The mechanics of compressive kinking in unidirectional fiber reinforced ductile matrix composites

Three distinct stages of kink band formation and propagation exist in ductile matrix composites subjected to compressive loading. These stages are called incipient kinking, transient kinking and kink band broadening. Each stage involves a different deformation mode. The mechanics governing each stage are discussed. Incipient kinking, where the peak load is attained, and kink band broadening, where the load attains a steady-state, are important in structural design. Two design philosophies are presented. References to pertinent literature are made throughout.     

Electrical and optical properties of fluorine-doped CdO films deposited by ultrasonic spray pyrolysis

The CdO:F samples have been deposited onto microscope glass substrates at 250 °C by ultrasonic spray pyrolysis method. With the incorporation of fluorine into CdO, the direct optical transition has shifted towards the shorter wavelengths, and the transparency of the material has increased at a given wavelength above the fundamental absorption edge. The shift in the absorption edge is explained by means of the Moss–Burstein effect, which is also supported with the results of the current–voltage characteristics. Here, a correlation has been established between the band broadening and the increase in conductivity due to the increase in carrier density.     

SiH4激光等离子体内H谱线的线型研究

本文利用OMA-Ⅲ系统测量了脉冲TEA CO_2激光诱发的SiH_4等离子体发光谱内H巴耳末系的H_α、H_β和H_γ线的线型及线宽。通过理论及实验分析,认为这些谱线的主要加宽机制为Stark加宽。由实验线型和理论线型的拟合得到等离子体的电子温度T≈40000K和电子密度N≈10~(17)cm~(-3)。     

Effects of calcination temperature on phase and microstructure evolution of BaTi4O9 powders

Calcining of the mixture of BaCO₃ and TiO₂ with a ratio 1:4 at different temperatures was carried out to synthesize BaTi₄O₉ powders. Phase evolution of the samples was studied using the differential thermal analysis (DTA) and X-ray diffractometry (XRD). Both techniques confirmed that the formation of BaTi₄O₉ started around 1000 °C. The XRD peaks showed that BaTi₄O₉ was most pronounced at 1250 °C. X-ray line broadening methods were employed to study the variation of particle size and microstrain of the BaTi₄O₉ powders. The Voigt function in a single line and the pseudo-Voigt function in the variance methods were used in our case. We found that both functions resulted in the same trends, i.e., the particle size increased with the temperature with the biggest size of 180 and 160 nm, whilst the microstrain yielded the opposite trend with the lowest values of 6.2 × 10^–3 and 1.1 × 10^–3. The scanning electron microscopy (SEM) study revealed the size of the large particles formed, due to agglomeration, to be about 0.5–1.9 μm. Furthermore, it was shown that irregular shapes of BaTi₄O₉ powders necked to each other appeared at 1000 °C and grew into ellipse and rod shapes at 1250 °C. Electronic Publication     

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al2O3

Coincidence Doppler broadening of annihilation radiation (CDBAR) and Vickers hardness techniques were performed to study pure Al₂O₃, pure polyvinyl chloride (PVC), and doped PVC with different concentrations of Al₂O₃ (10–50%). The CDBAR ratio curves with respect to pure PVC were presented and reflect the momentum distribution of all the samples. The peak around 14.5 ×10^?3 m_oC in the CDBAR ratio curves suggests a large contribution of positron annihilation with the Al₂O₃. There is a linear correlation between the height of this peak and the Al₂O₃ concentration. The S‐ and W‐parameters were extracted from the CDBAR spectra and increase with increasing the Al₂O₃ concentration showing discontinuity at 30% of Al₂O₃ concentration on PVC. The present data confirmed that there is no positronium formation in pure Al₂O₃ as a result of smaller S‐parameter. The Vickers hardness increases with increasing the Al₂O₃ concentration in PVC showing a linear dependence with two different slopes depend on the Al₂O₃ concentration range. A correlation between the Vickers hardness (macroscopic data) and the W‐parameter (microscopic data) was observed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

基于邻域彩色变化矢量场的图像边缘检测技术研究*

首先进行了边缘检测系统结构设计,建立了图像邻域彩色变化矢量场的数理模型,提出了用图像邻域彩色变化方向锐度描述图像边缘,进而应用模糊聚类自适应检测边缘.实验表明:与基于梯度的边缘检测技术相比,该方法在噪声抑制以及边缘准确定位上均取得了好的效果,是一种应用广泛的优秀边缘检测算法.     

图像质量快速盲检测及其在视觉系统中的应用

提出了一种新的图像质量快速盲检测方法,以锐利度作为图像质量准则,而锐利度可以归结为图像的模糊特性,并由边缘信息估计得到。为了提高系统效率,采用边缘对比度的估计方法,并以边缘对比度作为边缘锐利度的判据准则。分析了邻近边缘的相互影响,因而只需从有限的边缘点来提取出合理的线扩展函数(LSF),进而得到模糊参数。在LSF计算中,采用一种新的插值计算方法。实验结果表明:当图像不是特别模糊时,测量结果是准确的。     

拓展成人高等教育生源的思考

成人高等教育是我国高等教育的有机组成部分。由于受1999年以来高校持续扩招和国家对成人高等教育政策调整等影响,直接导致成人高等教育生源的萎缩。本文分析了成人高等教育生源下降的原因,并提出拓展成人高等教育生源的思考。     

光源谱宽通过光纤色散对AOCS输出的影响

基于光纤色散引起的脉冲展宽效应,在理论和实验上研究了有源光学电流传感器（AOCS）中宽带光源对系统输出的影响．理论结果表明：对于长度为500m的光纤,当光源谱宽在40—60nm之间变化时,多模光纤传输下的脉冲展宽范围在0．5～0．8ns,单模光纤传输下的脉冲展宽范围在2×10^-5～4×10^-5,信号衰减量对系统输出影响很小,且随光源谱宽的增加而有微弱的增加,实验与理论相符合．     

融合梯度信息与HVS滤波器的无参考清晰度评价

目的 目前无参考图像质量评价算法的性能存在较大的提升空间,为了提高清晰度评价技术,提出了一种基于梯度信息与HVS滤波器的无参考清晰度评价算法(GI-F)。方法 该算法首先利用梯度算子计算各像素点的梯度信息,再通过HVS滤波器得到加权和作为图像的清晰度指标。结果 在公开数据库LIVE、TID2008和CSIQ上进行的实验,GI-F与S3(Spectral and Spatial Sharpness)、CPBD(Cumulative Probability of Blur Detection)和LPC-SI(Local Phase Coherence-based Sharpness Index)相比,性能指标RMSE(Root Mean Squared Error)、PLCC(Pearson Linear Correlation Coefficient)和SROCC(Spearman Rank-Order Correlation Coefficient)分别提升了20.66%、4.61%和3.33%;同时GI-F还具有更低的计算复杂度,即使与目前最好的BRISQUE(Blind/Referenceless Image Spatial QUality Evaluator)算法相比,耗时也降低了79.72%。结论 该算法只需耗费更少的时间即可计算出与人眼感知更加接近的客观清晰度指标,可广泛用于无参考图像情况下的清晰度指标计算场合,同时还可以通过并行计算进一步降低其计算时间。