Global ETD Search
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 18 of 18 for “"pencil beam"”.
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A Methodology for the Design of Spaceborne Pencil-Beam Scatterometer Systems
… decades. These previous systems have been "fan-beam" scatterometers, where multiple antennas placed in fixed positions are used. The fan-beam scatterometer approach, however, has disadvantages which limit its utility for future missions. An alternate approach, the conically-scanning …
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Pencil beam dose calculation for proton therapy on graphics processing units
Radiotherapy delivered using scanned beams of protons enables greater conformity between the dose distribution and the tumour than conventional radiotherapy using X rays. However, the dose distributions are more sensitive to changes in patient anatomy, and tend to deteriorate in the presence of …
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Analysis of 2-axis pencil beam sonar microbathymetric measurements of mine burial at the Martha’s Vineyard Coastal Observatory
… larger, 16 total object investigation. A 2-axis pencil beam sonar was deployed concurrently with the mine to obtain microbathymetric measurements of the scour pit development and the progression of mine burial. Data correction techniques to correct for beam pattern induced bathymetry errors and a …
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Analysis of 2-axis pencil beam sonar microbathymetric measurements of mine burial at the Martha's Vineyard Coastal Observatory
… larger, 16 total object investigation. A 2-axis pencil beam sonar was deployed concurrently with the mine to obtain microbathymetric measurements of the scour pit development and the progression of mine burial. Data correction techniques to correct for beam pattern induced bathymetry errors and a …
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Analysis of 2-axis pencil beam sonar microbathymetric measurements of mine burial at the Martha's Vineyard Coastal Observatory
… larger, 16 total object investigation. A 2-axis pencil beam sonar was deployed concurrently with the mine to obtain microbathymetric measurements of the scour pit development and the progression of mine burial. Data correction techniques to correct for beam pattern induced bathymetry errors and a …
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2d dose measurement using a flat panel EPID
… spectrum and phantom material using a 6MV pencil beam. We found that flat panel EPID scatter kernel has as much as 80% more scattering power than the water scatter kernel in the region 1 cm away from the center of a 6MV pencil beam. This confirms that a flat panel EPID behaves significantly …
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Standards in clinical dual energy x-ray absorptiometry
… fracture. The original technology was based on a pencil beam x-ray source but later systems use a fan beam. Additional functionality includes measurement of hand BMD and vertebral fracture assessment (VFA). Smaller devices have also been developed to measure BMD at peripheral sites in the body. As …
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A High Power Microwave Zoom Antenna With Metal Plate Lenses
… the TEM mode with continuously variable diameter pencil beam output and approximately 10% bandwidth. Carbon Fiber Reinforced Polymer (CFRP) composites were demonstrated through experiment and simulation to have sufficient conductivity to replace metal for the lens elements and would provide a …
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An entropic framework for AUV sensor modelling
… entropic measure of sensor efficiency. 675-kHz pencil-beam sonar data acquired using the JASON remotely operated vehicle in a challenging shallow water environment and 200-kHz echo-sounder data acquired using the ABE AUV are used to demonstrate the utility of the en tropic framework. We show the …
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Development and Evaluation of Advanced Dose Calculations for Modern Radiation Therapy Techniques
… or the head&neck region, where commonly used pencil beam algorithms often fail to predict precisely the physical radiation dose distribution. Thus the clinical outcome of the treatment can not be properly evaluated by physicians. By using more sophisticated dose calculations based on …
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Treatment planning for manifold multi-ion particle therapy
… The library is then adapted for the pencil beam geometry and energy spread of a specific accelerator beamline; next, a raster grid of beam positions is constructed to cover the target volume, and the weighting of individual energy components of each ion beam required at each position …
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Development and validation of a theoretical model for optimizing signal-to-noise ratio in x-ray fluorescence imaging
… system sensitivity is by adjusting incident beam spectra shape. The predominant component of scattering noise originates from incident photons whose energy is several keV higher than fluorescence line. After Compton scattering with sample, those photons will lose energy to have the same …
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Evaluation of The Effectiveness of Anisotropic Analytical Algorithm In Flattened and Flattening-Filter-Free Beams For High Energy Lung Dose Delivery Using The Radiological Physics Center Lung Phantom
… flattened and flattening-filter-free high energy beams. Radiation treatment plans were developed following the Radiation Therapy Oncology Group and theRadiologicalPhysicsCenterguidelines for lung treatment using Stereotactic Radiation Body Therapy. The tumor was covered such that at least 95% of …
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Direct optimization of 3D dose distributions using collimator rotation
… First, Monte Carlo was used to generate pencil beam dose distributions for DAO inverse treatment planning (MC-DAO). The MC-DAO technique correctly models traditionally difficult treatment geometries such as small fields and tissue inhomogeneities. The MC-DAO also takes advantage of the …
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A Field-Wise Retrieval Algorithm for SeaWinds
… scatterometers in that it employs a rotating pencil-beam antenna as opposed to fixed fan-beam antennas. The scanning beam provides greater coverage but causes the wind retrieval accuracy to vary across the swath. This thesis develops a filed-wise wind retrieval algorithm to improve the overall …
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3D Scintillator Detector Quenching Characterization For Scanning Proton Beams
<p>Proton pencil beam scanning is becoming the standard treatment delivery technique for proton therapy centers. Scanned proton pencil beams provide a highly conformal dose distribution. The complex dose distribution poses challenges for quality assurance measurements leading to sophisticated …
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Galactic Stellar Haloes in the CDM Model
… We show that current observational data from pencil beam surveys of approximately 100 tracer stars (such as the Spaghetti Survey) are not sufficient to constrain the degree of structure in the Milky Way halo with this statistic. Larger area surveys with more than 1000 tracer stars (such BHB …
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A new prompt gamma spectroscopy-based approach for range verification in proton therapy
… inside the body. Ideally, the actual beam range in the patient should be equal to the value prescribed by the Treatment Planning System (TPS). However, there are sizeable uncertainties at the time of irradiation due to anatomical modifications, patient alignment, beam delivery, and …