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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 23 for “"attenuation coefficients"”.
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An Experimental re-evaluation of Photon Mass Attenuation Coefficients
Photon mass attenuation coefficients are indispensable input parameters for use in several disciplines. They are of value for medical diagnostics, radiation therapy, material science, etc. Currently, photon mass attenuation coefficients derived from model calculations are widely used. This project …
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The Determination of mass attenuation coefficients for some of the elements of the first row of the transition series and some of the elements of the lanthanide series over the energy range 26.3 to 2.3 kev
Mass attenuation coefficients have been determined for titanium, vanadium, iron, nickel, and copper over an energy range 17.5 to 2.3 kev and for praseodymium, gadolinium and erbium over the range 26.3 to 4.5 kev. Agreement within experimental error with recent measurements on the transition metals …
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Using X-ray Imaging Techniques to Determine Density of Foods
… for evaluation of food density. The x-ray attenuation through materials is dependent on the chemical composition and is proportional to density as described by the Beer-Lambert's law. This relationship forms the hypothesis of this study. The proposed experiments were conducted to verify and …
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The in situ compressional wave properties of marine sediments
… greater group velocities, greater effective attenuation coefficients and lower quality factors than silts, while the low velocities measured in silts imply that the bulk moduli of the silt sites examined are lower than expected owing to a considerable fraction of organic matter. Significant …
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High frequency ultrasonic characterization of human skin In vivo
… work, quantitative ultrasonic methods using the attenuation coefficient, backscatter coefficient, and echo envelope statistics were studied for their potential to characterize human skin tissues in vivo. A high frequency ultrasound system was developed using polymer transducers, a …
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Markov random field image modelling
… a priori information about the distribution of attenuation coefficients found in CT scans.
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Improving attenuation corrections obtained using singles-mode transmission data in small-animal PET
… necessary to correct for the effects of photon attenuation within the subject being imaged. These corrections can be obtained using singles-mode photon transmission scanning. Although suitable for small animal PET, these scans are subject to high amounts of contamination from scattered photons. …
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Exploring light transmission through ice-snow cover and water in lakes
… used to estimate water clarity and irradiance attenuation in the water column is the attenuation coefficient, which quantifies the exponential decrease of irradiance with depth. Although the attenuation coefficient can be determined from irradiance profiles measured with radiometers, their high …
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Alternating Minimization Algorithms for Dual-Energy X-Ray CT Imaging and Information Optimization
… energy. In turn, the estimates of the linear attenuation coefficients or the component images from dual-energy CT image reconstruction are used</p><p>to estimate the electron density and mean excitation. Therefore, the quantitative accuracy of the estimates of the linear attenuation …
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Fast neutron resonance radiography for element imaging : theory and applications
… the sum of elemental contents (weighted by the attenuation coefficients) and transmission measurements taken at different neutron energies form a set of linear equations, which can be solved to map individual elemental contents. Explosives and drugs can be identified by their characteristic …
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Statistical correlation as a tool in propagation studies
… correlating dB values of the satellite signal attenuation and polarization isolation with dBZ values of radar backscatter from each of 128 range gates. In it, Pearson product moment correlation coefficients are calculated for attenuation and backscatter and for isolation and backscatter. When …
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Optimization of a High-Energy X-Ray Inline Phase Sensitive Imaging System for Diagnosis of Breast Cancer
… x-ray imaging technique relies on the attenuation characteristics of a tissue to produce imaging contrast. However, the similar attenuation characteristics of normal and malignant breast tissue present a challenge in differentiating between them using conventional x-ray imaging. The …
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STABILITY OF TEMPORARY ANCHORAGE DEVICES IN VARYING PORCINE BONE DENSITIES
… samples was quantified by converting the x-ray attenuation coefficients to BMD. Twenty (n=20) Rocky Mountain TADs of 1.6 mm × 8 mm were inserted perpendicular to the surface of the bone samples. To evaluate TAD stability, all TADs were subjected to a tangential force on an Instron machine until …
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Cure monitoring of composite materials using optical techniques
… after the curing agent was mixed with the epoxy. Attenuation coefficients and travel times were calculated for each waveform. During the analysis phase of this research an algorithm was developed to find the exact onset of ultrasonic signals. Different thickness samples were made and the …
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Evaluation of New Zealand estuarine water properties using remote sensing
… (represented by dominant wavelength) and diffuse attenuation coefficients from Sentinel-2 imagery, in the case study estuary of Tauranga Harbour. The new methodology used direct measurement of bottom reflectance of intertidal areas while exposed, and used a regression estimator to derive subtidal …
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Measurement of optical properties of molten salts and metallic compounds for advanced solar and nuclear systems
… concentrated solar thermal system. The attenuation coefficient of light in a binary nitrate salt mixture (KNO 3-NaNO3 40-60 wt%) was measured over the wavelength range 833-2500 nm and the temperature range 300-400°C. This salt is the leading candidate for the first generation of a …
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Nonlinear ultrasonic testing using a non-collinear approach: application to heat treatment of steels and to asphalt concrete mixtures
… micro-structural dependence of acoustic wave attenuation, velocity, and a non-linear parameter, non-collinear scattered wave amplitude. Specimens of various microstructures were prepared by means of heat treatment for 1045 and 4140 Steel. Nonlinear investigation was also performed on two …
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Dual energy image reconstruction and systems for application in proton therapy treatment planning
… SECT scan results in a map of kilovoltage X-ray attenuation coefficients relative to the attenuation coefficient of water for the beam energy. This quantitative information is then converted to SPR via an empirically derived look-up table. If the patient tissues do not have a similar chemical …
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Effective dose enhancement using gold as a radiation sensitizer: a Monte Carlo study
… aims to create a gradient in the photon attenuation coefficients of the tumor compared to those of the surrounding healthy tissue. The goal of generating such a variation is to dramatically increase the amount of effective dose received by the tumor without increasing the amount received …
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Modeling, imaging and waveform-inversion in attenuative anisotropic media
Seismic attenuation, which is often anisotropic, has a profound influence on wave propagation and seismic processing. In addition to application of attenuation coefficients in lithology and fluid discrimination, compensation for angle-dependent attenuation and velocity dispersion is critically …
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