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1
Bowdalo, Dene. "Spectral analysis of atmospheric composition : application to surface ozone." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15697/.
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This thesis describes the undertaking of multiple studies designed to evaluate and reduce global modelled surface O3 biases in CTMs/ESMs. Specific focus is placed on the evaluation of rural surface O3 seasonal variability in a global CTM (GEOS-Chem). A major observational data collation is undertaken, processing 1,033,463,750 measurements of O3 and some of its major precursors, from 16,996 sites, through a number of rigorous data quality checks, to ensure data is of a high enough quality for global model evaluation. Through a model–measurement comparison, applying spectral analysis, substantial seasonal biases of surface O3 in GEOS-Chem are found, with a general overestimation of the seasonal amplitudes in North America and Europe (by up to 16 ppbv), together with delayed phase maxima by 1–5 months. The main cause of these biases is found to be homogenous overestimates of summertime O3 in all observed areas, by a minimum of 10 ppbv. An extensive global sensitivity study is undertaken to evaluate the sensitivity of modelled surface O3 biases to alterations of anthropogenic emissions, biogenic emissions, and the O3 dry deposition flux. Constraining model biases jointly by O3, NO and CO observations yields regional optimal monthly scaling factors. Driving GEOS-Chem with these derived factors results in the modelled summertime overestimates of surface O3 being removed almost entirely, across all regions. The removal of this bias is dominantly controlled through increases to the summertime O3 dry deposition flux (by factors of 2–4), with modifications to this term providing the only viable pathway for substantial reduction of modelled summertime biases, in all evaluated regions. Surface O3 is found to be NOx sensitive in all regions, with scalings of VOC emissions generally not imparting significant change on O3. General modelled winter underestimates of surface O3 are able to be removed through reductions of NOx emissions.
2
Lane, Joseph Robert, and n/a. "Application of electronic structure calculations to atmospheric trace species." University of Otago. Department of Chemistry, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080707.100923.
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The chemistry and dynamics of our atmosphere are complex and diverse. A plethora of different chemical reactions are thought to be important, of which only some are known, and even less are well understood. Many of these atmospheric reactions involve highly reactive or unstable trace species, which can be difficult to study experimentally. However, the advancement of computational methods and hardware now make it possible to investigate these chemical species theoretically to an accuracy that is useful for atmospheric chemistry. In this thesis, we have applied modern electronic structure methods to some prototypical hydrogen bonded complexes and sulfonic acid derivatives to better understand the roles of these trace species in the atmosphere. We have calculated fundamental and overtone vibrational spectra, electronic absorption spectra, and reaction energetics with high level ab initio methods. Where possible, we compare our calculated results to experiment and in the absence of experimental data we suggest that our theoretical findings may be of use to atmospheric modelers.
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Adress, Wameedh. "Physics and application of an atmospheric pressure plasma jet." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.669537.
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Atmospheric pressure plasma, APP, jets, are now attracting great interest because of their potential uses in many applications; for example surface modification and plasma medicine. These applications require an insight into their plasma chemistry, which is strongly influenced by the electron energy distribution function. In this work the dynamic behaviour of a 20 kHz-driven APP jet operating with helium as the main gas and oxygen as an additive is investigated. The jet has a commonly used configuration, a cylindrical quartz tube with two electrodes used to form a dielectric barrier discharge. This atmospheric pressure plasma jet was used to generate non thermal plasma bullets away from the production region. The characteristics of the plasma plume and streamer were diagnosed using, current-voltage measurements, ICCD imaging, and optical emission spectroscopy. Here, the use of Thomson scattering to measure the electron properties in the plasma plume created by 20 kHz was reported. The investigation reveals a "ring-like" radial distribution of both the electron density and temperature. A 532nm Nd:YAG laser beam was focused into the plasma plume. The temporally and spatially resolved spectra of light at 900 to the laser direction were detected. The spectra contain light from Thomson Scattering from electrons, along with Rayleigh and Raman scattering from atoms and molecules. The use of a atmospheric pressure helium non-thermal plasma jet to assist a SCR deNOx reaction over a silver-based catalyst at low temperature using simulated diesel fuels was explored. A coupled IR-plasma reactor was developed allowing direct interaction of the plasma with the catalyst bed whilst accommodating a FTIR spectrometer and NOx analyzer. Two KHz, quartz tube jet designs were developed to operate at low gas flows, one with a circular copper electrode but with a grounded electrode in the reaction area, and the other with a central powered electrode with the vessel as a ground. The catalyst was prepared by the impregnation of ?-AI203 with a silver nitrate solution. NOx and hydrocarbon conversions were studied with toluene and octane on an Ag-catalyst at two different temperatures.
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Capps, Shannon. "Advanced sensitivity analysis techniques for atmospheric chemistry models: development and application." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/51755.
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Trace gases and aerosols, or suspended liquid and solid material in the atmosphere, have significant climatological and societal impacts; consequently, accurate representation of their contribution to atmospheric composition is vital to predicting climate change and informing policy actions. Sensitivity analysis allows scientists and environmental decision makers alike to ascertain the role a specific component of the very complex system that is the atmosphere of the Earth. Anthropogenic and natural emissions of gases and aerosol are transported by winds and interact with sunlight, allowing significant transformation before these species reach the end of their atmospheric life on land or in water. The adjoint-based sensitivity method assesses the relative importance of each emissions source to selected results of interest, including aerosol and cloud droplet concentration. In this work, the adjoint of a comprehensive inorganic aerosol thermodynamic equilibrium model was produced to improve the representativeness of regional and global chemical transport modeling. Furthermore, a global chemical transport model adjoint equipped with the adjoint of a cloud droplet activation parameterization was used to explore the footprint of emissions contributing to current and potential future cloud droplet concentrations, which impact the radiative balance of the earth. In future work, these sensitivity relationships can be exploited in optimization frameworks for assimilation of observations of the system, such as satellite-based or in situ measurements of aerosol or precursor trace gas concentrations.
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Herek, Jennifer Lynn Zewail Ahmed H. Zewail Ahmed H. "Femtochemistry and reactive intermediates : application to atmospheric and organic chemistry /." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-04082008-084916.
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Kordova-Vyhnalikova, Jana. "Mathematical modelling of atmospheric pollution : application of some eulerian-lagrangian trajectographic models to the prediction of atmospheric pollution." Université Louis Pasteur (Strasbourg) (1971-2008), 1997. http://www.theses.fr/1997STR13207.
