A procedure for generating time-dependent arrivals for queueing simulations

This paper presents a method for modeling cyclic inputs to a congested system in a discrete event digital simulation. Specifically, we express the mean of the interarrival time conditional on the last arrival as a linear combination of harmonic components whose coefficients can be determined by stepwise regression. We also assume that the conditional interarrival time normalized by its corresponding mean follows a distribution that is independent of time. The result can, in turn, be used to generate the desired input for a simulation, An example based on a set of actual data is used to illustrate the process of parameter estimation for the model.     

Hybrid heuristics for minimum cardinality set covering problems

Minimum cardinality set covering problems (MCSCP) tend to be more difficult to solve than weighted set covering problems because the cost or weight associated with each variable is the same. Since MCSCP is NP-complete, large problem instances are commonly solved using some form of a greedy heuristic. In this paper hybrid algorithms are developed and tested against two common forms of the greedy heuristic. Although all the algorithms tested have the same worst case bounds provided by Ho [7], empirical results for 60 large randomly generated problems indicate that one algorithm performed better than the others.     

Ethnic targeting: A bad idea whose time has come

Wm. Roger Louis, Imperialism at Bay 1941–1945. The United States and the decolonization of the British Empire. Oxford: Clarendon Press, 1977. Pp. xvi + 595;£12.50.

Christopher Thorne, Allies of a Kind. The United States, Britain and the war against Japan, 1941–1945. London: Hamish Hamilton, 1978. Pp. xxii + 772; £15.00.

Michael Howard, editor, Restraints on War: Studies in the Limitation of Armed Conflict Oxford: Oxford University Press, 1979. Pp. viii + 173; £6.50.

Julian Lider, The Political and Military Laws of War: an Analysis of Marxist‐Leninist Concepts. Farnborough, Hants: Saxon House, 1979. Pp. vii + 266; £12.50.

Klaus‐Jürgen Müller and Eckardt Opitz (editors), Militär und Militarismus in der Weimarer Republik. Düsseldorf: Droste Verlag, 1978. Pp. 304; n.p.

Nicholas Bethell, The Palestine Triangle: The Struggle Between the British, the Jews and the Arabs 1935–1948. London: Steinmatsky's Agency Ltd. in association with Andre Deutsch, 1919. Pp. 384; £7.95.

Sir Maurice Dean, The Royal Air Force and Two World Wars. London: Cassell, 1979. Pp. 349; £8.95.

Wilfred Jay Holmes, Double‐Edged Secrets. Annapolis, Maryland: Naval Institute Press, 1979. Pp. 218, n.p.

S. G. Gorshkov, The Sea Power of the State. Oxford: Pergamon Press, 1979. Pp. 290; £15.00.

Kirk, Grayson and Wessell, N.H. eds., The Soviet Threat: Myths and Realities. New York and London: Praeger, 1978. Pp. 182; £12.00.

Kenneth E. Boulding, Stable Peace. Austin and London: University of Texas Press, 1978. Pp. 155;£2.80.

Kenneth E. Boulding (ed.), Peace and the War Industry. New Brunswick, NJ: Transaction Books, and Oxford: Basil Blackwell, 1973. Pp. vii + 213; £2.75.     

Approximate semieconomic design of control charts with multiple control limtis

Statistical quality control of complicated production processes subject to a multiplicity of assignable causes may require the utilization of control charts with multiple control limits. This article presents an approximate semieconomic design of such charts, which is easily implementable in practical situations. Evaluations of the semieconomic control chart design show that the proposed approximate method results in solutions that are very close to the true optima and can be obtained with minimal computational effort.     

On the robustness of the modified beta distribution for acceptance sampling in statistical quality control

The purpose of this article is to examine the robustness of the modified Beta distribution as a probability distribution of lot fraction defectives in Bayesian acceptance sampling for statistical quality control. In complex manufacturing systems, a production process may consist of multiple production stages in a serial or nonserial fashion. Hence, inputs to a production station can be a result of subassembly of several inputs, or outputs of some inspection stations for some prior work stages. We investigate the effectiveness of the modified Beta distribution as an approximation to the lot fraction defectives probability of inputs at intermediate work stations. The robustness of the modified Beta distribution simplifies both the determination of the optimal sampling plan for acceptance sampling, and the calibration of distributions resulted from subassembly or inspection operations in complex manufacturing systems.     

Discrete repairable reliability systems

Consider a reliability system consisting of n components. The failures and the repair completions of the components can occur only at positive integer-valued times k ϵ N₊₊ ϵ (1, 2, …). At any time k ϵ N₊₊ each component can be in one of two states: up (i.e., working) or down (i.e., failed and in repair). The system state is also either up or down and it depends on the states of the components through a coherent structure function τ. In this article we formulate mathematically the above model and we derive some of its properties. In particular, we identify conditions under which the first failure times of two such systems can be stochastically ordered. A variety of special cases is used in order to illustrate the applications of the derived properties of the model. Some instances in which the times of first failure have the NBU (new better than used) property are pointed out. © 1993 John Wiley & Sons, Inc.