Search results for "rayleigh"
showing 10 items of 182 documents
Soret Effect In Forced Rayleigh-scattering
1987
In forced Rayleigh scattering of mixtures or suspensions the temperature gratings generate, by the Soret effect, concentration gratings that may be very important since they produce both a phase and an amplitude grating superimposed on the principal one. The experimental evidence of their influence was given by Thyagarajan and Lallemand using a mixture of carbondisulfide and ethanol. In this paper we study the temporal behaviour of the concentration grating versus the sample properties and its effect on the detected diffracted beam. Explicit expressions are given for the output intensity taking into account both the generated amplitude and phase gratings.
Caracterización proteómica de la interacción y la inserción de proteínas de membrana
2019
Las proteínas de membrana tienen funciones muy diversas en la célula, desde controlar el tráfico molecular hasta facilitar la transducción de señales. Sin embargo, el estudio de estas proteínas supone todo un reto por sus particulares características fisico-químicas. Su naturaleza hidrofóbica requiere un elevado control durante su síntesis. Uno de los pasos críticos en esta síntesis es la inserción en la bicapa lipídica. Generalmente, este proceso se produce a través de un mecanismo (co-traduccional) acoplado al proceso de traducción. Esta vía co-traduccional ha sido ampliamente estudiada y la maquinaria implicada en el proceso se conoce con bastante profundidad. Sin embargo, algunas proteí…
A Rayleigh-Ritz approach for postbuckling analysis of variable angle tow composite stiffened panels
2018
Abstract A Rayleigh-Ritz solution approach for generally restrained multilayered variable angle tow stiffened plates in postbuckling regime is presented. The plate model is based on the first order shear deformation theory and accounts for geometrical nonlinearity through the von Karman’s assumptions. Stiffened plates are modelled as assembly of plate-like elements and penalty techniques are used to join the elements in the assembled structure and to apply the kinematical boundary conditions. General symmetric and unsymmetric stacking sequences are considered and Legendre orthogonal polynomials are employed to build the trial functions. A computer code was developed to implement the propose…
Optimal Sampling Period and Required Number of Samples for OSTBC-MIMO Rayleigh Fading Channel Capacity Simulators
2014
The purpose of this paper is to contribute to the performance assessment of channel capacity simulators. Here, we consider the instantaneous capacity (also referred to as the mutual information) in orthogonal space-time block code (OSTBC) transceiver systems over multiple-input multiple-output (MIMO) Rayleigh fading channels. To ensure that the level-crossing rate (LCR) of the instantaneous capacity can efficiently and accurately be simulated, we derive closed-form approximate solutions to the optimal sampling period and the required number of samples to be generated. Several numerical examples will be presented to illustrate the usefulness of our procedure. It will also be shown that the d…
Radiation Hardened Optical Frequency Domain Reflectometry Distributed Temperature Fiber-Based Sensors
2015
International audience; We study the performance of Optical Frequency Domain Reflectometry (OFDR) distributed temperature sensors using radiation resistant single-mode optical fibers. In situ experiments under 10 keV X-rays exposure up to 1 MGy( SiO 2 ) were carried out with an original setup that allows to investigate combined temperature and radiation effects on the sensors within a temperature range from 30 ° C to 250 ° C. Obtained results demonstrate that optical fiber sensors based on Rayleigh technique are almost unaffected by radiation up to the explored doses. We show that a pre-thermal treatment stabilize the sensor performance increasing the accuracy on temperature measurement fro…
Heat and mass transfer phenomena
2002
This section deals with main problems of the heat and mass transfer in magnetic colloids. The analysis is mainly based on the general model given in the Chapter written by R. E. Rosensweig. Hydrodynamic and thermal problems are simplified considering incompressible liquids and neglecting the effects of polarization and electric conductivity as well as ignoring some other secondary effects that usually can be neglected in ferrofluid experiments. Contrarily, the analysis of mass transfer accounts for new sedimentation phenomena and cross effects of interrelated heat and mass transfer. Since the description given by Rosensweig is of general theoretical nature, while the present work mainly foc…
The Influence of the Severity of Fading and Shadowing on the Statistical Properties of the Capacity of Nakagami-Lognormal Channels
2008
This paper deals with the study of the statistical properties of the capacity of Nakagami-lognormal (NLN) channels for various fading environments. Specifically, the impact of shadowing and the severity of fading on the channel capacity is investigated. We have derived analytical expressions for the probability density function (PDF), cumulative distribution function (CDF), level-crossing rate (LCR), and average duration of fades (ADF) of the channel capacity. These results are analyzed for different levels of shadowing and for various fading conditions, corresponding to different terrestrial environments. It is observed that the severity of fading and shadowing has a significant influence …
Performance analysis of binary DPSK modulation schemes over Hoyt fading channels
2009
This paper presents a performance analysis of differential phase shift keying (DPSK) modulation schemes over Hoyt fading channels. Based upon the theory of DPSK modulation and a recently derived formula for the probability density function (PDF) of the differential phase between two Hoyt vectors contaminated by additive white Gaussian noise (AWGN), the bit error probability (BEP) for DPSK systems with noncoherent demodulation over Hoyt channels is analyzed. In the analysis, the correlation between adjacent bits is taken into account. The obtained theoretical results are fully validated first by reducing them to the corresponding known solutions for the Rayleigh fading distribution being a s…
Rayleigh scattering of linear alkylbenzene in large liquid scintillator detectors.
2015
Rayleigh scattering poses an intrinsic limit for the transparency of organic liquid scintillators. This work focuses on the Rayleigh scattering length of linear alkylbenzene (LAB), which will be used as the solvent of the liquid scintillator in the central detector of the Jiangmen Underground Neutrino Observatory. We investigate the anisotropy of the Rayleigh scattering in LAB, showing that the resulting Rayleigh scattering length will be significantly shorter than reported before. Given the same overall light attenuation, this will result in a more efficient transmission of photons through the scintillator, increasing the amount of light collected by the photosensors and thereby the energy…
Anomalous tracer diffusion in film forming colloidal dispersions
2000
Film forming colloidal dispersions can be conceived as a material composed of interpenetrating hydrophobic (polymer) and hydrophilic (partially broken interfaces) phases where the transport properties of one phase are influenced by the geometric confinement effect imposed by the other. We studied the transport properties of film forming colloidal dispersions by introducing hydrophobic dye molecules into the colloidal particles and determining their motion with forced Rayleigh Scattering as a function of length scale (grating distance A) and water content. At water contents between 18 and 3 weight percent we find signatures of anomalous tracer diffusion, namely stretched exponential decay cu…