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Ce memoire concerne la dispersion turbulente de particules lourdes au sein d'une couche limite turbulente. Pour ce faire, un modele eulerien d'ecoulement porteur a ete couple a une approche lagrangienne de trajectographie. La premiere etape dans l'etude du comportement dispersif de particules est de disposer d'une description suffisamment precise de l'ecoulement porteur. Le modele eulerien piapblm est concu pour simuler les ecoulements turbulents de type couche limite atmospherique. Ce modele a ete modifie pour decrire l'ecoulement de la couche limite classique. Il a ete complete par des relations algebriques deduites d'une fermeture au second ordre pour prendre en compte l'anisotropie du fluide porteur et pour decrire l'ecoulement de la sous-couche visqueuse et de la zone de tampon. La deuxieme etape de cette etude concerne le modele de trajectographie utilisant une approche statistique pour la prediction des caracteristiques de la phase dispersee. Les modifications apportees au modele concerne la simulation de la particule fluide en resolvant l'equation de langevin, la force de portance due au cisaillement, l'influence de la proximite de la paroi et les collisions particule-paroi. Le modele eulerien-lagrangien a ete valide en comparant ses resultats a ceux d'une experience recente realisee dans une soufflerie de type eiffel. Les profils simules de la vitesse moyenne du fluide sont en accord avec les profils experimentaux. On a observe l'influence de la facon de simuler la particule fluide (liee avec le probleme de la turbulence vue par la particule lourde) sur les profils de vitesse moyenne et des ecarts-types de la vitesse fluctuantes des particules lourdes. La comparaison avec une experience realisee en soufflerie est concluante. Avant son application a l'outil meteorologique, une etude atmospherique a ete effectuee en supposant la couche limite atmospherique dans les conditions de stratification stable.
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Potvin, Guy. "The application of RASS in urban boundary layer meteorology." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0019/NQ44556.pdf.
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Jackson, David Morris. "Calibration of millimeter-wave radiometers with application to clear-air remote sensing of the atmosphere." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15786.
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Chen, Chuxing. "Local atmospheric electricity and its possible application in high-energy cosmic ray air shower detection." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184799.
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We have conducted an extensive experimental study on the subject of near ground atmospheric electricity. The main objective was to gain more understanding of this particular aspect of atmospheric phenomena, while testing the possible application to cosmic ray research. The results in atmospheric electricity show that there are certain patterns in ion grouping such as the size and lifetime. The average lifetime of ion group is 0.7 seconds and the average size is about 10 meters at our experimental site. Ultrahigh energy cosmic ray air showers should create sizable slow atmospheric electric pulses according to our theoretical calculations. Preliminary studies on air showers with total particle number N equal or greater than 10⁵ (10¹⁵ eV) have yielded strong evidence that slow atmospheric current pulses are associated with air showers. The theory and the experiment agree with each other fairly well when we average over large numbers of events. With our current experimental arrangement, when the air shower exceeds a certain size, the system response saturates. Therefore it is extremely desirable in future research that the counter array be designed for a much higher threshold level, since this prototype experiment indicates that interesting data would be obtained. Another reason for further experimental research being directed toward ultrahigh energy, e.g., N ≥ 10⁷ (10¹⁷ eV) and higher, is to establish a calibration of the slow atmospheric electric signals generated by cosmic rays as a function of primary cosmic ray energy and core location. This type of slow atmospheric electric signal, if fully understood and calibrated, offers a new and potentially less expensive technique to observe ultrahigh energy cosmic ray events, which hold some fundamental keys to the knowledge of the universe on a large scale.
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Breedt, Hendrik Johannes. "Atmospheric boundary layer stability and its application to computational fluid dynamics." Diss., University of Pretoria, 2005. http://hdl.handle.net/2263/66234.
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In the wind resource and wind turbine suitability industry Computational Fluid Dynamics has gained widespread use to model the airflow at proposed wind farm locations. These models typically focus on the neutrally stratified surface layer and ignore physical process such as buoyancy and the Coriolis force. These physical processes are integral to the accurate description of the atmospheric boundary layer and reductions in uncertainties of turbine suitability and power production calculations can be achieved if these processes are included. The present work focuses on atmospheric flows in which atmospheric stability and the Coriolis force are included. The study uses Monin-Obukhov Similarity Theory to analyse time series data output from a proposed wind farm location to determine the prevalence and impact of stability at the location. The output provides the necessary site data required for the CFD model as well as stability-dependent wind profiles from measurements. The results show non-neutral stratification to be the dominant condition onsite with impactful windfield changes between stability conditions. The wind flows considered in this work are classified as high Reynolds number flows and are based on numerical solutions of the Reynolds-Averaged Navier-Stokes equations. A two-equation closure method for turbulence based on the k __ turbulence model is utilized. Modifications are introduced to standard CFD model equations to account for the impact of atmospheric stability and ground roughness effects. The modifications are introduced by User Defined Functions that describe the profiles, source terms and wall functions required for the ABL CFD model. Two MOST models and two wall-function methods are investigated. The modifications are successfully validated using the horizontal homogeneity test in which the modifications are proved to be in equilibrium by the model�s ability to maintain inlet profiles of velocity and turbulence in an empty domain. The ABL model is applied to the complex terrain of the proposed wind farm location used in the data analysis study. The inputs required for the stability modifications are generated using the available measured data. Mesoscale data are used to describe the inlet boundary conditions. The model is successfully validated by cross prediction of the stabilitydependent wind velocity profiles between the two onsite masts. The advantage of the developed model is the applicability into standard wind industry loading and power production calculations using outputs from typical onsite measurement campaigns. The model is tuning-free and the site-specific modifications are input directly into the developed User Defined Functions. In summary, the results show that the implemented modifications and developed methods are applicable and reproduce the main wind flow characteristics in neutral and non-neutral flows over complex wind farm terrains. In additions, the developed method reduce modelling uncertainties compared against models and measurements that neglect non-neutral stratification.Dissertation (MEng)--University of Pretoria, 2018.
Mechanical and Aeronautical Engineering
MEng
Unrestricted
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Anderton, Blake Jerome. "Application of Digital Micromirror Devices to Atmospheric Lidar Measurement and Calibration." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/333349.
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A novel design for atmospheric laser radar (lidar) is presented, implementing a digital micromirror device (DMD) for use in (A) aligning transmitter and receiver boresight angles and in (B) field-of-view (FOV) control of such "DMD lidar" instruments. A novel technique is presented to extract the transmitter-receiver overlap-compensation function from ratioing data from different FOVs in the same pointing direction. DMD lidar design considerations and trades are surveyed. Principles of modeling DMD lidar performance are introduced and implemented in a performance-predictive system simulation with data-validated results. Operational capabilities of DMD lidar are demonstrated through a hardware prototype with field measurement examples. Additional capabilities offered by integrating DMD within lidar and other optical systems are presented, including single-pixel Radon-imaging techniques.
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Clifton, Roger L. "Processing methods for multichannel radiometric data with application to atmospheric radon." Thesis, Curtin University, 1989. http://hdl.handle.net/20.500.11937/80357.
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Airborne multichannel radiometric data are collected for lithology mapping. Established processing methods efficiently extract the potassium and thorium distributions, but confuse the uranium in the ground with the radon gas it releases into the atmosphere. This thesis uses the multichannel character to help separate the true uranium signal from the radon effects. The processing is reviewed and some methods for reducing the effects of radon are examined.
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Bozzo, Alessio <1979>. "Atmospheric radiative transfer in multiple scattering conditions. Application to NWP models." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1874/1/bozzo_alessio_tesi.pdf.
