模拟信号的恢复及其误差研究

数模混合仿真中模拟信号的恢复及其误差对整个仿真过程具有重要影响。本文探讨了用零阶保持和一阶保持进行信号恢复的方法，比较了它们的误差及工作特点。特别指出了一阶保持中，由于存在积分器复原时间及数字机操作时间的影响而会带来附加的误差，因此一阶保持方法较难达到其理论的精度。     

CMS/TiO2杂化材料电流变液的制备及其性能

利用特殊的溶胶凝胶方法原位制备了改性淀粉与无机钛氧化物杂化型电流变材料。实验表明,在强电场下其电流变效应比相同组份的淀粉、二氧化钛混合型电流变液有显著提高,直流电场4 kV/mm,剪切速率5 s-1时,静态剪切屈服强度可达4000 Pa以上。同时,抗沉降性明显改善,静置100 h几乎不沉淀。此外,温度效应也获得一定的优化,在10 ℃~90 ℃的工作温度范围内力学性能保持良好,70 ℃时剪切强度达到最大值。     

An analog circuit design environment based on cooperating blackboard systems

A novel approach to design automation for analog circuits is presented. The prototype implementation-OASE-has been realized as a set of cooperating expert systems with blackboard architecture. The circuit specific knowledge bases use hybrid representation schemes and are strictly separated from an execution engine containing the necessary control knowledge. This alleviates the knowledge acquisition process as well as the extension and maintenance of existing knowledge. OASE has been developed as a design assistant, featuring different levels of interactivity, a hierarchical design style and fully embedded algorithmic standard tools. In its current version it is able to design a broad range of different CMOS operational amplifiers.     

天然气管网输配气量优化研究

天然气管网系统管理部门为了明确天然气管网的输气能力和提高天然气管网的利用率，需要对天然气管网系统的输配气量进行优化。为此，以天然气管网系统的最大流量为目标函数，同时考虑了管道强度、节点压力和流量限制等约束条件，建立了天然气管网输配气量优化的数学模型。在研究遗传算法和模拟退火算法的基础上，提出了一种由二者结合构成的具有全域搜索、快速收敛和鲁棒性强等特点的混合遗传算法。结合实例，采用这一新算法求解了天然气管网输配气量优化的数学模型。实例优化结果表明，所建立的数学模型和采用的混合遗传算法是可行和有效的，能够对天然气管网系统输配气量的调度运行起到指导作用。     

裂隙岩体边坡稳定性的渗流与应力耦合分析

用裂隙岩体渗流与应力耦合分析的四自由度全耦合法对岩质边坡进行耦合分析,通过强度折减有限元法求解岩体边坡的稳定安全系数。四自由度全耦合法建立了同时以渗流水压和位移为未知量的耦合方程组,使得渗流场与应力场的求解能够一次性完成,与两场交叉迭代分析方法相比达到了彻底的完全耦合。通过强度折减,整个系统达到不稳定状态,有限元计算将不收敛,此时的折减系数就是安全系数。算例表明由此求得的边坡稳定安全系数和滑动面都与传统方法十分接近。     

有环境约束时完成一族跟踪任务的力控制

本文为工业机器人提出了一种极点配置控制法，这种控制方法的优点有：一是它的积分作用消除了机器人的微小扰动和稳态误差；二是能任意设置系统的极点，因此能保证闭环系统的稳定性和规定状态变量的暂态响应；三是加入了加速度反馈，抑制了由电枢电感所引起的机械手的振动，最后，给出了ＰＵＭＡ５６２机器人的计算机仿真和实验结果验证了此控制法的有效性。     

噪声测量作为筛选光电耦合器件的一种方法

本文针对目前用于光电耦合器件筛选方法的不足，提出了用测量耦合器件噪声功率谱的方法来筛选掉噪声值大的器件，给出一批光电耦合器件的测量统计结果及在不同工作点时的噪声功率谱，并给出相应的筛选标准，实验结果表明，这种方法是有效、可行的。     

AHMED experiments on hygroscopic and inert aerosol behaviour in LWR containment conditions: experimental results

Hygroscopic NaOH, CsI, CsOH and inert Ag aerosol behaviour at different temperatures and relative humidities (RH) has been studied in a well instrumented and controlled vessel of 1.81 m³ total free volume. Homogeneous thermal-hydraulic conditions for aerosol measurement in the vessel were achieved. The aerosol number and mass concentration were measured continuously during the experiments using a Condensation Nucleus Counter and a Tapered Element Oscillating Microbalance. The particle size distribution and chemical composition in the test conditions were measured by Berner low pressure impactors. In the case of NaOH the half life of the aerosol mass concentration was more than four times longer at low RH (22%) as compared to high RH (96%). The half lives of the CsOH and CsI aerosols were only twice as long at low RH as compared to high RH. Thus at high RH (96–97%) the half lives of CsOH and CsI were twice as long as the half life for the NaOH aerosol. The faster decay of the NaOH aerosol is due to the smaller density decrease of NaOH during water condensation. CsOH particles grew rapidly to their equilibrium size at all humidities. The measured equilibrium size for CsOH aerosol agree well with the calculated particle size at different RHs. Experimental results were also compared with calculations obtained by severe accident computer codes. These calculated results will be presented in a later paper.     

NUMERICAL SIMULATIONS OF WHOLE FIELD BEHAVIOR FOR ROUND BUOYANT JET

ＮＵＭＥＲＩＣＡＬＳＩＭＵＬＡＴＩＯＮＳＯＦＷＨＯＬＥＦＩＥＬＤＢＥＨＡＶＩＯＲＦＯＲＲＯＵＮＤＢＵＯＹＡＮＴＪＥＴＬｉＷｅｉ，ＨｕａｉＷｅｎ－ｘｉｎ（ＷｕｈａｎＵｎｉｖｅｒｓｉｔｙｏｆＨｙｄｒａｕｌｉｃａｎｄＥｌｅｃｔｒｉｃＥｎｇｉｎｅｅｒｉｎｇ，...     

An eight‐node hybrid‐stress solid‐shell element for geometric non‐linear analysis of elastic shells

This paper presents eight‐node solid‐shell elements for geometric non‐linear analysis of elastic shells. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. A selectively reduced integrated element is formulated with its membrane and bending shear strain components taken to be constant and equal to the ones evaluated at the element centroid. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger–Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid element, a hybrid‐stress solid‐shell element is formulated. Commonly employed geometric non‐linear homogeneous and laminated shell problems are attempted and our results are close to those of other state‐of‐the‐art elements. Moreover, the hybrid‐stress element converges more readily than the selectively reduced integrated element in all benchmark problems. Copyright © 2002 John Wiley & Sons, Ltd.