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Differential-Algebraic Equations and Beyond: From Smooth to Nonsmooth Constrained Dynamical Systems
(2022)
Schulungen in neun Prozessschritten gestalten! Digitalisierung des Masterfaches „Integrierte Managementsysteme“ im Studiengang „Material Science and Sustainability Methods“ im Fachbereich Naturwissenschaften an der Hochschule Bonn-Rhein-Sieg. Am Beispiel einer jahrelang in Präsenz gelehrten Lehrveranstaltung mit Vorlesungen und seminaristischen Übungen wird gezeigt, wie das Gestalten und Durchführen zur Vermittlung prüfungsrelevanter Kompetenzen auch „online“ gelingt. Das passende „Setting“ des Lehr- und Lernprozesses unter Beachtung von Qualitätskriterien und Handlungsempfehlungen ist für jede Art von Schulung in Universitäten, Behörden, Unternehmen und anderen Organsitationen relevant.
In her recent article, Bender discusses several aspects of research–practice–collaborations (RPCs). In this commentary, we apply Bender's arguments to experiences in engineering research and development (R&D). We investigate the influence of interaction with practice partners on relevance, credibility, and legitimacy in the special engineering field of product development and analyze which methodological approaches are already being pursued for dealing with diverging interests and asymmetries and which steps will be necessary to include interests of civil society beyond traditional customer relations.
Novel methods for contingency analysis of gas transport networks are presented. They are motivated by the transition of our energy system where hydrogen plays a growing role. The novel methods are based on a specific method for topological reduction and so-called supernodes. Stationary Euler equations with advanced compressor thermodynamics and a gas law allowing for gas compositions with up to 100% hydrogen are used. Several measures and plots support an intuitive comparison and analysis of the results. In particular, it is shown that the newly developed methods can estimate locations and magnitudes of additional capacities (injection, buffering, storage etc.) with a reasonable performance for networks of relevant composition and size.
The cube in cube approach was used by Paul and Ishai-Cohen to model and derive formulas for filler content dependent Young's moduli of particle filled composites assuming perfect filler matrix adhesion. Their formulas were chosen because of their simplicity, and recalculated using an elementary volume approach which transforms spherical inclusions to cubic inclusions. The EV approach led to expression of the composites moduli that allows introducing an adhesion factor kadh ranging from 0 and 1 to take into account reduced filler matrix adhesion. This adhesion factor scales the edge length of the cubic inclusions, thus reducing the stress transfer area between matrix and filler. Fitting the experimental data with the modified Paul model provides reasonable kadh for PA66, PBT, PP, PE-LD and BR which are in line with their surface energies. Further analysis showed that stiffening only occurs if kadh exceeds [Formula: see text] and depends on the ratio of matrix modulus and filler modulus. The modified model allows for a quick calculation of any particle filled composites for known matrix modulus EM, filler modulus EF, filler volume content vF and adhesion factor kadh. Thus, finite element analysis (FEA) simulations of any particle filled polymer parts as well as materials selection are significantly eased. FEA of cubic and hexagonal EV arrangements show that stress distributions within the EV exhibit more shear stresses if one deviates from the cubic arrangement. At high filler contents the assumption that the property of the EV is representative for the whole composite, holds only for filler volume contents up to 15 or 20% (corresponding to 30 to 40 weight %). Thus, for vast majority of commercially available particulate composites, the modified model can be applied. Furthermore, this indicates that the cube in cube approach reaches two limits: (i) the occurrence of increasing shear stresses at filler contents above 20% due to deviations of EV arrangements or spatial filler distribution from cubic arrangements (singular), and (ii) increasing interaction between particles with the formation of particle network within the matrix violating the EV assumption of their homogeneous dispersion.
This study investigates the initial stage of the thermo-mechanical crystallization behavior for uni- and biaxially stretched polyethylene. The models are based on a mesoscale molecular dynamics approach. We take constraints that occur in real-life polymer processing into account, especially with respect to the blowing stage of the extrusion blow-molding process. For this purpose, we deform our systems using a wide range of stretching levels before they are quenched. We discuss the effects of the stretching procedures on the micro-mechanical state of the systems, characterized by entanglement behavior and nematic ordering of chain segments. For the cooling stage, we use two different approaches which allow for free or hindered shrinkage, respectively. During cooling, crystallization kinetics are monitored: We precisely evaluate how the interplay of chain length, temperature, local entanglements and orientation of chain segments influence crystallization behavior. Our models reveal that the main stretching direction dominates microscopic states of the different systems. We are able to show that crystallization mainly depends on the (dis-)entanglement behavior. Nematic ordering plays a secondary role.
