Magnetite nanoparticles/chiral nematic liquid crystal composites with magnetically addressable and magnetically erasable characteristics

A magnetite (Fe₃O₄) nanoparticle/chiral nematic liquid crystal (N*-LC) composite was prepared and filled into a planar treated cell. The Fe₃O₄ nanoparticles had been modified by oleic acid so that they could be better dispersed in the composite. When a magnetic field was scanned on the outer surface of the cell locally, Fe₃O₄ nanoparticles moved towards the inner surface of the cell correspondingly, and the black expected information was displayed. When the magnet was applied to the opposite outer surface, the information was erased. After polymer network walls were prepared in the composite, the resolution of the information displayed increased. Then, through the formation of hydrogen bonds between the nanoparticles and chiral pyridine compound (CPC) doped in the composite, the pitch length of the N*-LC could be adjusted by altering the intensity of the applied magnetic field. The composite doped with CPC could potentially be used as a material for a type of reflective colour paper with magnetically controllable characteristics.     

A numerical method for problems in infinite strips with irregularities extending to infinity

The Dirichlet-to-Neumann (DtN) Finite Element Method is a combined analytic-numerical method for boundary value problems in infinite domains. The use of this method is usually based on the assumption that, in the infinite domain D exterior to the finite computational domain, the governing differential equations are sufficiently simple. In particular, in D it is generally assumed that the equations are linear, homogeneous, and have constant coefficients. In this article, an extension of the DtN method is proposed, which can be applied to elliptic problems with “irregularities” in the exterior domain D, such as (a) inhomogeneities, (b) variable coefficients, and (c) nonlinearities. This method is based on iterative “regularization” of the problem in D, and on the efficient treatment of infinite-domain integrals. Semi-infinite strip problems are used for illustrating the method. Convergence of the iterative process is analyzed both theoretically and numerically. Nonuniformity difficulties and a way to overcome them are discussed. © 1998 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 14:233–249, 1998     

Variable orderings and the size of OBDDs for random partially symmetric Boolean functions

The size of ordered binary decision diagrams (OBDDs) strongly depends on the chosen variable ordering. It is an obvious heuristic to use symmetric variable orderings, i.e., variable orderings where symmetric variables are arranged adjacently. In order to evaluate this heuristic, methods for estimating the OBDD size for random partially symmetric functions are presented. Characterizations of cases where, with high probability, only symmetric variable orderings and, with high probability, only nonsymmetric variable orderings lead to minimum OBDD size are obtained. For this analysis estimates for the number of different blocks of random Boolean matrices are used. © 1998 John Wiley & Sons, Inc. Random Struct. Alg., 13, 49–70, 1998     

Exponential inequalities for associated random variables and strong laws of large numbers

Some exponential inequalities for partial sums of associated random variables are established. These inequalities improve the corresponding results obtained by Ioannides and Roussas (1999), and Oliveira (2005). As application, some strong laws of large numbers are given. For the case of geometrically decreasing covariances, we obtain the rate of convergence n-1/2(log log n)1/2(logn) which is close to the optimal achievable convergence rate for independent random variables under an iterated logarithm, while Ioannides and Roussas (1999), and Oliveira (2005) only got n-1/3(logn)2/3 and n-1/3(logn)5/3, separately.     

���ع�ģ�͵�Smooth LASSO��Spline LASSO����ѡ��

??Considering a parameter estimation and variable selection problem in logistic regression, we propose Smooth LASSO and Spline LASSO. When the variables is continuous, using Smooth LASSO can select local constant coefficient in each group. However, in some case, the coefficient might be different and change smoothly. Using Spline Lasso to estimate parameter is more appropriate. In this article, we prove the reliability of the model by theory. Finally using coordinate descent algorithm to solve the model. Simulations show that the model works very effectively both in feature selection and prediction accuracy.     

A variable boundary model of storm surge flooding in generalized curvilinear grids

In this paper, generalized 2D shallow sea dynamic equations in movable curvilinear co-ordinates are derived. Through a differential co-ordinate transformation a self-adaptive grid is proposed to treat a continuously deforming lateral boundary and a kinematical boundary condition is adopted. The self-adaptive grid method (SAM) is used to simulate numerically the storm surge flooding in the Bohai Sea on 23 April 1969, which was one of the largest storm surge inundations in China.     

武汉地区雨强分维数随时间变化初探

对武汉大学电波综合观测站于１９９１年７月期间降雨自记纸曲线当积分时间为５ｍｉｎ时，用单变量雨强时间序列初步地研究了降雨这一大气过程中雨强分维数随时间变化特性．     

轴流式水力机械转轮中局限空化流动的面元奇点解法

轴流式水力机械转轮中局限空化流动的面元奇点解法刘四清，常近时（北京农业工程大学水利与建筑工程系北京１０００８３）关键词：空化，水力机械，转轮。ＳＯＬＵＴＩＯＮＴＯＰＡＲＴＩＡＬＣＡＶＩＴＡＴＩＯＮＦＬＯＷＩＮＩＭＰＥＬＬＥＲＯＦＡＸＩＡＬ－ＦＬＯＷＨ...     

变质量Birkhoff系统的Lie对称性和非Noether守恒量

采用嵌入质量法建立了变质量系统的Birkhoff方程.根据Lie对称性理论给出了变质量Birkhoff系统的Lie对称性确定方程，得到了系统的Lie对称直接导致非Noether守恒量的存在条件和形成.举例说明结果的应用. 关键词： 变质量 Birkhoff系统 Lie对称性 非Noether守恒量     

用L_1-罚函数作线性搜索函数的一种修正约束变尺度算法

本文对用Ｌ１－罚函数作线性搜索的约束变尺度算法，提出了一种新的修正方法，该方法的计算量小，可行性较好，并且仍能保持原有算法的收敛性．