TU Braunschweig: LeoPARD - Publications And Research Data
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Ergänzung zur Neufassung der Besonderen Ordnung über den Zugang und die Zulassung für den Bachelorstudiengang „Elektrotechnik und Informationstechnik" der Fakultät für Elektrotechnik, Informationstechnik, Physik der Technischen Universität Braunschweig: Umbenennung des Bachelorstudiengangs „Elektrotechnik" in „Elektrotechnik und Informationstechnik" an der Technischen Universität Braunschweig, Fakultät für Elektrotechnik, Informationstechnik, Physik
No full textParametric Study of Geometry and Process Parameter Influences on Additively Manufactured Piezoresistive Sensors Under Cyclic Loading.
Full text linkThe additive manufacturing of piezoresistive sensors offers several advantages, such as the elimination of assembly or installation steps, enabling integration into complex parts precisely where desired, and compatibility with soft robotics applications. Previous studies have demonstrated that several characteristics of additively manufactured sensors, such as their resistance and sensitivity, are significantly affected by the selected printing parameters. This work seeks to further the understanding of the relationships between process parameters, material, sensor design, and the resulting sensor characteristics. To this end, sensors made from two materials, with differing printing layer heights, infill angles, and thicknesses, are characterized under cyclic tensile loading. For these sensors, the nonlinearity, hysteresis, and drift are analyzed. The findings indicate that both nonlinearity and hysteresis are significantly affected by the material choice, as well as the selected parameters. Notably, parameters that affect the sensitivity of the sensor, e.g., the infill angle, can have significant indirect effects on the nonlinearity and hysteresis errors. Through correct parameter selection, nonlinearity errors can be reduced by up to 30.7% or 25.3%, depending on the material used. The hysteresis error can be reduced by up to 38.7% or 23.8%, depending on the material. The drift over multiple cycles is found to be strongly material dependent, but can also be affected by the process parameters, e.g., the infill angle. Understanding the interactions between material, design, process, and the resulting sensor characteristics provides valuable insights for the successful design and additive manufacturing of piezoresistive sensors
Experimental and Simulative Investigation of Deterministic Lateral Displacement and Dielectrophoresis Methods for Continuous Multi-Property Particle Sorting
Full text linkSimulative and experimental studies were carried out to address multi-dimensional particle fractionation of non-biological particles according to size, shape, and density inside a high-throughput DLD array. Density sensitive separation was achieved for melamine and polystyrene particles at a diameter of 5 µm at a Reynolds number (Re) of 82, corresponding to an overall flow rate of 11.3 mL/min. This process is very sensitive, as no fractionation occurred for Re = 85 (11.7 mL/min). For the first time, the fractionation of elliptical polystyrene particles (5 × 10 µm) at Re > 1 was investigated up to Re = 80 (11 mL/min). A separation of elliptical particles from spherical melamine particles (5 µm) was observed in single experiments at all investigated Reynolds numbers. However, the separation is not reliably repeatable due to partial clogging of ellipsoidal particles along the posts. In addition, higher concentrations of polydisperse silica suspensions were experimentally investigated by using polydisperse silica particles at concentrations up to 0.4% (m/V) up to Re = 80 (20 mL/min). The separation size generally decreased with increasing Reynolds number and increased with increasing concentration. Separation efficiency decreased with increasing concentration, independent of the Reynolds number. In order to investigate the material-dependent separation in a contactless dielectrophoresis system (cDEP), the resolved CFD-DEM software was extended to calculate dielectrophoretic forces on particles. With this, the second stage of a serial-combined DLD-DEP system was simulated, showing good separation at lower flow rates. For these systems, different fabrication methods to minimize the distance between the electrodes and the fluid as well as the requirement to withstand high-throughput applications, were investigated
