塞式喷管底部气动特性及其对性能的影响

在内喷管倾角为10°,20°,30°,40°和底部二次流为0.0%,0.4%,1.0%,1.4%,2.0%,3.0%的工况下,实验测量了两单元瓦状塞式喷管的底部压强。结果表明在不同的外界反压作用下,底部具有开放、闭合和开闭过渡三种气动状态,底部的这种特性不随内喷管倾角和底部二次流的变化而变化。实验研究了80%,40%,30%和20%截短两单元直排塞式喷管的高度特性,数值模拟计算了实验喷管的性能和塞锥表面的压强分布,数值模拟结果与实验测量数据吻合较好。结合实验数据和数值模拟结果分析了塞锥截短和底部气动特性对塞式喷管性能的影响。      

异构数据库集成的研究与实现

对异构数据库集成做了详细的研究并提出了具体的实现方法。通过分析比较了目前已有的集成方案,本文提出集成异构数据库可以有四个步骤,分别是用控制表变化法提取有效数据、用XML定义传输数据格式、用JMS传输数据、用全局数据模式集成数据来实现。     

南昌市城区大气污染物变化规律分析

本文通过对南昌市城区空气监测数据的统计结果,总结出了城区内大气污染物的变化规律,并对造成这一变化规律的原因进行分析,找出了有关污染特征,并提出减轻或消减城区大气污染的思路,为环境规划提供科学的依据。     

开通角控制的无刷直流电机转矩脉动抑制新方法

在分析无刷直流电机的等效电路模型和换相过程的基础上,考虑了电磁时间常数和反电势对换相转矩的影响。通过导出换相时关断相电流下降到零的时间和开通相电流上升到最大的时间,分析高、低速运行状态下两者的关系,引入一个开通角的变量,通过控制开通相的开通时刻来抑制换相时的转矩脉动；并且考虑非理想的气隙磁密等因素对开通角进行修正。结合场路耦合的有限元进行仿真,结果表明此思路是可行的。     

ZL109合金的变载荷蠕变行为研究

研究了350℃下ZL109铝合金在外加应力变化条件下的瞬时蠕变行为.当外加应力突然降低后,在瞬时蠕变过程中发生了弹性应变和滞弹性应变,整个降载过程中的应变变化值与应力变化值成线性关系.快速滞弹性应变后,在低的松弛应力下的蠕变应变继续增加,这不同于短纤维增强复合材料稳态蠕变过程中降载后在低应力下的蠕变行为.在不同的载荷变化过程中,应力变化越大,ZL109铝合金越容易断裂.     

新生代的气候效应与碳循环

对发生于新生代的６次巨大天体撞击作用（６５Ｍａ，３４Ｍａ，１５Ｍａ，２４Ｍａ，１．１Ｍａ，０．７Ｍａ）的气候效应进行的模拟表明，这６次巨大天体撞击作用产生的尘埃进入平流层后，可使全球平均温度下降至零度以下，降温效应持续时间最长可达３０年之久，首次在模拟中考虑全球性森林大火产生的ＣＯ２和死亡生物分解生成的ＣＯ２的温室效应，研究表明这两种作用使大气中ＣＯ２增量最大仅达６７％，其增温效应远远低于尘埃层产     

电弧加热器试验条件下端头烧蚀外形计算

对电弧加热器试验条件下端头的烧蚀外形进行了仿真计算，考察了碳-碳端头烧蚀外形随来流条件的变化规律。重点研究了电弧射流的非均匀性对烧蚀外形的影响以及表面粗糙度对边界层转捩和气动加热的影响。     

疲劳分散系数随应力的变化规律

 从《航空金属材料疲劳性能手册》中取出267个铝合金试件和139个钢合金试件的疲劳试验数据，研究了疲劳分散系数随疲劳试验应力的变化规律，即在一定应力范围内，疲劳分散系数随着应力的减小而增加。由此变化规律，绘制出它们的变化规律曲线。     

Stratospheric polar vortex as a possible reason for temporal variations of solar activity and galactic cosmic ray effects on the lower atmosphere circulation

Possible reasons for the temporal instability of long-term effects of solar activity (SA) and galactic cosmic ray (GCR) variations on the lower atmosphere circulation were studied. It was shown that the detected earlier ∼60-year oscillations of the amplitude and sign of SA/GCR effects on the troposphere pressure at high and middle latitudes (Veretenenko and Ogurtsov, Adv.Space Res., 2012) are closely related to the state of a cyclonic vortex forming in the polar stratosphere. The intensity of the vortex was found to reveal a roughly 60-year periodicity affecting the evolution of the large-scale atmospheric circulation and the character of SA/GCR effects. An intensification of both Arctic anticyclones and mid-latitudinal cyclones associated with an increase of GCR fluxes at minima of the 11-year solar cycles is observed in the epochs of a strong polar vortex. In the epochs of a weak polar vortex SA/GCR effects on the development of baric systems at middle and high latitudes were found to change the sign. The results obtained provide evidence that the mechanism of solar activity and cosmic ray influences on the lower atmosphere circulation involves changes in the evolution of the stratospheric polar vortex.     

The challenges in long-term altimetry calibration for addressing the problem of global sea level change

Long-term change of the global sea level resulting from climate change has become an issue of great societal interest. The advent of the technology of satellite altimetry has modernized the study of sea level on both global and regional scales. In combination with in situ observations of the ocean density and space observations of Earth’s gravity variations, satellite altimetry has become an essential component of a global observing system for monitoring and understanding sea level change. The challenge of making sea level measurements with sufficient accuracy to discern long-term trends and allow the patterns of natural variability to be distinguished from those linked to anthropogenic forcing rests largely on the long-term efforts of altimeter calibration and validation. The issues of long-term calibration for the various components of the altimeter measurement system are reviewed in the paper. The topics include radar altimetry, the effects of tropospheric water vapor, orbit determination, gravity field, tide gauges, and the terrestrial reference frame. The necessity for maintaining a complete calibration effort and the challenges of sustaining it into the future are discussed.