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1.
简要介绍了可靠性评估(REM)测试结构设计,并介绍了REM试验中与时问有关的栅氧化层击穿(TDDB)、热载流子注入(HCI)效应和电迁移(EM)效应的评价试验方法及实例。REM技术与工艺过程控制(PCM)、统计工艺控制(SPC)技术结合起来就可以实现对工艺的可靠性评价与控制,某集成电路生产公司将它应用于金属化工艺中.确定了工艺输入变量与电迁移可靠性的相关性,优化了金属化工艺试验条件,提高了金属化系统的抗电迁移能力。  相似文献   
2.
电子病历中包含大量有用的医疗知识,抽取这些知识对于构建临床决策支持系统和个性化医疗健康信息服务具有重要意义。自动分词是分析和挖掘中文电子病历的关键基础。为了克服获取标注语料的困难,提出了一种基于无监督学习的中文电子病历分词方法。首先,使用通用领域的词典对电子病历进行初步的切分,为了更好地解决歧义问题,引入概率模型,并通过EM算法从生语料中估计词的出现概率。然后,利用字串的左右分支信息熵构建良度,将未登录词识别转化为最优化问题,并使用动态规划算法进行求解。最后,在3 000来自神经内科的中文电子病历上进行实验,证明了该方法的有效性。  相似文献   
3.
在军队信息化建设过程中,电子军务的实现是至关重要的.其中军务中信息不泄漏、不破坏是亟待解决的问题,文中提出了一种基于强制访问控制的电子军务模型,此模型针对这些问题提出了解决方法.  相似文献   
4.
高强度电磁脉冲对光纤的影响及防护措施   总被引:1,自引:0,他引:1  
光缆在高强度电磁脉冲的作用下,会引起光纤传输特性的变化,导致模间色散的增加和信号的失真。主要论述了光缆在高强度电磁脉冲影响下的非线性效应,并提出了有效的防护措施。  相似文献   
5.
This paper is essentially composed of two parts for future synthesis. We developed 2D and 3D simulations, starting from a 0.35 μm standard CMOS technology, focusing on through silicon via or redistribution layer induced coupling; nMOSFET, pMOSFET, and the sensitive regions of the CMOS inverter are investigated. We also study stacked devices in 3D circuits, in the radiofrequency range, and propagation of electromagnetic waves along some interconnections with discontinuities. This study is performed in the time domain—a finite-difference time-domain method is applied to the analysis of some vias flanked by two striplines, all embedded in silicon. Electric and magnetic field distributions, transmission and reflexion parameters, and pulse propagations along a transverse via are presented.  相似文献   
6.
    
An improved variable-fidelity optimization algorithm for the simulation-driven design of microwave structures is presented. It exploits a set of electromagnetic-based models of increasing discretization density. These models are sequentially optimized with the optimum of the ‘coarser’ model being the initial design for the ‘finer’ one. The found optimum is further refined using a response surface approximation model constructed from the coarse-discretization simulation data. In this work, the computational efficiency of the variable-fidelity algorithm is enhanced by employing a novel algorithm for optimizing the coarse-discretization models. This allows reduction of the overall design time by up to 50% compared to the previous version. The presented technique is particularly suitable for problems where simulation-driven design is the only option, for example, ultra wideband and dielectric resonator antennas. Operation of the presented approach is demonstrated using two examples of antennas and a microstrip filter. In all cases, the optimal design is obtained at a low computational cost corresponding to a few high-fidelity simulations of the structure.  相似文献   
7.
Two magnetoresistive manganites, La0.83Sr0.17MnO3 and La0.7Sr0.3MnO3, are synthesized by the environmentally friendly “deposition by aqueous acetate solution (DAAS)” technique. The manganite film has a grain size of 100 nm, and can be processed as thinly as 0.03 μm per layer, while the powder form has a crystallite size of 40 nm. These magnetoresistive materials are shown to be effective and inexpensive electromagnetic interference (EMI) shield for the extremely low frequency (ELF) EM fields. The electrical resistance of manganites is very sensitive to external influences, such as temperature and electromagnetic fields. Both permeability (μ) and conductivity (σ) of manganites tend to increase with increasing applied magnetic field. The manganites have been shown to “react” to field increases in a way that is particularly useful for shielding EMI field fluctuations (e.g., due to current or voltage spikes).

