Ravin N. Deo

Characterization of aerosols generated in a steel processing factory

The levels of total suspended particulates (TSP) within the complex of a steel factory (Fletcher Pacific Steel Fiji) have been investigated through high volume air sampling. The levels of TSP inside and outside (in the ambient environment) the factory has been found to be in the range of 121-339 and 33-80 μg m-3 respectively. The levels inside the factory exceed the WHO guideline by a factor of 2-4. The management of the factory was very proactive to determine the air quality for records and to safeguard the health and safety of all the employees, contractors, and visitors. At the request of the factory, the exposed filters were analysed by neutron activation and gamma-ray spectroscopy techniques and the results are presented.

Denoising time-domain induced polarisation data using wavelet techniques

Time-domain induced polarisation (TDIP) methods are routinely used for near-surface evaluations in quasi-urban environments harbouring networks of buried civil infrastructure. A conventional technique for improving signal to noise ratio in such environments is by using analogue or digital low-pass filtering followed by stacking and rectification. However, this induces large distortions in the processed data. In this study, we have conducted the first application of wavelet based denoising techniques for processing raw TDIP data. Our investigation included laboratory and field measurements to better understand the advantages and limitations of this technique. It was found that distortions arising from conventional filtering can be significantly avoided with the use of wavelet based denoising techniques. With recent advances in full-waveform acquisition and analysis, incorporation of wavelet denoising techniques can further enhance surveying capabilities. In this work, we present the rationale for utilising wavelet denoising methods and discuss some important implications, which can positively influence TDIP methods. We have conducted the first application of wavelet-based denoising techniques for processing raw TDIP data. Our investigation included laboratory and field measurements to better understand the advantages and limitations of these techniques. It was found that distortions arising from conventional filtering can be significantly avoided with wavelet-based methods.

Spectral Induced Polarization Techniques in Soil Corrosivity Assessments

We presented a laboratory method for investigating the spectral induced polarization (SIP) response of soil samples and the implications for overall soil corrosivity. This study was important in order to advance the understanding of soil electrical properties, which can be used diagnostically to assess infrastructure integrity. Presently, isolated measurements of soil resistivity are the only (electrical) parameters that are routinely used to identify soil corrosivity. Our work showed that the low frequency soil spectral properties may lead to better soil corrosivity assessments when coupled effects from clay and salinity were present. In particular, unfolding and interpreting the soil spectral properties using the Cole-Cole model revealed that the normalized chargeability parameter mn was highly appropriate for identifying the character of potentially corrosive soils.

Trace element concentrations in sediments from Kadavu passage, Fiji

Grab sediments, collected from 11 locations from the Pacific Ocean floor in the region between Suva Peninsula and Kadavu Island, Fiji, were investigated for concentrations of 20 elements using neutron activation and high-resolution gamma ray spectroscopy techniques. The sediments were collected at distances between 5-35 km from the mainland and at ocean depths ranging from 500 to 2000 m. A comparison of the elemental abundances of these sediments with those of the Suva lagoon and other nearby locations indicates that the ocean sediments are likely to be derived from sediments washed out to sea from the mainland. The sediments also show no evidence of any metal contamination from the industrial activity in the Suva metropolitan area.

Wind regime in the proximity of the 20 kW experimental turbine site at Nabua, Fiji

Renewable energy generated as much electric power worldwide in 2005 as one-fifth of the worlds nuclear power plants excluding large hydropower that itself accounts to 16% of world’s electricity (REN 21 2005). Renewable energy is gaining prominence in providing the world’s primary energy needs. Solar, wind, biomass, and geothermal are considered as the premier renewable energy resources that are in direct competition with the conventional fuels. The fastest growing technology has been the photovoltaic (grid connected), however, wind power is steadily growing with an estimated existing capacity of 56 GW by the end of 2005 (REN21 2005). Wind power has been used for many centuries to provide mechanical and electrical power for a variety of uses. Since the beginning of the last century, however, the most important use has been the generation of electricity for supply to rural and remote areas, as well as providing energy into the electrical distribution system, i.e. the national grid. World wind energy capacity has doubled every three years since 1990 and each doubling has been accompanied by a 15% reduction in the price of wind turbines (Milbrow 2005). Turbine size has increased from 600 - 800 kW to 1 - 3 MW with blade diameters from 60 -100 m and the energy costs (c/kWh) has declined by at least 18% and is now half those of 1990. The practical size of a wind turbine is determined by the assessment of annual electrical load, site conditions, wind resource, installed cost, and utility rate (Lodge 2005).The major countries that utilize wind power for electricity generation include the USA, Spain, Germany, India, Britain, Sweden, Netherlands, China, and Denmark. However, Russia, South Africa, Brazil, and Mexico are in the transitional stage to develop large-scale commercial markets. The basic theory of the extraction of energy from a wind turbine is found in any standard textbook on wind energy. The power in the wind varies as the cube of the wind speed. If an obstacle is placed in the path of the wind, the wind’s kinetic energy does work on the obstacle and wind energy is converted to other forms, including the kinetic energy of rotating parts. Thus a turbine or rotor placed in the path of wind, with wind speed,