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排序方式: 共有4913条查询结果,搜索用时 31 毫秒
941.
Herbert?Due?as Edmundo?J.?HuertasEmail author Francisco?Marcellán 《Numerical Algorithms》2012,60(1):51-73
In this contribution we consider the asymptotic behavior of sequences of monic polynomials orthogonal with respect to a Sobolev-type
inner product
$ \left\langle p,q\right\rangle _{S}=\int_{0}^{\infty }p(x)q(x)x^{\alpha }e^{-x}dx+Np^{\prime }(a)q^{\prime }(a),\alpha >-1 $ \left\langle p,q\right\rangle _{S}=\int_{0}^{\infty }p(x)q(x)x^{\alpha }e^{-x}dx+Np^{\prime }(a)q^{\prime }(a),\alpha >-1 相似文献
942.
Manuel Lozano Abraham Duarte Francisco Gortázar Rafael Martí 《Journal of Heuristics》2012,18(6):919-938
In this paper, we address the optimization problem arising in some practical applications in which we want to maximize the minimum difference between the labels of adjacent elements. For example, in the context of location models, the elements can represent sensitive facilities or chemicals and their labels locations, and the objective is to locate (label) them in a way that avoids placing some of them too close together (since it can be risky). This optimization problem is referred to as the antibandwidth maximization problem (AMP) and, modeled in terms of graphs, consists of labeling the vertices with different integers or labels such that the minimum difference between the labels of adjacent vertices is maximized. This optimization problem is the dual of the well-known bandwidth problem and it is also known as the separation problem or directly as the dual bandwidth problem. In this paper, we first review the previous methods for the AMP and then propose a heuristic algorithm based on the variable neighborhood search methodology to obtain high quality solutions. One of our neighborhoods implements ejection chains which have been successfully applied in the context of tabu search. Our extensive experimentation with 236 previously reported instances shows that the proposed procedure outperforms existing methods in terms of solution quality. 相似文献
943.
944.
A general and easy-to-code numerical method based on radial basis functions
(RBFs) collocation is proposed for the solution of delay differential equations
(DDEs). It relies on the interpolation properties of infinitely smooth RBFs, which allow
for a large accuracy over a scattered and relatively small discretization support.
Hardy's multiquadric is chosen as RBF and combined with the Residual Subsampling
Algorithm of Driscoll and Heryudono for support adaptivity. The performance
of the method is very satisfactory, as demonstrated over a cross-section of
benchmark DDEs, and by comparison with existing general-purpose and specialized
numerical schemes for DDEs. 相似文献
945.
Francisco J. Valdés-Parada Jose Alvarez-Ramirez Benoît Goyeau J. Alberto Ochoa-Tapia 《Transport in Porous Media》2009,78(3):459-476
In this paper, mass transfer at the fluid–porous medium boundaries is studied. The problem considers both diffusive and convective
transport, along with adsorption and reaction effects in the porous medium. The result is a mass flux jump condition that
is expressed in terms of effective transport coefficients. Such coefficients (a total dispersion tensor and effective reaction
and adsorption coefficients) may be computed from the solution of the corresponding closure problem here stated and solved
as a function of the Péclet number (Pe), the porosity and a local Thiele modulus. For the case of negligible convective transport (i.e., ), the closure problem reduces to the one recently solved by the authors for diffusion and reaction between a fluid and a
microporous medium. 相似文献
946.
Francisco Rodríguez-González José Pérez-González Lourdes de Vargas Benjamín M. Marín-Santibáñez 《Rheologica Acta》2010,49(2):145-154
The continuous extrusion of a metallocene linear low-density polyethylene through a transparent capillary die with and without
slip was analyzed in this work by rheometrical measurements and particle image velocimetry (PIV). For this reason, a comparison
was made between the rheological behaviors of the pure polymer and blended with a small amount of fluoropolymer polymer processing
additive. Very good agreement was found between rheometrical and PIV measurements. The pure polymer exhibited stick-slip instabilities
with nonhomogeneous slip at the die wall, whereas the blend showed stable flow. The slip velocity was measured directly from
the velocity profiles and was negligible for the pure polymer before the stick-slip but increased monotonously as a function
of the shear stress for the blend. The flow curves and the slip velocity as a function of the shear stress deviated from a
power law and were well fitted by continuous “kink” functions. Comparison of PIV data with rheometrical ones permitted a direct
proof of the basic assumption of the Mooney theory. Finally, the analysis of the velocity profiles showed that there is a
maximum in the contribution of slip to the average fluid velocity, which is interpreted as the impossibility for the velocity
profile to become plug like in the presence of shear thinning. 相似文献
947.
In this work we show that homogeneous Neumann boundary conditionsinhibit the Coleman-Weinberg mechanism for spontaneous symmetry breakingin the scalar electrodynamics if the length of the finite region is small enough (a = e2M-1φ, where Mφ is the mass of the scalar field generated by the Coleman-Weinberg mechanism). 相似文献
948.
949.
Atala Daniel I. P. Costa Aline C. Maciel Rubens Maugeri Francisco 《Applied biochemistry and biotechnology》2001,91(1-9):353-365
A model of ethanol fermentation considering the effect of temperature was developed and validated. Experiments were performed
in a temperature range from 28 to 40°C in continuous mode with total cell recycling using a tangential microfiltration system.
The developed model considered substrate, product and biomass inhibition, as well as an active cell phase (viable) and an
inactive (dead) phase. The kinetic parameters were described as functions of temperature. 相似文献
950.
Gerardo R. Echevarría Andrea Basagoitia Jos G. Santos Francisco García Blanco 《Journal of molecular catalysis. A, Chemical》2000,160(2):2205-215
The macroscopic rate constants of formation (k1) and hydrolysis (k2) for the reactions of pyridoxal 5′-phosphate (PLP) with hydrazine (PLP-HY system), carbidopa (-hydrazino--methyl-β-(3,4-dihydroxyphenyl)propionic acid, PLP-CD system), hydralazine (1-hydrazinophthalazine, PLP-HL system) and isoniazid (4-pyridinecarboxylic acid hydrazide, PLP-ISO system) were fitted to a kinetic scheme that considers the different ionic species present in the medium, their protonation constants, and their individual rates of formation (k1i) and hydrolysis (k2i). The results obtained for the molecules bearing the hydrazine group are compared with those for the reactions of PLP with n-hexylamine (PLP-NHA system) and poly-
-lysine (PLP-LYS system). Some structural effects on the individual rate constants are also examined. 相似文献
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