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High spectral resolution radiative transfer (RT) codes are essential tools in the study of the radiative energy transfer in the Earth atmosphere and a support for the development of parameterizations for fast RT codes used in climate and weather prediction models. Cirrus clouds cover permanently 30% of the Earth's surface, representing an important contribution to the Earth-atmosphere radiation balance.
The work has been focussed on the development of the RT model LBLMS. The model, widely tested in the infra-red spectral range, has been extended to the short wave spectrum and it has been used in comparison with airborne and satellite measurements to study the optical properties of cirrus clouds. A new database of single scattering properties has been developed for mid latitude cirrus clouds. Ice clouds are treated as a mixture of ice crystals with various habits. The optical properties of the mixture are tested in comparison to radiometric measurements in selected case studies. Finally, a parameterization of the mixture for application to weather prediction and global circulation models has been developed. The bulk optical properties of ice crystals are parameterized as functions of the effective dimension of measured particle size distributions that are representative of mid latitude cirrus clouds. Tests with the Limited Area Weather Prediction model COSMO have shown the impact of the new parameterization with respect to cirrus cloud optical properties based on ice spheres.
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Bozzo, Alessio <1979>. "Atmospheric radiative transfer in multiple scattering conditions. Application to NWP models." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1874/.
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High spectral resolution radiative transfer (RT) codes are essential tools in the study of the radiative energy transfer in the Earth atmosphere and a support for the development of parameterizations for fast RT codes used in climate and weather prediction models. Cirrus clouds cover permanently 30% of the Earth's surface, representing an important contribution to the Earth-atmosphere radiation balance.
The work has been focussed on the development of the RT model LBLMS. The model, widely tested in the infra-red spectral range, has been extended to the short wave spectrum and it has been used in comparison with airborne and satellite measurements to study the optical properties of cirrus clouds. A new database of single scattering properties has been developed for mid latitude cirrus clouds. Ice clouds are treated as a mixture of ice crystals with various habits. The optical properties of the mixture are tested in comparison to radiometric measurements in selected case studies. Finally, a parameterization of the mixture for application to weather prediction and global circulation models has been developed. The bulk optical properties of ice crystals are parameterized as functions of the effective dimension of measured particle size distributions that are representative of mid latitude cirrus clouds. Tests with the Limited Area Weather Prediction model COSMO have shown the impact of the new parameterization with respect to cirrus cloud optical properties based on ice spheres.
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Hanley, Thomas Ryan. "The microwave opacity of ammonia and water vapor: application to remote sensing of the atmosphere of Jupiter." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24673.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Paul G. Steffes; Committee Member: Dr. Gregory D. Durgin; Committee Member: Dr. Robert D. Braun; Committee Member: Dr. Thomas K. Gaylord; Committee Member: Dr. Waymond R. Scott
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Krützmann, Nikolai Christian. "Application of Complexity Measures to Stratospheric Dynamics." Thesis, University of Canterbury. Physics and Astronomy, 2008. http://hdl.handle.net/10092/2020.
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This thesis examines the utility of mathematical complexity measures for the analysis of stratospheric dynamics. Through theoretical considerations and tests with artificial data sets, e.g., the iteration of the logistic map, suitable parameters are determined for the application of the statistical entropy measures sample entropy (SE) and Rényi entropy (RE) to methane (a long-lived stratospheric tracer) data from simulations of the SOCOL chemistry-climate model. The SE is shown to be useful for quantifying the variability of recurring patterns in a time series and is able to identify tropical patterns similar to those reported by previous studies of the ``tropical pipe'' region. However, the SE is found to be unsuitable for use in polar regions, due to the non-stationarity of the methane data at extra-tropical latitudes. It is concluded that the SE cannot be used to analyse climate complexity on a global scale. The focus is turned to the RE, which is a complexity measure of probability distribution functions (PDFs). Using the second order RE and a normalisation factor, zonal PDFs of ten consecutive days of methane data are created with a Bayesian optimal binning technique. From these, the RE is calculated for every day (moving 10-day window). The results indicate that the RE is a promising tool for identifying stratospheric mixing barriers. In Southern Hemisphere winter and early spring, RE produces patterns similar to those found in other studies of stratospheric mixing. High values of RE are found to be indicative of the strong fluctuations in tracer distributions associated with relatively unmixed air in general, and with gradients in the vicinity of mixing barriers, in particular. Lower values suggest more thoroughly mixed air masses. The analysis is extended to eleven years of model data. Realistic inter-annual variability of some of the RE structures is observed, particularly in the Southern Hemisphere. By calculating a climatological mean of the RE for this period, additional mixing patterns are identified in the Northern Hemisphere. The validity of the RE analysis and its interpretation is underlined by showing that qualitatively similar patterns can be seen when using observational satellite data of a different tracer. Compared to previous techniques, the RE has the advantage that it requires significantly less computational effort, as it can be used to derive dynamical information from model or measurement tracer data without relying on any additional input such as wind fields. The results presented in this thesis strongly suggest that the RE is a useful new metric for analysing stratospheric mixing and its variability from climate model data. Furthermore, it is shown that the RE measure is very robust with respect to data gaps, which makes it ideal for application to observations. Hence, using the RE for comparing observations of tracer distributions with those from model simulations potentially presents a novel approach for analysing mixing in the stratosphere.
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Ménard, Richard. "Kalman filtering of Burgers' equation and its application to atmospheric data assimilation." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41712.
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A study of Kalman filtering in atmospheric data assimilation is presented. Our research aims at an understanding of the physical and statistical mechanisms as well as the principles underlying its application to atmospheric data assimilation. Both the continuous and the discrete formulations of the filter were considered. Using nonlinear advection diffusion dynamics, a number of aspects in data assimilation were addressed, often by exploring the parameter space or by performing Monte Carlo simulations. The filtering properties, the spatial regularity and indirect inference about the model error covariance were examined with a discrete linear Kalman filter. The dynamics of the mean, variance, and correlation of forecast errors for Burgers' equation were studied. The validity of the tangent linear approximation for Burgers' equation was examined. An ensemble of realizations of the extended Kalman filter has permitted a statistical investigation of its performance, errors and limit of validity.
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Glagolenko, Stanislav Yurievich. "Single-ultrafine-particle mass spectrometer development and application." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1083.
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A single-ultrafine-particle mass spectrometer was constructed and deployed for size-resolved ultrafine aerosol composition measurements during the winter of 2002-2003 in College Station, Texas. Three separate experiments were held between December and March with six week intervals. Almost 128,000 mass spectra, corresponding to particles with aerodynamic diameters between 35 and 300 nm, were collected and classified. Fifteen statistically significant classes were identified and are discussed in this paper. Nitrate, potassium, carbon, and silicon/silicon oxide were the most frequently observed ions. Nitrate was present in most of the particles, probably due to the agricultural activity in the vicinity of the sampling site. The nitrate detection frequency was found to be sensitive to the ambient temperature and relative humidity. Another particle class, identified as an amine, exhibited strong relative humidity dependence, appearing only during periods of low relative humidity. There is evidence that some of the detected particles originated from the large urban centers, and were coated with nitrate, sulfate, and organics during transport.
