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MathEnergy – Mathematical Key Technologies for Evolving Energy Grids (2021)

Clees, Tanja ; Baldin, Anton ; Benner, Peter ; Grundel, Sara ; Himpe, Christian ; Klaassen, Bernhard ; Küsters, Ferdinand ; Marheineke, Nicole ; Nikitina, Lialia ; Nikitin, Igor ; Pade, Jonas ; Stahl, Nadine ; Strohm, Christian ; Tischendorf, Caren ; Wirsen, Andreas

Online-Lehre als neue Erfahrung – Erkenntnisse und Handlungsempfehlungen (2020)

Melcher, Paul

Am Beispiel einer jahrelang in Präsenz gelehrten Veranstaltung mit Vorlesungen, Übungen und Laborpraktika wird gezeigt, wie die Vermittlung prüfungsrelevanter Kompetenzen auch „online“ gelang. Das passende „Setting“ des Lehr- und Lernprozesses unter Beachtung von Handlungsempfehlungen ist auch für die Zukunft relevant.

Reaction behavior modeling of metal hydride based on FeTiMn using numerical simulations (2021)

Bedrunka, Mario ; Bornemann, Nils ; Steinebach, Gerd ; Reith, Dirk

In this contribution, we perform computer simulations to expedite the development of hydrogen storages based on metal hydride. These simulations enable in-depth analysis of the processes within the systems which otherwise could not be achieved. That is, because the determination of crucial process properties require measurement instruments in the setup which are currently not available. Therefore, we investigate the reliability of reaction values that are determined by a design of experiments. Specifically, we first explain our model setup in detail. We define the mathematical terms to obtain insights into the thermal processes and reaction kinetics. We then compare the simulated results to measurements of a 5-gram sample consisting of iron-titanium-manganese (FeTiMn) to obtain the values with the highest agreement with the experimental data. In addition, we improve the model by replacing the commonly used Van’t-Hoff equation by a mathematical expression of the pressure-composition-isotherms (PCI) to calculate the equilibrium pressure. Finally, the parameters’ accuracy is checked in yet another with an existing metal hydride system. The simulated results demonstrate high concordance with experimental data, which advocate the usage of approximated kinetic reaction properties by a design of experiments for further design studies. Furthermore, we are able to determine process parameters like the entropy and enthalpy.

Cubature rules for weakly and fully compressible off-lattice Boltzmann methods (2021)

Wilde, Dominik ; Krämer, Andreas ; Bedrunka, Mario ; Reith, Dirk ; Foysi, Holger

Off-lattice Boltzmann methods increase the flexibility and applicability of lattice Boltzmann methods by decoupling the discretizations of time, space, and particle velocities. However, the velocity sets that are mostly used in off-lattice Boltzmann simulations were originally tailored to on-lattice Boltzmann methods. In this contribution, we show how the accuracy and efficiency of weakly and fully compressible semi-Lagrangian off-lattice Boltzmann simulations is increased by velocity sets derived from cubature rules, i.e. multivariate quadratures, which have not been produced by the Gauss-product rule. In particular, simulations of 2D shock-vortex interactions indicate that the cubature-derived degree-nine D2Q19 velocity set is capable to replace the Gauss-product rule-derived D2Q25. Likewise, the degree-five velocity sets D3Q13 and D3Q21, as well as a degree-seven D3V27 velocity set were successfully tested for 3D Taylor-Green vortex flows to challenge and surpass the quality of the customary D3Q27 velocity set. In compressible 3D Taylor-Green vortex flows with Mach numbers Ma={0.5;1.0;1.5;2.0} on-lattice simulations with velocity sets D3Q103 and D3V107 showed only limited stability, while the off-lattice degree-nine D3Q45 velocity set accurately reproduced the kinetic energy provided by literature.

Day-Ahead Electric Load Forecast for a Ghanaian Health Facility Using Different Algorithms (2021)

Chaaraoui, Samer ; Bebber, Matthias ; Meilinger, Stefanie ; Rummeny, Silvan ; Schneiders, Thorsten ; Sawadogo, Windmanagda ; Kunstmann, Harald

Ghana suffers from frequent power outages, which can be compensated by off-grid energy solutions. Photovoltaic-hybrid systems become more and more important for rural electrification due to their potential to offer a clean and cost-effective energy supply. However, uncertainties related to the prediction of electrical loads and solar irradiance result in inefficient system control and can lead to an unstable electricity supply, which is vital for the high reliability required for applications within the health sector. Model predictive control (MPC) algorithms present a viable option to tackle those uncertainties compared to rule-based methods, but strongly rely on the quality of the forecasts. This study tests and evaluates (a) a seasonal autoregressive integrated moving average (SARIMA) algorithm, (b) an incremental linear regression (ILR) algorithm, (c) a long short-term memory (LSTM) model, and (d) a customized statistical approach for electrical load forecasting on real load data of a Ghanaian health facility, considering initially limited knowledge of load and pattern changes through the implementation of incremental learning. The correlation of the electrical load with exogenous variables was determined to map out possible enhancements within the algorithms. Results show that all algorithms show high accuracies with a median normalized root mean square error (nRMSE) <0.1 and differing robustness towards load-shifting events, gradients, and noise. While the SARIMA algorithm and the linear regression model show extreme error outliers of nRMSE >1, methods via the LSTM model and the customized statistical approaches perform better with a median nRMSE of 0.061 and stable error distribution with a maximum nRMSE of <0.255. The conclusion of this study is a favoring towards the LSTM model and the statistical approach, with regard to MPC applications within photovoltaic-hybrid system solutions in the Ghanaian health sector.

Einsatz von Künstlicher Intelligenz im internationalen Spitzensport – Eine Erhebung des Status Quo (2020)

Hammes, Fabian ; Link, Daniel ; Lames, Martin ; Hagg, Alexander ; Asteroth, Alexander ; Pfeiffer, Mark

Anhand eines Literaturreviews sowie Interviews mit ausgewählten Expert/innen aus 7 Ländern wird der aktuelle Stand der KI im internationalen Spitzensport beschrieben. Die Ergebnisse zeigen primär Aktivitäten in den Bereichen Bilderkennung, Signalverarbeitung und Regelerkennung.

Einsatzmöglichkeiten und Transfer von Künstlicher Intelligenz im internationalen Spitzensport – zwischen Small und Big Data (2020)

Hagg, Alexander ; Asteroth, Alexander ; Pfeiffer, Mark ; Hammes, Fabian ; Link, Daniel

Ausgehend von einer Sichtung aktueller Ergebnisse in der KI werden Faktoren identifiziert, die zur erfolgreichen Anwendung führen. Ein Abgleich mit den Gegebenheiten im Spitzen-sport führt zur Identifikation potenzieller Handlungsfelder.

Unraveling a Force-Generating Allosteric Pathway of Actomyosin Communication Associated with ADP and Pi Release (2021)

Franz, Peter ; Ewert, Wiebke ; Preller, Matthias ; Tsiavaliaris, Georgios

The actomyosin system generates mechanical work with the execution of the power stroke, an ATP-driven, two-step rotational swing of the myosin-neck that occurs post ATP hydrolysis during the transition from weakly to strongly actin-bound myosin states concomitant with Pi release and prior to ADP dissociation. The activating role of actin on product release and force generation is well documented; however, the communication paths associated with weak-to-strong transitions are poorly characterized. With the aid of mutant analyses based on kinetic investigations and simulations, we identified the W-helix as an important hub coupling the structural changes of switch elements during ATP hydrolysis to temporally controlled interactions with actin that are passed to the central transducer and converter. Disturbing the W-helix/transducer pathway increased actin-activated ATP turnover and reduced motor performance as a consequence of prolonged duration of the strongly actin-attached states. Actin-triggered Pi release was accelerated, while ADP release considerably decelerated, both limiting maximum ATPase, thus transforming myosin-2 into a high-duty-ratio motor. This kinetic signature of the mutant allowed us to define the fractional occupancies of intermediate states during the ATPase cycle providing evidence that myosin populates a cleft-closure state of strong actin interaction during the weak-to-strong transition with bound hydrolysis products before accomplishing the power stroke.

