Search results for "BAND"

Optical Properties of Irradiated Topaz Crystals

2015

The results of an investigation of UV-Visible absorption and photoluminescence spectra of colorless topaz before and after neutron irradiation, natural blue topaz from Ukraine, and yellow topaz are presented. We assume that the absorption band ~ 620 nm and broad emission band 300-700 nm in topaz crystals are associated with exchange interaction between a radiation defect (anion vacancies, which capture one or two electrons) and impurity ions Cr 3+ , Fe 3+ and Mn 2+ .

In-situ reflectance spectroscopy - analysing techniques for high-resolution pigment logging in sediment cores

2003

The temporal resolution of marine proxy data is limited by analytically required sample size. We present in-situ reflectance spectroscopy techniques (usually applied in remote sensing) to analyse the organic fraction of marine and terrestrial sediment. From absorption band depths, photosynthesis pigment variations are derived for sediments from the upwelling region off Peru, where productivity is related to the annual variability of El Nino strength. Quantitative estimations of diagenetic photosynthesis pigments derived from absorption band analysis in reflectance spectra are highly correlated to organic carbon content. The ratio of pigment fractions is related to chlorine concentration and…

A Simple Monte Carlo Model of a Hot Carrier Cell

2017

In the present work, a simplified model of a hot carrier cell is examined at different energy levels of carrier collection. Incident photons, Monte Carlo generated by employing the ASTM G173–03 data set, are accounted for individually as they interact with the cell. The hot carrier cells are examined in a transient state caused by a flash of photons with AM1.5 spectrum. Excess photon energy is recycled giving a form of thermalization of hot carriers. The sensitivity of contact variables and the device band gap on cell efficiency, has been studied.

Enabling Backoff and Eliminating Redundant Idle Period for Medium Access in LTE-U

2017

To address the burgeoning demand for mobile data, 3GPP is actively studying the capability of operating LTE in the unlicensed band, referred to as LTE-U. One of the main challenges of this approach is to maintain better coexistence between WiFi and LTE-U devices. To enable the coexistence, the listen before talk (LBT) principle has been adopted for LTE-U medium access with two flavors of mechanisms, i.e., load based equipment (LBE) and frame based equipment (FBE) access. In this paper, we consider the FBE mechanism and enhance its performance by introducing a backoff procedure for LTE devices. We investigate the original FBE mechanism defined by 3GPP and the enhanced FBE (E- FBE) mechanism fr…

Efficient Design of Waveguide Manifold Multiplexers Based on Low-Order EM Distributed Models

2015

In this paper, a new systematic technique to design manifold-coupled multiplexers in waveguide technology is proposed. The new technique uses generalized low-order electromagnetic (EM) distributed models, which constitute a half-way point between the fast, but imprecise, analytical models, and the more accurate, but costly, full-wave EM models. The method can be applied to contiguous and noncontiguous channel multiplexers, in both E-plane or H-plane configurations. This paper covers the complete design procedure for manifold multiplexers, starting from the required specifications and finishing with the physical dimensions. After explaining the general design technique for multiplexers with …

Conversion of nadir, narrowband reflectance in red and near-infrared channels to hemispherical surface albedo

1997

Abstract Measured nadir-viewed narrow-band reflectanees in red and near infrared channels simulating AVHRR Channels 1 and 2 are compared with measured integrated solar spectrum hemispherical albedos. Reflectanees and albedos were measured from an aircraft over four widely different vegetation surfaces in southeastern Tasmania (Australia). A linear function is used to simultaneously correct for narrow band to broad band conversion errors and to convert nadir viewed reflectances to hemispherical albedos. While the application of the conversion equation presented is limited to the vegetation types of the study, the equation is independent of vegetation type. Results indicate that the reflectan…

Probing the electronic states of high-TMR off-stoichiometric Co2MnSi thin films by hard x-ray photoelectron spectroscopy

2014

The tunnel magnetoresistance ratio (TMR) of fully epitaxial magnetic tunnel junctions with an off-stoichiometric Co${}_{2}$MnSi Heusler alloy has been shown to exhibit a systematic dependence on Mn content, reaching 1135% at 4.2 K for Co${}_{2}$Mn${}_{1.29}$Si. In this paper, we explain the behavior of the observed TMR ratio using ab initio calculations and hard x-ray photoelectron spectroscopy (HAXPES). For the Mn-deficient samples, we show that the the drop of the TMR is caused by Co antisite atoms, which impose extra states into the minority-spin band gap. On the other hand, Mn-excess composition shows nearly half-metallic behavior. This result can be intuitively understood since both Co…

Turbidez y profundidad de disco de Secchi con Sentinel-2 en embalses con diferente estado trófico en la Comunidad Valenciana

2019

[ES] En los estudios de calidad de aguas por teledetección, uno de los principales indicadores es la transparencia o turbidez del agua. La transparencia puede ser medida in situ mediante la profundidad del disco de Secchi (SD), y la turbidez con un turbidímetro. En las últimas décadas se han utilizado diferentes relaciones entre bandas de diferentes sensores obtenidas por teledetección para la estimación de estos parámetros. En este trabajo, a partir de datos de campo obtenidos a lo largo de 2017 y 2018 en embalses de la cuenca del Júcar con gran variedad de estados tróficos, se han calibrado diferentes índices y bandas para poder estimar la transparencia a partir de imágenes Sentinel-2 (S2…

El problema de la enseñanza: el asociacionismo burgués y el deseo de instrucción en el origen de las bandas de música valencianas

2017

Les quatre cents coups d'un latino au pays des cow-boys: l'identité d'Antonio Banderas

2004

Par conséquent, on ne saurait analyser la star Banderas uniquement à partir de ses films; la construction des valeurs du type de « latinité » qu'il incarne se joue aussi dans le domaine de la musique et sur Internet. On sait bien que les rapports entre les marchés musicaux et cinématographiques ont changé et que les stratégies de promotion peuvent prévoir la sortie d'un disque comme support d'un film bien avant que ce film que ne soit distribué en salles. Il n'est plus question de tropicalisation, mais de processus d'hybridation qui mènent a ce que les chercheurs en sciences sociales, notamment anglo-saxons, ont appelé marketing ethnicities. Pensées pour un marché mondial, ces ethnicities d…