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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 48 for “"shear velocity"”.
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Stability of the large low shear velocity provinces
… (such as the seismically observed Large Low Shear Velocity Provinces - LLSVPs). Our high-resolution numerical simulations suggest that the longevity of LLSVPs for up to three billion years, and possibly longer, can be ensured by a balance in the rate of segregation of high-density OC-material …
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Estimating Embeddedness From Bankfull Shear Velocity in Gravel Streambeds to Assess Sediment Impacts on Aquatic Biota
… streams, is negatively correlated with bankfull shear velocity (u*, m/s). This relationship can be modeled by emb = au*b, with baseline coefficient values of a = 10 and b = –1. The purpose of this thesis was to investigate the applicability of this relationship across the U.S., to begin to …
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Study of the average shear velocity of the inner-core of the earth using isolation filters
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994.
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Surface Wave Derived Shear Velocity Structure of the Gamburtsev Subglacial Mountains, Transantarctic Mountains, and West Antarctica and Shallow Seismicity of the Mariana and Tonga Subduction Zones
Recent advances in seismic instrumentation have allowed researchers to undertake focused investigations of regions previously inaccessible. From the bottom of the sea to the coldest, driest places on earth, we are now able to deploy seismometers to remote locations and be certain of collecting …
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Spatial Distribution of Fine Sediment and Juvenile Freshwater Mussel Settling in the Gravel Bedded Dan River, North Carolina
… of the river as well as the flow conditions. Shear velocity determines the particle size that can remain suspended in a given flow and therefore whether a particle can settle and accumulate on the riverbed. The purpose of this study is to investigate the spatial patterns of fine sediment …
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Effects of tool positions on borehole acoustic measurements : a stretched grid finite difference approach
… is focused on soft formations where formation shear velocity is slower than borehole fluid velocity, because shear velocity measurement, one of the key measurements that acoustic logging is designed
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A computational fluid dynamics model for sediment movement based on the unit stream power approach
… Number (Lui 1957), which represents the shear velocity-settling velocity ratio, is related to the unit stream power and is applied as an alternative incipient motion criterion. The Movability Number, as adapted by Armitage (2001) to account for topography, is utilised for scour hole …
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Numerical modeling of borehole acoustics : parallel implementation of a loggin-while-drilling (LWD) model
… tool are shown to asymptote to the Stoneley wave velocity, giving confirmation of the fluid velocity in the borehole. Parameter studies for simpler borehole geometries show that the Stoneley wave, in soft formations where no shear arrival is present, can be used to invert for the shear velocity of …
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Entrainment of Sediment by Unsteady Turbulent Flows
… distributions of sediment concentration, shear stress, and velocity for two types of flow conditions: tests where the flow was increased from rest to a peak velocity and was then held constant, and tests where the flow was accelerated from rest to a peak velocity and was then decelerated …
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Prediction of Gravel Streambed Embeddedness Using Explainable AI and Machine Learning Techniques
… reach-scale embeddedness using bankfull shear velocity derived from remotely sensed data. This study extends that work by developing two boosting machine learning models using remotely sensed data and explainable artificial intelligence (XAI) to uncover important variables related to …
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Seismic study of the crust and upper mantle structure in eastern Asia using ambient noise correlation and earthquake data
… are commonly applied to investigate the velocity structures of the crust and upper mantle. Among all these methods, seismic tomography is one of the most powerful tools to image the earth’s structure. Recent theoretical and experimental studies suggest that the media impulse response …
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Mapping the Core-Mantle Boundary Using Sdiff Postcursors
… continent-sized structures characterised by low velocity anomalies lie opposite to each other on the core-mantle boundary. These structures, known as large low shear velocity provinces (LLSVPs), are predominantly situated beneath the Pacific Ocean and the African continent. Smaller, more extreme …
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The Role of Streambed Biofilms in The Removal of Biodegradable Contaminants From Shallow Streams
… both the short-term and long-term effects stream velocity had on COD removal rates. The rate at which streambed biofilms removed COD from gravel and cobble streambeds was more sensitive to short-term changes in water velocity than would be predicted based on changes in mass transfer alone; this …
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Series expansion of the Modified Einstein Procedure
… is determined directly by calculating the fall velocity (ω) based on dsoss, the shear velocity (u. = -√ghS) and assuming the value of the von Karman constant (κ) is 0.4. For point concentration measurements, the Ro is calculated by fitting the concentration profile to the measured points. …
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Establishing an unambiguous connection between grain size and style of sediment transport in the Lower Niobrara River, Nebraska, USA
… grain sizes traveling in the water column. Local shear velocity is found by fitting the Rouse equation for suspended sediment transport to measured sediment concentrations. Empirical criteria for distinguishing between suspended load and bedload are used to determine the fraction of sediment …
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Sediment Transport and Wind Flow Around Hummocks
… the relationships between vegetation density, shear stress and sediment transport surrounding hummocks, a type of small dune. While qualitative observations and holistic, large-scale experiments regarding vegetation density and sediment transport have confirmed a negative correlation, fewer …
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Applications of time series analysis to geophysical data
… seismogram in the frequency domain. The group velocity is anomalously low in the period range of 15-50 s, and formal inversion of the data indicates both crustal thickening to 12.5 km and low shear velocity (4.25-4.35 km/s) to depths of 40-50 km. The electromagnetic induction fields at a deep …
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An incompressible three-dimensional turbulent boundary layer on the floor of a recurving rectangular channel
… three-dimensional turbulent boundary layer mean velocity profile models was presented, with emphasis on the applicability of these to predict cross flow profiles when skewing existed in any single profile. A recurving or s-shaped rectangular channel was used to experimentally investigate the …
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A Generalized Log-Law Formulation For a Wide Range of Boundary Roughness Conditions Encountered in Streams
It is demonstrated that the method for locating a velocity profile origin, or plane of zero velocity, by fitting log profiles to streamwise velocity measurements is applicable to a larger range of roughness scales than previously expected. Five different sets of detailed, experimental velocity …
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Near-surface void characterization and sensitivity analysis using enhanced processing procedures on passive Multi-Channel Analysis of Surface Waves (MASW) data
… (MASW) data were utilized to identify velocity anomalies above known salt solution voids in Hutchinson, Kansas, likely caused by the changing stress field due to the migration and/or expansion of the void. Previous geophysical studies within the study area provided information about the …
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