Semi-smooth Newton methods for mixed FEM discretizations of higher-order for frictional, elasto-plastic two-body contact problems

International audienceIn this article a semi-smooth Newton method for frictional two-body contact problems and a solution algorithm for the resulting sequence of linear systems are presented. It is based on a mixed variational formulation of the problem and a discretization by finite elements of higher-order. General friction laws depending on the normal stresses and elasto-plastic material behavior with linear isotropic hardening are considered. Numerical results show the efficiency of the presented algorithm

Doping of Hole Conducting Polymers Utilized to Enhance Polymer Electronics

For this thesis the system �poly(3,4-ethylenedioxythiophene) (PEDOT) utilized as electrochemically adjusted anodic material for organic devices� has been studied in-depth. PEDOT films were polymerized electrochemically being subsequently adjusted to a certain electrochemical potential. Afterwards the resulting work function of the adjusted oxidation level was determined by Kelvin Probe measurements. This thesis provides unambiguous evidence that the work function of the PEDOT film surface is directly (linearly) correlated to the adjusted electrochemical potential. This finding has been utilized for optimising electronic properties of organic devices. Organic semiconducting polymeric devices of the general structure indium tin oxide (ITO) / electrochemically deposited and doped PEDOT / electroactive polymer / metal electrode have been prepared and characterized. By means of electrochemical doping the PEDOT layer was adjusted to a desired potential and its influence on the respective devices was studied. The adjusted doping level of the PEDOT layer could be directly correlated to its work function. This was demonstrated by Kelvin probe measurements above the semi-freestanding film and by photovoltaic measurements in the finished devices. Thereafter this discovery was utilized to optimise organic light emitting devices (OLED) by adjusting their hole injection barrier. This barrier is given by the difference in work function between the anodic contact (PEDOT) and the highest occupied molecular orbital (HOMO) level of the adjoining polymer film. If this barrier equals the barrier on the cathodic (metal) side of the device an optimized efficiency can be expected in zero order approximation. Experiments verified this assumption. If current contributions of holes and electrons are balanced, in principle each charge carrier could find an opposite charge and decay radiatively with the highest efficiency. Although this consideration neglects other influences like different charge carrier mobilities, it is of high interest to gain a possibility which enables current determination for both sorts of charge carriers rather than just the measurement of an overall current. This thesis presents an approach which enables the separation of electron and hole currents for OLED�s. The utilization of the results of hole only devices (electrons are blocked) allowed predictions about the ratio of current contributions in devices with hole and electron currents. These current contributions also confirmed enhanced efficiencies caused by tuned barriers. Investigations of up-to-date bulk-heterojunction solar cells (OSC) allowed a deeper insight in physical properties which govern these devices. By using a completely undoped PEDOT film the work function of the initial cathodic (metal) electrode could be passed and the PEDOT took over the cathodic function. Slightly doped PEDOT films could be adjusted to the same level as the metal contact causing zero-built-in-field devices. These investigations enabled a correlation between the anodic and cathodic energy levels and a rough estimation of the adjustable absolute range of PEDOT work functions

EEG-Grundaktivität und Intelligenz

Um zu untersuchen, ob ein Zusammenhang zwischen EEG-Merkmalen und Leistung im Intelligenztest besteht, wurde retrospektiv bei 69 Kindern im Alter 10+-1Jahr, die in den Jahren 1996 und 1997 am Sozialpädiatrischen Zentrum Inn-Salzach in Altötting untersucht wurden, die Intelligenztestung mit dem HAWIK-R mit dem EEG verglichen. Die Hirnaktivität wurde mittels der Spektralanalyse analysiert. Die Ergebnisse wurden mit den Ergebnissen der 11 Subtests und der drei berechneten Intelligenzquotienten des HAWIK-R korreliert. Zunächst erfolgte ein Vergleich der Ergebnisse der 11 Subtests jeweils mit den Spektralwerten in 0,5 Hz Abständen sowie mit den klassichen EEG-Bändern. In weiteren Schritten wurde eine spektral- und bandbezogene Korrelations- und Varianzanalyse durchgeführt. Die Spektralanalyse zeigte die ausgeprägtesten Zusammenhäge bei 10,0-10,5 Hz. Die Bandanalyse ergab signifikante Ergebnisse im Alpha-Berich okzipital. Die besten Korrelationen zwischen Testergebnis und Alpha-Aktivität wurden bei sprachlich gebundenen kognitiven Fähigkeiten (HAWIK-R Verbal-IQ (H 12)) nachgewiesen, aber auch bei den Untertesten Allgemeines Wissen (H1), Wortschatz-Test (H5), Bilderordnen (H9) und Figurenlegen (H11). Bei der okzipitalen Alpha-Aktivität waren die Unterschiede zwischen Kindern mit hohen und niedrigem IQ signifikant auf dem Niveau < 5%

Projektbericht: Forschungswerkstatt zur Erstellung einer Digitalen Edition: Ein Lehr-Lern-Versuch

