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Frazier, Janay Amber Wright. "High-Definition Raman-based Distributed Temperature Sensing." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/95934.
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Distributed Temperature Sensing (DTS) has been used in a variety of different applications. Its ability to detect temperature fluctuations along fiber optic lines that stretch for several kilometers has made it a popular topic in various fields of science, engineering, and technology. From pre-fire detection to ecological monitoring, DTS has taken a vital role in scientific research. DTS uses the principle of backscattering by three different spectral components, e.g., Rayleigh scattering, Brillouin scattering, and Raman scattering. Although there have been various improvements to DTS, its slow response time and poor spatial resolution have been hard to overcome. Its repetition rate is low because the pulse must travel the distance of the fiber optic line and return to the detector to record the temperature change along the fiber. A spatial resolution of 7.4 cm with a response time as low as 1 second and a temperature resolution of the 0.196 ℃ is achieved from the current Raman-based DTS system. This research proves that high-spatial resolution can be obtained with the use of a Silicon Avalanche Photodetector with a 1 GHz bandwidth.MS
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Liu, Bo. "Sapphire Fiber-based Distributed High-temperature Sensing System." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82741.
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From the monitoring of deep ocean conditions to the imaging and exploration of the vast universe, optical sensors are playing a unique, critical role in all areas of scientific research. Optical fiber sensors, in particular, are not only widely used in daily life such as for medical inspection, structural health monitoring, and environmental surveillance, but also in high-tech, high-security applications such as missile guidance or monitoring of aircraft engines and structures. Measurements of physical parameters are required in harsh environments including high pressure, high temperature, highly electromagnetically-active and corrosive conditions. A typical example is fossil fuel-based power plants. Unfortunately, current optical fiber sensors for high-temperature monitoring can work only for single point measurement, as traditional fully-distributed temperature sensing techniques are restricted for temperatures below 800°C due to the limitation of the fragile character of silica fiber under high temperature.
In this research, a first-of-its-kind technology was developed which pushed the limits of fully distributed temperature sensing (DTS) in harsh environments by exploring the feasibility of DTS in optical sapphire waveguides. An all sapphire fiber-based Raman DTS system was demonstrated in a 3-meters long sapphire fiber up to a temperature of 1400°C with a spatial resolution of 16.4cm and a standard deviation of a few degrees Celsius.
In this dissertation, the design, fabrication, and testing of the sapphire fiber-based Raman DTS system are discussed in detail. The plan and direction for future work are also suggested with an aim for commercialization.Ph. D.
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Wang, Jing. "Distributed Pressure and Temperature Sensing Based on Stimulated Brillouin Scattering." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/78066.
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Brillouin scattering has been verified to be an effective mechanism in temperature and strain sensing. This kind of sensors can be applied to civil structural monitoring of pipelines, railroads, and other industries for disaster prevention. This thesis first presents a novel fiber sensing scheme for long-span fully-distributed pressure measurement based on Brillouin scattering in a side-hole fiber. After that, it demonstrates that Brillouin frequency keeps linear relation with temperature up to 1000°C; Brillouin scattering is a promising mechanism in high temperature distributed sensing.
A side-hole fiber has two longitudinal air holes in the fiber cladding. When a pressure is applied on the fiber, the two principal axes of the fiber birefringence yield different Brillouin frequency shifts in the Brillouin scattering. The differential Brillouin scattering continuously along the fiber thus permits distributed pressure measurement. Our sensor system was designed to analyze the Brillouin scattering in the two principal axes of a side-hole fiber in time domain. The developed system was tested under pressure from 0 to 10,000 psi for 100m and 600m side-hole fibers, respectively. Experimental results show fibers with side holes of different sizes possess different pressure sensitivities. The highest sensitivity of the measured pressure induced differential Brillouin frequency shift is 0.0012MHz/psi. The demonstrated spatial resolution is 2m, which maybe further improved by using shorter light pulses.Master of Science
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Dhliwayo, Jabulani. "Stimulated Brillouin scattering for distributed temperature sensing." Thesis, University of Kent, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242858.
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Read, Tom Oliver Trevett. "Applications of distributed temperature sensing in subsurface hydrology." Thesis, University of East Anglia, 2016. https://ueaeprints.uea.ac.uk/59401/.
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In the study of dynamic subsurface processes there is a need to monitor temperature and groundwater fluxes efficiently in both time and space. Distributed Temperature Sensing has recently become more accessible to researchers in Earth Sciences, and allows temperatures to be measured simultaneously, at small intervals, and over large distances along fibre optic cables. The capability of DTS in conjunction with heat injection to detect groundwater fluxes, is assessed in this thesis using a combination of numerical modelling, laboratory tests, and field trials at the Ploemeur research site in Brittany, France. In particular, three methodological approaches are developed: thermal dilution tests, point heating, and the hybrid cable method. A numerical model was developed to assess the sensitivity range of thermal dilution tests to groundwater flow. Thermal dilution tests undertaken at Ploemeur showed lithological contrasts, and allowed the apparent thermal conductivity to be estimated in-situ, but failed to detect previously identified transmissive fractures. The use of DTS to monitor in-well vertical flow is then investigated. This is first using a simple experiment deploying point heating (T-POT), which tracks a parcel of heated water vertically through the borehole. The method allowed for the relatively quick estimation of velocities in the well. The use of heated fibre optics is then trialled, and through a field test was shown to be sensitive to in-well vertical flow. However, the data suffered from a number of artefacts related to the cable installation. To address this, a hybrid cable system was deployed in a flume to determine the sensitivity relationship with flow angle and electrical power input. Additionally, a numerical model was developed, which suggested a lower limit for velocity estimation due to thermal buoyancy. With the emergence of Distributed Acoustic Sensing, fibre optics may become an increasingly practicable and complete solution for monitoring subsurface processes.
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Moa, Sandberg. "Distributed Temperature Sensing för kontroll av inläckage i spillvattenledningar." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-445633.
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Infiltration and inflow (I/I) are common problems in the foul sewer system. A method to detect I/I that is not commonly used in Sweden is DTS, Distributed Temperature Sensing. DTS is based on continuous measurements of temperature over a predetermined distance in the sewer system. The I/I is detected as temperature differences in the temperature data that is registered in the sewer system. The measurements often take place over a couple of weeks or months in the sewer system. The aim of this project was to review previous studies where DTS was used to detect I/I in foul sewers. Data from a wastewater treatment plant in Umeå together with meteorological data were analysed to be able to visualize the problem of I/I and then suggest how DTS can be applied in Sweden. Both automated and visual analyses was performed to find if there were any relationships between wastewater temperature, wastewater flow and precipitation. The outcome was that it is possible to apply DTS in the foul sewages to detect I/I. DTS seemed to be able to detect I/I in all types of sewage material, however it is dependent on that the I/I temperature differs from the temperature of the foul sewage water. It is an expensive technique but if it is meant to be used many times to analyse bigger areas it can be worth the costs. If larger areas are to be investigated, the costs for DTS and current methods are approximately the same. At the wastewater treatment plant in Umeå, a slight relationship between wastewater temperature, wastewater flow and precipitation could be detected. The degree of dilution was calculated to 1,34 which means that about 25% of the sewage water is I/I. The conclusion from this was that I/I exists in the foul sewers in Umeå. The leakage points could not be located with this analysis. DTS could be a possible method to detect the leakage points of I/I in foul sewers. Unlike smoke tests, colouring and video-inspection of the sewers, DTS might be able to detect smaller leakage points.Tillskottsvatten är ett vanligt problem i spillvattenledningsnätet. DTS, Distributed Temperature Sensing är en metod som inte är vanlig i Sverige för kontroll av spillvattenledningar. Tekniken bygger på kontinuerliga temperaturmätningar under en tidsperiod över en förutbestämd sträcka och registrerar temperaturavvikelser som kan uppstå i samband med inläckage av tillskottsvatten. Syftet med projektet var att granska tidigare utförda studier med DTS för att ta reda på hur tekniken kan användas för att lokalisera inläckage i spillvattenledningar. För att vidare illustrera problematiken med tillskottsvatten i spillvattennätet samt föreslå hur DTS kan appliceras i Sverige genomfördes en analys av mätdata på inkommande vatten till reningsverket på Ön, Umeå. Både visuella och automatiserade analyser genomfördes där tolkningar gjordes utifrån mätdata från reningsverket tillsammans med nederbörds- och lufttemperaturdata. En regressionsanalys genomfördes som automatiserad analys för att undersöka eventuella samband mellan spillvattentemperatur, spillvattenflöde och nederbörd. Projektet inleddes med en litteraturstudie där det utreddes hur DTS fungerar teoretiskt och praktiskt. Litteraturstudien visade att DTS är praktiskt möjligt att applicera i spillvattenledningsnätet för att leta inläckagepunkter för tillskottsvatten. Inläckage kan registreras som ökningar eller sänkningar i spillvattentemperaturen beroende på lufttemperaturen. Den är inte beroende av material på ledningarna men däremot är DTS beroende av att tillskottsvattnet är av annan temperatur än spillvattnet. Det är en dyr teknik men kan vara värt investeringskostnaderna om mätningar tänkt ske många gånger under längre perioder. Vid kontroll av större områden med hjälp av röktest kombinerat med färgning av vatten och filmning är kostnaderna ungefär de samma. Utifrån mätdatan från reningsverket och nederbördsdatan från Umeå universitet kunde vissa samband påvisas mellan spillvattentemperatur, spillvattenflöde och nederbörd. Ett visst samband kunde även urskiljas mellan spillvattentemperatur och spillvattenflöde. Utspädningsgraden av spillvattnet beräknades till 1,34 vilket innebär att cirka 25% av vattnet i spillvattenledningarna är tillskottsvatten. Slutsatsen som kunde dras utifrån detta var att tillskottsvatten existerar i spillvattenledningsnätet som leder till reningsverket på Ön i Umeå. Däremot kunde inga slutsatser dras för att säga var inläckage av tillskottsvatten sker. DTS skulle kunna appliceras i ledningsnäten för att undersöka närmare var inläckagepunkterna är och tillskillnad från rökning, färgning av vatten och filmning som används idag kan DTS sannolikt upptäcka fler typer av inläckage.