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Guérendel, Philippe. "Ultrasonic modeling--application to deep-water multiples imaging." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/52920.
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Adams, David Kenton. "Application of the heat engine framework to modeling of large-scale atmospheric convection." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280339.
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The heat engine framework is examined in terms of large-scale atmospheric convection in order to investigate several theoretical and modeling issues related to the steady-state convecting atmosphere. Applications of the heat engine framework to convective circulations are reviewed. It is shown that this framework provides fundamental insights into the nature of various atmospheric phenomena and estimates of their potential intensity. The framework is shown to be valid for both reversible and irreversible systems; the irreversible processes' sole effect is to reduce the thermodynamic efficiency of the convective heat engine. The heat engine framework is then employed to demonstrate that the two asymptotic limits of quasi-equilibrium theory are consistent. That is, the fractional area covered by convection goes to zero, σ → 0, as the ratio of the convective adjustment to large-scale time scale (e.g. radiative time scale) go to zero, tADJ/tLS →0 , despite recent arguments to the contrary. Furthermore, the heat engine framework is utilized to develop a methodology for assessing the strength of irreversibilities in numerical models. Using the explicit energy budget, we derive thermodynamic efficiencies based on work and the heat budget for both open (e.g., the Hadley circulation) and closed (e.g., the general circulation) thermodynamic systems. In addition, the Carnot efficiency for closed systems is calculated to ascertain the maximum efficiency possible. Comparison of the work-based efficiency with that of the efficiency based on the heat budget provides a gauge for assessing how close to reversible model-generated circulations are. A battery of experiments is carried out with an idealized GCM. The usefulness of this method is demonstrated and it is shown that an essentially reversible GCM is sensitive (i.e., becomes more irreversible) to changes in numerical parameters and horizontal resolution.
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Mighani, Saied 1989. "Some rock mechanics problems with application for hydraulic fracturing." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122224.
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Thesis: Ph. D. in Geophysics, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 185-205).
Hydraulic fracturing is an essential tool used to enhance connectivity in shale gas reservoirs by maximizing the intersection between the hydraulic fracture (HF) and pre-existing natural fractures (NF) or faults. The technique is most effective when the hydraulic fracture crosses natural fractures rather than arresting on them. Experiments conducted to examine the interaction between HF and artificial pre-existing faults suggest that the coupling of diffusivity and fault slip is an important element of the HF-fault interaction problem. Fault slip, once activated is associated with an apparent increase in diffusivity. Whether the hydrofracture crosses or arrests on the pre-existing fault is also affected by surface roughness, differential stresses, and fault slip mode (i.e., stable or stick-slip sliding). Calibrated piezoelectric transducers were used to measure acoustic emissions (AE) generated during HF and fault slip.
Moment tensor analysis of these events was used to distinguish pure tensile, shear, and possibly closure events during the experiments. Seismic moment magnitudes were approximately -7 for events during the initiation of the HF and about -5 for events during fault slip. Such a low ratio of seismic moments for tensile and slip events may explain the small numbers of tensile events recorded during reservoir stimulations. I also studied the time-dependent behavior in shales to gain insight into the post-stimulation efficiency of exploitations. Shale experiences strain hardening and compaction during loading by both isostatic (pressure-driven) and differential stress (shear-driven). Transient creep strain increased linearly with log(time), possibly transitioning to constant rate in timescale of several days. Motivated by the multi-scale nature of heterogeneities in shales, I examined the micromechanics of deformation using the nano-indentation technique.
Elastic and creep moduli found in nano-indentation and triaxial tests agreed within a factor of 2, but within that factor, the creep strength may depend on spatial scale.
by Saied Mighani.
Ph. D. in Geophysics
Ph.D.inGeophysics Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences
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廖俊豪 and Chun-ho Liu. "Numerical modelling of atmospheric boundary layer with application to air pollutant dispersion." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31239018.
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Gunther, Matthew. "Formulation and application of improved marine aerosol proxies for atmospheric corrosion studies." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/formulation-and-application-of-improved-marine-aerosol-proxies-for-atmospheric-corrosion-studies(058632b7-cec8-4a69-b50d-1f3b9ba24543).html.
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It has been the purpose of this PhD program to determine whether current laboratory-based methods of investigating Atmospherically-Induced Stress Corrosion Cracking (AISCC) of austenitic Stainless Steels (SS) are adequate in modelling realistic corrosion processes within a marine aerosol environment. Results obtained throughout the study have sought to address three key aims. Mainly, to understand the nature and behaviour of primary marine aerosol containing organic matter present within oceanic surface waters, the interfacial interactions of such aerosol droplets deposited on to austenitic stainless steels and, ultimately, their impact upon AISCC processes. Based upon the work conducted during this research, several conclusions may be deduced. The presence of primary organic components within a sea-salt aerosol leads to a reduction in surface tension at the liquid-vapour interface; highlighting the surface-active nature of algal exudates. Surface-active constituents also have the potential to aggregate at the liquid-solid interface. The inclusion of exudates, therefore, has the potential to maintain an electrolytic environment on an austenitic steel substrate for an elongated time period under ambient conditions. Following subsequent evaporation, organically-enriched seawater droplets typically produce an organic surface film. The results of these interfacial studies have informed AISCC measurements using U-bend specimens, which demonstrate a correlation between cracking and droplet size. Furthermore, the limiting factor for AISCC may not be a function of deposition density as previously thought but rather of droplet surface area.
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Liu, Chun-ho. "Numerical modelling of atmospheric boundary layer with application to air pollutant dispersion /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20158695.
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Henderson, John M. 1972. "An application of potential vorticity inversion to the position forecast problem of hurricane Opal /." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27339.
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Accurate forecasting of hurricane motion is required to prepare for hurricane landfall. The underpredicted acceleration of Hurricane Opal by the National Centers for Environmental Prediction's (NCEP) operational eta model during landfall and over-land passage is investigated using quasi-geostrophic potential vorticity (QGPV) inversion. We identify and explain model errors in the evironmental steering flow using a systematic procedure including removal of Opal's cyclonic circulation that builds upon previous work.The eastern ridge associated with the anticyclonic QGPV was persistently forecasted too weak and too distant from Opal, though the forecast of this feature improved at shorter ranges. The anticyclonic contribution to the retrieved flow increased from $-$11% of the observed vector (inhibiting the motion) to 15% (aiding the motion). This increase of 3.8 m s$ sp{-1}$ is alone sufficient to explain the slow forecast.
The eta forecasts likely did not sufficiently resolve the advection downstream of storm outflow and subsequent ridge building. This error propagated through the forecast cycle and prevented phase-locking with the ridge and increased flow. Representation of the ridge improved following advection of the outflow over the more dense U.S. upper air network.
This study emphasizes the need for accurate upper-air analyses and offers a real-time application of QGPV inversion that decomposes the steering flow. The need for further research into the intimate relationship between storm intensity and subsequent storm track is stated.
