While most filters are made of pleated fibrous media, almost all existing theories of aerosol filtration are developed for flat media placed perpendicular to the air flow. Expressions developed for flat sheet media do not provide accurate information directly useful for designing a pleated filter, and therefore, most progress made in developing pleated filters is based on empiricism. This study is aimed at establishing an enabling knowledge that allows for a better design and optimization of pleated aerosol filters. This study is focused on developing a predictive simulation method that accounts for the influence of a filter’s micro-scale geometric parameters, such as fiber orientation, as well as its macro-scale features, like pleat shape, in predicting the transient pressure drop and collection efficiency with or without the effects of dust loading. The dual-scale simulation method developed in this work is believed to be the only feasible approach for design and optimization of pleated aerosol filters with the current academic-level computational power. Our study is divided into two major tasks of micro- and macro-scale modeling. Our micro-scale studies are comprised of a series of CFD simulations conducted in virtual 2-D or 3-D fibrous geometries that resemble the internal micro-structure of a fibrous medium. These simulations are intended to isolate the effects of each micro structural parameter and study its influence on the performance of the filter medium. In detail, it is intended to propose a method to predict the performance of micro-structures with fiber size distribution. Also, the effects of micro-structural fiber orientation were investigated. Moreover, we offered methodology to predict the performance of noncircular fibers using available analytical expressions for circular fibers. It is shown that the circumscribed circle for a trilobal shaped fiber gives the best prediction for collection efficiency. In macro-scale simulations, on the other hand, the filter medium is treated as a lumped porous material with its properties obtained via micro-scale simulations. Our results showed that more number of pleats helps better performance of pleated filters, however, if the pleat channel becomes blocked by dust cake then this effect is no longer valid.

High-mass stars form within star clusters from dense, molecular regions (DMRs), but is the process of cluster formation slow and hydrostatic or quick and dynamic? We link the physical properties of high-mass star-forming regions with their evolutionary stage in a systematic way, using Herschel and Spitzer data. In order to produce a robust estimate of the relative lifetimes of these regions, we compare the fraction of DMRs above a column density associated with high-mass star formation, N(H-2) > 0.4-2.5 x 10(22) cm(-2), in the "starless" (no signature of stars >= 10 M circle dot forming) and star-forming phases in a 2 degrees x 2(degrees) region of the Galactic Plane centered at l = 30 degrees. Of regions capable of forming high-mass stars on similar to 1 pc scales, the starless (or embedded beyond detection) phase occupies about 60%-70% of the DMR lifetime, and the star-forming phase occupies about 30%-40%. These relative lifetimes are robust over a wide range of thresholds. We outline a method by which relative lifetimes can be anchored to absolute lifetimes from large-scale surveys of methanol masers and UCHII regions. A simplistic application of this method estimates the absolute lifetime of the starless phase to be 0.2-1.7 Myr (about 0.6-4.1 fiducial cloud free-fall times) and the star-forming phase to be 0.1-0.7 Myr (about 0.4-2.4 free-fall times), but these are highly uncertain. This work uniquely investigates the star-forming nature of high column density gas pixel by pixel, and our results demonstrate that the majority of high column density gas is in a starless or embedded phase.

The purpose of this study was to investigate whether the sampling points for measuring airborne dust deposition in the Aitik copper mine - the largest, most effective opencast copper mining in Europe - are well located regarding efficiency to collect monitoring data. Issues that were addressed, among others, include background levels, weather impacts and possible external influence. The study was carried out by analyzing monitoring data covering a seven-year period (2010–2016). Dust-and copper levels, precipitation patterns, wind direction and wind speed were the parameters analyzed. A further look into the sampling points and their actual location in terrain was also made. The result of the study indicates, according to different aspects, on decreasing dust fall levels even though the production has increased. For instance, many of the 19 sampling points shows to have lower dust and copper levels according to a comparison of measurement data from 2010 to 2016. A correlation test showed that precipitation and wind does not have a strong connection to dust levels. On the other hand, wind speed showed to have a strong impact on dust fall levels under periods when the highest dust amounts were measured. Many of the sampling points also showed to have a strong connection to each other. The study concludes that a better dust control programme can be obtained if sampling points are reorganized along with a better method for calculating the dispersion of airborne dust.