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Koob, Christopher E. "High temperature fiber optic strain sensing." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-02132009-171339/.
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Ek, Simon. "Distributed Temperature Sensing Using Phase-Sensitive Optical Time Domain Reflectometry." Thesis, KTH, Tillämpad fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-285902.
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This thesis explores and evaluates the temperature measuring capabilities of a phase-sensitive optical time-domain reflectometer (φ-OTDR), which exploits Rayleigh backscattering in normal single mode optical fibers. The device is constructed and its setup explained, and a protocol for making temperature measurements with it is developed. Performance tests are made and the device is shown to achieve fully distributed temperature measurements on fibers hundreds of meters in length with a spatial resolution of 1 m and a temperature resolution of 0.1 K. In addition, the capabilities of the device to measure normal strain in the measurement fiber are tested using the same approach, albeit with less success. The device is capable of very precise measurements, making it very sensitive to the environmental conditions around the measuring fiber but also susceptible to disturbances. Some discussion is had on how to avoid or deal with these disturbances. Furthermore, the technique is shown to be able to run in conjunction with other φ-OTDR measurement techniques from the same device simultaneously.Det här examensarbetet utforskar och utvärderar förmågorna att mäta temperatur hos en fas-känslig optisk tidsdomän-reflektometer (φ-OTDR), som utnyttjar bakåtriktad Rayleigh-spridning i vanliga optiska singelmodfibrer. Anordningen konstrueras och dess komponentstruktur förklaras, och ett protokoll tas fram för att utföra mätningar med den. Prestandatester utförs och anordningen visas kapabel att göra fullt distribuerade temperaturmätningar längs hundratals meter långa fibrer, med en rymdsupplösning på 1 m och en temperaturupplösning på 0.1 K. Dessutom testas förmågan att mäta normaltöjning hos testfibern med samma metod, dock med mindre framgång. Anordningen är väldigt känslig för förhållandena i omgivningen runt mätningsfibern, vilket gör den kapabel till mätningar med mycket hög precision, men också mottaglig för störningar. Lite diskussion hålls kring hur dessa störningar kan undvikas eller hanteras. Vidare visas att mätningstekniken kan köras samtidigt som andra φ-OTDR-baserade tekniker från samma anordning.
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Carver, Robert. "Inferring hydrogeologic processes with distributed temperature sensing in Indian River Bay, Delaware." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114580.
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The interaction between coastal aquifers and estuaries governs many important ecological and water quality processes. The purpose of this research is to use distributed temperature sensing (DTS) in the Indian River Bay estuary, Delaware, to detect differences in variance and mean of temperature at the sediment-water interface. DTS uses the scatter of laser light in a fibre optic cable as a means to repeatedly measure temperature to 0.1˚C at 1m intervals along the length of the cable. Low variances in temperature are interpreted as being the result of the moderating thermal influence of groundwater discharge. From September 16 to 19 2011, two kilometres of DTS cable were deployed in the near shore environment of Holts Landing State Park. Variance increases with distance from shore as the power function s2=-33.63(d ( 1.012)) + 2.685 (r2=0.78). Narrow zones with significantly lower temperature variances (Kruskal-Wallis with Tukey's HSD, p<0.05) and means (Friedman with Tukey's HSD, p<0.05) than adjoining zones exist within the near shore area. Zones of high variance at the western and eastern edges of the study site are associated with ancient shallow peat-filled valleys capped with fine sediments. A broad zone of low variance next to the western valley is interpreted to imply that over-pressured fresh groundwater is discharging at the paleo-valley margins, creating a pattern of submarine groundwater discharge which differs from existing models. An attempt to use diurnal temperature signal amplitudes at various sediment depths to calculate vertical porewater flux were unsuccessful, likely due to rapidly-rising temperatures, interference between tidal and diurnal signals, and a short measurement period. DTS appears to hold promise in detecting temperature patterns simultaneously across different scales, and can be used to rapidly fill in gaps of knowledge in hydrogeologic systems.Les interactions entre les aquifères côtiers et les estuaires régissent beaucoup de processus écologiques importants qui ont des implications sur la qualité de l'eau souterraine et marine. La compréhension de la nature et de l'ampleur de ces interactions est devenu un foyer de recherches, facilité par des avances récentes dans notre capacité de détecter la décharge submersible d'eaux souterraines. Cette étude emploie la détection distribuée de température (DDT) dans l'estuaire de la baie Indian River, sur la côte du Delaware, afin de détecter des différences dans la variance et la moyenne de la température des eaux à l'interface entre la baie et le sédiment dans la zone près du rivage du parc Holts Landing. Des variances basses sont interprétées comme étant le résultat de l'influence de modération des eaux souterraines, compatible avec les autres études, et le fait que les zones peu profondes près du rivage, qui devraient éprouver plus de variation de la température que des zones plus profondes, sont au contraire plus stables. La variance augmente avec la distance du rivage à mesure que la fonction s2=-33.63 (d(- 1.012)) +2.685 (r2=0.78). Près du rivage, il y a des endroits étroits avec des variances (Kruskal-Wallis avec Tukey's HSD, p<0.05) et moyens (Friedman avec Tukey's HSD, p<0.05) sensiblement plus basse que leurs zones proximales. Des zones de la variance élevée aux bords a l'ouest et l'est de l'emplacement d'étude sont associées aux anciennes vallées peu profondes remplies de la tourbe et maintenant couvertes avec les sédiments fins. Une large bande de bas désaccord à côté de la vallée occidentale implique que les eaux souterraines fraîches sosu pression élevée coulent aux marges de la vallée, créant un modèle du SGD qui n'équipe pas des modèles précédents. Une tentative d'employer des amplitudes de signal de la température à de diverses profondeurs de sédiment pour calculer le flux vertical d'eau interstitielle a échoué, probablement en raison des temperatures croissantes, interférence entre les signaux de la marée et diurne, et une période d'échantillon courte. DDT semble tenir la promesse en détectant des tendences de la température à travers différentes gammes simultanément, et peut être employé pour trouver les pieces manquantes de la connaissance des systèmes hydrogéologiques.
