Don Upul Jayasiri Sonnadara

Event shapes for Au + Au collisions at 11.4 GeV/c per nucleon were studied over nearly the full solid angle with the E877 apparatus. The analysis was performed by Fourier expansion of azimuthal distributions of the transverse energy (ET) measured in different pseudorapidity intervals. For semicentral collisions a pronounced event anisotropy is identified with a clear forward-backward anticorrelation. In the forward pseudorapidity interval up to 9% of the ET is in a directed component. The signal decreases for peripheral and very central collisions.Received 12 May 1994DOI:https://doi.org/10.1103/PhysRevLett.73.2532©1994 American Physical Society

Results are presented of an analysis of proton and charged pion azimuthal distributions measured with respect to the reaction plane in Au + Au collisions at a beam momentum of about 11A GeV/c. The azimuthal anisotropy is studied as a function of particle rapidity and transverse momentum for different centralities of the collisions. The triple differential (in rapidity, transverse momentum, and azimuthal angle) distributions are reconstructed. A comparison of the results with a previous analysis of charged-particle and transverse energy flow as well as with model predictions are presented.Received 30 June 1997DOI:https://doi.org/10.1103/PhysRevC.56.3254©1997 American Physical Society

Experimental results and a detailed analysis are presented of the transverse energy and charged particle azimuthal distributions measured by the E877 Collaboration for different centralities of Au+Au collisions at a beam momentum of 10.8A GeV/c. The anisotropy of these distributions is studied with respect to the reaction plane reconstructed on an event-by-event basis using the transverse energy distribution measured by calorimeters. Results are corrected for the reaction plane resolution. For semicentral events we observe directed flow signals of up to 10%. We observe a stronger anisotropy for slow charged particles. For both the charged particle and transverse energy distributions we observe a small but nonzero elliptic anisotropy with the major axis pointing into the reaction plane. Combining the information on transverse energy and charged particle flow we obtain information on the flow of nucleons and pions. The data are compared to event generators and the need to introduce a mean field or nucleon-nucleon potential is discussed.Received 15 October 1996DOI:https://doi.org/10.1103/PhysRevC.55.1420©1997 American Physical Society

We present proton and pion tranverse momentum spectra and rapidity distributions for Au+Au collisions at 10.8A GeV/c. The proton spectra exhibit collective transverse flow effects. Evidence of the influence of the Coulomb interaction from the fireball is found in the pion transverse momentum spectra. The data are compared with the predictions of the RQMD event generator.

Collisions of $^{28}\mathrm{Si}$+Al, Cu, Pb at ${\mathit{E}}_{\mathrm{lab}}$/A=14.6 GeV were studied in a calorimetry-based experiment at the BNL Alternating Gradient Synchrotron. Transverse-energy production was measured for pseudorapidities -0.50.8. Correlations with the spectra and multiplicity of neutrons and protons emitted into a forward 0.8\ifmmode^\circ\else\textdegree\fi{} cone demonstrate quantitatively the large amount of nuclear stopping observed in these reactions. Calculations in hadronic-fireball or nucleon-nucleon based models underpredict the measured transverse-energy production for Si+Pb and indicate the need to include rescattering of secondaries and /or contributions from target fragmentation.

We present a systematic study of transverse energy (${\mathit{E}}_{\mathit{T}}$) production in collisions of 11.4A GeV/c Au and 14.6A GeV/c Si ions with targets of Al, Au, and Pb. Comparison of data for Au+Au and Si+Al indicates that, for the heavier system, there is an increase in the amount of stopping which is accompanied by a decrease in the width of the ${\mathit{dE}}_{\mathit{T}}$/d\ensuremath{\eta} distribution. The ratio of the maximum ${\mathit{E}}_{\mathit{T}}$ observed for the two systems is significantly greater than the ratio of the total energy available in the center of mass frame.

We present measurements of pion transverse momentum (pt) spectra in central Si-nucleus collisions in the rapidity range 2.0 < y < 5.0 for pt down to and including pt = 0. The data exhibit an enhanced pion yield at low pt compared to what is expected for a purely thermal spectral shape. This enhancement is used to determine the Δ resonance abundance at freeze-out. The results are consistent with a direct measurement of the Δ resonance yield by reconstruction of proton-pion pairs and imply a temperature of the system at freeze-out close to 140 MeV.

We have measured cross sections for the synthesis of nuclei of mass A\ensuremath{\le}4 in collisions of 14.6A GeV/c $^{28}\mathrm{Si}$ nuclei with targets of Pb, Cu, and Al. The data are measured at close to center-of-mass rapidities, and are unique in their exploration of the centrality dependence of nucleosynthesis. Simple coalescence models that were used to study nucleosynthesis at lower energies are inadequate for the description of our measurements. Our data and improved models are used to extract parameters related to the size of the interaction volume at freeze-out.

Channel brightness of 500 mm long electrical discharges were measured by analyzing a set of digitized images taken by 3 cameras placed symmetrically around a discharge gap at a radial distance of 200 cm from the axis of the spark. The sparks were generated between a steel rod and a plane electrode. The distribution of the brightness across the channel represented a Gaussian distribution. A linear correlation was seen between the channel brightness measured by different cameras looking at the same spark channel. No correlation was seen between the channel brightness and the channel depth (direction perpendicular to the camera plane). The measured peak current and the brightness of the main spark channel show a high degree of correlation (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> =0.97). The sum of brightness of branches was equal to the brightness of the parent channel. One can use this result to calculate the relative distribution of branch currents in complex electrical discharges including natural lightning flashes. If the current in the parent channel is known, branch currents can be calculated by measuring the optical intensities using photographic techniques.

We have initiated a search for strange quark matter in the products of 14.6 GeV/c per nucleon 28Si collisions with nuclei, utilizing the apparatus of E-814 at Brookhaven National Laboratory's AGS. We report the first results of this search, which is sensitive to particles with charge-to-mass ratios between 0.1 and 0.3 (GeV/c2)−1 that are produced within approximately ±0.5 units of the center of mass rapidity.

A detailed study of the characteristics of cloud-to-ground (CG) lightning flashes over Sweden was carried out for the period 1987–2000 using data obtained from the Swedish lightning-locating network. Results are presented by analysing over half a million lightning ground flashes. The average variation of the annual mean of the total number of flashes was found to be 37%. About 12% of the CG flashes were positive flashes and their average variation about the annual mean was 26%. The average peak currents were fairly constant over the years with variations as little as 4% for negative flashes and 5% for positive flashes. The average peak current values for negative and positive flashes were −29.90 and +63.97 kA respectively. A correlation between the mean monthly flash count and percentage of positive flashes was seen. A similar relationship is seen with the mean monthly flash count and the peak currents for both polarities. In general, high flash density and high peak currents were observed in the southern part of Sweden where most of the major cities are located. Flash densities exceeding 0.4 flashes km−2 were observed for several large cities. The maximum flash rate of 32 flashes h−1 within a 10 km radius was seen in Jönköping (14.18°E, 57.78°N) in the province of Småland.

