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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

Modeling of stripper configurations for CO₂ capture using aqueous piperazine

Madan, Tarun 08 October 2013 (has links)
This thesis seeks to improve the economic viability of carbon capture process by reducing the energy requirement of amine scrubbing technology. High steam requirement for solvent regeneration in this technology can be reduced by improvements in the regeneration process. Solvent models based on experimental results have been created by previous researchers and are available for simulation and process modeling in Aspen Plus®. Standard process modeling specifications are developed and multiple regeneration processes are compared for piperazine (a cyclic diamine) in Chapter 2. The configurations were optimized to identify optimal operating conditions for energy performance. These processes utilize methods of better heat recovery and effective separation and show 2 to 8% improvement in energy requirement as compared to conventional absorber-stripper configuration. The best configuration is the interheated stripper which requires equivalent work of 29.9 kJ/mol CO₂ compared to 32.6 kJ/mol CO₂ for the simple stripper. The Fawkes and Independence solvent models were used for modeling and simulation. A new regeneration configuration called the advanced flash stripper (patent pending) was developed and simulated using the Independence model. Multiple complex levels of the process were simulated and results show more than 10% improvement in energy performance. Multiple cases of operating conditions and process specifications were simulated and the best case requires equivalent work of 29 kJ/mol CO₂. This work also includes modeling and simulation of pilot plant campaigns carried out for demonstration of a piperazine with a 2-stage flash on at 1 tpd CO₂. Reconciliation of data was done in Aspen Plus for solvent model validation. The solvent model predicted results consistent with the measured values. A systematic error of approximately +5% was found in the rich CO₂, that can be attributed to laboratory measurement errors, instrument measurement errors, and standard deviation in solvent model data. Stripper Modeling for CO₂ capture from natural gas combustion was done under a project by TOTAL through the Process Science and Technology Center. Two configurations were simulated for each of three flue gas conditions (corresponding to 3%, 6% and 9% CO₂). Best cases for the three conditions of flue gas require 34.9, 33.1 and 31.6 kJ/mol CO₂. / text
122

Jovian orbit capture and eccentricity reduction using electrodynamic tether propulsion

Schadegg, Maximilian Michael 29 April 2014 (has links)
The use of electrodynamic tethers for propulsion and power generation is attractive for missions to the outer planets, which are traditionally handicapped by large propellant requirements, large times of flight, and a scarcity of power available. The proposed electrodynamic tether propulsion scheme is shown to be capable at reducing or eliminating these mission constraints. In this work, the orbital dynamics of a spacecraft using electrodynamic tether propulsion during the mission phases of capture, apojove pump-down and perijove pump-up in the Jovian system are investigated. The main result is the mapped design space involving mission duration, tether length and minimum perijove radius. Phase-free flyby sequences and bang-bang control laws are also included, which provide performance upper bounds for a given mission architecture. It is found to be advantageous to utilize in-bound only flybys of the Galilean moons during capture, and few, if any, out-bound only flybys during apojove pump-down. The electrodynamic tether system is also shown to be capable of lowering the spacecraft’s orbit to a Europa-Ganymede Hohmann orbit with a total flight time after entering Jupiter’s sphere of influence of just under two years. The benefits of leveraging solar third body perturbations, ballistic flyby tours, and adding a secondary propulsion system are also considered. / text
123

When the well runs dry : groundwater management in Texas

Reel, Jennifer Lynne 30 November 2010 (has links)
Managing and protecting our water resources is one of the most pressing long-term issues facing Texas. In addition to population growth, Texas' vulnerability to drought makes long-term water planning both challenging and imperative. As competing interests vie for this limited natural resource, the State struggles to reach solutions that can provide sustainable water for everyone. This report, and the accompanying video, Tecolote, examine the management of Texas groundwater and the impact it has on Tecolote Farms. / text
124

Quantitative interpretation of pulsed neutron capture logs : fast numerical simulation and inversion in thinly-bedded formations

Mimoun, Jordan Gilles Attia 03 January 2011 (has links)
Pulsed neutron capture (PNC) logs are commonly used for formation evaluation behind casing and to assess time-lapse variations of hydrocarbon pore volume. Because conventional interpretation methods for sigma logs assume homogeneous formations, errors may arise, especially in thinly-bedded formations, when appraising petrophysical properties of hydrocarbon-bearing beds. There exist no quantitative interpretation methods to account for shoulder-bed effects on sigma logs acquired in sand-shale laminated reservoirs. Because of diffusion effects between dissimilar beds, sigma logs acquired in such formations do not obey mixing laws between the sigma responses of pure-sand and pure-shale end members of the sedimentary sequence. We introduce a new numerical method to simulate rapidly and accurately PNC logs. The method makes use of late-time, thermal-neutron flux sensitivity functions (FSFs) to describe the contribution of multi-layer formations toward the measured capture cross section. It includes a correction procedure based on 1D neutron diffusion theory that adapts the transport-equation-derived, base-case FSF of a homogeneous formation to simulate the response of vertically heterogeneous formations. Benchmarking exercises indicate that our simulation method yields average differences smaller than 2 c.u. within seconds of CPU time with respect to PNC logs simulated with rigorous Monte Carlo methods for a wide range of geometrical, petrophysical, and fluid properties. We develop an inversion method to reduce shoulder-bed effects on pulsed neutron capture (PNC) logs in the estimation of layer-by-layer capture cross sections, Σ. The method is based on the previously developed rapid approximation of PNC logs. Tests performed on synthetic examples that include a variety of lithology, saturating-fluid, and bed-thickness configurations confirm the efficiency, reliability, and stability of the inversion procedure. Inversion consistently improves the vertical resolution and Σ definition of PNC logs across beds thinner than 45 cm. Our fast, iterative algorithm inverts sigma logs in seconds of CPU time, and is therefore suitable for joint petrophysical interpretation with other open- and cased-hole logs. / text
125

