边缘检测技术在火箭发动机实验诊断中的应用

对高速运动分析仪拍摄的Ｕ型燃气发生器固体装药燃烧和双组元液体喷嘴雾化图像进行了边缘检测图像分析,根据被分析实物边缘层次性较强的特点,在简单边缘检测的基础上采用自动门限、二次门限和最佳滤波的方法,获得了固体燃气发生器在燃烧过程中的内部结构、推进剂瞬态燃速、绝热隔板烧蚀率等参数,获得了双组元液体喷嘴的雾化角、粒子分布等特性。     

深空探测对航天器热控技术的推动

工程热物理学广泛应用于航天领域,一方面解决了具体航天工程问题,另一方面逐步发展成为交叉学科——空间热物理。随着我国在深空探测领域不断拓展,以深空探测器研制中的工程热物理问题为需求背景,推动着航天器热控制技术、防热技术等取得新的发展。文章在介绍深空探测器技术体系的基础上,分析了热设计、热分析、热试验、热控硬件、防热等方面的技术进步,并就深空探测领域进一步拓展对工程热物理发展的牵引进行了展望,分析了工程热物理学与航天技术间相互促进、相互推动的关系。     

Ionospheric electron density over Resolute Bay according to E-CHAIM model and RISR radar measurements

In this study, predictions of the E-CHAIM ionospheric model are compared with measurements by the incoherent scatter radars RISR at Resolute Bay, Canada, in the northern polar cap. Reasonable coverage was available for all seasons except winter for which no conclusions were drawn. It is shown that ratios of the model-to measured electron densities are close to unity in the central part of the F layer, around its peak. This is particularly evident for summer daytime. Distributions of the ratios are wider for other seasons indicating larger number of cases when the model underestimates or overestimates. E-CHAIM underestimates the electron density at ionospheric topside and bottomside by ～ 10–20 %. At the bottomside, the underestimations are strongest in summer and equinoctial nighttime. At the topside, the underestimations are strongest in autumn nighttime. Model overestimations are noticeable in the middle part of the F layer during dawn hours in autumn. Overall, the model tends to not predict highest-observed peak electron densities and the largest-observed heights of the peak.     

考虑先验信息可信度的后验加权Bayes估计

 先验信息失真及先验样本数量过大会扭曲小子样条件下Bayes融合评估的效果,引入可信度可以改善这个问题。现有的可信度度量方法大都直接基于数据层,即通过判断两种样本是否属于同一分布,这种度量在小子样情况下不太可信,为此提出了一种基于数据物理来源的可信度度量方法。同时归纳了可信度融合评估的准则,分析了现有可信度融合评估方法的不足,并结合正态分布的参数估计问题,给出了一种考虑先验信息可信度的后验加权Bayes估计方法。理论分析和算例都证实了该方法优于常用的Bayes估计方法。     

国外燃烧诊断技术的新进展

对近十几年来国外燃烧流场参数的非接触式激光光学诊断技术的进展作了简要回顾和评述。     

Tearing,coalescence and fragmentation processes in solar flare current sheet and drifting pulsating structures

The paper presents a summary of results from two different simulations which study the tearing, coalescence and fragmentation of current sheets, the associated production of energetic electrons and of plasma waves from these electrons which could explain drifting pulsation structures observed at radio wavelengths. Using a 2.5-D particle-in-cell (PIC) model of the current sheet it is shown that due to the tearing mode instability the current sheet tears into plasmoids and these plasmoids later on coalesce into larger ones. During these processes electrons are accelerated and they produce observable electromagnetic waves. Furthermore, the 3-D PIC model with two current sheets extended in the electric current direction shows their fast fragmentation associated with the exponential dissipation of the free magnetic field energy. An example of the drifting pulsating structure which is considered to be a radio signature of the above mentioned processes in solar flares is shown.     

Cosmic Ray research in Armenia

Cosmic Ray research on Mt. Aragats began in 1934 with the measurements of East–West anisotropy by the group from Leningrad Physics-Technical Institute and Norair Kocharian from Yerevan State University. Stimulated by the results of their experiments in 1942 Artem and Abraham Alikhanyan brothers organized a scientific expedition to Aragats. Since that time physicists were studying Cosmic Ray fluxes on Mt. Aragats with various particle detectors: mass spectrometers, calorimeters, transition radiation detectors, and huge particle detector arrays detecting protons and nuclei accelerated in most violent explosions in Galaxy. Latest activities at Mt. Aragats include Space Weather research with networks of particle detectors located in Armenia and abroad, and detectors of Space Education center in Yerevan.     

Polarimetric shapes of spectral lines in solar observations

A century has elapsed since the first observation of the polarimetric profile of a line of the solar spectrum. Since then, dramatic progress has been made in the instrumentation, which is now reaching unprecedented levels of sensitivity in the measurement of polarization signals in solar spectral lines. At the same time, the theoretical framework needed for the interpretation of polarimetric observations has steadily evolved from the pioneering methods, based on simple formulae, to the sophisticated structure that is nowadays used with success in the interpretation of solar observations. The present paper is intended to give a historical perspective of the evolution of this research field and of its major achievements, with particular emphasis on the role played by the magnetic field in determining the polarimetric shapes of spectral lines.     

Electrostatic accelerometer with bias rejection for gravitation and Solar System physics

Radio tracking of interplanetary probes is an important tool for navigation purposes as well as for testing the laws of physics or exploring planetary environments. The addition of an accelerometer on board a spacecraft provides orbit determination specialists and physicists with an additional observable of great interest: it measures the value of the non-gravitational acceleration acting on the spacecraft, i.e. the departure of the probe from geodesic motion.     

Comparison of Polar and Equatorial Coronal Holes Observed by UVCS/SOHO: Geometry and Physical Properties

We analyzed UVCS/SOHO data and compared the H I Lyα (121.6 nm) and O VI (103.2 nm, 103.7 nm) emission in the polar and equatorial coronal holes. We found that the emission lines have similar characteristics in these two types of coronal holes. Both types show evidence for superradially diverging boundaries. The latitudinal distribution of the O VI line ratio may indicate that the equatorial coronal hole has O⁺⁵ outflow velocities lower than in the polar coronal holes. This revised version was published online in June 2006 with corrections to the Cover Date.