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基于JJG 147-2005《标准金属布氏硬度块》以及JJF 1059.1-2012《测量不确定度评定与表示》,给出了一种间接评定标准金属布氏硬度块测量不确定度的新方法。建立了硬度测量的新模型,并对该测量模型进行了较严密的分析,剔除了间接评定时,各耦合项对不确定度的重复贡献。按规程的测量条件和方法,以(125~225) HBW10/3000标尺标准块为例,对其测量不确定度进行了系统的间接评定。 相似文献
73.
针对超声波探伤试块表面裂纹长度、宽度及深度测量中遇到的测量难题.详细介绍用于长度测量的拓膜法胶样制作的标准流程.并对结果进行测量不确定度分析和测量数据验证。 相似文献
74.
空客针对龙骨梁主起舱门作动筒接头有可能产生裂纹的问题下发服务通告,提出需要对主起舱门作动筒接头进行无损检测。本文介绍了采用超声波仪器进行此检测的操作方法,并对操作中遇到的一些难点进行具体分析。 相似文献
75.
Jet Vectoring Control Using a Novel Synthetic Jet Actuator 总被引:3,自引:1,他引:2
LUO Zhen-bing XIA Zhi-xun XIE Yong-gao 《中国航空学报》2007,20(3):193-201
A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems. 相似文献
76.
Electro-hydrostatic actuator (EHA) pumps are usually characterized as high speed and small displacement. The tilting inertia moment on the cylinder block produced by the inertia forces of piston/slipper assemblies cannot be ignored when analyzing the cylinder block balance. A large tilting inertia moment will make the cylinder block tilt away from the valve plate, resulting in severe wear and significantly increased leakage. This paper presents an analytical expression for the tilting inertia moment on the cylinder block by means of vector analysis. In addition, a high-speed test rig was built up, and experiments on an EHA pump prototype were carried out at high speeds of up to 10,000 r/min. The predicted nature of the cylinder block tilt at high speeds corresponds closely to the witness marks on the dismantled EHA pump prototype. It is suggested that more attention should be given to the tilting inertia moment acting on the cylinder block of an EHA pump since both wear and leakage flow between the cylinder block and the valve plate are very much dependent on this tilting moment. 相似文献
77.
Caiya Yue Yamin Dang Huayang Dai Qiang Yang Xiankai Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(8):2180-2189
In order to obtain deformation parameters in each block of Sichuan-Yunnan Region (SYG) in China by stages and establish a dynamic model about the variation of the strain rate fields and the surface expansion in this area, we taken the Global Positioning System (GPS) sites velocity in the region as constrained condition and taken advantage of the block strain calculation model based on spherical surface. We also analyzed the deformation of the active blocks in the whole SYG before and after the Wenchuan earthquake, and analyzed the deformation of active blocks near the epicenter of the Wenchuan earthquake in detail. The results show that, (1) Under the effects of the carving from India plate and the crimping from the potential energy of Tibetan Plateau for a long time, there is a certain periodicity in crustal deformation in SYG. And the period change and the earthquake occurrence have a good agreement. (2) The differences in GPS velocity fields relative Eurasian reference frame shows that the Wenchuan earthquake and the Ya'an earthquake mainly affect the crustal movement in the central and southern part of SYG, and the average velocity difference is about 4–8?mm/a for the Wenchuan earthquake and 2–4?mm/a for the Ya'an earthquake. (3) For the Wenchuan earthquake, the average strain changed from 10 to 20 nanostrian/a before earthquake to 40–50 nanostrian/a after the earthquake, but before and after the Ya’an earthquake, the strain value increased from about 15 nanostrian/a to about 30 nanostrian/a. (4) The Wenchuan earthquake has changed the strain parameter of each active block more or less. Especially, the Longmen block and Chengdu block near the epicenter. The research provides fundamental material for the study of the dynamic mechanism of the push extrusion from the north-east of the India plate and the crimp from Qinghai Tibet Plateau, and it also provides support for the study of crustal stress variation and earthquake prediction in Sichuan Yunnan region. 相似文献
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研究了线性变参数系统的鲁棒变增益控制,介绍了基于LFT的鲁棒变增益控制的思想;针对目前基于LFT的鲁棒变增益控制的保守性,采用全块标量矩阵,通过减少对全块标量矩阵的结构约束;提出了一种保守性更小的稳定性判据,并且利用消元定理,给出了基于LFT的鲁棒变增益的输出反馈控制器存在的条件;同时给出了控制器的构建方式,并且给出了... 相似文献