

Zheng, G.; Bothe, M.; Schubert, M.; Hampel, U.; Gruenewald, M.
Multiphase contactors are the most important apparatuses for reaction and separation in chemical engineering. Limited by the measuring methods, the analysis of their hydrodynamic behavior is usually done using superficial liquid and gas flow velocities. Several new measuring techniques for the investigation of multiphase flows in vessel cross sections have been developed in the last decades. Especially the use of tomographic visualization techniques is of great interest since these are noninvasive and thus non-intrusive methods, and enable the visualization of phase distributions.
However, currently developed nonintrusive methods have considerable drawbacks. The computer tomography methods can obtain high spatial resolution. In comparison, the temporal resolution is relative low. For the application of topographic measurement techniques in multiphase flows, especially with fast changing flow patterns, a high temporal resolution is essential. Electrical tomography has a high temporal resolution. However, reconstruction algorithm is very complex and the electrical field lines are not linear, therefore spatial resolution rate is relative low. Therefore, no exact mass balance could be established and the resulting phase fractions cannot be applied for model developments.
  • Poster
    6th International Symposium on Process Tomography, 26.-28.03.2012, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-17633
Publ.-Id: 17633


Partial volume correction in arterial spin labeling using a Look-Locker sequence

Petr, J.; Schramm, G.; Hofheinz, F.; Langner, J.; Steinbach, J.; van den Hoff, J.
Purpose: Partial volume (PV) effects are caused by limited spatial resolution and significantly affect cerebral blood flow (CBF) investigations with arterial spin labeling (ASL). Therefore, accurate PV correction (PVC) procedures are required. PVC is commonly based on PV maps obtained from segmented high-resolution T1-weighted images. Segmentation of these images is error prone and it can be difficult to co-register these images accurately with the single-shot ASL images such as those created by echo-planar imaging (EPI). In this paper, an alternative method for PV map generation is proposed.
Methods: The Look-Locker EPI (LL-EPI) acquisition is used for analyzing the T1-recovery curve and for subsequent PV map generation. The new method was evaluated in five healthy volunteers (mean age 30±3.7 years).
Results: By applying a linear regression method for PVC, a 12% decrease in regression error was reached with the new method.
Conclusion: PV maps extraction from LL-EPI is a viable, possibly superior alternative to the standard approach based on segmentation of high-resolution T1-weighted images.

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Permalink: https://www.hzdr.de/publications/Publ-17632
Publ.-Id: 17632


Effect of solid propertices on the hydrodynamic flow behaviour in a slurry bubble column using ultra-fast electron beam X-ray tomography

Rabha, S.; Schubert, M.; Wagner, M.; Lucas, D.; Hampel, U.
Slurry bubble column (SBC) reactors find a wide range of application in the chemical process industries. Most important applications of SBC reactors are catalytic hydrogenation of oil, methanol synthesis, Fischer Trospch process, etc. (Shah, 1979; etc.). The size, density and concentration of the solid catalyst particles play an important role in the performance of the SBC reactors, e.g. large particles lead to poor mass transfer whereas smaller particles can be entrained in the product stream or agglomerate into a large cluster. Therefore, optimum particle size is very important to achieve high transfer rates and to minimize effort for catalyst exchange or product-fines separation. Only few literature is available which shows the effect of particle properties like size and density on gas hold-up in SBCs (Kato et al.1972; Kim et al. 1987; etc.). Also, the solid concentration changes the hydrodynamic parameters significantly in SBC reactors (Krishna et al., 1997; Pandit and Joshi, 1986; etc.), which need to be investigated systematically. In the present work, the effects of particle size (50 μm ≤ dP ≤ 150 μm) and solid concentration (0.01 ≤ Cs ≤ 0.2) on the flow behaviour (e.g. gas holdup and bubble size distribution) in a SBC at different superficial gas velocities (0.02 ≤ UG ≤ 0.05 m/s) were investigated.
Keywords: Slurry bubble column; particle size; bubble size distribution; gas hold-up; tomography
  • Lecture (Conference)
    11th International Conference on Gas-Liquid & Gas-Liquid-Solid Reactor Engineering, 18.-23.08.2013, Seoul, Korea

Permalink: https://www.hzdr.de/publications/Publ-17631
Publ.-Id: 17631


Investigations on the effect of liquid viscosity on the flow behaviour in bubble columns using wire mesh sensors

Schubert, M.; Rabha, S.; Hampel, U.
Bubble column reactors have been used in chemical, petrochemical, biochemical, and pharmaceutical industries for various processes, e.g. partial oxidation of ethylene to acetaldehyde, Fischer-Tropsch (FT) synthesis (Deckwer, 1992; Fan, 1989). Depending on operating and design parameters, bubble column reactor may exhibits different flow regimes e.g. homogeneous, heterogeneous and churn turbulent flow regime. These flow regimes have entirely different hydrodynamic characteristic which results in different mixing as well as heat and mass transfer.
Different maps have been proposed to differentiate flow regimes (Krishna and Sie, 1994; Shah et al., 1982; etc.) in bubble column. However, these maps are mainly limited to low viscosity systems (air-water) at ambient conditions. Previous works suggest that liquid phase viscosity has also a significant effect on the hydrodynamic characteristics. It stabilizes the bubbly flow and thereby results in a increasing bubble coalescence rate and decreasing breakup rate which may advance the flow regime transitions. Only few studies (Ruzicka et al. 2003; Thet et al. 2006, etc.) have been reported on the effect of liquid viscosity on the gas holdup in a bubble column. However, in all the previous works, smaller column diameter (< 140 mm) was considered. The effect of liquid viscosity on the flow regimes transition and hydrodynamic properties in large columns are yet to be investigated.
Therefore, the present work aims to study the effect of liquid viscosity (pure water vs. water+ glycerol mixtures with viscosity in the range of 1 ≤ µL ≤ 60 mPa•s on gas holdup and bubble size distribution at different superficial gas velocities (0.02 < UG < 0.32 m/s) for two different bubble column diameters (DC = 150 and 400 mm). Furthermore, the effects of liquid viscosity and column diameter on the regimes transition and on their dynamic behaviour in bubble columns will be studied.
Keywords: Bubble column; gas holdup;bubble size distribution; liquid viscosity; flow behavior; wire-mesh sensor.
  • Lecture (Conference)
    11th International Conference on Gas-Liquid & Gas-Liquid-Solid Reactor Engineering, 18.-23.08.2013, Seoul, Korea

Permalink: https://www.hzdr.de/publications/Publ-17630
Publ.-Id: 17630


Effect of Desflurane Anesthesia on the [18F]FDG Metabolism in Nude Mice

Bergmann, R.
Objectives:
Dynamic small animal PET studies in mice require often anesthesia to reduce motion related artifacts. The volatile anesthetic with the most rapid onset and offset and with low metabolism is desflurane, which is used for human general anesthesia, however not common in animals. Therefore, we evaluated the [18F]FDG distribution in awake and desflurane anesthetized NCIH292 tumor bearing nude mice.
Methods:
Fed NCIH292 tumor bearing NMRI nu/nu mice were divided into control mice (CM), which were freely moving in a cage at 27°C, and non-moving anesthetized mice (AM), which were kept under 9% desflurane in 0.2 L/min O2, 0.3 L/min air at 36°C. After 1 h adaption to the experimental setup the CM and AM were injected with [18F]FDG (5 MBq, i.v. bolus). Blood glucose was measured before the experiment, at 0.5 h and at 1 h. Then all mice were anesthetized and PET was measured over 30 min, the activity concentration data were calculated as SUV median (25%, 75% percentile).
Results:
There was no difference of [18F]FDG brain uptake between CM 1.9 (1.6, 2.2) and AM 1.9 (1.6, 2.3). An unexpected [18F]FDG increase was observed in the tumors of AM 2.47 (1.67, 3.17), which was higher than in the CM 0.81 (0.66, 1.14). The [18F]FDG uptake in the heart was also larger in the AM. As expected was the muscle (gluteus supeficialis, biceps femoris) uptake higher in the CM and the resulting tumor to muscle ratio was therefore in the CM 0.32 (0.28, 0.48) less than in the AM 3.9 (2.5, 6.8). The blood glucose was elevated in the AM only at 30 min post anesthesia induction with 10.3 (7.33, 11.8) mmol/L vs. CM 6.2 (5.8, 7.4) mmol/L.
Conclusions:
Desflurane affects the [18F]FDG uptake in the NMRI nu/nu mouse tissues. This has to be considered for glucose metabolic explorations with mice under anesthesia. An adaption period of one hour for the mice under anesthesia normalizes the elevated blood glucose often occurring after anesthesia induction stress. Thus, in terms of comparability and correct interpretation of results obtained from PET experiments with mice under anesthesia is a standardized experimental setup mandatory.
  • Poster
    World Congress of Molecular Imaging, 05.-08.09.2012, Dublin, Ireland

