Practical trainings, student assistants and theses

Fine-grained solid particles from various industrial sources, which would otherwise be discarded, should ideally be processed to valuable products or inert residues. They contain valuable residuals, such as metals, that can be returned to the industrial cycle instead of being landfilled. This is one aim of the Helmholtz project FINEST in which this work is embedded.
The different finest powders need to be mixed and agglomerated for further processing. Our work in the project deals with the granular mixing. One aim is to describe particle flow based on the rheology of the bulk good while describing the mixing process among the particles using a transport equation.
The mixing process among particles is described by the transport equation. It needs to be coupled with the flow field of the particle bulk. The latter can be modelled by CFD, using e.g. FEM. Here, a rheologic model is required.
We are looking for someone with experience in CFD or other modelling to continue the implementation of this model.

• Student of e.g. Process Engineering, Chemical Engineering, Computational Engineering, Mechanical Engineering, …
• General interest in fluid mechanics and simulations
• Preliminary experience in CFD, ideally OpenFOAM
• Preliminary experience in code development (C++) optional

• Start after September 2024
• Duration of internship or thesis according to study regulations
• Remuneration available, scholarship holders (e.g. ERASMUS+) welcome

The application of phage surface display (PSD) technology has accelerated developments in the field of biomolecular sensors and materials science. A practical complement to this technology is Next-Generation Sequencing (NGS). In this combination, a more comprehensive view of biopanning rounds with a deep insight into the entire sequence space is made possible. It is possible to identify sequencing artefacts, determine sequence number and structure, recognize binding motifs and observe the evolution of the phage library over the course of an experiment. PSD in combination with biopanning is able to select candidates with high affinity and selectivity to the desired substrates from large peptide libraries. In practice, this specific enrichment of peptides leads to a reduction in library diversity. It should therefore be possible to better visualize this reduction in sequence space using data clustering methods in order to better understand distances between similar sequence families.

Prerequisite is a valid enrollment in a Master's program in bioinformatics, biotechnology, molecular biology, biochemistry, biology or a related natural science program. Furthermore:

- Interest in data cluster methods and bioinformatics
- Basic knowledge in bioinformatics, statistics, stochastics and clustering
- Experience with a programming language (e.g. Python, R, C, C++ or other)
- Ability to work independently and in a team
Interested students are invited to submit their application documents including CV, last academic transcript and letter of motivation.

The topic is to be worked on as part of a Master's thesis in conjunction with a mandatory internship. This results in a duration of 12 months. The duration can be extended or adjusted in consultation with the supervisor. We can offer you:

- An innovative multidisciplinary research environment related to relevant issues in resource technology
- Supervision by experienced scientists and researchers
- Practical experience in the field of bioinformatics and directed evolution

At Helmholtz-Zentrum Dresden-Rossendorf (HZDR), over 1,500 employees from more than 70 nations are conducting cutting-edge research in the fields of ENERGY, HEALTH, and MATERIALS to address the major challenges facing society today.
The Center for Advanced Systems Understanding (CASUS), founded in Görlitz in 2019, is a German-Polish interdisciplinary research center focusing on data-intensive digital systems.
CASUS offers student internships in a wide range of scientific fields. You are welcome to apply and join CASUS if you are interested in gaining knowledge in the following research areas:

• Theoretical Chemistry
• Earth System Science
• Systems Biology
• Digital Health
• Computational Radiation Physics
• Theory of complex systems
• Dynamics of Complex Living Systems
• Machine Learning for Infection and Disease

• Student in computer science, physics, chemistry, or related fields
• Student already enrolled at the university in Germany, Poland or Czech Republic (close exchange and attendance in the office preferable and combined with the moblie working from Germany combinable)
• Eager to learn new skills
• Strong motivation to work in a collaborative environment
• Preliminary experience in code development is an advantage
• Excellent communication skills in English and/or German or Polish

• A vibrant research community in an open, diverse and international work environment
• Scientific excellence and extensive professional networking opportunities
• A wide range of qualification opportunities
• We support a good work-life balance with the possibility of part-time employment, mobile working and flexible working hours
• Either an immediate start or a start in 2024 is possible

Data acquisition in large industrial vessels such as bio reactor, biogas fermenters or wastewater treatment plants is limited to local measurement points due to the limited access to the vessel and the non-transparent fluid. To optimize these kinds of plants the three-dimensional flow field and the spatial distribution of e.g. temperature and electrical conductivity inside the vessel needs to be known. This can be done by the autonomous flow following lagrangian sensor particles (LSP) developed at the HZDR. Equipped with a pressure sensor, an accelerometer, two gyroscopes and a magnetometer, the sensor particle can track the flow movement inside of the vessels. From this, the flow field can be reconstructed.

To achieve a good flow following behavior, the density of the LSP can be adjusted before they are released into the vessel. While this works well for non-aerated systems, the influence of aeration on the flow following capability is unknown. Another unknown is how the velocities of the rising bubbles and of the continuous phase relates to the velocity measured by the LSP.
Therefore, the aim of this master thesis is to investigate the influence of aeration on the LSPs theoretically and experimentally by tracking the LSP with a camera. This includes the following tasks:

• Literature research on flow following behavior of large particles in fluids
• Experiments in a bubble column (330 mm ID) with LSPs and camera
• Data evaluation to retrieve the fluid velocity, bubble rising velocity and LSP velocity
• Comparison and conclusions on the flow following capability of LSPs in aerated reactors and comparison to the non-aerated case.

