共查询到20条相似文献，搜索用时 218 毫秒
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海洋生态经济系统非线性动力学模型的建立及分析,对我国海洋生态经济发展乃至社会经济的发展都具有重要意义.建立了新的海洋生态经济系统动力学模型,研究了模型的稳定性和分岔现象,揭示了该系统的非线性动力学特性. 相似文献
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本文研究了一类有脉冲影响的随机Nicholson果蝇模型,应用Lyapunov泛函、It■公式及某些不等式技巧给出了描述该模型方程的全局均方指数最终有界的充分性条件,并估计了指数收敛率和最终的一个界。进一步,给出了实例及仿真模拟,说明了本文所得结论的有效性。 相似文献
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The paper studies the parametric stochastic roll motion in the random waves. The differential equation of the ship parametric roll under random wave is established with considering the nonlinear damping and ship speed. Random sea surface is treated as a narrow-band stochastic process, and the stochastic parametric excitation is studied based on the effective wave theory. The nonlinear restored arm function obtained from the numerical simulation is expressed as the approximate analytic function. By using the stochastic averaging method, the differential equation of motion is transformed into Ito's stochastic differential equation. The steady-state probability density function of roll motion is obtained, and the results are validated with the numerical simulation and model test. 相似文献
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Stochastic virtual population analysis 总被引：2，自引：1，他引：1
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A moment method for analysing the stochastic stability of the surge motion of a tethered buoyant platform (TBP) in a random sea is examined. In the differential equation describing the surge motion the variation of tether tension caused by the vertical component of the wave forces is random-time dependent in form. The asymptotic moment behaviour of the solution is determined and approximated in terms of an integral equation. Under the assumption of a narrow band process imposed upon the random coefficient, the stability results are obtained with the aid of deterministic stability theory. The mean square stability is studied and criteria for stability are obtained in terms of the damping coefficient and the auto-correlation function of the random sea. 相似文献
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In conventional beamforming systems, the use of aperiodic arrays is a powerful way to obtain high resolution employing few elements and avoiding the presence of grating lobes. The optimized design of such arrays is a required task in order to control the side-lobe level and distribution. In this paper, an optimization method aimed at designing aperiodic linear sparse arrays with great flexibility is proposed. Simulated annealing, which is a stochastic optimization methodology, has been utilized to synthesize the positions and the weight coefficients of the elements of a linear array in order to minimize the peak of the sidelobes and to obtain a beam pattern that meets given requirements. An important novelty is the fact that the latter goal can be achieved in parallel to the minimization of both the number of elements and the spatial aperture, resulting in a “global” optimization of the array characteristics. The great freedom that simulated annealing allows in defining the energy function to be minimized is the main reason for the notable versatility and the good results of the proposed method. Such results show an improvement in the array characteristics and performances over those reported in the literature 相似文献
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对具有未建模动态特性且时滞任意的多维随机系统,通过采用有界外来激励和随机变界截尾方法,本文建立了推广最小二乘（ＥＬＳ）算法和加权ＥＬＳ算法的稳健估计,进而得到间接自适应模型参考控制的稳健性 相似文献
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This paper theoretically investigates three stochastic systems with cross-correlation Gaussian white noises. Both steady state properties of the stochastic nonlinear systems and the nonequilibrium transitions induced by the cross-correlated noises are studied. The stationary solutions of the Fokker-Planck equation for three specific examples are analysed. It is shown explicitly that the cross-correlation of white noises can induce nonequilibrium transitions. 相似文献
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The aim of this study is to examine both the stochastic rolling motion of ships in following seas by using analytical and numerical safe basin concept and to show how the concept of safe basin can be utilized for the assessment of the stability of ships. First, the boundary of the analytic safe basins of stochastic rolling motion is obtained by using the Lyapunov function used by Schurz (2009). Second, the safe basins of stochastic rolling motion are obtained numerically by using stochastic Euler (Euler–Maruyama) method. It is concluded that the analytically and numerically obtained safe basins are coherent. Lastly, the practical intact stability criterion for ships in following seaway is developed by proposing a formula given for the maximum width of analytic safe basin. 相似文献