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.

Effective permeability of inner ring shorted split ring resonator

Abstract: Analytical expression for effective permeability of inner ring shorted split ring resonator is derived in this paper. The resonant frequencies thus calculated are compared with published results and good agreement is observed for higher split lengths. Simulation results for effective permeability with different gap lengths in the split ring resonator are also included in this paper. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 624–627, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23149

Estimating arc temperature in a model high breaking capacity fuse

Abstract: We present estimates of the temperature at different times during the arcing period of an experimental model of a sand-filled, high-voltage, high breaking capacity fuse. The model fuse does not interrupt current automatically but the technique described here could well be used in actual current-limiting high-voltage fuses to measure the time-resolved arc temperature. The test fuse is energized using a synthetic test circuit, which supplies the fuse a prospective current of 4.5 kA at 6 kV, 50 Hz. An optical fibre is used to carry light from the fuse arc to a spectrograph which is used to isolate spectral lines of interest. The spectrum is recorded by an intensified photodiode array. By gating the image intensifier in front of the diode array a complete spectrum is recorded in several microseconds. By varying the timing of the gate pulse the arc spectrum can be obtained at any desired time during the arcing period. The arc temperature is determined from the relative intensities of Si II spectral lines. The arc temperature is found to vary between 7,000 and 27,000 K at different instants during the arcing period.

Photoanode annealing effect on charge transport in dye-sensitized solar cell

Abstract: Solar energy is an abundantly available form of clean and renewable energy resource that can be used to generate electricity using many different photovoltaic technologies. Dye-sensitized solar cells (DSSCs) have attracted attention of researchers due to their low cost and easy fabrication processes, when compared to conventional silicon-based photovoltaic devices. Performance enhancement of DSSCs continues to be the subject of recent research. In this work, FTO/TiO2/N719/electrolyte/Pt-type conventional DSSCs were fabricated with and without heat treatment of the FTO/TiO2 photoanode before sensitization and Pt counter electrode. Results of the photovoltaic and impedance spectroscopic measurements are reported and discussed. The photovoltaic data reveals relatively higher performance of the cell made after heat treatments of the photoanode and the counter electrodes. The objective of this research is to study the reason for high performance obtained employing the annealed photoanode. The overall power conversion efficiency and short-circuit current density of the device made after heat treatment are observed higher than the one without heat treatment by 165% and 206%, respectively. The impedance spectroscopic studies also confirmed high performance of the cell made after the heat treatments.

Multiphase flow simulations through Tarbela dam spillways and tunnels.

Abstract: Tarbela dam is one of the largest earth filled dam in the world used for power generation and irrigation purposes. Like all reservoirs the sediments inflow in the Tarbela reservoir has resulted in reduction in water storage capacity and is also causing damage to the tunnels, power generating units and ultimately to the plant equipment. This numerical study was performed to predict the flow patterns and characteristics in Tarbela dam. Tunnel 3 and 4 inlets; originally on the bed level were raised in the 3-D model and meshed. Analysis was performed using multiphase flow (water and air) for maximum inflow in the reservoir, i.e., considering summer season and discharging water through different locations, i.e., tunnels and spillways. Pressure, velocities, flow rate and free surface height results obtained were found in good agreement with the analytical and existing results where available. Results show uneven discharge through each gate due to maximum velocity near exits and overall stagnant phenomena of water within the reservoir. Maximum velocity was observed along the spillways outlet. Strong vortex motion was observed near the spillways outlet and tunnel inlets. New design of Tunnel 3 and 4 were suggested to WAPDA in order to decrease the sediment inflow and improvements in design of the spillways were suggested.

Improved Selective Harmonics Elimination Strategy for Multilevel Inverters with Optimal DC Values

Abstract: This paper examines the computation of optimal DC values and switching angles for eliminating higher order harmonics in Cascaded Multi-Level Inverters (CMLI) output voltage using Nelder Mead (NM) Simplex Algorithm. The goal is to solve the set of non-linear Selective Harmonic Elimination (SHE) equations in order to obtain the required fundamental component as well as eliminate the higher order harmonics. 2- and 3-stage CMLI for single and three phase output is investigated with equal and unequal DC sources and harmonics efficient suppression is reported. Superiority of NM method over Genetic Algorithm and Generalized Search Pattern with respect to convergence and computational time to reach the global minimum is discerned and demonstrated through MATLAB simulations. Results manifest that NM convergence rate and computational time is faster than GPS and GA for identical population of test points. For validation of results, 2- and 3-stage inverter is simulated in MATLAB Simulink for FFT analysis.