Volume Volume 7 No.1 1998

ABSTRACT: This third paper in the series is focused on the various methods which can be employed to suppress or prevent the ageing-induced tetragonal to monoclinic phase transformation and property deterioration. In particular, the use of sintering additives has been identified as a cost-effective method in achieving this goal. In addition, the sintering additives lead to the use of lower fabrication temperature thereby reducing the grain sizes of the ceramics. AUTHOR: Ramesh Singh

ABSTRACT: Photovoltaic thermal collector is a combination of thermal and photovoltaic systems. It generates both thermal and electrical energies simultaneously. An experimental setup of a double-pass photovoltaic thermal solar air collector was designed and fabricated to study the performance over a range of design and operating conditions. The thermal, photovoltaic and combined photovoltaic thermal performance characteristics curves of the photovoltaic thermal solar collector have been determined. Using these curves, the collector's ability to absorb solar, energy can be determined. In addition, the production of useful energy (electrical and thermal) can be predicted and the heat losses can be identified from the collector. AUTHOR: K. Sopian, H. T. Liu, S. Kakac and T.N. Veziroglu

ABSTRACT: The surface profile ofa computer hard disk was measured using an optical.flat and the results are presented. A low cost experimental setup is discussed which provides valuable information on the flatness of the disk. The fringe pattern on the disk was photographed and scanned into a computer for analysis. Perspective distortions io the image was corrected. using a transformation algorithm. The transformation and scaling matrices used in the algorithm were determined from selected datum points on a square grid pattern. Accuracy of the transformation was checked by transforming digitized grid points in pixel coordinates from the image back to the coordinate system of the optical setup. The optical flat is shown to be capable of providing both qualitative and quantitative data that contour the surface profile of the hard disk accurately. Problem related to the practical application of the technique are discussed. AUTHOR: Mani Maran Ratnam, Sabani Remian

ABSTRACT: Hydrolysis of starch from Artocarpus heterophyllus (jackfruit) using 0.50 M l:ICI for 4h at 75°C yielded 54. 7% (w/v) of glucose whereas under similar, conditions of 0.25 Mand 0.75 M HCI, it produced 25.7 and 34.4% (w/v) glucose, respectively. Increasing the acid concentrations or decreasing the temperature during the hydrolysis process did not show any increment in the glucose production. With 54.7% (w/v) of glucose obtained, the maximum yield of ethanol was 10.8 % (v/v) after 12 h of fermentation using Saccharomyces cerevisiae grown in batch cultures. AUTHOR: Othman Abdul Samah, Salihan Siais and Rohaiza Tapsir

ABSTRACT: This paper presents the applications of vibration and sound intensity signal to detect a defect in a bearing operating at low speed. Analysis of vibration and sound intensity signals has been carried out using spectrum, cepstrum and zoomed cepstrum analysis methods. Comparison study of the performance of these signals indicates that the sound intensity signal can be used to diagnose the bearing condition if the rotational speed is higher than 300rpm. However, vibration signals can indicate the presence of defect in the test bearing at a much lower speed. The repetitive impact frequency due to a defect can only be shown from sound intensity signals using the zoomed cepstrum analysis method. However, using vibration signals, the repetitive impact frequency due to defect can be seen from the harmonic signals in the frequency spectrum and also from the amplitude of the zoomed cepstrum analysis. AUTHOR: Mohd Jailani Mohd Nor and Clive Brashaw

ABSTRACT: Voltage instability problem in power systems is one of the major concerns in power system planning and operation. Various indicators of proximity to voltage collapse, have been proposed and this paper presents a static indicator that can give-a fast voltage stability assessment. The indicator is based on the line stability factors to predict voltage collapse in interconnected power systems. To investigate the effectiveness of the proposed indicator, it is compared with other voltage collapse indicators. The proposed indicator has also been tested on a real large size power system and the results have indicated its practical usefulness. AUTHOR: A.Mohamed, G.B.Jasmon and S. Yusof