Volume 24 (2012)
Table of Contents
Table of Contents
Perbandingan Model Jangkaan bagi Taburan Sintilasi Troposferik untuk Frekuensi Jalur Ku di Malaysia (Expectation Comparison Models of Tropospheric Scintillation Distribution for Ku Band Frequency in Malaysia)
This study has been performed base on an important of severely understanding about the characteristics of the local propagation signal data distribution and also the necessarily identified and predicted the overall impact of every significant attenuating factor along the propagation path as propagation impairment for the transmitted signal. The prediction of propagation impairment is the most important to do the link budget accurately and therefore a better designation of communication network system can be performed. According to that reason, this study has been conducted by using the sample data for one year data collection through Beacon satellite with the duration from April 2008 until April 2009. This collection of data with a frequency of 12.255 GHz (Ku-band) and the elevation angle of 40.1° had been analyse by getting the average value of signal amplitude, χ and also the standard deviation, σ that normally measured in dB to get the long-term distribution of scintillation intensity. The result from this analysis shows that the distribution of scintillation intensity followed the Gamma distribution for the long-term data distribution. Based on this result, then the selected existing prediction model which is Karasawa, ITU-R, Otung, and Akhondie has been compared to get the best performance of prediction model for the selected of data with the specific meteorological parameter. This all four models have been compared referring to the value of RMS error to determine the performances of each model compared with measurement value. The result from this study shows that Otung has the best overall performance compared to other model.
Pengaruh Perubahan Suhu Terhadap Modulus Elastik Lapisan Turapan Boleh Lentur (The Effect of Temperature Changes on Elastic Modulus of Flexible Pavements)
In general, the stiffness of flexible pavement is influenced by environmental changes, whereby temperature and rainfall affect the asphalt layer and non-asphalt layer, such as the subgrade, respectively. Normally, the effect of temperature on flexible pavement can be measured using two methods. The first is a destructive test whereby core samples are tested in a laboratory using a universal testing machine (UTM). The second is a non-destructive in situ test using equipment such as a falling weight deflectometer (FWD) and spectral analysis of surface waves (SASW). This study was conducted to investigate the effect of temperature at different tensile levels on the Soekarno-Hatta and Purwakarta Cikampek roads in Bandung, West Java, Indonesia. It is observed that different tensile levels and testing methods result in various elastic modulus values of flexible pavement. The higher the temperature applied to the flexible pavement layer, the more the elastic modulus values decrease. In contrast, the lower the temperature imposed on the flexible pavement layer, the more the elastic modulus values increase. Different testing methods (FWD, UTM and SASW) on the flexible pavement layer are also affected by temperature changes.
Kesan Agen Penyerak dan pH Ampaian dalam Pemprosesan Berkoloid Serbuk Nano Zirkonia (Effect of Dispersant Agent and Suspension pH in Colloidal Processing of Nano Zirconia Powder)
Nano-sized ceramic powder tends to agglomerate during powder processing because of the existence of van der Waals forces between the fine particles, which promote particle aggregation. Colloidal processing can help prevent the agglomeration of fine particles and allow particle dispersion to be controlled during powder processing. The influence of a dispersant agent and suspension pH in the colloidal processing of nano-zirconia powder (3Y-ZP) is studied in this paper. Dispersant agents Polyethyleneimine (PEI) and Polydiallyldimethyl Ammonium Chloride (PDADMAC) were used in the experiment, with the quantity of each dispersant agent at 0.0%, 0.3%, 0.4%, 0.5%, 0.6%, and 0.7 % of the zirconia weight. The type and optimum quantity of the dispersant agent that can maximize zirconia dispersion in the suspension is determined by using a viscometer. The effect of suspension pH was investigated in suspensions with and without a dispersant agent. A green body is then produced by slip casting and is presintered at 600 °C for 45 minutes, then further sintered at 1100 °C for 2 hours. This study shows that the dispersant agent PEI is suitable for use in an acidic condition. The density and hardness of the samples are high at pH 4 with the addition of 0.5 wt% PEI. The density is 98% of the theoretical density, and hardness is 4.35 GPa. It was found that mechanical properties of zirconia may be enhanced with the use of dispersion agent at the correct quantity as well as optimum suspension pH.
Mesokurtosis Zonal Nonparametric Signal Analysis for Dynamic Characterisation of Metallic Material
This paper presents the development and application of an alternative statistical signal analysis method called Mesokurtosis Zonal Nonparametric (M-Z-N) in characterising the elastic properties of metallic material. The transient vibration response and acoustic radiation from rectangular bar of various metallic materials excited by impact is statistically analysed to determine the pattern of the signal and to estimate the significance difference among those metallic materials. Prediction of the waveform and a method for reducing noise generation from the impact are derived by an extensive process of a new alternative Z-stem filtering technique that has been developed in this paper. The experimental curves obtained by the determination of M-Z-N coefficient for various impact forces and metallic materials found that the results are statistically significant and can be successfully used for determining the correlation between the characteristic of the curves and the relevant elastic properties of the metallic materials. Experimental test of this analysis method on four metallic materials shows a good agreement between the quadratic coefficients with the elastic properties of the metallic materials.
Analisis Antena Tampal Mikrojalur bagi Jalur L1 dan L2 bagi Aplikasi Sistem Penentududukan Global (Analysis of Microstrip Patch Antenna for L1 and L2 for Global Positioning System Applications)
A new dual-band antenna design with high gain have been developed for Global Positioning System (GPS)applications covering L1 and L2 frequencies of 1.575GHz and 1.227GHz using the latest widening bandwidth and downsizing techniques. This antenna is a single layer antenna consists of two L-shaped slot structure. The size of the radiation patch element that refers to the L2 frequency band is 0.441 λo x 0.441 λo x 0.016 λo while the size of the radiation patch element for L1 frequency band is 0.282 λo x 0.282 λo x 0.016 λo where λo corresponding to centre frequency. The design achieved an impedance bandwidth of 52 MHz from 1.213 GHz to 1.265 GHz to for the lower band, while the upper band covers 161 MHz (1.538 to 1.699 GHz) with maximum gain of 6.89 dBi and 7.26 dBi for both frequency bands. Design analysis conducted and presented in this paper shows a low-profile characteristics antenna makes this antenna is suitable for GPS applications.
Comparative Study of Manufacturing Strategy between Japanese and Western Approaches: An Overview
Japan and the West have contributed different manufacturing strategies based on their own unique practices and cultures. This study aims to identify and differentiate the approaches towards the manufacturing strategies of the Japanese from those of the West, which could provide important implications for manufacturing practice and performance. The factors being compared for both the Japanese and Western approaches include manufacturing strategy, basis, focus, production method, production line, operations, equipment, workforce, quality, organizational philosophy, business strategy, improvement, and overall aim. The Japanese and Western manufacturing are also compared in terms of culture, personnel, organization, management, and appraisal. Blending the advantages between Japan and the West will be a struggle that, if succeeded, would end in the enhancement of manufacturing strategies to pursue competitiveness.