Strain Dependence of Metal Anode Surface Properties

Dendrite growth poses a significant problem in the design of modern batteries as it can lead to capacity loss and short‐circuiting. Recently, it has been proposed that self‐diffusion barriers might be used as a descriptor for the occurrence of dendrite growth in batteries. As surface strain effects can modify dendritic growth, we present first‐principles DFT calculations of the dependence of metal self‐diffusion barriers on applied surface strain for a number of metals that are used as charge carriers in batteries. Overall, we find a rather small strain dependence of the barriers. We mainly attribute this to cancellation effects in the strain dependence of the initial and the transition states in diffusion

Toward the Formation of the Solid Electrolyte Interphase on Alkaline Metal Anodes: Ab Initio Simulations

The transition from lithium-based energy storage to post lithium systems plays a crucial part in achieving an environmentally sustainable energy infrastructure. Prime candidates for the replacement of lithium are sodium and potassium batteries. Despite being critical to battery performance, the solid electrolyte interphase (SEI) formation process for Na and K batteries remains insufficiently understood, especially compared to the well-established lithium systems. Using ab initio molecular dynamics (AIMD) simulations based on density functional theory (DFT) calculations, we study the first steps of SEI formation upon the decomposition of typical solvent molecules on lithium, sodium and potassium metal anodes. We find that two dominant products form during the early SEI formation of cyclical carbonates on alkali metal anodes, carbon monoxide and alkali-carbonate. The carbonate-producing reaction is thermodynamically favorable for all tested metals, however, Na and K exhibit a much stronger selectivity than Li towards carbonate formation. Furthermore, we propose a previously unknown reaction mechanism for the CO polymerization on metallic lithium

World and environment of early Mesolithic hunter-gatherers: Human-environment interactions in the northern European lowlands in the early Holocene

