一类双悬臂含间隙振动系统的混沌控制策略研究

由于一类双悬臂含间隙振动系统具有典型非光滑特性和有明显的非线性,这直接导致了系统发生分叉与混沌现象的可能性.为此针对该系统的混沌现象,利用基于能量的开环控制策略,构造有界控制器对混沌行为进行控制,混沌运动可被引导到稳定的目标周期轨道,并对控制的收敛速度进行分析,数值模拟结果表明了该控制策略的有效性与可行性,可为碰振系统的优化设计,振动控制和安全运行提供了理论参考.     

带有交易成本的均值——方差——下半方差投资组合模型

投资组合选择研究为投资决策和风险管理提供了可量化的途径和科学决策的依据．本文引入了非凹非凸的典型交易成本函数,建立了含有交易成本函数的均值--方差--下半方差投资组合模型．考虑到不同的投资者对风险的厌恶程度不同,引入风险厌恶系数,把双目标的投资组合优化模型转化为单目标的投资组合优化模型,并运用教与学算法对模型进行了求解,得到不同收益下的最优投资组合,同时给出了投资组合的有效边界,最后对算法的优越性进行了分析,得到了比较好的仿真结果．     

Removal of heavy metal lead(II) using nanoscale zero-valent iron with different preservation methods

In this study, different nanoscale zero-valent irons (nZVI) were prepared in order to improve their stability and reactivity to heavy metal lead (Pb (II)). The composition, particle size and morphology of obtained nZVI were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM). The effects of nZVI dosage, pH, initial Pb (II) concentration and reaction time on the removal efficacy of Pb (II) were investigated. The results show that undried nZVI has more active sites due to its weaker oxidation, and thus the removal efficiency of Pb(II) by undried nZVI was higher than that by dried nZVI. As a result, the same removal efficiency could be achieved with the use of less undried nZVI for the identical concentration of Pb(II). Furthermore, the experimental procedure could be apparently simplified, which eliminates the steps of washing, separation and dehydration compared with the traditional preparation method. The experimental data could be well fitted by the Langmuir adsorption isotherm model, and the maximum adsorption capacity of dried and undried nZVI is 671.14 and 807.23?mg·g^?1 at pH 6, respectively. The experimental data followed the pseudo second-order kinetic model with a kinetic constant of 7.65?×?10^?4 and 1.39?×?10^?3 for undried and dried nZVI, respectively. In conclusion, undried nZVI had high adsorption capacity and adsorption rate for Pb(II) in the solution.     

新型Ni-Cr-Co基高温合金的热腐蚀行为

利用热重分析法研究了一种将用作超临界锅炉过热器管材料的新型Ni-Cr-Co基高温合金在空气中的热腐蚀行为，并利用X射线衍射和扫描电镜等实验手段详细分析了腐蚀产物和腐蚀机理．研究表明：合金表面涂覆Na2SO4后在850℃的腐蚀动力学行为遵循抛物线规律，而在950℃时因表面腐蚀产物的挥发偏离抛物线规律，抛物线速度常数逐渐降低；合金表面生成的腐蚀产物有Cr2O3、（NiCo）Cr2O4、TiO2和A1203，内析出物为Al2O3、TiO2和Cr与Ti的硫化物；合金表面涂覆Na2SO4在850℃和950℃发生了高温热腐蚀，其原因在于表面熔融态Na2SO4盐的存在使得表面形成的Cr2O3膜产生了碱性熔融．     

浅析我国水质量的污染与监测

通过对我国水资源质量的调查和监测,分析了我国目前水体污染的现状、成因及对人体健康的影响,介绍了国家水质量等级标准及部分城市环境管理评价体系,提出了未来水资源保护与污染防治的研究方向.认为在重视防治化学污染的同时,须重视营养元素富集所引起的水体富营养化防治,并从源污染、生态环境、城市综合性污水处理等多方面加以治理,以保证水资源的有效供给和高效利用.     

基于因子分析的城市职能特征分析——以西部省会城市、直辖市为例

为了对我国西部省会城市和直辖市的城市职能特征及其类型划分有一个初步的认识,根据国家统计局《中国城市统计年鉴》的数据资料,对该地域的城市进行了职能特征分析与分类.以城市的基本经济活动作为确定城市职能的出发点,选取14个指标作为西部10个省会城市和一个直辖市的城市职能分析的原始指标,借助SPSS10.0统计软件,运用因子分析法对14个指标数据进行了分析处理,得到两位公因子.在此基础上计算出西部10个省会城市和一个直辖市的城市职能主因子的综合得分,同时对其城市职能进行了聚类分析,分出三大类两亚类,旨在从整体上把握西部城市的发展趋势.     

盐池地区地下水赋存规律与水化学特征研究

通过对盐池地区的水文地质调查和资料的综合研究,总结了该地区地下水的赋存规律与水化学特征,分析了地下水水化学成因类型,结果表明,第四系松散岩类孔隙水分布贫乏,且水质较差,多不具供水意义;白垩系碎屑岩类裂隙孔隙水水质普遍较差,但白垩系与第四系的混合潜水水质相对较好,须特别保护.     

An Internet-enabled Integration of Concurrent Engineering with Co-design

In this paper,the Web-based integration methodology and framework have been developed to facilitate collabora- tive and concurrent engineering design in distributed manufacturing environments.The distributed concurrent engineering and co- design are discussed as key components in the mechanism.The related integration system is presented,which includes four function- al modules:co-design,Web-based visualization,manufacturing analysis and look-up service.It can be used for a design team geo- graphically distributed to organize a collaborative and concurrent engineering design effectively.In particular,the collaborative mechanism incorporated with Java-based and Internet-enabled technologies can generate extended strategies for design and planning. Thus,the proposed integration architecture enables the system to be generic,open and scalable.Finally,for the trend of global manufacturing,a case study of Internet-enabled collaborative optimization is introduced and a discussion on teamwork capability is made.     

High-order compact ADI (HOC-ADI) method for solving unsteady 2D Schrödinger equation

In this paper, a high-order compact (HOC) alternating direction implicit (ADI) method is proposed for the solution of the unsteady two-dimensional Schrödinger equation. The present method uses the fourth-order Padé compact difference approximation for the spatial discretization and the Crank-Nicolson scheme for the temporal discretization. The proposed HOC-ADI method has fourth-order accuracy in space and second-order accuracy in time. The resulting scheme in each ADI computation step corresponds to a tridiagonal system which can be solved by using the one-dimensional tridiagonal algorithm with a considerable saving in computing time. Numerical experiments are conducted to demonstrate its efficiency and accuracy and to compare it with analytic solutions and numerical results established by some other methods in the literature. The results show that the present HOC-ADI scheme gives highly accurate results with much better computational efficiency.     

Image analysis by Bessel-Fourier moments

In this paper, we proposed a new set of moments based on the Bessel function of the first kind, named Bessel-Fourier moments (BFMs), which are more suitable than orthogonal Fourier-Mellin and Zernike moments for image analysis and rotation invariant pattern recognition. Compared with orthogonal Fourier-Mellin and Zernike polynomials of the same degree, the new orthogonal radial polynomials have more zeros, and these zeros are more evenly distributed. The Bessel-Fourier moments can be thought of as generalized orthogonalized complex moments. Theoretical and experimental results show that the Bessel-Fourier moments perform better than the orthogonal Fourier-Mellin and Zernike moments (OFMMs and ZMs) in terms of image reconstruction capability and invariant recognition accuracy in noise-free, noisy and smooth distortion conditions.