面向钢轨监测的无线传感器网络网关设计与性能测试

针对我国铁路钢轨实时广域监测的重大需求,通过研究异构无线传感器网络（WSNs）通信技术,设计并实现了一种基于Zig Bee-3G通信的无线传感器网络网关.进行了通信电路设计和电磁兼容设计,并在WinCE操作系统平台上实现了Zig Bee网络与3G网络之间的互联,开发了网关远程维护管理模块.对网关设备分别进行了网络传输性能测试和电磁兼容测试,测试结果表明：此网关传输效率高、抗电磁干扰能力强,能够满足铁路轨道监测现场的应用要求.     

基于FLDA、CPCA与HMM的人脸识别

为了获得具有较高识别率的算法,提出了一种将Fisher线性鉴别分析(Fisher Linear Discriminant Analysis)、复主分量分析(Principal Analysis in the Complex Space)与隐马尔可夫模型(Hidden Markov Models)相结合进行人脸识别的方法。对于输入的不同光照、人脸表情和姿势的图像先进行归一化处理,然后将归一化后的图像转化成一维向量,再用FLDA方法提取每幅图像的特征,形成新的复向量空间;通过运用复主分量分析,来抽取人脸图像的有效鉴别特征;最后通过HMM对这些特征进行训练,得到一个优化的HMM并应用于识别。在ORL人脸数据库中进行实验,实验结果表明,该方法具有较高的识别率。     

图的最大权团的DNA计算

给定顶点赋权的无向图,图的最大权团问题是寻找每个顶点都相邻的顶点子集(团)具有最大权.这个问题是寻找无权图的最大团问题的推广.图的最大团和最大权团都是著名的NP-完全问题,没有非常有效的算法.1994年Adleman博士首先提出用DNA计算解决NP-完全问题,使得NP-完全问题的求解可能得到解决.本文给出了基于质粒技术的无向图的最大权团问题的DNA算法,依据Head T等的实验手段,本文提出的算法是有效并且可行的.     

渐开线斜齿圆柱齿轮磨损的数值仿真

基于离散数学原理和计算机技术建立了渐开线斜齿圆柱齿轮磨损的数值仿真模型，引入温度对磨损的影响，使仿真更接近于实际的磨损过程，开发出模拟相应磨损过程的软件，实现对磨损过程的动态仿真，解决了动态和非线性磨损问题。通过算例验证，仿真的结果与实际测量的磨损量基本相符。     

Investigation of the role of Nb on Pd−Zr−Zn catalyst in methanol steam reforming for hydrogen production

Methanol steam reforming is regarded as a very promising process to generate H₂ suitable for fuel cells. Typically, the Pd-based catalysts can catalyze efficiently methanol steam reforming for hydrogen production. But their high selectivity to CO, a byproduct of methanol reforming reaction, severely limits their potential application. In this work, a series of Nb-modified Pd−Zr−Zn catalysts with different Nb loadings were prepared to study their catalytic activities with more focus on the role of Nb on Pd−Zr−Zn catalyst for methanol steam reforming. The prepared catalysts were fully analyzed by using various characterization techniques, for example, ICP, BET, SEM, XRD, H₂-TPR, NH₃-TPD, HRTEM, CO chemisorption, XPS, and Raman. The experimental results showed that an increase in Nb loading for the Nb-modified Pd−Zr−Zn catalysts led to a decrease of the methanol conversion and H₂ production rate. This was probably due to the decrease in the amount of oxygen vacancies on the catalyst surface. However, introduction of Nb into Pd−Zr−Zn catalyst increased the acid strength on the catalytic surface. The aldehyde species derived from methanol decomposition were readily transformed to HCOOH, thus yielding high selectivity to CO₂ for the Nb-modified Pd−Zr−Zn catalysts. Significantly, the addition of Nb to Pd−Zr−Zn catalyst facilitated the incorporation of Pd into the ZnO lattices, which led to the formation of Pd−Zn alloy. Consequently, the Nb-modified Pd−Zr−Zn catalysts exhibited significantly lower CO selectivity and production rate than the Pd−Zr−Zn catalyst. From the results, this work offers a new way to the rational design of selective methanol steam reforming catalysts to decrease the formation of byproduct CO.     

