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91.
Jean‐Pierre Coyette Karl Meerbergen Mickaël Robb 《International journal for numerical methods in engineering》2005,64(13):1752-1768
In this paper, we analyse the numerical time integration of models of exterior acoustics. The major challenge lies in the instabilities that may arise from the infinite elements. In this paper we consider the special case of spherical infinite elements formulations, which have shown their relevance for industrial applications. We propose a method that combines Crank–Nicholson's method with a filtering step by the backward Euler method. The paper is illustrated with an example relevant to industry. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Current concerns over reforming engineering education have focused attention on helping students develop skills and an adaptive expertise. Phenomenological guidelines for instruction along these lines can be understood as arising out of an emerging theory of thinking and learning built on results in the neural, cognitive, and behavioral sciences. We outline this framework and consider some of its implications, such as developing a more detailed understanding of the specific skill of using mathematics in modeling physical situations. This approach provides theoretical underpinnings for some best‐practice instructional methods designed to help students develop this skill and provides guidance for further research in the area. 相似文献
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According to DIN-ISO 898-1 high tensile bolts of class 8.8 must have a quenched and tempered structure. Therefore either quenched and tempered wire rod is used for cold heading or the bolts are quenched and tempered after the bolt forming process. This paper presents a new wire rod, which offers the chance to get comparable or even better final properties and lower production costs: a low-carbon MnSi wire rod is used as basic material. The final tensile strength is produced by drawing and cold forming. The conventional final quenching and tempering is omitted and for many cases also baking can be avoided. An increased fatigue resistance and the elimination of final straightening of the bolts are additional advantages of the new process. 相似文献
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Hans Kleemann Alrun A. Günther Karl Leo Björn Lüssem 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(21):3670-3677
Vertical organic thin‐film transistors (VOTFTs) are promising devices to overcome the transconductance and cut‐off frequency restrictions of horizontal organic thin‐film transistors. The basic physical mechanisms of VOTFT operation, however, are not well understood and VOTFTs often require complex patterning techniques using self‐assembly processes which impedes a future large‐area production. In this contribution, high‐performance vertical organic transistors comprising pentacene for p‐type operation and C60 for n‐type operation are presented. The static current–voltage behavior as well as the fundamental scaling laws of such transistors are studied, disclosing a remarkable transistor operation with a behavior limited by injection of charge carriers. The transistors are manufactured by photolithography, in contrast to other VOTFT concepts using self‐assembled source electrodes. Fluorinated photoresist and solvent compounds allow for photolithographical patterning directly and strongly onto the organic materials, simplifying the fabrication protocol and making VOTFTs a prospective candidate for future high‐performance applications of organic transistors. 相似文献
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Karl Jousten 《真空研究与实践》2023,35(1):40-46
To mark our anniversary, we are presenting articles that have been particularly appreciated by readers of our online edition once again in print. Here: By accurate vacuum measurement, it is possible to control processes in industry, to ensure the necessary environmental conditions for many experiments in science and research and to support the commercial relationship between manufacturers and users of vacuum equipment. The main task of vacuum metrology, the science of vacuum measurement, is to provide traceability of vacuum measurements to the SI. In recent years, also the characterization of vacuum by partial pressure analysis and outgassing rate measurement, and the dynamics of vacuum measurement became an issue for vacuum metrology. 相似文献