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91.
无源高温超导磁浮轴承两种方案比较 总被引:2,自引:0,他引:2
无源磁浮轴承的优点是结构简单、造价低廉、无需有源控制。文中探讨了两种无源磁浮轴承的方案 ;对两种方案的悬浮力、悬浮品质因数、悬浮刚度与悬浮稳定性进行了讨论、计算、比较 ;并且讨论了两种方案的优缺点及应用。比较结果表明 ,方案 1更适合于小型的飞轮储能系统 ,方案 2较适合于大中型飞轮储能系统。 相似文献
92.
Bangteng Xu 《Journal of Algebraic Combinatorics》2008,27(2):127-141
Sunder and Wildberger (J. Algebr. Comb.
18, 135–151, 2003) introduced the notion of actions of finite hypergroups, and studied maximal irreducible actions and *-actions. One of the
main results of Sunder and Wildberger states that if a finite hypergroup K admits an irreducible action which is both a maximal action and a *-action, then K arises from an association scheme. In this paper we will first show that an irreducible maximal action must be a *-action,
and hence improve Sunder and Wildberger’s result (Theorem 2.9). Another important type of actions is the so-called w-maximal actions. For a w-maximal action π:K→Aff (X), we will prove that π is faithful and |X|≥|K|, and |K| is the best possible lower bound of |X|. We will also discuss the strong connectivity of the digraphs induced by a w-maximal action. 相似文献
93.
Koji Nuida Satoshi Fujitsu Manabu Hagiwara Takashi Kitagawa Hajime Watanabe Kazuto Ogawa Hideki Imai 《Designs, Codes and Cryptography》2009,52(3):339-362
It has been proven that the code lengths of Tardos’s collusion-secure fingerprinting codes are of theoretically minimal order
with respect to the number of adversarial users (pirates). However, the code lengths can be further reduced as some preceding
studies have revealed. In this article we improve a recent discrete variant of Tardos’s codes, and give a security proof of
our codes under an assumption weaker than the original Marking Assumption. Our analysis shows that our codes have significantly
shorter lengths than Tardos’s codes. For example, when c = 8, our code length is about 4.94% of Tardos’s code in a practical setting and about 4.62% in a certain limit case. Our
code lengths for large c are asymptotically about 5.35% of Tardos’s codes.
A part of this work was presented at 17th Applied Algebra, Algebraic Algorithms, and Error Correcting Codes (AAECC-17), Bangalore,
India, December 16–20, 2007. 相似文献
94.
We study the Tardos’ probabilistic fingerprinting scheme and show that its codeword length may be shortened by a factor of
approximately 4. We achieve this by retracing Tardos’ analysis of the scheme and extracting from it all constants that were
arbitrarily selected. We replace those constants with parameters and derive a set of inequalities that those parameters must
satisfy so that the desired security properties of the scheme still hold. Then we look for a solution of those inequalities
in which the parameter that governs the codeword length is minimal. A further reduction in the codeword length is achieved
by decoupling the error probability of falsely accusing innocent users from the error probability of missing all colluding
pirates. Finally, we simulate the Tardos scheme and show that, in practice, one may use codewords that are shorter than those
in the original Tardos scheme by a factor of at least 16.
相似文献
95.
Yousef Hashem Zahran 《国际流体数值方法杂志》2008,57(6):745-760
We describe a hybrid method for the solution of hyperbolic conservation laws. A third‐order total variation diminishing (TVD) finite difference scheme is conjugated with a random choice method (RCM) in a grid‐based adaptive way. An efficient multi‐resolution technique is used to detect the high gradient regions of the numerical solution in order to capture the shock with RCM while the smooth regions are computed with the more efficient TVD scheme. The hybrid scheme captures correctly the discontinuities of the solution and saves CPU time. Numerical experiments with one‐ and two‐dimensional problems are presented. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
96.
The main result proved in the paper is the computation of the explicit equations defining the Hurwitz schemes of coverings with punctures as subschemes of the Sato infinite Grassmannian. As an application, we characterize the existence of certain linear series on a smooth curve in terms of soliton equations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
97.
High‐resolution total variation diminishing (TVD) schemes are widely used for the numerical approximation of hyperbolic conservation laws. Their extension to equations with source terms involving spatial derivatives is not obvious. In this work, efficient ways of constructing conservative schemes from the conservative, non‐conservative or characteristic form of the equations are described in detail. An upwind, as opposed to a pointwise, treatment of the source terms is adopted here, and a new technique is proposed in which source terms are included in the flux limiter functions to get a complete second‐order compact scheme. A new correction to fix the entropy problem is also presented and a robust treatment of the boundary conditions according to the discretization used is stated. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
98.
Vincent Guinot 《国际流体数值方法杂志》2001,37(3):341-359
Godunov‐type algorithms are very attractive for the numerical solution of discontinuous flows. The reconstruction of the profile inside the cells is crucial to scheme performance. The non‐linear generalization of the discontinuous profile method (DPM) presented here for the modelling of two‐phase flow in pipes uses a discontinuous reconstruction in order to capture shocks more efficiently than schemes using continuous functions. The reconstructed profile is used to define the Riemann problem at cell interfaces by averaging of the components of the variable in the base of eigenvectors over their domain of dependence. Intercell fluxes are computed by solving the Riemann problem with an approximate‐state solver. The adapted treatment of boundary conditions is essential to ensure the quality of the computational results and a specific procedure using virtual cells at both extremities of the computational domain is required. Internal boundary conditions can be treated in the same way as external ones. Application of the DPM to test cases is shown to improve the quality of computational results significantly. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
99.
Paola Fisicaro Soraya Amarouche Béatrice Lalere Guillaume Labarraque Marc Priel 《Accreditation and quality assurance》2008,13(7):361-366
Since the advent of the Guide to the Expression of Uncertainty in Measurement (GUM) founding the principles of uncertainty
evaluation, numerous projects have been carried out to develop alternative practical methods when it is impossible to model
technical or economical aspects of the measurement process. These methods can use all the experimental data available to the
laboratories, such as repeatability, reproducibility, quality-control charts, etc. The studies presented in this paper compare
the results obtained by the modelling method from GUM with the uncertainties found by applying alternative methods. They show
two examples, one in the field of environmental monitoring, the other in the biomedical field, based on the exploitation of
PT schemes results.
Presented at BERM-11, October 2007, Tsukuba, Japan. 相似文献
100.
K. N. Volkov 《Computational Mathematics and Mathematical Physics》2008,48(7):1181-1202
An unstructured-grid discretization of the Navier-Stokes equations based on the finite volume method and high-resolution difference schemes in time and space is described as applied to fluid dynamics problems in two and three dimensions. The control volume is defined as the cell-vertex median dual control volume. The fluxes through the faces of internal and boundary control volumes are written identically, which simplifies their software implementation. The gradient and the pseudo-Laplacian are calculated at the midpoint of a control volume face by using relations adapted to the computations on a strongly stretched grid in the boundary layer. 相似文献