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Wang, Haichao. "A fibre optic system for distributed temperature sensing based on raman scattering." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5498.
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This thesis is based on a research project to monitor the temperature profile along a power cable using the fibre optic Distributed Temperature Sensing (DTS) technology. Based on the temperature measured by a DTS system, real time condition monitoring of power cables can be achieved.
In this thesis, there are three main research themes.
1. Develop a DTS system for industrial applications. The entire hardware system and measuring software are developed to be an industrial product. Multiple functions are provided for the convenience of users to conduct temperature monitoring, temperature history logging and off-line simulation.
2. Enhance the robustness of the DTS system. An algorithm for signal compensation is developed to eliminate the signal fluctuation due to disturbance from the hardware and its working environment. It ensures robustness of the system in industrial environments and applicability to different system configurations.
3. Improve the accuracy of the DTS system. A calibration algorithm based on cubic spline fitting is developed to cope with non-uniform fibre loss in the system, which greatly improved the accuracy of the temperature decoding in real applications with unavoidable nonlinear
characteristics.
The developed DTS system and the algorithms have been verified by continuous experiments for about one year and achieved a temperature resolution of 0.1 degree Celsius, a spatial resolution of 1 meter, and a maximum error of 2 degree Celsius in an optic fibre with the length of 2910 metres.
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Dalzell, Craig John. "Two-photon excited fluorescence and applications in distributed optical fibre temperature sensing." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=17062.
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Zhang, Jian. "Nonlinear methods for distributed sensing in high birefringence optical fibres." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300417.
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Szajda, Kenneth S. (Kenneth Stanley). "A high resolution integrated circuit biomedical temperature sensing system." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11846.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Vita.
Includes bibliographical references (p. 226-235).
by Kenneth S. Szajda.
Ph.D.
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Wang, Jiajun. "Sapphire Fiber Based Sensing Technologies for High Temperature Applications." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77149.
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Sapphire fiber has been studied intensively for harsh environment sensing in the past two decades due to its supreme mechanical, physical and optical properties. It is by far the most reported and likely the best optical fiber based sensing technology for sensing applications in temperature beyond 1000°C.
Several sensing schemes have been proposed and studied to date including sapphire fiber extrinsic and intrinsic Fabry-Perot interferometers, fiber Bragg gratings and long period gratings inscribed in sapphire fibers. Lacking the cladding, sapphire fiber is highly multi-moded which renders sapphire fiber based sensor fabrication much more difficult than those based on silica fibers. Among all the reported work on sapphire fiber sensing, the vast majority is for single point temperature measurement.
In this work, different sensing schemes are proposed to enhance the capability of the sapphire fiber based sensing technology. For the single point sensing, a miniaturized sapphire fiber temperature sensor for embedded sensing applications was proposed and studied. The sensors are no more than 75 µm in diameter and are ideal for non-invasive embedded sensing applications. Unlike existing sapphire fiber sensors, the thin film sensors are batch-fabrication oriented and thus have a potential to permit mass production with low cost. In addition to single point sensors, multiplexed sapphire fiber sensing systems are investigated for the first time. Two multiplexed sensing solutions, named frequency-multiplexing and spatial-multiplexing, are proposed and studied to achieve multiplexed sensing based on sapphire fibers.Ph. D.
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Huang, Zhengyu. "Quasi-Distributed Intrinsic Fabry-Perot Interferometric Fiber Sensor for Temperature and Strain Sensing." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/26247.
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The motivation of this research is to meet the growing demand for the measurand high-resolution, high-spatial resolution, attenuation insensitive and low-cost quasi-distributed temperature and strain sensors that can reliably work under harsh environment or in extended structures. There are two main drives for distributed fiber sensor research. The first is to lower cost-per-sensor so that the fiber sensors may become price-competitive against electrical sensors in order to gain widespread acceptance. The second is to obtain spatial distribution of the measurand.
This dissertation presents detailed research on the design, modeling, analysis, system implementation, sensor fabrication, performance evaluation, sensor field test and noise analysis of a quasi-distributed intrinsic Fabry-Perot interferometric (IFPI) fiber sensor suitable for temperature and strain measurement. For the first time to our knowledge, an IFPI sensor using a different type of fiber spliced in between two single-mode fibers is proposed and tested. The proposed sensor has high measurement accuracy, excellent repeatability, a large working range and a low insertion-loss. It requests no annealing after the sensor is made, and the sensor is calibration-free. The sensor fabrication is low-cost and has a high yield rate. The goal for this research is to bring this sensor to a level where it will become commercially viable for quasi-distributed sensing applications.Ph. D.
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Smith, Jeffrey Peter. "Characterization of the Brillouin loss spectrum for simultaneous distributed sensing of strain and temperature." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0017/MQ54649.pdf.
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Wu, Nan. "Optical Frequency Domain Reflectometry Based Quasi-distributed High Temperature Sensor." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/76905.
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Temperature sensing in harsh environment is desired in many areas, such as coal gasification, aerospace, etc. Single crystal sapphire is an excellent candidate for construction of harsh environment sensors due to its superior mechanical and optical properties even at temperature beyond 1600°C. The temperature inside a coal gasifier can be as high as 1200°C. And there is dramatic temperature gradient between the inner and outer layers of the gasifier refractory. Previous work has been done at Virginia Tech's Center for Photonics Technology to design and fabricate a sapphire wafer based Fabry-Perot interferometer (FPI) sensor for temperature sensing in coal gasifiers. The sensor head is based on the use of sapphire wafer which is attached to a lead-in sapphire fiber to be applied in the ultrahigh temperature region; and the sapphire fiber is spliced to a multi-mode fused silica fiber for quality signal transmission in lower temperature areas. One of the challenges encountered by this approach is the shear force to the sapphire fiber, which is caused by the differential thermal expansion between the inner and outer layers of the gasifier refractory. This shear force may be so significant to break the sensor probe. This thesis proposed a free space based interrogation sensing system to address that problem. In this free space based interrogation sensing system, only the sensor head is placed in the inner refractory wall, while all the other parts of the system are placed in the outer refractory or outside the gasifier at the ambient room temperature. An optical frequency domain reflectometry (OFDR) based multiplexed technique is applied in the sensor design to realize temperature measurement at multiple locations along the optical path. In this work, three sapphire wafers based multiplexed temperature sensor is fabricated and calibrated in laboratory. This multiplexed high temperature sensor shows linear response in the range of 20°C ~ 1000°C, with a sensitivity of 1.602?10??/°C and a resolution of 1.3°C.Master of Science
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Marruedo, Arricibita Amaya Irene. "Upscaling of Lacustrine Groundwater Discharge by Fiber Optic Distributed Temperature Sensing and Thermal Infrared imaging." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19365.
