DSpaceCRIS@UNITENThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.http://dspace.uniten.edu.my/jspui2019-04-25T20:06:17Z2019-04-25T20:06:17Z50701A new experiential learning electromagnetism-like mechanism for numerical optimizationTan, J.D.Dahari, M.Koh, S.P.Koay, Y.Y.Abed, I.A.http://dspace.uniten.edu.my/jspui/handle/123456789/57802018-01-02T08:08:33Z2017-01-01T00:00:00ZTitle: A new experiential learning electromagnetism-like mechanism for numerical optimization
Authors: Tan, J.D.; Dahari, M.; Koh, S.P.; Koay, Y.Y.; Abed, I.A.
Abstract: The Electromagnetism-like Mechanism algorithm (EM) is a population-based search algorithm which has shown good achievements in solving various types of complex numerical optimization problems so far. To date, the study on experience-based local search mechanism is relatively limited, and there is no study in the literature to integrate experience-based features into the EM. This work introduces an experience-learning feature into the EM for the first time. A new Experiential Learning Electromagnetism-like Mechanism algorithm (ELEM) is proposed in this paper. The ELEM is integrated with two new components. The first component is the particle memory concept which allows the particles to remember the details of their past search experience. The second component is the experience analysing and decision making mechanisms which enables the particles to adjust the settings for the coming iterations. Combining the advantages of this strong exploitation strategy and the powerful exploration mechanism of the EM, the proposed ELEM strikes a good balance in providing well diversified solutions with high accuracy. The results from extensive numerical experiments carried out using 21 challenging test functions show that ELEM is able to provide very competitive solutions and significantly outperforms other optimization techniques. It can thus be concluded from the results that the proposed ELEM performs well in solving high dimensional numerical optimization problems. © 2017 Elsevier Ltd
2017-01-01T00:00:00ZAnalysis of the effect of search step size on the accuracy and convergence properties of electromagnetism-like mechanism algorithmTan, J.D.Dahari, M.Koh, S.P.Koay, Y.Y.Abed, I.A.http://dspace.uniten.edu.my/jspui/handle/123456789/57812018-01-02T08:18:04Z2017-01-01T00:00:00ZTitle: Analysis of the effect of search step size on the accuracy and convergence properties of electromagnetism-like mechanism algorithm
Authors: Tan, J.D.; Dahari, M.; Koh, S.P.; Koay, Y.Y.; Abed, I.A.
Abstract: An Electromagnetism-like Mechanism algorithm (EM) is a metaheuristic search algorithm known for its ability to solve complex global optimization problems. In a standard EM, the size of the search steps is randomly determined. In this paper, an investigation is carried out to analyze the effects of search step size on the overall convergence performance of EM. A standard EM is modified into two different sets of algorithms with different extremes of search step sizes. The modified algorithms are then tested in 10 standard benchmark functions to evaluate the effect of search step sizes on the performance of each. The results show that the modified EM with smaller search steps performed a much more detailed search for possible solutions in all dimensions. This enabled the overall convergence to achieve relatively higher accuracy in objective values. ©2017 Old City Publishing, Inc.
2017-01-01T00:00:00ZA scalable hybrid decision system (HDS) for Roman word recognition using ANN SVM: study case on Malay word recognitionAl-Boeridi, O.N.Syed Ahmad, S.M.Koh, S.P.http://dspace.uniten.edu.my/jspui/handle/123456789/57872018-01-03T01:44:18Z2015-01-01T00:00:00ZTitle: A scalable hybrid decision system (HDS) for Roman word recognition using ANN SVM: study case on Malay word recognition
Authors: Al-Boeridi, O.N.; Syed Ahmad, S.M.; Koh, S.P.
Abstract: An off-line handwriting recognition (OFHR) system is a computerized system that is capable of intelligently converting human handwritten data extracted from scanned paper documents into an equivalent text format. This paper studies a proposed OFHR for Malaysian bank cheques written in the Malay language. The proposed system comprised of three components, namely a character recognition system (CRS), a hybrid decision system and lexical word classification system. Two types of feature extraction techniques have been used in the system, namely statistical and geometrical. Experiments show that the statistical feature is reliable, accessible and offers results that are more accurate. The CRS in this system was implemented using two individual classifiers, namely an adaptive multilayer feed-forward back-propagation neural network and support vector machine. The results of this study are very promising and could generalize to the entire Malay lexical dictionary in future work toward scaled-up applications. © 2015, The Natural Computing Applications Forum.
2015-01-01T00:00:00ZOptimization of the Time of Task Scheduling for Dual Manipulators using a Modified Electromagnetism-Like Algorithm and Genetic AlgorithmAbed, I.A.Koh, S.P.Sahari, K.S.M.Jagadeesh, P.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/66832018-01-03T01:52:13Z2014-01-01T00:00:00ZTitle: Optimization of the Time of Task Scheduling for Dual Manipulators using a Modified Electromagnetism-Like Algorithm and Genetic Algorithm
Authors: Abed, I.A.; Koh, S.P.; Sahari, K.S.M.; Jagadeesh, P.; Tiong, S.K.
Abstract: A method based on a modified electromagnetism-like with two-direction local search algorithm (MEMTDLS) and genetic algorithm (GA) is proposed to determine the optimal time of task scheduling for dual-robot manipulators. A GA is utilized to calculate the near-optimal task scheduling for both robots, and the MEMTDLS is recommended as a suitable alternative in obtaining multiple solutions at each task point for both manipulators with minimal error. During the course of the tour, the robots move from point to point with a short cycle time, while ensuring that no collision occurs between the two manipulators themselves or between the dual manipulators and the static obstacles in the workspace. The movement and the configurations of the manipulators at the task points were illustrated using a simulator that was developed via Visual Basic.Net. The method is verified using two simulators that are used as examples for two identical four-link planar robots that work in the environment, with square-shaped obstacles cluttered at different locations. © 2014 King Fahd University of Petroleum and Minerals.
2014-01-01T00:00:00ZSolving the inverse kinematics for robot manipulators using modified electromagnetism-like algorithm with record to record travelAbed, I.A.Koh, S.P.Sahari, K.S.M.Tiong, S.K.Tan, N.M.L.http://dspace.uniten.edu.my/jspui/handle/123456789/57892018-01-03T01:49:09Z2014-01-01T00:00:00ZTitle: Solving the inverse kinematics for robot manipulators using modified electromagnetism-like algorithm with record to record travel
Authors: Abed, I.A.; Koh, S.P.; Sahari, K.S.M.; Tiong, S.K.; Tan, N.M.L.
Abstract: A new modification of Electromagnetism-like (EM) algorithm which incorporating the Record-to-Record Travel (RRT) local search algorithm; namely MEMR has been developed to solve the problem of Inverse Kinematics (IK) for a four Degree-of-Freedom (DOF) manipulator. The proposed method is able to generate multiple robot configurations for the IK test performed at different end effect or positions. In addition, the comparison between the proposed MEMR and Genetic Algorithm (GA) was carried out using two mathematical test functions; De Jong and Rastrigin. The tests results show that the proposed MEMR is comparable in performance to GA in terms of both convergence speed and error rate. © Maxwell Scientific Organization, 2014.
2014-01-01T00:00:00ZModified Direct torque control using algorithm control of stator flux estimation and space vector modulation based on fuzzy logic control for achieving high performance from induction motorsRashag, H.F.Koh, S.P.Abdalla, A.N.Tan, N.M.L.Chong, K.H.http://dspace.uniten.edu.my/jspui/handle/123456789/57962018-01-03T02:09:18Z2013-01-01T00:00:00ZTitle: Modified Direct torque control using algorithm control of stator flux estimation and space vector modulation based on fuzzy logic control for achieving high performance from induction motors
Authors: Rashag, H.F.; Koh, S.P.; Abdalla, A.N.; Tan, N.M.L.; Chong, K.H.
Abstract: Direct torque control based on space vector modulation (SVM-DTC) protects the DTC transient merits. Furthermore, it creates better quality steady-state performance in a wide speed range. The modified method of DTC using SVM improves the electrical magnitudes of asynchronous machines, such as minimizing the stator current distortions, the stator flux with electromagnetic torque without ripple, the fast response of the rotor speed, and the constant switching frequency. In this paper, the proposed method is based on two new control strategies for direct torque control with space vector modulation. First, fuzzy logic control is used instead of the PI torque and a PI flux controller to minimizing the torque error and to achieve a constant switching frequency. The voltages in the direct and quadratic reference frame (Vd, V q) are achieved by fuzzy logic control. In this scheme, the switching capability of the inverter is fully utilized, which improves the system performance. Second, the close loop of stator flux estimation based on the voltage model and a low pass filter is used to counteract the drawbacks in the open loop of the stator flux such as the problems saturation and dc drift. The response of this new control strategy is compared with DTC-SVM. The experimental and simulation results demonstrate that the proposed control topology outperforms the conventional DTC-SVM in terms of system robustness and eliminating the bad outcome of dc-offset.