High-order semi-Lagrangian kinetic scheme for compressible turbulence (2020)

Wilde, Dominik ; Krämer, Andreas ; Reith, Dirk ; Foysi, Holger

Turbulent compressible flows are traditionally simulated using explicit Eulerian time integration applied to the Navier-Stokes equations. However, the associated Courant-Friedrichs-Lewy condition severely restricts the maximum time step size. Exploiting the Lagrangian nature of the Boltzmann equation's material derivative, we now introduce a feasible three-dimensional semi-Lagrangian lattice Boltzmann method (SLLBM), which elegantly circumvents this restriction. Previous lattice Boltzmann methods for compressible flows were mostly restricted to two dimensions due to the enormous number of discrete velocities needed in three dimensions. In contrast, this Rapid Communication demonstrates how cubature rules enhance the SLLBM to yield a three-dimensional velocity set with only 45 discrete velocities. Based on simulations of a compressible Taylor-Green vortex we show that the new method accurately captures shocks or shocklets as well as turbulence in 3D without utilizing additional filtering or stabilizing techniques, even when the time step sizes are up to two orders of magnitude larger compared to simulations in the literature. Our new method therefore enables researchers for the first time to study compressible turbulent flows by a fully explicit scheme, whose range of admissible time step sizes is only dictated by physics, while being decoupled from the spatial discretization.

Das Elektrofahrrad im Spiegel der Medien (2020)

Seuser, Katharina ; Yasari, Aysegül ; Viehof, Andreas

Medien spielen eine Schlüsselrolle für die öffentliche Meinung und Akzeptanz neuer Technologien. Mit einer qualitativen Inhaltsanalyse journalistischer Artikel zum Elektrofahrrad wurden Akteure und ihre Einstellungen und Handlungen in Bezug auf das Elektrofahrrad untersucht. In die Analyse flossen 444 Artikel ausgewählter deutscher Qualitätsmedien aus dem Jahr 2018 ein. Die Untersuchung zeigt den gesellschaftlich relevanten Diskurs über Elektrofahrräder auf und bietet Anknüpfungspunkte für die Förderung von Individualmobilität und der Entwicklung zukunftsfähiger Mobilitätskonzepte.

An Analysis of Phenotypic Diversity in Multi-solution Optimization (2020)

Hagg, Alexander ; Preuss, Mike ; Asteroth, Alexander ; Bäck, Thomas

Bionik (2020)

Wawers, Welf

Wie machen die das... kann angesichts der erstaunlichen Fähigkeiten mancher Lebewesen gefragt werden. Die Bionik fragt noch weiter …und wie kann man das nachmachen? Hier liegt ein Schwerpunkt dieses Lehrbuches, das die Bionik nicht nur an zahlreichen Beispielen erklärt, sondern auch eine Vorgehensweise für die Identifizierung biologischer Lösungen und deren Übertragung auf technische Anwendungen vermittelt. Basisinformationen der Biologie und Grundlagen der Konstruktionstechnik gewährleisten einen leichten Zugang zum Stoff. Mit dem 3D-Druck als Schlüsseltechnologie und der Thematisierung der Nachhaltigkeit geht das Buch zudem auf aktuelle Entwicklungen ein. Dieser ganzheitliche Blick auf die Bionik soll den Leser zur Durchführung bionischer Projekte befähigen und motivieren. (Verlagsangaben)

Photovoltaic power potential in West Africa using long-term satellite data (2020)

Neher, Ina ; Crewell, Susanne ; Meilinger, Stefanie ; Pfeifroth, Uwe ; Trentmann, Jörg

This paper addresses long-term historical changes in solar irradiance in West Africa (3 to 20° N and 20° W to 16° E) and the implications for photovoltaic systems. Here, we use satellite irradiance (Surface Solar Radiation Data Set – Heliosat, Edition 2.1 – SARAH-2.1) and temperature data from a reanalysis (ERA5) to derive photovoltaic yields. Based on 35 years of data (1983–2017), the temporal and regional variability as well as long-term trends in global and direct horizontal irradiance are analyzed. Furthermore, a detailed time series analysis is undertaken at four locations. According to the high spatial resolution SARAH-2.1 data record (0.05°×0.05°), solar irradiance is largest (up to a 300 W m−2 daily average) in the Sahara and the Sahel zone with a positive trend (up to 5 W m−2 per decade) and a lower temporal variability (<75 W m−2 between 1983 and 2017 for daily averages). In contrast, the solar irradiance is lower in southern West Africa (between 200 W m−2 and 250 W m−2) with a negative trend (up to −5 W m−2 per decade) and a higher temporal variability (up to 150 W m−2). The positive trend in the north is mostly connected to the dry season, whereas the negative trend in the south occurs during the wet season. Both trends show 95 % significance. Photovoltaic (PV) yields show a strong meridional gradient with the lowest values of around 4 kWh kWp−1 in southern West Africa and values of more than 5.5 kWh kWp−1 in the Sahara and Sahel zone.

Characterisation of Bioactive Ingredients in Extracts of Fresh and Dried Coniferous Trees for the Development of Sustainable Packaging Materials (2020)

Havelt, Thomas ; Frase, Jan Niklas ; Pude, Ralf ; Schmitz, Michaela

Background: Coniferous woods (Abies nordmanniana (Stev.) Spach, Abies procera Rehd, Picea abies (L.) H.Karst, and Picea pungens Engelm.) could contain useful secondary metabolites to produce sustainable packaging materials, e.g., by substitution of harmful petrol-based additives in plastic packaging. This study aims to characterise the antioxidant and light-absorbing properties and ingredients of different coniferous wood extracts with regard to different plant fragments and drying conditions. Furthermore, the valorisation of used Christmas trees is evaluated. Methods: Different drying and extraction techniques were applied with the extracts being characterised by determining the total phenolic content (TPC), total antioxidant capacity (TAC), and absorbance in the ultraviolet range (UV). Gas chromatography coupled with mass spectrometry (GC-MS) and an acid–butanol assay (ABA) were used to characterise the extract constituents. Results: All the extracts show a considerably high UV absorbance while interspecies differences did occur. All the fresh and some of the dried biomass extracts reached utilisable TAC and TPC values. A simplified extraction setup for industrial application is evaluated; comparable TAC results could be reached with modifications. Conclusion: Coniferous woods are a promising renewable resource for preparation of sustainable antioxidants and photostabilisers. This particularly applies to Christmas trees used for up to 12 days. After extraction, the biomass can be fully valorised by incorporation in paper packaging.

Cubature Rules for Off-Lattice Boltzmann Methods in Two and Three Dimensions (2020)

Wilde, Dominik ; Kraemer, Andreas ; Bedrunka, Mario ; Reith, Dirk ; Foysi, Holger

Structural and Computational Insights into a Blebbistatin-Bound Myosin•ADP Complex with Characteristics of an ADP-Release Conformation along the Two-Step Myosin Power Stoke (2020)

Ewert, Wiebke ; Franz, Peter ; Tsiavaliaris, Georgios ; Preller, Matthias

The motor protein myosin drives a wide range of cellular and muscular functions by generating directed movement and force, fueled through adenosine triphosphate (ATP) hydrolysis. Release of the hydrolysis product adenosine diphosphate (ADP) is a fundamental and regulatory process during force production. However, details about the molecular mechanism accompanying ADP release are scarce due to the lack of representative structures. Here we solved a novel blebbistatin-bound myosin conformation with critical structural elements in positions between the myosin pre-power stroke and rigor states. ADP in this structure is repositioned towards the surface by the phosphate-sensing P-loop, and stabilized in a partially unbound conformation via a salt-bridge between Arg131 and Glu187. A 5 Å rotation separates the mechanical converter in this conformation from the rigor position. The crystallized myosin structure thus resembles a conformation towards the end of the two-step power stroke, associated with ADP release. Computationally reconstructing ADP release from myosin by means of molecular dynamics simulations further supported the existence of an equivalent conformation along the power stroke that shows the same major characteristics in the myosin motor domain as the resolved blebbistatin-bound myosin-II·ADP crystal structure, and identified a communication hub centered on Arg232 that mediates chemomechanical energy transduction.

