An integer programming algorithm for portfolio selection with fixed charges

A mean-variance portfolio selection model with limited diversification is formulated in which transaction and management costs are incorporated as the sum of a linear cost and a fixed cost. The problem is a fixed charge integer programming problem solved by hypersurface search using dynamic programming. Fathoming is performed in the forward pass of dynamic programming so that values of the state variable which correspond to infeasible solutions are eliminated from the tables. This logic permits the solution of problems with 20–30 possible investments.     

Cost analysis of pro rata and free-replacement warranties

This article examines the short run total costs and long run average costs of products under warranty. Formulae for both consumer cost under warranty and producer profit are derived. The results in the case of the pro rata warranty correct a mistake appearing in Blischke and Scheuer [5]. We also show that expected average cost to both the producer and the consumer of a product under warranty depends on both the mean of the product lifetime distribution and on its failure rate.     

Nonlinear integer programming for various forms of constraints

A theoretical and computational investigation is made of the performance of a dynamic-programming-based algorithm for nonlinear integer problems with various types of constraints. We include linear constraints, aggregated linear constraints, separable nonlinear constraints and constraints involving maxima and minima. Separability of the objective function is assumed. The new feature of the algorithm is that two types of fathoming or pruning are used to reduce the size of tables and number of computations: fathoming by bounds and fathoming by infeasibility.     

The logarithmic poisson gamma distribution: A model for leadtime demand

This paper considers an inventory system in which demand occurrences arise according to a stationary Poisson process, demand sizes at each occurrence follow a logarithmic distribution, and leadtimes are random variables with the gamma distribution. Both the exact and approximate distribution for leadtime demand are derived and computations are performed which compare the approximation to the exact distribution. The results have application to both repairable and consumable item inventory systems.     

Sandwich approximation of univariate convex functions with an application to separable convex programming

In this article an algorithm for computing upper and lower ? approximations of a (implicitly or explicitly) given convex function h defined on an interval of length T is developed. The approximations can be obtained under weak assumptions on h (in particular, no differentiability), and the error decreases quadratically with the number of iterations. To reach an absolute accuracy of ? the number of iterations is bounded by

     

Fitting Lanchester equations to the battles of Kursk and Ardennes

Lanchester equations and their extensions are widely used to calculate attrition in models of warfare. This paper examines how Lanchester models fit detailed daily data on the battles of Kursk and Ardennes. The data on Kursk, often called the greatest tank battle in history, was only recently made available. A new approach is used to find the optimal parameter values and gain an understanding of how well various parameter combinations explain the battles. It turns out that a variety of Lanchester models fit the data about as well. This explains why previous studies on Ardennes, using different minimization techniques and data formulations, have found disparate optimal fits. We also find that none of the basic Lanchester laws (i.e., square, linear, and logarithmic) fit the data particularly well or consistently perform better than the others. This means that it does not matter which of these laws you use, for with the right coefficients you will get about the same result. Furthermore, no constant attrition coefficient Lanchester law fits very well. The failure to find a good‐fitting Lanchester model suggests that it may be beneficial to look for new ways to model highly aggregated attrition. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

The Wilson government and the demise of TSR‐2, October 1964 – April 1965

Domestic factors play an important role in the formulation and evolution of a country's foreign and security policy. This is clearly seen in the case study of a Soviet successor state, Ukraine. The article brings together in seven sections theory with the key domestic factors that influence Ukrainian security policy, such as economics, energy, national identity, elites and political parties. The article provides an insight into how these domestic factors influence the course of Ukrainian security policy which is striking a balance between the twin extremes of Soviet re‐integration, which would be tantamount to the loss of independence, and nationalist maximalism which seeks to place as much distance as possible between Ukraine and Russia.     

The Rebirth of Insurgency in Peru

Peru has battled two major insurgent movements since 1980. Around 25,000 Peruvians have died in this war between the government against the Shining Path and the MRTA. The Peruvian military has been incapable of achieving total victory after several major operations and the capture of just about every major rebel leader. Even worse, after a few years of almost no activity, Shining Path seems to be re-emerging. The last remaining members of this insurgent group have made alliances with foreign terrorist groups, used drug traffic to fund their fight and sweet talked people who are very disappointed and mad at the current Toledo administration, to gain more supporters. Major changes have to occur to prevent both groups from becoming threats to national security and society as a whole, taking the country back to times when around half of the nation was declared to be under terrorist control. The defense budget must be increased to open new bases, buy new equipment and train soldiers better to fight the insurgents more effectively. At the same time, major social changes need to occur; Toledo and his government must gain the trust and sympathy of Peruvians again by working for and with them.