A general age replacement model with minimal repair

A general age replacement is introduced which incorporates minimal repair, planned and unplanned replacements, and costs which depend on time. Finite and infinite horizon results are obtained. Various special cases are considered. Furthermore, a shock model with general cost structure is considered.     

An adaptive dynamic programming algorithm for a stochastic multiproduct batch dispatch problem

We address the problem of dispatching a vehicle with different product classes. There is a common dispatch cost, but holding costs that vary by product class. The problem exhibits multidimensional state, outcome and action spaces, and as a result is computationally intractable using either discrete dynamic programming methods, or even as a deterministic integer program. We prove a key structural property for the decision function, and exploit this property in the development of continuous value function approximations that form the basis of an approximate dispatch rule. Comparisons on single product‐class problems, where optimal solutions are available, demonstrate solutions that are within a few percent of optimal. The algorithm is then applied to a problem with 100 product classes, and comparisons against a carefully tuned myopic heuristic demonstrate significant improvements. © 2003 Wiley Periodicals, Inc. Naval Research Logistics 50: 742–769, 2003.     

Looking ahead in India

India and China contain more than 40% of the world's population, yet in India it is painfully clear that the political commitment necessary to tackle India's greatest problem is not there in full measure. India's present per capita income is less than $300, and nearly 65% of the people live below the poverty line. The average Indian woman produces 5 children; even if the Indian government's efforts to reduce family size to 2 children is successful by the year 2040, India will have a population of 2.5 billion. The possibility that India will succeed in reducing average family size to 2 children appears remote. 30 years ago, India became the 1st developing country to formally make family planning a matter of national policy. In the early years of the national family planning programs, practitioners had access mostly to sterilization and condoms. Over the years, theIndian government persuaded the US and other western donors to give $2 billion to population control programs. Still, the population continues to grow annually at the rate of 2.1%. Government statistics reflect the ups and downs of national population control policies; thenumber of new family planning users increased from 4.3 million in 1974-1975 to 12.5 million in 1976-1977, due largely to a dramatic increase in vasectomies. Tge number of new contraceptive users fell to 4.5 million after the "emergency" was lifted in 1977. The present Indian generation is far more receptive culturally as well as sociologically to the concept of population control than most other developing countries. What is needed now is renewed political committment by the Gandhi adminiostration. India cannot afford to replicate the Chinese way of tackling overpopulation without inflicting human abuses and without undermining its painstakingly cultivated democratic system.     

Warranty design under buyer and seller risk aversion

This paper provides a framework in which warranty policies for non-repairable items can be evaluated according to risk preferences of both buyers and sellers. In particular, a warranty price schedule is established such that sellers are indifferent among the policies. Given this schedule, a buyer's response is expressed by selecting the price-warranty combination that minimizes disutility. Within this framework, a warranty can be viewed as an instrumet of risk management that can induce more sales and greater profitability. For given utility functions, analytical results for the development of a price schedule are developed. Numerical results illustrate the substitution effects between warranty terms, prices, and risk parameters.     

The interactive fixed charge linear programming problem

In many decision-making situations, each activity that can be undertaken may have associated with it both a fixed and a variable cost. Recently, we have encountered serveral practical problems in which the fixed cost of undertaking an activity depends upon which other activities are also undertaken. To our knowledge, no existing optimization model can accomodate such a fixed cost structure. To do so, we have therefore developed a new model called the interactive fixed charge linear programming problem (IFCLP). In this paper we present and motivate problem (IFCLP), study some of its characteristics, and present a finite branch and bound algorithm for solving it. We also discuss the main properties of this algorithm.     

求取鱼雷转角射击转角的实用算法

较为详细地推导了鱼雷转角射击公式,根据分鱼雷转向的不同总结出两类求解公式（各种态好都能用两类公式之一来解算）．最后还讨论了所导出的非线性方程的数值解算方法,该算法具有工程应用价值。     

纳米级定位的简单化设计——采用滚珠球轴承的扭轮摩擦传动

作者在前面的文章中报导了扭轮摩擦传动能实现亚纳米级的定位分辨率。然而,这套装置在结构上的复杂之处就是在于采用了静压轴承支撑扭轮。本文指出了扭轮摩擦传动在结构上如何可以简化为采用球轴承支撑扭轮。在简化之后,实验表明定位分辨率小于1纳米。本文得出结论,采用球轴承的扭轮摩擦传动对于在洁净环境下要求实现纳米级定位的制造过程变得更为方便,而且可以取代滚珠丝杠以及常规摩擦传动方式。