红外探测器比探测率与光学系统工作温度关系研究

针对低温光学系统自身辐射与红外探测器比探测率(D*)的关系,从红外辐射基本理论入手,建立了光学系统工作温度与背景限红外探测器D*之间的关系模型。由此计算出了典型四反光学系统不同工作温度下、不同谱段的背景限红外探测器D*值,综合考虑探测器处于非背景限情况,得出相关曲线;总结出了背景限红外探测器与光学系统工作温度之间关系的几点体会。     

基于新的数值积分粒子滤波的机载无源定位算法

针对机载无源定位这一多维非线性滤波问题,提出一种新的用3阶数值积分卡尔曼滤波算法来产生重要性密度函数的粒子滤波算法。新算法采用球形和径向数值积分规则选取积分点和确定相应的权值,得出的积分点数仅为状态维数的二倍,大幅的减少了计算量,较好地解决了求积分卡尔曼粒子滤波算法（Quadrature Kalman Particle Filter, QPF）在高维滤波时存在计算量大的问题;而且通过设定比例因子使得所产生的重要性密度函数在系统状态转移概率密度的基础上,融入最新的观测值,增加了粒子的多样性,提高了对系统状态后验概率的逼近程度。仿真结果表明：新算法在稳定性和定位精度上与QPF相当,但计算时间仅约为QPF的15%。     

粒子图像技术测量带尾缘吹气静子尾迹特征

采用粒子图像测试技术(PIV Particle Image Velocimetry)和热线相结合的方法,对静子尾缘有无吹气条件下尾迹区流场进行测量,得到了不同尾部吹气量下的静子尾迹区的流场,通过测量得到了尾迹区的流动显示、速度矢量图和涡量图,并根据无动量亏损厚度确定了纯尾迹、弱尾迹、无动量亏损尾迹和射流四种尾迹流动特征。同时对PIV测试结果和热线测试结果进行了对比,两个实验结果比较吻合,验证了PIV实验的准确性,实验结果认为无动量亏损尾迹区与纯尾迹流动相比具有速度周向变化小和脉动小等特点。     

Effective non-vertical and apparent cutoff rigidities for a cosmic ray latitude survey from Antarctica to Italy in minimum of solar activity

In this paper we will report the results of the computation of cutoff rigidities of vertical and non-vertical incident cosmic ray particles. Non-vertical effective cutoff rigidities have been computed by tracing particle trajectories through the “real” geomagnetic magnetic field comprising the International Geomagnetic Reference Field model (IGRF95, IAGA Division 5 Working Group 8, 1996: Sabaka, T.J., Langel, R.A., Baldwin, R.T., Conrad, J.A. The geomagnetic field, 1900–1995, including the large scale fields from magnetospheric sources and NASA candidate models for the 1995 IGRF revision. J. Geomag. Geoelect. 49, 157–206, 1997.) and the Tsyganenko [Tsyganenko, N.A. A magnetospheric magnetic field model with a warped tail current sheet. Planet. Space Sci. 37, 5–20, 1989.] magnetosphere model. The computation have been done for the backward route (from Antarctica to Italy) of the Italian Antarctic ship survey 1996–1997, for geographic points corresponding to the daily average coordinates of the ship; for zenith angles 15°, 30°, 45° and 60°, and azimuth angles from 0° to 360° in steps of 45°. By means of the obtained non-vertical cutoffs the apparent cutoff rigidities have been calculated. The information on integral multiplicities of secondary neutrons detected by the neutron monitor in dependence of the zenith angle of incoming primary cosmic ray particles have also been used. This information is based on the theoretical calculations of meson-nuclear cascades of primary protons with different rigidities arriving to the Earth’s atmosphere at the zenith angles of 0°, 15°, 30°, 45°, 60° and 75°. The difference between the computed apparent and vertical cutoff rigidities reaches ∼1 GV at rigidities >7–8 GV. At rigidities of 10–16 GV, the difference between the apparent and vertical cutoff rigidities is larger than that obtained earlier by Clem et al. [Clem, J.M., Bieber, J.W., Duldig, M., Evenson, P., Hall, D., Humble, J.E. Contribution of obliquely incident particles to neutron monitor counting rate. J. Geophys. Res. 102, 26919–26926, 1997.] and Dorman et al. [Dorman, L.I., Villoresi, G., Iucci, N., Parisi, M., Tyasto, M.I., Danilova, O.A., Ptitsyna, N.G. Cosmic ray survey to Antarctica and coupling functions for neutron component near solar minimum (1996–1997), 3. Geomagnetic effects and coupling functions. J. Geophys. Res. 105, 21047–21056, 2000.].     

