微型泵的物理模型与动态模拟

根据薄板的弹性振动理论和流体动力学理论 ,建立了能完整描述振膜式微机械泵的动态解析模型。导出了吸入过程和排出过程的流量、压力方程。揭示流量、压力等微机械泵性能参数与执行器输出以及负载之间的内在关系。而且在此基础上用有限元分析方法 ,建立了其数值模型 ,并且进行模拟 ,所得结果与实验符合较好。     

低压条件下热式气体流量传感器测量方法的研究

提出了一种建立在文丘利喷嘴基础上的,能够在低压条件下进行气体流量测量的方法,实现了较大压力范围内的气体流量测量.通过在绝对压力条件下和20kPa压力条件下的气体流量试验对比,分析了气体流量在常压下测量与在低压下测量所产生的差异的大小和原因.     

高机动雷达双级液压缸运动过程仿真分析

首先建立了某高机动雷达双级液压缸举升仿真模型，通过仿真得到了换级时压力与速度冲击现象；随后分析了系统流量对换级过程中压力与速度冲击的影响，结果表明：随着系统流量的减小，换级过程中压力与速度冲击逐渐减小；最后得到了某高机动雷达液压系统双级液压缸运动过程流量控制策略，该策略能显著地削弱双级液压缸运动过程中换级时的压力与速度冲击现象。     

锅炉流量测量在Honeywell Experion PKS系统中的实现

目前在热电厂锅炉蒸汽、风量管道流量计算中普遍采用常规仪表进行温压补偿,但其出现的结构复杂、调试难度大、维护困难等一系列问题造成精度偏低、设备监控不灵活等。为了提高热电厂锅炉蒸汽、风量管道中较大流量的测量精度,减小环境变化带来的误差,过程控制系统应利用更为精确数据进行合理调控。因此采用霍尼韦尔Experion PKS过程知识系统组态编程软件流量测量模块,可对流量计测量数据进行理论计算以及在环境改变时所带来的流量温度、压力补偿计算,实现不受环境变化影响下的过程控制中流量数据与现场流量数据的基本一致。该模块简化了复杂的过程控制逻辑编写与调试过程,增加了测量和控制精度,提高了生产效率。     

两腔压电泵结构与特性

介绍了两个压电振子所构成的两腔串联和两腔并联压电泵的结构及工作原理,分析了两个压电振子驱动方式(同步工作和交叉工作)对两种结构压电泵输出性能的影响规律。制作了两腔串联和两腔并联压电泵的试验样机,分别测试了两个腔体同步工作和交叉工作状态下压电泵的输出能力,并与理论分析的结果进行了对比。理论和试验两方面的研究结果表明,在相同驱动电压和频率条件下,两个腔体交叉工作时压电泵的输出能力较好,其中并联泵的流量最大,为单个腔体流量的2倍;而串联泵的流量串联泵压力最大,是单个腔体输出压力的2倍,同时其流量也有大幅度提高,约为单个腔体流量的1.4倍。     

复合计费法将可能成为主要的互联网计费方式

近一段时间,互联网的计费受到广泛关注,在BT的压力下,流量计费成了一个热点话题,尽管运营商一再否认按流量计费是针对BT的,网上调查也有多达85%以上的网民反对按照流量计费,但是在BT的压力下,“流量”已经是一个不可回避的问题。对于电信网而言,计费是一个复杂的工程,它不仅建立在技术发展基础上,同时也建立在经济理论基础上。语音的时代,网络上传输的信息流量是一定的,按照时间计费天经地义,因为打电话就是占用了资源。在数据时代,其实用户上网不但是占用了信道资源,同时也占用了流量的资源。在网上调查,大部分用户对于流量收费并不支持…     

一种基于激光自混合干涉的光纤压力传感器

文中理论和实验研究了一种基于激光自混和干涉技术的光纤压力传感器,阐述了其设计理论和实现方法,建立了光纤压力传感器模型,实验研究了应力与激光自混和干涉输出的对应关系;实验结果表明所设计的光纤压力传感器的原理是正确和可行的.     