Die vorliegende Arbeit setzt sich mit Mensch-Umwelt-Interaktionen im Frühholozän der mitteleuropäischen Tiefebene auseinander. Hierbei wird der Frage nachgegangen, inwiefern frühmittelsteinzeitliche Wildbeuter mit ihrem jeweiligen Lebensraum in Wechselwirkung standen. Ferner wird untersucht, ob die Besiedlung der nordmitteleuropäischen Tiefebene eine Folge des Biotopwandels der Nacheiszeit war oder ob die Jäger und Sammler des Frühholozäns aktiv neue Siedlungsgebiete erschlossen. Neben einer Einordnung in den geomorphologischen Kontext erfolgt am Beginn der Arbeit auch ein Überblick der ökologischen Veränderungen in der betrachteten Zeitscheibe. Da das Arbeitsgebiet ein deutlich anderes Aussehen als heute besaß, wird kurz auf die Entwicklung der Flüsse sowie von Nord- und Ostsee eingegangen. Anschließend erfolgt eine Zusammenfassung der klimatischen Veränderungen und deren Auswirkungen auf Flora und Fauna. Es wird besprochen, dass die Wiederbewaldung und der einhergehende Wandel der Tierwelt zu wesentlichen Änderungen in der ökologischen Zusammensetzung geführt haben. Die Erforschung des Frühmesolithikums im Arbeitsgebiet blickt auf eine rund hundertjährige Geschichte zurück. Im Lauf der Zeit wandelten sich die Fragestellungen von vornehmlich Artefaktstudien zu stärker kontextualisierenden Ansätzen. Seit jeher fanden ethnographische Vergleiche Betrachtung in der Archäologie zu prähistorischen Jägern und Sammlern, die neben weiteren quellenkritischen Aspekten in einem weiteren Abschnitt erörtert werden. Im Rahmen der Arbeit erfolgt außer der bereits beschriebenen Fragestellung die Vorlage des Fundplatzes Friesack 27a aus Brandenburg. In der Darstellung wird neben einer Fundvorlage auch die naturräumliche Einordnung geleistet, sodass die Ergebnisse als Kontrollvariable für die im Weiteren durchgeführten Analysen dienen. Letztere nutzen Daten von publizierten Fundplätzen, um sie anhand verschiedener Aspekte zu vergleichen. In den 1980er Jahren wurde auf dem Fundplatz Friesack 27a die ehemalige Uferzone einer Sanddüne eines im Boreal verlandeten Gewässers ausgegraben. Neben verschiedenen lithischen und organischen Artefakten lassen sich vier Schichtkomplexe trennen, die verschiedene Phasen menschlicher Besiedlung anzeigen. Anhand noch erhaltener Tierknochen und Holzreste ist es zudem möglich für die frühen Phasen die Besiedlungssaison zu ermitteln. In der Zusammenschau mit dem in rund 400 m Luftlinie liegenden und teilweise (archäologisch) zeitgleichen Fundplatz Friesack 4 ergibt sich ein relativ klares Bild der frühmesolithischen Besiedlung des Areals. Nach der Vorstellung von Friesack 27a erfolgt die vergleichende Analyse von Fundplätzen im gesamten Arbeitsgebiet. Neben der Bewertung der Repräsentativität und Qualität der Stationen, erfolgen Analysen zur ihrer Lage. Anschließend werden Biotoprekonstruktionen anhand von Pollenanalysen und Tierknochen durchgeführt, wie auch die Synthese der Ergebnisse beider Varianten. Durch die vergleichende Analyse der Artefaktinventare lassen sich die Stationen funktional untergliedern, wobei der Fokus auf deren Spezialisierungsgrad gelegt wird. Weitere Ausführungen zeichnen die Subsistenzstrategie der behandelten Wildbeuter nach, bevor Einschränkungen des verwendeten Ansatzes diskutiert werden. Abschließend werden die Ökodeterminiertheit frühmesolithischer Jäger und Sammler und deren Habitatbindung bewertet. Es wird gezeigt, dass die Besiedlung der mitteleuropäischen Tiefebene der Wiederbewaldung folgte und die betrachteten Menschengruppen erst Fuß fassten, nachdem sich Biotope etabliert hatten, die mit ihrem Ursprungsgebiet vergleichbar waren.This thesis deals with human-environment interactions in the Early Holocene of the northern European lowlands. The question addressed is to what extent early Mesolithic hunter-gatherers were interdependent with their environment. Furthermore, it is questioned if the settlement of the area under investigation is a consequence of biotope changes or, if the hunter-gatherers actively colonized new types of habitats. Besides a geomorphological contextualization, an introduction to the ecological changes is given for the Early Holocene. Since the area under investigation had a different appearance than today, a short introduction will be given to developments affecting rivers, the North Sea, and the Baltic Sea. Following this, climatic developments and their effects on flora and fauna are summarized. Discussion highlights how reforestation and the attending changes in fauna involved considerable alterations in the ecological composition. During the ca. 100 years of research on the Early Mesolithic, the topics under consideration changed from primarily artefact studies to more contextualizing approaches. Ever since its beginning, ethnographic analogies were used in hunter-gatherer archaeology. Apart from aspects of source criticism, those will be discussed. Besides the aforementioned questions, the excavations of the site Friesack 27a in Brandenburg, Germany, are described. In addition to a presentation of the finds and the dating of the site, it will be contextualized in regard to its environment. The latter will also be used in the subsequent analyses as a control variable where published data from other archaeological sites are used for comparison. The site Friesack 27a, on the former beach zone of a lake that became overgrown in the Boreal period, was excavated in the 1980s. Four layer complexes were distinguished showing several phases of occupation. By means of animal bones and wooden remains it is possible to show the season of occupation for the older phases at least. In conjunction with the site Friesack 4, which is located about 400 m distant as the crow flies and is (archaeologically) contemporaneous with Friesack 27a, quite a good picture of the early Mesolithic occupation of the area appears. Subsequent to the presentation of Friesack 27a, a comparative analysis of sites in the area of investigation is given. In addition to the evaluation of representativeness and quality of each site, analyses of their locations are conducted. In the following, biotopes are reconstructed by means of pollen and faunal remains. The synthesis of both analyses paints a convincing picture for environmental reconstructions. The comparison of the artefact spectra serves as a basis for functional differentiations of the sites, whereby focus is laid on their specialization. Further remarks are given on subsistence strategy, before limitations of the approach used are discussed. Finally, it is evaluated how ecologically-driven early Mesolithic hunter-gatherers were, such as their ties to a specific habitat type. It is shown that their settlement of the northern European lowlands followed reforestation, so that Mesolithic people first advanced northwards when biotopes were established that were comparable to the groups’ areas of origi