Improvement of Rosenbrock-Wanner Method RODASP (2020)

Steinebach, Gerd

Design of a Medium Voltage Generator and Power Converter for High Power Wind Energy Conversion Systems (2020)

Steffen, Jonas ; Lengsfeld, Sebastian ; Jung, Marco ; Ponick, Bernd ; Herranz Gracia, Mercedes ; Spagnolo, Aristide ; Schleicher, Klaus ; Schäfer, Klaus

Designing Air Flow with Surrogate-Assisted Phenotypic Niching (2020)

Hagg, Alexander ; Wilde, Dominik ; Asteroth, Alexander ; Bäck, Thomas

Ultrafine eutectic Ti-Fe-based alloys processed by additive manufacturing – A new candidate for high temperature applications (2020)

Gussone, Joachim ; Bugelnig, Katrin ; Barriobero-Vila, Pere ; da Silva, Julio Cesar ; Hecht, Ulrike ; Dresbach, Christian ; Sket, Federico ; Cloetens, Peter ; Stark, Andreas ; Schell, Norbert ; Haubrich, Jan ; Requena, Guillermo

The development of metals tailored to the metallurgical conditions of laser-based additive manufacturing is crucial to advance the maturity of these materials for their use in structural applications. While efforts in this regard are being carried out around the globe, the use of high strength eutectic alloys have, so far, received minor attention, although previous works showed that rapid solidification techniques can result in ultrafine microstructures with excellent mechanical performance, albeit for small sample sizes. In the present work, a eutectic Ti-32.5Fe alloy has been produced by laser powder bed fusion aiming at exploiting rapid solidification and the capability to produce bulk ultrafine microstructures provided by this processing technique. Process energy densities between 160 J/mm³ and 180 J/mm³ resulted in a dense and crack-free material with an oxygen content of ~ 0.45 wt.% in which a hierarchical microstructure is formed by µm-sized η-Ti4Fe2Ox dendrites embedded in an ultrafine eutectic β-Ti/TiFe matrix. The microstructure was studied three-dimensionally using near-field synchrotron ptychographic X-ray computed tomography with an actual spatial resolution down to 39 nm to analyse the morphology of the eutectic and dendritic structures as well as to quantify their mass density, size and distribution. Inter-lamellar spacings down to ~ 30–50 nm were achieved, revealing the potential of laser-based additive manufacturing to generate microstructures smaller than those obtained by classical rapid solidification techniques for bulk materials. The alloy was deformed at 600 °C under compressive loading up to a strain of ~ 30% without damage formation, resulting in a compressive yield stress of ~ 800 MPa. This study provides a first demonstration of the feasibility to produce eutectic Ti-Fe alloys with ultrafine microstructures by laser powder bed fusion that are suitable for structural applications at elevated temperature.

Dynamic model of photovoltaic module temperature as a function of atmospheric conditions (2020)

Barry, James ; Böttcher, Dirk ; Pfeilsticker, Klaus ; Herman-Czezuch, Anna ; Kimiaie, Nicola ; Meilinger, Stefanie ; Schirrmeister, Christopher ; Deneke, Hartwig ; Witthuhn, Jonas ; Gödde, Felix

The temperature of photovoltaic modules is modelled as a dynamic function of ambient temperature, shortwave and longwave irradiance and wind speed, in order to allow for a more accurate characterisation of their efficiency. A simple dynamic thermal model is developed by extending an existing parametric steady-state model using an exponential smoothing kernel to include the effect of the heat capacity of the system. The four parameters of the model are fitted to measured data from three photovoltaic systems in the Allgäu region in Germany using non-linear optimisation. The dynamic model reduces the root-mean-square error between measured and modelled module temperature to 1.58 K on average, compared to 3.03 K for the steady-state model, whereas the maximum instantaneous error is reduced from 20.02 to 6.58 K.

Long-term variability of solar irradiance and its implications for photovoltaic power in West Africa (2020)

Neher, Ina ; Crewell, Susanne ; Meilinger, Stefanie ; Pfeifroth, Uwe ; Trentmann, Jörg

West Africa is one of the least developed regions in the world regarding the energy availability and energy security. Located close to the equator West Africa receives high amounts of global horizontal irradiance (GHI). Thus, solar power and especially photovoltaic (PV) systems seem to be a promising solution to provide electricity with low environmental impact. To plan and to dimension a PV power system climatological data for global horizontal irradiance (GHI) and its variability need to be taken into account. However, ground based measurements of irradiances are not available continuously and cover only a few discrete locations.

Minisymposium: Simulation and Optimization of Water and Gas Networks (2017)

Steinebach, Gerd ; Jax, Tim ; Wagner, Lisa

Generalized ROW-Type Methods for Simulating Water Supply Networks (2017)

Jax, Tim ; Steinebach, Gerd

Neue Supply Chain: Wie verändert der 3-D-Druck die Lieferketten und was bedeutet das für den stationären Handel? (2018)

Wawers, Welf

Technik-Öffentlichkeiten für Mädchen: inwieweit können sich Mädchen und Frauen durch digitale Medienkommunikation die Welt der Technik erschließen? (2020)

Keil, Susanne ; Orth, Juliane

Technik wird in unserer Gesellschaft noch immer mit Männlichkeit assoziiert. Das Bild eines Mannes, der mit einer schweren Bohrmaschine arbeitet, erscheint uns vertrauter als das einer Frau, die dieselbe Tätigkeit ausführt. Derartige Repräsentationen von Technik und Geschlecht werden auch von den Medien verbreitet und könnten so bereits Mädchen und jungen Frauen den Zugang zu Technik erschweren. Digitalisierte Medienwelten bieten allerdings die Möglichkeit, neue Technik-Bilder zu entwerfen und dominante Vorstellungen dadurch zu verschieben. Hier könnten Öffentlichkeiten für Mädchen und Frauen entstehen, die eine Selbstverständigung über technische Interessen und damit einhergehend eine Erfahrung von Kompetenz vermitteln könnten. Anhand von fünf Gruppendiskussionen mit 12- bis 15-jährigen Gymnasiastinnen wurden deren Technikverständnis, deren Nutzung digitaler Medien zu Technikthemen, vor allem aber auch deren Ideen zu einer für sie attraktiven Vermittlung von Technikthemen erfragt. Dabei wurden insbesondere die Vorteile einer symmetrischen Kommunikation im Netz deutlich.

Sustaining complex projects by linking in- and off-curriculum elements: The BRSU Racing Engineer Certificate (2020)

Reith, Dirk ; Blume, Christian ; Grein, Martina ; Haedecke, Tobias ; Konemann, Daniel ; Malschützky, Michael

Teaching Technical Journalism with an Engineering Foundation (2020)

Kirschner, Karl N. ; Keil, Susanne ; Seuser, Katharina ; Siefer, Christine

"Modellierung und Optimierung Transdermaler Therapeutischer Systeme hinsichtlich Applikationskomfort und medizinischer Leistungsfähigkeit" : Abschlussbericht : FHProfUnt-Projekt "MOTTSAL" : Projektlaufzeit: 01.04.2016 bis 31.03.2019, kostenneutrale Verlängerung bis 31.08.2019 (2020)

Möginger, Bernhard ; Meurer, Michael ; Hülsmann, Marco

The Inverter: A Multi-Purpose Control Element (2019)

Alet, Pierre-Jean ; Adinolfi, Giovanna ; Barchi, Grazia ; Bründlinger, Roland ; Graditi, Giorgio ; Henze, Norbert ; Jung, Marco ; Stavrou, Andreas ; Yang, Guangya

The need for innovation around the control functions of inverters is great. PV inverters were initially expected to be passive followers of the grid and to disconnect as soon as abnormal conditions happened. Since future power systems will be dominated by generation and storage resources interfaced through inverters these converters must move from following to forming and sustaining the grid. As “digital natives” PV inverters can also play an important role in the digitalisation of distribution networks. In this short review we identified a large potential to make the PV inverter the smart local hub in a distributed energy system. At the micro level, costs and coordination can be improved with bidirectional inverters between the AC grid and PV production, stationary storage, car chargers and DC loads. At the macro level the distributed nature of PV generation means that the same devices will support both to the local distribution network and to the global stability of the grid. Much success has been obtained in the former. The later remains a challenge, in particular in terms of scaling. Yet there is some urgency in researching and demonstrating such solutions. And while digitalisation offers promise in all control aspects it also raises significant cybersecurity concerns.

Correlating mechanical rubber properties with moving die rheometer vulcanization curves under consideration of the material composition (2019)

Steinhaus, Johannes ; Almeida, Andre ; Lantermann, Ulrich ; Moeginger, Bernhard

Discovering Representations for Black-box Optimization (2020)

Gaier, Adam ; Asteroth, Alexander ; Mouret, Jean-Baptiste

The encoding of solutions in black-box optimization is a delicate, handcrafted balance between expressiveness and domain knowledge between exploring a wide variety of solutions, and ensuring that those solutions are useful. Our main insight is that this process can be automated by generating a dataset of high-performing solutions with a quality diversity algorithm (here, MAP-Elites), then learning a representation with a generative model (here, a Varia-tional Autoencoder) from that dataset. Our second insight is that this representation can be used to scale quality diversity optimization to higher dimensions-but only if we carefully mix solutions generated with the learned representation and those generated with traditional variation operators. We demonstrate these capabilities by learning an low-dimensional encoding for the inverse kinemat-ics of a thousand joint planar arm. The results show that learned representations make it possible to solve high-dimensional problems with orders of magnitude fewer evaluations than the standard MAP-Elites, and that, once solved, the produced encoding can be used for rapid optimization of novel, but similar, tasks. The presented techniques not only scale up quality diversity algorithms to high dimensions, but show that black-box optimization encodings can be automatically learned, rather than hand designed.

