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Wyświetlanie 1-15 z 21
Tytuł:
Acoustic cylindrical cloak
Autorzy:
Premarathna, S. M.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1192658.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Acoustic metamaterials
electromagnetic metamaterials
negative index
anisotropic’ cloaking
radially dependent FDTD method
reduced parameter model’ higher order parameter model
Opis:
Using the analogy between anisotropic acoustic metamaterials with magnetic metamaterials in transverse magnetic mode, an electromagnetic wave of 2 GHz n transverse magnetic mode, at normal incidence propagating through a two dimensional, anisotropic, semi infinite, double negative, metamaterial slab of 800 × 800 cells, embedded in free space, for the ideal loss case was simulated by a radially dependent finite difference time dependent method to study an ideal acoustic cylindrical cloak. For the simulations multiple cycle m-n-m pulses generating Gaussian beams were used as sinusoidal hard line sources. The simulations for acoustic cylindrical cloaking by a reduced parameter model and a higher order parameter model are also presented. The cloaking behaviour is largely dependent upon the transformation and not on the thickness of the cloak. The radial dependent model and the higher order transformation model are suited for acoustic cloaking.
Źródło:
World Scientific News; 2016, 47, 2; 75-88
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Complementary Wave Interpretation of the Dirac Equation
Autorzy:
Bulathsinghala, D. L.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/412244.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Dirac equation
energy-momentum equation
complementary waves
uncertainty relation
time's arrow
four-vector
Opis:
The Dirac equation consistent with the principles of quantum mechanics and the special theory of relativity, introduces a set of matrices combined with the wave function of a particle in motion to give rise to the relativistic energy-momentum relation. In this paper a new hypothesis, the wave function of a particle in motion is associated with a pair of complementary waves is proposed. This hypothesis gives rise to the same relativistic energy-momentum relation and achieves results identical to those of Dirac. Additionally, both the energy-time and momentum-position uncertainty relations are derived from the complementary wave interpretation. How the complementary wave interpretation of the Dirac equation is related to the time-arrow and the four-vectors are also presented.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 9, 2; 103-115
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A semiclassical model for a laser field inside an optical cavity
Autorzy:
Priyashanka, K. M.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1194053.pdf
Data publikacji:
2015
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Semi classical theory
cavity electric field
population inversion
pump parameter
resonance frequency
threshold population
Opis:
Treating the laser medium quantum mechanically and the laser electric field classically, a mathematical model was developed to study a laser field inside a single mode optical cavity by numerical and analytical techniques. The simulations for threshold population, population inversion and average population with electric field frequency for 500 kHz resonance frequency of the atom are presented. The gain coefficient and the pump parameter with the frequency of the cavity electric field for 1000 kHz resonance frequency of the atom were simulated. The threshold population is a minimum when the frequency of electric field is equal to the resonance frequency of the atom. The population inversion varies sinusoidal with time and the frequency of the electric field and is a maximum at the threshold frequency of the atom. The saturated laser intensity at steady state increases linearly with the pump parameter and for larger values of the pump parameter, a smaller time is needed to reach the saturation of the laser field.
Źródło:
World Scientific News; 2015, 13; 65-79
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy of strongly correlated electron systems
Autorzy:
Reza, M. A.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1182914.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
strongly correlated electron systems
constrained-path monte carlo method
hubbard model
dynamical mean field theory
Opis:
The constrained path Monte Carlo method was used to solve the Hubbard model for strongly correlated electrons systems analytically in arbitrary dimensions for one, two and three dimensional lattices. The energy variations with electron filling, electron-electron correlation strength and time as well as the kinetic and potential energies of these system were studied. A competition between potential and kinetic energies as well as a reduction of the rate of increase of the potential energy with increasing correlation were observed. The degenerate states of the lattice systems at zero correlation and the increase in the energy separation of the states at higher correlation strengths were evident. The variation of the energy per site with correlation strength of different lattice sizes and dimensions were obtained at half filling. From these it was apparent that the most stable lattices were the smallest for all the different dimensions. For one dimension, the convergence of the results of the constrained path method with the exact non-linear field theory results was observed.
Źródło:
World Scientific News; 2016, 49, 2; 59-77
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modeling of planar plasma diode
Autorzy:
Wijewardena Gamalath, K. A. I. L.
Samarakoon, A. M.