We present a comprehensive study of interstellar X-ray extinction using the extensive Chandra supernova remnant (SNR) archive and use our results to refine the empirical relation between the hydrogen column density and optical extinction. In our analysis, we make use of the large, uniform data sample to assess various systematic uncertainties in the measurement of the interstellar X-ray absorption. Specifically, we address systematic uncertainties that originate from (i) the emission models used to fit SNR spectra; (ii) the spatial variations within individual remnants; (iii) the physical conditions of the remnant such as composition, temperature, and non-equilibrium regions; and (iv) the model used for the absorption of X-rays in the interstellar medium. Using a Bayesian framework to quantify these systematic uncertainties, and combining the resulting hydrogen column density measurements with the measurements of optical extinction toward the same remnants, we find the empirical relation N-H = (2.87 +/- 0.12) x 10(21) A(V) cm(-2), which is significantly higher than the previous measurements.

Doctor of Philosophy / Department of Agronomy / DeAnn R. Presley / The abandoned lead (Pb) and zinc (Zn) mines in the Tri-State Mining District of Kansas, Missouri, and Oklahoma have left a legacy of environmental contamination. The waste materials are highly polluted, not only with Pb and Zn, but also cadmium (Cd), which often co-occurs geologically with Zn. The District includes Galena, Kansas, where mines operated between 1876 and 1970. Because limited information exists concerning these mines, three studies were done to characterize them and to investigate a way to remediate the mine waste materials. In the first study, the physical characteristics of the mine waste materials were determined. Plots at Galena that had been established by researchers in May 2006 were sampled in November 2014, 8.5 years after they had received amendments (combinations of compost, lime, and bentonite). Water content, bulk density, infiltration rate, unsaturated hydraulic conductivity, aggregate stability, and particle size distribution were determined. The physical characteristics were highly variable, and the amendments added 8.5 years earlier had no effect on them, except the wind erodible fraction (fraction <0.84 mm in diameter) which was low on treatments that contained bentonite. Because biosolids had never been applied to the mine waste materials at Galena for remediation, an experiment was done to see their effect on plant growth and availability of heavy metals. In 2014 the plots established in 2006 were sampled and a greenhouse study was set up with sudex [Sorghum bicolor (L.) Moench x S. Sudanese (P.) Staph]. Plants grew in the mine waste materials with and without biosolids, and 110-111 days after planting the roots, shoots, and heads with grain were harvested and analyzed for heavy metals. At the same time, the mine waste materials were analyzed for heavy metals, organic carbon (C), nitrogen (N), and phosphorus (P). Plants grew better with biosolids than without biosolids, and only the plants grown with biosolids produced heads . Plants grown without biosolids were stunted and showed severe heavy metal toxicity. Organic C and P were increased in the mine waste materials after the addition of biosolids. Thus, the biosolids increased organic C and P, and they apparently made the heavy metals less available for plant uptake. Many studies have shown the importance of attic dust in documenting metal pollution from a mine. Attic dust in Galena had never been studied, so in a third experiment, 14 dust samples in Galena were collected from interiors (attics and one basement) of nine different buildings using two methods: sweeping with a brush and vacuuming. Dust samples were analyzed for heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, and Zn), mineralogy using X-ray diffraction (XRD), scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDX), and particle size. Concentrations of Cu, Fe, Mn, Ni, and Zn in the dust were higher than in the mine waste materials. The results from XRD agreed with those from the SEM-EDX analysis. About 10% of each dust sample contained particulate matter (PM) with a diameter of less than 10 μm (PM₁₀), which is a health concern.

