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991.
具有阶段结构的竞争系统的持久性和稳定性 总被引:2,自引:0,他引:2
研究带有时滞和成长阶段的两种群竞争模型,第一个种群分成年和幼年两个阶段,第二个种群不具有阶段结构.本文证明了系统正解的有界性;利用比较原理得到了系统永久生存的充分条件;通过构造Lyapunov函数得到了系统全局渐近稳定的充分条件. 相似文献
992.
993.
In this paper we discuss two-stage Miistein methods for solving Ito stochastic differential equations (SDEs). Six fully explicit methods (TSM 1 -- TSM 6) are given in this paper. Their order of strong convergence is proved. The stability properties and numerical results show the effectiveness of these methods in the pathwise approximation of Ito SDEs. 相似文献
994.
研究了具有HollingII类型功能反应的一捕食者有两个食饵的时滞系统,通过构造Lyapunov泛函得到了与时滞有关的系统全局渐近稳定的充分条件. 相似文献
995.
996.
Guo‐Xu Zhang Ying Xie Hai‐Tao Yu Hong‐Gang Fu 《Journal of computational chemistry》2009,30(12):1785-1798
The structural and electronic properties of five terminations of cubic lead titanate (PbTiO3) (110) polar surface were investigated by first‐principles total‐energy calculations using a periodic slab model. On the PbTiO termination, an anomalous filling of conduction band was observed, whereas on the O2 termination, two surface oxygen atoms formed a peroxo group, demonstrating that the electronic structures of the two stoichiometric terminations undergo significant changes with respect to bulk materials. However, for the three nonstoichiometric TiO‐, Pb‐, and O‐terminated surfaces, their electronic structures are very similar to bulk. Charge redistribution results for the five terminations confirmed that electronic structure and surface composition changes are responsible for their polarity compensation. However, which mechanism actually dominates the stabilization process depends upon energetic considerations. A thermodynamic stability diagram suggested that the two stoichiometric terminations are unstable; however, the three nonstoichiometric terminations can be stabilized in some given regions. Furthermore, this study indicates that the very different stabilities and surface states filling behaviors of the PbTiO3 (110) polar surface with respect to SrTiO3 and BaTiO3 ones seem to originate from the partially covalent characteristics of Pb O pairs. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009 相似文献
997.
N.J. Rodríguez K. Davey J.A. Vázquez Feijoo A. Juárez-Hernandez 《Applied Mathematical Modelling》2009
Presented in this paper is a numerical methodology for the solution of the parabolic governing partial differential equation that describes unsteady advection–diffusion heat transfer. The formulation presented here is shown to be free from the numerical oscillation commonly associated with advection–diffusion heat transfer regardless of the value of the Peclet number. The formulation involves the absorption of the advection term in the unsteady heat equation into the capacitance term. This process is achieved with the use of a control volume methodology applied to each nodal element on a finite-volume mesh. This is shown to ensure that spurious energy losses and gains are avoided and provides for consistency between temperature and energy change. This approach provides unconditional stability and it is shown that good accuracy is achievable with relatively large time-steps. 相似文献
998.
Gui‐Zhong Yang Xiao‐Lei Chen Lu‐Min Wang Jian‐Gao Shi Chun‐Zhong Li Tianxi Liu 《先进技术聚合物》2009,20(2):104-110
A series of fluorene‐based rod–coil liquid crystal polymers with different lengths of the coil segments on backbones were designed and synthesized by a palladium‐catalyzed Suzuki coupling‐reaction. The thermal stability, the UV–Vis absorption and fluorescence spectra in chloroform solution and thin film, the electrochemical properties, thermal behavior, and morphology of these rod–coil polymers were investigated. The thermal stability of these polymers steadily decreased on increasing the length of the coil segments on the backbone; their optical and electrochemical properties did not exhibit noticeable dependence on the weight fraction of the coil segments. However, the shoulder emission and the full width at the half‐maximum (FWHM) in PL spectra of the films increased, whereas the oxidation onset potentials and the corresponding HOMO energy levels decreased with the increase in the weight fraction of the coil segments, which was assigned to microphase separation and formation of folded chain conformation as the weight fraction of the coil segments increased. These polymers displayed a characteristic liquid crystalline texture. The variation of the weight fraction of the coil segments obviously affected the thermal behavior and morphology of these rod–coil polymers. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
999.
Some stability results for the functional equations of Cauchy and Jensen in probabilistic setting are proved by using the fixed point method. 相似文献
1000.
Bruno Buonomo Deborah Lacitignola 《Journal of Mathematical Analysis and Applications》2008,348(1):255-266
In this paper, we consider a general bilinear three dimensional ODE system, whose structure generalizes many mathematical models of biological interest, including many from epidemics. Our main goal is to find sufficient conditions, expressed in terms of the parameters of the system, ensuring that the geometric approach to global stability analysis, due to [M.Y. Li, J.S. Muldowney, A geometric approach to global-stability problems, SIAM J. Math. Anal. 27 (4) (1996) 1070-1083], may be successfully applied. We completely determine the dynamics of the general system, including thresholds and global stability of the nontrivial equilibrium. The obtained result is applied to several epidemic models. We further show how the role of new parameters on stability of well-established models may be emphasized. 相似文献