共查询到20条相似文献,搜索用时 93 毫秒
1.
固定序算法是Bellman-Ford算法的一种基本改进算法。为了改变固定序算法在稀疏图上的劣势,本文通过预先订制参与迭代的点的计算顺序,对该算法进行了改进。实验表明,在稀疏图上, 改进后的算法相对于原算法计算效率提高了近50%, 并能够与国际流行的先进先出算法相媲美。本文的工作表明,固定序算法不仅在大规模稠密图上具有明显的优势,而且在稀疏图上也具有很强的竞争力。 相似文献
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介绍了一种求解TSP问题的算法—改进的蚁群算法,算法通过模拟蚁群搜索食物的过程,可用于求解TSP问题,算法的主要特点是:正反馈、分布式计算、与某种启发式算法相结合.通过对传统蚁群算法的改进可以得到较好的结果.计算机仿真结果表明了该算法的有效性. 相似文献
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蚂蚁算法是一种新型的模拟进化算法,也是一种随机型智能搜索算法.较为系统的总结了算法的基本理论,分析了其基本算法解决TSP问题的模型,针对蚂蚁算法易出现停滞的缺点,把小生境遗传算法和蚂蚁算法融合,仿真比较实验结果表明优于基本蚂蚁算法. 相似文献
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为解决模糊C均值算法对初始值敏感、容易陷入局部极值的问题,提出基于混合细菌趋药性的聚类分割算法,在简单细菌趋药性算法的基础上,将粒子群算法引入.新算法使用粒子群算法、细菌趋药性算法两步优化得到的结果作为模糊C均值算法的初始值,同时新算法中引入精英保持策略,进一步提高算法效率.实验结果表明,新算法具有较快的收敛速度,.同时能够获得较好的图像分割效果和质量. 相似文献
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针对模糊C均值算法用于图像分割时对初始值敏感、容易陷入局部极值的问题,提出基于混合单纯形算法的模糊均值图像分割算法.算法利用Nelder-Mead单纯形算法计算量小、搜索速度快和粒子群算法自适应能力强、具有较好的全局搜索能力的特点,将混合单纯形算法的结果作为模糊C均值算法的输入,并将其用于图像分割.实验结果表明:基于混合单纯形算法的模糊均值图像分割算法在改善图像分割质量的同时,提高了算法的运行速度. 相似文献
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讨论偏微分方程的局部保结构算法,它是原来的整体保结构算法的自然推广. 当边界条件适宜时, 局部保结构算法自然是整体保结构算法, 但整体保结构算法却不一定是局部保结构算法. 局部保结构算法的概念能解释不同保结构算法之间的差异性, 也能为分析和构造性能较好的保结构算法提供理论基础. 不仅如此, 合适的边界条件不再是局部保结构算法可应用于偏微分方程的必要条件, 从而拓宽了保结构算法的适用性. 还讨论了局部保结构算法的应用和系统构造问题, 得到了非线性Klein-Gordon方程的一些新的格式. 相似文献
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GA-BP嵌套算法的理论及应用 总被引:2,自引:0,他引:2
分析了BP算法、遗传算法以及GA-BP-APARTING算法的特点,提出了GA-BP-NESTING算法.在人工神经网络的在线学习和离线学习方式下,分别对BP算法、GA算法、GA-BP-APARTING算法和GA-BP-NESTING算法进行了比较研究,研究发现:第一,网络初始权值的赋值对人工神经网络训练影响很大;第二,离线学习方式下GA-BP-NESTING算法效果最佳. 相似文献
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A. A. Okhlopkova A. V. Vinogradov C. A. Sleptsova G. N. Alexandrov 《Mechanics of Composite Materials》1999,35(6):521-526
Composite polymer materials based on PTFE containing ultradisperse -sialon (1–10 wt.%) as the cross-linking agent are studied. It is shown that the injection of small amounts of fillers (1–2 wt.%) increases the degree of composite crystallinity. A correlation between the structure, element distribution on the surface layers of samples, and tribotechnical characteristics of composites is found. The change in the physicomechanical characteristics is associated with the effect of the interstructural plasticization.Ammosov Yakutsk State University, Yakutsk, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 6, pp. 797–806, November–December, 1999. 相似文献
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ZHENG ShiJun 《分析论及其应用》2004,20(3)
Schr(o)dinger operator is a central subject in the mathematical study of quantum mechanics.Consider the Schrodinger operator H = -△ V on R, where △ = d2/dx2 and the potential function V is real valued. In Fourier analysis, it is well-known that a square integrable function admits an expansion with exponentials as eigenfunctions of -△. A natural conjecture is that an L2 function admits a similar expansion in terms of "eigenfunctions" of H, a perturbation of the Laplacian (see [7], Ch. Ⅺ and the notes), under certain condition on V. 相似文献