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Weisberg, Ori (Ori J. ). 1970. "Nonlocalized faulting in a thick lithosphere : application to lunar contraction." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/58266.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 2001.Includes bibliographical references (p. 67-74).
We reexamine the longstanding hypothesis that lunar contraction is constrained by the lack of a visible global system of compressive faults. We model the lunar lithosphere as a layered elastic medium that fails according to a Mohr-Coulomb criterion. We use elastic constants inferred from lunar seismic profiles, and use a finite element code to model the response of this lithosphere to contraction. We find that fault localization and propagation are strongly affected by the thickness of the lithosphere. A thin lithosphere promotes fault localization by extending through the entire lithosphere and thus enabling large stress relief and large displacements. For a thick elastic lithosphere the mode of faulting is less localized and many faults form in the upper part of the lithosphere, each with small displacements. Furthermore, localization in a thin lithosphere enables fault propagation through a compliant layer, such as a 1-3 km megaregolith layer, while for a thick lithosphere faults cannot penetrate this layer. Thus, the lack of an observed global system of compressive faults, similar to the locate scarps observed on the surface of Mercury, may not be due to the absence of an episode of global contraction on the moon, but rather due to the thickness of the lithosphere at that time.
by Ori Weisberg.
S.M.
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Boyce, Jeremy Welles. "The development and application of microanalytical (U-Th)/He thermochronology." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34662.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2006.Includes bibliographical references.
The (U-Th)/He thermochronmeter is the foremost tool available to geoscientists for the purposes of constraining the thermal evolution of the crust below 250°C. However, the potential of the technique is far from fully explored. The existing de facto (U-Th)/He age standard, the fluorapatite of Cerro de Mercado (Durango, Mexico), does not yield reproducible dates, an observation confirmed at several laboratories. A series of experiments combining analytical and numerical techniques suggests that variations in U and Th measured in a single sectioned crystal could result in several percent apparent age variation due to unequal alpha recoil exchange across internal zone boundaries. Heterogeneities may also play a role in the variability observed in the diffusive behavior of He in strongly zoned minerals, such as monazite. He diffusion experiments on monazite indicate that the closure temperature for (U-Th)/He thermochronometry is between 206°C and 286°C, but varies from grain to grain, even within suites of crystals obtained from one rock. This may be due to compositional variations in the host monazite. Typically heterogeneous monazite crystals may have different closure temperatures, and single crystals may preserve large portions of the cooling history of a rock.
(cont.) None the less, monazite appears to have great potential for (U-Th)/He chronometry, and because of the high U and Th (and therefore 4He) concentrations observed in many monazites, it is a prime candidate for microanalytical (U-Th)/He. A microanalytical protocol for (U-Th)/He chronometry has been developed by applying the laser microprobe to polished crystals or crystal fragments of monazite. Agreement with conventional (U-Th)/He ages is to within -1.3%, with previously unavailable spatial resolution of -30pm. Large numbers of laser microprobe (U-Th)/He ages can be generated more rapidly than by conventional means, and this technique allows the dating of grains that would not be acceptable for conventional (U-Th)/He. Application of laser microprobe (U-Th)/He to monazites from Nanga Parbat, Pakistan, yields highly reproducible cooling ages within and between single crystals. Mean ages of 0.746 ± 0.049 Ma and 0.753 ± 0.036 Ma from two crystals, and the direct observation of negligible (U-Th)/He age gradients, support minimum mean cooling rates of > 325 K/m.y., and minimum mean rock uplift rates of > 4 km/m.y.. Laser microprobe (U-Th)/He of zircon produces no geologically useful dates, a consequence of the poor U and Th measurements provided by LA-ICPMS.
(cont.) Future efforts should employ better calibrated LA-ICPMS approaches or next-generation electron microprobe techniques, which can provide more accurate U and Th concentrations than LA-ICPMS, even for the low concentrations found in zircon.
by Jeremy Welles Boyce.
Ph.D.
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Thompson, Delaine Rebecca. "Nonlinear waveform tomography : theory and application to crosshole seismic data." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12666.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993.Includes bibliographical references (p. 175-183).
by Delaine Rebecca Thompson.
Ph.D.
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Park, Young-Gyu. "Rotating convection driven by differential bottom heating and its application." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/55050.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.Includes bibliographical references (leaves 133-137).
by Young-Gyu Park.
Ph.D.
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Weber, Marie Aimee. "N2O emissions from wheat agro-ecosystems under elevated atmospheric CO2." Thesis, The University of Arizona, 1997. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_etd_hy0146_sip1_w.pdf&type=application/pdf.
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Kindler, Thomas Paul. "The development of supercomputing tools in a global atmospheric chemistry model and its application on selected problems in global atmospheric chemistry modeling." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/26283.
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Hadjimitsis, Diofantos Glafkou. "The application of atmospheric correction algorithms in the satellite remote sensing of reservoirs." Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300296.
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Koch, T. "An application of matrix isolation and reflection-absorption infrared spectroscopy to reaction mechanisms in atmospheric cryochemistry." Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384825.
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Zhang, Huai-Min Ph D. Massachusetts Institute of Technology. "Application of an inverse model in the community modeling effort results." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/58152.
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Kenny, William T. "The Development and Application of the Hi-Resolution VOC Atmospheric Chemistry in Canopies Model." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439131044.
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Karim, Abbas Adel. "Application of a computational fluid dynamics (CFD) approach to model atmospheric air pollution." Thesis, London South Bank University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618684.
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Moore, Tim Orland II. "Application of a Mobile Flux Lab for the Atmospheric Measurement of Emissions (FLAME)." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/29046.
Full textAbstract:
According to the World Health Organization, urban air pollution is a high public health priority due its linkage to cardio-pulmonary disease and association with increased mortality and morbidity (1, 2). Additionally, air pollution impacts climate change, visibility, and ecosystem health. The development of effective strategies for improving air quality requires accurate estimates of air pollutant emissions. In response to the need for new approaches to measuring emissions, we have designed a mobile Flux Lab for the Atmospheric Measurement of Emissions (FLAME) that applies a proven, science-based method known as eddy covariance for the direct quantification of anthropogenic emissions to the atmosphere.
The mobile flux lab is a tool with novel, multifaceted abilities to assess air quality and improve the fidelity of emission inventories. Measurements of air pollutant concentrations in multiple locations at the neighborhood scale can provide much greater spatial resolution for population exposure assessments. The labâ s mobility allows it to target specific sources, and plumes from these can be analyzed to determine emission factors. Through eddy covariance, the lab provides the new ability to directly measure emissions of a suite of air pollutants.
We have deployed the FLAME to three different settingsâ a rural Appalachian town where coal transport is the dominant industry; schools in the medium-sized city of Roanoke, Virginia; and the large urban areas around Norfolk, Virginiaâ to measure neighborhood-scale emissions of air pollution. These areas routinely experience high ozone and particulate matter concentrations and include a diverse array of residential neighborhoods and industries. The FLAME is able to capture emissions from all ground-based sources, such as motor vehicles, rail and barge traffic, refuse fires and refueling stations, for which no direct measurement method has been available previously. Experiments focus on carbon dioxide (CO2), the principal greenhouse gas responsible for climate change; nitrogen oxides (NOx), a key ingredient in ground-level ozone and acid rain; volatile organic compounds (VOCs), a second key ingredient in ozone and many of which are air toxics; and fine particulate matter (PM2.5), a cause of mortality, decreased visibility, and climate change.