2013-01-01T00:00:00ZAvoiding self nulling by using linear constraint minimum variance beamforming in smart antennaSalem, B.Tiong, S.K.Koh, S.P.Darzi, S.http://dspace.uniten.edu.my/jspui/handle/123456789/57982018-01-03T02:43:17Z2013-01-01T00:00:00ZTitle: Avoiding self nulling by using linear constraint minimum variance beamforming in smart antenna
Authors: Salem, B.; Tiong, S.K.; Koh, S.P.; Darzi, S.
Abstract: The beam forming technique is important in smart antenna systems to enhance the data rates, null steering and coverage. This study presents two methods of beamformeing algorithm; Minimum Variance Distortion less Response (MVDR) and Linear Constraint Minimum Variance (LCMV). MVDR and LCMV techniques form radiation beams based on the received weight vector of the desired signal. The LCMV technique is found to be efficient than the MVDR in self-null even if the interference signal is closer from the desired signal. Simulation has been carried out to validate these two techniques. The four elements of the linear array smart antenna are used in our simulation program with the operation frequency around 2.3 GHz, noise power 0.5dB and the spacing between elements is 0.5 λ. The result of the simulation reveals that both the modes are capable of providing high output power; however they need the direction of all the incoming sources, which is practically difficult to obtain. Nevertheless the MVDR beam forming minimizes the multi-path fading problem, by adding the multi-path signal, which increases the strength of the desired signal and nullifies the interference. © Maxwell Scientific Organization, 2013.
2013-01-01T00:00:00ZComparison between genetic algorithm and electromagnetism-like algorithm for solving inverse kinematicsAbed, I.A.Koh, S.P.Mohamed Sahari, K.S.Tiong, S.K.Yap, D.F.W.http://dspace.uniten.edu.my/jspui/handle/123456789/58042018-01-03T03:46:34Z2012-01-01T00:00:00ZTitle: Comparison between genetic algorithm and electromagnetism-like algorithm for solving inverse kinematics
Authors: Abed, I.A.; Koh, S.P.; Mohamed Sahari, K.S.; Tiong, S.K.; Yap, D.F.W.
Abstract: A comparison study between Electromagnetism-Like Algorithm (EM) and Genetic Algorithm (GA) has been presented in this work to solve the Inverse Kinematics (IK) of a four-link planar robot manipulator. The comparison is focused on some points for both algorithms like the accuracy of the results and the speed of convergence. Different target points have been taken to check the performance of each algorithm to solve the IK problem. The results showed that EM algorithm needs less population size and number of generations to get the true solution. There are multiple robot configurations at the goal points and both algorithms are able to find these solutions at each point. Self developed software simulator is used to display some of these solutions at each goal position. © IDOSI Publications, 2012.
2012-01-01T00:00:00ZA hybrid artificial immune systems for multimodal function optimization and its application in engineering problemYap, D.F.W.Koh, S.P.Tiong, S.K.Prajindra, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/59982018-01-03T03:43:27Z2012-01-01T00:00:00ZTitle: A hybrid artificial immune systems for multimodal function optimization and its application in engineering problem
Authors: Yap, D.F.W.; Koh, S.P.; Tiong, S.K.; Prajindra, S.K.
Abstract: Lately, the field of Artificial Immune Systems (AIS) has attracted wide attention among researchers as the algorithm is able to improve local searching ability and efficiency. However, the rate of convergence for AIS is rather slow as compared to other Evolutionary Algorithms. Alternatively, Particle Swarm Optimization (PSO) has been used effectively in solving complicated optimization problems with simple coding and lesser parameters, but it tends to converge prematurely. Thus, the good features of AIS and PSO are combined in ordertoreduce their shortcomings. By comparing the optimization results of the mathematical functions and the engineering problem using hybrid AIS (HAIS) and AIS, it is observed that HAIS has better performances in terms of accuracy, convergence rate and stability. © Springer Science+Business Media B.V. 2011.
2012-01-01T00:00:00ZGlobal optimal analysis of variant genetic operations in solar trackingFam, D.F.Koh, S.P.Tiong, S.K.Chong, K.H.http://dspace.uniten.edu.my/jspui/handle/123456789/58102018-01-03T07:10:15Z2012-01-01T00:00:00ZTitle: Global optimal analysis of variant genetic operations in solar tracking
Authors: Fam, D.F.; Koh, S.P.; Tiong, S.K.; Chong, K.H.
Abstract: Genetic Algorithms (GAs), Evolution Strategies (ES), Evolutionary Programming (EP) and Genetic Programming (GP) are some of the best known types of Evolutionary Algorithm (EA)where it is a class of global search algorithms inspired by natural evolution. Lots of research has been carried out in solar tracking system using different types of Evolutionary Algorithm. In this research, genetic algorithm is explored to maximize the performance of solar tracking system. This work evaluates the best combination of GA parameters by always fine-tuning the position of solar tracking prototype to receive maximum solar radiation. Both software and hardware have been developed to simulate related genetic algorithm results using a combination of variant genetic operators. Under conventional genetic algorithm operation, it is concluded that genetic algorithm with selective clonal mutation is able to produce the best fitness value at 0.98027 with both axles X and Y with inclination of +2 degree to the sun position.
2012-01-01T00:00:00ZPerformance comparison of MVDR and LCMV beamforming algorithm in 2.3 GHz adaptive antenna systemSalem, B.Tiong, S.K.Koh, S.P.Hock, G.C.http://dspace.uniten.edu.my/jspui/handle/123456789/58122018-01-03T07:36:49Z2012-01-01T00:00:00ZTitle: Performance comparison of MVDR and LCMV beamforming algorithm in 2.3 GHz adaptive antenna system
Authors: Salem, B.; Tiong, S.K.; Koh, S.P.; Hock, G.C.
Abstract: The blind beamforming technique is employed in the broadband wireless mobile systems to enhance the cellular systems in the aspect of capacity, data rates, null steering and coverage. This paper presents two methods of beamforming algorithm; Minimum Variance Distortionless Response (MVDR) and Linear Constraint Minimum Variance (LCMV). MVDR and LCMV techniques form radiation beams based on the received weight vector of the desired signal. Simulation has been carried out to validate these two techniques. Four elements of the linear array antenna are used in our simulation program with the carrier frequency around 2.3 GHz, noise power 0.5dB, and the spacing between elements is 0.5 λ. The result of the simulation reveals that both the modes are capable of providing high output power; however direction of all the incoming sources is required, which is practically difficult to obtain. Nevertheless the MVDR beamforming, minimizes the multi-path fading problem, by adding the multi-path signal, which increases the strength of the desired signal and nullifies the interference. Overall, the MVDR technique is more accurate than the LCMV to null to find the interference source and directing radiation lobe with high power towards the desired signal. © 2012 Praise Worthy Prize S.r.l.-All rights reserved.
2012-01-01T00:00:00ZPath selection technique for highly transmission ratio and reliable routing in ManetJassim, H.S.Yussof, S.Tiong, S.K.Chong, K.H.Koh, S.P.http://dspace.uniten.edu.my/jspui/handle/123456789/58192018-01-03T08:12:02Z2011-01-01T00:00:00ZTitle: Path selection technique for highly transmission ratio and reliable routing in Manet
Authors: Jassim, H.S.; Yussof, S.; Tiong, S.K.; Chong, K.H.; Koh, S.P.
Abstract: Mobile ad-hoc network (MANET) is collection of wireless nodes that operates without using a centralized network infrastructure such as a base station. Since the wireless range is limited, the nodes mutually cooperate with their neighbors in order to extend the overall communication range of the network for forwarding packets. Ad-hoc On-demand Distance Vector (AODV) is one of the commonly used protocols in ad-hoc networks. AODV is a dynamic routing protocol that is able to find the shortest path from a source node to a destination node in MANET based on hop count. However, due to the nature of MANET, it is very easy to introduce malicious nodes in MANET. These malicious nodes may try to compromise the routing protocol functionality and make MANET vulnerable to security attacks which lead to unreliable routing. Therefore, security has become a primary concern in providing protected communication among nodes in MANET. In this study, we propose a Reliable Dynamic Trust-based Routing (RDTR) protocol by integrating a trust mechanism with a shortest path routing algorithm for establishing and maintaining trustworthy routes in MANET. © Asian Network for Scientific Information.