Pulse trains of irregular pulse characteristics and erratic amplitudes are observed in lightning flashes. These are termed “chaotic pulse trains” in this study. The average width of the individual pulses of these pulse trains is in the range of a few microseconds, with the lower limit of individual measurements extending into the sub-microsecond region. The typical pulse separation lies in the range of 2–20μs. The pulse duration shows a consistent distribution with the most probable value at 400–500μs. Chaotic pulse trains occur most often immediately prior to subsequent strokes. However, they occur also a few milliseconds to several tens of milliseconds prior to return strokes and sometimes do not precede return strokes at all. Twenty-six percent of the total subsequent strokes recorded in this study were preceded by chaotic pulse trains. A few of these pulse trains have occurred in a sequence of several tens of millisecond intervals in between return strokes. We have also found them to occur within very intense cloud flashes. These chaotic pulse trains have features that are different from those of other known pulse trains reported in the lightning literature. Hence, they may be caused by a physical process that has not yet been identified.

Electric radiation fields produced by lightning cloud flashes have been analyzed using Fourier methods to obtain amplitude spectra for frequencies in the range of 20 kHz to 20 MHz. Time to thunder measurements were used to extract the distances to the cloud flashes from the measurement site. The spectra were generated by analyzing the first 10 ms time window of cloud flashes with 10 ns sampling resolution, and they show f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> frequency dependence up to 2 MHz followed by f <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> dependence and higher for frequencies above 2 MHz. The results agree very well with previous measurements carried out for individual pulses produced by various lightning processes. By utilizing digital filters, it has been shown that measurements taken with narrowband filters agree with the results produced under wideband measurements

In this article the authors summarize recent results from the E814 forward spectrometer on proton and pion distributions that give insight into the initial baryon (and energy) density achieved in central collisions as well as the temperature of the system at freeze-out. An independent measure for the latter, complementing the slope constants of particle spectra, is the population of nucleon excited states, in particular the {Delta}(1232) resonance. Besides its influence on the pion spectra it has also been identified directly in the experiment and first results are discussed. The first results from E814 on kaon spectra at low transverse momentum p{sub t} are presented; the spectra show an unexpected very steep rise at the lowest p{sub t}. The two pion correlation function has been studied for positive and negative pions and the authors show that it is consistent with a large source size at freeze-out. Finally, they show that the present data give a consistent picture of a system in thermal and chemical equilibrium at freeze-out.

We present the rapidity and transverse momentum distributions of protons and neutrons from collisions between 14.6 GeV/nucleon beams of 28Si and targets of Al, Cu, and Pb. The data were measured in the forward spectrometer/target calorimeter detectors of the E814 apparatus. The results indicate the existence of two distinct domains, one of beam rapidity projectilelike nucleons, and the second of participant nucleons. From the former, the in-medium inelastic nucleon-nucleon cross section is deduced. It is found to agree, within 10%, with the ‘‘free’’ value of 30 mb although under present conditions one of the two colliding nucleons has been struck before with a high probability. We compare with the present data the predictions of a fragmentation model as well as of models dealing explicitly with the heavy-ion collision and particle creation and emission.Received 23 July 1991DOI:https://doi.org/10.1103/PhysRevC.45.819©1992 American Physical Society

Electromagnetic dissociation cross sections for one, two, and three nucleon removal were measured for an ${\mathit{E}}_{\mathrm{lab}}$/A=14.6 GeV $^{28}\mathrm{Si}$ beam impinging on $^{27}\mathrm{Al}$, $^{120}\mathrm{Sn}$, and $^{208}\mathrm{Pb}$ targets. The measured cross sections exhibit an approximate ${\mathit{Z}}_{\mathit{T}}^{2}$ dependence and are well reproduced by calculations convoluting the virtual photon spectrum with the experimental \ensuremath{\sigma}(\ensuremath{\gamma},N) photonuclear cross sections. Comparison with other experimental results and energy dependence of the cross sections are discussed.

The fractal dimension of 500 mm long electrical discharges is presented by analyzing a set of photographic images. Three popular fractal dimension estimation techniques, box counting, sandbox and correlation function methods were used to estimate the fractal dimension of the discharge channels. To remove the apparent thickness due to varying magnitudes of current in the discharge channels, edge detection algorithms were utilized. The estimated fractal dimensions for box counting, sandbox and correlation function for long laboratory sparks were 1.20 ± 0.06, 1.66 ± 0.05 and 1.52 ± 0.12 respectively. Within statistical uncertainties, the estimated fractal dimensions of positive and negative polarities agreed very well.

We have measured antiproton production cross sections as functions of centrality in collisions of 14.6 GeV/c per nucleon $^{28}\mathrm{Si}$ ions with targets of Al, Cu, and Pb. For all targets, the antiproton yields increase linearly with the number of projectile nucleons that have interacted, and show little target dependence. We discuss the implications of this result on the production and absorption of antiprotons within the nuclear medium.

The two-pion correlation function has been measured for charged pions produced in central 14.6 A GeV/c Si + Pb collisions at the AGS. Data for like-sign pions show a clear quantum interference effect as expected for identical bosons. The experimental correlation function agrees well with that obtained for events generated by a cascade code (RQMD). The present data are consistent with a time-averaged rms freeze-out radius of 8.3 fm and a mean duration of pion emission of 9 fm/c. The system has expanded considerably before freeze-out.

Collisions of 28Si+Al, Cu, and Pb at Elab=14.6 GeV/nucleon were studied at the Brookhaven National Laboratory Alternating Gradient Synchrotron. Charged particle multiplicity was measured over the pseudorapidity interval 0.875≤η≤3.86 with a silicon pad detector. A strong correlation is seen between the multiplicity and the transverse energy measured in the interval -0.5≤η≤0.8. Correlation with the energy going forward after the collision and comparison with calculations indicate that rescattering is required to explain the data. The data are compared under the assumption of Koba-Nielson-Olesen scaling. The measured multiplicity scales approximately with the total number of participant nucleons and less well with the available center-of-mass kinetic energy.Received 12 November 1991DOI:https://doi.org/10.1103/PhysRevC.46.312©1992 American Physical Society

Channel tortuosity of 50 cm long laboratory sparks were measured by analyzing a set of images taken by three cameras. The cameras were placed at a radial distance of 200 cm from the spark gap. The angle between any two cameras was 120°. The sparks were generated between a steel rod and a plane electrode. The distribution of the direction change of the channel was found to be Gaussian with a standard deviation of 15.3°. The average tortuosity of the channel defined as the mean absolute value of the direction change was 11.8±1.4°, which is smaller than the average tortuosity of natural lightning and close to the tortuosity of triggered lightning. The average tortuosity is dependent on the segment length used in calculating the direction change. A gradual increase in the average tortuosity (0.08°/cm) was seen when the sparks propagated towards the plane electrode.

In this study, an analysis of century scale climate trends in the central highlands of Sri Lanka is presented. Monthly rainfall and temperature records of the period 1869–2006 from five climatological stations were analyzed. The trend is calculated by the least square regression analysis and the significance of the observed trend is estimated using the Mann–Kendall statistic. The results clearly show that there is a statistically significant decrease in annual rainfall in the western slopes of the central highlands. Throughout the last century, the annual reduction of rainfall in Nuwara Eliya which is at an altitude of 1895 m was 5.2 mm/year. The decrease is largely due to the reduction in southwest monsoon rainfall which contributes to 75% of the total reduction. No significant change was observed on the eastern side of the central highlands which receives rainfall predominantly from the northeast monsoons. The mean annual temperature in the mountainous region shows a uniform increasing trend which is in line with the 100-year global temperature increase of 0.8 ± 0.2∘C. Kandy, which is at an altitude of 477 m and closely linked with the rainfall climatology of Nuwara Eliya, showed no significant change in the mean annual temperature. If the current trend continues, in another 100 years, western and eastern slopes of central highlands will receive the same amount of rainfall from the southwest monsoon and the northeast monsoon which will have far reaching consequences for Sri Lanka’s economy and the ecology of the hill country.

