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161.
We consider the unconstrained traveling tournament problem, a sports timetabling problem that minimizes traveling of teams. Since its introduction about 20 years ago, most research was devoted to modeling and reformulation approaches. In this paper we carry out a polyhedral study for the cubic integer programming formulation by establishing the dimension of the integer hull as well as of faces induced by model inequalities. Moreover, we introduce a new class of inequalities and show that they are facet-defining. Finally, we evaluate the impact of these inequalities on the linear programming bounds. 相似文献
162.
《Wave Motion》2018
The Extended Thermodynamic theory is used to derive a hyperbolic reaction–diffusion model for Chemotaxis. Linear stability analysis is performed to study the nature of the equilibrium states against uniform and nonuniform perturbations. A particular emphasis is given to the occurrence of the Turing bifurcation. The existence of traveling wave solutions connecting the two steady states is investigated and the governing equations are numerically integrated to validate the analytical results. The propagation of plane harmonic waves is analyzed and the stability regions in terms of the model parameters are shown. The frequency dependence of the phase velocity and of the attenuation is also illustrated. Finally, in order to have a measure of the non linear stability, the propagation of acceleration waves is studied, the wave amplitude is derived and the critical time is evaluated. 相似文献
163.
165.
《Physics letters. A》2020,384(36):126935
Neurodegenerative diseases are closely associated with the amplification and invasion of toxic proteins. In particular Alzheimer's disease is characterized by the systematic progression of amyloid-β and τ-proteins in the brain. These two protein families are coupled and it is believed that their joint presence greatly enhances the resulting damage. Here, we examine a class of coupled chemical kinetics models of healthy and toxic proteins in two spatial dimensions. The anisotropic diffusion expected to take place within the brain along axonal pathways is factored in the models and produces a filamentary, predominantly one-dimensional transmission. Nevertheless, the potential of the anisotropic models towards generating interactions taking advantage of the two-dimensional landscape is showcased. Finally, a reduction of the models into a simpler family of generalized Fisher-Kolmogorov-Petrovskii-Piskunov (FKPP) type systems is examined. It is seen that the latter captures well the qualitative propagation features, although it may somewhat underestimate the concentrations of the toxic proteins. 相似文献
166.
In this paper the Green’s function method and results about fixed point are used to get existence results on periodic traveling wave solution for non-homogeneous problems of generalized versions of the BBM and KdVB equations. It is shown through the constructions of explicit Green’s functions that the periodic boundary value problems for the traveling wave solutions of the BBM and KdVB equations are equivalent to integral equations which generate compact operators in the space of periodic functions. These integral representations allowed us to prove that if the speed of the wave propagation is suitably chosen, then the BBM and KdVB equations will admit periodic traveling wave solution. 相似文献
167.
This paper outlines an analysis of the traveling performance of a lunar rover. The analysis is in the form of numerical simulations and it uses soil properties, identified in vacuum, and mechanics of wheel-based travel. The wheel-to-ground contact model and soil parameters are determined first so they could be used in the numerical simulation. A soil test device is introduced and the soil parameters are identified from plate-pressing and shear tests. Finally, numerical simulations are conducted using the parameters identified and their results are discussed along with those of the traveling tests conducted in vacuum. The soil tests indicated that the wheel sinkage into the ground can increase in vacuum and that the shear stress acting beneath the wheel in vacuum is almost the same as that in the atmosphere. Because of these trends, the simulations and traveling tests showed that the traveling performance of the wheel can decrease in vacuum. Although it has been widely considered that the vacuum environments enhance the traveling performance of the wheel, this study confirmed that it is not always the case. 相似文献
168.
《Wave Motion》2017
Traveling gravity-capillary water waves on the interface of a three-dimensional fluid of infinite depth are computed. The vortex sheet formulation with the small scale approximation is used as the mathematical model for the fluid motion. The fluid interface is parameterized isothermally. The traveling wave ansatz for parameterized surfaces is described. Waves are computed using Fourier collocation and quasi-Newton iteration; large amplitude overturned traveling waves are computed via a dimension-breaking based numerical continuation method. 相似文献
169.
The existence of a family of traveling waves is established for a parabolic system modeling single species growth in a plug flow reactor, proving a conjecture of Kennedy and Aris (Bull. Math. Biol. 42 (1980) 397) for a similar system. The proof uses phase plane analysis, geometric singular perturbation theory and the center manifold theorem. 相似文献
170.