排序方式: 共有76条查询结果,搜索用时 338 毫秒
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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。 相似文献
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We consider a single-machine problem of scheduling n independent jobs to minimize makespan, in which the processing time of job Jj grows by wj with each time unit its start is delayed beyond a given common critical date d. This processing time is pj if Jj 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 pj)2) time and pj) space. © 1998 John Wiley & Sons, Inc. Naval Research Logistics 45: 511–523, 1998 相似文献
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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 相似文献
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Lieneke Eloff de Visser 《Small Wars & Insurgencies》2013,24(4):712-730
Efforts at winning hearts and minds (WHAM) impact on and are affected by perceptions of legitimacy. In the Namibian war for independence (1966–1989) efforts of the South African counterinsurgent forces at winning hearts and minds focused mainly on persuading the population to cooperate in exchange for material benefits and services. The article demonstrates that this successfully contributed to a dimension of legitimacy that is conceptualized as pragmatic legitimacy. However, other dimensions of legitimacy are identified in which the South Africans were lacking, that is in moral, legal, and identity-based legitimacy. Furthermore, in areas where control was contested and where the population could not be shielded from insurgent intimidation, it is argued that the effects of coercion outweighed legitimacy altogether. 相似文献
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Roland de Vries 《African Security Review》2013,22(4):79-97
“There is nothing more difficult to carry out, nor more doubtful of success, nor more dangerous to handle than to initiate a new order of things. For the reformer has enemies in all who profit by the old order, and only lukewarm defenders in all those who would profit by the new order”—Machiavelli This essay was written after a team of the Institute for Security Studies visited the Democratic Republic of the Congo (DRC) to share their experiences of the challenges of defence transformation with Congolese officials and members of civil society. It discusses the South African defence transformation process and experience in detail and highlights the imperative for visionary leadership, commitment and communication as prerequisites for successful transformation. The DRC faces a unique opportunity to design and create an optimal national defence force for itself, which will reflect its new and evolving national policy on defence, and therefore the needs of the nation. This poses an exciting challenge and true opportunity to move beyond survival into a new age. The essay aims to make a contribution to this process. 相似文献
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Rosalia de la Cruz Gitau 《African Security Review》2013,22(4):64-78
Recently, in July 2012, the high-profile and bitterly fought nine-month race for the post of Chair of the African Union (AU) Commission, between Dr Jean Ping of Gabon, and his main challenger, Dr Nkosazana Dlamini-Zuma, culminated in the latter's victory. Her victory came after the deadlock at the Eighteenth AU Summit in January 2012. Borne out of the considered need for a quick fix through reliance on a vote of expediency, the election of Dr Dlamini-Zuma represented a political resolution to the crisis that arose due to the earlier ongoing electoral deadlock. Far from being a competitive election by design, the 2012 AU Commission election by default became transformed into an intensely fought campaign that put the AU in the limelight. This article briefly introduces the electoral process, explains in detail the voting behaviour of AU member states, and offers five specific reasons for the victory of Dr Dlamini-Zuma. On the surface the election looks very competitive, but the article explains why this is not the case. To create greater competition for these posts, the AU needs to overhaul the nomination process and the voting procedure. In this regard, the article proffers detailed analysis and proposes a radical revision of the existing criteria for the nomination. The article also proposes specific recommendations for the amendment of the rules of procedure of the AU Assembly to allow for a qualified majority as a deadlock breaker in the fifth round. It also assesses whether the integrity of the AU Commission election was damaged during the campaigning and voting process. In this regard, it recommends the development of a code of conduct for future elections at the AU. 相似文献
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