Hydraulic modeling and energy view (2020)

Steinebach, Gerd ; Kolb, Oliver

Setup of simulation model and calibration (2020)

Steinebach, Gerd ; Dreistadt, David ; Hausmann, Patrick ; Jax, Tim

Abschlussbericht zum BMBF-Fördervorhaben Enabling Infrastructure for HPC-Applications (EI-HPC) (2020)

Berrendorf, Rudolf ; Asteroth, Alexander ; Hinkenjann, André ; Plöger, Paul G. ; Reith, Dirk

Variable Structure Controller for Plastic Injection Moulding System (2020)

Veligorskyi, Oleksandr ; Khomenko, Maksym ; Chakirov, Roustiam ; Vagapov, Yuriy

Semi-Lagrangian lattice Boltzmann method for compressible flows (2020)

Wilde, Dominik ; Krämer, Andreas ; Reith, Dirk ; Foysi, Holger

This work thoroughly investigates a semi-Lagrangian lattice Boltzmann (SLLBM) solver for compressible flows. In contrast to other LBM for compressible flows, the vertices are organized in cells, and interpolation polynomials up to fourth order are used to attain the off-vertex distribution function values. Differing from the recently introduced Particles on Demand (PoD) method , the method operates in a static, non-moving reference frame. Yet the SLLBM in the present formulation grants supersonic flows and exhibits a high degree of Galilean invariance. The SLLBM solver allows for an independent time step size due to the integration along characteristics and for the use of unusual velocity sets, like the D2Q25, which is constructed by the roots of the fifth-order Hermite polynomial. The properties of the present model are shown in diverse example simulations of a two-dimensional Taylor-Green vortex, a Sod shock tube, a two-dimensional Riemann problem and a shock-vortex interaction. It is shown that the cell-based interpolation and the use of Gauss-Lobatto-Chebyshev support points allow for spatially high-order solutions and minimize the mass loss caused by the interpolation. Transformed grids in the shock-vortex interaction show the general applicability to non-uniform grids.

Editorial: tailor-made approaches on use of multiscale modeling for research on soft materials – capabilities, restrictions and future possibilities (2020)

Carbone, Paula ; Faller, Roland ; Qian, Hu-Jun ; Reith, Dirk

AErOmAt Abschlussbericht (2020)

Asteroth, Alexander ; Gaier, Adam ; Hagg, Alexander ; Meng, Jakob ; Priesnitz, Andreas ; Prochnau, Lea ; Reith, Dirk

Das Projekt AErOmAt hatte zum Ziel, neue Methoden zu entwickeln, um einen erheblichen Teil aerodynamischer Simulationen bei rechenaufwändigen Optimierungsdomänen einzusparen. Die Hochschule Bonn-Rhein-Sieg (H-BRS) hat auf diesem Weg einen gesellschaftlich relevanten und gleichzeitig wirtschaftlich verwertbaren Beitrag zur Energieeffizienzforschung geleistet. Das Projekt führte außerdem zu einer schnelleren Integration der neuberufenen Antragsteller in die vorhandenen Forschungsstrukturen.

Elektromobilität im Spiegel der Medien (2020)

Seuser, Katharina ; Viehof, Andreas

The performance of Dunning, Jensen, and Karlsruhe basis sets on computing relative energies and geometries (2020)

Kirschner, Karl N. ; Reith, Dirk ; Heiden, Wolfgang

Determination of relevant mechanical properties for the production process of polyethylene by using mesoscale molecular simulation techniques (2020)

Grommes, Dirk ; Reith, Dirk

Thermal expansion of semi-crystalline polymers: Anisotropic thermal strain and crystallite orientation (2020)

Ramakers-van Dorp, Esther ; Möginger, Bernhard ; Hausnerova, Berenika

Processed-Induced Thermal and Viscoelastic Behavior of Extrusion Blow Molded Parts (2019)

Ramakers-van Dorp, Esther

Process-dependent thermo-mechanical viscoelastic properties and the corresponding morphology of HDPE extrusion blow molded (EBM) parts were investigated. Evaluation of bulk data showed that flow direction, draw ratio, and mold temperature influence the viscoelastic behavior significantly in certain temperature ranges. Flow induced orientations due to higher draw ratio and higher mold temperature lead to higher crystallinities. To determine the local viscoelastic properties, a new microindentation system was developed by merging indentation with dynamic mechanical analysis. The local process-structure-property relationship of EBM parts showed that the cross-sectional temperature distribution is clearly reflected by local crystallinities and local complex moduli. Additionally, a model to calculate three-dimensional anisotropic coefficients of thermal expansion as a function of the process dependent crystallinity was developed based on an elementary volume unit cell with stacked layers of amorphous phase and crystalline lamellae. Good agreement of the predicted thermal expansion coefficients with measured ones was found up to a temperature of 70 °C.

Double Threshold Soft Decision Rule for Improving Performance of Cognitive Radio Networks (2020)

Abdullah, Hikmat N. ; Bakr, Nuha Sh. ; Valenzuela, Alejandro A.

Acceleration of Portland cement with lithium, sodium and potassium silicates and hydroxides (2020)

Witzleben, Steffen Thomas

Local process-dependent structural and mechanical properties of extrusion blow molded high-density polyethylene hollow parts (2020)

Ramakers-van Dorp, Esther ; Eger, Benedikt ; Raschen, Clemens ; Urbanek, Michal ; Möginger, Bernhard ; Hausnerova, Berenika

Low Power Wireless Sensor Node Platform for Agriculture Monitoring in Argentina (2019)

Valenzuela, Alejandro A. ; Schwab, Mauro ; Silnik, Adolfo A. ; Debattista, Alfredo F. ; Kiessling, Roberto A.

We present the development and evaluation of a basic building block for a future wireless sensor network for agriculture monitoring in Argentina. The module consists of a compact battery-powered wireless sensor node capable of monitoring the ambient air parameters of temperature, humidity, gas and air pressure in the agriculture industry of Argentina's Pampa region. Further in-and outputs allow the system to be extended flexibly by adding more sensors. Throughout the development, a simple, low-cost and open-source-based approach together with a lightweight communication protocol was pursued. The sensor nodes cover ranges of over 400 metres and can be operated on two AAA alkaline batteries for several years. Detailed current consumption values, range limits and battery life estimates are presented.

Polysaccharide-Based Systems for Targeted Stem Cell Differentiation and Bone Regeneration (2019)

Witzler, Markus ; Büchner, Dominik ; Shoushrah, Sarah Hani ; Babczyk, Patrick ; Baranova, Juliana ; Witzleben, Steffen ; Tobiasch, Edda ; Schulze, Margit

Bone tissue engineering is an ever-changing, rapidly evolving, and highly interdisciplinary field of study, where scientists try to mimic natural bone structure as closely as possible in order to facilitate bone healing. New insights from cell biology, specifically from mesenchymal stem cell differentiation and signaling, lead to new approaches in bone regeneration. Novel scaffold and drug release materials based on polysaccharides gain increasing attention due to their wide availability and good biocompatibility to be used as hydrogels and/or hybrid components for drug release and tissue engineering. This article reviews the current state of the art, recent developments, and future perspectives in polysaccharide-based systems used for bone regeneration.

Probabilistic Performance Profiling (2020)

Asteroth, Alexander ; Ludwig, Melanie ; Bach, Kevin

Including the Past: Performance Modeling Using a Preload Concept by Means of the Fitness-Fatigue Model (2019)

Ludwig, Melanie ; Asteroth, Alexander ; Rasche, Christian ; Pfeiffer, Mark

In mathematical modeling by means of performance models, the Fitness-Fatigue Model (FF-Model) is a common approach in sport and exercise science to study the training performance relationship. The FF-Model uses an initial basic level of performance and two antagonistic terms (for fitness and fatigue). By model calibration, parameters are adapted to the subject’s individual physical response to training load. Although the simulation of the recorded training data in most cases shows useful results when the model is calibrated and all parameters are adjusted, this method has two major difficulties. First, a fitted value as basic performance will usually be too high. Second, without modification, the model cannot be simply used for prediction. By rewriting the FF-Model such that effects of former training history can be analyzed separately – we call those terms preload – it is possible to close the gap between a more realistic initial performance level and an athlete's actual performance level without distorting other model parameters and increase model accuracy substantially. Fitting error of the preload-extended FF-Model is less than 32% compared to the error of the FF-Model without preloads. Prediction error of the preload-extended FF-Model is around 54% of the error of the FF-Model without preloads.

