The fine structure of endothelial cells in freeze-fracture preparations

The viscoelastic properties of sputum samples obtained from bronchitic patients were measured and correlated with the speed at which the samples were transported by the ciliary action of isolated pharyngeal palates of bull frogs maintained in amphibian Ringers solution at 28 degrees C. The viscoelastic properties were measured at very low shear stress which allowed to express them in terms of Newtonian viscosity and linear elastic modulus, which greatly minimized the variations in such measurements previously experienced with sputum. Samples with lower values of viscosity and moduli (less than 10,000 poises and 15 dynes per square centimeter, respectively) showed faster transport rates in a system where ciliary beat frequency and volume of added mucus were kept relatively constant.     

Sluggish Pansition Between Tetragonal and Rhombohedral Phases of Pb(Zr,Ti)03 Prepared by Application of Electric Field

Tetragonal and rhombohedral phases always coexist in Pb(Zr_xTil_1−x)0₃ near the morphotropic phase boundary compositions (0.52≤x≤0.55) when prepared by solid-solid reaction among the constituent oxides. A special technique was developed to obtain perovskite ceramics exhibiting no co-existence in the boundary compositions, in which no compositional fluctuation occurred in the B site of the perovskite structure. Even these monophasic perovskite ceramics of the morphotropic phase boundary compositions were two-phase with the lapse of time after poling. This phenomenon is interpreted in terms of thermodynamics. It is suggested that this phenomenon may closely relate to the origin of aging in piezoelectrics.     

Crack-healing and mechanical behaviour of Al2O3/SiC composites at elevated temperature

Alumina/silicon carbide (Al₂O₃/SiC) composite ceramics with large self‐crack‐healing ability, high strength and high heat‐resistance limit temperature for strength were developed and subjected to three‐point bending. A semicircular surface crack 100 μm in diameter was made on each sample. Crack‐healing behaviour was systematically studied, as functions of crack‐healing temperature and healing time, and the fatigue strengths of the crack‐healed sample at room temperature and 1373 K were investigated. Four main conclusions were drawn from the present study. (1) Al₂O₃/SiC composite ceramics have the ability to heal after cracking from 1273to 1673 K in air. (2) The heat‐resistance limit temperature for strength of the crack‐healed sample is ?1573 K, and ?68% of the samples fractured from outside the crack‐healed zone in the testing‐temperature range 873–1573 K. (3) The crack‐healed sample exhibited very high fatigue limit at room temperature and also 1373 K. (4) The large self‐crack‐healing ability is a desirable technique for the high structural integrity of ceramic component.     

强磁场对不同磁化率非磁性金属凝固组织的影响

根据热力学分析,强磁场对晶体凝固过程均质形核的影响是通过改变熔点、系统Gibbs自由能,从而促进或抑制形核过程来实现的．实验研究表明,相同的磁场条件对不同磁性金属凝固组织的细化作用、取向作用效果是不同的,从磁能、Lorentz力和磁化力效果等热力学和动力学角度探讨了相关规律．强磁场可以改变金属材料的凝固组织,从而进一步改善材料的质量和性能．     

基于辐射压力控制的微型元件的加工与检测

We have been developing new fabrication tools based on optical radiation pressur e and related phenomena to develop aflexible and accurate microfabrication tec hnology. In this paper, the laser trapping probe for the nano-CMM for assessment, in addition to micromachining technique using a small particle controlled by optical radiation pressure and laser aggregation technique are discussed. As the positional detection probe for the nano-CMM, an optically trapped silica particle with 8 mm diameter in forced oscillation state is used. A probe sphere retains a stable position when applied with trapping force by Nd:YAG laser light formed an nu lar and is forced to oscillate by the driving force changed by modulating the in tensity of LD emission. Experintal results show that this vibrational microprobe h as the possibility to achieve positional sensing accuracy of less than 25 nm. As a new micromachining technique, nano-removal process using an optically trapped micro-grain is proposed. The laser trapping force enables not only to stably trap the diamond grain with asymmetrical shape but also to freely control the positi on with spinning. Using this micro machining tool, the machining experiments of h ydrocarbon film are performed. AFM observation confirmed that the fine groove wi th depths of about 3～4 nm can be fabricated. As an additive process based on ra diation pressure, a laser microstructure fabrication using laser agglomeration p h enomena of colloidal particles aided by radiation pressure is investigated. By c ontrolling laser beam scanning in slurry containing KOH solution and SiO₂ par ticles with a diameter of 140 nm, colloidal particles are aggregated and adhered firmly to a silicon wafer substrate. Using this laser agglomerating process, two-dimensional grid microstructures at the pitch of 5 mm can be fabricated.     

Effect of anion ordering in the superconducting phase of (TMTSF)2ClO4

The anion-ordering effect for the superconducting phase of (TMTSF)₂ClO₄ was investigated by both measurements of static magnetization and resistance for various cooling rate through the ClO₄⁻ anion ordering temperature (24K). With increasing cooling rate, the temperature of superconducting transition, T_c, determined through the measurements of Meissner effect continuously decreases. The resistance along the a-axis monotonically decreases as deceasing temperature below the cooling rate of 0.2K/sec and the residual resistance caused by imperfectness of anion ordering increases as increasing cooling rate. The decrease of T_c is attributed to the pair breaking effect of nonmagnetic scattering due to the suppression of anion ordering.     

一种永磁同步压缩机三相电流重构方法

为提高永磁同步电机无传感器控制的性能,需要对电动机三相电流进行有效采样.针对电动机相电流检测的原理和采样时间的要求,采用一种基于单电阻采样方式的电动机相电流重构方法.同时,对空间电压矢量非观测区域原理进行分析,提出一种通过附加观测矢量和补偿矢量的方法来合成目标矢量的方法,对非观测区域的三相电流进行了有效的重构.基于IRMCF343芯片设计了一套无传感器永磁同步电机控制的平台.实验结果表明该方法在低成本的变频空调领域具有实用价值.     

光纤光栅的封装效果对其性能的影响

In this paper, the effects of packaging material and structure of fiber Bragg grating sensor performance are investigated. The effects of thermal expansion coefficient of different embedding materials on the temperature sensitivities of the FBG sensors are studied both theoretically and experimentally with good agreement, which provides a means for selection of FBG packaging material to achieve desired temperature sensitivity. We also demonstrate a 4-point bending structured FBG lateral force sensor that measures up to 242N force with well-preserved reflection spectrum, whereas for 3-point bending structure, multiple-peaks start to occur when applied force reaches 72N.     

列车动力学模型时变环境参数自适应辨识

考虑列车制动性能与制动距离对列车安全的重要影响, 分析了列车运行的动力学特性, 构建了列车离散化制动模型,并针对影响列车制动性能的关键参数 — 钢轨粘着系数难以直接观测、随钢轨环境变化的特点, 提出基于滑动窗口与最大期望理论的轮轨粘着系数在线辨识算法. 首先, 依据数据特征确定滑动窗口位置与窗口尺寸; 然后, 构造列车动力学模型参数的条件数学期望, 并结合粒子滤波与粒子平滑算法以及贝叶斯理论, 估计预设模型参数下的列车运行状态; 在此基础上, 分析粘着系数的后验概率, 并极大化条件数学期望对模型参数预设进行优化更新, 进而实现模型真实参数的逐步逼近. 最后, 考虑雪地、隧道等场景下的粘着系数变化, 对本文方法进行了仿真验证, 并数值分析了粘着系数对制动距离的影响. 仿真结果表明本文算法可快速、准确地对粘着系数进行实时辨识, 掌握轮轨间实时粘着状态.