Vid väggsågning i betong uppkommer det mycket damm. Detta damm tas till viss del upp av det vatten som appliceras för att kyla klingan under sågning, vilket leder till en så kallad slurry. Slurryn samt dammet behöver efter avklarad sågning tas upp vilket resulterar i extra arbetsmoment för brukaren av sågen. Det största problemet här är dock det damm som inandas vilket kan leda till sjukdomar såsom silikos. Dessa sjukdomar kommer i framtiden antagligen leda till nya lagkrav kring hur dammet behöver tas hand om innan brukaren kan andas in det. Syftet med studien har därmed varit att utreda hur damm och slurry kan tas upp vid väggsågning. Problemet med väggsågning gentemot andra former av bearbetning i betong har varit svårigheten att täta av gentemot ytan som bearbetning sker i. I fallen med borrning är det tillexempel möjligt att sluta av området och skapa undertryck som då suger upp damm och slurry. För att ge en grund till konceptframtagning utfördes en observation av väggsågning för att skapa förståelse för hur dammet och slurryn beter sig under sågning. Vidare utfördes även en fallstudie för att samla data gällande hur problemet löses idag samt samla punkter från industrin gällande vilka egenskaper lösningen bör ha för att anses som attraktiv i håltagningsindustrin. Utifrån den insamlade empirin genererades koncept med hjälp av brainstorming samt morfologi. Dessa utvärderades sedan med Husqvarna samt med hjälp av Pughs matris där kriterierna för sållningen togs utifrån fallstudiens resultat. Resultatet här blev en pådragsenhet som fäster i klingskyddets befintliga geometrier och tar upp damm och slurry vid den punkt i klingskyddet där den största delen av damm och slurry koncentreras vid sågning. Efter sållningen togs en prototyp fram för att kunna verifiera att damm och slurry kunde tas upp samt för att mäta dess effektivitet. Resultatet av prototyptestet var att konceptet kunde ta upp cirka 23% av slurryn samt markant reducera det synliga dammet. Konceptet kunde därmed anses uppfylla studiens syfte, speciellt gällande dammet då dess skadliga effekter på så sätt kan reduceras. / Wall sawing in concrete generates a lot of dust. The dust is partly collected by the water that is applied as a coolant for the blade, which leads to a mixture called ”slurry”. The slurry as well as the dust needs to be removed after the sawing has been completed, which adds extra steps to the process for the user of the saw. The biggest issue here is the dust that is inhaled by the user, which can lead to diseases such as silicosis . This will probably lead to new regulations regarding how dust is managed, which has been the background of this thesis. The purpose of this study is therefore to evaluate how dust and slurry can be collected during wall sawing. The problem in wall sawing compared to other forms of processing of concrete is the difficulty in creating a seal towards the surface where the processing is being executed. It is for instance easier to create a sealed space around the are of processing during drilling where you can create a vacuum to collect the dust and slurry. An observation was conducted in order to give a basis for how the dust and slurry is acting during sawing. A case study was also executed to gather data regarding how the problem is solved today in the industry as well as to provide intel regarding important attributes that  concepts must have in order to be considered attractive to the industry. Concepts were generated with the collected data as a base through brainstorming and morphology. The concepts were evaluated together with Husqvarna as well as with pugh’s matrix, where the set of criterias had been collected from the case study. The result was a slide on unit that locks to existing geometries and collects dust and slurry at the point where the biggest concentration is achieved during sawing. After the evaluation, a prototype was constructed in order to verify that dust and slurry could be collected and to measure the efficiency of the concept. The result of the test was that the prototype could collect approximately 23% of the slurry as well as significantly reduce the amount of visible dust. The concept could thereby fulfil the purpose of the study, especially regarding the decreasion of dust since the harmful effects of inhalation could be reduced.

