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Influence of Geotechnical Properties on Sediment Dynamics, Erodibility, and Geomorphodynamics in Coastal Environments Based on Field MeasurementsBrilli, Nicola Carmine 06 June 2023 (has links)
Geotechnical sediment properties such as moisture content, relative density, bearing capacity, and undrained shear strength have been discussed in the context of coastal sediment dynamics. However, these properties have rarely been assessed in their respective relevance or quantitatively related to sediment transport and erodibility. Also, to date there is no framework available for collecting direct measurements of these properties for estimating initiation of motion and erosion rates. Here, it is postulated that improving the ability to measure geotechnical sediment properties in energetic foreshore environments can improve our ability to predict coastal response to climate change. Through a series of field measurements, the research presented here (1) provides a framework for conducting geotechnical measurements of beaches, (2) advances portable free fall penetrometer (PFFP) data analysis in intertidal environments through the introduction of an impact velocity dependent strain-rate correction factor, (3) relates textural and sediment strength properties derived from PFFP measurements to an erosion rate parameter and hydrodynamically driven bed-level change, and (4) uses PFFP measurements to develop a sediment classification scheme in terms of soil behavior and erosion behavior for a mixed sediment type Arctic environment. Relationships between sediment properties other than grain size, most significantly void ratio, and erodibility parameters highlight the relevance of these measurements in geomorphodynamically active sandy beach environments. For the cohesive sediments in the Arctic, undrained shear strength was also related to an erosion rate parameter, allowing for a categorical framework for erodibility classification to be developed. The cohesive framework was combined with the relationships developed for sandy sediments and used to highlight areas of active sediment transport in the context of local morphodynamic and ice gouging processes. Finally, a simple case study showed how implementing in-situ erodibility parameters was important for long-term morphological modelling. The results represent a step forward in our ability to predict and mitigate climate change related issues from coastal erosion. / Doctor of Philosophy / Climate change driven impacts on coastal environments include increasing frequency and severity of storms, coastal erosion, and inundation of populated areas. Specifically for Arctic environments, warming has caused more sediment to be introduced into coastal waters as well as accelerated rates of permafrost melting and shoreline retreat and decreases in sea ice. One aspect of understanding how these changes will continue to affect coastal communities and our ability to predict climate change effects is understanding the role of sediment properties on sediment erosion and shoreline change. Physical and geomechanical (strength) properties of coastal sediments are important for a variety of coastal applications but have rarely been investigated in the context of quantifying, predicting, and assessing erosion, specifically in the context of field measurements.
Towards this end, a series of field surveys were conducted along the coast of North Carolina at a sandy beach, and in Harrison Bay, Alaska, an Arctic coastal zone with both sandy and muddy sediments. Tools for taking physical samples of the beach and seabed, measuring the sediment strength, among other properties in place were used to characterize the local sediments. Once a framework was developed for characterizing the type of sediment, the measured properties were then related to measurements of erosion rate from a series of laboratory experiments performed on physical samples taken from the sites. Finally, one of the instruments for measuring sediment strength both on land and in the water was used to develop classification schemes for seabed sediments in terms of their erodibility.
The results of this work highlight the importance of geotechnical properties for coastal sediment transport processes, reveal new relationships between sediment properties and properties quantifying erosion behavior, and offer a framework for future research to classify erodibility of coastal environments in the field with a single piece of equipment. Overall, the work presented here contributes to our ability to measure, quantify, and predict coastal response to climate change.
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Study of Chip-Level EMI Based on Near-Field Measurement TechniquesHsieh, Hsin-Feng 08 August 2012 (has links)
This thesis proposed a near-field electromagnetic interference measurement framework to obtain sensitivity and spatial resolution of the characteristic parameters of magnetic probe based on International Electrotechnical Commission proposed for integrated circuits electromagnetic radiation measurement standards IEC 61967-6 : magnetic probe method. Using cross-coupled planar microwave bandpass filter which is realized by glass fiber board (FR4) for near-field measurement and electromagnetic simulation in comparsion. Nowadays, integrated circuits has become an important source of energy of overall electromagnetic interference in electronic systems. Finally, do near-field scanning measurement for a 64-pin wire-bond quad flat nonlead (WB-QFN) package and the voltage-controlled oscillator chip in 0.18 £gm CMOS technology by using high scanning resolution of microprobe. Then observes the chip-level and package-level electromagnetic interference, and achieve chip-level of near-field electromagnetic interference measurement techniques.
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