Multi-band circuit model of tunable THz absorber based on graphene sheet and ribbons

Terahertz (THz) absorbers due to the high potential of providing reliable applications in modern devices and technology are increasingly being investigated. Recently, a dual-band THz absorber based on a graphene sheet and ribbons has been proposed in which the results were obtained using Full-wave simulations and its authors have not provided any specific design method. In this work, we have proposed and investigated that tunable THz absorber by its circuit model. A developed transmission line method beside the analytical circuit model of graphene continues sheet and periodic arrays of graphene ribbons are used to obtain analytical expressions for the circuit model. Here, first of all, we have compared the results of the proposed method with the results of that paper and secondly, using impedance matching concept we have proposed multi-band tunable THz absorber with near-unity absorption by the same structure. Then, we have compared the results of our circuit method with the Full-wave simulations. In either case, our proposed method in addition to excellent performance in terms of runtime and memory sources, has an acceptable agreement with the results of the Full-wave simulations. The proposed method is general and can be applied to design and simulate the other sub-wavelength structures.     

光突发交换网络中的区分服务研究

为了在光突发交换网络中提供端到端的区分服务,提出了一种区分服务模型,并详细介绍了其功能.提出了一种控制分组的区分服务编码点,详细研究了一系列区分服务规则,包括编码点的改写和更新以及区分服务模型的可扩展性.同时提出了几个有待进一步研究的问题.     

空间信息系统在弹道导弹防御中的效能评估框架

针对空间信息系统在弹道导弹防御(BMD)中的效能评估问题,从系统整体性和复杂性角度提出了空间信息系统在BMD中的效能评估框架.该框架主要包括整体性分析、综合集成以及结果分析3个部分.在整体性分析中,通过系统学模型确定导弹防御的边界、要素集和关系集.在综合集成中,应用基于Agent的建模与仿真方法对系统要素进行建模,并对...     

CCD航空相机用长寿命帘幕式快门

CCD型航空侦察相机由于存储量大,一般每次可拍摄数千张图像,快门曝光次数频繁,因此对其工作的可靠性和使用寿命提出了更高的要求.设计了一种新型高可靠性、长寿命帘幕式焦面快门,帘幕采用金属的钛箔材料,无需齿轮组传动,克服了传统的该类型快门的诸多弊端,保障了帘幕快门的使用寿命;且通过DSP控制整个系统,提高了控制精度.实验结...     

SiGe HBT射频噪声模型研究

对现代的双极型晶体管而言,载流子在基极和集电极的空间电荷区（CB SCR）传输延迟可比基极渡越时间,甚至要大于后者。为了更精确地表征了SiGe HBT的射频噪声性能,对van Vliet模型做了扩展,使其包含基极集电极空间电荷区的延迟效应。用2个与噪声相关的延迟时间对transport模型进行了扩展,使得在没有非准静态Y参数的情况下仍然可以对基极和集电极电流噪声进行精确建模。最后,在JC=12.2 mA/μm2,AE=0.12×18μm2条件下,分别对2种模型的基极和集电极噪声电流谱及其归一化相关系数做图并与计算得出的解析值相比较,验证了模型的有效性。     

基于“当前”统计模型的自适应不敏卡尔曼滤波算法

基于机动目标"当前"统计模型在直角坐标系下建立了三坐标雷达跟踪系统的状态方程和观测方程。针对非线性自适应滤波这一问题,提出了一种基于"当前"统计模型的自适应不敏卡尔曼滤波算法(CS-UKF),并对算法作了说明。通过计算机仿真验证了CS-UKF算法的有效性,并且该算法跟踪效果良好,精度好于基于"当前"统计模型的自适应扩展卡尔曼滤波算法(CS-EKF)算法。     

A Markov-Based Channel Model Algorithm for Wireless Networks

Techniques for modeling and simulating channel conditions play an essential role in understanding network protocol and application behavior. In [11], we demonstrated that inaccurate modeling using a traditional analytical model yielded suboptimal error control protocol parameters choices. In this paper, we demonstrate that time-varying effects on wireless channels result in wireless traces which exhibit non-stationary behavior over small window sizes. We then present an algorithm that extracts stationary components from a collected trace in order to provide analytical channel models that, relative to traditional approaches, more accurately represent characteristics such as burstiness, statistical distribution of errors, and packet loss processes. Our algorithm also generates artificial traces with the same statistical characteristics as actual collected network traces. For validation, we develop a channel model for the circuit-switched data service in GSM and show that it: (1) more closely approximates GSM channel characteristics than traditional Markov models and (2) generates artificial traces that closely match collected traces' statistics. Using these traces in a simulator environment enables future protocol and application testing under different controlled and repeatable conditions.     

Experimental validation of a thermal modelling method dedicated to multichip power modules in operating conditions

In this paper, we present an implementation of a thermal modelling method applied to a multichip module used as a power converter. Analytical functions of thermal impedances, with original formulations for the mutuals are defined. They are derived from 3D thermal simulations and experimental validations with direct chips temperature measurements. Finally, simulations are performed in order to improve the capability of our model to assess, with fast computation, the thermal constraints applied on the multichip module in a real operating condition.     

浅谈基于WEB应用软件开发的制作过程

基于WEB的B／S模式的应用软件的开发方法,已成为当今计算机软件开发方面讨论和研究的主要课题。本文选择ASP ACCESS作为开发环境,首先对在ASP环境下开发基于WEB软件的调试环境的安装过程进行了简要的说明,然后以一个教学实验课申请实例的开发过程进行了较为详细的阐述,通过该实例,较详细地介绍了基于Web应用软件开发的过程。     

雷达对抗环境仿真模型

介绍了雷达和雷达对抗的基本概念以及雷达对抗的基本分类,阐明了雷达对抗环境下雷达和雷达对抗设备分别所面临的电磁信号环境以及雷达对抗仿真试验所需的仿真模型。