This research provides some of the first measurements of neighborhood-scale anthropogenic emissions of CO2, NOx, VOCs and PM2.5 and as a result, the first opportunity to validate official emission inventories directly. The results indicate that a mobile eddy covariance system can be used successfully to measure fluxes of multiple pollutants in a variety of urban settings. With certain pollutants in certain locations, flux measurements confirmed inventories, but in others, they disagreed by factors of up to five, suggesting that parts of the inventory may be severely over- or underestimated. Over the scale of a few kilometers within a city, emissions were highly heterogeneous in both space and time. FLAME-based measurements also confirmed published emission factors from coal barges and showed that idling vehicles are the dominant source of emissions of air toxics around seven schools in southwest Virginia.
Measurements from this study corroborate existing emission inventories of CO2 and NOx and suggest that inventories of PM2.5 may be overestimated. Despite the tremendous spatial and temporal variability in emissions found in dense urban areas, CO2 fluxes on average are very similar across the areas in this study and other urban areas in the developed world. Nevertheless, the high level of variability in spatial and temporal patterns of emissions presents a challenge to air quality modelers. The finding that emissions from idling vehicles at schools are likely responsible for creating hot spots of air toxics adds to the urgency of implementing no-idling and other rules to reduce the exposure of children to such pollutants. Ultimately, the results of this study can be used in combination with knowledge from existing emission inventories to improve the science and policies surrounding air pollution.Ph. D.
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Bozon, Nicolas. "Coupling atmospheric dispersion model and Geographical Information Systems : application to pesticide spray drift." Montpellier 2, 2009. http://www.theses.fr/2009MON20255.
Full textAbstract:
La pollution atmosphérique par les pesticides issus de la viticulture est un problème environnemental majeur affectant aussi bien la santé humaine que l'équilibre des écosystèmes. La modélisation de la dispersion atmosphérique et l'usage des systèmes d'information géographique peuvent permettre de quantifier spatialement la pollution atmosphérique sur le territoire. Cette thèse est fondée sur le couplage d'un modèle de dispersion atmosphérique des pesticides et d'un système d'information géographique, destiné à prédire et cartographier la pollution atmosphérique après les traitements phyto-sanitaires. L'introduction des modèles numériques de terrains et des changements d'échelle dans la modélisation à complexité réduite sont présentés et illustrés. La plateforme de simulation numérique découlant du couplage prend la forme d'un plugin au logiciel Quantum GIS, explorant ainsi le potentiel des SIG libres dans l'implémentation de modèles physiques complexes. La plateforme est finalement utilisée sur un bassin versant viticole du Sud de la France, et un scénario d'analyse des risques de pollution est proposéAtmospheric pollution due to agricultural pesticide for viticulture is a major concern today, regarding both public health, sustainable agriculture and ecosystems quality monitoring. Atmospheric dispersion modeling and the use of geographic information systems allow us to spatially quantify the atmospheric pollution on a given area. This thesis is based on the coupling of an atmospheric dispersion model and a geographic information system, in order to predict and map atmospheric pollution after pesticide spraying applications. Implementations of digital elevation models and scale changes into the reduced order modeling are described and illustrated. The resulting simulation platform is presented as a Quantum GIS software plugin, thus exploring the Open Source GIS capabilities to implement complex physical models. The platform is finally used on a typical Souther French wine-growing area, and a pollution risk analysis scenario is proposed
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Hettiyadura, Anusha Priyadarshani Silva. "Quantification of organosulfates and their application in source apportionment of atmospheric organic aerosols." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6132.
Full textAbstract:
Organic aerosol is a major constituent of atmospheric fine particulates (PM2.5), which adversely affect human health and change the Earth’s radiative energy balance. Primary organic aerosol is directly emitted from sources and secondary organic aerosol (SOA) is formed in the atmosphere following oxidation of volatile organic compounds (VOC) from anthropogenic and biogenic sources. Biogenic SOA is enhanced by anthropogenic pollutants such as sulfate and NOx that mainly come from fossil fuel combustion. However, the extent to which the anthropogenic pollutants enhance biogenic SOA in different environments is unknown. The central hypothesis of this thesis is that organosulfates, organic compounds containing a sulfate ester group, are useful as tracers for anthropogenically-influenced biogenic SOA. This research aims to provide a better understanding of the sources of PM2.5 organic carbon (OC), particularly secondary organic carbon (SOC), through the inclusion of organosulfates in an organic tracer-based source apportionment model. The specific objectives of this research include 1) development of a highly sensitive and accurate method to quantify highly polar organosulfates in atmospheric aerosols, 2) identification and quantification of major organosulfate species in the ambient air, and 3) determination of anthropogenic and biogenic sources and their contributions to PM2.5 OC using an organic tracer-based positive matrix factorization (PMF) model.
A highly sensitive and accurate method was developed and validated for the quantification of highly polar organosulfates using hydrophilic interaction liquid chromatography (HILIC) and tandem mass spectrometry (MS/MS). The developed method shows excellent retention of carboxylic acid and hydroxyl containing organosulfates. The HILIC-MS/MS method was applied to PM2.5 samples collected in summer 2013 at a rural site in Centreville, AL. Quantified organosulfates accounted for approximately 0.3% of PM2.5 OC. Other major organosulfates, for which standards are not available, were monitored by their fragmentation to the bisulfate anion and/ or sulfate ion radical. The major organosulfates were determined to be 2-methyltetrol sulfate and other isoprene-derived organosulfates. Eight sources of the PM2.5 OC in Centreville, AL were identified using PMF model through the application of organosulfates and commonly used organic tracers measured in samples collected during the daytime and nighttime: vehicle emissions (8%), prescribed burning (11%), isoprene SOC formed under low-NOx (13%) and high-NOx conditions (11%), SOC formed by photochemical reactions (9%), oxidatively aged biogenic SOC (6%), sulfuric acid-influenced SOC (21%), and monoterpene SOC formed under high-NOx conditions (21%). The organosulfates enabled organic tracer-based PMF to resolve sulfuric acid-influenced SOC, while the daytime and nighttime measurements enabled organic tracer-based PMF to resolve SOC formation pathways with diurnal variations (e.g. SOC formed by photochemical reactions). The PM2.5 OC in Centreville was mainly secondary in origin (81%) and was influenced by NOx, ozone (a product of photochemical reactions of NOx and VOC), and sulfuric acid. Together, primary and secondary OC influenced by the fossil fuel use was 76%. Thus, the majority of the PM2.5 OC in Centreville during summer can be controlled by the reduction of fossil fuel use.
