Local anodic oxidation by AFM tip developed for novel semiconductor nanodevices

The local anodic oxidation (LAO) by the tip of atomic force microscope (AFM) is used for fabrication of nanometer-scaled structures and devices. We study the technology of LAO applied to semiconductor heterostructures, theoretically and experimentally as well. The goal is to improve the LAO process itself, i.e., to create narrow LAO lines that form high-energy barriers in the plane with the 2D electron gas. In the first part we show the electric field distribution in the system tip-sample during LAO. For samples with low-conductive cap layer the maximum electric field is shifted apart the tip apex, which leads to wide oxide lines. Our Monte Carlo (MC) calculations show how the height of the energy barrier in the system depends on the geometry of the created lines (trenches), and on voltage applied to the structure. Based on the calculations, we have proposed a novel LAO technology and applied it to InGaP/AlGaAs/GaAs heterostructure with doping layer only 6 nm beneath the surface. The doping layer can be oxidized easily by the AFM tip in this case, and the oxide objects can be removed by several etchants. This approach to the LAO technology leads to narrow LAO trenches (60 nm) and to energy barriers high enough for room- and low-temperature applications.     

Sense of virtual community: A follow up on its measurement

Understanding the dynamics of virtual communities has become an important issue for research. One concept that explains the participation in online communities is a sense of virtual community (SOVC), which is based on the offline equivalent sense of community (SOC) and describes a “spirit of belonging together”. Although these two concepts are similar, their measurement is problematic. Inspired by earlier studies, which investigated whether traditional SOC measures are appropriate for measuring SOVC, we adopted the SOC index 2 (SCI2) recently developed by Chavis et al. in a virtual setting. Our aim was to determine whether the refined SOC measurement is more suitable for virtual communities than their forerunners. We tested the SCI2 in a popular German community on 312 respondents. Our results showed that a thorough measure of SOVC still needs further refinement. We also discuss possibilities for improvement.     

Smart Cities Concept for Historical Buildings

The article presents the literature review on building environment quality especially humidity of historical buildings. It is based on the research of the application of electro osmosis for drying of historical buildings in Bratislava conducted by the Department of the physics at the Faculty of Civil Engineering Slovak University of Technology in Bratislava. The applied technology is put in the context with the Smart Cities concept, to extend and improve the efficiency of the dehumidification process.

     

Modeling and simulating residential mobility in a shrinking city using an agent-based approach

Shrinking cities are characterized by a huge oversupply of dwellings and resulting residential vacancies. Discussions among urban planners and policymakers in Europe have focused on the consequences of urban shrinkage following demographic transition, fertility decline and individualization. In this study, the shrinking city of Leipzig in Eastern Germany is singled out as a case basis for the study of residential mobility and land use change using agent-based modeling techniques, in which social scientists developed a concept of household types based on empirical data that form a unique base; these techniques were used to construct a data-driven, agent-based model. The spatially explicit simulation model RESMOBcity presented here ‘translates’ these empirical data via behavioral rules of households. It computes spatially explicit household patterns, housing demands and residential vacancies. Based on three scenarios, population growth, stagnation and shrinkage, we show that population might stabilize within the coming years. The number of households is expected to further increase. We demonstrate that a selective demolition of vacant housing stock can counteract the enormous oversupply of dwellings and better balance housing demand and the number of available flats. Scenario simulation shows that the model can reproduce observed patterns of population, inner-urban migration and residential vacancy in a spatially explicit manner and thus can be applied to the analysis of scenarios of demographic change in urban regions. The presented model acts as a tool supporting the testing of hypotheses in social science research and allowing the quantification of land-use scenarios in urban regions based on household choices.     

Exploring Workflow Interoperability for Neuroimage Analysis on the SHIWA Platform

Neuroimaging is a field that benefits from distributed computing infrastructures (DCIs) to perform data processing and analysis, which is often achieved using Grid workflow systems. Collaborative research in neuroimaging requires ways to facilitate exchange between different groups, in particular to enable sharing, re-use and interoperability of applications implemented as workflows. The SHIWA project provides solutions to facilitate sharing and exchange of workflows between workflow systems and DCI resources. In this paper we present and analyse how the SHIWA Platform was used to implement various cases in which workflow exchange supports collaboration in neuroscience. The SHIWA Platform and the implemented solutions are described and analysed from a “user” perspective, in this case workflow developers and neuroscientists. We conclude that the platform in its current form is valuable for these cases, and we identify remaining challenges.     