Der Beitrag beschäftigt sich anhand eines Praxisbeispiels mit den Chancen und Herausforderungen der digitalen Bildung im Kontext der Hochschullehre. In Form eines Projektberichts wird das Format einer 'Forschungswerkstatt zur Erstellung einer Digitalen Edition' vorgestellt. In diesem Lehr-Lern-Versuch wurde den Studierenden anhand einer engen Theorie-Praxis-Verzahnung die methodische Herangehensweise für die digitale Aufbereitung von Quellenmaterial vermittelt. Als thematische Grundlage wurde der Umgang mit 'Tod und Sterben' in Mittelalter und Früher Neuzeit gewählt. Die Studierenden (ab dem 4. Semester) befassten sich mit Leichenpredigten, Autobiographien und Familienbucheinträgen und untersuchten anhand ausgewählter Beispiele die Aussagemöglichkeiten und -grenzen dieser Quellen für das Seminarthema. Dazu bereiteten sie Auszüge aus handschriftlichen, nicht-edierten Quellen inhaltlich und formal auf, nahmen eigenständig Recherchen und Transkriptionen vor und bereiteten die Texte für die Überführung in eine digitale (Teil-)Edition vor. Ziel der 'Forschungswerkstätten' war es nicht nur aufzuzeigen, welchen Mehrwert Digitale Editionen im Prozess historischen Forschens und Lernens haben, sondern vor allem, wie Studierende digitalisierte Quellen für die eigene Forschungen und Publikationen auswerten und in weiteren Projekten anwenden könnenBased on the evaluation of a teaching project at Kiel University, the article discusses the opportunities and challenges of digital education in the context of university teaching. Our chosen format, a 'research-based workshop' with the aim of creating a digital edition, is presented in the form of a project report. Over the course of this teaching-learning experiment, students were taught – in theory and practice – methodical approaches for the digital processing of source material. We chose as our thematic basis late medieval and early modern experiences and perceptions of 'death and dying'. The students studied sources such as funeral sermons, autobiographies, and family book entries, and examined the possibilities and limits of these sources. They prepared and transcribed excerpts from handwritten, unedited sources, carried out research independently, and prepared the texts for transfer to a digital (partial) edition. The aim of this teaching format was to demonstrate the added value of digital editions within the process of historical research and research-based learning. Moreover, students learned about the value of digitized sources for their own research, including possible publications, and how to make use of them in further projects

Selfie-Übergriffe

Für diesen Beitrag ist leider kein Abstract verfügbar. ----------

Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils

An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg Hg kg(-1) and > 30 mg Hg kg(-1)). The experiment was conducted under stepwise variation from reducing (approximately -350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10Me16:0, cy17:0, 10Me18:0, cy19:0) or Desulfovibrio species (18:2 omega 6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hg-t) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hg-t) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hg-t ratio (ln(DOC/Hg-t) ratio) (R-2 = 0.39, p < 0.0001, n = 63) whereas the relation between ln(MeHg/Hg-t) ratio and lnDOC is weaker (R-2 = 0.09; p < 0.05; n = 63). In conclusion, the DOC/Hg-t ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas EH and pH values, as well as concentration of dissolved Fe3+/Fe2+ and Cl-seem to play subordinate roles in Hg mobilization and methylation under our experimental condition

BDAQ53, a versatile pixel detector readout and test system for the ATLAS and CMS HL-LHC upgrades

BDAQ53 is a readout system and verification framework for hybrid pixel detector readout chips of the RD53 family. These chips are designed for the upgrade of the inner tracking detectors of the ATLAS and CMS experiments. BDAQ53 is used in applications where versatility and rapid customization are required, such as in laboratory testing environments, test beam campaigns, and permanent setups for quality control measurements. It consists of custom and commercial hardware, a Python-based software framework, and FPGA firmware. BDAQ53 is developed as open source software with both software and firmware being hosted in a public repository.Comment: 6 pages, 6 figure

Physics and Modeling of Submicron Devices. Annual Report: August I, 1987 - July 31, 1988

The work described in this report is directed at understanding quantum transport phenomena in sub-micron heterostructure devices, at developing computational techniques for modeling such devices, and at applying these techniques to develop new device concepts. During the past year we have (l) applied a previously developed collisionless quantum device model (SEQUAL) and Monte Carlo model (DEMON) to the design and study of heterojunction bipolar transistors (Chapter 2); (2) developed a technique for the analysis of arbitrarily shaped quantum devices with elastic scattering (Chapter 3); and (3) developed an approach for incorporating inelastic dissipative processes in quantum transport theory (Chapter 4). As a by-product of the research, several heterostructure device models have been developed: 1- and 2-D equilibrium models, 1- and 2-D drift-diffusion models, a I-D Monte Carlo simulator and a 1-D collisionless quantum device model. These simulation programs are being applied to advanced device analysis at a number of laboratories and are available to SRC members on reques