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1.
Martijn van Ee 《海军后勤学研究》2020,67(2):147-158
We consider the salvo policy problem, in which there are k moments, called salvos, at which we can fire multiple missiles simultaneously at an incoming object. Each salvo is characterized by a probability pi: the hit probability of a single missile. After each salvo, we can assess whether the incoming object is still active. If it is, we fire the missiles assigned to the next salvo. In the salvo policy problem, the goal is to assign at most n missiles to salvos in order to minimize the expected number of missiles used. We consider three problem versions. In Gould's version, we have to assign all n missiles to salvos. In the Big Bomb version, a cost of B is incurred when all salvo's are unsuccessful. Finally, we consider the Quota version in which the kill probability should exceed some quota Q. We discuss the computational complexity and the approximability of these problem versions. In particular, we show that Gould's version and the Big Bomb version admit pseudopolynomial time exact algorithms and fully polynomial time approximation schemes. We also present an iterative approximation algorithm for the Quota version, and show that a related problem is NP-complete. 相似文献
2.
We consider the problem of nonparametric multi-product dynamic pricing with unknown demand and show that the problem may be formulated as an online model-free stochastic program, which can be solved by the classical Kiefer-Wolfowitz stochastic approximation (KWSA) algorithm. We prove that the expected cumulative regret of the KWSA algorithm is bounded above by where κ1, κ2 are positive constants and T is the number of periods for any T = 1, 2, … . Therefore, the regret of the KWSA algorithm grows in the order of , which achieves the lower bounds known for parametric dynamic pricing problems and shows that the nonparametric problems are not necessarily more difficult to solve than the parametric ones. Numerical experiments further demonstrate the effectiveness and efficiency of our proposed KW pricing policy by comparing with some pricing policies in the literature. 相似文献
3.
如何培养学生高阶思维能力是目前社会各界非常关注的问题。知识建构教学在促进"浅层学习"转向"深度学习"方面取得的研究,已经得到了国际学习科学领域的广泛认可,而对于如何促进学生高阶思维能力发展具体途径,还需要不断进行探索。研究以小学二年级科学课程为例,按照知识建构的课堂组织了教学设计过程。通过研究发现,知识建构的课堂通过培养学生发散思维能力、发现问题、解决问题的能力和综合能力,可以有效促进学生高阶思维能力的培养。 相似文献
4.
Yoshinori Suzuki 《海军后勤学研究》2008,55(8):737-746
Fuel optimizers are decision models (software products) that are increasingly recognized as effective fuel management tools by U.S. truckload carriers. Using the latest price data of every truck stop, these models calculate the optimal fueling schedule for each route that indicates: (i) which truck stop(s) to use, and (ii) how much fuel to buy at the chosen truck stop(s) to minimize the refueling cost. In the current form, however, these models minimize only the fuel cost, and ignore or underestimate other costs that are affected by the models' decision variables. On the basis of the interviews with carrier managers, truck drivers, and fuel‐optimizer vendors, this article proposes a comprehensive model of motor‐carrier fuel optimization that considers all of the costs that are affected by the model's decision variables. Simulation results imply that the proposed model not only attains lower vehicle operating costs than the commercial fuel optimizers, but also gives solutions that are more desirable from the drivers' viewpoint. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008 相似文献
5.
试验研究了穿甲子弹垂直侵彻高强防弹钢的机理,提出了一个分析靶板极限速度和弹体剩余速度的理论模型,该模型综合考虑了材料的应变率与热软化效应,结果表明,理论值与试验值吻合很好.分析了失效准则的影响,研究了剪切带温度和靶板耗能随入射速度的变化规律. 相似文献
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7.
本文基于情绪安全感理论,探讨初中生情绪不安全感与攻击行为的关系,采用问卷调查的方式,对新疆某市区274名初中生进行调查。结果显示:①初三年级间接攻击水平显著高于初一年级(F=4.41,p<0.05);②初一、初二年级情绪不安全感水平显著高于初三年级(F=8.31,p<0.001);③初中生情绪不安全感与攻击行为之间存在显著正相关(r=0.32,p<0.01)。调查结果表明,降低初中生的情绪不安全感水平,有助于减少其攻击行为的发生。 相似文献
8.
赵子良 《中国人民武装警察部队学院学报》2008,24(3):58-60
提高“两课”教学的生动性,就要在备课和讲课时,注重追求思想上的深刻、资料上的精彩和语言上的震撼与精美。力求思想深刻,内容精彩,语言精美。 相似文献
9.
近年来,边防部队通过大力开展基层警营文化建设,取得了可喜的成绩,但整体情况仍然滞后,需从多方面分析其存在的问题及原因,才能进一步提出对策,使警营文化效能的发挥达到最佳。 相似文献
10.