Abstract Performance of a feed‐forward back‐propagation artificial neural network on forecasting the daily occurrence and annual depth of rainfall at a single meteorological station is presented. Both short‐term and long‐term forecasting was attempted, with ground level data collected by the meteorological station in Colombo, Sri Lanka (79° 52′E, 6° 54′N) during two time periods, 1994–2003 and 1869–2003. Two neural network models were developed; a one‐day‐ahead model for predicting the rainfall occurrence of the next day, which was able to make predictions with a 74·3% accuracy, and one‐year‐ahead model for yearly rainfall depth predictions with an 80·0% accuracy within a ± 5% error bound. Each of these models was extended to make predictions several time steps into the future, where accuracies were found to decrease rapidly with the number of time steps. The success rates and rainfall variability within the north‐east and south‐west monsoon seasons are also discussed. Copyright © 2007 John Wiley &amp; Sons, Ltd.

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

Abstract A study was carried out to compare the negative cloud to ground lightning discharges recorded using Swedish lightning locating system against time correlated direct field measurements. Only the first 200 ms time window was investigated. A total of 167 flashes were recorded and time matched against the lightning locating system records. The comparison shows that for negative cloud-to-ground lightning flashes, the stroke detection efficiency of lightning locating system is at 93% for detecting the first stroke accurately. The efficiency drops to about 77% in detecting all strokes accurately. Thus, the system tends to give a low value for average multiplicity and a significantly higher value for parameters such as percentage of single stroke flashes. In agreement with the direct field measurements, when the individual strokes are identified correctly, both systems show the expected 2:1 ratio between the first and subsequent stroke peak field. Data also shows that the LLS system has a tendency of identifying isolated cloud pulses as positive return strokes. Hence one must take into account the systematic deficiency in lightning locating systems when reporting characteristics of cloud to ground lightning flashes.

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.Cover :Leatherback (a), green (b - adult &amp; f - hatchling), hawksbill (c) and olive ridley (d) turtles who nest in Sri Lankan beaches, green turtle crawl marks (e) and by-catch of sea turtles in fisheries (c &amp; d)Photo credits: SJ Perera (a &amp; c), WPN Perera (b &amp; e), K Ekaratne (d &amp; f)

A detailed study on electric field characteristics of Narrow Bipolar Pulses (NBP) observed in Sri Lanka is presented here. NBPs analyzed in this work were recorded at a coastal location in the Southern part of Sri Lanka (Matara: 5.95 °N, 8.53 °E), from five highly active consecutive thunderstorm days during the month of May in 2013. The waveforms were recorded with a 10 ns resolution within a 100 ms time window. Both positive and negative NBPs were observed in this study with the negative type being the most frequent. Parameters presented in this study were the rise time (Tr), zero crossing time (Tz), the duration of slow front (Ts), the full width of half maximum (FWHM), the pulse duration and the ratio of amplitude of overshoot to the corresponding peak amplitude (Os/Pa). The corresponding average values of negative NBPs for these parameters were found to be 0.58 µs, 3.01 µs, 0.20 µs, 1.38 µs, 19.21 µs and 0.19 respectively. Similarly, for positive events corresponding values were 1.38 µs, 4.66 µs, 0.48 µs, 1.93 µs, 16.42 µs and 0.37 respectively. The above values conforms to a much narrower bipolar events when compared to previously reported values which is considered to be caused by the propagation effects of signals captured by the apparatus.

New data on Λ production in Au+Au collisions at 11.5A GeV/c are presented. The measurements cover the rapidity range from y=2.0 to 3.5 and transverse momenta from pt=0.15 GeV/c to 1.5 GeV/c. The rapidity distributions, transverse momentum spectra, and azimuthal distributions are presented for different centralities of the collision. A strong positive directed flow at forward rapidity is observed for semicentral collisions. The measured spectra, yields, and directed flow are compared with the predictions of relativistic quantum molecular dynamics (RQMD) v2.3 model.Received 6 July 2000DOI:https://doi.org/10.1103/PhysRevC.63.014902©2000 American Physical Society

Inclusive double differential multiplicities d2N/dy dpt and related quantities have been measured for protons and deuterons produced in 14.6A GeV/c Si+Al and Si+Pb collisions using the E814 forward spectrometer at the AGS at BNL. Collision ‘‘centrality’’ is determined by measuring Nc, the total charged particle multiplicity in the pseudorapidity range 0.85<η<3.8. For both systems Si + Al and Si + Pb, an increase in the proton rapidity distribution dN/dy at midrapidity and a corresponding decrease at higher rapidities are observed with increasing Nc. For Si+Pb, Boltzmann slope parameters TB increase significantly in the most central collisions. The measured distributions exhibit a centrality dependence even when σ/σgeo≲10%, where full overlap between the Si and Pb nuclei occurs in a simple geometric picture. The proton rapidity distribution dN/dy is presented for the symmetric system Si+Al over the entire rapididty interval. The total number of protons, which is the integral of this quantity over rapidity, varies with Nc. Results are compared with various model calculations, mostly using the hadronic cascade codes ARC and RQMD. No significant nuclear transparency is observed, indicating that large baryon and energy densities are produced in these collisions.Received 5 August 1994DOI:https://doi.org/10.1103/PhysRevC.50.3047©1994 American Physical Society

A license plate identification system can be used for numerous applications such as unattended parking lots, security control of restricted areas, traffic law enforcement and automatic toll collection. Such a system captures images of vehicles and identifies license plate numbers automatically. Here we present results of a system in identifying the vehicle license plate through digitized photographic images based on image processing techniques. The developed algorithm is based on two basic processing stages; locating the license plate, and, identifying the individual digits and characters in the license plate. The algorithm takes a raster image of the rear view of a vehicle as input and yields the recognized numbers and characters in the number plate as the output. The performance of the developed algorithm has been tested on a set of real images of vehicles. The first part of the system showed that the algorithm performs quite well in accurately locating the license plates (with 97% efficiency). In the second part which is based on neural network techniques, showed high performance in recognizing digits and characters in located plate regions.

The performance of neuro-fuzzy traffic signal control at two independent traffic junctions is discussed. In this work, traffic conditions at two 4-way traffic junctions were simulated and flow of traffic on the road connecting the two junctions under varying traffic conditions was studied. For a given data set, the developed neuro-fuzzy system automatically draws membership functions and the rules by itself, thus making the designing process easier and reliable compared to conventional fuzzy logic controllers. The traffic inflows of roads are given as inputs to the fuzzy control system which generate the corresponding green light time as the output to control the signal timing. The control systems try to minimize the delay experienced by the drivers at the two traffic junctions. As expected, when compared with a fixed-time signal control system, the neuro-fuzzy system tends to minimize vehicle delays at both junctions. Simulation results show, under variable traffic conditions, neuro-fuzzy control system perform efficiently by making average delay per vehicle under the red light phase smaller and increasing the synchronization of green light phases between junctions. When the volume of traffic at one of the junction changed abruptly, the green light timing of both junctions changed, adapting to the new traffic condition on the road connecting the two junctions.

