Open-Access-Journals @ Otto-von-Guericke-Universität Magdeburg
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Autoregressive neural networks for predicting the behavior of viscoelastic materials
No full textIn the present work, the capabilities of neural networks to describe viscoelastic material behavior are investigated. Using real one-dimensional test data from a tensile test, autoregressive neural networks were trained. The best networks were then used to calculate the stress and the stiffness in displacement- and force-driven simulations. The results were compared with both experimental data and simulation results of a classical material model.The viscoelasticity discussed here plays a special role in the description of complex rubber materials, in addition to long-term effects, failure or heat-induced mechanisms. Classical material models simplify the real behavior, which is the reason for the occurrence of simulation errors. To overcome these limitations, this paper presents a different way of material modeling by describing the strain-stress correlation using a neural network. Previous stress states from the time history are used in the calculation to account for the path-dependent behavior of viscoelastic materials. Other effects, such as the influence of different temperatures, are not addressed in this work, but can be included with an appropriately large training data set
Sustainability of Housing in Times of Crisis
No full textDer Artikel skizziert Nachhaltigkeit als Herausforderung der Wohnungspolitik im weiteren Sinne, welche auch die Wohnraumversorgung aus vergleichender Perspektive beinhaltet. Er nimmt Überlegungen auf, wie sich die Wohnungspolitik aufgrund aktueller Krisenphänomene (Corona-Pandemie und Krieg in der Ukraine) zukünftig entwickeln könnte.The article sketches the challenges of sustainability for housing policy in a broader perspective including housing provision from a comparative perspective. It also sheds light on how considera-tions about housing policy may have been changed due to the ongoing crises (the COVID pan-demic and the war in the Ukraine)
LES of a non-premixed hydrogen flame stabilized by bluff-bodies of various shapes
No full textDynamics of flames stabilized downstream of different shape bluff-bodies (cylindrical, square, star) with different wall topologies (flat, wavy) is investigated using large-eddy simulations (LES). A two-stage computational procedure involving the ANSYS software and an in-house academic high-order code is combined to model a flow in the vicinity of the bluff-bodies and a flame formed downstream. The fuel is nitrogen-diluted hydrogen and the oxidizer is hot air in which the fuel auto-ignites. After the ignition, the flame propagates towards the bluff-body surfaces and stabilizes in their vicinity. It is shown that the flames reflect the bluff-body shape due to large-scale strong vortices induced in the shear layer formed between the main recirculation zone and the oxidizer stream. The influence of the acute corners of the bluff-bodies on the flame dynamics is quantified by analysing instantaneous and time-averaged results. Compared to the classical conical bluff-body the largest differences in the temperature and velocity distributions are observed in the configuration with the square bluff-body. The main recirculation zone is shortened by approximately 15% and at its end temperature in the axis of the flame is almost 200~K larger. Simultaneously, their fluctuations are slightly larger than in the remaining cases. The influence of the wall topology (flat vs. wavy) in the configuration with the classical conical bluff-body turned out to be very small and it resulted in modifications of the flow and flame structures only in the direct vicinity of the bluff-body surface
Langevin Dynamics Prediction of the Effect of Shear Rate on Polymer-Induced Flocculation
No full textA novel potential-based model for resolving polymer-particle interaction in flows is presented and used to study theeffect of shear rate on the adsorption dynamics of polymer chains onto a stationary spherical particle surface. The polymeric phase is modelled as a sequence of bead-spring components using Langevin dynamics with the finite extensible nonlinear elastic (FENE) potential to represent the molecular interactions within the polymer chain. The effects of steric interactions and the Kratky-Porod bending rigidity potential are also included in the calculations. Particles are modelled as rigid computational spheres which interact sterically with the polymer beads through a modified, truncated Lennard-Jones potential. Dependencies of conformation properties such as the mean radius of gyration and end-to-end distance on the diffusion coefficient, bending rigidity and the shear flow rate are discussed and their implications on the collision cross section for polymer-particle interactions are considered. Polymer-particle adsorption events are studied, and it is shown from Monte-Carlo studies that low shear encourages full adsorption at the point of collision, whereas increased shear hinders it, with moderate shear causing shorter tail-like structures upon adsorption. Increasing the bending rigidity potential strength leads to higher adsorption rates, with rigid polymers more likely to form tails. At both low and high FENE potential strengths, an increase in adsorption efficiency as well as the frequency of tail-like final conformities is observed. The findings of this study are of importance to the development of behavioural modification techniques where bulk system parameters are tuned to obtain a desired behaviour in important industrial processes such as flocculation and settling
Die Rolle der Kommunen in einer sozial-ökologischen Wohnungspolitik
