轴承套圈机械加工机器人控制系统的设计与研究

为了提高轴承的生产效率,在其机械加工系统中采用机器人进行生产,符合市场需求。作者根据多年工作经验,通过参阅大量文献,设计了轴承套圈机械加工机器人控制系统,对搬运机器人、装箱机器人的结构及层次架构系统进行了研究,为提高企业效益,保证生产质量提供了技术支持。     

A Novel Dynamic Fault Restoration Mechanism Using a Multiple Ring Approach in WDM Mesh Networks

This work describes a distributed fault restoration algorithm, called the Dynamic Multiple Ring Algorithm (DMRA), for application in WDM mesh networks. This study explores the choice of restoration paths and the assignment of fault-tolerant bandwidth when a link, node, or channel failure occurs according to the change in traffic load, number of nodes, and transmission delay including propagation and switching delays. Accordingly, the primary aim of this work is to use networking segments near faults to share the restoration load throughout a mesh network. Each node searches for restoration paths in their near environment using the proposed DMRA. Nodes use distributed control to search for neighboring nodes and to establish the relationship between them to build numerous logical rings. Nodes can also locate faults in the logical rings. These rings establish the restoration paths. The traffic load over failed links or nodes can be diverted to other paths in the networking segments. The cost of the restoration paths is computed at each node based on both the current capacity and the transmission delay. The selected restoration paths are suitable transmission routes in the network neighborhood. Hence, restoration paths can be identified and wavelength assigned quickly according to network bandwidth and traffic load. Simulation results reveal that the proposed method works extremely quickly and has a high success rate. Consequently, it is very useful for applications in real WDM networks, where the status varies from minute to minute.Corresponding author is presently a guest scientist with the National Institute of Standards and Technology, USA. This research was partially supported by the Grant of National Science Council, ROC (NSC-92-2218-E-155-004 and NSC-93-2917-I-155-001).     

NUMERICAL SIMULATION OF THE TRANSPORT OF VORTEX RINGS IN AN INITIALLY STRATIFIED FLUID

A numerical study of the formation and transport of vortex rings in a cylindrical tank initially occupied by a thermally stratified fluid is presented. A control-volume based finite-difference technique (Patankar's SIMPLER method) is used. The formation of a vortex ring was simulated by injecting a quantity of a fluid through a tube centrally located near the free surface. Initially, the fluid in the tank was stably thermally stratified, with a low density in the upper half and higher density in the lower half. Buoyancy effects were considered. Modelling aspects are discussed and the formation and transport of a vortex ring in the stratified fluid as well as the resulting mixing characteristics are presented.     

An improved upperbound for distributed election in bidirectional rings of processors

We present a distributed algorithm for electing a leader (i. e., breaking symmetry) in bidirectional rings ofN processors with no global sense of orientation, that uses at most 1.44 ...N logN+O(N) messages in the worst case.Jan van Leeuwen received his M. Sc. degree in 1969 (cum laude) and the Ph.D. degree in 1972 from the University of Utrecht, Utrecht, The Netherlands. He held a postdoctorate fellowship in computer science at the University of California at Berkeley (1972–1973), visiting assistant professorship in computer science at the State University of New York at Buffalo (1973–1974, 1975–1976), and a visiting associate professorship in computer science at The Pennsylvania State University, University Park (1976–1977). In 1977 he was appointed Associate Professor of Computer Science at the University of Utrecht and became head of the new Department of Computer Science at this university. He is presently Full Professor of Computer Science. Dr. van Leeuwen is active in many disciplines within computer science. His primary research interests are fundamental studies in varied areas of computer science, viz. the analysis and complexity of computer algorithms, in both a theoretical and an applied sense (e. g. data structures, machine models, VLSI, parallel and distributed computing, and cryptography).Richard B. Tan is an Associate Professor of Mathematics and Computer Science at the University of Sciences and Arts of Oklahoma. He spends his summers at the University of Utrecht, the Netherlands. His research interests are in distributed computation and graph algorithms. He received the B. Sc. in Physics from Beloit College, WI., the M.S. in Computer Science and the Ph.D. (in 1980) in Mathematics from the University of Oklahoma.This work was done while the second author was visiting the University of Utrecht, supported by a grant of the Netherlands Organization for the Advancement of Pure Research (ZWO)     

Technical reports and theoretical studies about the structural behaviour of masonry domes in the 18th century

