TiO2/C纳米复合材料的制备及其电化学性能研究

以球状钛乙醇酸盐为TiO2前驱体,葡萄糖作碳源,通过水热法制得φ(300～400)nm的TiO2/C复合纳米微球.葡萄糖的浓度对产物的形貌、结构、碳含量有重要影响,进而影响产物的电化学性能.当碳含量为7wt%时,TiO2/C纳米复合材料的晶粒大小、BET比表面积、平均孔径分别为7.1 nm、157 m2/g和5.2 nm;该材料用作锂离子电池负极材料时,在0.2C的电流密度下循环80次后的嵌锂容量为160 mAh/g,并且具有较好的倍率性能.     

具有多级孔结构的丝光沸石的合成与性能研究

以表面活性剂十六烷基三甲基溴化铵(CTAB)作为模板剂, 在不添加晶种和有机共溶剂的情况下采用简单的一步水热合成法制备了含有2~4 nm介孔的多级孔纳米丝光沸石。 通过改变 CTAB引入量可以调节所得多级孔丝光沸石样品的外比表面积以及介孔孔容, 最大外比表面积和介孔孔容可分别达到191 m²/g和0.17 cm³/g。均三甲苯在丝光沸石样品上的吸附行为表明, 微孔丝光沸石仅能吸附少量的吸附质, 而多级孔丝光沸石吸附量较大, 并呈现出IV型等温线的特征, 展示出多级孔丝光沸石中介孔的特征。以均三甲苯与苄基氯的苄基化反应来考察多级孔丝光的催化性能。相比于传统微孔丝光沸石, 苄基化反应在多级孔丝光沸石的转化率提高了近7倍, 反应的表观速率常数提高了近19倍。这是由于多级孔丝光沸石较高的外表面积和介孔孔容可以有效地改善大分子反应物的可接近性和产物的传质速率, 从而提高了大分子催化反应的效率。     

空间超限邻域点云去噪算法的研究与实现

对获取的点云数据进行降噪处理,是曲面重构过程的关键技术之一。充分利用三维空间散乱点的深度信息,重新诠释图像去噪中的＂超限邻域平均法＂,使其对二维图像的运用转换为对三维图形数据点的操作,并结合运用空间解析几何理论,提出一种直接对三维无组织散乱点去噪算法。从试验结果来看,本算法在去除噪声点的同时很好地保留了散乱点模型的细节特征,噪声去除效果理想。     

复杂曲面加工精度检验中曲面法矢与刀具扫描体求交算法的研究

提出了一种用于实现矢量与扫描体（代表五轴数控加工铣刀的运动）求交的有效算法,该算法首先对曲面法矢和刀具扫描体进行预处理,将曲面法矢与刀具扫描体之间的求交问题转化为有向线段与三角网格之间的求交计算,然后建立有向线段和三角网格的求交子集,减少了不必要的求交计算,提高了乍法的效率。文中举例说明了该算法在复杂曲面NC精度检验中的应用。     

Realization of an on-line fiber-optic bending loss measurement system

In this paper, an on-line bending loss measurement system is studied and realized. To avoid complicated calculation of fiber bending loss, we propose a simplified theoretical model for on-line evaluation. A specific fiber adaptor is developed for light signal feeding and picking up through a free space optical fiber coupling technique. Relevant factors, including free space fiber misalignment, are considered. The signal-to-noise ratio of the whole system is improved by optimizing the spatial perturbation length of the fiber and the deformation of the bending fiber. The use of an on-line monitoring technique for measuring the bending loss of optical fibers is presented in this paper. With this technique, manufacturing efficiency can be improved, and the cost of maintaining fiber quality control can be reduced.     

面向延迟制造的MRP动态调整方法研究

延迟制造要求对相同的在制品根据不同的客户需求进行工艺区分. 过程质量的不确定性使得传统物料需求计划(Material requirement planning, MRP)难以满足延迟区分的实时性要求. 本文简要介绍了面向延迟制造的物料需求计划改进方法, 提出了基于累计实时合格率的物料需求计划动态调整方法, 开发了实现算法. 应用案例表明: 该方法能够实时地根据各生产阶段的质量波动对物料需求计划进行动态调整, 制定合理的在制品工艺区分决策.     

Friction and wear study of the hemispherical rotor bushing in a variable capacitance micromotor

Friction and wear are the most serious problems for micromotors in microelectromechanical systems (MEMS). In the paper, a linear-sliding wear model of the contact between the rotor bushing and the ground plane is presented to describe the wear and a corresponding simplified method is proposed to simulate the wearing process. The effects of geometry parameters, material properties and applied operating conditions on the evolution of dimensional and volumetric wear rates and frictional torques are explored for normally loaded rotating rotor bushing sliding on the ground plane. A hemispherical-bushing-on-ground-plane configuration finite element model (FEM) is set up and the implementation of the contact task based on ANSYS and the contact element approach is introduced to provide the numerical simulations acted as a guide to solution of the contact problems in micromotors. Numerical simulations and results of the wear rates, frictional torques, contact stresses and contact pressure are studied and the effects of roughness, material properties, geometry parameters and FEM mesh of the bushing and the ground plane are discussed. It is indicated that the nonlinear effects cannot be ignored and the results should not be used to predict the absolute wear lifetime whereas surface engineering, lower wear materials and rational designs for micromotors in MEMS should be applied to bring the friction and wear behaviors into the acceptable regimes.     

SiC表面氧化及其对SiC/Fe界面稳定性的影响

烧结致密的α-SiC在静态空气气氛中经1200℃×10h氧化,在其表面形成一层致密的氧化膜,该层氧化膜具有β-方石英晶体结构.氧化膜的生长由O     

SiC表面氧化及其对SiC/Fe界面稳定性的影响

烧结致密的α－ＳｉＣ在静态空气气氛中经１２００℃×１０ｈ氧化,在其表面形成一层致密的氧化膜,该层氧化膜具有β－方石英晶体结构．氧化膜的生长由Ｏ２通过ＳｉＯ２晶格间隙的扩散控制． ＳｉＣ／Ｆｅ界面反应剧烈,界面稳定性极差. ＳｉＣ表面氧化能有效阻挡该界面反应,提高其稳定性． ９００℃以下长时间保温,氧化 ＳｉＣ／Ｆｅ界面十分平直,无明显反应的迹象,界面十分稳定．但随着温度的升高,界面稳定性越来越低,在局部区域内开始发生反应,并逐渐扩展到整个界面,最终导致氧化膜遭到破坏,失去阻挡界面反应的作用．氧化膜与ＳｉＣ、Ｆｅ热膨胀系数不匹配所造成的应力集中,以及氧化膜中存在的孔隙可能是导致氧化膜在热处理过程中遭到破坏的主要原因．