Permalink: https://www.hzdr.de/publications/Publ-17629
Publ.-Id: 17629


Biodistribution of Gallium-68-Labeled DOTA-Bisphosphonates

Bergmann, R.; Meckel, M.; Fellner, M.; Kubicek, V.
Aim:
Main indications of oncologic skeletal imaging are metastatic diseases in skeleton, bone pain in patients with known cancer, and primary bone tumors. Benign bone diseases like pediatric/adult back pain, bone viability and Paget’s disease are also important indications of skeletal imaging. There are numerous studies with [18F]fluoride PET demonstrating the clinical utility. Similar characteristics show Tc-99m-labeled bisphosphonates. Combining the bone seeking properties, the advantages of PET, and the potential labeling with therapeutic radionuclides we studied DOTA-phosphonates radiolabeled with [68Ga]Ga3+.
Methods:
The following macrocyclic tetraaza based phosphonate chelators were used BPAMD ((4–{[(bis-phosphonomethyl) carbomoyl]methyl}–7,10–bis–(carboxymethyl)–1,4,7,10-tetraazacyclododec–1–yl)–acetic acid, BPAPD ((4–{[(bis–phosphonopropyl)carbomoyl]methyl}–7,10–bis–(carboxymethyl)–1,4,7,10-tetraazacyclododec–1–yl)–acetic acid and BPPED Tetraethyl 10-{[(2,2-bis-phosphonoethyl)hydroxyphosphoryl]methyl}-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid. The DOTA based phosphonate ligands were labeled with [68Ga]GaCl3. The radiochemical purity of the labeled products was >95% determined with radio thin-layer chromatography. The biodistribution and biokinetics were compared with [18F]fluoride and [99mTc]Tc-MDP in Wistar rats using dissection, small animal PET and SPECT. All activity concentration data were calculated as SUV.
Results:
The compounds were labeled with high yields in ammonium acetate buffer with 68Ga, followed by a purification step using a cation exchange resin. High uptake values were detected for all 68Ga-phosphonates in the femura. The accumulation of [68Ga]BPPED in the bone was the highest and comparable with the uptake of [18F]Fluoride and [99mTc]Tc-MDP. The blood clearance of the [68Ga]BPPED was the fastest with a biexponential kinetics and half-life of 0.4 min and 6.9 min. The [68Ga]BPPED bone to blood ratio was also superior, however, not so large like of [18F]Fluoride and [99mTc]Tc-MDP.
Conclusion:
The [68Ga]BPPED showed in a preclinical setting excellent characteristics for skeletal imaging. It seems to be also a potential candidate for radionuclide therapy in oncology
  • Poster
    World Molecular Imaging Congress 2012, 05.-08.09.2012, Dublin, Ireland

Permalink: https://www.hzdr.de/publications/Publ-17628
Publ.-Id: 17628


CFD for subcooled flow boiling: Parametric Variations

Rzehak, R.; Krepper, E.
In this work we investigate the present capabilities of CFD for wall boiling. The computational model used combines the Euler / Euler two-phase flow description with heat flux partitioning. Very similar modelling was previously applied to boiling water under high pressure conditions relevant to nuclear power systems. Similar conditions in terms of the relevant non-dimensional numbers have been realized in the DEBORA tests using Dichlorodifluoromethane (R12) as the working fluid. This facilitated measurements of radial profiles for gas volume fraction, gas velocity, liquid temperature and bubble size.

Robust predictive capabilities of the modelling require that it is validated for a wide range of parameters. In previous studies (Krepper and Rzehak, 2011, 2012) it was shown that a careful calibration of correlations used in the wall boiling model is necessary to obtain agreement with the measured data. We here consider tests under a variety of conditions concerning liquid subcooling, flow rate and heat flux. It is investigated to which extent a set of calibrated model parameters suffices to cover at least a certain parameter range.
Keywords: subcooled flow boiling, Euler Euler two-fluid model, CFD simulation, validation

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Permalink: https://www.hzdr.de/publications/Publ-17627
Publ.-Id: 17627


Bubble-induced Turbulence: Comparison of CFD Models

Rzehak, R.; Krepper, E.
Modeling of bubble-induced turbulence in dispersed gas-liquid multiphase flow is an important but still unresolved issue. Aside from its intrinsic interest, turbulence in this type of flow has a strong impact on other important processes like turbulent dispersion of the bubbles and bubble-coalescence and -breakup and thus is a central part of the overall model. A common approach is to add source terms to the single phase two-equation turbulence models, but no agreement on the precise form of these terms has been reached yet. We here report a comparison of different models of this type, some of which have been used previously and some of which are new. To qualify the validity of the different models a set of reference data has been selected from the literature. Conclusions towards best practice guidelines for modeling bubbly turbulence are drawn and needs for further research identified.
Keywords: dispersed gas liquid multiphase flow, bubble induced turbulence, Euler Euler two fluid model, CFD simulation, model validation

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Permalink: https://www.hzdr.de/publications/Publ-17626
Publ.-Id: 17626


Vorstellung und Diskussion der Untersuchungen des HZDR zur Rolle von Mikroorganismen bei der Endlagerung radioaktiver Abfälle.

Krawczyk-Bärsch, E.
In the underground rock characterization facility tunnel ONKALO in Finland massive biofilms were observed attached to the fractured bedrock at a depth of 70 m. Experiments were performed in the laboratory to study the effect on the behavior of uranium in biofilms by adding uranium to the fracture water with a final uranium concentration (4*10-5 M) relevant for what can be expected from an injured and leaking waste canister in the far-field during a nuclear event in a HLW repository. The results obtained by analysis, microsensor measurements, TRLFS investigation, EF-TEM/EELS studies and thermodynamic calculations clearly indicate that biofilms have to be considered as microenvironments, which differ significantly from the surrounding medium. Our studies clearly demonstrate that biological systems have to be considered as a part of natural systems that may have significant influence on the behavior of radionuclides. They are contributing to an improved understanding on the response mechanisms of biofilms towards radionuclides in respect to safety assessments of the radioactive waste repositories.
Keywords: uranium, nuclear waste deposit, biofilm
  • Lecture (others)
    Arbeitstreffen mit russischen Vertretern des PromTekhnologii (VNIPI PT) in Moskau, 12.-13.07.2012, Peine, Germany

Permalink: https://www.hzdr.de/publications/Publ-17625
Publ.-Id: 17625


Hydrodynamics and Gas-Liquid Mass Transfer in a Horizontal Rotating Foam Stirrer Reactor

Leon, M. A.; Maas, R. J.; Bieberle, A.; Schubert, M.; Nijhuis, T. A.; van der Schaaf, J.; Hampel, U.; Schouten, J. C.
This paper describes a new multiphase reactor, the horizontal rotating foam stirrer reactor, which uses a donut-shaped foam block mounted on a horizontal shaft as a stirrer and as a catalyst support. The effect of different operating conditions such as stirring speed, reactor length, foam porosity, foam thickness and the presence of baffles on the gas-liquid mass transfer and the gas-liquid flow distribution is discussed for the systems water/air and glycerol/air. The gas-liquid mass transfer is measured spectrometrically while the hydrodynamics of the reactor is studied by gamma-ray computed tomography (CT). For a partially filled reactor, two flow states could be distinguished: the ‘trickle state’ and the ‘slosh state’. In the trickle state the liquid flows in a thin stream over the foam while in the slosh state the liquid is pushed upward by the stirrer and sprayed, leading to the formation of fine liquid droplets and fine gas bubbles. The transition between the trickle state and the slosh state occurs at approximately 200 rpm . When the stirring speed is constant, the ‘ring state ’, which results in a cylindrical liquid layer on the inside wall, appears with increasing the liquid content in the reactor (above 70%). Due to a large gas-liquid interface in the slosh state, a high gas-liquid mass transfer is achieved. kGLaGL values up to 0.35 s-1 are found which is three times higher than in a slurry reactor equipped with a Rushton stirrer and comparable to other types of multiphase reactors such as bubble columns and rotating packed beds. It is shown that mass transfer coefficients decreased with increasing viscosity, while the centrifugal force revealed to be effective in enhancing mass transfer in a viscous media. Conclusions on the optimal reactor configuration are drawn for the application in the fine chemical industry.
Keywords: multiphase reactors, solid foams, hydrodynamics, mass transfer, computed tomography

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Permalink: https://www.hzdr.de/publications/Publ-17624
Publ.-Id: 17624


Baryonic resonances close to the Kbar N threshold: the case of Λ(1405) in pp collisions

Agakishiev, G.; Balanda, A.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Chernenko, S.; Dybczak, A.; Epple, E.; Fabbietti, L.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Göbel, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Müntz, C.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Schmah, A.; Schwab, E.; Siebenson, J.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.
We present an analysis of the Λ(1405) hyperon produced in p+p collisions at 3.5GeV kinetic beam energy measured with HADES at GSI. The two charged decay channels Λ(1405)->Σ±π∓ have been reconstructed for the first time in p+p collisions. The efficiency and acceptance-corrected spectral shapes show a peak position clearly below 1390MeV/c2 and a total production cross section of σΛ(1405)=9.2±0.9±0.7+3.3−1.0 μb has been extracted. The analysis of its polar angle distribution suggests that the Λ(1405) is produced isotropically in the p-p center of mass system.

