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排序方式: 共有4996条查询结果,搜索用时 15 毫秒
41.
SiC particulate preforms were infiltrated by TiN matrix from a gas mixture of TiCl4 (5%), nitrogen (30%) and hydrogen using a repeating pressure pulse between 760 and about 1 torr. SiC particle sizes of 5 and 20 m were used. For matrix packing into deep level, optimum temperature was determined between 800 and 850 °C, and the maximum packing ratio reached 67% after 4 × 104 pulses at 850 °C. The increase of TiCl4 concentration to 10% resulted in higher deposition rate and packing ratio. The decrease of nitrogen concentration led to slower deposition, that is, a similar effect to temperature lowering. The maximum flexural strength measured was 140 MPa. 相似文献
42.
针对巨量可选方案的群体决策问题,提出了一个新的基于参考点和投票规则的多目标粒子群优化算法。该算法把个体与参考点的支配关系或者距离作为一个重要因素,在选择引导者的锦标赛方法,局部最优更新规则,以及外部种群档案剪枝规则中都嵌入了基于支配关系或距离因素的投票规则,以找到群体决策解,并且提高搜索效率。仿真结果表明该算法有效。 相似文献
43.
44.
Colussi C Banfi C Brioschi M Tremoli E Straino S Spallotta F Mai A Rotili D Capogrossi MC Gaetano C 《Proteomics. Clinical applications》2010,4(1):71-83
Purpose: Histone Deacetylase Inhibitors (DI) ameliorates dystrophic muscle regeneration restoring muscular strength in the mdx mouse model of Duchenne muscular dystrophy (DMD). The further development of these compounds as drugs for DMD treatment is currently hampered by the lack of knowledge about DIs effect in large dystrophic animal models and that of suitable biomarkers to monitor their efficacy. Experimental design: In this study we applied proteomic analysis to identify differentially expressed proteins present in plasma samples from mdx mice treated with the Suberoylanilide hydroxamic acid (SAHA) and relative normal controls (WT). Results: Several differentially expressed proteins were identified between untreated wild type and mdx mice. Among these, fibrinogen, epidermal growth factor 2 receptor, major urinary protein and glutathione peroxidase 3 (GPX3) were constitutively up‐regulated in mdx, while complement C3, complement C6, gelsolin, leukaemia inhibitory factor receptor (LIFr), and alpha 2 macroglobulin were down‐regulated compared to WT mice. SAHA determined the normalization of LIFr and GPX3 protein level while apoliprotein E was de novo up‐regulated in comparison to vehicle‐treated mdx mice. Conclusions and clinical relevance: Collectively, these data unravel potential serological disease biomarkers of mdx that could be useful to monitor muscular dystrophy response to DI treatment. 相似文献
45.
Van Thanh Dau Thien Xuan Dinh Tanaka Katsuhiko Sugiyama Susumu 《Microsystem Technologies》2009,15(7):1039-1044
A gas-jet micro pump with novel cross-junction channel has been designed and fabricated using a Si micromachining process.
The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT) diaphragm actuator and fluidic network.
The design of the valveless pump focuses on a cross-junction formed by the neck of the pump chamber and one outlet and two
opposite inlet channels. The structure of cross-junction allows differences in fluidic resistance and fluidic momentum inside
the channels during each PZT diaphragm vibration cycle, which leads to the gas flow being rectified without valves. The flow
channels were easily fabricated by using silicon etching process. To investigate the effects of the structure of the cross-junction
on the gas flow rate, two types of pump with different cross-junction were studied. The design and simulation were done using
ANSYS-Fluent software. The simulations and experimental data revealed that the step-nozzle structure is much more advantageous
than the planar structure. A flow rate of 5.2 ml/min was obtained for the pump with step structure when the pump was driven
at its resonant frequency of 7.9 kHz by a sinusoidal voltage of 50 Vp–p. 相似文献
46.