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Der Zustrom von Grundwasser zu Seen (lacustrine groundwater discharge, LGD) kann signifikante Auswirkungen auf Qualität und Quantität des Seewassers haben. Viele Ansätze zur Identifikation und Quantifizierung von LGD basieren auf Temperaturunterschieden zwischen Grund- und Seewasser und der Messung des damit einhergehenden Wärmetransports. Ziel der Doktorarbeit ist es, Signalfortpflanzung und -ausbreitung des Grundwasserzustroms von der Punktskala an der Sediment-Wasser-Grenzfläche über den Wasserkörper bis zur Grenzfläche Wasseroberfläche-Atmosphäre zu untersuchen. Getestet wird die Hypothese, dass das im Verhältnis zum Umgebungswasser wärmere und daher leichtere Grundwasser in der kalten Wassersäule aufsteigt und die Detektion von LGD an der Wasseroberfläche mit thermalen Infrarot Aufnahmen (TIR) erlaubt. Zunächst wird mit der hierarchical patch dynamics ein Konzept entwickelt, das eine angemessene Kombination multipler Techniken zur Erfassung von Wärme- und Wasserflüssen anbietet (Kap. 2). Dabei werden verschiedene räumliche Skalen und ökohydrologische Grenzflächen abgedeckt. Darauf basierend werden in einem Mesokosmos-Experiment unterschiedliche LGD-Raten durch den Zustrom von warmem Wasser am Grund eines Outdoor-Pools simuliert (Kap. 3 und 4). Ein Glasfaserkabel (fibre-optic distributed temperature sensing, FO-DTS) wird in verschiedenen Tiefen installiert, um das Wärmesignal des Grundwasserzustroms unter verschiedenen Bedingungen zu verfolgen. Mit einer TIR-Kamera wird die Temperatur des Oberflächenwassers aufgezeichnet. Die Aufnahmen werden mit FO-DTS-Temperaturen von 2 cm unter der Wasseroberfläche validiert. Die Anwendung von TIR und FO-DTS ermöglicht die Detektion von LGD in der Wassersäule und an der Grenzfläche Wasseroberfläche-Atmosphäre. Wolkenbedeckung und der Tagesgang der Netto-Strahlung kontrollieren den Auftrieb von LGD und die Zuverlässigkeit der TIR-Ergebnisse. Die besten Ergebnisse werden bei Bewölkung und nachts erzielt.Lacustrine groundwater discharge (LGD) can have significant impacts on lake water quantity and quality. There is a need to understand LGD mechanisms and to improve measurement methods for LGD. Approaches to identify and quantify LGD are based on significant temperature differences between GW and lake water. The main goal of this PhD thesis is to trace heat signal propagation of LGD from the point scale at the sediment-water interface across the overlying water body to the water surface-atmosphere interface. The PhD thesis tests the hypothesis that the positive buoyancy of warm GW causes upwelling across the cold water column and allows detection of LGD at the water surface by thermal infrared imaging (TIR). First, a general conceptual framework is developed based on hierarchical patch dynamics (HPD). It guides researchers on adequately combining multiple heat tracing techniques to identify and quantify heat and water exchange over several spatial scales and ecohydrological interfaces (Chapter 2). Second, the conceptual framework is used for the design of a mesocosm experiment (Chapters 3 and 4). Different LGD rates were simulated by injecting relatively warm water at the bottom of an outdoor mesocosm. A fiber optic distributed temperature sensing (FO-DTS) cable was installed in a 3D setup in the water column to trace the heat signal of the simulated LGD under different weather conditions and over entire diurnal cycles. Finally, a TIR camera was mounted 4 meters above the mesocosm to monitor water surface temperatures. TIR images were validated using FO-DTS temperature data 2 cm below the water surface (Chapter 4). The positive buoyancy of relatively warm LGD allows the detection of GW across the water column and at the water surface-atmosphere interface by FO-DTS and TIR. Cloud cover and diurnal cycle of net radiation strongly control the upwelling of simulated LGD and the reliability of TIR for detection of LGD at the water surface-atmosphere interface. Optimal results are obtained under overcast conditions and during night.
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OLIVEIRA, LUIZ HENRIQUE PARAGUASSÚ DE. "METROLOGICAL ANALYSIS OF HIGH TEMPERATURE FIBER BRAGG GRATINGS FOR SENSING APPLICATIONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=18805@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA presente tese tem por objetivo estabelecer uma metodologia de caracterização metrológica de redes de Bragg do tipo I, tipo II e tipo regenerada estimando e validando estatisticamente o resultado de medição para medições de altas temperaturas voltadas para aplicações em sensoriamento. Além das telecomunicações, as fibras óticas estão sendo empregadas em aplicações de sensoriamento, visto que, a sílica que as compõem apresenta grande eficiência como meio de transmissão de dados. A crescente demanda por medição em alta temperatura nos processos industriais possibilitou o desenvolvimento de novas tecnologias de medição além das tecnologias tradicionais já utilizadas atualmente. Desta forma, criaram-se as condições necessárias para se introduzir uma nova tecnologia de medição de temperatura com redes de Bragg que apresenta algumas vantagens se comparadas com as tecnologias tradicionais de medição. Apesar de já existirem várias pesquisas a respeito de medição de temperatura com redes de Bragg, nenhuma delas aprofundou as questões metrológicas com as respectivas estimativas das incertezas de medição que envolve todo o processo de medição e caracterização de redes de Bragg em alta temperatura. A adaptação de um sistema tradicional de calibração de instrumentos de medição de temperatura foi projetado e desenvolvido, de tal forma que possibilitou a caracterização dos diferentes tipos de redes. Observou-se que os resultados de medição e as estimativas das incertezas de medição obtidos para todas as redes, se aproximaram satisfatoriamente dos modelos teóricos utilizados, confirmando a adequação dos sistemas de medição de temperatura e sensoriamento ótico.
This thesis aims to establish a methodology for the metrological characterization of Bragg gratings type I, type II and type regenerated statistically thereby estimating and validating the measurement results for high temperature sensing applications. Beyond telecommunications applications, optical fibers are still used for optical sensing, since the silica fiber has great optical efficiency for data transmission. The growing demand for high-temperature measurements in industrial processes has enabled the development of new measurement technologies beyond the traditional technologies already in use today. Thus were created the conditions necessary to introduce a new technology of temperature measurement with Bragg gratings which presents some advantages compared with traditional technologies of measurement. Although there are several prior studies none of those examined the by others about temperature measurement with Bragg gratings, metrological issues, and is particular, the estimate of the measurement uncertainties surrounding the whole process of measurement and characterization of Bragg gratings at high temperature. The adaptation of a traditional system of calibration instruments for temperature measurement was developed and designed in such a way that allowed the characterization of different types of gratings. It was observed that the measurement results and the estimated uncertainties of the measurements obtained for all gratings, successfully approached the theoretical models used, confirming the adequacy of the measurement of temperature and optical sensing.
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White, Julia. "OPTIC FIBER SENSOR FOR STRAIN MEASUREMENTS IN HIGH TEMPERATURE SENSING APPLICATIONS." International Foundation for Telemetering, 2017. http://hdl.handle.net/10150/626969.
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Optic fiber sensors are employed in a variety of applications for the remote measurement of various parameters such as strain, pressure, or temperature. These sensors offer an array of benefits as well including light weight, compactness, and high resolution. In particular, Fabry-Perot interferometers (FPIs) maintain these benefits and can also be made to withstand extremely high temperatures. This advantage of the FPI allows it to be used in harsh environments where many other tools for parameter measurement could not survive. An FPI strain sensor is constructed and tested which has the capabilities to be used at high temperatures of over 1000°C for applications in gas turbine engine testing. This paper discusses the need for high temperature strain sensors in engine testing and this sensor’s capabilities in this application.
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Belal, Mohammad. "Development of a high spatial resolution temperature compensated distributed strain sensor." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/336260/.
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Optical fibre sensors have offered such unrivalled distributed sensing features that they continue to be successfully exploited in various industries for performing continuous measurements of the physical parameters, such as, temperature and strain. However, there arise certain conditions in engineering or materials manufacturing and characterisation environments, when the user seeks to extract the knowledge about a single physical parameter only, say strain, whilst the environment is also subject to temperature. This thesis explores techniques to offer solutions under such conditions by developing a high spatial resolution temperature compensated distributed strain sensor. The preliminary exploration involved exploiting the high spatial resolution Brillouin frequency based Brillouin optical correlation domain analysis technique in combination with the anti Stokes Raman intensity based optical time domain reflectometry technique. This work resulted in achieving a temperature compensated strain resolution of 46με with a spatial resolution of 24cms over a sensing length of 135m. Tackling the impact of modest pump depletion effects on the Raman backscattered signal, a beneficial normalisation protocol was identified. During discussions the possible limitation imposed by the weaker backscattered Raman signal towards achieving any better results on the strain and spatial resolution values, seemed to emerge. In order to enhance the performance of the sensor, anti Stokes Brillouin, which is a stronger back scattered signal, was exploited for the time domain reflectometry measurements. This resulted in 22με of temperature compensated strain resolution with a spatial resolution capability of 10cms. Although the combined performance of the Brillouin frequency in combination with Brillouin intensity proved better than the performance of the Brillouin frequency in combination with Raman intensity, but since the electronic detection system was changed together with pulse widths between the two techniques that it was unclear as to which combinatory technique was best suited for designing the sensor. It is with this view that a theoretical analysis on the performance of the R-OTDR and B-OTDR was carried under similar sensor parameters. B-OTDR is identified as a better technique compared to the R-OTDR towards providing high spatial resolution temperature compensation feature to the Brillouin frequency based distributed strain measurements. The exploration also gave an opportunity to experimentally study for the first time the impact of simultaneously varying temperature and strain on the four Brillouin coefficients. This study proved useful in identifying the corrections to the Brillouin coefficients in order to estimate the true value of strain and temperature in a temperature controlled variable strain environment. The thesis culminates with a summary of work, discussing the thresholds of various non linear effects together with means to improve the performance of the sensor. With the view of enhancing the sensor applicability, schemes of loss compensation are also discussed. In conclusion work for the future is highlighted.
