Simulation Study on High Energy Cosmic Electron Detection by Shower Image     

S.Torii  K.Kasahara  T.Tamura  K.Yoshida 《中国天文和天体物理学报》2007,7(6):839-844

Many projects have recently been carried out and proposed for observing high energy electrons since it is realized that cosmic ray electrons are very important when study-ing the dark matter particles and the acceleration mechanism of cosmic rays. An imaging calorimeter,BETS (Balloon-borne Electron Telescope with Scintillator fiber),has been de-veloped for this purpose. Using pattern analysis of the shower development,the electrons can be selected from those primary cosmic ray proton events with flux heights one-tenth that of the electrons. The Monte-Carlo simulation is indispensable for the instrument design,the sig-nal trigger and the data analysis. We present different shower simulation codes and compare the simulation results with the beam test and the flight data of BETS. We conclude that the code FLUKA2002 gives the most consistent results with the experimental data.  相似文献   

Cross-Correlation Detection of Point Sources in the WMAP First Year Data     

Jian-Yin Nie  Shuang-Nan Zhang  Department of Physics  Center for Astrophysics  Tsinghua University  Beijing  Key Laboratory of Particle Astrophysics  Institute of High Energy Physics  Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2007,7(2):199-208

We apply a Cross-Correlation (CC) method developed previously for detecting gamma-ray point sources to the WMAP first year data by using the Point-Spread Function of WMAP and obtain a full sky CC coefficient map. We find that the CC method is a pow- erful tool to examine the WMAP foreground residuals which can be further cleaned accord- ingly. Evident foreground signals are found in the WMAP foreground cleaned maps and the Tegmark cleaned map. In this process 101 point sources are detected, and 26 of them are new sources additional to the originally listed WMAP 208 sources. We estimate the ?ux of these new sources and verify them by another method. As a result, a revised mask file based on the WMAP first year data is produced by including these new sources.  相似文献   

A New Feature Vector Using Selected Line Spectra for Pulsar Signal Bispectrum Characteristic Analysis and Recognition   总被引：1，自引：0，他引：1  

Zhen-Hua Xie Lu-Ping XU Guang-Ren Ni Yan Wang 《中国天文和天体物理学报》2007,7(4):565-571

Average pulse profiles of pulsar signals are analyzed using the bispectrum tech-nique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and prop-agation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for ex-tracting pulsar signal characteristic is proposed. Compared with selected bispectra, the pro-posed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance.  相似文献   

Velocity Curve Analysis of Spectroscopic Binary Stars AI Phe, GM Dra, HD 93917 and V502 Oph by Nonlinear Regression     

K. Karami R. Mohebi 《中国天文和天体物理学报》2007,7(4):558-564

We introduce a new method to derive the orbital parameters of spectroscopic bi-nary stars by nonlinear least squares of (o-c). Using the measured radial velocity data of the four double lined spectroscopic binary systems, AI Phe, GM Dra, HD 93917 and V502 Oph, we derived both the orbital and combined spectroscopic elements of these systems. Our numerical results are in good agreement with the those obtained using the method of Lehmann-Filhe's.  相似文献   

Stellar and HI Mass Functions Predicted by a Simple Preheating Galaxy Formation Model     

Zhi-Jian Luo Cheng-Gang Shu 《中国天文和天体物理学报》2007,7(4):590-594

According to the new preheating mechanism of galaxy formation suggested by Mo et al., we construct a simple model of formation of disk galaxies within the current paradigm of galaxy formation. It incorporates preheating, gas cooling, bulge formation and star for-mation. The predicted stellar and HI mass functions of galaxies are discussed and compared with the observations. It is found that our model can roughly match both the observed galaxy luminosity function and the observed HI-mass function.  相似文献   

A Survey of Newtonian Core-Shell Systems with Pseudo High Order Symplectic Integrator and Fast Lyapunov Indicator     

Jun-Fang Zhu Xin Wu Da-Zhu Ma 《中国天文和天体物理学报》2007,7(4):601-610

Newtonian core-shell systems, as limiting cases of relativistic core-shell models under the two conditions of weak field and slow motion, could account for massive circumstellar dust shells and rings around certain types of star remnants. Because this kind of systems have Hamiltonians that can be split into a main part and a small perturbing part, a good choice of the numerical tool is the pseudo 8th order symplectic integrator of Laskar ＆ Robutel, and, to match the symplectic calculations, a good choice of chaos indicator is the fast Lyapunov indicator （FLI） with two nearby trajectories proposed by Wu, Huang ＆ Zhang. Numerical results show that the FLI is very powerful when describing not only the transition from regular motion to chaos but also the global structure of the phase space of the system.  相似文献   

湘西地质灾害发生发展规律及防治措施探讨     

杜胜东 《湖南地质》1998,17(1):45-48

湘西是滑坡、崩塌、泥石流等突发性地质灾害多发地区。笔者对近几年来的实际调查资料进行综合分析，认为本地突发性地质灾害多集中在５月至８月，软弱岩层及碎屑岩残坡积层中灾害体最发育，山坡由陡变缓的转折部位易拉张形成滑坡体后缘。并根据灾害体的形成机理提出了相应的防治措施。  相似文献   

Disk Thicknesses and Some Parameters of 108 Non-Edge-On Spiral Galaxies     

Tao Hu Qiu-He Peng Hong-Shi Zong 《中国天文和天体物理学报》2007,7(4):579-589

We present disk thicknesses, some other parameters and their statistics of 108 non-edge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r 0 to the galactic center) of the spiral arm, and finally the thickness.  相似文献   

怎样避免和防止人为因素导致滑坡和崩塌？     

科文 《河南国土资源》2006,(5):44

夏天是地质灾害的多发期，尤其是滑坡和崩塌比较频发。但只要我们研究其规律，掌握其“习性”，注意以下几点，也是可以防止和避免的。  相似文献   

多季相混合像元部分分解特征的不透水面分类     

陈姣  黄远程  李朋飞 《测绘科学》2021,46(4):90-99

针对利用光谱混合分解提取不透水面特征通常受到端元类型和数量的限制,同时植被变化会影响估计精度的问题,该文提出 了一种综合季相和植被变化信息的不透水面提取框架.基于混合像元部分分解算法——混合调谐匹配滤波(MTMF),设计了多季相组合MTMF(SCMTMF)特征和多季相叠加MTMF(SSMTMF)两种策略,构造了不透水面的多季相MTMF特征,将不透水特征与多季相植被指数结合利用支持向量机实现对不透水面的精确分类.结果表明,利用多季相特征得到的不透水面提取效果相较于单季相有较明显的改善,该文所提出的策略有利于提高不透水面的估计精度.  相似文献