Dissertations / Theses on the topic 'Emissions monitoring'

Master of Science
Department of Mechanical and Nuclear Engineering
Kirby S. Chapman
The increased emissions monitoring requirements of industrial gas turbines have created a demand for less expensive emissions monitoring systems. Typically, emissions monitoring is performed with a Continuous Emissions Monitoring System (CEMS), which monitors emissions by direct sampling of the exhaust gas. An alternative to a CEMS is a system which predicts emissions using easily measured operating parameters. This system is referred to as a Parametric Emissions Monitoring System (PEMS). A review of the literature indicates there is no globally applicable PEMS. Because of this, a PEMS that is applicable to a variety of gas turbine manufacturers and models is desired. The research presented herein includes a literature review of NOx reduction techniques, NOx production mechanisms, current PEMS research, and combustor modeling. Based on this preliminary research, a combustor model based on first-engineering principles was developed to describe the NOx formation process and relate NOx emissions to combustion turbine operating parameters. A review of available literature indicates that lean-premixed combustion is the most widely-used NOx reduction design strategy, so the model is based on this type of combustion system. A review of the NOx formation processes revealed four well-recognized NOx formation mechanisms: the Zeldovich, prompt, nitrous oxide, and fuel-bound nitrogen mechanisms. In lean-premixed combustion, the Zeldovich and nitrous oxide mechanisms dominate the NOx formation. This research focuses on combustion modeling including the Zeldovich mechanism for NOx formation. The combustor model is based on the Siemens SGT-200 combustion turbine and consists of a series of well-stirred reactors. Results show that the calculated NOx is on the same order of magnitude, but less than the NOx measured in field tests. These results are expected because the NOx calculation was based only on the Zeldovich mechanism, and the literature shows that significant NOx is formed through the nitrous oxide mechanism. The model also shows appropriate trends of NOx with respect to various operating parameters including equivalence ratio, ambient temperature, humidity, and atmospheric pressure. Model refinements are suggested with the ultimate goal being integration of the model into a PEMS.

Global climate change is becoming a central issue in contemporary science as well as politics. There is a long-lasting debate about the cause of the climate change: anthropogenic activity versus the natural cycle. However, a scientific consensus is coming a conclusion that the contemporary climate change is mainly caused by anthropogenic emissions of the greenhouse gases (GHG), including carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). The main objective of the thesis is the monitoring of such GHG emissions from two ecosystem types: a forest and a rice paddy ecosystem. The forest site is a EMEP experimental station, taking part of the activity of GHG-AGOLU of FP7-JRC project, while the agricultural ecosystem was included in the CarboEurope project and represents also a Level 3 site in the frame of NitroEurope project. The gas monitoring was carried out in 2008. The thesis is composed by 4 chapters, corresponding to specific objectives. The first chapter is relative to the study of the spatial variability of the main soil chemical and physical properties on the basis of which the gas monitoring points were selected. The second and the third chapters are relative to a cropland site. In particular, the second chapter includes monitoring data of CH4, N2O and CO2 fluxes from the paddy field, both during the crop growth season and the fallow period, and the validation results of the DeNitrification DeComposition (DNDC) model, a process-oriented biogeochemical model used for simulating soil gas emissions from the paddy field, are reported. The third chapter contains the study of characterization of microbial community composition using phospholipid fatty acid analysis (PLFA), at eight sampling dates representative of different soil conditions and crop stages and consequently characterized by distinct soil greenhouse emission rates. The fourth and last chapter includes the monitoring study of soil respiration in a forest site and its partitioning into autotrophic and heterotrophic components, applying the indirect linear regression method.

The construction industry is one of the largest emitters of greenhouse gases and health-related pollutants. Monitoring and benchmarking emissions will provide practitioners with information to assess environmental impacts and improve the sustainability of construction. This research focuses on real-time measurement of emissions from non-road construction equipment and development of a monitoring-benchmarking tool for comparison of expected vs. actual emissions. First, exhaust emissions were measured using a Portable Emission Measurement System (PEMS) during the operation of 18 pieces of construction equipment at actual job sites. Second-by-second emission rates and emission factors for carbon dioxide, carbon monoxide, nitrogen oxides, and hydrocarbons were calculated for all equipment. Results were compared to those of other commonly used emission estimation models. Significant differences in emission factors associated with different activities were not observed, except for idling and hauling. Moreover, emission rates were up to 200 times lower than the values estimated using EPA and California Air Resources Board (CARB) guidelines. Second, the resulting database of emissions was used in an automated, real-time environmental assessment system. Based on videos of actual construction activities, this system enabled real-time action recognition of construction operations. From the resulting time-series of activities, emissions were estimated for each piece of equipment and differed by only 2% from those estimated by manual action recognition. Third, the actual emissions were compared to estimated ones using discrete event simulation, a computational model of construction activities. Actual emissions were 28% to 144% of those estimated by manual action recognition. Results of this research will aid practitioners in implementing strategies to measure, monitor, benchmark, and possibly reduce air pollutant emissions stemming from construction.
Master of Science

The ceramic glazing techniques of vapour glazing, reduction lustre, Raku and fuming all require specialised firing conditions with the use of potentially hazardous kiln atmospheres and specialist kiln designs for their successful execution. The technique of reduction lustre is an ancient, highly decorative technique in which pigments or glazes containing reducible metal oxides such as copper, silver and bismuth are subjected to a reducing atmosphere which results in the formation of stable iridescent lustrous colour effects. Conventionally hydrocarbons are used to produce a reducing atmosphere, the combustion of which can lead to potentially high levels of CO. This research has concentrated on the technique of reduction lustre with the aim of producing a safe, environmentally friendly firing system. Reduction lustre effects were reproduced using a 100 litre down draft gas kiln designed and constructed for the purpose. A 40 litre electric kiln was modified for use with reducing atmospheres and a laboratory muffle kiln was also adapted to provide closely controlled firing conditions. Alternative reducing atmospheres were assessed, consisting of either 5% H2 in N2 or hydrocarbon vapour in N2 The former is reliable, safe, environmentally friendly and is recommended for studio pottery use. A theoretical design for a reduction lustre kiln incorporating a gas control system based on the use of a 5% H2 in N2 gas mixture and a gas tight outer casing was developed. Thermoanalytical methods were used to investigate the reduction behaviour of raw materials, glazes and frits under different atmospheric conditions. Diffusional and topochemical models of reduction reactions occurring in a typical lustre glaze have been evaluated. In-glaze lustres reduce with thecharacteristics of diffusion processes. Water diffusion out of the glaze may be rate determining. Studies carried out using energy dispersive x-ray analysis andphoto electron spectroscopy show that lustres are associated with the presence of metallic copper, the actual colour being dependent on the surface concentration of the metal. The aesthetic results of the various firing methods developed were assessed using a perceptual study based on the use of a semantic differential test developed from a multiple sorting survey carried out using lustred tiles. The survey used both lustred tiles to represent a 2-dimensional surface and lustred vases which represented a 3-dimensional lustre glazed surface. The survey showed that statistically significant differences were observed between lustred ceramics fired in different systems, allowing comparisons to be made in an objective manner.

Acoustic Emission (AE) monitoring can be used to detect the presence of damage as well as determine its location in Structural Health Monitoring (SHM) applications. Information on the time difference of the signal generated by the damage event arriving at different sensors is essential in performing localization. This makes the time of arrival (ToA) an important piece of information to retrieve from the AE signal. Generally, this is determined using statistical methods such as the Akaike Information Criterion (AIC) which is particularly prone to errors in the presence of noise. And given that the structures of interest are surrounded with harsh environments, a way to accurately estimate the arrival time in such noisy scenarios is of particular interest. In this work, two new methods are presented to estimate the arrival times of AE signals which are based on Machine Learning. Inspired by great results in the field, two models are presented which are Deep Learning models - a subset of machine learning. They are based on Convolutional Neural Network (CNN) and Capsule Neural Network (CapsNet). The primary advantage of such models is that they do not require the user to pre-define selected features but only require raw data to be given and the models establish non-linear relationships between the inputs and outputs. The performance of the models is evaluated using AE signals generated by a custom ray-tracing algorithm by propagating them on an aluminium plate and compared to AIC. It was found that the relative error in estimation on the test set was < 5% for the models compared to around 45% of AIC. The testing process was further continued by preparing an experimental setup and acquiring real AE signals to test on. Similar performances were observed where the two models not only outperform AIC by more than a magnitude in their average errors but also they were shown to be a lot more robust as compared to AIC which fails in the presence of noise.