An ANN-Based Temperature Controller for a Plastic Injection Moulding System (2019)

Khomenko, Maksym ; Veligorskyi, Oleksandr ; Chakirov, Roustiam ; Vagapov, Yuriy

This paper proposes an approach to an ANN-based temperature controller design for a plastic injection moulding system. This design approach is applied to the development of a controller based on a combination of a classical ANN and integrator. The controller provides a fast temperature response and zero steady-state error for three typical heaters (bar, nozzle, and cartridge) for a plastic moulding system. The simulation results in Matlab Simulink software and in comparison to an industrial PID regulator have shown the advantages of the controller, such as significantly less overshoot and faster transient (compared to PID with autotuning) for all examined heaters. In order to verify the proposed approach, the designed ANN controller was implemented and tested using an experimental setup based on an STM32 board.

Synthesis of Substituted Hydroxyapatite for Application in Bone Tissue Engineering and Drug Delivery (2019)

Büchner, D. ; Gericke, M. ; Heinze, T. ; Tobiasch, E. ; Witzleben, S. ; Schulze, M.

Model Reduction in the Design of Alkaline Methanol Fuel Cells (2019)

Clees, Tanja ; Klaassen, Bernhard ; Nikitin, Igor ; Nikitina, Lialia ; Pott, Sabine ; Krewer, Ulrike ; Haisch, Theresa

Topological Reduction of Gas Transport Networks (2019)

Baldin, Anton ; Clees, Tanja ; Fuchs, Barbara ; Klaassen, Bernhard ; Nikitin, Igor ; Nikitina, Lialia ; Torgovitskaia, Inna

The paper presents the topological reduction method applied to gas transport networks, using contraction of series, parallel and tree-like subgraphs. The contraction operations are implemented for pipe elements, described by quadratic friction law. This allows significant reduction of the graphs and acceleration of solution procedure for stationary network problems. The algorithm has been tested on several realistic network examples. The possible extensions of the method to different friction laws and other elements are discussed.

Development and Evaluation of a Prototype Scratch Apparatus for Wound Assays Adjustable to Different Forces and Substrates (2019)

Grimmig, Roman ; Babczyk, Patrick ; Gillemot, Philipp ; Schmitz, Klaus-Peter ; Schulze, Margit ; Tobiasch, Edda

Scratch assays enable the study of the migration process of an injured adherent cell layer in vitro. An apparatus for the reproducible performance of scratch assays and cell harvesting has been developed that meets the requirements for reproducibility in tests as well as easy handling. The entirely autoclavable setup is divided into a sample translation and a scratching system. The translational system is compatible with standard culture dishes and can be modified to adapt to different cell culture systems, while the scratching system can be adjusted according to angle, normal force, shape, and material to adapt to specific questions and demanding substrates. As a result, a fully functional prototype can be presented. This system enables the creation of reproducible and clear scratch edges with a low scratch border roughness within a monolayer of cells. Moreover, the apparatus allows the collection of the migrated cells after scratching for further molecular biological investigations without the need for a second processing step. For comparison, the mechanical properties of manually performed scratch assays are evaluated.

Molecular Dynamics in the Energy Sector: Experiment and Modeling of the CO2/CH4 Mixture (2020)

Schenk, Martin R. ; Köddermann, Thorsten ; Kirschner, Karl N. ; Knauer, Sandra ; Reith, Dirk

Mathematical Modeling of Alkaline Methanol Oxidation for Design of Efficient Fuel Cells (2020)

Clees, Tanja ; Nikitin, Igor ; Nikitina, Lialia ; Pott, Sabine ; Krewer, Ulrike ; Haisch, Theresa

Impact of atmospheric aerosols on solar power (2019)

Neher, Ina ; Buchmann, Tina ; Crewell, Susanne ; Pospichal, Bernhard ; Meilinger, Stefanie

Atmospheric aerosols affect the power production of solar energy systems. Their impact depends on both the atmospheric conditions and the solar technology employed. By being a region with a lack in power production and prone to high solar insolation, West Africa shows high potential for the application of solar power systems. However, dust outbreaks, containing high aerosol loads, occur especially in the Sahel, located between the Saharan desert in the north and the Sudanian Savanna in the south. They might affect the whole region for several days with significant effects on power generation. This study investigates the impact of atmospheric aerosols on solar energy production for the example year 2006 making use of six well instrumented sites in West Africa. Two different solar power technologies, a photovoltaic (PV) and a parabolic through (PT) power plant, are considered. The daily reduction of solar power due to aerosols is determined over mostly clear-sky days in 2006 with a model chain combining radiative transfer and technology specific power generation. For mostly clear days the local daily reduction of PV power (at alternating current) (PVAC) and PT power (PTP) due to the presence of aerosols lies between 13 % and 22 % and between 22 % and 37 %, respectively. In March 2006 a major dust outbreak occurred, which serves as an example to investigate the impact of an aerosol extreme event on solar power. During the dust outbreak, daily reduction of PVAC and PTP of up to 79 % and 100 % occur with a mean reduction of 20 % to 40 % for PVAC and of 32 % to 71 % for PTP during the 12 days of the event.

Pseudoentropic derivation of the regularized lattice Boltzmann method (2019)

Krämer, Andreas ; Wilde, Dominik ; Küllmer, Knut ; Reith, Dirk ; Foysi, Holger

Seaweed polysaccharide based materials: From chemical derivatization to functional composite hydrogels and advanced applications (2019)

Gericke, Martin ; Witzler, Markus ; Büchner, Dominik ; Enkelmann, Astrid ; Ottensmeyer, Patrick ; Schneider, Gerlind ; Tobiasch, Edda ; Schulze, Margit ; Heinze, Thomas

Ressourcenoptimierte Bauteilentwicklung durch systematische Verzahnung von Experiment und multiskaligen Simulationsansätzen, Akronym: ReBauVES (2018)

Reith, Dirk ; Geilen, Johannes ; Joppich, Wolfgang ; Bruch, Olaf ; Möginger, Bernhard ; Ramakers-van Dorp, Esther ; Grommes, Dirk ; Michels, Patrick ; Schirrmeister, Christopher

TREE Jahresbericht 2018 (2019)

Pseudopotentialbasierte Lattice-Boltzmann-Verfahren für Mehrphasenströmungen (2019)

Küllmer, Knut

Pseudopotential (PP)-basierte Lattice-Boltzmann-Methoden werden zunehmend für die Simulation von Mehrphasenströmungen eingesetzt. Da sie auf einem phänomenologischen Ansatz basieren, ist ihr Einsatz mit einem hohen Modellierungsaufwand verbunden. Zudem entstehen an den Phasengrenzen sogenannte Scheingeschwindigkeiten, welche Genauigkeit und numerische Stabilität beeinträchtigen. Daher werden PP-Modelle in dieser Arbeit um drei neue Aspekte erweitert. Erstens wird gezeigt, dass bei der Modellierung unterschiedlicher Kontaktwinkel mit gängigen Methoden in Kombination mit verbesserten Kräfteschemata Scheintröpfchen entstehen. Diese werden durch einen neuartigen Ansatz eliminiert, der auf zusätzlichen Randbedingungen für alle Wechselwirkungskräfte basiert. Diese Technik verhindert nicht nur das Auftreten der Scheintröpfchen, sondern erhöht auch die Stabilität in wandgebundenen Strömungen. Zweitens wird ein neuartiges Verfahren zur Reduktion von Scheingeschwindigkeiten eingeführt. Dabei wird die Diskretisierung der Interaktionskräfte erweitert und die zusätzlichen, freien Koeffizienten in Simulationen statischer Tropfen numerisch optimiert. Die resultierende Diskretisierung wurde in Simulationen stationärer und dynamischer Testfälle validiert, wobei Scheingeschwindigkeiten deutlich reduziert werden konnten. Drittens und letztens wurden die Diffusionseigenschaften in Mehrstoffsystemen detailliert untersucht, wobei eine kritische Abhängigkeit zwischen den makroskopischen Diffusionskoeffizienten und dem Kräfteschema aufgezeigt wird. Diese Analyse bildet die Grundlage für den Vergleich und die zukünftige Entwicklung neuer Potentialfunktionen (für Mehrstoffsysteme) und reduziert den Modellierungsaufwand.

