Potential Formation in a Bounded Plasma System which is Terminated by an Electron Emitting Floating Collector Studied by a Particle‐in‐Cell Computer Simulation

Potential formation in one‐dimensional bounded plasma system terminated by a floating, electron emitting collector is studied by particle‐in‐cell (PIC) computer simulation. Attention is focused to the case of rather strong space charge limited emission. Formation of a potential well (virtual cathode) in front of the collector is observed. As emission increases the floating potential of the electrode and the potential of the bottom of the potential well both increase. The floating potential increases faster than the virtual cathode potential and consequently the depth of the potential well in front of the collector increases also. As long as the emission is not to large (up to approximately 40 times the critical emission) the relation between the depth of the potential well and the normalized emission follows a simple logarithmic formula. For larger emissions the depth of the potential well is larger than predicted by the model. It seems that at very large emission the floating potential of the collector might even exceed the zero reference potential of the source electrode. Such phenomenon has been reported by [A. Marek et al. Contrib. Plasma Phys., 48 , 491 (2008)], where it was observed that the floating potential of a strongly emissive probe exceeded the plasma potential determined from the knee of the current‐voltage characteristics when the same probe was used as a Langmuir probe. But before this actually happens the simulation breaks down. When positive ions start to be repelled by the positive collector back towards the source the system becomes unstable so that a steady state can not be reached and no results can be read from the output of the simulations. That electron emission may destabilize the sheath in front of it, was found also in Hall thrusters, see e.g. [Daren Yu et al. Phys. Plasmas, 15 , 104501, 2008] and [F. Taccogna et al Appl. Phys. Lett., 94 , 251502, 2009]. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

利用虚拟仪器平台演示李萨如图形

基于Labview平台设计了虚拟仪器。直观的演示了李萨如图形。     

遗传算法在供应链演化研究中的应用

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基于虚拟仪器及PXI技术的传感器标定

为了借助虚拟仪器技术实现对叶轮机械各种测试技术的集成,本文将虚拟仪器及PXI技术运用于传感器的标定中。文中阐述了基于虚拟仪器及PXI技术的传感器静态特性标定系统的结构、标定方法、数据处理以及被标定传感器的静态特性指标,并与传统仪器组成的标定系统进行了比较。结果表明,基于虚拟仪器及PXI技术的传感器静态特性标定系统,比用其它手段更精确、快捷和方便,为虚拟仪器在叶轮机械试验测试中的进一步应用打下了基础。     

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根据虚拟仪器的设计思想,运用LabVIEW设计了用于测量网络频率特性的虚拟仿真仪器.该虚拟仪器兼有任意波形发生器和数字存储示波器功能,能够根据不同的参量设定,产生一系列不同频率的激励信号,可快速显示所测网络的幅频和相频特性.     

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如何运用数学模型测度企业中不同层次的人力资本价值，为人力资本参与企业利润分配提供科学的依据是当前学术界与实业界研究的热点与难点课题。本在分析研究不同层次的人力资本价值传递机制及其测度方法，并用一个案例来检验。     

On Invariants of Virtual Links

We propose a new method of generalizing classical link invariants for the case of virtual links. In particular, we have generalized the knot quandle, the knot fundamental group, the Alexander module, and the coloring invariants. The virtual Alexander module leads to a definition of VA-polynomial that has no analogue in the classical case (i.e. vanishes on classical links).     

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基于大型企业产品结构优化的传统模型，分析了企业面临的不确定因素，提出了柔性线性规划模型。