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Reinsch, Thomas [Verfasser]. "Structural integrity monitoring in a hot geothermal well using fibre optic distributed temperature sensing / Thomas Reinsch." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2012. http://d-nb.info/1028623232/34.
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Rabhiou, Abderahman. "Phosphorescent thermal history sensing for advanced condition monitoring in high temperature environment." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/39125.
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Knowledge of the temperatures surfaces are exposed to is crucial in many processes, particularly above 300°C. It is often not possible to measure temperature of all surfaces of interest in real-time. Off-line temperature measurement techniques can be used to record exposure temperatures in such a way that these can be retrieved later off-line, at room temperature. Thermal paint changes colour or surface properties permanently, depending on the maximum temperature they have been exposed to. Thermal paints have been a valuable tool of engine developers for many years, but the use of the existing paints presents a number of challenges if reliable results are to be obtained. Feist et al. [1] proposed a thermal history sensor based on phosphors that undergo permanent changes in their luminescence properties when exposed to high temperatures. These luminescence properties can be interrogated with a light source and measured with standard spectroscopic instrumentation. Phosphorescent thermal history sensors might be applied as paint, coating or as point-sensors. The proposed concept has several advantages over the existing sensors. As the main embodiment is a paint or coating, the proposed sensor would be a direct competing technology to thermal paints. The present study reports on the three main concepts responsible for the permanent changes in some phosphors that have been identified. The mechanisms behind these concepts are outlined and examples are given of phosphors which could be used as sensors. The amorphous-to-crystalline and the thermal damaging concepts were demonstrated in laboratory tests in this work. An extensive characterisation of the luminescence properties dependency on thermal history was conducted on several phosphors: BAM : Eu, BAM : Eu;Mn, Y2O2S : Eu, SrAl2O4 : Eu, Y2SiO5 : Tb, Y AG : Dy and Y SZ=Y AG : Dy. Calibration curves of powder, paint and/or coating embodiments of these phosphors are presented. The amorphous-to-crystalline concept revealed to be the most promising for the application as thermal history sensor, covering a temperature range from 300°C to 1300°C. The amorphous-to-crystalline phosphor Y2SiO5 : Tb was synthesised by sol-gel technique and applied as a paint on a stainless steel disk, which was subsequently exposed to a jet impinging flame. A luminescence readout of the paint after the exposure to the flame revealed a map of temperatures between 300°C and 800°C. The paint was able to highlight the asymmetrical set-up of the impinging flame. The phosphor Y SZ=Y AG : Dy was APS-coated on a rotating turbine blade and inner flame tube of a Rolls-Royce Viper 201 jet engine, which was operated for several hours. Temperature profile maps were obtained after interrogation of the luminescence changes of the coating. These revealed that the probed surface of inner flame tube was exposed to temperatures generally not exceeding than 500°C, apart from local hotspots of 700°C located above the dilution holes. The interrogation of the turbine blade indicated the areas cooled by air streams and maximum temperatures in excess of 800°C.
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Trontz, Adam J. "Metal-Ceramic Coaxial Cable Sensors for Distributed Temperature Monitoring." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1522165065943505.
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Yu, Guo. "Sapphire Based Fiber-Optic Sensing for Extreme High Temperatures." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76982.
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Temperature sensing is one of the most common and needed sensing technique, especially in harsh environment like a coal gasifier or an airplane engine. Single crystal sapphire has been studied in the last two decades as a candidate for harsh environment sensing task, due to its excellent mechanical and optical properties under extreme high temperature (over 1000°C).
In this research, a sapphire wafer based Fabry-Perot (FP) interferometer sensor has been proposed, whose functional temperature measurement can go beyond 1600°C. The size of the sensors can be limited to a 2cm-length tube, with 2mm outer diameter, which is suitable for a wide range of harsh environment applications. The sensors have shown linear sensing response during 20~1200°C temperature calibration, with high sensitivity and resolution, and strong robustness, which are ready for the field test in real-world harsh environment.Master of Science
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Allen, Emily. "Fiber Optic Distributed Temperature Sensing and Vadose Zone Measurements in Mini Anaheim Recharge Basin Orange County, California." Thesis, California State University, Long Beach, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10978729.
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Managed Aquifer Recharge (MAR) systems have become an increasingly important approach to the management of groundwater in Southern California in recent years. This thesis describes an experimental investigation of the vadose zone dynamics beneath a recharge basin used by the Orange County Water District. Soil moisture probes, pressure transducers, and fiber optic distributed temperature sensing (FODTS) at multiple depths beneath the basin were used to monitor infiltration. The purpose was to measure the diurnal temperature flux using heat as a tracer of infiltrating water to gain insight on the influence of basin stage (i.e., water level) on infiltration rate. To increase the temperature resolution from the standard 1 m, we installed a wrapped fiber optic cable at two locations using direct push technology. The wrapped FODTS cable was spliced to a trenched cable that ran laterally across the basin at depths of 30 cm and 1 m, installed during a previous experiment. The wrapped cable was then installed vertically at two locations to observe both the spatial distribution and vertical dynamics of fluid flow at 10 cm intervals. Propagation of the diurnal heat flux at the surface was related to water velocity. The infiltration behavior was affected by subtle changes in stratigraphy below the basin. The heat tracer suggests strong components of horizontal flow due to the presence of thin fine-grained hydrostratigraphic units. Water movement during initial saturation was particularly complex and suggested that simple one-dimensional vertical flow models will not accurately predict infiltration rates. The FODTS system provided high-resolution dynamic imaging of percolation that is not possible using a multi-level transducer system.
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Ma, Lingmei. "High-Speed Quasi-Distributed Optical Fiber Sensing Based on Ultra-Weak Fiber Bragg Gratings." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/74429.
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Invention of silica based optical fiber not only led to revolution in communication but also provided fundamental basis for many research areas. One example area is distributed optical fiber sensing, which has been attracting research interests for decades. Optical fiber sensors are immune to electromagnetic interference, and resistant to corrosion and can endure harsh environment so they have found applications such as structural health monitoring, intrusion detection and oil downhole measurement.
Significant research efforts have been paid to fiber sensing area, many techniques have been developed and some of them have been successfully demonstrated, however achieving both high-speed and long-range is still under intensive research.
This dissertation proposes and demonstrates a technique with the capability of simultaneous long-range and high-speed sensing by employing serial ultra-weak fiber Bragg gratings (UW-FBGs) and dispersive components. Various factors which have influence on the system performance, including wavelength resolution, spatial resolution and sensing rate, are analyzed. Different types of light sources and dispersive units were designed and a sensing system was built. With this system, both static and dynamic response were measured, and a sensing link consisting of more than 2000 UW-FBGs was successfully measured at the speed of 20kHz. The noise sources of the system were also theoretically analyzed and experimentally measured. This demonstrated sensing technique can be applied to long range temperature and strain sensing.Ph. D.
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Benn, Gregory (Gregory Scott) 1977. "Design of a silicon carbide micro-hotplate geometry for high temperature chemical sensing." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/17535.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2001.Includes bibliographical references (p. 127-129).