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Permalink: https://www.hzdr.de/publications/Publ-17623
Publ.-Id: 17623


Angle-dependent evolution of the Fulde-Ferrell-Larkin-Ovchinnikov state in an organic superconductor

Beyer, R.; Bergk, B.; Yasin, S.; Schlueter, J. A.; Wosnitza, J.
We report magnetic-field and angular-dependent high-resolution specific-heat measurements of the organic superconductor β′′-(BEDT-TTF)2SF5CH2CF2SO3. When the magnetic field is aligned precisely within the conducting BEDT-TTF layer, at low temperatures a clear upturn of the upper critical field beyond the Pauli limit of 9.73 T is observed, hinting at the emergence of a Fulde-Ferrell-Larkin-Ovchinnikov state. This upturn disappears when the field is oriented out of plane by more than ∼0.5  deg. For smaller out-of-plane angles, the specific-heat anomaly at Tc sharpens and a second peaky phase transition appears within the superconducting state.

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Permalink: https://www.hzdr.de/publications/Publ-17622
Publ.-Id: 17622


H2Ti6O13, a new protonated titanate prepared by Li+/H+ ion exchange: synthesis, crystal structure and electrochemical Li insertion properties

Perez-Flores, J. C.; Baehtz, C.; Hoelzel, M.; Kuhn, A.; Garcia-Alvarado, F.
The hexatitanate H2Ti6O13 is obtained by a simple successive Na+/Li+/H+ ion exchange of Na2Ti6O13. The crystal structure of H2Ti6O13 was solved from both synchrotron and neutron powder diffraction. H2Ti6O13 crystallizes in the monoclinic space group C2/m, with a = 14.6702(3) angstrom; b = 3.7447(1) angstrom; c = 9.2594(2) angstrom; beta = 96.941(2)degrees. The monoclinic symmetry of the [Ti6O13](2-) framework is preserved during the exchange reaction. When compared to the positions of Na and Li in Na2Ti6O13 and Li2Ti6O13, the position of the proton is shifted towards the O3 atomic position, where it forms a covalent O-H bond. The vicinity of the proton to the O5 atom across the tunnel allows for the formation of a classical (asymmetric) hydrogen bond. H2Ti6O13 has been tested as a Li insertion material to assess its use as an electrode in lithium rechargeable batteries. It reacted irreversibly with ca. 6 Li ions per formula unit at an average voltage of 1.5 V vs. Li+/Li, with a specific discharge capacity of 315 mA h g(-1). However, after first discharge, a reversible specific capacity of 170 mA h g(-1) was developed. H2Ti6O13 then yielded a higher reversible specific capacity than Na2Ti6O13 and comparable to Li2Ti6O13. Besides structural details, IR spectroscopy has been used to further assess possible reaction mechanisms pointing to the transformation of H2Ti6O13 to Li2Ti6O13 when reacting with the very first two lithium ions.
Keywords: RECHARGEABLE LITHIUM BATTERIES; NEUTRON POWDER-DIFFRACTION; LAYERED STRUCTURE; INTERCALATION; LI2TI6O13; ELECTRODE; BEHAVIOR; NA2TI3O7; LIMNO2; TIO2

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Permalink: https://www.hzdr.de/publications/Publ-17621
Publ.-Id: 17621


In situ investigations of a Li-rich Mn–Ni layered oxide for Li-ion batteries

Simonin, L.; Colin, J.-F.; Ranieri, V.; Canévet, E.; Martin, J.-F.; Bourbon, C.; Baehtz, C.; Strobel, P.; Daniel, L.; Patoux, S.
A Li-rich layered oxide with the formula Li[Li0.2Mn0.61Ni0.18Mg0.01]O2 was successfully synthesised and characterised using several in situ characterisation techniques. The electronic state and structural evolution of the material upon cycling were investigated using in situ XRD, EXAFS and XANES measurements. XANES and SQUID magnetic measurements showed that the initial material contains a certain amount of Mn3+ in a low spin configuration (average Mn oxidation state: +3.75). In situ measurements showed that the first part of the charge (up to 4.4 V vs. Li+/Li) corresponds to oxidation of the Mn3+ fraction, and that the oxidation of nickel occurs only later, on the main charge plateau at 4.5 V. Electrochemical and structural results tend to show that the main first-charge plateau is a twophase process where a new phase is created. This new phase is structurally very close to the starting one, and could be an oxygen-deficient spinel with a ¼ 8.25 A. This process is non-reversible, and further cycling occurs in the new phase formed in situ.
Keywords: lithium ion battery, x-ray diffraction, EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-17620
Publ.-Id: 17620


Full structural and electrochemical characterization of Li2Ti6O13 as anode for Li-ion batteries

Pérez-Flores, J. C.; Baehtz, C.; Hoelzel, M.; Kuhn, A.; García-Alvarado, F.
A detailed structural and electrochemical study of the ion exchanged Li2Ti6O13 titanate as a new anode for Li-ion batteries is presented. Subtle structural differences between the parent Na2Ti6O13, where Na is in an eightfold coordinated site, and the Li-derivative, where Li is fourfold coordinated, determine important differences in the electrochemical behaviour. While the Li insertion in Na2Ti6O13 proceeds reversibly the reaction of lithium with Li2Ti6O13 is accompanied by an irreversible phase transformation after the first discharge. Interestingly, this new phase undergoes reversible Li insertion reaction developing a capacity of 170 mAh/g at an average voltage of 1.7 V vs. Li+/Li. Compared with other titanates this result is promising to develop a new anode material for lithium ion rechargeable batteries. Neutron powder diffraction revealed that Na in Na2Ti6O13 and Li in Li2Ti6O13 obtained by Na/Li ion exchange at 325 1C occupy different tunnel sites within the basically same (Ti6O13)2- framework. On the other hand, electrochemical performance of Li2Ti6O13 itself and the phase released after the first full discharge is strongly affected by the synthesis temperature. For example, heating Li2Ti6O13 at 350 1C produces a drastic decrease of the reversible capacity of the phase obtained after full discharge, from 170 mAh/g to ca. 90 mAh/g. This latter value has been reported for Li2Ti6O13 prepared by ion exchange at higher temperature.
Keywords: lithiumtitanate, lithium ion batterie, x-ray diffraction

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Permalink: https://www.hzdr.de/publications/Publ-17619
Publ.-Id: 17619


On the Mechanisms of Ni-Catalysed Graphene Chemical Vapour Deposition

Weatherup, R. S.; Bayer, B. C.; Blume, R.; Baehtz, C.; Kidambi, P. R.; Fouquet, M.; Wirth, C. T.; Schlögl, R.; Hofmann, S.
How does your graphene grow? In situ X-ray photoelectron spectroscopy and X-ray diffraction measurements during chemical vapor deposition on Ni catalyst films show that graphene forms both isothermally and by precipitation on cooling (see picture). A coherent graphene growth model is devised and sub-surface dissolved carbon is shown to play an important role.
Keywords: chemical vapor deposition; graphene; nickel; photoelectron spectroscopy; X-ray diffraction

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Permalink: https://www.hzdr.de/publications/Publ-17618
Publ.-Id: 17618


