基于坐标变换的圆环面/球面相交分析

利用坐标变换使圆环中心轴与球心同在XOZ平面内,讨论了在该平面内圆环截圆与球圆的位置不相交、相切和相交时圆环面和球面的相交情况,并给出了判别圆环面、球面相交情况的流程图以及圆环面和球面相交实例。     

一种基于节点比较法的三相四桥臂并网逆变器模型预测控制方法

三相四桥臂并网逆变器在三相四线制系统中得到了广泛的应用。建立了三相四桥臂LCL型并网逆变器的精确模型,采用模型预测控制并综合考虑跟踪误差与开关损耗,求出最合适的开关序列,其效果优于传统控制方法。为了解决运算量大的问题,使用球形译码算法,把代价函数匹配为球形译码的标准形式,同时引入一种新的初始半径选取方法,即节点比较法,进而减小计算量。仿真结果表明,所提方法中电流波形的跟踪误差和谐波失真均满足要求,并有较好的动态响应。     

基于信噪比判决的多维信号检测方法

在多输人多输出系统中,采用球形解码检测算法和QRD-M算法均能在相对复杂度较低的情况下取得逼近最大似然检测算法的性能.虽然球形检测算法在高信噪比的情况下的平均复杂度要低于QRD-M算法,但其在低信噪比的情况下复杂度会急剧上升.针对这一问题,在分析球形解码算法与QRD-M算法平均复杂度的基础上,通过在解码检测之前设置信噪...     

水平气力输送系统中颗粒波状流的模拟

对用于两相流计算的硬球模型进行简化，模拟了水平气力输送系统中颗粒波的动态流型。模型中，气体状态由两相耦合的Navier—Stokes方程描述，颗粒运动通过单颗粒的运动轨迹描述。并且，颗粒的碰撞运动由冲量守恒原理控制，颗粒的悬浮运动由力平衡方程决定，相间耦合作用依据牛顿第三定律处理。模拟结果从介观层次呈现了水平气力输送系统中与实验特征吻合的颗粒波状流，说明了颗粒波的传播速度取决于气体速度，它并不敏感地依赖于系统中的存料量及物料密度。     

低温无模板法制备Tio2空心球及其光电性能

基于Ostwald熟化作用的机理,采用无模板法,在低温水热条件下制备了TiO2空心球（TiO2-HS）。探讨了水热反应时间和表面活性剂的种类对TiO2-HS形貌的影响。在以Ti（SO2）：为钛源,尿素为表面活性剂,180℃水热反应15h后得到了微米级、锐钛矿型的TiO2-HS,比表面积和孔容积分别达到了100．728m2／g、0．270cm3／g,平均吸附孔径为10．718nm。将TiO2-HS应用于染料敏化太阳能电池的光阳极,光电转换效率达到5．48％。表明空心球结构提高了材料的比表面积,增强了光子吸收效率,光电性能得到了很大提高。     

One-pot synthesis of hematite-alumina hollow sphere composite by ultrasonic spray pyrolysis technique with high adsorption capacity toward PAHs

A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al₂O₃ – Fe₂O₃ nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al₂O₃ or Fe₂O₃ showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g^?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance.     

高温矿井用蓄冰球受控循环风降温技术的研究

随着矿井开采深度的增加和采掘机械化水平的不断提高,矿井高温热害问题越来越严重。为保障采矿工业持续健康发展,必须采取相应措施进行治理。文章就近年来国内外高温矿井降温技术发展的现状和趋势及井下循环风的利用方面进行了研究,提出了高温矿井用蓄冰球受控循环风降温技术。     

Algorithms and tools for high-throughput geometry-based analysis of crystalline porous materials

Crystalline porous materials have a variety of uses, such as for catalysis and separation. Identifying suitable materials for a given application can, in principle, be done by screening material databases. Such a screening requires automated high-throughput analysis tools that calculate structural properties for all materials contained in a database so they can be compared with search queries, grouped or classified. One important aspect of the structural analysis of materials such as zeolites and metal organic frameworks is the investigation of the geometrical parameters describing pores. Here, we present algorithms and tools to efficiently calculate some of these important parameters. Our tools are based on the Voronoi decomposition, which for a given arrangement of atoms in a periodic domain provides a graph representation of the void space. The resulting Voronoi network is analyzed to obtain the diameter of the largest included sphere and the largest free sphere, which are two geometrical parameters that are frequently used to describe pore geometry. Accessibility of nodes in the network is also determined for a given guest molecule and the resulting information is later used to retrieve dimensionality of channel systems as well as in Monte Carlo sampling of accessible surfaces and volumes. The presented algorithms are implemented in a software tool, Zeo++, which includes a modified version of the Voro++ library. We present example applications of our algorithms and tools using zeolite frameworks currently listed in the Atlas of Zeolite Frameworks.     

Role of moving planes and moving spheres following Dupin cyclides

We provide explicit representations of three moving planes that form a μ-basis for a standard Dupin cyclide. We also show how to compute μ-bases for Dupin cyclides in general position and orientation from their implicit equations. In addition, we describe the role of moving planes and moving spheres in bridging between the implicit and rational parametric representations of these cyclides.     

基于激光积分球反射计的集成黑体发射率测量研究

集成黑体发射率是评价其有效光谱辐射亮度不确定度的关键贡献项。建立了激光积分球反射计测量系统,对中国计量科学研究院制备的集成空腔的法向光谱发射率进行了实验研究和模拟验证。在633nm的波长下测量了集成黑体法向光谱发射率,测量结果的标准不确定度优于0.043%。结果表明:集成黑体辐射源在室温条件下的有效发射率高于0.998,与STEEP3蒙特卡罗模拟计算结果偏差在0.04%之内。实验结果与数值模拟的一致性在测量结果不确定度内吻合良好,验证了激光积分球发射计法用于评价集成黑体发射率的可行性。