The HILIC-MS/MS method was also applied to daily PM2.5 samples collected from an urban site in Atlanta, GA during August 2015. The major organosulfate species identified in Atlanta were dominated by 2-methyltetrol sulfate and other isoprene-derived organosulfates, similar to Centreville. They contributed 16% of PM2.5 OC and accounted for the majority of the isoprene-derived SOA that had not previously been identified at the molecular level. The concentrations of the major isoprene-derived organosulfates in Atlanta were two to six times higher than in Centreville. The greatest enhancement was obtained for 2-methylglyceric acid sulfate, a known isoprene SOA tracer formed under high-NOx conditions, reflecting the 15 times higher average NOx concentration in Atlanta during August 2015 compared to Centreville in summer 2013. These results indicate that NOx had a stronger influence on isoprene-derived organosulfate formation in urban Atlanta compared to rural Centreville.
Overall, these results indicate that organosulfates are useful tracers for anthropogenically-influenced biogenic SOA. Thus, it is important to quantify them for use in organic tracer-based PMF modeling to determine the anthropogenically-influenced biogenic SOC in PM2.5 OC.
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DI, NOIA ANTONIO. "Application of neural networks to atmospheric ozone retrievals from the ozone monitoring instrument." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2012. http://hdl.handle.net/2108/204185.
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Yip, Zheng. "North Atlantic tropical cyclogenesis potential in climate change: An application of artificial neural networks." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95238.
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A new methodology employing artificial neural networks is used to project changes in North Atlantic tropical cyclone (TC) genesis potential (GP) and potential intensity (PI) in warming climate. The input data is from simulations of 5 climate models. Emanuel's revised Genesis Potential Index is used to measure the GP. Changes are identified in the 1st (P1) and 2nd (P2) half of the 21st century. The early and late summer GP decreases throughout the 21st century over most of the eastern half of the basin and increases off the east coast of USA and the north coast of Venezuela during P1. The peak summer GP over the region of frequent TC genesis is projected to decrease more substantially in P1 than in P2. PI changes are generally positive and more apparent over the western half of the basin. Vertical wind shear (850-200hPa), temperature (600hPa), and PI are the most important controls of TC genesis in the NAB under changing climate.Nous présentons une nouvelle approche à base de réseaux de neurones artificiels pour étudier les changem ents que connaîtraient le potentiel de formation (PF) et l'intensité potentielle (IP) des cyclones tropicaux dans le Bassin de l'Atlantique Nord, dans un futur réchauffement climatique. Les données utilisées sont issues de simulations de 5 modèles climatiques. L'indice de Potentiel de Formation révisé par Emanuel est utilisé pour évaluer le PF des cyclones. Des changements sont identifiés pour la 1ère (P1) et 2ème (P2) moitié du 21ème siècle. Le PF en début et fin d'été diminue au cours du 21ème siècle sur la majeure partie de la moitié est du bassin, alors qu'il augmente au large de la côte est des États-Unis et au large de la côte nord du Venezuela pendant P1. Le point culminant du PF estival au-dessus de la région où génération de cyclones tropicaux est fréquente est projetée à diminuer plus nettement pendant P1 que P2. Les changements que connaîtrait l'IP sont généralement positifs et plus marqués sur la moitié ouest du bassin. Le cisaillement des vents verticaux (850-200hPa), la température (600hPa) et l'intensité potentielle sont, dans un contexte de changement climatique, les facteurs les plus importants dans la formation de cyclones tropicaux dans le Bassin de l'Atlantique Nord.
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Inomura, Keisuke. "Development of a cell flux model and its application to nitrogen fixers." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107105.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
.Quantifying and modeling the macroscopic ecological and biogeochemical effects of cellular physiology and metabolism is a challenge: most quantitative "systems biology" models are focused at the metabolic and individual scale. In this study, we develop and apply a simplified metabolic model at the individual scale, which we call "the cell flux model", in order to quantify costs and benefits of nitrogen fixers. In Chapter 2, we develop the cell flux model for heterotrophic nitrogen fixers in order to examine and quantify the direct and indirect energy costs of nitrogen fixation. We have tested the model using data from Azotobacter vinelandii grown in continuous culture. The model indicates that the direct energy cost of nitrogen fixation is relatively small, whereas oxygen management to protect nitrogenase becomes dominant as the oxygen concentration increases. In Chapter 3, we have adapted the cell flux model of Azotobacter vinelandii to consider the organisms' response to the presence of ammonium in the environment. The model shows that even under high oxygen concentrations and with high ambient concentrations of fixed nitrogen, nitrogen fixation occurs if there is sufficient carbohydrate resource available to fully consume intracellular oxygen. Most nitrogen fixers in the ocean are photoautotrophic. Thus, in Chapter 4, we extend the cell flux model to resolve phototrophy and use it simulate and study light and nutrient colimitation of Synechococcus spp. as observed in published continuous culture studies. In order to capture the observed variations in elemental composition with light and resource availability, we resolve the macromolecular composition of the cells. The highly simplified model is able to simulate key aspects of the laboratory cultures including explicit prediction of the average elemental composition and maximum growth rates under different environmental limitations. In Chapter 5, we have applied the cell flux model to simulate laboratory studies, and interpreted the ecological costs for the photoautotrophic nitrogen fixer Crocosphaera watsonii. Our model suggests that these organism also utilize multiple oxygen protection strategies, including scavenging oxygen with excess respiration, changing their size, and using extracellular polymeric substances as a barrier to the invasion of oxygen into the cell.
by Keisuke Inomura.
Ph. D.
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Dennedy-Frank, P. James (Peter James). "Low-degree convection with melting and application to the Martian northern hemisphere." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37983.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2006.Includes bibliographical references (leaves 57-64).
I investigate the hypothesis that the young and smooth surface of the Martian northern hemisphere is due to volcanic resurfacing driven by degree-one convection. I implement a batch melting process in a finite element convection model and run numerical experiments to quantify the melt fraction, timing of melting, and timing of the onset of degree-one convection. All models include a stratified viscosity to induce degree-one flow. To assure that the model's result is robust I vary the model's initial conditions, core-mantle boundary temperature and radius, and the thickness of the lithospheric lid. Long-wavelength convection is a consistent result of the viscosity stratification, and degree-one occurs in one third of the numerical experiments. I compare the melt fraction and onset of degree-one convection to the geological evidence from Martian orbiters, rovers, and meteorites. Good agreement is found between the numerical models and geological evidence, so this model suggests that volcanism driven by degree-one convection may play a significant role in the young age of the northern hemisphere of Mars.
by P. James Dennedy-Frank.
S.M.
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Titov, Mikhail. "Investigation of winter aerosol dispersion using the MM5/WRF-CAMx4 numerical modelling system : application to the aerosol abatement strategy for the city of Christchurch : a thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Environmental Science at the University of Canterbury /." Thesis, University of Canterbury. Geography, 2008. http://hdl.handle.net/10092/1581.