Water and n-heptane volume fractions in a rotor-stator spinning disc reactor

Visscher, F.; Bieberle, A.; Schubert, M.; van der Schaaf, J.; de Croon, M.; Hampel, U.; Schouten, J.
This paper presents the volume fractions of n-heptane and water measured in a rotor-stator spinning disc reactor. The volume fractions were measured using γ-ray tomography and photographic image analysis. The volume fractions were determined as a function of rotational disc speed, flow ratio, position in the reactor, and rotor material. In addition, the effect of the density difference between water and n-heptane was determined by dissolving potassium iodide in the water phase. Below a rotational disc speed of 75 RPM the volume fraction measured by tomography and photographic image analysis are within 10% deviation. For low rotational disc speeds, the n-heptane volume fraction decreases slightly with increasing rotational disc speed: the centrifugal force accelerates the larger n-heptane droplets to the center. At higher rotational disc speeds the droplets become smaller accordingly, the friction between the phases determines the flow and the n-heptane volume fraction becomes equal to the n-heptane to total flow ratio. An increase in density difference from 0.31 to 0.79 kg/dm³ did not influence the volume fractions.
Keywords: Rotor-stator spinning disc reactor, liquid-liquid flow, hydrodynamics, γ-ray tomography, multiphase reactor.
  • Industrial & Engineering Chemistry Research 51(2012)51, 16670-16676
    DOI: 10.1021/ie301439s

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Permalink: https://www.hzdr.de/publications/Publ-17617
Publ.-Id: 17617


Investigation of gas-liquid two-phase flow in multiphase contactor using low-intrusive measuring methods

Zheng, G.; Schlusemann, L.; Schubert, M.; Hampel, U.; Gruenewald, M.
Multiphase contactors are the most important apparatuses for reaction and separation in chemical engineering. Limited by the measuring methods, the analysis of their hydrodynamic behavior is usually done using superficial liquid and gas flow velocities. Several new measuring techniques for the investigation of multiphase flows in vessel cross sections have been developed in the last decades. Especially the use of tomographic visualization techniques is of great interest since these are noninvasive and thus non-intrusive methods, and enable the visualization of phase distributions.
However, currently developed nonintrusive methods have considerable drawbacks. The computer tomography methods can obtain high spatial resolution. In comparison, the temporal resolution is relative low. For the application of topographic measurement techniques in multiphase flows, especially with fast changing flow patterns, a high temporal resolution is essential. Electrical tomography has a high temporal resolution. However, reconstruction algorithm is complex and the electrical field lines are not linear, therefore spatial resolution rate is relative low. Therefore, no exact mass balance could be established and the resulting phase fractions cannot be applied for model developments.
  • Lecture (Conference)
    AIChE Annual Meeting, 28.10.-02.11.2012, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-17616
Publ.-Id: 17616


Hydrodynamic investigation of a flow reactor with foam packings

Mohammed, I.; Bauer, T.; Schubert, M.; Lange, R.
The effects of superficial liquid and superficial gas velocities, cell density of the foam and liquid properties on liquid holdup, residence time distribution, axial dispersion and pressure drop were investigated. Hydrodynamic multiplicity was found in flow reactor with different solid foam packings depending on the pre-wetting conditions. Furthermore, liquid distribution, and regime transition as well as stability of flow conditions were studied. The study was based on novel wire mesh sensors aligned along the vertical axis of the reactor.
Keywords: solid foam, hydrodynamics, multiplicity, pressure drop, wire-mesh sensor
  • Lecture (Conference)
    International Symposium on Chemical Reaction Engineering, ISCRE22, 02.-05.09.2012, Maastricht, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-17615
Publ.-Id: 17615


Hydrodynamics and mass transfer in the horizontal rotating foam stirrer reactor

Leon, M. A.; Maas, R. J.; Bieberle, A.; Schubert, M.; Nijhuis, T. A.; van der Schaaf, J.; Hampel, U.; Schouten, J. C.
The rotating foam stirrer reactor is a novel type of multi-phase reactor where highly open-celled materials, solid foams, are used both as a catalyst support and as a stirrer. One of the advantages of rotating foam stirrer reactors compared to e.g. slurry reactors is the absence of a catalyst separation step. Moreover, in the standard foam stirrer configuration, i.e., the foam structures (blades or donut-shaped foam blocks) are mounted on a vertical shaft, the formation of finely dispersed bubbles and the fast refreshment of the catalyst surface lead to better mass transfer rates.
In this work, a new foam stirrer design is presented. A donut-shaped foam block is mounted on a horizontal shaft. Using gamma-ray tomography, the hydrodynamics of the system is described. When the reactor is partially filled with liquid, a "spray regime" is observed which leads to the formation of fine liquid droplets and fine gas bubbles enhancing the gas-liquid mass transfer rate. Furthermore, due to the centrifugal forces at high rotational speeds, the gas is separated from the catalyst only by a very thin liquid film. This enhances the liquid-solid mass transfer of the gas reactant, which is often the limiting component in hydrogenation or oxidation reactions. Mass transfer measurements will be discussed for different operation conditions.
Keywords: multiphase reactors; solid foams; hydrodynamics; mass transfer; computed tomography
  • Lecture (Conference)
    AIChE Annual Meeting, 28.10.-02.11.2012, Pittsburgh, USA

Permalink: https://www.hzdr.de/publications/Publ-17614
Publ.-Id: 17614


Investigating annular flows and the effect of functional spacers in an adiabatic double-subchannel model of a BWR fuel bundle by ultra-fast X-ray tomography

Zboray, R.; Guetg, M.; Kickhofel, J.; Barthel, F.; Sprewitz, U.; Hampel, U.; Prasser, H.-M.
Dryout of the coolant liquid film at the upper part of the fuel assemblies of a boiling water reactor (BWR), where annular flow prevails, represents a safety concern and an economical constraint. To be able to deal with this issue, annular flows must be well understood. Therefore we have investigated such flows in a double-subchannel model of a BWR fuel bundle using X-ray imaging at the Rossendorf Ultrafast Electron Beam X-ray Tomograph (ROFEX) facility. Adiabatic experiments slightly above atmospheric conditions using air-water annular flows have been carried out. In annular flows a significant portion of the liquid is present as droplets in the gas flowing in the middle of the conduit. Using functional spacer grids is the common method in nuclear technology to influence the annular flow such to enhance the deposition of droplets into the liquid film on the fuel pins thereby increasing dryout margins. The tests include, besides investigating the liquid film thickness in the plain channel, the investigation of the effect of a functional spacer on the liquid film. Using NaI as contrast agent in water enhances the image quality. The high time-resolution of the tomography enables to follow the wavy structure of the annular film flow. The paper aims at extracting quantitative information on the liquid film thickness distributions from the reconstructed tomographic images.
Keywords: boiling water reactor, dry-out, ultrafast X-ray tomography, fuel rods
  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada
    Proceedings

Permalink: https://www.hzdr.de/publications/Publ-17613
Publ.-Id: 17613


Measurement of liquid distributions in separation columns

Schubert, M.; Hampel, U.; Kenig, E. Y.; Grünewald, M.
Design and optimization of separation units, e.g. distillation and absorption columns, both reactive and non-reactive, require detailed knowledge about the underlying phenomena and their impact on the process behaviour. Although the separation efficiency is pre-determined by complex hydrodynamic conditions in the columns, current studies are mainly based on conventional techniques with strongly limited insights, e.g. on using compartment-type liquid collectors below packings. Except for the Chemical Engineering group at the University of Liège (e.g., Aferka et al., 2010) tomographic imaging technique so far has not found a proper place in investigations of separation columns with structured internals.
Compared to catalytic packings that contain active elements for heterogeneous reaction, column internals are mainly designed to provide sufficient mass transfer area and to generate local turbulence for high mass transfer rates. To meet this goal, both structured packings (e.g., corrugated sheet Sulzer KatapakTM and MellapakTM) and random packings (e.g., Pall rings, Raschig rings, Bearl saddles) have been designed. The strong challenge in flow visualization in such packings is attributed to the flow patterns that incorporate thin liquid films on the surface of the structures, and to their dynamics. Thus, high temporal and spatial resolution is required. In this regard, the application of up-to-date measurement techniques and new visualization concepts would make a step forward in evaluating such processes and in re-designing the apparatuses and internals. In the present work, a detailed study was performed focusing on important hydrodynamic aspects in packings, namely:
- liquid distribution in the cross-section in and below the packing
- resolution of the packing structure
- visualization of liquid film structures, dynamics and their detection limit
- classification of by-passing wall flow and utilizable core flow
- disturbance of the disperse liquid flow using new wire-based sensors
- dynamics of the transition from the loading to the flooding point
Ultra-fast X-ray tomography, high resolution gamma-ray tomography and wire-mesh sensor techniques were applied. In our contribution, the potential of the new measurement techniques for separation columns is discussed and new insights on the hydrodynamic behaviour are provided.
Keywords: Separation columns, hydrodynamics, tomography
  • Lecture (Conference)
    10th Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering, 26.-29.06.2011, Braga, Portugal

