Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 71 for “"trace gas"”.
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Trace gas spectrometry using quantum cascade lasers
… the absorption of infrared light by molecular gases using a still relatively new light source. This thesis will present the results of experimental work carried out during studies on the detection of gases and the nonlinear optical effects that arise from the absorption of light from a rapid …
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Modeling and Sensitivity Analysis for Trace Gas Sensors
Trace gas sensors can detect very low concentrations of gases such as methane and sulfur dioxide. An important class of trace gas sensors are quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors, which employ a quartz tuning fork (QTF) and modulated laser to detect trace gases. Existing …
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Trace Gas-Induced Brine and Disordered Interfacial Layers on Ice
… to significantly alter the interaction between trace gases and ice surfaces. In order to better predict the impact of a warming climate on atmospheric composition, a quantitative physical understanding of the interaction between ice surfaces and key atmospheric trace gases is essential. In the …
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Near-infrared tunable diode laser absorption spectrometer for trace gas detection
… high resolution spectroscopic measurements of gases of atmospheric interest, including, methane, nitrous oxide and ammonia has been carried out. A rotational analysis of nitrous oxide was performed. A coolable Herriott cell capable of operating between 77 and 298 K has been designed, built and …
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Mechanisms and controls of trace gas releases from a northern peatland
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1991.
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Characterization of reactive and non reactive trace gas fluxes in and above soil
… and serves as the only long-lived atmospheric tracer of human perturbations of the global nitrogen cycle. Nitrogen oxides belong to the so called indirect greenhouse gases. These indirect greenhouse gases control the abundances of direct greenhouse gases through atmospheric chemistry and …
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Tomographic Reconstruction of 2-D Atmospheric Trace Gas Distributions from Active DOAS Measurements
… technique for the measurement of atmospheric trace gas distributions. Standard analytical methods for the reconstruction of a scalar field from its line integrals cannot be used due to low numbers of light paths (10-50) and their irregular arrangement, so that the concentration field is …
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Analysis of Trace Gas Heterogeneity using In-Situ and Remote Sensing Measurement Techniques
… of retrieving vertical column densities of trace gases in the atmosphere. While the technique can be used to retrieve vertical profiles of trace gases this retrieval is not applicable to Mobile-DOAS measurements due to the lengthy measurement times. In addition, the requirement for rapid …
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Marine atmospheric influences on trace gas observations and transport during the ICARTT 2004 campaign
<p>The transport of pollutant trace gases and aerosols above coastal waters is of eminent importance to air quality and global climate processes. The research presented in this dissertation is a two-part investigation of this transport as observed during the ICARTT campaign, with focus devoted to …
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Airborne Multi AXis DOAS instrument and measurements of two-dimensional tropospheric trace gas distributions
… a qualitatively good observation of tropospheric trace gases (e.g. NO2 and HCHO) additional information about the mixing layer height and the aerosol extinction is essential. This information can be gained from either independent measurements or retrieved from the measurements themselves. For …
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Derivation of Trace Gas Information combining Differential Optical Absorption Spectroscopy with Radiative Transfer Modelling
… To derive quantitative distribution data of trace gas distributions it is necessary to combine novel measurement techniques like Multi-Axis DOAS with realistic radiative transfer modelling. In this thesis three three-dimensional spherical Monte Carlo based radiative transfer model TRACY is …
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Deducing trace gas emissions using an inverse method in three-dimensional chemical transport models
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993.
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Trace gas imaging in the atmosphere with a Fabry-Pérot interferometer - a case study for sulfur dioxide
Atmospheric trace gas imaging allows the direct assessment of chemical dynamics, transport and mixing processes and is therefore desired in atmospheric physics and chemistry. For instance, the application of imaging measurements at trace gas point sources can substantially improve the determination …
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Development and Application of a Versatile Balloon-Borne DOAS Spectrometer for Skylight Radiance and Atmospheric Trace Gas Profile Measurements
… Carlo RT model. The new method of atmospheric trace gas profiling by balloon-borne UV/vis limb scatter measurements is tested against simultaneous measurements of the same parameters available from in-situ, or UV/vis/near IR solar occultation observations performed on the same payload. …
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Investigating the effect of variability in biomass burning emissions inventories on GEOS-Chem modeled trace gas and aerosol concentrations
Over the past century, global wildfire activity has intensified due to increasing mean temperatures. However, emissions inventories used for modeling the impact of fires on air quality and climate exhibit several discrepancies in emissions estimates, largely due to the different types of satellite …
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Laser spectroscopic trace chemical sensors for environmental sensor networks and portable medical devices
… of the first laser spectroscopy based trace-gas sensors with sensor characteristics which simultaneously satisfy low cost, handheld footprint, low power, and long term autonomous operation while still providing part-per-billion detection sensitivity and negligible interference to enable …
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