Development of an optical trap for microparticle clouds in dilute gases

Long-duration experiments with clouds of microparticles are planned for the ICAPS facility on board the International Space Station ISS. The scientific objectives of such experiments are widespread and are ranging from the simulation of aerosol behaviour in Earths atmosphere to the formation of planets in the early solar system. It is, however, even under microgravity conditions, impossible to sustain a cloud of free-floating, microscopic particles for an extended period of time, due to thermal diffusion and due to unavoidable external accelerations. Therefore, a trap for dust clouds is required which prevents the diffusion of the particles, which provides a source of relative velocities between the dust grains and which can also concentrate the dust to higher number densities that are otherwise not achievable. We are planning to use the photophoretic effect for such a particle trap. First short-duration microgravity experiments on the photophoretic motion of microscopic particles show that such an optical particle-cloud trap is feasible. First tests of a two-dimensional trap were performed in the Bremen drop tower.     

Positive Reachability for Diffusion Equations

Counterexamples are constructed for some plausible conjectures. Typical of these: as the Maximum Principle ensures that positive boundary data give a positive state at time T from 0 initial data, one might (plausibly, but falsely) conjecture that all positive terminal states should be approximately reachable in this way, i.e., subject to the requirement that the boundary data stays nonnegative.     

Optimal strategy policy in batch arrival queue with server breakdowns and multiple vacations

This paper considers a like-queue production system in which server vacations and breakdowns are possible. The decision-maker can turn a single server on at any arrival epoch or off at any service completion. We model the system by an M^[x]/M/1 queueing system with N policy. The server can be turned off and takes a vacation with exponential random length whenever the system is empty. If the number of units waiting in the system at any vacation completion is less than N, the server will take another vacation. If the server returns from a vacation and finds at least N units in the system, he immediately starts to serve the waiting units. It is assumed that the server breaks down according to a Poisson process and the repair time has an exponential distribution. We derive the distribution of the system size through the probability generating function. We further study the steady-state behavior of the system size distribution at random (stationary) point of time as well as the queue size distribution at departure point of time. Other system characteristics are obtained by means of the grand process and the renewal process. Finally, the expected cost per unit time is considered to determine the optimal operating policy at a minimum cost. The sensitivity analysis is also presented through numerical experiments.     

On the Geometry of Inner Approximations to the Set of Null Controllability for Constrained Linear Systems

The problem of obtaining inner approximations to the set of null controllability for linear systems is considered, and the geometry of certain sets arising in the approximation of using linear feedback is explored. A two-dimensional example is worked in detail in order to delineate the limitations to the use of linear feedback.     

高压变频器在扬州水厂的应用

本文简述了6kV变频器的主电路拓朴结构及控制方式，介绍了变频器比较选择和PowerFlex7000变频器用于扬州四水厂的工程实例。     

Stabilizing the intensity of a wave amplified by a beam of particles

The intensity of an electromagnetic wave interacting self-consistently with a beam of charged particles as in a free electron laser, displays large oscillations due to an aggregate of particles, called the macro-particle. In this article, we propose a strategy to stabilize the intensity by re-shaping the macro-particle. This strategy involves the study of the linear stability (using the residue method) of selected periodic orbits of a mean-field model. As parameters of an additional perturbation are varied, bifurcations occur in the system which have drastic effect on the modification of the self-consistent dynamics, and in particular, of the macro-particle. We show how to obtain an appropriate tuning of the parameters which is able to strongly decrease the oscillations of the intensity without reducing its mean-value.     

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利用组态软件编程设计监控界面,监控节点通过与现场总线控制器及高压监控节点的通信,实现对极向场电源状态的实时、可靠监控,并经ODBC接口将状态数据发送至数据库节点备份。简述了电源监控系统的构成,及通过不同的通信协议实现实时数据传输和处理的过程。     

矿井无线定位导航与安全监控系统研究

针对当前国内煤矿坍塌爆炸等安全事故问题，本文对井下导航与安全监控系统进行了分析研究，提出了一种基于ZigBee短距离无线通信技术的矿井定位导航与安全监控系统。文中讨论分析了ZigBee的特点，详细介绍了井下定位导航、环境信息采集与传输的过程，并针对单片机的控制系统方案、工作原理以及实现过程进行了全面介绍。实验表明，通过该系统可实时了解井下安全生产作业情况，并切实保证矿井工作人员人身安全。     

P2P流量识别和管控技术分析

基于P2P模式的业务和应用给互联网的发展带来了巨大影响,本文在简要分析了现网中P2P流量分布类型的基础上,重点探讨了互联网P2P流量的三种识别检测技术和两种流量管控技术,给出了对P2P流量管控技术的运营选用建议。     

变频器在纺织机械中的推广应用

本文介绍了交流变频调速技术在纺织机械中的应用情况，分析了交流变频调速技术在纺织机械中推广应用的必要性及在纺织机械中的应用实例等。