Fast Segmentation of Solar Extreme Ultraviolet Images     

T. Dudok De Wit 《Solar physics》2006,239(1-2):519-530

A segmentation scheme for identifying large-scale structures (coronal holes, active regions, etc.) in solar extreme ultraviolet images, is presented. Unlike standard approaches, both the image intensity and the relative contribution of different wavelengths are used. Spectral information is important for compensating luminosity changes. The approach is illustrated with images taken in the extreme ultraviolet by the EIT telescope onboard SOHO. This supervised segmentation scheme, which incorporates a Bayesian classifier, is computationally simple, and can easily be used to track in near-real time structures, such as coronal holes.  相似文献   

The dynamical structure of dwarf elliptical galaxies     

W.W. Zeilinger  S. De Rijcke  H. Dejonghe  G.K.T. Hau 《Astrophysics and Space Science》2003,284(2):607-610

Deep imaging and long-slit spectroscopy was obtained for a sample of dwarf ellipticals in the Fornax cluster, NGC 5044 and NGC 5898 groups using the ESO VLT. The observational data extend out to typically 1.5–2 effective radii and indicate a kinematic dichotomy in the family of ellipticals. The observed stellar kinematics indicate a luminosity–velocity dispersion relation largely supporting Supernova-driven stellar mass loss scenarios for the formation of dwarf ellipticals. Stellar dynamical models favour dark matter halos with typical mass-to-light ratios in the range of 3 to 9 solar units. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

同震阶变异常的特征与机制分析     

李兰生  刘建华 《大地测量与地球动力学》1992,(3)

本文对徐州地震台JB—72水平摆倾斜仪1988年11月至1989年5月间所记录到的24次同震阶变进行了深入分析,认为:a.造成同震阶变的原因是多方面的,而反应了地球应变场准静态调整的同震阶变才是有价值的价变异常;b.多观测手段的地震台站,同震阶变应该在不止一台仪器上得到响应。  相似文献   

陕西关中古代天文遗存     

刘次远  张铭洽 《时间频率学报》1992,15(2):111-120

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黄金的成色     

刘儒 《吉林地质》1994,13(3):81-83,45

黄金的成色并不是一成不变的，它成色的高低是与成矿温度、成矿阶段、深度、时代、变质程度、水溶液及风化作用等有一定关系，我们从这些关系中可以寻找到我们找矿的捷径和依据。  相似文献   

The Magnetic Field, Horizontal Motion and Helicity in a Fast Emerging Flux Region which Eventually forms a Delta Spot     

Jihong Liu  Hongqi Zhang 《Solar physics》2006,234(1):21-40

We studied the behavior of magnetic field, horizontal motion and helicity in a fast emerging flux region NOAA 10488 which eventually forms a δ spot. It is found that the rotation of photospheric footpoints forms in the earlier stage of magnetic flux emergence and the relative shear motion of different magnetic flux systems appears later in this active region (AR). Therefore the emerging process of the AR can be separated into two phases: rotation and shear. We have computed the magnetic helicity injected into the corona using the local correlation tracking (LCT) technique. Furthermore we determined the vertical component of current helicity density and the vertical component of induction electric fields E_z = (V× B)_z in the photosphere. Particularly we have presented the comparison of the injection rate of magnetic helicity and the variation of the current helicity density. The main results are as follows: (1) The strong shear motion (SSM) between the new emerging flux system and the old one brings more magnetic helicity into the corona than the twisting motions. (2) After the maturity of the main bipolar spots, their twist decreases and the SSM becomes dominant and the major contributor of magnetic non-potentiality in the solar atmosphere in this AR. (3) The positions of the maxima of E_z (about 0.1 ∼ 0.2 V cm⁻¹) shift from the twisting areas to the areas showing SSMs as the AR evolved from the rotation phase to the shear one, but no obvious correlation is found between the kernels of Hα flare and E_z for the M1.6 flare in this AR. (4) The coronal helicity inferred from the horizontal motion of this AR amounts to −6 × 10⁴³ Mx². It is comparable with the coronal helicity of ARs producing flares with coronal mass ejections (CMEs) or helicity carried away by magnetic clouds (MCs) reported in previous studies (Nindos, Zhang, and Zhang, 2003; Nindos and Andrews, 2004). In addition, the formation of the δ configuration in this AR belongs to the third formation type indicated by Zirin and Liggett (1987), i.e., collision of opposite polarities from different dipoles, and can be naturally explained by the SSM.  相似文献   

On the Period Variation of the W UMa-type Contact Binary V502 Ophiuchi     

Qing-Yao Liu  Yu-Lan Yang National Astronomical Observatories/Yunnan Observatory  Chinese Academy of Sciences  Kunming   《中国天文和天体物理学报》2006,6(3):331-337

The variation in the orbital period of the W UMa type contact binary V502 Oph is analyzed. The orbital period exhibits a wavelike variation with a periodicity of 23.0 years and an amplitude of △P = 1.24×10~(-6) days superimposed on secular decrease of dP/dt = 1.68×10-7 day per year. The long-term decrease may be accompanied by the contraction of the secondary at a rate of 83 m per year and a mass transfer rate from the primary to the secondary of 4.28×10~8 M per year. The short-term oscillation may be explained by the presence of a third component. Orbital elements of the third body and its possible mass are presented.  相似文献   

Beam Mode Expansion of Corrugated Conical Horns with Phase Correcting Lens: Application to Radioastronomy Receivers     

E. García  L. De Haro  C. O'Sullivan  G. Cahill  J. A. López Fernández  F. Tercero  B. Galocha  J. L. Besada 《Experimental Astronomy》2003,15(3):173-193

A classical radioastronomy receiver is fed with a corrugated horn and an independent lens, both placed in a cryostat to lower the noise temperature. The beam is focused and directed using a combination of elliptical and plane mirrors. This paper proposes modifying the initial feeding system by placing the lens onto the horn aperture, thereby allowing a size reduction of the horn and lens, and a simplification of their mechanical design. The profiled lens is shaped to correct the phase error on the horn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam Mode Expansion (BME). Results using both a hyperbolic-planar lens and a spherical-elliptical lens, as well as results obtained by using Geometrical Optics (GO) with a Kirchoff–Huygens integration to get the far-field pattern, have been compared with measurements. As a direct application, a full focusing system for the new 40-m radiotelescope at the “Centro Astronómico de Yebes” is presented for the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn with a phase-correcting lens. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The comparison between allozyme and RAPD makers for the population genetic structure analysis of scallop Chlamys farreri     

刘保忠 尤锋董波  相建海 《中国海洋湖沼学报》2006,24(3):295-299

1INTRODUCTION Since the first use in human genetic research in1966,allozyme has become the most popular genetic marker for population genetics studies for almost all groups of animals and plants(Lewontin and Hubby,1966;Murphy et al.,1996).In the past seve…  相似文献   

铜川王石凹黑色高岭石粘土岩的成因分析     

柳淑霞  白开寅 《地球科学与环境学报》1996,(1)

黑色高岭石粘土岩，是铜川王石凹煤矿石炭纪煤系地层顶部，五号煤层的上部一层稳定的煤矸石。经偏光显微镜及费氏台测试光性特征、化学试验及分析鉴定表明，这是一种由高岭石组成的，成分很纯、颗粒大、结晶良好的高岭石粘土岩。据微量元素含量分析，此高岭石系淡水沉积物。  相似文献