Double Beam Instability for the Mercury Upstream Waves
Full text linkMercury shock-upstream region is plasma physically of great interest, as the solar wind plasma may encounter two ion beams, forming a double-beam plasma system. Properties of the double-beam instability are studied semianalytically using the magnetoionic theory (cold plasma waves including beams), such as the unstable mode, the resonance wavenumbers, and the growth rates, for various beam configurations. The cold plasma wave theory supports the idea that both the foreshock ions and the pickup ions can potentially drive the right-hand beam instability, and moreover, the instability may run simultaneously for the two beam species. Further nonlinear wave evolution scenarios are discussed, such as independent parametric instabilities and driven wave–wave couplings causing low-frequency and high-frequency splits of the waves. The double-beam instability is testable against numerical simulations of the plasma waves as well as magnetic field observations by the MESSENGER spacecraft and the upcoming BepiColombo spacecraft
Wave propagation over a submerged bar: benchmarking of VoF, sigma transformation, and SPH numerical models against physical wave flume tests
Full text linkAccurate prediction of wave transformation is key in the design of coastal and nearshore structures which typically depends on numerical models. Turbulent and rotational effects call for the use of Computational Fluid Dynamics (CFD) solvers of which a large range of formulations including free surface treatments exists. Physical wave flume tests of wave propagation over a submerged bar with various levels of nonlinearity, regularity, and wave-breaking, dedicated to numerical model benchmarking or validation, were carried out in the Ocean and Coastal Engineering Laboratory of Aalborg University. Three fundamentally different CFD models each widespread within their category are benchmarked against the experimental data. The CFD models are based on (i) the Volume of Fluid (VoF) based interFoam solver of OpenFOAM, (ii) the sigma-transformation solver of MIKE 3 Waves Model FM, and (iii) the weakly compressible delta-SPH solver of DualSPHysics. Accuracy of the numerical models is assessed from surface elevation time series, evaluation metrics (averaged errors on surface elevations, amplitudes, phases, and wave set-up), and spectral analyses to calculate the amplitude and phase contents of primary and higher-order components along the wave flume. Applicability is assessed from computational costs and ease-of-use factors such as the effort to configure the numerical models and achieve convergence. In general, the numerical models have high correlation to the physical tests and are as such suitable to model complex wave transformation with an accuracy sufficient for most coastal engineering applications. The VoF model performs more accurately under the turbulent conditions of breaking waves, increasing its relative accuracy in the prediction of downwave surface elevation. The sigma transformation model has simulation times one to two orders of magnitude lower than those of the VoF and SPH models
Herausforderungen und Möglichkeiten für neuartige Antibiotika gegen Pseudomonas aeruginosa IspE
Full text linkResearch into new antibiotics is vital to address the escalating problem of antimicrobial resistance (AMR). IspE, a kinase in the MEP pathway, is a promising target for developing antibiotics. This study focused on identifying inhibitors for IspE from Pseudomonas aeruginosa (PaIspE) using innovative Structure-Based and Fragment-Based Drug Design (SBDD and FBDD). PaIspE was characterized, and its crystal structure with CDP-ME was resolved at 2.3 Å. Experimental SEC-MALS measurements and analysis of other Protein Data Bank (PDB) entries confirmed PaIspE as a monomer in solution, invalidating strategies to target its oligomerisation. Despite prior work showing IspE bound ATP in an unusual syn-conformation, this pocket was rarely