Location of Magnetic Reconnection in the Magnetotail

It is a crucial issue to know where magnetic reconnection takes place in the near-Earth magnetotail for substorm onsets. It is found on the basis of Geotail observations that the factor that controls the magnetic reconnection site in the magnetotail is the solar wind energy input. Magnetic reconnection forms close to (far from) the Earth in the magnetotail for high (low) solar wind energy input conditions.With the early Vela spacecraft observations, it was believed that magnetic reconnection started inside the Vela position, likely at 15 R_E. The later ISEE/IRM observations put magnetic reconnection beyond 20 R_E. The Vela event studies were made for highly active conditions, while the ISEE/IRM survey studies were made for moderate or quiet conditions. The finding of the factor that controls the site of magnetic reconnection in the magnetotail resolves the apparent discrepancy among various spacecraft results, and suggests solar cycle variation of the magnetotail reconnection site.     

Relationship Between Substorm Auroras and Processes in the Near-Earth Magnetotail

Although the auroral substorm has been long regarded as a manifestation of the magnetospheric substorm, a direct relation of active auroras to certain magnetospheric processes is still debatable. To investigate the relationship, we combine the data of the UV imager onboard the Polar satellite with plasma and magnetic field measurements by the Geotail spacecraft. The poleward edge of the auroral bulge, as determined from the images obtained at the LHBL passband, is found to be conjugated with the region where the oppositely directed fast plasma flows observed in the near-Earth plasma sheet during substorms are generated. We conclude that the auroras forming the bulge are due to the near-Earth reconnection process. This implies that the magnetic flux through the auroral bulge is equal to the flux dissipated in the magnetotail during the substorm. Comparison of the magnetic flux through the auroral bulge with the magnetic flux accumulated in the tail lobe during the growth phase shows that these parameters have the comparable values. This is a clear evidence of the loading–unloading scheme of substorm development. It is shown that the area of the auroral bulge developing during substorm is proportional to the total (magnetic plus plasma) pressure decrease in the magnetotail. These findings stress the importance of auroral bulge observations for monitoring of substorm intensity in terms of the magnetic flux and energy dissipation.     

对我国高等教育扩招的正负效应的思考

我国高等教育扩大招生规模,并进入到马丁.特罗教授理论中的“大众化“阶段,这是中国高等教育的进步。一方面,扩招带来的机遇和动力显而易见,这样可以促进经济发展,缩小我国同发达国家差距,使更多的人可以接受到良好的教育;另一方面,扩招带来的负效应不容忽视,这主要表现在高等教育质量下滑,学费高昂和就业压力增大等问题上。为此提出一些建设性意见,希望从根本上减少由于扩招后的负效应给我国高等教育带来的种种冲击。     

Energy flux in the Earth's magnetosphere: Storm – substorm relationship

Three ways of the energy transfer in the Earth's magnetosphere are studied. The solar wind MHD generator is an unique energy source for all magnetospheric processes. Field-aligned currents directly transport the energy and momentum of the solar wind plasma to the Earth's ionosphere. The magnetospheric lobe and plasma sheet convection generated by the solar wind is another magnetospheric energy source. Plasma sheet particles and cold ionospheric polar wind ions are accelerated by convection electric field. After energetic particle precipitation into the upper atmosphere the solar wind energy is transferred into the ionosphere and atmosphere. This way of the energy transfer can include the tail lobe magnetic field energy storage connected with the increase of the tail current during the southward IMF. After that the magnetospheric substorm occurs. The model calculations of the magnetospheric energy give possibility to determine the ground state of the magnetosphere, and to calculate relative contributions of the tail current, ring current and field-aligned currents to the magnetospheric energy. The magnetospheric substorms and storms manifest that the permanent solar wind energy transfer ways are not enough for the covering of the solar wind energy input into the magnetosphere. Nonlinear explosive processes are necessary for the energy transmission into the ionosphere and atmosphere. For understanding a relation between substorm and storm it is necessary to take into account that they are the concurrent energy transferring ways. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phase Space Density Analysis of Energy Transport in the Earth’s Magnetotail

Two energetic events in the Earth’s magnetotail detected by Geotail are examined with detailed analysis of three-dimensional velocity phase space density. It is found that the occurrence of multiple ion components is high during these dynamic episodes. Different populations evolve independently of each other, suggesting particles from multiple activity sites contributing to the observed phase space density. The transport properties with consideration of multiple components are evaluated, with the result showing significant differences from those based on a single fluid approach. This comparison indicates that precise evaluation of the energy and magnetic flux transport of energetic events in the magnetotail requires resolving individual populations in the phase space density.     