Silicon carbide, high temperature, chemical sensors are the next step in chemical detection technology; allowing for the development of low cost, robust, lower power, and widely applicable chemical sensors. SiC offers the thermal conductivity, electrical properties, and operating temperatures not currently available in silicon sensors. Boston Micro Systems, a Wobum, Massachusetts based company, has developed technologies for bulk manufacturing of single crystal SiC material. Using this technology, geometries optimizing thermal and electrical performance have been developed to create a SiC micro-hotplate for chemical sensors. Under etching allows for the manufacturing of micro-hotplates. Micro hotplates allow sensors to discriminate between chemical species by controlling absorption and desorption of chemicals. Optimization of the performance of such a device is achieved by developing hotplates that are suspended by necked tethers. Tether designs minimize heat lose from the hotplate and necking creates heat generation regions. The excellent thermal properties of SiC allow heat to be transferred from the necked tethers to the hotplate; producing a hotplate with a uniform temperature distribution, important to the sensitivity and accuracy of the sensing film. Testing of tethered and necked hotplates identified several areas of improvement in hotplate design. These include under etching, improvement in the plates response to thermal stresses, and p-n junction performance improvements. Using such design improvements as tethers and necking the thermal performance of SiC micro-hotplates has improved by two orders of magnitude. This thesis discusses the design, modeling, and testing of single crystal SiC micro-hotplates.
Gregory Benn.
S.M.
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Connolly, William John Cleveland. "An investigation into the use of β-aluminas for high temperature sulphur sensing." Thesis, University of Cambridge, 2000. https://www.repository.cam.ac.uk/handle/1810/251711.
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Over three quarters of the world's flat glass is produced by the float method, in which molten glass is solidified on large baths of liquid tin. Sulphur is a major contaminant in these baths, causing a defect known as top speck. This dissertation describes the design, construction and evaluation of a sensor based upon a solid electrolyte, intended for use in the detection of this sulphur. Three solid electrolytes were produced: strontium and sodium β-alumina by direct methods, and silver β-alumina by ion exchange. The effects of material composition and sintering cycle on density were investigated, and conductivities, atomic structures and microstructures were characterised and shown to agree with published data. A number of cell designs were constructed to investigate the electrolytes' responses to different partial pressures of sulphur and oxygen, which were produced using mixtures of the metals copper, iron and molybdenum with their respective sulphides and oxides. A non-equilibrium electrolyte response was observed, caused by slow interaction between the electrolyte and the metals. A mixture of molten tin and solid tin sulphide was investigated using a silver-referenced, silver β-alumina cell, and reproducible emfs corresponding to thermodynamic expectations were observed. A non-unity value was determined for the activity of a proposed silver sulphide auxiliary layer at the surface of the β-alumina and shown to be in agreement with a theoretically-calculated value. Experiments were carried out using this cell in molten tin baths of varying sulphur content. Results were generally consistent with the previously-determined values of silver sulphide activity; however, at low sulphur values this activity was not constant and decreased to zero. The minimum level of sulphur which could be detected by this technique was calculated and tested both in laboratory molten tin and in industrial trials.
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Shen, Fabin. "UV-Induced Intrinsic Fabry-Perot Interferometric Fiber Sensors and Their Multiplexing for Quasi-Distributed Temperature and Strain Sensing." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28053.
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Distributed temperature and strain sensing is demanded for a wide range of applications including real-time monitoring of industrial processes, health monitoring of civil infrastructures, etc. Optical fiber distributed sensors have attracted tremendous research interests in the past decade to meet the requirements of such applications.
This research presents a multiplexed sensor array for distributed temperature and strain sensing that can multiplex a large number of UV-induced sensors along a single fiber. The objective of this research is to develop a quasi-distributed sensing technology that will greatly increase the multiplexing capacity of a sensor network and can measure temperature and strain with a high accuracy and high resolution.
UV-induced intrinsic Fabry-Perot interferometric (IFPI) optical fiber sensors, which have low reflectance and low power loss, are good candidates for multiplexed sensors networks. Partial reflectors are constructed by irradiating photosensitive fiber with a UV laser beam. A pair of reflectors will form a Fabry-Perot interferometer that can be used for temperature and strain sensing. A sensor fabrication system based on a pulsed excimer laser and a shadow mask is developed.
A spectrum-based measurement system is presented to measure the interference fringes of IFPI sensors. A swept coherent light source is used as the light source. The spectral responses of the IFPI sensors at different wavelengths are measured. A frequency division multiplexing (FDM) scheme is proposed. Multiple sensors with different optical path differences (OPD) have different sub-carrier frequencies in the measured spectrum of the IFPI sensors. The multiplexing capacity of the sensor system and the crosstalk between sensors are analyzed.
Frequency estimation based digital signal processing algorithms are developed to determine the absolute OPDs of the IFPI sensors. Digital filters are used to select individual frequency components and filter out the noise. The frequency and phase of the filtered signal are estimated by means of peak finding and phase linear regression methods. The performance of the signal processing algorithms is analyzed.
Experimental results for temperature and strain measurement are demonstrated. The discrimination of the temperature and strain cross sensitivity is investigated. Experimental results show that UV-induced IFPI sensors in a FDM scheme have good measurement accuracy for temperature and strain sensing and potentially have a large multiplexing capacity.Ph. D.
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Hashem, Nadeem. "Use of high resolution remote sensing and GIS to parameterise spatially-distributed soil erosion models." Thesis, King's College London (University of London), 2002. https://kclpure.kcl.ac.uk/portal/en/theses/use-of-high-resolution-remote-sensing-and-gis-to-parameterise-spatiallydistributed-soil-erosion-models(de9a0828-c481-4b60-8acf-c2664f1ee1f1).html.
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Raheem-Kizchery, Ayesha Rubiath. "Ceramic coatings for silica and sapphire optical waveguides for high temperature embedding and sensing." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-09052009-040217/.
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Pal, Suchandan. "Characterisation and high-temperature sensing potential of fibre Bragg gratings in specialised optical fibres." Thesis, City University London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407547.
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Wooster, Martin John. "Spaceborne monitoring of high temperature volcanic thermal features : studies using the ERS Along Track Scanning Radiometer." Thesis, Open University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264468.
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Kubina, Bernd [Verfasser], Rolf [Akademischer Betreuer] Jakoby, and Martin [Akademischer Betreuer] Vossiek. "Chipless Wireless High-Temperature Sensing in Time-Variant Environments / Bernd Kubina ; Rolf Jakoby, Martin Vossiek." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/1140166239/34.
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Song, Junghui. "Fabrication and Characterization of AlGaN/GaN Heterostructure Devices for Hydrogen Gas Sensing at High Temperature." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1250296506.
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Prasad, Ravi Mohan. "Polymer-Derived Microporous Ceramics for Membranes and Sensors for High Temperature Hydrogen Purification and Sensing." Phd thesis, tuprints, 2012. http://tuprints.ulb.tu-darmstadt.de/3181/1/PhD_Dissertation_Ravi_Mohan_Prasad_%28TU_Darmstadt%29.pdf.
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The growing interest in the use of hydrogen as main fuel has increased the need for pure hydrogen (H2) production and purification. There are several by-products (CO, H2O, CO2) associated with the production of hydrogen which might damage the production rate. Therefore, separation of hydrogen from other gases is an important step in the hydrogen production process. If H2 can be selectively removed from the product side during hydrogen production in membrane reactors, then it would be possible to achieve complete CO conversion in a single-step under high temperature conditions.
The main goal of the present work is the high temperature H2 purification and sensing by applying polymer-derived ceramics. To prove the concept, the microporous SiBCN, Si3N4 and SiCN ceramic membranes have been synthesized by the polymer-pyrolysis route and their performance for the hydrogen separation have been evaluated in tubular membranes as well as in planar chemiresistors.
The synthesis of amorphous SiBCN ceramics has been realized through pyrolysis of poly(organoborosilazanes) in argon. Multilayered amorphous SiBCN/γ-Al2O3/α-Al2O3 membranes with gradient porosity have been realized and assessed with respect to the thermal stability, pore-size distribution and H2/CO permeance. N2-adsorption measurement indicates micropores in the range of 0.68-0.73 nm for three-fold SiBCN/γ-Al2O3/α-Al2O3 membrane. SEM characterization of three-fold SiBCN/γ-Al2O3/α-Al2O3 membrane shows the thickness of SiBCN membrane layer is 2.8 μm; gas permeance measurements of the membrane shows H2/CO selectivity of about 10.5 and the H2 permeance of about 1.05x10-8 mol m-2 s-1 Pa-1. The observed gas permeation properties point out that the transportation of gas molecules through the membrane is governed by both activated and Knudsen diffusion.
