改善全息圆锥准直线及提高准直精度的一种方法

用一张计算全息图可产生锥面波,锥面波衍射图样的中心在空间是连续的,可作为直线基准。本文提出了提高锥面波直线准直精度的一种方法即空间滤波法。实验结果与理论分析一致。     

Bootstrap tests for multivariate directional alternatives

Tests on multivariate means that are hypothesized to be in a specified direction have received attention from both theoretical and applied points of view. One of the most common procedures used to test this cone alternative is the likelihood ratio test (LRT) assuming a multivariate normal model for the data. However, the resulting test for an ordered alternative is biased in that the only usable critical values are bounds on the null distribution. The present paper provides empirical evidence that bootstrapping the null distribution of the likelihood ratio statistic results in a bootstrap test (BT) with comparable power properties without the additional burden of assuming multivariate normality. Additionally, the tests based on the LRT statistic can reject the null hypothesis in favor of the alternative even though the true means are far from the alternative region. The BT also has similar properties for normal and nonnormal data. This anomalous behavior is due to the formulation of the null hypothesis and a possible remedy is to reformulate the null to be the complement of the alternative hypothesis. We discuss properties of a BT for the modified set of hypotheses (MBT) based on a simulation study. The resulting test is conservative in general and in some specific cases has power estimates comparable to those for existing methods. The BT has higher sensitivity but relatively lower specificity, whereas the MBT has higher specificity but relatively lower sensitivity.     

《飘》叙事话语的女性特征

文章以叙事话语为视角,指出《飘》的可读性源于作家密契尔创作中的诸多女性特征,如遵循女性阅读习惯构建文本体系,用女性眼光发言,以女性心态轨迹组合戏剧性情节,借助话语对答,巧用心理分析等,并阐明女作家在叙事话语领域的继承与创新.     

The role of reversals in order‐restricted inference

A statistical model is said to be an order‐restricted statistical model when its parameter takes its values in a closed convex cone C of the Euclidean space. In recent years, order‐restricted likelihood ratio tests and maximum likelihood estimators have been criticized on the grounds that they may violate a cone order monotonicity (COM) property, and hence reverse the cone order induced by C. The authors argue here that these reversals occur only in the case that C is an obtuse cone, and that in this case COM is an inappropriate requirement for likelihood‐based estimates and tests. They conclude that these procedures thus remain perfectly reasonable procedures for order‐restricted inference.     

牙轮钻头滑动轴承用钢粉末渗钒的试验研究

本文着重研究了牙轮钻头轴承用钢的粉末渗钒配方、工艺和渗层的组织结构。运用扫描电镜对渗层进行观察和成分分析;用X射线衍射仪确定渗层的相结构;初步探讨了渗钒层的形成机理。     

牙轮钻头牙齿与岩石垂向互作用仿真模型

建立钻头牙齿与岩石的互作用仿真模型是实现钻头与岩石互作用仿真研究的核心问题之一。本文以岩石破碎力学为基础，从钻头牙齿与岩石的互作用特.点出发，突破通常的力/侵深曲线描述方法，推导出了钻头牙齿与岩石垂向互作用仿真模型。并在该模型中用岩石硬度、塑性系数和弹性系数来反映岩石的力学性质，从而使模型具有较宽的应用范围。     

A Simple New Algorithm for Quadratic Programming with Applications in Statistics

Problems involving estimation and inference under linear inequality constraints arise often in statistical modeling. In this article, we propose an algorithm to solve the quadratic programming problem of minimizing for positive definite Q, where is constrained to be in a closed polyhedral convex cone , and the m × n matrix is not necessarily full row rank. The three-step algorithm is intuitive and easy to code. Code is provided in the R programming language.     

Sharp upper mean-variance bounds for trimmed means from restricted families

We apply the method of projection to derive sharp upper mean-variance bounds on trimmed means of order statistics of i.i.d. samples coming from restricted families of probability measures. Two families are considered: distributions with decreasing density and decreasing failure rate. We also present some numerical results.     

Constrained penalized splines

The penalized spline is a popular method for function estimation when the assumption of “smoothness” is valid. In this paper, methods for estimation and inference are proposed using penalized splines under additional constraints of shape, such as monotonicity or convexity. The constrained penalized spline estimator is shown to have the same convergence rates as the corresponding unconstrained penalized spline, although in practice the squared error loss is typically smaller for the constrained versions. The penalty parameter may be chosen with generalized cross‐validation, which also provides a method for determining if the shape restrictions hold. The method is not a formal hypothesis test, but is shown to have nice large‐sample properties, and simulations show that it compares well with existing tests for monotonicity. Extensions to the partial linear model, the generalized regression model, and the varying coefficient model are given, and examples demonstrate the utility of the methods. The Canadian Journal of Statistics 40: 190–206; 2012 © 2012 Statistical Society of Canada     

Reconciliation as a Frame for Rethinking Racism in Australia

This paper begins with a brief reading of Australia's ‘signature racism’ and ponders the question of what we might do about it. As a novel way to this problematic, the paper considers the national reconciliation process, exemplified by the work as of the Council for Aboriginal Reconciliation (CAR), as a ‘good movement’ in Derrida's terms and as a site for investigating antiracist work in Australia. The CAR provides conceptual resources for considering the pedagogical challenge for a cultural politics of antiracism. Importantly the challenge is understood in terms of a terrain of affect in which in which anger is simultaneously silenced, repressed and denied. The paper concludes by contemplating the possibility of a post-indignation pedagogy.