[en] A statistical-based method for adaptive control of weld pool penetration and joint following in Tungsten Inert Gas Welding as an approach to process and trajectory control of robotic GTA welding has been designed and simulated. Welding process parameters such as: base current and time, pulse current and time, electrode tip to work piece distance, filler travelling speed, torch speed and work piece thickness were used for finding the equations which describe the interrelationship between the aforementioned variables and penetration depth as well as bead width. The calculation of these equations was developed from the statistical regression analysis of 80 welds deposited using various combinations of welding parameters. For monitoring of the work piece thickness variations, an ultrasonic device was used. In order to control the weld trajectory, a CCD camera was also used. The results showed that the misalignment of the progressive heat affected zone which is adjacent to the weld puddle can be detected, and used for control of the weld trajectory. Also, it was found that scanning of a certain region of the captured image in front of the weld puddle decreases the data processing time drastically

[en] The transmission line modelling (TLM) method for design of analogue filters is adapted for cascaded unit element wave digital filters (UEWDFs) design. The design variables are the coefficients of the UEWDFs. Sensitivities with respect to the coefficients are easily obtained and used in optimisation. Simplifications in the sensitivity expressions are afforded over analogue filter design

[en] Visual observations of flow patterns for the developing steady air-water two phase flow were obtained in a 54 mm diameter test section with 10 m long. A flow regime map for the developing two phase flow was developed in the form of two dimensional graph which was separated into area corresponding to various flow patterns. The present flow regime map was compared with those of other researchers. The map will be useful for predicting the flow patterns at given conditions and will be a basis to derive the flow regime maps for the transient conditions

[en] A finite element method for analysis of viscous incompressible flow is presented. The finite element formulation and the computational procedure are described. The corresponding computer program that can be executed on standard personal computers has been developed. The method is combined with adaptive meshing technique to increase the solution accuracy, and at the same time, to minimise the computational time and computer memory required. The efficiency of the combined method is evaluated by examples of flow past a cylinder, flow in a sudden enlargement duct, and flow through an orifice. (author)

[en] The elastic and nonlinear acoustic vibrational properties of yttrium metaphosphate glasses have been determined from measurements of the effect hydrostatic pressure on ultrasonic wave velocity at room temperature. The objective is to compare the acoustic vibrational behaviour of these glasses with those of metaphosphate glasses containing europium, gadolinium, samarium or terbium ions which are known to exhibit softening of the long wavelength acoustic mode: these glasses become easier to squeeze when subjected to high pressure. The hydrostatic pressure derivatives (∂ C_IJ'S/∂P)_P=0 of the elastic stiffnesses C_IJ'S and also (∂B₀'S/∂P)_P=0 of the bulk modulus B₀'S are negative. The longitudinal γ_L and shear γ_S acoustic mode Grueneisen parameters are also negative: application of pressure softens the long-wavelength acoustic phonon mode frequencies. The nonlinear acoustic mode softening effects similar to that of europium metaphosphate glasses. The fractal bond connectivity of these glasses, obtained from the elastic stiffness determined from ultrasonic wave velocities, has a value around 3, indicating that their connectivity have a three-dimensional character (author)

[en] A relatively simple analytical expression was derived that provided a description of the radius and thermal properties of a single particle from the change in grey body radiation emission subsequent to pulse laser heating of the particle

[en] In this paper, a PC-based simulator for state of the art oversampled switched-capacitor sigma-delta analog-to-digital converters is presented. The proposed simulator employs behavioral model of switched-capacitor integrator and non-linear quantizer to stimulate the system. The behavioral simulation of the integrator is also verified with SPICE. The simulator is fully integrated and standalone. It integrates an input netlist file interpreter, a behavioral simulator, a generic part library and a powerful post-processor to evaluate the SNR, SDR And TSNR. Both passive and active sensitivities can be investigated by the proposed simulator. The simulator is coded in C++, and is very fast

[en] Thermo acoustical parameters of polymers viz. Polystyrene, Nylon-6 and Teflon have been evaluated at temperature between 173 degree K and 383 degree K in terms of the coefficient of volume expansion, on the assumption that the Moelwyn-Hughes parameter is the dominant factor. Parameters such as the Beyer's nonlinearity parameter, Moelwyn-Hughes parameter, the isothermal, isobaric and isochoric Gruineisen parameters, the repulsive exponent of intermolecular potential, fractional available volume, and the Sharma thermo acoustical parameter S sub 0 have been evaluated through simple relationships. The interrelationships between the isobaric and isochoric Gruneisen and acoustical, parameters have been examined and analysed in these polymers over a wide temperature range. The results have been used to develop understanding of the significance of microscopic factors such as molecular order and intermolecular forces upon macroscopic thermo acoustical properties. The Sharma's parameter S sub 0 remains invariant with temperature over a wide range and retains its characteristic value i.e. 1.1 1+/- 0.01 as observed in case of several systems existing either in a liquid state or in a solid state. The present treatment has the distinct advantage of calculating several thermo acoustical parameters through simple interrelationships from the knowledge of volume expansivity alone

[en] Although acid rain and its harmful environmental consequences have been recognised and documented in the industrialised countries of Europe and North America there have been few studies of this phenomenon in other regions of the globe. Recent measurements in some tropical countries have demonstrated the occurrence of acid rain. It was therefore considered necessary to set up a routine rainwater acidity monitoring programme in Brunei Darussalam in order to provide a database which would be of use in assessing any potential environmental impacts in the country. This paper describes the rainwater acidity monitoring programme that was initiated in 1995 by the Brunei Meteorological Service as part of the World Meteorological Organisation (WMO) Global Atmosphere Watch (GAW). Wet-only deposition samples were collected using an automatic precipitation collector. Rainwater pH was determined in an on-site laboratory immediately upon sample collection. The pH of 185 samples collected so far varied between 4.27 and 6.27. 91% of the samples had pH below 5.6 indicating the occurrence of acid rain in Brunei Darussalam

[en] The Institute of Higher Learning (IHL) of the University of Malaya, with support from the Malaysian Meteorological Service, has recently completed the development of a PC based oil spill trajectory model for application in the Straits of Malacca under a project awarded by the Dept of Environment, Ministry of Science, Technology and the Envvironment, Malaysia. Compared with the previous models, this one takes into more detailed consideration of the major meteorological and oceanographic contributions to the transport processes in the Straits of Malacca. For the wind component of the model, an analytical local wind model is used to estimate the land-sea breezes along the Peninsular Malaysia and Sumatra coastal stretches which run along the strait. The local wind estimates are combined with the predicted synoptic winds (for real-time operations) or the monthly mean winds (for risk and environmental impact assessment) to serve as wind inputs to the model. In the case of surface currents, a 2-dimensional depth averaged model is used to stimulate the tidal motion in the strait. The tidal currents are added to the seasonal drift (climatological) currents and local wind induced drift to produce the resultant drift vector. The model also provides for the estimation of wave parameters (wind seas and swells) which together with parameters like wind speed, sea surface temperature and oil characteristics are used to assess the physical and chemical changes to the oil spill