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排序方式: 共有8339条查询结果,搜索用时 15 毫秒
91.
评述了液相沉积(类)金刚石薄膜的研究现状,介绍了液相合成(类)金刚石薄膜的装置、液态源及薄膜的性能,分析了如何更好地提高(类)金刚石薄膜质量,并在此基础上提出了一种可能制备出高质量金刚石薄膜的脉冲电弧放电沉积装置. 相似文献
92.
类金刚石薄膜的折射率研究 总被引:1,自引:0,他引:1
利用脉冲真空电弧镀方法在硅基底上沉积类金刚石薄膜,研究薄膜折射率和工艺参数以及折射率与薄膜本征硬度的关系,结果表明:无氢类金刚石薄膜的折射率在2.5~2.7之间;不同的工艺参数可以得到不同折射率的薄膜;通过改变工艺条件来制备不同折射率的薄膜,和不同的基底材料的折射率匹配,使其有一定的机械强度。 相似文献
93.
The paper discusses mode locking use in pulsed lasers for precision measurement of large lengths. 相似文献
94.
C. M. BRANCO V. INFANTE R. BAPTISTA 《Fatigue & Fracture of Engineering Materials & Structures》2004,27(9):785-798
Rehabilitation of a welded structure, which involves repair of cracked joints, is achieved when the local treatment for repair gives a fatigue strength in the joint equal or above the fatigue strength of the uncracked original detail. If the treatment is properly applied the rehabilitation of the detail is assured, and the nature of the weld toe improvement methods can produce a joint, after repair, with a fatigue strength and residual life greater than the initial detail. The paper presents the results obtained on a fatigue study on the rehabilitation of non‐load carrying fillet welded joints loaded in bending at the main plate and with fatigue cracking at the weld toes of the attachment in the main plate and though the plate thickness. Residual stresses were measured at the surface, with X‐ray diffraction. The residual stresses induced by hammer peening at the weld toe were found to be greater along the longitudinal direction of the plate than in the transverse direction. The peak residual stresses near the weld toe were found to be close to yield in compression, justifying the great benefit of hammer peening. Results of a derived gain factor, g, in fatigue life were obtained as a function of the crack depth repaired by hammer peening. 相似文献
95.
A method of taking into account the fluctuation modulation of the reflected signal is proposed. This modulation leads to power losses in the functional processing of the signal in the channel of a single-pulsed direction finder. An algorithm of the functioning of a single-pulse direction finder with long-term coherent storage which eliminates these power losses is developed. 相似文献
96.
97.
The existence of spectro-temporal receptive fields and evidence for population coding in auditory cortex motivate the development
of such models, that explicitly operate in the time-frequency domain and are based on a pulsed neural network. In presenting
such a model, a formal connection of the fields of Time Frequency Analysis and Pulsed Neural Networks is established. The
resulting neural time-frequency signal representation is shown to be representable as a signal-dependent overcomplete dictionary.
It is derived from neural population coding. Signal decomposition and filtering effects are presented, indicating obvious
technical applications of the proposed model.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
98.
WU Junfeng CHEN Shanben ZHANG Mingjun 《机械工程学报(英文版)》2007,20(5):32-36
The robust control law for gas tungsten arc welding dynamic process, which is a typical sampled-data system and full of uncertainties, is presented. By using the Lyapunov second method, the robust control and robust optimal control for a class of sampled-data systems whose underlying continuous-time systems are subjected to structured uncertainties are discussed in time-domain. As a result, some sufficient conditions of robust stability and the corresponding robust control laws are derived. All these results are designed by solving a class of linear matrix inequalities (LMIs) and a class of dynamic optimization problem with LMIs constraints respectively. An example adapted under some experimental conditions in the dynamic process of gas tungsten arc welding system in which the controlled variable is the backside width of weld pool and controlling variable pulse duty ratio, is worked out to illustrate the proposed results, it is shown that the sampling period is the crucial design parameter. 相似文献
99.
后热温度对1000MPa级高强钢焊缝组织与性能的影响 总被引:3,自引:0,他引:3
采用GHS90高强焊丝为填充材料对1 000 MPa级工程机械用高强钢进行熔化极活性气体保护(Metal active gas,MAG)焊,并对接头进行250℃、480℃、600℃保温2 h的焊后热处理。通过拉伸试验、显微硬度测试、光学显微镜(Optical microscope,OM)、扫面电镜(Scanning electron microscope,SEM)、透射电镜(Transmission electron microscopy,TEM)及电子背散射衍射(Electron back-scattered diffraction,EBSD)观察不同热处理温度后的焊缝微观组织及力学性能进行对比研究。结果表明,随后热温度从250℃升高到600℃,接头抗拉强度从1 014.5 MPa降低到934.5 MPa;焊缝平均冲击吸收能量从66 J降低到24 J;随后热温度升高,焊缝板条组织粗化,碳化物析出长大且连续分布是导致焊缝韧性降低的原因之一;同时焊缝有效晶粒尺寸变大和大角度晶界密度降低也是导致其韧性降低的原因。 相似文献
100.