Unique nontransitive measurement on finite sets

Two themes in the theory of measurement that have been studied extensively in the past few years are numerical representations of nontransitive binary comparison structures and uniqueness in finite measurement systems. This paper brings the two together by exploring the solutions to a nontransitive, additive model that are unique up to multiplication by a positive constant. The model relates to various contexts including decision under risk, evaluation of objectives, comparative probability, and voting theory. The family of unique solutions for the model is shown to be extremely rich and varied.     

Objective Tests versus Subjective tests

objective test has only one correct answer, while subjective test has a range of possible answers. Because of this feature, reliability will not be difficult to achieve in the marking of the objective item, while the marking of the subjective items is reliable. On the whole, a good test must contain both subjective and objective test items.     

基于有限差分的化学剂平面运移规律数值模拟

在化学驱中，各种化学剂在地层中的浓度对于驱油是极为关键的，理想的情况是合理设计化学剂注入参数（注 入浓度、注入量和注入速度），使得地层各处化学剂的浓度接近实验室设计的最佳浓度，从而驱油效率最高。化学剂在 地层中除正常的对流外，还会发生扩散和吸咐，而平面渗流中，各处渗流速度的不同，使得化学剂在平面的浓度分布比 一维情况复杂得多。依据有限差分法和雅可比迭代方法，根据达西渗流定律确定平面渗流速度场和压力场分布，再根 据已求得的速度场结合化学剂运移的对流弥散方程，求解得到了化学剂的浓度场。数值模拟结果给出了不同时刻化 学剂在地层中的浓度分布，并针对不同的运移滞后系数、弥散系数和化学剂注入量，分析了这些参数对于化学剂分布 的影响。     

The likelihood ratio test for homogeneity in finite mixture models

The authors study the asymptotic behaviour of the likelihood ratio statistic for testing homogeneity in the finite mixture models of a general parametric distribution family. They prove that the limiting distribution of this statistic is the squared supremum of a truncated standard Gaussian process. The autocorrelation function of the Gaussian process is explicitly presented. A re‐sampling procedure is recommended to obtain the asymptotic p‐value. Three kernel functions, normal, binomial and Poisson, are used in a simulation study which illustrates the procedure.     

D-optimal design for a quadratic log contrast model for experiments with mixtures

A practical method is suggested for solving complicated D-optimal design problems analytically. Using this method the author has solved the problem for a quadratic log contrast model for experiments with mixtures introduced by J. Aitchison and J. Bacon-Shone. It is found that for a symmetric subspace of the finite dimensional simplex, the vertices and the centroid of this subspace are the only possible support points for a D-optimal design. The weights that must be assigned to these support points contain irrational numbers and are constrained by a system of three simultaneous linear equations, except for the special cases of 1- and 2-dimensional simplexes where the situation is much simpler. Numerical values for the solution are given up to the 19-dimensional simplex     

基于波导模式正交的新吸收边界条件

提出了一种可同时吸收波导内行波和雕落波型的新型吸收边界条件。与常规的吸收边界条件相结合，在这种新的吸收边界条件下，可将边界紧置于不连续区附近而保持计算精度，使计算时间和对计算机内存的要求都大大下降。数值计算的例子表明用新的边界条件计算出的结果与用常用吸收边界条件计算出的结果吻合得很好     

理论教学、传统实验与“有限元分析”有机结合的探索与研究

＂有限元分析＂是工程领域进行数值计算的极为重要的方法之一。为使学生掌握有限元方法的基本原理和编程技巧,更好地应用有限元分析这一强有力的数值计算工具,文章将理论分析、传统实验与计算机数值模拟有机结合,结合工程应用的具体实践,在有限元教学中不断渗透学科发展的前沿知识,从教学方式、内容选择、实验设计等几个方面作了一系列探索。     

ROBUST ESTIMATION OF SMALL‐AREA MEANS AND QUANTILES

Small‐area estimation techniques have typically relied on plug‐in estimation based on models containing random area effects. More recently, regression M‐quantiles have been suggested for this purpose, thus avoiding conventional Gaussian assumptions, as well as problems associated with the specification of random effects. However, the plug‐in M‐quantile estimator for the small‐area mean can be shown to be the expected value of this mean with respect to a generally biased estimator of the small‐area cumulative distribution function of the characteristic of interest. To correct this problem, we propose a general framework for robust small‐area estimation, based on representing a small‐area estimator as a functional of a predictor of this small‐area cumulative distribution function. Key advantages of this framework are that it naturally leads to integrated estimation of small‐area means and quantiles and is not restricted to M‐quantile models. We also discuss mean squared error estimation for the resulting estimators, and demonstrate the advantages of our approach through model‐based and design‐based simulations, with the latter using economic data collected in an Australian farm survey.     

软件无线电中正交数字变频的DSP实现

介绍了软件无线电的概念及DSP基本原理,利用DSP实现软件无线电中的正交数字变频技术,给出了中频下变频的数字化实现的主程序.