Thesis (M.S.)--West Virginia University, 2001.
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Due to economic, accessibility and security constraints, the majority of developing countries within the low-latitudes lack the capacity to establish networks of ground-based air pollution monitoring stations. As a result, there is a lack of systematic and consistent measurements and monitoring of the concentrations of air pollutants in most of these countries. In addition, there is the lack of verifiable inventories of sources of atmospheric emissions. In order to mitigate these constraints, this research presents an investigation into the relevance of currently available satellite sensors to estimate concentrations of air pollutants (carbon monoxide, nitrogen dioxide and tropospheric ozone) and carbon dioxide over the Niger Delta, a developing region in southern part of Nigeria. It further presents a methodological framework designed to interpolate column concentrations from satellite sensors over the entire study area using ordinary kriging interpolation techniques in ArcGIS Geostatistical Analyst. The study also carries out an assessment of the reliability and resolution of the interpolated surfaces based on a subjective categorisation of the number of column measurements available from satellites sensors and the mean of the Euclidean distances between the column measurements. The results indicate varying degrees of reliability and resolution depending on the climatic seasons in the Niger Delta. The results further show that measurements from satellite sensors are reliable means of measuring and monitoring total and tropospheric column concentrations of air pollutants over the Niger Delta. However, ground-based measurements are required to infer ground-level concentration of pollutants from satellite sensor measurements. Seasonal variations observed in the concentrations of air pollutants indicate higher concentrations during the dry season than during the wet season. In addition to the satellite sensor-based assessment of concentrations of air pollutants and CO2, this research designed and constructed a GIS-based Niger Delta Emission Inventory (NDEI) infrastructure for criteria air pollutants (carbon monoxide, particulate matter, nitrogen oxides and sulphur dioxide), methane, non-methane volatile organic compounds and carbon dioxide. The NDEI has point-source, line-source and area-source components. The construction of the inventory infrastructure effectively relied on the interoperability of GIS and spreadsheet. Due to the lack of access to data, the infrastructure is populated with data generated based on a series of assumptions. This produced estimates with varying degree of uncertainties. Despite these uncertainties, the methods applied in generating data are transferrable to other developing regions where there is limited access to data required for estimating emissions. In addition, the process successfully validates the functionality of the infrastructure to produce accurate emission estimates as and when data that are more accurate are available. Although the estimates of emissions generated from the inventory have limited accuracy, the spatial distributions of the emissions have varying degree of accuracy. The most reliable estimates and spatial distribution of estimates are generated from the area-source (residential) component of the inventory due to the available data and the assumptions applied. The spatial distribution of emissions generated from the inventory are accurate to the extent of the available input spatial data. The thesis concludes by recommending further research work to explore opportunities to infer ground level concentrations of pollutants from satellite sensor measurements. In addition, the thesis recommends the implementation of a site survey to collect site-specific information in order to refine the input data into the NDEI to produce accurate estimates of emissions. The recommendations made from this study aim towards enhancing the development of relatively inexpensive means of measuring and assessing air quality for developing regions within the low latitudes.

This thesis sets out to examine the proposal that, by using tomography and gas sensing techniques to detect and image gas concentration in fast moving flows, engineers can improve the combustion diagnostics and emissions performance of gas turbines, enabling a better understanding of combustion and design optimisation of greener engines. The key factor is the combination of tomography with Tunable Diode Laser Absorption Spectroscopy (TDLAS) gas sensing technology, implemented simultaneously along many beams, to image the gas concentration distribution in the exhaust plume of a gas turbine, in a plane perpendicular to the plume flow direction. The target gas species is carbon dioxide, CO2, and the absorption feature chosen is at a wavelength of 1997.2 nm. The narrow spectral absorption properties of such small molecules present a considerable challenge for a multi-beam tomographic implementation. Moreover, the design, oriented to harsh and industrial environments, presents key challenges for the design of robust optics and electronics for the collection of reliable data. The development of a 126-beam tomography system required the investigation of recently developed TDLAS techniques and their compatibility with data acquisition (DAQ) system firmware strategies to be implemented by custom DAQ electronics. A novel FPGA-based single channel TDLAS CO2 detection system has been designed and built to demonstrate the feasibility for the replication of 126-channels in the full system. Further proof-of-concept experiments carried out at full scale have produced tomographic images of phantom CO2 distributions that demonstrate the utility of the CST technique.

Fiber reinforced polymers (FRP) are an efficient and inexpensive method of repairing deteriorating infrastructure. FRP sheets can be applied to spalling bridge sections and columns to prevent further deterioration and increase stiffness. However, the effect of the environment on the long-term durability of FRP and how the various damage mechanisms initiate and develop are not known. Systems for structural health monitoring are being sought as a means of managing important components in transportation systems as assets in light of modern life cycle cost concepts. This study characterizes a fiber optic sensor for use in detecting acoustic emissions (AE) in FRP. The results of AE analysis (signal amplitude, frequency spectra, MARSE, and in-plane displacement) caused by simulated fiber fracture experiments and other types of mechanical loading in FRP test coupons are reported. The applications to the development of FRP structural health monitoring systems are also discussed.
Master of Science

[Truncated abstract] The cochlea presumably possesses a number of regulatory mechanisms to maintain cochlear sensitivity in the face of disturbances to its function. Evidence for such mechanisms can be found in the time-course of the recovery of CAP thresholds during experimental manipulations, and in observations of slow oscillations in cochlear micromechanics following exposure to low-frequency tones (the “bounce phenomenon”) and other perturbations. To increase our understanding of these oscillatory processes within the cochlea, and OHCs in particular, investigations into cochlear regulation were carried out using a combination of mathematical modelling of the ionic and mechanical interactions likely to exist within the OHCs, and electrophysiological experiments conducted in guinea pigs. The electrophysiological experiments consisted of electrocochleographic recordings and, in some cases, measurement of otoacoustic emissions, during a variety of experimental perturbations, including the application of force to the cochlear wall, exposure to very-low-frequency tones, injection of direct current into scala tympani, and intracochlear perfusions of artificial perilymph containing altered concentrations of potassium, sodium, and sucrose. To obtain a panoramic view of cochlear regulation under these conditions, software was written to enable the interleaved and near-simultaneous measurement of multiple indicators of cochlear function, including the compound action potential (CAP) threshold, amplitude and waveshape at multiple frequencies, the OHC transfer curves derived from low-frequency cochlear microphonic (CM) waveforms, distortion-product otoacoustic emissions (DPOAEs), the spectrum of the round-window neural noise (SNN), and the endocochlear potential (EP). ... The mathematical model we have developed provided a physiologically-plausible and internally-consistent explanation for the time-courses of the cochlear changes observed during a number of different perturbations. We show that much of the oscillatory behaviour within the cochlea is consistent with underlying oscillations in cytosolic calcium concentration. We conclude that a number of the discrepancies between the simulation results and the experimental data can be resolved if the cytosolic calcium functions as two distinct pools: one which controls basolateral permeability and one which controls slow motility. This two-calcium-pool model is discussed.

An evaluation of the VOC (Volatile Organic Compound) emissions monitoring system of Natref (National Refiners of South Africa) was conducted to determine the effectiveness of the system. Natref monitors fugitive plant equipment VOC emissions, VOC emissions from the wastewater treatment area and the tank farm as separate entities. The hiatus in the VOC emissions monitoring system is the absence of an overall VOC emission scenario at Natref. Data of VOC emissions from Natref's field data were used to determine the overall VOC emission scenario at the refinery. Since no control guidelines are available for VOC emissions in South Africa. it was necessary to with refineries in the USA and Western Europe to determine how effective Natref’s VOC emissions monitoring system is. The percentage VOC emissions at Natref from the three areas fell outside the benchmark ranges and different scenarios were simulated to determine the possible causes. The results of this evaluation brought to light inadequacies in the VOC emissions monitoring system at Natref and an estimated loss of approximately three million rand per annum due to VOC emissions. The absence of a coherent picture of VOC emissions at the refinery can lead to sub-optimal expenditure of resources to reduce VOC emissions. The value of a monitoring system lies therein that information obtained from it can be used to implement effective control measures in order to make a contribution to the protection of the environment and therefore towards sustainable development.
Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2005.

