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971.
In this article, we address a stochastic generalized assignment machine scheduling problem in which the processing times of jobs are assumed to be random variables. We develop a branch‐and‐price (B&P) approach for solving this problem wherein the pricing problem is separable with respect to each machine, and has the structure of a multidimensional knapsack problem. In addition, we explore two other extensions of this method—one that utilizes a dual‐stabilization technique and another that incorporates an advanced‐start procedure to obtain an initial feasible solution. We compare the performance of these methods with that of the branch‐and‐cut (B&C) method within CPLEX. Our results show that all B&P‐based approaches perform better than the B&C method, with the best performance obtained for the B&P procedure that includes both the extensions aforementioned. We also utilize a Monte Carlo method within the B&P scheme, which affords the use of a small subset of scenarios at a time to estimate the “true” optimal objective function value. Our experimental investigation reveals that this approach readily yields solutions lying within 5% of optimality, while providing more than a 10‐fold savings in CPU times in comparison with the best of the other proposed B&P procedures. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 131–143, 2014 相似文献
972.
Alessio Patalano 《战略研究杂志》2014,37(3):403-441
AbstractThis article draws upon previously unavailable document materials to question views pointing to a degree of stagnation in Japanese maritime thinking. It similarly reviews claims about trends to compensate the decline of national military power with the build-up of projection capabilities. The article’s main argument is that Japanese seapower is not declining. The Japanese Navy is evolving to combine enhanced capabilities to retain sea control in the Sea of Japan and the East China Sea with extended operational reach and flexibility, including an expeditionary component to meet alliance and diplomatic commitments in East Asia and beyond its confines. 相似文献
973.
防空作战是大型水面舰艇编队的主要作战样式之一。运用PEPA(性能评价过程代数)方法对舰艇编队防空作战全过程进行有效建模,形式化描述了预警探测、情报传递、命令下达、防空拦截等作战主要过程。建立的PEPA模型具有层次化结构,考虑了要素间相互协作,体现了编队防空作战分布、并发的特点。通过对建立的PEPA模型进行性能指标选择和稳定状态分析,得到了不同因素对编队能力发挥的影响情况,获得了防空作战的基本要素组成,从而提供了一种解决舰艇编队问题的新方法。 相似文献
974.
为了满足远距离海底探测对发射信号大功率的需求,选用了一种大功率可控硅开关功率放大器。在临界换流、自然换流和强迫换流3种工作状态下,分析了该功率放大器的工作原理,并建立了等效电路模型。运用Or CAD仿真了临界换流状态时的等效电路模型;在自然换流状态和强迫换流状态下,为获得功放电流值和负载电流值,对其等效电路模型分别建立了非线性数学模型,并通过Matlab和VC++采用四阶Runge-Kutta法对非线性数学模型进行求解。以上方法能够求得该功率放大器电路在任意时刻、任意点处的电流电压值,能较客观、真实地反映电路的工作状况,对工程应用具有一定的参考价值。 相似文献
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针对全球定位系统在信号失锁条件下与航位推算组合导航的系统误差快速累积问题,提出一种基于压缩扩展卡尔曼滤波的同时定位与制图的辅助的全球定位系统/航位推算组合导航方法。该方法利用同时定位与辅助实现运动平台在全球定位系统信号无效时连续稳定导航,抑制航位推算定位误差的累积,并利用全球定位系统定位结果校正同时定位与辅助制图误差,减小地图的不确定性。设计基于压缩扩展卡尔曼滤波的同时定位与辅助/全球定位系统组合滤波器,实现大尺度环境下同时定位与辅助/全球定位系统的实时解算。真实实验数据计算结果分析表明,相对于同时定位与辅助定位结果,同时定位与辅助的全球定位系统/航位推算组合导航可有效提高系统定位性能,使得制图精度提高10m。 相似文献
979.
Romain Esmenjaud 《African Security Review》2014,23(2):172-177
The creation of an African Capacity for Immediate Response to Crisis (ACIRC) is a sign of Africa's willingness to take its destiny into its own hands. Presented as a reaction to the slowness of the development of the African Standby Force (ASF), it is also a response to some of the ASF's conceptual weaknesses. This decision reflects a wish to establish an instrument better equipped to deal with the challenges Africa is facing. Departing from the (sub)regional logic of the ASF results from a desire to take into account the transnational nature of threats, while its enlarged mandate is meant to offer Africa the capacity to intervene in all kinds of conflicts, including by undertaking peace enforcement activities. But the obstacles on the road towards the actual creation and mobilisation of this capacity should not be underestimated. These include material difficulties, but also political tensions, between ‘small’ and ‘big’ states as well as between the African Union and subregional organisations. The risk then is high that the ACIRC, whose announcement came as a reaction to France's intervention in Mali, ends up joining the ranks of the many ‘anti-imperialist’ phantoms haunting the history of the Organization of African Unity/African Union (OAU/AU). Confronted by events considered ‘neocolonial’ initiatives, African actors have indeed traditionally reacted by launching grand projects that never got off the ground. However, by actually establishing this new instrument, they may also demonstrate that times have definitively changed. 相似文献
980.
Malte Brosig 《African Security Review》2014,23(3):225-242
This article presents survey data on the African Peace and Security Architecture (APSA). It focuses explicitly on two aspects: the internal constitution and achievements of the APSA; and coordination and cooperation with external actors, such as Regional Economic Communities, the United Nations and the European Union. The survey, conducted between October 2011 and December 2012, targeted 198 security experts in international organisations, think tanks, academia and non-governmental organisations. It reveals the APSA's current stage of development, achievements and challenges. 相似文献