钻机液压系统中的散热设计

从实际应用出发,以实例阐述液压油的选择、液压系统散热计算及冷却器、冷却风扇的选择,液压冷却回路设计.     

如何选择数控车床

从实际工作中,总结了选择数控车床应注意的几个问题。     

论低压无功功率补偿装置的选择

从低压无功功率补偿装置的发展现状、分类及特点出发,对实际选择时应当把握的原则、需要注意的问题及选择的方法进行了详细阐述。     

自卸车前保险杠结构设计方法综述

从保险杠的设计原则、材料选择、结构设计方面进行了简要介绍,主要对解决自卸车实际使用中的问题,从结构设计方面提供了新的思路.     

合理选择机床功率——机床节能措施

确定机床功率是一项比较复杂的工作。机床功率选择过大,会增加使用过程中电能的浪费;如机床功率选择过小,往往又不能满足工艺要求。我们所使用的机床,功率已被选定,能否按照机床使用的实际情况来重新选择功率呢?我们从机床功率的近似计算分析出发,按照机床的实际切削用量,重新选择机床功率,经多年使用证明是一项行之有效的节能措施。     

AutoCAD开发环境的比较和选择

从实际应用出发，从多方面分析了AutoCAD几种开发环境的优劣，提出了AutoCAD开发环境的选择原则。     

尿素企业设备的润滑管理

以摩擦学和润滑理论结合生产实际提出应不断改进设备润滑管理,分析了设备原始技术资料存在的问题;从用油粘度选择、润滑剂极压性选择、高温和水汽环境用油选择、进口设备用油改代五方面阐述了润滑剂的选择和改进;从污染油的治理、润滑状态监测换油、实用再生法、利用再生油、节油等方面,论述了尿素企业设备的润滑管理。     

10kV用户配电系统中保护用电流互感器的选择

从实际工作出发,分析用户配电设计中选择保护用电流互感器时所遇到的问题,提出系统短路电流对选择电流互感器准确限值系数的影响,以引起电气设计人员、用电管理及设备制造者的重视。     

数控加工中提高精度和效率的有效途径

结合数控车床和铣床加工实际情况,从合理的加工路线、刀具的选择和正确安装、切削用量的合理选择、编程技巧、尺寸精度快速控制等5个方面阐述了提高数控加工精度和效率的有效途径。     

数控加工中提高精度和效率的有效途径

结合数控车床和铣床加工实际情况,从合理的加工路线、刀具的选择和正确安装、切削用量的合理选择、编程技巧、尺寸精度快速控制等5个方面阐述了提高数控加工精度和效率的有效途径。     

Mice embryology: A microscopic overview

In this work, we studied the embryology of mice of 12, 14, and 18 days of gestation by gross observation, light microscopy, and scanning electron microscopy. Grossly, the embryos of 12 days were observed in C‐shaped region of the brain, eye pigmentation of the retina, first, second, and third pharyngeal arches gill pit nasal region on the fourth ventricle brain, cervical curvature, heart, liver, limb bud thoracic, spinal cord, tail, umbilical cord, and place of the mesonephric ridge. Microscopically, the liver, cardiovascular system and spinal cord were observed. In the embryo of 14 days, we observed structures that make up the liver and heart. At 18 days of gestation fetuses, it was noted the presence of eyes, mouth, and nose in the cephalic region, chest and pelvic region with the presence of well‐developed limbs, umbilical cord, and placenta. Scanning electron microscopy in 18 days of gestation fetuses evidenced head, eyes closed eyelids, nose, vibrissae, forelimb, heart, lung, kidney, liver, small bowel, diaphragm, and part of the spine. The results obtained in this work describe the internal and external morphology of mice, provided by an integration of techniques and review of the morphological knowledge of the embryonic development of this species, as this animal is of great importance to scientific studies. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Research on the calibration method of precipitation micro- physical characteristics sensor

