气膜磁头的非线性运动轨迹计算和测试分析

本文对计算机外部设备中广泛使用的双轨气膜磁头轴承的稳定性进行了研究.考虑到现代磁头-磁盘气膜间隙已进入亚微米级,甚至达0.1μm,因此利用磁盘盘面上故意做成的凸台对磁头进行激励,计算了气膜磁头的非线性运动轨迹,并用激光多普勒振荡仪进行了测试.理论计算和试验数据吻合,证明计算方法和理论分析是正确可靠的.通过对三种磁头稳定性的比较,发现其中表面开槽的磁头稳定性最好,这对实际磁头的参数和结构设计具有实用价值.     

Measurement of the Relative Motion Between an Implant and Bone under Cyclic Loading

Abstract:  The measurement of the relative motion between a prosthesis and the surrounding bone is important for the pre-clinical testing of prostheses and implants. A technique that allows measurements to be made over several million loading cycles was developed by Maher et al. ( Clin. Biomech. 2001; 16: 307–314). However, the measurement of implant/bone motion is fraught with difficulties because: (i) testing over millions of cycles can take several days and errors because of diurnal temperature variations can occur, (ii) elastic deformations of the stem could have a dominant effect on 'inducible displacements', the rate of change of which is hypothesised to be a measure of loosening, and (iii) the use of this method for the analysis of cementless prostheses has yet to be demonstrated. This paper addresses these methodological issues with respect to testing hip prostheses, and concludes with a comparative evaluation of pre-clinical testing methods.     

Comparison Between Different Experimental Set-Ups for Measuring the Magnetic Barkhausen Noise in a Deformed 1050 Steel

The magnetic Barkhausen emission is investigated in deformed ANSI 1050 steel samples using four experimental configurations. These configurations vary according the type of magnetization (solenoid or yoke) and the recording the magnetic signal (bobbin above or around sample).The level of total strain was 0.4, 0.8, 1.0 and 3.0%. In all cases the same monotonous decrease dependence of emission magnetic with strain was obtained, showing that the four configurations give similar results. However, the yoke–pancake configuration was the most sensitive.     

聚合物真实黏度流变仪收缩流道轴向速度场的PIV实验研究及分析EI北大核心CSCD

为研究测量聚合物真实黏度流变仪收缩流道轴向速度分布规律,建立了收缩流道实验模型及实验方案。利用粒子图像测速(PIV)系统拍摄牛顿流体聚丁二烯在收缩流道流场中粒子的图像,利用Tecplot、Origin软件对图像和数据进行分析处理,得到聚合物真实黏度流变仪收缩流道的轴向速度曲线。同时将PIV实验、Polyflow仿真、理论计算结果相比较,发现三者规律基本吻合。证明了从PIV实验中得到牛顿流体聚丁二烯收缩流道速度场的方法是可行的。     

Experimental Technique for Measuring the Long‐term Transfer Length in Prestressed Concrete

Abstract: This article presents a proposal of a test set‐up and methodology for testing the transfer length evolution through time of prestressing reinforcement in pretensioned prestressed concrete members, aimed at providing a basis for standardization. The proposed test method is based on the instantaneous and time‐related analysis of the prestressing reinforcement force profile at only one end of a pretensioned prestressed concrete member. The basis of the test method and the requirements of the prestressing frame and its components are presented, as well as the test procedure stages and the measurement devices. The interpretation of the test results and the criteria to determine both the initial and the long‐term transfer lengths are explained. A test method application and the equipment for testing seven‐wire prestressing strands have been designed. Some experimental results are provided to validate the test. A comparative analysis of test reliability with other existing experimental methods is also included.     

对JJF1069-2003《法定计量检定机构考核规范》中的计量标准和测量设备期间核查的理解和实施

计量标准和测量设备的期间核查是保持其在检定/校准间隔有效运行的重要举措.本文主要对计量标准和测量设备期间核查的意义、对象、方法以及实施作简要介绍.     

Determination of the Initial Velocity and Duration of Motion of a Fluid in Capillaries

The method of determination of the initial velocity and duration of motion of a fluid in capillaries which is based on reduction of the boundaryvalue problem under study to Cauchy problems for systems of ordinary differential equations is presented.     

铁路轮对内距尺检具测微装置检定方法的探讨

本文探讨了铁路轮对内距尺检具测微装置的检定方法,比较分析了检定规程中采用的方法和本文所采用的方法之间的优劣,并就新检定方法进行不确定度验证分析。     

Modeling the 3-D Rotational and Translational Motion of a Halbach Rotor Above a Split-Sheet Guideway

When a Halbach rotor is simultaneously rotated and translationally moved above a split-sheet aluminum guideway a traveling time-varying magnetic field is created in the air gap. This field induces eddy currents in the guideway that can simultaneously create suspension and propulsion forces. If the rotor is offset from the center then a re-centering guidance force can also be created. As the forces are created in a highly inductive way the use of magnets circumvents any low power factor issues and enables a relatively high lift-to-weight ratio to be attained in comparison to using windings. The conductive and nonconductive regions are modeled by using a steady-state convective A- $phi$ formulation. The Halbach rotor is modeled using a 3-D analytic based model and is coupled to the conductive guideway region using boundary conditions. The steady-state rotation of the Halbach rotor is modeled by incorporating complex terms in the analytic model. The accuracy of the steady-state model is confirmed by comparing it with a 3-D transient finite-element Magsoft Flux model (with no translation) and with experimental results (with both rotation and translation). The effect of the rotor width on performance is also investigated.      

