A geophysical device for automation of multielectrode electrical prospecting

A self-contained unit used in the resistance method of the geophysical electrical prospecting in order to switch two supply and two receiving lines with 24 electrodes installed on the Earth’s surface is described. The possibility of connecting in series several devices and their soft-and hardware interfacing to the control personal computer allows the number of electrodes to be increased to several hundred. As a result, the performance and flexibility of the data acquisition system as a whole increase, allowing one to conduct investigations at a higher methodological level. The unit is a portable device with a built-in storage battery and a control panel. There are connectors for ensuring control from the computer and connecting other devices.     

Structural observations and biomechanical measurements of clarinet reeds made from Arundo donax

Plant anatomy was examined for two clarinet reeds made out of Arundo donax by different means of microscopy: light microscopy, low‐energy secondary electron scanning electron microscopy (SEM), backscattered electron SEM, and helium ion microscopy (HiM). The local indentation hardness H_IT and Young's modulus E_IT of different tissues on their cross sections were measured. A vascular bundle (Vb) (H_IT = 60–100 MPa, E_IT = 1,500–2,000 MPa) that includes soft tissues of phloem and xylem and a vascular bundle sheath (Bs) (H_IT = 300–500 MPa, E_IT = ～7,000 MPa) form a pipe of the strong string along the longitudinal direction of the cane. This Vb/Bs string is connected transversally with a net of thin cell‐walls of parenchyma cells (Pa) (H_IT = 70–200 MPa, E_IT = 2,000–3,000 MPa) that also range along the longitudinal direction of the cane. It was turned out that the acoustic quality of a reed is mainly ascribed to the shape and configuration of Vb and the size of Pa. A reed where Vb bundles with continuous Bs rings are homogeneously distributed with higher proportion among a softer network of small Pa cells enables musical performance.     

Reliability Assessment of the Compressor Connecting Rods

The article presents an analysis of the stress condition of a connecting rod’s small ends. The strains acting in the most stressed section of the connecting rod’s small end are defined experimentally and using the numerical experiment. The probability of the failure of the connecting rods, depending on the acting load and conjunction clearances, is estimated. It is proposed to harden the working surface to increase the probability of a failure-free operation.     

基于Vb6.0的滚齿机挂轮选配系统开发

选配挂轮是滚齿机加工调整的主要内容之一,但一般计算和查表过程较繁琐,且不一定符合配备齿轮齿数和挂轮架结构尺寸的要求,在分析滚齿机挂轮计算的特点基础上,采用Vb6.0开发的系统可以快速、准确地同时选出范成运动与差动运动传动链的所需挂轮,并符合机床挂轮架结构尺寸与传动比相对误差最小的要求.     

基于共形几何代数的两种6自由度串并混联机构位置逆解分析

基于共形几何代数（Conformal geometric algebra,CGA）基本理论,解决了（3-PRS）+（3-SPR）和（3-RPS）+（3-SPS+UP）两种典型串并混联机构的位置逆解问题。首先根据机构的几何结构特征选择合适的未知参数,基于共形几何代数的基本运算建立了与该参数相关的机构中间平台某一顶点的数学表达式;然后根据该顶点坐标表达式和机构中存在的几何和尺寸约束,构造若干相关的平面或球面几何体,并对其进行外积求交运算得出中间平台其他两个顶点坐标的共形几何表达式;最后结合得到的顶点坐标与共形几何代数中的矢量内积运算,推导出只含有一个未知参数的多项式方程,由此得到机构的全部位置反解。该方法具有计算简明、高效、几何直观性强的特点,避免了传统方法求解串并混联机构位置逆解时冗长复杂的计算过程,为此类机构位置逆解的研究提供了参考。     

连杆衬套内表面磨损的正交试验研究

在连杆衬套内表面磨损的试验研究中,分别选取间隙值、载荷和转速作为试验因子。用正交试验法进行摩擦磨损试验,并用极差分析法分析了试验结果。结果表明：对连杆衬套内表面磨损影响主次顺序为转速、载荷、间隙值。从中得到了连杆衬套内表面最大磨损量和最小磨损量的工况。     

Dynamics analysis of leg mechanism of six-legged firefighting robot

Journal of Mechanical Science and Technology - A novel 3-DOF Leg mechanism (LM), which consists of a 2RUS+RU PM, a space parallelogram mechanism and a connecting spherical joint is proposed. The LM...     

