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51.
Simple expressions are given for the mean delay, mean waiting time, and mean busy period length in a multiplexer. Data streams with active periods having a general distribution are permitted, and the data rate during the active periods can be random. Data can also arrive in batches. The key restrictions of the model are that the sources are independent, idle periods are exponentially distributed, and a source generates at least enough data during an active period to keep the server busy throughout the period. The exact formulas allow evaluation of the error in approximations such as a heavy traffic diffusion approximation.Both continuous and discrete time models are considered. The discrete-time model includes that studied by Viterbi and subsequently generalized by Neuts. The Pollaczek-Khinchine formula for the mean amount of work in anM/GI/1 queue is retrieved as a limiting case.Preliminary version presented at IEEE INFOCOM, San Francisco, April 1993. 相似文献
52.
A. Gorban' 《Mathematical and Computer Modelling》2002,35(13):7047-1370
An explicitly solvable Riabouchinsky model with a partially penetrable obstacle is introduced. This model applied to the estimation of the efficiency of free flow turbines allows us to take into account the pressure drop past the lamina. 相似文献
53.
We consider the least squares approximation of gridded 2D data by tensor product splines with free knots. The smoothing functional to be minimized—a generalization of the univariate Schoenberg functional—is chosen in such a way that the solution of the bivariate problem separates into the solution of a sequence of univariate problems in case of fixed knots. The resulting optimization problem is a constrained separable least squares problem with tensor product structure. Based on some ideas developed by the authors for the univariate case, an efficient method for solving the specially structured 2D problem is proposed, analyzed and tested on hand of some examples from the literature. 相似文献
54.
采用无规相近似(RPA)方法,用空心图作为试探波函数,利用Feymann?Hellman定理计算七阶2?+?1维SU(2?)格点规范场的胶球质量,在弱耦合区1/g2?=1.0?–?1.8胶球质量表现出良好的标度行为,基本趋于常数(m/e2?≈1.2?0±0?.0?1)?. 相似文献
55.
J. M. Speight 《Theoretical and Mathematical Physics》2007,152(1):1043-1055
We study the dynamics of magnetic bubble solitons in a two-dimensional isotropic antiferromagnetic spin lattice in the case
where the exchange integral J(x, y) is position dependent. In the near-continuum regime, this system is described by the relativistic
O(3) sigma model on a space-time with a spatially inhomogeneous metric determined by J. We use the geodesic approximation
to describe the low-energy soliton dynamics in this system: the n-soliton motion is approximated by geodesic motion in the
moduli space M
n
of static n-solitons equipped with the L
2 metric γ. We obtain explicit formulas for γ for various natural choices of J(x, y). Based on these, we show that single soliton
trajectories are refracted with J−1 being analogous to the refractive index and that this refraction effect allows constructing simple bubble lenses and bubble
guides. We consider the case where J has a disk inhomogeneity (with the value J
+ outside a disk and J
− < J
+ inside) in detail. We argue that for sufficiently large J
+/J
−, this type of antiferromagnet supports approximate quasibreathers: two or more coincident bubbles confined within the disk
spin internally while their shape oscillates with a generically incommensurate period.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 152, No. 1, pp. 191–208, July, 2007. 相似文献
56.
This note outlines an algorithm for solving the complex ‘matrix Procrustes problem’. This is a least‐squares approximation over the cone of positive semi‐definite Hermitian matrices, which has a number of applications in the areas of Optimization, Signal Processing and Control. The work generalizes the method of Allwright (SIAM J. Control Optim. 1988; 26 (3):537–556), who obtained a numerical solution to the real‐valued version of the problem. It is shown that, subject to an appropriate rank assumption, the complex problem can be formulated in a real setting using a matrix‐dilation technique, for which the method of Allwright is applicable. However, this transformation results in an over‐parametrization of the problem and, therefore, convergence to the optimal solution is slow. Here, an alternative algorithm is developed for solving the complex problem, which exploits fully the special structure of the dilated matrix. The advantages of the modified algorithm are demonstrated via a numerical example. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
57.
Markus Hegland Jochen Garcke Vivien Challis 《Linear algebra and its applications》2007,420(2-3):249-275
The combination technique has repeatedly been shown to be an effective tool for the approximation with sparse grid spaces. Little is known about the reasons of this effectiveness and in some cases the combination technique can even break down. It is known, however, that the combination technique produces an exact result in the case of a projection into a sparse grid space if the involved partial projections commute.
The performance of the combination technique is analysed using a projection framework and the C/S decomposition. Error bounds are given in terms of angles between the spanning subspaces or the projections onto these subspaces. Based on this analysis modified combination coefficients are derived which are optimal in a certain sense and which can substantially extend the applicability and performance of the combination technique. 相似文献
58.
Numerical analysis for stochastic age-dependent population equations with Poisson jumps 总被引:1,自引:0,他引:1
In this paper, stochastic age-dependent population equations with Poisson jumps are considered. In general, most of stochastic age-dependent population equations with jumps do not have explicit solutions, thus numerical approximation schemes are invaluable tools for exploring their properties. The main purpose of this paper is to develop a numerical Euler scheme and show the convergence of the numerical approximation solution to the true solution. 相似文献
59.
设Λ={λn}n∞=1为正的实数数列,且当n→∞时,有λn↘0.本文给出了当λn≤Mn-1/2,n=1,2,…,(其中M>0为一正常数)时Müntz系统{xλn}的有理函数在Lp[0,1]空间的逼近速度,主要结论为Rn(f,Λ) Lp≤CMω(f,n-1/2)Lp,1≤p≤∞. 相似文献
60.
Andreas Rößler 《BIT Numerical Mathematics》2006,46(1):97-110
A general class of stochastic Runge–Kutta methods for Itô stochastic differential equation systems w.r.t. a one-dimensional Wiener process is introduced. The colored rooted tree analysis is applied to derive conditions for the coefficients of the stochastic Runge–Kutta method assuring convergence in the weak sense with a prescribed order. Some coefficients for new stochastic Runge–Kutta schemes of order two are calculated explicitly and a simulation study reveals their good performance. 相似文献