A comprehensive field investigation was conducted at Potrero Hills Landfill (PHL) located in Suisun City, California to quantify emissions of twelve (hydro)chlorofluorocarbons (i.e. F-gases). The specific target constituents for this study included CFC-11, CFC-12, CFC-113, CFC-114, HCFC-21, HCFC-22, HCFC-141b, HCFC-142b, HCFC-151a, HFC-134a, HFC-152a, and HFC-245fa. The majority of the F-gas emission studies have been conducted outside of the United States and very limited field landfill emission data are available in the United States. Because of historical usage of blowing agents in insulation foams including CFC-11, HCFC-142b, HFC-134a, and HFC-245fa, models reported in literature predicted high F-gas emissions from a landfill environment, but very limited field data are available to verify such predictions. In this investigation, the surface flux of the twelve F-gases, methane, and carbon dioxide was quantified from various landfill cover systems and in areas with different waste ages, waste heights, and cover thicknesses at Potrero Hills Landfill. In addition, destruction efficiencies for the twelve F-gases were determined based on inlet and outlet concentrations of the onsite flare system. Lastly, the surface flux values were scaled up to a facility-wide emission value to estimate the total fugitive emissions from the landfill. The F-gas flux values for the daily covers were in the 10 -8 to 10-1 g m-2 day -1 range and 10-7 to 10-2 g m-2 day-1 range for the wet and dry season, respectively. The F-gas flux values for the intermediate covers in the -10-6 to 10-4 g m-2 day-1 range and -10-6 to 10-4 g m-2 day-1 range for the wet and dry season, respectively. The F-gas flux values for the final covers were in the 10-7 to 10-5 g m-2 day-1 range and -10-7 to 10-6 g m-2 day-1 range for the wet and dry season, respectively. F-gas fluxes for the final covers had the highest number of below detection limit cases as well as lower than R2 threshold cases. Thest F-gas fluxes were measured from daily cover system constructed with auto shredder residue (i.e. auto fluff) for the both the wet and dry seasons. The highest fluxes were measured for CFC-11, HCFC-21, and HCFC-141b in the wet season and for CFC-11, HCFC-141b, and HFC-134a in the dry season across the seven cover locations. Lower level of variation was observed for methane and carbon dioxide with flux values ranging over five orders of magnitude for the seven tested locations. The methane flux values for the daily covers were in the 10-2 to 10+1 g m-2 d-1 range and 1 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. The carbon dioxide flux values for the daily covers were in the -10+1 to 10+2 g m-2 day-1 range and -10+1 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. The methane flux values for the intermediate covers were in the -10-2 to 10+1 g m-2 d-1 range and -10-3 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. The carbon dioxide flux values for the intermediate covers were in the 1 to 10+2 g m-2 day-1 range for both seasons. The methane fluxes for the final cover were -10 -3 g m-2 day-1 and 10-4 g m-2 day-1 for the wet and dry season, respectively. The carbon dioxide flux values for the final cover were in the 10+1 g m-2 d-1 range and 1 to 10+1 g m-2 day-1 range for the wet and dry season, respectively. Negative flux values were typically observed during the wet season and at the intermediate and final covers. The destruction efficiencies for the twelve F-gases were above 99.5% for the onsite flare. Highest F-gas raw gas concentrations were measured for HFC-134a while the lowest F-gas concentration was measured for CFC-113. The F-gas concentrations in the raw gas ranged from 103 to 106 pptv. Similar to what has been reported in the literature, the landfill gas flare system was an efficient abatement device in controlling F-gas emissions. The surface emission measurement values from the field investigation were scaled up to estimate facility-wide fugitive emission values using the relative surface areas of the daily, intermediate, and final cover distributions in the landfill. The total fugitive emissions from the landfill including twelve F-gases, methane, and carbon dioxide ranged from 6,900 to 94,000 CO2E tonnes per year during the wet season, from 21,000 to 47,000 CO2E tonnes per year during the dry season, and from 13,000 to 75,000 CO2E tonnes per year during the year, prorated by the season (representing weighted average of 58% wet season emission rate and 42% dry season emission rate in a 12-month calendar year). The total fugitive F-gas emissions ranged from 1,600 to 4,800 CO2E tonnes per year during the wet season, from 140 to 600 CO2E tonnes per year during the dry season, and from 1,000 to 3,000 CO2E tonnes per year, prorated by the season. The total fugitive methane emissions ranged from 530 to 75,000 CO2E tonnes per year during the wet season, 17,000 to 35,000 CO2E tonnes per year during the dry season, and from 7,500 to 58,000 CO2E tonnes per year, prorated by the season. The total fugitive carbon dioxide emissions ranged from 5,000 to 14,000 CO2E tonnes per year during the wet season, 4,200 to 12,000 CO2E tonnes per year during the dry season, and from 4,500 to 13,000 CO2E tonnes per year, prorated by the season. In comparison to the total fugitive emission value derived from the first-order decay (FOD) model reported by USEPA and the total fugitive emission values calculated using waste-in-place (WIP) – landfill gas correlation equation presented in Spokas et al. (2015), the field-derived methane emission values were one to three orders of magnitude lower.

Electron density irregularities influence Global Navigation Satellite System (GNSS) signals, manifesting as ionospheric scintillation. Scintillation poses a service risk to safety-critical GNSS applications at high latitudes. It is difficult to predict, as ionospheric instability processes are not yet fully characterised. This research combines the fields of ionospheric imaging and scintillation monitoring, to investigate the causes of scintillation in the Antarctic and Arctic. Results revealed a plasma patch structure above Antarctica, in response to the impact of a solar wind shock front. Measurements from a network of Global Positioning System scintillation receivers across the continent revealed moderate levels of phase scintillation associated with Total Electron Content (TEC) gradients at the patch break-off point. Scintillation was also driven by solar particle precipitation at E and F region altitudes, verified with in situ spectrometers on polar-orbiting satellites. The current receiver coverage in the region provided the Multi-Instrument Data Analysis Software (MIDAS) tomography tool with sufficient data to track the lifetime of the plasma patch without a convection model. A second experiment was performed at the South Pole, using a collocated GPS scintillation receiver and auroral imager. This allowed simultaneous line-of-sight tracking of GPS signals through the optical auroral emissions. Results showed the first statistical evidence that auroral emissions can be used a proxy for ionospheric irregularities causing GPS scintillation. The relationship was strongest during the presence of discrete auroral arcs. Correlation levels of up to 74% were found over periods of 2-3 hours. The use of multiple emission wavelengths provided basic altitude discrimination. Current capability of ionospheric TEC mapping in the Arctic was tested, where GPS receiver distribution is extensive compared to present Antarctic coverage. Analysis of the ionosphere’s response to a storm event revealed a sequential picture of polar cap patch activity, without the aid of plasma convection modelling. The electron density enhancements of the auroral oval were imaged in completeness for the first time using GPS tomography. Reconstructions were verified using ultraviolet auroral imagery from polar-orbit satellites, and vertical profiles from an incoherent scatter radar.

To improve engine operational performance and reliability, this study focuses on the investigation into the behaviour of tribological conjunction between the ring - liner based on a comprehensive analysis of non-intrusive acoustic emission (AE) measurement. Particularly, the study will provide more knowledge of using AE for online monitoring and diagnosing the performances of the conjunction. To fulfil this study, it integrates analytical predictions of the theoretical modelling for the AE generation mechanism with extensive experimental evaluations. Moreover, effective signal processing techniques are implemented with a combination of the model based AE predictions to extract the weak and nonstationary AE contents that correlate more with the tribological behaviour. Based on conventional tribological models, tribological AE is modelled to be due to two main dynamic effects: asperity-asperity collision (AAC) and fluid-asperity interaction (FAI), which allows measured AE signals from the tribological conjunction to be explained under different scenarios, especially under abnormal behaviours. FAI induced AE is more correlated with lubricants and velocity. It presents mainly in the middle of engine strokes but is much weaker and severely interfered with AEs from not only valve landings, combustion and fuel injection shocks but also the effect of considerable AACs due to direct contacts and solid particles in oils. To extract weak AEs for accurately diagnosing the tribological behaviours, wavelet transform analysis is applied to AE signals with three novel schemes: 1) hard threshold based wavelet coefficients selection in which the threshold value and wavelet analysis parameters are determined using a modified velocity of piston motion which has high dependence on the AE characteristics predicted by the two models; 2) Adaptive threshold wavelet coefficients selection in which the threshold is gradually updated to minimise the distance between the AE envelopes and the predicted dependence; and 3) wavelet packet transform (WPT) analysis is carried out by an optimised Daubechies wavelet through a novel approach based on minimising the time and frequency overlaps in WPT spectrum. Based on these optimal analyses, the local envelope amplitude (LEA) and the average residual wavelet coefficient (ARWC) are developed from AE signals as novel indicators to reflect the tribological behaviours. Both the hard threshold based LEA and wavelet packet transform LEA values allow two different new lubricants to be diagnosed in accordance with model predictions whereas they produce less consistent results in differentiating the used oil under several operating conditions. Nevertheless, ARWC can separate the used oil successfully in that it can highlight the AAC effects of particle collisions in used oils. Similarly, LEA shows little impacts of two alternative fuels on the tribological behaviours. However, ARWC shows significantly higher amplitudes in several operating conditions when more particles can be produced due to unstable and incomplete combustions of both the biodiesel and FT diesel, compared with pure diesel, indicating they can cause light wear.

