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81.
Gerhard Voss 《真空研究与实践》2002,14(4):228-233
Graphs of “high‐vacuum pressure as a function of backing pressure” (“pHV versus pVV”) and “compression as a function of backing pressure” (“K versus pVV”) are presented in this article. The performance of any turbomolecular pump can be fully and reliably evaluated with the aid of these graphs. Until now these graphs have only seldom been shown in catalogs. The catalogs generally lack the so‐called “limit lines” (“Q as a function of pVV, Kmax”). For a prescribed gas throughput Q, the limit line indicates what minimum pressure must be generated by the backing pump at the fore‐line port of the turbomolecular pump so that a stable pressure exists at the high‐vacuum side of the turbomolecular pump. Using the gas‐type‐specific limit line and the corresponding, usually well‐documented pumping‐speed curve, one can already describe the functional proficiency and performance of a selected combination of turbomolecular pump plus backing pump in an approximate manner – but not yet completely. In this article we also indicate analytical functions which excellently describe the pressure dependence of the compression and pumping speed. 相似文献
82.
C.‐D. Munz R. Schneider E. Sonnendrücker E. Stein U. Voss T. Westermann 《International journal for numerical methods in engineering》1999,44(4):461-487
A new conceptual framework solving numerically the time‐dependent Maxwell–Lorentz equations on a non‐rectangular quadrilateral mesh in two space dimensions is presented. Beyond a short review of the applied particle treatment based on the particle‐in‐cell method, a finite‐volume scheme for the numerical approximation of the Maxwell equations is introduced using non‐rectangular quadrilateral grid arrangements. The coupling of a high‐resolution FV Maxwell solver with the PIC method is a new approach in the context of self‐consistent charged particle simulation in electromagnetic fields. Furthermore, first simulation results of the time‐dependent behaviour of an externally applied‐B ion diode developed at the Forschungszentrum in Karlsruhe are presented. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
83.
S. Voss R. SteinbrückM. Kautz E. SchießwohlM. Arendt J. Tom FeldeJ. Volkert D. Trimis 《International Journal of Hydrogen Energy》2011,36(5):3697-3703
The advance of efficient hydrogen-air combustion systems has increasingly become of interest in the framework of the development of fuel cell systems, especially for the automotive sector. Therefore, compact modulating systems are required, with the additional demand of low emissions, to be integrated in a fuel cell system. A modulating combustion system based on combustion within inert porous media and an integrated heat exchanger has been developed and investigated. The system is able to handle premixed combustion of lean H2/air mixtures at a surface load range of 1075 kW/m2-2150 kW/m2, and a global equivalence ratio of ?=0.5. The special hydrogen-air mixing concept eliminates the risk of flame flashback and enables operation with very low NOx emissions. 相似文献
84.
The hydroxylation activity of the Thr268Ala mutant of P450(BM3) has been shown to occur to varying degrees with small alterations in the structure of a fatty-acid substrate. Ten substrates were investigated, including straight chain, branched chain and cis-cyclopropyl substituted fatty acids with a straight-chain length that varied between 12 and 16 carbon atoms. The efficacy of the hydroxylation activity appeared to be governed by the chain length of the substrate. Substrates possessing 14 to 15 carbons afforded the highest levels of activity, which were comparable with the wild-type enzyme. Outside of this window, straight-chain fatty acids showed reduced activity over the other substrate types. These results provide a cautionary tale concerning the loss of ferryl activity in such cytochrome P450 threonine to alanine mutants, as the nature of the substrate can determine the extent to which hydroxylation chemistry is abolished. 相似文献
85.
Yasin Kanbur Mihai Irimia-Vladu Eric D. Głowacki Gundula Voss Melanie Baumgartner Günther Schwabegger Lucia Leonat Mujeeb Ullah Hizir Sarica Sule Erten-Ela Reinhard Schwödiauer Helmut Sitter Zuhal Küçükyavuz Siegfried Bauer Niyazi Serdar Sariciftci 《Organic Electronics》2012,13(5):919-924
We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C60 as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm2/Vs. Devices with pentacene showed a mobility of 0.16 cm2/Vs. Devices using tyrian Purple as semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ~0.3 cm2/Vs. These devices demonstrate low hysteresis and operational stability over at least several months. Grazing-angle infrared spectroscopy of evaporated thin films shows that the structure of the polyethylene is similar to solution-cast films. We report also on the morphological and dielectric properties of these films. Our experiments demonstrate that polyethylene is a stable dielectric supporting both hole and electron channels. 相似文献
86.
Nagamatsu Lindsay S.; Voss Michelle; Neider Mark B.; Gaspar John G.; Handy Todd C.; Kramer Arthur F.; Liu-Ambrose Teresa Y. L. 《Canadian Metallurgical Quarterly》2011,26(2):253
Successful mobility requires appropriate decision-making. Seniors with reduced executive functioning—such as senior fallers—may be prone to poor mobility judgments, especially under dual-task conditions. We classified participants as “At-Risk” and “Not-At-Risk” for falls using a validated physiological falls-risk assessment. Dual-task performance was assessed in a virtual reality environment where participants crossed a simulated street by walking on a manual treadmill while listening to music or conversing on a phone. Those “At-Risk” experienced more collisions with oncoming cars and had longer crossing times in the Phone condition compared to controls. We conclude that poor mobility judgments during a dual-task leads to unsafe mobility for those at-risk for falls. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
87.
