Existence, uniqueness, and stability of periodic solutions of an equation of duffing type
Hongbin Chen Yi Li
We consider a second-order equation of Duffing type. Bounds for the derivative of the restoring force are given which ensure the existence and uniqueness of a periodic solution. Furthermore, the unique periodic solution is asymptotically stable with sharp rate of exponential decay. In particular, for a restoring term independent of the variable $t$, a necessary and sufficient condition is obtained which guarantees the existence and uniqueness of a periodic solution that is stable.
keywords: stability. topological degree Periodic solution
Asymptotic behavior of linearized viscoelastic flow problem
Yinnian He Yi Li
In this article, we provide some asymptotic behaviors of linearized viscoelastic flows in a general two-dimensional domain with certain parameters small and the time variable large.
keywords: Viscoelastic flows; Navier-Stokes flows; Euler flows; Asymptotic behavior.
Local stability of traveling-wave solutions of nonlinear reaction-diffusion equations
Xiaojie Hou Yi Li
We investigate the local stability of traveling-wave solutions of the nonlinear reaction-diffusion equations in various weighted Banach spaces. New methods are used in analyzing the location of the spectrum. The result covers the stability results of the traveling-wave solutions of reaction-diffusion equations including the well known Fisher-KPP-type nonlinearity.
keywords: Nonlinear Fisher-KPP-type nonlinearity. Banach spaces reaction diffusion
Global existence of solutions to a cross-diffusion system in higher dimensional domains
Yi Li Chunshan Zhao
We consider a strongly coupled nonlinear parabolic system which arises from population dynamics in $N$-dimensional $(N\geq 1)$ domains. We establish global existence of classical solutions under certain restrictions on diffusion coefficients, self-diffusion coefficients and cross-diffusion coefficients for both species.
keywords: nonlinear parabolic system population dynamics self-diffusion Shigesada-Kawasaki-Teramoto model. Global existence cross-diffusion
Stability of travelling waves with noncritical speeds for double degenerate Fisher-Type equations
Yi Li Yaping Wu
This paper is concerned with the asymptotic stability of travel- ling wave solutions for double degenerate Fisher-type equations. By spectral analysis, each travelling front solution with non-critical speed is proved to be linearly exponentially stable in some exponentially weighted spaces. Further by Evans function method and detailed semigroup estimates each travelling front solution with non-critical speed is proved to be locally algebraically stable to perturbations in some polynomially weighted spaces, and it is also locally exponentially stable to perturbations in some polynomially and exponentially weighted spaces.
keywords: asymptotic stability semigroup estimates travelling waves algebraic decay Evans function. spectral analysis
Existence of traveling wave solutions for a nonlocal reaction-diffusion model of influenza a drift
Joaquin Riviera Yi Li
In this paper we discuss the existence of traveling wave solutions for a nonlocal reaction-diffusion model of Influenza A proposed in Lin et. al. (2003). The proof for the existence of the traveling wave takes advantage of the different time scales between the evolution of the disease and the progress of the disease in the population. Under this framework we are able to use the techniques from geometric singular perturbation theory to prove the existence of the traveling wave.
keywords: multifractal analysis. Poincaré recurrences Dimension theory
Traveling waves in a three species competition-cooperation system
Xiaojie Hou Yi Li

This paper studies the traveling wave solutions to a three species competition cooperation system, which is derived from a spatially averaged and temporally delayed Lotka Volterra system. The existence of the traveling waves is investigated via a new type of monotone iteration method. The upper and lower solutions come from either the waves of KPP equation or those of certain two species Lotka Volterra system. We also derive the asymptotics and uniqueness of the wave solutions.

keywords: Traveling wave spatio-temporal delay Lotka Volterra competition cooperation existence
Traveling wave solutions for a reaction diffusion equation with double degenerate nonlinearities
Xiaojie Hou Yi Li Kenneth R. Meyer
This paper studies the traveling wave solutions for a reaction diffusion equation with double degenerate nonlinearities. The existence, uniqueness, asymptotics as well as the stability of the wave solutions are investigated. The traveling wave solutions, existed for a continuance of wave speeds, do not approach the equilibria exponentially with speed larger than the critical one. While with the critical speed, the wave solutions approach to one equilibrium exponentially fast and to the other equilibrium algebraically. This is in sharp contrast with the asymptotic behaviors of the wave solutions of the classical KPP and $m-th$ order Fisher equations. A delicate construction of super- and sub-solution shows that the wave solution with critical speed is globally asymptotically stable. A simpler alternative existence proof by LaSalle's Wazewski principle is also provided in the last section.
keywords: Asymptotics Uniqueness Heteroclinc Orbits. Traveling Wave Existence
Coordinate descent optimization for l1 minimization with application to compressed sensing; a greedy algorithm
Yingying Li Stanley Osher
We propose a fast algorithm for solving the Basis Pursuit problem, minu $\{|u|_1\: \Au=f\}$, which has application to compressed sensing. We design an efficient method for solving the related unconstrained problem minu $E(u) = |u|_1 + \lambda \||Au-f\||^2_2$ based on a greedy coordinate descent method. We claim that in combination with a Bregman iterative method, our algorithm will achieve a solution with speed and accuracy competitive with some of the leading methods for the basis pursuit problem.
keywords: Bregman iteration Basis Pursuit shrinkage greedy sweep constrained problem.
Parameter identification of nonlinear delayed dynamical system in microbial fermentation based on biological robustness
Lei Wang Jinlong Yuan Yingfang Li Enmin Feng Zhilong Xiu
In this paper, the nonlinear enzyme-catalytic kinetic system of batch and continuous fermentation in the process of glycerol bio-dissimilation is investigated. On the basis of both glycerol and 1,3-PD pass the cell membrane by active and passive diffusion under substrate-sufficient conditions, we consider the delay of concentration changes on both extracellular substances and intracellular substances. We establish a nonlinear delay dynamical system according to the batch and continuous fermentation of bio-dissimilation of glycerol to 1,3-propanediol(1,3-PD) and we propose an identification problem, in which the biological robustness is taken as a performance index, constrained with nonlinear delay dynamical system. An algorithm is constructed to solve the identification problem and the numerical result shows the values of time delays of glycerol, 3-HPA, 1,3-PD intracellular and extracellular substances. This work will be helpful for deeply understanding the metabolic mechanism of glycerol in batch and continuous fermentation.
keywords: biological robustness parameter identification Nonlinear time-delay system continuous and batch fermentation.

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