对几种国外引进的异型弹性密封填料的结构及密封机理的探讨

本文通过笔者对在实际工作中所遇到的国外引进设备中一些异型弹性密封填料的结构、材料，应用效果及其密封机理的分析和探讨，从而试图解决常用弹性密封填料中存在的一些问题，为对弹性密封填料的研究工作提供一些参考。     

螺旋密封技术探讨

从工程应用角度，探讨螺旋密封的封液能力，结构型式，螺旋槽截面形状等问题，提出了实用性较好的螺旋密封封液能力计算式，供螺旋封装置设计或选用时参考。     

O圈密封的应用及进展

文章较详细地介绍了O圈密封在各个不同发展阶段的主要型式及技术，跟踪国际新动态，列出了各种密封型式的结构，工作原理，适用范围等。对工程机械生产厂家以及其他液压机械的生产厂家的密封的设计和选用具有指导意义。     

橡胶密封机理

橡胶密封机理苏州阀门厂潘仁度１．橡胶密封机理的微观特性橡胶压缩后产生３种变形，即弹性变形、力求恢复原状的收缩弹性变形和塑性变形。在图１中，分子１～４处于斥力作用范围，故分子１和４对两侧的橡胶产生斥力挤入。橡胶弹性力Ｐ２对介质分子产生摩擦力，或由于Ｐ２...     

离心泵新型填料密封

阐述了离心泵填料密封的机理，剖了圆柱形填料腔填料密封的使用缺陷，提出了锥形填料腔的新型填料密封结构形式，锥形填料腔填料密封效果好，寿命长，值得推广应用。     

动压环槽端面密封的泄漏量影响因素

对端面开环形槽的动压式机械密封进行了研究，根据周向波度模型，以雷诺方程为基础，运用有限差分法进行数值计算，求解二维压力场和泄漏量，编制了相应的计算程序，通过计算，从理论上分析了压差，转速，波度等因素对泄漏量的影响，重点分析了泄漏量与膜量的关系，指出了膜厚－泄漏量之间的关系指数与传统公式的不同之处，并实验验证了计算程序的可靠性。     

机械端面密封技术的热点问题

根据时代特点和当前机械端面密封技术发展趋势，提出了21世纪初机械密封技术的若干热点问题；流体动压型机械密封是密封技术中最活跃的领域，可控型机械密封是防止密封失效的可靠保障，新型材料的合成与加工是开发新型机械密封的基础，传统型机械密封处于进一步提高的阶段，应重视密封技术（机理和性能和预测）的基础研究、CAD设计技术和新型密封技术的推广应用。     

一种动、静密封兼顾的新型密封圈密封机理研究

同一密封结构既要完成灵活转动又要完成静密封，既要保证运动副的运动灵活性，又要保证静密封的可靠性，的确是一个矛盾，是一个难题。本文讨论了一种动、静密封功能要求分明的密封结构，分析了这种密封结构的密封机理，推导了有关公式，得出了一些结论，并与传统的密封结构进行了对比，指出了其优越性。     

常用旋转密封件的选型与应用

该文分析了几种旋转轴唇形密封件密封机理，提出合理的选型方案及使用注意点。     

O形密封圈合理使用探讨

O形密封圈是一种常见的密封元件，它具有密封性可靠、密封部位简单、易拆卸、运动摩擦力阻力小等特点，在液压设备中广泛使用。在实际工作中，由于忽略O形密封圈的使用条件，装配后密封部位容易出现泄漏或损坏，本文就合理使用O形密封圈进行如下分析与探讨。     

以制图大赛为契机 全面提升学生的综合创新能力

介绍了近三年全国大学生先进图形技能与创新大赛情况,并以此为契机,优化教学内容、调整教学方式,运用重点突出、方法多样的教学及集中强化训练的方式,全面提升学生的识图和绘图以及综合创新能力,取得了良好的教学效果.     

Vibration of circular plate with multiple eccentric circular perforations by the Rayleigh-Ritz method

The free vibration of a circular plate with multiple perforations is analyzed by using the Rayleigh-Ritz method. Admissible functions are assumed to be separable functions of radial and tangential coordinates. Trigonometric functions are assumed in the circumferential direction. The radial shape functions are the boundary characteristic orthogonal polynomials generated following the Gram-Schmidt recurrence scheme. The assumed functions are used to estimate the kinetic and the potential energies of the plate depending on the number and the position of the perforations. The eigenvalues, representing the dimensionless natural frequencies, are compared with the results obtained using Bessel functions, where the exact solution is available. Moreover, the eigenvectors, which are the unknown coefficients of the Rayleigh-Ritz method, are used to present the mode shapes of the plate. To validate the analytical results of the plates with multiple perforations, experimental investigations are also performed. Two unique case studies that are not addressed in the existing literature are considered. The results of the Rayleigh-Ritz method are found to be in good agreement with those from the experiments. Although the method presented can be employed in the vibration analysis of plates with different boundary conditions and shapes of the perforations, circular perforations that are free on the edges are studied in this paper. The results are presented in terms of dimensionless frequencies and mode shapes.     

