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

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

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

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

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

Surface morphology and electrical properties of pulse electrodeposition of NiFe films on copper substrates in ultrasonic field

NiFe films were pulse electrodeposited on conductive copper substrates under galvanostatic mode with and without the presence of an ultrasonic field at different pulse current magnitudes and duty cycles. The optimum deposition condition was found to be at a current magnitude of 40 mA and a duty cycle of 50.00% under ultrasonic treatment. This deposition condition has significantly reduced the surface roughness from 39.01 ±1.1 nm to 6.96 ±1.1 nm and the spherical grain size in the range from 579.40 nm - 623.30 nm to 29.00 nm - 46.90 nm. On the other hand, the resistivity was reduced to 19.86 µωcm from 54.00 µωcm as the Ni content increased from 76.08% to 80.12 % for achieving good stoichiometry for NiFe thin films. Through the optimization study, the deposition current is observed to be the dominant factor in determining the single phase deposition of NiFe film whereas ultrasonic field and duty cycle significantly reduces the surface roughness and the spherical grain size, all of which combine to reduce film resistivity

Millimetre-Wave Dual-Polarized Differentially-Fed 2D Multibeam Patch Antenna Array

In this paper, a novel millimetre-wave dual-polarized 2D multibeam antenna array incorporating differentially-fed antenna elements is proposed to achieve high cross-polarization discrimination (XPD) when the beams scan to the maximal pointing angles. The antenna element is composed of a SIW cavity with four shorted patches placed inside, and it is differentially excited for dual-polarization by a pair of feeding strips and transverse slots beneath the patches. Differential excitation is realized by a power divider designed on two laminate layers. Two Butler Matrices placed perpendicularly with each other in different laminates are employed to generate four tilted beams with dual-polarization. A 2 × 2 dual-polarized 2D multibeam antenna array working at 28 GHz is designed, fabricated, and measured. The operation bandwidth of the antenna is 26.8 GHz – 29.2 GHz. The improvement in the XPD is experimentally demonstrated by far-field measurement. When the beams scan to 30◦ off the boresight, the measured XPDs are 28 dB at the centre frequency and higher than 25 dB over the operation bandwidth, which confirms that the cross-polarized radiation in the 2D multibeam antenna array is suppressed by using the differential-feeding technique. The measured gain is in the range from 7.6 dBi to 10.5 dBi

Effects of nano-SiC addition on the superconducting properties of magnesium diboride

In this study, we report the results on phase formation, microstructures, and superconducting properties of a series of MgB2 samples with different level of SiC additions. The polycrystalline samples were prepared via solid state reaction by mixing magnesium, boron and silicone carbide powders according to the ratio of Mg:B:SiC = 1:2:x. XRD spectra showed that MgB2 is the primary phase while Mg2Si, MgO and MgB4, together with some unreacted SiC are the secondary phases as the addition increases. The presence of Mg2Si became more significant as the addition level increased. SEM images showed smaller grains as the addition level increases indicating more grain boundaries were formed. The Tc was as low as 30.5K for x=15wt%. The field dependence of Jc showed that x=1wt% sample gave the best performance at both 5K and 20K

A Dual-Polarized Planar Antenna Array Differentially-Fed by Orthomode Transducer

This paper presents a new design of a differentially-fed substrate integrated planar antenna array with dual-polarization. Compared with the traditional dual-polarized antenna arrays, the proposed array antenna has the advantages of simple configuration, high cross-polarization discrimination (XPD) and high gain. 2×2-element subarray design with a vialoaded crossover structure is used, which reduces the complexity of the array antenna. The operation bandwidth is improved by generating three resonances in the subarray. One 8×8 antenna array is designed, prototyped and tested to exemplify its potential applications in large dual-polarized antenna arrays. A planar orthomode transducer is used to achieve differential excitation for the antenna array. The measured results show that the proposed antenna array has an impedance bandwidth of 19.2–20.7 GHz for |S11| < −10 dB and port isolation higher than 20 dB. The array antenna exhibits a high XPD of 43 dB and a flat gain about 22.2 dBi within the bandwidth