Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 2-5

Effects of Mo⁶⁺ Doping on Electrical Conductivity of TiO₂
W, G, D, Dharmaratna and P. R. T. N. de Silva
Department of Physics, University of Ruhuna, Matara

The effect of incorporation of Mo⁶⁺ ions into the srystal structure of TiO₂ was studied. Doped sample was prepared by the method of high-temperature diffusion of molibdenum into the crystal matrix of TiO₂. MoO₃ was used as the dopant precursor. TiO₂ in rutile form was used as the parent crystal. The conductivity increases (by two orders of magnitude at 250 ⁰C) and the activation energy decreases (by 45%) as a result of doping, which indicates the modification of electronic structure. The new result is in very good agreement with the previous results on the effects of altervalent cation doping on electrical conductivity of platinized titania, namely, the Fermi level increases with the valancy of the cation.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 6-11

Variation of Sea Surface Temperature (SST) in the Indian Ocean During El Nino Year
N. B. P. Punyadeva and W. L. Sumathipala
Department of Physics, The Open University of Sri Lanka, Nawala, Nugegoda

An attempt has been made to study the variation of SST during El Nino year and normal year over the Indian ocean by using monthly mean Sea Surface Temperature (SST) composites. It is obvious that during El Nino year high SST (<29 ⁰C) field lie just over the equator and spreads over a large area in the Indian ocean as compared to normal year. The high SST areas begin to emerge from the eastern Indian ocean in the month of February. During the period from March to June area north of the equator in the Indian ocean warms very rapidly and gradually moves northward. Prior ro rhe El Nino year, an increase in SST field is observed in the east coast of Africa. When compared to normal year, El Nino year has large area of SST which is greater than 29 ⁰C in the Indian ocean.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 12-19

Variation of Rainfall of Sri Lanka in Relation to El Ninio

W. L. Sumathipala and N. D. P. Punyadeva
Department of Physics, The Open University of Sri Lanka, Nawala, Nugegoda

Fluctuation of rainfall over Sri Lanka in relation to El Nino events is examined by using monthly rainfall composite during El Nino year and normal year. Rainfalls of 12 principal meteorological stations for a period of 97 years are used and during that period there were 23 El Ninos. Percentage departure for every month is plotted using an index computed for each station. It is obvious that during an EI Nino there is a reduction in rainfall over the northern part of the island. The most affected region is the north and east of the country mainly because over these regions strong negative percentages are found during the North East Monsoon (NEM0. During February the northeast region received greater than 60% below normal rainfall. As a whole even the First Inter Monsoon (FIM) recorded less than normal rainfall. However, during the Second Inter Monsoon (SIM) months of October and November rainfalls were above normal. It is interesting to note that the two months which start the two monsoons namely May and December recorded above normal rainfall. However the regions of the country where above rainfall is received are unusual. During may/December central and northern/southwestern part receives more rain.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 20-33

Characterization of Sinhala Sounds in Electronic Speech Recognition
W. M. N. S. Wanasundara, M. K. Jayananda and Asiri Nanayakkara
Department of physics, University of Sri Jayawadenepura, Gangodawila, Nugegoda

There has been tremendous progress made on speech recognition of English and other European languages during last twenty years. However, comparatively very little progress has been made on speech recognition system; we are engaged in analyzing Sinhala speech using various methods. In the present paper, we report preliminary results on characterization of some Sinhala characters using Fourier spectra.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 34-40

Text to Speech Conversion in Sinhala Language
Asiri Nanayakkara and M. K. Jayananda
Department of Physics, Universiity of Sri Jayawardanapura, Gangodawila, Nugegoda.

An important part of improving communication between computers and humans is giving the computers the ability to talk natural languages. This ability already exists for some languages such as English through a number of commercially available packages. We are engaged in developing such a package for Sinhala language. The package includes a Microsoft Windows based software for entering Sinhala text, a data base of basic sounds, and an inexpensive piece of hardware for playing back sound.

