A generalized assignment model for dynamic supply chain capacity planning

We consider a generalization of the well‐known generalized assignment problem (GAP) over discrete time periods encompassed within a finite planning horizon. The resulting model, MultiGAP, addresses the assignment of tasks to agents within each time period, with the attendant single‐period assignment costs and agent‐capacity constraint requirements, in conjunction with transition costs arising between any two consecutive periods in which a task is reassigned to a different agent. As is the case for its single‐period antecedent, MultiGAP offers a robust tool for modeling a wide range of capacity planning problems occurring within supply chain management. We provide two formulations for MultiGAP and establish that the second (alternative) formulation provides a tighter bound. We define a Lagrangian relaxation‐based heuristic as well as a branch‐and‐bound algorithm for MultiGAP. Computational experience with the heuristic and branch‐and‐bound algorithm on over 2500 test problems is reported. The Lagrangian heuristic consistently generates high‐quality and in many cases near‐optimal solutions. The branch‐and‐bound algorithm is also seen to constitute an effective means for solving to optimality MultiGAP problems of reasonable size. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

Modeling the operation of multireservoir systems using decomposition and stochastic dynamic programming

Stochastic dynamic programming models are attractive for multireservoir control problems because they allow non‐linear features to be incorporated and changes in hydrological conditions to be modeled as Markov processes. However, with the exception of the simplest cases, these models are computationally intractable because of the high dimension of the state and action spaces involved. This paper proposes a new method of determining an operating policy for a multireservoir control problem that uses stochastic dynamic programming, but is practical for systems with many reservoirs. Decomposition is first used to reduce the problem to a number of independent subproblems. Each subproblem is formulated as a low‐dimensional stochastic dynamic program and solved to determine the operating policy for one of the reservoirs in the system. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

Analysis of a new vehicle scheduling and location problem

We consider a container terminal discharging containers from a ship and locating them in the terminal yard. Each container has a number of potential locations in the yard where it can be stored. Containers are moved from the ship to the yard using a fleet of vehicles, each of which can carry one container at a time. The problem is to assign each container to a yard location and dispatch vehicles to the containers so as to minimize the time it takes to download all the containers from the ship. We show that the problem is NP‐hard and develop a heuristic algorithm based on formulating the problem as an assignment problem. The effectiveness of the heuristic is analyzed from both worst‐case and computational points of view. © 2001 John Wiley & Sons, Inc. Naval Research Logistics 48: 363–385, 2001     

The shortest queue model with jockeying

In this article we deal with the shortest queue model with jockeying. We assume that the arrivals are Poisson, each of the exponential servers has his own queue, and jockeying among the queues is permitted. Explicit solutions of the equilibrium probabilities, the expected customers, and the expected waiting time of a customer in the system are given, which only depend on the traffic intensity. Numerical results can be easily obtained from our solutions. Several examples are provided in the article.     

Case Study Commentary and Analysis: The Moral Sword of Damocles

Case summary, by James Cook (Case Study Editor):

In the final issue of the 2015 volume of the Journal of Military Ethics, we published a case study entitled “Coining an Ethical Dilemma: The Impunity of Afghanistan’s Indigenous Security Forces”, written by Paul Lushenko. The study detailed two extra-judicial killings (EJKs) by Afghan National Police (ANP) personnel in an area stabilized and overseen by a US-led Combined Task Force (CTF). To deter further EJKs following the first incident, the CTF’s commander reported the incidents up his chain of command and used the limited tools at his disposal to influence local indigenous officials directly. Apparently, the ANP unit took no notice. In his commentary on the case study, Paul Robinson considered moral compromise in war more generally. Coalition troops in Afghanistan, for instance, have encountered not just EJKs but also sexual abuse of minors, killing of non-combatants, kidnapping, torture, and widespread corruption. What should the soldier on the ground do if indigenous personnel violate Laws of Armed Conflict (LOAC) with impunity? Refusing to serve will not right or prevent moral wrongs, while staying on to fight the good but futile fight will mire the soldier in moral compromise. “?… [S]oldiers faced with this dilemma have no good options. The systemic failings surrounding them mean that it is probable that nothing they do will help”. In a concluding note, I suggested that while an individual soldier may indeed have no good options, as Paul Robinson suggests, that soldier’s military and nation at large are obliged to do what they can. At least, they must keep to the moral high ground so as not to give indigenous security forces an excuse to misbehave, and determine the nature of crimes such as EJKs: are they outlaw acts or in fact endorsed by the indigenous culture and perhaps even government? Below Colonel Dave Barnes, himself a veteran of Operation Enduring Freedom, analyzes Paul Lushenko’s case study at “?…?the local, tactical level: If a commander is in this situation – where her unit witnesses an EJK or other war crime – what should she do?”     

‘The People are Revolting’: An Anatomy of Authoritarian Counterinsurgency

Rather than win hearts and minds, authoritarian counterinsurgency is said to rely heavily on coercion. It has a reputation for effectiveness, if also for its amorality. Still, the research into authoritarian counterinsurgency is surprisingly lacking. By distilling common features from key cases, this article concludes that this approach goes beyond the indiscriminate violence that typically captures the imagination. Like their democratic counterparts but differently, authoritarian regimes also engage in mobilisation, create narratives, and turn military advantage into political gain. The analysis explains how these tasks are undertaken and, by contradistinction, sheds light on more liberal approaches as well.     

An error components model of cost overruns and schedule slip on army R&D programs

What has been causing cost overruns and schedule slippages in Army major weapon-system R&D programs during the past ten years? This article addresses this question with emphasis on the effectiveness of an Army acquisition strategy entitled Total Risk Assessing Cost Estimating (TRACE). An empirical study employed a questionnaire and interviews with key personnel from all of the major Army Program Management Offices involved with R&D. The major research question was the following: What explanatory variables have been affecting R&D cost overruns and development time? This includes an evaluation of TRACE as a potential explanatory variable. Data was collected and analyzed using an error components multiple regression model. The major explanatory variables that appeared to explain cost overruns were technological risk of the program, education and experience of key program management office personnel, and the degree of “buy in” by the prime contractor. Strong statistical results indicate that TRACE is having little or no effect on cost overruns. In the case of development time, the major explanatory variables were seen to be technological risk of the program, testing, TRACE, education, and length of the R&D contract.