Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 25 for “"Dipole Approximation"”.
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Limits of long wavelength High Harmonic Generation
… Most of the current literature on HHG uses the Dipole Approximation for calculation of harmonic spectrum. The physical ramification of the Dipole Approximation is that it neglects the magnetic field component to the driver field. It is well known that a charge moving in a magnetic field …
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Micromagnetic modelling of thin film media
… field is carried out. The model initially uses a dipole approximation to calculate the total contribution from the magnetostatic field. A more accurate magnetostatic calculation, based on volume and surface charges of the triangles, was implemented to calculate the close range magnetostatic …
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Magneto-Optic Spectroscopy and Near-Field Optical Coupling in Nanoparticle Composite Materials
… A theory is presented based on the dipole approximation which accounts for optical coupling between magnetite particles. Qualitative correlations between theoretical calculations and experimental data suggest the shifts in spectral peak position depend on both interparticle distance …
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A Study of GPR Performance in the Presence of Buried Biomass
… For the numerical simulations, the discrete dipole approximation (DDA) was employed to model scattering from roots in a homogeneous medium. Slight modifications permitted it to model the GPR data. Comparisons of the DDA code's results against those of well-known codes and various experiments …
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Ultra-low frequency wireless transmitter design using resonant oscillating permanent magnets
… I formulate a theoretical model using point dipole approximation, and compare the results with finite-element simulations. The analytical model brings out the nonlinear dependence of magnetic torsional stiffness on the rotor oscillation amplitude. Further, it shows that the resonance …
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Computational Studies of Electrorheological Emulsions
… columns comprising two or more chains. Point-dipole approximation is used to analyze the structure formation and it is shown that it is also applicable to region II where the hydrodynamic effect is weak and the behavior of the system is mainly governed by the dielectrophoretic forces. It is …
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Self-Assembled Nanoantenna Enhance Optical Activity and Transport in Scalable Thin Films and Interfaces
… within 2% using rapid semi-analytic coupled-dipole approximation (rsa-CDA) simulations when contained within patterned PDMS and transferred onto glass substrates. Two biocompatible transfer approaches were developed and implemented to transfer ordered arrangements of nanoantenna to the …
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An analysis of cryovolcano plumes on Enceladus by light scattering and polarimetry
… by light scattering codes Amsterdam Discrete Dipole Approximation (ADDA) and T-Matrix for both single scattering and using a multiple-scattering approximation. The Pearson correlation coefficient is used to quantify the fit of each morphology to the Cassini data in the clear CLR (611 nm), GRN …
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Engineering the Optical Properties of Gold Nanostructures for Biomedical Applications
… were developed. With a series of discrete dipole approximation calculations: DDA), I illustrated how the edge length and ridge thickness of the nanoframe can affect the LSPR peak. I validated the calculated predictions by experimental measurements. I functionalized the surface of the Au …
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Partial Radiative Recombination Cross Sections for Excited States of Hydrogen
… H II regions usually only the electric dipole term in the expansion of the interaction Hamiltonian is kept. However, conditions present in these regions permit recombination into highly excited states and the "effective size" of the atom is not much less than the wavelength of the …
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Applied molecular quantum electrodynamics: geometric aspects of the efficiency of photonic interactions
… in the condensed phase. Within the electric-dipole approximation, hyper-Rayleigh scattering (HRS) is considered forbidden for centrosymmetric molecules: By including higher-multipole interactions, mechanisms enabling conventionally-forbidden HRS are discovered. For each process analysed, the …
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Study of Copper Nanowires With Five-Twinned Structure Grown by Chemical Vapor Deposition and Their Applications
… CuNWs were measured and verified by the discrete dipole approximation (DDA) simulation. The optical tunability of the CuNWs with respect to the aspect ratio might enable us to use their optical characteristics as optical modulating tools or optical filters.
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Fast algorithms for small particle scattering problems
… surface and volume integral equations. Discrete dipole approximation (DDA) is an alternate and useful discretization technique to solve these problems where the continuum scatterer is replaced by a set of polarizable dipoles. It is an alternative to volume integral equations and produces a dense …
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A physical model to estimate snowfall over land using microwave measurements
… water in the upper atmosphere.The Discrete Dipole Approximation (DDA) method was employed to generate the single scattering parameters for nonspherical snow crystals. Comparisons show that neither equivalent spheres nor dielectric mixing theories could account for all measurements. …
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A data storage system based on patterned magnetic media and magnetic force microscopy
… were generated using a model based on the dipole approximation and compared with the experimental data. A good agreement was obtained. This thesis, also, discusses some of the system level issues including the design related to the high data rate and the tracking of the individual bits for …
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Two-photon absorption and nonlinear polariton effects in organic crystals
… it is both one- and two-photon allowed in the dipole approximation. Consequently, polariton states and SHG play a role in the two-photon process. In the polariton model, both TPA and SHG are understood as resulting from the process of polariton fusion;Polarized TPE spectra of the 350 nm …
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Towards sustainable plasmonics: a study on the shapes and plasmonic properties of magnesium nanoparticles
… electromagnetic simulations in the discrete dipole approximation and single-particle dark-field scattering measurements are employed to unravel size, shape and environment effects in the near-field and far-field optical response of the nanoparticles. Finally, a summary and a concluding …
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Optical Nanoantennas for Ultrafast Nonlinear Spectroscopy of Individual Nanosystems
… einen Punkt-Dipol Ansatz auf Basis der ’Discrete Dipole Approximation’, um im Weiteren besonderen Wert auf die elementaren Wechselwirkungsmechanismen zwischen Nanopartikel und Antenne zu legen. Weiterhin erlaubt uns der stark reduzierte Rechenaufwand riesige, zuvor unzugängliche Parameterräume zu …
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A study of oxide superconductors by electron energy loss spectroscopy in STEM.
… with different collection conditions, the dipole approximation can be investigated for commonly used apertures in the STEM. The decomposition of the experimental spectra can be used to investigate the effect of specimen orientation on the " quantified result.
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Electro hydrodynamic manipulation of the process of self-assembly of particles at fluid-fluid interfaces
… of the DNS results with those from the point-dipole approximation shows that the accuracy of the latter diminishes when the distance between the particles becomes comparable to the particle diameter, the domain size is comparable to the diameter, and also when the dielectric mismatch between …
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