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951.
952.
TiNi形状记忆合金与317L不锈钢耐腐蚀性能的对比研究 总被引:1,自引:0,他引:1
用电化学阳极极化、原子吸收谱及金相等方法研究了TiNi形状记忆合金和317L不锈钢在37℃的1%NaCl溶液中的腐蚀性能。 相似文献
953.
毛培法 《浙江工业大学学报》1992,(4)
本文提出容差扩展的三原则,并按该原则分析了电压比较器μA710(SN52510,TEXAS),提出了改进方案.按该方案集成的电压比较器FBC_(01)与同样条件下的μA710相比,成品率提高两倍,迟延时间缩小四倍,参数一致性显著提高. 相似文献
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956.
IDES: An Internet Distance Estimation Service for Large Networks 总被引:2,自引:0,他引:2
Mao Y. Saul L. K. Smith J. M. 《Selected Areas in Communications, IEEE Journal on》2006,24(12):2273-2284
The responsiveness of networked applications is limited by communications delays, making network distance an important parameter in optimizing the choice of communications peers. Since accurate global snapshots are difficult and expensive to gather and maintain, it is desirable to use sampling techniques in the Internet to predict unknown network distances from a set of partially observed measurements. This paper makes three contributions. First, we present a model for representing and predicting distances in large-scale networks by matrix factorization which can model suboptimal and asymmetric routing policies, an improvement on previous approaches. Second, we describe two algorithms-singular value decomposition and non-negative matrix factorization-for representing a matrix of network distances as the product of two smaller matrices. Third, based on our model and algorithms, we have designed and implemented a scalable system-Internet Distance Estimation Service (IDES)-that predicts large numbers of network distances from limited samples of Internet measurements. Extensive simulations on real-world data sets show that IDES leads to more accurate, efficient and robust predictions of latencies in large-scale networks than existing approaches 相似文献
957.
Antioxidants such as probucol and alpha-tocopherol have been shown to attenuate the oxidation of low-density lipoproteins (LDL) and atherosclerotic lesions in animal models of atherosclerosis. The purpose of this study is to determine the protection effect of antioxidants on endothelial cells when exposed to oxidized and native LDL. In a cell-free system, we found that probucol, alpha-tocopherol, and ascorbic acid inhibited copper-induced LDL oxidation by a dose-dependent fashion (from 1 microM to 10 mM). In porcine aortic endothelial cells, antioxidants alone did not change basal endothelin-1 (ET-1) secretion. When porcine aortic endothelial cells were exposed to LDL and oxidized-LDL, both of them stimulated ET-1 secretion dose-dependently, whereas oxidized-LDL elicited higher ET-1 secretion. However, probucol, alpha-tocopherol, and ascorbic acid did not prevent LDL or oxidized-LDL induced ET-1 secretion. Furthermore, nimodipine inhibited both of native and oxidized LDL induced ET-1 secretion. Since Ca2+ channel blocker reduced the elevation of induced ET-1 secretion, the [Ca2+]i is possibly involved for the regulation of ET-1 secretion. Our results suggest that antioxidants can only prevent the oxidation of LDL rather than oxidized and native LDL-induced ET-1 secretion in vascular endothelial cells. The increase in the [Ca2+]i of endothelial cells through the opening of voltage-dependent Ca2+ channels may be involved in the LDL-induced ET-1 release. 相似文献
958.
HJD04系列交换机是目前国内首选的优秀机种,系统中三方通话和会议电话功能的实现有其独到之处,本文对此作一简要介绍。 相似文献
959.
The effect of local mixing on the performance of a reactor system is derived by the perturbation technique. It is found that the sign of the inner product of the adjoint vector λ and the acceleration vector ? is the only indicator as to whether or not local mixing at a certain point of a reaction path is desirable. A complex reaction system with competing side reactions of different order is treated as an example. The possibility of applying the results in this work to the selection of the optimal type of reactor is also discussed. 相似文献
960.