计算方法教学与工科学生的素质培养

科学计算能力是二十一世纪人才不可或缺的,在提倡素质教育的今天,尤其对工科学生,更应该注重培养他们的数学素质和科学素质.本文从"计算方法"这门课的研究对象和特点出发,论述了它在工科学生素质教育中占有重要的地位;结合这门课的特点,阐述了在教学过程中如何加强学生的数学素质和科学素质的培养.     

Stability in a general oligopoly model

We analyze a general but parsimonious price competition model for an oligopoly in which each firm offers any number of products. The demand volumes are general piecewise affine functions of the full price vector, generated as the “regular” extension of a base set of affine functions. The model specifies a product assortment, along with their prices and demand volumes, in contrast to most commonly used demand models. We identify a fully best response operator which is monotonically increasing so that the market converges to a Nash equilibrium, when firms dynamically adjust their prices, as best responses to their competitors' prices, at least when starting in one of two price regions. Moreover, geometrically fast convergence to a common equilibrium can be guaranteed for an arbitrary starting point, under an additional condition for the price sensitivity matrix.     

基于动量流量法对喷水推进系统推力的CFD计算

采用结构化网格与非结构化网格相结合的方式划分了喷水推进系统的流场区域,采用稳态多参考系方法进行了数值计算。在此基础上,定义并求解一用户自定义标量函数标记整个流场,并根据标记结果将被喷水推进器吸入的流体与其它流体区分开。在后处理过程采用标量函数的等值面来确定喷水推进系统控制体上的流管分界面和进流面。利用数值计算所得的速度场对喷水推进系统喷口和进流面上的动量流量变化率进行计算,间接地得到喷水推进系统的推力。计算结果表明,采用CFD手段计算和分析喷水推进系统包括推力在内的各项性能指标是可行的。     

库存控制条件下弹药供应链稳定性研究

由于弹药供应链系统中存在牛鞭效应问题,为了减少牛鞭效应对弹药供应系统的影响,研究系统的稳定性,建立了一阶弹药供应链系统。分析了弹药供应链系统的构成,对系统进行了数学建模分析与仿真验证分析。分析得出,决策参数调整系数β对弹药供应链系统稳定性的影响明显,部队需求量变化及订货量决策参数安全系数α影响较弱。并得出系统稳定时或系统出现震荡、混沌现象时调整系数β的取值范围。     

Chinese views of the nuclear endgame in North Korea

ABSTRACT

This article examines Chinese views of North Korea’s nuclear-weapon program during the Donald J. Trump administration. It shows that China has portrayed itself as a responsible country that promotes regional stability, unlike the United States, which has engaged in military brinkmanship with North Korea. Some Chinese foreign-policy experts have asserted that Beijing should back Pyongyang in the event of war because of their shared history of humiliation by great powers, while others have favored working with other regional partners. Another theme in Chinese discourse about North Korea is that Pyongyang is an impetuous, ungrateful regime that impedes Beijing’s ability to attain its core interests of regional stability, economic development, and heightened global influence. This negative assessment of North Korea drove Beijing’s endorsement of stricter UN sanctions in 2017. While Beijing has punished Pyongyang for its wayward policies, China responded favorably to North Korea’s decision in April 2018 to stop nuclear tests and partake in international dialogue. Beijing seeks to help Pyongyang gradually disarm and develop its economy within a Chinese-led East Asian order. The article concludes by explaining how Beijing’s recent, more positive view of Pyongyang is likely to affect its support for American efforts to dismantle North Korea’s nuclear-weapon program.     

大口径牵引火炮海绵轮胎改装充气轮胎稳定性研究

以某型大口径牵引火炮为例,通过机动性验证,射击稳定性试验和计算机模拟仿真,对海绵轮胎改装充气式轮胎后的火炮稳定性进行分析。结果表明,改装后,火炮能够保持良好的稳定性,大幅提高装备的机动能力,为大口径牵引火炮海绵轮胎改装充气轮胎提供参考。     

Rethinking strategic culture: A computational (social science) discursive-institutionalist approach

ABSTRACT

The strategic culture approach has been suffering from a prolonged theoretical stalemate, despite a surge in case studies, which culminated in the Johnston-Gray debate and subsequent schism. The present paper outlines a new approach designed to overcome this deadlock, and consists of three arguments. First, the three previous generations of strategic culture studies have failed to explain how strategic culture influences behaviour. Second, aligning strategic culture theory-building with discursive institutionalism offers a way to overcome this fundamental fallacy. Third, a research programme for strategic culture should draw on computational social science to enable it to present and test middle-range theories.     

具时滞的比率型三种群捕食系统的全局渐近稳定性

研究了一类具有时滞的比率型三种群捕食者-食饵系统,给出了系统持续生存的条件。通过构造Lyapunov泛函的方法得到了该系统正平衡态全局渐近稳定的充分条件。     

尾空泡对水下航行体流体阻尼力影响数值计算分析

针对航行体尾空泡对流体阻尼力影响的问题,结合动坐标系技术和空泡多相流数值模拟方法,通过求解雷诺平均的纳维-斯托克斯方程组,进行阻尼力计算研究。试验数据对比结果表明,该方法具有较好的精度。数值计算研究表明,尾空泡会削弱航行体尾部压力的不对称性,使航行体尾部流体阻尼力减小。当尾空泡增加到一定尺寸时,流体阻尼力减小的幅度逐渐趋缓,同时尾空泡也改变了流体阻尼力随攻角的变化趋势。研究充分表明了航行体流体力设计中考虑尾空泡影响的必要性。     

声场波数积分最大截止波数自动选取算法

为了提高声场波数积分传递函数矩阵法的计算稳定性与精确性，提出基于预估-校正思想的最大截止波数自动选取算法，具有简单可靠、附带计算量小的优点。自由空间球面波算例测试结果表明，传递函数自下而上（单向）求解顺序的计算稳定性相对较差，在声源上方易出现积分核函数非物理发散，需要在不同深度上采用不同的截止波数才能计算出正确结果；而上下对进（双向）求解顺序的计算稳定性与计算精度均较高。