Search results for "Difference"

Correlations between a Hawking particle and its partner in a 1+1D Bose-Einstein condensate analog black hole

2020

The Fourier transform of the density-density correlation function in a Bose-Einstein condensate (BEC) analog black hole is a useful tool to investigate correlations between the Hawking particles and their partners. It can be expressed in terms of $⟨{^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{ext}}\text{ }\text{ }{^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{int}}⟩$, where ${^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{ext}}$ is the annihilation operator for the Hawking particle and ${^{\mathrm{out}}\stackrel{^}{a}}_{\mathrm{up}}^{\mathrm{int}}$ is the corresponding one for the partner. This basic quantity is calculated for three different models for the BEC f…

2015

In this study we present a hyperspectral flying goniometer system, based on a rotary-wing unmanned aerial vehicle (UAV) equipped with a spectrometer mounted on an active gimbal. We show that this approach may be used to collect multiangular hyperspectral data over vegetated environments. The pointing and positioning accuracy are assessed using structure from motion and vary from σ = 1° to 8° in pointing and σ = 0.7 to 0.8 m in positioning. We use a wheat dataset to investigate the influence of angular effects on the NDVI, TCARI and REIP vegetation indices. Angular effects caused significant variations on the indices: NDVI = 0.83–0.95; TCARI = 0.04–0.116; REIP = 729–735 nm. Our analysis high…

Recent progress on Frequency Difference Electrical Impedance Tomography

2009

Although time-dierence EIT(tdEIT) has shown promise as a medical EIT imaging tech- nique such as monitoring lung function, static EIT has suered from forward computational model errors including boundary geometry and electrode positions uncertainty combined with the ill-posed and highly nonlinear nature of the corresponding inverse problem. Since 1980s, there has been great endeavor to create forward computational models with the necessary accuracy required for EIT recon- struction, but these eorts were not successful in clinical environment. This is the main reason why we consider frequency-dieren ce EIT (fdEIT) where we take advantage of frequency dependance of biological tissue by inject…

SPECIAL HPERBOLIC TYPE APPROXIMATION FOR SOLVING OF 3-D TWO LAYER STATIONARY DIFFUSION PROBLEM

2019

In this paper we examine the conservative averaging method (CAM) along the vertical z-coordinate for solving the 3-D boundary-value 2 layers diffusion problem. The special parabolic and hyperbolic type approximation (splines), that interpolate the middle integral values of piece-wise smooth function, is investigated. With the help of these splines the problems of mathematical physics in 3-D with respect to one coordinate are reduced to problems for system of equations in 2-D in every layer. This procedure allows reduce also the 2-D problem to a 1-D problem and the solution of the approximated problem can be obtained analytically. As the practical application of the created mathematical mode…

Analysis of the finite difference time domain technique to solve the Schrödinger equation for quantum devices

2004

An extension of the finite difference time domain is applied to solve the Schrödinger equation. A systematic analysis of stability and convergence of this technique is carried out in this article. The numerical scheme used to solve the Schrödinger equation differs from the scheme found in electromagnetics. Also, the unit cell employed to model quantum devices is different from the Yee cell used by the electrical engineering community. A bound for the time step is derived to ensure stability. Several numerical experiments in quantum structures demonstrate the accuracy of a second order, comparable to the analysis of electromagnetic devices with the Yee cell. a!Electronic mail: Antonio.Sorian…

Finite difference time domain simulation of soil ionization in grounding systems under lightning surge conditions

2004

This paper proposes a Maxwell’s equations finite difference time domain (FDTD) approach for electromagnetic transients in ground electrodes in order to take into account the non linear effects due to soil ionization. A time variable soil resistivity method is used in order to simulate the soil breakdown, without the formulation of an initial hypothesis about the geometrical shape of the ionized zone around the electrodes. The model has been validated by comparing the computed results with available data found in technical literature referred to concentrated earths. Some application examples referred to complex grounding systems are reported to show the computational capability of the propos…

The finite element method for fractional non-local thermal energy transfer in non-homogeneous rigid conductors

2015

Abstract In a non-local fractional-order model of thermal energy transport recently introduced by the authors, it is assumed that local and non-local contributions coexist at a given observation scale: while the first is described by the classical Fourier transport law, the second involves couples of adjacent and non-adjacent elementary volumes, and is taken as proportional to the product of the masses of the interacting volumes and their relative temperature, through a material-dependent, distance-decaying power-law function. As a result, a fractional-order heat conduction equation is derived. This paper presents a pertinent finite element method for the solution of the proposed fractional…

High performance for refractive index sensors via symmetry-protected guided mode resonance.

2021

The symmetry breaking in a typical dielectric GMR-grating structure allows the coupling of the incident wave with the so-called Symmetry-Protected Modes (SPM). In this present work, the excitation conditions of such particular modes are investigated. A parametric study including the grating dimensions is carried out to exploit them for a blood refractive index sensing with higher Sensitivity (S) and Figure Of Merit (FOM). To our knowledge, the performances obtained by FDTD calculations (Q = 2.1 × 104, S = 657 nm/RIU and FOM ≃ ~9 112 RIU−1) and FMM calculations (Q = 3 × 106, S = 656 nm/RIU and FOM ≃ ~1.64 × 106 RIU−1) are the highest level reached.

Röntgenkleinwinkeluntersuchungen zur struktur der fehlgeordneten bereiche in verstreektem polyäthylen. Teil I: Absolutintensität der röntgenkleinwink…

1968

Aus Absolutmessungen der Intensitat der Rontgenkleinwinkelstreuung an verstrecktem Polyathylen wurden die durch Tempern verursachten Anderungen des mittleren Schwankungsquadrates der Dichtefluktuation berechnet. Unter Zugrundelegung eines Zweiphasenmodells wurde hieraus die mittlere Dichtedifferenz zwischen kristallinen und fehlgeordneten Bereichen in Abhangigkeit von der Tempertemperatur bestimmt. Gleichzeitig vorgenommene Rontgenweitwinkelmessungen erlaubten es, daraus die effektiven Dichten der beiden Phasen sowie eine sogenannte „Rontgenkleinwinkelkristallinitat” zu berechnen, wie sie von PETERLIN vorgeschlagen wurde. Die Ergebnisse der Rontgenkleinwinkeluntersuchungen legen es nahe, di…

Size effects of small-scale beams in bending addressed with a strain-difference based nonlocal elasticity theory

2019

Abstract A strain-difference based nonlocal elasticity model devised by the authors elsewhere (Polizzotto et al., Int. J. Solids Struct. 25 (2006) 308–333) is applied to small-scale homogeneous beam models in bending under static loads in the purpose to describe the inherent size effects. With this theory —belonging to the strain-integral nonlocal model family, but exempt from anomalies typical of the Eringen nonlocal theory— the relevant beam problem is reduced to a set of three mutually independent Fredholm integral equations of the second kind (each independent of the beam’s ordinary boundary conditions, only one depends on the given load), which can be routinely solved numerically. Appl…