Drift solitary structures in inhomogeneous degenerate quantum plasmas with trapped electrons     

H. A. Shah  W. Masood  M. T. Asim  M. N. S. Qureshi 《Astrophysics and Space Science》2014,350(2):615-622

In the present work, we have considered the nonlinear effects due to trapped electrons in an inhomogeneous degenerate quantum plasma. The formation of drift solitary structures has been investigated for both fully and partially degenerate plasmas. The Sagdeev potential approach has been employed to obtain arbitrary amplitude solitary structures. Interestingly, for a fixed value of density, not only compressive but rarefactive solitary structures have been obtained for a certain temperature range. Furthermore, it has been observed that the drift solitary structures exist only for the case when the drift velocity is smaller than the velocity of the nonlinear structure. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs and the relevance of the results with regard to white dwarf asteroseismology is also pointed out.  相似文献   

The regional and the seasonal variability of extreme precipitation trends in Pakistan   总被引：1，自引：0，他引：1  

Mian Sabir Hussain  Seungho Lee 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(4):421-441

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Application of Continuous Wavelet Transform in?Examining Soil Spatial Variation: A?Review   总被引：1，自引：0，他引：1  

Asim Biswas  Bing Cheng Si 《Mathematical Geosciences》2011,43(3):379-396

An adequate understanding of soil spatial variation as a function of space and scale is necessary in ecological modeling, environmental prediction, precision agriculture, soil quality assessment and natural resources management. Soil spatial variation can be partitioned into frequencies (scale) and positions (location) by the wavelet transform. This review focuses mainly on different applications of the continuous wavelet transform (CWT) for the identification of the scale and location dependence of soil attributes. We discussed both wavelet spectra and wavelet coherence in our analysis of soil spatial variation. Global wavelet spectra, being the sum of wavelet spectra over all spatial locations at a scale, can be used to examine the dominant scale of variation. Furthermore, some variations at a particular scale persist over all locations (termed global features), whereas others are present at only a few locations (localized features). Wavelet spectra can be used to identify both localized and global features. The combination of localized and global features provides a complete picture of the scale-location information of different processes in the field and may provide better guidance in designing efficient management practices. Wavelet coherency partitions the total correlation between two variables into correlations at different scales and locations, while also revealing the scale- and location-specific relationship between those two variables. This relationship may be helpful in developing predictive links between one property and another.  相似文献   

Hubble Space Telescope observations of SV Cam – II. First derivative light-curve modelling using phoenix and atlas model atmospheres     

S. V. Jeffers  J. P. Aufdenberg  G. A. J. Hussain  A. Collier Cameron  V. R. Holzwarth 《Monthly notices of the Royal Astronomical Society》2006,367(3):1308-1316

The variation of the specific intensity across the stellar disc is an essential input parameter in surface brightness reconstruction techniques such as Doppler imaging, where the relative intensity contributions of different surface elements are important in detecting star-spots. We use phoenix and atlas model atmospheres to model light curves derived from high precision (signal-to-noise ratio ≃ 5000) Hubble Space Telescope ( HST ) data of the eclipsing binary SV Cam (F9V+K4V), where the variation of specific intensity across the stellar disc will determine the contact points of the binary system light curve. For the first time, we use χ² comparison fits to the first derivative profiles to determine the best-fitting model atmosphere. We show the wavelength dependence of the limb darkening and that the first derivative profile is sensitive to the limb-darkening profile very close to the limb of the primary star. It is concluded that there is only a marginal difference (<1σ) between the χ² comparison fits of the two model atmospheres to the HST light curve at all wavelengths. The usefulness of the second derivative of the light curve for measuring the sharpness of the primary's limb is investigated, but we find that the data are too noisy to permit a quantitative analysis.  相似文献   

The coronal structure of AB Doradus determined from contemporaneous Doppler imaging and X-ray spectroscopy   总被引：1，自引：0，他引：1  

G. A. J. Hussain  M. Jardine  J.-F. Donati  N. S. Brickhouse  N. J. Dunstone  K. Wood  A. K. Dupree  A. Collier Cameron  F. Favata 《Monthly notices of the Royal Astronomical Society》2007,377(4):1488-1502

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Shocks in multicomponent cylindrical and spherical Lorentzian plasmas     

S. Hussain  N. Akhtar  S. Mahmood 《Astrophysics and Space Science》2013,343(1):329-333

Nonlinear cylindrical and spherical ion acoustic shocks have been studied in unmagnetized dissipative non-Maxwellian electron-positron-ion (e-p-i) plasmas. Modified Korteweg-de Vries Burgers (mKdVB) has been derived by using reductive perturbation method. Two level finite difference scheme is used with the help of Runge Kutta method to simulate the mKdVB. It is noticed that positron concentration, spectral indices of electrons and positrons, kinematic viscosity of ions significantly modifies the strength of shocks in cylindrical and spherical geometries.  相似文献   

Screening Indian Mustard Genotypes for Phytoremediating Arsenic‐Contaminated Soils     

Mohd Kafeel Ahmad Ansari  Shahid Umar  Altaf Ahmad  Shahid Hussain Ansari  Muhammad Iqbal  Gary Owens  Hong‐Bo Shao 《洁净——土壤、空气、水》2013,41(3):313-314

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Snow and stream-water chemistry of the Ganga headwater basin,Garhwal Himalaya,India     

SARFARAZ AHMAD  SYED IQBAL HASNAIN 《水文科学杂志》2013,58(1):103-111

Abstract

Studies of the chemical composition of snowpack and stream water were carried out in a catchment having an area of 53km² (31°03′-30°55′N and 78°40′-78°51′E) in the Garhwal Himalaya, India. The dominant ions in the snowpack and stream water were Ca²⁺, Na⁺, NO^? ₃, SO^2- ₄ and HCO^? ₃. Solute patterns in the snowpack show preferential elution. Investigation of the chemical composition of stream water shows that meltwater changes its composition substantially as it passes through soil pathways to the stream. The groundwater flushing perhaps controls the chemical composition of meltwater in the early spring. However, in the period from July to September, the stream water carries the chemical signature of monsoonal precipitation.  相似文献   

Noether gauge symmetry approach in f(R) gravity     

Ibrar Hussain  Mubasher Jamil  F. M. Mahomed 《Astrophysics and Space Science》2012,337(1):373-377

We discuss the f(R) gravity model in which the origin of dark energy is identified as a modification of gravity. The Noether symmetry with gauge term is investigated for the f(R) cosmological model. By utilization of the Noether Gauge Symmetry (NGS) approach, we obtain two exact forms f(R) for which such symmetries exist. Further it is shown that these forms of f(R) are stable.  相似文献   

Warm generalized cosmic Chaplygin gas inflation inspired by generalized dissipative coefficient     

Abdul Jawad  Shahzad Hussain 《Astrophysics and Space Science》2018,363(1):4

We examine the warm inflationary universe model in the presence of generalized cosmic Chaplygin gas and standard scalar field. We assume the generalized dissipative coefficient and corresponding weak and strong dissipative regimes. In this framework, we analyze the characteristics of inflationary dynamics under the slow-roll approximations. Under these approximations, we formulate the important inflationary parameters, such as scalar spectral index, scalar and tensor power spectrum, tensor-to-scalar ratio etc. It is interesting to note that our results for these inflationary parameters are well corroborated with the recent observational data like WMAP7, WMAP9 and Planck data.  相似文献