深圳城市气溶胶物理光学特性的观测研究

气溶腔是影响气候变化和空气污染的重要因子,在深圳地区展开气溶胶观测实验,可以获得可靠的光学物理特征,进而有助于准确评估气溶胶在新型超极城市区域的气像和环境效应,本文利用2010年12月至2011年8月太阳光度计、黑碳和浊度计等气溶胶观测资料,分析了新型超级城市深圳地区的气溶胶物理光学特性,深圳地区气溶胶呈明显季节变化,冬、春季由于城市污染性气溶胶的影响,气溶胶光学厚度和Angstrom波长指数都较大,夏季受海盐气溶胶的影响,光学厚度较小Angstrom波长指数也较小,光学厚度与Angstrom波长指数对比表明城市综合性污染是引起深圳气溶胶高光学厚度的主要原因,深圳地区气溶胶的散射系数、吸收系数的平均值(标准偏差)分别为178.7×10-6 m-1 (126.6×10-6m-1和32.5×1O-6m 1 (18.1×10-6m1),均低于珠三角腹地多年观测平均值的二分之一和国内其他大型城市观测值,而单次散射反照率为0.81,与珠三角其他地区得到的结果接近.此外,气溶胶吸收、散射和单次散射反照率呈明显日变化,可能主要受大气边界层变化的影响.     

Structural and electronic properties of cobalt carbide Co2C and its surface stability: Density functional theory study

Density functional theory calculations have been performed to investigate the structural and electronic properties of bulk Co₂C and the stability of low index Co₂C surfaces. We found that the formation of Co₂C is exothermic with the formation energy of ? 0.81 eV/Co₂C with respect to Co under the presence of syngas (mixture of CO and H₂). While formed Co₂C can be decomposed further to metal Co and graphite carbon with modest energy gain of 0.37 eV/Co₂C. This suggests that Co₂C is only metastable in Fischer–Tropsch synthesis, which agrees well with experimental findings. The density of states (DOSs) reveals that the Co₂C is paramagnetic and strong metallic-like. The difference of charge density analysis indicates that the bond of Co₂C is of the mixtures of metallic, covalent, and ionic properties. A variety of low index Co₂C surfaces with different terminations are studied. We find that the surface energy of low index stoichiometric Co₂C highly relies on the surface area, the number of coordination of surface atoms and the surface dipole, with the decreased stability order of (101) > (011) > (010) > (110) > (100) > (001) = (111). Our results indicate that under Co-poor condition, the formation of non ? stoichiometric surface (011) and (111) without terminated cobalt is energetically more favorable, while under Co-rich condition the formation of non ? stoichiometric (111) surface with cobalt overlayer are preferential.     

An effective method for evaluating the image-sticking effect of TFT-LCDs by interpretative modelling of optical measurements

The conventional method of evaluating the image-sticking effect of a LCD module is inspection by sight, because the residual optical difference between two stressing areas is small and viewing angle-dependent, so that it is difficult to obtain a significant optical difference value by instrumental measurement. We propose an effective method for evaluating the image-sticking effect of a TFT-LCD module by directly measuring its time evolution of transmission with the TFT glass turned off after a period of pattern stress. In this way, the liquid crystal system under charge equilibrium in constant-charge mode shows a dramatically amplified optical difference. Further, we interpret the measured results by a modelling that combines the calculation of liquid crystal director orientation and ionic charge distribution. It is supposed that there are four time constants that dominate the overall sticking phenomenon and belong to four transient processes: adsorption of ions, desorption of free ions, desorption of stuck ions, and TFT leakage. The modelling shows good accordance between measured and simulated results when fitting parameters are properly chosen.     

A modular approach to the synthesis of 1,4,5-substituted-2-aminoimidazoles

Diversified 1,4,5-substituted-2-aminoimidazoles were rapidly assembled via sequential N–H insertion and Grignard addition to α-diazoesters. Lead compounds were identified as antibiotics against Gram-positive bacteria with an MIC value as low as 2 μg/mL.     

Sorption equilibria of CO2 on silica-gels in the presence of water

The sorption equilibria of carbon dioxide on three types of silica gel (SG) with different pore size distributions in the presence of water were studied experimentally using a volumetric method at 275?K with pressures from 0 to 3.7?MPa. Both the pore size distribution of the silica gel and the quantity of pre-sorbed water impact the formation of the CO₂ hydrates. For wet silicon gel A(SG-A) with water loading ratio of 0.75, the highest CO₂ sorption was about 2.5?mmol of CO₂ per gram of dry sorbent at 275?K. Similarly, the highest sorption was about 2.7?mmol for wet SG-B with R _w =0.81. However, CO₂ hydrate did not form on the wet surface of SG-C due to its large pore sizes.     

高压下Al0.77Mn0.19Yb0.04合金准晶T相的形成及结构

利用静高压(4.2GPa)熔态(1300℃)淬火(10~2℃/S)方法,对含稀土的铝锰合金Al_(0.77)Mn_(0.10)Yb_(0.04)进行了研究。首次发现了准晶T相的形成。利用选区透射电子衍射技术,对合金中准晶态的结构对称性进行了观察和分析。根据X射线和电子衍射对其衍射峰进行了指标化。使用扫描电镜和能谱技术进行了成份分析。