scholarly journals Plasmonic modes in cylindrical nanoparticles and dimers

2020 ◽  
Vol 476 (2244) ◽  
pp. 20200530
Author(s):  
Charles A. Downing ◽  
Guillaume Weick
Keyword(s):  
Theoretical Model ◽  
Collective Modes ◽  
Quantum Mechanical ◽  
Localized Surface Plasmons ◽  
Static Approximation ◽  
Coupled Mode ◽  
Nanoparticle Separation ◽  
Resonance Frequencies ◽  
Metallic Cylinder ◽  
Analytical Expressions

We present analytical expressions for the resonance frequencies of the plasmonic modes hosted in a cylindrical nanoparticle within the quasi-static approximation. Our theoretical model gives us access to both the longitudinally and transversally polarized dipolar modes for a metallic cylinder with an arbitrary aspect ratio, which allows us to capture the physics of both plasmonic nanodisks and nanowires. We also calculate quantum mechanical corrections to these resonance frequencies due to the spill-out effect, which is of relevance for cylinders with nanometric dimensions. We go on to consider the coupling of localized surface plasmons in a dimer of cylindrical nanoparticles, which leads to collective plasmonic excitations. We extend our theoretical formalism to construct an analytical model of the dimer, describing the evolution with the inter-nanoparticle separation of the resultant bright and dark collective modes. We comment on the renormalization of the coupled mode frequencies due to the spill-out effect, and discuss some methods of experimental detection.

scholarly journals Thermo-Elasticity of Materials from Quasi-Harmonic Calculations

Minerals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 16 ◽  
Author(s):  
Maurizio Destefanis ◽  
Corentin Ravoux ◽  
Alessandro Cossard ◽  
Alessandro Erba
Keyword(s):  
Thermal Expansion ◽  
Elastic Constants ◽  
Helmholtz Free Energy ◽  
Elastic Stiffness ◽  
Elastic Response ◽  
Quantum Mechanical ◽  
Effective Algorithm ◽  
Thermal Dependence ◽  
Static Approximation ◽  
Energy Derivatives

An effective algorithm for the quasi-harmonic calculation of thermo-elastic stiffness constants of materials is discussed and implemented into the Crystal program for quantum-mechanical simulations of extended systems. Two different approaches of increasing complexity and accuracy are presented. The first one is a quasi-static approximation where the thermal dependence of elastic constants is assumed to be due only to the thermal expansion of the system. The second one is fully quasi-harmonic, takes into account thermal expansion, and explicitly computes Helmholtz free energy derivatives with respect to strain. The conversion of isothermal into adiabatic thermo-elastic constants is also addressed. The algorithm is formally presented and applied to the description of the thermo-elastic response of the forsterite mineral.

scholarly journals Manifestation of the spontaneous parity-time symmetry breaking phase transition in hot-electron photodetection based on a tri-layered metamaterial

Nanophotonics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 495-504 ◽  
Author(s):  
Qiang Bai
Keyword(s):  
Phase Transition ◽  
Theoretical Model ◽  
Symmetry Breaking ◽  
Pt Symmetry ◽  
Coupled Mode Theory ◽  
Hot Electron ◽  
Electron Device ◽  
Coupled Mode ◽  
Time Symmetry ◽  
Existence Conditions

AbstractWe theoretically and numerically demonstrate that the spontaneous parity-time (PT) symmetry breaking phase transition can be realized respectively by using two independent tuning ways in a tri-layered metamaterial that consists of periodic array of metal-semiconductor Schottky junctions. The existence conditions of PT symmetry and its phase transition are obtained by using a theoretical model based on the coupled mode theory. A hot-electron photodetection based on the same tri-layered metamaterial is proposed, which can directly show the spontaneous PT symmetry breaking phase transition in photocurrent and possesses dynamical tunability and switchability. This work extends the concept of PT symmetry into the hot-electron photodetection, enriches the functionality of the metamaterial and the hot-electron device, and has varieties of potential and important applications in optoelectronics, photodetection, photovoltaics, and photocatalytics.

