National Engineering and Scientific Commission

Islamabad, Pakistan

National Engineering and Scientific Commission

Islamabad, Pakistan
Time filter
Source Type

Saeed S.,Allama Iqbal Open University | Rashid N.,Allama Iqbal Open University | Jones P.G.,TU Braunschweig | Ali M.,University of Punjab | Hussain R.,National Engineering and Scientific Commission
European Journal of Medicinal Chemistry | Year: 2010

Five series of thiourea derivatives bearing benzothiazole moiety (20 compounds) were efficiently synthesized and evaluated for antimicrobial and anticancer activities. The results indicated that the compounds possessed a broad spectrum of activity against the tested microorganisms and showed higher activity against fungi than bacteria. Compounds 1b, 2b, 3b, 4b and 5b exhibited the greatest antimicrobial activity. Preliminary study of the structure-activity relationship revealed that electronic factors in benzothiazole rings had a great effect on the antimicrobial activity of these compounds. In preliminary MTT cytotoxicity studies, the thiourea derivatives (2d, 5c and 5d) were found most potent. In MCF-7 and HeLa cells, the IC 50 values were observed in the range of 18-26 μM and 38-46 μM, respectively. © 2009 Elsevier Masson SAS. All rights reserved.

Malik S.N.,University of Manchester | Mahboob S.,University of Manchester | Mahboob S.,Quaid-i-Azam University | Haider N.,National Engineering and Scientific Commission | And 2 more authors.
Nanoscale | Year: 2011

CuInSe2, CuGaSe2 and CuIn(1-x)Ga xSe2 (CIGS) nanoparticles were synthesised from the diisopropyldiselenophosphinatometal complexes Mx[iPr 2PSe2]n (M = Cu(i), In(iii), Ga(iii); n = 1, 3) by thermal decomposition of the precursors in HDA/TOP at 120-210 °C or 250 °C. The semiconductor nanoparticles obtained were characterized by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis. The diameters of the nanoparticles for CuInSe2, CuGaSe2 and CuIn0.7Ga0.3Se2 were found to be 4.9 ± 0.6 nm (at 180 °C), 13.5 ± 2.9 nm (at 250 °C) and 14 ± 2.22 nm (at 250 °C) respectively. The p-XRD patterns for the nanoparticulate samples were assigned to the corresponding ICDD patterns for tetragonal chalcopyrite phase. © 2011 The Royal Society of Chemistry.

Abbas S.H.,National Engineering and Scientific Commission | Hong S.H.,Hanyang University
Journal of Communications and Networks | Year: 2013

In this paper, we present a technique for obtaining conflict-free schedules for real-time automation protocol for industrial Ethernet (RAPIEnet) switches. Mathematical model of the switch is obtained using graph theory. Initially network traffic entry and exit parts in a single RAPIEnet switch are identified, so that a bipartite conflict graph can be constructed. The obtained conflict graph is transformed to three kinds of matrices to be used as inputs for our simulation model, and selection of any of the matrix forms is application-specific. A greedy edge-coloring algorithm is used to schedule the network traffic and to solve the minimum coloring problem. After scheduling, empty slots are identified for forwarding the non real-time traffic of asynchronous devices. Finally, an algorithm for synchronizing the schedules of adjacent switches is proposed using edge-contraction and minors. All simulations were carried out using Matlab. © 2011 JCN.

Tariq M.,Quaid-i-Azam University | Ali S.,Quaid-i-Azam University | Ahmad F.,National Engineering and Scientific Commission | Ahmad M.,Quaid-i-Azam University | And 3 more authors.
Fuel Processing Technology | Year: 2011

Biodiesel was synthesized from rocket seed oil by base-catalyzed transesterification with methanol. The synthesis of biodiesel was confirmed by FT-IR and NMR (1H and 13C) spectroscopy. Various fuel properties of the synthesized biodiesel were determined using ASTM methods and discussed accordingly. A total of eleven fatty acid methyl esters (FAMEs) were identified in rocket seed oil biodiesel (RSOB) by the retention time and the fragmentation pattern data of GC/MS analysis. The identified FAMEs were, methyl 9-hexadecenoate (C16:1), 14-methyl pentadecanoate (C16:0), methyl 9,12-octadecadienoate (C18:2), methyl 9-octadecenoate (C18:1), methyl octadecanoate (C18:0), methyl 11-eicosenoate (C20:1), methyl eicosanoate (C20:0), methyl 13-docosenoate (C22:1), methyl docosanoate (C22:0), methyl 15-tetracosenoate (24:1) and methyl tetracosanoate (C24:0). The percentage conversion of triglycerides to corresponding methyl esters determined by 1H NMR was 88.49%. © 2010 Elsevier B.V. All rights reserved.

Khan S.U.,Hong Kong University of Science and Technology | Iqbal K.,National Engineering and Scientific Commission | Munir A.,National Engineering and Scientific Commission | Kim J.-K.,Hong Kong University of Science and Technology
Composites Part A: Applied Science and Manufacturing | Year: 2011

The influence of nanoclay on the fracture resistance and mechanical properties of epoxy-based nanocomposites and the corresponding continuous carbon fiber-epoxy matrix composites (CFRPs) has been studied. The incorporation of nanoclay into epoxy and CFRP enhances the impact and quasi-static fracture resistance, as well as the flexural strength and modulus of the composites. Microscopic examination based on the double-notch bending test identifies pertinent toughening mechanisms responsible for the enhanced toughness of clay nanocomposites, namely microcracking, crack pining, crack tip bifurcation and deflection, and microvoids along the clay galleries. Multi-layer delaminations are among the key toughening mechanisms identified for the clay-CFRP hybrid composites. © 2010 Elsevier Ltd. All rights reserved.