2011-01-01T00:00:00ZInvestigation of induction motor parameter identification using particle swarm optimization-based RBF neural network (PSO-RBFNN)Rashag, H.F.Koh, S.P.Tiong, S.K.Chong, K.H.Abdalla, A.N.http://dspace.uniten.edu.my/jspui/handle/123456789/58202018-01-03T08:14:54Z2011-01-01T00:00:00ZTitle: Investigation of induction motor parameter identification using particle swarm optimization-based RBF neural network (PSO-RBFNN)
Authors: Rashag, H.F.; Koh, S.P.; Tiong, S.K.; Chong, K.H.; Abdalla, A.N.
Abstract: High dynamic performance of induction motor drives is required for accurate system information. From the actual parameters, it is possible to design high performance induction motor drive controllers. In this paper, improving the induction motor performance using intelligent parameter identification was proposed. First, machine model parameters were presented by a set of time-varying differential equations. Second, estimation of each parameter was achieved by minimizing the experimental response based on matching of the stator current, voltage and rotor speed. Finally, simulation results demonstrate the effectiveness of the proposed method and great improvement of induction motor performance. © 2011 Academic Journals.
2011-01-01T00:00:00ZArtificial immune system based remainder method for multimodal mathematical function optimizationYap, D.F.W.Koh, S.P.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/58172018-01-04T02:57:20Z2011-01-01T00:00:00ZTitle: Artificial immune system based remainder method for multimodal mathematical function optimization
Authors: Yap, D.F.W.; Koh, S.P.; Tiong, S.K.
Abstract: Artificial immune system (AIS) is one of the nature-inspired algorithm for solving optimization problems. In AIS, clonal selection algorithm (CSA) is able to improve global searching ability compare to other meta-heuristic methods. However, the CSA rate of convergence and accuracy can be further improved as the hyper mutation in CSA itself cannot always guarantee a better solution. Conversely, Genetic Algorithms (GAs) and Particle Swarm Optimization (PSO) have been used efficiently in solving complex optimization problems, but they have an inclination to converge prematurely. In this work, the CSA is modified using the best solutions for each exposure (iteration) namely Single Best Remainder (SBR) - CSA. Simulation results show that the proposed algorithm is able to enhance the performance of the conventional CSA in terms of accuracy and stability for single objective functions. © IDOSI Publications, 2011.
2011-01-01T00:00:00ZA swarm-based artificial immune system for solving multimodal functionsYap, D.F.W.Koh, S.P.Tiong, S.K.Prajindra, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/60002018-01-04T02:47:51Z2011-01-01T00:00:00ZTitle: A swarm-based artificial immune system for solving multimodal functions
Authors: Yap, D.F.W.; Koh, S.P.; Tiong, S.K.; Prajindra, S.K.
Abstract: Artificial Immune Systems (AIS) have attracted enormous attention among researchers because the algorithms are able to improve global searching ability and efficiency. Nevertheless, the rate of convergence for AIS is relatively slow compared to other metaheuristic algorithms. On the other hand, genetic algorithms (GAs) and particle swarm optimization (PSO) have been used successfully in solving optimization problems, although they tend to converge prematurely. Therefore, the good attributes of AIS and PSO are merged in order to reduce this limitation. It is observed that the proposed hybrid AIS (HAIS) achieved better performances in terms of convergence rate, accuracy, and stability against GA and AIS by comparing the optimization results of the mathematical functions. A similar result was achieved by HAIS in the engineering problem when compared to GA, PSO, and AIS. Copyright © 2011 Taylor & Francis Group, LLC.
2011-01-01T00:00:00ZDesign a PID controller of BLDC motor by using hybrid genetic-immuneAli, M.O.Koh, S.P.Chong, K.H.Hamoodi, A.S.http://dspace.uniten.edu.my/jspui/handle/123456789/58262018-01-04T03:32:13Z2011-01-01T00:00:00ZTitle: Design a PID controller of BLDC motor by using hybrid genetic-immune
Authors: Ali, M.O.; Koh, S.P.; Chong, K.H.; Hamoodi, A.S.
Abstract: In this paper hybridization between two optimization methods that are Genetic Algorithm (GA) and Artificial Immune System (AIS) is presented for determining the optimal proportional-integral derivative (PID) controller parameters, for speed control of a linear brushless DC motor. The brushless DC motor is modeled in Simulink and the Hybrid GA-AIS algorithm is implemented in MATLAB. The capability of overcoming the shortcomings of individual algorithms without losing their advantages makes the hybrid techniques superior to the stand-alone ones based on the dominant purpose of hybridization. The Hybrid GA-AIS method has superior features, stable convergence characteristic and good computational efficiency. The results that get it from hybridization are improved compares with that results can get from GA and AIS alone. The hybrid GA-AIS consists of two processes, the first one is a genetic algorithm (GA) is typically initialized population randomly. Hybridization is faster and more accurate compare with GA AIS alone. © Canadian Center of Science and Education.
2011-01-01T00:00:00ZA comparative analysis on the performance of particle swarm optimization and artificial immune systems for mathematical test functionsYap, D.F.W.Koh, S.P.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/58372018-01-05T01:47:01Z2009-01-01T00:00:00ZTitle: A comparative analysis on the performance of particle swarm optimization and artificial immune systems for mathematical test functions
Authors: Yap, D.F.W.; Koh, S.P.; Tiong, S.K.
Abstract: Over the years, the area of Artificial Immune Systems (AIS) has drawn wide attention among researchers as the algorithm is able to enhance local searching ability and efficiency. Alternatively, Particle Swarm Optimization (PSO) has been used effectively in solving optimization problems. This paper compares the optimization results of the mathematical functions using AIS and PSO. The numerical results show that both PSO and AIS give comparable fitness solutions with the former performing about 56 percent faster than the latter. Conversely, for simpler mathematical functions, AIS performs marginally faster than PSO at about 14 percent while maintaining good accuracy of the objective value. © 2009, INSInet Publication.
2009-01-01T00:00:00ZEffects of second order dispersion in free space optical communicationYap, D.F.W.Wong, V.C.Koh, S.P.Tiong, S.K.Mohd Tahir, M.A.E.http://dspace.uniten.edu.my/jspui/handle/123456789/58352018-01-04T08:32:08Z2010-01-01T00:00:00ZTitle: Effects of second order dispersion in free space optical communication
Authors: Yap, D.F.W.; Wong, V.C.; Koh, S.P.; Tiong, S.K.; Mohd Tahir, M.A.E.
Abstract: Free Space Optic (FSO) can be considered as an attractive option to fiber optic. FSO has the capability to go beyond the limit of fiber optics. Unfortunately, due to the effects of dispersion in the atmosphere, FSO, as a point-to-point communication system that requires line-of-sight transmission; suffers from attenuation and signal loss. Thus, practical and detailed research is needed to improve this wireless system. In this study, simulation on FSO propagation using measured parameter values was carried out in order to gain better understanding on the pulse behavior in free space with better level of accuracy. Using MATLAB and experimental parameter values, a more precise model can be obtained and analyzed. This will allow some level of prediction on the behavior of the propagating light pulse in the atmosphere and subsequently the FSO system performance can be further improved. © 2010 Asian Network for Scientific Information.
2010-01-01T00:00:00ZScaling effects on the dynamic characteristics of long-wavelength vertical-cavity surface-emitting lasers (VCSELs)Yap, D.F.W.Koh, S.P.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/58542018-01-08T07:19:38Z2008-01-01T00:00:00ZTitle: Scaling effects on the dynamic characteristics of long-wavelength vertical-cavity surface-emitting lasers (VCSELs)
Authors: Yap, D.F.W.; Koh, S.P.; Tiong, S.K.
Abstract: The influence of the oxide aperture radius on the characteristics of a long-wavelength vertical-cavity surface-emitting laser (VCSEL) lasing at 1550 nm is presented in this paper. While previous works in the literature mostly investigate the scaling effects of short-wavelength VCSELs. The importance of studying the effects of long-wavelength operation should not be underestimated, as it could be used in fiber optics communication to mitigate dispersion and attenuation of the channel. Using the oxide-confined VCSEL model, the dynamic operations were examined taking into account the carrier-noise, photon-noise and phase-noise, including feedback of the external cavity. Our simulations show that by reducing the oxide aperture up to a given optimal radius, an improvement in the device's characteristics can be demonstrated. Below this value, performance degradation is expected due to increased diffraction losses, reduced confinement factor and enhanced spontaneous emission. © 2007 Elsevier Ltd. All rights reserved.
