An inventory control model with consideration of remanufacturing and product life cycle

This paper investigates inventory control policies in a manufacturing/remanufacturing system during the product life cycle, which consists of four phases: introduction, growth, maturity, and decline. Both demand rate and return rate of products are random variables with normal distribution; the mean of the distribution varies according to the time in the product life cycle. Closed-form formulas of optimal production lot size, reorder point, and safety stock in each phase of the product life cycle are derived. A numerical example is presented with sensitivity analysis. The result shows that different inventory control policies should be adopted in different phases of the product life cycle. It is also found that the optimal production lot size and reorder point are not sensitive to the phase length and the demand changing rate.     

Fuzzy logic in manufacturing: A review of literature and a specialized application

Manufacturing decisions inherently face uncertainties and imprecision. Fuzzy logic, and tools based on fuzzy logic, allow for the inclusion of uncertainties and imperfect information in decision making models, making them well suited for manufacturing decisions. In this study, we first review the progression in the use of fuzzy tools in tackling different manufacturing issues during the past two decades. We then apply fuzzy linear programming to a less emphasized, but important issue in manufacturing, namely that of product mix prioritization. The proposed algorithm, based on linear programming with fuzzy constraints and integer variables, provides several advantages to existing algorithm as it carries increased ease in understanding, in use, and provides flexibility in its application.     

Two state capital accumulation with heterogenous products: Disruptive vs. non-disruptive goods

The paper considers the problem of a firm that, while producing a standard product, has the option to introduce an innovative product. The innovative product competes with the standard product and will therefore reduce revenues of the standard product. A distinction is made between innovative products that do or do not become even more relatively appealing as their market share grows (e.g., because of network externalities). It is shown that in the former case, which we call a “disruptive” good, history dependent long run equilibria can occur, which are in line with recent real life economic examples.     

Returns to scale and externalities in the consumption and investment sectors

Using data on US manufacturing, I estimate internal returns to scale and external effects for the consumption and investment sectors. I construct panels of data at the industry level and use results of gross output production function estimation to derive implied estimates in a value added specification. For the investment sector, returns to scale appear to be slightly increasing, with evidence of a positive external effect. For consumption, the evidence indicates decreasing to constant returns to scale. I discuss the implications of these results for the empirical plausibility of indeterminacy in recent multi-sector models of the business cycle.     

Mean Reversion in the Short Horizon Returns of UK Portfolios

This paper will show that short horizon stock returns for UK portfolios are more predictable than suggested by sample autocorrelation co-efficients. Four capitalisation based portfolios are constructed for the period 1976–1991. It is shown that the first order autocorrelation coefficient of monthly returns can explain no more than 10% of the variation in monthly portfolio returns. Monthly autocorrelation coefficients assume that each weekly return of the previous month contains the same amount of information. However, this will not be the case if short horizon returns contain predictable components which dissipate rapidly. In this case, the return of the most recent week would say a lot more about the future monthly portfolio return than other weeks. This suggests that when predicting future monthly portfolio returns more weight should be given to the most recent weeks of the previous month, because, the most recent weekly returns provide the most information about the subsequent months' performance. We construct a model which exploits the mean reverting characteristics of monthly portfolio returns. Using this model we forecast future monthly portfolio returns. When compared to forecasts that utilise the autocorrelation statistic the model which exploits the mean reverting characteristics of monthlyportfolio returns can forecast future returns better than the autocorrelation statistic, both in and out of sample.     

Bargaining, binding contracts, and competitive wages

In a model where many workers bargain with one firm and sign binding contracts, we show existence of a stationary subgame perfect equilibrium. If the production function satisfies decreasing returns, each worker receives a share of his marginal product (treating all other workers as employed) in equilibrium. Thus, wages are competitive. This is in contrast to Stole and Zweibel (1996, Rev. Econ. Stud. 63, 375–410), who assume that contracts are non-binding and find that the payoff of a worker is a weighted average of the inframarginal contributions. Hence, binding contracts imply lower wages than non-binding contracts.     

The impact of news,oil prices,and global market developments on Russian financial markets1

This paper analyses the impact of news, oil prices, and international financial market developments on daily returns on Russian bond and stock markets. First, regarding returns, energy news affects returns, while news from the war in Chechnya is not significant. Market volatility does not appear to be sensitive to either type of news. Second, a significant effect of the growth in oil prices on Russian stock returns is detected. Third, the international influence on Russian financial markets depends upon the degree of financial liberalization. The higher the degree of financial liberalization, the stronger is the impact of US stock returns on Russian financial markets. In addition, banking reform and interest rate liberalization efforts seem to dictate the globalization of Russian stock markets, while it is the progress in liberalizing securities markets and non‐bank financial institutions that matters more for the globalization of Russian bond markets.     

Information flows within and across sectors in Chinese stock markets

We examine the patterns of information flows within and across sectors of the two Chinese stock exchanges in Shanghai and Shenzhen during 1994–2001. Using the generalized forecast error variance decomposition, we find a high degree of interdependence, indicating that the sectors are highly integrated and sector prices reflect information from other sectors. Industry is the most influential sector in both exchanges, while Finance in Shenzhen is the least integrated with other sectors. Implications of the findings for investors and policymakers are also discussed.     

Commercial versus open source software: the role of product heterogeneity in competition

The emergence and market success of Linux in recent years has been impressive. The paper investigates the question of why some producers of a proprietary software support the development of open source software (OSS) while others refuse any support. As an analytical framework, a simple Launhardt–Hotelling model is used to show that the emerging price pressure on the former monopolists depends on the extent of the current heterogeneity between OSS and the proprietary software of the incumbents. The paper argues that the product heterogeneity can explain the differing real-world behavior of commercial software producers.     

浅析水利水电工程的合同管理

合同管理是我国水利水电建设工程项目管理的薄弱环节，也是我国水利水电施工承包企业的管理弱点。加强合同管理是市场经济的需要，也是国际一体化的要求。施工过程中，承包商面对干扰事件，详细分析索赔理由，及时编制索赔报告，才有机会获得显著的工程效益。