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.

Experimental evaluation of sustainable geopolymer mortars developed from loam natural soil

Abstract: Natural soil can play an important role in the production of geopolymer due to having required aluminosilicate precursors and abundant availability. Numerous aluminosilicate materials have been use...

Symmetric accelerating beam generation via all-dielectric metasurfaces

Abstract: Traditionally, symmetric accelerating beam (SAB) generation requires bulky optical components, which hinder the miniaturization of optical systems. Recently, metasurfaces, which are composed of sub-wavelength features, have provided a captivating boulevard for the realization of ultra-thin and flat optical devices. Therefore, for the first time, we design and simulate all-dielectric metasurfaces based on an optical caustic approach to generate highly efficient SABs by tailoring the phase of an incident wave. The designed metasurface utilizes spatial distribution of optimized Nb2O5 nano-rods on SiO2 substrate to perform the phase modulation. In contrast with conventional accelerating beams, the generated SABs can follow any predefined propagation trajectory with unique features, such as symmetric intensity profile, autofocusing, and thin needle-like structure in their intensity profile. In addition to this, these beams have also shown the ability to avoid obstacles, placed in the direction of propagation of main lobes. We believe that these beams can be useful in applications, including Raman spectroscopy and fluorescent imaging, and multiparticle manipulation.

Improved Water Retention and Positive Behavior of Silica Based Geopolymer Utilizing Granite Powder

Abstract: This research aims to study the behavior of silica based geopolymeric material (22–28%Si) from granitic waste. Granitic waste in powder form was used as main precursor in combination of activating alkaline-solution (18% Na2SiO3, 7% NaOH and 75% distilled water). The ratio between Na2SiO3 and NaOH was kept constant (2.57) in all experiments to achieve appropriate geopolymerization but solid to liquid ratio was varied. Five different compositions of geopolymeric material were prepared with varying proportions of granite waste in the range of 70–78%, combined-alkaline-solution in range of 28–20% and 2% water. Curing of the samples was done in a heating oven at 70 °C for 24 h. After that samples were de-moulded and placed in a heating furnace for further curing at 220 °C for 2 h. After curing, compressive strength, density (bulk, apparent and true) and porosity (open, close and total) were measured. Phase analysis, degree of geopolymerization and microstructural analysis were evaluated by XRF (X-ray Fluorescence), FTIR (Fourier Transform Infrared Spectroscopy) and SEM (Scanning Electron Microscopy), respectively. XRF analysis revealed 28.38% Si and 5.96% Al which are the main constituents for the synthesis of geopolymer. Maximum achieved compressive strength was 22 MPa with minimum porosity of 19.487% in 78% granite based geopolymer. Minimum bulk density of 1.441 g/cm3 was achieved using 70% granite waste. FTIR results confirmed geopolymerization and optimized composition in the resultant samples which is 78% granite and 20% combined-alkaline-solution. Further, SEM results revealed most homogenous and dense structure in the same composition. The durability of the geopolymeric samples was evaluated by water absorption index. Maximum water absorption index of 3.09 was found in 72% granite based sample having 26.79% Si while minimum 2.018 in 78% granite based geopolymeric material having 22.97% Si. Positive compositional effect on various construction properties has been achieved in this study.

Accelerated Multi Stress Aging and Life Estimation of Polymeric Insulators

Abstract: Ceramic insulating materials are widely used for HV and EHV applications and were used for many decades. However, these materials response in a polluted environment and lack of hydrophobicity, high maintenance cost, etc., make them vulnerable. From the past decade, polymeric insulators evolved as the best replacement of these traditional materials. However, improvement in long term performance, service life and their aging behavior under different stresses in the field is still a challenging task for researchers. The impact of the environment on the performance of these insulators may vary depending on the severity of environment which necessitates, the proper investigation of performance for different environmental conditions, specifically for the regions having polluted environment. To understand the aging behavior and effects of different stresses on polymeric insulators, various aging techniques are applied worldwide. A lot of research is going on the natural as well as multi stress aging of polymeric insulators. Multi stress accelerated aging is an attractive technique used to simulate the effects of actual field environment and to analyze the long term service performance in a quite short time span. In this paper, the results of 10,000 hours of the aging test under accelerated multi stresses of the polymeric insulators are presented. Silicon rubber (SiR) is chosen from thermoset type and thermoplastic elastomeric (TPE) is chosen from the thermoplastic group. These insulators were applied multi stresses in accelerated weather chamber to be aged. The seasons (summer/winter) and time (day/night) are simulated for the weather cycles. The environmental region of Hattar, Pakistan, was simulated for designing the weather cycles which is an industrial area having high pollution index. The environmental stresses include heat, UV-A, acid rain and salt fog. The insulators selected for aging in this study are known as 10 kV distribution class insulators. The electrical analysis is based on leakage current and physical analysis are discoloration & classification of hydrophobicity, while material analysis technique considered here is Fourier Transform Infrared Spectroscopy (FTIR). This study showed that the TPE insulator lost its hydrophobicity initially with aging while SiR showed better hydrophobicity. Both TPE and SiR showed better leakage current suppression under the simulated environment of Hattar. Investigation of SiR and TPE insulators performance for the long term in the polluted industrial zone and their comparison under the same stresses condition with each other are the two main objectives of the study. Results revealed that both of the insulators are appropriate for the environment.