Integration of communicative hand movements into human-computer-interaction

During face-to-face communication, the dialog partners can see and hear each other. Each speaker produces a variety of phenomena parallel to speech. Some of them, e.g. intonation, are coded vocally, others are coded by motor responses (facial expression, gestures, etc.). If human-computer-interaction (HCI) tries to mimic this situation, at least some non-verbal phenomena have to be integrated into natural language input and output. A multitude of new devices (mouse, joystick, touch-screens, etc.) have enabled this transition to multimodal HCI. Gestures which illustrate the content of the verbal message are especially suitable for integration into HCI. A relevant subset of them is pointing gestures, which specify elements of the visual context. They are performed frequently because their use shortens and simplifies the verbal output. As an illustration of these considerations, the NL dialog system XTRA (University of Saarbrücken) is presented. It allows reference to elements of a tax form by the combination of textual input and simulated pointing gestures. In order to explore the regularities of this form deixis, an experiment has been carried out within the framework of the XTRA-project. Furthermore, its results were taken for an evaluation of the currently used simulation technique.Michael Wille is a researcher in the AI laboratory at the University of Saarbrücken. He has studied computer science, economics and cognitive psychology. he has worked on expert systems for SIEMENS (hardware diagnosis). His master's thesis (1989) was called Evaluation and Extension of a Module for the Simulation and Analysis of Pointing Gestures. His main research interest is multimedia interaction.Dagmar Schmauks is a researcher in the AI laboratory at the University of Saarbrücken. She has pursued studies in philosophy, linguistics and psychology. Her doctoral thesis (1990) was entitled Deixis in Man-Machine-interaction. Since 1985 she has worked in a special collaborative program on AI and knowledge-based systems at the University pf Saarbrücken. Her main research interest is multimedia interaction.     

A corrosion mechanism of titanium diboride in KF−AlF3−Al2O3 melt

TiB₂ samples were exposed to molten KF?AlF₃?Al₂O₃: 54.8-42.1-3.1 mol% salt, at 680 °C for 50, 100 and 200 h. The corroded samples of TiB₂ were investigated by SEM-EDX, EBSD, XRD, FT-IR and MAS NMR analysis. Corrosion was noted to occur predominantly as pitting attacks on the surface of the investigated materials. An inter-crystal and trans-crystal corrosion were identified on the cross-sections of the samples. A perturbation of TiB bonds was detected (SEM-EDX and NMR analysis), at which a formation of orthorhombic TiO₂ was also identified (EBSD analysis). The subsequent NMR, XRD and FT-IR analysis of the behaviour of TiB₂ powder in molten KF?AlF₃?Al₂O₃ supports the statement about the formation of orthorhombic TiO₂ and mullite type of aluminium borates.     

Seasonal variation of lipids in femoral gland secretions of male green iguanas (Iguana iguana)

Femoral gland secretions were collected from 21 captive adult male green iguanas (Iguana iguana) in Orotina, Costa Rica, and San Diego, California, during the breeding (November) and nonbreeding (March) seasons. Lipids were extracted with methylene chloride, weighed, separated by thin-layer chromatography, and analyzed by gas chromatography-mass spectrometry. Free and esterified C₁₄-C₂₆ fatty acids, 5-cholestan-3-ol (epico-prostanol), cholest-5-en-3-ol (cholesterol), cholest-5-en-24-methyl-3-ol (campesterol), cholesta-5,22-dien-24b-ethyl-3-ol (stigmasterol), cholesta-8,24(5)-dien-4,4,14-trimethyl-3-ol (lanosterol), cholest-5-en-24-ethyl-3-ol (-sitosterol), and two uncharacterized sterols were indicated. More lipids were recovered from femoral gland secretions obtained during the breeding than the nonbreeding months, indicating that secretion deposits may be more detectable during the mating season.     

Elektrische Antriebe für die Raumfahrt

Electric Propulsion for Space Flight This article describes electric rocket motors for satellites, probes and manned spacecraft based on principles used for material processing, too. The need for high exhaust velocities is explained and the limitations of conventional chemical thrusters are pointed out. Two important electric propulsion technologies, arcjet thrusters and gridded ion thrusters, together with their applications are described. Both types are currently successfully operated in space. Finally, a hybrid engine using an arcjet thruster and propellant heating by radiofrequency power is introduced. This concept is a potential solution for the propulsion demands of a future piloted mission to Mars.