targeted in drug discovery. Collaborative analysis with BioSolveIT showed that syn-ATP was present in only 4% of over 8000 PDB entries and was more common in prokaryotes than eukaryotes, suggesting the ATP-binding pocket is a promising target. Additionally, the thesis reported three complementary and parallel approaches for the discovery of new fragments and molecules targeting PaIspE. In the first project in collaboration with the company SPECS e-Molecules, 152 commercially available fragments were screened for PaIspE binding utilising thermal shift assay (TSA), a classical biophysical method. Three molecules showed 33-100% inhibition of PaIspE. They shared the same scaffold, corroborating the hypothesis that it could be a new promising IspE inhibitor. The optimization of an apo-crystal of Aquifex aeolicus IspE was pivotal for a crystallographic fragment screen (CFS) performed in collaboration with Helmoltz-Zentrum Berlin and MAV IV Laboratories. The project yielded four fragment hits, one of which bound in the active site. Although it was expected to be the primary target of the screen, the ATP binding pocket was not targeted by any fragment. The result was possibly due to the repulsive forces of the negatively charged AaIspE surface and the poor accessibility of the active site in the unit cell. Three fragments were identified binding to obscure pockets of AaIspE. The relevance of the results and the possibility to exploit the unexpected binding modes of these three fragments would require future careful analysis. The last approach was conducted in collaboration with BioSolveIT and aimed to target the adenine syn-conformation of ATP. The chemical space docking (CSD) was performed using the AaIspE-ATP structure as a template. Five of the forty-two molecules purchased from the company Enamine were validated as PaIspE inhibitors. The CSD yielded a higher percentage of active molecules than the previous two protects, demonstrating that the combination of SBDD and FBDD with a novel computational method that allows exploration of a chemical space to develop synthesis-on-demand compounds was a successful strategy for the first step of drug discovery, even for non-trivial targets such as IspE. Structural and biophysical studies of the hits obtained in these studies are currently being carried out. In conclusion, this study resulted in the structural characterization a new ortholog of IspE from the highly relevant pathogen P. aeruginosa. Consequently, ten molecules targeting PaIspE were identified through a combination of methods and techniques that provide new routes for hit-to-lead optimisation.Die Forschung an neuen Antibiotika ist entscheidend, um das wachsende Problem der antimikrobiellen Resistenz (AMR) anzugehen. IspE, eine Kinase im MEP-Weg, ist ein vielversprechendes Ziel für die Entwicklung neuer Antibiotika. Diese Studie konzentrierte sich darauf, Inhibitoren für IspE aus Pseudomonas aeruginosa (PaIspE) mithilfe innovativer Struktur- und Fragment-basierter Wirkstoffdesign-Ansätze (SBDD und FBDD) zu identifizieren. PaIspE wurde charakterisiert, und seine Kristallstruktur mit CDP-ME wurde bei einer Auflösung von 2,3 Å bestimmt. Experimentelle SEC-MALS-Messungen und die Analyse anderer Einträge in der Protein Data Bank (PDB) bestätigten, dass PaIspE in Lösung als Monomer vorliegt, wodurch Strategien zur Hemmung durch Oligomerisierung des Proteins ausgeschlossen wurden. Trotz früherer Arbeiten, die zeigten, dass IspE ATP in einer ungewöhnlichen Syn-Konformation bindet, wurde diese Bindungstasche selten in Wirkstoffforschungsprojekten ins Visier genommen. Eine kollaborative Analyse mit BioSolveIT zeigte, dass Syn-ATP in nur 4% von über 8000 PDB-Einträgen vorkam und in Prokaryoten häufiger anzutreffen war als in Eukaryoten. Dies deutet darauf hin, dass die ATP-Bindungstasche ein vielversprechendes Ziel darstellt. Darüber hinaus wurden in der Dissertation drei komplementäre und parallele Ansätze zur Entdeckung neuer Fragmente und Moleküle, die auf PaIspE abzielen, vorgestellt. Im ersten Projekt, in Zusammenarbeit mit dem Unternehmen SPECS e-Molecules, wurden 152 kommerziell erhältliche Fragmente mithilfe des Thermal Shift Assay (TSA), einer klassischen biophysikalischen