Technische Universität Darmstadt

About: Technische Universität Darmstadt is a education organization based out in Darmstadt, Germany. It is known for research contribution in the topics: Neutron & Finite element method. The organization has 17316 authors who have published 40619 publications receiving 937916 citations. The organization is also known as: Darmstadt University of Technology & University of Darmstadt.

A roadmap for island biology: 50 fundamental questions after 50 years of The Theory of Island Biogeography

Abstract: Aims The 50th anniversary of the publication of the seminal book, The Theory of Island Biogeography, by Robert H. MacArthur and Edward O. Wilson, is a timely moment to review and identify key research foci that could advance island biology. Here, we take a collaborative horizon-scanning approach to identify 50 fundamental questions for the continued development of the field. Location Worldwide. Methods We adapted a well-established methodology of horizon scanning to identify priority research questions in island biology, and initiated it during the Island Biology 2016 conference held in the Azores. A multidisciplinary working group prepared an initial pool of 187 questions. A series of online surveys was then used to refine a list of the 50 top priority questions. The final shortlist was restricted to questions with a broad conceptual scope, and which should be answerable through achievable research approaches. Results Questions were structured around four broad and partially overlapping island topics, including: (Macro)Ecology and Biogeography, (Macro)Evolution, Community Ecology, and Conservation and Management. These topics were then subdivided according to the following subject areas: global diversity patterns (five questions in total); island ontogeny and past climate change (4); island rules and syndromes (3); island biogeography theory (4); immigration–speciation–extinction dynamics (5); speciation and diversification (4); dispersal and colonization (3); community assembly (6); biotic interactions (2); global change (5); conservation and management policies (5); and invasive alien species (4). Main conclusions Collectively, this cross-disciplinary set of topics covering the 50 fundamental questions has the potential to stimulate and guide future research in island biology. By covering fields ranging from biogeography, community ecology and evolution to global change, this horizon scan may help to foster the formation of interdisciplinary research networks, enhancing joint efforts to better understand the past, present and future of island biotas.

Enhanced energy density of polymer nanocomposites at a low electric field through aligned BaTiO3 nanowires

Abstract: In practical application, new dielectric capacitors with greater energy density at lower operating voltage will be promising candidates for high-performance electrical devices. Theoretically, it is possible to achieve large electric polarization at a low electric field via embedding aligned ferroelectric nanowires in a polymer matrix, which could release high energy density. However, in terms of practice, the design of nanocomposites with aligned nanowires poses a great technical challenge. Here, a new physical-assisted casting method was developed to tune the orientation of elongated BaTiO3 nanowires in a P(VDF-CTFE) matrix. In the Z-aligned nanocomposites, a large (Dmax − Pr) value of 9.93 μC cm−2 can be induced at a low electric field of 2400 kV cm−1 by aligning 3 vol% ferroelectric BaTiO3 nanowires in the poling direction. Compared with X–Y-aligned nanocomposites even at a high electric field of 3400 kV cm−1, the Z-aligned nanocomposites could exhibit simultaneously an enhanced energy density of 10.8 J cm−3 and a discharge efficiency of 61.4% at 2400 kV cm−1. To the best of our knowledge, among ferroelectric nanocomposites, this is the highest energy density ever obtained at such a low electric field. This work is of critical significance in making dielectric nanocomposites viable for energy storage devices in current electrical and electronic applications.

Changes in the crystal and electronic structure of LiCoO2 and LiNiO2 upon Li intercalation and de-intercalation

Abstract: LixCoO2 and LixNiO2 (0.5 < x < 1) are used as prototype cathode materials in lithium ion batteries. Both systems show degradation and fatigue when used as cathode material during electrochemical cycling. In order to analyze the change of the structure and the electronic structure of LixCoO2 and LixNiO2 as a function of Li content x in detail, we have performed X-ray diffraction studies, photoelectron spectroscopy (PES) investigations and band structure calculations for a series of compounds Lix(Co,Ni)O2 (0 < x⩽ 1). The calculated density of states (DOS) are weighted by theoretical photoionization cross sections and compared with the DOS gained from the PES experiments. Consistently, the experimental and calculated DOS show a broadening of the Co/Ni 3d states upon lithium de-intercalation. The change of the shape of the experimental PES curves with decreasing lithium concentration can be interpreted from the calculated partial DOS as an increasing energetic overlap of the Co/Ni 3d and O 2p states and a change in the orbital overlap of Co/Ni and O wave functions.

Tecnologia de células a combustível

Abstract: The fuel cell principle was discovered by Sir Grove 150 years ago. However material problems prohibited its commercialization for a long time. A change has been occurring during the last 30 years, so two types of fuel cell technologies can be distinguished: low and high temperature operation cells. Nowadays, only phosphoric acid cells are commercially offered as 200 kWel power plants. Membrane cells are more suitable for automobile electrotraction with a very low (or no) environmental impact. The fuel continues, however, to play a very particular role, since hydrogen is not easy to store and to transport. The more promising target is the utilization of liquid methanol. The Brazilian scenario concerning this kind of technology is discussed.