平面任意力系的平衡方程及应用——高职教学中一道典型的例题

平面任意力系的平衡方程及应用是教学的重点和难点,它是解决物体系统平衡问题的基础,学生应理解并熟练掌握。本文举一典型例题来说明平面任意力系的平衡方程的三种形式的具体运用。     

谈同声传译中的"有稿同传"

有稿同传作为同声传译中最常见的工作方式有其独特的表现形式和特点。通过培养译员注意力转移和分散能力、注重翻译技巧和心理素质的训练,可以提高翻译质量。     

市场支持、产业互动与中国服务业发展

本文利用最新投入产出数据,分析了中国制造业和服务业互为中间投入的逻辑关系,进而揭示了两者之间的内生性,并从需求视角对中国供给导向型的服务业发展政策进行了反思。在构建联立方程的基础上,利用2000～2008年中国省级层面的面板数据进行了经验分析,得出的结论是:中国服务业作为高级要素投入促进了制造业发展,而以代工生产和加工贸易为主要特征的制造业并没有形成服务业发展的市场支持。由此得出的政策含义是:在制定服务业发展政策时,应考虑制造业对服务业发展的市场支持作用,进而形成产业互动的良性发展循环。     

基于螺旋谐振环结构的UWB同步开关噪声抑制电源平面

针对目前印制电路板中采用的同步开关噪声抑制方法抑制带宽较窄、全向性较差、电源平面有效使用面积小、结构复杂及对信号质量影响大的问题,提出了一种基于螺旋谐振环结构的超宽带同步开关噪声抑制平面,具有结构简单、阻带宽、抑制方向具有全向性、无需周期性电磁带隙结构的特点。通过研究其等效电路模型,使用三维有限元法（FEM）对所设计的结构提取了S参数,并进行了频域与时域分析与仿真。仿真结果表明：所提出的结构其同步开关噪声抑制深度在-40 dB时,阻带范围为0.13~20 GHz,抑制带宽达到19.87 GHz,有效降低了带隙中心频率;当注入噪声电压为1 V时,可将噪声电压抑制到0.25 mV;对比UC-EBG和Planar EBG结构,在-40 dB抑制深度时,抑制带宽分别提高了16.97 GHz和17.73 GHz。     

A discrete and a continuous-time model based on a technical trading rule

In this article we propose a model in discrete and continuoustime that incorporates explicitly a technical trading rule inthe specification of the volatility. The proposed discrete-timemodel is an alternative to GARCH-type processes. We derive conditionsfor the covariance and strict stationarity of the discrete-timeprocess and we study the estimation and inference problems.We also analyze the conditions under which the discrete-timeprocess converges in distribution to a diffusion process. Toillustrate the proposed model and compare it with the GARCHspecification, we analyze the daily closing stock prices oftwo major U.S. companies (Microsoft and Oracle), two stock indices(DAX and NASDAQ) and two U.S. Dollar exchange rates (Euro andSterling)     

线性代数教学实践中的体会

结合线性代数课程本身的特点和学生实际情况,通过对线性代数课程的教学实践,提出了线性代数抽象概念讲解要与具体实例相结合,激发学生的学习兴趣,提高学生分析、归纳、总结和演绎的基本素质,改进教学方法和手段等措施来提高课程的教学质量。     

Bartlett adjustments for systems of linear equations with linear restrictions

Simple matrix formulae are derived for calculating a Bartlett adjustment to the likelihood ratio test statistic for testing linear parameter restrictions in a system of linear equations. For the special case of column and/or row restrictions on the matrix of coefficients the adjustment is a simple function of matrix dimensions being invariant to sample observations and the error covariance matrix. An example of testing for homogeneity and symmetry in a demand system is given.     

Production planning and inventories optimization: A backward approach in the convex storage cost case

We study the deterministic optimization problem of a profit-maximizing firm which plans its sales/production schedule. The firm controls both its production and sales rates and knows the revenue associated to a given level of sales, as well as its production and storage costs. The revenue and the production cost are assumed to be respectively concave and convex. In Chazal et al. [Chazal, M., Jouini, E., Tahraoui, R., 2003. Production planning and inventories optimization with a general storage cost function. Nonlinear Analysis 54, 1365–1395], we provide an existence result and derive some necessary conditions of optimality. Here, we further assume that the storage cost is convex. This allows us to relate the optimal planning problem to the study of a backward integro-differential equation, from which we obtain an explicit construction of the optimal plan.     

Repeated Dichotomous Choice Formats for Elicitation of Willingness to Pay: Simultaneous Estimation and Anchoring Effect

Repeated dichotomous choice contingent valuation data are generated from responses to a succession of binary questions regarding alternative prices for an environmental good. In this paper we propose a simultaneous equation model that allows for endogeneity and error correlation across the responses at each stage of the bidding process. The model allows us to study the evolution of anchoring effects after the second dichotomous choice question. Estimation involves the Bayesian techniques of Gibbs sampling and data augmentation, and the application focuses on the preservation value of a natural area. The results for a data set involving up to four successive dichotomous choice questions show that restricted multiple-bounded models are rejected by the data with the general model. In addition, willingness to pay tends to stabilize after the second stage in the elicitation process for the general unrestricted model. When taking anchoring effects into consideration, it is revealed that individuals’ responses in the latter stages are influenced by the sequence of bid prices offered in earlier questions. Nevertheless, they do not have a significant effect on welfare estimates.      

Avoiding arbitrary exclusion restrictions using ratios of reduced-form estimates

We show how to obtain coherent structural-form (SF) exclusion restrictions using the reduced-form (RF) parameter ratios. It will be shown that an over-identified SF corresponds to a group of regressors sharing the same RF ratio value; those regressors should be excluded jointly from the SF. If there is no group structure, then the SF is just-identified; in this case, however, it is no longer clear which regressor should be excluded. Hence, just-identified SF’s are more arbitrary than over-identified SF’s in terms of exclusion restrictions. This is in stark contrast to the notion that the former is less arbitrary than the latter, because the former excludes fewer regressors. We formalize these points, and then suggest to find the number of modes in the estimated RF ratios as a way to find groups in the ratios. For this purpose, an informal graphical method using a kernel nonparametric method and a formal modality test are employed. An empirical example with selling price in a residential real estate market and duration on the market as two endogenous variables is provided. The authors are grateful to the editor and two anonymous referees for their comments