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791.
本文应用从亚夸克理论获得的夸克——结模型,分析了强子碎片的强子、反强子谱的行为.碎片演化能由夸克或双夸克的级联衰变机制来实现。据此计算了质子碎片的某些内含强子、反强子谱的比,其结果令人满意并与实验相符。 相似文献
792.
Bjørnar Sæther 《Systemic Practice and Action Research》2007,20(1):15-25
This paper describes the change in a researcher's practices from one of studying regional industrial development at a distance to one of working closely with a network of agri-food managers. This is accompanied by a discussion of the methodological and theoretical possibilities for an action research inspired economic geography. Some of the core characteristics of a pragmatic conceptualization of action research are revised. It is argued that theoretical developments within economic geography make possible a dialogue between researchers and local actors and that economic geography is challenged to accept that knowledge is generated through such a dialogue. Attempts to create a dialogue between action research and economic geography in a specific Norwegian industrial and geographical context are described. These attempts indicate that the researcher's methodological approach has been transformed from a narrow one relying solely on conventional social science methods to a broader one including participatory action research. 相似文献
793.
YANG XinLin CHEN Zhe MENG XianMei LI Bo TAN Xin 《科学通报(英文版)》2007,52(13):1802-1806
Activities of trimalonic acid fullerene (TMA C_60) on DNA restrictive enzymatic reaction were investigated by using two restrictive endonucleases Hind III and EcoR I and plasmid pEGFP-N1 with single restric-tive site for both enzymes. Meanwhile, TMA C60 was also tested to clarify its effects on polymerase chain reaction (PCR) with the catalyst of Taq DNA polymerase and the template of plasmid pEGFP-N1. The products from restrictive reactions or PCR were detected by agarose gel electrophoresis. It was found that the product amounts from restrictive reactions or PCR decreased significantly with addition of TMA C60. The inhibition by TMA C60 was dose-dependent and IC50 values for reactions of Hind III, EcoR I and PCR were 16.3, 6.0 and 6.0 μmol/L, respectively. Addition of two scavengers of reactive oxygen species (ROS), L-ascorbic acid-2-phosphate ester magnesium and sodium azide at the con-centrations of 2―10 mmol/L did not antagonize the activities of TMA C60 against PCR and two restrictive reactions. However, increase of Taq DNA polymerase amounts in PCR system antagonized the activities of TMA C60. These data implied that TMA C60 was able to inhibit the activities of the three above-mentioned enzymes involved in DNA metabolism, and that this inhibition probably did not correlate to ROS. 相似文献
794.
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
795.
为了优化教学过程和提高教学效率,利用多媒体教学软件和相应设施辅助教学是一种有效的办法.详细介绍了织机主机构及其运动配合的多媒体教学软件的制作.并阐述了三维动画制作和集成打包的具体步骤.该教学软件包易于使用在相关课程中,并对教学具有明显的改进效果. 相似文献
796.
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
797.
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
798.
799.
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
800.
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