The onset, retreat and the length of growing season in the north-eastern region of Sri Lanka were investigated using daily rainfall data for the period 1961 to 2000. Data from three weather stations situated in the coastal belt in the northern and eastern parts of Sri Lanka (Jaffna, Trincomalee and Batticaloa) that receive rainfall predominantly from the northeast monsoon were selected for this study. A method based on cumulative rainy days was utilized in the determination of the onset and retreat dates. It is shown that there is substantial interannual variability in onset and retreat dates. The mean onset and retreat dates fall on the standard week 38.3 ± 2.7 and 53.0 ± 2.9, respectively. The mean duration of the growing season is 14.7 ± 3.4 weeks. The retreat date and thus the length of growing season could be extended by 2 weeks if the probability of occurrence of rain during the onset is favourable for the retreat. The results indicate that there has been no significant trend in the onset and retreat dates during the last 40 years in the dry zone of Sri Lanka. The onset date and the length of growing season are weakly correlated with early onset dates leading to longer growing seasons. The study concludes that rainy days could be used successfully to determine the mean rainfall onset and retreat dates in the dry zone of Sri Lanka.

In this paper, an analysis of temporal variation of wind speed and wind direction recorded at 10 min intervals are presented. The measurements were carried out at Hambanthota, a site located in the southern coastal belt of Sri Lanka which has a high potential for wind power generation. The multifractal detrended fluctuation analysis was used to analyze the temporal scaling properties of wind speeds and wind directions. The analysis was carried out for seasonal variation of wind speed and wind direction. It was observed that the scaling behavior of wind speed in Hambanthota is similar to the scaling behavior observed in previous studies which were carried out in other parts of the world. The seasonal wind and wind direction change exhibits different scaling behavior. No difference in scaling behavior was observed with heights. The degree of multifractality is high for wind direction when compared with wind speed for each season.

We present the results of an analysis of charged particle pseudorapidity distributions in the central region in collisions of a Au projectile with Al, Cu, Au, and U targets at an incident energy of 10.8~GeV/c per nucleon. The pseudorapidity distributions are presented as a function of transverse energy produced in the target or central pseudorapidity regions. The correlation between charged multiplicity and transverse energy measured in the central region, as well as the target and projectile regions is also presented. We give results for transverse energy per charged particle as a function of pseudorapidity and centrality.

Directed flow of antiprotons is studied in Au+Au collisions at a beam momentum of 11.5A GeV/c. It is shown that antiproton directed flow is anti-correlated to proton flow. The measured transverse momentum dependence of the antiproton flow is compared with predictions of the RQMD event generator.

An adaptive neuro-fuzzy inference system is developed and tested for traffic signal controlling. From a given input data set, the developed adaptive neuro-fuzzy inference system can draw the membership functions and corresponding rules by its own, thus making the designing process easier and reliable compared to standard fuzzy logic controllers. Among useful inputs of fuzzy signal control systems, gap between two vehicles, delay at intersections, vehicle density, flow rate and queue length are often used. By considering the practical applicability, the average vehicle inflow rate of each lane is considered in this work as inputs to model the adaptive neuro-fuzzy signal control system. In order to define the desired objectives of reducing the waiting time of vehicles at the signal control, the combined delay of vehicles within one signal cycle is minimized using a simple mathematical optimization method The performance of the control system was tested further by developing an event driven traffic simulation program in Matlab under Windows environment. As expected, the neuro-fuzzy logic controller performed better than the fixed time controller due to its real time adaptability. The neuro-fuzzy controlling system allows more vehicles to pass the junction in congestion and less number of vehicles when the flow rate is low. In particular, the performance of the developed system was superior when there were abrupt changes in traffic flow rates.

Two-proton correlation functions have been measured in Si+Pb collisions at 14.6A GeV/c and Au+Au collisions at 11.5A GeV/c by the E814/E877 collaboration. Data are compared with predictions of the transport model RQMD and the source size is inferred from this comparison. Our analysis shows that, for both reactions, the characteristic size of the system at freeze-out exceeds the size of the projectile, suggesting that the fireball created in the collision has expanded. For Au+Au reactions, the observed centrality dependence of the two-proton correlation function implies that more central collisions lead to a larger source sizes.

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.Cover :Leatherback (a), green (b - adult &amp; f - hatchling), hawksbill (c) and olive ridley (d) turtles who nest in Sri Lankan beaches, green turtle crawl marks (e) and by-catch of sea turtles in fisheries (c &amp; d)Photo credits: SJ Perera (a &amp; c), WPN Perera (b &amp; e), K Ekaratne (d &amp; f)

Inclusive double differential multiplicities of deuterons, ${}^{3}\mathrm{H},$ ${}^{3}\mathrm{He},$ and ${}^{4}\mathrm{He}$ measured by E877 for $11.5A \mathrm{GeV}/c$ Au+Au collisions at the Brookhaven's Alternating Gradient Synchrotron (AGS) are presented. Light fragments at beam rapidity are measured for the first time at AGS energies. Beam rapidity deuteron and ${}^{4}\mathrm{He}$ yields and transverse slope parameters are found to be strongly dependent on the impact parameter, and the shape of the deuteron spectra is not consistent with that expected for a simple thermal distribution. The deuteron yields relative to proton yields are analyzed in terms of a simple coalescence model. While results indicate an increase in source size compared to collisions of lighter systems at the same energy, they are inconsistent with a simple coalescence model reflected by a rapidity dependence of the coalescence parameter ${B}_{d}.$ A new approach utilizing an expanding thermalized source combined with a coalescence code is developed for studying deuteron formation in heavy-ion collisions. The strong dependence of deuteron yields on collective motion implies that deuteron yields relative to those of protons can be used for constraining source parameters.

Isolated Narrow Bipolar Pulses (NBP) have been observed in the past in sub tropical and tropical regions. This study presents detail electric field characteristics of NBP pulses observed in Sri Lanka in the tropic. NBP analyzed in this work were recorded at Matara (5.95 °N, 8.53 °E), southern coast of Sri Lanka from four highly active thunderstorm days in May 2013. The waveforms were recorded with a 10 ns resolution within a 100 ms time window. In contrary to previous observations at the same geographical region, both positive and negative NBP pulses were observed in this study. Parameters related to Narrow Negative Bipolar Pulses (NNBP) are presented in this study since majority of the observations were in that category. The parameters measured for NNBP's were rise time (Tr), zero crossing time (Tz), the duration of slow front (Ts), the full width at half maximum (FWHM) and the ratio of amplitude of overshoot to the corresponding peak amplitude (Os/Pa). The corresponding average values for these parameters were found to be 0.49 μs, 2.83 μs, 0.18 μs, 1.18 μs and 0.17 respectively. The above values conforms to a much narrower bipolar pulses when compared to values reported in earlier studies.

A simulation and a pilot scale implementation of a vision based robot navigation system was carried out to determine the feasibility and the efficiency of using optical flow based algorithms in autonomous robot navigation. For the simulation work, VRML 97 was used to create the virtual world and the robot. Simulink was used to implement the algorithm and the optical flow calculations. The video stream captured through a virtual camera as seen by the robot was used to calculate the optical flow to determine the direction and the speed of the robot for the next step. A mathematical model was used to solve the problem analytically. The same algorithm was implemented and tested in real-time in a controlled environment. Data gathered through the simulation and the actual implementation showed that it is possible to use optical flow based algorithms in robot navigation.

