求多元函数条件极值应注意的几个问题

指出高等数学教学中关于求多元函数条件极值应注意的几个问题，并给出二元函数及三元函数取得条件极值的若干充分条件。     

微分中值定理中辅助函数构造的方法

通过对微分中值定理的应用研究,发现在解决此类命题中,大多采用构造辅助函数的方法来证明,如何构造辅助函数成为证明此类问题的关键。本文给出了三类关于辅助函数的构造的方法和技巧,并给出例题并加以应用。     

利用二次型求一类多元函数的最值

根据二次型的定义，本文给出了二次型的一个特殊性质，指出了其性质在求多元函数最值的用处，举例说明结果的有效性。     

基于R语言的多元数据统计图形可视化

多元数据可视化越来越受到应用研究的重视,特别是多元数据的统计图形的实现得到了很多人的研究,本文综合介绍了常见的多元数据统计图形(箱须图、星相图、脸谱图、气泡图),并在R语言的环境下,给出了相应的程序函数语言。     

多元线性回归模型对于荒漠区植物生物量的分析

多元线性回归模型是根据得到的若干有关变量的一组数据，寻找因变量与多个自变量之间的一个函数，使这个函数对那组数据拟合的最好。然后利用方差分析方法对模型误差进行分析，对拟合的优劣给出评价，本文利用此种方法对荒漠区不同干扰下植物地上生物量的变化趋势进行研究，对实际的生态环境提出一些合理建议。     

价格、时间敏感性应链收益混合分配契约模型研究

供应链企业通过何种契约方式进行协同合作,以达到整体目标的最优,是供应链管理的一个重要研究课题。在一个两阶供应链系统中,面对价格和响应时间敏感性市场需求,文章通过引入供应商的激励—响应时间函数和市场关于价格和响应时间的需求函数,构建了供应链的收益混合分配契约模型,最后文章给出了算例分析,验证了该模型的可行性。     

新一代产品几何技术规范(GPS)研究(3)--尺寸、公差及表面特征

1 现代GPS的尺寸标准体系分析1.1 尺寸的定义 在标准ISO 286-1中给出了尺寸的定义: "尺寸是用一个特定的单位表示一个直线尺度值的数。" 根据定义,尺寸必须理解为一个线性尺度。 图1是ISO／WD 14405关于尺寸的未来草案的描述。     

对于价值工程中对象选择方法的比较研究

价值工程中关于改进对象的选择始终是一个基本问题,如何选取准则是关键。现在就20世纪中期至今的7种主流方法一一进行比较分析,从区域几何特征(包括区域关于标准直线的渐进性以及非对称性)、解析表达式在价值工程上的经济意义、待定常数的易得性、应用中的便利性四个方面进行比较,并给出初步结论。     

价格、时间敏感性供应链收益混合分配契约模型研究

供应链企业通过何种契约方式进行协同合作，以达到整体目标的最优，是供应链管理的一个重要研究课题。在一个两阶供应链系统中，面对价格和响应时间敏感性市场需求，文章通过引入供应商的激励——响应时间函数和市场关于价格和响应时间的需求函数，构建了供应链的收益混合分配契约模型，最后文章给出了算例分析，验证了该模型的可行性。     

单位根检验中的Wald统计量研究

本文研究了不同情形下单位根的Wald检验.首先从理论上推导了各种Wald检验统计量的极限分布;然后,运用蒙特卡罗试验,模拟了有限样本容量常用检验水平下的临界值,拟合了临界值关于样本容量的响应面函数,给出了检验统计量的分位数表,并总结了用于单位根检验的Wald统计量有限样本容量下的统计特性.     

n维线性商品空间中的比较优势效率

迄今为止，人们对一般情况下的比较优势的效率结构尚缺乏清楚的了解。本文在假定只有两个国家，且每个国家的生产可能性边界均为线性的基础上，从相对简单的三维商品空间开始分析，然后讨论四维商品空间中的比较优势问题，最后通过对所得结果的观察、分析和归纳，建立任意维商品空间中的比较优势的一般理论。     

绥宁连接线第43合同段K31+650～K31+770路堑工程地质评述

K31+650～K31+770为路堑段,起点设计路面高程510.60 m,止点设计路面高程507.78 m,设计路面纵坡-1.5%,线路左右两侧均为切坡,切坡最大高度约15.00 m,但是其地质条件较为复杂。文章对其地质条件进行评述,以期为设计和施工提供技术支持。     

Spatial distribution of economic activities: a network approach

The aim of this paper is to analyse co-location patterns of manufactures and service industries at a microgeographic level using Spanish data from the Mercantile Register. Our approach allows us to analyse joint-location and co-location patterns of firms in different industries, and to overcome previous technical constraints in this type of analyses, partially thanks to using homogeneous cells instead of administrative units. This paper contributes to the empirical literature on industry location by developing a multisectorial co-location index computed by comparing differences between observed data about firms’ location and randomly generated data. Multisectorial relationships are analyzed by transposing bilateral relations onto an n-dimensional space. Our results show that dispersed industries tend to locate jointly and that industries with lower joint-location patterns have spatial structures similar to those obtained through input–output relationships, suggesting weak role of co-location patterns as interindustry linkages are not the main location determinants.

