一类二维非线性奇异方程的有限元方法

本文考虑了一类二维非线性奇异稳态问题的有限元方法，并给出有限元解的加权L2-模和加权H1-模估计．     

广义次正定复矩阵及其性质

继续研究决正定矩阵的理论，定义了复数域上的广义次正定矩阵，讨论了它的一系列性质．     

On the skew-normal calibration model

In this article, we present the EM-algorithm for performing maximum likelihood estimation of an asymmetric linear calibration model with the assumption of skew-normally distributed error. A simulation study is conducted for evaluating the performance of the calibration estimator with interpolation and extrapolation situations. As one application in a real data set, we fitted the model studied in a dimensional measurement method used for calculating the testicular volume through a caliper and its calibration by using ultrasonography as the standard method. By applying this methodology, we do not need to transform the variables to have symmetrical errors. Another interesting aspect of the approach is that the developed transformation to make the information matrix nonsingular, when the skewness parameter is near zero, leaves the parameter of interest unchanged. Model fitting is implemented and the best choice between the usual calibration model and the model proposed in this article was evaluated by developing the Akaike information criterion, Schwarz’s Bayesian information criterion and Hannan–Quinn criterion.     

On optimal linear equivariant estimation under progressive censoring

We consider best linear equivariant estimation in a particular location-scale family based on several progressively type II censored samples. The censoring schemes that minimize the mean squared error matrix of the estimators with respect to the Löwner ordering are obtained. Uniqueness of the schemes, which minimize the smallest and the largest eigenvalue of the matrix is shown under some condition.     

An alternative approach to minimize model inadequacy

In this article Bock's (1975) approach is used to fit a class of lower order polynomials to a higher order response function. For a wide class of conditions our fitted models offer greater protection, in some sense, against model inadequacies than the one fitted by Karson, Manson and Hader (1969). However, our approach is applicable to the situations where the assumption of normality about the distribution of the response variable is appropriate.     

Comments on a Paper by Lachenbruch and Flack

Razzaghi (1987) conjectured that a wrong choice of covariance matrix in a restricted linear model results in loss of efficiency. This conjecture was proved correct by Kabe and Gupta for a wrong choice of constant covariance matrix. The present paper demonstrates that this loss of efficiency persists even with an estimated covariance matrix, thereby resulting in inefficient estimation, prediction, and confidence intervals.     

A note on generalized ridge estimators

It is shown that a necessary and sufficient condition derived by Farebrother (1984)for a generalized ridge estimator to dominate the ordinary least-squares estimator with respect to the mean-square-error-matrix criterion in the linear regression model admits a similar interpretation as the well known criterion of Toro-Viz-carrondo and Wallace (1968)for the dominance of a restricted least-squares estimator over the ordinary least-squares estimator. Two other properties of the generalized ridge estimators, referring to the concept of admissibility, are also pointed out.     

On the solution of renewal-type integral equations

A simple method (here called the RS-method) established for solving renewal-type integral equations based on direct numerical Riemann-Stieltjes integration is presented and evaluated. In almost all situations it has shown surprisingly good results in terms of simplicity, convergence and applicability compared with the other known methods. The RS-method is particularly useful when the probability density function has singularities.     

整数矩阵集上的Fermat方程

设A 是 m 阶整数矩阵,A 是由A 的全体方幂构成的集合.本文证明了:当 m > 9 时,如果A 的行列式｜ A｜ ≠0 ,而且A 的特征根不全为单位根,则A 上的Fermat 方程无解.     

也谈欧氏空间的等角变换

在文[1]的基础上，推出了等角变换的几个新的判别法，并给出了等角变换可对角化的几个充要条件。