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Beijing, China

Zhu Z.,Tsinghua University | Zhu Z.,Logistics Academy | Liu L.,Tsinghua University | Wang J.,Long Island University
Computers and Industrial Engineering

China is in the process of building Strategic Petroleum Reserve (SPR) as a utility for its oil supply security. In this paper we develop a stochastic dynamic programming model to optimize China's stockpile policy with the objective of minimizing the discounted SPR policy costs over a finite time horizon. It is shown that a deterministic and Markovian policy is optimal to the model. A recursive procedure is designed to construct the value functions and derive the optimal stockpile acquisition and release rates over time. Post-optimality analysis is performed to investigate sensitivities of the optimal policy to primary parameter assumptions. © 2011 Elsevier Ltd. All rights reserved. Source

Cai Y.,The Academy of Management | Zhu J.,The Academy of Management | Li T.,Logistics Academy
Proceedings of the World Congress on Intelligent Control and Automation (WCICA)

Hot point recognition algorithm is designed in this paper. It is used to work out recognition of hot point in some encrypt wireless network based on OSPF protocol. We use traffic relevance to descript the character of hot point area. We recognize the area of hot point by means of calculating covariance of different reconnaissance nodes flux. Then we design the hot point recognition algorithm. Simulation results got in the NS2 show that this algorithm is well performed in hot point recognition. © 2014 IEEE. Source

Wei Z.,Beijing Jiaotong University | Wang M.,Logistics Academy
Applied Mechanics and Materials

The structural problem is the key and difficult point for the study of material composed of granules. In this paper, theory of full state function for material structure is put forward by examining the structural morphology of the material. The full state function of material structure reflects the structural properties of material. Thus it can also reflect the variations in of mechanical and geometric properties of material under external force, i.e. the constitutive relationship of material. The constitutive relationship established based on full state function is abbreviated as "full constitutive relationship", which considers the structural properties of material. The constitutive relationship not only can derive constitutive relationship which considers material structure, but also the constitutive relationship with the identical form as that in classical theory when material degenerates into typical ideal elastic-plastic material. The theoretical method proposed in this paper transforms dynamic analysis of structural evolution into state analysis. By associating granular scale with macroscopic scale, a foundation is laid for solving of the structural problems of material macroscopically. © (2012) Trans Tech Publications. Source

Hou L.,Logistics Academy | Hou L.,University of Western Australia | Small M.,University of Western Australia | Lao S.,National University of Defense Technology

Several methods exist to construct complex networks from time series. In general, these methods claim to construct complex networks that preserve certain properties of the underlying dynamical system, and hence, they mark new ways of accessing quantitative indicators based on that dynamics. In this paper, we test this assertion by developing an algorithm to realize dynamical systems from these complex networks in such a way that trajectories of these dynamical systems produce time series that preserve certain statistical properties of the original time series (and hence, also the underlying true dynamical system). Trajectories from these networks are constructed from only the information in the network and are shown to be statistically equivalent to the original time series. In the context of this algorithm, we are able to demonstrate that the so-called adaptive k-nearest neighbour algorithm for generating networks out-performs methods based on ε-ball recurrence plots. For such networks, and with a suitable choice of parameter values, which we provide, the time series generated by this method function as a new kind of nonlinear surrogate generation algorithm. With this approach, we are able to test whether the simulation dynamics built from a complex network capture the underlying structure of the original system; whether the complex network is an adequate model of the dynamics. © 2015 by the authors. Source

Wei Z.H.,Logistics Academy | Wang M.S.,Beijing Jiaotong University | Zhang D.L.,Beijing Jiaotong University
Applied Mechanics and Materials

Strength criteria for materials in the classical elastoplastic theory are formed mostly based on experiments and some assumptions [1, 2]. However, no concensus has been achieved though many strength models were put forward to explore the applicable material strength criteria previously. Even the influence of material structures on strength has not been realized. In this article, the tensile failure strength criterion, shear strength criterion and strength criterion of friction materials are explored on the basis of the model of material with a structure of uniformly random distribution. Through analysis, it can be discovered that the strength criteria in the classical elastoplastic theory can be derived from the complex material theory based on the concept of material structure. However, as the theoretical basis, conditions of derivation and assumptions of concepts are totally different, it is proved that the complex material theory used for studying the material structures can fully cover the contents and conclusions obtained in classical elastoplastic theory. © (2014) Trans Tech Publications, Switzerland. Source

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