Efficient Multi-Task RGB-D Scene Analysis for Indoor Environments

Semantic scene understanding is essential for mobile agents acting in various environments. Although semantic segmentation already provides a lot of information, details about individual objects as well as the general scene are missing but required for many real-world applications. However, solving multiple tasks separately is expensive and cannot be accomplished in real time given limited computing and battery capabilities on a mobile platform. In this paper, we propose an efficient multi-task approach for RGB-D scene analysis~(EMSANet) that simultaneously performs semantic and instance segmentation~(panoptic segmentation), instance orientation estimation, and scene classification. We show that all tasks can be accomplished using a single neural network in real time on a mobile platform without diminishing performance - by contrast, the individual tasks are able to benefit from each other. In order to evaluate our multi-task approach, we extend the annotations of the common RGB-D indoor datasets NYUv2 and SUNRGB-D for instance segmentation and orientation estimation. To the best of our knowledge, we are the first to provide results in such a comprehensive multi-task setting for indoor scene analysis on NYUv2 and SUNRGB-D.Comment: To be published in IEEE International Joint Conference on Neural Networks (IJCNN) 202

Saharan dust contribution to the Caribbean summertime boundary layer - a lidar study during SALTRACE

Dual-wavelength lidar measurements with the small lidar system POLIS of the Ludwig-Maximilians-Universitat Munchen were performed during the SALTRACE experiment at Barbados in June and July 2013. Based on high-accuracy measurements of the linear depolarization ratio down to about 200m above ground level, the dust volume fraction and the dust mass concentration within the convective marine boundary layer can be derived. Additional information from radiosonde launches at the ground-based measurement site provide independent information on the convective marine boundary layer height and the meteorological situation within the convective marine boundary layer. We investigate the lidar-derived optical properties, the lidar ratio and the particle linear depolarization ratio at 355 and 532 nm and find mean values of 0.04 (SD 0.03) and 0.05 (SD 0.04) at 355 and 532 nm, respectively, for the particle linear depolarization ratio, and (26 +/- 5) sr for the lidar ratio at 355 and 532 nm. For the concentration of dust in the convective marine boundary layer we find that most values were between 20 and 50 mu g m(-3). On most days the dust contribution to total aerosol volume was about 30-40 %. Comparing the dust contribution to the column-integrated sun-photometer measurements we see a correlation between high dust contribution, high total aerosol optical depth and a low Angstrom exponent, and of low dust contribution with low total aerosol optical depth

Ion Mobility in Crystalline Battery Materials

Ion mobility in electrolytes and electrodes is an important performance parameter in electrochemical devices, particularly in batteries. In this review, the authors concentrate on the charge carrier mobility in crystalline battery materials where the diffusion basically corresponds to hopping processes between lattice sites. However, in spite of the seeming simplicity of the migration process in crystalline materials, the factors governing mobility in these materials are still debated. There are well-accepted factors contributing to the ion mobility such as the size and the charge of the ions, but they are not sufficient to yield a complete picture of ion mobility. In this review, possible factors influencing ion mobility in crystalline battery materials are critically discussed. To gain insights into these factors, chemical trends in batteries, both as far as the charge carriers as well as the host materials are concerned, are discussed. Furthermore, fundamental questions, for example, about the nature of the migrating charge carriers, are also addressed

On the Use of Network Flow Techniques for Assigning Evacuees to Exits

We apply network flow techniques to find good exit selections for evacuees in an emergency evacuation. More precisely, we present two algorithms for computing exit distributions using both classical flows and flows over time which are well known from combinatorial optimization. The performance of these new proposals is compared to a simple shortest path approach and to a best response dynamics approach by using a cellular automaton model

The formation of physician altruism

We study how patient-regarding altruism is formed by medical education. We elicit and structurally estimate altruistic preferences using experimental data from a large sample of medical students ( = 733) in Germany at different progress stages in their studies. The estimates reveal substantial heterogeneity in altruistic preferences of medical students. Patient-regarding altruism is highest for freshmen, significantly declines for students in the course of medical studies, and tends to increase again for last year students, who assist in clinical practice. Also, patient-regarding altruism is higher for females and positively associated to general altruism. Altruistic medical students have gained prior practical experience in healthcare, have lower income expectations, and are more likely to choose surgery and pediatrics as their preferred specialty