Maintaining systems with heterogeneous spare parts

We consider the problem of optimally maintaining a stochastically degrading, single‐unit system using heterogeneous spares of varying quality. The system's failures are unannounced; therefore, it is inspected periodically to determine its status (functioning or failed). The system continues in operation until it is either preventively or correctively maintained. The available maintenance options include perfect repair, which restores the system to an as‐good‐as‐new condition, and replacement with a randomly selected unit from the supply of heterogeneous spares. The objective is to minimize the total expected discounted maintenance costs over an infinite time horizon. We formulate the problem using a mixed observability Markov decision process (MOMDP) model in which the system's age is observable but its quality must be inferred. We show, under suitable conditions, the monotonicity of the optimal value function in the belief about the system quality and establish conditions under which finite preventive maintenance thresholds exist. A detailed computational study reveals that the optimal policy encourages exploration when the system's quality is uncertain; the policy is more exploitive when the quality is highly certain. The study also demonstrates that substantial cost savings are achieved by utilizing our MOMDP‐based method as compared to more naïve methods of accounting for heterogeneous spares.     

IED casualties mask the real problem: it's us

Casualty figures suggest that the US/Allied Counter Improvised Explosive Device (C-IED) policy and the present allocation of national assets, resources, and intellectual capital have not been very successful. A number of explanations for why this has been the case are discussed and critiqued here.     

Planning versus Chaos in Clausewitz's On War

Clausewitz laid great emphasis on the planned construction of war, but this idea has received little attention from his commentators, who generally attach far greater importance to what he said about the chaotic elements of war, in particular its interactive nature and the friction inseparable from its conduct. This article gives long-overdue recognition to planning as a dominant theme of On War. The essential point Clausewitz makes concerning interaction is not that the enemy's responses are bound to disrupt our plans, but that our plans must aim to predict and incorporate his responses. Clausewitz acknowledges that friction creates enormous difficulties for the realization of any plan, but it is precisely in respect of this challenge that he develops the concept of military genius, whose capabilities are seen above all as the executive arm of planning.     

Blood on the Ground: Canada and the Southern Campaign in Afghanistan

For the Americans, it's no longer just “boots on the ground”: it's blood on the ground that counts.

Joel J. Sokolsky

     

How do sources of traditional legitimacy constrain popular uprisings? The case of the Kingdom of Swaziland

ABSTRACT

Research concerning authoritarian stability and peace usually investigates co-optation and repression. Recently, several studies argue that traditional legitimacy is also important for stability in monarchies. However, existing research rarely considers how legitimacy constrains rebellions and help the royal family to stay in power. Hence, this article explores the causal links between sources of traditional legitimacy and absence of uprisings. The study investigates the relationship with a case study of the Kingdom of Swaziland. In line with my expectations, I find a causal relationship between sources of traditional legitimacy and absence of popular uprisings. First, the royal family actively uses traditional legitimacy to justify their rule. Second, the Afrobarometer indicates that the Swazi people trust the King more than citizens in other African countries trust their head of state. Third, opposition actors have limited opportunities to mobilize the broader population against the monarchy. Fourth, traditional legitimacy dampens ongoing protests and thereby hinders their escalation into popular uprisings or political violence. Repression is clearly an important explanation for limited rebellion in Swaziland, but this article shows that also traditional legitimacy sources play a role.     

A note comparing glover's and young's simplified primal algorithms

Glover and Young, References [4] and [8], respectively, present convergent primal integer programming algorithms. The algorithm outlined in Young's paper (which was deliberately specialized) is shown to be a special case of the Glover algorithm under his acceptable source row selection, Rule 1.