Nor Hisham Haji Khamis

Comparison Studies of Electrical Discharge Machining (EDM) Process Model for Low Gap Current

This paper aims to compare the material removal rate, ν between a Dimensional Analysis (DA) model, an Artificial Neural Network (ANN) model and an experimental result for a low gap current of an Electrical Discharge Machining (EDM) process. The data analysis is based on a copper electrode and steel workpiece materials. The DA and ANN model that have been developed and reported earlier by authors are used to compare the material removal of EDM process. The result indicated that the ANN model provides better accuracy towards the experimental results.

Study of Underwater Channel Estimation Based on Different Node Placement in Shallow Water

Acoustic underwater sensor network (UWSN) is important in terms of business and for military applications. Optimum UWSN design provides a reliable connection with maximum connectivity, minimal multipath, low technical cost, and emphasis on energy conservation. This paper examines the channel estimation parameters, such as channel impulse response, coherence bandwidth, BER due to delay for differentially detected MSK receiver, and transmission loss impact of underwater node placement in three scenarios (ground-based, buoys-based, and horizontal point-to-point sensor node). All data (bathymetry, altimetry, temperature, salinity, and depth) are real and have been sourced from different satellite databases. The case study of this paper is the Desaru beach in the eastern shore of Johor Bahru in Malaysia. In this investigation, Acoustics Toolbox of BELLHOP through MATLAB and mathematical analyzing method has been utilized. As a result, this paper indicates the maximum received power, and the lowest delay time characteristics and TL belong to horizontal point-to-point scenario; moreover, the ground-based scenario has the highest delay time and maximum coherence bandwidth among three scenarios.

Rainfall rate from meteorological radar data for microwave applications in Malaysia

This paper present the rainfall rate obtained from the analysis of a meteorological radar data in Malaysia. Rainfall rate is an important parameter for a microwave link because it enables the attenuation due to rain to be determined. An important parameter in rain attenuation studies is the rain rate for 0.01% of the time or R/sub 0.01/. Design and system engineers use this value to construct communications system such that the link is available for 99.99% of the time. This result is obtained by utilizing the radar data from the Malaysian Meteorological Department. Knowing the rainfall rate, rain attenuation can be calculated. This information is useful for microwave link applications.

Determination of rain cell size distribution for microwave link design in Malaysia

In designing or planning for a microwave link, attenuation due to rain is often a major obstacle to overcome. Sometimes, a mitigation technique such as space diversity is also considered. However, a rain event occurring in an area is not constant. Rain does not distribute evenly in a region experiencing precipitation. This is especially true in tropical regions as rain has been found to be more convective in nature rather than widespread. Tropical regions also suffer heavier rainfall rates as compared to temperate regions. Important information are rain cell size and rain distribution inside a cell. Results from this study confirmed that the rain cell in Malaysia is highly convective and a rain cell with a center rainfall rate of 120 mm/hr has a diameter of about 1.2-1.5 km.

PID controller tuning by particle swarm optimization on electrical discharge machining servo control system

Electrical Discharge Machining (EDM) is included in a stochastic process. So maintaining gap between electrode and workpiece is not easy. In order to control the gap, a proportional integral derivative (PID) controller is designed for EDM servo actuator system. The main goal of this work is to get PID parameters through Particle Swarm Optimization (PSO) algorithm to ensure a stable, robust and controlled system. The controller and the model for EDM die sinking are verified by simulation of the control system using MATLAB and simulink program. Simulation results verify the effectiveness of the PID controller in which its parameter determined by PSO to control the electrode position towards workpiece.

Application of microwave technology for home industry

Conventional methods have been used to dehydrated fruits and vegetables for the purpose of preservation and to extend the storage life of flowers, fruits and vegetables. However, these conventional methods have low drying efficiency, long drying time and the quality of the dried flowers, fruits and vegetable are rather poor. The application of microwave in flowers, fruits and vegetables dehydration is studied to verify the effectiveness of microwave dehydration, and to maintain the quality of dried flowers, fruits and vegetables as compared to conventional methods. Microwave dehydration provides volumetric heating effect where heat is generated within the product itself and heats the entire volume at a faster rate. The parameters to be controlled during microwave dehydration had been identified to give better quality output, higher drying efficiency and shorter drying time. A simple microwave dehydration system had been build to understand better the architecture of microwave dehydration system. Microwave dehydration had decreased the dehydration time of flowers, fruits and vegetables with higher energy and drying efficiency. In this study, the microwave dehydration process was able to dry flowers that have better color and texture. It was also able to dry the moisture content of carrot that is 4 to 8 times faster than hot air dehydration. This study has shown the potential of the application of microwave technology for the benefit of home industry.

Evaluation of underwater acoustical intermittent ambient noise

This paper focused on the analysis of underwater intermittent biological noises produced by dolphin, shrimp, seahorse, bubble samples. We analyzed the noise frequency spectrum and calculate sound level pressure for every sample in its frequency distribution. Using stationary test, signal changes in the interval of 0.1 second is observed. Assuming Gaussian distribution, normality trial is investigated. Simulations and examinations are done using MATLAB programs in order to illustrate signal noise behavior to optimize filtering and detection purpose. From this study, all samples exhibit stationary and normality distribution properties, in addition the bubble and shrimp have a higher sound pressure level compare to other samples.

Rain Attenuation Prediction Model for Lagos at Millimeter Wave Bands

AbstractLagos, Nigeria (6.35°N, 3.2°E), is a coastal station in the rain forest area of southwestern Nigeria with an altitude of 38 m. Since most communication now takes place above the X band because of congestion of lower bands, it was necessary to look into ways of maximizing X-band usage. There are inadequate data for use in rain propagation studies at microwave frequencies, and even less so at millimeter wave bands where most of the signal depolarization and fading has been discovered to exist. The proposed model is a modification of the International Telecommunication Union–Radio Communication Sector (ITU-R) model combined with locally obtained regression coefficients for estimating specific attenuation as proposed by G. Olalere Ajayi. The Dissanayake, Allnutt, and Haidara (DAH), Simple Attenuation Model (SAM), and ITU-R attenuation prediction models were investigated along with the proposed model. The ITU-R model was observed to produce the best results at 40 GHz, with percentage error values of 0....

Month-to-month variability of the melting layer boundaries

The Bright-band is the typical enhancement in radar reflectivity during the melting process, which is still not completely determined. The seasonal variation over the year can give the characteristics that are valuable for designing and planning of a satellite link. The Malaysian meteorological radar data, from Kluang radar station (Johor), is used to trace the signature of the melting layer during stratiform precipitations events. The trends of the boundaries of the melting layer were studied by considering data extended to cover a six-month period (January-June 1998). It was observed that the boundaries and the thickness of the melting layer are found to be seasonally dependent.

Derivation of path reduction factor from the Malaysian meteorological radar data

Rain does not distribute evenly in a region experiencing precipitation. This is especially true in tropical regions as rain has been found to be more convective in nature rather than widespread. ITU-R has given the necessary information to calculate the attenuation due to rain in dB/km. However, to predict the total amount of attenuation due to rain that a microwave link might suffer, a path reduction factor is needed to account for the variability of rain rate occurring along the propagation path.