The manganite properties, e.g., crystal structure, film morphology, radiation absorption and reflection, electrical resistivity, and magnetization, etc., have been measured. The ceramic manganites have a metal–insulator transition at 300 K or higher, and are suitable for a room temperature operation. A thin film (approx. 0.1 μm) of La0.83Sr0.17MnO3 was fabricated on a quartz tube or refractory ceramic fiber blanket. Using this thin manganite film, the EMI shielding effectiveness for the measured E-field attenuation is similar to that of a 25 μm thickness of copper tube, aluminum foil, and silver–nickel particle-dispersed paper. The silver–nickel impregnated paper has an EMI shielding effectiveness of 35 dB at 10 kHz, and 15 dB at 60 Hz (or frequency above 1 MHz). The ceramic manganites are chemically inert, thermally stable, and mechanically flexible. They provide low cost EMI shielding against directed energy pulses and may serve as a “signature reduction” barrier.  相似文献   

8.
Because of its potential applications in agriculture, environment monitoring and so on, wireless underground sensor network(WUSN) has been researched more and more extensively in recent years. The main and most important difference of WUSN to terrestrial wireless sensor network(WSN) is the channel characteristics, which determines the design methodology of it. In this paper, the propagation character of electromagnetic(EM) wave in the near surface WUSN is analyzed, as well as the path loss model of it is given. In addition, the influence of human's ankle to the channel characteristics of near surface WUSN is investigated by electromagnetic theory analysis, simulation and experiment. A novel path loss model of near surface WUSN which takes the interference of human's ankle into consideration is proposed. It is verified that the existing of human above the WUSN system may cause additional attenuation to the signal of near surface WUSN which propagates as lateral wave along the ground. Moreover, the relation of the attenuation and operating frequency is deduced, which gives a reference to extend the frequency band applied in WUSN.  相似文献   
9.
    
Design of microwave components is an inherently multiobjective task. Often, the objectives are at least partially conflicting and the designer has to work out a suitable compromise. In practice, generating the best possible trade‐off designs requires multiobjective optimization, which is a computationally demanding task. If the structure of interest is evaluated through full‐wave electromagnetic (EM) analysis, the employment of widely used population‐based metaheuristics algorithms may become prohibitive in computational terms. This is a common situation for miniaturized components, where considerable cross‐coupling effects make traditional representations (eg, network equivalents) grossly inaccurate. This article presents a framework for accelerated EM‐driven multiobjective design of compact microwave devices. It adopts a recently reported nested kriging methodology to identify the parameter space region containing the Pareto front and to render a fast surrogate, subsequently used to find the first approximation of the Pareto set. The final trade‐off designs are produced in a separate, surrogate‐assisted refinement process. Our approach is demonstrated using a three‐section impedance matching transformer designed for the best matching and the minimum footprint area. The Pareto set is generated at the cost of only a few hundred of high‐fidelity EM simulations of the transformer circuit despite a large number of geometry parameters involved.  相似文献   
10.
    
Accurate performance evaluation of microwave components can be carried out using full‐wave electromagnetic (EM) simulation tools, routinely employed for circuit verification but also in the design process itself. Unfortunately, the computational cost of EM‐driven design may be high. This is especially pertinent to tasks entailing considerable number of simulations (eg, parametric optimization, statistical analysis). A possible way of alleviating these difficulties is utilization of fast replacement models, also referred to as surrogates. Notwithstanding, conventional modeling methods exhibit serious limitations when it comes to handling microwave components. The principal challenges include large number of geometry and material parameters, highly nonlinear characteristics, as well as the necessity of covering wide ranges of operating conditions. The latter is mandatory from the point of view of the surrogate model utility. This article presents a novel modeling approach that incorporates variable‐fidelity EM simulations into the recently reported nested kriging framework. A combination of domain confinement due to nested kriging, and low‐/high‐fidelity EM data blending through cokriging, enables the construction of reliable surrogates at a fraction of cost required by single‐fidelity nested kriging. Our technique is validated using a three‐section miniaturized impedance matching transformer with its surrogate model rendered over wide range of operating frequencies. Comprehensive benchmarking demonstrates superiority of the proposed method over both conventional models and nested kriging.  相似文献   
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