Parameter estimation of integrating and time delay processes using single relay feedback test

Autotuning using relay feedback is widely used to identify low order integrating plus dead time (IPDT) systems as the method is simple and is operated in closed-loop without interrupting the production process. Oscillatory responses from the process due to ideal relay input are collected to calculate ultimate properties of the system that in turn are used to model the responses as functions of system model parameters. These theoretical models of relay response are validated. After adjusting the phase shift, input and output responses are used to find land mark points that are used to formulate algorithms for parameter estimation of the process model. The method is even applicable to distorted relay responses due to load disturbance or measurement noise. Closed-loop simulations are carried out using model based control strategy and performances are calculated.     

一种数字频率电压紧急控制装置的设计与实现

介绍了一种频率电压紧急控制装置的设计与实现方法。装置采用32位嵌入式单片机作为核心控制芯片,利用双电压回路进行电压测量,硬件和软件相结合实现频率测量,提高可靠性,确保测量准确。对任一故障的判断和决策都采用多个不同的条件,多重闭锁机制,有效防止误动和拒动;大屏幕液晶实时显示电压、频率等信息。嵌入式双网通信接口,采用国际标准或按用户要求定制通信规约。     

制造加工约束下连续体拓扑优化的数值实现

针对两类常见的制造加工约束即对称性和重复性下的连续体拓扑优化问题,提出了将敏度值在每轮优化前的修正方法,该方法简单且易于编程实现,实现了对称性或重复性约束条件下连续体拓扑优化设计,通过数值算例对不同制造加工约束下的拓扑结果进行了分析对比,结果表明,研究方法具有可行性和有效性。     

Laser Doppler Vibrometry: Development of advanced solutions answering to technology's needs

The new trends on Laser Doppler Vibrometry (LDV) development are outlined with particular attention to the innovative solutions answering to the most recent technological requirements which are not met by the current systems.Several LDV application areas are described and the limitations of actual technologies highlighted. The possible solutions needed to overcome these limits are anticipated and emerging technologies which are not completely entered the market but could positively answer to the industrial requirement are described.     

Analytical mass spectrometry of herbicides

Herbicides are chemical substances that are applied to agricultural soils, gardens, lawns, or plants to destroy or to prevent the growth of undesirable vegetation. The herbicides included in this review are generally synthetic organic compounds that are ingredients in commercial herbicide products that were designated active during late 2002 in the U.S. Environmental Protection Agency's database of registered and canceled pesticide products. The compounds are organized into 21 categories according to their general chemical structures or a common structural group. The herbicides in each category are discussed in terms of their structures, their database electron ionization mass spectra, and their amenability to separation and measurement with gas chromatography, reversed-phase liquid chromatography, and capillary electrophoresis combined with mass spectrometry. Ionization techniques that are considered here are mainly electron ionization, electrospray, and atmospheric pressure chemical ionization. Sixty-six references are provided to herbicide reviews, and to the recent herbicide analytical chemistry and mass spectrometry research literature.     

实体法铣削仿真效率改善及应用算法

轴向切削深度和径向切削宽度是铣削仿真模型求解的几何边界条件,也称为啮合几何参数。根据对啮合参数提取的三类途径的比较,针对直接布尔操作途径仿真效率低的问题,运用集合论描述了实体法铣削仿真中模拟材料去除的布尔运算过程,从时间复杂性角度分析影响实体法铣削仿真效率的因素,提出改善仿真运行效率的4种途径;在此基础上,从几何造型和切削过程两方面给出在仿真计算位置处布尔运算次数由4次减少为1次的可行性分析,提出在简化布尔运算次数情况下的切削几何边界条件的识别和判断算法,对判断算法的有效性和减少布尔运算的时间复杂性进行分析、给出在铣削力仿真中的应用示例,并说明应用范围,从而在保证切削几何边界条件准确提取的同时提高仿真效率,为铣削力等仿真模型的求解奠定基础,推动相关物理仿真研究成果在工程实际中得到切实应用。     

开敞式混流泵内流的数值模拟与出水机构选择

为了给新型开敞式混流泵的设计积累经验并为特殊出水流道结构设计提供方法,对具有不同出水机构的开敞式混流泵进行数值模拟,分析从小流量到最大流量下的内部流动和水力性能,提出适应特殊液压动力需求的开敞式出水机构方案。给出内部流动数值模拟和性能预测的方法,通过外特性预测结果与模型试验数据的比较,验证数值计算的可靠性。在模型分析基础上,针对轴向有导叶、轴向无导叶和径向无导叶等不同的开敞式出水结构形式,进行整机内部流动分析和外特性预测,对不同结果进行比较分析,给出不同出水机构对于特定结构和动力需求的适应性。     

Three-dimensional reconstruction from electron micrographs of disordered specimens. II. Implementation and results

The computational procedures to implement the method described in the companion paper for three-dimensional reconstruction from projections of a disordered collection of single particles are presented. Computer simulations are used to demonstrate the way the method functions, and practical aspects are discussed in detail. Examples are given of how different symmetries can be exploited by imposing selection rules on the model equations. Applications to negatively stained 50S ribosomes and to cryo-electron micrographs of thin vitrified layers of unstained and unsupported tomato bushy stunt and Semliki Forest viruses are described, and the resulting reconstructions are presented.