Efficiency of equilibria in restricted uniform machine scheduling with total weighted completion time as social cost

In the last decade, there has been much progress in understanding scheduling problems in which selfish jobs aim to minimize their individual completion time. Most of this work has focused on makespan minimization as social objective. In contrast, we consider as social cost the total weighted completion time, that is, the sum of the agent costs, a standard definition of welfare in economics. In our setting, jobs are processed on restricted uniform parallel machines, where each machine has a speed and is only capable of processing a subset of jobs; a job's cost is its weighted completion time; and each machine sequences its jobs in weighted shortest processing time (WSPT) order. Whereas for the makespan social cost the price of anarchy is not bounded by a constant in most environments, we show that for our minsum social objective the price of anarchy is bounded above by a small constant, independent of the instance. Specifically, we show that the price of anarchy is exactly 2 for the class of unit jobs, unit speed instances where the finite processing time values define the edge set of a forest with the machines as nodes. For the general case of mixed job strategies and restricted uniform machines, we prove that the price of anarchy equals 4. From a classical machine scheduling perspective, our results establish the same constant performance guarantees for WSPT list scheduling. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

Terrorism in Nigeria

Using the Boko Haram terrorist group in Nigeria as a point of departure, this paper examines the implications of the operations of terrorist groups on the security and stability of states in West Africa. It predominantly utilises secondary sources of data. Findings indicate that the membership and operations of this terrorist group are spreading across the sub-region. This spread is consequent upon Boko Haram's collaboration with other terrorist groups within West Africa and beyond. This constitutes threats to the security and stability of states in the sub-region. Thus, the paper recommends, among other things: a thorough understanding of the operational strategies of terrorist groups by states and those involved in security policymaking in the sub-region; and for agreements to be reached among Economic Community of West African States (ECOWAS) member states and their governments for collaboration in various areas in order to curtail transnational crime and terrorism, and reduce socio-economic inequality that generates aggressive behaviours among the less privileged.     

Comparative analysis of Arab Spring determinants

The Arab Spring, a pro-democracy uprising that has been sweeping through North Africa and the entire Arab world since 2010, has been described as a cataclysmic revolutionary wave that has left the overthrow of political regimes in its wake. Studies have comprehensively x-rayed the political and socio-economic circumstances that gave rise to the uprising. Apart from the impact of the uprising on political developments and democratic governance in the Arab world in particular and the world in general, the circumstances that resulted in the revolutions constitute empirical security implications for Nigeria. This is the focus of this article. Using the Ibrahim Index of African Governance (IIAG) and other selected indicators, this article draws a comparative analysis of the key factors that led to the uprisings in Egypt, Libya and Tunisia, pointing out areas of social and security tensions in Nigeria. Based on these findings, it points out the urgency of and imperative for security sector reforms in Nigeria.     

On the asymptotic optimality of algorithms for the flow shop problem with release dates

We consider the nonpermutation flow shop problem with release dates, with the objective of minimizing the sum of the weighted completion times on the final machine. Since the problem is NP‐hard, we focus on the analysis of the performance of several approximation algorithms, all of which are related to the classical Weighted Shortest Processing Time Among Available Jobs heuristic. In particular, we perform a probabilistic analysis and prove that two online heuristics and one offline heuristic are asymptotically optimal. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005.