Defected wheel are one the major reasons endangered state of railroad vehicles safety statue, due to vehicle derailment and worsen the quality of freight and passenger transportation. Therefore, timely defect detection for monitoring and detecting the state of defects is highly critical. This thesis presents a passive non-contact acoustic structural health monitoring approach using ultrasonic acoustic emissions (UAE) to detect certain defects on different structures, as well as, classifying the type of the defect on them. The acoustic emission signals used in this study are in the ultrasonic range (18-120 kHz), which is significantly higher than the majority of the research in this area thus far. For the proposed method, an impulse excitation, such as a hammer strike, is applied to the structure. In addition, ultrasound techniques have higher sensitivity to both surface and subsurface defects, which make the defect detection more accurate. Three structures considered for this study are: 1) a longitudinal beam, 2) a lifting weight, 3) an actual rail-wheel. A longitudinal beam was used at the first step for a better understanding of physics of the ultrasound propagation from the defect, as well, develop a method for extracting the signature response of the defect. Besides, the inherent directionality of the ultrasound microphone increases the signal to noise ratio (SNR) and could be useful in the noisy areas. Next, by considering the ultimate goal of the project, lifting weight was chosen, due to its similarity to the ultimate goal of this project that is a rail-wheel. A detection method and metric were developed by using the lifting weight and two type of synthetic defects were classified on this structure. Also, by using same extracted features, the same types of defects were detected and classified on an actual rail-wheel.
Master of Science

This thesis presents a generic passive non-contact based acoustic health monitoring approach using ultrasonic acoustic emissions (UAE) to facilitate classification of bearing health via neural networks. This generic approach is applied to classifying the operating condition of conventional ball bearings. The acoustic emission signals used in this study are in the ultrasonic range (20-120 kHz), which is significantly higher than the majority of the research in this area thus far. A direct benefit of working in this frequency range is the inherent directionality of the microphones capable of measurement in this range, which becomes particularly useful when operating in environments with low signal-to-noise ratios. Using the UAE power spectrum signature, it is possible to pose the health monitoring problem as a multi-class classification problem, and make use of a multi-layer artificial neural network (ANN) to classify the UAE signature. One major problem limiting the usefulness of ANN's for failure classification is the need for large quantities of training data. Artificial training data, based on statistical properties of a significantly smaller experimental data set is created using the combination of a normal distribution and a coordinate transformation. The artificial training data provides a sufficient sized data set to train the neural network, as well as overcome the curse of dimensionality. The combination of the artificial training methods and ultrasonic frequency range being used results in an approach generic enough to suggest that this particular method is applicable to a variety of systems and components where persistent UAE exist.
Master of Science

Ion beam therapy (IBT) is a promising treatment option in radiotherapy. The characteristic physical and biological properties of light ion beams allow for the delivery of highly tumour conformal dose distributions. Related to the sparing of surrounding healthy tissue and nearby organs at risk, it is feasible to escalate the dose in the tumour volume to reach higher tumour control and survival rates. Remarkable clinical outcome was achieved with IBT for radio-resistant, deep-seated, static and well fixated tumour entities. Presumably, more patients could benefit from the advantages of IBT if it would be available for more frequent tumour sites. Those located in the thorax and upper abdominal region are commonly subjected to intra-fractional, respiration related motion. Different motion compensated dose delivery techniques have been developed for active field shaping with scanned pencil beams and are at least available under experimental conditions at the GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt, Germany. High standards for quality assurance are required in IBT to ensure a safe and precise dose application. Both underdosage in the tumour and overdosage in the normal tissue might endanger the treatment success. Since minor unexpected anatomical changes e.g. related to patient mispositioning, tumour shrinkage or tissue swelling could already lead to remarkable deviations between planned and delivered dose distribution, a valuable dose monitoring system is desired for IBT. So far, positron emission tomography (PET) is the only in vivo, in situ and non-invasive qualitative dose monitoring method applied under clinical conditions. It makes use of the tissue autoactivation by nuclear fragmentation reactions occurring along the beam path. Among others, β+-emitting nuclides are generated and decay according to their half-life under the emission of a positron. The subsequent positron-electron annihilation creates two 511 keV photons which are emitted in opposite direction and can be detected as coincidence event by a dedicated PET scanner. The induced three-dimensional (3D) β+-activity distribution in the patient can be reconstructed from the measured coincidences. Conclusions about the delivered dose distribution can be drawn indirectly from a comparison between two β+-activity distributions: the measured one and an expected one generated by a Monte-Carlo simulation. This workflow has been proven to be valuable for the dose monitoring in IBT when it was applied for about 440 patients, mainly suffering from deep-seated head and neck tumours that have been treated with 12C ions at GSI. In the presence of intra-fractional target motion, the conventional 3D PET data processing will result in an inaccurate representation of the β+-activity distribution in the patient. Four-dimensional, time-resolved (4D) reconstruction algorithms adapted to the special geometry of in-beam PET scanners allow to compensate for the motion related blurring artefacts. Within this thesis, a 4D maximum likelihood expectation maximization (MLEM) reconstruction algorithm has been implemented for the double-head scanner Bastei installed at GSI. The proper functionality of the algorithm and its superior performance in terms of suppressing motion related blurring artefacts compared to an already applied co-registration approach has been demonstrated by a comparative simulation study and by dedicated measurements with moving radioactive sources and irradiated targets. Dedicated phantoms mainly made up of polymethyl methacrylate (PMMA) and a motion table for regular one-dimensional (1D) motion patterns have been designed and manufactured for the experiments. Furthermore, the general applicability of the 4D MLEM algorithm for more complex motion patterns has been demonstrated by the successful reduction of motion artefacts from a measurement with rotating (two-dimensional moving) radioactive sources. For 1D cos^2 and cos^4 motion, it has been clearly illustrated by systematic point source measurements that the motion influence can be better compensated with the same number of motion phases if amplitude-sorted instead of time-sorted phases are utilized. In any case, with an appropriate parameter selection to obtain a mean residual motion per phase of about half of the size of a PET crystal size, acceptable results have been achieved. Additionally, it has been validated that the 4D MLEM algorithm allows to reliably access the relevant parameters (particle range and lateral field position and gradients) for a dose verification in intra-fractionally moving targets even from the intrinsically low counting statistics of IBT-PET data. To evaluate the measured β+-activity distribution, it should be compared to a simulated one that is expected from the moving target irradiation. Thus, a 4D version of the simulation software is required. It has to emulate the generation of β+-emitters under consideration of the intra-fractional motion, their decay at motion state dependent coordinates and to create listmode data streams from the simulated coincidences. Such a revised and extended version that has been compiled for the special geometry of the Bastei PET scanner is presented within this thesis. The therapy control system provides information about the exact progress of the motion compensated dose delivery. This information and the intra-fractional target motion needs to be taken into account for simulating realistic β+-activity distributions. A dedicated preclinical phantom simulation study has been performed to demonstrate the correct functionality of the 4D simulation program and the necessity of the additional, motion-related input parameters. Different to the data evaluation for static targets, additional effort is required to avoid a potential misleading interpretation of the 4D measured and simulated β+-activity distribu- tions in the presence of deficient motion mitigation or data processing. It is presented that in the presence of treatment errors the results from the simulation might be in accordance to the measurement although the planned and delivered dose distribution are different. In contrast to that, deviations may occur between both distributions which are not related to anatomical changes but to deficient 4D data processing. Recommendations are given in this thesis to optimize the 4D IBT-PET workflow and to prevent the observer from a mis-interpretation of the dose monitoring data. In summary, the thesis contributes on a large scale to a potential future application of the IBT-PET monitoring for intra-fractionally moving target volumes by providing the required reconstruction and simulation algorithms. Systematic examinations with more realistic, multi-directional and irregular motion patterns are required for further improvements. For a final rating of the expectable benefit from a 4D IBT-PET dose monitoring, future investigations should include real treatment plans, breathing curves and 4D patient CT images
Die Ionenstrahltherapie (englisch: ion beam therapy, IBT) ist eine vielversprechende Behandlungsoption im Bereich der Strahlentherapie. Die charakteristischen physikalischen und biologischen Eigenschaften der Ionenstrahlen werden genutzt, um tumorkonformale Dosisverteilungen zu erzeugen. Die verbesserte Schonung des an den Tumor angrenzenden Normalgewebes und eventuell naheliegender Risikoorgane ermöglicht eine Dosissteigerung im Zielgebiet und somit potentiell höhere Tumorkontroll- und Überlebensraten. Für tiefliegende, gegenüber konventioneller Strahlung resistente, statische und gut fixierte Tumore wurden bereits beachtliche klinische Resultate erzielt. Wahrscheinlich könnten noch mehr Patienten von den Vorteilen der IBT profitieren, wenn diese auch für häufiger auftretende und intrafraktionell bewegliche Tumore uneingeschränkt nutzbar wäre. Verschiedene bewegungskompensierte Bestrahlungsmethoden wurden entwickelt und stehen zumindest unter experimentellen Bedingungen für weitere Untersuchungen am GSI Helmholtzzentrum für Schwerionenforschung (GSI) in Darmstadt zur Verfügung. Um eine sichere und präzise Dosisapplikation in der IBT zu ermöglichen, werden hohe Anforderungen an die Qualitätssicherung gesetzt. Sowohl auftretende Überdosierungen im Normalgewebe als auch Unterdosierungen im Tumor können den Therapieerfolg gefährden. Da bereits kleine, unerwartete anatomische Veränderungen, zum Beispiel durch Fehlpositionierung des Patienten, Schrumpfung des Tumors oder Schwellungen, zu erheblichen Abweichungen zwischen geplanter und applizierter Dosisverteilung führen können, gibt es Bestrebungen, die applizierte Dosis zumindest qualitativ zu verifizieren. Die Positronen-Emissions-Tomografie (PET) ist derzeit die einzige, bereits klinisch erprobte Methode für ein in vivo, in situ und nicht-invasives qualitatives Dosismonitoring. Diese Methode ist im Stande, die Autoaktivierung des bestrahlten Gewebes zu erfassen, welche aufgrund von Kernfragmentierungsprozessen entlang des Strahlweges erzeugt wird. Unter anderem werden in diesen Reaktionen instabile Nuklide erzeugt, die entsprechend ihrer Halbwertszeit unter Emission eines Positrons zerfallen. Bei der anschließenden Positron-Elektron-Annihilation werden zwei 511keV Photonen in entgegengesetzter Richtung emittiert und können mittels eines geeigneten PET-Scanners als Koinzidenzereignis detektiert werden. Die im Patienten induzierte dreidimensionale (3D) β+-Aktivitätsverteilung kann aus den gemessenen Koinzidenzen rekonstruiert werden. Ein Vergleich der gemessenen mit einer erwarteten, mittels Monte-Carlo Simulation erzeugten β+-Aktivitätsverteilung erlaubt es, Schlussfolgerungen über die tatsächlich im Patienten deponierte 3D Dosisverteilung zu ziehen. Diese Art der Datenauswertung wurde erfolgreich für die qualitative Dosisverifikation von über 440 Patienten eingesetzt, deren Tumore (vorwiegend im Kopf- und Halsbereich) an der GSI mit 12C-Ionen bestrahlt wurden. Bei der konventionellen 3D IBT-PET-Datenverarbeitung wird eine mögliche intrafraktionelle Bewegung des Zielgebietes nicht berücksichtigt und fehlerhaft rekonstruierte β+-Aktivitätsverteilungen sind die Folge. Daher werden vierdimensionale, zeitaufgelöste (4D) Rekonstruktionsalgorithmen benötigt, die für die spezielle Geometrie eines in-beam PET-Scanner adaptiert wurden und eine Kompensation der bewegungsinduzierten Artefakte ermöglichen. Im Rahmen der vorliegenden Arbeit wurde für den an der GSI installierten Doppelkopf-PET-Scanner Bastei ein 4D Maximum-Likelihood-Expectation-Maximization (MLEM) Algorithmus implementiert. Die Funktionsfähigkeit des Algorithmus sowie dessen verbesserte Reduktion von Bewegungsartefakten im Vergleich zu einem bereits vorhandenen Koregistrierungsansatz wurde anhand verschiedener Messungen mit bewegten radioaktiven Quellen und bestrahlten Phantomen sowie einer vergleichenden Simulationsstudie dargelegt. Für die Experimente wurden entsprechende Phantomgeometrien (zumeist aus Polymethylmethacrylat (PMMA)) sowie ein Bewegungstisch für reguläre eindimensionale (1D) Bewegungsmuster entworfen und gefertigt. Zudem wurde durch die erfolgreiche, quasi-statische und nahezu artefaktfreie Rekonstruktion einer rotierenden und sich damit zweidimensional bewegenden Aktivitätsverteilung die prinzipielle Anwendbarkeit des 4D MLEM Algorithmus für komplexere Bewegungsmuster gezeigt. Systematische Punktquellenmessungen mit 1D cos^2- und cos^4-förmigen Bewegungsmustern haben deutlich gemacht, dass der Bewegungseinfluss mit der gleichen Anzahl an Bewegungsphasen besser kompensiert werden kann, wenn die Bewegungsphasen entsprechend der Bewegungsamplitude anstelle der -phase unterteilt sind. In jedem Fall können aber zufriedenstellende Rekonstruktionsergebnisse erzielt werden, wenn durch geeignete Parameterwahl eine mittlere Restbewegung pro Bewegungsphase von maximal etwa der halben Größe eines Detektorkristalls eingestellt wird. Durch weitere Experimente konnte gezeigt werden, dass nach der Rekonstruktion mit dem 4D MLEM Algorithmus die relevanten Parameter für die qualitative Dosisverifikation (Teilchenreichweite, laterale Feldposition und -gradienten) zuverlässig erfasst werden können. Dies ist auch dann der Fall, wenn nur eine verminderte Anzahl an Koinzidenzereignissen, so wie sie unter klinischen Bedingungen zu erwarten ist, für die Auswertung verwendet wird. Um die gemessene β+-Aktivitätsverteilung besser zu beurteilen, sollte sie mit einer simulierten, für die bewegungskompensierte Bestrahlung erwarteten Verteilung verglichen werden und es bedarf deshalb einer 4D Version der Simulationssoftware. Diese muss die Erzeugung sowie den Zerfall der Positronenemitter unter Berücksichtigung der intrafraktionellen Bewegung simulieren und aus den gültigen Koinzidenzereignissen Listmode-Datensätze erstellen. Eine derart überarbeitet Version des Simulationsprogramms wurde für den Bastei PET-Scanner erstellt und wird in dieser Arbeit vorgestellt. Informationen über den exakten Verlauf der bewegungskompensierten Bestrahlung werden durch das Therapiekontrollsystem geliefert. Diese Informationen sowie die intrafraktionelle Bewegung werden in die Simulation realistischer β+-Aktivitätsverteilungen bzw. der zugehörigen Listmode-Datensätze einbezogen. Anhand einer präklinischen Phantom-Simulationsstudie wurde die korrekte Funktionsweise des Simulationsprogramms sowie die Notwendigkeit der zusätzlichen Parameter gezeigt. Im Gegensatz zur Datenauswertung für statische Zielvolumina bedarf es bei intrafraktioneller Bewegung gegebenenfalls zusätzlichen Aufwand, um eine Fehlinterpretation aus dem Vergleich der gemessenen und simulierten β+-Aktivitätsverteilung zu vermeiden. In der vorliegenden Arbeit wird beispielhaft gezeigt, dass sich bei fehlerhafter Bewegungskompensation die gemessene und simulierte β+-Aktivitätsverteilung einander ähneln können, obwohl die applizierte Dosisverteilung deutlich von der geplanten abweicht. Im Gegensatz dazu können auch Abweichungen zwischen Messung und Simulation auftreten, die nicht auf anatomische Veränderungen, sondern auf eine ungenaue 4D Datenverarbeitung zurückzuführen sind. Es werden Vorschläge unterbreitet, um den Prozess der 4D IBT-PET Datenauswertung zu optimieren und somit Fehlinterpretationen zu vermeiden. Die vorliegende Dissertationsschrift enthält durch die Bereitstellung der benötigten 4D Rekonstruktions- und Simulationsprogramme grundlegende Arbeiten für eine mögliche zukünftige Anwendung der 4D IBT-PET als qualitatives Dosismonitoring bei intrafraktionell bewegten Zielvolumina. Für weitere Verbesserungen des Verfahrens sind zusätzliche systematische Betrachtungen mit realistischeren, mehrdimensionalen und unregelmäßigen Bewegungsmustern notwendig. Zukünftige Untersuchungen sollten außerdem echte Bestrahlungspläne, Atemkurven sowie 4D Patienten-CT-Daten einschließen, um den erwartbaren Nutzen eines 4D IBT-PET Dosismonitorings besser abschätzen zu können