A kinetic model involving oxidation and volatilization in SiC-B4C-xAl2O3 ceramics system

In this paper, a new kinetic model considering both oxidation and volatilization kinetics is established and applied to analyze the oxidation of SiC-B₄C-xAl₂O₃ ceramics and other systems in various oxidation conditions. The effects of diffusion area and volume changes during the oxidation process are considered in this model. The physical meaning of each parameter in this model is explicit and simple. According to this model, the diffusion coefficient of species and the corresponding diffusion activation energy are easily available. The practicability of this model is well verified by the experimental data of SiC-B₄C-xAl₂O₃ and other systems oxidized under different conditions. In addition, the practice shows that the model is applicable not only to the systems where oxidation and volatilization coexist, but also to the system where only oxidation plays a major role. We hope the model proposed in this work can be used in other materials with more complex environments.     

机械零件磨损仿真与概率寿命估算

基于离散数学理论和计算机技术,用数值仿真方法,建立通用数值仿真模型。提出磨损概率寿命概念,利用Monte Carlo法,以斜齿圆柱齿轮摩擦副磨损状态为研究对象,通过算例实现对斜齿圆柱齿轮机构磨损失效概率寿命分布的计算,解决了零件磨损概率寿命的预测问题,所建立的磨损仿真方法和模型具有良好的工程应用前景。     

涡旋盘啮合条件下流固耦合分析与结构改进

针对涡旋齿变形量通过试验难以测得,进而动、静涡旋盘之间的啮合间隙值难以确定的问题,建立了带有轴向和径向泄漏间隙涡旋盘三维流体域模型,结合CFD动网格技术对涡旋盘内部流场进行模拟,得到压力场和温度场的瞬态分布.将流场计算结果施加到固体边界上,得到涡旋盘的应力分布和变形规律,其中固体变形考虑了包括涡旋齿和端板在内的整体变形...     

图与图学

图与文字、数字一样,在人类的社会进步、经济建设和科技发展过程中起着不可替代的作用。但图与图学的定义与地位从历史和当前角度来看,仍是一个没有深刻和系统阐明的问题。现在的工程图学、计算机图形学、计算机图像学等各有自己的学科定义、定位以及各自独立的发展道路,但由于没有与图和图学相关联,致使这些学科呈现出某种分散性和局限性。从形(几何)的角度揭示图的本质,给出了形与图的科学表述。提出"大图学"概念,整合分散在其他学科中的与图相关的科学与技术。重新认识与定位图学的地位和作用,给出它的定位与定义,构建了图学学科的整体框架和三级学科分类体系。认为文学、数学、图学三者构成了科学与工程发展的基础,昭示了图学的基础性和重要性。     

Hydrogen production from steam reforming of methanol over Cu-based catalysts: The behavior of ZnxLaxAl1-xO4 and ZnO/La2O3/Al2O3 lined on cordierite monolith reactors

The effect of ceramic support on the performance of methanol reforming process catalysts was studied by synthesizing Cu/Zn_1.11La_1.26Al_0.5O_4.27 and comparing it with optimized, conventional γAl₂O₃ based catalyst in a monolithic reactor. The physicochemical properties of the synthetic catalysts were studied using BET, FESEM, FTIR, XRD, TGA, TPR, TEM and XPS analyses for better evaluation of their catalytic performance. The results showed that the sponge like ceramic support Cu/Zn_1.11La_1.26Al_0.5O_4.27 catalyst is very highly efficient and active, has a lower reduction temperature and possess better pore size and pore volume compared with γ-Al₂O₃ based catalysts. Comparison of Cu/γAl₂O_3, Cu/La-γAl₂O_3, Cu-Zn/La-γAl₂O₃ and Cu-Zn/γAl₂O₃ catalysts shows that the presence of Zn undesirably affects methanol conversion at higher temperatures while positively affecting the conversion at lower temperatures. Unlike Zn, La functions better at higher temperatures with respect to conversion and selectivity to H_2. Therefore, Cu-Zn/La-γAl₂O₃ catalyst function better works uniformly at all temperatures. The conversion and selectivity to H₂ of the new Cu/Zn_1.11La_1.26Al_0.5O_4.27 catalyst (97% and 91% respectively) are greater than the alumina supported catalysts such as Cu-Zn/La-γAl₂O₃ (90% and 73% respectively)_. The obtained results show that in this process, the designed Monolith/Zn_1.11La_1.26Al_0.5O_4.27 structure has a remarkable impact on methanol conversion and carbon monoxide selectivity.