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111.
本文提出基于切削振动相关性识别刀具磨损状态的研究思想,建立了车削中刀杆双向横振动系统及其单输入双输出系统的数学模型。理论和实验均表明,刀杆双向横振动之加速度响应在固有基频处的相干函数与刀具磨损状态之间有很好的规律性,它反映了两者之间的本质机理,并提供了识别刀具磨损状态的新途径。 相似文献
112.
本文研究了一种Zn-Ti合金新镀层,经盐水浸泡、中性盐雾和大气暴露试验结果试验,其耐蚀明显超过镀Zn层,并与镀Cd层相近,用缺口持久拉伸试验检验氢脆性,拉伸持续时间超过200h,达到原航空部部颁标准(HB5067-85),该镀层适用于高强度钢防护。 相似文献
113.
114.
在辽宁省工业城市进行 A3钢大气暴露试验。两年后测出不同地点腐蚀率。依据所记录的各试验点的气象数据和污染数据,讨论了 A3钢的大气腐蚀规律。 相似文献
115.
Addressing the potential for drop impact failure of Pb-free interconnects, the shear ductility after extensive aging of Sn-Ag-Cu
(SAC) solders has been improved radically by Co or Fe modifications. Several other SAC+X candidates (X=Mn, Ni, Ge, Ti, Si,
Cr, and Zn) now have been tested. Solder joint microstructures and shear strength results show that new SAC+X alloys also
suppress void formation and coalescence at the Cu (substrate)/Cu3Sn interface (and embrittlement) after aging at 150°C for up to 1,000 h. Microprobe measurements of 1,000 h aged samples suggest
that Cu substitution by X is usually accentuated in the intermetallic layers, consistent with X=Co and Fe results. 相似文献
116.
Multi-User MIMO Mobile CDMA Uplink System Employing Turbo Coding and Joint Detection Through a Multipath Rayleigh Fading Channel 总被引:1,自引:1,他引:0
Yasmine A. Fahmy Hebat-Allah M. Mourad Emad K. Al-Hussaini 《Wireless Personal Communications》2006,38(3):325-341
In this paper, a generalized multiple-input multiple-output (MIMO) antenna system that can be fitted to the uplink of a wireless communication system is considered for the general case of multi-user. At the transmitter, the information bits are Turbo coded, then interleaved and passed through a serial-to-parallel converter. The channel is assumed bad urban suffering from multipath Rayleigh fading resulting in inter-symbol and multiple access interferences (ISI and MAI). At the front-end of the receiver, a number of receiving antennas are used followed by a joint multi-user estimator based on the Minimum Mean Square Error Block Linear Equalizer (MMSE-BLE).Computer simulations demonstrate a significant performance improvement in both single user and multi-user cases.This paper depends in parts on that presented at the 11th European Wireless Conference, Cyprus, Nicosia, pp. 187–192, April 2005.
Yasmine A. Fahmy was born in Guiza, Egypt, on June 4, 1976. She received the B.Sc., M.Sc. and Ph.D. degrees in Communication and Electronics engineering from Cairo University, Egypt on 1999, 2001 and 2005 respectively. She is presently an assistant professor at Cairo University, Egypt. Her current field of interest is wireless communication and channel estimation.
Hebat-Allah M. Mourad received her B.Sc., M. Sc. and Ph.D. degrees in electrical communication engineering from Cairo University, Egypt, in 1983, 1987 and 1994 respectively. Since 1983, she has been with the Department of Electronics and Communications, Faculty of Engineering, Cairo University, and is currently associate professor there. Her research interests include optical fiber communications, mobile and satellite communications.