Analytical solutions for turbulent Boussinesq fountains in a linearly stratified environment

2011 ◽  
Vol 691 ◽  
pp. 487-497 ◽  
Author(s):  
Rabah Mehaddi ◽  
Olivier Vauquelin ◽  
Fabien Candelier
Keyword(s):  
Theoretical Model ◽  
Asymptotic Analysis ◽  
Flow Rate ◽  
Vertical Velocity ◽  
Analytical Solutions ◽  
Boussinesq Approximation ◽  
Singular Case ◽  
Maximal Height ◽  
Analytical Integration ◽  
Analytical Expressions

AbstractThis paper theoretically investigates the initial up-flow of a vertical turbulent fountain (round or plane) in a linearly stratified environment. Conservation equations (volume, momentum and buoyancy) are written under the Boussinesq approximation assuming an entrainment proportional to the vertical velocity of the fountain. Analytical integration leads to exact values of both density and flow rate at the maximal height reached by the fountain. This maximal height is expressed as a function of the release conditions and the stratification strength and plotted from a numerical integration in order to exhibit overall behaviour. Then, analytical expressions for the maximal height are derived from asymptotic analysis and compared to experimental correlations available for forced fountains. For weak fountains, these analytical expressions constitute a new theoretical model. Finally, modified expressions are also proposed in the singular case of an initially non-buoyant vertical release.

A Theoretical Model for Ship–Wave Impact Generated Sea Spray

2020 ◽  
Vol 143 (4) ◽  
Author(s):  
Shafiul Mintu ◽  
David Molyneux ◽  
Bruce Colbourne
Keyword(s):  
Theoretical Model ◽  
Field Measurements ◽  
Operating Conditions ◽  
Ship Motions ◽  
Wave Impact ◽  
Fishing Vessels ◽  
Semi Empirical ◽  
Wave Induced ◽  
Analytical Expressions ◽  
Ship Speed

Abstract Spray generated by ships traveling in cold oceans often leads to topside icing, which can be dangerous to vessels. Estimation of the spray flux is a first step in predicting icing accumulation. The amount of spray water, the duration of exposure to the spray, and the frequency at which the spray is generated are all important parameters in estimating the spray flux. Most existing spray flux formulae are based on field observations from small fishing vessels. They consider meteorological and oceanographic parameters but neglect the vessel behavior. Ship heave and pitch motions, together with ship speed, determine the frequency of spray events. Thus, the existing formulae are not generally applicable to different sizes and types of vessels. This paper develops simple methods to quantify spray properties in terms that can be applied to vessels of any size or type. Formulae to estimate water content and spray duration are derived based on principles of energy conservation and dimensional analysis. To estimate spray frequency considering ship motions, a theoretical model is proposed. The model inputs are restricted to ship’s principal particulars, operating conditions, and environmental conditions. Wave-induced motions are estimated using semi-empirical analytical expressions. A novel spray threshold is developed to separate deck wetness frequency from spray frequency. Spray flux estimates are validated against full-scale field measurements available in the open literature with reasonable agreement.

scholarly journals Air exchange through doorways. The effect of temperature difference, turbulence and ventilation flow

1977 ◽  
Vol 79 (1) ◽  
pp. 141-154 ◽  
Author(s):  
O. M. Lidwell
Keyword(s):  
Theoretical Model ◽  
Temperature Difference ◽  
Effect Of Temperature ◽  
Air Mass ◽  
Excess Air ◽  
Outflow Velocity ◽  
Simple Theoretical Model ◽  
Air Supply ◽  
Air Mixing ◽  
Analytical Expressions

SUMMARYAnalytical expressions have been derived for the exchange of air across doorways or similar apertures, in terms of the temperature difference between the spaces on both sides of the opening and the net volume of air flowing through this as a result of unbalanced air supply or extract. A simple allowance for turbulence which gives reasonable correspondence with observation is included. The formulae, which assume complete air mixing on both sides of the doorway up to the plane of the aperture, predict outflows from the warmer side, when there is an excess air supply to this side, which are progressively smaller than those observed as the temperature difference rises above 2–3 °C and the volume of excess air supply increases to produce an averaged outflow velocity greater than 0·1–0·15m/s. This seems to be due to lack of mixing of the warm outflowing air with the cooler air mass. A correction factor for this can be deduced as a function of the pressure difference due to the excess air supply. The limiting magnitude and general form of this function are compatible with a simple theoretical model of the air flow patterns involved.

