Volume 23 (2011)

Table of Contents

No. Article Detail
1. Partially Connected Steel-Concrete Composite Plate Girders
Mohd Yazmil Md Yatim, Nandivaram E. Shanmugam & Wan Hamidon Wan BadaruzzamanAbstract
A method to predict the bending behaviour and load carrying capacity of steel-concrete composite plate girders with partial shear connection under different load condition is presented. Based on curvature compatibility principle, the analytical solutions were performed by incorporating the degree of composite interaction and post-buckling strength. It is observed that the bending stiffness and ultimate load drops accordingly with decreasing degree of interaction. Accuracy of the proposed method is assessed by comparing the results with corresponding non-linear finite element analysis using LUSAS software. A satisfactorily correlation between the results has been observed.
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2. Analisis Pencirian Parameter Ketebalan dan Kebertelusan Substrat bagi Elemen Cincin Segiempat
Sepusat Bersela Antena Tatasusun Pantulan (Analysis of Parameterization Substrate Thickness and Permittivity for Concentric Split Ring Square Reflectarray Element)
Norbahiah Misran, Siti Hafizah Yusop, Mohammad Tariqul Islam & Muhammad Yusof IsmailAbstract
A series of parameterization analysis consists of the substrate thickness and permittivity is carried out to enhance the bandwidth performance of reflectarray antenna element. The parameter to measure the bandwidth performance is including the phase curve slope and linear phase range according to reflection phase to the frequency graph. Return loss is also analysed to determine loss performance occurred by substrate material. The concentric split ring square element is designed and analysed using computer software tool CST Microstripes. The analysis shows that both substrate thickness and permittivity affects the bandwidth performance of element where the suitable selection of substrate material should be done to achieve the optimum performance of element especially the phase slope and phase range.

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3. Kajian Perbandingan Teknik Kawalan SPWM dan THIPWM untuk PWM-VSI Menggunakan Pemodelan
Matematik dan Simulasi (Comparative Study between SPWM Control Techniques THIPWM for PWM-VSI using Mathematical Modeling and Simulation)
Yushaizad Yusof & Nasrudin Abd. RahimAbstract
This paper discusses the comparative study between two pulse width modulation (PWM) control techniques namely sinusoidal PWM (SPWM) and third harmonic injection PWM (THIPWM) to drive a single phase voltage source inverter (VSI) circuit system based on mathematical modeling and computer simulation using Matlab Simulink software. The dynamic mathematical model of PWM-VSI is designed based an simplified switching function concept. Hence, the gating signals generation method, fundamental output voltage amplitude, output current magnitude, output power, efficiency, harmonics filter size and total harmonics distortion (THD) content in the output voltage of PWM-VSI inverter are selected as the comparison parameters. The results show that the comparative study of mathematical model design of PWM-VSI utilizing SPWM and THIPWM control techniques have been successfully implemented and verified via computer simulation.

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4. Kesan Perubahan TEC, Profil Ionosfera dan Arah Kedudukan Stesen Penerima Terhadap Ralat Ionosfera
Isyarat GPS (The Effect of the Changes in the TEC, Inosphere Profile and the Position of Receiver Station towards Inosphere Error Experienced by GPS System)
Mardina Abdullah, Siti Sarah Nik Zulkifli & Mahamod IsmailAbstract
Global Positioning System (GPS) is a satellite-based navigation radio system which is used to determine the location of a site. Since the termination of selective availability (SA) on 1 May 2000, ionospheric error has become the largest source of error in GPS positioning. The aim of this research is to analyse ionospheric error that is caused by the changes in TEC value and the ionospheric  profile experienced by GPS signals. Apart from that, analysis was also carried out to find out the effect of the changes in the direction of mobile station positions in short distance differential GPS application (dGPS) (≤10 km) on the ionospheric error experienced by the GPS system. The data was based on GPS stations in UKM (2° 55’ N, 101°46’E) and in UPM Serdang, UPMS (2º 59’ N, 101º 43’ E). From the analysis on the effect of TEC changes, it was found that the increase in the TEC value led to the increment of the ionospheric error because in the TEC analysis, a profile with 100 TECU yielded ionospheric error of 46.7 m while a profile with 11 TECU yield only 5.13 m. The analysis of the ionospheric profile changes did not give any significant results. Meanwhile, the analysis on the effect of the position changes of the rover stations showed that the irregularities of the ionospheric behaviours gave different range of ionospheric errors for the signal propagation orientation between the satellite and its receiver. The difference in ionospheric error for the separation of the rover station at North 0º direction was equal to the difference in ionospheric error at South 180º, while the ionospheric error at East 90º was found equal to the West 270º, and North-West 315º equal to the South-East 135º, while North-East 45º was equal to the South-West 225º. All these factors should be considered in order to obtain an accurate GPS precise positioning.

