Transportation problems with some xij negative and transshipment problems

The general solution process of the Hitchcock transportation problem resulting from the application of the method of reduced matrices may give solutions with some negative x_ij values. This paper is devoted to a review of the reduced matrices method, an examination of suitable interpretation of sets of x_ij which include some negative values, and ways of interpreting these values in useful modifications of the Hitchcock problem. Such modifications include a) the reshipment problem, b) the overshipment problem, and c) the transshipment problem. Techniques are developed for determining and eliminating c_ij which are not optimal. These techniques and results are useful in solving the problems indicated above. The natural applicability of the simple and general method of reduced matrices is emphasized.     

MILITARY EXPENDITURE AND GRANGER CAUSALITY: A CRITICAL REVIEW

A large literature has used tests for Granger (1969) non‐causality, GNC, to examine the interaction of military spending with the economy. Such tests answer a specific although quite limited question: can one reject the null hypothesis that one variable does not help predict another? If one can reject, there is said to be Granger causality, GC. Although the limitations of GNC tests are well known, they are often not emphasised in the applied literature and so may be forgotten. This paper considers the econometric and methodological issues involved and illustrates them with data for the US and other countries. There are three main issues. First, the tests may not be informative about the substantive issue, the interaction of military expenditure and the economy, since Granger causality does not correspond to the usual notion of economic causality. To determine the relationship of the two notions of causality requires an identified structural model. Second, the tests are very sensitive to specification. GNC testing is usually done in the context of a vector autoregression, VAR, and the test results are sensitive to the variables and deterministic terms included in the VAR, lag length, sample or observation window used, treatment of integration and cointegration and level of significance. Statistical criteria may not be very informative about these choices. Third, since the parameters are not structural, the test results may not be stable over different time periods or different countries.     

SAVING THE NPT

For more than forty years, the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) has provided major security benefits to the international community; however, the treaty is suffering from internal and external pressures, and benign neglect on the part of its members is undermining its authority. To ensure the treaty's continued viability, it is time for member states to start showing the NPT the respect it deserves and to renew their commitments to its fundamental purposes. Achieving this requires remedial action in at least four areas of vulnerability: reinvigorating nuclear disarmament; strengthening nonproliferation; overcoming the NPT's institutional deficit; and fostering a rapprochement between NPT and non-NPT states that does not abandon the goal of treaty universalization. There is still time before the 2010 NPT Review Conference for concerted action to restore the NPT's vitality and for the United States to resume its leadership role on behalf of the treaty and its membership.     

America and public opinion in France: 1939–45

Julian G. Hurstfield, America and the French Nation, 1939–1945. London: University of North Carolina Press, 1986. Pp.309; £25.45.

John F. Sweets, Choices in Vichy France: The French under Nazi Occupation. New York: Oxford University Press, 1986. Pp.306; £22.50.     

Optimal stocking policies for low usage items in multi-echelon inventory systems

Multi-echelon logistic systems are essential parts of the service support function of high technology firms. The combination of technological developments and competitive pressures has led to the development of services systems with a unique set of characteristics. These characteristics include (1) low demand probabilities: (2) high cost items; (3) complex echelon structures; (4) existence of pooling mechanisms among stocking locations at the same echelon level; (5) high priority for service, which is often expressed in terms of response time service levels for product groups of items: (6) scrapping of failed parts; and (7) recycling of issued stock due to diagnostic use. This article develops a comprehensive model of a stochastic, multi-echelon inventory system that takes account of the above characteristics. Solutions to the constrained optimization problem are found using a branch and bound procedure. The results of applying this procedure to a spare parts inventory system for a computer manufacturer have led to a number of important policy conclusions.     

Bounding methods for facilities location algorithms

Single- and multi-facility location problems are often solved with iterative computational procedures. Although these procedures have proven to converage, in practice it is desirable to be able to compute a lower bound on the objective function at each iteration. This enables the user to stop the iterative process when the objective function is within a prespecified tolerance of the optimum value. In this article we generalize a new bounding method to include multi-facility problems with l_p distances. A proof is given that for Euclidean distance problems the new bounding procedure is superior to two other known methods. Numerical results are given for the three methods.     

Book reviews

Managing International Conflict, From Theory to Practice: a Teaching Tool Using CASCON by Lincoln P. Bloomfield and Allen Moulton, New York: St Martin's Press, 1997, ISBN 0-312-13675-7 (pbk), £18.99.

The American Century: the Rise and Decline of the United States as a World Power by Donald W. White, London: Yale University Press, 1997, ISBN 0-300-05721-0 (hbk), £25.

Humanitarian Intervention in Contemporary Conflict by Oliver Ramsbotham and Tom Woodhouse, Cambridge: Blackwell, 1996.

The US Military/NGO Relationship in Humanitarian Interventions by Chris Seiple, Peacekeeping Institute, Center for Strategic Leadership, US Army War College, 1996.

Uncivil Wars: International Security and the New Internal Conflicts by Donald M. Snow, London: Lynne Rienner Publishers, 1996, ISBN 1-55587-655-2 (pbk), £15.50, ISBN 1-55587-648-X (hbk), £33.50.

Intelligence Power in Peace and War by Michael Herman, Royal Institute for International Affairs, Cambridge: Cambridge University Press, 1996, ISBN 0-521-56231-7 (hbk), £50, ISBN 0-521-56636 (pbk), £16.95.

UK Eyes Alpha: Inside British Intelligence by Mark Urban, London: Faber and Faber, 1996, ISBN 0-571-17689-5 (hbk), £16.99.

New Cloak, Old Dagger by Michael Smith, London: Victor Gollancz, 1996, ISBN 0-575-06150-2 (hbk), £20.

Conversion Survey 1997: Global Disarmament and Disposal of Surplus Weapons by Bonn International Center for Conversion, Oxford: Oxford University Press, 1997.

Plutonium and Highly Enriched Uranium 1996: World Inventories, Capabilities and Policies by David Albright, Frans Berkhout and William Walker, Oxford: SIPRI and Oxford University Press, 1997.

The Wars of Eduard Shevardnadze by Carolyn McGiffert Ekedahl and Melvin A. Goodman, University Park, PA: Penn State University Press, 1997.