针对电力系统经济负荷分配问题,提出一种有效的差分蜂群算法.受差分进化算法的启发,该算法基于差分进化操作改进了雇佣蜂的搜索方式,提高了探索能力和收敛速度.此外,提出一种有效的修复机制以保证新个体的可行性.该算法在带有阀点效应和多燃料特征的典型电力系统经济负荷分配问题上进行了测试.仿真结果验证了所提算法的有效性. 相似文献
47.
Fabrication techniques of microstructures with high resolution and high aspect ratio are necessary for practical microelectromechanical
systems (MEMS) that have high performance and integration. In order to fabricate microstructures with sub-micron resolution
and high aspect ratio, deep X-ray lithography has been investigated using the compact synchrotron radiation (SR) light source
called “AURORA”. An X-ray mask for sub-micron deep X-ray lithography, which is composed of 1 μm thick Au as absorbers, 2 μm
thick SiC as a membrane and 625 μm thick Si as a frame, was designed. In preliminary experiments, the following results were
achieved: EB resist microstructures with an aspect ratio of 22 corresponding with 0.07 μm width and 1.3 μm height were formed;
a 10 μm thick PMMA resist containing no warp was formed by direct polymerization, enabling more precise gap control. 相似文献
48.
介绍了利用红外线的发射与接收所构成的光束保护系统。红外线的发射与接收形成一“安全网” ,利用其档光性能 ,可以实现安全防范功能。为提高系统抗干扰性能 ,采用调制的红外光线 ,经过信号处理 ,驱动继电器动作 ,从而实现报警和保护。重点阐述了光束保护系统的基本工作原理 ,并给出了主要硬件原理图。 相似文献
49.
The static and impact fracture toughnesses of a polybutylene terephthalate/polycarbonate/impact modifier (PBT/PC/IM) blend
were studied at different temperatures. The static fracture toughness of the blend was evaluated via the specific fracture
work concept and the J-integral analysis. A comparison of these two analytical methods showed that the specific essential fracture work, W
e, was equivalent to the
obtained by the ASTM E813-81 procedure, representing the crack initiation resistance of the material. The discrepancy between
W
e and
of ASTM E813-89 was caused by the extra energy component in
consumed by a 0.2 mm crack growth. Impact fracture toughness was also analysed using the specific essential fracture work
approach. When the fracture was elastic, W
e was equivalent to the critical potential energy release rate, G
IC, obtained via LEFM analysis. Temperature and strain-rate effects on the fracture toughness were also studied. The increase
in impact toughness with temperature was attributed to two different toughening mechanisms, namely, the relaxation processes
of the rubbery particles and the parent polymers in a relatively low-temperature range and thermal blunting of the crack tip
at higher temperatures. The enhancement in static fracture toughness at temperatures below — 60 °C was thought to be caused
by plastic crack-tip blunting, but the monotonic reduction in yield stress was largely responsible for the toughness decreasing
with higher temperatures. The temperature-dependent fracture toughness data obtained in static tests could be horizontally
shifted to match roughly the data for the impact tests, indicating the existence of a time-temperature equivalence relationship. 相似文献
50.
A simple energy balance analysis is presented for the tearing of ductile sheet metals using the trousers test. It is shown that the specific essential work of fracture (w
e
) for tearing can be estimated by extrapolating the straight line relationship between the tearing force per unit thickness and the trousers leg width to zero leg width. There are two contributions to the specific essential work of fracture: one is due to the localised plastic shearing work in a zone contiguous with the torn edges (w
e1
) and the other is the final out-of-plane tearing work (w
e2
).
Résumé En utilisant le Trousers Test, on présente une analyse simple d'équilibre énergétique dans le cas du déchirement de feuilles métalliques ductiles. On montre qu'il est possible d'estimer le travail spécifique de rupture en déchirement w e en extrapolant la relation linéaire qui lie la force de déchirement par unité d'épaisseur et la largeur de l'échantillon caractéristique entre une valeur 0 et une valeur donnée. Deux éléments contribuent au travail spécifique essentiel de rupture, l'un est dû au travail de cisaillement plastique local dans une zone contigue aux bords de l'arrachement (w e1 ) et l'autre est le travail de déchirement final hors du plan de la feuille (w e2 ).相似文献