The Effect of Chucking Methods on Roundness Error in the Boring Process

1976 ◽  
Vol 98 (1) ◽  
pp. 233-238 ◽  
Author(s):  
C. H. Kahng ◽  
H. W. Lord ◽  
T. L. Davis
Keyword(s):  
Theoretical Model ◽  
Beam Theory ◽  
Geometric Parameters ◽  
Curved Beam ◽  
Roundness Error ◽  
Cylindrical Workpiece ◽  
Analytical Expressions ◽  
Good Agreement

Curved-beam theory is used to obtain a theoretical model to describe deformations in a cylindrical workpiece during boring processes. Analytical expressions are obtained for roundness error due to two-, three-, and four-jaw chucks. Experiments are carried out and theory is compared with measured values of roundness errors for several combinations of material and geometric parameters, showing good agreement.

scholarly journals Exact quasi-relativistic wavefunctions of Hydrogen-like atoms

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Luis Grave de Peralta
Keyword(s):  
Bound States ◽  
Relativistic Quantum ◽  
Quantum Mechanical ◽  
Solid State Physics ◽  
Mechanical Wave ◽  
Atomic Orbitals ◽  
Exact Analytical Expression ◽  
Quantum Particles ◽  
Software Packages ◽  
Analytical Expressions

Abstract Exact solutions of a novel quasi-relativistic quantum mechanical wave equation are found for Hydrogen-like atoms. This includes both, an exact analytical expression for the energies of the bound states, and exact analytical expressions for the wavefunctions, which successfully describe quantum particles with mass and spin-0 up to energies comparable to the energy associated to the mass of the particle. These quasi-relativistic atomic orbitals may be used for improving ab-initio software packages dedicated to numerical simulations in physical-chemistry and atomic and solid-state physics.

The driven quantum-mechanical two-level system: small fields and long relaxation times

1987 ◽  
Vol 65 (1) ◽  
pp. 82-87
Author(s):  
J. Grindlay
Keyword(s):  
Relaxation Times ◽  
Formal Theory ◽  
Quantum Mechanical ◽  
Third Harmonic ◽  
Resonance Frequencies ◽  
Small Fields ◽  
Rotating Wave ◽  
Upper Level ◽  
Term Response

A formal theory of the long-term response of a dissipative two-level quantum-mechanical system to a monochromatic applied electric field is used to describe the fundamental and third-harmonic resonances in the small-field and long relaxation-times regime. Resonance frequencies, including Bloch–Siegert shifts, and resonance amplitudes for the dipole-moment components and the upper level probability function are obtained. A comparison with the rotating-wave approximation is made.

Direct Parametric Analysis of Resonance Regimes for Nonlinear Vibrations of Bladed Discs

2006 ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Large Scale ◽  
Contact Stiffness ◽  
Design Parameters ◽  
Strongly Nonlinear ◽  
Resonance Frequencies ◽  
Interface Parameters ◽  
First Time ◽  
Analytical Expressions ◽  
Contact Stiffness Coefficients

A method has been developed to calculate directly resonance frequencies and resonance amplitudes as functions of design parameters or as a function of excitation levels. The method provides, for a first time, this capability for analysis of strongly nonlinear periodic vibrations of bladed discs and other structures with nonlinear interaction at contact interfaces. A criterion for determination of major, sub- and superharmonic resonance peaks has been formulated. Analytical expressions have been derived for accurate evaluation of the criterion and for tracing resonance regimes as function of such contact interface parameters as gap and interference values, friction and contact stiffness coefficients, normal stresses. High accuracy and efficiency of the new method have been demonstrated on numerical examples including large-scale nonlinear bladed disc model and major types of contact interfaces including friction contact interfaces, gaps and cubic nonlinearities.

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