In order to diminish the effect of the ambient light and CCD pixel non-uniformity to the Precipitation Micro-physical Characteristics Sensor,a modified calibration scheme was designed and calibration experiments in sunny,cloudy,night,different location of sample space were carried out. Firstly,the characteristics of particle images which affected by ambient light and different location of sample space were analyzed. Secondly,the relevance betw een particle image features and parameters of image processing were discussed. Finally,the parameter setting scheme were determined,the radium of median filtering algorithm is 3 pixels,the defocusing radius of point spread function( PSF) is 7 pixels,the radium of erosion is 3 pixels,and the binary threshold is obtained from the Area-thresh relationship. The results show that the new scheme could deal with the image calibration well,the average errors of equivolumetric diameter was 0. 041 mm with standard deviation of 0. 115 mm,and the average errors of the axis ratio was 0. 011 with standard deviation of 0. 085. The new scheme works well in the field observation too,the observed axis ratio is consistent with the empirical relationship that proposed by Beard. The relative error of accumulation precipitation is-3. 06% after calibration,w hich is improved 1. 94% low er than the initial one without calibration.     

Estimation of surface area and length with the orientator

The orientator is a new technique for the estimation of length and surface density and other stereological parameters using isotropic sections. It is an unbiased, design-based approach to the quantitative study of anisotropic structures such as muscle, myocardium, bone and cartilage. A simple method for the practical generation of such isotropic planes in biological specimens is described. No special technical equipment is necessary. Knowledge of an axis of anisotropy can be exploited to optimize the efficiency. To randomize directions in space, points are selected with uniform probability in a square using various combinations of simple random, stratified random, and systematic random sampling. The point patterns thus produced are mapped onto the surface of a hemisphere. The mapped points define directions of sectional planes in space. The mapping algorithm ensures that these planes arc isotropic, hence unbiased estimates of surface and length density can be obtained via the classical stereological formulae. Various implementations of the orientator are outlined: the prototype version, the orientator-gencrated ortrip, two systematic versions, and the smooth version. Orientator sections can be generated without difficulty in large specimens; we investigated human skeletal muscle, myocardium, placenta, and gut tissue. Slight practical modifications extend the applicability of the method to smaller organs like rat hearts. At the ultrastructural level, a correction procedure for the loss of anisotropic mitochondrial membranes due to oblique orientation relative to the electron beam is suggested. Other potential applications of the orientator in anisotropic structures include the estimation of individual particle surface area with isotropic nucleators, the determination of the connectivity of branching networks with isotropic disectors, and generation of isotropic sections for second-order stereology (three-dimensional pattern analysis).     

浅议机械论世界观主导地位之确立

占现代人类主导思想地位的机械论世界观,它的统治地位的确立是一个循序渐进的过程,先后经历了机械论大门的开启者培根,机械论世界观的架构者笛卡尔,机械论世界观主导地位确立和宣扬者牛顿,以及机械论世界观的社会意识形态补充者洛克,机械论世界观的经济意识形态的确立者斯密,再加上机械论世界观进步思想的巩固者达尔文等在各自不同领域的不懈探索和大力倡导,再加上其它意识形态领域潜移默化地影响而逐步得以确立。     

The actuality and progress of whole sky infrared cloud remote sensing techniques

Clouds are crucial regulators of both weather and climate. Properties such as the amount,type,height,distribution and movement of them have an impact on the earth's radiation budget and the hydrological cycle,thus cloud observation is very important. The disadvantages of zenith pointing measuring instruments and whole sky visible imagers limit the application of them.A summary of the actuality and application of ground-based whole sky infrared cloud measuring instruments and analyses of the techniques of radiometric calibrations,removal of atmospheric emission and calculation of cloud cover,amount,type are conducted to promote the automatically observation of the whole sky. Fully considering whole sky infrared cloud sounding theories,techniques and applications,there are still a lot of studies on improving the properties of instruments,enhancing the techniques of cloud base height measurements and establishing instrumental cloud classification criterion before actual operations.     

