Journal of Science and Technology https://publisher.uthm.edu.my/ojs/index.php/JST <p class="MsoNormal" style="text-align: justify;">The Journal of Science and Technology (JST) is a peer reviewed journal that publishes twice a year&nbsp; (June and December) on articles concerning&nbsp;all areas of science and technology in both theoretical and applied research. JST welcome article submissions from all science and technology research areas including Physics, Chemistry, Biology, Mathematics, Statistics, Biodiversity, Food Science Technology, Engineering Science and Educational Science. JST is intended to provide a forum for the expression of new ideas, as well as a place for exposition of these areas of knowledge&nbsp;that can further understanding of science and technology issues and concerns.</p> en-US <p><strong>Open access licenses</strong></p> <p>Open Access is by licensing the content with a&nbsp;<a href="http://creativecommons.org/choose/">Creative Commons (CC) license</a>.&nbsp;</p> <p><a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" rel="license"><img src="https://i.creativecommons.org/l/by-nc-sa/4.0/88x31.png" alt="Creative Commons License"></a><br>This work is licensed under a&nbsp;<a href="https://creativecommons.org/licenses/by-nc-sa/4.0/" rel="license">Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License</a>.</p> <p>&nbsp;</p> jst@uthm.edu.my (Ahmad Hadi Ali) pt@uthm.edu.my (Penerbit UTHM) Sun, 30 Jun 2019 00:00:00 +0800 OJS 3.1.2.1 http://blogs.law.harvard.edu/tech/rss 60 Numerical Optimization for Source-Drain Channel Resistance of AlGaN/GaN HEMTS https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/3944 <p>A numerical model for the source-drain channel resistance based high electron mobility transistors has been developed that is capable to predict accurately the effects of polarization Coulomb Field Scattering (PCF), multi sub-band on source-drain channel resistance. Salient features of the model are incorporated of fully and partially occupied sub-bands in the interface quantum well, combined with a self-consistent solution of the Schrödinger and Poisson equations. In addition, to develop the model, accurate two-dimensional electron gas mobility and modified wave function in barrier AlGaN have been used. According to the numerical calculations, the effect of multi sub-band and PCF scattering on the increase of source-drain channel resistance is 35% and 65%, respectively, with the effect of PCF being almost twice as high as multi sub-band. The calculated model results are in very good agreement with existing experimental data for high electron mobility transistors device.</p> Rajab Yahyazadeh, Zahra Hashempour Copyright (c) 2019 Journal of Science and Technology https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/3944 Mon, 10 Jun 2019 00:00:00 +0800 Four Element Microstrip Antenna Array with Electromagnetic Band Gap Structure and Silver Material Deposition for Reduced Mutual Coupling https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/3848 <p class="JESTECAbstract">This paper presents the performance of four element microstrip antenna array. The overall bandwidth of the microstrip antenna array with silver material coating is equal to 228.53 % as compared to 75.91 % without silver material coating. The microstrip antenna array with silver material coating of 30 mm thickness is producing good reduction in mutual coupling values at the resonant frequency of 5.53 GHz. Moreover, the radiation properties of antenna array are improved with good reduction in power radiated in the undesired direction. FR-4 glass epoxy substrate is used as dielectric substrate which has a dielectric constant of 4.2 and loss tangent of 0.0245. The microstrip antenna arrays are designed using Mentor Graphics IE3D software and the measured results are obtained using vector network analyzer.</p> K. Prahlada Rao, Vani R M, Hunagund P V Copyright (c) 2019 Journal of Science and Technology https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/3848 Sat, 15 Jun 2019 00:00:00 +0800 Optimised Photocatalytic Degradation of Crystal Violet Over 1wt% MgO-ZnO Composite Catalyst https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/4297 <p>Crystal violet is a member of toxic, environmentally ubiquitous basic dyes that must be eliminated. In this paper, the performance of 1wt % MgO-ZnO suspensions in the photocatalytic degradation of this dye is reported. The catalyst was characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The degradation and mineralization of crystal violet were monitored UV-Visible spectrophotometer and total organic carbon analyzer. The XRD analysis of the catalyst revealed a hexagonal wurtzite structure. The effect of operating variables such as initial crystal violet concentration, catalyst concentration and pH of the solution was optimized using the Box-Behnken design and response surface methodology. The degradation model was statistically remarkable with p&lt;0.0001%. The maximum degradation efficiency of prepared catalyst was found to be 95 %. The degradation kinetics agreed with the Langmuir-Hinshelwood model. However, only 60% of total crystal violet-based organic carbon was removed from the solution due to recalcitrance of this environmentally important compound.