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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Quantification of acoustic emission from soils for predicting landslide failure

Spriggs, M. P. January 2005 (has links)
Acoustic emission (AE) is a natural phenomenon that occurs when a solid is subjected to stress. These emissions are produced by all materials during pre failure. In soil, AE results from the release of energy as particles undergo small strains. If these emissions can be detected, then it becomes possible to develop an early warning system to predict slope failure. International research has shown that AE can be used to detect ground deformations earlier than traditional techniques, and thus it has a role to play in reducing risk to humans, property and in mitigating such risks. This thesis researches the design of a system to quantify the AE and calculate the distance to the deformation zone, and hence information on the mechanism of movement. The quantification of AE is derived from measuring the AE event rate, the output of which takes the form of a displacement rate. This is accurate to an order of magnitude, in line with current standards for classifying slope movements The system also demonstrates great sensitivity to changes within the displacement rate by an order of magnitude, making the technique suitable to remediation monitoring. Knowledge of the position of the shear surface is critical to the planning of cost effective stabllisation measures. This thesis details the development of a single sensor source location technique used to obtain the depth of a developing or existing shear surface within a slope. The active waveguide is used to reduce attenuation by taking advantage of the relatively low attenuation of metals such as steel. A method of source location based on the analysis of Lamb wave mode arrival times at a smgle sensor is summansed. An automatic approach to source location is demonstrated to locate a regular AE source to within one metre. Overall consideration is also given to field trials and towards the production of monitoring protocols for data analysis, and the implementation of necessary emergency/remediation plans.
2

Investigation of odor and its improvement in Kaohsiung city

Chen, Wen-wen 16 July 2006 (has links)
This study investigates characteristics of odorous materials and their odor intensities emitted from various commercial and industrial sources in the Kaohsiung City. An overview of odor complaints from the city people is presented and discussed. Results indicate that, due to the increasing people concerns about the odor emission problems, more frequent checks done by the City EPA officers, governmental assistances to the pollution makers on the pollution control technologies, and the enforcement of more stringent environmental protection regulations, odor-complaint cases in this city are decreasing in recent years. However, people are giving more attention to odors from food-cooking emissions and the associated complaint cases are increasing. Emissions from restaurants and plants become the two major odor sources in this city. For the plant emissions, odorous chemicals emitted from the Kaohsiung Refinery, located in northern Zouying District, were detected to be benzene, toluene, xylenes, and styrene. The Chianjhen storage and pumping station, located by the Kaohsiung Harbor, emits some 40 different chemicals. The majors among them are methanol, ammonia, ethylene, n-pentane, chlorodifluoromethane, methyl tert-butyl ether (MTBE), propylene, cyclohexane, styrene, acetone, 1,2-dichloroethane, propylene oxide and vinyl chloride. Prompt leaks from the storage tanks and during the loading and unloading operations account for the emissions. Plants located in the Chianjhen Export Processing Zone emit chemicals, mainly methyl methacrylate, toluene, propylene glycol monomethyl ether acetate (PGMEA), ammonia, ethyl acetate and ethanol, which cause only a few complaint cases. The emitted chemicals are among the ones used by the plants as feed stokes or solvents. Restaurant located in Chianjhen and Hsiogang Districts emit large amount of food-cooking odorants, however, the percentage of odorous complaining for the emissions is relatively high in the Zouying District as compared to the other administrative districts investigated in this study. Major components of the food-cooking emissions include hydrogen sulfide, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), ammonia, and methylamine. Relative percentages among these chemicals depend on the cooking materials and styles. Results also indicate that industries or businesses, such as petrochemical, surface coating, paint manufacturing, fuel station, storage vessels, semiconductor manufacturing, adhesive tape manufacturing and cloth dry-cleaning, are major odor and chemical emission sources which need to be continuously implemented for getting more emission reductions in the near future.
3

Investigation of Emission Source Heights in FLEXPART 10.02 for the Wildfire in Pedrógão Grande, Portugal, 2017 / Undersökning av utsläppshöjder i FLEXPART 10.02 för skogsbranden i Pedrógão Grande, Portugal, 2017

