基于单位球面生成的等距双NURBS刀具路径规划

目前由离散刀位点数据生成的2条NURBS曲线刀具路径中,刀轴点NURBS曲线与刀具中心点NURBS曲线间 距有可能存在不相等的问题,提出一种单位球面下优化刀轴矢量NURBS曲线的方法,用以解决生成的等距双NURBS刀 具路径中2条NURBS曲线间距有可能不相等的问题。算例表明,本算法可以对工件坐标系下的线性刀路进行光顺,确 保双NURBS样条曲线的间距相等。     

秩估计及向量广义线性模型在风险投资中应用

从风险投资案例中整理发现内在变化规律,有助于把握投资方向和路径。以2001—2011年全球投资公司每轮平均投资数据为例,由于数据不具备正态性和方差齐次性,基于秩估计方差分析,结果表明,各年之间均值存在显著差异。假设平均投资服从伽玛分布,其形状参数和尺度参数是年份的二次函数,基于向量广义线性模型估计各参数。最后预测2015年伽玛分布形状参数为1．1959,尺度参数为5816．186。风险投资位于任何区间的概率都可以通过分布函数计算。     

基于董事会特征调节效应的R&D与绩效关系研究——来自新一代信息技术企业的经验数据

文章以2009至2012年为研究区间,选取沪深A股主板137家新一代信息技术上市公司的347个样本数据作为研究对象,对基于董事会特征调节效应的R&D投入与企业绩效的关系进行实证分析。研究结果表明,新一代信息技术企业R&D投入与企业绩效呈正相关的关系;董事持股比例和关键董事年龄都是同质调节变量,对R&D投入与企业绩效关系的形态和方向进行调节,董事持股比例越高或关键董事年龄越低对二者关系的影响越强;董事会会议强度不是调节变量。     

The two-dimensional vector packing problem with piecewise linear cost function

The two-dimensional vector packing problem with piecewise linear cost function (2DVPP-PLC) is a practical problem faced by a manufacturer of children׳s apparel that ships products using courier service. The manufacturer must ship a number of items using standard-sized cartons, where the cost of a carton quoted by the courier is determined by a piecewise linear function of its weight. The cost function is not necessarily convex or concave. The objective is to pack all given items into a set of cartons such that the total delivery cost is minimized while observing both the weight limit and volume capacity constraints. This problem is commonly faced by many manufacturers that ship products using courier service. We formulate the problem as an integer programming model. Since the 2DVPP-PLC generalizes the classical bin packing problem, it is more complex and challenging. Solving it directly using CPLEX is successful only for small instances. We propose a simple heuristic that is extremely fast and produces high-quality solutions for instances of practical size. We develop an iterative local search algorithm to improve the solution quality further. We generate two categories of test data that can serve as benchmark for future research.     

An online copy number variant detection method for short sequencing reads

The availability of the next generation sequencing (NGS) technology in today's biomedical research has provided new opportunities in scientific discovery of genetic information. The high-throughput NGS technology, especially DNA-seq, is particularly useful in profiling a genome for the analysis of DNA copy number variants (CNVs). The read count (RC) data resulting from NGS technology are massive and information rich. How to exploit the RC data for accurate CNV detection has become a computational and statistical challenge. We provide a statistical online change point method to help detect CNVs in the sequencing RC data in this paper. This method uses the idea of online searching for change point (or breakpoint) with a Markov chain assumption on the breakpoints loci and an iterative computing process via a Bayesian framework. We illustrate that an online change-point detection method is particularly suitable for identifying CNVs in the RC data. The algorithm is applied to the publicly available NCI-H2347 lung cancer cell line sequencing reads data for locating the breakpoints. Extensive simulation studies have been carried out and results show the good behavior of the proposed algorithm. The algorithm is implemented in R and the codes are available upon request.     

Complete consistency for the estimator of nonparametric regression models based on extended negatively dependent errors

In this paper, we provide some exponential inequalities for extended negatively dependent (END) random variables. By using these exponential inequalities and the truncated method, we investigate the complete consistency for the estimator of nonparametric regression model based on END errors. As an application, the complete consistency for the nearest neighbour estimator is obtained.     

Approximating moments of continuous functions of random variables using Bernstein polynomials

Bernstein polynomials have many interesting properties. In statistics, they were mainly used to estimate density functions and regression relationships. The main objective of this paper is to promote further use of Bernstein polynomials in statistics. This includes (1) providing a high-level approximation of the moments of a continuous function $g\left(X\right)$ of a random variable $X$, and (2) proving Jensen’s inequality concerning a convex function without requiring second differentiability of the function. The approximation in (1) is demonstrated to be quite superior to the delta method, which is used to approximate the variance of $g\left(X\right)$ with the added assumption of differentiability of the function. Two numerical examples are given to illustrate the application of the proposed methodology in (1).     

‘A ondi queras’: Ranchero identity construction by U.S. born Mexicans on Facebook

This study describes how transnational second‐generation Mexican bilinguals use a stigmatized variety of Mexican Spanish to communicate on Facebook and construct an identity. The stereotyped features of this variety index a ranchero identity. Historically, ranchero is an ambivalent identity for Mexican society in general. On the one hand, ranchero culture is a positive reminiscence of Mexico's agrarian past, while on the other, rancheros, along with indigenous Mexicans, are at the bottom of the hierarchy in Mexican society. A discourse‐centered, ethnographic analysis of digitally mediated conversations demonstrates how language use allows participants to reminisce about their collective past, maintain Mexican identities tied to their ancestors, fit their identities to contemporary U.S. Mexican culture, and distance themselves from the stigma associated with the ranchero background.     

The problem of social generations: a critique of the new emerging orthodoxy in youth studies

Over the previous seven years the application of a social generation paradigm or ‘theory’ has gained increasing currency as a method in analysing young people's relationship with the life course. Whilst not a new concept or approach its resurgence and reconfiguration to ‘new’ times has seen some writers positioning it as a ‘new orthodoxy’ or ‘consensus’ within youth studies. In this it is seen as providing a conceptual framework that better helps us understand the complexity of circumstances and conditions that shape youth identities in late modern society. In this paper we examine and explore the underlying assumptions and claims that are made by those advocating the social generational paradigm, raising questions and seeking further clarification on a number of key themes. We accept youth studies needs to move beyond ‘old models’ that define and understand social context as a simply a tension between ‘structure or/and agency’ or as a ‘flavour’ to social action. To conclude therefore we propose the need to have an approach that is ecological and both accepts ‘social change’ and ‘continuity’ as critical parts of the life course, one that recognises the nature and influence of power and social reproduction, especially for different social classes, in shaping the experience of being young.     

基于加权案例推理模型族的软件成本SVR组合估算

精确地估算软件成本是软件项目成功开发的一个重要保证,直接影响着软件的风险控制和质量保证.为了更好地解决单一估算模型的不足,提出了集成多案例推理(CBR)模型的软件成本组合估算模型.首先,采用六种距离计算公式刻画新旧项目相似度,构建了六种CBR模型,并运用粒子群算法(PSO)来优化CBR模型族中的属性权重.其次,在CBR模型族的基础上,运用支持向量回归机(SVR)模型将不同CBR模型的估算结果进行集成,提高软件成本估算结果的精度.利用Deshamais数据库对模型有效性进行检验,实证结果表明,在六种CBR模型中Euc-CBR、Min-CBR、Gau-CBR和Mah-CBR模型估算结果没有明显差异,Gre-CBR和Man-CBR模型略优;提出的SVR组合估算模型估算精度明显优于单CBR模型和其他线性组合估算模型,能有效提高软件成本的估算精度.