Scientific Research Journal

Classification and Identification of Power System Disturbances Using Wavalet and Artificial Neural Network Technique

Noraliza Hamzah — 2005-12-31

Power Quality disturbances problems have gained widespread interest worldwide due to the proliferation of power electronic load such as adjustable speed drives, computer, industrial drives, communication and medical equipments. This paper presents a technique based on wavelet and probabilistic neural network to detect and classify power quality disturbances, which are harmonic, voltage sag, swell and oscillatory transient. The power quality disturbances are obtained from the waveform data collected from premises, which include the UiTM Sarawak, Faculty of Science Computer in Shah Alam, Jati College, Menara UiTM, PP Seksyen 18 and Putra LRT. Reliable Power Meter is used for data monitoring and the data is further processed using the Microsoft Excel software. From the processed data, power quality disturbances are detected using the wavelet technique. After the disturbances being detected, it is then classified using the Probabilistic Neural Network. Sixty data has been chosen for the training of the Probabilistic Neural Network and ten data has been used for the testing of the neural network. The results are further interfaced using matlab script code. Results from the research have been very promising which proved that the wavelet technique and Probabilistic Neural Network is capable to be used for power quality disturbances detection and classification.

Free Space Microwave Characterization of Silicon Wafers for Microelectronic Applications

Zaiki Awang — 2005-12-31

A contactless and non-destructive microwave method has been developed to characterize silicon semiconductor wafers from reflection and transmission measurements made at normal incidence using MNDT. The measurement system consists of a pair of spot-focusing horn lens antenna, mode transitions, coaxial cables and a vector network analyzer (VNA). In this method, the free-space reflection and transmission coefficients, S₁₁ and S₂₁ are measured for silicon wafers sandwiched between two Teflon plates of 5mm thickness which act as a quarter-wave transformer at mid-band. The actual reflection and transmission coefficients, S₁₁ and S₂₁ of the silicon wafers are then calculated from the measured S₁₁ and S₂₁ using ABCD matrix transformation in which the complex permittivity and thickness of the Teflon plates are known. From the complex permittivity, the resistivity and conductivity can be obtained. Results for p-type and n-type doped silicon wafers are reported in the frequency range of 11 – 12.5 GHz. The dielectric constant of silicon wafer obtained by this method agrees well with that measured in the same frequency range by other conventional methods.

Influence of Waste Concrete Aggregates on the Performance and Durability of OPC Concrete

Ahmad Ruslan Mohd Ridzuan — 2005-12-31

The effects of using crushed waste concrete as course aggregates upon compressive strength and carbonation were investigated. Waste concrete cubes, which had been tested for compressive strength in compliance with construction specification, were crushed and utilized as coarse recycled aggregates in new concrete. It is important to mention that, in order to simulate the real life conditions, waste concrete with very minimal information about its originality was used in its natural moisture condition. Tests on the aggregates showed that the recycled concrete aggregates have lower specific gravity and bulk density but have higher water absorption capacity than the natural aggregates. The resistance to mechanical actions such as impact and crushing for recycled concrete aggregates is also lower. Concrete mixes with design strength of 30 N/mm², 35 N/mm² and 40 N/mm² were prepared using these recycled aggregates as coarse aggregates and tested. From the strength point of view the recycled aggregate concrete compared well with natural aggregate concrete. Therefore, it could be considered for various potential applications. With respect to resistance to carbonation the recycled aggregate concrete shows comparable performance.

Design and Fabrication of a Robotic Arm for Material Handling

P Nageswara Rao — 2005-12-31

The commercial robots are expensive for use in the educational institutions. The operation of them will not leave room for experimentation, which is necessary in an educational institution. Further a large number of components that can be used for building a robot are readily available in the market. Hence this project has been taken up to allow us to build a working robot using as many of the off the shelf components to provide the necessary flexibility. This would make it a low cost robot with enough flexibility for the students to experiment the various functions of the robot. The mechanical component of the manipulator was built with three degrees of freedom, one revolute and two prismatic joints. This configuration is most common to be used as a material-handling device for machine tools. The revolute joint was achieved by making use of a pneumatic rotary table and one prismatic joint is realized by means of a pneumatic cylinder. The second prismatic joint in the Z-direction is achieved by the use of an AC servomotor with a ball screw and linear motion elements to provide for accurate positioning capability. The gripper had been designed for cylindrical components, since this robot was conceived as a material handling unit for a CNC turning center. All the necessary design calculations had been done and the finite element analysis was carried out for the main structure. The control system of the robot was one of the crucial elements. A PC is used as a controller. The motion control was carried out with the help of a motion control card DC2-PC100. It had the ability to control 2 servo and 2 stepper motors in addition to other digital and analogue controls. Several types of sensors and actuators were used for the robot to be fully automatic. The signal conditioning circuitry was designed in house for the interfacing between sensors, actuators and controllers. The control algorithm was developed with the necessary functioning to coordinate all the joint movement as well as gripper manipulation.

Effect of Varied Probe Length on the Resonant Frequency of a Circular Cross-Sectional Cavity

Mohd Khairul Mohd Salleh — 2005-12-31

A simple design of a metallic circular cross-sectional air-filled cavity is presented. Two probes of varied lengths are used to excite TE₁₁₂-mode wave into the cavity to give a resonant frequency of 5.86 GHz. The experiments show that the resonant frequency of the cavity resonator decreases as the lengths of the probes are increased. The shortest probe in the range of study gives the closest resonant frequency to the one desired.

An Intelligent Optical Fibre pH Sensor Based on Sol-Gel Advanced Material and Artificial Neural Network

Mohd Nasir Taib — 2005-12-31

The application of artificial neural network (ANN) in signal processing of optical fibre pH sensor is presented. The pH sensor is developed based on the use of bromophenol blue indicator immobilized in a sol-gel thin film as a sensing material. A three layer feed-forward network was used and the network training was performed using the back-propagation algorithm. Spectra generated from the pH sensor at several selected wavelengths are used as the input for the ANN. The bromophenol blue indicator, which has a limited dynamic range of 3.00-5.50 pH units, was found to show higher pH dynamic range of 2.00-12.00 and low calibration error after training with ANN. The trained ANN was successfully employed to predict several spectra from unknown buffer solution with an average error of 0.06 pH units.

Microwave Non-Destructive Testing of Coatings and Paints Using Free Space Microwave Measurement

Norhayati Hamzah — 2005-12-31

Microwave nondestructive testing (MNDT) techniques are applied to evaluate quality of anti-corrosive protective coatings and paints on metal surfaces. A tree-space microwave measurement (FSMM) system is used for MNDT of protective coatings. The FSMM system consists of transmit and receive spot-focusing horn lens antennas, a vector network analyzer, mode transitions and a computer. Diffraction effects at the edges of the sample are minimized by using spot-focusing horn lens antennas. Errors due to multiple reflections between antennas are corrected by using free-space LRL (line, reflect, line) calibration technique. We have measured complex reflection coefficient of polyurethane based paint which is coated on brass plates.