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排序方式: 共有433条查询结果,搜索用时 15 毫秒
41.
《核技术(英文版)》2016,(6):168-174
Abstracts High-accuracy position monitoring of key components is required for modern synchrotron sources, such as free-electron lasers and diffraction-limited storage rings. Although various position monitoring sensors have been adopted to monitor the displacement of key compo-nents in each direction in real time, these monitoring sys-tems are usually based on their own coordinate system. Data from such systems are meaningful when evaluating and examining the data from each positioning monitoring system in a unified coordinate system. This paper presents the design and construction of a multi-sensor position monitoring system (MPMS). A hydrostatic levelling sys-tem, a wire position sensor (WPS) and a tiltmeter are fixed to a stainless steel plate that has been calibrated by a coordinate-measurement machine. Several plates form the MPMS. The system must compensate for the sag of the stretched wires so that the WPSs create a straight line. The method of the coordinate transformation from the sensor coordinate system to the MPMS coordinate system was thoroughly studied. An experimental MPMS that includes five plates was setup in a 20-m tunnel, and a validation study to verify fully the feasibility of the MPMS was performed. 相似文献
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介绍了大力值标准测力机中使用的一种新型静压润滑原理的工作缸塞系统。由于油缸不转动,其有效长度得以减少,从而使工作油缸和活塞的超精加工成为现实。这种带有高压密封和零压槽的缸塞结构,还有助于消除工作油压控制的波动而造成的力值波动,从而可以改善液压式标准测力机的计量性能。实验表明,使用静压缸塞系统的20MN基准测力机,其力值不确定度优于0.01%,而灵敏阀优于0.001%。 相似文献
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Effect of heat-treatment and hydrostatic loading upon the poro-elastic properties of a mortar 总被引:1,自引:0,他引:1
This contribution aims at identifying experimentally the poro-elastic properties of a cement-based material under different levels of confining pressure, and after a heat-treatment up to 400 °C. The model material used is a normalized mortar, with a (W/C) ratio of 0.5. After a given heating/cooling cycle, drained bulk modulus Kb, solid matrix bulk modulus Ks and Biot's coefficient b are measured at different confining pressure levels (with a maximum of 25 MPa).Results show that under drained conditions, mortar stress-strain relationship evolves with increasing heat-treatment temperature from linear elastic with brittle failure (up to 105 °C heat treatment) to plastic and ductile (from 200 °C and above). Plastification testifies of material degradation under gradual confining pressure. At the microstructure scale, this is attributed to thermal damage after heat treatment above 105 °C, which consists mainly in various micro-cracking. This leads to easier failure of solid skeleton bridges (or trabecules), and to pore network collapse. Concomitantly to this, at given confining pressure Pc, secant drained bulk modulus Kb decreases monotonously, for heat-treatment temperatures above 105 °C. On the opposite, at given heat-treatment temperature above 105 °C, secant drained bulk modulus Kb increases when confining pressure is increased. This testifies of a solid matrix rigidification in the elastic domain, and it is attributed to increased skeleton compactness linked with pore network collapse. This is directly attributable to heat treatment followed by confinement.At given confining pressure Pc, matrix bulk modulus Ks and Biot's coefficient b increase with heat-treatment temperature above 105 °C. The increase in b means that mortar becomes less and less cohesive and more and more of a granular nature. Moreover, Biot's coefficient b and solid matrix bulk modulus Ks are independent of confining pressure Pc for intact mortar, whereas they decrease for heat-treated mortars when Pc increases. From literature analysis alone, it was quite unexpected that after heat treatment, Ks should vary under confinement. This is interpreted as the closure, under confining pressure, of micro-void connections and of micro-cracks created by heat-treatment. Therefore, increasing confinement induces more and more occluded pores in the solid matrix, whereby Ks diminishes. 相似文献
46.
本文介绍了一种新型的模块化自升降脚手架遥控系统,该系统采用无线遥控模块实现提升过程控制,克服了普通自升降脚手架控制系统控制器过大,控制不灵活的缺点.对系统进行了可靠性分析,给出了遥控器和提升控制器原理图,程序流程图. 相似文献
47.
ZHAO Ming HUANG Zhengdong LI Bin CHEN Liping 《机械工程学报(英文版)》2007,20(5):16-22
Aiming at the approximate error of commonly used methods on calculation of hydrostatic pressures of closed hydrostatic guideways with multiple pockets, a more accurate solution is proposed. Taking design of beam & slide-rest guideways for a heavy duty CNC vertical turning mill as an example, under an assumption that stiffnesses of guideways and their jointing structure are sufficiently large, the pressures of the pockets can be attained by adding a co-planarity equation that con strains pocket centers. Then, an optimization model is built to minimize the highest pocket pressure under additional constraints that are posed on the highest seal margin pressure, the highest levitating pressure of the pockets, and the maximum deformation of the guideways. The optimization problem is solved sequentially by using the methods of design of experiments and adaptive simulated annealing on iSIGHT software platform. The results show significant improvements to the original design. Optimized maximum hydrostatic pressure meets the requirement of hydraulic system. 相似文献
48.
二次调节静液驱动系统的智能PID控制 总被引:9,自引:1,他引:8
针对二次调节静液驱动系统的特点,基于常规的PID控制方法,设计了一种简单的智能PID控制器,试验研究表明,智能PID控制器能改善系统的动态性能,提高系统的抗参数变化能力。 相似文献
49.
提出了一种基于液压伺服控制节流的静压推力油膜轴承的新型可控节流方式,建立了该节流方式下静压推力轴承的流量连续性方程、轴承-主轴系统动力学方程。利用MATLAB中的SIMULINK进行了仿真计算,并将该节流方式与毛细管节流进行了全面对比。研究结果表明:基于液压伺服控制节流的静压推力油膜轴承具有更优越的性能,如能够控制油膜厚度,轴向定位精度更高,动态过渡过程更短,稳定性更好,油膜刚度更大,抗冲击能力更强,更适合于高速、重载等极端工况。 相似文献
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