MATLAB在工程图学中的应用

计算机技术的发展为工程图学注入了新的活力。从引入计算机辅助设计理念到融合数学与计算机图形学技术,都影响着工程图学课程的内容和教学方式。本文分析了传统图学投影理论中所包含的数学信息,增强了"图"与"数"的内在联系,为传统图学理论更加实用发掘新的契合点。     

广州方言底层词"栏"与"墟

广州方言中的底层词,除保留在地名和口语中之外,有的既是口语词,同时又是构成地名的词语,本文所讨论的"栏"与"墟"就是这一类词语。通过对它们在广州方言中的留存、变异以及衍生出来的系列词语的考察,不仅可以探索它们从少数民族语言进入到汉语的过程,更能深入地了解粤语与少数民族语言的关系,而且对认识社会经济的发展给词义演变所带来的影响,也是有意义的。     

The Apparent‐Time Construct and stable variation: Final /z/ devoicing in northwestern Indiana1

As real‐time language data becomes increasingly available for sociolinguistic research, a growing number of studies are benefitting from it in order to study language changes in progress, some of which even explicitly seek to scrutinize the Apparent‐Time Construct itself. Vanishingly few real‐time studies, however, have focused specifically on stable sociolinguistic variables, leaving an important gap in our understanding of the Apparent‐Time Construct's abilities to model real‐time facts. In an effort to address this gap, the present study analyzes a presumably stable sociolinguistic variable – final /z/ devoicing – in extreme northwestern Indiana through real and apparent time. A series of Varbrul analyses indicate that this variable is, indeed, stable throughout the 20 years of real time covered by the data and that its stability is successfully modeled in apparent time. Additionally, similarities in /z/ devoicing between this community and some other communities where it has also been studied are identified and discussed.     

外汇市场冲击与国内资本市场波动的关联机理解析

运用三元VAR-GARCH(1,1)-Asymmetric-BEKK模型,解析了汇市、股市和债市间的关联机制。结果显示,汇市对股市和债市有显著的均值与波动溢出,而股市和债市对汇市仅有波动溢出,且汇市对股市的溢出效应大于对债市的溢出。基于新闻冲击曲面的分析揭示了资本市场对汇市冲击呈明显的非对称性。为此,政府应将金融市场开放度的扩大与资本流动的监管相结合,构建针对资本市场风险的多层次测度与监控体系,并完善资本市场的制度架构,增强信息披露的有效性。     

一般截面复合曲梁在复杂受力下的正应力研究

给出了一般截面形状的复合曲梁在复杂载荷作用下正应力的计算公式，作为特殊情况，该梁在平面弯曲时的相应公式也可以从上述公式得到。最后给出了计算实例。     

基于信托方式的曲线MBO模式再设计

管理层收购作为国企产权制度改革的一种途径,在我国的实施过程中面临一些问题与障碍。通过对基于信托方式的曲线MBO模式的再设计,引入员工持股计划、公开竞价机制、战略投资者以及风险共担机制,重视对MBO完成后目标公司的整合,以期达到规范曲线MBO实施过程、完善公司治理结构的目的。     

光学平台隔振系统结构参数的优化设计

针对使用空气弹簧隔振器的光学平台传递函数进行了研究.对平台固有频率和传递函数的计算结果进行曲面拟合,并利用拟合曲面形成目标函数,进行平台隔振系统结构参数的优化设计计算.结果表明,要获得最佳隔振效果,应取相对阻尼系数ξ越小越好,但ξ过小使系统稳定性变差.最优值ξ为0.1～0.15,主空气室与附加空气室的容积比k为0.28.     

A Geometric Approach to Nonlinear Econometric Models

Conventional tests for composite hypotheses in minimum distance models can be unreliable when the relationship between the structural and reduced‐form parameters is highly nonlinear. Such nonlinearity may arise for a variety of reasons, including weak identification. In this note, we begin by studying the problem of testing a “curved null” in a finite‐sample Gaussian model. Using the curvature of the model, we develop new finite‐sample bounds on the distribution of minimum‐distance statistics. These bounds allow us to construct tests for composite hypotheses which are uniformly asymptotically valid over a large class of data generating processes and structural models.     

Substrate reinforcement and dialectal differences in Melanesian Pidgin

Stabilization of a new contact language involves a process of levelling, or the reduction of variants. One of the factors influencing which grammatical variants are retained in the process is substrate reinforcement – the existence in the substrate languages of a congruent structure with a similar function. This article illustrates substrate reinforcement in the development of the three current dialects of Melanesian Pidgin. First, evidence of earlier variability is presented and the sociolinguistic conditions that later led to greater stability are described. Second, five grammatical features that differentiate the dialects are examined. For each feature, it is shown first that at least two variants were previously in use. Then evidence is presented illustrating correspondence between the particular variant retained in the dialect and a feature of the substrate languages of that geographic area. Differing substrates reinforced different variants, and this accounts for these dialectal differences.     

Rapid reconstruction method of curved surface model in reverse design of bucket teeth

零件的曲面模型是获得其逆向设计数据等后续处理的关键环节。为了快速获得具有复杂外形和内腔的某型挖掘机斗齿的设计数据,研究了该斗齿点云曲面原型的获取方法。鉴于斗齿不同部位对逆向设计精度的要求不同,采用Imageware和Geomagic Studio对斗齿的内腔、销孔和外形点云分别进行曲面重构之后,再进行整个模型的曲面整合策略。介绍了应用两种软件完成斗齿曲面模型的主要处理过程及关键环节。该方法能快速获得符合精度要求的斗齿曲面模型,可行且高效,为斗齿曲面模型的实体化及其后续处理提供了可靠依据。