半球功率输入和高纬电离层电导

综述和介绍了由TIROS—NOAA系列卫星资料制定高纬沉降粒子能流和电离层积分电导经验模式的方法,绘制了不同粒子沉降活动的Pedersen和Hall电导在磁纬-磁地方时坐标内的等值线分布图．同时给出了不同季节内受太阳电磁辐射控制的电导等值线分布．具体地分析了电导经验模式与磁层-电离层耦合过程的内在联系。     

存在初始引导场情况下的无碰撞磁场重联

采用二维三分量的全粒子模拟方法研究了不同初始引导场情况下的无碰撞磁场重联及初态为一维的Harris电流片.结果表明,Bz0＞0.5B0的强引导场不仅会显著改变粒子的运动轨迹,而且会改变重联区附近的电场和流场结构,从而影响重联率和电子加速.运用广义欧姆定律解释了不同引导场下电场的结构特征.另外,通过对扩散区附近束流电子的跟踪研究发现,在二维模型中,不论引导场强弱,位于扩散区中心垂直模拟平面的感应电场对电子加速起主要作用,而扩散区外平面电场的贡献很小.      

大功率高频无线电波对赤道E区双流不稳定性的影响--PIC静电粒子模拟研究

地面入射的大功率高频无线电波(泵波)和电离层等离子体之间的参数相互作用，能够引起静电波的激发，在一定条件下，产生不稳定性．本文用PIC静电粒子模拟方法，研究泵波与赤道电离层E区等离子体的相互作用．研究结果表明，泵波能够控制双流不稳定性的发生，在不同条件下，泵波对双流不稳定性起着稳定与不稳作用，模拟结果定性地与理论研究结果相符合，这为我们对不规则体产生的地面人工控制提供了依据．     

极性采样倒相编码数字脉冲压缩处理器的检测性能

本文阐述了极性采样倒相编码数字脉冲压缩处理器的非参量恒虚警率(CFAR)特性。这种处理器实质上是简化的Dicke-fix,也是窄带信号的符号检测器。确定了高斯和非高斯噪声中的检测性能。说明了这种处理器相对于非相干匹配滤波器的信噪比损失随码长增加而减小;在高斯噪声中的渐近损失为1.96dB;在Weibull噪声中的损失随Weibull分布形状参数减小而减小,甚至可转为得益。     

分析采用集成鉴频-鉴相器的锁相环捕捉性能的一种近似方法

本文简要推导了在数字锁相环中广泛使用的集成鉴频-鉴相器的鉴相特性与鉴频特性,并对鉴频特性采用线性近似方法,用来分析、计算使用这种鉴相器的锁相环的捕捉性能。     

Enhancing the ATIC charge resolution

The Advanced Thin Ionization Calorimeter (ATIC) experiment is designed to investigate the charge composition and energy spectra of primary cosmic rays over the energy range from about 10¹¹ to 10¹⁴ eV during Long Duration Balloon (LDB) flights from McMurdo, Antarctica. Currently, analysis from the ATIC-1 test flight and ATIC-2 science flight is underway and preparation for a second science flight is in progress. Charge identification of the incident cosmic ray is accomplished, primarily, by a pixilated Silicon Matrix detector located at the very top of the instrument. While it has been shown that the Silicon Matrix detector provides good charge identification even in the presence of electromagnetic shower backscatter from the calorimeter, the detector only measures the charge once. In this paper, we examine use of the top scintillator hodoscope detector to provide a second measure of the cosmic ray charge and, thus, improve the ATIC charge identification.