The stability and sensing characteristics of SnO2 sensors coated with amorphous microporous SiBCN layers have been studied in oxygen-free atmospheres. The SiBCN layers coated on SnO2 sensors are amorphous, crack-free and microporous. The diameter of micropores (about 0.70 nm) is larger than the kinetic diameter of H2 (0.289 nm) and CO (0.376 nm) molecules, allowing in this way their diffusion towards the bottom SnO2 sensing layer. Transient response characteristics and sensor signals of uncoated SnO2, three-fold and five-fold SiBCN-coated SnO2 sensors exposed to CO (10, 20 and 120 ppm) and H2 (40, 400 and 900 ppm) in nitrogen at 350 and 530 °C are obtained. Uncoated SnO2 sensor is reduced at 530 °C in H2 to tin while SiBCN-coated SnO2 sensors show reversible resistance changes while exposed to CO and H2.
Si3N4-ceramics have been synthesized via a dry ammonia pyrolysis of commercially available polysilazane (KiON HTT 1800). Amorphous microporous-Si3N4 ceramic layers deposited on the top of GaN sensing layer followed by dry ammonia treatment leads to the improved H2 to CO selectivity of Si3N4/GaN sensors in the oxygen-free atmosphere. Transient response of the uncoated-, three-fold Si3N4 coated- and ammonia treated-GaN sensors exposed to CO (10, 20 and 120 ppm) and H2 (40, 400 and 900 ppm) in pure nitrogen at 350 and 530 °C are investigated. The results indicate that uncoated-GaN sensor shows high response towards both CO and H2 whereas for microporous Si3N4 coated- and ammonia treated-GaN gas sensors the sensitivity towards the interfering gas CO is significantly reduced.
High-surface area micro- and mesoporous carbon-rich SiCN ceramics have been obtained by controlled thermolysis of a carbon-rich poly(diphenylsilylcarbodiimide) precursor under argon. The formation of porous SiCN ceramics is due to the carbothermal reaction of amorphous silicon nitride phase with excess carbon, which leads to materials with high specific surface area of about 500-600 m2 g−1. High-resolution Transmisson Electron Microscopy indicates that pores are embedded only in the free carbon phase. The transformation from micro- to mesoporous ceramics after heat treatment between 1600 and 1700 °C, due to the organization of graphene-like free carbon phase, is discussed.
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Hawkins, Adam J. "Measurement of the spacial distribution of heat exchange in a geothermal analog bedrock site using fiber-otic distributed temperature sensing." Thesis, California State University, Long Beach, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1527320.
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Ellis, Weston. "Determining Spatial and Temporal Variability of Percolation Rates from a River-Side Recharge Basin Using Fiber Optic Distributed Temperature Sensing." Thesis, California State University, Long Beach, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10743513.
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Percolation rates in Managed Aquifer Recharge (MAR) facilities, such as recharge basins and stream channels, can vary widely through both time and space. Natural variations in sediment hydraulic conductivity can create “dead zones” in which percolation rates are negligible. Clogging is a constant problem, leading to decays in facility percolation rates. Measuring percolation rate variations is important for management, maintenance, and remediation of surface MAR facilities.
We have used Fiber Optic Distributed Temperature Sensing (FODTS) to monitor percolation in a long narrow river channel separated from an active river by a levee. The alluvial sediment in the river channel varies widely in texture and water balance is difficult to monitor independently. The off-river channel was monitored by installing a fiber optic cable in the subsurface and measuring the propagation rate of the diurnal temperature oscillations carried downward with infiltrating water. In this way, heat was used as a tracer of percolation rates along the section defined by the 1800 meters of buried cable. We were able to confirm the FODTS measurements of percolation in the Off River Channel and demonstrate its wide applicability. Results from the measurements have been used to understand both the hydraulic behavior of percolation in the facilities and to make management decisions regarding facility operations and the potential need for additional surface sediment remediation.
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DePew, Keith Alan. "Development of a Miniature, Semi-Distributed Sapphire Fiber Optic Thermometer for Harsh and High Temperature Environments." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/19224.
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Fiber optic temperature sensing has become a well-defined field in the past few decades [1] through the use of Fiber Bragg Gratings, Fabry-Perot interferometry, and pyrometry, to list several techniques in use today. The use of fiber optics offers significant advantages over electronic sensing in terms of size and insensitivity to harsh conditions such as extreme temperatures and corrosive environments. The availability of optical sapphire materials, including fibers, has allowed the creation of fiber optic sensing elements able to continuously operate at temperatures of 1600"C [2] or more, thus outstripping the abilities of many commonly used thermocouples (excluding platinum types R, S, and B) [3] which will also exhibit a sensitivity to electromagnetic fields. In addition to the aforementioned benefits, fiber optic sensing techniques provide a great deal of accuracy in temperature measurement over the entire working range of the sensor.
The work documented in this thesis consists of efforts to minimize the overall footprint of a sapphire based extrinsic Fabry-Perot interferometry (EFPI) temperature sensing element, as well as strides made in multiplexing the same element and reducing the error potential from cross sensitivity of the thermometer with applied strain. This work has been variously funded by Pratt & Whitney and the Department of Energy.
Master of Science
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Cangialosi, Chiara. "Performances of Raman and Brillouin fiber-based sensing of temperature and strain in harsh environments." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSES018/document.
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La Thèse a été réalisée en cotutelle entre l’Université Jean Monnet de Saint Etienne (France) et l’université de Palerme (Italie) et en collaboration avec l’Agence nationale pour la gestion des déchets radioactifs (ANDRA). Le travail de recherche concerne l'étude des capteurs répartis à fibres optiques (utilisant la lumière rétrodiffusée Raman et Brillouin) destinés à l’observation et à la surveillance des ouvrages dédiés au stockage géologique de déchets radioactifs de haute activité et moyenne activité à vie longue (projet CIGEO : centre industriel de stockage géologique). Dans ce contexte, les fibres optiques sont envisagées en tant qu’élément sensible de capteurs pour la mesure de paramètres environnementaux tels que la température ou la déformation. Les conditions environnementales extrêmes d’exploitation entrainent la dégradation des propriétés de la fibre optique et des performances du capteur. La réponse des capteurs Brillouin et Raman est influencée par la présence de rayonnement y et d’hydrogène dans l’atmosphère Cigéo. Dans les deux cas, une diminution de la transmission linéique de la fibre optique est observée. Ce phénomène est dû à l’atténuation induite par radiation (RIA) ou par hydrogène (HIA) réduisant ainsi la portée de la mesure. En outre le rayonnement y et l’hydrogène provoquent des erreurs sur la mesure de température ou de déformation pour les deux types de capteurs. L’étude a permis d’établir les lignes directrices pour la sélection et le développement des capteurs repartis à fibre optique appropriés pour travailler dans l’environnement CigéoThis PhD thesis is conducted in the joint supervision of both the University Jean Monnet of Saint Etienne (France) and the University of Palermo (Italy) in collaboration with the French national agency for the management of radioactive wastes (ANDRA). The aim of the Thesis is to evaluate the performances of distributed optical fiber sensors (based on Raman and Brillouin scattering technologies) that will be employed for monitoring industrial site for deep geological disposal for high and long-lived intermediate level activity radioactive waste (HL-W and LL/IL-W, respectively), called Cigéo. In this context, the distributed optical fiber sensors will provide a time and spatial cartography of the strain and temperature inside the disposal cell. The severe environment of Cigéo requires the sensor evaluation taking into account the resulting degradation of the sensing optical fiber. The sensor response is affected by y-rays and hydrogen presences inside the storage cells. In both cases a decrease of the optical fiber transmission, due to the radiation or hydrogen induced attenuation (RIA or HIA) is observed and limits the sensing distance range of the sensor. Moreover, the two different environment constraints lead to errors in the temperature or strain evaluation for both sensor technologies. This Thesis work establishes the guidelines to select and design distributed optical fiber sensors suitable to operate in radiation environment such as Cigéo one
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Nützmann, Gunnar [Gutachter], Jörg [Gutachter] Lewandowski, and Jan [Gutachter] Fleckenstein. "Upscaling of Lacustrine Groundwater Discharge by Fiber Optic Distributed Temperature Sensing and Thermal Infrared imaging / Gutachter: Gunnar Nützmann, Jörg Lewandowski, Jan Fleckenstein." Berlin : Humboldt-Universität zu Berlin, 2018. http://d-nb.info/1185579257/34.