Mahboob S.,University of Manchester | Mahboob S.,Quaid-i-Azam University | Malik S.N.,University of Manchester | Malik S.N.,National University of Sciences and Technology | And 4 more authors.
Journal of Crystal Growth | Year: 2014

The tetragonal chalcopyrite phases CuInSe2, CuGaSe2 and CuIn0.7Ga0.3Se2 have been deposited onto the glass substates by Aerosol Assisted Chemical Vapour Deposition (AACVD) from a mixture of [Mx(iPr2PSe2) y] complexes (M=In, Ga, Cu) at temperatures between 300 C and 500 C. The thin films were characterized by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The bulk compositional properties have been studied by energy dispersive X-ray (EDX) analysis. SEM and AFM studies demonstrate a significant variation in morphology of the deposited materials at different deposition temperatures. © 2014 Elsevier B.V.

Sappurd A.,National Engineering and Scientific Commission
Clean Technologies and Environmental Policy | Year: 2011

Oil Refineries surrounding the gulf are the largest source of environmental pollution in the region. Air dispersion models are powerful tools for assessing the consequences of environmental air pollutant concentrations. This study was carried out to investigate the transport and dispersion patterns of SO 2 originating from Mina Al-Fahal refinery, in the Sultanate Oman by employing California Puff (CALPUFF) dispersion modeling system. The major goal of this study is to make a comparison of the results produced by this modeling system with a previous study which was conducted for the same area using Industrial Source Complex Short Term (ISCST) model. In order to obtain the meteorological fields of the study area the CALPUFF modeling system was coupled with Weather Research and Forecasting (WRF), a prognostic meteorological model. The results indicated that the performance of the CALPUFF was better than that of ISCST; however, a difference in magnitudes of predicted and measured concentrations of SO2 was found. This difference can be reduced using high-resolution terrain elevation data, site-specific observational meteorological data and buoy data. The complex geography and variable wind regimes played an important role in distribution of SO2 in and around the refinery. The land-sea interaction also influenced the predicted results. © 2010 Springer-Verlag.

Khattak A.R.,National Engineering and Scientific Commission
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering | Year: 2013

Joints are an important source of vibration damping in built-up structures. Their mathematical modelling is, however, complex due to microslip with highly nonlinear nature. This is a major reason for developing a reduced-order model of dynamics in joints. The singular value decomposition is applied to decompose the time history and arrive at a linear model for joint dynamics while preserving the physics of the model at the same time. The model, which is a linearization of joint dynamics, is obtained by the introduction of certain functions of time which replace the nonlinear forces in the reduced space for harmonic excitation. A two-fold computational advantage is achieved by (1) increasing the size of the stable time step and (2) reducing the number of generalized coordinates substantially. Several configurations of joint, having different geometry and dynamic parameters, are studied with the help of the reduced-order model. The state of the system as well as the hysteretic behaviour is successfully modelled showing very good agreement with full model. © IMechE 2012.

Majid A.,Pakistan Institute of Engineering and Applied Sciences | Majid A.,Gwangju Institute of Science and Technology | Khan A.,Pakistan Institute of Engineering and Applied Sciences | Javed G.,National Engineering and Scientific Commission | Mirza A.M.,National University of Computer and Emerging Sciences
Computational Materials Science | Year: 2010

In the study of crystalline materials, the lattice constant (LC) of perovskites compounds play important role in the identification of materials. It reveals various interesting properties. In this study, we have employed Support Vector Regression, Artificial Neural Network, and Generalized Regression Neural Network based Computational Intelligent (CI) techniques to predict LC of cubic and monoclinic perovskites. Due to their interesting physiochemical properties, investigations in modeling the structural properties of perovskites have gained considerable attention. A dataset of a reasonable number of cubic and monoclinic perovskites are collected from the current literature. The CI techniques can efficiently correlate the LC of the perovskites materials with the ionic radii of constituent elements. A performance analysis of CI techniques is carried out with Multiple Linear Regression techniques, SPuDS software, and Density-Functional Theory. We have observed that the CI techniques yield accurate LC prediction as against the conventional approaches. Availability: Matlab based computer program developed for this work is available on request. © 2010 Elsevier B.V. All rights reserved.

Khan S.U.,Clear Technology | Munir A.,National Engineering and Scientific Commission | Hussain R.,National Engineering and Scientific Commission | Kim J.-K.,Clear Technology
Composites Science and Technology | Year: 2010

The effects of nanoclay inclusion on cyclic fatigue behavior and residual properties of carbon fiber-reinforced composites (CFRPs) after fatigue have been studied. The tension-tension cyclic fatigue tests are conducted at various load levels to establish the S-N curve. The residual strength and modulus are measured at different stages of fatigue cycles. The scanning electron microscopy (SEM) and scanning acoustic microscopy (SAM) are employed to characterize the underlying fatigue damage mechanisms and progressive damage growth. The incorporation of nanoclay into CFRP composites not only improves the mechanical properties of the composite in static loading, but also the fatigue life for a given cyclic load level and the residual mechanical properties after a given period of cyclic fatigue. The corresponding fatigue damage area is significantly reduced due to nanoclay. Nanoclay serves to suppress and delay delamination damage growth and eventual failure by improving the fiber/matrix interfacial bond and through the formation of nanoclay-induced dimples. © 2010 Elsevier Ltd.

Loading National Engineering and Scientific Commission collaborators
Loading National Engineering and Scientific Commission collaborators