Optimal policies for stochastic clearing systems with time-dependent delay penalties

We study stochastic clearing systems with a discrete-time Markovian input process, and an output mechanism that intermittently and instantaneously clears the system partially or completely. The decision to clear the system depends on both quantities and delays of outstanding inputs. Clearing the system incurs a fixed cost, and outstanding inputs are charged a delay penalty, which is a general increasing function of the quantities and delays of individual inputs. By recording the quantities and delays of outstanding inputs in a sequence, we model the clearing system as a tree-structured Markov decision process over both a finite and infinite horizon. We show that the optimal clearing policies, under realistic conditions, are of the on-off type or the threshold type. Based on the characterization of the optimal policies, we develop efficient algorithms to compute parameters of the optimal policies for such complex clearing systems for the first time. We conduct a numerical analysis on the impact of the nonlinear delay penalty cost function, the comparison of the optimal policy and the classical hybrid policy (ie, quantity and age thresholds), and the impact of the state of the input process. Our experiments demonstrate that (a) the classical linear approximation of the cost function can lead to significant performance differences; (b) the classical hybrid policy may perform poorly (as compared to the optimal policies); and (c) the consideration of the state of the input process makes significant improvement in system performance.     

Constructive Ambiguity and the Peace Process in Northern Ireland

The Belfast Agreement of 1998 was hailed at the time as a breakthrough in conflict resolution both in Northern Ireland and as a model for international emulation. In fact it has turned out to be neither; rather it has been a sad exercise in surrendering to terrorism and the cause of increased sectarian segregation and enmity. The core of the problem lies in the 'constructive ambiguity' at the heart of the Agreement - that is, a form of words that all could sign up to because each party could interpret them differently. This may have enabled everyone to sign up, but also implied they were signing up to different things and therefore were not in agreement. Consequently clever word games and spin by politicians and senior civil servants have created an, in some ways, worse situation, largely because real, substantive issues were ducked. This in turn has its roots in postmodernism, whose baleful influence can be seen throughout not only the Agreement but most government policy over the past 20 odd years.     

Majority rule,minority issues: The Macedonian question in the Dekemvriana

This article examines the role of the Macedonian Question in the 1944 December Uprising (Dekemvriana) in Greece. While the Dekemvriana is commonly portrayed in right–left terminology in the historiography, this article argues that part of the reason for the left’s failure was their inability to manage the Macedonian ethnic component of the struggle, either within their armed forces or in their relationship with Yugoslavia. As such, this article integrates the early phases of the Greek Civil War into the broader literature on minorities in civil conflict, while simultaneously exposing some of the myths about Macedonian involvement that result from its contemporary political ramifications.     

CYLINDRICITY ERROR COMPENSATION IN DIAMOND TURNING VIA P－INTEGRATOR REPETITIVE CONTROL

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Derivation and application of unit cost expressions perturbed by design changes

Learning curves have been used extensively to predict future costs in the airframe and other industries. This paper deals with the effect of perturbations induced by design changes on the learning curves. Equations that are developed and applied make it possible to predict future costs accurately in a perturbed environment. The formulations can be used effectively in EDP programs.