Search results for "attenuation"
showing 10 items of 283 documents
La atenuación en conversaciones coloquiales argentinas y españolas: un estudio contrastivo
2018
El objetivo de este artículo es presentar el resultado de un análisis contrastivo realizado entre las manifestaciones de atenuación en conversaciones coloquiales argentinas y españolas. La atenuación, como fenómeno pragmático que reduce la fuerza ilocutiva de los actos comunicativos, en el que intervienen la imagen y las responsabilidades de los hablantes respecto a sus mensajes (Caffi 1999, 2007; Thaler; Albelda 2016), ha sido ampliamente estudiada para el español, a partir de la década de los 90, desde la perspectiva de los estudios de cortesía (Haverkate; Briz 1995, 2007), la pragmática (Schneider) o la sociolingüística (Samper Hernández; Cestero). Sin embargo, son escasos los trabajos q…
Characterization of opal photonic hetero-crystals by light scattering
2006
Spectra of the light scattered in the heterogeneous photonic crystal based on the thin triple-film opal, which was prepared by successive, convective force-assisted crystallisation of colloidal suspensions containing spheres of 374, 474 and again 374 nm in diameter, have been studied in the wavelength range of low order photonic bandgaps. If the ballistic regime of light propagation is preserved, the forward scattered light becomes the subject of the diffraction attenuation, whereas the backscattered light experiences both the diffraction enhancement and attenuation. A variety of possible configurations of scattered light measurements have been examined and corresponding spectra of scattere…
Light Propagation in Heterogeneous Opal-Based Photonic Crystals
2006
Ballistic light propagation in the heterogeneous photonic crystals based on the thin triple-film opal have been studied in the wavelength range of low order photonic bandgaps. Since the scattered light experiences the diffraction attenuation, the spectra and the angle diagrams of the transmitted and forward scattered light have been used to identify the effect of heterostructuring.
Enhanced diffraction of light in GaAs microcavities
1995
We theoretically analyze the diffraction of light by gratings that are photogenerated in Fabry–Perot microcavities. The coupled-wave theory of volume gratings is combined with appropriate boundary conditions to yield expressions for the diffraction efficiency. Multiple round trips within the cavity are seen to increase the effective grating thickness and therefore the efficiency. Numerical calculations specific to GaAs microcavities show that the diffraction efficiency can be enhanced by more than 2 orders of magnitude at the resonant wavelengths.
The Dissociation Constant of Pyruvic Acid: Determination by Spectrophotometric Measurements
1991
Aqueous solutions of sodium pyruvate/hydrochloric acid mixtures were studied with regard to changes in the intensity of optical absorption at 317 nm wavelength, caused by varying pH and temperature. The data were evaluated to determine the pyruvic acid apparent dissociation constant at infinite dilution. Its temperature dependence followed the relation ln Kod = −(0.55 ± 0.47) − (1538 ± 135)/T or, if previous results of Pedersen at two temperatures are included, In Kod = −(0.97 ± 0.35) − (1418 ± 102)T. The effective absorption coefficient for pyruvic acid and its anion differ because the former species is largely hydrated, whereas the latter is not. The known hydration constant and its tempe…
Closeness and distance through the agentive authorial voice: construing credibility in promotional discourse.
2020
Credibility is a function associated with promotional genres and persuasion, and a powerful marketing concept (Eisend, 2006; Ming, 2006) which provides trustworthiness about the quality of products or services offered by hotels (Suau-Jiménez, 2012a, 2019). It is partly attained through the hotel‘s self-mentioning in websites. When this self-mentioning is agentive with action verbs, the main instantiation is the pronoun we, projecting closeness and assertiveness. However, this self-representation is also construed with depersonalized realizations like the hotel‘s proper name, other nominalizations or even pronouns like it and they, which provide attenuating aspects and create a sense of dist…
Urbach absorption edge of silica: reduction of glassy disorder by fluorine doping
2004
Abstract The vacuum-ultraviolet fundamental absorption edge (‘Urbach edge’) of four types of synthetic silica glasses, ‘wet’, ‘dry’, and doped by 570 and 6010 ppm wt. fluorine, was studied in the absorption coefficient range (1 cm−1–500 cm−1) at room temperature. The absorption edge has exponential form in agreement with the Urbach’s rule. The well-documented increase of vacuum-ultraviolet transparency upon fluorine doping is due to a steeper absorption edge (shorter ‘Urbach tail’) as compared to undoped silicas. The increase of the edge slope in F-doped silica occurs already the lower dopant concentration (570 ppm), the slope does not increase further in the 6010 ppm doped glass. These fin…
Efficient Low-Frequency Modal Analysis of Anechoic Chamber
2007
An efficient method to analyze the electromagnetic field inside rectangular anechoic and semianechoic chambers from 30 to 100 MHz is shown. A modal expansion is employed to develop the homogeneous and the inhomogeneous field. This is combined with circuital techniques to compute the effect of the layers of ferrite and dielectrics in the walls of the chamber. Several numerical results of the Free Space Transmission Loss (FSTL) of an anechoic chamber and the Normalized Site Attenuation (NSA) of a semianechoic chamber are provided.
Optimization and finite-frequency H ∞ control of active suspensions in in-wheel motor driven electric ground vehicles
2015
Abstract In this paper, the parameter optimization and H ∞ control problem of active suspensions equipped in in-wheel motor driven electric ground vehicles are investigated. In order to better isolate the force transmitted to motor bearing, dynamic vibration absorber (DVA) is installed in the active suspension. Parameters of the vibration isolation modules are also optimized in order to achieve better suspension performances. As the human body is much sensitive to vibrations between 4 and 8 Hz, a finite-frequency state-feedback H ∞ controller is designed to achieve the targeted disturbance attenuation in the concerned frequency range while other performances such as road holding capability …
Delay-dependent control for 2-D switched delay systems in the second FM model
2013
This paper is concerned with the problem of delay-dependent H∞ control for 2-D (two-dimensional) switched discrete state delay systems described by the second FM (Fornasini and Marchesini) state-space model. Firstly, some sufficient conditions for the exponential stability and weighted H∞ disturbance attenuation performance of the underlying system are derived via the average dwell time approach. Then, based on the obtained results, a state feedback controller design is proposed to guarantee that the resulting closed-loop system is exponentially stable and achieves a prescribed disturbance attenuation level γ. Finally, a numerical example is provided to verify the effectiveness of the propo…