Powiązania:
https://bibliotekanauki.pl/articles/412368.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Plasma diode
plasma boundary
current density
Particle-In-Cell simulation
anode cathode gap
potential field
Opis:
To investigate the dynamics of a planar plasma diode system (PDS), a model based on the current density equilibrium at the interface was developed. The current densities and plasma boundary variations with the potential fields were obtained by simulating a single square pulse. The variation of an observed overshoot current density with the applied voltage is presented. Planar plasma diode system was also simulated for periodic, sine, square, triangular and saw tooth voltage patterns by varying the amplitude and frequencies. A method to find the lower bound of the electron density of plasma for a specified PDS is presented. Particle-In-Cell simulation technique was used to investigate the plasma particles and electric field distributions over the anode cathode gap for different intensities of external electric fields. The system became stable after few time steps and this time depends upon the intensity and polarization of the external field.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 8, 3; 220-242
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron dynamics in a strong laser field
Autorzy:
Gunatilaka, C. C.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1190112.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Strong laser field
high harmonic generation
electron propagation
ponderomotive energy
Argon
Helium-Neon
Ti-Sapphire lasers
Opis:
The three step model of high harmonic generation was used to investigate the electron behaviour in a strong laser field. The electron propagation was analyzed classically and the electron recombination with the parent atom was analyzed quantum mechanically. Three laser fields Argon with 500 nm, Helium-Neon with 632.8 nm and Ti-Sapphire with 800 nm wavelengths were used to analyze the electron behaviour for different intensities and the electron propagation was analyzed in cosine and sine electric laser fields. For a strong applied laser field, the atomic potential get distorted and the barrier potential is reduced. The maximum kinetic energy of the emitted electron, the ponderomotive energy was 8Up in both cases and there were three points which gave the maximum kinetic energy for the laser field with sine electric field. When the laser intensity was increasing, the electron has a higher probability to move away from the parent atom. When the laser field changed its direction, electron recombined with the parent atom with a maximum kinetic energy of 3.17Up.
Źródło:
World Scientific News; 2016, 35; 1-16
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Three dimensional photonic crystals
Autorzy:
Dissanayake, S. E.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1194049.pdf
Data publikacji:
2015
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Fcc lattice and diamond lattice
GaAs
Photonic crystal
dielectric contrast
filling fraction
plane wave expansion
Opis:
The plane wave expansion method was implemented in modelling and simulating the band structures of three dimensional photonic crystals with FCC lattice formed from air spheres drilled in GaAs and diamond lattice formed by GaAs spheres drilled in air. Both these structures lead to a complete band gap not allowing EM waves with the frequency of the band gap to propagate through the crystal in any direction. Diamond lattice photonic crystal has a complete band gap for a wider range of filling fraction than FCC photonic crystal and also it has a wider band gap width.
Źródło:
World Scientific News; 2015, 12; 12-23
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation of two dimensional photonic band gaps
Autorzy:
Dissanayake, S. E.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/411904.pdf
Data publikacji:
2014
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Photonic crystal
square lattice
triangular lattice
honeycomb lattice
plane wave expansion
mode field distribution
GaAs
dielectric kontrast
filling fraction
gap maps
Opis:
The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circular and hexagonal GaAs rods as well as triangular lattice of circular and hexagonal air holes in GaAs whereas square lattice of square or circular air holes in a dielectric medium ε = 18 gave complete band gaps. The variation of these band gaps with dielectric contrast and filling factor gave the largest gaps for all configurations for a filling fraction around 0.1.The gap maps presented indicated that TM gaps are more favoured by dielectric rods while TE gaps are favoured by air holes. The geometrical gap maps operating at telecommunication wavelength λ = 1.55 m showed that a complete band gap can be achieved for triangular lattice with circular and hexagonal air holes in GaAs and for honeycomb lattice of circular GaAs rods.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2014, 5; 58-88
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical approach to the physics of fuel cells
Autorzy:
Wijewardena Gamalath, K. A. I. L.
Peiris, B. M. P.