De senaste åren har utsläppsreglerna för sjöfarten blivit allt hårdare och under de kommande åren skärps de ännu mer. För att svaveldirektiven för sjöfarten ska fungera effektivt så krävs det också att de efterlevs. Syftet med den här studien var därför att undersöka hur länderna i Europeiska SECA områdena agerar och kommer att agera i framtiden för att se till att svaveldirektiven efterlevs. Studien syftar också till att undersöka hur efterlevnadskontroller genomförs, samt se om länderna har infört sanktioner mot överträdelser och vad dessa innebär. För att få svar på detta studerades lagar och förordningar, men framförallt skickades frågeformulär ut till de ansvariga myndigheterna i flera olika länder kring SECA områdena. Slutsatsen av det här arbetet är att samtliga länder anser att efterlevnadskontroll sker i tillräcklig omfattning och alla länder använder sig av samma metod. I Sverige pågår utveckling av en optisk mätmetod för att mäta svavelhalt i avgaserna ifrån luften, men än är metoden inte tillräckligt säker för att kunna användas. Det framkom också att i flera länder anses det på grund av flera faktorer vara svårt att fälla någon ifall de bryter mot gällande svavelförordningar, därför anses det också finnas en risk för överträdelser. Detta trots att det i andra länder faktiskt sker ingripande mot överträdelser och samtliga länder använder sig av samma metoder för efterlevnadskontroll. Det saknas i dagsläget även sanktioner mot överträdelser i flera länder.

