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## Eigenmode frequencies calculations in the charge-density-wave states of 2H-TaSe2

Fonte: Sociedade Brasileira de Física
Publicador: Sociedade Brasileira de Física

Tipo: Artigo de Revista Científica
Formato: text/html

Publicado em 01/09/1998
EN

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We have performed some calculations involving two eigenmode frequencies of 2H - TaSe2. We have obtained a good comparison with some well established Raman scattering data for the commensurate and incommensurate charge-density-wave phases in this compound. We outline an approximated method to compute the determinantal equation.

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## On the difference between negative damping and eigenmode synchronization as two phonation onset mechanisms

Fonte: Acoustical Society of America
Publicador: Acoustical Society of America

Tipo: Artigo de Revista Científica

Publicado em /04/2011
EN

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Negative damping and eigenmode synchronization as two different mechanisms of phonation onset are distinguished. Although both mechanisms lead to a favorable phase relationship between the flow pressure and the vocal fold motion as required for a net energy transfer into the vocal folds, the underlying mechanisms for this favorable phase relationship are different. The negative damping mechanism relies on glottal aerodynamics or acoustics to establish before onset and maintain after onset the favorable phase relationship, and therefore has minimum requirements on vocal fold geometry and biomechanics. A single degree-of-freedom vocal fold model is all that is needed for self-oscillation in the presence of a negative damping mechanism. In contrast, the mechanism of eigenmode synchronization critically depends on the geometrical and biomechanical properties of the vocal folds (at least 2-degrees-of-freedom are required), and has little requirement on the glottal aerodynamics other than flow separation. The favorable phase relation is established once synchronization occurs, regardless of the phase relationship imposed by glottal aerodynamics before onset. Unlike that of the negative damping mechanism, initiation of eigenmode synchronization requires neither a velocity-dependent flow pressure nor an alternating convergent-divergent glottis. The clinical implications of the distinctions between these two mechanisms are discussed.

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## Spatially-Resolved Eigenmode Decomposition of Red Blood Cells Membrane Fluctuations Questions the Role of ATP in Flickering

Fonte: Public Library of Science
Publicador: Public Library of Science

Tipo: Artigo de Revista Científica

Publicado em 10/08/2012
EN

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Red blood cells (RBCs) present unique reversible shape deformability, essential for both function and survival, resulting notably in cell membrane fluctuations (CMF). These CMF have been subject of many studies in order to obtain a better understanding of these remarkable biomechanical membrane properties altered in some pathological states including blood diseases. In particular the discussion over the thermal or metabolic origin of the CMF has led in the past to a large number of investigations and modeling. However, the origin of the CMF is still debated. In this article, we present an analysis of the CMF of RBCs by combining digital holographic microscopy (DHM) with an orthogonal subspace decomposition of the imaging data. These subspace components can be reliably identified and quantified as the eigenmode basis of CMF that minimizes the deformation energy of the RBC structure. By fitting the observed fluctuation modes with a theoretical dynamic model, we find that the CMF are mainly governed by the bending elasticity of the membrane and that shear and tension elasticities have only a marginal influence on the membrane fluctations of the discocyte RBC. Further, our experiments show that the role of ATP as a driving force of CMF is questionable. ATP...

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## Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case

Fonte: Beilstein-Institut
Publicador: Beilstein-Institut

Tipo: Artigo de Revista Científica

Publicado em 18/03/2013
EN

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We present an overview of the bimodal amplitude–frequency-modulation (AM-FM) imaging mode of atomic force microscopy (AFM), whereby the fundamental eigenmode is driven by using the amplitude-modulation technique (AM-AFM) while a higher eigenmode is driven by using either the constant-excitation or the constant-amplitude variant of the frequency-modulation (FM-AFM) technique. We also offer a comparison to the original bimodal AFM method, in which the higher eigenmode is driven with constant frequency and constant excitation amplitude. General as well as particular characteristics of the different driving schemes are highlighted from theoretical and experimental points of view, revealing the advantages and disadvantages of each. This study provides information and guidelines that can be useful in selecting the most appropriate operation mode to characterize different samples in the most efficient and reliable way.