Les nombreux avantages que présenteraient la fusion thermonucléaire, en particulier la configuration tokamak, en font un candidat idéal en vue de la transition énergétique. Cependant, un certain nombre de difficultés technologiques et physiques restent à résoudre avant que l'étape d'une centrale électrique à fusion puisse voir le jour. La production de poussières est l'une des principales difficultés rencontrées dans les tokamaks. Ces petites particules composées de matériaux présents dans les parois de la machine sont créées par l'érosion de ces parois par le plasma dans lequel les réactions de fusion doivent avoir lieu. Les poussières peuvent être transportées dans le plasma et y libérer de grandes quantités d'impuretés, ce qui a pour conséquence de baisser les performances de la machine (en augmentant les pertes radiatives et en créant des instabilités), et qui peut mettre en danger les composants face au plasma. Dans le but de comprendre le transport de ces poussières, des expériences d'injection sont réalisées sur le tokamak coréen \KSTAR. Les trajectoires des poussières dans le plasma sont observées par des caméras rapides et sont extraites des films à l'aide de routines de traitement d'images. Un code numérique implémentant les derniers modèles d'interactions plasma-poussières est développé, et des comparaisons avec les données expérimentales sont faites, confirmant la tendance générale de ces modèles à la sous-estimation de la longueur des trajectoires des poussières. Des pistes d'amélioration sont présentées. Concernant les sources et puits de poussières, l'accent est porté sur l'adhésion et remise en suspension de particules sur les parois de la machine. / Thermonuclear fusion could play an important role amongst the numerous alternative energy sources, especially though the tokamak configuration. It could be a prime candidate for the energy transition, owing to its significant advantages (fuel abundance, low amount of wastes generated, low risks of accidents). However, a certain amount of technological and physical challenges require solving before any fusion power plant can be built. Dust production is one of the major difficulties encountered in tokamaks. These small particles, made out of wall material, are created by erosion of the plasma-facing components by the plasma, where the fusion reactions occur. Dust particles can be transported in the plasma, thereby unleashing large amounts of impurities, which in turn reduces the plasma performances (by raising radiative losses and generating instabilities) and can even jeopardize plasma-facing components. Aiming to understand dust transport, injection experiments are performed on the Korean tokamak \KSTAR. Trajectories are recorded on film via fast cameras and are extracted by image processing routines. A numerical tool implementing the latest models for dust-plasma interactions is developed, and comparisons with experimental data is made, confirming the overall tendency of these models to underestimate the trajectory lengths. Leads of improvements are presented. Concerning dust sources and sinks, the focus is made on dust adhesion and resuspension of dust on the machine walls.

ABSTRACT Asbestos has been extensively used to insulate boilers and associated heated pipe work throughout the world. Managing human health risks posed by asbestos during the removal of lagging poses many challenges. For this reason, acquiring a better understanding of factors that lead work tasks to produce high airborne fibre concentrations is important for the development of improved control methods. Aim: The aim of this study was to link observed work tasks and work practices with measured airborne concentrations of fibres in order to identify those factors contributing to high airborne concentrations generated during boiler de-lagging. The investigation was based on a study of two employees working on a boiler de-lagging contract lasting twenty-one days and resulting in a total of 79 measurements of airborne asbestos fibres. The primary form of asbestos dust control for the duration of the contract was the application of non-amended water. Objectives: To definitively identify the presence and type of asbestos lagging as well as quantify airborne fibre concentrations for two work tasks i.e. Stripping (removing lagging) and Bagging (placing removed lagging into bags as well as cleaning spills), in order to demonstrate how they may influence airborne fibre concentrations. Methodology: The type of asbestos was confirmed by Scanning Electron Microscopy. Phase Contrast Microscopy (PCM) was selected as the primary measure of airborne asbestos fibres. A Work Practice Checklist was developed to link observed daily Work Tasks and Work Practices with the concurrent airborne fibre concentrations. The geometric mean was a useful measure of central tendency for the data since it was highly skewed to the right (positively skewed). However, for public health purposes the arithmetic mean was also considered because it provides some idea of health risk where the human respiratory system is assumed to accumulate fibres linearly with concentration. Results: Bulk sample analysis confirmed the presence of both chrysotile and amosite asbestos lagging. Work Practices such as Wetting, Stripping and Bagging asbestos, were undertaken in a relatively uncontrolled manner during the first three days of the project resulting in mean airborne fibre concentrations of 1.171 f/ml for the Stripper, ranging from 0.612 to 1.236 f/ml and 0.315 f/ml for the Bagger, ranging from 0.107 to 0.631f/ml. These means were 4.5 times and 2.3 times respectively, greater than the means calculated for the entire project. The overall mean