Scheduling with earliest start and due date constraints on multiple machines

We consider the scheduling of n jobs on m identical machines when the jobs become available for processing at ready times a_i, a_i, ? 0, require d_i time units for processing and must be completed by times b_i for i = 1, 2, … n. The objective chosen is that of minimizing the total elapsed time to complete all jobs subject to the ready time and due date constraints, preemption is not allowed. We present a multi-stage solution algorithm for this problem that is based on an implicit enumeration procedure and also uses the labelling type algorithm which solves the problem when preemption is allowed.     

On sequencing with earliest starts and due dates with application to computing bounds for the (n/m/G/Fmax) problem

Recent efforts to improve lower bounds in implicit enumeration algorithms for the general (n/m/G/F_max) sequencing problem have been directed to the solution of an auxiliary single machine problem that results from the relaxation of some of the interference constraints. We develop an algorithm that obtains optimal and near optimal solutions for this relaxed problem with relatively little computational effort. We report on computational results achieved when this method is used to obtain lower bounds for the general problem. Finally, we show the equivalence of this problem to a single machine sequencing problem with earliest start and due date constraints where the objective is to minimize the maximum lateness.     

Multiproduct batching and scheduling with buffered rework: The case of a car paint shop

We study a problem of scheduling products on the same facility, which is motivated by a car paint shop. Items of the same product are identical. Operations on the items are performed sequentially in batches, where each batch is a set of operations on the same product. Some of the produced items are of the required good quality and some items can be defective. Defectiveness of an item is determined by a given simulated function of its product, its preceding product, and the position of its operation in the batch. Defective items are kept in a buffer of a limited capacity, and they are then remanufactured at the same facility. A minimum waiting time exists for any defective item before its remanufacturing can commence. Each product has a sequence independent setup time which precedes its first operation or its operation following an operation of another product. A due date is given for each product such that all items of the same product have the same due date and the objective is to find a schedule which minimizes maximum lateness of product completion times with respect to their due dates. The problem is proved NP‐hard in the strong sense, and a heuristic Group Technology (GT) solution approach is suggested and analyzed. The results justify application of the GT approach to scheduling real car paint shops with buffered rework. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 458–471, 2014     

Scheduling with earliest start and due date constraints

We consider the scheduling of n tasks on a single resource. Each task becomes available for processing at time a_i, must be completed by time b_i, and requires d_i time units for processing. The aim is to find a schedule that minimizes the elapsed time to complete all jobs. We present solution algorithms for this problem when job splitting is permitted and when job splitting is not permitted. Then we consider several scheduling situations which arise in practice where these models may apply.     

The Gravity of Arms

The aim of this paper is to investigate the determinants of international arms transfers in a gravity model framework. By distinguishing between the decision to export arms (extensive margin) and the value of the arms exported (intensive margin), while also considering its interdependence, is what differentiates this paper from previous research. A theoretically justified gravity model of trade augmented with political and security motives is estimated using a two-stage panel data approach for 104 exporting countries over the period from 1950 to 2007. In addition to the usual gravity variables related to the economic mass of the trading countries and the trade cost factors, the model is extended with political and security factors. The level of democracy in both trading partners, political differences between trading partners and voting similarity with the United States in the UN General Assembly of the countries engaged in trade are the main political factors, whereas the existence of conflicts, military pacts, and embargoes are taken as security motives. The key result indicates that both political and security motives are an important determinant of an arms trade, but their effects on the extensive margin of exports (the decision to order a transfer) differs from their effect on the intensive margin (average value of exports). Moreover, the relative importance of the factors under study has changed since 1989. In the post-cold war period, countries that are less democratic are more likely to export arms, military pacts are less relevant and embargoes play a role.     

Fencing the bear? Explaining US foreign policy towards Russian interventions

Despite the burgeoning literature on Russia’s renewed power politics, little attention has been paid to the fact that US reactions towards Russia’s military interventions were all but coherent. The USA has chosen weak measures in Georgia in 2008 (shaming) compared to its assertive response in Ukraine in 2014 (sanctions, hard deterrence). This article assesses the explanatory power of neorealist, liberal and constructivist theories for the variation in US reactions towards Russian interventions in Georgia and Ukraine. Our argument is that the constructivist perspective explains the cases best as it highlights the power and communality of normative assessments. The Ukraine crisis was perceived by the USA as a violation of core international norms, especially the non-use of force and the principle of territorial integrity. Relevant international norm carriers shared this assessment of the conflict. In contrast, the perception of the Georgian war centred on the issue of democracy promotion. While democracy is an important aim of US foreign policy, it does not summon the same normative importance as general principles of international law. Furthermore, the perception of the Georgian war remained contested among Western allies, which decreased the communality of the normative assessment.