In this paper, modeling of piston and generic type gas compressors for a globally convergent algorithm for solving stationary gas transport problems is carried out. A theoretical analysis of the simulation stability, its practical implementation and verification of convergence on a realistic gas network have been carried out. The relevance of the paper for the topics of the conference is defined by a significance of gas transport networks as an advanced application of simulation and modeling, including the development of novel mathematical and numerical algorithms and methods.
In this paper, an analysis of the error ellipsoid in the space of solutions of stationary gas transport problems is carried out. For this purpose, a Principal Component Analysis of the solution set has been performed. The presence of unstable directions is shown associated with the marginal fulfillment of the resistivity conditions for the equations of compressors and other control elements in gas networks. Practically, the instabilities occur when multiple compressors or regulators try to control pressures or flows in the same part of the network. Such problems can occur, in particular, when the compressors or regulators reach their working limits. Possible ways of resolving instabilities are considered.
The cube in cube approach was used by Paul and Ishai-Cohen to model and derive formulas for filler content dependent Young´s moduli of particle filled composites assuming perfect filler matrix adhesion. Their formulas were chosen because of their simplicity, recalculated using an elementary volume approach which transforms spherical inclusions to cubic inclusions. The EV approach led to expression for the composites moduli that allow for introducing an adhesion factor kadh ranging from 0 and 1 to take into account none perfect reduced filler matrix adhesion. This adhesion factor scales the edge length of the cubic inclusions, thus, reducing the stress transfer area between matrix and filler. Fitting the experimental data with the modified Paul model provides reasonable kadh for PA66, PBT, PP, PE-LD and BR which are in line with their surface energies. Further analysis showed that stiffening only occurs if kadh exceeds <span class="math-tex">\( { \ \sqrt{E^M/E^F} \ }\) and depends on the ratio of matrix modulus and filler modulus. The modified model allows for a quick calculation of any particle filled composites for known matrix modulus EM, filler modulus EF, filler volume content vF and adhesion factor kadh. Thus, finite element analysis (FEA) simulations of any particle filled polymer parts as well as materials selection are significantly eased. FEA of cubic and hexagonal EV arrangements show that stress distributions within the EV exhibit more shear stresses if one deviates from the cubic arrangement. At high filler contents the assumption that the property of the EV is representative for the whole composite, holds only for filler volume contents up to 15 or 20 % (corresponding to 30 to 40 weight %). Thus, for vast majority of commercially available particulate composites, the modified model can be applied. Furthermore, this indicates that the cube in cube approach reaches two limits: i) the occurrence of increasing shear stresses at filler contents above 20 % due to deviations of EV arrangements or spatial filler distribution from cubic arrangements (singular), and ii) increasing interaction between particles with the formation of particle network within the matrix violating the EV assumption of their homogeneous dispersion.
The utilization of simulation procedures is gaining increasing attention in the product development of extrusion blow molded parts. However, some simulation steps, like the simulation of shrinkage and warpage, are still associated with uncertainties. The reason for this is on the one hand a lack of standardized interfaces for the transfer of simulation data between different simulation tools, and on the other hand the complex time-, temperature- and process-dependent material behavior of the used semi crystalline polymers. Using a new vendor neutral interface standard for the data transfer, the shrinkage analysis of a simple blow molded part is investigated and compared to experimental data. A linear viscoelastic material model in combination with an orthotropic process- and temperature-dependent thermal expansion coefficient is used for the shrinkage prediction. A good agreement is observed. Finally, critical parameters in the simulation models that strongly influence the shrinkage analysis are identified by a sensitivity study.
In this paper, a gas-to-power (GtoP) system for power outages is digitally modeled and experimentally developed. The design includes a solid-state hydrogen storage system composed of TiFeMn as a hydride forming alloy (6.7 kg of alloy in five tanks) and an air-cooled fuel cell (maximum power: 1.6 kW). The hydrogen storage system is charged under room temperature and 40 bar of hydrogen pressure, reaching about 110 g of hydrogen capacity. In an emergency use case of the system, hydrogen is supplied to the fuel cell, and the waste heat coming from the exhaust air of the fuel cell is used for the endothermic dehydrogenation reaction of the metal hydride. This GtoP system demonstrates fast, stable, and reliable responses, providing from 149 W to 596 W under different constant as well as dynamic conditions. A comprehensive and novel simulation approach based on a network model is also applied. The developed model is validated under static and dynamic power load scenarios, demonstrating excellent agreement with the experimental results.
