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Articles by A. Mohamed
Total Records ( 14 ) for A. Mohamed
  A. Mohamed , B. Jamilah , K.A. Abbas , R. Abdul Rahman and K. Roselina
  This study was a part of a research project aiming to investigate the texture characteristics of protein - starch interaction in fish based product keropok lekor. Accordingly, the current review study focused on some physicochemical (molecular weight, viscosity, chemical composition and swelling power) and thermorheological (gelatinization, retrogradation and viscoelsticity) characteristics of sago starch alone and in mixtures with other ingredients such as sucrose, salts and hydroclloids. The inferred outcome of this extensive survey revealed that the gelatinisation temperature for sago-water mixture ranged from 69.4-70.1°C which was low compared to sweet potato, tania and yam starches. The role of using hydrocolloids in starch-based foods was to control the rheological properties as well as modifying the texture of the products, enhaning or modifying the gelatinization and retrogradation behaviour and improving water-holding capacity of the system. In the presence of sucrose or sodium chloride, the gelatinisation temperatures of sago starch shifted to higher temperatures and its enthalpy decreased. The addition of salts caused an elevation or depression of gelatinization temperature and gelatinization enthalpy, depending on their types and concentrations used. However, sodium chloride appeared to exhibit a maximum inhibitory effect on starch gelatinisation at a concentration of 6-9%.
  Abbas K.A. , A. Mohamed , A.S. Abdulamir and H.A. Abas
  This review study summarized the Supercritical Fluid Extraction (SFE) as new analytical method. The advantage and disadvantage of CO2 (SC-CO2 )as well as special applications of SFE in food processing such as removal of fat from food, enrichment of vitamin E from natural sources, removal of alcohol from wine and beer, encapsulation of liquids for engineering solid products and extraction and characterization of functional compounds were also highlighted. The study also covered the application of SFE in food safety such as rapid analysis for fat content, rapid analysis for pesticides in foods as well as the recent applications of SFE in food such as supercritical particle formation and nan particle formation and ssupercritical drying. The outcome finding confirmed that SFE was found to be advance, fast, reliable, clean and cheap methods for routine food analysis.
  K.A. Abbas , A. Mohamed , B. Jamilah and M. Ebrahimian
  Freshness of fish in most markets was found to be the significant quality parameter. The state of fish freshness was assessed by various methods but most of them were costly, time-consuming and not user friendly tools which made the development of simple, easy, undemanding and reliable system for the evaluation of fish freshness unresolved goal. The findings of many researchers revealed that there was remarkable correlation between the pH and the fish freshness which suggested that this physical characteristic could be used as suitable tool for the analysis and fish freshness evaluation rather than sensory evaluation method which inherent many uncertainties. Based on this demand, this paper was established with the objective of reviewing the literature which focused on the pH as one of the simple and reliable freshness indicator for cold stored fish samples.
  M.A. Hannan , A. Mohamed , A. Hussain and Majid al Dabbay
  This study describes the derivation of an analytical model and simulation for the unified series-shunt compensator (USSC) for investigating power quality in power distribution system. The USSC simulation comprises of two 12-pulse inverters which were connected in series and in shunt with the system. A generalized sinusoidal pulse width modulation (SPWM) switching technique was developed in the proposed controller for fast control action of the USSC. Simulations were carried out using the PSCAD/EMTDC electromagnetic transient programs to examine the performance of the USSC model. Simulation results from the proposed model demonstrated the performance of the USSC and its effectiveness for voltage sag compensation, flicker reduction, voltage unbalance mitigation, power flow control and harmonics elimination.
