哈佛大学监事会章程的调整与变革

监事会章程是哈佛大学章程体系的重要组成部分.1781～1869年间,哈佛大学监事会章程进行了一系列修订和变革,扩大了监事会的自主权力,调整了监事会成员的选举制度和办法,加强了对宗教人士和政府官员作为监事会成员的限制,增加了校友等校外人士.监事会成员结构呈现出多元化、世俗化趋势.通过考察哈佛大学监事会成员结构的变化以及校友、教师等世俗力量的加强对哈佛大学发展所产生的影响,发现大学章程在大学治理结构中具有重要的地位和作用.     

The stabilization of the position of the body of walking machinesLa stabilisation de la position du corps d'une machine marchante

This paper shows that in the task of the maintenance of constant orientation of the body of a walking robot the determination of the actual position of the body, i.e. absolute altitudes of its points and remoteness from the supporting surface, is the most complicated problem. Two possible systems of measurement and stabilization of the position by the height of the body of the walking mechanism are compared, i.e. a system of adaptation automatically adjusting the length of the supporting leg to the roughness of the terrain, and the system of the maintenance of constant remoteness of the body from the terrain. The inefficiency of a solitary application of any described system is revealed and the possibility of an accumulation of errors of the position of the body by the walking on the soft terrain is shown. Possible approaches for raising the quality of stabilization of the body by the walking are evaluated.     

SDB-80型转向架轮对损耗分析

针对轮轨型面磨损问题,首先,对青岛地铁3号线现有的轮对测量数据进行分析,报告了轮对存在偏磨现象且轮对镟修损耗占轮对寿命比值较大的现状。然后,对轮对异常磨耗进行研究,指出轮对缺少润滑、线路曲线分布不对称和列车长时间不掉头运行是导致轮对产生异常磨耗的主要原因。最后,根据线路实际情况,提出了采用轮缘润滑或小半径曲线外轨轨侧涂油等方式降低轮轨摩擦系数、车辆定期掉头运行和采用薄轮缘镟修的方式对轮对进行镟修等解决措施,降低轮对的损耗速率,增加轮对的使用寿命。     

Synchronization of two non-identical coupled exciters in a non-resonant vibrating system of plane motion

In the average method of modified small parameters, the synchronization of two coupled exciters is converted to a problem on the existence and stability of zero solutions for the average differential equations of small parameters over the average period of two exciters. To implement frequency capture, the torque of frequency capture should be greater than or equal to the absolute value of the difference between the residual electromagnetic torques of the two motors. Because each exciter is involved in the motion of the vibrating system it has excited, its relative moment of inertia is reduced. The reduction is proportional to half its coefficient of cosine effect of phase angles (CCEPA). Because one of the exciters is involved in the motion excited by the other, a coupled moment of inertia exists for the two exciters. The stability of the synchronization of the two exciters is affected by the reduction of their relative moments of inertia and their moment of coupling inertia. For the synchronization to be stable, two conditions must be satisfied: (1) the non-dimensional relative moments of inertia of the two exciters are all greater than zero, and (2) four times the product of their non-dimensional relative moments is greater than the square of the coefficient of coupled cosine effect (CCCPA). The stability of synchronization depends solely on the ratios of the masses of the two exciters to the mass of the vibrating system and the ratio of the distance between one exciter and the centroid of the rigid frame to the equivalent rotating radius of the vibrating system about its centroid of the rigid frame, and is independent of the parameters of the two induction motors.     

Thermal friction problem and its development: Part 2. The role of heat phenomena in fracture of tooth wheels of cylindrical involute gears of real dimensions

The local pattern of initial of fracture of machine parts is discussed and the practical significance of determination of the zone of manifestation is highlighted. The temperature is considered the main factor in the process of improvement of the thermal friction problem governing operation of a heavily stressed contact. The results of calculation of brakes with the method of thermal dynamics of friction and wear are demonstrated.     