We report a direct measurement of the final-state energy spectrum in the electromagnetic dissociation of $^{28}\mathrm{Si}$ into p+ $^{27}\mathrm{Al}$ at an energy of 14.6 GeV/nucleon. The final-state energy is obtained through a calculation of the p${\mathrm{\ensuremath{-}}}^{27}$Al invariant mass in kinematically reconstructed events. The final-state energy spectrum for all targets is peaked near the isovector giant-dipole resonance in $^{28}\mathrm{Si}$ and the dependence of the magnitude of the cross section on target charge confirms that the excitation is largely electromagnetic. By exploiting the expected scaling behavior on target Z and A, the background from nuclear interactions is evaluated and subtracted, leaving a pure electromagnetic dissociation final-state energy distribution. This distribution is well reproduced by simulated events, in which the photon spectrum calculated in the Weisz\"acker-Williams approximation is combined with experimental data on the photonuclear reaction $^{28}\mathrm{Si}$(\ensuremath{\gamma},p) $^{27}\mathrm{Al}$, and slight differences are observed only at low final-state energy.

Experiments play a vital role in science education. In high school physics, especially in mechanics, many experiments are conducted where tracking a single or multiple objects are required. In most situations students visually observe the motion of objects and take the measurements. This manual method is time consuming, generates higher error and incapable of producing multiple readings rapidly. The research described in this work introduces a simple mechanism to integrate computer vision based tracking to enhance the quality of measurements and to new ways of looking at experiments. The case study consists of three standard experiments. In the first experiment a motion of the simple pendulum was tracked. Using computer vision students were able to obtain a correlation of 0.99 between the calculated period and the theoretical period. In addition, it was possible to calculate the position and the velocity of the bob more than 30 times during a single oscillation. Students were able to plot the extra data points for a better understanding of the simple harmonic motion, which was not possible in the manual method. Second experiment was focused on measuring the terminal velocity of a ball moving through a viscous medium. Final case study was on tracking multiple particles in a moving fluid. In all three experiments computer vision based system provided more accurate and higher number of data points than the manual method. This helps students to understanding the underline theory better. The tracking system was consisted of a digital camera, image preprocessing sub system, feature extraction subsystem, object identification subsystem and data export subsystem. The system was successfully tested on a normal PC which is cost effective to be used in high schools. Based on the case studies it was concluded that such systems can be used in high schools to improve the quality of experiments conducted.

A basic broadband digital interferometer was developed, which is capable of locating Very High Frequency (VHF) radiation sources in two spatial dimensions and time. Three antennas sensed the time series of broadband electromagnetic (EM) signals and digitized with 4 ns sampling interval for a duration of several milliseconds. A technique based on cross-correlations has been implemented for mapping lightning source locations. A map of the first return stroke (RS) and the preceding stepped leader was mapped successfully, using the system with a time resolution of few milliseconds. The result was compared with the visible events of the ground flash to validate the system.

We have studied in detail the electromagnetic dissociation of Si28 projectiles at 14.6 GeV/(c nucleon), interacting with Pb, Sn, Cu, and Al targets. Exclusive cross sections were measured for several decay channels, including final states involving the emission of protons, neutrons, and α particles. Excitation energy distributions for the 1n+27Si and 2p+26Mg decay channels were reconstructed with a resolution of 2 MeV, using a constrained kinematic fit. The energy distributions obtained for 1n+27Si are in good agreement with the σ(γ,n) photoneutron cross sections multiplied by the virtual photon spectrum obtained in the Weizsäcker-Williams approximation. A search for the double photon excitation process, based on the dependence of the cross sections on the target atomic number, was performed.Received 7 July 1994DOI:https://doi.org/10.1103/PhysRevC.51.865©1995 American Physical Society

We present the results of a study of amplitude and timing measurements made in a liquid krypton electromagnetic calorimeter, using multiply sampled signals of the shaped waveform. The measurements were designed to emulate the type of data that will be available from a calorimeter operating at future hadron-hadron colliders with short (∼ 20 ns) spacing between bunch crossings. Data have been collected with 18 ns sample spacing on waveforms from individual calorimeter sections with a shaping time of 40 ns and from 5 × 5 tower analog sums with a shaping time of 50 ns. The amplitude was measured using the analog sum signal, and the timing was measured using the signal from the individual sections. The data were processed using the method of optimal filtering, and a reduction in the noise of about a factor of two over that for a single sample is seen when using multiple samples for determining the amplitude. We find an energy resolution of 6.7%E, in agreement with the resolution measured for the same calorimeter using a single sample measured at the peak of the waveform. The timing resolution for a section of a calorimeter tower with deposited energy ∈ can be expressed as (c∈)2 + σcal2, with a value of c of 0.38 GeV ns for the front section (the first 6 radiation lengths) and 0.70 GeV ns for the back section, and a value of 0.15 ns for σcal.

This paper presents an image processing approach for the detection of the vehicle license plate area in digitized photographic images. The algorithm takes a raster image of the rear view of a vehicle as input and yields the segment of the photograph that contains the plate as the output. The developed algorithm is based on three basic processing stages; yellow regions extraction, dilation of yellow regions and extraction of the plate region. The performance of the developed algorithm has been tested on a set of real images of vehicles. Preliminary tests show that the algorithm performs quite well in accurately locating the license plates (with 97% efficiency). The results of this work can be extended for the automatic detection and recognition of vehicle license plates for vehicle identification.

We present the results of an analysis of two charged particle and transverse energy correlations in Si+Pb collisions at BNL AGS at 14.6 GeV/c per nucleon. The measured semi-inclusive normalized two particle pseudorapidity corrleation function exhibits short range correlations similar to the correlations observed in hadron-hadron and hadron-nucleus collisions at higher energies, although the observed correlations are smaller than the values scaled from hp and hA data. Estimates, provided by the observed correlations, of the intermittency indices as well as of the parameters of the cluster model are presented. Predictions using the fritiof event generator, which at this level of statistical accuracy show no pseudorapidity correlations, are not in agreement with our data. Azimuthal angle two particle correlations show nonzero back-to-back correlations in the central region (consistent with fritiof predictions) and are almost flat in the projectile fragmentation region. We also present results on the transverse energy azimuthal correlation function, which are similar to those from the two particle correlation function.

Temporal variation of the luminosity of seven natural cloud-to-cloud lightning channels were studied, and results were presented. They were recorded by using a high-speed video camera with the speed of 5000 fps (frames per second) and the pixel resolution of 512 × 512 in three locations in Sri Lanka in the tropics. Luminosity variation of the channel with time was obtained by analyzing the image sequences. Recorded video frames together with the luminosity variation were studied to understand the cloud discharge process. Image analysis techniques also used to understand the characteristics of channels. Cloud flashes show more luminosity variability than ground flashes. Most of the time it starts with a leader which do not have stepping process. Channel width and standard deviation of intensity variation across the channel for each cloud flashes was obtained. Brightness variation across the channel shows a Gaussian distribution. The average time duration of the cloud flashes which start with non stepped leader was 180.83 ms. Identified characteristics are matched with the existing models to understand the process of cloud flashes. The fact that cloud discharges are not confined to a single process have been further confirmed from this study. The observations show that cloud flash is a basic lightning discharge which transfers charge between two charge centers without using one specific mechanism.

