Modeling of glass sintering applied for the fabrication of porous glass bodies

The sintering behavior of borosilicate and soda-lime mono-sized glass beads was investigated with the aim to fabricate transparent porous glass balls and cylinders. As the glasses tend to crystallize, temperatures where the sintering was in advantage compared to crystallization were used. Isothermal studies were undertaken for modeling the evolution of sintering necks as a function of radii of beads, temperature and time. The Frenkel model of viscous flow was applied to predict first and second stage of sintering. As the sintering of the glasses without crystallization was only possible at high temperatures the process is very fast and has to be controlled precisely. The results of this work were applied for the fabrication of porous bodies with specific characteristics: different geometries and sizes, transparency, high porosities to be achieved during first stage sintering of spherical glass beads. The porous parts with these characteristics are used for the investigation of hydrodynamic processes in the pore network of glass parts.     

Entwicklung eines webbasierten Dokumentenmanagement-Systems für eine Fluggesellschaft

Ohne Zusammenfassung Zuschriften zum Studierendenforum bitte an: Universit?t Bayreuth Lehrstuhl BWL VII (Wirtschaftsinformatik) Prof. Dr. Torsten Eymann Redaktion Studierendenforum z. Hd. Dipl.-Wirtschaftsinformatiker Stefan K?nig Universit?tsstra?e 30 95447 Bayreuth E-Mail: stefan.koenig@uni-bayreuth.de     

Simlab 1 - A Laboratory Workflow Recorder for Process Assessment

Process management and workflow optimisation have become key issues of good laboratory management and now seem to be predominant over traditional challenges such as the quality of analytical testing. The first author of this paper has conducted several workflow optimisation studies for clinical laboratories in Europe (Universities of Zurich and Amsterdam, Manchester Royal Infirmary and others) and in the US (University of Virginia), using a laboratory-specific simulation software called Simlab™ for realistic computer modeling of laboratory scenarios. Since data input and calibration of the models against reality have always been a challenge in these studies, we looked into possibilities of using automated data extraction to extract as much information as possible from the laboratory information system. In this paper we describe our first experience with a Microsoft Excel™-based software program called Simlab 1, which uses the ASCII file transfer protocol to extract data from the LIS.     

Effect of MOVPE growth interruptions on the gallium arsenide interior interface morphology

We have studied MOVPE-grown interior GaAs/AlAs interfaces using highly selective etching combined with atomic force microscopy. We observe substantial restructuring for samples grown on both (100) exact and vicinal substrates. Interface structures differ significantly from sample surfaces after cool-down. On (100) exact substrates, the macroscopic monolayer island and terrace structure smoothes during growth interruptions over the whole 2 min period of time studied. A new, mesoscopic scale of roughness is detected for the first time. This structure does not depend on growth interruption time but does change its typical size at different growth temperatures. On vicinal substrates, we observe and quantify step bunching during growth interruption. The growing surface itself is smooth, in sharp contrast to the corresponding macrostepped GaAs sample surface obtained after cooling down.     

The history of alternative fuels in transportation: The case of electric and hybrid cars

The article describes and presents a critical analysis of the long history of alternative fuels and propulsion technologies, particularly in automobile applications. Cases are electric and hybrid cars. The term “critical analysis” refers to the analysis of the various alternative technologies in relation to their societal contexts. In particular, these are the varying contexts of energy security, energy policy, environmental problems, sustainability, and also the later more explicit climate change context. This approach gives some knowledge with relevance to the current discussions on implementation issues. The work is first of all founded on the knowledge field of “Social Studies of Technological Systems”.     

Parametrizing compactly supported orthonormal wavelets by discrete moments

We discuss parametrizations of filter coefficients of scaling functions and compactly supported orthonormal wavelets with several vanishing moments. We introduce the first discrete moments of the filter coefficients as parameters. The discrete moments can be expressed in terms of the continuous moments of the related scaling function. To solve the resulting polynomial equations we use symbolic computation and in particular Gröbner bases. The cases of four to ten filter coefficients are discussed and explicit parametrizations are given.     

Die chemischen Ver?nderungen des Weines durch Kahm

Ohne Zusammenfassung     

Trilateral Intercomparison of Photometric Units Maintained at NIST (USA), NPL (UK), and PTB (Germany)

A trilateral intercomparison of photometric units between NIST (USA), NPL (UK), and PTB (Germany) has been conducted to update the knowledge of the relationship between the photometric units disseminated in the three countries. The luminous intensity unit (cd), the luminous responsivity scale (A/lx), and the luminous flux unit (lm) maintained at each laboratory were compared by circulating transfer standard lamps and photometers. The results showed that the relative luminous intensity values, with respect to the average, measured by NIST, NPL, and PTB were 1.0014, 1.0021, and 0.9966; the relative inverse values of the luminous responsivity (corresponding to illuminance) were 1.0023, 1.0011, and 0.9965; the relative luminous flux values were 0.9994, 1.0034, and 0.9972, respectively. The results agreed within the stated uncertainties of the units maintained at the three laboratories.