关于产品设计的建模研究

产品设计是一种复杂的人类创造性思维活动。在分析产品设计及其过程的基础上,利用集合与映射的理论与方法,依次建立了产品设计、产品设计过程、产品概念设计过程的模型,给出了产品概念设计过程的网络算法框图,并且详细定义了后者的分解与综合的流程,为产品设计过程的模型化、规律化打下了良好的基础,同时也为产品全生命周期设计过程计算机软件支持工具的开发作出了有益的探索。     

球形机器人的跳跃运动分析

球形机器人除了能进行滚动运动外，还可以实现跳跃运动。跳跃运动方式与滚动运动方式的结合，可以扩大其活动范围，进而提高球形机器人的机动性和灵活性，拓展其应用领域。因而球形机器人的跳跃运动是一种重要的运动方式。在分析球形机器人滚动行走的基础上。推导出了球形机器人的起跳每件；利用拉格朗日方程得到了球形机器人跳跃运动微分方程；通过求解该跳跃运动微分方程得到了球形机器人跳跃高度和跳跃长度的公式。最后，对球形机器人的跳跃运动进行了仿真。这些工作的完成为球形机器人跳跃运动的进一步研究打下了基础。     

制造误差对四杆机构轨迹综合精度的影响分析

通过建立杆长制造误差对平面四杆机构轨迹综合精度影响的数学模型,确定了杆长制造误差的敏感系数,分析了杆长制造误差对轨迹综合精度的影响规律。设计实例说明,合理设计四杆机构杆长制造公差,可使机构既满足精度要求又降低制造成本。     

A mechanism of lubricant trapping in slow speed compression

A mechanism for the trapping of liquid lubricant in compressive metal forming is suggested. The basis of this mechanism is the interaction of elastic deformation of the tool and the hydrodynamic behaviour of the lubricant. A computer simulation of the process of slow speed compression of a cylindrical rigid-plastic billet between semi-infinite elastic tools with films of lubricant illustrates the validity of the proposed mechanism. From the result of the simulation together with dimensional analysis, the thickness of the trapped lubricant film is determined as a function of the lubricant viscosity, the elastic constant of the tool, the speed of compression and the radius of the billet.     

45钢膏剂渗硼及耐蚀性研究

通过试验探讨了45钢渗硼后的组织和工艺参数对渗硼层厚度影响规律以及渗硼层的耐蚀性。结果表明：渗硼时间一定，渗硼层深度和渗硼温度呈负指数方关系;渗硼温度一定，渗硼层深度与渗硼时间呈抛物线关系;渗硼试样耐蚀性明显优于未渗硼试样，而单相渗硼层的耐蚀性又明显优于双相渗硼层。     

卧螺离心机转鼓主要参数对其模态的影响

研究清楚离心机转鼓参数与转鼓应力、变形的关系，是保证其在安全的工作状态下，对转鼓进行参数优化的基础。在诸多参数中，对转鼓3个主要参数：转速、转鼓壁厚和液池深度进行分析研究。结果表明，各种载荷下转鼓的最大径向位移均与转速的二次方成比例，且随着转速的增加，会导致转鼓径向变形增大；正常工况（Fw＋Pc）下的应力SINT（SINT为第三强度理论的等效应力）最大值随着转鼓壁厚的减小而增大，但增大的幅度较小；转鼓的总径向位移最大值和物料离心压力引起的径向位移的最大值均随着液池深度的增加而增大，但增长速度缓慢；转鼓自身质量离心力产生的径向位移与转鼓的液池深度无关。这些数据将为己有的卧螺离心机的改造优化和工程实际应用提供设计依据。     

Analysis of temperature influence on the informative parameters of single-coil eddy current sensors

This paper describes the study of temperature in the flowing part of a turbine on the informative parameters (equivalent inductances of primary windings of matching transformers) of single-coil eddy-current sensors with a sensitive element in the form of a conductor section, which are used as part of automation systems for testing gas-turbine engines. In this case, the objects of temperature influences are both sensors and controlled turbine blades. The existing model of electromagnetic interaction of a sensitive element with the end part of a controlled blade is used to obtain quantitative estimates of temperature changes of equivalent inductances of sensitive elements and primary windings of matching transformers. This model is also used to determine the corresponding changes of the informative parameter of the sensor in the process of experimental studies of temperature influences on it (in the absence of blades in the sensitive region). This paper also presents transformations in the form of relationships of informative parameters with radial and axial displacements at normal (20 °C) and nominal (1000 °C) temperatures, and their difference is used to determine the families of dominant functions of temperature, which characterize possible temperature errors for any radial and axial displacements in the ranges of their variation.     