Simultaneous measurement of both vertical and horizontal electric field signatures of lightning was carried out in an elevated location in Colombo, Sri Lanka. The experimental setup used in this work was similar to an earlier study carried out by a different group in the late 1980s. To our knowledge, this is the first instance that such a study is conducted in this region. Data were acquired during the active months (April–May) of the southwest monsoon period in 2014. Lightning flashes from the most active thunderstorm was analyzed by selecting 65 Return Strokes (RS), 50 Negative Narrow Bipolar Pulses (NNBP) and 40 Positive Narrow Bipolar Pulses (PNBP). The wave shapes were initially validated against results of a previous study and subsequently via a theoretical method as well. Since the direction and the distance information was not available, rather than the amplitudes, ratios of the peak amplitudes of vertical electric field (Ev) and corresponding horizontal electric field (Eh) were compared. The average ratio for the return stroke was 0.024 ± 0.008. The same for the NNBP was 0.041 ± 0.004. The PNBP had a ratio of 0.031 ± 0.006. The average 10%–90% rise times (Tr) for Ev for RS, NNBP and PNBP was 2.124 ± 1.088 μs, 0.734 ± 0.077 μs and 1.141 ± 0.311 μs respectively. The Tr values for Eh for RS, NNBP and PNBP were 1.865 ± 1.200 μs, 0.538 ± 0.061 μs and 1.086 ± 0.423 μs.

Luminosity variations of natural cloud lightning channels were studied using high speed video recordings in Sri Lanka in the tropic. Five cloud flashes were selected for the study, which were recorded with 5000 fps with 512X512 pixel resolution. Luminosity variation along channels and along selected channel segment, duration of cloud activities was studied. It was found that the average duration of selected flashes is 266.44 ms. No particular pattern was observed for the luminosity variation along channel segments. However the luminosity variation across the channel followed a Gaussian distribution pattern. Pattern of the luminosity variation along channels were compared with existing models to understand the development process of cloud flashes. Results show that it is hard to collaborate the observation to a single process for cloud discharges.

We present the present status of the E877 studies of anisotropic transverse flow at the AGS energy. Flow is quantified by Fourier analysis of the azimuthal distributions of transverse energy and charged particle multiplicity. Additionally, the mean transverse momentum of identified particle spectra with respect to the reaction plane are measured near the beam rapidity. Analysis shows the presence of nucleon flow at AGS energies and a small pion flow in the direction opposite to that of the nucleon.

Modelling daily wind speed data by using the two parameter Weibull distribution for ten selected weather stations in Sri Lanka is presented. The daily wind speed data measured by the Department of Meteorology at the heights of 6m-15m during the years 2001 and 2004 were used in this work. The annual variation of the fitted Weibull parameters, the shape parameter k and the scale parameter c ranged from 0.80 to 3.58 and 2.79 ms -1 to 19.78 ms -1 respectively. The highest values of the parameters were found in Hambantota and the lowest values were found in Kurunegala. It was seen that the daily wind speed distribution can be modelled with a reasonable accuracy, using the two parameter Weibull distribution for the stations considered in this work. Sri Lanka is an island with a land area of approximately 65,610 Sq. km situated in the southern tip of the Indian subcontinent between longitudes 80° - 82° East and latitudes 6° - 10° North. The island has a population of about 16 million inhabitants. The gross energy supply of the country is fulfilled by non-commercial fuel wood (57%), fossil fuels (31%) and electricity (11%), which is generated mainly through Hydro and Thermal power. Although, Sri Lanka has no mineral resources, the country has adequate natural resources such as, Hydro, Solar and Wind. However, 90% of the electricity in Sri Lanka is still produced through Hydro power. Thus, assessment of other alternative resources such as Wind and Solar is important for policy implications [1, 2]. Sri Lanka is situated in the belt of monsoon climates in South Asia. The climate of the island is governed by its tropical location as well as by the monsoonal regime, thus has a strong seasonal and spatial dependence. On the basis of the two monsoons and two transitional periods in-between, four seasons are identified. They are the North-East monsoon from December to February, First inter-monsoon from March to mid May, South-West monsoon from mid May to September and Second inter-monsoon from October to November. In general the winds during the monsoons are somewhat stronger. During the intermonsoon periods the winds are weaker and variable. Based on extensive analysis of the existing wind data, it has been concluded from past studies that the Southern lowlands have the most favourable wind resources throughout the year [3].

Daily rainfall records for 50 years (1961 to 2010) were used to determine the start and end of rainy seasons in the southwestern region of Sri Lanka. The study was based on data records obtained from two weather stations in Colombo and Galle situated in the western and southern coastal belts of Sri Lanka, respectively, that have two growing seasons, Yala and Maha. The start and end dates were determined by using a method that is based on cumulative rainfall measured during a season. Substantial interannual variability is seen in start and end of rainy seasons in this study. For the Yala season, the mean start and end dates are in the standard weeks 12.0 ± 2.3 and 24.1 ± 2.0 (March 24 to June 20), respectively. For the Maha season, the mean start and end dates are in the standard weeks 35.4 ± 2.0 and 49.6 ± 2.0 (September 5 to December 15), respectively. The mean durations of the rainy season for Yala and Maha are 12.1 ± 2.6 weeks and 14.2 ± 2.3 weeks respectively. The start date and the duration of the rainy season for both Yala and Maha are correlated, leading to early start dates resulting in longer rainy seasons. It can be concluded from this study that it is possible to use daily rainfall records to determine the mean start and end dates of rainy seasons in the southwestern region of Sri Lanka.

Transverse momentum distributions of light mass beam rapidity fragments 1H, 3He, and4He in reactions of 28Si + Al, Cu and Pb are presented. The widths of the distributions are found to increase with increasing projectile-target overlap. This dependence is not consistent with the observed distributions being associated with the Fermi momentum of the nucleons in the projectile nucleus.

To monitor the acidity of rain water in real time, a rain water sampling system was developed. The rain sampler detects the initial rain after a dry spell and collects a water sample. Before performing the measurements, the pH probe is calibrated using a standard buffer solution whereas the conductivity probe is calibrated using deionized water. After calibrating the probes the pH and the conductivity of the collected rain water sample are measured using the pH and the conductivity probe. Weather parameters such as air temperature, humidity and pressure are also recorded simultaneously. The pH and conductivity measurement data including weather parameters are transmitted to central station using a GSM modem for further analysis. The collected rain water sample is preserved at the remote monitoring station for post chemical analysis. A programmable logic controller controls the entire process.

Honey bees use optical flow to avoid obstacles effectively. In this research work similar methodology was tested on a simulated mobile robot. Simulation framework was based on VRML and Simulink in a 3D world. Optical flow vectors were calculated from a video scene captured by a virtual camera which was used as inputs to a fuzzy logic controller. Fuzzy logic controller decided the locomotion of the robot. Different fuzzy logic rules were evaluated. The robot was able to navigate through complex static and dynamic environments effectively, avoiding obstacles on its path.

