Linear programming and the reliability of multicomponent systems

Several problems in the assignment of parallel redundant components to systems composed of elements subject to failure are considered. In each case the problem is to make an assignment which maximizes the system reliability subject to system constraints. Three distinct problems; are treated. The first is the classical problem of maximizing system reliability under total cost or weight constraints when components are subject to a single type of failure. The second problem deals with components which are subject to two types of failure and minimizes the probability of one mode of system failure subject to a constraint on the probability of the other mode of system failure. The third problem deals with components which may either fail to operate or may operate prematurely. System reliability is maximized subject to a constraint ori system safety. In each case the problem is formulated as an integer linear program. This has an advantage over alternative dynamic programming formulations in that standard algorithms may be employed to obtain numerical results.     

What U.S. Navy strategists and defense planners should think about in the era of maritime great power competition

ABSTRACT

For the first time in a generation, the US Navy finds itself in an era of great power competition. As US naval strategists and defense planners begin to organise materially and conceptually to confront the strategic and operational-level challenges posed by China and Russia, what should they keep in mind? What should frame their thinking? Absorbed with the day-to-day tasks associated with managing how the fleet is being built, operated, and rationalised, these busy officers and civilians seldom can step back and gain some perspective on fundamental aspects of the security environment and relate those to naval purpose. To that end, this article provides a primer on what to keep in mind and how to think in an era of maritime great power competition.     

Walking the Line: Brokering Humanitarian Identities in Conflict Research

ABSTRACT

Increasingly, academic research in conflict-affected contexts relies on support from humanitarian organizations. Humanitarian organizations constitute sites of study in and of themselves; they partner with academics to roll out surveys or randomized program interventions; and they frequently facilitate security, logistics and transportation for independent researchers. We use a research partnership between IRC, the World Bank, and academic researchers in the UK, the US and eastern DR Congo, to explore the effects of humanitarian affiliation on conflict field research. In investigating when, how and under what conditions humanitarian identities are adopted by researchers (and how these affiliations shape research dynamics) we identify three paradoxes. First, “wearing humanitarian clothes” to facilitate research logistics can both facilitate and constrain access. Second, humanitarian affiliations invoked by researchers to ensure security and protection in volatile research sites can undermine the “insider” status of local staff. Finally, working through humanitarian organizations allows local and international researchers to benefit from the protections and privileges afforded to humanitarian employees without providing any of the services on which privileged access rests. In this article, we map out decisions faced by local and international researchers concerning when to adopt and discard humanitarian identities, and the fraught logistical, ethical and methodological consequences of these decisions.