Full textAbstract:
Air circulation and air pollution dispersion models are used by a range of stakeholders involved in managing air quality in New Zealand following the recent establishment and implementation of the National Environmental (Air Quality) Standards by the Ministry for the Environment. MM5-CAMx4 and WRF-CAMx4 numerical modelling systems were utilized to air circulation over the complex terrain of the Christchurch area for investigation applied to winter aerosol pollution, following the recent establishment and implementation of the National Environmental Standards. A new method using several different chemical scenarios is developed to calculate optimal chemical composition of the input gridded aerosol emissions. This method improves the accuracy of predicted PM concentrations. The MM5-CAMx4.2 numerical system is evaluated to predict aerosol concentrations over a 48-72 hour time period for Christchurch for winter 2005. The aerosol concentrations are obtained for four different chemical compositions of the input aerosol emissions. The fine-total PM regression error between observed and modelled aerosol is used to find the minimum difference between modelled and ambient aerosol. Combination of the chemical scenarios with the minimum error between modelled and ambient data is employed to create a new complex chemical scenario. A reduction of the systematic error in the scenario method is achieved by applying the MM5/WRF - CAMx4.2 numerical system and observations for winter 2006, aerosol data from 2 observation sites. Assessment of the efficiency of PM abatement strategies for the period 2005- 2013 is undertaken using winter 2005 meteorology and application of a linear reduction in emissions according to Environment Canterbury proposed plan for aerosol reduction. A new numerical approach to selection of PM monitoring sites optimal localisation is also developed and could be applied to any air pollutant to find the optimal positions for installing new observation sites.
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LeBeau, Raymond Paul. "Simulations of time-dependentthree-dimensional vortices with application to Neptune's Great Dark Spot." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/17433.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997.Includes bibliographical references (p. 201-204).
by Raymond Paul LeBeau, Jr.
Ph.D.
46
Shang, Xuefeng Ph D. Massachusetts Institute of Technology. "Inverse scattering : theory and application to the imaging of the Earth's seismic discontinuities." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87511.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references.
In this thesis we further develop concepts in inverse scattering, which enable higher resolution imaging with data from dense networks and arrays. We apply the new methods to studies of the crust beneath south Tibet and the core-mantle boundary (CMB) region beneath Central America and East Asia. First, we develop a new method, which we call passive source reverse time migration (RTM), for subsurface imaging with teleseismic array data. Multi-component array data are first propagated backward by solving the elastic wave equation. After polarization separation, a modified cross-correlation imaging condition between P and S wave constitutes is applied to obtain an inverse scattering transform. From synthetic experiments it is evident that for complex geological structures RTM is superior to traditional receiver functions analysis, such as common conversion point (CCP) stacking. Two preprocessing steps are required for RTM application on sparsely sampled teleseismic dataset: source normalization and trace interpolation. The source radiation pattern, especially the polarity of traces, is corrected by multi-channel cross-correlation technique. The unknown source signature is then estimated by principle component analysis and deconvolved from raw data by Wiener deconvolution. Curvelet interpolation with sparsity promotion is employed to interpolate irregularly and sparsely sampled traces into regular and dense grids. Synthetic and real data examples demonstrate that for typical teleseismic acquisition geometry, with 50% to 85% missing traces, the curvelet-based interpolation works remarkably well. The application on Hi-CLIMB array data in Tibetan plateau reveals clear and continuous Moho discontinuity at the depth of about 70 km, as well as fine crustal structures. Second, we use a high-frequency approximation of inverse scattering, generalized Radon transform (GRT), to probe the lowermost mantle beneath Central America and East Asia. Inverse scattering of about 130,000 ScS traces and 120,000 SKKS traces reveals multiple reflectors above the conventional D" region. This result is inconsistent with expectations from a pure thermal response of a single isochemical post-perovskite transition but can be explained with post-perovskite transitions in differentiated slab materials. Our results imply that the lowennost mantle is more complex than hitherto thought and that the presence of interfaces and compositional heterogeneity beyond the D" region.
by Xuefeng Shang.
Ph. D.
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Campbell, Jeffrey William. "Evaluation of GEOSTAT data and application to variability of the Northeast Pacific Ocean." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/51465.
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Rodgers, Michael O. "Development and application of a photofragmentation/laser-induced flourescence detection system for atmospheric nitrous acid by Michael Owen Rodgers." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/25954.
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Pencheva, Mariana. "Modelling of atmospheric pressure argon plasmas: application to capacitive RF and surface microwave discharges." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209451.
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This work is focused on modelling of atmospheric pressure high frequency (HF) discharges operated at relatively low power densities. Two types of devices are considered – the radio frequency capacitively coupled atmospheric pressure plasma jet and the microwave discharge sustained by surface electromagnetic waves. They are addresses as the plasma shower and the surface-wave discharge (SWD). Both of the considered devices operate in argon at atmospheric pressure (p = 1 bar). However, the difference in the frequency of the power coupling mechanism induces a big difference in plasma properties. This implies also that different modelling approaches have to be employed.Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Crawley, Louise Helen. "Application of Non-Dispersive Infrared (NDIR) Spectroscopy to the Measurement of Atmospheric Trace Gases." Thesis, University of Canterbury. Chemistry, 2008. http://hdl.handle.net/10092/2160.
Full textAbstract:
Gaseous pollutants have been an environmental concern since 1956, when the first clean air act was established in the United Kingdom. Monitoring of gaseous emissions is a legal requirement in most countries, and this has generated a large demand for inexpensive, portable, and versatile gas analysers for the measurement of gaseous emissions. Many of the current commercial gas analysers have differing advantages and disadvantages, however, high cost is an important factor. Instruments with low detection limits and the ability to measure multiple gases tend to be very expensive, whereas, single gas analysers tend to be much more affordable. A non-dispersive infrared (NDIR) spectrometer, originally developed for a previous M.Sc. project, has been further developed in order to increase the sensitivity and to extend the instrument to the measurement of multiple gases. This type of instrument would be useful for environmental, industrial, and research applications. The instrument was inexpensive to construct when compared with the cost of current commercial gas analysers, is robust, and is partially portable around the laboratory. Infrared radiation from two infrared sources, pass through adjacent sample and reference cells and into corresponding detector cells. A sample comprising the analyte gas is contained in the sample cell, a non-absorbing gas, such as argon, is contained in the reference cell, and pure analyte gas of interest is contained in the detector cells. The two identical detector cells, which follow the reference and sample cells in the infrared optic paths, communicate only through a differential capacitance manometer which accurately measures small pressure differences between the otherwise identical cells. Any trace amount of the analyte gas in the sample cell absorbs radiation, depleting the appropriate infrared frequencies. This results in lower energy incident on the sample detector cell, reducing the infrared induced pressure rise in that detector cell compared to the reference side detector cell. The pressure difference is ii proportional to the concentration of absorbing gas in the sample cell, which is then determined using a calibration graph. Carbon dioxide, methane, and nitrous oxide calibration graphs from 40 ppm to 1000 ppm have been successfully established, and detection limits of 10.33 ppm for CO₂, 8.81 ppm for N₂O and 9.17 ppm for CH₄ were determined. Dried air samples measured using the spectrometer gave an average value of 382 ± 9.6 ppm which can be compared to the latest global atmospheric loading of 382.4 ppm.