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## Optical Characteristic Research on Fiber Bragg Gratings Utilizing Finite Element and Eigenmode Expansion Methods

Fonte: MDPI
Publicador: MDPI

Tipo: Artigo de Revista Científica

Publicado em 19/06/2014
EN

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Compared with coupled-mode theory (CMT), which is widely used for studies involving optical fiber Bragg gratings (FBGs), the proposed investigation scheme is visualized, diagrammatic, and simple. This method combines the finite element method (FEM) and eigenmode expansion method (EEM). The function of the FEM is to calculate all guided modes that match the boundary conditions of optical fiber waveguides. Moreover, the FEM is used for implementing power propagation for HE11 in optical fiber devices. How the periodic characteristic of FBG causes this novel scheme to be substantially superior to CMT is explained in detail. Regarding current numerical calculation techniques, the scheme proposed in this paper is the only method capable of the 3D design and analysis of large periodic components. Additionally, unlike CMT, in which deviations exist between the designed wavelength λD and the maximal reflection wavelength λmax, the proposed method performs rapid scans of the periods of optical FBG. Therefore, once the operating wavelength is set for the component design, the maximal reflection wavelength of the final products can be accurately limited to that of the original design, such as λ = 1550 nm. Furthermore, a comparison between the period scan plot and the optical spectra plot for FBG indicated an inverse relationship between the periods and wavelengths. Consequently...

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## Dynamic calibration of higher eigenmode parameters of a cantilever in atomic force microscopy by using tip–surface interactions

Fonte: Beilstein-Institut
Publicador: Beilstein-Institut

Tipo: Artigo de Revista Científica

Publicado em 29/10/2014
EN

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We present a theoretical framework for the dynamic calibration of the higher eigenmode parameters (stiffness and optical lever inverse responsivity) of a cantilever. The method is based on the tip–surface force reconstruction technique and does not require any prior knowledge of the eigenmode shape or the particular form of the tip–surface interaction. The calibration method proposed requires a single-point force measurement by using a multimodal drive and its accuracy is independent of the unknown physical amplitude of a higher eigenmode.

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## The impact of magnetic geometry on wave modes in cylindrical plasmas

Fonte: Universidade Nacional da Austrália
Publicador: Universidade Nacional da Austrália

Tipo: Thesis (PhD); Doctor of Philosophy (PhD)

EN_AU

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Both space and laboratory plasmas can be associated with static magnetic field, and the field geometry varies from uniform to non-uniform. This thesis investigates the impact of magnetic geometry on wave modes in cylindrical plasmas. The cylindrical configuration is chosen so as to explore this impact in a tractable but experimentally realisable configuration. Three magnetic geometries are considered: uniform, focused and rippled.
For a uniform magnetic field, wave oscillations in a plasma cylinder with axial flow and azimuthal rotation are modelled through a two-fluid flowing plasma model. The model provides a qualitatively consistent description of the plasma configuration on a Radio Frequency (RF) generated linear magnetised plasma (WOMBAT, Waves On Magnetised Beams And Turbulence [Boswell and Porteous, Appl. Phys. Lett. 50, 1130 (1987)]), and yields agreement between measured and predicted dependences of the wave oscillation frequency with axial field strength. The radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of the oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode...

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## Pressure Effects on the Ensemble Dynamics of Ubiquitin Inspected with Molecular Dynamics Simulations and Isotropic Reorientational Eigenmode Dynamics

Fonte: The Biophysical Society
Publicador: The Biophysical Society

Tipo: Artigo de Revista Científica

EN

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According to NMR chemical shift data, the ensemble of ubiquitin is a mixture of “open” and “closed” conformations at rapid equilibrium. Pressure perturbations provide the means to study the transition between the two conformers by imposing an additional constraint on the system's partial molar volume. Here we use nanosecond-timescale molecular dynamics simulations to characterize the network of correlated motions accessible to the conformers at low- and high-pressure conditions. Using the isotropic reorientational eigenmode dynamics formalism to analyze our simulation trajectories, we reproduce NMR relaxation data without fitting any parameters of our model. Comparative analysis of our results suggests that the two conformations behave very differently. The dynamics of the “closed” conformation are almost unaffected by pressure and are dominated by large-amplitude correlated motions of residues 23–34 in the extended α-helix. The “open” conformation under conditions of normal pressure displays increased mobility, focused on the loop residues 17–20, 46–55, and 58–59 at the bottom of the core of the structure, as well as the C-terminal residues 69–76, that directly participate in key protein-protein interactions. For the same conformation...