Permalink: https://www.hzdr.de/publications/Publ-17612
Publ.-Id: 17612


Wire-mesh based hydrodynamic and thermal studies in packed beds

Schubert, M.; Schäfer, T.; Kryk, H.; Hampel, U.
Gas/liquid operated packed bed reactors are the workhorses in the wide field of chemical and petrochemical industry. Intense research effort has been undertaken to explore all sub-processes of hydrodynamics, mass and heat transfer, to predict process behaviour, to define reliable scale-up and design rules etc. However, still many details are unsolved and require deeper insights at multiple scales. Particularly in co-current downflow trickling bed reactors (TBR), the interactions between fluid phases and packings and in turn, hydrodynamics and transfer steps are very complex and not yet fully understood.
Catalyst utilization and reactor efficiency suffers clearly from maldistribution of liquid in the cross-section of packings, channelling effects and bypassing liquids. Accompanied by maldistribution, local hot spots may form in packed bed reactors. If not detected early, they can have a detrimental impact on the yield of the desired products and, in addition, they may pose safety hazards, i.e. reaction runaway due to phase transition and accelerated reaction rate which are main reason for major chemical plant accidents.
To take corrective action, indicators of conditions, such as non-irrigated zones and emerging elevated temperature zones must be detected. In the past two decades, considerable effort has been made to visualize and characterize multiphase flows in packings. Since local sensors inserted at selected locations in the bed fail to provide information about spatial distributed phenomena, powerful tomographic methods well known from medical imaging were successfully transferred into chemical engineering applications. However, tomographic techniques are expensive, low speed and don’t yield any information about fluid velocities. Considering industrially suitable temperature monitoring systems, no spatial-resolved array-type system is available.
Prasser et al. (1998) developed an electrode-mesh tomograph for gas-liquid flows in bubble columns which is advantageous considering costs, simplicity and safety. Based on this principle, our contribution presents results of spatially resolved hydrodynamic studies in a pilot-scale TBR using new capacitance wire-mesh sensors for determination of liquid saturation and axial liquid velocities simultaneously for all sensing points of the whole cross-section depending on gas and liquid flow. Furthermore, a new temperature-monitoring sensor was developed installing Pt2000 elements at the cross-points of a wire-mesh based array system.
  • Lecture (Conference)
    19th International Congress of Chemical and Process Engineering CHISA 2010 and the 7th European Congress of Chemical Engineering (ECCE-7), 28.08.-01.09.2010, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-17611
Publ.-Id: 17611


Anwendung von Optical Flow Verfahren für die Atembewegungskorrektur in der Positronen-Emissions-Tomographie

Langer, B.
kein Abstract verfügbar
  • Diploma thesis
    TU Dresden, 2011
    68 Seiten

Permalink: https://www.hzdr.de/publications/Publ-17610
Publ.-Id: 17610


Multiphase flow investigations with ultrafast electron beam X-ray tomography

Hampel, U.; Barthel, F.; Bieberle, M.; Schubert, M.; Schleicher, E.
We introduce ultrafast electron beam X-ray tomography as an imaging modality for multiphase flow studies. A dedicated electron beam tomography scanner (ROFEX) has been developed which allows cross-sectional X-ray tomography with 1 mm spatial resolution and up to 7000 cross-sectional images per second recording speed. It is applicable to flow problems in vessels with up to 120 mm diameter and moderate X-ray attenuation. The tomography system has been applied in various flow studies, including gas-liquid two-phase flow in vertical pipes and channel structures.
Keywords: electron beam tomography, multiphase flow measurement
  • Lecture (Conference)
    The 7th International Symposium on Measurement Techniques for Multiphase Flows ISMTMF-2011, 17.-19.09.2011, Tianjin, China

Permalink: https://www.hzdr.de/publications/Publ-17609
Publ.-Id: 17609


Study of multiphase flow in bubble - and packed columns using low-intrusive measuring methods

Zheng, G.; Schubert, M.; Hampel, U.; Grünewald, M.
Multiphase contactors are the most important apparatuses for reaction and separation in chemical engineering. Limited by the measuring methods, the analysis of their hydrodynamic behavior is usually done using superficial liquid and gas flow velocities. Several new measuring techniques for the investigation of multiphase flows in vessel cross sections have been developed in the last decades. Especially the use of tomographic visualization techniques is of great interest since these are noninvasive and thus non-intrusive methods, and enable the visualization of phase distributions.
However, currently developed nonintrusive methods have considerable drawbacks. The computer tomography methods can obtain high spatial resolution. In comparison, the temporal resolution is relative low. For the application of topographic measurement techniques in multiphase flows, especially with fast changing flow patterns, a high temporal resolution is essential. Electrical tomography has a high temporal resolution. However, reconstruction algorithm is very complex and the electrical field lines are not linear, therefore spatial resolution rate is relative low. Therefore, no exact mass balance could be established and the resulting phase fractions cannot be applied for model developments.
In this research, Wire-Mesh Sensor (WMS) is used for the study of phase distribution in multiphase contactors. The WMS comprises two planes, in each plane there are sensing wires. Wires from different planes are orthogonally arranged. Since water and air have different electrical permittivity values and thus, produce different capacitances in the sensing points of the WMS, images of phase distributions can be generated from the measurements of the local capacitance.
Phase distribution in multiphase contactor, e.g. bubble column and packed column, were studied with a WMS. It was shown that the flow regime in bubble column at various gas superficial velocity ((a) uG=8.4 cm/s; (b) uG=16.8 cm/s). Gas-liquid phase distribution in packed column measured with WMS and that measured with gamma-tomography can be characterized.
Measurements of phase distribution with WMS could supply more accurate information of spatial phase distribution to update the theoretical models used in multiphase flow.
  • Lecture (Conference)
    Jahrestreffen der Fachgruppe "Mehrphasenströmungen", 15.-21.03.2012, Weimar, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17608
Publ.-Id: 17608


New insights into gas/liquid textures in rotating solid foams

Bieberle, A.; Schubert, M.; Hampel, U.; Tschentscher, R.; Njihuis, T. A.; van der Schaaf, J.; Schouten, J. C.
For flexible production of fine chemicals and pharmaceuticals still slurry catalysts in batch reactors are used. However, production efficiency suffers from necessary filtration after reaction is finished and abrasion effects make re-usage of catalyst often not possible. Additionally, the mass transfer rates are limited due to low relative velocities between particles and the gas/liquid phases.
Alternatively, a new three-phase reactor design based on rotating solid foams were developed by the Chemical Reactor Engineering group at Eindhoven University of Technology (Tschentscher et al., 2010). The solid foam is applied both as catalyst support and stirrer in order to mix the gas and liquid phases and to create fine bubbles.
Measurements of the gas-liquid mass transfer revealed clearly improved reactor performance compared to Rushton stirrers. The visual observation suggested that the rotation of the foam block leads to a structuring of the reactor volume into sections with considerable different gas holdup, flow behaviour and bubble size distribution. However, access to the patterns in the solid foam was so far not possible.
In our contribution, results of a comprehensive non-invasive tomographic study will be presented. A high-resolution gamma-ray setup was applied to visualize the gas/liquid textures in the reactor, especially in the solid foam block. Therefore, an acrylic reactor system was built that ensure minimal attenuation. Two different reactor heights, stirrer speed from 150 to 300 rpm and two solid foams with different geometric properties were applied. To study the effect of the liquid viscosity, glycerol-water mixtures as well as pure liquids were used. Additionally, flow patterns of non-Newtonian liquids (carboxy methyl cellulose, CMC), foaming liquids (cetyltrimethyl ammonium bromide, STAB) and non-Newtonian foaming liquids (CMC+STAB) were compared with the air-water system.
The observed flow patterns can be related to the mass transfer characteristics and conclusions on an optimized reactor/foam design can be drawn.
Keywords: Multiphase reactor, solid foam, tomography, flow texture
  • Lecture (Conference)
    10th Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering, 26.-30.06.2011, Braga, Portugal

Permalink: https://www.hzdr.de/publications/Publ-17607
Publ.-Id: 17607


Untersuchungen zu Flüssigkeitsholdup und -verteilung in strukturierten Packungen mittels schneller Elektronenstrahl-Röntgen-Tomographie. Jahrestreffen der Fachgruppen CFD und Fluidverfahrenstechnik

