带BRB的高层钢框架梁柱节点的抗震性能

应用非线性有限元软件ABAQUS对带有BRB和带有普通支撑这2种高层钢框架梁柱节点进行了数值模拟,分析比较了2种支撑对框架梁柱节点的抗震影响,针对带有BRB的梁柱节点,对其进行支撑内芯的屈服强度,节点板的大小、厚度以及节点板上面外加劲肋长度的参数分析。结果表明:BRB在外包钢管和混凝土的约束下具有很好的耗能性能,并且随着支撑内芯屈服强度的降低,节点板尺寸和厚度的增大以及面外加劲肋长度的增加,梁柱节点的滞回曲线更加饱满,拥有更好的抗震性能。     

On learning and development, Piagetian style: I. A reply to Lefebvre-Pinard.

Examines the equilibration theory of Piaget (learning vs development, stage transitions) to make more explicit the methodological foundations of B. Inhelder et al (1974). In this connection, the "problem-solving" learning method used by these authors is analyzed by means of the new concept of "learning loops." Similarly, the successful equilibration learning method used by M. Lefebvre and A. Pinard (1974) is analyzed and shown to involve executive facilitation and chunking (coordination) of 2 crucial schemes. A process-structural model of conservation acquisition previously developed by the present author, and its empirical tests by R. Case (1975) and by G. M. Parkinson (1975), are used to illustrate and to empirically support the process-structural differences theoretically found between these 2 equilibration methods. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preparation and Characterization of PZT films Fabricated on Si Substrate

Lead zirconium titanate (PZT) films (Zr/Ti=45:55) with a high dielectric constant are prepared successfully on the low-resistance Si substrate in sol–gel dip-coating process with PT film used as the buffer layer. The dielectric and ferroelectric properties of the films as well as the relationship between crystallization and preparing condition are studied. It is shown that the PZT ferroelectric thin films with a (110) preferred orientation and a well-crystallized perovskite structure could be obtained after annealing at 800°C for 15 min. The particle size of the sample is about 14–25 nm. The P–E hysteresis loops are measured by means of the Sawyer-Tower test system with a compensation resistor at room temperature. The remanent polarization (P _r) and coercive electric field (E _c) of the measured PZT thin films are 47.7 μC/cm² and 18 kV/cm, respectively. The relative dielectric constant ε _r and the dissipation factor tgδ of the PZT thin films were measured with an LCR meter and were found to be 158 and 0.04–0.005, respectively. Translated from “Preparation and Characterization of PZT Films Fabricated on Si Substrates” published in Chinese Journal of Semiconductors, 2004, 25(4): 404–409 (in Chinese)     

（Pb1-x Srx）TiO3铁电薄膜电滞回线的测试分析

采用磁控溅射法制备了PST薄膜,讨论了其制备工艺并着重对其电滞回线进行了测试分析.从测试结果来看,其饱和极化强度Ps典型值为19.0μC/cm2,剩余极化强度为6.6μC/cm2,矫顽场强为16 kV/cm,热释电系数为10-4量级.表明所制备的PST薄膜具有较好的铁电性能.     

基于有效交叉点搜索的点串等距边界环生成算法

提出了一种根据零件截面点串边界曲线生成等距加工轨迹的新算法。当点串边界曲线的等距环自交或内外环相交时,根据边界上交叉点的穿越深度判定出有效交叉点,在有效交点处的四段进出边中选取一对转角最大的进边与出边连入环中,形成环形加工轨迹。该算法已在自主开发的RPM数据处理软件中成功应用。该算法提高了已有数据处理软件的稳定性;并在此基础上实现了RPM的OFFSET加工轨迹的生成。     

基于双闭环控制的单端反激式多路隔离输出开关电源的实现

以UC3842电流型控制芯片为核心,以MOSFET IRFPG40作为功率开关器件,设计及研制了一种单端反激式、双闭环电流控制、5路稳定电压输出的40W开关稳压电源,用作于变频器逆变侧IPM模块的专用驱动电源以及其他外围电路工作电源,实验证明所设计的开关电源具有高稳定性。     

核壳型碳铁纳米粉体的制备及磁性能研究

采用直流碳弧法制备碳包铁纳米粒子,用透射电子显微镜(TEM)、X射线衍射仪(XRD)对产物的形貌和尺寸、物相结构组成进行分析,并在真空和氮气气氛下在200～800℃对制备的碳包铁纳米粒子进行热处理,用振动样品磁强计测量处理前后的碳包铁纳米粒子的剩磁强度、矫顽力和饱和磁化强度.结果表明,碳包铁纳米粒子的磁滞回线显示出较好的超顺磁特性;剩磁强度、矫顽力和饱和磁化强度随着粉体中铁含量的增加而增大.对碳包铁纳米粒子进行热处理,其磁性能随温度的升高首先改善,温度进一步升高又逐步劣化.在450℃退火,粉体磁性能最佳.     

一个支持多分支循环最优执行的VLIW体系结构

本首先提出一个能够支持多分支循环程序最优执行的ＶＬＩＷ体系结构模型，然后在这个模型的基础上设计了一个新的主要用于数字信号处理及图象处理应用领域的单片体系结构－ＵＲＰＲ－２。在这个体系结构中，属于不同路径和不同循环体的多个分支操作可以在一个节拍内同时被执行，因此可以在更大范围内开发指讼级并行性，同时还提出了一个种叫作流水控制黑板的机制来支持条件分支操作。ＵＲＰＲ－２不仅能够以很高的速度执行只含有基     

电力网络支路参数估计新方法

基于新息图法,提出了一种电力网络中支路参数估计的新方法.根据系统中某支路存在网络参数错误时,该支路及其相连支路的新息值比较大的特点识别网络参数错误.然后利用回路新息相角和,估计存在网络参数错误的支路的参数值.该方法辨识和估计网络参数错误较快,且简单有效.通过IEEE-5节点系统算例的计算,表明此方法能够比较准确地估计网络参数错误,并验证了网络参数错误与坏数据、拓扑错误同时发生时该方法的有效性.     

直流调速系统与Matlab仿真

对于6RA70西门子直流调速装置进行原理上的分析与阐述,并以其为基础,运用Matlab中的Simulink进行相应的仿真.结合实际的一套飞剪直流调速系统,从数学模型和电路模型两方面对6RA70西门子直流调速装置进行相应的仿真,精确定量的分析直流调速装置在应用中的工作特性,并且利用数学模型计算出电流环与速度环的PI参数,为调试人员提供一个参考数值,使其更好地完成了调试工作.