fibre concentration was approximately five times greater for personal samples, 0.198 f/ml (± 1.647) than for the concurrent static samples, 0.039 f/ml (± 0.129). The analysis of log transformed data revealed several strong tendencies for airborne fibre concentrations when related to Work Tasks and Work Practices. The difference between stripping asbestos in small manageable as opposed to larger unmanageable pieces was highly significant (p < 0.001). Smaller manageable pieces resulted in much lowerconcentrations. The manner with which asbestos was bagged was also highly significant (p < 0.001). Bagging in an uncontrolled manner resulted in much higher airborne concentrations. Surprisingly, the degree of wetting was not as important as expected: working dry did not generate significantly more fibres than working with saturated insulation but did generate significantly more fibres (p < 0.005) than working with partially wet insulation (which lead to the highest concentrations). A limitation to interpreting the Wetting work practice was the low number of samples taken within the dry category (n = 5). The difference in mean sample concentrations between personal and static samples for this study demonstrates the importance of spatial and temporal proximity as a determinant for airborne fibre concentrations. It also showed clear associations between what can be described as rushed, reckless Work Practices, and the resulting high levels of airborne fibre concentrations (exceeding the OEL). Within the context of this project, these findings demonstrate the utmost importance of providing the appropriate training and supervision of employees, not only for protecting themselves against airborne asbestos fibres, but for removing asbestos in manner that results in the generation of the least amount of airborne fibres possible

M.P.H., Faculty of Health Sciences, 2008 / Introduction The Department of Minerals and Energy (DME) in South Africa issued a Directive B7, titled “A Guideline for the Ventilating of Mechanical Miner Sections” to the coal mining industry. The main purpose of this directive was to reduce respirable dust exposures at the coal face with the long term objective of reducing the incidence of Coal Workers Pneumoconiosis (CWP). This study attempts to evaluate the appropriateness of the DME approach by comparing respirable coal dust results from personal samples from occupations at the coal face to the results obtained from engineering samples at the continuous miner. Objectives The objectives of this study are to: • Describe personal respirable coal dust concentrations of the occupations within the continuous miner Homogeneous Exposure Group (HEG) in five underground coal mines in Mpumalanga from January 2005 to December 2006. • Describe environmental engineering respirable coal dust concentrations of the continuous miner operator position in five underground coal mines in Mpumalanga from January 2005 to December 2006. • Compare personal respirable coal dust concentrations to Environmental Engineering Dust (EED) concentrations in five coal mines in Mpumalanga from January 2005 to December 2006. Methodology This study is descriptive in nature and was carried out utilizing historical respirable coal dust data from underground coal bord and pillar production sections. Data was supplied by Collieries Environmental Control Services (CECS) who provided a coal sampling and analysis service to South African collieries. Data provided was from five large underground coal mines in the Mpumalanga coal fields. The study population consisted of occupations within the HEG of workers deployed at the coal face who were linked to Continuous Miner (CM) production activities and results from EED sampling. Results When comparing the personal sampling results to EED sampling results for each individual mine, it is evident that all the mines had lower personal sampling results than EED results, thus establishing a definite trend. When combining all the mines in the two data sets it is also evident that EED sampling results are significantly higher than personal sampling results confirming the trend observed on individual mines. Correlation tests carried out between the two data sets indicated that there is no correlation between the personal and EED sampling results. The poor correlation between the two data sets indicates that the EED sampling position is not ideal and does not take account of the actual contaminant levels leaving the coal-winning heading. Discussion and conclusion The DME directive by way of a simple calculation took the countries personal Occupational Exposure Limit (OEL) of 2 mg/m3 and formulated a limit of 5 mg/m3 for EED sampling results. Simple extrapolation of the EED results indicates that personal exposure is exceeded more than two-fold and thus the limit of 5 mg/m3 as set by Directive B7 cannot be compared to the personal respirable coal dust OEL of 2 mg/m3. The basis of the initial calculation used to derive the 5 mg/m3 limit assumed that the shift lengths were in the region of 8 hours and cutting times around 40% of the shift, while most coal mines now have shift lengths ranging from 9 to 10 hours. In conclusion it is evident that the required limit of 5 mg/m3 as set out by Directive B7 cannot be related to the personal exposures limit of 2 mg/m3. Poor correlation results observed indicate that the EED sampling position does not account for the respirable dust concentrations leaving coal-winning headings and may be affected by the re-circulation of contaminated air over the sampling position. In addition the EED sampling position does not give an indication of the respirable dust capture efficiency of scrubber fans.