Narrow Bipolar Pulses (NBP) of a single thunderstorm from a coastal location in Sri Lanka were subjected to S-transformation in order to study their time-frequency information. This study is an extension to a similar study carried out by the authors where properties of NBPs were analyzed using the wavelet transformation. Keeping in line with the previous study, 18 events pertaining to equal number of positive and negative NBPs with the narrowest temporal widths were studied. The data was obtained from the southern coastal area of Sri Lanka (Matara −5.95° N, 8.53° E) from a highly active thunderstorm, which occurred during the month of May in 2013. The waveforms were recorded with a 10 ns resolution within a 100 ms time window. The spanning (width) and the ratio of peak power amongst the initial and overshoot pulses were measured and compared for each polarity. The negative NBPs had an average spanning of 134–371 kHz. The overshoot of the same had an average range of 127–255 kHz. The positive NBPs had an average spanning of 103–245 kHz. The overshoot of the same had an average range of 102–195 kHz. The ratio of peak power of NBPs to overshoot had an average of 1.08 for both positive and negative pulses. The spectrogram reveals the initial and overshoots pulses to be relatively equal in power intensities.

To monitor the acidity of rain water in real time, a rain water sampling system was developed. The rain sampler detects the initial rain after a dry spell and collects a water sample. Before performing the measurements, the pH probe is calibrated using a standard buffer solution whereas the conductivity probe is calibrated using deionized water. After calibrating the probes the pH and the conductivity of the collected rain water sample are measured using the pH and the conductivity probe. Weather parameters such as air temperature, humidity and pressure are also recorded simultaneously. The pH and conductivity measurement data including weather parameters are transmitted to central station using a GSM modem for further analysis. The collected rain water sample is preserved at the remote monitoring station for post chemical analysis. A programmable logic controller controls the entire process.

Modeling visually realistic trees is a challenging problem in computer graphics due to the complex variation of tree forms and interactions with the surrounding environment [Palubicki et. al., 2009; Pirk et. al., 2012].

An investigation of the production of neutron-rich isotopes from the fragmentation of $^{28}\mathrm{Si}$ projectiles at ${\mathit{p}}_{\mathrm{lab}}$=14.6 GeV/c per nucleon was performed using the BNL-AGS-E814 spectrometer. We have measured the inclusive production cross sections of neutron-rich fragments ${(}^{6}$He, $^{8}\mathrm{He}$, $^{8}\mathrm{Li}$, $^{9}\mathrm{Li}$, $^{10}\mathrm{Be}$, $^{11}\mathrm{Be}$, and $^{13}\mathrm{B}$). We have also measured the transverse momentum distributions for $^{6}\mathrm{He}$ and $^{9}\mathrm{Li}$, and the forward and transverse energy distributions associated with $^{6}\mathrm{He}$ production. The momentum distributions were analyzed in the context of the Goldhaber model. The question of whether the fragments are produced in the decay of the projectile following its electromagnetic excitation was also investigated.

We present the transverse energy distributions, d\ensuremath{\sigma}/${\mathit{dE}}_{\mathit{T}}$ and ${\mathit{dE}}_{\mathit{T}}$/d\ensuremath{\eta}, and the charged particle multiplicity distributions, d\ensuremath{\sigma}/${\mathit{dN}}_{\mathit{c}}$ and ${\mathit{dN}}_{\mathit{c}}$/d\ensuremath{\eta}, produced in p+Al and p+Pb collisions at 14.6 GeV/c. The data exhibit a weak correlation between these global variables. While a significant increase of the mean multiplicity with the mass of the target is observed, the transverse energy distributions show little target dependence. The ${\mathit{dE}}_{\mathit{T}}$/d\ensuremath{\eta} distribution shifts backward as the mass of the target increases, indicating the presence of rescattering. The data are compared to the predictions of the relativistic quantum molecular dynamic model (RQMD) and Fritiof event generators. RQMD reproduces well the main features of the data while Fritiof predicts too forward peaked transverse energy and particle multiplicity pseudorapidity distributions.

Recent results from the E814 collaboration are presented for reactions of 14.6 GeV/nucleon 28Si projectiles with targets of Al, Cu, and Pb. This includes transverse energy distributions over the full solid angle and the distribution of charged particle multiplicity in the forward hemisphere. Furthermore we present recent results on transverse momentum spectra and rapidity distributions for protons and discuss them in terms of stopping and/or transparency. A fraction of nucleons emerges at beam rapidity, even for the most central collisions. These ‘punch-through’ distributions are shown to yield information on the in-medium nucleon-nucleon cross section. Finally, we discuss antiproton production at 0° as a function of event centrality to shed some light on possible reabsorption.

A detailed study of the electromagnetic dissociation of 28Si in extremely peripheral collisions at 14.6 GeV/nucleon was carried out with 28Si projectiles interacting on Pb, Sn, Cu and Al targets. The excitation energy is determined by measurements of the invariant mass of the excited system. We examine the decay channels 1p+27Al, 1n+27Si and 2p+26Mg. The excitation energy distributions are well reproduced by combining the photon spectrum calculated using the Weizsäcker-Williams approximation with the experimental data on the photonuclear cross sections. No evidence for double photon excitation of 28Si is observed.

We have conducted a search for bound states of a negative pion and a number of neutrons (pineuts) using the E814 spectrometer. A beam of Si28 at a momentum of 14.6A GeV/c was used to bombard targets of Al, Cu, Sn, and Pb. We describe our experimental technique, present measured upper limits for pineut production, and discuss the significance of our results.Received 2 August 1995DOI:https://doi.org/10.1103/PhysRevC.52.2679©1995 American Physical Society

Simultaneously captured vertical and horizontal (total) electric field signatures of lightning negative Return Strokes (RS) were analyzed to obtain Time-Frequency (TF) variation using Stockwell Transformation (ST). In the study, ST was utilized since it is known to possess comparatively better time resolution at high frequency regions compared to other available TF methods. The data were obtained during the monsoon season of April–May 2014. The vertical and horizontal component of fifty negative RSs was utilized in the study. The resultant ST spectrum was analyzed and the regions of interest were demarcated based on the color which represented their relative power output intensities for different frequency components of the signal. The spread area was identified as the region of frequencies which consisted of power intensity equal or above 90th percentile when compared to the maximum possible value. The spectral area was identified as the area of frequencies in the borderline to the natural background noise. The spread region for the vertical E field had a range between 10 kHz and 650 kHz. Its average values were in between 126 kHz and 331 kHz. The spectral region of the vertical electric field change spanned from 1 kHz to 1020 kHz. Its average distribution was 44 kHz–660 kHz. Horizontal electric fields had a range of 20 kHz–1940 kHz in the spectral region. The same for the spread region was 80 kHz–910 kHz. The averages of the horizontal E field's spectral region were 46–1112 kHz and its spread region varied between 227 and 599 kHz. The results display a higher frequency range for all aspects of the horizontal E field changes which implies that its influence on the high frequency radiation is much higher than its vertical counterpart.

Thunder signatures have been categorized into three types using recorded peak pressure. The variation in fundamental frequency initiated by ground flashes has been studied by using an acoustic spectrum of thunder. Stransformation has used to estimate the dominant frequency variation around the peak pressure. The mean fundamental frequencies of type 3 ground and cloud flashes are 160 Hz and 98 Hz respectively. The mean frequencies of type 2 ground and cloud flashes are 108 Hz and 82 Hz respectively. The mean fundamental frequencies of type 1 ground and cloud flashes are 88 Hz and 123 Hz respectively.

