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31.
杜香当 《太原师范学院学报(自然科学版)》2004,3(2):90-92
通过调查研究,结果表明山西省高校高水平田径运动员竞赛焦虑品质与焦虑状态女子均高于男子;运动项目不同,运动员产生赛前焦虑也不同;并且随着比赛赛次的进展,焦虑程度也随之增高;高水平田径运动员适宜的焦虑区域为32-50之间。 相似文献
32.
J. Bruce Brackenridge 《Archive for History of Exact Sciences》2003,57(4):313-336
In the 1687 Principia, Newton gave a solution to the direct problem (given the orbit and center of force, find the central force) for a conic-section
with a focal center of force (answer: a reciprocal square force) and for a spiral orbit with a polar center of force (answer:
a reciprocal cube force). He did not, however, give solutions for the two corresponding inverse problems (given the force
and center of force, find the orbit). He gave a cryptic solution to the inverse problem of a reciprocal cube force, but offered no solution for the reciprocal square force. Some take this omission as an indication that Newton could not solve the reciprocal square, for, they ask, why else
would he not select this important problem? Others claim that ``it is child's play' for him, as evidenced by his 1671 catalogue
of quadratures (tables of integrals). The answer to that question is obscured for all who attempt to work through Newton's
published solution of the reciprocal cube force because it is done in the synthetic geometric style of the 1687 Principia rather than in the analytic algebraic style that Newton employed until 1671. In response to a request from David Gregory
in 1694, however, Newton produced an analytic version of the body of the proof, but one which still had a geometric conclusion.
Newton's charge is to find both ``the orbit' and ``the time in orbit.' In the determination of the dependence of the time on orbital position, t(r), Newton
evaluated an integral of the form ∫dx/x
n
to calculate a finite algebraic equation for the area swept out as a function of the radius, but he did not write out the
analytic expression for time t = t(r), even though he knew that the time t is proportional to that area. In the determination
of the orbit, θ (r), Newton obtained an integral of the form ∫dx/√(1−x2) for the area that is proportional to the angle θ, an integral he had shown in his 1669 On Analysis by Infinite Equations to be equal to the arcsin(x). Since the solution must therefore contain a transcendental function, he knew that a finite
algebraic solution for θ=θ(r) did not exist for ``the orbit' as it had for ``the time in orbit.' In contrast to these two
solutions for the inverse cube force, however, it is not possible in the inverse square solution to generate a finite algebraic
expression for either ``the orbit' or ``the time in orbit.' In fact, in Lemma 28, Newton offers a demonstration that the
area of an ellipse cannot be given by a finite equation. I claim that the limitation of Lemma 28 forces Newton to reject the
inverse square force as an example and to choose instead the reciprocal cube force as his example in Proposition 41.
(Received August 14, 2002)
Published online March 26, 2003
Communicated by G. Smith 相似文献
33.
断裂带中岩石的硅化现象,通常称之为硅化岩或硅化破碎带,即经动力变质作用的断层岩,通过微束技术对其观察,它们显示出下列特征:在扫描电镜(SEM)下,硅化物质表现为细脉状,而在偏光里微镜下则表现为浸染状;对硅化岩进行组构观察,可见压扁 S 面和剪切 S 面;在透射电镜(TEM)下,可进一步区别不同的位错现象;断裂带岩石的硅化现象是受组成岩石的化学元素的构造地球化学作用所制约的,包括动力分异和化学亲和作用,动热变质作用和退化变质作用,氧化和还原作用以及脱水和水解作用。 相似文献
34.
本文用扫描电镜(SEM)和示差扫描量热法(DSC)研究了XeCl准分子激光辐照Fe_(81.5)P_(18.4)Yb_(0.1)非晶合金的晶化特征。结果发现,辐照样品的断面上有类冲击波纹样的层状规则的晶粒分布,其晶粒尺寸由辐照表面向样品内部逐渐减小,最后是近纳米尺度的微晶排布,样品的热稳定性也明显改善。 相似文献
35.
Zhongsheng WANG Zhigang ZENG Xiaoxin LIAODepartment of Control Science Engineering Huazhong University of Science Technology Wuhan Hubei P. R. China 《系统科学与系统工程学报(英文版)》2003,12(2):204-209
Some stability criteria are obtained for a class of uncertain systems with time-delay usingLyapunov functional and analytic techniques. It is easy to check the criteria by making use of theboundedness of the uncertainties. 相似文献
36.
Ju-liang ZHANG Jian CHENDepartment of Management Science EngineeringSchool of Economics Management Tsinghua University Beijing China. 《系统科学与系统工程学报(英文版)》2003,12(3):360-371
This paper investigates the impact of a secondary market, where retailers can buy and sell excessinventories, on the supply chain. We develop a two-period model with a single manufacturer and tworetailers. At the beginning of the first period the retailers order and receive products from themanufacturer, but at the beginning of the second period, they can trade surplus products betweenthemselves in the secondary market. We investigate the impact of the correlated dependence ofretailers' demand on both the quantity effect and the allocation effect under the secondary market.Lastly,we study potential strategies for the manufacturer to increase sales with the existence of thesecondary market. 相似文献
37.
FROM MANUFACTURING SCHEDULING TO SUPPLY CHAIN COORDINATION:THE CONTROL OF COMPLEXITY AND UNCERTAINTY
Peter B.LUH 《系统科学与系统工程学报(英文版)》2003,12(3):279-297
With time-based competition and rapid technology advancements, effective manufacturingscheduling and supply chain coordination are critical to quickly respond to changing marketconditions. These problems, however, are difficult in view of inherent complexity and variousuncertainties involved. Based on a series of results by the authors, decomposition and coordination byusing Lagrangian relaxation is identified in this paper as an effective way to control complexity anduncertainty.A manufacturing scheduling problem is first formulated within the job shop context withuncertain order arrivals, processing times, due dates, and part priorities as a separable optimizationproblem. A solution methodology that combines Lagrangian relaxation, stochastic dynamicprogramming, and heuristics is developed. Method improvements to effectively solve large problemsare also highlighted. To extend manufacturing scheduling within a factory to coordinate autonomicmembers across chains of suppliers, a decentralized supply chai 相似文献
38.
杜建正 《西南师范大学学报(自然科学版)》1994,(6)
运用模糊统计对10个持续时间词进行了初步研究,然后选出其中2个,让不同个性特征的男女被试对其赋值。结果表明:在时间词的估计值和估值范围上,A型行为类型者的赋值都小于B型行为类型者;低焦虑者的时间词的估值范围大于高焦虑者;在赋值特征上性别差异不显著. 相似文献
39.
40.
Shape skeletonization (i.e., medial axis extraction) is powerful in many visual computing applications, such as pattern recognition, object segmentation, registration, and animation. In this paper, the authors expand the use of diffusion equations combined with distance field information to approximate medial axes of arbitrary 3D differential properties. It offers an alternative solids represented by polygonal meshes based on their but natural way for medial axis extraction for commonly used 3D polygonal models. By solving the PDE along time axis, this system can not only quickly extract diffusion-based medial axes of input meshes, but also allow users to visualize the extraction process at each time step. In addition, the proposed model provides users a set of manipulation toolkits to sculpt extracted medial axes, then use diffusion-based techniques to recover corresponding deformed shapes according to the original input datasets. This skeleton-based shape manipulation offers a fast and easy way for animation and deformation of complicated mesh objects. 相似文献