一个多边形快速等距偏移方法

多边形的等距偏移是CAD/CAM领域中的一个基础性问题 ,是型腔环切加工刀具轨迹生成的关键。根据无效环在原始多边形上的对应连续线段必有一凸或凹点 ,从多边形的凸点和干涉凹点出发 ,利用干涉边的连贯性逐步确定无效环 ,最后对多边形中的非干涉区域作等距偏移 ,实现多边形的等距偏移。该方法利用干涉区域的连贯性避免了大量不必要的求交计算 ,同时支持带有孤岛的多边形等距偏移。其算法复杂度接近于O(n) ,其中n为多边形顶点个数。     

偏心渐开线齿轮传动的等分模型

基于两齿轮的几何中心连线等分回转中心连线的假设 (等分模型 ),建立了偏心渐开线齿轮传动分析和设计方程,分析了模型的误差。等分模型存在模型误差,但计算比较简便,当精度要求较低或者离心率较小时,可以用等分模型进行设计和计算,以便简化设计和计算过程,便于工程技术人员掌握。     

发动机连杆裂解槽激光加工机床的加减速控制

发动机连杆裂解槽激光加工机床的主要功能是完成对连杆大头孔内表面两侧的高速,高精度切槽加工。在编制该激光机床的NC程序的过程中,为了解决由于M功能的引入而产生的过切及残留问题,该篇文章提出了一种基于前瞻思想的方法对该激光机床的加减速进行了预先的处理,并将处理的结果与程序相结合,编制出新的NC加工程序。最后对激光切槽后得到的连杆进行裂解,并且经过特定的工具检测后,结果表明,对于各种型号的连杆,切割出来的裂解槽左右保持对称（两侧的槽深度公差为±0.025mm）,无中心偏移,并且无过切及残留。说明该方法的使用大大提高了该连杆裂解槽激光加工机床的稳定性及精度。     

Components of the radio-frequency system for traveling-wave deflecting structures

Components of a radio-frequency system for deflecting structures of the S-frequency range, which are included in the electron-beam diagnostic complexes for a free-electron laser (XFEL, Germany), were designed. Waveguide-coaxial and waveguide-strip directional couplers, a waveguide absorbing load, a waveguide window, and an E-bend were developed. A connecting element between two deflecting structures in the form of a U-shaped rectangular-waveguide section was also calculated.     

潜艇气动发射装置泄放阀调整设计

在分析泄放阀技术特点的基础上,通过对泄放阀开启时间和出流面积控制的计算,得出鱼雷发射深度与泄放阀开启时间的变化规律。不同发射深度下,无泡系统的海水回收量,只取决于泄放阀的有效流通面积大小及开启时间的长短,也就是取决于泄放阀通径和小孔放气时间。     

基于螺钉连接接触问题有限元分析的探讨

螺钉连接是典型的机械连接方式,连接面的接触问题是机械连接最常面临的问题。由于接触面的应力状态很难测定,属于接触非线性问题。本文利用有限元软件建立了两块螺钉连接的板结构有限元模型。基于所建立的有限元模型,本文运用Partran2003进行线性分析和ABAQUS6.4进行非线性分析,计算两块螺钉连接板的受重力变形情况。计算结果表明,用非线性方法分析得到的结果更合理．准确。提出对典型连接的接触问题,用非线性有限元分析的方法。     

反求工程与连杆的快速成形

对数字化测量技术和快速成形技术进行了概述,并对研究中所采用的便携式三维照相测量仪、立体彩色打印快速成形机及光固化激光快速成形机从原理和技术参数上进行了介绍。结合连杆成形工艺特点和要求。对连杆实物模型进行了反向造型研究,提出了一套适合于连杆逆向造型的方法;分别采用两种快速成形工艺制作了连杆的原型,并对其成形工艺、精度及材料性能进行了对比研究,获得了各自的技术特点和适用范围,讨论了反求工程和快速成形集成中的数据流和接口格式。此外,还提出了下一步连杆成形新的研究方向及其快速制造方法。     

