A Class of TVD Type Combined Numerical Scheme for MHD Equations With a Survey About Numerical Methods in Solar Wind Simulations

It has been believed that three-dimensional, numerical, magnetohydrodynamic (MHD) modelling must play a crucial role in a seamless forecasting system. This system refers to space weather originating on the sun; propagation of disturbances through the solar wind and interplanetary magnetic field (IMF), and thence, transmission into the magnetosphere, ionosphere, and thermosphere. This role comes as no surprise to numerical modelers that participate in the numerical modelling of atmospheric environments as well as the meteorological conditions at Earth. Space scientists have paid great attention to operational numerical space weather prediction models. To this purpose practical progress has been made in the past years. Here first is reviewed the progress of the numerical methods in solar wind modelling. Then, based on our discussion, a new numerical scheme of total variation diminishing (TVD) type for magnetohydrodynamic equations in spherical coordinates is proposed by taking into account convergence, stability and resolution. This new MHD model is established by solving the fluid equations of MHD system with a modified Lax-Friedrichs scheme and the magnetic induction equations with MacCormack II scheme for the purpose of developing a combined scheme of quick convergence as well as of TVD property. To verify the validation of the scheme, the propagation of one-dimensional MHD fast and slow shock problem is discussed with the numerical results conforming to the existing results obtained by the piece-wise parabolic method (PPM). Finally, some conclusions are made. This revised version was published online in August 2006 with corrections to the Cover Date.     

飞机生产中产生不协调问题的原因及解决办法

根据笔者多年来从事工艺技术的经验，总结了在飞机生产中，由于协调路线设计不合理、铆接装配变形、温度影响、在重量作用下引起的变形以及误差积累所产生的不协调问题，并结合具体的实例对上述不协调问题产生的原因提出了解决的办法。     

Theoretical Advances in Prominence Seismology

Prominence seismology is a rapidly developing topic which seeks to infer the internal structure and properties of solar prominences from the study of its oscillations. An extensive observational background about oscillations in quiescent solar prominences has been gathered during the last 70 years. These observations point out the existence of two different types of oscillations: Flare-induced oscillations (winking filaments) which affect the whole prominence and are of large amplitude and small amplitude oscillations which seem to be of local nature. From the theoretical point of view, few models have been set up to explain the phenomenon of winking filaments while, on the contrary, for small amplitude oscillations a large number of models trying to explain the observed features have been proposed.     

低马赫数流动数值模拟方法的研究

在文献[1，2]提出的一种低马赫数流动数值模拟新方法的基础上，本文作者进一步优化了算法，确定了该方法适用的马赫数范围，讨论了参数σ对计算的影响。大量的定常／非定常、低雷诺数流动的计算结果表明这种方法具有计算精度高、收敛速度快以及计算花销小的特点。     

用凝固模拟方法预测铝合金铸件缩松的形成

用有限元法和六节点等参数单元对铝合金金属型铸造过程进行了温度场的数值模拟，对铸件不同典型部位进行了金相分析，结果表明，参数Ｇ／可有效地预测铝合金缩松形成倾向的大小，计算值与实测值基本一致。     

统一分区加强解算法解物体穿越激波非定常流场

使用统一分区加强解算法求解非定常可压缩Navier-Stokes方程，模拟了物体分别以超音速和亚声速穿越与之同向运动激波的全过程，并且通过和单区计算结果的详细对比，说明统一分区加强解算法能够简便、有效的处理复杂几何外形和提高网格分辨率。     

神经网络在下颌运动轨迹图测量中的应用

介绍了采用小型磁石测量下颌运动轨迹图Electrognathography(EGN)的方法。给出利用磁偶极子模型代替小磁石模型的理论及实际依据。利用神经网络解决由磁石产生的磁感应强度推定其空间参数的反演问题 ,并且采用了分割网络及修正网络的方法来提高磁石运动测量的推定准确度。     

CAM后置处理研究

分析了数控加工后置处理技术的特征、面临的问题和当前的发展趋势,介绍了应用通用后置处理器开发定制专用后置处理器的实践。     

铝合金T型材拉弯成形的有限元模拟

针对目前拉弯成形中的问题,采用有限元模拟的方法,对带下陷拉弯过程进行计算机仿真,得到优化后的工艺参数,避免了盲目的试拉,提高了加工效率,降低了拉弯成本,积累了带下陷拉弯成形的经验,提高了公司拉弯工艺水平。     

提高铂电阻温度计测量精度的方法研究

分析了检定规程对铂电阻温度计的要求,通过研究铂电阻温度计的测温特性,提出了提高铂电阻温度计测量精度的方法,并给出了在温度校准点的测量不确定度.