Nondestructive evaluation of the characteristics of degraded materials using backward radiated ultrasound

The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris’ law that can predict the crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion.     

A novel cyclic process using CaSO4/CaS pellets for converting sulfur dioxide to elemental sulfur without generating secondary pollutants: Part II. Hydrogen reduction of calcium-sulfate pellets to calcium sulfide

The reduction of calcium sulfate to produce calcium sulfide is a part of the cyclic process for converting sulfur dioxide to elemental sulfur that is described in Part I. The kinetics of the hydrogen reduction of nickel-catalyzed calcium-sulfate pellets were investigated using a thermogravimetric analysis (TGA) technique at reaction temperatures between 1023 and 1088 K and hydrogen partial pressures between 12.9 and 86.1 kPa. The reactivity of nickel-catalyzed calcium-sulfate pellets was demonstrated by the conversion of 70 pct fresh nickel-catalyzed calcium sulfate to calcium sulfide in 20 minutes at 1073 K under a hydrogen partial pressure of 86.1 kPa. Furthermore, the reactivity remained relatively intact after ten cycles of reactions and regenerations. This observed characteristic of the pellets is important because the solids must be reusable for repeated cycles to avoid generating secondary pollutants. The nucleation and growth rate expression was found to be useful in describing the kinetics of the reaction, which had an activation energy of about 167 kJ/mol (∼40 kcal/mol) in all reaction cycles except for the first regenerated samples that were lower at 146 kJ/mol (35 kcal/mol). The reaction order with respect to hydrogen partial pressure was 0.22 in all cycles with the exception of the first regenerated sample for which it was 0.37.     

Effects of extended dislocations on charge distribution in GaN epilayer

We have investigated the effect of extended dislocations (0.5-3 μm) on charge distribution in GaN epilayer grown by metalorganic chemical vapor deposition on (0001) sapphire using atomic force microscopy (AFM) and scanning surface potential microscopy (SSPM). It has been observed for the surface at the extended dislocations present in undoped GaN film to be negatively charged showing 0.04-0.2 V higher potential relative to regions that contain no dislocations. In addition to the higher potential at the dislocation core, the surrounding surfaces, including the edge of the dislocations, are also negatively charged in a symmetric way around the dislocations revealing crater-shaped higher potential regions (∼0.04 V) relative to surrounding dislocation-free area. The experimental results show that the protrusion-type of dislocation is also negatively charged and its potential is dependent on the size of dislocation.     

基于公钥加密算法和PPCT动态图编码的软件指纹方案

提出了一种综合PPCT动态图编码方法和椭圆曲线加密算法的软件指纹方案,该方案将公钥加密技术和软件水印技术综合应用于软件版权的保护和验证过程中,充分利用两者的优势,具有安全性高和抗恶意篡改能力强的特点.     

Novel T-rail electrodes for substrate removed low-voltage high-speed GaAs/AlGaAs electrooptic modulators

A novel traveling-wave electrode utilizing capacitively loaded T-rail elements was developed for low-voltage high-speed substrate-removed GaAs/AlGaAs electrooptic modulators. Electrodes with varying dimensions were fabricated and characterized. Electrode phase velocity, characteristic impedance, loss coefficient, and capacitive loading were extracted from the measured s-parameters up to 40 GHz. Electrode was also simulated using a finite-element solver. The measured and calculated electrode capacitance values were found to be in excellent agreement, showing that the electrode can be precisely designed. Approaches were outlined to provide a group velocity-matched very high-speed modulator electrode suitable for a low drive-voltage substrate-removed GaAs/AlGaAs electro-optic modulator     

Holographic polymer‐dispersed liquid crystal fabrication under electric field

The transmission mode of holographic polymer‐dispersed liquid crystals (HPDLCs) was developed an under electric field. It is reported that orientation of LC molecules under an electric field induces orientation of oligomer molecules giving rise to low off‐state diffraction and small grating shrinkage. Copyright © 2005 Society of Chemical Industry     

首钢烧结配加扬地粉试验研究

介绍了首钢原料条件下配加扬地粉对烧结生产影响的实验室研究.随着扬地粉配入量的增加,烧结矿转鼓强度、成品率改善,燃耗有少量上升,利用系数增加,低温还原粉化指数变差.研究结果表明:在首钢目前条件下,配入10%～20%的扬地粉是可行的.二烧车间进行了扬地粉工业试验,其最高配比达到30%,工业试验时烧结各项指标变化与实验室试验结果基本一致.     

在LabVIEW程序运行中实现控件的动态移动

通过两种在LabVIEW程序运行中实现控件移动的方法的对比,着重介绍了结合了VI Sever技术的动态注册事件结构的用法,从而总结出其具有优化程序、减少内存、提高CPU利用率等方面的优点.     

Effects of gallia additions on sintering behavior of gadolinia-doped ceria

The effects of gallia additions on the sintering behavior of gadolinia-doped ceria were systematically investigated from the following aspects: the variation in sintered density, the variation in grain size, and the existing forms of Ga₂O₃ in CeO₂.Sintered density increased with increasing Ga₂O₃ content up to 5 mol.% and then it decreased with further addition of Ga₂O₃. Grain size also increased with increasing Ga₂O₃ content up to 5 mol.% and then decreased with further addition of Ga₂O₃. Decrease in grain size was caused by a pinning effect of Ga₂O₃ precipitation at grain boundaries. Lattice constant decreased with increasing Ga₂O₃ content up to 5 mol.%. This decrease will be due to the substitution of smaller Ga³⁺ ions for Ce⁴⁺ ions in the CeO₂ structure. According to the results obtained from scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses, the solubility limit of Ga₂O₃ in Ce_0.8Gd_0.2O_1.9 ceramics can be estimated to be nearly 5 mol.%. The addition of Ga₂O₃ up to the solubility limit was found to promote the sintering properties of Gd₂O₃-doped CeO₂.