Considerations on modelling the market for softwood lumber in the United States

The analysis in this paper looks at two important elements in modelling the market for timber in the United States. First, the issue of directional causality between price and quantity and its implications in a modelling effort is investigated. Second, the extent of the geographic market for timber is discussed and a method of detecting it is suggested. The method for detecting the extent of the geographical market is tractable and can be applied in a straightforward way. Both considerations are applied to the softwood lumber market in the United States.     

A coordination system for seasonal demand problems in the supply chain

This article considers a single product coordination system using a periodic review policy, participants of the system including a supplier and one or more heterogeneous buyers over a discrete time planning horizon in a manufacturing supply chain. In the coordination system, the demand of buyer in each period is deterministic, the supplier replenishes all the buyers, and all participants agree to plan replenishment to minimize total system costs. To achieve the objective of the coordination system, we make use of small lot sizing and frequent delivery policies (JIT philosophy) to transport inventory between supplier and buyers. Moreover, demand variations of buyers are allowed in the coordination system to suit real-world situations, especially for hi-tech industries. Furthermore, according to the mechanisms of minimizing the total relevant costs, the proposed method can obtain the optimal number of deliveries, shipping points and shipping quantities in each order for all participants in the coordination system.     

中国货币需求函数的实证研究

本文以1998年东南亚金融危机后为背景,从经典的凯恩斯货币需求理论分析出发,运用协整检验和误差修正模型对我国货币需求问题进行了研究。结果显示,货币需求、国民收入、贷款利率和通货膨胀率之间存在协整关系,货币需求函数表现出高收入弹性和高利率弹性,货币量、利率和货币政策最终目标之间存在短期均衡关系,M1主要受收入因素影响而呈现出长期稳定性特征,贷款利率对货币需求有显著调节作用。     

The simplified solution procedure for deteriorating items under stock-dependent demand and two-level trade credit in the supply chain management

Min et al. [1] (J. Min, Y.W. Zhou, J. Zhao, An inventory model for deteriorating items under stock-dependent demand and two-level trade credit, Appl. Math. Model. 34 (2010) 3273–3285.) develop an inventory model for deteriorating items under stock-dependent demand and two-level trade credit. They provide the necessary and sufficient conditions of the existence and uniqueness of the optimal solutions that could maximize the retailer’s average profit per unit time. Basically, their paper is correct and interesting. Recently, several researchers have been showing a huge interest in developing simple and easy to implement solution procedures in management science. Therefore this paper indicates that Min et al.’s solution procedure can be further improved and simplified. So, the main purpose of this paper is to present simple and easy to understand solution procedures to locate the optimal solutions of an inventory model that considers deteriorating items under stock-dependent demand and two-level trade credit.     

On a dynamical hierarchical model for prismatic shells in the theory of elastic mixtures

The present paper is devoted to the design of a hierarchy of two‐dimensional models for dynamical problems within the theory of multicomponent linearly elastic mixtures in the case of prismatic shells with thickness which may vanish on some part of its boundary. The hierarchical model is obtained by a semidiscretization of the three‐dimensional problem in the transverse direction. In suitable weighted Sobolev spaces we investigate the well‐posedness of the two‐dimensional problems, prove pointwise convergence of the sequence of approximate solutions restored from the solutions of the reduced problems to the exact solution of the original problem and estimate the rate of convergence. Copyright © 2005 John Wiley & Sons, Ltd.     

Existence and uniqueness of coexistence states for an elliptic system coupled in the linear part

In this paper, we discuss the existence, uniqueness and stability of coexistence states for an elliptic system coupled in the linear part. The linear part of this system is co-operative. Our approaches are based on the maximum principle and some properties of linear cooperative system.     

多孔介质中的具有热源的Brinkman方程解的收敛性

研究多孔介质中的一类含有热源的Brinkman方程的结构稳定性,得到解对Brinkman系数的收敛.即当Brinkman系数趋于零时,Brinkman方程组的解收敛于相应的Darcy方程组的解.     

多因素交互作用及可信区间的估计

有一类研究是观测某个结局事件发生的时间,分析时需要考虑影响该结局事件发生的因素.由于因素之间往往存在交互作用,因而一个因素对结局事件发生的时间的影响量受到另一个因素的修饰.因此分析因素之间是否存在交互作用,对正确认识各因素对结局事件的发生的作用是十分重要的.对以时间为观测指标的多元分析中因素之间交互作用的分析方法作探讨,推导出了估计交互作用及95%可信区间的计算公式.并应用于肿瘤患者生存时间的影响因素之间的交互作用分析.