A. Meftah W. AssmannN. Khalfaoui J.P. StoquertF. Studer M. ToulemondeC. Trautmann K.-O. Voss 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(9):955-958
The results of present paper have shown that sputtering of yttrium iron garnet (Y3Fe5O12) under swift heavy ions in the electronic energy loss regime is non-stoichiometric. Here we are presenting additional experimental results for gadolinium gallium garnet (Gd3Ga5O12) as target. The irradiations were performed with different ions (50Cr (589 MeV), 86Kr (195 MeV) and 181Ta (400 MeV)) impinging perpendicularly to the surface. As earlier, the sputtering yield was determined by collecting the emitted gadolinium and gallium atoms on a thin aluminium foil, placed upstream above the target and analyzing the Al catcher by Rutherford backscattering. Also for Gd3Ga5O12, the emission of Gd and Ga is non-stoichiometric. Sputtering appears above a critical electronic stopping power of Sth = 11.6 ± 1.5 keV/nm, which is larger than the threshold for track formation, in agreement with other amorphisable materials. In addition, the angular distribution of the sputtered species was measured for Y3Fe5O12 and Gd3Ga5O12 using 200 MeV Au ions impinging the surface at 20° relatively to the surface. For the two garnets the ratio of Y/Fe (and Gd/Ga) varies with the angle of emitted species and the stoichiometry seems to be preserved only for an emission perpendicular to the surface. 相似文献
88.
Ana Patricia Silva Gerry Jager Hannelize Van Zyl Hans-Peter Voss Manuela Pintado Tim Hogg 《Critical reviews in food science and nutrition》2017,57(7):1340-1349
Wine and beer consumption are an integral part of European culture: Southern Europe is associated with wine and Northern Europe is associated with beer. When consumed in moderation, these alcoholic beverages can be part of a balanced and healthy diet. In the 1990s, non-alcoholic beer (NAB), which has no cultural roots, became available in the market. This review identifies determinants for consumption of wine, beer, and NAB, using data on consumption patterns from Portugal and the Netherlands. Since the 1960s the image of Portugal as a wine country declined, whereas the image of the Netherlands as a beer country remained stable. In each country beer is now the most consumed alcoholic beverage and is mainly a men's beverage, whereas wine is the second most consumed and is consumed by both genders. Cultural differences define Portuguese as “outdoors, everyday drinkers”, within a meal context, and Dutch as “at home, weekend drinkers.” Wine is perceived as the healthiest beverage, followed by NAB, and regular beer. Motivation for consumption is related to context: wine for special occasions, beer for informal occasions, and NAB for occasions when alcohol is not convenient. Moderate wine and beer consumption seems to be surrounded by positive emotions.
This review is relevant for public health, for industry market strategies, and identifies opportunities of future research on drinking behaviour. 相似文献
89.
Adhesion studies of CVD copper metallization 总被引:2,自引:0,他引:2
Srinivas Gandikota Steve Voss Rong Tao Alain Duboust Dennis Cong Liang-Yuh Chen Sesh Ramaswami Daniel Carl 《Microelectronic Engineering》2000,50(1-4):547-553
The adhesion of chemical vapor deposition (CVD) Cu thin films to various barriers was observed to improve with a post-deposition anneal or a physical vapor deposition (PVD) Cu flash layer on the barrier before depositing CVD Cu. The ambient exposure of the barrier before the deposition of CVD Cu has been observed to lead to degradation of adhesion in both CVD Cu seed and CVD/PVD Cu high vacuum integrated metallization schemes. The integrated CVD and PVD Cu deposition scheme exhibits better adhesion due to the inherent annealing provided during the PVD deposition which is carried out at temperatures between 300 and 400°C. We have evaluated both qualitative and quantitative tests — tape test, Stud pull test and 4-point bend test — in understanding adhesion and observed that each of these tests give different details of interface breakdown. 相似文献
90.
Voss A Schulz S Schroeder R Baumert M Caminal P 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2009,367(1887):277-296
Methods from nonlinear dynamics (NLD) have shown new insights into heart rate (HR) variability changes under various physiological and pathological conditions, providing additional prognostic information and complementing traditional time- and frequency-domain analyses. In this review, some of the most prominent indices of nonlinear and fractal dynamics are summarized and their algorithmic implementations and applications in clinical trials are discussed. Several of those indices have been proven to be of diagnostic relevance or have contributed to risk stratification. In particular, techniques based on mono- and multifractal analyses and symbolic dynamics have been successfully applied to clinical studies. Further advances in HR variability analysis are expected through multidimensional and multivariate assessments. Today, the question is no longer about whether or not methods from NLD should be applied; however, it is relevant to ask which of the methods should be selected and under which basic and standardized conditions should they be applied. 相似文献