Schubert, M.; Janzen, A.; Barthel, F.; Kenig, E. Y.; Hampel, U.
Strukturierte Packungen werden vielfältig als trennwirksame Einbauten in Destillations- und Absorptionskolonnen eingesetzt. In Gegenstromfahrweise stellt der Flutpunkt den oberen Punkt des Betriebsfensters dar, bei dem in den Packungskanälen Flüssigkeit akkumuliert und die Gasphase dispergiert wird. Durch die Modifikation der Packungsgeometrie kann der Flutpunkt zu höheren Durchsätzen verschoben und damit die Kapazität von Kolonnen erhöht werden. Zur Optimierung der Packungsstruktur sowie zur Prozessmodellierung ist eine genaue Kenntnis der Strömung in der Packung notwendig.
Zur Untersuchung der Phasenverteilung in Gas-Flüssig-Kontaktapparaten wurde eine neue Messtechnik eingesetzt. Im Gegensatz zu klassischen strahlungsbasierten Tomographieverfahren benötigt die schnelle Elektronenstrahl-Röntgen-Tomographie keine Rotation von Objekt oder Messsystem. Stattdessen erzeugt ein ablenkbarer Elektronenstrahl auf einem ringförmigen Target um das Objekt einen bewegten Röntgenfleck. Die Schwächung der Röntgenstrahlung in Abhängigkeit der vorliegenden Phasenverteilung wird durch den kreisförmig angeordneten Detektor gemessen. Damit kann die Phasen-Verteilung in der Packung mit einer sehr schnellen Bildrate von 2000 Hz und höher visualisiert werden.
Die Verteilung der Flüssigphase wurde in einer 80 mm Kolonne bei unterschiedlichen Gas- und Flüssigkeits-Beladungen (Stoffsystem Wasser/Luft) gemessen. Zwei Packungen unterschiedlicher spezifischer Oberfläche (Montz B1-350MN, B1-500MN) wurden eingesetzt, um den Einfluss der Packungsgeometrie zu untersuchen. Die rekonstruierten Bilder der tomographischen Messungen wurden aufbereitet und die Verteilung der Flüssigphase analysiert. Der sich einstellende Holdup wurde vor und am Flutpunkt berechnet und mit konventionell gemessenen Werten verglichen. Die schnelle Röntgentomographie erlaubt ganz neue Einblicke in die Dynamik der Flüssigkeitsströmung innerhalb der strukturierten Packung.
  • Lecture (Conference)
    Jahrestreffen der Fachgruppen Computational Fluid Dynamics und Fluidverfahrenstechnik, 12.-14.03.2012, Weimar, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17606
Publ.-Id: 17606


Tomographic imaging for multiphase flows

Schubert, M.; Reinecke, S.
Multiphase flows are a common phenomenon in many processes and systems in the chemical and mineral oil industry. Those flows occur in many different forms such as disperse gas-liquid flows in bubble column reactors, gas-solid flows in fluidized-beds or bubble-, splash- and film flows in distillation systems. Due to their nature, they are difficult to record by means of standard measurement techniques, challenging to characterize theoretically and complex to model numerically. In order to monitor and characterize those flows in industrial systems as well as in research facilities it is necessary to apply methods with the ability to measure the phase distribution, phase interface density, turbulence- and velocity parameters in continuum phases and also the thermal-, material- and impulse transports between the different phases with high spatial and temporal resolution. Because in many cases multiphase flows are opaque, the application of common optical measurement principles is limited. In addition, industrial processes run at high pressure and temperature in vessels with thick metal walls. This limits the means of instrumentation and demands for robust measurement equipment.
In the recent past, the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has undertaken great efforts in the development of tomographic imaging principles that allow the understanding of multiphase flows with high spatial and temporal resolution. Some results of these developments, like the wire-mesh-sensors, the gamma ray computed tomography and the ultrafast X-ray computed tomography will be presented in the talk. With the wire mesh sensor, it was possible to analyze transient gas liquid flows with frame rates up to 10,000 pictures per seconds and a spatial resolution of 2 mm for the first time. The gamma ray computed tomography allows the investigation on high-pressure instruments and facilities with a spatial resolution of 2 mm. Finally, the Ultrafast X-ray computed tomography combines various positive features, such as contactless measurement with high spatial (~ 1 mm) and temporal (~ 10,000 frames per second) resolution as well as the visualization of opaque and solids-bearing flows. The talk introduces the described measurement technologies regarding their physical and technological principle and provides an insight into potential applications and methods for image data analysis.
  • Lecture (others)
    ACHEMA 2012, 18.-22.06.2012, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17605
Publ.-Id: 17605


Investigation of liquid hold-up in structured packings under flooding conditions using ultra-fast electron beam X-ray tomography

Janzen, A.; Barthel, F.; Schubert, M.; Hampel, U.; Kenig, E. Y.
Structured packings are column internals widely used in countercurrent separation processes, such as distillation or absorption. Due to the countercurrent flow, flooding of the packed column represents the upper operation limit. At this point, the high shear stresses between the phases cause a liquid-phase accumulation accompanied by the dispersion of the gas phase. Shifting the flooding point towards higher loads by modifying the packing geometry would result in a capacity increase of the column. Therefore, understanding of the fluid flow character inside the packing is necessary both for process modelling and for packing optimisation.
In this work, a new measurement technique, ultra-fast electron beam X-ray tomography, is applied to investigate dynamic phase distribution in gas-liquid contact devices. Contrary to classical tomographic systems, electron beam X-ray tomography does not require a rotating object or a source-detector setup. Instead, an electron beam is very rapidly swept across a target producing a moving X-ray spot. Thus, a high temporal resolution with frame rates of 2000 images per second and higher can be achieved.
The liquid-phase distribution in an experimental setup containing a DN80 column was measured for the system water/air at different gas and liquid loads. Two packing types with different specific surface area (Montz B1-350MN and B1-500MN) were used to investigate the influence of the packing geometry. The reconstructed image series were post-processed and analysed with respect to the spatial distribution of the liquid and its hold-up before and at the flooding point. Furthermore, the liquid hold-up measurement results were compared with those obtained from a conventional draining method. The new fast measurement technique is capable of providing new insights on the liquid flow dynamics.
  • Lecture (others)
    ACHEMA 2012, 18.-22.06.2012, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17604
Publ.-Id: 17604


Geschüttelt oder gerührt oder …? - Mehrphasenströmungen in der chemischen Industrie.

Schubert, M.
Viele Produkte des täglichen Lebens werden in Industrieapparaten hergestellt, in denen Gase und Flüssigkeiten gemeinsam strömen. Der Vortrag gibt einzigartige Einblicke in die komplexe Welt der Mehrphasenströmungen und zeigt Forschungsansätze für eine effiziente und ressourcenschonende Produktion.
  • Lecture (others)
    Lange Nacht der Wissenschaften, TU Dresden, 06.07.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17603
Publ.-Id: 17603


Charakterisierung von Mehrphasenströmungen in der Verfahrenstechnik

Schubert, M.
Der Vortrag zeigt exemplarisch den Einsatz neuer bildgebender Messverfahren für die Untersuchung von Mehrphasenströmungen in der Verfahrenstechnik.
  • Lecture (others)
    Prozessverfahrenstechnisches Seminar, TU Dresden, 05.07.2011, 05.07.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17602
Publ.-Id: 17602


Visualisation of gas-liquid two-phase flow in opaque systems

Hampel, U.; Schubert, M.; Barthel, F.; Szalinski, L.; Bieberle, M.
Measurement and visualisation of two-phase flow is of high scientific and engineering relevance, for instance in mineral oil processing, chemical reaction engineering, and energy systems engineering. However, it is also a great challenge, because traditional visualisation tools, such as high-speed camera imaging and ultrasound measurements fail in multiphase systems. Tomographic methods are being considered as the key technology for multiphase flow visualisation, however, to date only few methods are suited because of stringent requirements for high spatial and temporal resolution. In particular, methods are sought, which can visualize two-phase flow in complex geometries. Examples are reactor vessels with internals, rod bundles of heat exchangers or nuclear fuel rod assemblies, but also porous media of fixed bed reactors or rock samples.
The presentation introduces two novel imaging modalities, namely wire mesh sensors and ultrafast X-ray tomography and their use in two-phase flow measurement in complex flow domain geometries. It will be shown, how gas-liquid flows can be visualized in fixed bed packings and flow channels intransparent walls.
Keywords: Keywords two-phase flow measurement, wire mesh sensor, electron beam tomography
  • Invited lecture (Conferences)
    4th International Workshop on Process Tomography, 21.-23.09.2011, Chengdu, China
  • Contribution to proceedings
    4th International Workshop on Process Tomography, 21.-23.09.2011, Chengdu, China
    Proceedings