2008-01-01T00:00:00ZAnalysis of In-P based 1.55νm electrically pumped vertical-external- cavity surface-emitting lasersYap, D.F.W.Low, A.L.Y.Koh, S.P.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/58552018-01-08T07:22:15Z2007-01-01T00:00:00ZTitle: Analysis of In-P based 1.55νm electrically pumped vertical-external- cavity surface-emitting lasers
Authors: Yap, D.F.W.; Low, A.L.Y.; Koh, S.P.; Tiong, S.K.
Abstract: In this paper, theoretical analysis of the In-P based 1.55νm electrically pumped vertical-external-cavity surface-emitting lasers is presented. Computational experimental results show that short-cavity VCSELs (vertical-cavity surface-emitting lasers) with weak external feedback exhibit an increase of 37% output power compared with the conventional VCSELs. In addition, with an optimized external feedback, the -3dB modulation bandwidth can be increased by approximately 5% and having a wider eye opening in a 40Gbits-1 transmission system. © IOP Publishing Ltd.
2007-01-01T00:00:00ZPendulum-like algorithm as a local search techniqueAbed, I.A.Koh, S.P.Sahari, K.S.M.Tiong, S.K.Younis, H.A.-K.Abed, A.A.http://dspace.uniten.edu.my/jspui/handle/123456789/69482018-01-11T08:27:25Z2016-01-01T00:00:00ZTitle: Pendulum-like algorithm as a local search technique
Authors: Abed, I.A.; Koh, S.P.; Sahari, K.S.M.; Tiong, S.K.; Younis, H.A.-K.; Abed, A.A.
Abstract: The Pendulum-like algorithm is based on the concepts of the pendulum. All the ideas that are derived have been embedded into the suggested method. The Pendulum-like algorithm introduced, is expected to provide very good results in solving the optimization problems. This is due to the fact that Pendulum-like algorithm is a method with directed force which is reduced gradually with approximation to the global solution and it also uses the idea of back and forth movement to enhance the solution. Thus, the Pendulum-like algorithm would be integrated with the attraction-repulsion mechanism to introduce a very promising problem solving algorithm. The parameters of the proposed algorithm are evaluated and tested to prove the effect of each one on the algorithm. Also, the results of the algorithm are simulated the same behavior for the parameters of physical pendulum. © 2016 IEEE.
2016-01-01T00:00:00ZOptimization of the Time of Task Scheduling for Dual Manipulators using a Modified Electromagnetism-Like Algorithm and Genetic AlgorithmAbed, I.A.Koh, S.P.Sahari, K.S.M.Jagadeesh, P.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/69842018-01-11T08:27:44Z2014-01-01T00:00:00ZTitle: Optimization of the Time of Task Scheduling for Dual Manipulators using a Modified Electromagnetism-Like Algorithm and Genetic Algorithm
Authors: Abed, I.A.; Koh, S.P.; Sahari, K.S.M.; Jagadeesh, P.; Tiong, S.K.
Abstract: A method based on a modified electromagnetism-like with two-direction local search algorithm (MEMTDLS) and genetic algorithm (GA) is proposed to determine the optimal time of task scheduling for dual-robot manipulators. A GA is utilized to calculate the near-optimal task scheduling for both robots, and the MEMTDLS is recommended as a suitable alternative in obtaining multiple solutions at each task point for both manipulators with minimal error. During the course of the tour, the robots move from point to point with a short cycle time, while ensuring that no collision occurs between the two manipulators themselves or between the dual manipulators and the static obstacles in the workspace. The movement and the configurations of the manipulators at the task points were illustrated using a simulator that was developed via Visual Basic.Net. The method is verified using two simulators that are used as examples for two identical four-link planar robots that work in the environment, with square-shaped obstacles cluttered at different locations. © 2014 King Fahd University of Petroleum and Minerals.
2014-01-01T00:00:00ZSolving the inverse kinematics for robot manipulators using modified electromagnetism-like algorithm with record to record travelAbed, I.A.Koh, S.P.Sahari, K.S.M.Tiong, S.K.Tan, N.M.L.http://dspace.uniten.edu.my/jspui/handle/123456789/69852018-01-11T08:27:44Z2014-01-01T00:00:00ZTitle: Solving the inverse kinematics for robot manipulators using modified electromagnetism-like algorithm with record to record travel
Authors: Abed, I.A.; Koh, S.P.; Sahari, K.S.M.; Tiong, S.K.; Tan, N.M.L.
Abstract: A new modification of Electromagnetism-like (EM) algorithm which incorporating the Record-to-Record Travel (RRT) local search algorithm; namely MEMR has been developed to solve the problem of Inverse Kinematics (IK) for a four Degree-of-Freedom (DOF) manipulator. The proposed method is able to generate multiple robot configurations for the IK test performed at different end effect or positions. In addition, the comparison between the proposed MEMR and Genetic Algorithm (GA) was carried out using two mathematical test functions; De Jong and Rastrigin. The tests results show that the proposed MEMR is comparable in performance to GA in terms of both convergence speed and error rate. © Maxwell Scientific Organization, 2014.
2014-01-01T00:00:00ZUsing Electromagnetism-like algorithm and genetic algorithm to optimize time of task scheduling for dual manipulatorsAbed, I.A.Sahari, K.S.M.Koh, S.P.Tiong, S.K.Jagadeesh, P.http://dspace.uniten.edu.my/jspui/handle/123456789/69872018-01-11T08:27:45Z2013-01-01T00:00:00ZTitle: Using Electromagnetism-like algorithm and genetic algorithm to optimize time of task scheduling for dual manipulators
Authors: Abed, I.A.; Sahari, K.S.M.; Koh, S.P.; Tiong, S.K.; Jagadeesh, P.
Abstract: A method based on Electromagnetism-Like algorithm (EM) and Genetic Algorithm (GA) is proposed to determine the time-optimal task scheduling for dual robot manipulators. GA is utilized to calculate the near-optimal task scheduling for the two robots. On top of that, the EM is recommended as a suitable alternative to obtain multiple solutions at each task points for both manipulators with less error. During the course of the tour, the dual robots move from point to point with less cycle time, while ensuring that no collision occurs between the two manipulators or between the dual manipulators and the static obstacles in the workspace. The movement and the configurations of the manipulators at the task points were visualized using a simulator developed via Visual Basic. Net. The method is verified using two simulators acting as examples for two identical four-link planar robots working in the environment, with square-shaped obstacles cluttered at different locations. © 2013 IEEE.
2013-01-01T00:00:00ZComparison between genetic algorithm and electromagnetism-like algorithm for solving inverse kinematicsAbed, I.A.Koh, S.P.Mohamed Sahari, K.S.Tiong, S.K.Yap, D.F.W.http://dspace.uniten.edu.my/jspui/handle/123456789/69942018-01-11T08:27:48Z2012-01-01T00:00:00ZTitle: Comparison between genetic algorithm and electromagnetism-like algorithm for solving inverse kinematics
Authors: Abed, I.A.; Koh, S.P.; Mohamed Sahari, K.S.; Tiong, S.K.; Yap, D.F.W.
Abstract: A comparison study between Electromagnetism-Like Algorithm (EM) and Genetic Algorithm (GA) has been presented in this work to solve the Inverse Kinematics (IK) of a four-link planar robot manipulator. The comparison is focused on some points for both algorithms like the accuracy of the results and the speed of convergence. Different target points have been taken to check the performance of each algorithm to solve the IK problem. The results showed that EM algorithm needs less population size and number of generations to get the true solution. There are multiple robot configurations at the goal points and both algorithms are able to find these solutions at each point. Self developed software simulator is used to display some of these solutions at each goal position. © IDOSI Publications, 2012.
2012-01-01T00:00:00ZAn improved electromagnetism-like algorithm for numerical optimizationTan, J.-D.Dahari, M.Koh, S.-P.Koay, Y.-Y.Abed, I.-A.http://dspace.uniten.edu.my/jspui/handle/123456789/57852018-01-14T23:45:21Z2015-01-01T00:00:00ZTitle: An improved electromagnetism-like algorithm for numerical optimization
Authors: Tan, J.-D.; Dahari, M.; Koh, S.-P.; Koay, Y.-Y.; Abed, I.-A.
Abstract: This paper presents a new Electromagnetism-like Mechanism (EM) algorithm with Split, Probe and Compare feature (SPC-EM). The proposed algorithm replaces the local search segment of a standard EM with a new search scheme named Split, Probe, and Compare (SPC). A nonlinear equation is designed to systematically and dynamically adjust the length of the probes based on the outcome of the Compare segment in each iteration. Extensive computational simulations and comparisons on 10 different benchmark problems from the literature were carried out. Results show that the new modified mechanism outperformed all other algorithms involved in the benchmarking. We thus conclude that the proposed SPC-EM works well with the designed probe-length tuning equation in solving numerical optimization problems. © 2016.