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Roa, Christian Raphael. "Smart Power Module for Distributed Sensor Power Network of an Unmanned Ground Vehicle." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/64467.
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Energy efficiency is a driving factor in modern electronic design particularly in power conversion where conversion losses directly set the upper limit of system efficiency. A wide variety of commercially available DC-DC conversion elements have inefficiencies in the 90-97% range. The efficiency range of most common commercial-off-the-shelf (COTS) power supplies is 75-85%, highlighting the fact that COTS power supplies have not kept pace with efficiency improvements of modern conversion elements.
Unmanned ground vehicles (UGVs) is an application where efficiency can be crucial in extending tight power budgets. In autonomous ground vehicles, geographic diversity with regard to sensor location is inherent because sensor orientation and placement are crucial to performance. Sensor power, therefore, is also distributed by nature of the devices being supplied.
This thesis presents the design and evaluation of a smart power module used to implement a distributed power network in an autonomous ground vehicle. The module conversion element demonstrated an average efficiency of 96.7% for loads from 1-4A. Current monitoring and an adjustable output current limit were provided through a second circuit board within the same module enclosure. The module processing element sends periodic updates and receives commands over a CAN bus. The smart power modules successfully supply critical sensing and communication components in an operational autonomous ground vehicle.Master of Science
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Nomnqa, Myalelo Vuyisa. "Design of a domestic high temperature proton exchange membrane fuel cell cogeneration system : modelling and optimisation." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2574.
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Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2017.Fuel cells are among power generation technologies that have been proven to reduce greenhouse gas emissions. They have the potential of being one of the most widely used technologies of the 21st century, replacing conventional technologies such as gas turbines in stationary power supplies, internal combustion engines in transport applications and the lithium-ion battery in portable power applications. This research project concentrates on the performance analysis of a micro-cogeneration system based on a high temperatureproton exchange membrane (HT-PEM) fuel cell through modelling and parametric analysis. A model of a 1kWe micro-cogeneration system that consists of a HT-PEM fuel cell, a methane steam reformer (MSR) reactor, a water-gas-shift (WGS) reactor, heat exchangers and an inverter was developed. The model is coded/implemented in gPROMS Model Builder, an equation oriented modelling platform. The models predictions for the HTPEM fuel cell, MSR and WGS, and the whole system were validated against experimental and numerical results from literature. The validation showed that the HT-PEM fuel cell model was able to predict the performance of a 1kWe fuel cell stack with an error of less than 6.4%. The system model is rstly used in a thermodynamic analysis of the fuel processor for a methane steam reforming process and investigated in terms of carbon monoxide produced. The combustor fuel and equivalence ratios were shown to be critical decision variables to be considered in order to keep the carbon monoxide from the fuel processor at acceptable levels for the fuel cell stack.
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Mullen, Max Robertson. "Electrochemical Sensing for a Rapidly Evolving World." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440408652.
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Ziegler, Silvio. "New current sensing solutions for low-cost high-power-density digitally controlled power converters." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2009. http://theses.library.uwa.edu.au/adt-WU2010.0077.
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[Truncated abstract] This thesis studies current sensing techniques that are designed to meet the requirements for the next generation of power converters. Power converters are often standardised, so that they can be replaced with a model from another manufacturer without an expensive system redesign. For this reason, the power converter market is highly competitive and relies on cutting-edge technology, which increases power conversion efficiency and power density. High power density and conversion efficiency reduce the system cost, and thus make the power converter more attractive to the customer. Current sensing is a vital task in power converters, where the current information is required for monitoring and control purposes. In order to achieve the above-mentioned goals, existing current sensing techniques have to be improved in terms of cost, power loss and size. Simultaneously, current information needs to be increasingly available in digital form to enable digital control, and to allow the digital transmission of the current information to a centralised monitoring and control unit. All this requires the output signal of a particular current sensing technique to be acquired by an analogue-to-digital converter, and thus the output voltage of the current sensor has to be sufficiently large. This thesis thoroughly reviews contemporary current sensing techniques and identifies suitable techniques that have the potential to meet the performance requirements of the next-generation of power converters. After the review chapter, three novel current sensing techniques are proposed and investigated: 1) The usefulness of the resistive voltage drop across a copper trace, which carries the current to be measured, to detect electrical current is evaluated. Simulations and experiments confirm that this inherently lossless technique can measure high currents at reasonable measurement bandwidth, good accuracy and low cost if the sense wires are connected properly. 2) Based on the mutual inductance theory found during the investigation of the copper trace current sense method, a modification of the well-known lossless inductor current sense method is proposed and analysed. This modification involves the use of a coupled sense winding that significantly improves the frequency response. Hence, it becomes possible to accurately monitor the output current of a power converter with the benefits of being lossless, exhibiting good sensitivity and having small size. 3) A transformer based DC current sense method is developed especially for digitally controlled power converters. This method provides high accuracy, large bandwidth, electrical isolation and very low thermal drift. Overall, it achieves better performance than many contemporary available Hall Effect sensors. At the same time, the cost of this current sensor is significantly lower than that of Hall Effect current sensors. A patent application has been submitted. .... The current sensing techniques have been studied by theory, hardware experiments and simulations. In addition, the suitability of the detection techniques for mass production has been considered in order to access the ability to provide systems at low-cost.
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Aslan, Hatice. "Using remote sensing in soybean breeding: estimating soybean grain yield and soybean cyst nematode populations." Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/18830.
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Master of ScienceDepartment of Agronomy
William T. Schapaugh
Remote sensing technologies might serve as indirect selection tools to improve phenotyping to differentiate genotypes for yield in soybean breeding program as well as the assessment of soybean cyst nematode (SCN), Heterodera glycines. The objective of these studies were to: i) investigate potential use of spectral reflectance indices (SRIs) and canopy temperature (CT) as screening tools for soybean grain yield in an elite, segregating population; ii) determine the most appropriate growth stage(s) to measure SRI’s for predicting grain yield; and iii) estimate SCN population density among and within soybean cultivars utilizing canopy spectral reflectance and canopy temperature. Experiment 1 was conducted at four environments (three irrigated and one rain-fed) in Manhattan, KS in 2012 and 2013. Each environment evaluated 48 F4- derived lines. In experiment 2, two SCN resistant cultivars and two susceptible cultivars were grown in three SCN infested field in Northeast KS, in 2012 and 2013. Initial (Pi) and final SCN soil population (Pf) densities were obtained. Analyses of covariance (ANCOVA) revealed that the green normalized vegetation index (GNDVI) was the best predictive index for yield compared to other SRI’s and differentiated genotype performance across a range of reproductive growth stages. CT did not differentiate genotypes across environments. In experiment 2, relationships between GNDVI, reflectance at single wavelengths (675 and 810 nm) and CT with Pf were not consistent across cultivars or environments. Sudden death syndrome (SDS) may have confounded the relationships between remote sensing data and Pf. Therefore, it would be difficult to assess SCN populations using remote sensing based on these results.
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Lowder, Tyson Lee. "Surface Relief D-Fiber Bragg Gratings for Sensing Applications." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2644.pdf.
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Eise, Justin. "A Secure Architecture for Distributed Control of Turbine Engine Systems." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1552556049435026.
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Prasad, Ravi Mohan [Verfasser], Ralf [Akademischer Betreuer] Riedel, Christina [Akademischer Betreuer] Roth, Wolfgang [Akademischer Betreuer] Ensinger, and Jörg [Akademischer Betreuer] Schneider. "Polymer-Derived Microporous Ceramics for Membranes and Sensors for High Temperature Hydrogen Purification and Sensing / Ravi Mohan Prasad. Betreuer: Ralf Riedel ; Christina Roth ; Wolfgang Ensinger ; Jörg Schneider." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2012. http://d-nb.info/110625709X/34.
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