Search results for "electromagnetic [radiation]"
showing 10 items of 873 documents
Elastic Wave Near-Cloaking
2020
Cloaking elastic waves has, in contrast to the cloaking of electromagnetic waves, remained a fundamental challenge: the latter successfully uses the invariance of Maxwell's equations, from which the field of transformational optics has emerged, whereas the elastic Navier equations are not invariant under coordinate transformations. Our aim is to overcome this challenge, at least in practical terms, and thereby unlock applications in mechanics, ultrasound, vibration mitigation, non-destructive evaluation and elastic wave control. We achieve near-cloaking by recognising that, despite the lack of invariance, a decoupling into a system of form invariant potential equations together with a quant…
Colloquium: The Shape of Hadrons
2012
This Colloquium addresses the issue of the shape of hadrons and, in particular, that of the proton. The concept of shape in the microcosm is critically examined. Special attention is devoted to properly define the meaning of shape for bound-state systems of near massless quarks. The ideas that lead to the expectation of nonsphericity in the shape of hadrons, the calculations that predict it, and the experimental information obtained from recent high-precision measurements are examined. Particular emphasis is given to the study of the electromagnetic transition between the nucleon and its first excited state, the Δ(1232) resonance. The experimental evidence is critically examined and compare…
Electromagnetic Scattering by a Strip Grating with Plane-Wave Three-Dimensional Oblique Incidence by Means of Decomposition into E-Type and H-Type Mo…
1993
A numerical algorithm to analyze the plane-wave three-dimensional oblique incidence on a strip grating is presented. Electromagnetic field is decomposed into vector Floquet harmonics of the E-type and H-type modes. To impose boundary conditions on the incident, reflected and transmitted waves, two integral equations of Fredholm of first kind are obtained. These equations are solved numerically with the standard Galerkin procedure, and the convergence of the algorithm is examined numerically. Since the superficial current near the edges of a conducting strip have been taken into account, the computational algorithm shows a fast convergence. Results are compared with other numerical results a…
Nanohybrid for Photodynamic Therapy and Fluorescence Imaging Tracking without Therapy
2018
Theranostic upconversion nanoparticles (UCNPs) are ideal candidates for personalized medicine. We present a smart, easy-to-prepare nanohybrid (NH) suitable for NIR-theragnosis and imaging tracking without triggering therapy simultaneously. The photophysical features of each component have been carefully selected in order to maximize the capabilities for theragnosis, in particular, the upconversion emission and the photosensitizer absorption. In addition, NH presents a fluorescent marker with one-photon absorption in the green and two-photon absorption cross-section at NIR wavelengths where the UCNP does not absorb, thus enabling innocuous tracking. Thus, the NH consists of NaYF4:Yb, Er, Tm …
Combined effect of turbulence and aerosol on free-space optical links
2017
[EN] Despite the benefits of free-space optical (FSO) communications, their full utilization is limited by the influence of atmospheric weather conditions, such as fog, turbulence, smoke, snow, etc. In urban environments, additional environmental factors such as smog and dust particles due to air pollution caused by industry and motor vehicles may affect FSO link performance, which has not been investigated in detail yet. Both smog and dust particles cause absorption and scattering of the propagating optical signal, thus resulting in high attenuation. This work investigates the joint impact of atmospheric turbulence and dust particle-imposed scattering on FSO link performance as part of the…
Core (XUV/VUV) and boundary (UV/vis/IR) plasma spectroscopy in fusion devices
2021
This contribution describes the basic applications of passive optical emission spectroscopy in the visible and far-UV region of electromagnetic radiation to diagnostics of the magnetic confinement fusion plasma. To simplify and condense the broad topic it presents the most common ways of analyzing the spectra of atoms, ions and molecules in fusion plasma and disseminating results of those analysis to the non-spectroscopists. It provides the reasons for choosing some particular regions, elements and charge states to determine the impurity content and plasma-surface interactions in MCF (Magnetic Confinement Fusion) reactor. Examples used in the contribution are predominantly from measurements…
Spatial modulation of the electromagnetic energy transfer by excitation of graphene waveguide surface plasmons
2019
We theoretically study the electromagnetic energy transfer between donor and acceptor molecules near a graphene waveguide (WG). The surface plasmons (SPs) supported by the structure provide decay channels which lead to an improvement in the energy transfer rate when the donor and acceptor are localized on the same side or even on opposite sides of the WG. The modification of the energy transfer rate compared to its value in absence of the WG are calculated by deforming the integration path into a suitable path in the complex plane. Our results show that this modification is dramatically enhanced when the symmetric and antisymmetric SPs are excited. Notable effects on the spatial dependence …
Indium surfactant effect on AlN/GaN heterostructures grown by metal-organic vapor-phase epitaxy: Applications to intersubband transitions
2006
We report on a dramatic improvement of the optical and structural properties of AlN/GaN multiple quantum wells (MQWs) grown by metal-organic vapor-phase epitaxy using indium as a surfactant. This improvement is observed using photoluminescence as well as x-ray diffraction. Atomic force microscopy shows different surface morphologies between samples grown with and without In. This is ascribed to a modified relaxation mechanism induced by different surface kinetics. These improved MQWs exhibit intersubband absorption at short wavelength (2 mu m). The absorption linewidth is as low as 65 meV and the absorption coefficient is increased by 85%.
Estimation of the emission temperature of an electrodeless discharge lamp and determination of the oscillator strength for the I(2P3/2) 183.038 nm re…
2001
Abstract The 183.038 nm resonance absorption transition of I( 2 P 3/2 ) has been studied using a flash photolysis set-up for gas-phase chemistry and a radio frequency powered electrodeless discharge lamp filled with iodine. The dependence of self-absorption and self-reversal on iodine partial pressure in the discharge volume was measured. The optimum iodine partial pressure, with self-absorption minimized and acceptable intensity, is determined to be approximately 2.5×10 −3 mbar. A method is described to estimate the temperature of the emitting atoms using direct measurements of relative absorption at different absorber concentrations. This yields an emission temperature of 923±50 K. Using …
Brown and green LAI mapping through spectral indices
2015
Abstract When crops senescence, leaves remain until they fall off or are harvested. Hence, leaf area index (LAI) stays high even when chlorophyll content degrades to zero. Current LAI approaches from remote sensing techniques are not optimized for estimating LAI of senescent vegetation. In this paper a two-step approach has been proposed to realize simultaneous LAI mapping over green and senescent croplands. The first step separates green from brown LAI by means of a newly proposed index, ‘Green Brown Vegetation Index (GBVI)’. This index exploits two shortwave infrared (SWIR) spectral bands centred at 2100 and 2000 nm, which fall right in the dry matter absorption regions, thereby providing…