A class of exact isotropic solutions of Einstein’s equations and relativistic stellar models in general relativity

In this paper we have studied a particular class of exact solutions of Einstein’s gravitational field equations for spherically symmetric and static perfect fluid distribution in isotropic coordinates. The Schwarzschild compactness parameter, GM/c ² R, can attain the maximum value 0.1956 up to which the solution satisfies the elementary tests of physical relevance. The solution also found to have monotonic decreasing adiabatic sound speed from the centre to the boundary of the fluid sphere. A wide range of fluid spheres of different mass and radius for a given compactness is possible. The maximum mass of the fluid distribution is calculated by using stellar surface density as parameter. The values of different physical variables obtained for some potential strange star candidates like Her X-1, 4U 1538–52, LMC X-4, SAX J1808.4?3658 given by our analytical model demonstrate the astrophysical significance of our class of relativistic stellar models in the study of internal structure of compact star such as self-bound strange quark star.     

Continental-array measurements ofP-wave velocities in the mantle

Summary A velocity model for theP-wave is obtained for the entire mantle, by inversion ofdT/d-data from travel times of 473 earthquakes and explosions registered at 13 seismological observatories in Sweden and Finland. As a check, the travel times resulting from this model are found to be in good agreement with our observed travel times. The observations are distributed over the entire azimuth range with respect to the recording stations. The effect of the core upon the observeddT/d-values is significant from about 95° distance outwards. The estimate of the core radius from this model is 3480 km which corresponds to about 97° of epicentral distance. The resulting model has sudden changes inP-velocity gradient at about 65, 115, 400, 780, 970, 1100, 1350, 2320, 2600 and 2710 km depth, which correspond roughly to 10°, 14°, 19.5°, 29°, 40°, 46°, 54°, 80°, 86° and 90° epicentral distance, respectively.On leave from Geophysical Institute, Tehran University, Tehran, Iran     

Influence of Load Path and Effective Stress on One-Dimensional Deformation of Cemented Paste Backfill (CPB) During Deposition and Curing

Geotechnical and Geological Engineering - Pore water pressure and effective stress development within cemented paste backfill (as one of the most popular local and regional underground mining...     

Vulnerability of ordinary moment resistant concrete frames

The effects of structural modeling (bar slip in lap splice), ground motion selection process (epsilon effect) and size of a structure (number of bays and stories) on the fragility of reinforced concrete ordinary moment resisting frames are investigated. An analytical model is developed to account for bar slip in lap splice, which exhibits good correlation with existing experimental data. Then, incremental dynamic analysis is used to derive the fragility curves for four model structures. The model structures simulate frames with a different number of bays and stories. Finally, the fragility curves are corrected for the epsilon effect. The results show that slip in the lap splice can significantly increase the failure probability, especially for the collapse prevention limit state. At the same time, it is found that spectral shape has a significant impact on the fragility curves. It is also found that accounting for or ignoring bar slip or epsilon effects increases the probability of failure for larger structures. This indicates an unconservative bias in the safety of larger structures.     

New exact cosmologies on the brane

We develop a method for constructing exact cosmological solutions in brane world cosmology. New classes of cosmological solutions on Randall–Sandrum brane are obtained. The superpotential and Hubble parameter are represented in quadratures. These solutions have inflationary phases under general assumptions and also describe an exit from the inflationary phase without a fine tuning of the parameters. Another class solutions can describe the current phase of accelerated expansion with or without possible exit from it.     

FEA of Urban Rock Tunnels Under Impact Loading at Targeted Velocity

Geotechnical and Geological Engineering - This paper presents the effect of impact load and weathering of surrounding rockmass on the deformation behavior of urban underground structures. The FEM...     

Python based location analysis of wind mills in urban environment

GeoJournal - Identification of appropriate location for windmills in landlocked states, like the state of Iowa requires consideration of multiple factors and analysis of a large database, which is...