Ghulam Ishaq Khan Institute of Engineering Sciences and Technology

About: Ghulam Ishaq Khan Institute of Engineering Sciences and Technology is a education organization based out in Topi, Pakistan. It is known for research contribution in the topics: Thin film & Quantum efficiency. The organization has 618 authors who have published 940 publications receiving 10674 citations.

A TEM study of deformation substructure in high strain rate and explosively shock-loaded polycrystalline iron

Abstract: Residual microstructures developed in polycrystalline iron after deformation at high rates of strain were characterized using transmission electron microscopy (TEM). Long, screw- type dislocations were observed in Hopkinson bar and impacted specimens compared to deformation twinning and dislocation cell structures found in shocked specimens. Localized deformation bands were observed in the impacted specimen. No evidence for deformation twinning was found in the Hopkinson bar and impacted specimens. The effect of substructure produced in the specimens on the hardness of these specimens is also observed.

Gamow-Teller strength and lepton captures rates on 66−71Ni in stellar matter

Abstract: Charge-changing transitions play a significant role in stellar weak-decay processes. The fate of the massive stars is decided by these weak-decay rates including lepton (positron and electron) captures rates, which play a consequential role in the dynamics of core collapse. As per previous simulation results, weak interaction rates on nickel (Ni) isotopes have significant influence on the stellar core vis-a-vis controlling the lepton content of stellar matter throughout the silicon shell burning phases of high mass stars up to the presupernova stages. In this paper, we perform a microscopic calculation of Gamow–Teller (GT) charge-changing transitions, in the β-decay and electron capture (EC) directions, for neutron-rich Ni isotopes (66−71Ni). We further compute the associated weak-decay rates for these selected Ni isotopes in stellar environment. The computations are accomplished by employing the deformed proton–neutron quasiparticle random phase approximation (pn-QRPA) model. A recent study showed that the deformed pn-QRPA theory is well suited for the estimation of GT transitions. The astral weak-decay rates are determined over densities in the range of 10–1011g/cm3 and temperatures in the range of 0.01 × 109–30 × 109K. The calculated lepton capture rates are compared with the previous calculation of Pruet and Fuller (PF). The overall comparison demonstrates that, at low stellar densities and high temperatures, our EC rates are bigger by as much as two orders of magnitude. Our results show that, at higher temperatures, the lepton capture rates are the dominant mode for the stellar weak rates and the corresponding lepton emission rates may be neglected.

Lie symmetries of the Ricci and energy-momentum tensors

Abstract: Though the Ricci and energy-momentum tensors have the same algebraic symmetries and appear in a similar way in the Einstein equations, in that interchanging them and inverting the gravitational coupling leaves the equations invariant, their differential symmetry Lie algebras are not identical in general. For cylindrically symmetric static spacetimes their inter-relationship is studied in this paper. Neither set of symmetries is a subset of the other in general.