铁磁性金属簿膜磁特性的研究

讨论了铁磁性金属薄膜中的各向弄性磁阻效应。通过对晶体结构分析和实验验证,提出了一种假设:在外磁场作用下,产生了原子对的方向有序化,导致感生磁各向异性,并使晶体织构消失。根据对5种样品的实测数据,讨论了薄膜的动态磁化过程。     

On the Estimation of the Density of a Directional Data Stream

Many directional data such as wind directions can be collected extremely easily so that experiments typically yield a huge number of data points that are sequentially collected. To deal with such big data, the traditional nonparametric techniques rapidly require a lot of time to be computed and therefore become useless in practice if real time or online forecasts are expected. In this paper, we propose a recursive kernel density estimator for directional data which (i) can be updated extremely easily when a new set of observations is available and (ii) keeps asymptotically the nice features of the traditional kernel density estimator. Our methodology is based on Robbins–Monro stochastic approximations ideas. We show that our estimator outperforms the traditional techniques in terms of computational time while being extremely competitive in terms of efficiency with respect to its competitors in the sequential context considered here. We obtain expressions for its asymptotic bias and variance together with an almost sure convergence rate and an asymptotic normality result. Our technique is illustrated on a wind dataset collected in Spain. A Monte‐Carlo study confirms the nice properties of our recursive estimator with respect to its non‐recursive counterpart.     

Small‐sphere distributions for directional data with application to medical imaging

We propose novel parametric concentric multi‐unimodal small‐subsphere families of densities for p ? 1 ≥ 2‐dimensional spherical data. Their parameters describe a common axis for K small hypersubspheres, an array of K directional modes, one mode for each subsphere, and K pairs of concentrations parameters, each pair governing horizontal (within the subsphere) and vertical (orthogonal to the subsphere) concentrations. We introduce two kinds of distributions. In its one‐subsphere version, the first kind coincides with a special case of the Fisher–Bingham distribution, and the second kind is a novel adaption that models independent horizontal and vertical variations. In its multisubsphere version, the second kind allows for a correlation of horizontal variation over different subspheres. In medical imaging, the situation of p ? 1 = 2 occurs precisely in modeling the variation of a skeletally represented organ shape due to rotation, twisting, and bending. For both kinds, we provide new computationally feasible algorithms for simulation and estimation and propose several tests. To the best knowledge of the authors, our proposed models are the first to treat the variation of directional data along several concentric small hypersubspheres, concentrated near modes on each subsphere, let alone horizontal dependence. Using several simulations, we show that our methods are more powerful than a recent nonparametric method and ad hoc methods. Using data from medical imaging, we demonstrate the advantage of our method and infer on the dominating axis of rotation of the human knee joint at different walking phases.     

文化认知中定向思维模式的建构与解构——以中国少数民族文化范式为研究视阈

定向思维模式的建构与解构实际上反映出认知结构的二重性特征，两者在文化认知活动中可互为挹注共存于对立统一关系里。因此，对中国少数民族文化范式的研究，不仅要重视建构之功能催生的符号化文化构成，还应关注解构之功能显现的非常见的文化元素。同时，只有弄清楚定向思维模式的建构与解构在文化认知中的意涵，才能明确定向思维模式的“趋向”和“专注”特点以及“惰化”和“孤立”倾向，从而为牵及民族文化事项的认知固化与迁移提供理论工具并用以指导多元文化实践。     

Comparisons of Test Statistics Arising from Marginal Analyses of Multivariate Survival Data

We investigate the properties of several statistical tests for comparing treatment groups with respect to multivariate survival data, based on the marginal analysis approach introduced by Wei, Lin and Weissfeld [Regression Analysis of multivariate incomplete failure time data by modelling marginal distributians, JASA vol. 84 pp. 1065–1073]. We consider two types of directional tests, based on a constrained maximization and on linear combinations of the unconstrained maximizer of the working likelihood function, and the omnibus test arising from the same working likelihood. The directional tests are members of a larger class of tests, from which an asymptotically optimal test can be found. We compare the asymptotic powers of the tests under general contiguous alternatives for a variety of settings, and also consider the choice of the number of survival times to include in the multivariate outcome. We illustrate the results with simulations and with the results from a clinical trial examining recurring opportunistic infections in persons with HIV.     

方向导数和偏导数

通过对方向导数和偏导数两者间区别与联系的论述，揭示了它们是同属于函数变化率问题的两个平行的不同的概念．     

导数与微分概念的推广

本文将数学分析中单值函数f:R→R 的导数与微分的概念推广到向量值函数f :Rn →Rm 和集值函数f:Rn → 2 Rm 上     

H_(01)~○—H_(10)~□高功率定向耦合器的改进设计

提出了一种从圆波导 TE_(01)模到矩形波导 TE_(10)模的定向耦合器的设计方法。利用这种方法设计的用于高功率回旋速调管的-50dB 定向耦合器表明,改变矩形波导尺寸可以提高对圆波导 TE_(11)模的抑制度,而调整最后两个耦合孔的距离则可以优化方向性。     

以人为本:数字媒介生态与广告传播

为了把握当今数字化时代媒介生态环境与广告传播的变革,运用尼尔·M·波兹曼(Neil M.Postman)提出的“媒介生态”理论与当前广告传播实践相结合的研究方法,研究认为以人为本的数字媒介生态正在形成,广告传播以此为背景,呈现出以人为本的娱乐化价值取向、定向多维传播模式和非线性创意思维的特征。     

基于DEA方法的科研机构方向规模收益研究

DEA模型是目前公共部门(包括科研机构)规模收益分析的常用方法之一.现有通过DEA方法估算科研机构规模收益的研究都是从传统规模收益经济学定义出发,假定多种投入和产出按相同比例进行变化,从而定性定量判定DMU单元的规模收益情况.由于科研活动的复杂性,在科研组织中各类投入或产出的变化往往并不相同.因此,现有DEA框架中关于规模收益的定义(基于径向测度)不能满足多投入多产出情况下科研机构规模收益估算的需要.本文采用可变比例规模收益思想,将DEA方法框架下规模收益定义扩展为方向规模收益,并研究提出科研机构方向规模收益分析的新方法.最后,本文以2009年中国科学院16个基础领域研究所为案例,进行深入分析.