  Ensaf G. Taha , A. Mohamed , K.K. Srivastava and P.G. Reddy
  The main objective of this study was to standardize and compare rapid methods for the detection of Salmonella in meat samples using Immuno-Magnetic Separation (IMS) followed by culturing in CHROMagar Plus media, Enzyme-Linked Immunosorbent Assay (ELISA) and Real-Time Polymerase Chain Reaction (RT-PCR). Ten-fold dilutions of bacterial suspension (S. typhymurium, ATCC13311) were prepared from the original concentration of 1.6 x 106cfu/ml. Chicken wing samples of 25 g each negative for Salmonella were spiked with six different concentrations of bacteria ranging from 106 to 101. These samples were incubated in buffered peptone water for 4 h as pre-enrichment step and were tested repeatedly. The IMS technique involved the use of paramagnetic polystyrene microscopic beads coated with purified antibodies against Salmonella. The CHROMagar Plus media containing chromomeric substrate facilitated detection of Salmonella species from other flora. The Assurance EIA Salmonella Kit with polyclonal antibodies directed against Salmonella facilitated easy and rapid detection. In the RT-PCR primers targeting invA gene was used which amplified a 378 bp fragment. Comparing to conventional culture method (4 days), CHROMagar plate culture following IMS showed light mauve to mauve-colored colonies of Salmonella in 23 h with high sensitivity (99%) at 1.6 cfu/ml. IMS-ELISA combination also showed high sensitivity (75%) at 1.6 x 103 cfu/ml in 8 h and minimized cross-reactivity with many Enterobacteraceae. The combination of IMS with RT-PCR took less than 7 h and was even more sensitive (100%) at 1.6 cfu/ml. Sensitivities of IMS-RT-PCR and IMS-CHROMagar were higher compared to IMS-ELISA. IMS-CHROMagar was easier to perform and detects only living Salmonella. These methods will be highly suitable for routine detection and may significantly assist the processing industry in avoiding costly recalls and the timely investigation of outbreaks.
  M.F. Faisal and A. Mohamed
  This study presents a relatively new technique for the identification of multiple power quality disturbances recorded in industrial power systems in Malaysia. The new technique, which was developed based on the S-transform and the rule-based classification technique, was evaluated for its’ functionality in the identification of both single and multiple power quality disturbances. Sixty numbers of single disturbances and ninety seven numbers of multiple power quality disturbances were used in the evaluation tests. The results of both tests showed that the new technique has a perfect accuracy in the identification of all types of disturbances. Based on these results, this new technique has the potential to be used in the existing on-line power quality monitoring system in Malaysia to expedite the analysis on the recorded disturbance waveforms.
  Tamer T.N. Khatib , A. Mohamed , R.J. Khan and N. Amin
  This study presents a novel electromechanical controller that tracks the sun direction in order to maximize the solar system output and therefore reduces the cost of the KWh produced by PV systems. The electrical part of this controller consists of a stepper motor driven by a PIC and motor driving circuit. This controller is based on an open loop tracking algorithm that depends on a mathematical module to calculate the optimum tilt angle at which the installed collector should be slanted to collect the maximum radiation. A gear system has been attached to the stepper motor shaft to step up the motor torque in order to move the collector along the desired direction. Malaysia, a tropical country, which usually faces a lot of cloudy days has been considered as the case study. A MATLAB simulation has been developed and a PIC positioning controller has been implemented to compare the real sun angle with the proposed controller in order to estimate the system feasibility.
  M.A. Hannan , A. Hussain , A. Mohamed and S.A. Samad
  The main objective of the study is to analyze Tire Pressure Monitoring System (TPMS) data that contributes significantly towards the enhancement of the intelligent vehicle performance evaluation. TPMS pressure and temperature data were collected from the prototype model of the MEMS Tire Pressure Module (TPM) that was fitted on to an intelligent tire rim through its receiver. In this study, we are focusing only analytical data analysis of TPMS. In the analytical study, a novel method for data classification, goodness of fit and hypothesis testing was proposed. A classification scheme was employed to classify the temperature and pressure data based on ID at the quadrant basis operating zone of the Front Right (FR), Front Left (FL), Rear Left (RL) and Rear Right (RR) tires. Principle Component Analysis (PCA) with polynomial fitting for exploring goodness of fit of tire data was also applied. Finally, hypothesis testing using Satterthwaite statistic was carried out. Results obtained are in agreement with the null hypothesis and as such validate the usefulness of the TPMS system in maintaining and enhancing vehicle performance.
  H. Zayandehroodi , A. Mohamed , H. Shareef and M. Mohammadjafari
  High penetration of Distributed Generation (DG) units will have unfavorable impacts on the traditional fault location methods because the distribution system is no longer radial in nature and is not supplied by a single main power source. This study presents an automated fault location method using Radial Basis Function Neural Network (RBFNN) for a distribution system with DG units. In the proposed method, the fault type is determined first by normalizing the fault currents of the main source. Then to determine the fault location, two RBFNNs have been developed for various fault types. The first RBFNN is used for detraining fault distance from each source and the second RBFNN is used for identifying the exact faulty line. Several case studies have been used to verify the accuracy of the method. Furthermore, the results of RBFNN and the conventional Multi Layer Perception Neural Network (MLPNN) are also compared. The results showed that the proposed method can accurately determine the location of faults in a distribution system with several DG units.
