We construct a vintage capital model of economic growth in which the decision to replace old technologies with new ones is modeled explicitly. Depreciation in this environment is an economic, not a physical concept. We describe the balanced growth paths and the transitional dynamics of this economy. We illustrate the importance of vintage capital by analyzing the response of the economy to fiscal policies designed to stimulate investment in new technologies. A revised version of this paper is published in the Journal of Monetary Economics, v. 40, no. 3(December 1997):457-499.
Simulation of a dairy herd over a period of 15 years was used to examine replacement strategies among six operationally practical systems of culling cows which whould maximize income over feed costs. The strategies or criteria used to remove the lower ranking cows to a relatively constant herd size were: (1) Mature Equivalent (M.E.) milk production, (2) M.E. gross milk income, (3) actual milk production, (4) actual gross income, (5) income over feed cost, and (6) present value of expected gross income of cow and her subsequent replacements. Two each of prices of milk, fat differential, feed, and operational costs totaled 2 4 x 6 x 2 replications per trial or 192 replications. The following were treated as stochastic variables: (a) variation in milk production and milkfat percentage between cows and between lactations of the same cow, (b) chance of a calf being a heifer or bull, (c) chance of involuntary death or removal of cows and youngstock, and (d) chance of month of the year of involuntary removals. The mean and variance of the base herd approximated the average Michigan DHIA Holstein population in 1966. The sire value, approximating the best bulls used in A.I. was identical for any given year through all strategies and replications, but improved over time at the rate of 130 1b milk per year. Culls or cows removed because of low in each respective strategy were removed at the most profitable point to cull in their respective lactations by equating the milk income of the marginal month with the sun of the month's feed costs and monthly operational charges. Practical use of this simple method of determining when to cull cows within a lactation was demonstrated. A complete factorial design to analyze the generates data showed no significant differences between strategies under alternative combinations of prices in average income including salvage over feed cost per cow discounted to the present. This income was affected by the level of milk price (P
The scope of this book is Operations Research methods in Agriculture and a thorough discussion of derived applications in the Agri-food industry. The book summarizes current research and practice in this area and illustrates the development of useful approaches to deal with actual problems arising in the agriculture sector and the agri-food industry. This book is intended to collect in one volume high quality chapters on Methods and Applications in Agriculture and Agri-food industry considering both theoretical issues and application results. Methods applied to problems in agriculture and the agri-food industry include, but are not restricted to, the following themes: Dynamic programming Multi-criteria decision methods Markov decision processes Linear programming Stochastic programming Parameter estimation and knowledge acquisition Learning from data Simulation Descriptive and normative decision tree techniques, including: agent modelling and simulation, and state of the art surveys Each chapter includes some standard and traditional methodology but also some recent research advances. All the applications presented in the chapters have been inspired and motivated by the demands from the agriculture and food production areas.
Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 34 (thesis year 1989) a total of 13,377 theses titles from 26 Canadian and 184 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work. While Volume 34 reports theses submitted in 1989, on occasion, certain univer sities do report theses submitted in previous years but not reported at the time.
