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Wyświetlanie 1-15 z 21
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:
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:
The changing shape of a liquid drop in an electric field
Autorzy:
Jayalal, A. A. S. N.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/411766.pdf
Data publikacji:
2012
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
gęstość ładunku powierzchniowego
stała dielektryczna
kąt stożka
napięcie powierzchniowe
minimalne pole elektryczne
surface charge density
dielectric constant
cone angle
surface tension
minimum electric field
Opis:
An approximate extension of the slender body theory was used to determine the static shape of a conically ended dielectric fluid drop in an electric field. Using induced surface charge density, hydrostatic pressure and the surface tension of the liquid with interfacial tension stresses and Maxwell electric stresses, a governing equation was obtained for Spender geometries for the equilibrium configuration and numerically solved for 3D. For an applied electric field, the electric energy on a spherical drop can be maximized in a weak dielectric by increasing the applied electric field. The minimum dielectric constant ratio needed to produce a conical end is 14.5 corresponding to a cone angle 31.25° .There is a sharp increment of the aspect ratio after reaching the threshold value of the applied field strength and the deformation of the fluid drop increases with the increase in dielectric constant of the fluid drop. For a particular dielectric constant ratio, the threshold electric field producing conical interface increases with the increased surface tension of the liquid. The threshold electric field for a water drop is 1.0854×104 units and the corresponding aspect ratio is 15. For the minimum dielectric ratio the cone angle of the drop decreases with applied field making the drop more stable at higher fields.
Źródło:
International Letters of Chemistry, Physics and Astronomy; 2012, 3; 24-40
2299-3843
Pojawia się w:
International Letters of Chemistry, Physics and Astronomy
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:
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:
Simulation of Rotating Black Holes
Autorzy:
Vindana, W. M. H. P.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1158501.pdf
Data publikacji:
2018
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Hawking radiation
Hawking temperature
Kerr black hole
Kerr-Newman black hole
entropy
mass variation
rotating black holes
thermodynamic parameters
Opis:
Considering the analogy between classical thermodynamic parameters and black hole parameters, the four laws of thermodynamics are reinterpreted for Kerr and Kerr-Newman black holes. A simple model for the dynamic relationships was obtained by considering the surface area of the outer horizon of a Kerr and Kerr-Neumann black hole as the area of a perfect black body. Finding the conditions these black holes should satisfy, the equations were numerically solved and simulated for the Hawking temperature, Hawking radiation and entropy variations of Kerr and Kerr-Newman black holes. The Hawking temperature and Hawking radiation of a given rotating black hole drastically increases at the final stage of the black hole evaporation. In the meantime, the entropy of a rotating black hole drastically decreases through the time. The additional angular momentum and the charge effects gain high Hawking temperatures and high Hawking radiation values for the black holes while these effects reduce the entropy of the black holes.
Źródło:
World Scientific News; 2018, 114; 106-125
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:
Particle localization via measurement induced entanglement
Autorzy:
Vasura Jayaweera, K. K. Y.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1059506.pdf
Data publikacji:
2019
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Fluffy-Bunny entanglement
Quantum entanglement
photons
position probability density
relative position
scattering angle
spatial localization
variance
Opis:
To explore the boundary between quantum and classical physics in the context of quantum entanglement, the particle localization via measurement induced entanglement on photons incident onto a distinguishable, massive non-interacting two-particle system was studied. The specific case of how particles acquire well defined spatial localization when light is scattered off and detected was considered. The localization process studied both qualitatively and quantitatively was observed to be valid for particles which were initially localized as well as initially completely delocalized. The localization scheme was also observed to be extremely sensitive to its initial conditions. Furthermore, a difference in the localization scheme in terms of the number of scattering events was observed between monochromatic photons and photons with variable frequencies. From all these results it was apparent that we can interpret the uniquely quantum features of entanglement in terms of classicality.
Źródło:
World Scientific News; 2019, 128, 2; 234-254
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:
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
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:
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:
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:
Electronic structures of CdSe quantum dots embedded in ZnSe
Autorzy:
Jayawardhana, M. R. P. I.
Wijewardena Gamalath, K. A. I. L.
Powiązania:
https://bibliotekanauki.pl/articles/1178287.pdf
Data publikacji:
2017
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
LCAO method
Quantum dot
Sparse matrices
adjacency matrix
folded spectrum method
optical matrix elements
strain effects
valence band offset
Opis:
The electronic structures and optical matrix elements of CdSe semiconductor quantum dots of near cubical, hemispherical and cylindrical shape embedded in ZnSe were calculated. Bulk Hamiltonian matrices were obtained using the empirical tight binding method including spin-orbital coupling and relativistic effects. All quantum dots were simulated in reciprocal space and the number of atoms in each quantum dot was kept nearly equal for the comparison purpose. An adjacency matrix was produced which indicates the adjacencies of unit cells and the bulk Hamiltonian was included for each adjacency point in order to obtain the quantum dot Hamiltonians. The strain effects, valence band offset and spin orbital coupling were included in the calculations. The quantum dot Hamiltonian was solved to obtain the highest and lowest eigenvalues from which the electronic structure was obtained. Then eigenvalues near integers ranging from the lowest eigenvalue to highest eigenvalue was generated for the point.
Źródło:
World Scientific News; 2017, 86, 3; 205-225
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron dynamics in a strong laser field with Gaussian Potential well
Autorzy:
Gunatilaka, C. C.
Gamalath, K. A. I. L. Wijewardena
Powiązania:
https://bibliotekanauki.pl/articles/1191504.pdf
Data publikacji:
2016
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Helium-Neon
Ti-Sapphire
time dependant Schrodinger equation
Strong laser field
Gaussian potential well
Argon
Opis:
The time dependant Schrodinger equation was solved for one dimensional and two dimensional Gaussian potential wells in the presence of a strong laser field. Three laser fields Argon, Helium-Neon and Ti-Sapphire with different intensities with cosine and sine laser electric fields were used for the simulation. The Gaussian potential well get distorted in two different ways with the intensity change and the wavelength change of the laser. The wave functions and the position probabilities are presented. The Gaussian potential distortion for He-Ne laser occur in the opposite way compared to Ar and Ti-Sapphire for cosine electric field while Ar laser behaves differently than He-Ne and Ti-Sapphire for sine electric field of the laser in the case of two dimensional potential.
Źródło:
World Scientific News; 2016, 40; 264-283
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 21

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