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: Quantum efficiency & Diode. The organization has 618 authors who have published 940 publications receiving 10674 citations.

Analysis of caustic region fields of a cassegrain system having PEMC reflectors embedded in homogeneous chiral medium

Abstract: Analysis of high frequency field expressions for the Cassegrain system having perfect electromagnetic conducting (PEMC) boundaries are studied. Both the reflectors of Cassegrain system are PEMC and are embedded in chiral medium. Two different cases have been analyzed depending upon the values of chirality parameter (kβ). In the first case, chiral medium supports positive phase velocity (PPV) for both the left circularly polarized (LCP) and right circularly polarized (RCP) modes. In the second case, chiral medium supporting PPV for one mode and negative phase velocity (NPV) for the other mode is taken into account. Mathematical recipe proposed by the Maslov is used to obtain the field expressions in the focal region because geometrical optics (GO) causes non-realistic singularity in this region. Field patterns of focal plane are given in the paper for different values of admittance (M ) of the PEMC boundary and the chirality parameter (kβ).

Microstructure, mechanical properties and residual stress distribution in pulsed tungsten inert gas welding of Ti–5Al–2.5Sn alloy

Abstract: Pulsed tungsten inert gas welding with full penetration was performed on 1.6 mm thick Ti–5Al–2.5Sn alloy sheet. Hole-drill strain measurement method was employed to measure the distribution of residual stresses across the weld line. Tensile tests were performed on the specimens sectioned in transverse direction of the welded sample. The evolved microstructure in the welded zone was investigated by metallography and X-ray diffraction. Transverse residual stresses of tensile nature were present at different depths below the surface and decreased the yield strength and ultimate tensile strength. However, this decrease was not dependent on the maximum value of transverse residual stress. Fracture location was found to be dependent on the micro-hardness profile and fracture took place in base metal where micro-hardness was the lowest. Furthermore, the presence of tensile residual stresses in the welded sample had no influence on the fractured surface morphology. Peak current and background current had a significant influence on the fusion zone width, heat-affected zone width, and fusion zone grain size.

Impact Toughness of Hybrid Carbon Fiber-PLA/ABS Laminar Composite Produced through Fused Filament Fabrication.

Abstract: Nowadays, the components of carbon fiber-reinforced polymer composites (an important material) are directly produced with 3D printing technology, especially Fused Filament Fabrication (FFF). However, such components suffer from poor toughness. The main aim of this research is to overcome this drawback by introducing an idea of laying down a high toughness material on the 3D-printed carbon fiber-reinforced polymer composite sheet, thereby making a hybrid composite of laminar structure. To ascertain this idea, in the present study, a carbon-reinforced Polylactic Acid (C-PLA) composite sheet was initially 3D printed through FFF technology, which was then laid upon with the Acrylonitrile Butadiene Styrene (ABS), named as C-PLA/ABS hybrid laminar composite, in an attempt to increase its impact toughness. The hybrid composite was fabricated by varying different 3D printing parameters and was then subjected to impact testing. The results revealed that toughness increased by employing higher layer thickness and clad ratio, while it decreased by increasing the fill density, but remained unaffected due to any change in the raster angle. The highest impact toughness (23,465.6 kJ/m2) was achieved when fabrication was performed employing layer thickness of 0.5 mm, clad ratio of 1, fill density of 40%. As a result of laying up ABS sheet on C-PLA sheet, the toughness of resulting structure increased greatly (280 to 365%) as compared to the equivalent C-PLA structure, as expected. Two different types of distinct failures were observed during impact testing. In type A, both laminates fractured simultaneously without any delamination as a hammer hit the sample. In type B, the failure initiated with fracturing of C-PLA sheet followed by interfacial delamination at the boundary walls. The SEM analysis of fractured surfaces revealed two types of pores in the C-PLA lamina, while only one type in the ABS lamina. Further, there was no interlayer cracking in the C-PLA lamina contrary to the ABS lamina, thereby indicating greater interlayer adhesion in the C-PLA lamina.

General solution for TEM, TE, and TM waves in fractional dimensional space and its application in rectangular waveguide filled with fractional space

Abstract: This work presents general solution to the Maxwell’s equations inside a waveguide or transmission line where space is assumed to be of noninteger dimensions. The solution is a generalization of wave equation inside a waveguide or transmission line from integer dimensional space to fractional dimensional space. General analytical expressions for TE, TM, and TEM waves in fractal medium are also developed from the obtained general solution. Using the same notion, wave propagation inside rectangular waveguide is mathematically modeled and analyzed when it is filled fractal medium. The results obtained are analyzed and compared with the waveguide filled with nonfractal medium and substantial changes are observed to be present between the two cases. It is also observed that the classical results are recovered from all our results by considering integer dimensional space.