动力锂离子电池热失控燃烧特性研究进展

频发的电动汽车火灾事故引起了对动力锂离子电池燃烧特性与火灾消防的日益重视。在动力锂离子电池起火燃烧演进的三阶段划分中,首先是外部滥用条件引发了动力锂离子电池内部材料化学反应的自我加速过程,随着化学反应放热累积和产气气体增加,导致在一定的压力下动力锂离子电池进入释放阀打开进入泄气过程,最后释放气在多种着火源引导下进入起火燃烧过程。事实上,在动力锂离子电池的热失控燃烧过程中,这三个阶段并非完全割裂,是一个复杂的并列发生现象。与传统的火灾相比,动力锂离子电池的燃烧有其特殊性,如燃烧受控条件涉及化学反应释放的热量、动力锂离子电池电能内短路后转化生成的热量、动力锂离子电池材料体系中的可燃成份、动力锂离子电池泄气中易燃气体组成等。综述动力锂离子电池热失控的演化进程、泄气的组分与浓度及毒性、动力锂离子电池单体和模组的燃烧放热量和放热速率以及燃烧过程的质量损失等燃烧特性、电池包的火灾蔓延特点与灭火剂筛选原则。针对动力锂离子电池火灾的机理及特点,总结现有研究中存在的不足、可能的改进措施以及研究尚未涉及的关键研究点。     

基于ADuC812单片机和CAN总线的液压挖掘机泵控系统实现

在挖掘机实验平台上使用单片机ADuC812和工控机PC104,通过CAN总线连接,在PC104E和ADuC812之间进行数据的通信,从而构建了一个分布式控制系统。在该系统上采取一些现代控制算法,使泵的排量根据工作状况实时的改变、通过CAN总线的通信,可以在上位机上实时观测到挖掘机的工作状况,同时根据实际工况做出合理的调整、实验结果表明,通过这样的控制策略和算法,可以大大降低泵功率的损耗。     

卸输灰控制系统设计PLC型号选择探析

卸输灰控制系统是很复杂的系统,各部分部件的不同,对其功能的影响很大,通过对PLC机型、CPU、电源、输入输出模块及存储器各部件的参数、性能的阐述,掌握该系统的设计原则,并对其结构设计提出新思路。     

Kinematic analysis and optimal design of 3-PPR planar parallel manipulator

This paper proposes a 3-PPR planar parallel manipulator, which consists of three active prismatic joints, three passive prismatic joints, and three passive rotational joints. The analysis of the kinematics and the optimal design of the manipulator are also discussed. The proposed manipulator has the advantages of the closed type of direct kinematics and a void-free workspace with a convex type of borderline. For the kinematic analysis of the proposed manipulator, the direct kinematics, the inverse kinematics, and the inverse Jacobian of the manipulator are derived. After the rotational limits and the workspaces of the manipulator are investigated, the workspace of the manipulator is simulated. In addition, for the optimal design of the manipulator, the performance indices of the manipulator are investigated, and then an optimal design procedure is carried out using Min-Max theory. Finally, one example using the optimal design is presented.     

基于试验测试的桥梁与路堤区段高速列车车外噪声特性分析

高铁因线路形式不同使得其车外噪声特性有差异。为研究桥梁和路堤两种主要线路形式处的高速列车车外噪声特性,参考ISO 3095标准,使用78通道轮辐式声阵列、基于反卷积波束形成算法,对高速列车进行车外声源识别测试,使用自由场麦克风,对高速列车进行通过噪声测试,对比研究不同行车速度下两种线路形式处的高速列车车外噪声特性。结果表明,相同运行情况下,路堤段的通过噪声要比桥梁段的高0.1 dBA到1.8 dBA,且此差值会随列车运行速度的增加而增长。从车外声源分布特性来看,无论是桥梁段还是路堤段,300 km/h匀速运行时,高速列车的受电弓区域噪声均是最为显著的,其次是转向架区域。在桥梁段运行时,转向架区域噪声要略高于路堤段,这可能与桥梁段轨道整体刚度有关。在路堤段运行时,列车车身表面的噪声更大,这可能和路堤段的声音的地面反射有关。随列车运行速度的提高,两种线路对应的受电弓噪声差值逐渐减小,而转向架区域噪声的差值基本不随速度变化。