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951.
乙酸乙酯合成实验的方法、产品产率计算几种情况的分析讨论。 相似文献
952.
953.
J González de Dios M Moya Benavent MC Sirvent Mayor T Durá Travé 《Canadian Metallurgical Quarterly》1996,45(4):403-408
Cytomegalovirus is the main agent of congenital viral infections. The aim of this study was to compare the incidence of congenital cytomegalovirus infections of two groups of newborns of differing socioeconomic status. Cytomegalovirus was isolated from urine or oropharingeal secretions in 218 children born in a private clinic and 471 born in a public hospital. Positive viral isolates were confirmed with indirect immunofluorescence using monoclonal antibodies. Infection was detected in 12 children (1.82%), four coming from the private clinic (1.86%) and 8 coming from the public hospital (1.81%). Ninety two percent of infected children were asymptomatic. Urine and oropharingeal secretion samples had the same yield for viral isolation. It is concluded that the incidence of congenital cytomegalovirus infection is similar to that described in developed countries. 相似文献
954.
气凝胶──一种结构可控的新型功能材料 总被引:2,自引:0,他引:2
气凝胶是一种结构可控的新型轻质纳米多孔性非晶固态材料,具有许多特殊性质,因而蕴藏着广阔的应用前景。本文综述了气凝胶材料的制备方法、结构控制原理、性质和各种可能的应用。 相似文献
955.
956.
Wu Zhaohao 《电子科学学刊(英文版)》1987,4(4):273-281
Some data of emission and evaporation properties related to tungsten matrix structures of the impregnated cathodes are analyzed.
The results indicate that the particle size of tungsten powder and the pore size in the porous matrix determine the total
inside surface area of all pores, the diffusion length of barium atoms over tungsten grain surfaces, and the diameter and
length of the path through which barium atoms are transported. These factors all relate to the properties and operation mechanism
of an impregnated cathode; therefore, it would not be strictly correct to use only the matrix porosity for characterizing
the cathode properties. Finally, the preferred structures of porous tungsten matrix depending on different applications of
impregnated, cathodes are proposed. 相似文献
957.
958.
软磁材料中存在巨磁阻抗 (giantmagneto impedance ,GMI)效应以及与之相同来源的应力阻抗 (stress impedance ,SI)效应 ,利用这两种效应可以制成具有高灵敏度的微型化的磁场和应力 应变传感器。本文基于传感器的实际应用 ,对图形化的、较大磁致伸缩的FeSiB单层和多层薄膜的巨磁阻抗和应力阻抗效应中频率和退火的影响进行了研究。结果表明 ,对于两种效应 ,经过退火处理的单层和多层膜均可在较低的频率下得到较高的灵敏度 ,而多层膜中的应力阻抗效应将为新型高灵敏传感器的设计和研制开辟一条崭新的途径 相似文献
959.
A system-on-chip (SOC) usually consists of many memory cores with different sizes and functionality, and they typically represent a significant portion of the SOC and therefore dominate its yield. Diagnostics for yield enhancement of the memory cores thus is a very important issue. In this paper we present two data compression techniques that can be used to speed up the transmission of diagnostic data from the embedded RAM built-in self-test (BIST) circuit that has diagnostic support to the external tester. The proposed syndrome-accumulation approach compresses the faulty-cell address and March syndrome to about 28% of the original size on average under the March-17N diagnostic test algorithm. The key component of the compressor is a novel syndrome-accumulation circuit, which can be realized by a content-addressable memory. Experimental results show that the area overhead is about 0.9% for a 1Mb SRAM with 164 faults. A tree-based compression technique for word-oriented memories is also presented. By using a simplified Huffman coding scheme and partitioning each 256-bit Hamming syndrome into fixed-size symbols, the average compression ratio (size of original data to that of compressed data) is about 10, assuming 16-bit symbols. Also, the additional hardware to implement the tree-based compressor is very small. The proposed compression techniques effectively reduce the memory diagnosis time as well as the tester storage requirement. 相似文献
960.
萃取精馏回收环己烷的双组分溶剂的研究 总被引:3,自引:0,他引:3
在研究萃取精馏分离回收环己烷的单溶剂的基础上,研究了双组分溶剂。当剂油比为7:1时,环己醇和四甘醇双组分溶剂可以将正庚烷对环己烷的相对挥发度由单溶剂时的小于1提高到1.11;将2,3—二甲基戊烷对环己烷的相对挥发度由单溶剂时的小于1.07提高到1.21。用该溶剂在小型萃取精馏实验装置上运行,结果表明,环己烷的纯度为98.5%,收率为80%。 相似文献