Emissions of hydrogen sulfide (H2S) from construction and demolition (C & D) landfills can result in odors that are a significant nuisance to nearby neighborhoods and businesses. As Florida's population continues to grow and create development pressures, housing is built closer to existing landfills. Additionally, new landfills will be created in the future. This research project was undertaken to develop a detailed modeling methodology for use by counties and other landfill owners to provide them with an objective and scientifically defensible means to establish odor buffer zones around C & D landfills. A technique for estimating methane (and odorous gas) emissions from municipal solid waste (MSW) landfills was recently developed by researchers at the University of Central Florida. This technique was based on measuring hundreds of ambient methane concentrations near the surface of the landfill, and combining that data with matrix inversion mathematics to back-solve the dispersion equations. The technique was fully documented in two peer-reviewed journal articles. This project extends that methodology. In this work the author measured ambient H2S concentrations at various locations in a C & D landfill, and applied those same matrix inversion techniques to determine the H2S emission rates from the landfill. The emission rates were then input into the AERMOD dispersion model to determine H2S odor buffer distances around the landfill. Three sampling trips to one C & D landfill were undertaken, data were taken, and the modeling techniques were applied. One problem encountered was that H2S emissions from C & D landfills are typically about 1000 times smaller than methane emissions (from MSW landfills). Thus, H2S ambient concentrations often are near the detection limits of the instruments, and the data may not be as reliable. However, this approach could be used for any particular C & D landfill if the appropriate amount of data were available to characterize its emissions with some certainty. The graphical tool developed in this work shows isopleths of "H2S" concentrations at various distances, and color codes the isopleths into a "green-yellow-red" scheme (analogous to a traffic signal) that depicts zones where private landowners likely will not detect odors, where they may experience some odors, or where they likely will experience odors. The “likelihood” can be quantified by selecting the Nth highest hourly concentrations in one year to form the plot. In this study, N was conservatively selected as 8. Requiring that concentrations be at or below the 8th highest concentration in a year corresponds to a 99.9% probability of not exceeding that concentration at that distance in any future year. The graphical tool can be applied to any C & D landfill but each landfill is different. So this technique depends on having a fairly good estimate of the rate of emissions of H2S from the landfill in question, and at least one year's worth of hourly meteorological data (wind speed, direction, and stability class) that is representative of the landfill location. The meteorological data can be obtained with relative ease for most locations in Florida; however, the emission data must be obtained from on-site measurements for any given landfill.
ID: 031001460; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: .; Title from PDF title page (viewed July 8, 2013).; Thesis (M.S.Env.E.)--University of Central Florida, 2012.; Includes bibliographical references (p. 76-77).
M.S.Env.E.
Masters
Civil, Environmental, and Construction Engineering
Engineering and Computer Science
Environmental Engineering

The problem of waste management and waste generation in the shipbuilding sector is crucial in the context of sustainability, in which context the concept of a circular economy system for both re-use and recycling of waste should also be included. For these considerations, the proposed study examines a combined system for optimising ship waste management and evaluates its possible use for energy purposes. In addition, this work aims to develop indicators to monitor and assess the instantaneous environmental impact in the air from different types of ships. With regard to the first point, a number of systems were analysed in relation to their potential to reduce greenhouse gas emissions, regardless of the routes and ports of destination. As a re- sult of this analysis, the case studies of particular interest were identified: the thermochemical treatment of waste oils and sludges to obtain fuel oils, the installation of a waste-to-energy plant and subsequent energy recov- ery on board, a potential innovative pattern of recycling food waste from cruise ships for use as feed in aquaculture and potential green practices with particular attention to paper input and output flows in a waste mini- mization perspective. UNFCCC (United Nations Framework Convention on Climate Change) methodologies were applied to two of these case stud- ies to calculate the reduction in greenhouse gas emissions resulting from their implementation. The results obtained are presented with the aim of supporting sustainable on-board waste management strategies in a carbon circular economy perspective. With regard to the second point, the main objective was to make an objective assessment of the ship’s environmental impact in real time to allow for possible adjustments and improve energy efficiency. The definition of these new indicators can be used as a decision support system for shipboard personnel. Environmental performance indi- cators are developed following the evaluation of data collected on board by specific instrumentation, marine exhaust cleaning systems, existing legis- lation. Different ship types, characterised by different propulsion system configurations, are considered using real experimental data provided by CETENA, a Fincantieri Group company. The indicators allow to compare the performance of the ship and the efficiency of the exhaust cleaning sys- tems under different operating conditions. They can be used as new tools, added to existing instrumentation that can be implemented to minimize the ship’s environmental footprint.

In the context of Structural Health Monitoring, the Acoustic Emission Technique may be efficiently used to detect damage on aerospace structures. This study focuses on the development of a source identification algorithm to distinguish different acoustic emission events in aluminium sheets, which have been collected during experimental tests. The future goal will be the design of a Holistic Structural Health Monitoring System which will make the complete aircraft an intelligent structure able to diagnose its own structural damage based on the condition of the structure while maintaining safety.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
Since the signing of the Nuclear Nonproliferation Treaty, the technical community has been working to develop verification options that provide confidence in the reduction or elimination of nuclear warheads, while respecting countries' requirement of limited access to national secrets. This dissertation used a simplified open-source warhead model as a vehicle to investigate the use of secondary gammas, generated passively by neutron interactions inside high explosive (HE), as a signature for the presence of a warhead-like object. Analytical calculations were done to estimate the detectability of radiative capture and inelastic scatter emissions generated within the warhead model. Results showed the emission of gammas from nitrogen, between 5-7 MeV, to be detectable above background with dwell-times exceeding 90 minutes. These calculations motivated the systematic study of the signal experimentally using surrogate materials to represent the warhead's weapons-grade plutonium and HE. The experiment did not show the expected signals. This motivated a simulation of the mock-up experiment using the radiation transport code MCNP6 to help understand the observed results. The experimental and simulation data suggest that correlated backgrounds from neutron interactions with environmental materials dominate the signal. This finding helped provide a basis for understanding the feasibility and challenges to detecting this neutron-induced gamma signal. Three sets of pulse-height spectra have been analyzed: experimental spectra that looked at the effect of the HE surrogate on the overall detected counts; simulated spectra that helped to understand the underlying contributors to the observed experimental result; and a data-MCNP6 comparison that assessed the accuracy of the simulated results. Each set contributed to the quantification of detectability for the emissions of interest. The findings suggest the passive detection of the expected high-energy gamma signal is not feasible, unless backgrounds can be better controlled. The difficulty is attributed to low solid-angle coverage of the neutron source by the melamine explosive surrogate, and competing backgrounds produced by neutron-source interactions with surrounding materials. This thesis also examined the benefits and tradeoffs of this particular verification approach by investigating the non-technical context of the verification, such as the preferences of negotiators. The tradeoffs between confidence and intrusiveness highlight the need for technical verification solutions that span the diversity of options. Factors limiting the development of warhead verification systems, from the bias of researchers to issues of classification and sensitive geometries, were discussed.
by Mareena Robinson Snowden.
Ph. D.

En contexte de réservoirs géologiques, les veines sont des fractures dans lesquels des espèces chimiques ont précipité et qui ont été longtemps associées avec le modèle de ‘fissuration-minéralisation’. Cependant, certaines veines présentent des caractéristiques laissant penser que la précipitation provoquerait la fissuration en s’appuyant sur le concept de pression de cristallisation. En partant de là, deux expériences ont été développées. Pour commencer, nous avons fait précipiter un front de barytine, par diffusion de deux solutions respectivement enrichies en baryum et sulfate à travers deux milieux poreux : un calcaire de Lavoux et un grès des Vosges contenant une fraction d’argile. Le front de barytine précipité a été investigué par l’acquisition de donnés de micro tomographie rayon X, de la microscopie optique et à balayage électronique et de la spectroscopie rayon X. En pratique, aucun endommagement n’a été détecté mais la barytine a nucléé et précipité en relation avec la distribution des pores, l’état de cristallisation des minéraux de la matrice et la présence des complexes argileux. On suspecte une augmentation de volume en lien avec ce dernier point. L’étude de l’endommagement des sels dans le contexte de la préservation des monuments historiques est à la base de notre deuxième expérience réalisée sous un confinement isotrope dans une cellule triaxial du laboratoire de géologie de l’école normale supérieur de Paris. Un front de sulfate de sodium ou de sulfate de magnésium déshydraté est préalablement précipité dans un grès des Vosges et réhydraté pendant l’expérience par imbibition capillaire d’eau milli-Q. De l’endommagement a été mesuré jusqu’à une pression de 27 MPa par l’acquisition d’émissions acoustiques, la propagation d’onde élastique, des jauges de déformation et données de micro tomographie rayons X. Ces experiences montrent une compétition entre la cimentation par le sel du milieu poreux et l'endommagement par crystallisation. Ceci est confirmé par la modélisation des propriétés mécaniques du milieu poreux saturé en sel lors de son hydratation
Veins in geological reservoir settings are mineral-filled fractured long being associ- ated with the model of ‘crack seal’. However, some veins exhibit features that do not match with the model of ‘crack seal’ but would better fit with a ‘seal-crack’ model driven by the concept of crystallisation pressure. From this, two main experimental tests are conducted. We start with an experiment of counter diffusion to precipitate a barite front in an oolite limestone, the Lavoux limestone, and a sandstone with a shale fraction, the Adamswiller sandstone. The reacted samples are analysed via 3D X-ray microtomography, microscopy and SEM-EDS microanalysis. Although we do not ob- serve damage, we show that barite nucleation and crystallisation is linked to the pore distribution and the matrix mineral. In particular, barium interacts with clay min- erals like the smectite-chlorite complex. Ultimately, this interaction may expand the complex basal space when barite precipitates. Then salt studies for the understanding of damage induced on cultural heritage are the starting point of a new protocol with Na2SO4 and MgSO4 to be tested under isotropic confining pressure inside a triaxial cell (ENS Paris). It consists of precipitating an anhydrous salt layer in an Adamswiller sandstone. Later the anhydrous salt layer is rewetted to precipitate a more hydrated salt phase. The damage is monitored at a confining pressure up to 27 MPa with acous- tic emission, elastic wave propagation, strain gauges and 3D X-ray microtomography. These experiments emphasize the competition between salt cementation of the porous medium and salt crystallisation induced damage. The last point is confirmed by the ef- fective modeling of the elastic properties of a porous medium impregnated with sodium sulphate when it is rewetted without confining pressure