2015-01-01T00:00:00ZNew development of analysis tool for optimizing generation cost with gas emission via an electromagnetism like algorithmAlbert, F.Y.C.Koh, S.P.Chen, C.P.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/57842018-02-08T00:54:56Z2016-01-01T00:00:00ZTitle: New development of analysis tool for optimizing generation cost with gas emission via an electromagnetism like algorithm
Authors: Albert, F.Y.C.; Koh, S.P.; Chen, C.P.; Tiong, S.K.
Abstract: This paper addresses the preliminary new development results of the evolutionary algorithm technique to optimize the formulated problems incorporating the generation cost with emission gas as objective function or constraints. The power generation cost with emission gas are a complex problem which also the major concerns in electric power generation systems in the Environmental or Economic Dispatch Problems (EDP). Thus, due to environmental concern the electrical utilities required to minimize the emission level while optimizing the thermal generating units at a minimum generating cost and hence, satisfying the load demand and the emissions. In this work the electromagnetism-Like algorithm (EML) has been employed for optimizing generation cost and emission constraints economic dispatch problem. The proposed decision analysis tool software in this work will optimize the generation cost with emission gas objective function. The best generation cost with emission gas solution are obtained from different fuel technology via the developed software. © 2016 Penerbit UTM Press. All rights reserved.
2016-01-01T00:00:00ZHigh performance of space vector modulation direct torque control SVM-DTC based on amplitude voltage and stator flux angleRashag, H.F.Koh, S.P.Chong, K.H.Tiong, S.K.Tan, N.M.L.Abdalla, A.N.http://dspace.uniten.edu.my/jspui/handle/123456789/57972018-02-09T01:02:51Z2013-01-01T00:00:00ZTitle: High performance of space vector modulation direct torque control SVM-DTC based on amplitude voltage and stator flux angle
Authors: Rashag, H.F.; Koh, S.P.; Chong, K.H.; Tiong, S.K.; Tan, N.M.L.; Abdalla, A.N.
Abstract: Various aspects related to controlling induction motor are investigated. Direct torque control is an original high performance control strategy in the field of AC drive. In this proposed method, the control system is based on Space Vector Modulation (SVM), amplitude of voltage in direct- quadrature reference frame (d-q reference) and angle of stator flux. Amplitude of stator voltage is controlled by PI torque and PI flux controller. The stator flux angle is adjusted by rotor angular frequency and slip angular frequency. Then, the reference torque and the estimated torque is applied to the input of PI torque controller and the control quadrature axis voltage is determined. The control d-axis voltage is determined from the flux calculator. These q and d axis voltage are converted into amplitude voltage. By applying polar to Cartesian on amplitude voltage and stator flux angle, direct voltage and quadratures voltage are generated. The reference stator voltages in d-q are calculated based on forcing the stator voltage error to zero at next sampling period. By applying inverse park transformation on d-q voltages, the stator voltages in α and β frame are generated and apply to SVM. From the output of SVM, the motor control signal is generated and the speed of the induction motor regulated toward the rated speed. The simulation Results have demonstrated exceptional performance in steadand transient states and shows that decrease of torque and flux ripples is achieved in a complete speed range. © Maxwell Scientific Organization, 2013.
2013-01-01T00:00:00ZDTC-SVM based on PI torque and PI flux controllers to achieve high performance of induction motorRashag, H.F.Tan, N.M.L.Koh, S.P.Abdalla, A.N.Chong, K.H.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/57882018-02-09T00:59:50Z2014-01-01T00:00:00ZTitle: DTC-SVM based on PI torque and PI flux controllers to achieve high performance of induction motor
Authors: Rashag, H.F.; Tan, N.M.L.; Koh, S.P.; Abdalla, A.N.; Chong, K.H.; Tiong, S.K.
Abstract: The fundamental idea of direct torque control of induction machines is investigated in order to emphasize the property produced by a given voltage vector on stator flux and torque variations. The proposed control system is based on Space Vector Modulation (SVM) of electrical machines, Improvement model reference adaptive system, real time of stator resistance and estimation of stator flux. The purpose of this control is to minimize electromagnetic torque and flux ripple and minimizing distortion of stator current. In this proposed method, PI torque and PI flux controller are designed to achieve estimated torque and flux with good tracking and fast response with reference torque and there is no steady state error. In addition, design of PI torque and PI flux controller are used to optimize voltages in d-q reference frame that applied to SVM. The simulation Results of proposed DTC-SVM have complete excellent performance in steady and transient states as compared with classical DTC-SVM. © Maxwell Scientific Organization, 2014.
2014-01-01T00:00:00ZIssues of matrix converters: Technical reviewGhoni, R.Abdalla, A.N.Koh, S.P.Rashag, H.F.Razali, R.http://dspace.uniten.edu.my/jspui/handle/123456789/58232018-03-12T10:03:18Z2011-01-01T00:00:00ZTitle: Issues of matrix converters: Technical review
Authors: Ghoni, R.; Abdalla, A.N.; Koh, S.P.; Rashag, H.F.; Razali, R.
Abstract: Matrix converter is a powerful AC-AC converter for the application of induction motor drives with sinusoidal input currents and no DC-link capacitor. It offers remarkable advantages over other alternatives in applications requiring improved utility interaction and critical weight/volume reduction. This paper presents a technical review on related issues of induction motor drive fed by matrix converters (MC). The first discussions presented the special difficulties involved in matrix converters. These are partly conceptual, partly concerning circuit topology, and current commutation technique. The second discussion analyzes the control and modulation which are of particular interest. The third discussion describes the hardware development modes studies. ©2011 Academic Journals.
2011-01-01T00:00:00ZIssues and temperature compensation techniques for hot wire thermal flow sensor: A reviewKhamshah, N.Abdalla, A.N.Koh, S.P.Rashag, H.F.http://dspace.uniten.edu.my/jspui/handle/123456789/58252018-03-12T10:03:18Z2011-01-01T00:00:00ZTitle: Issues and temperature compensation techniques for hot wire thermal flow sensor: A review
Authors: Khamshah, N.; Abdalla, A.N.; Koh, S.P.; Rashag, H.F.
Abstract: The hot-wire anemometer is used extensively to measure velocity and turbulence quantities. Hot-wire measurement of non-isothermal flows necessitate the use of thermal compensation or error correction. This paper focus of issues and techniques for thermal compensation and error correction in industrial application was studied. Firstly, comprehensive review on the theory of several types of the most commonly used hot-wires anemometry in the field. Secondly, it considered the compensation techniques both in CTA and CCA hot-wire anemometry. Results of compensating techniques are presented for both CTA and CCA and were compare with different techniques. Finally, computational intelligent can be suitable for those systems where it is very complex or impossible to obtain the model by means of classical methods. © 2011 Academic Journals.
2011-01-01T00:00:00ZModified Direct torque control using algorithm control of stator flux estimation and space vector modulation based on fuzzy logic control for achieving high performance from induction motorsRashag, H.F.Koh, S.P.Abdalla, A.N.Tan, N.M.L.Chong, K.H.http://dspace.uniten.edu.my/jspui/handle/123456789/89982018-02-21T04:49:48Z2013-01-01T00:00:00ZTitle: Modified Direct torque control using algorithm control of stator flux estimation and space vector modulation based on fuzzy logic control for achieving high performance from induction motors
Authors: Rashag, H.F.; Koh, S.P.; Abdalla, A.N.; Tan, N.M.L.; Chong, K.H.
Abstract: Direct torque control based on space vector modulation (SVM-DTC) protects the DTC transient merits. Furthermore, it creates better quality steady-state performance in a wide speed range. The modified method of DTC using SVM improves the electrical magnitudes of asynchronous machines, such as minimizing the stator current distortions, the stator flux with electromagnetic torque without ripple, the fast response of the rotor speed, and the constant switching frequency. In this paper, the proposed method is based on two new control strategies for direct torque control with space vector modulation. First, fuzzy logic control is used instead of the PI torque and a PI flux controller to minimizing the torque error and to achieve a constant switching frequency. The voltages in the direct and quadratic reference frame (Vd, V q) are achieved by fuzzy logic control. In this scheme, the switching capability of the inverter is fully utilized, which improves the system performance. Second, the close loop of stator flux estimation based on the voltage model and a low pass filter is used to counteract the drawbacks in the open loop of the stator flux such as the problems saturation and dc drift. The response of this new control strategy is compared with DTC-SVM. The experimental and simulation results demonstrate that the proposed control topology outperforms the conventional DTC-SVM in terms of system robustness and eliminating the bad outcome of dc-offset.