多参量一体化光纤传感器及标校系统的研制与开发

提出一种集温度、压力和流量多参数同时测量的新型光纤传感器,并对其原理和结构、工艺设计展开研究工作。采用靶式与悬臂梁结构相结合的机敏结构、薄壁压力应变筒结构等集成在同一传感器探头上,并利用四只光纤光栅使得温度、压力和流量三个参数得以同时检测。利用光纤光栅两两之间波长移动量相差或相和,使温度与流量、压力交叉敏感问题得以解决。同时开发了光纤传感器标校系统,这一系统可以较准确实现对所研发的多参量一体化传感器的测试结果进行检测和标校。     

一种智能蒸汽压力与流量测控器的研制

本文介绍了一种用于蒸汽压力和流量测量与控制的智能测控器。该测控器可同时测量蒸汽压力、蒸汽流量和蒸汽流量累计，同时可控蒸汽压力或蒸汽流量，并具备与上位计算机通讯功能。     

一种智能蒸汽压力与流量测控器的研制

本文介绍了一种用于蒸汽压力和流量测量与控制的智能测控器。该测控器可同时测量的蒸汽压力、蒸汽流量和蒸汽流量累计，同时可控蒸汽压力或蒸汽流量，并具备与上位计算机通讯功能。     

Energy-optimal electrical excitation of nerve fibers

We derive, based on an analytical nerve membrane model and optimal control theory of dynamical systems, an energy-optimal stimulation current waveform for electrical excitation of nerve fibers. Optimal stimulation waveforms for nonleaky and leaky membranes are calculated. The case with a leaky membrane is a realistic case. Finally, we compare the waveforms and energies necessary for excitation of a leaky membrane in the case where the stimulation waveform is a square-wave current pulse, and in the case of energy-optimal stimulation. The optimal stimulation waveform is an exponentially rising waveform and necessitates considerably less energy to excite the nerve than a square-wave pulse (especially true for larger pulse durations). The described theoretical results can lead to drastically increased battery lifetime and/or decreased energy transmission requirements for implanted biomedical systems.     

异质结双极晶体管的计算机模拟分析和优化设计

<正> 一、引言 宽带隙发射极晶体管是Shockly于1951年提出的,70年代初发展起来的LEP,MBE和MOCVD外延技术才使这种器件得以实现,并充分体现出这种器件的优越性;同时也促进了OEIC的发展。本文对HBT直流稳态性能、频率及开关参数进行分析,对器件性能进行了优化设计。     

Cylindrical cell membranes in uniform applied electric fields: validation of a transport lattice method

The frequency and time domain transmembrane voltage responses of a cylindrical cell in an external electric field are calculated using a transport lattice, which allows solution of a variety of biologically relevant transport problems with complex cell geometry and field interactions. Here we demonstrate the method for a cylindrical membrane geometry and compare results with known analytical solutions. Results of transport lattice simulations on a Cartesian lattice are found to have discrepancies with the analytical solutions due to the limited volume of the system model and approximations for the local membrane model on the Cartesian lattice. Better agreement is attained when using a triangular mesh to represent the geometry rather than a Cartesian lattice. The transport lattice method can be readily extended to more sophisticated cell, organelle, and tissue configurations. Local membrane models within a system lattice can also include nonlinear responses such as electroporation and ion-channel gating.     

Analytical Electron-Mobility Model for Arbitrarily Stressed Silicon

It was experimentally and numerically indicated that both the valley splitting and effective-mass variation contribute to the stress-induced enhancement of electron mobility in the MOSFET channel. In this paper, an analytical electron-mobility model for arbitrarily strained silicon is presented. The electron-mobility model includes the strain effects of both the effective-mass variation and valley degeneration. The expression of strained conduction band used in the analytical model is based on the theory and accords well with numerical results of nonlocal empirical pseudopotential method (EPM). By using the mobility model, mobilities under different stresses are investigated.     

