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排序方式: 共有691条查询结果,搜索用时 31 毫秒
681.
In this paper we consider a nonautonomous two dimensional Lotka-Volterra system with impulsive effect. We prove that one of components is driven to extinction while the other stabilizes at a certain solution of an impulsive logistic equation under some conditions. 相似文献
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684.
WU Qin FANG Mao-Fa LI Shao-Xin LI Ying HU Yao-Hua 《理论物理通讯》2008,50(12):1411-1416
The entropy squeezing properties for a two-level atom interacting with a two-mode field via two different competing transitions are investigated from a quantum information point of view. The influences of the initial state of the system and the relative coupling strength between the atom and the field on the atomic information entropy squeezing are discussed. Our results show that the squeezed direction and the frequency of the information entropy squeezing can be controlled by choosing the phase of the atom dipole and the relative competing strength of atom-field, respectively. We find that, under the same condition, no atomic variance squeezing is predicted from the HUR while optimal entropy squeezing is obtained from the EUR, so the quantum information entropy is a remarkable precision measure for the atomic squeezing in the considered system. 相似文献
685.
理论分析了背景光辐照在光折变晶体中从自散焦向自聚焦特性转化过程中的作用,得到了R>1是不同类型(Δn<0和Δn>0)晶体中这种转变的条件.实验观察到了铌酸锂晶体中这种转变的现象.并依据Glass常量的光伏打效应表征意义,提出了光伏孤子形成过程中载流子的竞争效应模型.基于此,分析了折射率变化为负的光生伏打晶体在背景光和信号光Glass常量比大于1条件下的载流子竞争效应,得到了与实验现象和已知理论分析相一致的结论.研究表明,背景光引起的载流子竞争效应是影响晶体自散焦向自聚焦特性转换的内在物理本质. 相似文献
686.
利用溶胶-凝胶法制备了一系列的La0.8Sr0.2Co1-xFexO3样品.通过研究在不同外加磁场下磁化强度和温度变化的关系发现,在较高的外场下La0.8Sr0.2Co1-xFexO3样品的磁性反转现象没有被观察到;在低场下La0.8Sr0.2Co1-xFexO3系统磁性反转现象被实现.这说明Fe的掺杂引起了La0.8Sr0.2Co1-xFexO3样品中铁磁和反铁磁之间的竞争,导致了La0.8Sr0.2Co1-xFexO3样品磁性反转;同时外加磁场的强弱影响了La0.8Sr0.2Co1-xFexO3系统磁性反转现象的发生,外加磁场增大使得在La0.8Sr0.2Co1-xFexO3样品中Co离子的自旋平行趋势更强,在铁磁和反铁磁之间的竞争中铁磁耦合占主导优势,因此在较高的外场下磁性反转现象没有被观察到. 相似文献
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Traveling direction (outgoing or ingoing) of target waves sustained by a localized inhomogeneity and their competition rules in the complex Ginzburg-Landau equation (CGLE) are studied. We show that even a local positive (negative) frequency shift is capable of creating ingoing (outgoing) target waves. A novel transition between ingoing and outgoing target waves, as we find, can be switched by the size of the inhomogeneity. The competition rules for wave patterns (e.g., target waves) are also studied systematically. All the numerical findings are found to be in perfect agreement with the theoretical criteria that are derived based on the fundamental conceptions (e.g., group velocity, phase velocity). 相似文献
688.
1IntroductionTwomodelasers(TML)havebenthesubjectofextensiveinterestinrecentyears.Modecompotitionefectisoneoftheimportantpro... 相似文献
689.
In this paper, the traveling wave problem for a two-species competition reaction–diffusion–chemotaxis Lotka–Volterra system is investigated. Upper and lower solutions method and fixed point theory are employed to show the existence of traveling wave solutions connecting the coexistence constant steady state with zero state for all large enough wave speed , and conversely, when is small, we prove there is no traveling wave solution. 相似文献
690.
Dynamic Analysis of an Impulsive Chemostat Model with Microbial Competition and Nonlinear Perturbation 下载免费PDF全文
In this paper, we propose an impulsive chemostat model with microbial competition and nonlinear perturbation. First, thresholds for the extinction of both microoganisms are given. Second, we investigate the persistence in mean and boundedness of the chemostat system by constructing Lyapunov function. Moreover, we obtain the sufficient condition for the existence of an ergodic stationary distribution of the system. At last, numerical simulations are presented, and the results show that the competition between two species tends to make one species disappear from their common habitat, especially when the competition is concentrated in a single resource. 相似文献