  R. Sirjani , A. Mohamed and H. Shareef
  Capacitors in power systems are generally used to supply reactive power for the purpose of loss minimization and voltage profile improvement. The appropriate placement of capacitors is also important so as to ensure that system power loss and total capacitor costs can be reduced. The main objective of this study is to determine optimal placement of capacitors so as to reduce the power loss and improve the voltage profile. Presently, the capacitor placement problem is widely solved by using heuristic optimization methods. In this study, the Harmony Search (HS) algorithm which is a relatively new meta-heuristic method is applied to solve the optimal capacitor placement problem. An effective and simple power flow method based on the backward/forward sweep power flow is also employed for the power flow simulations. The performance of the proposed HS algorithm is validated on the 9 and 34-bus radial distribution systems and the obtained capacitor placement results using HS are compared with other optimization methods.
  M. Marsadek , A. Mohamed and Z.M. Norpiah
  Power system security assessment based on the concept of risk is required in the current power environment. In risk based static security assessment, the likelihood and severity of security violation are the two main factors that determine the security level of a power system. The objectives of this study was to perform a feasibility study of non-sequential Monte Carlo in probability estimation of contingency and provides an indepth interpretation of risk index value by classifying the risk into low, medium and high risk operating point. The probability estimation of contingency that causes security violation is determined using non-sequential Monte Carlo simulation. In this approach, the continuous severity function is used due to its ability to capture both near violating and violating impact of a contingency. A risk classification technique is also developed so as to provide a qualitative interpretation of the risk index value by classifying the risk as low, medium and high degree of risk. Implementation of the feasibility study of the proposed approach to determine the probabilistic risk in risk based static security assessment using the non-sequential Monte Carlo simulation and to classify the risk has been demonstrated on the IEEE RTS-96 test system.
  M. Farhoodnea , A. Mohamed and H. Shareef
  This study presents a method for determining the contribution of harmonic distortions generated by utility and customer at the Point of Common Coupling (PCC) in power distribution systems. The method is known as the RLC method as the customer load is modeled with RLC components using measured voltage and current at the PCC and the system is represented by a Norton equivalent circuit. The contributions of harmonic voltage and current distortions from utility and customer sides of the system are derived by estimating the customer impedance and then calculating the harmonic currents at customer and utility sides. Several case studies have been made to verify the accuracy of the proposed RLC method in determining the contribution of utility and customer harmonic distortions by making a comparison with the IEEE1459–2000 standard based method. Results showed that the proposed RLC method can accurately determine the harmonic contributions of utility and customer for measurements made at the PCC.
  R. Wahab , A. Mohamed , M.T. Mustafa and A. Hassan
  Two age-groups (2 and 4 years old culms) of cultivated Bambusa vulgaris Schrad. were harvested and investigated for their physical characteristics and anatomical properties. The physical characteristics did not show significant differences between both the 2 and 4 year-old bamboo. However, variation in anatomical properties was observed between the two age-group bamboos. The anatomical structure in bamboo has a very strong correlation with the age, location where the samples were taken, moisture content and the basic density. The basic density is higher in the 4 year-old culms than in the 2 year-old by 5 to 8% and increases from lower to upper internodes showing that there is a maturation process going on between the two age-groups relative to the two of tissue types. The frequency of vascular bundles is greater at the bottom and top portion than in the middle portion of both age-groups. There was no difference in vessel diameter between the 2 and 4 year-old culms at the middle of the culms wall thickness. The cell wall thickness of both parenchyma and fibre were greater in the 4 year-old than in the 2 year-old culms.
  M.A. Hannan , R.A. Begum , M.F. Romely , A. Mohamed and A. Hussain
  The Power Quality (PQ) is one of the main issues in the Malaysian industries. The issue is not just a power quality but also loss of profit as well. Thus, the industrial PQ problem is an important area of research in term of classification, assessment and awareness development. This study developed a framework of survey design, data collection and an analytical model for the statistical classification of the PQ problem and its severity level in Malaysia based on the practical perception of industrial respondents. A statistical classification is done by affected equipments and the matching correlation value between PQ severity level and the normalization duration. The identified PQ Severity Factors (PQSF) are considered for different types of equipment for industrial PQ problem. The findings will assist in the formulation of appropriate policies that address the industrial PQ problem in Malaysia as well as indirectly improving the industrial PQ in the country.
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