恒温热源条件下实际回热式布雷顿循环的功率密度优化

计人工质与高、低温侧换热器和回热器的热阻损失、压气机和涡轮机中不可逆压缩和膨胀损失及管路系统中的压力损失，用有限时间热力学方法，导出了恒温热源条件下实际回热式布雷顿循环功率密度与压比间的解析式，借助于数值计算，研究了高、低温侧换热器和回热器的热导率分配对最大功率密度的影响。     

Variations of the magnetic fields in large solar flares

We present preliminary results from high resolution observations obtained with the Michelson Doppler Imager (MDI) instrument on the SOHO of two large solar flares of 14 July 2000 and 24 November 2000. We show that rapid variations of the line-of-sight magnetic field occured on a time scale of a few minutes during the flare explosions. The reversibility/irreversibility of the magnetic field of both active regions is a very good tool for understanding how the magnetic energy is released in these flares. The observed sharp increase of the magnetic energy density at the time of maximum of the solar flare could involve an unknown component which deposited supplementary energy into the system. This revised version was published online in August 2006 with corrections to the Cover Date.     

不同生命周期项目组合的约束资本预算优化模型及算法

文章给出了约束资本预算优化模型的一般数学表达式.根据詹姆斯*范霍恩的共同生命周期法的理论,提出了一种对不同生命周期项目组合的约束资本预算优化的新算法.通过算例,说明了新算法与原有算法的差别,结果表明新算法考虑了项目的重置,在满足各种约束的前提下,按照净现值指数的大小选择项目组合,从总体上寻优,得到的净现值总和更大,具有更为优化的特征.     

What do Cosmogenic Isotopes Tell us About Past Solar Forcing of Climate?

In paleoclimate studies, cosmogenic isotopes are frequently used as proxy indicators of past variations in solar irradiance on centennial and millennial timescales. These isotopes are spallation products of galactic cosmic rays (GCRs) impacting Earth's atmosphere, which are deposited and stored in terrestrial reservoirs such as ice sheets, ocean sediments and tree trunks. On timescales shorter than the variations in the geomagnetic field, they are modulated by the heliosphere and thus they are, strictly speaking, an index of heliospheric variability rather than one of solar variability. Strong evidence of climate variations associated with the production (as opposed to the deposition) of these isotopes is emerging. This raises a vital question: do cosmic rays have a direct influence on climate or are they a good proxy indicator for another factor that does (such as the total or spectral solar irradiance)? The former possibility raises further questions about the possible growth of air ions generated by cosmic rays into cloud condensation nuclei and/or the modulation of the global thunderstorm electric circuit. The latter possibility requires new understanding about the required relationship between the heliospheric magnetic fields that scatter cosmic rays and the photospheric magnetic fields which modulate solar irradiance.     

High-Frequency Radio Signatures of Solar Eruptive Flares

Several examples of the radio emission of eruptive solar flares with high-frequency slowly drifting structures and type II bursts are presented. Relationships of these radio bursts with eruptive phenomena such as soft X-ray plasmoid ejection and shock formation are shown. Possible underlying physical processes are discussed in the framework of the plasmoid ejection model of eruptive solar flares. On the other hand, it is shown that these radio bursts can be considered as radio signatures of eruptive solar flares and thus used for the prediction of heliospheric effects. This revised version was published online in August 2006 with corrections to the Cover Date.     

绳索断裂对二维二次太阳翼展开过程影响分析

为识别二维二次太阳翼关键环节和预示其在轨展开故障模式，开展不同位置绳索断裂失效对太阳翼展开的影响程度分析。采用考虑绳索断裂的绳索联动轮力学模型，建立了适应于不同联动轮半径的联动轮受力模型，提出角度触发约束消除方法，解决了太阳翼第2次展开过程连续仿真问题，建立了太阳翼第2次展开动力学方程，分析了不同位置绳索断裂失效对太阳翼各板展开角度、展开构型和其他绳索张力的影响。分析表明，越靠近星体的绳索联动机构失效对太阳翼展开过程的影响越大，其中连接架上绳索联动机构失效可直接导致二维二次太阳翼在轨展开失败。     

低轨卫星月影事件预报优化

针对卫星月影问题,提出了一种低轨卫星优化的月影预报策略,可以有效提高目前低轨卫星在轨管理时对月影事件预报的效率.结合仿真对产生月影事件的太阳、地球、月球的三体关系进行了分析,首先给出了月影产生的解析分析方法,并通过对一个三维月影影响模型的分析,得到了月影影响区间的判定要素——月影临界角;然后进一步通过对月影临界角的分析,提出了基于太阳与白道面的位置关系和月影临界角对低轨卫星月影事件的优化预报方法;最后基于大量的随机低轨卫星场景对本方法的正确性进行了验证.研究结果表明,此方法能够较大地提高月影预报效率,可以将月影预报频率从每月1次降低到每年2次,从而简化了低轨卫星在轨运行管理的任务复杂度,为卫星的在轨可靠运行提供支持.     

视觉测振技术在柔性太阳翼模态试验中的应用

针对8 m×5 m的柔性太阳翼在倒立状态下进行模态试验,设计数字摄像视觉测振系统,基于图像特征跟踪法实现了从相机标定、图像采集、信息提取到三维振动数据获取的过程,通过工况模态辨识方法获取了柔性太阳翼模态频率及振型等动力学参数。并考虑空气和重力影响建立太阳翼有限元模型,通过与基于基恩士激光位移传感器的传统模态试验结果及仿真分析结果进行对比,验证了基于视觉测振工况模态试验方法的准确性,为柔性太阳翼在轨模态辨识奠定基础。     

二元曲面可调进气道流量系数精确预测方法

为了满足二元曲面可调进气道模态转换马赫数范围(来流马赫数为2.2~3.2)的流量要求,针对唇口平移、转动和转动+平移三种调节方案,基于理论分析和基准进气道的流场,提出了一种流量系数精确预测方法,并通过数值计算进行验证且获得了进气道的总体性能。结果表明:调节后的进气道流量系数与预测值完全相等,而且无需多次试算,符合设计预期,可拓展应用于轴对称进气道。相对基准进气道,唇口前移时流量系数和压缩效率同时增加,来流马赫数为2.5时出口总压恢复系数相等而增压比增加了14.6%;在降低相同流量系数条件下,后移唇口使得增压比和压缩效率均降低,来流马赫数为2.5时出口总压恢复系数基本相等而增压比减小了12.9%,转动唇口使增压比进一步减小了9.1%,唇口后移方案性能更优。      

涡轮盘多轴低循环疲劳寿命可靠性分析

多轴低循环疲劳是航空发动机涡轮盘的主要失效模式,应用多轴疲劳寿命预测的等效应变模型和临界面模型对某涡轮盘中心孔的疲劳寿命进行了预测,并与试验寿命进行了对比,得出等效应变模型预测结果均偏于危险,并且误差较大,而临界面模型误差较小,尤其拉伸型破坏的SWT模型误差在10%以内。进一步选取SWT模型进行了涡轮盘的寿命可靠性分析,鉴于多轴疲劳试验复杂、费用高并缺少统计数据,利用现有单轴疲劳试验数据将疲劳性能参数表示为标准正态随机变量的函数,将SWT模型随机化建立多轴疲劳寿命概率模型,得到可靠度0.998 7的涡轮盘寿命,与试验估计给出的技术寿命较为接近。