A volume and material handling cost based heuristic for designing cellular manufacturing cells

One of the major problems in a group technology or cellular manufacturing environment is the formation of part groups and machine cells. Because of the combinatorial nature of the cell formation problem, it is difficult to solve the problem optimally. Most of the procedures related to cell design in cellular manufacturing operate on the part-machine incidence matrix in an attempt to identify block diagonality. If complete block diagonality does not exist, the decision about cell configuration is left to the subjective judgement of the designer. These procedures are also generally based on part routing only, and do not consider part volume and material handling costs.In this paper we develop an integer programming model, as well as a heuristic to effectively assign machines to cells. In these procedures we consider component volumes, costs related to movement of components between and within cells, and penalty for not using all machines in a cell visited by a component. Since the integer programming formulation becomes large even for small problems, an efficient heuristic is developed to solve larger problems. The heuristic solutions to 180 randomly generated small problems were compared against the optimal solutions obtained by the integer programming model. The heuristic has been found to identify optimal solutions in all 180 cases.This heuristic is also compared to several well known algorithms on 900 larger test problems. These problems were generated to cover a wide range of environmental situations such as varying levels of block diagonality in the part-machine incidence matrix, and diversity in the component volumes and material handling costs. In 99% of the problems our heuristic generated solutions which are better or as good as the best solution obtained by other algorithms. Further, in situations where complete block diagonality in the part-machine incidence matrix did not exist, our heuristic produced even better results. Since the maximum number of iterations required in our heuristic is the number of machines in the problem, the heuristic is computationally efficient.     

Optimal fishery harvesting rules under uncertainty

This paper derives the optimal fishery harvest policy in a real-option model with a stochastic logistic growth process, harvest-sensitive output price, and both fixed and variable harvesting costs. The policy specifies the harvest trigger and harvest size, while outputs from the model include the value of the fishery and the risk of extinction. The optimal policy is illustrated with data from the Pacific Halibut Fishery. For this particular case, the optimal policy recommends harvesting when the fish stock rises to about three-quarters the environmental carrying capacity, and the amount harvested should be approximately a quarter of the prevailing stock. This harvesting policy maximizes the value of the fishery, and importantly, the resulting risk of extinction is negligible. We also carry out some sensitivity analysis to see how the optimal policy (and the resulting fishery value and risk of extinction) change when the input parameters are varied, particularly the ecological parameters intrinsic growth rate and volatility of the stock, and also the economic parameters that have been ignored in previous papers (price sensitivity and fixed cost). If the optimal policy is followed, the risk of extinction will be negligible, except for very low growth rate and high volatility.     

News Trading and Speed

We compare the optimal trading strategy of an informed speculator when he can trade ahead of incoming news (is “fast”), versus when he cannot (is “slow”). We find that speed matters: the fast speculator's trades account for a larger fraction of trading volume, and are more correlated with short‐run price changes. Nevertheless, he realizes a large fraction of his profits from trading on long‐term price changes. The fast speculator's behavior matches evidence about high‐frequency traders. We predict that stocks with more informative news are more liquid even though they attract more activity from informed high‐frequency traders.     

An optimal stopping problem in risk theory

Abstract

In classical risk theory often stationary premium and claim processes are considered. In some cases it is more convenient to model non-stationary processes which describe a movement from environmental conditions, for which the premiums were calculated, to less favorable circumstances. This is done by a Markov-modulated Poisson claim process. Moreover the insurance company is allowed to stop the process at some random time, if the situation seems unfavorable, in order to calculate new premiums. This leads to an optimal stopping problem which is solved explicitly to some extent.     

出口退税与就业增进——基于我国数据的协整研究

在一个出口决策模型的基础之上,建立了一个出口退税的就业影响模型。并采用我国1985-2009年的数据,研究了出口退税政策对我国就业水平的影响,结果显示:我国的出口退税政策显著促进了国内就业的增长。进一步把出口退税分解为增值税退还与关税退还两部分,研究了不同类别出口退税对国内就业的影响,结果仍然稳定。结果同时表明:国内投资、FDI以及汇率贬值显著促进了国内就业的增长,而技术水平的提升则抑制了国内就业的增长,这一结果说明,我国的技术发展选择的仍然是劳动节约型而非资本节约型技术进步。     

Tabaksteuer in Griechenland: steuerpolitische Fehlentscheidungen

Both Germany and Greece increased tobacco taxes beginning in 2010. Tobacco taxation in both countries is primarily aimed at generating revenues and at steering the behaviour of individuals affected by the taxation. The tobacco tax structure particularly in Greece has evolved from a mainly ad valorem excise to a specific excise. The comparison of both countries shows that the German tax system is able to generate stable revenues while Greek tobacco taxation policy leads to tax evasion activities among smokers.     

Consumer Preference and Willingness to Pay for a Local Label Attribute in Western Australian Fresh and Processed Food Products

This study investigates Western Australia’s consumer attitudes toward and preferences for locally produced food products signified by a state-funded campaign logo, Buy West Eat Best (BWEB). A choice experiment using both a fresh and a processed food product (skinless chicken breast and fruit yogurt) is conducted to assess willingness to pay for a local production attribute and other label claims. We find that consumer awareness and preference for local foods is high. However, this high preference is not because the product is locally produced but because of the local attributes associated with high-quality products. The study highlights the importance of successfully differentiating products through credible labeling schemes in order to capture market premium.