2013-01-01T00:00:00ZHigh performance of space vector modulation direct torque control SVM-DTC based on amplitude voltage and stator flux angleRashag, H.F.Koh, S.P.Chong, K.H.Tiong, S.K.Tan, N.M.L.Abdalla, A.N.http://dspace.uniten.edu.my/jspui/handle/123456789/89992018-02-21T04:49:49Z2013-01-01T00:00:00ZTitle: High performance of space vector modulation direct torque control SVM-DTC based on amplitude voltage and stator flux angle
Authors: Rashag, H.F.; Koh, S.P.; Chong, K.H.; Tiong, S.K.; Tan, N.M.L.; Abdalla, A.N.
Abstract: Various aspects related to controlling induction motor are investigated. Direct torque control is an original high performance control strategy in the field of AC drive. In this proposed method, the control system is based on Space Vector Modulation (SVM), amplitude of voltage in direct- quadrature reference frame (d-q reference) and angle of stator flux. Amplitude of stator voltage is controlled by PI torque and PI flux controller. The stator flux angle is adjusted by rotor angular frequency and slip angular frequency. Then, the reference torque and the estimated torque is applied to the input of PI torque controller and the control quadrature axis voltage is determined. The control d-axis voltage is determined from the flux calculator. These q and d axis voltage are converted into amplitude voltage. By applying polar to Cartesian on amplitude voltage and stator flux angle, direct voltage and quadratures voltage are generated. The reference stator voltages in d-q are calculated based on forcing the stator voltage error to zero at next sampling period. By applying inverse park transformation on d-q voltages, the stator voltages in α and β frame are generated and apply to SVM. From the output of SVM, the motor control signal is generated and the speed of the induction motor regulated toward the rated speed. The simulation Results have demonstrated exceptional performance in steadand transient states and shows that decrease of torque and flux ripples is achieved in a complete speed range. © Maxwell Scientific Organization, 2013.
2013-01-01T00:00:00ZImproved close loop stator flux estimation of direct torque control driveRashag, H.F.Koh, S.P.Abdalla, A.N.Tan, N.M.L.Chong, K.H.Tiong, S.K.Jaber, A.S.http://dspace.uniten.edu.my/jspui/handle/123456789/90042018-02-21T04:49:51Z2012-01-01T00:00:00ZTitle: Improved close loop stator flux estimation of direct torque control drive
Authors: Rashag, H.F.; Koh, S.P.; Abdalla, A.N.; Tan, N.M.L.; Chong, K.H.; Tiong, S.K.; Jaber, A.S.
Abstract: In conventional direct torque controlled (DTC) induction motor drive, there is usually undesired torque and flux ripple. In this paper close loop stator flux estimation of DTC with space vector modulation under heavy load at low speed was proposed. First, brief description of stator currents in direct-quadrature reference frame with voltage model. Second, close loop stator flux feedback used through PID controller to correct the value of stator flux estimation and eliminate error. In addition, low pass filter also used instead of pure integration to avoid saturation problem. Finally, simulation results show that the flux and torque ripples are greatly reduced when compared with open loop of stator flux estimation. © 2012 Published by Elsevier Ltd.
2012-01-01T00:00:00ZDTC-SVM based on PI torque and PI flux controllers to achieve high performance of induction motorRashag, H.F.Tan, N.M.L.Koh, S.P.Abdalla, A.N.Chong, K.H.Tiong, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/89902018-02-21T04:49:46Z2014-01-01T00:00:00ZTitle: DTC-SVM based on PI torque and PI flux controllers to achieve high performance of induction motor
Authors: Rashag, H.F.; Tan, N.M.L.; Koh, S.P.; Abdalla, A.N.; Chong, K.H.; Tiong, S.K.
Abstract: The fundamental idea of direct torque control of induction machines is investigated in order to emphasize the property produced by a given voltage vector on stator flux and torque variations. The proposed control system is based on Space Vector Modulation (SVM) of electrical machines, Improvement model reference adaptive system, real time of stator resistance and estimation of stator flux. The purpose of this control is to minimize electromagnetic torque and flux ripple and minimizing distortion of stator current. In this proposed method, PI torque and PI flux controller are designed to achieve estimated torque and flux with good tracking and fast response with reference torque and there is no steady state error. In addition, design of PI torque and PI flux controller are used to optimize voltages in d-q reference frame that applied to SVM. The simulation Results of proposed DTC-SVM have complete excellent performance in steady and transient states as compared with classical DTC-SVM. © Maxwell Scientific Organization, 2014.
2014-01-01T00:00:00ZSolving the inverse kinematics for robot manipulators using modified electromagnetism-like algorithm with record to record travelAbed, I.A.Koh, S.P.Sahari, K.S.M.Tiong, S.K.Tan, N.M.L.http://dspace.uniten.edu.my/jspui/handle/123456789/89952018-02-21T04:49:47Z2014-01-01T00:00:00ZTitle: Solving the inverse kinematics for robot manipulators using modified electromagnetism-like algorithm with record to record travel
Authors: Abed, I.A.; Koh, S.P.; Sahari, K.S.M.; Tiong, S.K.; Tan, N.M.L.
Abstract: A new modification of Electromagnetism-like (EM) algorithm which incorporating the Record-to-Record Travel (RRT) local search algorithm; namely MEMR has been developed to solve the problem of Inverse Kinematics (IK) for a four Degree-of-Freedom (DOF) manipulator. The proposed method is able to generate multiple robot configurations for the IK test performed at different end effect or positions. In addition, the comparison between the proposed MEMR and Genetic Algorithm (GA) was carried out using two mathematical test functions; De Jong and Rastrigin. The tests results show that the proposed MEMR is comparable in performance to GA in terms of both convergence speed and error rate. © Maxwell Scientific Organization, 2014.
2014-01-01T00:00:00ZPath selection technique for highly transmission ratio and reliable routing in ManetJassim, H.S.Yussof, S.Tiong, S.K.Chong, K.H.Koh, S.P.http://dspace.uniten.edu.my/jspui/handle/123456789/90612018-02-21T04:53:18Z2011-01-01T00:00:00ZTitle: Path selection technique for highly transmission ratio and reliable routing in Manet
Authors: Jassim, H.S.; Yussof, S.; Tiong, S.K.; Chong, K.H.; Koh, S.P.
Abstract: Mobile ad-hoc network (MANET) is collection of wireless nodes that operates without using a centralized network infrastructure such as a base station. Since the wireless range is limited, the nodes mutually cooperate with their neighbors in order to extend the overall communication range of the network for forwarding packets. Ad-hoc On-demand Distance Vector (AODV) is one of the commonly used protocols in ad-hoc networks. AODV is a dynamic routing protocol that is able to find the shortest path from a source node to a destination node in MANET based on hop count. However, due to the nature of MANET, it is very easy to introduce malicious nodes in MANET. These malicious nodes may try to compromise the routing protocol functionality and make MANET vulnerable to security attacks which lead to unreliable routing. Therefore, security has become a primary concern in providing protected communication among nodes in MANET. In this study, we propose a Reliable Dynamic Trust-based Routing (RDTR) protocol by integrating a trust mechanism with a shortest path routing algorithm for establishing and maintaining trustworthy routes in MANET. © Asian Network for Scientific Information.
2011-01-01T00:00:00ZSpace-Charge-Limited Dark Injection (SCL DI) transient measurementsYap, B.K.Koh, S.P.Tiong, S.K.Ong, C.N.http://dspace.uniten.edu.my/jspui/handle/123456789/88112018-02-21T04:29:39Z2010-01-01T00:00:00ZTitle: Space-Charge-Limited Dark Injection (SCL DI) transient measurements
Authors: Yap, B.K.; Koh, S.P.; Tiong, S.K.; Ong, C.N.
Abstract: It is not an easy task to probe the mobility of nanoscale thin layers without using expensive and sophisticated equipments such as Time-of-flight photocurrent charge carrier mobility measurement. We present here a powerful yet cost-effective technique, namely the Space-Charge-Limited Dark Injection (SCL DI) Transient Measurement that allows us to confirm an ohmic injecting interface, to determine the mobility values of the bulk materials and to study the injection efficiency of the interfaces of the semiconductor materials. © 2010 IEEE.
2010-01-01T00:00:00ZThermal stress test for PLEDYap, B.K.Koh, S.P.Tiong, S.K.Ong, C.N.http://dspace.uniten.edu.my/jspui/handle/123456789/88102018-02-21T04:29:38Z2010-01-01T00:00:00ZTitle: Thermal stress test for PLED
Authors: Yap, B.K.; Koh, S.P.; Tiong, S.K.; Ong, C.N.
