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1.
In this paper we define wheel matrices and characterize some properties of matrices that are perfect but not balanced. A consequence of our results is that if a matrixA is perfect then we can construct a polynomial number of submatricesA
I,,A
n
ofA such thatA is balanced if and only if all the submatricesA
1,,A
n
ofA are perfect. This implies that if the problem of testing perfection is polynomially solvable, then so is the problem of testing balancedness.Partial support under NSF Grants DMS-8606188, ECS-8800281 and DDM-8800281. 相似文献
2.
We investigate wave-breaking and dispersive shock wave formation driven by a pulse undergoing second-harmonic generation in a quadratic medium. We show that the process is accessible in the regime of high phase-mismatch (cascading limit) and weak dispersion. Insight into the phenomenon is obtained by means of a suitable hydrodynamic reduction of the equations that govern the mixing. 相似文献
3.
A consequence of Seymour's characterization of binary clutters with the Max Flow Min Cut property is that the minimum cardinality of a T-cut is equal to the largest number of edge-disjoint T-joins in every graph that cannot be T-contracted to an odd K2,3. We give a simple “graphic” proof of this fact. © 1996 John Wiley & Sons, Inc. 相似文献
4.
We consider Maxwell’s equations with periodic coefficients as it is usually done for the modeling of photonic crystals. Using Bloch/Floquet theory, the problem reduces in a standard way to a modification of the Maxwell cavity eigenproblem with periodic boundary conditions. Following [8], a modification of edge finite elements is considered for the approximation of the band gap. The method can be used with meshes of tetrahedrons or parallelepipeds. A rigorous analysis of convergence is presented, together with some preliminary numerical results in 2D, which fully confirm the robustness of the method. The analysis uses well established results on the discrete compactness for edge elements, together with new sharper interpolation estimates. 相似文献
5.
Menichini F Tundis R Bonesi M de Cindio B Loizzo MR Conforti F Statti GA Menabeni R Bettini R Menichini F 《Natural product research》2011,25(8):789-799
The chemical composition of the essential oil of Citrus medica L. cv. Diamante peel obtained by hydrodistillation, cold-pressing and supercritical carbon dioxide extraction techniques was determined by GC/MS analysis. Forty-six components were fully characterised. Limonene and γ-terpinene were the major components of the oils obtained by hydrodistillation (HD) and cold-pressing (CP), while citropten was the major constituent in the oil obtained by supercritical carbon dioxide extraction (SFE). Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were evaluated. The essential oil obtained by hydrodistillation exerted the highest inhibitory activity against BChE (IC?? value of 154.6 μg mL?1) and AChE (IC?? value of 171.3 μg mL?1. Interestingly, the oil obtained by cold-pressing exhibited a selective inhibitory activity against AChE. The essential oils have also been evaluated for the inhibition of NO production in LPS induced RAW 264.7 macrophages. The oil obtained by hydrodistillation exerted a significant inhibition of NO production with an IC?? value of 17 μg mL?1 (IC?? of positive control 53 μg mL?1). 相似文献
6.
Theories and models are presented for gas sorption in polymers above and below the glass transition temperature. With the exception of predictive theories that do not represent the data well, the models are fit to data for the carbon dioxide/silicone rubber and carbon dioxide/polycarbonate systems for the purposes of comparison. During the past decade, a number of new models and theories have been proposed specifically for gas sorption in glassy polymers. Each new model attempts to incorporate aspects of the gas sorption process that are unique to polymers below the glass transition temperature. This review discusses these recent advances, the assumptions used in their development and their advantages and disadvantages. 相似文献
7.
8.
Antonio Degasperis Matteo Conforti Fabio Baronio Stefan Wabnitz Sara Lombardo 《Letters in Mathematical Physics》2011,96(1-3):367-403
The spectral theory of the integrable partial differential equations which model the resonant interaction of three waves is considered with the purpose of numerically solving the direct spectral problem for both vanishing and non vanishing boundary values. Methods of computing both the continuum spectrum data and the discrete spectrum eigenvalues are given together with examples of such computations. The explicit spectral representation of the Manley-Rowe invariants is also displayed. 相似文献
9.
Water distribution networks are important systems that provide citizens with an essential public service which is crucial for the normal development of most basic activities of life. Despite many water distribution network problems have been extensively investigated in the literature, the presence of uncertainty in the data has often been neglected. This paper studies the challenging problem of designing an isolation system for water distribution networks under different failure scenarios. To solve the problem, three heuristic methods are presented and analyzed on a real case study taken from the literature. Numerical results show the merits of the suggested techniques for solving the problem. 相似文献
10.