Scentimo

Komatsu, Yui January 2015 (has links)
In today's world, digital data is often stored away and wiped out by tech upgrades.The memory of scents, however, is persistent. The sense of smell can retrieve past memories instantaneously. In this projekt, I am enriching family lives using the sense of smell, which is not yet taken advantage of in the design field but has a tremendous potential for innovation. I aim at result that will allow parents to capture and collect scent and visual stories and also brings new perspective on how their children view and smell their life moments.
126

Adsorptive Removal of CO2 by Amine Functionalized Sorbents: Experimental and Kinetics Study

Zhao, An Unknown Date
No description available.
127

Optimization of the GTRR epithermal neutron filter for BNCT applications

Newby, Peter George 08 1900 (has links)
No description available.
128

The best use of biomass? : greenhouse gas lifecycle analysis of predicted pyrolysis biochar systems

Hammond, James A. R. January 2009 (has links)
Life cycle analysis is carried out for 11 predicted configurations of pyrolysis biochar systems to determine greenhouse gas balance, using an original spreadsheet model. System parameters reflect deployment in Scotland, and results demonstrate that all major crop and forestry feedstocks offer greater GHG abatement than other bioenergy technologies, regardless of system configuration. Sensitivity analysis determines the relative importance of uncertain variables in the model and optimistic to pessimistic scenarios are used for system operation. Slow pyrolysis is compared to fast pyrolysis and biomass co-firing for GHG abatement and electricity production, using various scenarios for availability of indigenous Scottish feedstocks.
129

Motion capture och skräck : Hur skakiga rörelser påverkar skräckupplevelsen hos en zombie-spelkaraktär / Motion capture and horror : How distorted movements affect the horror experience of a zombie game character

Åsén, Kristina Helene January 2014 (has links)
Det här arbetet syftade till att undersöka om de skakningar och ryck som uppstår vid en dålig motion capture-inspelning, kan användas till fördel i skräcksammanhang och utveckla den skrämmande egenskapen hos en zombiekaraktär. Som bakgrund har undersökningen gått igenom litteratur kring Zombies, The uncanny valley, Das Unheimliche och deras förhållande till spel.Till det material som skapades till undersökningen genomfördes en motion capture-inspelning och sedan skapades tre stycken videoklipp föreställande en zombie. Datan ur inspelningen redigerades på tre olika sätt och varierade mängden ryckighet i zombiens rörelser. Undersökningen utfördes med intervjuer av både icke-skräckerfarana och skräckerfarna informanter.Resultatet visade att det klipp där skak och ryck tillförts uppfattades som mest läskigast av en majoritet av informanterna. Slutsatsen skulle däremot ha kunnat validerats i högre utsträckning med fler intervjuade informanter.
130

CO2 Capture from Dilute Sources via Lime-Based Sorbents

Samari, Mohammad 30 April 2014 (has links)
Direct capture of CO2 from ambient air is a developing technology, which is capable of removing CO2 directly from the atmosphere. Moreover, this technology is independent from sources of CO2 emissions. Hence, it can be set up at locations where pure stream of CO2 is needed such as in enhanced oil recovery. In this research, the performance of pelletized and natural limestone for CO2 capture from air in a fixed bed is studied. To compare the performance of sorbents for air capture, the effects of particle type (natural limestone and pelletized limestone), particle size (250-425 µm and 425-600 µm), gas flowrate (0.5 L/min and 1 L/min), and relative humidity, on the breakthrough time, breakthrough shape, and the global reaction rate are examined. Moreover, carbonation decay of sorbents over series of capture and regeneration cycles is studied. If the inlet stream (air) is humidified at 50% relative humidity, but the lime sorbents are not pre-hydrated, an axially non-uniform carbonated bed results. This phenomenon is due to the partial carbonation of sorbents at the first layers of the bed. While there is a competition between CO2 and water to react with CaO, partial carbonation reaction on the surface of the sorbents not only prevents further hydration, but also decreases the reaction rate at the surface. However, in comparison with a dry system where relative humidity was negligible and sorbents were not pre-hydrated, the observed carbonation conversion was higher. The best results were seen from experiments with pre-hydrated sorbents and humidified inlet stream. The smaller sorbent particles had a better performance (sharper breakthrough curve and longer breakthrough time) due to their greater surface area. A gas-solid reaction model was fitted to the breakthrough curves. Since at the beginning of carbonation there is no resistance of the product layer, it can be assumed that the process is reaction controlled. While after formation of the product layer (CaCO3), it becomes diffusion controlled. Results from fitted data also confirmed these conclusions. Moreover, each of sorbent went through 9 cycles and after each cycle the carbonation conversion of the sorbents was measured by TGA and the surface area by BET.

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