Abstract: This work presents thermal stability studies of PLEDs involving the comparison of electrical performance before and after thermal treatment. Two cycles of continuous thermal stress test from room temperature to 100 deg Celsius did not significantly affect the total photoluminescence intensity from the light-emitting polymer in the PLED suggesting that the layer of light-emitting polymer is intact. However, the rapid degradation of the electrical performance of the PLED right after the first cycle of thermal stress test suggests that the electrodes have degraded hence hindering charge injection into the polymeric layer. © 2010 IEEE.
2010-01-01T00:00:00ZAn automated gravimetric & PWM based fluid dispensing system with GA parameter fine tuningSim, E.Y.S.Koh, S.P.Tiong, S.K.Yap, B.K.http://dspace.uniten.edu.my/jspui/handle/123456789/88122018-02-21T04:29:39Z2009-01-01T00:00:00ZTitle: An automated gravimetric & PWM based fluid dispensing system with GA parameter fine tuning
Authors: Sim, E.Y.S.; Koh, S.P.; Tiong, S.K.; Yap, B.K.
Abstract: In this paper we present a gravimetric and Pulse Width Modulation (PWM) based fluid dispensing technique for a maximum dispense batch of 30kg. In addition, a Genetic Algorithm (GA) Parameter Fine Tuning technique is presented as well. Based on the combination of both techniques, the system is able to dispense up to 50 samples with an accuracy of +/- 2g with the dispensing speed varies between 50 seconds to 60 seconds for a 5.2kg batch within one dispense valve. The reported dispensing technique is based on PWM technique in the dispensing sequence and GA technique in the parameter fine tuning. This technique could overcome limitations of the volumetric dispensing and manual parameter tuning presently applied in the coatings industry. The fast and accurate system which is modularly built out of individual dispense valve is able to handle different fluids with varying viscosity. The working principles of the system as well as its accuracy results are presented. ©2009 IEEE.
2009-01-01T00:00:00ZNTL detection of electricity theft and abnormalities for large power consumers in TNB malaysiaNagi, J.Yap, K.S.Nagi, F.Tiong, S.K.Koh, S.P.Ahmed, S.K.http://dspace.uniten.edu.my/jspui/handle/123456789/89172018-02-21T04:42:14Z2010-01-01T00:00:00ZTitle: NTL detection of electricity theft and abnormalities for large power consumers in TNB malaysia
Authors: Nagi, J.; Yap, K.S.; Nagi, F.; Tiong, S.K.; Koh, S.P.; Ahmed, S.K.
Abstract: Electricity consumer dishonesty is a problem faced by all power utilities. Finding efficient measurements for detecting fraudulent electricity consumption has been an active research area in recent years. This paper presents an approach towards detection of Non-technical Losses (NTLs) of Large Power Consumers (LPC) in Tenaga Nasional Berhad (TNB) Malaysia. The main motivation of this study is to assist Tenaga Nasional Berhad (TNB) Sdn. Bhd. in Malaysia to reduce its NTLs in the LPC distribution sector. Remote meters installed at premises of LPC customers transmit power consumption data including remote meter events wirelessly to TNB Metering Services Sdn. Bhd. The remote meter reading (RMR) consumption data for TNB LPC customers is recorded based on half-hourly intervals. The technique proposed in this paper correlates the half-hourly RMR consumption data with abnormal meter events. The correlated data provides information regarding consumption characteristics i.e. load profiles of LPC customers, which helps to expose abnormal consumption behavior that is known to be highly correlated with NTL activities and electricity theft. Pilot testing results obtained from TNB Distribution (TNBD) Sdn. Bhd. for onsite inspection of LPC customers in peninsular Malaysia indicate the proposed NTL detection technique is effective with a 55% detection hitrate. With the implementation of this intelligent system, NTL activities of LPC customers in TNB Malaysia will reduce significantly. ©2010 IEEE.
2010-01-01T00:00:00ZA routing protocol based on trusted and shortest path selection for mobile ad hoc networkJassim, H.Sh.Yussof, S.Kiong, T.S.Koh, S.P.Ismail, R.http://dspace.uniten.edu.my/jspui/handle/123456789/90672018-02-21T04:53:21Z2009-01-01T00:00:00ZTitle: A routing protocol based on trusted and shortest path selection for mobile ad hoc network
Authors: Jassim, H.Sh.; Yussof, S.; Kiong, T.S.; Koh, S.P.; Ismail, R.
Abstract: A mobile ad-hoc network (MANET) is a peer-to-peer wireless network where nodes can communicate with each other without the use of infrastructure such as access points or base stations. Nodes can join and leave the network at anytime and are free to move randomly and organize themselves arbitrarily. Due to this nature of MANET, it is possible that there could be some malicious and selfish nodes that try compromise the routing protocol functionality and makes MANET vulnerable to security attacks. In this paper, we present a security-enhanced AODV (Ad hoc On-demand Distance Vector Routing) routing protocol called R-AODV (Reliant Ad hoc On-demand Distance Vector Routing). The implementation of this work is done by modified a trust mechanism known as direct and recommendations trust model and then incorporating it inside AODV which will allow AODV to not just find the shortest path, but instead to find a short path that can be trusted. This enhances security by ensuring that data does not go through malicious nodes that have been known to misbehave. The R-AODV protocol has been implemented and simulated on NS-2. Based on the simulation result, it can be shown that R-AODV does provide a more reliable data transfer compared to the normal AODV if there are malicious nodes in the MANET. ©2009 IEEE.
2009-01-01T00:00:00ZPerformance comparison of MVDR and LCMV beamforming algorithm in 2.3 GHz adaptive antenna systemSalem, B.Tiong, S.K.Koh, S.P.Hock, G.C.http://dspace.uniten.edu.my/jspui/handle/123456789/93292018-02-23T06:50:17Z2012-01-01T00:00:00ZTitle: Performance comparison of MVDR and LCMV beamforming algorithm in 2.3 GHz adaptive antenna system
Authors: Salem, B.; Tiong, S.K.; Koh, S.P.; Hock, G.C.
Abstract: The blind beamforming technique is employed in the broadband wireless mobile systems to enhance the cellular systems in the aspect of capacity, data rates, null steering and coverage. This paper presents two methods of beamforming algorithm; Minimum Variance Distortionless Response (MVDR) and Linear Constraint Minimum Variance (LCMV). MVDR and LCMV techniques form radiation beams based on the received weight vector of the desired signal. Simulation has been carried out to validate these two techniques. Four elements of the linear array antenna are used in our simulation program with the carrier frequency around 2.3 GHz, noise power 0.5dB, and the spacing between elements is 0.5 λ. The result of the simulation reveals that both the modes are capable of providing high output power; however direction of all the incoming sources is required, which is practically difficult to obtain. Nevertheless the MVDR beamforming, minimizes the multi-path fading problem, by adding the multi-path signal, which increases the strength of the desired signal and nullifies the interference. Overall, the MVDR technique is more accurate than the LCMV to null to find the interference source and directing radiation lobe with high power towards the desired signal. © 2012 Praise Worthy Prize S.r.l.-All rights reserved.
2012-01-01T00:00:00ZAn electromagnetism-like mechanism algorithm approach for photovoltaic system optimizationTan, J.D.Koh, S.P.Tiong, S.K.Ali, K.Koay, Y.Y.http://dspace.uniten.edu.my/jspui/handle/123456789/107202018-12-06T07:40:00Z2018-01-01T00:00:00ZTitle: An electromagnetism-like mechanism algorithm approach for photovoltaic system optimization
Authors: Tan, J.D.; Koh, S.P.; Tiong, S.K.; Ali, K.; Koay, Y.Y.
Abstract: Solar energy has become one of the most studied topic in the field of renewable energy. In this paper, an artificial intelligent approach is proposed for the optimization of a photovoltaic solar energy harvesting system. An Electromagnetism-Like Mechanism Algorithm (EM) has been developed to search for the hourly optimum tilt angles for photovoltaic panels. In order to investigate the effect of the search step size on the efficiency and overall accuracy of the algorithm, the EM has also been modified into several variants with different search step size settings. Experimental findings show that EM with bigger search lengths has the advantage of reaching a near optimum tilt angle in earlier iterations but less accurate. EM with smaller step lengths, on the other hand, can hit a relatively more optimum tilt angle in the process. During the peak of the power generation at noon, EM with smaller search stes found an optimum tilt angle which yielded additional 3.17W of power compared to a fixed panel. We thus conclude that the proposed EM performs well in optimizing the tilt angle of a photovoltaic solar energy harvesting system. © 2018 Institute of Advanced Engineering and Science All rights reserved.
2018-01-01T00:00:00ZImplementation of voltage optimization for sustainable energyTan, J.D.Koh, S.P.Au, M.T.Tiong, S.K.Ali, K.http://dspace.uniten.edu.my/jspui/handle/123456789/112082018-12-07T00:33:16Z2018-01-01T00:00:00ZTitle: Implementation of voltage optimization for sustainable energy
Authors: Tan, J.D.; Koh, S.P.; Au, M.T.; Tiong, S.K.; Ali, K.
