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21.
Shun-Chen Niu 《Queueing Systems》1988,3(2):157-178
We give in this paper a detailed sample-average analysis of GI/G/1 queues with the preemptive-resume LIFO (last-in-first-out) queue discipline: we study the long-run state behavior of the system by averaging over arrival epochs, departure epochs, as well as time, and obtain relations that express the resulting averages in terms of basic characteristics within busy cycles. These relations, together with the fact that the preemptive-resume LIFO queue discipline is work-conserving, imply new representations for both actual and virtual delays in standard GI/G/1 queues with the FIFO (first-in-first-out) queue discipline. The arguments by which our results are obtained unveil the underlying structural explanations for many classical and somewhat mysterious results relating to queue lengths and/or delays in standard GI/G/1 queues, including the well-known Bene's formula for the delay distribution in M/G/l. We also discuss how to extend our results to settings more general than GI/G/1. 相似文献
22.
本文介绍了一种以氟气和惰性气体为原料合成 Kr F2 和 Xe F2 的热催化合成方法并对合成机理和条件作了简单的讨论 ,利用合成的 Kr F2 作为氟化剂合成了含氟高能氧化剂 NF4BF4,纯度约为 93%,其红外光谱和拉曼光谱基本与文献值吻合。元素分析结果表明产品 NF4BF4中含 B5.8%(mass) ,自由氟原子含量为 9.95%(mass) ,与理论值基本一致 ,此结果也间接证明了 Kr F2 质量的可靠性。粉末状的 Xe F2 经升华 -再结晶纯化后可得纯净晶体产品。 相似文献
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报告了143例沈阳市健康人血清中Mg、Zn、Cu、Se、Cr含量及Cu/Zn值,并指出健康人血清中Mg与Cu量正相关,Mg与Cr呈负相关,Mg与Cu/Zn值呈正相关.Zn与Cr呈正相关.Zn与Cu/Zn呈负相关.Cu与Cr呈负相关。Cu与Cu/Zn值呈负相关.Cr与Cu/Zn值呈负相关. 相似文献
25.
Asiswellknown,thetheoryfornonlinearpolymerizationswasinitiatedbyFloryandStockmayer[1—3].MillerandMacosko[4—6]proposedarecursivemethodfordealingwiththeproblemofthepostgelpropertiesofthenetworkformingpolymerization.Stepto[7]investigatedthegelgelreactionofRAft… 相似文献
26.
Lingjun Chou Yingchun Cai Bing Zhang Jianzhong Niu Shengfu Ji Shuben Li 《Reaction Kinetics and Catalysis Letters》2002,76(2):311-315
Na-Mn-W/SiO2 catalysts were prepared and their catalytic performance for oxidative coupling of methane (OCM) was evaluated in a stainless-steel microreactor at elevated pressure. The results show that a CH4 conversion of 15.1% with a C2+ selectivity of 71.8% was obtained under 750oC, 1.0×105h-1 GHSV, CH4/O2 ratio of 8 and 1.0 MPa. Moreover, 17.3% CH4 conversion with 51.6% C2 selectivity and 23.6% C3-C4 selectivity was obtained under 750oC, 2.0×105h-1 GHSV, CH4/O2 ratio of 8 and 1.0 MPa. 相似文献
27.
~(13)C and ~1H NMR technique was used to study the interaction of Gly-Gly with heavy lanthanide cations Dy~(3+), Ho~(3+), Er~(3+), Tm~(3+) and Yb~(3+) in aqueous solution. The stability constants for the 1:1 and 1:2 complexes of Gly-Gly with Ho~(3+) and Yb~(3+) were determined from the titration curves of chemical shift versus concentration ratio of lanthanide to Gly-Gly. The solution structure of the Ln-Gly-Gly complex was analyzed based upon the ~(13)C and ~1H lanthanide-induced shifts and the results show that in the complex Gly-Gly is coordinated to the lanthanide ion through the carboxyl oxygens with the backbone of the ligand in an extended state. 相似文献
28.
Weihong Ji Tianlu Zhang Zhiguo Lu Jie Shen Jing Hu Yunwei Niu Zuobing Xiao Xin Zhang 《中国化学快报》2019,30(3):747-749
Mesoporous silica nanospheres loaded with sandela 803 (S803@MS-S) are prepared for application to wallpaper. The nano-fragrance has high encapsulation efficiency and property of photo-driven release. 相似文献
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30.
Xi‐Zhao Wang Jiong Jia Yan Zhang Wei‐Ren Xu Wei Liu Fang‐Niu Shi Jian‐Wu Wang 《中国化学会会志》2007,54(3):643-652
The synthesis of a series of new 5‐isoxazolpenicillins is described, which were obtained by coupling substituted isoxazoles with 6‐APA. Concise large‐scale synthesis of 3,5‐disubstituted isoxazoles by 1,3‐dipolar cycloaddition using copper(I) as catalyst was also investigated. Representative compounds were assayed for antimicrobial activities, showing satisfactory antimicrobial activities against Gram‐negative bacteria. 相似文献