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Abd El-Aal A.K.,National Research Institute of Astronomy and Geophysics
Natural Hazards and Earth System Science | Year: 2010

This paper reviews the likely source characteristics, focal source mechanism and fault patterns of the nearest effective seismogenic zones to Greater Cairo Area. Furthermore, Mmax and ground accelerations related to the effective seismic events expected in future from those seismogenic zones are well evaluated. For this purpose, the digital waveform of earthquakes than MLCombining double low line3 that occurred in and around Greater Cairo Area from 1997 to 2008 which have been recorded by the Egyptian National Seismological Network, are used to study source characterization, focal mechanism and fault pattern of the seismogenic zones around Greater Cairo Area. The ground motions are predicted from seismogenic zones to assess seismic hazard in the northeastern part of Greater Cairo, where three effective seismogenic zones, namely Abou Zabul, southeast Cairo trend and Dahshour area, have the largest effect to the Greater Cairo Area. The M max was determined, based upon an empirical relationship between the seismic moment and the rupture length of the fault during the earthquake. The estimated Mmax expected from Abou Zabul, southeast Cairo trend, Dahshour seismic sources are of Mw magnitudes equal to 5.4, 5.1, and 6.5, respectively. The predominant fundamental frequency and soil amplification characteristics at the area were obtained using boreholes data and in-situ ambient noise measurement. © 2010 Author(s). Source

Sanad M.R.,National Research Institute of Astronomy and Geophysics
Astrophysical Journal | Year: 2015

Ultraviolet spectra of two intermediate polars (IPs), PQ Gem and V405 Aur, observed with Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph and Faint Object Spectrograph and International Ultraviolet Explorer (IUE) satellites were analyzed during the period between 1994-2000. We estimated the reddening of the two systems from the 2200 feature. Six spectra of the two systems revealing modulations of line fluxes at different times are presented. PQ Gem and V405 Aur are featured by spectral lines in different ionization states. This paper focuses on the third ionized carbon emission line at 1550 and the first ionized helium emission line at 1640 produced in the optically thin outer region of the accretion curtain for the two systems by calculating spectral line fluxes. From HST and IUE data, we deduced ultraviolet luminosities and ultraviolet accretion rates for the two binary stars. The average temperature of the accretion streams for PQ Gem and V405 Aur are ∼4500 K and 4100 K, respectively. The results reveal that there are modulations in fluxes of spectral lines, ultraviolet luminosities, and ultraviolet accretion rates with time for both systems. These modulations are referred to the changes of both density and temperature as a result of the variations of mass transfer rate from the secondary star to the primary star. The current results are consistent with an accretion curtain model for IPs. © 2015. The American Astronomical Society. All rights reserved. Source

Tadross A.L.,National Research Institute of Astronomy and Geophysics
Research in Astronomy and Astrophysics | Year: 2012

We present the first in a series studying the astrophysical parameters of open clusters using the PPMXL* database whose data are applied to study Ruprecht 15. The astrophysical parameters of Ruprecht 15 have been estimated for the first time. © 2012 National Astronomical Observatories of Chinese Academy of Sciences and IOP Publishing Ltd.. Source

Abd El-Aal A.K.,National Research Institute of Astronomy and Geophysics
Journal of Geophysics and Engineering | Year: 2010

The importance of the northeastern part of the greater Cairo metropolitan area is due to the presence of a nuclear power plant and the dense population and its extent towards seismic sources. This paper reviews the likely ground acceleration related to the effective seismic events initiated from the closest seismic sources to the area. For this purpose, a deterministic seismic hazard approach followed by ground stochastic simulation was performed to assess the seismic hazard in the area. Seismic sources of hazardous effects were defined. A controlling earthquake was determined, based upon an empirical relationship between the seismic moment and the rupture length of the fault during the earthquake. The soil amplification characteristics in the area were obtained by in situ ambient noise measurements with great precautions. An H/V technique has been used to estimate the fundamental frequency and amplification factors at the sites of ambient noise measurements. The values of the fundamental frequency and the corresponding amplification factor were estimated at the investigated sites within the area of interest. The maximum possible earthquake magnitude Mmax was estimated for the effective seismic sources surrounding the study area and the hazard parameter peak ground acceleration (PGA) calculated for given zones. The work on the estimation of PGAs will contribute to the determination of national seismic codes, giving guidance on which buildings must take seismic risk into consideration and the necessity to re-appraise the seismic risk for existing buildings. © 2010 Nanjing Institute of Geophysical Prospecting. Source

Ahmed N.,National Research Institute of Astronomy and Geophysics | Moss I.G.,Newcastle University
Nuclear Physics B | Year: 2010

Moduli stabilisation is explored in the context of low-energy heterotic M-theory to show that a small value of the cosmological constant can result from a balance between the negative potential energy left over from stabilising the moduli and a positive Casimir energy from the higher dimensions. Supersymmetry breaking is induced by the fermion boundary conditions on the two branes in the theory. An explicit calculation of the Casimir energy for the gravitino reveals that the energy has the correct sign, although the size of the contribution is close to the edge of the parameter range for which the calculation is valid. © 2010 Elsevier B.V. Source

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