具有电阻场板的薄膜SOI-LDMOS的精确解析

介绍了一种对具有电阻场板的薄膜SOI LDMOS的精确解析设计方法.在对电场分析的基础上,提出了新的电离率模型,并求出了电离率积分的准确路径,进而得到击穿电压、漂移区掺杂、漂移区长度与SOI硅层厚度、埋氧层厚度的关系.模拟结果表明,解析与模拟结果具有很好的一致性,而且设计的器件具有击穿电压大、比导通电阻极小的优点.该解析理论为在薄膜SOI材料上制作性能优良的高压功率器件提供了一个很好的参考     

Study of intermodulation in RF MEMS variable capacitors

This paper provides a rigorous study of the causes and physical origins of intermodulation distortion (IMD) in RF microelectromechanical systems (MEMS) capacitors, its analytical dependence on the MEMS device design parameters, and its effects in RF systems. It is shown that not only third-order products exist, but also fifth order and higher. The high-order terms are mainly originated by the nonlinear membrane displacement versus applied voltage and, in the case considered in this study, with an additional contribution from the nonlinear dependence of the reflection coefficient phase on the displacement. It is also shown that the displacement nonlinear behavior also contributes to the total mean position of the membrane. In order to study these effects in depth, an analytical frequency-dependent IMD model for RF MEMS based on a mobile membrane is proposed and particularized to the case of a MEMS varactor-a device for which IMD can be significant. The model is validated, up to the fifth order, theoretically (using harmonic balance) and empirically (the IMD of a MEMS varactor is measured). To this end, a two-tone IMD reflection measurement system for MEMS is proposed.     

基于解析电导率模型的相变存储器SPICE模型

在相变存储器的外围电路设计中,相变存储单元的电路模型是连接器件与电路的桥梁。在本文中,提出了一种基于解析电导率模型的相变存储器电路模型,与前面的工作相比,该模型利用解析电导率模型代替了使用传统模型中需要利用测试结果建模的缺点,可以通过材料的参数计算相变存储单元的电阻,能够反映相变材料中的载流子传输特性。同时,基于等温假设,提出了解析温度模型,并基于JMA方程建立的相变动力学模型,结果表明,该模型能够进行相变存储单元瞬态与稳态电路仿真,并与测试结果符合较好。     

Microscopic noise modeling and macroscopic noise models: how good aconnection? [FETs]

Based on the active line concept, a novel approach for the calculation of the high frequency noise performance of field effect transistors (FET) is proposed. By using a simple analytical theory, the FET small signal equivalent circuit as well as the macroscopic noise sources and their correlation are calculated for different two-port terminations. Values of the usual dimensionless noise parameters P, R, C, gate noise temperature T_g and drain noise temperature T _d are then given and discussed. By comparison with a more realistic numerical modeling of the noise performance, the validity of the analytical noise model is discussed. The validity of Pospieszalski's noise model and its relations with Pucel's one is emphasized     

Analytical study of crosstalk propagation in all-optical networks using perturbation theory

The performance of current optical networks is inherently limited by the speed of electronic components and, in particular, by electronic switches. A new generation of optical networks, referred to as all-optical networks, overcomes this limitation by switching data entirely optically using all-optical crossconnects (OXCs). However, all-optical networks are prone to phenomena that are unknown to current optical networks with electrical regeneration: OXCs are subject to optical leaks, called crosstalk, resulting in unwanted components being added to transmitted signals, and this crosstalk is transmitted over very long paths without any signal regeneration. In this paper, we consider the interplay between fiber nonlinearity and crosstalk signals over long distances as the source of performance degradation, measured in terms of Q factor. We present an analytical crosstalk model for all-optical networks and give expressions for the performance degradation resulting from the joint propagation of a signal [using a continuous-wave (CW) assumption and perturbation theory] and crosstalk in large networks. Analytical calculations required by this model are shown to be much less computationally intensive than simulations. Simulations are carried out to validate our analytical model and good agreement is found between the analytical model and simulations for wide ranges of parameters.