Powiązania:
https://bibliotekanauki.pl/articles/411573.pdf
Data publikacji:
2012
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
ogniwa paliwowe
transport jonów
gradient stężenia
straty polaryzacyjne
krzywa polaryzacji
krzywa mocy
fuel cell
ion transport rate
concentration gradient
polarization losses
polarization curve
power curve
Opis:
Ion transport rate of PAFC, AFC, PEMFC, DMFC and SOFC fuel cells under the influence of an electric field and concentration gradient were evaluated for static electrolytes. AFC are the best fuel cells for high er current applications while direct methanol fuel cells DMFC are the best for lower current applications AT lower temperatures. An equation for voltage output of a general fuel cell was obtained in terms of temperature and partial pressure of reactants. Performance of a 2D fuel cell was analyzed by simulating polarization and power curves for a fuel cell operating at 60 ?C with a limiting current density of 1.5 A cm- 2. The maximum power for this fuel cell was 8.454 W delivering 82% of maximum loading current density. When the temperature was increased by one third of its original value, the maximum power increased by 6.75% and at 60 ?C for a 10 times increment of partial pressure of reactants, the maximum power increased by 2.43%.The simulated power curves of the fuel cells were best described by cubic fits.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2012, 2; 15-27
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Study of Quantum Effects in General Relativity
Autorzy:
Sooriyaarachchi, V. K. C.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1058092.pdf
Data publikacji:
2019
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Hawking effect
Rindler observer
Schwarzschild black hole
Unruh effects
event horizon
information loss paradox
scalar curvature
surface gravity
transplanckian problem
Opis:
The present work discusses the conceptual and technical issues encountered in formulating a quantized theory of gravity, via the reconciliation of quantum mechanics and general relativity. Quantum effects arising in a classically defined space-time derived through a semi classical approximation are studied at length and the significance of the particle interpretation in quantum field theory in the origin of such effects is established. The contradicting nature of the quantum effects against classically established principles is studied by considering the Hawking effect in a Schwarzschild black hole space-time. Further, the limits of prominent manifestation of the quantum effects with regards to the black hole mass is calculated taking into consideration the cosmic microwave background and the lifetime of the universe. Quantum effects are established as essential in incorporating thermal physics and black hole mechanics in a consistent formulation. Finally, the validity of the semi classical approximation is studied in terms of Planck scale black holes, transplanckian problem and the information loss paradox and the requirement for a fully quantized theory of gravity is realized.
Źródło:
World Scientific News; 2019, 134, 2; 198-219
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation of Primary Spectra of Particle Radiation from Black Holes
Autorzy:
Wijewardhana, C. N. T.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1193473.pdf
Data publikacji:
2021
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Hawking radiation
Higgs boson emission
Kerr black hole
Planck mass
Primary emission spectra
Schwarzschild black hole
W±
Z0
primordial black hole
quark and gluon emission
Opis:
The instantaneous primary emission spectra of particles radiating from Schwarzschild black holes and maximally rotating Kerr black holes of masses 1013 – 1015 g were investigated and C code, BlackHawk was used for the simulations. From a Schwarzschild black hole of mass 3.53×1013 g, gluons had the lowest cutoff energy, 199 MeV. The emission spectra were dominated by coloured particles, quarks having with the highest overall emission rate, 2.826×1022 GeV-1s-1 at energy 1.205 GeV. The leptons e±, μ±, τ± showed similar variation in emission rates. The only particles emitted with energies below the rest mass of u quarks were neutrinos, photons, and e±. At greater particle energies (> ~ 2 GeV) the emission rates of all particles were almost equivalent. The emission of vector bosons, Z0 and W± were negligible and became significant when the mass reduced to ~1011 g and then gluons, W±, Z0 and photons were emitted similar to each other with a peak at energy, 280 GeV. The emitting rates of gluons, quarks, neutrinos, W±, e±, μ±, τ±, Z0, photons, and Higgs bosons are in decreasing order respectively. As the mass of the black hole is reduced to 1.06×108 g, quarks were emitted at the highest rate 2.826×1022 GeV-1s-1 at 4010 GeV peak energy and at energies between rest mass energy of Higgs boson and 1.25×105 GeV, the emission of Higgs bosons exceeded the emission of quarks. For maximally rotating Kerr black hole of mass 3.53×1013 g, W±, Z0 and Higgs boson were emitted at higher emission rates 1012 – 1015 GeV-1s-1 and for mass 1.06×108 g, the gluons had the highest overall emission rate at the peak energy. At extremely high energies, the gluon emission rates are less than the emission rates of Higgs bosons, quarks, neutrinos, and e±, μ±, τ±. The spin-dependent behaviour of spectra is also present.
Źródło:
World Scientific News; 2021, 158; 105-129
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Strain distributions in group IV and III-V semiconductor quantum dots
Autorzy:
Wijewardena Gamalath, K. A. I. L.