Antimicrobial Activity of Lignin-Derived Polyurethane Coatings Prepared from Unmodified and Demethylated Lignins (2019)

Klein, Stephanie Elisabeth ; Alzagameem, Abla ; Rumpf, Jessica ; Korte, Imke ; Kreyenschmidt, Judith ; Schulze, Margit

Due to global ecological and economic challenges that have been correlated to the transition from fossil-based to renewable resources, fundamental studies are being performed worldwide to replace fossil fuel raw materials in plastic production. One aspect of current research is the development of lignin-derived polyols to substitute expensive fossil-based polyol components for polyurethane and polyester production. This article describes the synthesis of bioactive lignin-based polyurethane coatings using unmodified and demethylated Kraft lignins. Demethylation was performed to enhance the reaction selectivity toward polyurethane formation. The antimicrobial activity was tested according to a slightly modified standard test (JIS Z 2801:2010). Besides effects caused by the lignins themselves, triphenylmethane derivatives (brilliant green and crystal violet) were used as additional antimicrobial substances. Results showed increased antimicrobial capacity against Staphylococcus aureus. Furthermore, the coating color could be varied from dark brown to green and blue, respectively.

Investigations into the influence of chemical activators and templates on cement hydration (2019)

Witzleben, Steffen

Non-Cytotoxic Agarose/Hydroxyapatite Composite Scaffolds for Drug Release (2019)

Witzler, Markus ; Ottensmeyer, Patrick Frank ; Gericke, Martin ; Heinze, Thomas ; Tobiasch, Edda ; Schulze, Margit

Healing of large bone defects requires implants or scaffolds that provide structural guidance for cell growth, differentiation, and vascularization. In the present work, an agarose-hydroxyapatite composite scaffold was developed that acts not only as a 3D matrix, but also as a release system. Hydroxyapatite (HA) was incorporated into the agarose gels in situ in various ratios by a simple procedure consisting of precipitation, cooling, washing, and drying. The resulting gels were characterized regarding composition, porosity, mechanical properties, and biocompatibility. A pure phase of carbonated HA was identified in the scaffolds, which had pore sizes of up to several hundred micrometers. Mechanical testing revealed elastic moduli of up to 2.8 MPa for lyophilized composites. MTT testing on Lw35human mesenchymal stem cells (hMSCs) and osteosarcoma MG-63 cells proved the biocompatibility of the scaffolds. Furthermore, scaffolds were loaded with model drug compounds for guided hMSC differentiation. Different release kinetic models were evaluated for adenosine 5′-triphosphate (ATP) and suramin, and data showed a sustained release behavior over four days.

Are quality diversity algorithms better at generating stepping stones than objective-based search? (2019)

Gaier, Adam ; Asteroth, Alexander ; Mouret, Jean-Baptiste

The route to the solution of complex design problems often lies through intermediate "stepping stones" which bear little resemblance to the final solution. By greedily following the path of greatest fitness improvement, objective-based search overlooks and discards stepping stones which might be critical to solving the problem. Here, we hypothesize that Quality Diversity (QD) algorithms are a better way to generate stepping stones than objective-based search: by maintaining a large set of solutions which are of high-quality, but phenotypically different, these algorithms collect promising stepping stones while protecting them in their own "ecological niche". To demonstrate the capabilities of QD we revisit the challenge of recreating images produced by user-driven evolution, a classic challenge which spurred work in novelty search and illustrated the limits of objective-based search. We show that QD far outperforms objective-based search in matching user-evolved images. Further, our results suggest some intriguing possibilities for leveraging the diversity of solutions created by QD.

Prediction of neural network performance by phenotypic modeling (2019)

Hagg, Alexander ; Zaefferer, Martin ; Stork, Jörg ; Gaier, Adam

Surrogate models are used to reduce the burden of expensive-to-evaluate objective functions in optimization. By creating models which map genomes to objective values, these models can estimate the performance of unknown inputs, and so be used in place of expensive objective functions. Evolutionary techniques such as genetic programming or neuroevolution commonly alter the structure of the genome itself. A lack of consistency in the genotype is a fatal blow to data-driven modeling techniques: interpolation between points is impossible without a common input space. However, while the dimensionality of genotypes may differ across individuals, in many domains, such as controllers or classifiers, the dimensionality of the input and output remains constant. In this work we leverage this insight to embed differing neural networks into the same input space. To judge the difference between the behavior of two neural networks, we give them both the same input sequence, and examine the difference in output. This difference, the phenotypic distance, can then be used to situate these networks into a common input space, allowing us to produce surrogate models which can predict the performance of neural networks regardless of topology. In a robotic navigation task, we show that models trained using this phenotypic embedding perform as well or better as those trained on the weight values of a fixed topology neural network. We establish such phenotypic surrogate models as a promising and flexible approach which enables surrogate modeling even for representations that undergo structural changes.

Artificial Neural Network Motor Control for Full-Electric Injection Moulding Machine (2019)

Veligorskyi, Oleksandr ; Chakirov, Roustiam ; Khomenko, Maksym ; Vagapov, Yuriy

This paper proposes a new artificial neural network-based position controller for a full-electric injection moulding machine. Such a controller improves the dynamic characteristics of the positioning for hot runners, pin valve and the injection motors for varying moulding parameters. Practical experimental data and Matlab’s System Identification Toolbox have been used to identify the transfer functions of the motors. The structure of the artificial neural network, which used positioning error and speed of error, was obtained by numerical modelling in Matlab/Simulink. The artificial neural network was trained using back-propagation algorithms to provide control of the motor current thus ensuring the required position and velocity. The efficiency of the proposed ANN-based controller has been estimated and verified in Simulink using real velocity data and the position of the injection moulding machine and pin valve motors.

An integrative simulation concept for extrusion blow molded plastic bottles (2019)

Michels, Patrick ; Grommes, Dirk ; Oeckerath, Andre ; Reith, Dirk ; Bruch, Olaf

TiGL: An Open Source Computational Geometry Library for Parametric Aircraft Design (2019)

Siggel, Martin ; Kleinert, Jan ; Stollenwerk, Tobias ; Maierl, Reinhold

Autonomous Track and Follow UAV for Aerodynamic Analysis of Vehicles (2019)

Drak, Ahmad ; Asteroth, Alexander

This work addresses the issue of finding an optimal flight zone for a side-by-side tracking and following Unmanned Aerial Vehicle(UAV) adhering to space-restricting factors brought upon by a dynamic Vector Field Extraction (VFE) algorithm. The VFE algorithm demands a relatively perpendicular field of view of the UAV to the tracked vehicle, thereby enforcing the space-restricting factors which are distance, angle and altitude. The objective of the UAV is to perform side-by-side tracking and following of a lightweight ground vehicle while acquiring high quality video of tufts attached to the side of the tracked vehicle. The recorded video is supplied to the VFE algorithm that produces the positions and deformations of the tufts over time as they interact with the surrounding air, resulting in an airflow model of the tracked vehicle. The present limitations of wind tunnel tests and computational fluid dynamics simulation suggest the use of a UAV for real world evaluation of the aerodynamic properties of the vehicle’s exterior. The novelty of the proposed approach is alluded to defining the specific flight zone restricting factors while adhering to the VFE algorithm, where as a result we were capable of formalizing a locally-static and a globally-dynamic geofence attached to the tracked vehicle and enclosing the UAV.

Modeling User Selection in Quality Diversity (2019)

Hagg, Alexander ; Asteroth, Alexander ; Bäck, Thomas

The initial phase in real world engineering optimization and design is a process of discovery in which not all requirements can be made in advance, or are hard to formalize. Quality diversity algorithms, which produce a variety of high performing solutions, provide a unique chance to support engineers and designers in the search for what is possible and high performing. In this work we begin to answer the question how a user can interact with quality diversity and turn it into an interactive innovation aid. By modeling a user's selection it can be determined whether the optimization is drifting away from the user's preferences. The optimization is then constrained by adding a penalty to the objective function. We present an interactive quality diversity algorithm that can take into account the user's selection. The approach is evaluated in a new multimodal optimization benchmark that allows various optimization tasks to be performed. The user selection drift of the approach is compared to a state of the art alternative on both a planning and a neuroevolution control task, thereby showing its limits and possibilities.

