Antiresonant reflecting optical waveguide-type vertical-cavity surface emitting lasers: comparison of full-vector finite-difference time-domain and 3-D bidirectional beam propagation methods

The cold-cavity modal characteristics of an antiresonant optical waveguide-type cylindrical vertical-cavity surface-emitting laser (VCSEL) are investigated through numerical simulations using a three-dimensional (3-D) bidirectional beam propagation method (BD-BPM) and a full-vector axisymmetric finite-difference time-domain (FDTD) method. Good agreement between the BPM- and FDTD-computed radial mode profiles as well as the mode-dependent radiation losses is obtained. The results of this paper establish the accuracy of the BD-BPM technique for simulating this class of devices and confirm effective-index method predictions that antiresonance conditions for cylindrical geometry devices (i.e., VCSELs) differ from those of planar geometry devices (i.e., edge emitters).     

LDAP在PKI应用中的缺陷研究

现今的LDAP轻量级目录访问协议,作为提供目录访问服务的协议,已成为支持PKI颁发证书和撤销证书列表的主流协议。本文讨论了LDAPv2和v3版本协议在PKI应用中存在的不足,并对LDAP在单机和多机目录服务的应用方面进行了分析,提出其缺陷和相对应的解决方案。     

HSDPA部署策略及覆盖、容量规划

本文介绍了HSDPA的发展背景,针对HSDPA的主要技术特点,依据市场发展规划、用户需求等方面对HSDPA部署进行探讨,并对HSDPA的覆盖与容量方面进行规划分析.     

基于逆浓度扩散及直方图的Mumford-Shah模型的MRA血管分割

直径的差别和造影剂的厚度不同造成血管在MRA成像中灰度不均匀,加上图像噪声的影响,使得血管的分割非常困难。而本文从血管在MRA图像中的特性出发,提出了逆浓度扩散模型,实现了血管的增强;另外本文还提出了基于直方图的Mumford-Shah模型计算方法,实现了图像的快速分割。实验表明,本文提出的方法能有效应用于二维及三维MRA图像中的血管分割。     

Inductor Current Sampled Feedback Control of Chaos in Current-Mode Boost Converter

A chaos control strategy for chaotic current-mode boost converter is presented by using inductor current sampled feedback control technique.The quantitative analysis of control mechanism is performed by establishing a discrete alterative map of the controlled system.The stability criterion,feedback gain,and corresponding critical duty ratio are obtained from the eigenvalue of the map.The simulation results verify the t heoretical analysis results of the control strategy.     

瞬态热阻测试在贴片二极管在线测试中的应用

表面贴装整流极管的焊接质量直接影响其可靠性.提出了通过测试与瞬态热阻等价的热敏电压增量来评价焊接质量、筛选焊接不良的产品.利用TRR8000测试仪对样品进行合适条件下的在线筛选,能够有效剔出焊接不良产品,提高表面贴装整流二极管的可靠性.     

Power-aware provisioning strategy with shared path protection in optical WDM networks

As the Internet continues to grow, the power consumption of telecommunication networks is rising at a considerable speed, which seriously increases the operational expenditure and greenhouse gas emission. Since optical Wavelength Division Multiplexing (WDM) networks are currently the most promising network infrastructures, power saving issue on these networks has received more attention in recent years. In traditional optical WDM networks, a large amount of power is drained by the redundant idle resources and reserved backup resources although these powered on resources do not carry traffic in most of the time. In order to reduce the network power consumption, turning off the corresponding network components or switching them to a low-power, standby state (or called sleep mode) is a promising greening approach. In this paper, we study the power-aware provisioning strategies and propose a sleep mode based Power-Aware Shared Path Protection (PASPP) heuristic algorithm to achieve the power efficiency of optical WDM networks. By jointly utilizing link-cost and fiber-cost in path routing, resource assignment, and resource release, PASPP makes working paths and backup paths converge on different fibers as much as possible, and switch idle and backup components to sleep mode to realize power saving. Simulation results show that our PASPP can obtain notable power saving and achieve satisfactory tradeoff between power efficiency and blocking probability with respect to Power-Unaware Shared Path Protection (PUSPP).     

[110]晶向近本征硅单晶双光子吸收各向异性

以沿[110]晶向切割的近本征硅单晶为样品,通过研究样品对连续波固体激光器所产生的1.3μm的近红外光的双光子吸收所诱导的光电流对入射光偏振方向的依赖关系,研究了双光子吸收的各向异性.测得了硅单晶对该波长的光的三阶极化率张量χ(3)的各向异性系数为-0.25,两个独立分量的比值χxxxx/χxxyy的幅度为2.4,并基于前期工作所得的χxxyy的结果,进而确定了另一分量χxxxx的值大约为1.49×10-19m2/V2.     

Advance in Using Plasma Technology for Modification or Fabrication of Carbon-Based Materials and Their Applications in Environmental,Material, and Energy Fields

Plasma technology is an eco-friendly way to modify or fabricate carbon-based materials (CBMs) due to plasmas’ distinctive abilities in tuning the surface physicochemical properties by implanting functional groups or incorporating heteroatoms into the surface without changing the bulk structure. However, the mechanisms of functional groups formation on the carbon surface are still not clearly explained because of the variety of different discharge conditions and the complexity of plasma chemistry. Consequently, this paper contains a comprehensive review of plasma-treated carbon-based materials and their applications in environmental, materials, and energy fields. Plasma-treated CBMs used in these fields have been significantly enhanced in recent years because these related materials possess unique features after plasma treatment, such as higher adsorption capacity, enhanced wettability, improved electrocatalytic activity, etc. Meanwhile, this paper also summarizes possible reaction routes for the generation of functional groups on CBMs. The outlook for future research is summarized, with suggestions that plasma technology research and development shall attempt to achieve precise control of plasmas to synthesize or to modify CBMs at the atomic level.     

同轨构型下LBF双基谱精度分析

双基谱精度分析是设计成像算法的前提,该文针对同轨等速构型详细给出了LBF(Loffelds bistatic formula)的谱精度分析,当半双基角的余弦值为1和基线长与目标到航线的最近距离的比值等于半双基角的正切值这两个条件同时满足时,LBF谱是完全严格解析的。谱精度不受基线长度和斜视角大小的影响,通过仿真实验分析讨论了各种约束对于谱精度的影响。