Fernando, M.A.I.P.
Powiązania:
https://bibliotekanauki.pl/articles/411953.pdf
Data publikacji:
2013
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
quantum dot
strain distribution
hydrostatic strain
biaxial strain
Opis:
A theoretical model was developed using GreenˇŚs function with an anisotropic elastic tensor to study the strain distribution in and around three dimensional semiconductor pyramidal quantum dots formed from group IV and III-V material systems namely, Ge on Si, InAs on GaAs and InP on AlP. A larger positive strain in normal direction which tends to zero beyond 6nm was observed for all three types while the strains parallel to the substrate were negative. For all the three types of quantum dots hydrostatic strain and biaxial strain along x and z directions were not linear but described a curve with a maximum positive value near the base of the quantum dot. The hydrostatic strain in x-direction is mostly confined within the quantum dot and practically goes to zero outside the edges of the quantum dot. For all the three types, the maximum hydrostatic and biaxial strains occur in x-direction around �{1nm and around 2nm in z-direction. The negative strain in x-direction although realtively weak penetrate more deeper to the substrate than hydrostatic strain.The group IV substrate gave larger hydrostatic and biaxial strains than the group III-V semiconductor combinations and InAs /GaAs was the most stable. The results indicated that the movements of atoms due to the lattice mismatch were strong for group III-V.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2013, 2; 36-48
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Axiomatic Approach to Quantum Mechanics
Autorzy:
Rajakaruna, M. A. I. S.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1076342.pdf
Data publikacji:
2019
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Du Bois Raymond Lemma
Fisher Information
Quantum Mechanics
Schrödinger’s Wave Equation
Variational Principle
Opis:
We have shown that the Schrödinger wave equation can be explained and derived from fundamental postulates that are based on the conservation of probability, significance of measurements at infinity and nature’s tendency of maintaining a system as unbiased as possible. As a reasonable measure for the local randomness, Fisher information is considered. The presented approach provides an axiomatic derivation for the Schrödinger wave equation, avoiding imperfect models borrowed from classical mechanics such as direct application of the energy conservation, statistical mechanics or vibrating string models.
Źródło:
World Scientific News; 2019, 116; 209-221
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelling of Exciton-Polaritons
Autorzy:
De Silva, L. M. S.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1166216.pdf
Data publikacji:
2018
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
AlGaAs/AlAs
CdSe/ZnS
Exciton-polaritons
GaAs
distributed Bragg reflectors
microcavity
quantum well
Opis:
To study the generation of exciton polaritons in a quantum well embedded in a semiconductor Fabry-Pérot microcavity with distributed Brag reflectors, a simple semi-classical auxiliary differential equation based model is proposed. The solutions are obtained using FDTD method considering only the excitations from ground to next excited states and one single QW resonance. The simulations are presented for GaAs quantum well in Al0.1Ga0.9As microcavity and a ZnS quantum well embedded in CdSe microcavity with 12 DBR layers on either side. Model is proved to be stable and agrees with properties of polarization associated with polariton dispersion. Results show that GaAs is a better quantum well material to generate polaritons than CdSe.
Źródło:
World Scientific News; 2018, 106; 194-213
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear optical properties of photonic crystals
Autorzy:
Fernando, M. G. Pravini S.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1177892.pdf
Data publikacji:
2018
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
AlGaAs
All-optical switch
FDTD
GaAs
Ge
Kerr nonlinearity
Limiter
Photonic crystals
ZnS
side coupled Micro cavities
Opis:
A model for optical switching and limiting in 2D photonic crystals of square and hexagonal lattice structures having Kerr nonlinearity is introduced with a side-coupled cavity and a waveguide. MATLAB was used to implement FDTD algorithm with perfectly matched layer boundaries. Photonic crystals formed from AlGaAs, GaAs, ZnS and Ge, rods in air were simulated to obtain the optimal parameters. The best refractive index range for the proposed switch and the limiter to be operated is 2.5 to 3.2. The results showed best performance for group III-V materials. The lattice constant for the most commonly used telecommunication wavelength (1.55 µm) was found to be 0.5479 µm for AlGaAs and 0.550 µm for GaAs respectively. As an optical limiter, AlGaAs showed the best performance with the threshold refractive index change at 0.05.
Źródło:
World Scientific News; 2018, 97; 1-27
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 21

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