用胞映射方法讨论一类MKdV方程

利用简单胞映射方法对一类MKdV(Modified Korteweg de Vries)方程未受扰系统，周期激励系统进行了讨论.首先利用行波法将MKdV方程化为常微分方程组并用四阶Runge kutta方法画出其相图，然后用简单胞映射方法得到了MKdV方程的全局吸引域和有限步吸引域.该结果与相应的相图很好的吻合起来.     

Polyaniline as a Gas-Sensor Material

Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized by UV-visible, FTIR, and XRD analyses. The electrical conductivity of the PANI film was studied by a four-point probe method at room temperature. Finally, ammonia gas-sensing characteristics of the prepared polyaniline film were studied by measuring the change in electrical conductivity on exposure to ammonia gas at different concentrations. The influence of concentration of acid during polymerization of aniline and dopant concentration on the gas sensing characteristics of PANI film are reported in this paper.     

Growth of La2Mo2O9 films on porous Al2O3 substrates by radio frequency magnetron sputtering

Synthesis conditions of La₂Mo₂O₉ thin film by radio frequency (RF) sputtering technique on Al₂O₃ ceramic substrates are studied. It is found that the deposition temperature and oxygen partial pressure are the most important factors for obtaining pure La₂Mo₂O₉ films. Varying both parameters, Mo-rich, stoichiometric, and Mo-deficient films are obtained. With increasing the La:Mo ratio, films become denser. A crust layer is observed on top of the Mo-rich and the Mo-deficient films. The formation of the La₂Mo₂O₉ phase is discussed with respect to the sputtering mechanism.     

Analysis of Nodular Cast Iron Microstructures for Micromechanical Model Development

Abstract:  One of the main factors in determining the different grades of ductile iron is the matrix structure. In the as-cast condition, the matrix will consist of varying proportions of pearlite and ferrite, and as the amount of pearlite increases, the strength and hardness of the iron also increase. Three different nodular cast irons are here considered and their microstructure characterised in detail using metallographic methods. Then micromechanics models based on the unit cell approach and the finite element method are introduced to describe the actual constitutive response of the materials and the predicted behaviours are compared with experiments.     

Characteristics of electrocodeposited Ni-Co-SiC composite coating

Electrodeposited composites are gaining importance for their advantages including low cost, ease and simplicity of operation to tailor made coatings for tribological applications. Generally, composites containing carbides (like SiC) are preferred for high wear resistance along with increased hardness, improved corrosion resistance, and high temperature oxidation resistance as compared to alloy and pure metal electroplating. In the present work, electrolytic codeposition technique was adopted in the deposition of Ni-Co-SiC composite coating on mild steel substrate, using nickel alloyed with cobalt as the binder phase with SiC as dispersed particles. To improve the properties of coating further, Cr plating was also performed. Since the particle size and volume percent variation of dispersoid have great importance in codeposition, so the effect of these two variables on the process of codeposition and properties was observed. Morphological studies of Ni-Co-SiC coating were carried out with scanning electron microscopy and X-ray diffraction analysis to correlate the mechanical and corrosion behaviour of the coating.     

基于差补调制方式的级联H桥逆变器单元故障控制方法

为了增加级联H桥型逆变器单元故障后的输出能力,采用逆变器中性点偏移的工作方式,使逆变器非故障部分继续工作,输出最大幅值的对称线电压,但同时中性点的偏移也造成了电压谐波的增加。该文以6单元串联H桥系统为例进行分析,提出中性点偏移前后采用差补调制方式来控制逆变器,可以减少电压的谐波含量,且参数易于调整。与目前所采用的其它控制方法相比,该方法不仅提升输出合成电压的幅值,而且有效控制了电压的谐波含量,从而减少故障对系统的影响,提高级联H桥逆变器系统的可靠性。系统故障前后的仿真和实验结果表明所提出的控制方法是正确和有效的。     

燃料电池分布式并网发电系统结构研究

本文分析了燃料电池分布式并网发电系统的特点，要求。按照功率变换级数对燃料电池分布式式发电系统结构进行了分类，并对典型的单级和多级系统结构进行了分析综合，最后对比了实用的单级和多级系统结构     

基于电流加权平均法的LCL滤波并网逆变器控制技术

针对传统并网逆变器电流控制时存在的幅值和相位误差以及谐波失真问题，提出了一种基于电流加权平均法的控制技术，可获得较小的输出稳定误差和电流谐波失真。本文给出了该控制策略的理论依据和实现方法，分析比较了新方法与传统控制方法的特性差异。通过对5kVA燃料电池逆变并网发电电源的仿真和试验验证了该控制策略。     

Preparation of Pt supported on mesoporous carbons for the reduction of oxygen in polymer electrolyte membrane fuel cell (PEMFC)

Porous carbon materials (SM-C, HS-C and TM-C) were prepared using commercial colloidal silicas (SM-30, HS-40 and TM-50) and a resorcinol-formaldehyde resin as a removable template and a carbon precursor, respectively. All of the prepared carbons had high surface areas with narrow pore size distributions. In particular, the pore diameter of the carbons could be controlled over a range of mesopore size by the use of an appropriate silica employed as a template. Mesoporous carbon templated using TM-50 had the largest pore size, while that for SM-C, was the smallest. Pt nanoparticles were supported on these mesoporous carbons for use as a catalyst in a polymer electrolyte membrane fuel cell (PEMFC). The crystallite size of the Pt catalyst was found to be closely related to the properties of the corresponding carbon support. A carbon support with a large pore size and a high surface roughness was found to favor the dispersion of Pt crystallite. In a single cell test, the Pt catalysts supported on mesoporous carbons exhibited higher cell performance than that on activated carbon. In particular, the Pt/TM-C catalyst showed the best cell performance among the catalysts tested. In addition to the high surface area of the active metal, the large pore size of the Pt/TM-C appears to have positive effect on the distribution of ionomer, resulting in facile formation of a triple-phase boundary.