14 Externe wissenschaftliche Einrichtungen

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    Cohesive properties of bcc and fcc rubidium from ab initio pseudopotentials
    (1985) Maysenhölder, Waldemar; Louie, Steven G.; Cohen, Marvin L.
    Total-energy calculations have been performed for Rb at zero temperature using a self-consistent ab initio pseudopotential approach within a local-density-functional scheme. The energy difference between fcc and bcc Rb, and the energy barrier between these structures, are found to be extremely small near the equilibrium volume. Agreement of the calculated cohesive properties of bcc Rb with experimental values is good in view of the softness of the material. A transition from bcc to fcc has been calculated to occur at a pressure of about 52 kbar for T=0 K, which compares favorably with the observed value of 70 kbar for this transition at room temperature.
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    Storage technologies for the electricity transition : an analysis of actors, actor perspectives and transition pathways in Germany
    (2020) Frey, Ulrich J.; Wassermann, Sandra; Deissenroth-Uhrig, Marc
    This article analyses actors in the storage niche during the German electricity transition. Thus, we develop a more differentiated understanding of actors and their storage activities. For that, we employ the analytical multi-level-perspective (MLP) framework to focus on interactions between old and new storage technologies. Using data from expert interviews, we investigate whether the storage pathway resembles any of the four ideal types of transition pathways for interactions between niche and regime. Through our interviews, we identify five types of actor in the storage market: Big 4 (EnBW, RWE, E.ON, Vattenfall), project developers, innovative municipal utilities, small rural municipal utilities and independent green electricity providers. For each actor, we analyse four main aspects (1) previous orientation and motivation, (2) structural strategies, (3) institutional strategies, and (4) product-related strategies. Parallel to the classification of actors, we also classify available storage technologies according to their primary field of application. We conclude that interactions between regime and niche actors are cooperative, but weak, and no specific actor type currently dominates the niche activities. Hence, applications in the storage niche are not yet ready for a larger market. In sum, our results point to a future system that is characterized by reconfiguration, not substitution or transformation of current market actors.
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    Some didactical and some practical remarks on free plate waves
    (1987) Maysenhölder, Waldemar
    It is recalled how wave equations can be generated from dispersion relations. The bending wave equation for thin plates including some higher-order terms is obtained by this general method and compared to the corresponding equation of Timoshenko. Further, the dispersion of free plate waves is derived in a concise and elementary manner without using a scalar potential and a vector potential for the displacements. Finally, as a matter of practical interest, exact and approximate expressions for the ratio of parallel to perpendicular displacements at a plate surface are calculated. Under favourable circumstances measurement of this ratio allows decomposing an observed wave into its quasi-longitudinal and bending components.
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    Ultrasonic attenuation due to the neutral acceptor Mn in GaAs
    (1976) Lassmann, Kurt; Schad, Hanspeter
    We report on measurements of the ultrasonic attenuation in GaAs: Mn at frequencies between 400 and 2000 MHz and at temperatures between 1 and 35 K. The results indicate that there is a level 3 meV above the acceptor round state.
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    Calculations of point-defect properties in copper, silver, and gold based on three-body interactions
    (1982) Bauer, Rolf; Maysenhölder, Waldemar; Seeger, Alfred
    Long-term trends in the calculation of defect properties in the noble metals are criticezed. On physical grounds it is argued that the model potentials used should allow for many-body interactions. Results based on potentials which include three-body interaction terms are presented for Cu, Ag, and Au.
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    Integrated multidimensional sustainability assessment of energy system transformation pathways
    (2021) Naegler, Tobias; Becker, Lisa; Buchgeister, Jens; Hauser, Wolfgang; Hottenroth, Heidi; Junne, Tobias; Lehr, Ulrike; Scheel, Oliver; Schmidt-Scheele, Ricarda; Simon, Sonja; Sutardhio, Claudia; Tietze, Ingela; Ulrich, Philip; Viere, Tobias; Weidlich, Anke
    Sustainable development embraces a broad spectrum of social, economic and ecological aspects. Thus, a sustainable transformation process of energy systems is inevitably multidimensional and needs to go beyond climate impact and cost considerations. An approach for an integrated and interdisciplinary sustainability assessment of energy system transformation pathways is presented here. It first integrates energy system modeling with a multidimensional impact assessment that focuses on life cycle-based environmental and macroeconomic impacts. Then, stakeholders’ preferences with respect to defined sustainability indicators are inquired, which are finally integrated into a comparative scenario evaluation through a multi-criteria decision analysis (MCDA), all in one consistent assessment framework. As an illustrative example, this holistic approach is applied to the sustainability assessment of ten different transformation strategies for Germany. Applying multi-criteria decision analysis reveals that both ambitious (80%) and highly ambitious (95%) carbon reduction scenarios can achieve top sustainability ranks, depending on the underlying energy transformation pathways and respective scores in other sustainability dimensions. Furthermore, this research highlights an increasingly dominant contribution of energy systems’ upstream chains on total environmental impacts, reveals rather small differences in macroeconomic effects between different scenarios and identifies the transition among societal segments and climate impact minimization as the most important stakeholder preferences.
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    On the determination of interaction parameters from correlations in binary alloys
    (1987) Maysenhölder, Waldemar
    The determination of interaction parameters from correlation functions in binary alloys is discussed by means of high-temperature expansions for the correlations. The inherent nonlinearity of this "inverse problem" of statistical mechanics leading to non-unique solutions is emphasized. The formulation includes pair and triplet interactions. Some results of a specific "inverse Monte Carlo calculation" are criticized. The paper provides a collection of formulae, especially for probabilities and correlations, which should prove useful for clarifying the subject.
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    Körperschallausbreitung in Gebäuden : Untersuchungen mit einem Intensitätsmeßverfahren
    (1988) Maysenhölder, Waldemar
    Bauakustische Körperschallmessungen haben sich bisher fast ausschließlich auf die Messung von Schwingungsamplituden beschränkt ("Körperschallpegel"). Die für einen wirksamen Schallschutz so wichtige Frage, wie sich die Schwingungsenergie ausbreitet, wird aber durch eine reine Pegelmessung meistens nicht zuverlässig beantwortet. Zu diesem Zweck muß die Körperschallintensität gemessen werden. Unter gewissen Bedingungen läßt sich die Körperschallintensität relativ einfach aus dem Kreuzspektrum zweier Beschleunigungssignale bestimmen. Die Grundzüge dieser in der Bauakustik noch neuen Meßtechnik werden erläutert. Ihr Einsatz bei der Lokalisierung von Schallbrücken und beim Studium der Schalllängsdämmung zeigt die deutliche Überlegenheit gegenüber reinen Körperschallpegelmessungen.
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    Investigation and design of an impact actuated micro shift valve
    (2013) Fischer, Christian; Fritz, Karl-Peter; Eberhard, Peter; Kück, Heinz
    New concepts for an impact actuated micro shift valve are presented which are useful e.g. as im plant for the hydrocephalus disease. Such an implant must fulfil requirements, such as using biocompatible materials, a separation of the actuator from the fluid, MRT safety and low energy consumption in order to allow a battery powered system. The concepts are based on impacts that transmit an impulse into the interior of the valve through the casing, switching the valve. In order to predict the energy transmitted into the valve, an elastic multibody model is created, verified with full finite element simulations and experiments on scaled-up models. Using this model, the most important effects and parameters are discussed. Also, fluid effects are included into the elastic multibody model for a qualitative assessment of its influence on the efficiency. The simulations are compared to experiments performed with a scaled model for two different cases. Two designs of a shift valve based on impact actuation are built as prototypes and tested.