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111.
英国兰开夏大学的物理实验教学 总被引:4,自引:1,他引:4
简要介绍了英国兰开夏大学的物理实验教学和成绩评定方法,分析了其特色,可以看出该大学较重视学生创造性综合能力的培养. 相似文献
112.
Data assimilation-based parameter estimation can be used to deterministically tune forecast models. This work demonstrates that it can also be used to provide parameter distributions for use by stochastic parameterization schemes. While parameter estimation is (theoretically) straightforward to perform, it is not clear how one should physically interpret the parameter values obtained. Structural model inadequacy implies that one should not search for a deterministic “best” set of parameter values, but rather allow the parameter values to change as a function of state; different parameter values will be needed to compensate for the state-dependent variations of realistic model inadequacy. Over time, a distribution of parameter values will be generated and this distribution can be sampled during forecasts. The current work addresses the ability of ensemble-based parameter estimation techniques utilizing a deterministic model to estimate the moments of stochastic parameters. It is shown that when the system of interest is stochastic the expected variability of a stochastic parameter is biased when a deterministic model is employed for parameter estimation. However, this bias is ameliorated through application of the Central Limit Theorem, and good estimates of both the first and second moments of the stochastic parameter can be obtained. It is also shown that the biased variability information can be utilized to construct a hybrid stochastic/deterministic integration scheme that is able to accurately approximate the evolution of the true stochastic system. 相似文献
113.
We derive a representation formula for the solutions of the navier-Stokes flow in three dimensions in absence of boundary in terms of stochastic current lines. This pictures generalizes an analogous one given in two dimensions and on the other hand the classical Lafrangian picture for the Euler flow. We prove a Vanishing viscosity limit for the whole structure 相似文献
114.
We prove some new degeneracy results for integral points and entire curves on surfaces; in particular, we provide the first examples, to our knowledge, of a simply connected smooth variety whose sets of integral points are never Zariski-dense. Some of our results are connected with divisibility problems, i.e. the problem of describing the integral points in the plane where the values of some given polynomials in two variables divide the values of other given polynomials. 相似文献
115.
C. Bekh-Ochir 《代数通讯》2013,41(8):2697-2706
We describe the T-ideal of identities and the T-space of central polynomials for the unitary finite dimensional Grassmann algebra over a finite field. 相似文献
116.
John Conrad Merkel 《Journal of Dynamics and Differential Equations》2008,20(3):653-668
In the spirit of Palmore and Pacella, Morse Theory is used to obtain a lower bound for the number of central configurations
in the spatial N-body problem. The homology of the configuration ellipsoid with the collision and collinear manifolds removed and the SO(3) symmetry quotiented out is calculated. As intermediate steps, homology calculations are carried out for several additional
manifolds naturally arising in the N-body problem. 相似文献
117.
We present a new algorithm for continuation of limit cycles of autonomous systems as a system parameter is varied. The algorithm
works in phase space with an ordered set of points on the limit cycle, along with spline interpolation. Currently popular
algorithms in bifurcation analysis packages compute time-domain approximations of limit cycles using either shooting or collocation.
The present approach seems useful for continuation near saddle homoclinic points, where it encounters a corner while time-domain
methods essentially encounter a discontinuity (a relatively short period of rapid variation). Other phase space-based algorithms
use rescaled arclength in place of time, but subsequently resemble the time-domain methods. Compared to these, we introduce
additional freedom through a variable stretching of arclength based on local curvature, through the use of an auxiliary index-based
variable. Several numerical examples are presented. Comparisons with results from the popular package, MATCONT, are favorable
close to saddle homoclinic points. 相似文献
118.
We consider a system of diffusing particles on the real line in a quadratic external potential and with a logarithmic interaction potential. The empirical measure process is known to converge weakly to a deterministic measure-valued process as the number of particles tends to infinity. Provided the initial fluctuations are small, the rescaled linear statistics of the empirical measure process converge in distribution to a Gaussian limit for sufficiently smooth test functions. For a large class of analytic test functions, we derive explicit general formulae for the mean and covariance in this central limit theorem by analyzing a partial differential equation characterizing the limiting fluctuations. 相似文献
119.
Central limit theorem and almost sure central limit theorem for the product of some partial sums 总被引:1,自引:0,他引:1
Miao Yu 《Proceedings Mathematical Sciences》2008,118(2):289-294
In this paper, we give the central limit theorem and almost sure central limit theorem for products of some partial sums of
independent identically distributed random variables. 相似文献
120.
We investigate when the set of finite products of distinct terms of a sequence 〈x
n
〉
n=1∞ in a semigroup (S,⋅) is large in any of several standard notions of largeness. These include piecewise syndetic, central, syndetic, central*, and IP*. In the case of a “nice” sequence in (S,⋅)=(ℕ,+) one has that FS(〈x
n
〉
n=1∞) has any or all of the first three properties if and only if {x
n+1−∑
t=1
n
x
t
:n∈ℕ} is bounded from above.
N. Hindman acknowledges support received from the National Science Foundation via Grant DMS-0554803. 相似文献