     

On the existence of the ex post symmetric random entry model

This paper studies symmetry among countably infinitely many agents who randomly enter into a stochastic process, one for each period. Upon entry, they observe only the current period signal and try to draw inference about the underlying state governing the stochastic process. We show that there exist random entry models under which agents are ex post symmetric. That is, all agents have identical posterior belief about the underlying states, although they are not ex ante symmetric. The form of the posterior belief is uniquely pinned down by ex post symmetry and a stationarity condition. Our results provide a common prior foundation for the model studied in Liu and Skrzypacz (2014).     

A flexible logistic growth model with applications in telecommunications

In this paper, we develop a four-parameter generalization of the logistic growth curve, the flexible-logistic (FLOG) model. It is shown that the FLOG model is sufficiently general to locate its point of inflection anywhere between its upper and lower bounds: it can offer wide variation in its degree of symmetry for a given point of inflection. Although additional parameters always produce a better within-sample fit. the specific flexibility introduced by the FLOG class of models emphasises the forecast properties by controlling the saturation level and the approach to that level. The model is subjected to a number of theoretical and empirical tests and is applied to three sets of telecommunications data.     

信息对称的新探索

笔者在以往信息对称研究基础上,结合撰写博士学位论文,对此研究成果进行了重新梳理和细化,对实现信息对称的"三九四"工程继续深化研究,运用综评论分析法、层次分析法,创造性地提出实施九大机制的三种崭新技术,即信息分离技术、信息还原技术和信息核对技术,以期实现信息对称,从根本上改变公司治理。     

Forecasting dynamically asymmetric fluctuations of the U.S. business cycle

The generalized smooth transition autoregression (GSTAR) parametrizes the joint asymmetry in the duration and length of cycles in macroeconomic time series by using particular generalizations of the logistic function. The symmetric smooth transition and linear autoregressions are nested in the GSTAR. A test for the null hypothesis of dynamic symmetry is presented. Two case studies indicate that dynamic asymmetry is a key feature of the U.S. economy. The GSTAR model beats its competitors for point forecasting, but this superiority becomes less evident for density forecasting and in uncertain forecasting environments.     

基于PLC的汽车输送主副线速同步控制系统的设计

本文基于PLC、变频器、编码器组成汽车输送主、副线主从控制的双闭环随动控制系统，采用主输送线的实际运行速度作为副输送线的设定值，实现汽车输送主副线的传动速度同步、高精度稳速控制；该系统可有效抑制外部干扰，消除速度偏差，稳定程度高；实际应用效果达到设计要求。     

Efficiency and deficiency considerations in the symmetry problem

Summary Usually, two statistical procedures A and B are compared by means of their asymptotic relative efficiency e. If e = 1, however, it is more informative to compare A and B by means of the concept of deficiency, which was introduced by H odges and L ehmann [7]. In the present paper we use this concept for the comparison of linear rank tests and parametric tests for the symmetry problem. In this problem, the hypothesis has to be tested that a sample comes from a distribution that is symmetric about zero. The results provide new and strong edivence for the nice performance of linear rank tests for the symmetry problem. The present paper gives a survey of the results obtained by A lbers , B ickel and van Z wet [1] and by A lbers [2].     

室内配制混凝土单轴试验全应力-应变曲线试验研究

本文采用TAW-2000微机控制岩石伺服三轴压力试验机,对室内配制普通混凝土圆柱体试件(高径比约2:1)进行单轴受压实验。测定了普通混凝土全应力-应变曲线。通过对试验的研究,循环加载条件下,确实形成了一个封闭的塑性滞回环,且峰后塑性滞回环随循环的次数的增加而变小变窄;加载应力和加载段变形模量呈一定的线性关系;峰后卸载点的应力和峰值应力差越大,峰后曲线的变化越明显,变得越平缓,重新加载曲线的趋近线斜率与初始变形曲线的趋近线斜率相差越大。