Simulation of X-ray and gamma ray detector response and spectral deconvolution

A detailed Monte-Carlo code has been developed from basic principles that simulates the responses of high energy photon detectors to incident beams of photons. The detector response matrice (DRM)s are calculated using this code. Deconvolution of an artificially generated spectrum is presented.     

Assessment of plant vitality detection through fluorescence and reflectance imagery

Recent studies of the vegetation fluorescence show that it can be successfully used as an intrinsic indicator of plant photosynthetic activity. With respect to the vegetation spectral reflectance, the chlorophyll (Chl) fluorescence is more specific as an observable of basic biophysical processes in the plant cells. Laser induced fluorescence is widely used in near range remote sensing, but it is not suitable for the global monitoring of vegetation. Decades of active fluorometry studies have collected useful information of leaf reaction to natural and anthropogenic stress. Still the passive fluorescence, the one that could be registered from satellite orbit has still to prove its advantage over widely used reflectance signature. The weakness of the signal and the lack of experience with passive fluorescence measurements require extensive technical, theoretical and experimental studies. New imaging fluorometres are to be designed for measuring steady state fluorescence in controlled and natural conditions.

In order to compare reflectance and steady state fluorescence sensitivity to stress impact, a set of experiments have been conducted under controlled illumination conditions in a bio-chamber, designed by the author’s team. The equipment allows plant vitality to be monitored both by passive fluorescence and spectral reflectance imaging. Different types of stress factors (heat and drought stress, acid impact) were investigated to demonstrate equipments ability in monitoring changes of fluorescence signal. Selected fluorescence images of foliage illustrate an early detection of plant dysfunction and the temporal and spatial spreading of the stress impact. Analysis shows that fluorescence imaging of green plants can be developed as a highly effective early warning remote sensing method, which could have application for an ecosystems’ monitoring along with high-spectral reflectance imagery.     

利用谱熵解决零前缀正交频分复用系统的符号盲同步算法

针对低信噪比多径条件下的ZP OFDM系统符号盲同步问题,提出了基于谱熵的ZP OFDM系统的符号盲同步算法。该算法不需要数据辅助,对接收到的ZP OFDM信号进行双滑动窗的谱熵比运算,通过寻找其峰值点来实现符号同步。给出了算法的具体步骤和性能分析。算法是对接收信号的功率谱进行求熵运算,可以有效克服能量检测法易受信道噪声影响的缺点,并且不需要针对信道调整窗口宽度。仿真结果表明,在低信噪比多径信道条件下,算法仍然具有较好的同步性能。     

空间目标的地面光谱特性和星等估计

针对自适应光学系统将要探测的空间非自发光目标,进行了光谱特性和星等估计的研究;研究了空间非自发光目标反射太阳光穿过大气层而进入自适应光学系统的波前探测器的子孔径内的光子速率;同时还针对反射太阳光的空间目标亮度太低,研究了激光照射目标后的相应情况。     

Measured properties of the cosmic background radiation

After a pioneering period when the observers were mainly interested in checking the general properties of the Cosmic Background Radiation through observations at still higher frequencies, the observational efforts are now devoted to the discovery of features in the mean panorama, in particular :i) Distortions in the frequency spectrum, ii) Spatial anisotropies at various angular scales; iii) Polarization. The observational information is reviewed.     

SATI image processing and mesopause temperature determination

The Spectral Airglow Temperature Imager (SATI) instrument registers airglow coming from an annular mesopause segment. The temperatures of various points of this segment are retrieved by sectors of the registered images containing spectral information. A stage of SATI spectrogram processing connected with deriving spectral information from images and the determination of the rotational temperature of oxygen molecules emitting at the altitude of the mesopause is considered.     

真空紫外探测器关键参数校准装置

当前真空紫外空间探测技术迅猛发展,真空紫外载荷应用越来越广,其中的核心器件真空紫外探测器的特性校准变得越来越重要,针对国内真空紫外探测器关键参数校准能力缺失问题,研制了一套真空紫外探测器关键参数校准装置,实现光谱响应率、线性度等参数的校准。论述了真空紫外探测器光谱响应率、线性度参数的校准方法,介绍了校准装置的硬件组成、校准方法和软件功能,并对其进行了测量不确定度评定。测试结果证明表明,该校准装置可以对真空紫外探测器进行主要参数的校准,校准结果准确、有效。     

Calculating the simultaneous effect of ion dynamics and oscillating electric fields on Stark profiles

We calculate hydrogen line shapes resulting from the simultaneous Stark effect of the plasma microfield and an oscillating electric field. Like laboratory plasmas, many kinds of space plasmas are affected by oscillating electric fields with a magnitude similar to that of the microfield. Here we focus on conditions where we expect that the effect of ion dynamics and oscillating electric are both significant. The combined effect of their dynamics on the quantum emitter is retained by a computer simulation coupled to a numerical integration of the Schrödinger equation. Our calculations are applied for conditions and transitions where significant changes in the line shape allow for a diagnostic of the plasma and oscillating field.     

基于高阶谱约简的变结构模糊神经网络

针对先验知识不完备和不确定的情况下海量数据造成的冗余和互斥，模糊神经网络结构变得复杂化并不能很快逼近和分类输出对象的情况，提出了一种基于高阶谱完成规则约简的变结构模糊神经网络的模型。相同结论属性的模糊规则的条件属性值可以被认为是由若干个谐波成分组成的平稳信号，并且此信号可以采用高阶谱分析来估计其谐波成分，规则的最小约简集与谐波对应。在完成了谐波估计后，神经网络结构和连接权值发生改变，神经网络的性能也得到优化。最后给出了此模型在航迹融合中应用的一个例子，得到了较好的结果。     

扩频谱相关自适应滤波技术的研究

被高速伪随机码调制的扩频信号,其伪随机码是具有随机编码信号特征的周期信号。所以,扩频信号应被建模为周期信号(循环平稳信号)。循环平稳信号与其信号的频移副本之间具有很强的谱相关性,充分利用这种谱相关性可以实现对窄带和宽带干扰的抑制。基于循环平稳理论和自适应滤波理论,提出了一种基于改进的LMS算法的扩频信号谱相关自适应滤波技术。这种变步长的谱相关自适应LMS滤波器能实现对窄带和宽带干扰的抑制,仿真结果证明了其有效性。