"数值方法"课程教学改革探讨

文章探讨了"数值方法"课程教学改革的尝试,通过优化课堂教学、加强工程实践、开拓学生思维,有效地提高了教学效果.     

高速IGBT的二维数值分析

借助双极传输理论导出了高速绝缘栅双极晶体管（ＩＧＢＴ）传输特性的物理模型。稳态时，其工作原理与普通ＩＧＢＴ完全相同，但瞬态时，由于Ｎ＋阳极对基区非平衡载流子的抽出作用，使其关断速度比普通ＩＧＢＴ大大提高。文中利用二维器件数值分析软件（ＰＩＳＣＥＳ－ＩＢ）对其稳态和瞬态工作特性进行了详细的模拟分析，获得了其工作时的浓度分布、电流分布等内部物理参数，并得到了它的关断时间Ｔｏｆ，其模拟结果与实验值比较吻合     

CO2泡沫压裂裂缝三维延伸及温度场的数值模拟

针对深层油气田压裂施工的实际情况，考虑CO2泡沫压裂液变物性的影响，建立了新的拟三维模型和热力学模型，计算了陕西长庆上古油田某油井的现场压裂施工工况，计算结果表明，所建模型能较准确地预测压裂液在裂缝中的延伸与温度特性的变化，对相关油井的压裂工艺实施、参数选择及效果评估具有一定的借鉴价值。     

平面板状天线

研究了自由空间下平的面板状天线,用矩量法求解了这种二维天线的电流分布及其输入阻抗,进行了大量的数值计算,把计算二维积分的运算从 N×N 元减少到 N 元,从而缩短了运算,节约机时。对不同尺寸的平面板状天线进行了输入阻抗实验验证,理论与实验较一致。     

Getting the most out of reverse e-auction investment

In 1990s, with dramatic price reductions, reverse e-auctions were projected to be a widely used procurement tool. However, not all buyers saw the economic benefits of reverse e-auctions and the current usage is more limited than expected. This study identifies important organizational characteristics that determine the net return of e-auction programs and addresses why adopters of e-auctions experience varying profitability levels from their usage. The first step in the study concentrated on gathering interview and archival data from five large U.S. manufacturing firms that have used reverse e-auctions. Based on the field study findings, controlled experiments were conducted using a simulation model to assess identified influential factors for e-auctions. Implications for supply managers are presented and future research directions are discussed.     

基于自适应性学习的财务预警机理研究

缺乏规范的理论机理是目前财务预警研究中的薄弱环节。通过界定基本概念,揭示了财务预警的柔性决策实质。吸收经济演化论的观点建立了企业的柔性生存模型,通过模型数值模拟结果分析得到了重要的财务柔性决策规律,基于研究建立的财务柔性决策的系统结构及其学习机理,提炼出了以自适应学习为核心的财务预警机理。分析发现,制定决策时的环境学习能力和预警策略执行中的自适应调整能力是决定财务预警管理有效性的关键因素。     

变导流能力下压裂井生产动态研究

人工裂缝长期导流能力随时间变化, 据此建立了考虑人工裂缝长期导流能力变化的数学模型。应用数值模拟方法研究长期导流能力变化对地层压力场及流场分布和压裂井产能的影响。数模结果表明： 裂缝长期导流能力的损失, 会导致地层流体更多地通过井底附近的裂缝流入井底, 优化了裂缝内的流场, 减缓了压裂井产能递减速率; 其他情况相同时, 裂缝半长越长, 裂缝长期导流能力的损失对压裂井产能的影响越大。     

金刚石线锯制造中气固两相流的数值模拟

对金刚石线锯制造中的喷覆装置进行了三维气固两相流数值模拟。在Euler坐标系中计算气相流场,在Lagrange坐标系下跟踪颗粒运动轨迹,考虑了颗粒之间碰撞,颗粒与壁面的碰撞,固相对气相的相互影响。数值模拟结果与实验吻合良好。模拟结果表明,多数颗粒为锯丝经过喷嘴时喷覆到锯丝上,只有少数经过壁面的碰撞反弹后粘到锯丝上。     

缝洞型油藏离散介质网络数值试井模型

针对多重介质试井模型不符合缝洞型油藏网络状分布、非均质性极强的地质特征,建立了新的试井模型,将大尺度溶洞（流体主要的储集空间）视作零维模型,裂缝、孔洞发育的条带状地层（沟通溶洞的渗流通道）作为控制流体流动的一维模型,从而构成离散介质网络（DMN）模型。用有限差分法建立了缝洞型油藏离散介质网络油水两相数值试井模型,对渗流通道的储渗性能、大尺度溶洞的容积和距测试井的距离等因素对测试井压力响应特征的影响进行了研究。结果表明：缝洞型油藏试井压力导数曲线上类似“凹子”的特征是由大尺度溶洞向渗流网络的窜流造成的。实例分析表明,新模型解释结果与缝洞型油藏地质特征一致。     

Numerical Simulation of Population Distribution in China

A model for simulating population distribution (MSPD) of China is developed based on the grid generation method and the Control of MapObjects of geographical information system. Elevation, net primary productivity, land use and land cover, city sizes and their spatial distribution, and spatial distribution of transport infrastructures are taken into full account in the MSPD. The result from the MSPD shows that in 2000, 90.8% of the total population of China distributed on the southeastern side of the Heihe-Tengchong line. The ratio of population on the northwestern side to total population of China has been increasing since 1935. The yearly growth rate was 0.8% from 1935 to 1990 and 6.1% from 1990 to 2000. One important advantage of the MSPD is that when scenarios of land cover, spatial distributions of transport infrastructures and cities are available, scenarios of spatial population distribution can be developed on the basis of total population forecast.