Nygren, Anton January 2019 (has links)
One of the worst wildfires in Portugal in 2017 on June17- 21 started at the central part of Pedrógão Grande and spread fast to the surrounding areas Góis, Pampilhosa da Serra and Arganil. The wildfire took 64 lives and a large smoke plume was observed. The interest in smoke plumes from wildfires is partly due to their emitting of greenhouse gases (CO2), a large source of aerosols, CO, oxides of nitrogen and other trace gases that can affect the air quality at local and regional scale. The regional scale can be affected because the smoke from wildfires can get elevated and be transported into the free troposphere and the lower stratosphere by either pyro convection or radiative driven convection and can be transported long distances, for example from Canada to Germany. This thesis investigates how the emission source height in a model affects the transport of the smoke plume and compares the simulations with observations. Observations of transport of emissions from wildfires are often done with satellites and in this thesis data from the second modern-era retrospective analysis for research and applications (MERRA2) is used as the observations. In this thesis the numerical model FLEXPART 10.02 is used to calculate the transportation of CO from the wildfire in Pedrógão Grande. The altitude of the emission source top height and bottom height in FLEXPART was changed to see how it affected the smoke plume in the simulation. The agreement between plumes from the observations and the simulation plumes were calculated with the structural similarity (SSIM) index and the change of SSIM index was investigated. The results were that the best similarity for horizontal images was with an emission source height of 100- 300 m, for vertical images at 40°N with an emission source height 0- 1500 m and for vertical images at 41°N with an emission source height 100- 1200. The overall best simulation was the simulation with emission source height 100- 1200 m (average of the three similarity calculations). Some uncertainty occurs in the results due to for example differences in resolutions between MERRA2 and FLEXPART and the weather condition may have contributed. To improve the results there is a need to compare simulations with more wildfires to see that the SSIM index behaves the same. / En av de värsta skogsbränderna i Portugal 2017 var den 17–21 juni och började i centrala Pedrógão Grande och spred sig snabbt till de omgivande områdena Góis, Pampilhosa da Serra och Arganil. Skogsbranden tog 64 liv och stora rökplymer observerades. Rökplymer från skogsbränder är intressanta därför att de bland annat är en källa av växthusgaser till exempel koldioxid (CO2), aerosoler, kolmonoxid (CO) och andra spårgaser som kan påverka luftkvaliteten på lokal och regional skala. Den regionala skalan kan påverkas eftersom rök från skogsbränder kan sprida sig upp till den fria troposfären och den nedre stratosfären med konvektion. Konvektion är när luften blir varm av olika skäl och stiger, luften kyls av när den stiger och blir då tyngre och till slut sjunker luften. Det som kan driva konvektion vid en brand är branden själv och strålning och kan transportera röken från branden långa avstånd, till exempel från Kanada till Tyskland. Den här uppsatsen undersöker hur utsläppshöjden (mellan vilka höjder röken släpps ut från) påverkar transporten av rök och jämför beräkningarna med observationer. Observationer av transport av utsläpp från bränder sker ofta med satelliter och i denna uppsats används data från en återanalys av en samling observationer från MERRA2 (the second modern-era retrospective analysis for research and applications) som observationer. En återanalys är ett dataset som räknas med en modell från i tid och rum oregelbundna observationer från historiska och nutida data. I denna uppsats används den numeriska transportmodellen FLEXPART 10.02 för att beräkna transport av kolmonoxid från skogsbranden i Pedrógão Grande. Höjden av utsläppskällans topphöjd och bottenhöjd i FLEXPART ändrades för att se hur det påverkat rökplymen i simuleringen. Likheten mellan rökplymen från observationerna och simuleringarna beräknades sedan med ett test kallat SSIM och förändringen av SSIM indexet undersöktes. Resultaten var att den bästa simuleringen för de horisontella bilderna med en utsläppshöjd på 100– 300 m, för de vertikala bilderna på 40°N en utsläppshöjd på 0– 1500 m och för de vertikala bilderna på 41°N en utsläppshöjd på 100– 1200 m. Totalt sett (medelvärde från de tre simuleringarna) hade emissions höjden 100- 1200 m den bästa likheten med observationerna. Det finns en osäkerhet i resultaten på grund av tillexempel att det är olika upplösning i MERRA2 och FLEXPART och att väderförhållanden kan ha påverkat beräkningarna. För att förbättra resultatet så kan man göra simuleringar av fler skogsbränder för att se om SSIM indexet uppför sig densamma.

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