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41.
42.
43.
罗永超 《贵州师范大学学报(自然科学版)》1994,12(4):21-30
本文给出一类整系数多项式最多存在i(i=0,1,2,…,n-2)个有理根的判别法。并将文[3,4]中的主要结果作了进一步的推广。 相似文献
44.
构建素质教育评价模式,对素质教育的实施和评价有直接的推进和指导作用。构建素质教育评价模式,应当遵循导向性、科学性、系统性、有效性原则。在构建素质教育评价模式时,有多种方法可供我们选择;但在此过程中,要注意研究模式,防止“模式化”。 相似文献
45.
46.
LIUYan HUYi-jun 《武汉大学学报:自然科学英文版》2004,9(4):399-403
We consider a risk model with a premium rate which varies with the level of free reserves. In this model, the occurrence of claims is described by a Cox process with Markov intensity process, and the influence of stochastic factors is considered by adding a diffusion process. The integro-differential equation for the ruin probability is derived by a infinitesimal method. 相似文献
47.
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
48.
罗博尔 《湖南科技大学学报(自然科学版)》1994,(2)
本文以资兴满春岭井为例,运用方案比较法系统分析了笔者提出的“投产采区片盘斜井开拓准备方式”,指出该法简化了开拓部署,改革了采区布置,具有明显的社会经济效益,尤其适合在南方小井推广。图2,表1,参4。 相似文献
49.
采用“单粒柱”新技术,测定了水蒸汽在粒状调湿剂中的有效扩散系数。以不同粒度、不同种类载气、不同吹扫气速进行测定,结果一致。表明:水蒸汽在粒状调湿剂中的扩散为粒子内扩散控制。以本法测定和对比了不同调湿剂中水蒸汽的有效扩散系数。 相似文献
50.
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