Search results for "attenuation"
showing 10 items of 283 documents
On a Fractional in Time Nonlinear Schrödinger Equation with Dispersion Parameter and Absorption Coefficient
2020
This paper is concerned with the nonexistence of global solutions to fractional in time nonlinear Schrö
Acoustic detection of neutrinos in bedrock
2019
We propose to utilize bedrock as a medium for acoustic detection of particle showers following interactions of ultra-high energy neutrinos. With the density of rock three-times larger and the speed of sound four-times larger compared to water, the amplitude of the generated bipolar pressure pulse in rock should be larger by an order of magnitude. Our preliminary simulations confirm that prediction. Higher density of rock also guarantees higher interaction rate for neutrinos. A noticeably longer attenuation length in rock reduces signal dissipation. The Pyh\"asalmi mine has a unique infrastructure and rock conditions to test this idea and, if successful, extend it to a full-size experiment.
Three-dimensional kernel-based coda attenuation imaging of caldera structures controlling the 1982-84 Campi Flegrei unrest
2019
Abstract Coda-wave attenuation imaging has risen as a state-of-the-art technique to depict volcanic structures using their dispersion effects. The 1982–84 seismic and deformation unrest at Campi Flegrei caldera (Italy) is a unique example of non-eruptive volcanic activity in a structured caldera. Here, we propose the first application of 3D coda-attenuation kernels to image caldera structures at multiple frequencies during unrest. Using sensitivity kernels is necessary to assess the effective resolution of coda imaging in highly heterogeneous volcanoes. The technique relies on the solution of Paasschens' equations in the framework of radiative transfer theory. The results map coda attenuati…
Scattering and absorption imaging of a highly fractured fluid-filled seismogenetic volume in a region of slow deformation
2020
Regions of slow strain often produce swarm-like sequences, characterized by the lack of a clear mainshock-aftershock pattern. The comprehension of their underlying physical mechanisms is challenging and still debated. We used seismic recordings from the last Pollino swarm (2010–2014) and nearby to separate and map seismic scattering (from P peak-delays) and absorption (from late-time coda-wave attenuation) at different frequencies in the Pollino range and surroundings. High-scattering and high-absorption anomalies are markers of a fluid-filled fracture volume extending from SE to NW (1.5–6 Hz) across the range. With increasing frequency, these anomalies approximately cover the area where t…
The attenuation and the attenuators: strategies and tactics
2013
Este trabalho se inscreve em um projeto de pesquisa (ES.POR.ATENUAÇÃO) que busca analisar e explicar a atividade atenuadora em diferentes variedades regionais do espanhol e do português, com o fim de realizar, posteriormente, diferentes estudos contrastivos intralinguísticos e interlinguísticos. Neste artigo, pretendemos explicar alguns dos princípios teóricos e metodológicos nos quais se sustenta a análise qualitativa e quantitativa. E, principalmente, iremos referir-nos ao conceito de atenuação (Briz 1995, 2002, 2003, 2005, 2007a, 2012). This work is inscribed in a research project (ES.POR.ATENUAÇÃO) that seeks to analyze and explain the attenuator activity in different regional varieties…
PO-0965: Clinical investigation of inter seed attenuation effects in prostate I-125 seed implant brachytherapy
2013
Origins of radiation-induced attenuation in pure-silica-core and Ge-doped optical fibers under pulsed x-ray irradiation
2020
We investigated the nature, optical properties, and decay kinetics of point defects causing large transient attenuation increase observed in silica-based optical fibers exposed to short duration and high-dose rate x-ray pulses. The transient radiation-induced attenuation (RIA) spectra of pure-silica-core (PSC), Ge-doped, F-doped, and Ge + F-doped optical fibers (OFs) were acquired after the ionizing pulse in the spectral range of [∼0.8–∼3.2] eV (∼1500–∼380 nm), from a few ms to several minutes after the pulse, at both room temperature (RT) and liquid nitrogen temperature (LNT). Comparing the fiber behavior at both temperatures better highlights the thermally unstable point defects contribut…
Optical properties and photosensitivity of vacuum synthesized Ge-doped sol-gel amorphous SiO/sub 2/
2005
We report optical and electron paramagnetic resonance investigations of gamma ray irradiation effects in sol-gel Ge-doped amorphous SiO/sub 2/. The studied materials have Ge-doping levels up to 10/sup 4/ molar part per million and were densified by two routes differing for the atmosphere: O/sub 2/+N/sub 2/ or vacuum. The obtained results evidence that irradiation affects matrix sites inducing paramagnetic defects. Furthermore, the comparison between the two densification procedures shows that vacuum atmosphere induces higher radiation sensitivity.
Radiation Response of Ce-Codoped Germanosilicate and Phosphosilicate Optical Fibers
2016
We report an experimental investigation on the effects of Ce-codoping in determining the radiation response of germanosilicate and phosphosilicate Optical Fibers (OFs) in the UV-Visible domain and up to doses of $1~\hbox{MGy}({\rm SiO}_{2})$ . We show that the addition of Ce strongly impacts the Radiation Induced Attenuation (RIA) of both types of fibers. In the first case the radiation induced losses increase, whereas in the second one decrease. By combining the online RIA measurements with the Electron Paramagnetic Resonance (EPR) ones, we are able to infer the basic microscopic mechanisms taking place under irradiation, which involve the cerium codopant and some of the known Ge-related o…
On-Line Characterization of Gamma Radiation Effects on Single-Ended Raman Based Distributed Fiber Optic Sensor
2016
We report distributed temperature measurements based on Raman scattering performed during steady state $\gamma $ -ray irradiation at a dose rate of 1 kGy( ${\rm SiO}_{2}$ )/h and up to a total ionizing dose (TID) of $\sim 0.1\ \hbox{MGy}$ . We characterize on-line the evolution of the performances of a single-ended Raman distributed temperature sensor (RDTS) during the $\gamma $ -ray exposure of different classes of commercial multimode fibers (MMFs) acting as the sensing element. RDTS is influenced by the radiation-induced attenuation (RIA) phenomena leading to both large errors in the temperature measurements and a diminution of the useful sensing length. The amplitude of the radiation-in…