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Articles by David F.W. Yap
Total Records ( 4 ) for David F.W. Yap
  David F.W. Yap , Y.C. Wong , S.P. Koh , S.K. Tiong and M.A.E. Mohd Tahir
  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.
  David F.W. Yap , S.K. Tiong , Johnny Koh , D.P. Andito , K.C. Lim and W.K. Yeo
  Wireless Sensor Networks (WSN) is formerly created to support text-based data communication. However, by improving link level mechanism of WSN with Error Control Coding (ECC), reliable multimedia transmission could be realized. This paper addresses the performance issue of transferring multimedia data, particularly still image data, using real sensor motes platform. An X-ray image is transferred from one mote to other mote in one hop scenario. Forward Error Correction (FEC) and interleaving technique are used to design the code that capable of handling both erasure and noise in the received packet. The results show that erasure code can effectively combat the effect of random noise in one packet despite its number as well as recover small quantity of lost packet. Furthermore, the scheme can increase the image PSNR (Peak Signal to Noise Ratio) up to 18.41 dB as compared to the uncoded counterpart.
  S.K. Tiong , David F.W. Yap and S.P. Koh
  This study proposes a novel method of introducing chaotic induced genes into Genetic Algorithms (GA) in order to solve unimodal and multimodal mathematical test functions. The integration of chaotic elements based on logistic map into GA has significantly improved the accuracy in the aspect of the best fitness value. Simulation results show that the influence of Chaos theory does improve the optimization accuracy of the mathematical functions used.
  Mohammed Waadalla , C.K. Yong , David F.W. Yap and R. Abd. Rahim
  Underwater global localization is an essential tool for underwater researchers. In this study global gocalization for underwater mobile robot has been developed using Feedforward Backpropagation Neural Network (FBNN). Twelve sonar sensors have been recorded with the x and y location of the robot using MobotSim software. There are a total of 58081 points and 12 sonars that are used to record each point. These recordings have been used for supervised training by using MATLAB software. The results are determined by using four random points to calculate the location of the robot from the sonar sensor readings. The proposed method that is used in calculating x and y points has accuracy equal to 0.01 m. The result shows that in 10 layers network, the 0.000511 absolute error value with percentage error of 0.035% in x point and the 0.0028893 absolute error value with percentage error of 0.13% in y point are achieved. While, in 12 layers network, the 4.43x10-05 absolute error value with percentage error of 0.003% in x point and the 0.0001767 absolute error value with percentage error of 0.008% in y point are achieved. This study illustrates that feedforward backpropagation neural network can be used to determine the location of the robot with marginal percentage error. Moreover, the resulted percentage error is internationally accepted by electronic engineers.
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