Methode, auf ihre Bindung an PaIspE untersucht. Drei Moleküle zeigten eine 33-100%ige Hemmung von PaIspE. Sie wiesen dasselbe molekulare Grundgerüst auf, was die Hypothese bestätigte, dass es sich dabei um einen neuen vielversprechenden IspE-Inhibitor handeln könnte. Die Optimierung eines Apo-Kristalls von Aquifex aeolicus IspE war entscheidend für ein kristallographisches Fragment-Screening (CFS), das in Zusammenarbeit mit dem Helmholtz-Zentrum Berlin und den MAV IV Laboratories durchgef¨uhrt wurde. Das Projekt ergab vier Fragmenttreffer, von denen einer im aktiven Zentrum gebunden wurde. Obwohl erwartet wurde, dass es das primäre Ziel des Screenings sein würde, wurde die ATP Bindungstasche von keinem Fragment ins Visiergenommen. Das Ergebnis war möglicherweise auf die abstosenden Kräfte der negativ gela-denen Oberfläche von AaIspE und die schlechte Zugänglichkeit des aktiven Zentrums in der Einheitszelle zurückzuführen. Es wurden drei Fragmente identifiziert, die an verborgene Taschen von AaIspE binden. Die Relevanz der Ergebnisse und die Möglichkeit, die unerwarteten Bindungsmodi dieser drei Fragmente zu nutzen, müssten in Zukunft sorgf ¨ altig analysiert werden. Der letzte Ansatz wurde in Zusammenarbeit mit BioSolveIT durchgeführt und zielte auf die Adenin-syn-Konformation von ATP ab. Die Chemical Space Docking (CSD) wurde unter Verwendung der AaIspE-ATP-Struktur als Vorlage durchgeführt. Fünf der zweiundvierzig von der Firma Enamine gekauften Molek¨ ule wurden als PaIspE-Inhibitoren validiert. Das CSD ergab einen höheren Prozentsatz aktiver Moleküle als die beiden vorherigen Verfahren, was zeigt, dass die Kombination von SBDD und FBDD mit einer neuartigen Berechnungsmethode, die die Erkunvdung eines chemischen Raums zur Entwicklung von Synthese-on-Demand-Verbindungen ermöglicht, eine erfolgreiche Strategie für den ersten Schritt der Arzneimittelentdeckung war, selbst für nicht triviale Ziele wie IspE. Die in diesen Studien erzielten Treffer werden derzeit strukturell und biophysikalisch untersucht. Zusammenfassend führte diese Studie zur strukturellen Charakterisierung eines neuen Orthologs von IspE aus dem hochrelevanten Pathogen P. aeruginosa. Infolgedessen wurden zehn Moleküle, die auf PaIspE abzielen, durch eine Kombination von Methoden und Techniken identifiziert, die neue Wege für die Hit-to-Lead-Optimierung bieten
Does tablet shape and height influence survival of fluidized bed-granulated living microorganisms during compaction?
Full text linkThe provision of effective probiotic formulations requires gentle processing to maintain the viability of the probiotic microorganisms, which is essential for their health-promoting effects. The drying of microorganisms by fluidized bed spray granulation and subsequent processing of the granules into tablets has proven to be a promising process route in previous studies of the same authors. In these, the influence of various factors was considered using cylindrical tablets with a diameter of 11.28 mm and a mass of 450 mg. These flat tablets are unpleasant to ingest and other tablet geometries should be considered for administration of probiotics but to date, no studies exist on the influence of geometric factors of the tableting tool and of the tablets on the survival of microorganisms. To address this aspect, the survival of Saccharomyces cerevisiae during the production of flat, round tablets with different tablet masses and thus heights as well as differently shaped convex tablets is determined and related to the physical-mechanical tablet properties to derive process-structure-property relationships. It turned out that higher tablet heights were advantageous regarding microbial survival and mechanical strength which is attributed to a lower elastic recovery. However, the use of differently shaped tools had a smaller influence on microbiological and mechanical tablet properties since the global tablet porosity was hardly affected
Thermogravimetric And Microscale Calorimeter Data on Cast PMMA (Version 1.0)