Long‐term changes in extreme air temperature at Nuwara Eliya (a high‐elevation observatory located in the western slopes of the central mountainous region of Sri Lanka) are examined. The present work is limited to a linear trend analysis of daily maximum and minimum air temperature series of the period 1926–2015. The statistical significance of the trend is estimated using the Mann‐Kendall test. There is a significant reduction in the diurnal temperature range (DTR) in Nuwara Eliya. The magnitude of the reduction is −0.23 degC per decade and is due to the increase in the daily minimum air temperature. No significant increase or decrease in the daily maximum air temperature was evident from the data. There is a strong inverse correlation between the standard deviation (which is related to the temperature variability) and the mean daily minimum air temperature. The increase in minimum temperature is not uniform throughout the year as the minimum temperature of the cold season has increased, while it has remained the same for the warm season, thereby reducing the overall DTR.

A simple voice recognizer was implemented with the aim of building voice control devices by utilizing a cascade LPC with adaptive fuzzy interface system (FIS). The accuracy of the voice recognizer depends on the complexity of the voice commands, the number of frequency components used, and the weights that are utilized in FIS. The quality of the voice recognizer depends both on the time and the frequency resolution of the digitizing hardware. With a limited set of sounds the technique discussed in this paper can be used to produce a speaker dependent voice control system. The performance of the system improves with time due to the adaptive nature of the system. The highly flexible backend (fuzzy interface) enables usage of the device in noisy industrial environments. Speech, being the dominant source of communication, has played a crucial role in the evolution of the human race. Due to the rapid advancement in the technology and the ever-increasing complexity of electro-mechanical devices, research is carried out to develop methods that ease the human-device interactions. Today, electronic devices have taken over a majority of the work carried out by humans a decade ago. However, the communication between electronic devices and humans is still at its infancy. The work presented in this paper was carried out to develop a suitable methodology to increase the ease of communication between humans and electronic devices. During the last twenty years many scientists have proposed various techniques to increase the effectiveness of speech recognition. So far, most of the research related to analyzing sound signals is restricted to one domain, either the time domain or the frequency domain. For example, a technique such as Linear Predictive Coding (LPC) [1] which is generally accepted for speech recognition, completely ignores the frequency domain information. On the other hand frequency domain techniques such as Fourier transforms, completely ignore the time domain information. If information encoded in both time and frequency domains is utilized in interpreting speech signals, it could be possible to achieve better accuracy in the interpretation. This hypothesis is supported by the natural functionality of human auditory systems [2].

Abstract Daily rainfall records for 50 years (1961 to 2010) were used to determine the start and end of rainy seasons in the south western region of Sri Lanka. The study was based on data records obtained from two weather stations in Colombo and Galle situated in the western and southern coastal belts of Sri Lanka respectively, that have two growing seasons Yala and Maha. The start and end dates were determined by using a method that is based on cumulative rainfall measured during a season. Substantial interannual variability is seen in start and end of rainy seasons in this study.For the Yala season, the mean start and end dates are in the standard weeks 12.0±2.3 and 24.1±2.0 (March 24 th to June 20 th ) respectively. For the Maha season the mean start and end dates are in the standard weeks 35.4±2.0 and 49.6±2.0 (September 5 th to December 15 th ) respectively. The mean duration of the rainy season for Yala and Maha are 12.1±2.6 weeks and 14.2±2.3 weeks respectively. The start date and the duration of the rainy season for both Yala and Maha are correlated, leading to early start dates resulting in longer rainy seasons. It can be concluded from this study that it is possible to use daily rainfall records to determine the mean start and end dates of rainy seasons in the south-western region of Sri Lanka.

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2020 Impact Factor: 0.515The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.

The production of pions, protons and deuterons is studied at a laboratory angle of 144° in 28Si+Pb collisions at 14.6 GeV/c per nucleon. The centrality dependence of the pion yields is studied over the full impact parameter range using a zero degree calorimeter. The results are compared with the hadronic cascade model RQMD. These calculations are generally in agreement with the experimental results. According to these calculations, the pion yield in our acceptance is completely dominated by Δ-decay at freeze-out. Our measurements thus support the importance of baryon resonance production as one of the central features of relativistic heavy ion collisions at AGS energies. Although the strength of the pion spectrum is adequately described for kinetic energies above 50 MeV, an additional very soft component is observed in the pion spectra which is not predicted by RQMD. This very soft component accounts for a significant fraction of the total pion yield in this rapidity range but remains unexplained.

The CP -violating weak phase ϕs and the decay width difference ΔΓs between the light and heavy Bs0 mass eigenstates are measured with the CMS detector at the LHC in a sample of 48500 reconstructed Bs0→J/ψϕ(1020)→μ+μ−K+K− events. The measurement is based on a data sample corresponding to an integrated luminosity of 96.4fb−1, collected in proton-proton collisions at s=13TeV in 2017–2018. To extract the values of ϕs and ΔΓs, a time-dependent and flavor-tagged angular analysis of the μ+μ−K+K− final state is performed. The analysis employs a dedicated tagging trigger and a novel opposite-side muon flavor tagger based on machine learning techniques. The measurement yields ϕs=−11±50(stat)±10(syst)mrad and ΔΓs=0.114±0.014(stat)±0.007(syst)ps−1, in agreement with the standard model predictions. When combined with the previous CMS measurement at s=8TeV, the following values are obtained: ϕs=−21±44(stat)±10(syst)mrad, ΔΓs=0.1032±0.0095(stat)±0.0048(syst)ps−1, a significant improvement over the 8 TeV result.

We have used the E814 apparatus to make a systematic study of antiproton production in collisions of 28Si ions at 14.6 GeV/c per nucleon with targets of Pb, Cu, and Al. We have measured the antiproton yield per interaction as a function of transverse energy and have found the yield to increase by a factor of ≈ 2 in going from the least to the most central collisions on the Pb target. A simple first-collision picture of antiproton production predicts the yield to increase by a factor of ≈ 11. We suggest that the discrepancy may result from the annihilation of antiprotons within the nuclear medium.

We have used the E814 forward spectrometer to conduct searches for rare particles formed in collisions of 14.6 GeV per nucleon 28Si ions with targets of Al, Sn, Cu, and Pb. Preliminary results of the searches for anti-matter nuclei, positively charged strange matter, and pion-neutron bound states are discussed.

In the following we will present selected aspects of recent data on central nucleus-nucleus collisions taken by the E814/E877 collaboration at the BNL-AGS. We will first demonstrate that stopping is nearly complete in these collisions, and discuss the initial energy and baryon densities inferred from model comparisons with the data. Next we will discuss the amount of expansion the system undergoes from the initial phase until freeze-out by presenting recent results on pion-pion correlations. The (baryonic) resonance composition of the system at freeze-out is obtained by analyzing pion spectra at low transverse momentum P t and by inspection of direct measurements of the ∆(1232) resonance. Based on analysis of these measurements we will then discuss a “local” freeze-out scenario, where the freeze-out volume is connected with the temperature averaged pion-nucleon cross section. A summary of the current results and of future plans for Au-Au collisions with the E877 apparatus concludes the paper.