Because Sinhala is a phonetic language, text to speech conversion is a straightforward process to a certain degree. However, for producing natural sounding speech, it is necessary to incorporate various rules of the language. In this paper we describe physical properties of Sinhala sounds relevant to text to speech conversion, rules of the langusge and how they were implemented in software.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 41-44

An Electronic Surveillance System for Night-Flying Birds
C.M. Edirisinghe¹, D.U.J. Sonnadara¹ and V. Yapa^2
1Department of Physics, University of Colombo, Colombo 3, ²Department of Zoology, University of Colombo, Colombo 3

The construction of an electronic surveillance system that can be used to count night-flying birds passing through a 2-D window is presented. The surveillance system has been designed primarily to estimate the number of bats (although they are not birds) flying in or flying out of a cave. In addition to counting bats, this detector can be used to study the population, seasonal variations and the habits of bats and how they react to environmental changes.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 45-49

Low Cost Data Acquisition and Control Systems for Personal Computers
M. K. Jayananda¹ and D. U. J. Sonnadara^2
1Department of Physics, University of Sri Jayewardenepura, Nugegoda, ²Department of Physics, University of Colombo, Colombo 3

A detailed study of building low cost data acquisition and equipment control systems for personal computers containing analog-to-digital (ADC) and digital-to analog (DAC) converters is carried out. Two types of boards (based on AD7569 and ADC0816) were successfully constructed and implemented for the standard 8-bit ISA bus. These boards can be constructed under SLR 7,500 /- each and give much more flexibility than the expensive data acquisition cards that are sold in the market. By writing the control system software, the same card can be used for various purposes.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 50-53

Construction of a near-ideal Nanometer
R. P. Wijesundara, S. R. D. Kalingamudali and K. D. Jayasuriya
Department of Physics, University of Keleniya, Kelaniya

A near ideal ac/dc nanometer was constructed using two operational amplifiers (op-amp) and a voltmeter. Small currents were converted into a voltage by the first op-amp and this was amplified into a larger voltage by the second op-amp. The amplified voltage was measured by the voltmeter. The constructed meter has 10 and 100 nA ranges for the dc current measurements and 100 nA range for the ac current measurements. All the ranges calibrated using a digital picoammeter.

As compared to commercially available nanoammeters with similar features this meter has higher advantages such as almost zero internal resistance and negligible operating bias current. The construction cost of the meter is very low compared to a commercial ac/dc nanoammeter.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 54-60

Passive infrared counting system for vehicular traffic
I. J. Dayawansa
Department of Electronics & Telecommunication Engineering, University of Moratuwa, Moratuwa

This paper presents preliminary results f a vehicle traffic counting system that was designed using a pyroelectric cell as a sensor. The pyroelectric cell responds to a change in the incident infrared radiation. The rate of change of radiation incident on the pyroelectric sensor generated a current. This signal was used to count moving objects and the count was displayed on a seven segment LED display. The system is passive and it is able to count moving objects from a distance of over a meter and can be used to count moving vehicles.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 61-69

Gravity Anomaly Map and an Interpretation for the Mahapelessa Hot Spring Region, Southern Sri-Lanka
G.M. Fonseka¹ and T. Daves^2
1Department of Physics, The Open University of Sri Lanka, Nawala, Nugegoda, ²Department of Geology and Geophysics, University of Edinburgh, U.K.

A gravity survey was conducted in an area of ~27 Sq.km region around the Mahapelessa hot spring in southern Sri Lanka using a La-Coste and Romberg gravity meter. Sampling was carried out at 100 m intervals along the country roads and jungle tracks centered round hot springs. The local anomaly map shows northward regional gradient of ~ -10 gu/km and a N-S trending major fault with a well defined western flank. That runs for a few kilometers. The local anomaly near the hot springs gives an anomaly of amplitude ~ -2.5gu. This anomaly is interpreted as a NE-SW trending localized fault dipping approximately NW within the basement rocks at Mahapelessa. This fault is overlain by prisms of weathered rock with triangular cross section. The prism has a maximum depth of ~350 m at its apex. The uprising thermal waters are expected to flow along this local fault within the major fault.

Proceedings of the Technical Session of Institute of Physics, Sri Lanka 14 (1998) 70-77

Total Field Magnetic Anomaly at Mahapelessa Hot Spring and a Comparison with Resistivity Soundings
G.M. Fonseka¹ and S. Taylor^2
1Department of Physics, The Open University of Sri Lanka,Nawala, Nugegoda, ²Department of Geology and Geophysics, University of Edinburgh, U.K.

A proton precision total field magnetic survey was conducted along 45 km of country roads and jungle tracts of a 20 km2 region around the Mahapelessa thermal spring in southern Sri Lanka. A computer based automatic magnetometer at a base station recorded the daily variations of the geometric field while the field data was recorded manually at 25 m intervals by a mobile magnetometer. A total field residual geometric map is presented after the removal of the regional field taken as the least square plane of the original data set. Anomaly map indicate a E-NE magnetically high feature of ~1 km long but may continue further. Subsurface magnetism modeled across the strike direction with GRAVMAG indicates fracture zones dipping ~ 450 towards N-NW and is consistent with the resistivity and self potential analysis reported earlier.