广义线性系统的解

:研究了广义线性系统初值问题可解的充要条件和解的结构     

Confidence regions based on inefficient estimators

We consider an unbiased estimator of a function of mean value parameters, which is not efficient. This inefficient estimator is correlated with a residual vector. Thus, if a unit dispersion is unknown, it is impossible to determine the correct confidence region for a function of mean value parameters via a standard estimator of an unknown dispersion with the exception of the case when the ordinary least squares (OLS) estimator is considered in a model with a special covariance structure such that the OLS and the generalized least squares (GLS) estimator are the same, that is the OLS estimator is efficient. Two different estimators of a unit dispersion independent of an inefficient estimator are derived in a singular linear statistical model. Their quality was verified by simulations for several types of experimental designs. Two new estimators of the unit dispersion were compared with the standard estimators based on the GLS and the OLS estimators of the function of the mean value parameters. The OLS estimator was considered in the incorrect model with a different covariance matrix such that the originally inefficient estimator became efficient. The numerical examples led to a slightly surprising result which seems to be due to data behaviour. An example from geodetic practice is presented in the paper.     

An Extension of the Epsilon-Skew-Normal Distribution

This article is related with the probabilistic and statistical properties of an parametric extension of the so-called epsilon-skew-normal (ESN) distribution introduced by Mudholkar and Hutson (2000 Mudholkar , G. S. , Hutson , A. D. ( 2000 ). The epsilon-skew-normal distribution for analyzing near-normal data . J. Statist. Plann. Infer. 83 : 291 – 309 .[Crossref], [Web of Science ®] , [Google Scholar]), which considers an additional shape parameter in order to increase the flexibility of the ESN distribution. Also, this article concerns likelihood inference about the parameters of the new class. In particular, the information matrix of the maximum likelihood estimators is obtained, showing that it is non singular in the special normal case. Finally, the statistical methods are illustrated with two examples based on real datasets.     

Some comments on escoufier's RV- coefficient as a sensitivity measure in principal component analysis

The RV-coefficient (Escoufier, 1973; Robert and Escoufier, 1976) is studied as a sensitivity coefficient of the subspace spanned by dominant eigenvectors in principal component analysis. We use the perturbation expansion up to second order term of the corresponding projection matrix. The relationship with the measures by Benasseni (1990) and Krzanowski (1979) is also discussed.     

Error bounds for the perturbation solution of the transition density under a multi-factor CIR term structure model with weak mean-reversion effect

Abstract

We consider a multi-factor Cox-Ingersoll-Ross (CIR) model of the term structure of interest rates with weak mean-reversion effect. We use perturbation theory to analyze its conditional characteristic function illustrated by a system of Riccati equations and derive the error bounds for the perturbation approximations. Using the Fourier inversion theorem, we clarify that the perturbation approximation of the conditional characteristic function can be applied to estimate the transition density and likelihood function. We provide their error bounds and accuracy orders. Finally, we discuss the performance of the perturbation approximation in estimating the transition density via simulation.     

Adaptive-Cox model averaging for right-censored data

In medical studies, Cox proportional hazards model is a commonly used method to deal with the right-censored survival data accompanied by many explanatory covariates. In practice, the Akaike's information criterion (AIC) or the Bayesian information criterion (BIC) is usually used to select an appropriate subset of covariates. It is well known that neither the AIC criterion nor the BIC criterion dominates for all situations. In this paper, we propose an adaptive-Cox model averaging procedure to get a more robust hazard estimator. First, by applying AIC and BIC criteria to perturbed datasets, we obtain two model averaging (MA) estimated survival curves, called AIC-MA and BIC-MA. Then, based on Kullback–Leibler loss, a better estimate of survival curve between AIC-MA and BIC-MA is chosen, which results in an adaptive-Cox estimate of survival curve. Simulation results show the superiority of our approach and an application of the proposed method is also presented by analyzing the German Breast Cancer Study dataset.     

Buck变换器在酒泉太阳能光伏发电中的应用

太阳能光伏发电作为一种新能源,易受季节变化、昼夜交替的影响,因此其输出电压很不稳定.鉴于此,本文采用Buck变换器,采用扰动观察法的MPPT控制策略,可应用到酒泉的太阳能光伏发电中,可使得输出电路的等效阻抗跟随光伏电池的输出阻抗,使光伏阵列在任何条件下获得最大功率输出,跟踪最大功率的优点.仿真表明,MPPT(最大功率跟踪)控制策略的可行性,该方法有效地提高了输出电压的稳定性.     

广义系统的快速终端滑模控制

研究了一类广义系统的快速终端滑模控制问题。通过非奇异线性变换把广义系统变换成受限等价形式,利用Lyapunov函数的方法,提出了一种新的指数型快速终端滑模控制策略,给出了特殊的指数型终端滑模超曲面,设计了相应的终端滑模控制器,使得闭环系统渐进稳定,实现了滑模运动,保证了系统状态变量以较快的收敛速度在有限时间内到达平衡点。给出了数值算例,说明了设计的可行性和有效性。     

一个非 Kerr 黑洞的拓扑结构和该黑洞时空中的 Dirac 能级(英)

一个非 Kerr 黑洞时空中的 Dirac 能级分布与黑洞的质量多极矩(用参数αn 表示)有关,此黑洞的视界面上出现内禀奇性处的 Dirac 能级有明显的分布特征.     

俄语动词单数第二人称命令式的转义用法

俄语动词单数第二人称命令式用于转义用法 ,谓语在人称、数、形式上与主语不一致 ,表现了丰富的情态意义 ,在口语及文艺作品中用的最多