Surabaya, Indonesia

Hang Tuah University
Surabaya, Indonesia
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Saad F.,Bayer AG | Saad F.,Gulf Medical University | Saad F.,Hang Tuah University
Diabetes/Metabolism Research and Reviews | Year: 2012

Obesity, hypertension, insulin resistance (IR), dyslipidaemia, impaired coagulation profile and chronic inflammation characterize cardiovascular risk factors in men. Adipose tissue is an active endocrine organ producing substances that suppress testosterone (T) production and visceral fat plays a key role in this process. Low T leads to further accumulation of fat mass, thus perpetuating a vicious circle. In this review, we discuss reduced levels of T and increased cardiovascular disease (CVD) risk factors by focusing on evidence derived from three different approaches. (i) epidemiological/ observational studies (without intervention); (ii) androgen deprivation therapy (ADT) studies (standard treatment in advanced prostate cancer); and (iii) T replacement therapy (TRT) in men with T deficiency (TD). In epidemiological studies, low T is associated with obesity, inflammation, atherosclerosis and the progression of atherosclerosis. Longitudinal epidemiological studies showed that low T is associated with an increased cardiovascular mortality. ADT brings about unfavourable changes in body composition, IR and dyslipidaemia. Increases in fibrinogen, plasminogen activator inhibitor 1 and C-reactive protein have also been observed. TRT in men with TD has consistently shown a decrease in fat mass and simultaneous increase in lean mass. T is a vasodilator and in long-term studies, it was shown to reduce blood pressure. There is increasing evidence that T treatment improves insulin sensitivity and lipid profiles. T may possess anti-inflammatory and anti-coagulatory properties and therefore TRT contributes to reduction of carotid intima media thickness. We suggest that T may have the potential to decrease CVD risk in men with androgen deficiency. © 2012 John Wiley & Sons, Ltd.

Izyan Z.N.,Hang Tuah University | Shuhaimi M.,Petronas University of Technology
Energy | Year: 2014

Inefficient furnaces and heat exchangers contribute to the depletion of fossil fuel problem due to higher fuel demand and higher carbon emission. The method of exergy analysis is applied to the furnace and crude preheat train (CPT) in a crude distillation unit (CDU) to determine performance benchmark of the system. This paper presents exergy analysis and strategies to reduce exergy loss through process modification. The highest exergy loss was found to be located at the inlet furnace. The proposed options for fuel reduction strategies are reduction of heat loss from furnace stack and overall cleaning schedule of CPT. The feasibility and economic analysis for both options are investigated. From the results, overall cleaning schedule of CPT contributes to the highest energy saving of 5.6%. However, reduction of heat loss from furnace stack is the highest cost saving by about 6.4%. © 2014 Elsevier Ltd.

Hannan M.A.,National University of Malaysia | Azidin F.A.,National University of Malaysia | Azidin F.A.,Hang Tuah University | Mohamed A.,National University of Malaysia
Renewable and Sustainable Energy Reviews | Year: 2014

There are numbers of alternative energy resources being studied for hybrid vehicles as preparation to replace the exhausted supply of petroleum worldwide. The use of fossil fuel in the vehicles is a rising concern due to its harmful environmental effects. Among other sources battery, fuel cell (FC), super capacitors (SC) and photovoltaic cell i.e. solar are studied for vehicle application. Combinations of these sources of renewable energies can be applied for hybrid electric vehicle (HEV) for next generation of transportation. Various aspects and techniques of HEV from energy management system (EMS), power conditioning and propulsion system are explored in this paper. Other related fields of HEV such as DC machine and vehicle system are also included. Various type models and algorithms derived from simulation and experiment are explained in details. The performances of the various combination of HEV system are summarized in the table along with relevant references. This paper provides comprehensive survey of hybrid electric vehicle on their source combination, models, energy management system (EMS) etc. developed by various researchers. From the rigorous review, it is observed that the existing technologies more or less can capable to perform HEV well; however, the reliability and the intelligent systems are still not up to the mark. Accordingly, this review have been lighted many factors, challenges and problems sustainable next generation hybrid vehicle. © 2013 Elsevier Ltd.

