基于全天空极光图像方向能量表征方法的极光事件分类          下载免费PDF全文

张军 胡泽骏王倩  梁继民 《极地研究》2015,27(3):255-263

针对基于全天空极光图像的极光事件自动分类问题,提出一种基于方向能量二元编码重组表征的自动分类方法。首先,通过对多个方向上能量分解来描述极光事件中的局部纹理和各个方向上的运动信息,并且结合分块策略获得极光事件的全局形态信息;然后,借鉴一种二元编码重组的方式对多个方向能量进行融合,从而使得极光事件的表征具有同时表征局部纹理、全局形态和运动信息的能力。该表征方法完全不依赖于极光事件的长度,可用于表征不同持续时间的极光事件,并且不需要复杂的训练过程。利用最近邻和支撑向量机分类器分别对从中国北极黄河站拍摄到的极光图像中挑选的特定极光事件进行自动分类,结果表明,与其他两种典型的动态纹理描述方法相比,本文所提出的表征方法结合最近邻分类器,得到了最好的分类效果,能有效用于极光事件的分析,为海量数据中的极光事件自动分类提供了一种新方法。  相似文献   

Determination of Ga,Ge, Mo,Ag, Cd,In, Sn,Sb, W,Tl and Bi in USGS Whole‐Rock Reference Materials by Standard Addition ICP‐MS          下载免费PDF全文

Richard M. Gaschnig  Roberta L. Rudnick  William F. McDonough 《Geostandards and Geoanalytical Research》2015,39(3):371-379

A procedure for determining a wide range of chalcophile and siderophile elements in typical crustal rocks using standard addition and ICP‐SFMS (inductively coupled plasma sector field mass spectrometry) is presented. New results for Ga, Ge, Mo, Ag, Cd, In, Sn, Sb, W, Tl and Bi abundances in USGS whole‐rock reference materials AGV‐2, BHVO‐1, BIR‐1, G‐2, GSP‐1 and W‐2 are reported using this analytical procedure. Intermediate precision of means based on multiple dissolved aliquots of each USGS reference material was 10% RSD or better for Ga, Ge, In and Sn in all, and similarly good for Ag, Cd, Sb, Tl and Bi in most reference materials. Poorer intermediate precision of Mo and W measurements in several reference materials is probably due to higher analytical blanks on these elements and powder heterogeneity due to a sulfide‐related nugget effect in the specific case of Mo in GSP‐1. Results for all elements fell within the range of available published data with the exception of Ag, which yielded systematically higher concentrations than found in the literature for five of the six reference materials, likely reflecting interference from unresolved polyatomic species.  相似文献   

UTEVA树脂分离纯化珊瑚中铀、钍的改进研究     

汤震宇  瞿建国  张安余  李秀保  杜金洲 《海洋学报》2022,44(2):11-20

珊瑚是记录海洋环境变化信息的载体之一,测定其U/Ca比值可重建海水温度或测定Th/U同位素比值可计算年龄重建海平面高度等.准确测定珊瑚中U、Th含量及同位素比值是提取所记载的海洋环境变化信息的前提,其难点在于高Ca基体分离和痕量U、Th富集纯化.基于此,本研究拟采用UTEVA树脂改进了一步富集分离珊瑚中U、Th的前处理...  相似文献   

O_2和H_2O对脉冲电晕分解NO的影响     

黄忠洲  李利新  杜健航 《广东海洋大学学报》2006,26(4):81-84

在脉冲电晕放电条件下,探讨了O2和H2O对NO分解反应过程的影响,并对复杂组分中NO的分解特性进行了实验研究。研究结果表明,脉冲电晕放电对NO分解反应具有一定的促进作用,可有效地分解模拟烟气中的NO,脱除效率随脉冲电压的增加而缓慢增加;受O2和H2O影响,NO分解转化率较N2氛围略有降低。  相似文献   

O2和H2O对脉冲电晕分解NO的影响     

黄忠洲李利新  杜健航 《广东海洋大学学报》2006,26(4):81-84

在脉冲电晕放电条件下，探讨了O2和H=O对NO分解反应过程的影响，并对复杂组分中NO的分解特性进行了实验研究。研究结果表明，脉冲电晕放电对NO分解反应具有一定的促进作用，可有效地分解模拟烟气中的NO，脱除效率随脉冲电压的增加而缓慢增加；受O2和H2O影响，NO分解转化率较N2氛围略有降低。  相似文献   

