变电运行动态培训仿真系统的研制

本文重要介绍用于电气运行人员培训的动态仿真专家系统的设计思想、实现方法及其应用效果。     

车床应力断料辅具的设计及动态特性研究

介绍了一种能够应用于车床的应力断料辅具的结构及工作原理,通过pro/e三维实体建模,并在ADAMS软件中进行动力学仿真获得了关键部件的动态性能参数,证明了机构设计的合理性.     

逻辑阀概述

对逻辑阀的特性、参数进行了总结,介绍了逻辑阀的使用方法和注意事项.     

常规定量的理想选择——安捷伦6420三重串联四极杆液质联用仪

本文主要介绍了安捷伦6420三重串联四极杆液质联用仪的的性能特点。重点介绍了6420的可升级功能,触发式多反应监测功能和动态多反应监测功能,以及这些功能所能带来的优势。并指出了6420所针对的应用领域。     

Adaptive Online Voltage Scaling Scheme Based on the Nash Bargaining Solution

In an effort to reduce energy consumption, research into adaptive power management in real‐time systems has become widespread. In this paper, a novel dynamic voltage scaling scheme is proposed for multiprocessor systems. Based on the concept of the Nash bargaining solution, a processor's clock speed and supply voltage are dynamically adjusted to satisfy these conflicting performance metrics. In addition, the proposed algorithm is implemented to react adaptively to the current system conditions by using an adaptive online approach. Simulation results clearly indicate that the superior performance of the proposed scheme can strike the appropriate performance balance between contradictory requirements.     

An asymptotic analysis of dynamic crack growth in rubber

Asymptotic analyses of the mechanical fields in front of stationary and propagating cracks are important for several reasons. For example, they facilitate the understanding of the mechanical and physical state in front of crack tips, and they enable prediction of crack growth. Furthermore, efficient modelling of arbitrary crack growth by use of XFEM (extended finite element method) requires accurate knowledge of the asymptotic crack tip fields. The present study focuses on the asymptotic fields in front of a crack that propagates dynamically in rubber. Static analyses of this type of problem have been made in previous studies. In order to be able to compare the present results with these earlier studies, the constitutive model from Knowles and Sternberg (J. Elast. 3:67–107, 1973) was adopted. It is assumed that viscoelastic stresses become negligible compared with the singular elastic stresses close to the crack tip. The present analysis shows that in materials with a significant hardening, the inertia term in the equations of motion becomes negligible in the asymptotic analysis. However, for a neoHookean type of model, inertia comes into play and causes a maximum theoretical crack speed that equals the shear wave speed.     

Deformation band and texture of a cast Mg-RE alloy under uniaxial hot compression

Microstructural evolution and texture of a cast Mg-9Gd-4Y-0.6Zr ingot under hot compression were studied in this paper. Post-deforming microstructures were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy, while crystallographic orientation information was obtained from X-Ray macro-texture measurement and EBSD micro-texture analysis. Dynamic recrystallization (DRX) initiated from the deformation bands (DB) forming on original grain boundaries; the DB became widen with continuously conversion of low-angle-boundary grains into high-angle-boundary grains. The tendency of strain localization increased with Z parameter. The macro-texture analysis indicates that uniaxial compression yielded out the randomized basal texture component. This texture component was found to be strengthened with increasing Z parameter. The micro-texture analysis shows that the deviation from the ideal basal texture arose from orientated growth within DBs. Moreover, the localization deformation promoted dynamic precipitation within DBs, which inhibited the development of DRX.     

Sequence Algebra, Sequence Decision Diagrams and Dynamic Fault Trees

A large attention has been focused on the Dynamic Fault Trees in the past few years. By adding new gates to static (regular) Fault Trees, Dynamic Fault Trees aim to take into account dependencies among events. Merle et al. proposed recently an algebraic framework to give a formal interpretation to these gates.In this article, we extend Merle et al.'s work by adopting a slightly different perspective. We introduce Sequence Algebras that can be seen as Algebras of Basic Events, representing failures of non-repairable components. We show how to interpret Dynamic Fault Trees within this framework. Finally, we propose a new data structure to encode sets of sequences of Basic Events: Sequence Decision Diagrams. Sequence Decision Diagrams are very much inspired from Minato's Zero-Suppressed Binary Decision Diagrams. We show that all operations of Sequence Algebras can be performed on this data structure.     

Dynamic leg volume changes when sitting in a locked and free floating tilt oé ce chair

It is well established that prolonged sitting may lead to swelling of the lower extremities. However, activation of the vein pump system by repeated walking breaks or dynamic tiltable foot-rests have been shown to reduce foot and leg oedema. Some oé ce chairs incorporate tilt mechanisms facilitating movements of the body from the feet up. The present study was undertaken to establish whether a beneficial effect on the transcapillary fluid balance of the legs by enabling such mechanisms could be documented. An oé ce chair where the tilt mechanism could be locked or open was used for the study. The seat position and seat activity level was recorded by a transducer system developed for the study. Calf volume and calf muscle pump activity was detected by mercury strain gauge plethysmography. In the locked position there was a steady increase in volume of mean=1.2% (range=0.8–1.8%) for all participants in the 30-min study period. On the other hand, for all participants there was a decrease in calf volume (mean=0.7%, range=0.1–1.2%, p=0.008) when the tilt mechanism was open (30-min period), irrespective of what study period came first. The study showed that upward seat deflection was not associated with concomitant venous obstruction, since such obstruction was detected in less than 2% of the time period with more than 50% of maximal upward deflection. A locked seat mechanism does not prevent activation of the vein pump mechanism, but the study indicates that oé ce chairs that permit variation in seat angle per se stimulate movements of the leg. This, in turn, activates vein pumps and counteracts local oedema formation in seated working postures.     

SOME RELATIONSHIPS OF ISOMETRIC STRENGTH,ISOTONIC STRENGTH,AND ANTHROPOMETRIC MEASURES

The purpose of this study was to investigate the relationship between isometric strength scores, the ability to lift weights before and after a weight training programme, and selected anthropometric measurements in untrained men. The subjects significantly increased the amount of weight they could handle in the training exercises, but there was no accompanying increase in the isometric tension they could exert, and correlations between measurements of arm size and strength were not significant. Weight was the most important determinant of arm size and arm strength, but the correlations involved were too low to justify the usual assumption that the bigger the man the stronger.