Inventory model for an inventory system with time-varying demand rate

The standard inventory problems of the multi-period have been modeled under different situations. Specifically we have considered the demand subjects of a continuous distribution and a discrete distribution, and whether the demand of each period is unchanged or not. A method to get an economic order quantity in inventory systems with discrete and unchanged demand was presented in a previous paper, and this method has been generalized to an inventory model with varying continuous demand. However, it was not achieved due to there being many classified cases in the general situations. In this article the above method is discussed in the case discrete demand to determine whether it increases or decreases from period to period. A theoretical method is presented by using previous results and some examples are given which suggest how the concept can handle on inventory system. In order to make the decision, an algorithm is also presented under some conditions, and examples are shown by using the computer software program, Mathematica, which helps to explain the findings. In general cases, we view the optimal policy in the inventory problems in only a few periods.     

Drivers and barriers to cross-border e-commerce: Evidence from Spanish individual behavior

This paper explores the determinants of the individual's decision to perform cross-border e-commerce (CBeC). The European Union (EU) is especially interested in the promotion of CBeC because it is an important tool in its strategy to achieve the Digital Single Market in Europe. In this paper official data is used from a representative survey of 16,209 individuals on ICT usage by households and individuals that was carried out in Spain by the National Institute of Statistics (INE) for the year 2016. Using a standard neoclassical utility maximization framework, and logistic regression techniques, the results show that being a male is positively related to the probability of practicing CBeC. Education is positively and significantly related to the probability of being involved in CBeC with EU countries. Computer and Internet Skills are significant and positive factors in explaining CBeC (either with EU countries or with the rest of the world). The variable “how often the consumer sees other customer reviews before buying online”, has a positive effect. Foreign nationality also increases the likelihood of using CBeC. To promote CBeC in Spain measures towards developing digital skills, Internet trust and use of online information reviews of goods and services are discussed.     

Cooperative membership and farmers’ choice of marketing channels – Evidence from apple farmers in Shaanxi and Shandong Provinces,China

Cooperatives are established to improve farmers' production conditions, to increase their bargaining power and to enable them to benefit from modern value chains. In China, farmers are members of a cooperative for multiple reasons. Little is known on whether and how cooperative membership affects farmers’ choice of marketing channels. This paper examines determinants of farmers’ choice of marketing channels, especially how cooperative membership impacts upon this choice. Our analysis is based on survey data collected in 2015 among 625 apple growing farm households in the provinces Shaanxi and Shandong. We employ endogenous switching probit models to deal with potential endogeneity of membership in estimating the determinants of marketing channel choices. We find that cooperative membership has a positive impact on selling to wholesalers and a negative impact on selling to small dealers, but no significant impact on selling to the cooperative itself. As products sold through cooperatives generally comply with relatively stringent food quality and safety standards, these results imply that policies promoting cooperative members to sell their products through cooperatives are likely to have a significant impact on food quality and food safety in China.     

桥梁加固设计方案的技术经济评价研究

桥梁加固设计方案的选择既是一个技术问题,更是一个经济问题,目前还没有较为成熟和系统的方法。运用工程经济学的基本原理,对既有桥梁加固在其寿命周期内可能产生的各项费用进行了详细的对比分析,建立了桥梁技术改造的经济分析比选模型,提出了基于寿命周期成本的桥梁加固的经济评价方法。列举实例说明方案比选过程,由计算结果可知该方法能较准确地反映桥梁加固工程的经济效果,能够为既有桥梁改造方案的合理选择提供参考。     

关于油田企业导入卓越绩效模式的探讨

在辽河油田多年推进实施卓越绩效模式的基础上,结合油田企业的特点,对导入卓越绩效模式工作进行了探讨,从导入卓越绩效模式的思路、步骤、组织领导及启动实施等6个方面,阐述了相应的观点和方法。     

Does ICT investment widen the growth gap?

This paper builds a model of cumulative growth to examine the dynamic interdependent relationship between Information and Communication Technology (ICT) investment and economic growth for a sample of 29 countries in the 1990s. We confirm the following facts: First, there is a positive correlation between ICT investment and economic growth. Second, non-ICT investment has as much influence on the growth gap as ICT investment. Third, those countries with a solid economic infrastructure and open trade regime experience more active ICT investments. Fourth, those countries with a comparatively lower productivity level can reduce the gap using knowledge spillovers from more advanced countries. Fifth, reinforcement of patent rights has a positive influence on economic growth by stimulating the accumulation of ICT capital. Finally, ICT investment does not have a strong interdependent relationship with economic growth, while non-ICT investment has a cumulative causal relationship with economic growth and plays a key role in the process of widening the growth gap.     

International Housing Markets and the U.S. Subprime Crisis

We propose a novel decomposition approach to study the degree of co-movement of international housing markets while distinguishing among different economic drivers. We find that the housing market variability for an average country was mainly driven by the common housing risk premium components during the years leading up to the 2007–08 subprime financial crisis. A decrease in the common housing risk premium was followed by a housing boom and economic expansion in the United States prior to the crisis. Our findings add to the understanding of the role of common risk factors across international housing markets before the crisis.     

FDI对区域经济增长、就业影响研究——基于丝绸之路经济带我国西北段省区

本文基于丝绸之路经济带我国西北段区域1985～2014年的时间序列数据,采用VAR模型分析FDI 、经济增长与就业三者之间的动态关系。结果表明：FDI是经济增长和就业的格兰杰原因, 但经济增长不是FDI的格兰杰原因;FDI对经济增长有明显的促进作用,对就业的促进作用不 明显,经济增长未明显带动FDI流入。丝绸之路经济带我国西北段区域应牢牢抓住“丝绸之 路经济带”战略机遇,因地制宜地制定符合科学发展的引资策略,优化投资环境以吸引跨国 公司进驻该区域,并鼓励企业加大对研发、设计等价值链高端的投资。     

Heavy tails versus long-range dependence in self-similar network traffic

Empirical studies of the traffic in computer networks suggest that network traffic exhibits self-similarity and long-range dependence. The ON/OFF model considered in this paper gives a simple 'physical explanation' for these observed phenomena. The superposition of a large number of ON/OFF sources, such as workstations in a computer lab, with strictly alternating and heavy-tailed ON- and OFF-periods, can produce a cumulative workload which converges, in a certain sense, to fractional Brownian motion. Fractional Brownian motion exhibits both self-similarity and long-range dependence. However, there are two sequential limits involved in this limiting procedure, and if they are reversed, the limiting process is stable Levy motion, which is self-similar but exhibits no long-range dependence. We study simulations limit regimes and provide conditions under which either fractional Brownian motion or stable Levy motion appears as limiting process.     

Efficiency comparisons between two estimators based on matrix determinant Kantorovich-type inequalities

We first establish two matrix determinant Kantorovich-type inequalities. Then, based on these two and other inequalities, we introduce new efficiency criteria and present their upper bounds to make efficiency comparisons between the ordinary least squares estimator and the best linear unbiased estimator in the general linear model. We provide numerical examples to examine the upper bounds of some new and old efficiency criteria. Received: June 1999