WDM光网中虚拓扑重构的优化设计

采用优化方法来研究光网络业务发生改变时的虚拓扑重构问题,并提出了相应的混合整数线性规划算法.主要的思路是当业务发生改变时,寻找既能保证网络性能又对现有业务中断最小的虚拓扑.对影响虚拓扑重构的因素进行了研究,发现,如果使网络性能达到次优而不是最优可以大大减少对现有业务的中断.     

In Appreciation

Leslie Foldy’s diminutive stature and modest demeanor gave little clue to the powerful intellect responsible for several significant advances in theoretical physics.Two were particularly important. His 1945 theory of the multiple scattering of waves laid out the fundamentals that most modern theories have followed (and sometimes rediscovered), while his work with Siegfried Wouthuysen on the nonrelativistic limit of the Dirac equation opened the way to a wealth of valuable insights. In this article we recall some of the milestones along Foldy’s path through a life in physics. Some of the anecdotes we report here were related to one of the authors (PLT) just before an event in 2000 celebrating Foldy’s 80th birthday, while others were told to us over the course of the nearly forty years during which we were colleagues. Still others were uncovered during the course of WJF’s research for his book, Physics at a Research University: Case Western Reserve 1830–1990 (Cleveland: Case Western Reserve University, 2006). Other details were provided by Foldy’s widow, Roma. Philip L. Taylor is the Perkins Professor of Physics and Professor of Macromolecular Science and Engineering at Case Western Reserve University. William J. Fickinger is Professor Emeritus of Physics at Case Western Reserve University.     

Feasibility Study of Axially- Extracted Virtual Cathode Oscillator

In this paper, we have analyzed the design parameters of the axially - extracted virtual cathode oscillator, which is high-power microwave source based on the concept of the virtual cathode associated with the intense relativistic electrons beam oscillations in the electrostatic potential well. The microwave emission by the virtual cathode oscillator results from both the space and time oscillations of virtual cathode and reflexing electrons trapped in the potential well between the virtual and real cathodes. In the X-band frequency spectrum 700 MW microwave peak power has been obtained analytically by the solid electron beam of 300 kV and 20 kA for feasible design parameters. The analysis has been performed by 2-dimensional, relativistic, electromagnetic particle-in-cell simulation code XOOPIC.     

Acoustic analysis of damping structure with response surface method

Analysis of vibro-acoustic systems is challenged by their highly non-linear and complex properties, especially for the damping structure. So, an approximate response surface method (RSM) method is utilized to analysis the effect of design parameters on the sound radiation from a vibrating panel. A simple case study was illustrated to demonstrate the capabilities of the developed procedure. In details, sound radiated from vibrating panel with a point force excitation has been analyzed by numerical method. The structure-born noise problem is approximated by a series of second-degree polynomials. Three analysis objectives are considered, namely, mean quadratic velocity, sound radiation power and system loss factor. In this way, the trend of sound radiation varying with design parameters can be obtained conveniently and effectively.     

Novel optical packet with non-return-to-zero label and duobinary carrier-suppressed return-to-zero payload

A novel packet format with non-return-to-zero (NRZ) label and duobinary carrier-suppressed return-to-zero (DCS-RZ) payload is proposed for optical packet switching networks.NRZ label is followed by DCS-RZ payload with a certain guard time.The spectra of the low-rate NRZ label locate around the optical carrier frequency where some parts of the corresponding spectra of the high-rate DCS-RZ payload have been suppressed due to DCS-RZ modulation.At the switching node,the label or payload extraction can be realized simply through an optical bandpass or notch filter respectively.The feasibility of the scheme is verified by the simulation on the famous photonic design platform designed by Virtual Photonics Inc.(VPI).The effects of optical filter bandwidth on the received signal quality are discussed by analyzing bit error rate(BER)and contrast ratio performances.     

Sensitivity and Approximation of Coupled Fluid-Structure Equations by Virtual Control Method

The formulation of a particular fluid--structure interaction as an optimal control problem is the departure point of this work. The control is the vertical component of the force acting on the interface and the observation is the vertical component of the velocity of the fluid on the interface. This approach permits us to solve the coupled fluid--structure problem by partitioned procedures. The analytic expression for the gradient of the cost function is obtained in order to devise accurate numerical methods for the minimization problem. Numerical results arising from blood flow in arteries are presented. To solve the optimal control problem numerically, we use a quasi-Newton method which employs the analytic gradient of the cost function and the approximation of the inverse Hessian is updated by the Broyden, Fletcher, Goldforb, Shano (BFGS) scheme. This algorithm is faster than fixed point with relaxation or block Newton methods.     

Acoustic properties of cenosphere reinforced cement and asphalt concrete

A detailed experimental study has been conducted to determine the effect of adding hollow ceramic-micro balloons, also known as cenospheres, on the acoustic properties of cement matrix and asphalt concrete. The motivation for this study was to explore the feasibility of using cenospheres in developing lightweight sound absorbing structural materials. Cement and asphalt concrete specimens with different volume fractions of cenospheres and varying diameter and thickness were tested to determine their acoustic characteristics over the range of frequencies (0-4000 Hz). Experimental results showed that a 40% volume fraction addition of cenospheres to cement matrix increased the Noise Reduction Coefficient by 100%. In contrast to cenosphere rich cement, the sound absorption coefficient of asphalt concrete decreased with an increase of cenosphere, volume fraction.     

Virtual worlds as meeting places for formal systems

Over the last seven years, we have been exploring the use of collaborative virtual environments called Virtual Worlds (VWs) as a new type of testbed for experimenting with ways of organizing and integrating diverse types of computational and human processes. In other papers, we have discussed a wide variety of applications to fields as diverse as education and software engineering. In this paper, we focus on some of the mathematical experiments we are currently building in these environments.     

A cycle augmentation algorithm for minimum cost multicommodity flows on a ring

Minimum cost multicommodity flows are a useful model for bandwidth allocation problems. These problems are arising more frequently as regional service providers wish to carry their traffic over some national core network. We describe a simple and practical combinatorial algorithm to find a minimum cost multicommodity flow in a ring network. Apart from 1 and 2-commodity flow problems, this seems to be the only such “combinatorial augmentation algorithm” for a version of exact mincost multicommodity flow. The solution it produces is always half-integral, and by increasing the capacity of each link by one, we may also find an integral routing of no greater cost. The “pivots” in the algorithm are determined by choosing an >0, increasing and decreasing sets of variables, and adjusting these variables up or down accordingly by . In this sense, it generalizes the cycle cancelling algorithms for (single source) mincost flow. Although the algorithm is easily stated, proof of its correctness and polynomially bounded running time are more complex.     

血流动力学数值模拟与动脉粥样硬化研究进展

血流动力学因素被认为与动脉粥样硬化等病理改变密切相关。目前血流动力学数值模拟的对象,主要集中于分支动脉、弯曲动脉以及因血管内膜增生而导致的局部狭窄动脉,这些都是动脉粥样硬化多发的病灶部位。精确的血流动力学数值模拟,必须依赖于解剖精确的血管几何模型和生理真实的血流与管壁有限变形的非线性瞬态流－固耦合。只有在“虚拟血液流动”的基础上,综合考虑血管内的壁面剪应力、粒子滞留时间和氧气的跨血管壁传输等多种因素,血流动力学的数值模拟才能真正有助于人们理解动脉粥样硬化的血流动力学机理,才有可能应用于有关动脉疾病的外科手术规划中。