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     

Rhetoric versus reality: Canadian defence planning in a time of austerity

As Canada's military mission in Afghanistan winds down and the country faces several years of fiscal austerity, all of Canada's major political parties are agreed that Canadian defence budgets must stay level or be cut. This comes at a time when the defence department is slated to replace the Canadian Forces’ (CF) major equipment fleets. Canada's defence establishment thus faces some critical decisions. One option is to try to maintain its expeditionary capabilities across all three services: army, navy and air force. Absent substantial new infusions of funds, however, this approach is likely to lead to an overall and largely chaotic reduction of capabilities. Another option is to make some difficult choices as to which expeditionary capabilities to maintain as part of a strategic review of Canada's future military needs. Such an option would ensure that Canada has at least some military capacities which can reliably be devoted to the most demanding international operations, while maintaining those capabilities required for domestic duties and North American defence. Pursuing this option would accord with the new North Atlantic Treaty Organization Strategic Concept and the call for “Smart Defense” within the Alliance. This article assesses the arguments for and against the option of specialising Canada's future defence capabilities and explores scenarios as to what a future CF may look like.     

基于云模型的无人机作战系统效能评估

对无人机作战系统进行效能评估有利于了解无人机的能力和不足,为无人机的后继研发提供有效依据。针对作战系统指标的相对性、模糊性与不确定性,通过层次分析法建立无人机作战系统效能评估的指标体系,采用云模型实现作战系统指标的定性属性与定量属性的相互结合与转换,结合专家打分法给出作战系统指标的定性权重和评价,并利用正态云拟合算法得出无人机作战系统的综合效能。通过实例分析,表明该方法具有可行性。     

Worst‐case performance of approximation algorithms for tool management problems

Since the introduction of flexible manufacturing systems, researchers have investigated various planning and scheduling problems faced by the users of such systems. Several of these problems are not encountered in more classical production settings, and so‐called tool management problems appear to be among the more fundamental ones of these problems. Most tool management problems are hard to solve, so that numerous approximate solution techniques have been proposed to tackle them. In this paper, we investigate the quality of such algorithms by means of worst‐case analysis. We consider several polynomial‐time approximation algorithms described in the literature, and we show that all these algorithms exhibit rather poor worst‐case behavior. We also study the complexity of solving tool management problems approximately. In this respect, we investigate the interrelationships among tool management problems, as well as their relationships with other well‐known combinatorial problems such as the maximum clique problem or the set covering problem, and we prove several negative results on the approximability of various tool management problems. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 445–462, 1999     

Scheduling deteriorating jobs to minimize makespan

We consider a single-machine problem of scheduling n independent jobs to minimize makespan, in which the processing time of job J_j grows by w_j with each time unit its start is delayed beyond a given common critical date d. This processing time is p_j if J_j starts by d. We show that this problem is NP-hard, give a pseudopolynomial algorithm that runs in time and O(nd) space, and develop a branch-and-bound algorithm that solves instances with up to 100 jobs in a reasonable amount of time. We also introduce the case of bounded deterioration, where the processing time of a job grows no further if the job starts after a common maximum deterioration date D > d. For this case, we give two pseudopolynomial time algorithms: one runs in O(n²d(D − d) time and O(nd(D − d)) space, the other runs in p_j)²) time and p_j) space. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 511–523, 1998     

Sweden and the issue of NATO membership: exploring a public opinion paradox

The past decade has seen substantial shifts in Swedish security policy and major change in the domestic debate about NATO. For the first time, all of the right-of-centre “alliance parties” are calling for a full NATO membership, and popular support for NATO has increased. Yet public opinion contains ambiguities and paradoxes that complicate the picture. At the same time as support for NATO has increased, the public is overwhelmingly for continued military non-alignment. Drawing on previous research, longitudinal data from national surveys, and other sources on defence and security issues, this article aims to increase our understanding of the development and change in Swedish public opinion on NATO. A key argument is that Erving Goffman’s theatre metaphor, combined with neo-institutional decoupling theory, to a large degree can help understand the public opinion paradox.     

A Cryptographic Escrow for Treaty Declarations and Step-by-Step Verification

The verification of arms-control and disarmament agreements requires states to provide declarations, including information on sensitive military sites and assets. There are important cases, however, in which negotiations of these agreements are impeded because states are reluctant to provide any such data, because of concerns about prematurely handing over militarily significant information. To address this challenge, we present a cryptographic escrow that allows a state to make a complete declaration of sites and assets at the outset and commit to its content, but only reveal the sensitive information therein sequentially. Combined with an inspection regime, our escrow allows for step-by-step verification of the correctness and completeness of the initial declaration so that the information release and inspections keep pace with parallel diplomatic and political processes. We apply this approach to the possible denuclearization of North Korea. Such approach can be applied, however, to any agreement requiring the sharing of sensitive information.     

惰性气体中电爆丝爆炸激励冲击波的理论分析

建立了惰性气体中电爆丝爆炸激励的冲击波模型。对于冲击波马赫数与光辐射强度的关系、惰性气体种类对冲击波强度的影响以及电爆丝根数对冲击波强度的影响,进行了理论计算与分析,所得结论对红外脉冲强光辐射源的研究有重要作用。     

Capitalism & the “new wars”: free markets and societal insecurity before and after the cold war, 1970–2013

Critics of globalisation suggest that growing free-market conditions generate anomie, leading ultimately to what some term ‘new wars’ and new insecurities. Others argue that liberal economies dissuade violence since people gain from peace. This study argues for a micro perspective that views predatory economic policies driving higher investment in rebellion-specific capital, such as shadow economic activity that easily translates into insurgency in weak-state settings. Investment in the shadows determines survivability against superior state forces, and survivability determines rebellion, by definition. Using civil war onset data from 1970 to 2013, as well as the Global Peace Index (GPI) and several of its individual components, which capture societal insecurity above and beyond the absence of armed violence, this study finds that countries that are more capitalistic have a lower risk of civil war and societal insecurity. The results are robust to alternative models, testing methods, and uphold when examining several relevant subcomponents of the index, such as internal conflict, violent crime, homicides, ease of access to small arms, and political instability. Surprisingly, democracy tends not to be associated with peace but associates with increased criminality whereas strong autocracy reduces it, suggesting that capitalism, more than democracy, associates with conditions favourable to societal security, independently of a country’s level of development.