共查询到20条相似文献，搜索用时 101 毫秒
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在随机需求条件下，配送系统设计除了使系统总费用的期望值最小外，还要满足各需求地对配送响应时间的要求。在说明了建模的假设条件后，建立了考虑随机需求和时间约束的单源、p个中转点的配送系统随机模型。通过等价变换，将随机模型转化为确定性等价问题，从而方便了问题的求解。 相似文献
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在车辆路径问题中,由于配送过程中各种不确定状况的出现,使得随机VRP逐渐成为研究者关注的焦点.数据仓库和数据挖掘技术的出现,给解决随机VRP问题提供了技术支持.针对随机需求VRP问题构建了相应的数据库及数据挖掘模型,最后用启发式算法对给定数据用例进行了求解,取得良好的效果. 相似文献
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为了优化网络结构,寻求最佳配送策略,最终找出成本最小的供应链,针对需求拖动式供应链中,多供应商、多产品、多客户分销配送网络的优化设计问题,在考虑需求分配的情况下,提出了分销配送网络的优化模型 相似文献
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配送车辆优化调度问题是物流系统中的一个重要环节,本软件借助VB语言,在分析静态配送的基础上,针对不断变化的市场需求,建立动态的物流配送模型,在生成路网的平台上,通过研究物流配送货物过程中路径、车辆选择的问题,提出对物流配送最优路径的动态选择方案,提高物流配送效率,满足客户需求,更符合实际。 相似文献
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本文研究了在客户需求随机和混合运输模式环境下,综合考虑了工厂单产能水平、客户时间窗、最大服务距离限制等因素,构建供应链配送网络模型,采用嵌入随机模拟的变异PSO算法进行求解,最后通过算例说明所建模型及求解算法的有效性。 相似文献
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通过对逆向物流系统复杂性的描述,分析逆向配送的成本问题,提出逆向配送成本模型的假设并建立模型。通过模型的建立及对物流系统的整体优化,可以实现逆向配送过程中的总成本最小化,同时节约资源,减少对环境的压力。 相似文献
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通过对逆向物流系统复杂性的描述,分析逆向配送的成本问题,提出逆向配送成本模型的假设并建立模型.通过模型的建立及对物流系统的整体优化,可以实现逆向配送过程中的总成本最小化,同时节约资源,减少对环境的压力. 相似文献
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The purpose of fault diagnosis of stochastic distribution control (SDC) systems is to use the measured input and the system output probability density functions (PDFs) to obtain the fault information of the SDC system. When the target PDF is known, the purpose of fault tolerant control of stochastic distribution control system is to make the output PDF still track the given distribution using the fault tolerant controller. However, in practice, time delay may exist in the data (or image) processing, the modeling and transmission phases. When time delay is not considered, the effectiveness of the fault detection, diagnosis and fault tolerant control of stochastic distribution systems will be reduced. In this paper, the rational square-root B-spline is used to approach the output probability density function. In order to diagnose the fault in the dynamic part of such systems, it is then followed by the novel design of a nonlinear neural network observer-based fault diagnosis algorithm. The time delay term will be deleted in the stability proof of the observation error dynamic system. Based on the fault diagnosis information, a new fault tolerant controller based on PI tracking control is designed to make the post-fault probability density function still track the given distribution, which is dependent of the time delay term. Finally, simulations for the particle distribution control problem are given to show the effectiveness of the proposed approach. 相似文献
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提出了将科学期刊的累积引文分布函数看作是一个线性系统的脉冲响应,从而可以找到与其相联系的线性系统。可以看到,文中所找到的线性系统模型要比国外文献中的更为清晰。于是,可以应用时域分析法来研究引文分布函数。文中分析了几个著名分布的时域的重要特性,引入了上升时间的概念,用来表征引文分布的变化之快慢。对于几个著名的引文分布,推导了它们的上升时间和半衰期的计算公式。 相似文献
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The existence and uniqueness of stationary distribution and ergodic properties of a stochastic system are obtained. Especially, different from the existing methods, a new method is introduced to analyze almost sure permanence and uniform boundedness of the stochastic predator–prey model. This new idea is based on geometric structure of invariant set for a stochastic system. More specifically, we obtain our main conclusions by showing the invariant set for the stochastic population system lies in the interior of the first quadrant. It is interesting and surprising that the stochastic population model can guarantee a uniform boundedness almost surely. Some numerical simulations are carried out to support our results. 相似文献
