Real-time task scheduling with overheads considered

n periodic tasks are to be processed by a single machine, where each task i has a maximum request rate or periodicity F_i, a processing time E_i, a deadline D_i, relative to each request of task i, a task-request interrupt overhead I_i, and a task-independent scheduling overhead S. Two scheduling strategies are considered for sequencing the execution of an arbitrary arrangement of task requests in time: the preemptive and the nonpreemptive earliest-deadline algorithms. Necessary and sufficient conditions are derived for establishing whether a given set of tasks can be scheduled by each scheduling strategy. The conditions are given in the form of limited simulations of a small number of well-defined task-request arrangements. If all simulations succeed, the schedule is feasible for the given set of tasks. If any simulation fails, the schedule is infeasible. While interrupt handling and scheduling overheads can be handled by such simulations, context switching overhead resulting from preemption cannot. A counterexample illustrates how the simulations fail to uncover unschedulable task sets when context switching overhead is considered.     

Robust preallocated preferential defense

The problem is to protect a set of T identical targets that may come under attack by A identical weapons. The targets are to be defended by D identical interceptors, which must be preallocated to defend selected targets. The attacker is aware of the number of interceptors, but is ignorant of their allocation. The size of the attack is chosen by the attacker from within a specified range. The robust strategies developed in this article do not require the defender to assume an attack size. Rather, the defender chooses a strategy which is good over a wide range of attack sizes, though not necessarily best for any particular attack size. The attacker, knowing that the defender is adopting a robust strategy, chooses the optimal attack strategy for the number of weapons he chooses to expend. The expected number of survivors is a function of the robust defense strategy and optimal attack strategy against this robust defense.     

The Imperfect Peace: Explaining Paramilitary Violence in Northern Ireland

This article examines why paramilitary campaigns in Northern Ireland have continued despite the current peace process. In advancing three instrumental explanations of paramilitary violence, the author provides a useful analytical framework which shows that while organizational interpretations are dominating the public discourse, republicans and loyalists continue to use paramilitary violence as a strategic means of threat and coercion. Furthermore, even though policy implications are not discussed in detail, it will be demonstrated that the dominance of organizational imperatives has resulted in excessive leniency by the state, which - in turn - has contributed to the fragility of the peace process.     

Technical note: Traffic intensity estimation

This note examines estimation of the traffic intensity in an M/G/1 queue. We show that the ratio of sample mean service times to the sample mean interarrival times has undesirable sampling properties. To remedy this, two alternative estimators are introduced. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009     

The impact of military spending and income inequality on economic growth in Turkey

An extensive literature on the effect of military expenditures on economic growth yields conflicting results. However, a crucial issue that has not been investigated in this context is the possible effect of inequality. The impact of military expenditures on economic growth in Turkey has also received substantial attention. Yet, the majority of these studies are not constructed based on a structural model, but rather examine the causality between the variables in question. Considering these two shortcomings in the literature and the lack of consistent results, this study attempts to provide further evidence for the relationship between military expenditures and economic growth for the case of Turkey by considering income inequality within an augmented Solow growth model. Our findings for the 1963–2008 period show that while income inequality has a positive impact on economic growth, military expenditures have no significant effect.     

A characterization of optimal base‐stock levels for a multistage serial supply chain

In this article, we present a multistage model to optimize inventory control decisions under stochastic demand and continuous review. We first formulate the general problem for continuous stages and use a decomposition solution approach: since it is never optimal to let orders cross, the general problem can be broken into a set of single‐unit subproblems that can be solved in a sequential fashion. These subproblems are optimal control problems for which a differential equation must be solved. This can be done easily by recursively identifying coefficients and performing a line search. The methodology is then extended to a discrete number of stages and allows us to compute the optimal solution in an efficient manner, with a competitive complexity. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 32–46, 2016     

Flexibility and complexity in periodic distribution problems

In this paper, we explore trade‐offs between operational flexibility and operational complexity in periodic distribution problems. We consider the gains from operational flexibility in terms of vehicle routing costs and customer service benefits, as well as the costs of operational complexity in terms of modeling, solution methods, and implementation challenges for drivers and customers. The period vehicle routing problem (PVRP) is a variation of the classic vehicle routing problem in which delivery routes are constructed for a period of time; the PVRP with service choice (PVRP‐SC) extends the PVRP to allow service (visit) frequency to become a decision of the model. For the periodic distribution problems represented by PVRP and PVRP‐SC, we introduce operational flexibility levers and a set of quantitative measures to evaluate the trade‐offs between flexibility and complexity. We develop a Tabu Search heuristic to incorporate a range of operational flexibility options. We analyze the potential value and the increased operational complexity of the flexibility levers. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

‘Kadyrovtsy’: Russia’s Counterinsurgency Strategy and the Wars of Paramilitary Clans

This article analyses the steps taken by the Russian government, with the aid of a powerful local clan, the so-called Kadyrovtsy, to subdue the Chechen insurgency. It highlights the strategy used by Russia, under whose patronage former anti-Russian guerrilla fighters were transformed into paramilitary allies of the Russian government; later these former insurgents were incorporated into the regular Russian army and other state security forces. The article also identifies problems that are connected with the activities of the Kadyrovtsy in Chechnya and Russia, and the spillover into the diaspora; it also contextualises the issues faced by the contemporary Chechen ruling clan and the geopolitics of the Caucasus within the research framework of paramilitarism and counterinsurgency.