数控线切割三维直纹面直接刀补算法的研究

分析了四轴数控线切割机床所能加工的三维直纹面类型,以二维C型刀补为基础,根据各类型形状的特点采用了不同的刀补处理方法,分析了用二维刀补原则解决三维直纹面刀补的可行性,提出了一种不需将加工轨迹线形化的三维直纹面的直接刀补算法,指出了降低复杂直纹面刀补误差的措施。     

风洞试验中测压管路信号畸变及修正研究

采用分布摩擦模型和试验方法分析了简单测压管路系统的信号畸变,分析了数学方法和机械方法修正测试信号的优缺点;讨论了不同参数对管路系统传递函数的影响,同时说明了试验中常见管路连接、弯折、挤压对管路系统的影响,提出了合理利用管路共振效应提高测试数据信噪比的思想,并基于此提出了管路系统的选择及定量的评价准则。结果表明：采用分布摩擦模型理论修正测压管路系统脉动畸变信号是可行的;管路等内径连接、轻度弯折、轻度挤压不会对管路的传递函数造成影响;通过笔者提出的定量评价标准可以高效的选取合理的管路长度。     

跨声速L型气动补偿空速管有限元解

本文应用有限元法求解跨声速流中带有斜支架的任意型面空速管(L型空速管)的压强分布,控制方程为全速位方程,来流可具有迎角。本文方法为设计气动补偿空速管提供一种有效手段,能大量节省方案筛选的风洞实验工作量。对典型型号的计算结果与风洞实验数据的比较表明本文方法是有效的。     

我国国债宏观经济效应的实证研究

采用多元Granger因果测试模型和1980～2003年的相关数据实证检验我国国债的宏观经济效应。实证结果表明，我国国债融资实际上并未对宏观经济产生显著影响。这主要是因为我国利用国债融资的时间较短，国债的宏观经济效应尚未显现；利用国债融资的多为基础设施项目，周期较长，真正发挥效应尚需一段时间；尤其是国债资金管理不到位，使得国债融资未对实体经济作出积极贡献。因此，政府当务之急是完善国债投资管理和审批体制，增加国债资金运用的透明度，加大对国债资金管理和使用的监督和检查力度，提高国债项目的投资效益。     

稀薄流热化学非平衡效应的DSMC研究

以钝体绕流驻点线流场为例，应用直接仿真蒙特卡罗法，模拟了五组元混合气体（Ｎ２，Ｏ２，Ｎ，Ｏ，ＮＯ）中的碰撞能松弛，离散反应，交换反应及复合反应，给出了碰撞分子各自由度间的能量交换模式及各类化学反应的选择模式。ＤＳＭＣ仿真结果与宏观粘性激波层方程计算结果，在飞行高度较低时基本相符，表明采用的热化学非平衡非模式是令人满意的，随着飞行高度增高稀薄气体效应增大，二者在激波附近有显著差异，表明高空飞行必须考     

光学头罩超声速绕流流场光学传输效应风洞试验研究

在Ma=3连续超声速风洞中,开展了光学头罩绕流流场光学传输效应的风洞模拟试验方法研究,进行了现场振动测量与隔离,研制了专用试验装置,采用哈特曼传感器和剪切干涉仪两种手段进行了光学传输效应的试验测量。试验中,针对试验装置各部分的不同组合状态,进行了大量的测试,研究了试验装置有效性以及试验数据重复性,着重分析了探测光束的PV值与RMS值。结果表明：导流板可明显抑制风洞洞壁边界层干扰,试验装置与方法可行,对于连续式风洞中模型绕流流场光学传输效应测试有一定参考价值。     

薄壁结构固有频率的p型有限元数值计算收敛性研究

通过使用MSC．Patran／Nastran中的p型有限元评价多种典型薄壁结构构件动力学品质分析中的特征值计算收敛问题,并对高阶形函数的作用进行了深入分析,从而说明高阶p型体元在薄壁结构建模中的优越性。     

Damage localization effects of the regeneratively-cooled thrust chamber wall in LOX/methane rocket engines

To investigate the damage localization effects of the thrust chamber wall caused by combustions in LOX/methane rocket engines, a fluid-structural coupling computational methodology with a multi-channel model is developed to obtain 3-demensioanl thermal and structural responses. Heat and mechanical loads are calculated by a validated finite volume fluid-thermal coupling numerical method considering non-premixed combustion processes of propellants. The methodology is subsequently performed on an LOX/methane thrust chamber under cyclic operation. Results show that the heat loads of the thrust chamber wall are apparently non-uniform in the circumferential direction. There are noticeable disparities between different cooling channels in terms of temperature and strain distributions at the end of the hot run phase, which in turn leads to different temperature ranges, strain ranges, and residual strains during one cycle. With the work cycle proceeding, the circumferential localization effect of the residual strain would be significantly enhanced. A post-processing damage analysis reveals that the low-cycle fatigue damage accumulated in each cycle is almost unchanged, while the quasi static damage accumulated in a considered cycle declines until stabilized after several cycles. The maximum discrepancy of the predicted lives between different cooling channels is about 30%.     

Correlation analysis of combined and separated effects of wing deformation and support system in the CAE-AVM study

The Chinese Aeronautical Establishment (CAE) Aerodynamic Validation Model (AVM) is a dual-purpose test geometry dedicated to verify the aerodynamic performance of a conceptual intercontinental jet aircraft and to provide a dataset for CFD software validation. To this end, a scaled model of the AVM was tested in the High-Speed Tunnel (HST) of the German-Dutch Wind-tunnels (DNW) with special test consideration and instrumentation. For complementary analysis of experimental results, specific CAE-AVM geometries are analyzed using a CAE in-house CFD code. The specific geometries consist of a baseline aircraft, an aircraft with a deformed wing shape, and an aircraft with both a deformed wing shape and a representation of the model support system used in the wind tunnel. Detailed analysis of numerical and experimental results is presented; both the combined and individual attributions of wing deformation and support system interference on wing pressure distributions and longitudinal aerodynamic characteristics are summarized.