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5. Merekabentuk Sistem Laci Pintar untuk Penjejakan Dokumen dengan Menggunakan Identifikasi
Frekuensi Radio (RFID) (Designing Smart Drawer System for Document Tracking by using Radio Frequency Identification (RFID))
Mandeep Singh Jit Singh & Ng Yin FenAbstract
Document tracking is becoming more important nowadays, especially for those companies which are handling several types of documents daily. Those companies require an effective way to track the location and provide the users an easy and efficient medium to use and manage all the folders. Besides that, they also required a system which can create, access and check the records regarding the usage and any details regarding the document. Thus Radio Frequency Identification (RFID) technology is applied to be a solution to the problem stated. In this research, by using RFID components which are CSL CS-461 reader, CS-771 antenna and RFID tags, a smart drawer system is designed to improve the document tracking and management system in a company. RFID tags are used as label on the folder and document to represent its identity. Besides, it is also used as an identity tracker for the user to login into the system. Besides, a database for smart drawer system is built using Microsoft SQL Server 2008 and a controlling and interfacing application is developed by using Microsoft Visual C# 2008 Express Edition. The database is used for storing data of documents, folders and users. The controlling and interfacing application is then created to provide an effective medium for use of documents/folders, management and record of the documents and folders. Therefore, with the application of the RFID technology, a smart drawer system could be created to make document tracking process to be much easier, more effective and accurate.

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6. Model Penyelakuan Berangkap Dipermudah untuk Penyongsang PWM-VSI Satu
Fasa Menggunakan Konsep Rangkap Pensuisan (Functional Simulation Model for Single Phase Pulse Width Modulation-voltage Source Inverter (PWM-VSI) using Switching Function Concept)
Yushaizad Yusof & Nasrudin Abd. RahimAbstract
This paper proposes a functional simulation model for single phase pulse width modulation-voltage source inverter (PWM-VSI) using switching function concept based on actual implementation of the model using Matlab Simulink software. Through this developed functional model, the simplification of a single phase bridge voltage source inverter circuit can be achieved, so that the convergence and long run-time in computer calculating process problems can be solved. The general switching function concept is reviewed briefly, and the designed functional model of single phase PWM-VSI and its implementation using Matlab Simulink are explained in detail. By the simulation of this functional model, the inverter’s output voltage and current are obtained and the output current total harmonics distortion (THD) is calculated using Fast Fourier Transform (EFT) technique. Finally, several informative simulation results verify the validity of the simplified functional model design.

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7. Effect of Soil Porosity and Slope Gradient on the Stability of Weathered Granitic Hillslope
Muhammad Mukhlisin & Mohd Raihan TahaAbstract
Modeling rainwater infiltration in slopes is vital to the analysis of rainfall induced slope failure. Amongst the soil hydraulic properties, the hydraulic conductivity K and considered as the most dominant factor affecting the slope stability. Of less prominent was the effect of water retention characteristics. In this study, a numerical model was developed to estimate the extent of rainwater infiltration into an unsaturated slope, the formation of a saturated zone, and the change in slope stability. This model is then used to analyze the effects of the soil porosity parameters (i.e., saturated soil water content qs and effective soil porosity (ESP)) and slope gradient on the occurrence of slope failure. Results showed that when the surface soil of a slope has a relatively large ESP value, it has a greater capacity for holding rainwater, and therefore delays rainwater infiltration into the subsurface layer. Consequently, the increase in pore water pressure in the subsurface layer is also delayed. In this manner, a relatively large surface layer ESP value contributes to delaying slope failure. In addition, the slope gradient of slope is also a significant parameter in slope stability analysis. The time taken for gentle slope to reach failure is longer compared to similar cases with 40o slope gradient.

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