用点形图描述运动链的结构

阐述了顶点的邻接线及闭合形的邻接角等新概念 ,论述了用点形图及转置图描述运动链拓扑结构、距离尺度结构和相对位形尺度结构的方法。本研究表明 :点形图可以描述任何运动链的拓扑结构和尺度结构     

Machine degradation analysis using fuzzy CMAC neural network approach

Traditionally, machine condition is described as a dichotomous problem: normal or failure. In fact, machines go through a series of degrading states until failure occurs. Degrading states do not make machines breakdown, but they do decrease performance reliability and increase the potential for faults and failures. In this paper, a neural network approach based on fuzzy cerebellar model articulation controller (FCMAC) is proposed to analyze machine degradation severity. Two kinds of situations are discussed: (1) machine signature from different levels of degradation severity are available to train the network; (2) machine signature from only normal perfect state are available to train the network. A degradation index is developed to reflect the degradation degree. The FCMAC network works as a ‘classifier’ or a ‘condition discriminator’ in these two situations. An example is presented to demonstrate this method and the results show that the FCMAC network is capable of ranking machine degradations quantitatively in both situations. With degradation analysis, maintenance activities can be implemented before failure eventually occurs, thus preventing fatal breakdowns more effectively.     

高炉称重式铁水液面计的全面升级

一直以来,常规的高炉铁水液面计主要功能只有大屏幕可以显示实时重量和报警.经过我们对原有系统硬件的重新组合,再融入受铁车对位指示和车号识别等实用功能,更是配备了一套功能齐全的铁水液面计管理软件,使高炉铁水液面计的作用得到了极致的发挥.其中高炉铁水液面计管理软件亮点在于自动判断铁口状态,并自动生成数据齐全的统计报表.这种新...     

实现特定杆长的曲柄摇杆机构设计

提出了在给定摇杆CD的长度lCD及其摆角φ和从动件的行程速度变化系数K的条件下,再给出曲柄、连杆、或机架三者之一,来设计曲柄摇杆机构的图解方法。避免了作椭圆或双曲线,简化了设计过程,使手工图解成为可能,且从理论上证明了方法的正确性。     

运动链拓扑胚图的同构判断

平面并联机构基于胚图的综合方法中,拓扑胚图的同构判断是关键的环节。针对不含二元杆的运动链拓扑胚图,解决它们之间的同构判断问题。运动链的拓扑胚图与拓扑图相比有着独特的个性,由于在支链上没有二元点,所以图的顶点之间的关系主要是顶点之间的相对位置。根据拓扑胚图的特性,从关于图的邻接矩阵的经典理论出发,建立图的任意顶点之间的路径数矩阵,将路径数矩阵的元素按照一定规则排列成路径数组。论证了拓扑胚图同构的条件。在度序列和一阶路径数组相等的前提下,利用二阶路径数组来判断拓扑胚图是否同构。举实例说明判断过程及具体应用。拓扑胚图同构判断问题的解决不仅为基于胚图的型综合奠定了基础,而且对于某些运动链拓扑图的同构判断也具有普遍意义。     

A numerical study on the characteristics of transient flow in a pressure regulator resulting from closure of the pressure control valve

This study investigates characteristics of transient flow and the possibility of freezing in a pressure regulator and the rear connecting pipe of the pressure regulator during the closing process of the pressure control valve (PCV), which is an essential element in the operation of a natural gas pipeline network. For this purpose, the study develops a numerical model for the PCV and its rear connecting pipe by applying computational fluid dynamics method. The analysis is conducted in each of two cases: (1) a steady-state analysis in the case of normal operation and (2) an unsteady-state analysis in the case of emergency closure in problematic situations. First, we closely examine characteristics of internal flow in the pressure regulator and the rear connecting pipe when the PCV operates regularly with a 50% opening ratio in a steady state. Afterwards, unsteady-state analysis examines characteristics of transient flow, such as lowered pressure and temperature, velocity change, etc., of rear flow in the pressure regulator when the PCV is closed because of trouble in the pressure control system.