In my master thesis I focus on evaluation of gas emissions from the Nuclear Power Station (NPS) Dukovany. My goal is to judge a fulfilment of czech legislative demands and Euratom “Commison recommendation on standartised information on radioactive airborne and liquid discharges into the environment form nuclear power reactors in normal operation” by operator of the NPS Dukovany. I give an acount of resources of gas radioaktive waste in the NPS Dukovany, methods of their cleaning and monitoring in air-conditioning systems in the NPS. Moreover, I sumarize czech legislative demands on monitoring of gas emissions from nuclear power stations and valide decisions of State Office for Nuclear Safety (SONS) for discharges of radionuclids from NPS Dukovany into environment, where autorised limits for gas emissions into atmosphere are set. In the folowing part of the thesis, I describe separate elements bound for monitoring of gas emissions, including technical parameters of individual measuring instruments. Sumary of radioactive emissions to athmosphere during 2007 and sumary of emissions within last 10 years are also included. Finaly, I deal with an analysis on the fulfilment of Euratom Commission demands for monitoring of gas emissions in the NPS Dukovany and I evaluate imperfections to be found during the proces of monitoring of gas emissions from the NPS Dukovany and I make some recommendatios for their correction and improvement of the monitoring. In conclusion, the NPS Dukovany fulfils demands of the czech legislation and decisions of SONS in the field of monitoring of gas emissions into atmosphere. The NPS Dukovany is aware of above mentioned imperfections and focuses on up-dating of measuring instruments in the course of investments, which are under preparation.

Air pollutants pose a high risk for humans, and the environment, and this pollution is one of the major environmental problems facing modern society. Active air sampling is the technique that has been traditionally used to monitor nonpolar aromatic air pollutants. However, active high volume samplers (HiVols) require a power supply, maintenance and specialist operators, and the equipment is often expensive. Thus, there is a need to develop new, less complicated sampling techniques that can increase the monitoring frequency, the geographical distribution of the measurements, and the number of sites used in air monitoring programs. In the work underlying this thesis, the use of semipermeable membrane devices (SPMDs) as tools for monitoring gas phase concentrations of nonpolar aromatic compound was evaluated using the compound classes polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs) and nitrated PAHs (nitro-PAHs) as test compounds.

High wind-speeds increased the uptake and release in SPMDs of PAHs and PCBs with log K_OA values > 7.9, demonstrating that the uptake of most nonpolar aromatic compounds is controlled by the boundary layer at the membrane-air interface. The use of a metal umbrella to shelter the SPMDs decreased the uptake of PAHs and PCBs by 38 and 55 percent, respectively, at high wind/turbulence, and thus reduced the wind effect. Further, the use of performance reference compounds (PRCs) to assess the site effect of wind on the uptake in SPMDs reduced the between-site differences to less than 50 percent from as much as three times differences in uptake of PCBs and PAHs. However, analytical interferences reduced the precision of some PRCs, showing the importance of using robust analytical quality control.

SPMDs were shown to be efficient samplers of gas phase nonpolar aromatic compounds, and were able to determine local, continental and indoor spatial distributions of PAHs, alkyl- PAHs and nitro-PAHs. In addition, the use of the SPMDs, which do not require electricity, made sampling possible at remote/rural areas where the infrastructure was limited. SPMDs were also used to determine the source of PAH pollution, and different approaches were discussed. Finally, SPMDs were used to estimate the importance of the gas phase exposure route to the uptake of PAHs in plants. The results demonstrate that SPMDs have several advantages compared with HiVols, including integrative capacity over long times, reduced costs, and no need of special operators, maintenance or power supply for sampling. However, calibration data of SPMDs in air are limited, and spatial differences are often only semi-quantitatively determined by comparing amounts and profiles in the SPMDs, which have limited their use in air monitoring programs. In future work, it is therefore important that SPMDs are properly sheltered, PRCs are used in the sampling protocols, and that calibrated sampling rate data, or the SPMD-air partition data, of specific compounds are further developed to make determination of time weighted average (TWA) concentrations possible.

Urban air pollution is responsible for high levels of morbidity and mortality in exposed populations due to its effects on cardiovascular and respiratory function. Transportation-related air pollutants account for the majority of harmful air pollution in urban areas. Forests are known to reduce air pollution through their ability to facilitate dry deposition and atmospheric gas exchange. This work characterizes the interactions between transportation air pollutants and urban forests in Hillsborough County, Florida. A highly spatially resolved passive air sampling campaign was conducted to characterize local concentrations of nitrogen oxides, benzene, toluene, ethylbenzene, and xylenes (BTEX) in Hillsborough County, Florida. Sampling locations included a proportion of densely forested urban areas in order to determine the effects of Hillsborough County's urban forest resources on localized concentrations of selected transportation pollutants. Recommended approaches for the use of urban forests as an effective air pollution mitigation technique in Hillsborough County were generated based on results from the sampling campaign. Results show mean concentrations of 2.1 parts per billion and 6.5 µg/m3 for nitrogen oxides and total BTEX, respectively. High spatial variability in pollutant concentrations across Hillsborough County was observed, with the coefficient of variation found to be 0.61 for nitrogen oxides and 0.79 for total BTEX. Higher concentrations were observed along interstate highways, in urban areas of the county, and near select point sources in rural areas. Differences in concentrations within forested areas were observed, but were not statistically significant at the 95%#37; confidence level. These results can be used to identify elements of urban design which contribute to differences in concentrations and exposures. This information can be used to create more sustainable urban designs which promote health and equity of the population.

Billions of people use biomass burning cookstoves in their homes and suffer serious health repercussions. Additionally, global warming is exacerbated by cookstove emissions containing greenhouse gases and particulate matter. Improved cookstoves (ICSs) mitigate the problem, but accurate and affordable emission gas measurements, particularly of Carbon Dioxide (CO2) and Carbon Monoxide (CO), are required in order to confidently declare ICSs cleaner burning than traditional cookstoves. The aim of this research is to assess the suitability of photoacoustic (PA) CO2 detection technology for cookstove emissions monitoring. The designs of several longitudinally resonant, photoacoustic, LED, CO2 sensors of varying levels of functionality are presented. Three aluminum cell designs allowed the detection of a photoacoustic signal: a 4cm long cylinder with a ~1cm diameter (Design 3), a 3.9cm long cylindrical resonator with ~1in diameter and quarter-acoustic-wavelength buffer volumes (Designs 4a,b), and a 3.7cm long cylinder with ~1in diameter (Design 5). All three cell designs operate in the longitudinal resonant mode via the irradiation of gases inside the PA cell with a 4.3um wavelength LED, driven at an on-off frequency in the kHz range by a square wave from an Arduino. A rudimentary lock-in amplifier (LIA) based on the AD630 was considered, but the SR830 LIA was actually used to extract the desired MEMS microphone signal from noise. Designs 3-4b produced PA signals dominated by wall-absorption, but the final design (Design 5) yielded a resonant PA signal proportional to CO2 concentration. It was discovered that photoacoustic gas detection is challenging to design and set up without extensive experience and equipment. Practical lessons learned are shared. Primary limitations with the presented designs are identified as the extremely low power of the 4.3um LEDs, wall absorption due to insufficient collimation of LED radiation, dependence on temperature, and reliance on an expensive, high performance, lock-in amplifier. Further testing and development of designs like Design 5 (short cylinder with large diameter-to-length ratio) is necessary to evaluate their potential for in-field, real-time CO2 concentration measurement. Though LED PA CO2 sensing was demonstrated to be possible, it is concluded that NDIR CO2 sensors are currently better suited for cookstove use. In addition to photoacoustic detection, a method of detecting CO2 concentration by measuring resonant frequency of the gas cell (The Acoustic Method) is presented.