同时测量粒子尺寸和速度的激光散射系统

提出了同时测量粒子尺寸和速度的三光束激光散射系统，叙述了系统的组成、测量原理、以及信号采集和数据处理。并给出了应用本系统对电动喷枪喷雾水滴的尺寸和速度分布的同时测量结果。     

Application of Piezoelectric Actuator and Compliant Structures to Achieve Flapping Wing Motion for a MAV

Micro Aerial Vehicles(MAVs)are the smallest artificial aircraft.Most of the flapping wings MAVs are powered by electric motors of various capacities.We report in this paper the application of piezoelectric actuators as power system for a flapping wing MAV using a compliant displacement amplification mechanism.The actuator used for this application is a pre-stressed cut piece of TH-7R type Thunder actuator.A two-bar compliant mechanism with two flexures has been developed to convert the linear displacement into angular movement and amplification.The specimens were made from carbon fiber links and nylon flexures.We also proposed to use the product of frequency(F)and tip displacement(D),F*D as a criteria for the characterization of an amplifying mechanism.The best specimen according tO this criterion is obtained for a 5mm length flexure specimen made of three layers of nylon.The F*D value obtained for this specimen was 0.58 Hz.m.ANSYS finite element analysis results for different flexural thickness and Iengths were obtained and have been compared to the experimental results.The effect of both the thickness and length of the flexure on a particular arrangement has been discussed.     

如何填写检定装置中计量标准技术报告?(第二部分)

正7计量标准的测量重复性试验选择一台比较稳定的紫外可见分光光度计(型号:UV-2401PC,编号A10833300189LP)为被测对象,对波长与透射比两个技术参数,分别用氧化钬滤光片1#(在279.3nm和637.7nm两点)和透射比标准滤光片(J450-2在235nm点,G276-20在635nm点)于2013年1月22日进行重复性试验(6次),试验结果如表4:     

如何填写检定装置中计量标准技术报告？（第三部分）

9测量不确定度评定 9.1概述9.1.1测量依据：JJG178-2007《紫外、可见、近红外分光光度》检定规程。9.1.2环境条件：温度（10～35）℃;相对湿度≤85%。9.1.3测量标准（1）波长1汞灯U=0.01nm,k=2;2氧化钬滤光片,扩展不确定度为：200nm-380nm U=（0.2-0.5）nm,k=2;380nm-700nm U=（0.1-0.4）nm,k=23干涉滤光片,扩展不确定度为：U=（0.5～1）nm（k=2）;     

如何填写检定装置中计量标准技术报告？（第四部分）

10计量标准的测量不确定度验证10.1波长示值误差测量不确定度验证（传递比较法）选取一台相对稳定的紫外可见分光光度计（型号：UV2401PC,编号A10833300189LP）,分别用Hg灯（型号：1701,编号8810075）和氧化钬滤光片（1#）进行波长示值误差测量（2012年10月30日）,选择特征峰峰值波长相近的点得到一组数据。     

如何填写检定装置中计量标准技术报告(第一部分)

如何填写检定装置中计量标准技术报告?在JJF1033-2008《计量标准考核规范》中已有描述,但是在实际使用、应用过程中存在理解的偏差或错误,导致填写内容有误或不完整,如:在计量标准的工作原理及其组成中,有的填写的是被检计量器具的工作原理及其组成;在计量标准的重复性试验和计量标准的稳定性考核以及测量不确定度的评定中有多个主要计量指标及参数,有的填写时只有一个或不完整;在计量标准的测量不确定度验证中没有填写或不正确等等。笔者从事化学计量多年,现将填写的"紫外可见分光光度计(含可见分光光度计)"检定装置中计量标准技术报告提供出来,供大家参考和探讨(版面所限,连续刊载)。     

Numerical Verification of the Cross-Property Connections Between Electrical Conductivity and Fluid Permeability of a Porous Material

In this paper we provide numerical verification on the cross-property connection between effective fluid permeability and effective electrical conductivity. A set of 10 different microstructural patterns has been generated using a molecular dynamics algorithm. The problems are solved numerically using homogenous boundary conditions. The volumetric average over a cubic volume is used to obtain with the effective electrical conductivity and the effective fluid permeability. The tortuosity of the porous phase ?? _p was estimated by assuming a non-conductive solid phase, the inverse problem was solved to get the tortuosity of the matrix ?? _s . The accuracy of the cross-property connection developed by Sevostianov and Shrestha (2010) is verified, an error of less than 1% is found.     

实现电功率双路测量的方法及电路的非线性度分析

提出了一种实现有功功率和真无功功率双栖测量的方法,对测量方法的原理进行了数学证明,并根据数学公式提出了实现其测量方法的各部分电路原理及其实现方法。对影响测量准确度的关键电路,即功率测量电路的测量非线性度进行了动态分析,提出了电路测量线性度的计算公式,并就影响测量误差线性度的电路关键参数进行了计算机仿真研究。     

验光镜片箱中各类滤光片的检定方法研究

JJG579-2010《验光镜片箱》检定规程对各类镜片都规定了计量性能要求、检定方法和结果处理等规定,对辅助验光镜片中的各类滤光片的检定只作了简单的用途说明和简单的检定方法,因此不能有效保证各类滤光片的质量。本文以验光过程中各类滤光片的作用为基础,提出有效的检定方法,以保证各类滤光片的质量,以作探讨。