No full textPlease use the latest version 2.0 of the data set available under: https://doi.org/10.24355/dbbs.084-202508070641-0 Thermogravimetric analyses (TGA) and micro-scale combustion calorimeter (MCC) experiments were carried out for a study on influences on micro-scale experiments in the context of kinetic modelling of the decomposition of cast polymethyl methacrylate (PMMA). Two different sample configurations (preparation methods) were used for the experiments: pieces and powder
Numerical Experiments on the Origin of the Global Magnetic Field on Mercury
Full text linkDie globalen Magnetfelder planetarer Körper wie des Merkurs oder der Erde entstehen durch Bewegungen eines elektrisch leitfähigen Fluids im Inneren des Planeten. Die Bewegungen des Fluids werden dabei meist durch Auftriebskräfte angetrieben, sogenannte Konvektion. Die Corioliskraft strukturiert die Strömung zusätzlich, was die Erzeugung und die Verstärkung des Magnetfelds begünstigt. Der Prozess der Magnetfelderzeugung über diese Effekte wird als Dynamoprozess bezeichnet. Ein wesentlicher Teil der aktuellen Forschung zu planetaren Dynamos besteht darin, die physikalischen Prozesse im Planeteninneren anhand numerischer Experimenten besser zu verstehen. Ein grundlegendes Modell zur Untersuchung des Dynamoprozesses ist das Childress-Soward-Modell, das aus einer rotierenden, elektrisch leitfähigen Fluidschicht besteht. Der erste Teil dieser Arbeit untersucht den Einfluss der Randbedingungen auf dieses Modell, da in der bestehenden Literatur oft auf recht einfache, jedoch geophysikalisch nicht relevante Randbedingungen eingegangen wird. Ein wichtiges Ergebnis dieser Studie ist, dass bei mechanisch festen Rändern die Nusselt-Zahl signifikant ansteigt, vorausgesetzt, dass der Wärmefluss an den Rändern konstant ist. Dies kann durch ein Zusammenspiel des Ekman-Pumpens und der Struktur der thermischen Grenzschicht erklärt werden. Des Weiteren zeigt sich, dass die thermischen Randbedingungen kaum einen Einfluss auf die Dynamik und Magnetfelderzeugung des Dynamos haben. Wie schon aus nicht-magnetischer rotierender Konvektion bekannt ist, haben die mechanischen Randbedingungen einen großen Effekt auf die Dynamik des Systems und somit auf die Magnetfelderzeugung des Dynamos. So unterdrücken die viskosen Grenzschichten bei mechanisch festen Rändern die Ausbildung großskaliger Wirbel. Die magnetischen Randbedingungen beeinflussen vor allem die Struktur des Feldes. Es zeigt sich bei einer elektrisch perfekt leitenden Umgebung, dass sich ein starkes Magnetfeld in einem kleinen Bereich nahe der Ränder aufbaut, insbesondere für hohe magnetische Reynolds-Zahlen. Der zweite Teil dieser Arbeit beschäftigt sich mit der Erzeugung des einzigartigen Magnetfelds des Merkurs anhand eines Dynamoprozesses. Das Magnetfeld des Planeten kann über einen axialen Dipol mit einer signifikanten Quadrupolkomponente charakterisiert werden. Außerdem ist die Neigung des Dipols gegenüber der Rotationsachse kleiner als ein Grad und das Feld zeigt eine Verschiebung des magnetischen Äquators nach Norden um 20 % des planetaren Radius. Das einzige Dynamomodell, das kontinuierlich diese Eigenschaften des Magnetfelds ohne unrealistische Wärmeflussprofile an der Kern-Mantel-Grenze erzeugen kann, ist das doppelt-diffusive Modell von Takahashi et al. (2019). Dieses Modell nimmt eine dicke thermisch stabile Schicht im äußeren Bereich des Kerns an, wobei der feste innere Kern recht klein ist. In dieser Arbeit wird die Abhängigkeit der Kontrollparameter auf dieses Modell untersucht. Es zeigt sich, dass das Modell sehr sensitiv auf die Wahl der Kontrollparameter reagiert und womöglich unrealistisch für Merkur ist. In einem nächsten Schritt wird ein neues einfach-diffusives Modell vorgestellt, das die Eigenschaften des Merkurmagnetfelds für lange Zeiträume hervorragend erzeugen kann. Die Perioden eines Merkur-ähnlichen Magnetfelds werden von Umkehrungen des Dipolfeldes unterbrochen, die dazu führen, dass der magnetische Äquator zwischen der nördlichen und südlichen Hemisphäre wechselt. Eine wichtiger Faktor für ein Magnetfeld ähnlich zu dem des Merkurs ist, dass der Dynamoprozess mit einer äquatorialsymmetrischen Magnetfeldmode einsetzt.The global magnetic fields of planetary bodies such as Mercury or the Earth are generated by motions of an electrically conducting fluid inside the planet. The motions of the fluid are often driven by buoyancy forces, so-called convection. The Coriolis