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A cumulative-capacitated transportation problem is studied. The supply nodes and demand nodes are each chains. Shipments from a supply node to a demand node are possible only if the pair lies in a sublattice, or equivalently, in a staircase disjoint union of rectangles, of the product of the two chains. There are (lattice) superadditive upper bounds on the cumulative flows in all leading subrectangles of each rectangle. It is shown that there is a greatest cumulative flow formed by the natural generalization of the South-West Corner Rule that respects cumulative-flow capacities; it has maximum reward when the rewards are (lattice) superadditive; it is integer if the supplies, demands and capacities are integer; and it can be calculated myopically in linear time. The result is specialized to earlier work of Hoeffding (1940), Fréchet (1951), Lorentz (1953), Hoffman (1963) and Barnes and Hoffman (1985). Applications are given to extreme constrained bivariate distributions, optimal distribution with limited one-way product substitution and, generalizing results of Derman and Klein (1958), optimal sales with age-dependent rewards and capacities.To our friend, Philip Wolfe, with admiration and affection, on the occasion of his 65th birthday.Research was supported respectively by the IBM T.J. Watson and IBM Almaden Research Centers and is a minor revision of the IBM Research Report [6]. 相似文献
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Two polyester-based polymer concretes with various volume content of diabase as an extender and aggregate are tested in creep
under compression at different stress levels. The phenomenological and structural approaches are both used to analyze the
experimental data. Common features of changes in the instantaneous and creep compliances are clarified, and a phenomenological
creep model which accounts for the changes in the instantaneous compliance and in the retardation spectrum depending on the
stress level is developed. It is shown that the model can be used to describe the experimental results of stress relaxation
and creep under repeated loading. Modeling of the composite structure and subsequent solution of the optimization problem
confirm the possibility of the existence of an interphase layer more compliant than the binder. A direct correlation between
the interphase volume content and the instantaneous compliance of the composite is revealed. It is found that the distinction
in nonlinearity of the viscoelastic behavior of the two polymer concretes under investigation can be due to the difference
in their porosity.
Submitted to the 11th International Conference on Mechanics of Composite Materials (Riga, June 11–15, 2000.)
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 2, pp. 147–164, 2000. 相似文献
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The shear failure of reinforced concrete beams needs more attention than the bending failure since no or only small warning
precedes the failure. For this reason, it is of utmost importance to understand the shear bearing capacity and also to be
able to undertake significant rehabilitation work if necessary. In this paper, a design model for the shear strengthening
of concrete beams by using fiber-reinforced polymers (FRP) is presented, and the limitations of the truss model analogy are
highlighted. The fracture mechanics approach is used in analyzing the bond behavior between the FRP composites and concrete.