Abstract: The voltage control in the power distribution network is challenged firstly by constantly increasing in power demand and secondly by a growing number of distributed connections, which significantly changes the load flow in the network. Situation is worsening with the current heavily implemented micro-generation of Solar PV. Consequently, the uncontrollable rapid changes in the power distribution network would affect voltage instability at the feeder with wide area power demand. Voltage instability would affect the energy efficiency of the electrical equipment. Moreover, the lifespan of some equipment would be shortened due to the excessive and unstable voltage supplied. The proposed research aims to implement the low impedance voltage optimization system in solving the existing problem. The voltage optimization system had been tested on both resistive and inductive loads. The power consumption of the loads had been measured at a few discrete values of voltage optimization within the statutory region. Further tests were conducted on industrial water pump, general lightings with mixed loads, office building, restaurant and plastic injection moulding machine. The power measurements were logged and the results in term of power consumption were analysed. The results showed that the proposed optimization mechanism successfully optimize and saved 6.81%, 14.42%, 13.97%, 12.23%, and 26.23% of the power consumptions in respective tests. © 2018 Institute of Advanced Engineering and Science All rights reserved.
2018-01-01T00:00:00ZFuzzy logic enhanced direct torque control with space vector modulationTan, J.-D.Koh, S.-P.Tiong, S.-K.Ali, K.Abdalla, A.http://dspace.uniten.edu.my/jspui/handle/123456789/115722019-01-11T00:08:19Z2018-01-01T00:00:00ZTitle: Fuzzy logic enhanced direct torque control with space vector modulation
Authors: Tan, J.-D.; Koh, S.-P.; Tiong, S.-K.; Ali, K.; Abdalla, A.
Abstract: Over the past few years, multiple types of modifications have been proposed onto the Direct Torque Control (DTC) scheme. Among others is the implementation of Space Vector Modulation (SVM). In this paper, two new control strategies are proposed onto an SVM-DTC. Instead of using PI torque and flux controllers, a fuzzy logic control method is implemented in the proposed modification to achieve a more constant switching frequency while minimizing the torque error. The fuzzy logic controller controls the voltages in direct and quadratic reference frame (Vd, Vq). This approach fully utilizes the switching capability of the inverter and thus improving the overall system performance. To overcome issues in open loop stator flux such as DC drift and saturation, a closed loop estimation method of stator flux is also proposed based on voltage model and low pass filter. The performance of the proposed control strategy is benchmarked with that of a conventional DTC– SVM. Simulations and experiments were carried out and the results show that the proposed method outperforms the conventional DTC-SVM in terms of DC-offset elimination and overall system robustness. © 2018 Institute of Advanced Engineering and Science. All rights reserved.
2018-01-01T00:00:00ZImplementation of voltage optimization for sustainable energyTan, J.D.Koh, S.P.Au, M.T.Tiong, S.K.Ali, K.http://dspace.uniten.edu.my/jspui/handle/123456789/107212019-01-11T00:53:07Z2018-01-01T00:00:00ZTitle: Implementation of voltage optimization for sustainable energy
Authors: Tan, J.D.; Koh, S.P.; Au, M.T.; Tiong, S.K.; Ali, K.
Abstract: The voltage control in the power distribution network is challenged firstly by constantly increasing in power demand and secondly by a growing number of distributed connections, which significantly changes the load flow in the network. Situation is worsening with the current heavily implemented micro-generation of Solar PV. Consequently, the uncontrollable rapid changes in the power distribution network would affect voltage instability at the feeder with wide area power demand. Voltage instability would affect the energy efficiency of the electrical equipment. Moreover, the lifespan of some equipment would be shortened due to the excessive and unstable voltage supplied. The proposed research aims to implement the low impedance voltage optimization system in solving the existing problem. The voltage optimization system had been tested on both resistive and inductive loads. The power consumption of the loads had been measured at a few discrete values of voltage optimization within the statutory region. Further tests were conducted on industrial water pump, general lightings with mixed loads, office building, restaurant and plastic injection moulding machine. The power measurements were logged and the results in term of power consumption were analysed. The results showed that the proposed optimization mechanism successfully optimize and saved 6.81%, 14.42%, 13.97%, 12.23%, and 26.23% of the power consumptions in respective tests. © 2018 Institute of Advanced Engineering and Science All rights reserved.
2018-01-01T00:00:00ZFuzzy logic enhanced direct torque control with space vector modulationTan, J.-D.Koh, S.-P.Tiong, S.-K.Ali, K.Abdalla, A.http://dspace.uniten.edu.my/jspui/handle/123456789/106222018-12-06T00:32:01Z2018-01-01T00:00:00ZTitle: Fuzzy logic enhanced direct torque control with space vector modulation
Authors: Tan, J.-D.; Koh, S.-P.; Tiong, S.-K.; Ali, K.; Abdalla, A.
Abstract: Over the past few years, multiple types of modifications have been proposed onto the Direct Torque Control (DTC) scheme. Among others is the implementation of Space Vector Modulation (SVM). In this paper, two new control strategies are proposed onto an SVM-DTC. Instead of using PI torque and flux controllers, a fuzzy logic control method is implemented in the proposed modification to achieve a more constant switching frequency while minimizing the torque error. The fuzzy logic controller controls the voltages in direct and quadratic reference frame (Vd, Vq). This approach fully utilizes the switching capability of the inverter and thus improving the overall system performance. To overcome issues in open loop stator flux such as DC drift and saturation, a closed loop estimation method of stator flux is also proposed based on voltage model and low pass filter. The performance of the proposed control strategy is benchmarked with that of a conventional DTC– SVM. Simulations and experiments were carried out and the results show that the proposed method outperforms the conventional DTC-SVM in terms of DC-offset elimination and overall system robustness. © 2018 Institute of Advanced Engineering and Science. All rights reserved.
2018-01-01T00:00:00ZPendulum-like algorithm as a local search techniqueAbed, I.A.Koh, S.P.Sahari, K.S.M.Tiong, S.K.Younis, H.A.-K.Abed, A.A.http://dspace.uniten.edu.my/jspui/handle/123456789/57822018-01-02T08:20:48Z2016-01-01T00:00:00ZTitle: Pendulum-like algorithm as a local search technique
Authors: Abed, I.A.; Koh, S.P.; Sahari, K.S.M.; Tiong, S.K.; Younis, H.A.-K.; Abed, A.A.
Abstract: The Pendulum-like algorithm is based on the concepts of the pendulum. All the ideas that are derived have been embedded into the suggested method. The Pendulum-like algorithm introduced, is expected to provide very good results in solving the optimization problems. This is due to the fact that Pendulum-like algorithm is a method with directed force which is reduced gradually with approximation to the global solution and it also uses the idea of back and forth movement to enhance the solution. Thus, the Pendulum-like algorithm would be integrated with the attraction-repulsion mechanism to introduce a very promising problem solving algorithm. The parameters of the proposed algorithm are evaluated and tested to prove the effect of each one on the algorithm. Also, the results of the algorithm are simulated the same behavior for the parameters of physical pendulum. © 2016 IEEE.
2016-01-01T00:00:00ZUsing Electromagnetism-like algorithm and genetic algorithm to optimize time of task scheduling for dual manipulatorsAbed, I.A.Sahari, K.S.M.Koh, S.P.Tiong, S.K.Jagadeesh, P.http://dspace.uniten.edu.my/jspui/handle/123456789/66842018-01-03T02:03:40Z2013-01-01T00:00:00ZTitle: Using Electromagnetism-like algorithm and genetic algorithm to optimize time of task scheduling for dual manipulators
Authors: Abed, I.A.; Sahari, K.S.M.; Koh, S.P.; Tiong, S.K.; Jagadeesh, P.
Abstract: A method based on Electromagnetism-Like algorithm (EM) and Genetic Algorithm (GA) is proposed to determine the time-optimal task scheduling for dual robot manipulators. GA is utilized to calculate the near-optimal task scheduling for the two robots. On top of that, the EM is recommended as a suitable alternative to obtain multiple solutions at each task points for both manipulators with less error. During the course of the tour, the dual robots move from point to point with less cycle time, while ensuring that no collision occurs between the two manipulators or between the dual manipulators and the static obstacles in the workspace. The movement and the configurations of the manipulators at the task points were visualized using a simulator developed via Visual Basic. Net. The method is verified using two simulators acting as examples for two identical four-link planar robots working in the environment, with square-shaped obstacles cluttered at different locations. © 2013 IEEE.
2013-01-01T00:00:00Z