No full textAngesichts multipler Krisen hat eine soziale, resiliente und nachhaltige Stadtentwicklungs- und Wohnungspolitik in der jüngeren Vergangenheit erheblich an Bedeutung gewonnen. Angespannte Wohnungsmärkte verbunden mit hohen Wohnkosten prägen die Situation in vielen Städten und Gemeinden. Hinzu kommen Extremwetterereignisse, die infolge des Klimawandels an Intensität und Häufigkeit gewonnen haben. Die sozial-ökologische Wohnungs- und Stadtentwicklungspolitik befindet sich hier in einem Spannungsfeld: Sie muss die Rahmenbedingungen für eine gesteigerte Wohnungsbautätigkeit schaffen, damit trotz knapper Flächenressourcen bezahlbares Wohnen ermöglicht und gesichert werden kann. Gleichzeitig steht sie unter dem Druck der notwendigen Transformation städtebaulicher Strukturen an die Anforderungen einer klimaresilienten Stadt. Insbesondere im Ringen um das knappe und nicht vermehrbare Gut Boden wird deutlich, dass neben handlungs- und steuerungsfähigen Kommunen dem gemeinwohlorientierten Umgang mit Grund und Boden bei der Bewältigung heutiger und zukünftiger Herausforderungen in der integrierten Stadtentwicklung eine Schlüsselfunktion zukommt.In the face of multiple crises, a social, resilient and sustainable urban development and housing policy has gained considerable importance in the recent past. Tight housing markets combined with high housing costs and the increased intensity and frequency of extreme weather events as a result of climate change are increasingly shaping the image of German cities and communities. In view of the increasingly scarce urban land resources, a socio-ecological housing and urban development policy is also caught between the conflicting demands of creating and securing affordable housing through increased housing construction activity and the necessary transformation of urban structures to meet the requirements of a climate-resilient city. Particularly in the struggle for the scarce and non-replicable resource of land, it becomes clear that, in addition to municipalities that are capable of acting and managing, the public welfare-oriented handling of land has a key function in coping with current and future challenges in integrated urban development
Der Stabelgabler
No full textIm Rahmen des Projektseminars Elektrotechnik und Informationstechnik wurde die Aufgabe gestellt, einen Automaten zu entwerfen, der Lego Mindstorms (Abbildung [1]) als strukturelle Basis verwendet. Dieser sollte mit Hilfe von Matlab als Programmiersoftware umgesetzt werden. Der in diesem Projekt realisierte Automat ist ein selbstfahrender Gabelstapler. Im Folgenden wird sowohl auf die Hard- und Softwarekonzepte als auch auf die Umsetzung, die dabei aufgetretenen Probleme und deren Lösungen eingegangen. Abschließend werden die Einsatzmöglichkeiten und mögliche Verbesserungen diskutiert
Hinderniserkennungsroboter
No full textIn diesem Paper wird ein Ultraschall-Hindernisvermeidungssystem für das autonome Fahren vorgestellt. Das System ist in der Lage, Hindernisse zu erkennen und eine Vermeidung zu erm¨oglichen. Die Ergebnisse zeigen, dass das System eine hohe Genauigkeit aufweist und eine zuverl¨assige Hindernisvermeidung erm¨oglicht
Dynamic Assignment of Delivery Order Bundles to In-Store Customers
No full textMany larger grocery stores offer home delivery services. However, the delivery cost is usually high and such services are rarely profitable. One way of reducing cost is by outsourcing some orders to in-store customers for a compensation. While initially single orders were dynamically assigned to customers, companies started exploring the assignment of order bundles instead to reduce per-order compensation and exploit consolidation potential. We investigate the value of dynamic assignment of bundles in this work. To this end, we consider a setting where all orders are known and, over time, unknown in-store customers enter the system for a short time and offer transportation of bundles of orders for compensation. The store decides dynamically which bundle to assign to which in-store customer (if any). At the end of the time horizon, the remaining orders are delivered by a dedicated fleet of store employees. The goal of the store is to minimize the compensation prices together with the delivery cost. We propose a threshold based policy tuned by a stochastic lookahead procedure. Popularity and compensation price thresholds are determined a priori by solving a set of perfect information scenarios. In every state, bundles are only assigned if they are popular enough and the compensation is comparably low. The thresholds are adapted over time to account for the decrease in assignment opportunities. We show the effectiveness of our policy in a comprehensive computational study and highlight the value of bundle assignments compared to assigning individual orders. We further show that our strategy not only reduces the compensation paid to in-store customers but also the final routing cos
Dynamic learning-based Search for Multi-criteria Itinerary Planning
No full textTravelers expect integrated and multimodal itinerary planning while addressing their individual expectations. Besides common preferences such as travel time and price, further criteria such as walking and waiting times are of importance as well. The competing features of these preferences yield a variety of Pareto-optimal itineraries. Finding the set of Pareto-optimal multimodal travel itineraries in efficient run time remains a challenge in case multiple traveler preferences are considered. In this work, we present a sampling framework to approximate the set of Pareto-optimal travel itineraries that scales well in terms of considered preferences. In particular, we guide the search process dynamically to uncertain areas of the complex multimodal solution space. To this end, we learn the structure of the Pareto front during the search with Gaussian Process Regression (GPR). The GPR sampling framework is evaluated integrating an extensive amount of real-world data on mobility services. We analyze long-distance trips between major cities in Germany. Furthermore, we take up to five traveler preferences into account. We observe that the framework performs well, revealing origin and destination specifics of Pareto fronts of multimodal travel itineraries
LEGO Drink Partner
No full textIm Rahmen des j¨ahrlichen Lego-Seminars wurde ein lang ersehntes, aber aus Platzgr¨unden nicht realisierbares Projekt verwirklicht: der Bau eines Roboters, der als Begleiter für Heißgetr¨anke dienen sollte. Mit Hilfe von Legosteinen, einem NXT-Controller, drei Sensoren und drei Motoren konnte der Prototyp gebaut und getestet werden. Im Laufe des Projekts wurde deutlich, dass der erste Prototyp mit entsprechenden Weiterentwicklungen ein echtes Potenzial für einen n¨ützlichen automatisierten Roboterassistenten hat. In den folgenden Abschnitten werden die technischen Daten des Projekts im Detail vorgestellt und sein Anwendungspotenzial beschrieben