Sustainable Extraction and Characterisation of Bioactive Compounds from Horse Chestnut Seed Coats for the Development of Bio-Based Additives (2019)

Havelt, Thomas ; Brettschneider, Sarah ; Do, Xuan Tung ; Korte, Imke ; Kreyenschmidt, Judith ; Schmitz, Michaela

Background: To protect renewable packaging materials against autoxidation and decomposition when substituting harmful synthetic stabilizers with bioactive and bio-based compounds, extracts from Aesculus hippocastanum L. seeds were evaluated. The study objectives were to determine the antioxidant efficacy of bioactive compounds in horse chestnut seeds with regard to different seed fractions, improve their extraction, and to evaluate waste reuse. Methods: Different extraction techniques for field samples were evaluated and compared with extracts of industrial waste samples based on total phenolic content and total antioxidant capacity (2,2’-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS)). The molecular weight distribution and absorbance in ultraviolet range (UV) of seed coat extracts were determined, and the possibility of extracts containing proanthocyanidins was examined. Results: Seed coat extracts show a remarkable antioxidant activity and a high UV absorbance. Passive extractions are efficient and much less laborious. Applying waste product seed coats leads to a reduced antioxidant activity, total phenolic content, and UV absorbance compared to the field sample counterparts. In contrast to peeled seed extracts, all seed coat extracts contain proanthocyanidins. Discussion: Seed coats are a potential source of bioactive compounds, particularly regarding sustainable production and waste reuse. With minimum effort, highly bioactive extracts with high potential as additives can be prepared.

ACPYPE update for nonuniform 1–4 scale factors: Conversion of the GLYCAM06 force field from AMBER to GROMACS (2019)

Bernardi, Austen ; Faller, Roland ; Reith, Dirk ; Kirschner, Karl N.

Herein we report an update to ACPYPE, a Python3 tool that now properly converts AMBER to GROMACS topologies for force fields that utilize nondefault and nonuniform 1–4 electrostatic and nonbonded scaling factors or negative dihedral force constants. Prior to this work, ACPYPE only converted AMBER topologies that used uniform, default 1–4 scaling factors and positive dihedral force constants. We demonstrate that the updated ACPYPE accurately transfers the GLYCAM06 force field from AMBER to GROMACS topology files, which employs non-uniform 1–4 scaling factors as well as negative dihedral force constants. Validation was performed using β-d-GlcNAc through gas-phase analysis of dihedral energy curves and probability density functions. The updated ACPYPE retains all of its original functionality, but now allows the simulation of complex glycomolecular systems in GROMACS using AMBER-originated force fields. ACPYPE is available for download at https://github.com/alanwilter/acpype.

Modellbildung-und-Simulation: Online Lehrbuch (2019)

Kleinert, Jan ; Reith, Dirk ; Steinebach, Gerd

Version 0.1.1 -02/09/2019 Add changelog Version 0.1 -/02/2019 Initial release

Low-Input Crops as Lignocellulosic Feedstock for Second-Generation Biorefineries and the Potential of Chemometrics in Biomass Quality Control (2019)

Alzagameem, Abla ; Bergs, Michel ; Do, Xuan Tung ; Klein, Stephanie Elisabeth ; Rumpf, Jessica ; Larkins, Michael ; Monakhova, Yulia ; Pude, Ralf ; Schulze, Margit

Lignocellulose feedstock (LCF) provides a sustainable source of components to produce bioenergy, biofuel, and novel biomaterials. Besides hard and soft wood, so-called low-input plants such as Miscanthus are interesting crops to be investigated as potential feedstock for the second generation biorefinery. The status quo regarding the availability and composition of different plants, including grasses and fast-growing trees (i.e., Miscanthus, Paulownia), is reviewed here. The second focus of this review is the potential of multivariate data processing to be used for biomass analysis and quality control. Experimental data obtained by spectroscopic methods, such as nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR), can be processed using computational techniques to characterize the 3D structure and energetic properties of the feedstock building blocks, including complex linkages. Here, we provide a brief summary of recently reported experimental data for structural analysis of LCF biomasses, and give our perspectives on the role of chemometrics in understanding and elucidating on LCF composition and lignin 3D structure.

The International Chair - Concept and Benefits of a New Interdisciplinary Faculty Position (2019)

Kirschner, Karl ; Bode, Jürgen ; Reith, Dirk

In this contribution we present the concept for creating an “International Chair” position at a German University of Applied Sciences and our experiences in its first implementation. Our primary goal was to increase the diversity of the university’s teaching personalities and enrich student education by including content, methods, examples and experiences from other cultures. This gives students an international and intercultural learning experience that is otherwise only acquired through studying abroad. We conclude that the International Chair is a valuable and powerful university tool for increasing international exposure to the departments, their staff and students.

Developing Health Technology Innovators: A Collaborative Learning Approach (2019)

Agterbos, Marieke ; Aldershoff, Frank ; Cawley, Oisin ; Jung, Norbert ; Kehoe, Joseph ; Klok, Eric ; Kunz, Andreas ; Nilsen, Jan Harald ; Jost, Patrick ; Rothe, Irene ; Sandstrak, Grethe ; Skar, Reidun ; Weidman, Karl-Heinz

Development of an Advanced Dynamic Microindentation System to Determine Local Viscoelastic Properties of Polymers (2019)

Ramakers-van Dorp, Esther ; Haenel, Thomas ; Ciongwa, Dominik ; Möginger, Bernhard ; Hausnerova, Berenika

This study presents a microindentation system which allows spatially resolved local as well as bulk viscoelastic material information to be obtained within one instrument. The microindentation method was merged with dynamic mechanical analysis (DMA) for a tungsten cone indenter. Three tungsten cone indenters were investigated: tungsten electrode, tungsten electrode + 2% lanthanum, and tungsten electrode + rare earth elements. Only the tungsten electrode + 2% lanthanum indenter showed the sinusoidal response, and its geometry remained unaffected by the repeated indentations. Complex moduli obtained from dynamic microindentation for high-density polyethylene, polybutylene terephthalate, polycarbonate, and thermoplastic polyurethane are in agreement with the literature. Additionally, by implementing a specially developed x-y-stage, this study showed that dynamic microindentation with a tungsten cone indenter was an adequate method to determine spatially resolved local viscoelastic surface properties.

Process-dependent structural and deformation properties of extrusion blow molding parts (2019)

Ramakers-van Dorp, Esther ; Blume, Christian ; Haedecke, Tobias ; Pata, Vladimir ; Reith, Dirk ; Bruch, Olaf ; Möginger, Bernhard ; Hausnerova, Berenika

Deeper Theoretical Understanding by Means of Practical Experience in Electric and Electronic Circuits for Freshmen (2019)

Groß, Ingo ; Reith, Dirk ; Grein, Martina ; Groß, Iris

A traditional way to teach bachelor students in electrical engineering is organized such that theoretical knowledge is predominant in the first year while applications and practical experiences are reserved for later stages of their education. In this contribution, we want to introduce a reverse approach: In a freshmen course at Bonn-Rhein-Sieg University of Applied Science, students gain hands-on experience with resistances, condensers and other active parts, like transistors or relays from the very first day. We present how the combination of practical experience directly linked with theoretical knowledge enhances students' learning. It promotes deeper understanding of the theory and a better transfer between theory and practice. This teaching approach is adapted to address two main goals: First, to give practical experience to first-semester students as a basis for further laboratory and working situations. Second, to create a deeper and more sustainable understanding of physics by directly observing the effects that are described in formulas. The key to success is to find an efficient solution to carry out this approach with the given spatial and financial resources-which means, to do it in the lecture hall with very few material resources. To show that this innovative teaching concept really enhances the competencies of the students, an innovative evaluation approach was used where the students have to reflect upon their competencies before and after the course.

A Convolution Model for Prediction of Physiological Responses to Physical Exercises (2019)

Ludwig, Melanie ; Grohganz, Harald G. ; Asteroth, Alexander

An analytical convolution-based model is used to predict a person’s physiological reaction to strain. Heart rate, oxygen uptake, and carbon dioxide output serve as physiological measures. Cycling ergometer tests of five male subjects are used to compare the proposed Convolution Model with a machine learning approach in form of a black box Wiener model. In these experiments, the Convolution Model yields smaller errors in prediction for all considered physiological measures. It performs very similar to other analytical models, but is based on only four parameters in its original form. A parameter reduction to one single degree of freedom is shown with comparable prediction accuracy and without significant loss of fitting accuracy.

Antioxidant activity of unmodified kraft and organosolv lignins to be used as sustainable components for polyurethane coatings (2019)

Klein, Stephanie E. ; Rumpf, Jessica ; Alzagameem, Abla ; Rehahn, Matthias ; Schulze, Margit

Interactions of Water and Alkanes: Modifying Additive Force Fields to Account for Polarization Effects (2019)

Krämer, Andreas ; Pickard, Frank C. ; Huang, Jing ; Venable, Richard M. ; Simmonett, Andrew C. ; Reith, Dirk ; Kirschner, Karl N. ; Pastor, Richard W. ; Brooks, Bernard R.