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## Gap eigenmode of radially localized helicon waves in a periodic structure

Fonte: Institute of Physics Publishing
Publicador: Institute of Physics Publishing

Tipo: Artigo de Revista Científica

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An ElectroMagnetic Solver (Chen et al 2006 Phys. Plasmas 13 123507) is employed to model a spectral gap and a gap eigenmode in a periodic structure in the whistler frequency range. A radially localized helicon mode (Breizman and Arefiev 2000 Phys. Rev. Le

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## Quantum Chaos Analysis of the Ideal Interchange Spectrum in a Stellarator

Fonte: Cambridge University Press
Publicador: Cambridge University Press

Tipo: Artigo de Revista Científica

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#Keywords: Chaos theory#Magnetic fields#Plasma confinement#Plasma stability#Plasma turbulence#Quantum theory#Spectrum analysis#Statistical methods#Eigenmode spectrum#Eigenvalue spacings#Quantum chaos theory

The eigenmode spectrum is a fundamental starting point for the analysis of plasma stability and the onset of turbulence. Quantum chaos theory provides tools for characterizing the spectrum statistically, from the regular spectrum of the separable case (in

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## Eigenmode Analysis of Radial Velocities

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/09/1999

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Radial velocity surveys are examined in terms of eigenmode analysis within
the framework of CDM-like family of models. Rich surveys such as MARK III and
SFI, which consist of more than $10^{3}$ radial velocities, are found to have a
few tens of modes that are not noise dominated. Poor surveys, which have only a
few tens of radial velocities, are noise dominated across the eigenmode
spectrum. In particular, the bulk velocity of such surveys has been found to be
dominated by the more noisy modes. The MARK III and SFI are well fitted by a
tilted flat CDM model found by a maximum likelihood analysis and a $\chi^{2}$
statistics . However, a mode-by-mode inspection shows that a substantial
fraction of the modes lie outside the $90% $ confidence level. This implies
that although globally the CDM-like family of models seems to be consistent
with radial velocity surveys, in detail it does not. This might indicate a need
for a revised power spectrum or for some non-trivial biasing scheme.; Comment: Contribution to ``Cosmic Flows. Towards an Understanding of
Large-Scale Structure'', Workshop Victoria B.C., July 1999, eds. S. Courteau,
M. Strauss, and J. Willick (ASP). 8 pages of LaTeX including 9 postscript
figures

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## Eigenmode in a misaligned triangular optical cavity

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 27/10/2010

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We derive relationships between various types of small misalignments on a
triangular Fabry-Perot cavity and associated geometrical eigenmode changes. We
focus on the changes of beam spot positions on cavity mirrors, the beam waist
position, and its angle. A comparison of analytical and numerical results shows
excellent agreement. The results are applicable to any triangular cavity close
to an isosceles triangle, with the lengths of two sides much bigger than the
other, consisting of a curved mirror and two flat mirrors yielding a waist
equally separated from the two flat mirrors. This cavity shape is most commonly
used in laser interferometry. The analysis presented here can easily be
extended to more generic cavity shapes. The geometrical analysis not only
serves as a method of checking a simulation result, but also gives an intuitive
and handy tool to visualize the eigenmode of a misaligned triangular cavity.; Comment: 17 pages, 21 figures

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## Optical eigenmode imaging

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/05/2011

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We present an indirect imaging method that measures both amplitude and phase
information from a transmissive target. Our method is based on an optical
eigenmode decomposition of the light intensity and the first-order cross
correlation between a target field and these eigenmodes. We demonstrate that
such optical eigenmode imaging does not need any a priori knowledge of the
imaging system and corresponds to a compressive full-field sampling leading to
high image extraction efficiencies. Finally, we discuss the implications with
respect to second-order correlation imaging.

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## Dynamic Calibration of Higher Eigenmode Parameters of a Cantilever in Atomic Force Microscopy Using Tip-Surface Interactions

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

27.39%

We present a theoretical framework for the dynamic calibration of the higher
eigenmode parameters (stiffness and optical lever responsivity) of a
cantilever. The method is based on the tip-surface force reconstruction
technique and does not require any prior knowledge of the eigenmode shape or
the particular form of the tip-surface interaction. The calibration method
proposed requires a single-point force measurement using a multimodal drive and
its accuracy is independent of the unknown physical amplitude of a higher
eigenmode.; Comment: 4 pages, 4 figures

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## Statistical Eigenmode Transmission over Jointly-Correlated MIMO Channels

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 11/03/2009

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We investigate MIMO eigenmode transmission using statistical channel state
information at the transmitter. We consider a general jointly-correlated MIMO
channel model, which does not require separable spatial correlations at the
transmitter and receiver. For this model, we first derive a closed-form tight
upper bound for the ergodic capacity, which reveals a simple and interesting
relationship in terms of the matrix permanent of the eigenmode channel coupling
matrix and embraces many existing results in the literature as special cases.
Based on this closed-form and tractable upper bound expression, we then employ
convex optimization techniques to develop low-complexity power allocation
solutions involving only the channel statistics. Necessary and sufficient
optimality conditions are derived, from which we develop an iterative
water-filling algorithm with guaranteed convergence. Simulations demonstrate
the tightness of the capacity upper bound and the near-optimal performance of
the proposed low-complexity transmitter optimization approach.; Comment: 32 pages, 6 figures, to appear in IEEE Transactions on Information
Theory

