用强度系列成象法获取或显示高动态范围图象

提出一种适合于高动态范围图象的获取和显示的强度系列成象法。改变输入图象的强度，微机控制的图象采集系统进行记录得到一组磁盘文件，形成强度图象系列。基于记录的系列图象，可以进行信息提取、变换和显示等操作。基于获得的图象系列，提出一种剪贴操作进行快速的非线性图象变换。给出对光学功率谱处理的一个实例，它相当于进行锯齿形的非线性变换。     

Failure analysis of aluminum cable steel reinforced (ACSR) conductor of the transmission line crossing the Paraná River

The failure of the conductor of the 460 kV overhead transmission line located along the crossing of the Paraná River was investigated. As a result of this failure, a blackout took place in the southern states of Brazil in January of 2002, reaching approximately 67 million inhabitants. Investigation of the external aluminium layer of the ACSR conductor near the fracture showed typical static deformation marks and dynamic fretting wear tangential marks, both associated with the presence of Al₂O₃ debris. Additionally, encrusted silicon particles were observed on the external surface of the strands. The internal Al layer showed elliptical deformation marks also associated with Al₂O₃ debris. Both Al₂O₃ and Si particles are efficient abrasive material, which associated with slight relative motion of metallic surfaces (clamp/strand and strand/strand) can promote fretting wear. Two types of fracture surface of the Al strands were identified: 45° and quasi-normal surfaces, the former being the predominant type. Delamination and particle detachment were the mechanisms of superficial degradation observed on the Al strands, indicating that the rupture of the strands occurred under a gross slip fretting regime induced by sub-conductor oscillation. Inspection of the internal surface of as-cast Al–10%Si spacer clamps revealed different stages of intense circumferential wear caused by the preferential cracking and particle detachment of the eutectic constituent of the as-cast microstructure. This intense wear reduces the clamping contact pressure, which allows higher displacement amplitude and leads to the critical fretting regime. Finally, a few suggestions are discussed to minimise the occurrence of future failures.     

Micro-Analysis of the Contact Zone of Tribologically Loaded Second-Phase Reinforced Sol-Gel-Abrasives

Abrasives manufactured via the Sol-Gel route have increased the grinding efficiency of conventional abrasive grinding tools to a remarkable degree in the past ten years. Little is known, however, about detailed wear mechanisms of the abrasive on a nanometer scale. Sliding tests on a pin-on-disk tribometer and single grit scratching tests have therefore been performed in order to identify the wear mechanisms of these innovative materials. TEM-analysis has revealed that severe plastic deformation combined with both crack bridging and crack deflecting effects in the second phase characterise the abrasive rim zone. The surface of the abrasive is covered with an oxide debris layer which substantially improves the tribological behaviour.     

Semiparametric Estimation in Time‐Series Regression with Long‐Range Dependence

Abstract. We consider semiparametric estimation in time‐series regression in the presence of long‐range dependence in both the errors and the stochastic regressors. A central limit theorem is established for a class of semiparametric frequency domain‐weighted least squares estimates, which includes both narrow‐band ordinary least squares and narrow‐band generalized least squares as special cases. The estimates are semiparametric in the sense that focus is on the neighbourhood of the origin, and only periodogram ordinates in a degenerating band around the origin are used. This setting differs from earlier studies on time‐series regression with long‐range dependence, where a fully parametric approach has been employed. The generalized least squares estimate is infeasible when the degree of long‐range dependence is unknown and must be estimated in an initial step. In that case, we show that a feasible estimate which has the same asymptotic properties as the infeasible estimate, exists. By Monte Carlo simulation, we evaluate the finite‐sample performance of the generalized least squares estimate and the feasible estimate.     

现行规范对“锁住区”起点高度简化处理的影响

通过工程实例及理论分析 ,对横向风振“锁住区”问题进行了探讨 ,对《建筑结构荷载规范》(GB5 0 0 0 9— 2 0 0 1 )中有关这一方面内容存在的一些问题进行了分析 ,希望对工程设计人员能有所帮助     

冲击噪声背景下的近场源二维参数估计方法

本文针对背景噪声为冲击噪声的情况,提出了一种新的近场源二维参数估计方法.本方法利用协变异(或协变异系数)构造矩阵,并通过求根的方法估计近场源的方向角和距离参数.该算法可以抑制冲击噪声对估计性能的影响,同时具有无需谱峰搜索的优点.仿真实验证明了该算法的有效性.     

Influence of protein and lipid concentration of the test lubricant on the wear of ultra high molecular weight polyethylene

To gain a better understanding of the ultra-high molecular weight polyethylene (UHMWPE) wear mechanism in the physiological environment, the effects of protein and lipid constituents of synovial fluid on the specific wear rate of UHMWPE were examined experimentally. The multidirectional sliding pin-on-plate wear tester was employed to simulate the simplified sliding condition of hip joint prostheses. Bovine serum γ-globulin and synthetic l--DPPC were used as model protein and lipid constituents of synovia, respectively. Results of the wear test indicated that the UHMWPE wear rate primarily depended on the protein concentration of the test lubricant. Lipids acted as a boundary lubricant and reduced polyethylene wear in the low protein lubricants. However, the polyethylene wear rate increased with increasing lipid concentrations if the protein concentration was within the physiological level. Increased interactions between protein and lipid molecules and lipid diffusion to polyethylene surface might be responsible for the increased wear.     

Threshold and growth mechanism of fatigue cracks under mode II and III loadings

ABSTRACT The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔK_IIth. The relationship ΔK_IIth > ΔK_Ith caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory‐roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both mode II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory‐roofs were formed by crack branching into mode I. Crack branching started from small semi‐elliptical cracks nucleated by shear at the tip of the original circumferential crack.     

亚毫米波系统探测距离分析

本文提出了距离的概率分布函数作为系统的性能指标，提高了系统评价的准确性。     

一种新型陶瓷材料及其耐磨性

对新型Ａｌ２Ｏ３－ＴｉＣ－Ｃｏ陶瓷的磨粒磨损，冲蚀磨损及其在单颗粒作用下的摩擦磨损行为进行了研究。与ＡＴ３０（７０ｗｔ％Ａｌ２Ｏ３－３０ｗｔ％ＴｉＣ）陶瓷相比，Ａｌ２Ｏ３－ＴｉＣ－Ｃｏ陶瓷具有更为良好的耐磨性，金属钴的存在提高了基体的韧性，细化了晶粒，其综合力学性能得到了显著提高，ＡＴＣ陶瓷样品耐磨性与其强韧化水平和细致的组织结构有关。