• Studies in the area of chemical or mechanical engineering or similar
• Basic chemical and fluid engineering knowledge
• Data analysis in Python
• Independent and structured way of working

• Immediate start possible
• Duration according to the respective study regulations

The presence of geometrical singularities in pipes may significantly affect the behavior of two-phase flow and subsequently the liquid film thickness or bubble shape. Therefore, it is an important subject of investigation in particular when the application concerns industrial safety and design.
In this work, the shape of individual air Taylor bubble in vertical tubes with constrictions subjected to counter-current liquid is experimentally performed and the influence of the obstacle on the bubble shape is analyzed. The restrictions that the constrictions on narrow tubes imposes on the motion of the interface, and its effect on the bubble shape, will be addressed in terms of geometrical and flow parameters.

In this work, the student will experimentally investigate and record high quality images and gain knowledge about experimental work regarding two-phase flow, image acquisition with MATLAB and data organization. The results will lead to the development of a flow regime map in function of diameter and viscosity.

General interest in fluid mechanics;
Preliminary experience in experimental work is desirable;
Good written and oral communication skills in either English or German.

Immediate start;
Duration of the internship is anticipated to be 3 months but can be modified according to study regulations;
Remuneration according to HZDR internal regulations.

Ion flotation and solvent extraction are promising separation processes to separate and/or remove low concentrated metals from process waters. The demand for developing special collectors (ion flotation reagent)/extractants for enhanced separation efficiency of metals using these processes is increasing due to increased demand for the metals. Further to make these processes sustainable, these special molecules need to be highly selective, efficient and ecofriendly. Strong metal binding ability is the main requisite for such novel molecules and further depending on their application, they need to behave as flotation or solvent extraction reagent. However, synthesizing novel collectors having both abilities is a challenging task. Thus, the main aim is to modify the molecules with already known metal specificity, to introduce the hydrophobicity required for the ion flotation or solvent extraction process.
This student work aims to modify the molecules by adding new functionalities and synthesizing them for improved metal complexation and process application. Additionally, their characterization as possible reagents in either flotation or solvent extraction processes will be investigated. The results will help in fundamental understanding of modified molecules in terms of their interaction with metals as well as form the basis for the development of a sustainable metal recovery process. This interdisciplinary project offers a unique integration of approaches, competences and resources in biotechnology, chemistry and process and environmental engineering and involves different departments at HIF.

Tasks:

• Selection of hydrophobic group
• Modification, synthesis and purification of novel molecules
• Characterization of developed molecules, Ion flotation or solvent extraction tests

• Field of study: Chemistry, Chemical Engineering
• Experience in organic chemistry, knowledge of the techniques to synthesize compounds and to characterize them; experience in coordination chemistry, biochemistry and/or technical chemistry is advantageous
• Good communication skills in German and English, spoken and written
• Ability to work independently and systematically

Working in a multi-disciplinary and international team, with world class research environment at HZDR and HIF.
Can get cross functional working experience and exposure to organic synthesis, modified biomolecules, solution and extractive hydrometallurgy, process biotechnology, chemical and environmental engineering

• Working place HZDR: Location Dresden or Freiberg (HIF)
• Start date: Either an immediate start or a start in 2023 is possible
• Duration: 6 month
• Remuneration according to HZDR internal regulation

Background:

Currently, there is a broad discussion whether ventilation by frequent window opening is sufficient for providing a sufficient amount of fresh air or if technical air purification devices based on e.g. HEPA filters are better solutions for public spaces. Furthermore, there is another discussion ongoing, whether a well-guided laminar flow or a high degree of mixing within a room is more beneficial. The latter, on the one hand distributes the potentially virus-laden aerosols in the whole room, but on the other hand reduces the peak concentrations of these aerosols clouds by magnitudes.

Objectives:

The objective is to perform aerosol propagation experiments and to estimate the potential aerosol inhalation of people in dynamic situations. To achieve this, an aerosol generator will be used in a demonstrator room under different flow conditions. The data from different scenarios will be processed in order to obtain a transference function that can relate the aerosol source with the aerosol receivers.

Tasks:

• Literature survey
• Aerosol experiments in different scenarios.
• Post-processing of the results.

• Student of natural sciences or engineering
• Willingness to conduct experimental work

Duration:

4-6 months

Remuneration:

According to HDZR guidelines

The separation of aerosol particles by a moving gas-liquid fluidic interface is central to a wide variety of industrial and natural applications, among which stand out air purification systems and precipitation scavenging. The particle size significantly affects the separation rate. The diffusion of particles in the nanometer range is largely dominated by molecular diffusion. In this regime, predictive models accurately estimate the separation rates. Model inaccuracy increases, however, significantly when the particle size ranges from 0.1 μm to 2.5 μm. In this impaction-dominated regime, the complex interplay between the flow dynamics on both sides of the fluidic interface and the particle inertia makes it difficult to develop suitable models.
In this work, the student will numerically investigate whether enforcing bubble deformation into a non-spherical shape leads to a higher deposition rate, hereby making the particle separation process more efficient. The results will lead to the development of an improved and reliable separation model accounting for the deformation of the fluidic interface and the associated flow changes.

• General interest in fluid mechanics
• Preliminary experience in code development (C++) is desirable
• Good written and oral communication skills in either English or German

• Either an immediate start or a start in 2024 is possible
• Duration of the internship is anticipated to be 6 months but can be modified according to study regulations
• Remuneration according to HZDR internal regulations