Hannan M.A.,National University of Malaysia | Azidin F.A.,National University of Malaysia | Azidin F.A.,Hang Tuah University | Mohamed A.,National University of Malaysia
Energy Conversion and Management | Year: 2012

This paper presents the multi-sources energy models and ruled based feedback control algorithm of an energy management system (EMS) for light electric vehicle (LEV), i.e., scooters. The multiple sources of energy, such as a battery, fuel cell (FC) and super-capacitor (SC), EMS and power controller, DC machine and vehicle dynamics are designed and modeled using MATLAB/SIMULINK. The developed control strategies continuously support the EMS of the multiple sources of energy for a scooter under normal and heavy power load conditions. The performance of the proposed system is analyzed and compared with that of the ECE-47 test drive cycle in terms of vehicle speed and load power. The results show that the designed vehicle's speed and load power closely match those of the ECE-47 test driving cycle under normal and heavy load conditions. This study's results suggest that the proposed control algorithm provides an efficient and feasible EMS for LEV. © 2012 Elsevier Ltd. All rights reserved.

Sutikno T.,Ahmad Dahlan University | Sutikno T.,University of Technology Malaysia | Idris N.R.N.,University of Technology Malaysia | Jidin A.,Hang Tuah University
Renewable and Sustainable Energy Reviews | Year: 2014

The first and the most important step in solving the environmental problems created by cars with internal combustion engines is research and development of electric vehicles. Selection of a proper drive and optimal control strategy of electric vehicles are the major factors to obtain optimal energy management in order to extend the running distance per battery charge. This paper presents a brief review of direct torque control (DTC) of induction motors (IM) as well as its implementation for electric vehicle (EV) applications. First, the basic DTC technique based on hysteresis controllers will be introduced, and then an overview of the major problems in a basic DTC scheme will be presented and explained, as well as some efforts for improving the technique. The main section presents a critical review of DTC for EV applications, taking into consideration the vehicle mechanics and aerodynamics of electric vehicles. The review is very important to provide guidelines and insights for future research and development on the DTC of IM drives for sustainable reliability and energy efficient EV applications. © 2014 Published by Elsevier Ltd. All rights reserved.

Tokit E.M.,Hang Tuah University | Mohammed H.A.,University of Technology Malaysia | Yusoff M.Z.,University of Tenaga Nasional
International Communications in Heat and Mass Transfer | Year: 2012

An interrupted microchannel heat sink (IMCHS) using nanofluids as working fluids is analyzed numerically to increase the heat transfer rate. The rectangular IMCHS is designed with length and width of 10mm and 0.057mm respectively while optimum cut section number, n c=3. The three dimensional governing equations (continuity, momentum and energy) were solved using finite volume method (FVM). Parametric study of thermal performance between pure water-cooled and nanofluid-cooled IMCHS are evaluated for particle diameter in the range of, 30nm to 60nm, volume fraction in the range of, 1% to 4%,nanofluid type of Al 2O 3, CuO, and SiO 2 at Reynolds number range of 140 to 1034 are examined. The effects of the transport properties, nanofluid type, nanoparticle volume fraction and particle diameter are investigated on the IMCHS performance. It is inferred that the Nu number for IMCHS is higher than the conventional MCHS with a slight increase of the pressure drop. It is found that highest thermal augmentation is predicted for Al 2O 3, followed by CuO, and finally for SiO 2 in terms of Nu nf/Nu pw in the IMCHS. The Nu number increased with the increase of nanoparticle volume fraction and with the decrease of nanoparticle diameter. © 2012 Elsevier Ltd.

