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Gas flux estimation from surface gas concentrationsShahnaz, Sabina 27 May 2016 (has links)
A gradient-independent model of gas fluxes was formulated and tested. The
model is built on the relationship between gas flux and the time history of surface gas
concentration, known as half-order derivative (HOD), when the transport of the gas in the
boundary layer is described by a diffusion equation. The eddy-diffusivity of gas is
parameterized based on the similarity theory of boundary layer turbulence combined with
the MEP model of surface heat fluxes. Test of the new model using in-situ data of CO2
concentration and fluxes at several locations with diverse vegetation cover, geographic
and climatic conditions confirms its usefulness and potential for monitoring and
modeling greenhouse gases. The proposed model may also be used for estimating other
GHGS fluxes such as methane (CH4) and Water vapor flux. This proof-of-concept study
justifies the proposed model as a practical solution for monitoring and modeling global
GHGS budget over remote areas and oceans where ground observations of GHGS fluxes
are limited or non-existent. One focus of the on-going research is to investigate its
application to producing regional and global distributions of carbon fluxes for identifying
sinks and sources of carbon and re-evaluating the regional and global carbon budget at
monthly and annual time scales.
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Gas flux estimation from surface gas concentrationsShahnaz, Sabina 27 May 2016 (has links)
The goal of this study is to develop a gradient-independent method for modeling surface gas flux using surface gas concentration data. The proposed method is built on the relationship between gas flux and the time history of surface gas concentration, known as half-order derivative (HOD), when the transport of gas in the boundary layer is described by a diffusion equation. The new model is tested using in-situ data of CO2 concentration time series at half hour (or hour) intervals from Ameriflux Network at several locations in US, Canada, Mexico and Brazil to estimate CO2 fluxes. In this research the estimated CO2 flux using HOD method are compared with observed CO2 fluxes from four study sites out of 160+ sites with diverse vegetation cover, geographic and climatic conditions to test the generality of model within reasonable endeavor. The sites are Cedar Bridge National Forest, New Jersey, Delta Junction 1920 Control, Alaska, Lucky Hills Shrub land, Arizona, and LBA Tapajos Mature Forest, Brazil. The modeled CO2 flux demonstrates close agreement with field observations confirming the usefulness and potential of HOD model for estimating CO2 gas fluxes.
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Examining the Impacts of Wildfire on Throughfall and Stemflow Chemistry and Flux at Plot and Catchment ScalesWhite, Alissa Marie January 2015 (has links)
This study investigates the effects of fire on the chemistry and flux of precipitation diverted to the forest floor as stemflow and throughfall by observing the impact of the June 2013 Thompson Ridge Wildfire in the Jemez River Basin of New Mexico. The loss of canopy cover from wildfire drastically modifies landscapes and alters ecosystems as fire replaces leafy canopies with charred branches and trunks, changes soil composition and erosion processes, and affects hydrologic flow paths and water chemistry. In order to track these changes, throughfall and stemflow collectors were installed beneath burned and unburned canopies in two catchments impacted by the Thompson Ridge Fire. Throughfall, stemflow, and open precipitation samples were analyzed for major cations, anions, dissolved inorganic and organic carbon, trace metals, and rare earth elements to determine how fire affects the chemical composition of the precipitation that interacts with burned canopies. Precipitation samples collected from both burned and unburned sites during the 2014 summer monsoon season show variations across burn severity, specifically in calcium, strontium, phosphate, and dissolved inorganic carbon concentrations, and across collector type with stemflow concentrations generally higher than throughfall and open precipitation concentrations. A stem count model was used to determine tree density for individual plots and catchments from LiDAR images taken before the 2013 fire. The stem count model was used to upscale event and monsoon season solute fluxes from plot to catchment scale. Higher nutrient concentrations combined with higher volumes of precipitation diverted as stemflow in burned forests have a multiplicative effect resulting in greater nutrient fluxes via stemflow creating nutrient hot spots surrounding burned tree trunks. Upscaling these plot scale concentrations and solute fluxes allows this study to represent changes to an entire catchment and quantify effects of wildfire on chemical loads and water chemistry.
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Interaction of turbulent plumesKaye, Nigel Gregory January 1998 (has links)
No description available.
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The study of quantum oscillations in the normal and superconducting states of Vâ†3SiSankarappa, Talari January 1998 (has links)
No description available.
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Improved direct torque control of induction machine drivesOkumus, Halil Ibrahim January 2001 (has links)
No description available.
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The glacial to holocene sedimentary regime in the Northeast Atlantic OceanManighetti, Barbara January 1993 (has links)
No description available.
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Circulation and fluxes in the Sub-Polar North AtlanticBacon, Sheldon January 1996 (has links)
No description available.
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MHD analysis of the solar-terrestrial interaction : development of tools for studying magnetopause reconnection and the plasma depletion layerLawrence, Gareth Rhys January 1998 (has links)
No description available.
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High performance switched reluctance drives for electric vehicle applicationWeiner, Christian January 2000 (has links)
No description available.
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