force additionally structures the flow, which favours the generation and amplification of the magnetic field. The process of magnetic field generation via these effects is known as the dynamo process. An essential part of the current research on planetary dynamos consists of understanding the physical processes in the planet’s interior using numerical experiments. A basic model for investigating the dynamo process is the Childress-Soward model, which consists of a rotating, electrically conducting fluid layer. The first part of this thesis examines the influence of the boundary conditions on this model, as in the existing literature often rather simple but geophysically irrelevant boundary conditions are found. An important result of this study is that the Nusselt number increases significantly with mechanical no-slip boundaries, provided that the heat flux at the boundaries is constant. This can be achieved through an interplay between Ekman pumping and the structure of the thermal boundary layer. Furthermore, it can be seen that the thermal boundary conditions have almost no effect on the dynamics and magnetic field generation of the dynamo. As is already known from non-magnetic rotating convection, the mechanical boundary conditions have a major effect on the dynamics of the system and thus the magnetic field generation in dynamos. For example, the viscous boundary layers for no-slip boundaries suppress the formation of large-scale vortices. The magnetic boundary conditions mainly influence the structure of the field. It can be seen in an electrically perfectly conducting exterior region that a strong magnetic field builds up in a small area near the boundaries, especially for high magnetic Reynolds numbers. The second part of this thesis deals with the generation of Mercury’s unique magnetic field by a dynamo process. The magnetic field of the planet can be characterised by an axial dipole with a significant quadrupole component. Furthermore, the dipole tilt is less than one degree and the field shows that its magnetic equator is shifted northward by 20 % of the planetary radius. The only dynamo model that continuously achieves these properties of the magnetic field without assuming unrealistic heat flux patterns at the core-mantle boundary is the double-diffusive model by Takahashi et al. (2019). This model assumes a thick thermally stably stratified layer in the outer region of the core, whereas the solid inner core is rather small. In this work, the dependence of the control parameters on this model is investigated. The results show that the model is very sensitive to the choice of control parameters and is likely unrealistic for Mercury. In a next step, a new single-diffusive model is presented, which reproduces the properties of Mercury’s magnetic field very well for long periods of time. The periods of a Mercury-like magnetic field are interrupted by reversals of the dipole field, which cause the magnetic equator to switch between the northern and southern hemispheres. An important factor for a magnetic field similar to that of Mercury is that dynamo action starts with an equatorially symmetric magnetic field mode
A mortar-based cavitation formulation using NURBS-based isogeometric analysis
No full textThis paper applies NURBS-based isogeometric analysis to hydrodynamic lubrication problems considering cavitation effects. For this purpose, a mass-conserving cavitation formulation analog to the Augmented Lagrangian method is developed. It describes the complementarity constraints between pressure and void fraction and converts the constrained problem to an unconstrained one. This formulation is discretized using a mortar-based approach to avoid oscillations resulting from overconstrained issues. Additionally, both NURBS basis functions and Lagrange polynomials are employed to discretize the fluid domain for comparison. Several numerical examples indicate that the proposed cavitation formulation can provide more accurate and robust solutions when combined with the mortar method and NURBS basis functions. Furthermore, this combination is adopted to investigate systems with rough surfaces and gaps partially filled with lubricants to demonstrate its excellent performance