CIELAB与CIECAM02色空间均匀性比较研究

采用均匀色空间Munsell系统检验和验证了CIELAB和色貌模型CIECAM02色空间的均匀性。利用Mun- sell色卡所对应的三刺激值X,Y,Z作为模型的输入值,预测色空间模型的明度、彩度和色调,并通过预测结果比较和检验了CIELAB色空间和CIECAM02模型色空间的均匀性。研究表明:在预测明度方面,两个色空间的结果相似;在预测彩度时,CIECAM02模型较好于CIELAB色空间;在预测色调时,当色调逐渐从BG变化到B时,CIELAB所预测的色调角与由Munsell色空间计算出来的色调角之差逐渐增大,最大时超过6%,而CIECAM02所预测的色调角与Munsell色空间的色调角之差在2.5%以内,CIECAM02优于CIELAB色空间。     

Blue emission from InGaN/GaN hexagonal pyramid structures

Cathodoluminescence (CL) from InGaN grown on GaN hexagonal pyramid structures has been investigated. The facet structure can be controlled by the growth temperature and reactor pressure. GaN pyramid structures surrounded with facets were grown at 1020 C at a pressure of 500 Torr by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). The indium mole fraction in the InGaN film depends on the facet structure. The thickness of the InGaN and the peak wavelength and intensity of the CL from the InGaN gradually increased from the bottom to the top of the facets.     

Ag3PO4溶解热力学函数的晶面效应与温度效应

在室温下制备了立方体{100}、 四面体{111}、 菱形十二面体{110}和块体Ag₃PO₄微晶, 并进行了表征. 测定了其在不同温度下水溶液中的电导率, 结合强电解质溶液和溶解热力学理论, 得到了Ag₃PO₄微晶的溶解热力学函数. 以具有不同晶面的Ag₃PO₄微晶为模型, 研究了纳米材料溶解热力学函数的晶面效应和温度效应. 结果表明, 具有{110}晶面的菱形十二面体Ag₃PO₄的标准摩尔溶解吉布斯自由能()、 标准摩尔溶解焓()和标准摩尔溶解熵()最大, 具有{100}晶面的立方体Ag₃PO₄次之, 具有{111}晶面的四面体Ag₃PO₄最小; 溶解平衡常数(K_{\mathrm{SP}})和随着温度的升高而增大.     

Investigation of thermal evolution of nanodomain structures in nonlinear barium sodium niobate crystals

By the 90°elastic light scattering investigation and far field observation in the range of 20-800℃,the relation between behavior of light scattering anomalies and evolution of nanodomain structures in lattice of barium sodium niobate(Ba2NaNb5O15,BSN)crystal was clarified.The correlation between anomalies on the temperature curves of the elastic light scattering intensity and temperature transformations of nanodomains was studied by X-ray and electron microscope methods.Phase transition near 500℃ and movement in field of scattering light could be explained by appearance of a new incommensurate phase.     

高功率二极管激光器失效特性研究

利用统计分析手段,对高功率二极管激光器封装中各工艺环节引起器件失效的原因进行了分析和归类.根据几种失效模式的分析结果,焊接空隙、结短路、腔面退化是引起高功率DL失效的主要模式,针对高功率二极管激光器失效的主要模式,对焊料沉积夹具及焊接工艺参数进行了改进和优化,大大提高了封装工艺水平,使封装的器件成品率由原来的77%提高到了85%以上.     

Size Effect of the Immediate Surround for the Border between the Natural and Unnatural Object Color Appearance

The border luminance of the test stimulus between the natural and unnatural object color, y_ynB_u was obtained for different spatial sizes of the immediate surround to prove that _nB_u can be determined based on a new recognized visual space of illumination (RVSI) that is assumed to be constructed for the immediate surround separately from the RVSI for the subjects room itself. The _nB_u of five test stimuli were determined for six different sizes covering from zero to 1866 cm² with four different lightnesses, N4, N6 and N8, while keeping the room illuminance constant at 100 or 600 lx. The results showed that luminance of the border _nB_u gradually decreased as the size of the immediate surround was increased and that the decrease was larger for immediate surround with lower lightness. The results were interpreted as showing a new RVSI constructed for the spatial extent of the immediate surround of the test stimulus, and the RVSI was more completely constructed for larger spatial size of the immediate surround. © 2005 The Optical Society of Japan     

A Color Appearance Model Applicable in Mesopic Vision

We propose a color vision model that can be used to predict color appearance in mesopic vision as well as photopic and scotopic vision. It is based on a two-stage model which consists of the cone and opponent stages and it assumes rod intrusion at the opponent stage. The model has the following features to describe the color appearance in mesopic vision. First, it includes a gradual and nonlinear shift in spectral luminous efficiency from V (LD) to V (LD) to cope with the spectral sensitivity difference between photopic and scotopic vision and the nonlinearity of rod influence on the luminance channel. Second, the model assumes decrease of the chromatic component with decreasing illuminance to explain the reduction of saturation at low illuminance levels. Third, it assumes that red/green and yellow/blue components change with illuminance levels independently, thus explaining hue shifts with decreasing illuminance. We applied the model for color appearance simulation of natural scenes in a mesopic visual environment.     

A nondestructive method for estimation of the fracture toughness of CrMoV rotor steels based on ultrasonic nonlinearity

The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K(IC)) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel. The nondestructive procedure for estimating the K(IC) consists of two steps. First, the correlations between the nonlinearity parameter and the FATT are sought. The FATT values are then used to estimate K(IC) using the K(IC) versus excess temperature (i.e., T-FATT) correlation that is available in the literature for CrMoV rotor steel.