O presente estudo foi desenvolvido para caracterizar a área de influência dos corredores de tráfego, através do monitoramento da concentração de elementos-traço em cascas de árvores. Amostras (n = 98) de cascas de árvores de diversas espécies foram coletadas em cinco parques urbanos da cidade de São Paulo. Para controle, foram coletadas cascas de árvores numa zona rural de Embu-Guaçu, longe de tráfego ou de indústrias. As concentrações de Ba, Co, Cr, Cu, Fe, Ca, Pb, S e Zn foram determinadas nas amostras de cascas de árvores por espectrometria de fluorescência de raios-X. Amostras coletadas nos parques urbanos apresentaram níveis mais elevados de elementos-traço em comparação com as da região controle. Elementos relacionados a atividades antropogênicas exibiram maiores concentrações nas amostras coletads na periferia dos parques, diminuindo gradativamente para os seus centros. Áreas próximas a grandes avenidas ou próximas a semáforos e cruzamentos apresentaram maiores concentrações de elementos nas cascas. Em conclusão, o estudo mostrou que medidas de acúmulo de elementos traço em cascas de árvore, associadas a métodos geoestatísticos, podem auxiliar a determinação das zonas de maior influência da poluição veicular no cenário urbano
The present study was designed to characterize the area of influence of high traffic corridors by monitoring trace element concentrations on tree barks. Samples (n=98) of tree barks were collected from several tree species in five urban parks of the city of São Paulo. For controlling purposes, we collected tree barks in a rural area of Embu-Guaçu which is far from traffic or industries. Concentrations of Ba, Co, Cr, Cu, Fe, Ca, Pb, S and Zn were determined in these barks by X-ray fluorescence spectrometry. Samples from urban parks exhibited higher levels of trace elements in comparison with those from control region. Elements related to anthropogenic activities exhibited higher concentrations in tree barks at the periphery of the parks, decreasing when moving towards their centers. Areas facing the busy streets or those close to traffic lights or traffic junctions presented higher concentrations of elements in barks. In conclusion, the present study showed that measures of trace elements accumulation in tree barks within geostatistical methods can indicate areas of strong influence of vehicular pollution in the urban scene

There has been an influx of air-quality systems in indoor and outdoor environments. The main purpose of these systems is to gauge the air quality with parameters known to cause harmful effects to humans. Generally, an index is drawn by using these parameters to indicate the scale of pollution. Existing work in outdoor air quality systems spans across community driven sensing, mobile sensing, and city or nationally supported sensing. The large body of related work appears fragmented, and has not shown to be explored in a cradle to grave fashion. This thesis explores an integrated system built using wireless sensor network for measuring air quality in the city of Uppsala, Sweden. An in-depth study was performed to evaluate the operational performance of the system, assess the quality of data, comparison with reference monitoring stations, and analysis to study patterns.

Este trabalho apresenta os resultados da construção de um espectrômetro utilizando a espectroscopia ótica por absorção diferencial (DOAS) para determinação de poluentes na atmosfera. A determinação e a quantificação de gases-traço contaminantes na atmosfera são possíveis pelo registro da transmitância, e posterior avaliação das estruturas de absorção características de cada espécie, em um caminho ótico aberto conhecido na atmosfera. As partes óticas e eletrônicas foram caracterizadas e o software de comando e processamento espectral foi desenvolvido. O sistema construído foi testado em laboratório e medidas de emissões veiculares de quatro automóveis foram realizadas. Os resultados das emissões veiculares apresentaram uma sensível diferença entre os veículos no regime de operação (motor frio e quente) por um fator que varia entre 5 e 8.
This work presents the results of the construction of a spectrometer using the differential optical absorption spectroscopy (DOAS) for determination of pollutants in the atmosphere. The determination and quantification of trace gas contaminations in atmosphere is possible by recording and later evaluation of characteristic absorption structures in a known path length in open atmosphere. The parts optics and electronic had been characterized and the software of command and spectral processing was developed. The system was built and tested in laboratory and vehicle emissions measures of four cars were performed. The results in vehicle emissions showed a noticeable difference between vehicles in the system of operation (hot and cold engine) by a factor ranging between 5 and 8.

Devido à dispersão heterogênea da poluição do ar, é importante compreender as fontes de poluição local para avaliar os impactos sobre a saúde humana. Os elementos químicos, especialmente metais, podem afetar a saúde humana, causando efeitos genotóxicos, indução de câncer e danos nos sistemas imunes e neurológicos. Alguns elementos são considerados marcadores de emissões veiculares. Por conseguinte, é de grande interesse avaliar se existe uma relação entre o fluxo de tráfego de veículos e a deposição de elementos usando a técnica biomonitoramento. Neste estudo, casca de árvore de 171 diferentes pontos de amostragens coletados no centro expandido da cidade de São Paulo foi utilizada como biomonitora. As concentrações dos elementos químicos (Al, Ba, Ca, Cl, Cu, Fe, K, Mg, Mn, Na, P, Pb, Rb, S, Sr e Zn) foram determinadas por meio da espectrometria de fluorescência de raios x por dispersão de energia (EDXRF). A técnica estatística da análise de componentes principais (PCA) foi aplicada aos resultados analíticos obtidos para identificar as fontes de poluentes de elementos químicos. A principal fonte de poluentes do ar encontrada no Centro expandido da cidade de São Paulo pôde ser atribuída à emissão veicular principalmente de processos de desgastes de suas peças e da ressuspensão das poeiras das vias (caracterizados por Al, Ba, Cu, Fe, Mn e Zn), explicando 27,1 % da variância, seguida de cimento das construções (14,8 %), sal marinho (11,6 %) e queima de madeira (10 %) O modelo receptor conhecido como fatoração de matriz positiva utilizado para identificação das fontes de poluição do ar mostrou também que a emissão veicular é a principal fonte de origem dos poluentes na área de estudo. Foi verificado ainda que os elementos relacionados à emissão veicular apresentaram diferentes concentrações em uma mesma rua, e estes resultados permitiram obter uma nova classificação das ruas de acordo com a concentração dos elementos. Os mapas de distribuição espacial das concentrações dos elementos foram obtidos para avaliar os diferentes níveis de poluição em ruas e avenidas. Os resultados indicaram que a técnica de biomonitoramento pode ser aplicada para avaliar a dispersão da poluição do ar
Due to the heterogeneous dispersion of air pollution, it is important to understand sources of local pollution to assess impacts on human health. Chemical elements, especially metals, can affect human health, causing genotoxic effects, cancer induction, and damage in the immune and neurological systems. Some elements are considered markers of vehicle emissions. Consequently it is of great interest to evaluate if there is a relationship between the vehicular traffic flow and deposition of elements measured using the biomonitoring technique. In this study, tree barks from 171 sampling sites in the inner city of São Paulo were collected. The chemical elements (Al, Ba, Ca, Cl, Cu, Fe, K, Mg, Mn, Na, P, Pb, Rb, S, Sr and Zn) were determined by the energy dispersive x-ray fluorescence (EDXRF) spectrometry. The principal component analysis (PCA) statistical technique was applied to the analytical results in order to identify the origin of element pollutants. The results indicated that major source of air pollution is due to vehicular emission derived mainly from wear processes and road dust resuspension (characterized by Al, Ba, Cu, Fe, Mn and Zn), which was explained by 27.1 % of the variance, followed by cement from building constructions and road pavements (14.8 %), sea salt (11.6 %) and wood burning (10 %) at São Paulo inner city. The algorithm called positive matrix factorization (PMF) likewise used to identify the air pollution sources showed that the vehicular emission is also the main source of atmospheric pollution. We also verified that the elements related to vehicular emission presented different concentrations at different sampling sites of the same street, which might be possible to identify a new street classification according to the elemental concentration. The spatial distribution maps of element concentrations were obtained to evaluate the different levels of pollution on streets and avenues. Results indicated that biomonitoring technique can be applied to evaluate dispersion of air pollution

Acoustic emission (AE) is one of many technologies for health monitoring and diagnosis of rotating machines such as gearboxes. Although significant research has been undertaken in understanding the potential of AE in monitoring gearboxes this has been solely applied to spur gears and slow speed roller bearings. This research presents an experimental investigation that assesses the effectiveness of both AE and vibration technologies in identifying various types of defects on in a helical gearbox; the first known attempt. Furthermore, the application of advanced signals processing techniques such as Spectral kurtosis (SK) and wavelet analysis were studied on AE and vibration signatures. It is shown that the application of advanced signal processing methods is particularly necessary for monitoring helical gears. The application of SK and wavelet analysis was found to be effective in denoising the acquired signals. The first chapter of this thesis is an introduction to this research and briefly explains motivation and theoretical background supporting this research. The second chapter summaries the relevant literature to establish the current level of the knowledge in this field. The third chapter describes methodologies and experimental arrangement utilized for this investigation. Chapter 4 discusses helical gear diagnosis for both natural and seeded surface defect. Chapter 5 reports on an experimental investigation in which several technologies such as AE, vibration and motor current signature analysis, were applied to identify the presence of a naturally fatigued pinion shaft in an operating gearbox. Chapter 6 details an investigation which compared the applicability of AE and vibration technologies in monitoring a naturally degraded roller bearing. It has been concluded that AE is a strong diagnostic tool for early diagnosis of bearings faults. However, the application of condition monitoring for helical gear diagnosis was fraught with some degree of complexity as compared to spur gears. This implies that condition monitoring of the gears using AET can be challenging. On the contrary, the applicability of AET for bearing diagnosis was promising and it offered an absolute advantage over the conventional vibrationdiagnosis. Furthermore, the application advanced signals processing methods such as Spectral Kurtosis and wavelet was found to be promising in denoise the recorded AE signals. It was also concluded that the use of different signal processing methods is often necessary to achieve meaningful diagnostic information from the signals.