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951.
对以红花油为原料,生产亚油酸的工艺进行了研究。得出了原料配比、反应时间和反应温度等诸项工艺条件。所得产品各项指标完全符合国家药典规定。与现有的以大豆油为原料生产亚油酸的工艺相比较,本工艺具有投资少、见效快、成本低、质量好等优点。 相似文献
952.
This review presents the scintillators requirements for the medical imaging modalities. The history and the development in
recent years of the medical scintillators (mainly for GSO:Ce, LSO:Ce, LuAP:Ce) are expatiated in detail. 相似文献
953.
龚乐年 《东南大学学报(自然科学版)》1994,24(1):71-76
本文就汽轮发电机组轴系固有扭频与振型实测用变频励磁激振激发源-三相全控整流桥触发角a按正弦规律变化时,整流电压对应交变分量中基波频率与幅值的确定及其同激振频率之关系进行了分析与研究。所得结论可为变频励磁激振的实际应用提供依据。 相似文献
954.
稚鳖腹面颜色的差异与鳖种鉴别关系探讨 总被引:1,自引:0,他引:1
通过对我国现有不同鳖种的稚鳖的研究发现:不同种的稚鳖腹部表皮颜色(色斑)均有明显差异,同种稚鳖的颜色基本一致,并在一定时期内不因环境变化而改变颜色,同时发现人工养殖中华鳖种源混杂而导致人工繁殖的稚鳖腹面颜色(色斑)分化,对称状黑斑出现的比例与混杂程度有关。腹面有无对称状黑色斑点的两种类型稚鳖经生化测定和对比养殖均存在差异。说明稚鳖腹面颜色特征可作鳖种鉴别的外观依据,还可作为鳖种资源提纯复壮的指标。 相似文献
955.
Weiping BI 《系统科学与复杂性》2007,20(4):545-553
This paper studies the robust H∞ disturbance attenuation with internal stability for uncertain nonlinear control systems. By adding one power integrator technique, this paper designs a explicit smooth robust dynamic feedback law while rejecting the disturbance to any specified degree of accuracy. Further, the example and simulation results show the effectiveness of the proposed schemes. 相似文献
956.
The distribution function of the hyperbranched polymers formed from the self-condensing vinyl polymerization with unequal reactivities was derived and the differential equations for the second moments are established, based on the variable of the conversion of B^* groups. The various average degrees of branching can be designed by suitable values of reactivities ratio (r) and the conversion of A group (x). In order to reach the maximum degree of branching at a specified x, r needed is dependant on the value of x. The higher the x, the less the r needed is for the maximum value of degree of branching. At the end of the reaction, the maximum degree of branching reaches 0.5 with r=2.59. 相似文献
957.
958.
龚修焕 《黔西南民族师范高等专科学校学报》2002,(1):48-51
随着通讯技术的不断更新和发展,我国与西方国家的交流越来越多,我们要端正英语教学思想,使英语教学适应时代的要求和发展,语言所传递的化信息是英语教学听 重要组成部分。因此,教师在教学中,不但要训练和提高学生的语言水平,同时还应注意化差异,加强化对比,提高学生的跨化意识。 相似文献
959.
Probabilistic D-Clustering 总被引:1,自引:1,他引:0
We present a new iterative method for probabilistic clustering of data. Given clusters, their centers and the distances of
data points from these centers, the probability of cluster membership at any point is assumed inversely proportional to the
distance from (the center of) the cluster in question. This assumption is our working principle.
The method is a generalization, to several centers, of theWeiszfeld method for solving the Fermat–Weber location problem.
At each iteration, the distances (Euclidean, Mahalanobis, etc.) from the cluster centers are computed for all data points,
and the centers are updated as convex combinations of these points, with weights determined by the above principle. Computations
stop when the centers stop moving. 相似文献
960.
Number crunching vs. number theory: computers and FLT,from Kummer to SWAC (1850–1960), and beyond 总被引:1,自引:1,他引:0
Leo Corry 《Archive for History of Exact Sciences》2008,62(4):393-455
The present article discusses the computational tools (both conceptual and material) used in various attempts to deal with
individual cases of FLT, as well as the changing historical contexts in which these tools were developed and used, and affected
research. It also explores the changing conceptions about the role of computations within the overall disciplinary picture
of number theory, how they influenced research on the theorem, and the kinds of general insights thus achieved. After an overview
of Kummer’s contributions and its immediate influence, I present work that favored intensive computations of particular cases
of FLT as a legitimate, fruitful, and worth-pursuing number-theoretical endeavor, and that were part of a coherent and active,
but essentially low-profile tradition within nineteenth century number theory. This work was related to table making activity
that was encouraged by institutions and individuals whose motivations came mainly from applied mathematics, astronomy, and
engineering, and seldom from number theory proper. A main section of the article is devoted to the fruitful collaboration
between Harry S. Vandiver and Emma and Dick Lehmer. I show how their early work led to the hesitant introduction of electronic
computers for research related with FLT. Their joint work became a milestone for computer-assisted activity in number theory
at large. 相似文献