A poeira doméstica tem sido identificada como um importante vetor de exposição por substâncias inorgânicas e orgânicas, potencialmente tóxicas, em crianças e adultos. A composição da poeira tem uma forte influência de contaminantes provenientes de ambientes internos e externos. Durante o uso normal ou por intempéries, de uma variedade de artefatos e materiais, as substâncias químicas são desincorporadas para o meio ambiente. Uma vez liberadas, elas tendem a se acumular e enriquecer na poeira doméstica; e por meio de exposição contínua (mecanismos de inalação, ingestão e contato direto com a pele) afeta a saúde humana. Neste trabalho, foi realizada uma avaliação da contaminação por constituintes inorgânicos e ésteres ftálicos em poeira doméstica; e a correlação com as prováveis fontes antropogênicas. As amostras de poeira foram coletadas de 69 residências, nos bairros Pirituba, Freguesia do Ó, Jaraguá e Perus, da região metropolitana de São Paulo, entre 2006 e 2008. As amostras foram separadas nas frações: 850, 850-300, 300-150, 150-75, 75- 63 e <63 &mu;m. A análise por fluorescência de raios X (WDXRF) mostrou a presença de Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr e Pb. A análise por cromatografia de fase gasosa acoplada o espectrômetro de massa (GCMS) a presença de ésteres ftálicos (DEHP, DnBP, DEP, DEHA, BBP e DMP). A partir do fator de enriquecimento (FE), os elementos P, S, Cr, Ni, Cu, Zn e Pb foram classificados como sendo significantemente e extremamente enriquecidos na poeira. As contribuições naturais e antropogênicas foram identificadas por meio de ferramentas estatísticas como análise de fatores (AF) e cluster (AC). Os elementos Cr, Ni, Cu, Zn e Pb foram encontrados em concentrações significativamente elevadas com relação aos valores de exposição total (ingestão, inalação e contato dérmico) e de risco. / Household dust has been identified as an important vector of exposure by inorganic and organic substances potentially toxic in children and adults. The dust composition has a strong influence of contaminants provided from internal and external environments. During the natural process of wearing or weather incidents of artifacts and materials variety, the chemical substances are released into the environment in the steam form or by leaching from final products. Once released, they can be accumulated and enriched in the dust; and by continuous exposure (inhalation, ingestion and dermal contact mechanisms), these substances are harmful to human health. In this work, a study to determine the inorganic constituents and phthalate esters concentrations in residential indoor environment dust samples, correlating them with the probable anthropogenic sources was proposed. Dust samples were collected from 69 residences in neighborhoods Pirituba, Freguesia do Ó, Jaraguá and Perus of the São Paulo metropolitan region, using a domestic vacuum cleaner, between 2006 and 2008. The samples were sieved in the fractions of 850, 850-300, 300-150, 150-75, 75-63 and <63 &mu;m. The analysis by X-ray fluorescence (WDXRF) showed the presence of Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, Zr and Pb. The presence of phthalate esters (DEHP, DnBP, DEP, DEHA, DMP and BBP) was detected, by GCMS analyses. From the enrichment factor (EF), the elements P, S, Cr, Ni, Cu, Zn and Pb were classified as being significant and extremely enriched in the dust. The natural and anthropogenic contributions by statistical tools as factor analysis (AF) and cluster were identified. The elements Cr, Ni, Cu, Zn and Pb were present significantly elevated concentrations in relation to the total exposure values (ingestion, inhalation and skin contact) and to risk.