Othmana I.S.,Hang Tuah University
Key Engineering Materials | Year: 2016

The time-transition curve of open circuit potential (Eoc) during the single zincating process of aluminium alloy 7075 (AA7075) was recorded. Then, a suitable single zincating duration was selected from the Eoc slope, in order to get the optimum zincating duration. The evolution of surface morphology and composition of AA7075 substrate at various single zincating durations were characterized by scanning electron microscopy (SEM) and energy dispersive analysis of x- rays (EDX). The coating adhesions of single zincated samples produced at various durations were investigated using a scratch tester. SEM results showed that the substrates produced at a longer zincating duration were fully covered by a dense layer of zinc particles. The adhesion of the electrodeposited nickel on single zincated samples produced at longer zincating duration was higher than the conventional single zincating process. This morphology has contributed to the improvement of coating adhesion. © 2016 Trans Tech Publications, Switzerland.

Ahmad A.,Hang Tuah University
Procedia Engineering | Year: 2013

This study presents simulation of land cover classification for RazakSAT satellite. The simulation makes use of the spectral capability of Landsat 5 TM satellite that has overlapping bands with RazakSAT. The classification is performed using Maximum Likelihood (ML), a supervised classification method that is based on the Bayes theorem. ML makes use of a discriminant function to assign pixel to the class with the highest likelihood. Class mean vector and covariance matrix are the key inputs to the function and are estimated from the training pixels of a particular class. The accuracy of the classification for the simulated RazakSAT data is accessed by means of a confusion matrix. The results show that RazakSAT tends to have lower overall and individual class accuracies than Landsat mainly due to the unavailability of mid-infrared bands that hinders separation between different plant types. © 2013 The Authors.

Ifayefunmi O.,Hang Tuah University
Ocean Engineering | Year: 2015

The paper examines the effect of material modeling behavior on the elastic-plastic buckling of relatively thick unstiffened steel cones subjected to axial compression. Cones are assumed to be made from mild steel with radius-to-thickness ratio, (r2/t) of 34.3 and cone angle of 26.56°. Three material models were considered: (i) elastic-perfectly plastic, (ii) engineering stress-strain and (iii) true stress true strain. The accuracy of numerical predictions as compared to experimental results was seen to be strongly dependent on the material modeling strategy. Plastic mechanism design approach previously proposed for cones under axial compression was modified to widen the range of its applicability by catering for the effect of excessive plastic deformation. The proposed model utilizes the concept of true stress true strain nature of constitutive equation in determining the squash load. Predictions of collapse load given by the modified constitutive model were compared with initial plastic mechanism design approach and available design codes (API, ECCS, and ASME code case 2286-2) for published experimental data on axially compressed unstiffened steel cones in the elastic-plastic range. Results indicate that the proposed model gives much better predictions of load carrying capacity than both the initial design approach and the available design codes. © 2015 Elsevier Ltd. All rights reserved.

Putra A.,Hang Tuah University | Thompson D.J.,University of Southampton
Journal of Sound and Vibration | Year: 2011

The accurate prediction of sound radiation from plate-like structures remains a challenging problem. Although the case of a plate set in a rigid baffle can be solved analytically, when the plate radiates sound into free space the problem is more difficult to solve; nevertheless, several approaches have been proposed to determine the sound radiation from an unbaffled plate. The present study extends the consideration to the situation of an unbaffled plate which is located close to a rigid reflecting surface. For this purpose, Laulagnets model for the radiation efficiency of an unbaffled plate is extended by modifying the Greens function to include an image source due to the reflecting surface. The results show that, depending on the distance between the plate and the rigid surface, the radiation efficiency is considerably reduced at low frequencies. Additional reduction of sound radiation can be achieved by introducing perforation to the plate. However, at higher frequencies, the radiation efficiency is amplified relative to that for the plate in the absence of the rigid surface, both with and without perforation. These results have also been validated experimentally. © 2011 Elsevier Ltd.

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