</p> Umar Gaya, Sa’adatu Abdul-Aziz Umar Copyright (c) 2019 Journal of Science and Technology https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/4297 Mon, 17 Jun 2019 00:00:00 +0800 Histopathological Biomarkers of Exposure to Monocyclic Aromatic Hydrocarbons in Clarias Ggariepinus (African Catfish) https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/4163 <p>The pollution of the environment with petroleum products through spills in oil producing countries has resulted in the widespread distribution of benzene, toluene, ethylbenzene and xylene. The aim of this study was to identify histopathological alterations in <em>Clarias gariepinus</em> (catfish) that can be used as biological markers for detection of petroleum hydrocarbon contamination which can be included in monitoring programmes. The toxicological evaluations of benzene, toluene, ethylbenzene and xylene were carried out against <em>Clarias gariepinus</em><em>.</em> The histopathological effects of benzene, toluene, ethylbenzene and xylene (BTEX) on different organs were investigated in <em>C. gariepinus,</em> <em>Ti</em><em>lapia zillii, </em>and<em> Chrysichthys nigrodigitatus </em>taken from the impacted areas of the Lagos Lagoon. Toxicological evaluations of the monocyclic aromatic components, benzene, toluene, ethylbenzene and xylene on <em>Clarias gariepinus</em> showed that ethylbenzene (0.479 ml/l) was the most toxic compound tested followed by xylene (0.519 ml/l), benzene (0.666 ml/l) and toluene (1.190 ml/l). The results from the histological study identified necrosis and deformation of the gills, inflammations in the liver, and wrinkling of the oocyte membrane in the gonads of fish, as good histopathological biomarkers of hydrocarbon related stressors. The combination of chemical analysis with these identified biomarkers can be used during environmental monitoring programmes for the protection of aquatic ecosystem.</p> Funmilayo V. Doherty, Abdullahi Adeola, Idowu A. Aneyo, Adebayo A. Otitoloju Copyright (c) 2019 Journal of Science and Technology https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/4163 Wed, 19 Jun 2019 00:00:00 +0800 Adsorption of Chromium (VI) onto Metakaolin: Isotherms, Modelling and Optimization https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/4101 <p>This paper focuses on the application of metakaolin as an adsorbent for the removal of hexavalent chromium (Cr(VI)) from aqueous solution. Metakaolin was prepared and characterized using x-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), specific surface area and pH at point of zero charge analysis. Batch adsorption experiments were designed and conducted with the aid of the statistical central composite design in order to study the effects of pH (2–10), initial concentration of Cr(VI) (25–100 mg/L) and adsorbent dosage (2–10 mg/L). Adsorption of Cr(VI) onto metakaolin was described by a model quadratic equation. Analysis of variance revealed significance of the model quadratic equation. The predicted optimum values of the process variables were:&nbsp; pH of 2.48, initial Cr(VI) concentration of 32.16 mg/L and adsorbent dosage of 7.08 g/L. The experimental percentage adsorption of Cr(VI) obtained under the predicted optimum conditions (34.43 %.) is very to the predicted value of 37.51 %. The adsorption equilibrium data were analyzed using Langmuir, Freundlich and Dubinin-Radushkevich isotherms. The adsorption equilibrium data is best described by the Freundlich isotherm. The maximum adsorption capacity (q<sub>max</sub>) for Cr(VI) adsorption onto metakaolin&nbsp; is 6.36 mg/g. The results showed that metakaolin is a promising adsorbent for the removal of hexavalent chromium from water.</p> Abdulhamid Hamza, Abubakar Mashood Alao, Mohammed Sani Galadima Copyright (c) 2019 Journal of Science and Technology https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/4101 Thu, 20 Jun 2019 00:00:00 +0800 Sorted Min-Max-Mean Filter for Removal of High Density Impulse Noise https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/3861 <p>This paper presents an improved Sorted-Min-Max-Mean Filter (SM3F) algorithm for detection and removal of impulse noise from highly corrupted image. This method uses a single algorithm for detection and removal of impulse noise. Identification of the corrupted pixels is performed by local extrema intensity in grayscale range and these corrupted pixels are removed from the image by applying SM3F operation. The uncorrupted pixels retain its value while corrupted pixel’s value will be changed by the mean value of noise-free pixels present within the selected window. Different images have been used to test the proposed method and it has been found better outcomes in terms of both quantitative measures and visual perception. For quantitative study of algorithm performance, Mean Square Error (MSE), Peak-Signal-to-Noise Ratio (PSNR) and image enhancement factor (IEF) have been used. Experimental observations show that the presented technique effectively removes high density impulse noise and also keeps the originality of pixel’s value. The performance of proposed filter is tested by varying noise density from 10% to 90% and it is observed that for impulse noise having 90% noise density, the maximum PSNR value of 30.03 dB has been achieved indicating better performance of the SM3F algorithm even at 90% noise level. The proposed filter is simple and can be used for grayscale as well as color images for image restoration.</p> Prity Kumari, Deepti Kakkar, Neetu Sood Copyright (c) 2019 Journal of Science and Technology https://publisher.uthm.edu.my/ojs/index.php/JST/article/view/3861 Tue, 25 Jun 2019 00:00:00 +0800