Device for Characterization of the Diffraction Pattern of Computer-Generated Holograms in a Wide Angular Range

Results of the development and testing of a device for detecting and analyzing the diffraction pattern of computer-generated holograms are reported. It is demonstrated that this device allows characterization of the diffraction pattern of radiation reflected from the surface microrelief of the considered element or transmitted through it in the angular range of diffraction of the order of ±90° and 360° in terms of the azimuthal angle. A possibility of determining the periods, duty cycle, and angular orientation of diffraction structures and also the diffraction efficiency of all diffraction orders of the examined element is described. The device is designed for real-time monitoring of the microrelief depth and shape of computer-generated holograms in the course of their fabrication.     

刀面粗糙度及刀刃锯齿状态对已加工表面质量的影响

为研究刀面粗糙度及刀刃锯齿状态对已加工表面质量的影响,特别采用不同刀面粗糙度和刀刃锯齿状态的硬质合金刀具进行薄切削铝合金的对比试验。试验表明:刀具各刀面粗糙度对已加工表面粗糙度和加工硬化有较大影响,刀面粗糙度增大,已加工表面粗糙度和加工硬化随之增大;刀刃锯齿状态对巳加工表面质量的影响程度可用锯齿影响系数来表征,随着锯齿影响系数的增大,巳加工表面粗糙度和加工硬化程度也增大。     

Theoretical and experimental methods for study of deformation and destruction characteristics of tribotechnical topocomposites

The results of theoretical and experimental studies conducted at the Institute of Machine Science of the Russian Academy of Sciences and devoted to the estimation of the operational capability of solid bodies with thin coatings, in terms of the action of high local contact loads with and without friction are summarized. The question of the objective estimate of the parameters of quality and operational capability of tribotechnical topocomposites is analyzed.     

Spectroscopy of the cross section of inelastic scattering of electrons in SiO2/Si(100) layered systems

Spectra of the cross section of inelastic scattering of electrons (product of the mean free path of inelastic scattering and its differential cross section) are obtained for SiO₂/Si(100) layered structures from experimental spectra of energy losses of reflected electrons with different energies of primary electrons. Computer simulations of the spectra of the cross section of inelastic scattering of reflected electrons for these layered structures are performed with the use of the dielectric function of the film and substrate materials. It is found that the SiO₂ layer thickness determined through comparisons of experimental and model spectra agrees with results of ellipsometric measurements.     

A new class of lubricants based on stable dispersions of solid nanosized powders

At present, the possibilities of improvement of the operating characteristics of greases via application of traditional technologies, including introduction of powder fillers of soft metals and solid lubricants, are exhausted. The paper reports the findings of experimental testing of a grease obtained by chemical grinding of aggregates of solid aluminosilicate nanosized powders and their uniform distribution through the volume by wave technology. It is found that the wear resistance of the steel friction surfaces increases at least two-fold and the coefficient of friction of the studied pairs declines with application of the grease containing solid nanosized aluminosilicate particles. The efficiency of lubrication with the tested grease after a single application significantly surpasses the respective characteristics of the best commercial greases.     

Applications of electron microscopy in materials science and technology (microscopy in the modern world)*

A personal overview is presented attempting to show something of the broad range of applications of techniques associated with electron microscopy in the field of materials science and technology. The importance of electron microscopy in understanding microstructure/property relationships and the evolution of microstructure is stressed. In addition, some of the important uses of electron optical techniques in the more applied areas of materials technology are surveyed. The format adopted in this presentation is to illustrate the applications of electron microscopy in materials science and technology by citing recent studies. These include investigations of deformation, of grain growth, of precipitation and phase transformations and of the determination of the structure of interfaces.     

液压机械传动中机械变速箱传动比规律研究

提出了液压机械无级传动系统的正相位、反相位和等差式、等比式的概念，明确了等差式液压机械无级传动和等比式液压机械无级传动的一般性组成环节，分析了正相位工况和反相位工况下功率的分流和汇流情况，揭示了功率分流点和汇流点的不同是两类方案具有不同工作特性的根本原因。通过分析各液压机械段纯机械点的输出转速，推导了两类方案机械变速箱传动比的规律及机械变速箱传动比与汇流排机械路传动比的关系。根据各自的特性，等差式液压机械无级传动适用于履带车辆的无级转向系统；等比式液压机械无级传动适用于车辆的直驶推进系统。