2,187 research outputs found

    Spatially-Dense, Multi-Spectral, Frequency-Domain Diffuse Optical Tomography of Breast Cancer

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    Diffuse optical tomography (DOT) employs near-infrared light to image the concentration of chromophores and cell organelles in tissue and thereby providing access to functional parameters that can differentiate cancerous from normal tissues. This thesis describes research at the bench and in the clinic that explores and identifies the potential of DOT breast cancer imaging. The bench and clinic instrumentation differ but share important features: they utilize a very large, spatially dense, set of source-detector pairs (10E7) for imaging in the parallel-plate geometry. The bench experiments explored three-dimensional (3D) image resolution and fidelity as a function of numerous parameters and also ascertained the effects of a chest wall phantom. The chest wall is always present but is typically ignored in breast DOT. My experiments clarified chest wall influences and developed schemes to mitigate these effects. Mostly, these schemes involved selective data exclusion, but their efficacy also depended on reconstruction approach. Reconstruction algorithms based on analytic (fast) Fourier inversion and linear algebraic techniques were explored. The clinical experiments centered around a DOT instrument that I designed, constructed, and have begun to test (in-vitro and in-vivo). This instrumentation offers many features new to the field. Specifically, the imager employs spatially-dense, multi-spectral, frequency-domain data; it possesses the world\u27s largest optical source-detector density yet reported, facilitated by highly-parallel CCD-based frequency-domain imaging based on gain-modulation heterodyne detection. The instrument thus measures both phase and amplitude of the diffusive light waves. Other features include both frontal and sagittal breast imaging capabilities, ancillary cameras for measurement of breast boundary profiles, real-time data normalization, and mechanical improvements for patient comfort. The instrument design and construction is my most significant contribution, but first imaging experiments with tissue phantoms and of cancer bearing breasts were also carried out. A parallel effort with simulated data has yielded important information about new reconstruction regularization issues that arise when phase and amplitude are measured. With these gains in device implementation and DOT reconstruction, my research takes valuable steps towards bringing this novel imaging technique closer to clinical utilization

    Research on Roadway Performance and Distress at Low Temperature

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    This research project investigated the performance and damage characteristics of Nebraska roadways at low-temperature conditions. To meet the research objective, laboratory tests were incorporated with mechanistic numerical modeling. The three most common pavement structures in Nebraska were selected and modeled considering local environmental conditions and pavement materials with and without truck loading. Cracking of asphalt overlay was predicted and analyzed by conducting finite element simulations incorporated with cohesive zone fracture. Parametric analyses were also conducted by varying pavement geometries and material properties, which could lead to helping pavement designers understand the mechanical sensitivity of design variables on the overall responses and performance characteristics of pavement structures. This better understanding is expected to provide NDOR engineers with more scientific insights into how to select paving materials in a more appropriate way and to advance the current structural pavement design practices

    Impact of Truck Loading on Design and Analysis of Asphaltic Pavement Structures

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    Mechanistic-Empirical Pavement Design Guide (MEPDG) is an improved methodology for pavement design and the evaluation of paving materials. However, in spite of significant advancements to pre-existing traditional design methods, the MEPDG is known to be limited in its accurate prediction of mechanical responses and damage in asphaltic pavements. This restriction is both due to the use of simplified structural analysis methods, and a general lack of understanding of the fundamental constitutive behavior and damage mechanisms in paving materials. This is additionally affected by the use of circular tire loading configurations. Performance prediction and pavement life are determined based on the simple layered elastic theory and the empirically-developed failure criteria: the so-called transfer functions. To model pavement performance in a more appropriate manner, this study attempts finite element modeling to account for viscoelastic paving materials. Mechanical responses between the finite element simulations and the MEPDG analyses are compared to monitor any significant differences that are relevant to better pavement analysis and design. Pavement performance and the corresponding design life between the two approaches are further compared and discussed

    Strategies to connect and integrate urban planning and environmental planning through focusing on sustainability: case study of Cheongju City, Korea

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    This study has intended to find strategies which connect and integrate urban planning and environmental conservation planning through acquiring sustainability applied to Cheongju City, a local government of Korea. To overcome inefficiency happened during the process of urban and environmental planning practice in Korea, it is necessary to find strategies to integrate both planning practices through focusing on 'sustainable urban development.' This study, therefore, has suggested to make 'sustainable city development law' for national level and 'sustainable urban development ordinance' for local level, and provided the process and contents of the 'sustainable urban development planning' based on the suggested law and the ordinance, so that unmatched planning period of both plans could be adjusted (for 20 years), and the overlapped contents could be removed through identifying future goal of sustainable development

    Strategies to connect and integrate urban planning and environmental planning through focusing on sustainability: case study of Cheongju City, Korea

    Get PDF
    This study has intended to find strategies which connect and integrate urban planning and environmental conservation planning through acquiring sustainability applied to Cheongju City, a local government of Korea. To overcome inefficiency happened during the process of urban and environmental planning practice in Korea, it is necessary to find strategies to integrate both planning practices through focusing on 'sustainable urban development.' This study, therefore, has suggested to make 'sustainable city development law' for national level and 'sustainable urban development ordinance' for local level, and provided the process and contents of the 'sustainable urban development planning' based on the suggested law and the ordinance, so that unmatched planning period of both plans could be adjusted (for 20 years), and the overlapped contents could be removed through identifying future goal of sustainable development

    Searching for Majorana Neutrinos at a Same-Sign Muon Collider

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    Majorana properties of neutrinos have long been a focus in the pursuit of possible new physics beyond the standard model, which has motivated lots of dedicated theoretical and experimental studies. A future same-sign muon collider is an ideal platform to search for Majorana neutrinos through the Lepton Number Violation process. Specifically, this t-channel kind of process is less kinematically suppressed and has a good advantage in probing Majorana neutrinos at high mass regions up to 10 TeV. In this paper, we perform a detailed fast Monte Carlo simulation study through examining three different final states: 1) pure-leptonic state with electrons or muons, 2) semi-leptonic state, and 3) pure-hadronic state in the resolved or merged categories. Furthermore, we perform a full simulation study on the pure-leptonic final state to validate our fast simulation results.Comment: 15 pages, 8 figure

    Effect of sintering temperature on the superconducting properties of MgB2 superconductor co-added with a high concentration of Si and C

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    In this study, as much as 10 and 15 wt.% nanosized silicon and carbon (Si+C) were reacted with (Mg+2B) at 650°C and 850°C, respectively, for 1 hour. The phase formation, surface morphology and superconducting properties of these samples were evaluated. The relative peak intensity as calculated from the XRD patterns indicates the formation of large Mg2Si volume fraction at low sintering temperature. MgB4 phase was detected in the samples sintered at high temperature as a result of Mg deficiency. The C substitution level as estimated from the lattice parameters, was shown to increase in the samples reacted with a higher amount of (Si+C) at high temperature. Scanning electron micrograph showed that (Si+C) co-addition had refined the grain size and improved the grain coupling of MgB2. The superconducting transition temperature was found to decrease with increasing addition level. The superconducting transition width was also broadened because of a large volume fraction of secondary phases. The improved field dependent critical current density at both 5 K and 20 K is accounted to enhanced scattering by C substitution and grain boundary pinning
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