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## Gap eigenmode of radially localised helicon waves in a periodic structure

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 18/10/2012

Relevância na Pesquisa

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An ElectroMagnetic Solver (EMS) [Chen et al., Phys. Plasmas, 13, 123507
(2006)] is employed to model a spectral gap and a gap eigenmode in a periodic
structure in the whistler frequency range. A Radially Localised Helicon (RLH)
mode [Breizman and Arefiev, Phys. Rev. Lett, 84, 3863 (2000)] is considered. We
demonstrate that the computed gap frequency and gap width agree well with a
theoretical analysis, and find a discrete eigenmode inside the gap by
introducing a defect to the system's periodicity. The axial wavelength of the
gap eigenmode is close to twice the system's periodicity, which is consistent
with Bragg's law. Such an eigenmode could be excited by energetic electrons,
similar to the excitation of Toroidal Alfv\'{e}n Eigenmodes (TAE) by energetic
ions in tokamaks.; Comment: Submitted to Plasma Physics and Controlled Fusion on 18 Oct 2012

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## Eigenmode decomposition of the near-field enhancement in localized surface plasmon resonances of metallic nanoparticles

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 29/05/2013

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I present a direct and intuitive eigenmode method that evaluates the
near-field enhancement around the surface of metallic nanoparticles of
arbitrary shape. The method is based on the boundary integral equation in the
electrostatic limit. Besides the nanoparticle polarizability and the far-field
response, the near-field enhancement around nanoparticles can be also
conveniently expressed as an eigenmode sum of resonant terms. Moreover, the
spatial configuration of the near-field enhancement depends explicitly on the
eigenfunctions of both the BIE integral operator and of its adjoint. It is also
established a direct physical meaning of the two types of eigenfunctions. While
it is well known that the eigenfunctions of the BIE operator are electric
charge modes, it is less known and used that the eigenfunctions of the adjoint
represent the electric potential generated by the charge modes. For the
enhanced spectroscopies the present method allows an easy identification of hot
spots which are located in the regions with maximum charge densities and/or
regions with fast variations of the electric potential generated by the charge
modes on the surface. This study also clarifies the similarities and the
differences between the far-field and the near-field behavior of plasmonic
systems. Finally...

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## The Strange Eigenmode in Lagrangian Coordinates

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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For a distribution advected by a simple chaotic map with diffusion, the
"strange eigenmode" is investigated from the Lagrangian (material) viewpoint
and compared to its Eulerian (spatial) counterpart. The eigenmode embodies the
balance between diffusion and exponential stretching by a chaotic flow. It is
not strictly an eigenmode in Lagrangian coordinates, because its spectrum is
rescaled exponentially rapidly.; Comment: 15 pages, 6 figures. RevTeX4 format with psfrag

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## Eigenmode analysis of the susceptibility matrix of the four-dimensional Edwards-Anderson spin-glass model

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 04/07/2002

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The nature of spin-glass phase of the four-dimensional Edwards-Anderson Ising
model is numerically studied by eigenmode analysis of the susceptibility matrix
up to the lattice size 10^4. Unlike the preceding results on smaller lattices,
our result suggests that there exist multiple extensive eigenvalues of the
matrix, which does not contradict replica-symmetry-breaking scenarios. The
sensitivity of the eigenmodes with respect to a temperature change is examined
using finite-size-scaling analysis and an evidence of anomalous sensitivity is
found. A computational advantage of dual formulation of the eigenmode analysis
in the study of large lattices is also discussed.; Comment: 4 pages, 2 figures

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## MIMO Identical Eigenmode Transmission System (IETS) - A Channel Decomposition Perspective

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 19/09/2010

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In the past few years considerable attention has been given to the design of
Multiple-Input Multiple-Output (MIMO) Eigenmode Transmission Systems (EMTS).
This paper presents an in-depth analysis of a new MIMO eigenmode transmission
strategy. The non-linear decomposition technique called Geometric Mean
Decomposition (GMD) is employed for the formation of eigenmodes over MIMO
flatfading channel. Exploiting GMD technique, identical, parallel and
independent transmission pipes are created for data transmission at higher
rate. The system based on such decomposition technique is referred to as MIMO
Identical Eigenmode Transmission System (IETS). The comparative analysis of the
MIMO transceiver design exploiting nonlinear and linear decomposition
techniques for variable constellation is presented in this paper. The new
transmission strategy is tested in combination with the Vertical Bell Labs
Layered Space Time (V-BLAST) decoding scheme using different number of antennas
on both sides of the communication link. The analysis is supported by various
simulation results.

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