二氧化碳间接转化制化学品的研究进展

二氧化碳直接利用较为困难, 因此先将其转化为环碳酸酯等二氧化碳衍生物, 进而间接转化为其它化学品是实现二氧化碳资源化利用的重要手段之一, 具有良好的应用前景. 本文综合评述了二氧化碳转化为环碳酸酯继而间接利用的近期研究进展, 重点介绍了环碳酸酯的加氢反应、 醇解反应和氨解反应中的均相和多相催化体系, 对反应机理进行了阐述, 并展望了该领域仍待解决的问题和发展前景.     

西湖风景区游客逗留时间决定因素研究

随着近年来城际交通条件的改善,游客在旅游目的地的逗留时间普遍缩短,极大地影响了一个旅游城市旅游产业的赢利能力;但另一方面,热点景区的游客众多,又需要对游客的逗留时间进行控制,以利于景区环境和文物保护.本研究以杭州西湖风景区为例,运用生存分析中的Cox及Weibull模型,分析游客逗留时间的决定因素.调研数据来源于2009年夏天在西湖风景区调查的243份问卷,对象是完成西湖游览行程的来杭游客.研究发现:①家庭收入的增长、个体出行、亲友结伴、住宿开支减少等因素均能够显著增加在西湖景区的逗留时间,而随团出行、多次来杭旅行、住宿星级酒店等因素则会促使逗留时间减少.②景区的游览设施及服务质量、住宿接待的服务质量、西湖景区的整体改造、自然及文化吸引力、夜间景观及活动项目吸引力、景区门票制度的改变这几项对于增加游客逗留时间具有重要作用.③杭州整体旅游形象塑造、景区主管部门的宣传推广、亲友及网络口碑等几项对于增加游客逗留时间的效果并不明显.全文最后对西湖风景区的相关管理部门和旅游企业提出建议,以寻求景区发展面临不同影响因素时可采取的相应对策.     

变截面梁横向振动固有频率数值计算

根据边界条件对变截面梁横向振动四阶变系数微分方程降阶, 形成关于挠度和弯矩的二 阶非显式递推变系数微分方程组; 利用有限差分法, 研究了变截面简支梁横向振动固有频率 的数值计算方法及其精度. 理论分析和正交计算的算例表明: 数值计算算法简单, 计算精度 取决于计算步长的数目和梁横截面竖向渐变率, 与梁宽和梁长无关; 对于给定的计算步长或 数目, 可以估算数值计算的精度; 对于给定的精度要求, 可以确定合理的计算步长或数目.     

非晶碳化硅材料与光学微腔的制备与发光

利用等离子体化学气相沉积技术在100℃的衬底温度下,制备了具有不同组分比的系列非晶碳化硅薄膜。结合傅里叶变换红外光谱与喇曼光谱对所制备的薄膜微结构进行了表征与分析,同时,对具有不同组分比的非晶碳化硅薄膜室温光致发光性质进行了系统的研究。结果表明在Ar⁺离子激光和Xe灯紫外光的激发下,不同组分的样品显示出不同的光致发光特性,并对样品的发光特性与其微结构的联系进行了讨论。在此基础上,用碳化硅薄膜设计和制备了全固体光学微腔,研究了微腔对碳化硅发光行为的调制作用。     

尺寸可控的纳米硅的生长模型和实验验证

基于经典热力学理论，对a-SiN_x/a-Si:H/a-SiN_x三明治结构或a-Si:H/a-SiN_x多层膜结构中纳米硅成核，以及从球形到鼓形的生长过程进行了研究. 建立了限制性晶化理论模型：在纳米硅生长过程中，由于界面能增大将导致生长停止，给出限制性晶化条件——a-Si:H子层厚度小于34 nm. 在激光晶化和常规热退火两种方法形成的a-SiN_x/nc-Si/a-SiN_x三明治结构和nc-Si/a-SiN_x多层膜结构中验证了该理论模型. 关键词： 非晶硅 纳米硅 激光辐照 结晶     

Nonlinear Doping,Chemical Passivation and Photoluminescence Mechanism in Water-Soluble Silicon Quantum Dots by Mechanochemical Synthesis

A series of boron-and phosphorus-doped silicon wafers are used to prepare a series of doped silicon nanocrystals(nc-Si) by high-energy ball milling with carboxylic acid-terminated surface. The sizes of the nc-Si samples are demonstrated to be 5 nm. The doping levels of the nc-Si are found to be nonlinearly dependent on the original doping level of the wafers by x-ray photoelectron spectroscopy measurement. It is found that the nonlinear doping process will lead to the nonlinear chemical passivation and photoluminescence(PL) intensity evolution.The doping, chemical passivation and PL mechanisms of the doped nc-Si samples prepared by mechanochemical synthesis are analyzed in detail.     

Correlation between Light Emissions from Amorphous-Si：H/SiO2 and nc-Si/SiO2 Multilayers

We investigate the properties of light emission from amorphous-Si：H/SiO2 and nc-Si/SiO2 multilayers （MLs）. The size dependence of light emission is well exhibited when the a-Si：H sublayer thickness is thinner than 4 nm and the interface states are well passlvated by hydrogen. For the nc-Si/Si02 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.     

铅球飞行距离与其影响因素的力学分析

通过对滑步掷球时铅球飞行距离及其影响力学因素的相互关系的分析,详细讨论了决定飞行距离的独立力学变量对飞行距离的影响,同时指出了最佳用力角的物理意义及一些对实际有益的重要结论.     

Pseudo nanocrystal silicon induced .luminescence enhancement in a-Si/SiO2 multilayers

Enhanced photoluminescence （PL） at room temperature from thermally annealed a-Si：H/SiO2 multilayers is observed through the step-by-step thermal post-treatment. The correlation between the PL and the crystallization process is studied using temperature-dependent PL, Raman, cross section high-resolution transmission electron microscopy （XHRTEM） and x-ray diffraction （XRD） techniques. An intensified PL band around 820 nm is discovered from the sample annealed near the crystallization onset temperature, which is composed of two peaks centred at 773 nm and 863 nm, respectively. It is found that the PL band centred at 863 nm is related to the pseudo nanocrystal （p-nc-Si） silicon, and the PL band centred at 773 nm is attributed to Si = O bonds stabilized in the p-nc-Si surface.     

Eigenmode Splitting in all Hydrogenated Amorphous Silicon Nitride Coupled Microcavity

Hydrogenated amorphous silicon nitride based coupled optical microcavity is investigated theoretically and ex- perimentally. The theoretical calculation of the transmittance spectra of optical microcavity with one cavity and coupled microcavity with two-cavity is performed. The optical eigenmode splitting for coupled microcavity is found due to the interaction between the neighbouring localized cavities. Experimentally, the coupled cavity samples are prepared by plasma enhanced chemical vapour deposition and characterized by photoluminescence measurements. It is found that the photoluminescence peak wavelength agrees well with the cavity mode in the calculated transmittance spectra. This eigenmode splitting is analogous to the electron state energy splitting in diatom molecules.