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991.
A. Veillère J.-M. Heintz N. Chandra J. Douin M. Lahaye G. Lalet C. Vincent J.-F. Silvain 《Materials Research Bulletin》2012,47(2):375-380
This study focuses on the fabrication, for power electronics applications, of adaptive heat sink material using copper alloys/carbon fibers (CF) composites. In order to obtain composite material with good thermal conductivity and a coefficient of thermal expansion close to the ceramic substrate, it is necessary to have a strong matrix/reinforcement bond. Since there is no reaction between copper and carbon, a carbide element (chromium or boron) is added to the copper matrix to create a strong chemical bond. Composite materials (Cu–B/CF and Cu–Cr/CF) have been produced by a powder metallurgy process followed by an annealing treatment in order to create the carbide at the interphase. Chemical (Electron Probe Micro-Analysis, Auger Electron Spectroscopy) and microstructural (Scanning and Transmission Electron Microscopies) techniques were used to study the location of the alloying element and the carbide formation before and after diffusion. Finally, the thermo-mechanical properties have been measured and a promising composite material with a coefficient of thermal expansion 25% lower than a classic copper/carbon heat sink has been obtained. 相似文献
992.
The structural, electronic and magnetic properties of a 9-layer symmetrical FeMoO terminated (001)-oriented slab of double perovskite Sr2FeMoO6 have been studied by using the first-principle projector augmented wave potential within the generalized gradient approximation taking into account the on-site Coulomb repulsive (U = 2.0 eV for Fe and 1.0 eV for Mo). An outward relaxation is observed for each layer of the first four layers and the accompanying layer's rumpling has a decreasing trend from layer 1 to layer 4. Along Fe-O-Mo-O-Fe or Mo-O-Fe-O-Mo chain, the oxygen atom is closer to the adjacent Mo atom than to the adjacent Fe atom. The half-metallic nature ensures the symmetrical FeMoO terminated (001)-oriented slab of double perovskite Sr2FeMoO6 to be a potential application in spintronic devices. The Jahn-Teller structural distortions and the outward relaxations lead to the differences between pz state and similar px and py states, between dxy state and similar dyz and dxz states as well as between dz2 and dx2 − y2. The reduction in the restrictions from the reduction in the number of the near neighbors, especially the vanishing of the nearest neighbor oxygen atom just above the transition-metal (TM) atoms on the first layer makes not only the remaining axial TM-O distances slightly shorter than the four equatorial TM-O distances but also shifts toward higher energy region the occupied up-spin and down-spin states with respect to the cases of the TM atoms on the third and fifth layers. 相似文献
993.
994.
<正>本案建筑层高不理想,而且轮廓和横梁的棱角也较多,但是设计师在充分考量了空间结构和功能需求之后,却将其转化为两个关键的设计元素。首先,设计师采用之字形的回环路径巧妙地解决了 相似文献
995.
996.
A study of convergence in decentralized design processes 总被引:1,自引:1,他引:0
The decomposition and coordination of decisions in the design of complex engineering systems is a great challenge. Companies
who design these systems routinely allocate design responsibility of the various subsystems and components to different people,
teams or even suppliers. The mechanisms behind this network of decentralized design decisions create difficult management
and coordination issues. However, developing efficient design processes is paramount, especially with market pressures and
customer expectations. Standard techniques to modeling and solving decentralized design problems typically fail to understand
the underlying dynamics of the decentralized processes and therefore result in suboptimal solutions. This paper aims to model
and understand the mechanisms and dynamics behind a decentralized set of decisions within a complex design process. By using
concepts from the fields of mathematics and economics, including Game Theory and the Cobweb model, we model a simple decentralized
design problem and provide efficient solutions. This new approach uses matrix series and linear algebra as tools to determine
conditions for convergence of such decentralized design problems. The goal of this paper is to establish the first steps towards
understanding the mechanisms of decentralized decision processes. This includes two major steps: studying the convergence
characteristics and finding the final equilibrium solution of a decentralized problem. Illustrations of the developments are
provided in the form of two decentralized design problems with different underlying behavior. 相似文献
997.
Phoebe A. Stapleton Valerie C. Minarchick Amy M. Cumpston Walter McKinney Bean T. Chen Tina M. Sager David G. Frazer Robert R. Mercer James Scabilloni Michael E. Andrew Vincent Castranova Timothy R. Nurkiewicz 《International journal of molecular sciences》2012,13(11):13781-13803
Engineered nanomaterials have been developed for widespread applications due to many highly unique and desirable characteristics. The purpose of this study was to assess pulmonary inflammation and subepicardial arteriolar reactivity in response to multi-walled carbon nanotube (MWCNT) inhalation and evaluate the time course of vascular alterations. Rats were exposed to MWCNT aerosols producing pulmonary deposition. Pulmonary inflammation via bronchoalveolar lavage and MWCNT translocation from the lungs to systemic organs was evident 24 h post-inhalation. Coronary arterioles were evaluated 24–168 h post-exposure to determine microvascular response to changes in transmural pressure, endothelium-dependent and -independent reactivity. Myogenic responsiveness, vascular smooth muscle reactivity to nitric oxide, and α-adrenergic responses all remained intact. However, a severe impact on endothelium-dependent dilation was observed within 24 h after MWCNT inhalation, a condition which improved, but did not fully return to control after 168 h. In conclusion, results indicate that MWCNT inhalation not only leads to pulmonary inflammation and cytotoxicity at low lung burdens, but also a low level of particle translocation to systemic organs. MWCNT inhalation also leads to impairments of endothelium-dependent dilation in the coronary microcirculation within 24 h, a condition which does not fully dissipate within 168 h. The innovations within the field of nanotechnology, while exciting and novel, can only reach their full potential if toxicity is first properly assessed. 相似文献
998.
999.
1000.
Filoteo J. Vincent; Maddox W. Todd; Davis Jennifer D. 《Canadian Metallurgical Quarterly》2001,115(4):786
Linear and nonlinear categorization rule learning was examined in patients with Huntington's disease (HD) and a group of controls using the perceptual categorization task. Participants learned to categorize simple line stimuli into 1 of 2 categories over 600 trials. In addition to traditional measures of accuracy, quantitative model-based analyses were applied to each participant's data to characterize better the nature of any observed deficits. In the linear rule condition, HD patients displayed an early-training deficit relative to controls, whereas later in training the HD patients were not statistically different from controls. In the nonlinear rule condition, HD patients displayed both an early- and late-training deficit. The quantitative model-based analyses revealed that the HD patients' deficits in the linear condition were due to an impairment in learning the experimenter-defined rule and not in applying a learned rule inconsistently. In the nonlinear condition, in contrast, the HD patients' deficits were due to an impairment in learning the experimenter-defined rule and in applying a learned rule inconsistently. Overall, these results suggest that HD can result in a deficit in learning both linear and nonlinear categorization rules. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献