Interstellar scintillation and clouds of the interstellar turbulent plasma     

V.I. Shishov 《Astrophysics and Space Science》2001,278(1-2):163-169

Data on interstellar diffraction and refraction scintillation of pulsars are analyzed. Comparison between theory and the observational data shows that two types of spectra for electron density fluctuations are realized in the interstellar medium: pure power law and piecewise with a break. The distribution of turbulent plasma in the Galaxy has a three component structure. Component A is diffuse and it is distributed outside of the spiral arms of the Galaxy. Component BI is cloudy and associated with Galactic arms. Component BII is extremely nonuniform and associated with HII regions and supernova remnants. The origin of the interstellar plasma turbulence is considered, and possible sources of turbulent energy are discussed. The contribution of supernova bursts in the interstellar gas ionization and generation of turbulence are analyzed among other factors. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A model for the coherent emission of solar radio moving type IV bursts     

Wang De-yu   《Chinese Astronomy and Astrophysics》2004,28(4):404-411

A theoretical model is proposed for interpreting the coherent emissionmechanism of solar radio moving type IV bursts. Energetic electrons produced in flares captured by an expanding and rising magnetic flux tube exhibit a beam-like distribution of velocities on the top of the flux tube. These excite beaming plasma instability and directly amplifies O-mode electromagnetic waves. The instability growth rate sensitively depends on the coronal plasma parameter, ƒ_pe/ƒ_ce and the beam-temperature T_b. This can qualitatively explain the high brightness temperature and high degree of polarization as well as the broad spectrum observed in this type of solar radio bursts.  相似文献   

Weibel Turbulence in Laboratory Experiments and GRB/SN Shocks     

Mikhail V. Medvedev 《Astrophysics and Space Science》2007,307(1-3):245-250

It has recently been realized that the Weibel instability plays a major role in the formation and dynamics of astrophysical shocks of gamma-ray bursts and supernovae. Thanks to technological advances in the recent years, experimental studies of the Weibel instability are now possible in laser-plasma interaction devices. We, thus, have a unique opportunity to model and study astrophysical conditions in laboratory experiments – a key goal of the Laboratory Astrophysics program. Here we briefly review the theory of strong non-magnetized collisionless GRB and SN shocks, emphasizing the crucial role of the Weibel instability and discuss the properties of radiation emitted by (isotropic) electrons moving through the Weibel-generated magnetic fields, which is referred to as the jitter radiation. We demonstrate that the jitter radiation field is anisotropic with respect to the direction of the Weibel current filaments and that its spectral and polarization characteristics are determined by microphysical plasma parameters. We stress that the spectral analysis can be used for accurate diagnostics of the plasma conditions in laboratory experiments and in astrophysical GRB and SN shocks.  相似文献   

Coronal expansion and the transfer of solar angular momentum to the interplanetary space     

Li Zhong-yuan  Chen Zong-yi  Mo Guo-biao 《Chinese Astronomy and Astrophysics》1992,16(4):450-456

We discuss the question of loss of angular momentum through coronal expansion. From a large volume of data on Type-1 cometary tails we have confirmed the presence of a tangential component in the coronal expansion, which has not only a stochastic component but also a constant component of 9.8 km/s. Through coronal expansion the Sun has lost 80% of its angular momentum since it evolved on to the main sequence and the angular velocity of the Sun is decreasing exponentially. This result should have a large effect on the dynamical evolution of the Sun.  相似文献   

Propagation of Extremely Low Frequency Waves Through the Ionosphere     

Singh  Ashok K.  Narayan  D.  Singh  R. P. 《Earth, Moon, and Planets》2002,91(3):161-179

The propagation features of extremely low frequency electromagnetic waves through the multicomponent ionospheric plasma are studied. It is shown that at relatively lower frequencies refractive index for right hand mode is higher than the left-hand mode, which is reversed at higher frequencies. The thermal temperature of plasma particle causes decrease in phase and group velocities of both right and left-hand modes. The crossover frequencies for different plasma models are computed and variation with ion concentration and thermal velocity is studied. Explicit expression for group velocity and travel time has been derived and studied numerically. Finally, we have presented simulation of the ion whistler spectrograms for Hydrogen, Helium and Oxygen ions present in the ionospheric plasma. The results are compared with the experimentally detected hydrogen and helium ion whistlers. The importance of the present study in the exploration of ionospheric plasma is illustrated.  相似文献