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Showing 1 to 19 of 19 for “"Photoacoustic Spectroscopy"”.
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Extensions of quartz-enhanced photoacoustic spectroscopy
… of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trace concentrations of NH3 in the 1.53 pm region with a DFB laser without the use of a resonating cavity. I analyzed the process of QEPAS both analytically and experimentally. First, absorption spectroscopy was …
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Toward ultra-broadband photoacoustic spectroscopy of supercooled liquids
… broad a range of frequencies and time scales. Photoacoustic spectroscopy is an ideal technique for probing the dynamics of supercooled liquids because it provides direct access to mechanical relaxation. Currently, photoacoustic spectroscopy of supercooled liquids has been carried out in the …
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Standoff Laser Interferometric Photoacoustic Spectroscopy for the Detection of Explosives
… safer and this is the impetus for this work. Photoacoustic spectroscopy is well suited to the task of explosive detection at a standoff distance. A detailed theory of the standoff measurement of the physical response of a system to photoacoustic excitation with an interferometric sensor has …
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Photoacoustic measurement of bandgaps of thermoelectric materials
… on the order of microns for thermoelectrics. Photoacoustic spectroscopy is used in this work to optically probe the thermoelectric bandgap, without the need to produce thin samples. Photoacoustic spectroscopy allows simultaneous measurements of the thermal conductivity and optical absorption …
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Analysis of the single scatter albedo and imaginary index of refraction of fused silica nanospheres via a photoacoustic technique and a novel aerosol generator
… silica spheres using the in-situ technique of photoacoustic spectroscopy. Through the use of a novel aerosol generator, sample aerosol streams were generated and sampled via a 4 wavelength photoacoustic spectrometer system. The measured SSA was used to calculated a value for the imaginary index …
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Photoacoustic photonic crystal fiber gas sensor
Photoacoustic spectroscopy (PAS) is a form of laser spectroscopy that has demonstrated very high sensitivity for gas detection. Typically, PAS involves the absorption of a modulated laser beam by the gas species of interest, and the subsequent generation of acoustic waves at the modulation …
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Aspects of radiation curing
… salts was monitored in situ by infrared and UV spectroscopy and hydrogen fluoride is credited as the true initiator of the cationic polymerisation of epoxides in an open system. The UV photolysis of the aforementioned onium salts led to the production of volatiles, resulting in the …
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Photoexcited hypersonic surface acoustic waves propagating under periodic metal grating
… SAW are scientifically significant for photoacoustic spectroscopy and metrology of nanostructures in addition to investigations of phonon mediated heat transport. \\ In this work, we study the propagation of hypersonic surface acoustic waves (~10-20 GHz) in silicon with aluminum gratings …
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Investigations of ultra shallow junction ion implanted biaxial tensile strained silicon by means of X-Ray, Raman and photoacoustic techniques
… x-ray diffraction and micro-Raman (µ-Raman) spectroscopy. Synchrotron x-ray topography is used to identify the strain relaxation processes in both the "-Si epilayer and the Si1!xGex virtual substrate. Data obtained during the project called into question the validity of traditional µ-Raman …
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The degradation of gel-spun poly(beta-hydroxybutyrate) fibrous matrix
… diameter distributions and Fourier infra-red photoacoustic spectroscopy. The accelerated degradation model was used to predict the degradation of the samples in the physiological model and this provided a clearer picture as to the samples potential biodegradation as medical implantation …
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Dynamics of Atmospherically Important Triatomics in Collisions with Model Organic Surfaces
… analysis techniques: cavity ring-down aerosol spectroscopy (CRD-AS) at 355 nm and 532 nm, photoacoustic spectroscopy (PAS) at 532 nm, and an aerosol mass spectrometer (AMS). Heterogeneous reactions may lead to the nitration of organic-coated aerosols, which may account for atmospheric …
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Miniaturization and integration of photoacoustic detection
Photoacoustic spectroscopy (PAS) is an absorption spectroscopy technique that is currently used for low-level gas detection, biological studies, and catalyst characterization. In PAS, the incident radiation is modulated at an acoustic frequency. In the presence of an absorbing species, the periodic …
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Modeling and Sensitivity Analysis for Trace Gas Sensors
… 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 models of QEPAS sensors employ one-way coupling from the fluid to the structure that requires prior experimental …
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Mid-Infrared Spectral Characterization of Aflatoxin Contamination in Peanuts
… research focused on development of vibrational spectroscopy based methods for detection and separation of contaminated peanut samples. Aflatoxin incidence, as a chemical contaminant in peanut paste samples, was investigated, in terms of spectral characteristics using FTIR-ATR. The effects of …
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Effect of pretreatment on the breakdown of lignocellulosic matrix in barley straw as feedstock for biofuel production
… physical qualities. Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) was further applied on the RF alkaline and SE samples in light of the need for rapid and easy quantification of biomass chemical components (cellulose, hemicellulose, and lignin). The results obtained show that …
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Development Of A Supercontinuum Based Photoacoustic Aerosol Light Absorption And Albedo Spectrometer (PALAAS)
… of a supercontinuum based multi-wavelength photoacoustic instrument to measure the light absorption and scattering coefficients of aerosols. Collimation techniques for supercontinuum sources using lens-based and off-axis parabolic mirror-based collimators were evaluated and it was determined …