The development of the scientific theory on the stability of vaulted structures was driven mainly during the 18th century based on applying the laws of Mechanics and the knowledge of the properties of materials. In the specific case of structures such as domes, the development of the theory is closely related to the theory of arches and vaults. Still, the main contributions are made in technical reports on the construction, stability, and repair of domes, such as the dome of Saint Peter's in Rome and Sainte-Geneviève or Pantheon in Paris. This article, therefore, analyses the relationship between theory and practice and the development achieved in the specific subject of masonry domes during the 18th century from the point of view of the Limit Analysis of Masonry Structures. In a more general sense, the objective of this research is to study in greater depth the theory of Limit Analysis itself, that is, to learn from the work carried out in the 18th century by mathematicians, architects, and engineers, who, although unaware of the existence of the theoretical framework of Limit Analysis as such, moved within it.     

Synthesis of ionic liquids based on alkylimidazolium salts and their coal dissolution and dispersion properties

A series of new bis (imidazolium) cation-based ionic liquids, wherein two imidazole rings are tethered by alkyl ether chains (oxygen numbers) of different lengths, were prepared, and their coal dissolution and dispersion properties were studied. It was found these ionic liquids can be used to fragment, disperse, and partially dissolve micrometer-size coal particles by simply mixing ionic liquid/coal dispersions. Dissolution performances and light hydrocarbon production were found to be sensitively increased by increasing the lengths of alkyl ether chains between imidazolium rings.     

传统古村落的保护与发展——以张家口市蔚县西古堡为例

我国古村落数量大,历史悠久,历史和艺术价值不容忽视,但当今社会快速发展,人们生活方式发生巨大变革,原始古村落难以满足现代人生活需求,古村落发展和保护面临许多现实问题,该文以张家口市西古堡为例,探讨古村落的保护和发展问题。     

Mn18Cr18N护环钢静态再结晶组织及模型

在Gleeble-1500D热模拟机上,采用双道次热压缩试验研究Mn18Cr18N护环钢高温变形后不同停留时间内的静态软化行为,分析热变形温度、应变速率、变形程度以及初始奥氏体晶粒对静态再结晶行为的影响.通过应力补偿法计算静态再结晶软化率,并结合金相组织作了修正.建立其静态再结晶动力学模型,获得静态再结晶激活能249.3 k J/mol.研究表明:Mn18Cr18N钢静态再结晶软化曲线呈"S"形,符合Avrami方程.静态再结晶体积分数随着停留时间延长而增加,热变形温度越高,静态再结晶分数越大,而在较低温度和较小变形程度时,孕育时间较长,主要发生静态回复,将静态再结晶动力学模型的预测结果与实测值进行比较,二者吻合较好,为护环钢后续热镦粗工艺模拟提供更为详尽的模型.     

Frictional behavior of piston rings of small utility two-stroke engine under secondary motion of piston

The secondary motion of the piston head of a motorized engine is captured using two laser displacement sensors to obtain the piston motion and tilt angle. The controlled parameters of the measurement are engine speed, quantity of oil and oil-fuel mixture and its ratio. The reduction in friction force is more significant at dead center at high speed as the quantity of oil supplied increases. Changes in tilt direction of piston head occur at the inlet port. The relationship between the friction force and piston tilt angle showed weak correlation at low speed and increases with the engine speed.     

钛合金大型环件热辗扩成形应力-应变场演变规律的尺寸效应(英文)

基于可靠的钛合金大型环件热辗扩成形过程热力耦合三维有限元模型,研究并对比了不同尺寸环件的应力应变场演变规律。结果表明:对于不同尺寸环件的成形过程,当γ(整个成形过程的当量每转进给量分配比)减小时,成形结束时的Mises应力峰值可能从环件的驱动辊侧咬入点转移至芯辊侧咬入点,而等效塑性应变峰值有从环件外表面向内表面转移的可能性;当L(整个成形过程的当量变形区长度)增大时,成形结束时的Mises应力峰值可能出现在中间层。成形结束时Mises应力峰值和等效塑性应变峰值的位置是以上两方面综合作用的结果。在成形环件的变形区,环件表层金属处于三向压缩应力状态,中间层金属处于一向压缩、两向拉伸或者两向压缩、一向拉伸应力状态;整个环件处于一向压缩、两向拉伸应变状态。