The fracture energy of concrete and the axial rigidity of the FRP are considered to be the most important parameters. The
effective strain in the FRP when the debonding occurs is determined. The limitations of the anchorage length over the cross
section are analyzed. A simple iterative design method for the shear debonding is finally proposed.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 357–372, May–June, 2008. 相似文献
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Coordinate and subspace optimization methods for linear least squares with non-quadratic regularization 总被引:2,自引:0,他引:2
Michael Elad Boaz Matalon Michael Zibulevsky 《Applied and Computational Harmonic Analysis》2007,23(3):346-367
This work addresses the problem of regularized linear least squares (RLS) with non-quadratic separable regularization. Despite being frequently deployed in many applications, the RLS problem is often hard to solve using standard iterative methods. In a recent work [M. Elad, Why simple shrinkage is still relevant for redundant representations? IEEE Trans. Inform. Theory 52 (12) (2006) 5559–5569], a new iterative method called parallel coordinate descent (PCD) was devised. We provide herein a convergence analysis of the PCD algorithm, and also introduce a form of the regularization function, which permits analytical solution to the coordinate optimization. Several other recent works [I. Daubechies, M. Defrise, C. De-Mol, An iterative thresholding algorithm for linear inverse problems with a sparsity constraint, Comm. Pure Appl. Math. LVII (2004) 1413–1457; M.A. Figueiredo, R.D. Nowak, An EM algorithm for wavelet-based image restoration, IEEE Trans. Image Process. 12 (8) (2003) 906–916; M.A. Figueiredo, R.D. Nowak, A bound optimization approach to wavelet-based image deconvolution, in: IEEE International Conference on Image Processing, 2005], which considered the deblurring problem in a Bayesian methodology, also obtained element-wise optimization algorithms. We show that the last three methods are essentially equivalent, and the unified method is termed separable surrogate functionals (SSF). We also provide a convergence analysis for SSF. To further accelerate PCD and SSF, we merge them into a recently developed sequential subspace optimization technique (SESOP), with almost no additional complexity. A thorough numerical comparison of the denoising application is presented, using the basis pursuit denoising (BPDN) objective function, which leads all of the above algorithms to an iterated shrinkage format. Both with synthetic data and with real images, the advantage of the combined PCD-SESOP method is demonstrated. 相似文献
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This paper builds upon the Lp-stability results for discrete orthogonal projections on the spaces Sh of continuous splines of order r obtained by R. D. Grigorieff and I. H. Sloan in (1998, Bull. Austral. Math. Soc.58, 307–332). Properties of such projections were proved with a minimum of assumptions on the mesh and on the quadrature rule defining the discrete inner product. The present results, which include superapproximation and commutator properties, are similar to those derived by I. H. Sloan and W. Wendland (1999, J. Approx. Theory97, 254–281) for smoothest splines on uniform meshes. They are expected to have applications (as in I. H. Sloan and W. Wendland, Numer. Math. (1999, 83, 497–533)) to qualocation methods for non-constant-coefficient boundary integral equations, as well as to the wide range of other numerical methods in which quadrature is used to evaluate L2-inner products. As a first application, we consider the most basic variable-coefficient boundary integral equation, in which the constant-coefficient operator is the identity. The results are also extended to the case of periodic boundary conditions, in order to allow appplication to boundary integral equations on closed curves. 相似文献
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Two kinds of model composite materials with finely divided (1) crystal fillers—LiF or polyethylene-filled epoxy resin cured by polyethylenepolyamine — are investigated by X-ray diffractometry. It is found that tensile stresses arise in LiF crystals, which show a strong adhesion interaction with the binder, for all degrees of filling (from =2.2 to =74 vol.%) examined. Their values remain constant up to a degree of filling at which the boundary layers come into contact with one another. Then, the inner stresses decrease with increasing . In the crystalline regions of polyethylene, where the adhesion between the binder and crystals is weak, the inner stresses are compressive. It is shown that the thickness of the boundary layer of the matrix on the surface of filler particles can be evaluated by the method used.Institute of Polymer Mechanics, Latvian University, Riga, LV-1006 Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 6, pp. 807–820, November–December, 1999. 相似文献
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A rigid isotopy of nonsingular real algebraic curves on a quadric is a path in the space of such curves of a given bidegree.
We obtain the rigid isotopy classification of nonsingular real algebraic curves of bidegree (3, 3) on a hyperboloid and on
an ellipsoid. We also study of the space of real algebraic curves of bidegree (3, 3) with a single node or cusp.
Translated fromMatematicheskie Zametki, Vol. 66, No. 6, pp. 810–815, December, 1999. 相似文献
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M. V. Medvedeva 《Mathematical Notes》1998,64(5):616-621
In this paper we study functions belonging to the classesV
ε and ΛBV, which are encountered in the theory of Fourier trigonometric series. Necessary and sufficient conditions for the embedding
of the classesH
ω in the classesV
ϕ and ABV are obtained.
Translated fromMatematicheskie Zametki, Vol. 64, No. 5, pp. 713–719, November, 1998.
This research was supported by the program “Leading Scientific Schools” under grant No. 96/97-15-96073. 相似文献