Permalink: https://www.hzdr.de/publications/Publ-17601
Publ.-Id: 17601


Multiphase flow investigations with ultrafast electron beam X-ray tomography

Hampel, U.; Barthel, F.; Bieberle, M.; Schubert, M.; Schleicher, E.
We introduce ultrafast electron beam X-ray tomography as an imaging modality for multiphase flow studies. A dedicated electron beam tomography scanner (ROFEX) has been developed which allows cross-sectional X-ray tomography with 1 mm spatial resolution and up to 7000 cross-sectional images per second recording speed. It is applicable to flow problems in vessels with up to 120 mm diameter and moderate X-ray attenuation. The tomography system has been applied in various flow studies, including gas-liquid two-phase flow in vertical pipes and channel structures.
Keywords: electron beam tomography, multiphase flow measurement
  • Contribution to proceedings
    The 7th International symposium on measurement techniques for multiphase flows ISMTMF-2011, 17.-19.09.2011, Tianjin, China
    AIP Conf. Proc.: American Institute of Physics 1428, 978-0-7354-1011-4, 167-174
  • AIP Conference Proceedings 1428(2012), 167-174
    DOI: 10.1063/1.3694703

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Permalink: https://www.hzdr.de/publications/Publ-17600
Publ.-Id: 17600


Ultrafast tomography for multiphase flow measurement in process applications

Hampel, U.; Fischer, F.; Bieberle, M.; Schubert, M.
The study of multiphase flows in process engineering requires sufficiently fast observation tools. Studies of hydrodynamics in bubble columns, fluidized beds, or mixing drums for instance, would enormously profit form cross-sectional or even volume imaging with at least 1000 frames per second speed. Unfortunately, optical techniques, such as high speed cameras and PIV, which are widely used to study transparent single phase flows, fail in multiphase flows due to their opaqueness. In the past electrical imaging techniques, such as electrical impedance tomography and wire mesh sensors, were frequently used for multiphase flow studies. But these techniques have some severe drawbacks. Thus electrical tomography has a very low spatial resolution. Wire mesh sensors are intrusive and cannot be used for particulate systems. Recently our group has introduced ultrafast electron beam X-ray tomography for multiphase flow studies. We developed the ROFEX scanner which is able to visualise different types of multiphase flows, such as gas-liquid or gas-particle systems, with scan rates up to 7000 frames per second, one millimetre spatial resolution and for cross-sections up to 120 mm diameter. The scanner utilizes electron beam technology. An electron beam of up to 150 keV energy is produced by an electron gun, focussed onto a semicircular X-ray production target and swept rapidly across the target by means of an electromagnetic deflection system. This way X-rays are generated from a fast moving focal spot. A fast detector inside the scanner head records the X-ray projection data which is subsequently reconstructed to cross-sectional images of the density distribution of the object of interest.
In an overview presentation we will discuss the applicability of this new imaging technology to different multiphase processes which are to be found in chemical and mechanical process engineering. The repertory includes hydrodynamics in pipes, bubble columns, stirred tanks, powder mixing drums, monoliths, foams, fixed beds, fluidized beds, and corrugated sheets of destillation packings. The presentation will address measuring accuracy with respect to disperse and separated flows, limits of the methods and implications for process optimization and CFD code development.
Keywords: Keywords Electron beam tomography, X-ray tomography, flow measurement, two-phase flow
  • Lecture (Conference)
    10th Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering, 26.-30.06.2011, Braga, Portugal

Permalink: https://www.hzdr.de/publications/Publ-17599
Publ.-Id: 17599


General overview of the TOPFLOW-PTS experimental program

Péturaud, P.; Hampel, U.; Barbier, A.; Dreier, J.; Dubois, F.; Hervieu, E.; Martin, A.; Prasser, H.-M.
During a hypothetical loss-of-coolant accident, cold emergency core cooling water may be injected in a partially uncovered cold leg, and related two-phase CFD simulations are required to demonstrate the reactor pressure vessel integrity further to the resulting pressurized thermal shock. To complement the physical validation of the two-phase CFD codes in this configuration, a dedicated integral-type experimental program – TOPFLOW-PTS – has been setup; this paper (i) supports the validation data needs, (ii) presents the related experimental setup, and (iii) provides the general guidelines of the test matrix definition and test procedure.
Keywords: pressurized thermal shock, TOPFLOW
  • Contribution to proceedings
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada
    Proceedings
  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-17598
Publ.-Id: 17598


Investigating annular flows and the effect of functional spacers in an adiabatic double-subchannel model of a BWR fuel bundle by ultra-fast X-ray tomography

Zboray, R.; Guetg, M.; Kickhofel, J.; Barthel, F.; Sprewitz, U.; Hampel, U.; Prasser, H.-M.
Dryout of the coolant liquid film at the upper part of the fuel assemblies of a boiling water reactor (BWR), where annular flow prevails, represents a safety concern and an economical constraint. To be able to deal with this issue, annular flows must be well understood. Therefore we have investigated such flows in a double-subchannel model of a BWR fuel bundle using X-ray imaging at the Rossendorf Ultrafast Electron Beam X-ray Tomograph (ROFEX) facility. Adiabatic experiments slightly above atmospheric conditions using air-water annular flows have been carried out. In annular flows a significant portion of the liquid is present as droplets in the gas flowing in the middle of the conduit. Using functional spacer grids is the common method in nuclear technology to influence the annular flow such to enhance the deposition of droplets into the liquid film on the fuel pins thereby increasing dryout margins. The tests include, besides investigating the liquid film thickness in the plain channel, the investigation of the effect of a functional spacer on the liquid film. Using NaI as contrast agent in water enhances the image quality. The high time-resolution of the tomography enables to follow the wavy structure of the annular film flow. The paper aims at extracting quantitative information on the liquid film thickness distributions from the reconstructed tomographic images.
Keywords: boiling water reactor, dry-out, ultrafast X-ray tomography, fuel rods
  • Lecture (Conference)
    The 14th International Topical Meeting on Nuclear Reactor Thermalhydraulics, NURETH-14, 25.-30.09.2011, Toronto, Canada

Permalink: https://www.hzdr.de/publications/Publ-17597
Publ.-Id: 17597


Time-dependent Hamiltonians with 100% evolution speed efficiency

Uzdin, R.; Günther, U.; Rahav, S.; Moiseyev, N.
The evolution speed in projective Hilbert space is considered for Hermitian Hamiltonians and for non-Hermitian (NH) ones. Based on the Hilbert-Schmidt norm and the spectral norm of a Hamiltonian, resource-related upper bounds on the evolution speed are constructed. These bounds are valid also for NH Hamiltonians and they are illustrated for an optical NH Hamiltonian and for a non-Hermitian PT-symmetric matrix Hamiltonian. Furthermore, the concept of quantum speed efficiency is introduced as measure of the system resources directly spent on the motion in the projective Hilbert space. A recipe for the construction of time-dependent Hamiltonians which ensure 100% speed efficiency is given. Generally, these efficient Hamiltonians are NH, but there is a Hermitian efficient Hamiltonian as well. Finally, the extremal case of a non-Hermitian non-diagonalizable Hamiltonian with vanishing energy difference is shown to produce a 100% efficient evolution with minimal resources consumption.
Keywords: non-Hermitian Hamiltonian, projective Hilbert space, resource efficiency, PT-symmetric Hamiltonian, exceptional point, evolution speed, Hilbert-Schmidt norm, spectral norm

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Permalink: https://www.hzdr.de/publications/Publ-17596
Publ.-Id: 17596


Hydrodynamik und Transportprozesse in Strukturapparaten

Schubert, M.; Hampel, U.
Durch den Einsatz neuer bildgebender Messverfahren werden strukturierter Mehrphasenreaktoren hydrodynamisch charakterisiert und Strömungsdaten aus sonst optisch unzugänglichen Strukturen, wie keramischen Monolithen und Schäumen sowie metallischen zellularen Packungen vor allem unter prozessnahen Betriebsbedingungen gewonnen.
  • Lecture (others)
    Dresden-internes Auftakttreffen HGF-Energie-Allianz, 13.07.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17595
Publ.-Id: 17595


Energieeffiziente Chemische Mehrphasenprozesse (Vorstellung der Helmholtz‐Energie‐Allianz)

Schubert, M.; Hampel, U.
Visionäres Ziel der Forschung ist es, neue Reaktorkonzepte für energie- und ressourceneffiziente chemische Prozesse auf Basis prozess- und reaktionsangepasster strukturierter Mehrphasenapparate zu entwickeln. Im Rahmen der HGF-Energie-Allianz werden dazu umfassende Grundlagenarbeiten im Bereich der Reaktionsaufklärung, zur Herstellung neuer funktionalisierter Strukturelemente, auf den Gebieten Mehrphasenströmungsmechanik und Mehrphasenthermodynamik, sowie in der numerischen Simulation und der Prozessmesstechnik durchgeführt.
  • Lecture (others)
    Dresden-internes Auftakttreffen HGF-Energie-Allianz, 13.07.2012, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-17594
Publ.-Id: 17594


Propagation of Spectral Functions and Dilepton Production at SIS Energies

Wolf, G.; Kämpfer, B.; Zetenyi, M.
The time evolution of vector meson spectral functions is studied within a BUU-type transport model. Applications focus on ρ and ω mesons being important pieces for the interpretation of the dielectron invariant mass spectrum. Since the evolution of the spectral functions is driven by the local density, the inmedium modifications turn out to compete, in this approach, with the known vacuum contributions.