Antimicrobial Activity of Lignin and Lignin-Derived Cellulose and Chitosan Composites Against Selected Pathogenic and Spoilage Microorganisms (2019)

Alzagameem, Abla ; Klein, Stephanie Elisabeth ; Bergs, Michel ; Do, Xuan Tung ; Korte, Imke ; Dohlen, Sophia ; Hüwe, Carina ; Kreyenschmidt, Judith ; Kamm, Birgit ; Larkins, Michael ; Schulze, Margit

The antiradical and antimicrobial activity of lignin and lignin-based films are both of great interest for applications such as food packaging additives. The polyphenolic structure of lignin in addition to the presence of O-containing functional groups is potentially responsible for these activities. This study used DPPH assays to discuss the antiradical activity of HPMC/lignin and HPMC/lignin/chitosan films. The scavenging activity (SA) of both binary (HPMC/lignin) and ternary (HPMC/lignin/chitosan) systems was affected by the percentage of the added lignin: the 5% addition showed the highest activity and the 30% addition had the lowest. Both scavenging activity and antimicrobial activity are dependent on the biomass source showing the following trend: organosolv of softwood > kraft of softwood > organosolv of grass. Testing the antimicrobial activities of lignins and lignin-containing films showed high antimicrobial activities against Gram-positive and Gram-negative bacteria at 35 °C and at low temperatures (0-7 °C). Purification of kraft lignin has a negative effect on the antimicrobial activity while storage has positive effect. The lignin release in the produced films affected the activity positively and the chitosan addition enhances the activity even more for both Gram-positive and Gram-negative bacteria. Testing the films against spoilage bacteria that grow at low temperatures revealed the activity of the 30% addition on HPMC/L1 film against both B. thermosphacta and P. fluorescens while L5 was active only against B. thermosphacta. In HPMC/lignin/chitosan films, the 5% addition exhibited activity against both B. thermosphacta and P. fluorescens.

Towards Finding an Optimal Flight Zone for a Side-by-Side Tracking UAV w.r.t Extraction of Dynamic Vector Fields (2019)

Drak, Ahmad ; Asteroth, Alexander

Hochschuldidaktik - Reden über Verantwortung (2019)

Groß, Iris ; Lehmann, Klaus

Effects of Silicon Compounds on Biomineralization, Osteogenesis, and Hard Tissue Formation (2019)

Götz, Werner ; Tobiasch, Edda ; Witzleben, Steffen ; Schulze, Margit

Bioinspired stem cell-based hard tissue engineering includes numerous aspects: The synthesis and fabrication of appropriate scaffold materials, their analytical characterization, and guided osteogenesis using the sustained release of osteoinducing and/or osteoconducting drugs for mesenchymal stem cell differentiation, growth, and proliferation. Here, the effect of silicon- and silicate-containing materials on osteogenesis at the molecular level has been a particular focus within the last decade. This review summarizes recently published scientific results, including material developments and analysis, with a special focus on silicon hybrid bone composites. First, the sources, bioavailability, and functions of silicon on various tissues are discussed. The second focus is on the effects of calcium-silicate biomineralization and corresponding analytical methods in investigating osteogenesis and bone formation. Finally, recent developments in the manufacturing of Si-containing scaffolds are discussed, including in vitro and in vivo studies, as well as recently filed patents that focus on the influence of silicon on hard tissue formation.

Identifizierung und Charakterisierung bioaktiver Inhaltsstoffe in Thymian (2018)

Havelt, Thomas ; Schmitz, Michaela

Bei Thymian (Thymus vulgaris) handelt es sich um eine sehr varietätenreiche Art, die aufgrund ihres Gehaltes an therapeutisch wirksamen Inhaltsstoffen als Arzneipflanze monographiert ist. Insbesondere das ätherische Öl mit dem Hauptbestandteil Thymol (ca. 50%) hat eine hohe antioxidative Wirkung. Ziel ist es, dieses Potential als nachhaltig produzierte Additive zu nutzen. Hierfür eignen sich antioxidativ bzw. antimikrobiell wirksame sowie UV-absorbierende Substanzen, die das Produkt bei Zusatz vor oxidativem Stress, mikrobiellem Abbau und Qualitätsverlust schützen. Hierzu werden zunächst sechs Varianten auf verschiedene Parameter analysiert, um die potenteste Variante auszuwählen. Auf diese Variante wird sich die weitere Forschung konzentrieren. Daher wird das ätherische Öl durch azeotrope Destillation extrahiert und mittels GCMS analysiert. In Extrakten werden zudem das AP und Absorptionsverhalten bestimmt. Auch die chemische Zusammensetzung des Extrakts sowie die flüchtigen Stoffe des Thymians werden untersucht. Generell gibt es wenig qualitative, teilweise jedoch quantitative Unterschiede: Eine Variante weist u.a. einen deutlich höheren Thymolgehalt im Öl (ca. 65 %) und ein hohes hydrophiles AP auf. Somit ist eine vielversprechende Variante für die weitere Entwicklung und Optimierung bioaktiver Additive gefunden.

An Approach to Assessing Learning Outcomes over Consecutive Courses (2019)

Rothe, Irene ; Winzker, Marco ; Salega, Cathleen

Miscanthus x giganteus Stem Versus Leaf-Derived Lignins Differing in Monolignol Ratio and Linkage (2019)

Bergs, Michel ; Völkering, Georg ; Kraska, Thorsten ; Pude, Ralf ; Do, Xuan Tung ; Kusch, Peter ; Monakhova, Yulia ; Konow, Christopher ; Schulze, Margit

As a renewable, Miscanthus offers numerous advantages such as high photosynthesis activity (as a C4 plant) and an exceptional CO2 fixation rate. These properties make Miscanthus very attractive for industrial exploitation, such as lignin generation. In this paper, we present a systematic study analyzing the correlation of the lignin structure with the Miscanthus genotype and plant portion (stem versus leaf). Specifically, the ratio of the three monolignols and corresponding building blocks as well as the linkages formed between the units have been studied. The lignin amount has been determined for M. x giganteus (Gig17, Gig34, Gig35), M. nagara (NagG10), M. sinensis (Sin2), and M. robustus (Rob4) harvested at different time points (September, December, and April). The influence of the Miscanthus genotype and plant component (leaf vs. stem) has been studied to develop corresponding structure-property relationships (i.e., correlations in molecular weight, polydispersity, and decomposition temperature). Lignin isolation was performed using non-catalyzed organosolv pulping and the structure analysis includes compositional analysis, Fourier transform infradred (FTIR), ultraviolet/visible (UV-Vis), hetero-nuclear single quantum correlation nuclear magnetic resonsnce (HSQC-NMR), thermogravimetric analysis (TGA), and pyrolysis gaschromatography/mass spectrometry (GC/MS). Structural differences were found for stem and leaf-derived lignins. Compared to beech wood lignins, Miscanthus lignins possess lower molecular weight and narrow polydispersities (<1.5 Miscanthus vs. >2.5 beech) corresponding to improved homogeneity. In addition to conventional univariate analysis of FTIR spectra, multivariate chemometrics revealed distinct differences for aromatic in-plane deformations of stem versus leaf-derived lignins. These results emphasize the potential of Miscanthus as a low-input resource and a Miscanthus-derived lignin as promising agricultural feedstock.

Kommunikation, Beteiligung und Naturschutz als Einflussfaktoren auf die Akzeptanz von Windenergieanlagen (2018)

Seuser, Katharina ; Koch, Wolfgang ; Ockenga, Julia ; Müller, Robert

Functional polysaccharide hydrogels through chemical derivatization of agarose (2017)

Gericke, Martin ; Witzler, Markus ; Schulze, Margit ; Heinze, Thomas

Möglichkeiten und Grenzen der Baustoffanalytik und anwendungstechnische Prüfungen an Objekten (2018)

Witzleben, Steffen

Untersuchungen zum Einfluss von chemischen Aktivatoren und Templaten auf die Zementhydratation (2018)

Witzleben, S. T. ; Leiendecker, A. ; Thelen, M.

Lignin-Depolymerisation via UV-Photolyse und Titandioxid-Photokatalyse (2017)

Schulze, M. ; Witzleben, S. ; Nietsch, A. ; Jung, C. ; Do, X. T.

Novel Hydroxyapatite/Agarose Composites for Bone Tissue Engineering and Drug Delivery (2017)

Schulze, M. ; Ottensmeyer, P. ; Witzleben, S. ; Tobiasch, E. ; Gericke, M. ; Heinze, T. ; Witzler, M.

Synthese von Lignin-basierten flexiblen, hydrophoben Polyurethan-Beschichtungen (2017)

Schulze, M. ; Rumpf, J. ; Rehahn, M. ; Klein, S. E. ; Witzleben, S.

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