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排序方式: 共有103条查询结果,搜索用时 15 毫秒
101.
M. I. Nouh S. M. Saad B. Korany M. A. Elkhamisy 《Journal of Astrophysics and Astronomy》2013,34(3):193-205
The eclipsing binary α CrB, is a well-known double-lined spectroscopic binary. The system is considered unique among main-sequence systems with respect to its small mass ratio and large magnitude difference between the components. Our aim in the present paper is to compute the orbital parameters and to model the atmospheric parameters of the system. Synthetic spectral analysis of both the individual and disentangled spectra has been performed and yielded effective temperatures T eff?=?10000±250 K, surface gravities logg?=?4±0.25 and projected rotational velocities $\emph{v}$ sini?=?110±5 km/sec for the primary component, and T eff?=?6000±250 K and logg?=?4.5±0.25 for the secondary component. Evolutionary state of the system is investigated using stellar models. 相似文献
102.
Using multivariate statistical analyses to evaluate groundwater contamination in the northwestern part of Saudi Arabia 总被引:1,自引:1,他引:1
Taisser Zumlot Awni Batayneh Yousef Nazal Habes Ghrefat Saad Mogren Haider Zaman Eslam Elawadi Abdalaziz Laboun Saleh Qaisy 《Environmental Earth Sciences》2013,70(7):3277-3287
Chemical characteristics of groundwater in the Midyan Basin (northwestern Saudi Arabia) were investigated and evaluated. A total of 72 water samples were collected from existing shallow wells and analyzed for different elements. Two multivariate statistical methods, hierarchical cluster analysis (HCA) and principal components analysis (PCA), were applied to a subgroup of the data set in terms of their usefulness for groundwater classification, and to identify the processes controlling groundwater geochemistry. The subgroup consisted of 46 water samples out of 72 samples and 24 variables included major elements (Ca2+, Na+, Mg2+, K+, Cl?, HCO3 ?, NO3 ?, SO4 2?), minor and trace element (SiO2, Al, As, B, Ba, Cd, Cr, F, Fe, Mo, P, Pb, Sb, Sn, Ti, and V). For water samples, four geochemically distinct clusters (i.e., C1, C2, C3 and C4) have been observed by hierarchical cluster analysis. Cr, F and Pb are the dominant ions in cluster C2. Al, As, Cd, Mo, Sb and Ti are the dominant ions in cluster C3, while B, Ca, Cl, HCO3, K, Mg, Na, SO4 and V are identified as dominant ions in the cluster C4. In the PCA, a total of five components are extracted form the data set, which explained 73.37 % of the total data variability. Among them the first component reveals strong associations between As, B, Cd, Cr, F, Mo, Pb, Sb and Ti. The second component reveals the associations between Ca, Cl, HCO3, Mg, Na, SO4 and V. 相似文献
103.
In this paper, a literal analytical solution is developed for the abundances differential equations of the helium burning phase in hot massive stars. The abundance for each of the basic elements 4He,12C,16O and 20Ne is obtained as a recurrent power series in time, which facilitates its symbolic and numerical evaluations. Numerical comparison between the present solution and the numerical integration of the differential equations for the abundances show good agreement. 相似文献