Emad K. Al-Hussaini received his B.Sc degree in Electrical Communication Engineering from Ain-Shams University, Cairo, Egypt, in 1964 and his M.Sc and Ph.D. degrees from Cairo University, Giza, Egypt, in 1974 and 1977, respectively. From 1964 to 1970, he was with the General Egyptian Aeroorganization. Since 1970, he has been with the Department of Electronics and Communications, Faculty of Engineering, Cairo University, and is currently professor there. He was a research fellow at Imperial College, London, UK, and at the Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA, in the academic years 1976/1977 and 1981/1982, respectively. In 1990, he received the Egyptian national encouragement award for outstanding engineering research. He has written several papers for technical international journals and conferences. His research interests include signal processing, fading channel communication, modulation, and cellular mobile radio systems. Dr Al-Hussaini is a senior member of IEEE. He is listed in Marquis Whos Who in the World and in the IBC (International Biographical Center, Cambridge) for outstanding people of the 20th century. 相似文献
117.
For environmental considerations, the substitution of the conventionally used oil-based grinding fluids has nowadays become strongly recommended. Although several alternatives have been proposed, cryogenic cooling by liquid nitrogen is the non-polluting coolant that has been given relatively more attention because of its very low temperature. In this investigation, in order to contribute to developing this promising cooling mode, its beneficial effects on the ground surface integrity of the AISI 304 stainless steel and their consequences on the fatigue lifetime are explored. Results of this investigation show that grinding under cryogenic cooling mode generates surfaces with lower roughness, less defects, higher work hardening and less tensile residual stresses than those obtained on surfaces ground under oil-based grinding fluid. These surface enhancements result into substantial improvements in the fatigue behaviour of components ground under this cooling mode. An increasing rate of almost 15% of the endurance limit at 2 × 106 cycles could be realized. SEM analyses of the fatigue fracture surfaces have shown that the fatigue cracks observed on the specimens ground under cryogenic cooling are shorter (i.e., 30-50 μm) than those generated under oil-based cooling mode (i.e., 150-200 μm). The realized improvements in the surface integrity and in the fatigue behaviour are thought to be related to the reduction of the grinding zone temperature observed under cryogenic cooling, as no significant differences between the grinding force components for both cooling modes have been observed. 相似文献
118.
V. E. Kahle 《Journal of Failure Analysis and Prevention》2006,6(4):23-28
Three reconditioned rail car couplers, arbitrarily identified as couplers, failed during service due to cracking of the front
face. The three couplers were reportedly upgraded by quenching and tempering to enhance strength and toughness. The objective
of this investigation was to determine the mode of crack propagation and the root cause of the observed failures.
Verl E. (Bud) Kahle, P.E., was a professional failure analyst for more than forty years. After receiving his Bachelor of Science
degree in physical metallurgy from Washington State University 1957, Bud was employed by the General Electric Company at a
facility in Hanford, Washington. He later was employed by the Aerojet General Corporation and eventually was head of the Southern
Pacific Materials Science Laboratory in Sacramento. After retirement from Southern Pacific he owned and operated his own firm,
Kahle Metallurgical Consulting Services, for fifteen years. He came to be known as “the man with the answers” to clients in
a variety of industries. Bud was a Life Member of ASM International.
Many of Bud’s clients remarked on the high quality of his failure analysis case histories and encouraged him to have them
published. After Bud passed away in 1999, his wife, Suzanne, approached ASM International to see if the society would be interested
in publishing any of his work. Mrs. Kahle was able to supply a large number of reports, which Bud had carefully archived over
the years. Journal of Failure Analysis and Prevention Associate Editor Michael Stevenson read through the collected case histories, selected the ones to be included in this issue,
and edited them for journal publication.
ASM International wishes to thank Mrs. Kahle for providing these case histories for publication. 相似文献
119.
机械锁定式测试技术操作简单,测试一次成功率高,资料录取准确全面,且测试结束后可直接进行封堵作业;解封时,机械锁紧产生一个向上的震击力,有利于解封,没有换位机构的测试阀在关井期间使管柱处于自由拉伸状态,有利于保护油管。在N阀上部管柱中加1-2根伸缩接头,便可用于海洋井测试。 相似文献
120.