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This paper investigates the problem of secure control for networked control systems (NCSs) under randomly occurring zero-value attacks (ROZVAs). Specifically, ROZVAs only offset the true signal without injecting obfuscated information or noises, and possess the minimum energy of the added malicious information. To protect system stability against ROZVA, randomly occurring integrity check protection (ROICP) is introduced which prevents malicious data injection with less energy cost than persistently occurring protection. Besides the random phenomena of ROZVA and ROICP, which are characterized by two mutually independent random variables obeying the Bernoulli distribution, the randomly occurring time delays caused by ROICP are also considered in system modelling. According to the built stochastic linear system model, security analysis of the NCS with ROICP subject to ROZVA is carried out and sufficient condition for stochastic stability is derived via a linear matrix inequality (LMI) approach. Based on the proposed condition, a compensation feedback controller is designed to facilitate system stability. Finally, simulation results show the effectiveness of the proposed method. 相似文献
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Incorporating the environmental perturbations and available resources of the public health system, we construct both deterministic and stochastic models of SIRS type. The deterministic model exhibits very rich dynamics, such as Hopf bifurcation and backward bifurcation which leads to the co-existence of the stable disease-free state and a stable endemic equilibrium. For the stochastic model, we show that under mild extra conditions, if the basic reproduction number is less than one, then the disease will be eradicated almost surely, and if the basic reproduction number is greater than one, the stochastic model will admit a unique ergodic stationary distribution, which implies that the disease persists almost surely. Part of our numerical simulations indicate that: (i) The introduction of environmental perturbations may drift the endemic equilibrium to the disease-free equilibrium, or vice versa; (ii) Increasing available resources is necessary in order to mitigate the infections. 相似文献
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A method for nuclear norm-based recursive subspace prediction of time-varying continuous-time stochastic systems via distribution theory is proposed. The random distribution theory is adopted to describe the time-derivative of stochastic processes, which is the key to obtain the input–output algebraic equation. The low-rank matrix approximation of the input–output projection matrix is established by nuclear norm minimization instead of the singular value decomposition. Moreover, the optimization problem is deduced by the alternating direction method of multipliers. According to the angle rotation between past and present subspaces spanned by the extended observability matrices, the future signal subspace is predicted by the present subspace. Further, the system matrices are predicted and the corresponding system model is obtained. The results of simulation studies show the effectiveness of the presented method. 相似文献
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考虑市场的随机需求,研究从制造商到最终客户的多层供应链与供应链的竞争问题,根据给定的假设条件和存在的问题进行分析,选取供应链网络的利润最大化为择优标准,利用变分不等式理论构建了具有随机需求的多供应链竞争网络模型,刻画了多供应链之间的竞争行为。通过用修正投影算法求解文中算例,对算例计算结果进行了分析,分析结果验证了模型的合理性。为以后分析供应链形成过程奠定一定的理论基础。 相似文献
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ＣＬＴＡＮＤＬＩＬＦＯＲＴＨＥＳｔＡＴＩＯＮＡＲＹＳＥＱＵＥＮＣＥＯＦＡＤＯＵＢＬＹＳＴＯＣＨＡＳＴＩＣＴＩＭＥＳＥＲＩＥＳＡＲ－ＭＡＭＯＤＥＬＣＬＴＡＮＤＬＩＬＦＯＲＴＨＥＳｔＡＴＩＯＮＡＲＹＳＥＱＵＥＮＣＥＯＦＡＤＯＵＢＬＹＳＴＯＣＨＡＳＴＩＣ￥... 相似文献
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《Journal of The Franklin Institute》2019,356(13):7347-7370
In this paper, we study a stochastic SIR epidemic model with distributed delay and degenerate diffusion. Firstly, we transform the stochastic model into an equivalent system which contains three equations. Since the diffusion matrix is degenerate, the uniform ellipticity condition is not satisfied. The Markov semigroup theory is used to obtain the existence and uniqueness of a stable stationary distribution. We verify the densities of the distributions of the solutions can converge in L1 to an invariant density. Then we establish sufficient conditions for extinction of the disease. Some examples and numerical simulations are introduced to illustrate our analytical results. 相似文献