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Permalink: https://www.hzdr.de/publications/Publ-17592
Publ.-Id: 17592


Spectroscopic Studies of Complexation Behaviour of Uranium(VI) by Schiff Bases

Lindner, K.; Günther, A.; Bernhard, G.
Uranium can be released into the natural environment especially from mining areas by weathering, erosion and anthropogenic activities as well as by nuclear incidents and thus represents a hazard potential for humans. New supramolecular complexing agents with N, O, S donor function are developed for the use in nuclear field and environmental protection to separate the metals of the d- and f-block and thus to clean contaminated areas. An essential basic component of these new organic ligands are Schiff bases.
In this study the complexation of uranium(VI) with Schiff bases N-benzylideneaniline (NBA), 2-(2-hydroxybenzylidenamino)phenol (HBAP) and alpha-(4-hydroxyphenylimino)-p-cresol (HPIC) was investigated in alcoholic solution using the UV-vis spectroscopy and time-resolved laser fluorescence spectroscopy with ultrashort laser pulses (fs-TRLFS). Through the change of the absorption or emission properties of organic ligands can be observed the complexation with uranium(VI).
The complexation of uranium(VI) with NBA was observed by a hypsochromic shift in the NBA band to 237 nm with the UV-vis spectroscopy. Investigations with the ligand HBAP show a bathochromic shift to 281 nm. The UV-vis absorption spectra of HPIC with uranium(VI) show no spectral shift, but a decrease in intensity of the double band at 283nm and 332 nm in comparison to the free ligand. All three ligands form complexes MLx with more ligand molecules (x=2,3).
The fs-TRLFS as a sensitive speciation technique was used to determine the luminescence properties of formed complexes in the uranium(VI)-NBA, uranium(VI)-HBAP and uranium(VI)-HPIC systems. The emission signals had a hypsochromic, bathochromic and hypsochromic shift in comparison to the emission maxima of the uncomplexed ligand. This fs-TRLFS investigation opens up the possibilities for the determination of very short-lived complex species via the fluorescence of the organic compounds by delocalized -electron systems. The calculation of corresponding complex formation constants is shown and discussed.
Keywords: Uranium(VI), Schiff Bases, fs-TRLFS, UV-vis
  • Open Access Logo Contribution to proceedings
    EuCheMS International Conference on Nuclear and Radiochchemistry (NRC-8), 16.-21.09.2012, Como, Italien
  • Poster
    EuCheMS International Conference on Nuclear and Radiochchemistry (NRC-8), 16.-21.09.2012, Como, Italien

Permalink: https://www.hzdr.de/publications/Publ-17591
Publ.-Id: 17591


Release of helium from vacancy defects in yttria-stabilized zirconia under irradiation

Ou, X.; Kögler, R.; Zhou, H.; Anwand, W.; Grenzer, J.; Hübner, R.; Voelskow, M.; Butterling, M.; Zhou, S.; Skorupa, W.
Fission gas retention or release has a critical impact on the function of advanced nuclear materials. Helium trapping in, and release from, radiation defects induced by neutrons and by α decay in YSZ (yttria-stabilized zirconia) is experimentally simulated using synchronized Zr+ and He+ dual ion beam irradiation. The measured damage profiles consist of two peaks which agree well with the calculated profiles of implantation induced excess point defects. This special implantation related effect has to be carefully considered in the evaluation of experimental investigations which simulate isotropic irradiation effects such as α decay. First-principles calculations show that helium is energetically favorable to be trapped by Zr vacancies in YSZ. Implanted helium alone in YSZ is accumulated in undesirable helium bubbles and results in local surface swelling and lift-off. However, under dual beam irradiation helium is released from vacancy defects and is out-diffused at room temperature. Helium is mobilized by a vacancy-assisted trapping/detrapping mechanism induced by the simultaneous Zr+ ion implantation. This behavior avoids the deleterious helium bubble formation and contributes to the suitable application characteristics of YSZ which result in its excellent radiation hardness.
Keywords: yttria-stabilized zirconia, dual beam irradiation, He release, “½Rp” effect

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Permalink: https://www.hzdr.de/publications/Publ-17590
Publ.-Id: 17590


Nonlinear PT−symmetric plaquettes

Li, K.; Kevrekidis, P.; Malomed, B.; Günther, U.
Four basic two-dimensional (2D) plaquette configurations are introduced with onsite cubic nonlinearities, which may be used as building blocks for 2D PT-symmetric lattices. For each configuration, a dynamical model is developed and its PT symmetry is examined. The corresponding nonlinear modes are analyzed starting from the Hamiltonian limit, with zero value of the gain-loss coefficient. Once the relevant waveforms have been identified (chiefly, in an analytical form), their stability is examined by means of linearization in the vicinity of stationary points. This reveals diverse and, occasionally, fairly complex bifurcations. The evolution of unstable modes is explored by means of direct simulations. In particular, stable localized modes are found in these systems, although the majority of identified solutions is unstable.
Keywords: PT quantum mechanics, PT oligomers, 2D plaquettes, 2D PT-symmetric lattices, nonlinear dynamics, bifurcations, stationary solutions, stability analysis, exceptional points

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Permalink: https://www.hzdr.de/publications/Publ-17589
Publ.-Id: 17589


Call for papers: Special issue on quantum physics with non-Hermitian operators

Bender, C.; Fring, A.; Günther, U.; Jones, H.; (Editors)
This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to quantum physics with non-Hermitian operators. The main motivation behind this special issue is to gather together recent results, developments and open problems in this rapidly evolving field of research in a single comprehensive volume. We expect that such a special issue will become a valuable reference for the broad scientific community working in mathematical and theoretical physics. The issue will be open to all contributions containing new results on non-Hermitian theories which are explicitly PTsymmetric and/or pseudo-Hermitian or quasi-Hermitian. The main novelties in the past years in this area have been many experimental observations, realizations, and applications of PT symmetric Hamiltonians in optics and microwave cavities. We especially invite contributions on the theoretical interpretations of these recent PT-symmetric experiments and on theoretical proposals for new experiments.
Keywords: PT symmetry, PT quantum mechanics, pseudo-Hermitian operators

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Permalink: https://www.hzdr.de/publications/Publ-17588
Publ.-Id: 17588


Bypassing the bandwidth theorem with PT symmetry

Ramezani, H.; Schindler, J.; Ellis, F.; Günther, U.; Kottos, T.
The beat time associated with the energy transfer between two coupled oscillators is dictated by the bandwidth theorem which sets a lower bound. We show, both experimentally and theoretically, that two coupled active LRC electrical oscillators with parity-time (PT) symmetry bypass the lower bound imposed by the bandwidth theorem, reducing the beat time to zero while retaining a real valued spectrum and fixed eigenfrequency difference. Our results foster design strategies which lead to (stable) pseudo-unitary wave evolution, and may allow for ultrafast computation, telecommunication, and signal processing.
Keywords: PT symmetry, PT quantum mechanics, LRC circuits, bandwidth theorem, PT-brachistochrone, tachistochrone, evolution time contraction, evolution time dilation, beat time reduction

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Permalink: https://www.hzdr.de/publications/Publ-17587
Publ.-Id: 17587


Two PT symmetry topics

Günther, U.
New results are reported on two PT-symmetry topics. In the first part of the talk, an entanglement related quantum state discrimination scheme is described which is based on the fine-tuned Naimark-dilation of a PT-symmetric subsystem in 2D Hilbert space. (Work together with Carl M. Bender, Dorje C. Brody and Boris F. Samsonov). In the second part of the talk, the stability properties of nonlinear PT-symmetric 2D
plaquettes are discussed. Specific emphasis is laid on the role of the nonlinear terms in shifting the PT-threshold of associated linear systems. This part of the talk is based on common work with Panayotis Kevrekidis, Kai Li and Boris Malomed (arXiv:1204.5530[quant-ph]) as well as on newer results going beyond the findings in this e-print.
Keywords: PT quantum mechanics, quantum state discrimination, Naimark dilation, POVM, Helstrom bound, PT oligomers, 2D plaquettes, 2D PT-symmetric lattices, nonlinear dynamics, bifurcations, stationary solutions, stability analysis, exceptional points
  • Lecture (Conference)
    PHHQP XI: Non-Hermitian Operators in Quantum Physics, 27.-31.08.2012, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-17586
Publ.-Id: 17586


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