West Africa has great potential for the use of solar energy systems, as it has both a high solar radiation rate and a lack of energy production. West Africa is a very aerosol-rich region, whose effects on photovoltaic (PV) use are due to both atmospheric conditions and existing solar technology. This study reports the variability of aerosol optical properties in the city of Koforidua, Ghana over the period 2016 to 2020, and their impact on the radiation intensity and efficiency of a PV cell. The study used AERONET ground (Giles et al., 2019) and satellite data produced by CAMS (Gschwind, et al., 2019), which both provide aerosol optical depth (AOD) and metrological parameters used for radiative transfer calculations with libRadtran (Emde, et al., 2016). A spectrally resolved PV model (Herman-Czezuch et al., 2022) is then used to calculate the PV yield of two PV technologies: polycrystalline and amorphous silicon. It is observed that for both data sets, the aerosol is mainly composed of dust and organic matter, with a very increased AOD load during the harmattan period (December-February), also due to the fires observed during this period.
Intention: Within the research project EnerSHelF (Energy-Self-Sufficiency for Health Facilities in Ghana), i. a. energy-meteorological and load-related measurement data are collected, for which an overview of the availability is to be presented on a poster.
Context: In Ghana, the total electricity consumed has almost doubled between 2008 and 2018 according to the Energy Commission of Ghana. This goes along with an unstable power grid, resulting in power outages whenever electricity consumption peaks. The blackouts called "dumsor" in Ghana, pose a severe burden to the healthcare sector. Innovative solutions are needed to reduce greenhouse gas emissions and improve energy and health access.
The design of a fully superconducting wind power generator is influenced by several factors. Among them, a low number of pole pairs is desirable to achieve low AC losses in the superconducting stator winding, which greatly influences the cooling system design and, consecutively, the efficiency of the entire wind power plant. However, it has been identified that a low number of pole pairs in a superconducting generator tends to greatly increase its output voltage, which in turn creates challenging conditions for the necessary power electronic converter. This study highlights the interdependencies between the design of a fully superconducting 10 MW wind power generator and the corresponding design of its power electronic converter.
Comparing Armature Windings for a 10 MW Fully Superconducting Synchronous Wind Turbine Generator
(2022)
The electricity grid of the future will be built on renewable energy sources, which are highly variable and dependent on atmospheric conditions. In power grids with an increasingly high penetration of solar photovoltaics (PV), an accurate knowledge of the incoming solar irradiance is indispensable for grid operation and planning, and reliable irradiance forecasts are thus invaluable for energy system operators. In order to better characterise shortwave solar radiation in time and space, data from PV systems themselves can be used, since the measured power provides information about both irradiance and the optical properties of the atmosphere, in particular the cloud optical depth (COD). Indeed, in the European context with highly variable cloud cover, the cloud fraction and COD are important parameters in determining the irradiance, whereas aerosol effects are only of secondary importance.
This paper investigates the effect of voltage sensors on the measurement of transient voltages for power semiconductors in a Double Pulse Test (DPT) environment.We adapt previously published models that were developed for current sensors and apply them to voltage sensors to evaluate their suitability for DPT applications. Similarities and differences between transient current and voltage sensors are investigated and the resulting methodology is applied to commercially available and experimental voltage sensors. Finally, a selection aid for given measurement tasks is derived that focuses on the measurement of fast-switching power semiconductors.
How self-reliant Peer Teaching can be set up to augment learning outcomes for university learners
(2022)
Digitaltechnik
(2022)
Moderne Digitaltechnik, umfassend und kompakt: Dieses Lehr- und Übungsbuch spannt den Bogen von den Grundlagen der Digitaltechnik über den Entwurf mit VHDL und Komponenten digitaler Systeme bis zu modernen Mikrocontrollern der STM32-Serie.
Die 8. Auflage wurde aktualisiert und die Themenbereiche Mikroprozessoren und Mikrocontroller grundlegend überarbeitet.
Der vorliegende Beitrag setzt sich mit der Bedeutung von Lernorten der beruflichen Bildung im Zuge einer BBNE sowie der diesbezüglichen Kompetenzentwicklung auseinander. Dabei wird entlang des BIBB-Modellversuchs „NAUZUBI“ ein möglicher Ansatz skizziert, der darauf ausgerichtet ist, eine integrative Kompetenzentwicklung in Nachhaltigkeitsthemen zu ermöglichen. Ausgangspunkt sind dabei betriebliche Nachhaltigkeitsaudits, die im vorliegenden Ansatz als kontextualisierte Zugänge für berufliche Lernanlässe dienten. Diese wurden in aufeinander abgestimmten Schritten im betrieblichen und schulischen Lernen reflektiert. Im Beitrag werden das Grundkonzept sowie die entsprechenden Umsetzungserfahrungen beschrieben. Es werden ferner Herausforderungen und Potenziale für das betriebliche, berufsschulische und das lernortkooperative Lernen und damit die integrative Kompetenzentwicklung dargestellt.
Buch-Aisthesis
(2022)
Literatur kann auch als Verbund von Medien betrachtet werden, die in Kooperations- und Konkurrenzverhältnissen auftreten. Dies wird umso deutlicher, wenn aus literatur- und designwissenschaftlicher Perspektive auf die Beobachtung der Differenz von typographischen und anderen, grundsätzlich nonverbalen visuellen Daten abgestellt wird. Die Beiträger*innen des Bandes leiten daraus ein Verhältnis von Literatur- und Kunstwissenschaft zu ihren Gegenständen ab, das nicht zuletzt zu einer neuen Aufmerksamkeit für die skripturale und typographische Materialität und Medialität der Literatur führt. Dabei geht es um die Theorie der Reflexion und die Praxis der Erzeugung einer je spezifischen Buch-Ästhetik.
Buch-Diskurse
(2022)
Die folgenden Überlegungen versuchen einerseits, die Arbeit an einer ins besondere medienwissenschaftlich fundierten Auslegung der sogenannten Kriminalliteratur1 weiter zu denken und in den Zusammenhang einer Lektüre zu stellen, die das Dispositiv ›Literatur und ihre Medien‹ als Bezugnahme bzw. Verhältnismäßigkeit versteht: als »Verhältnis der Literatur zu ihren Medien« und/oder als »Verhältnis der Medien zur Literatur«.2
From Conclusion to Coda
(2022)
Medienkulturwissenschaft
(2022)
Der Band erklärt die Entstehung, Entwicklung und inhaltliche Breite der Medienkulturwissenschaft. Deren Felder werden ebenso demonstriert wie Forschungsfragen entworfen. Ein spezielles Augenmerk liegt auf interdisziplinären Verhältnissen, etwa zur Kommunikations- und Literaturwissenschaft. Zudem wird aus dieser Perspektive die Historie von Einzelmedien vorgestellt und ausgewählte Phänomene mit der medienkulturwissenschaftlichen „Brille“ skizziert. Dadurch kann die Geschichte und Philosophie der Medienkulturwissenschaft ebenso diskutiert werden wie deren Anwendungsfälle sowie ihre Positionen innerhalb eines Medienstudiums mit starkem Praxisbezug, bei dem die Theorien und Ästhetiken der Medien nicht außer Acht gelassen werden. (Verlagsangaben)
论“数字化大学”的内涵及发展
(2022)
Technik-Ästhetik
(2022)
Von Technik und Ästhetik zu sprechen, heißt, sich bereits begrifflich auf ein Feld einzulassen, das mindestens zwei divergente Perspektiven gemeinsam denkt. Dabei haben das Technische wie das Ästhetische die Bedeutung einer Interdependenz aufzuweisen: Das Technische konstituiert einerseits Funktionen, Formen und Gebrauchsaspekte - ästhetische Zustände evozieren andererseits zeichenhafte Realisierungen, phantasmatische Urteile und wahrnehmungsvermittelte Phänomene des Erscheinens. Die Beiträger*innen des Bandes zeigen, wie bei der Konfrontation von Technik und Ästhetik eine Art Verkopplung und intrinsische Dynamik qua techno-ästhetischer Evokation entstehen kann.
Haut und Design
(2022)
Was ist ein Labor?
(2022)
Medien-›Eingriffe‹
(2022)
Einleitung
(2022)
Vorwort
(2022)
Vorwort
(2022)
Harald Schmidt
(2022)
Als Medien- und insbesondere Fernsehphänomen hat Harald Schmidt die TV-Kultur im deutschsprachigen Raum maßgeblich beeinflusst. So ist es etwa der Harald Schmidt Show gelungen, halbironische Sprechweisen diskursfähig zu machen, die sich bis in die Gegenwart der Social Media verfolgen lassen. Die Beiträger*innen des Bandes untersuchen vor diesem Hintergrund die »Methode Harald Schmidt«, d.h. die Unterminierung gängiger sozialer Vorstellungen bei gleichzeitiger Affirmation derselben. Die zentrale These lautet: Harald Schmidt hat grundlegende Voraussetzungen dafür geschaffen, eine weitestgehend neue Populärkultur ästhetisch wie kulturpraktisch zu etablieren.
Bionik
(2022)
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. Die vorliegende Auflage wurde überarbeitet und um aktuelle Forschungserkenntnisse und Entwicklungen ergänzt. (Verlagsangaben)