Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: THz emission sources.
Дисертації з теми "THz emission sources"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "THz emission sources".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Abdul, Hadi Zeinab. "Terahertz emission spectroscopy of multiferroic bismuth ferrite : insights into ultrafast currents and phonon dynamics." Electronic Thesis or Diss., Le Mans, 2024. http://www.theses.fr/2024LEMA1030.
Повний текст джерелаАнотація:
La technologie térahertz (THz) a suscité un intérêt significatif dans la communauté scientifique en raison de sa position unique dans le spectre électromagnétique, complétant le gap entre les régions des micro-ondes et de l'infrarouge. Cette radiation est non ionisante et peut pénétrer divers matériaux sans les endommager, ce qui la rend très attirante pour de nombreuses applications potentielles. Les avancées récentes dans la technologie des lasers ultra-rapides ont élargi l'exploration du rayonnement THz à un large éventail de technologies passionnantes. Elle est désormais utilisée dans des domaines tels que la médecine pour de nouvelles techniques d'imagerie, en spectroscopie pour l'analyse des matériaux, dans les technologies de l'information et de la communication pour le transfert de données plus rapide, et même dans la sécurité, l'agriculture, le contrôle de qualité et la science des matériaux fondamentaux.Par conséquent, le développement de sources THz efficaces et réglables est devenu un défi au sein de la communauté THz pour développer davantage ces applications, motivant l'exploration de nouveaux matériaux et mécanismes d'émission THz. Dans mon projet de doctorat, j'ai exploré un nouvel émetteur THz : le matériau multiferroïque le plus connu, le ferrite de bismuth (BiFeO3). Ce matériau multiferroïque est particulièrement intéressant en raison de ses propriétés multiferroïques distinctives. Le BiFeO3 présente à la fois une large polarisation ferroélectrique et un ordre antiferromagnétique à température ambiante, offrant une interaction unique des ordres ferroélectriques et magnétiques et faisant de ce matériau un candidat prometteur pour la génération de THz.En utilisant un montage de spectroscopie d'émission THz que j'ai construit, avec sa détection électro-optique, j'examine l'émission THz de trois échantillons de BiFeO3 distincts. Le premier avec une polarisation dans le plan, un autre avec une polarisation hors plan, et un troisième présentant deux domaines avec deux différentes orientations de polarisation. Cette technique permet l'observation et l'analyse directes du rayonnement THz émis par ces échantillons suite à l'excitation laser au-dessus du gap.Les études expérimentales impliquent une analyse détaillée des signaux THz émis par les échantillons de BiFeO3 dans des conditions expérimentales variées. En variant les longueurs d'onde de la pompe, les orientations des échantillons, les directions de polarisation de la lumière de la pompe, et la puissance de la pompe, nous pouvons explorer comment ces facteurs influencent l'émission THz. Ensuite, nous séparent la dynamique ultra-rapide des porteurs (courant ultra-rapide) et les vibrations du réseau (phonons optiques) contribuant à ce signal THz émis. Enfin, en analysant leur réponse aux changements des paramètres expérimentaux, nous pouvons approfondir notre compréhension des mécanismes physiques contribuant à ces dynamiques ultra-rapides et à l'émission THz dans BiFeO3Terahertz (THz) technologies have attracted significant interest in the scientific community due to their unique position in the electromagnetic spectrum, bridging the gap between the microwave and infrared regions. This radiation is non-ionizing and can penetrate various materials without causing damage, making it highly attractive for numerous potential applications. Recent advances in ultrafast laser technology have expanded the exploration of THz radiation into a wide range of exciting technologies. It’s now being used in fields like medicine for new imaging techniques, in spectroscopy for analyzing materials, in information and communication technology for faster data transfer, and even in security, agriculture, quality control and fundamental material science. Consequently, the development of efficient and tunable THz sources has become a major focus within the THz community to expand these applications further, motivating the exploration of new materials and emission mechanisms. In my PhD project, I have explored a promising new THz emitter: the well-known multiferroic material ‘Bismuth Ferrite’ (BiFeO3). This multiferroic material is particularly interesting due to its distinctive multiferroic properties. BiFeO3 exhibits both a large ferroelectric polarization and a antiferromagnetic order at room temperature offering a unique interplay of ferroelectric and magnetic orders and making this material a promising candidate for THz generation. Using a THz emission spectroscopy setup that I constructed, with its electro-optical sampling detection, I examine THz emission from three distinct BiFeO3 samples. First one with in-plane polarization, another with out-of-plane polarization, and a third presenting striped domains with two orientations of polarization. This technique allows for the direct observation and analysis of THz radiation emitted by these samples upon above gap laser excitation. The experimental investigation involves a detailed study of the THz transient signals emitted from the BiFeO3 samples under varying experimental conditions. By varying the pump wavelengths, sample orientations, directions of pump light polarization, and pump power levels, we can explore how these factors influence the THz emission. Following this, we extract the carrier dynamics (ultrafast current) and lattice vibrations (optical phonons) contributions to this THz transient. And finally, by analyzing their response to experimental parameters changes, we can have a deeper understanding of the physical mechanisms contributing to these ultrafast dynamics and THz emission in BiFeO3
2
Ayoub, Anas. "Sources laser ultrarapides performantes dans le moyen IR et le Tz." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR044.
Повний текст джерелаАнотація:
La sonde atomique tomographique est un instrument d’analyse de la matière à trois dimensions avec une résolution atomique. Cet instrument s’appuie sur l’effet de champ électrique généré à l’extrémité d’un échantillon taillé sous la forme d’une aiguille nanométrique pour faire évaporer les atomes de surface qui sont collectés par un détecteur à deux dimensions. La mesure du temps de vol des ions dont l’évaporation est déclenchée par une impulsion électrique ou optique permettent de remonter à la composition chimique en plus de la localisation 3D des atomes. Dans les sondes atomiques actuelles, l’évaporation atomique est déclenchée par un laser ultrarapide émettant dans l’UV. Cependant, l’interaction de la lumière UV avec la matière induit un échauffement thermique qui limite la résolution en masse de l’instrument et empêche son exploitation pour l’analyse de matériaux fragiles comme les composants biocompatibles. Ces travaux de thèse visent à étudier des solutions pour favoriser l’évaporation rapide tout en inhibant les effets thermiques indésirables dans le cadre d’une sonde atomique laser. Notre approche consiste à exploiter des impulsions ultracourtes dans le domaine du moyen infrarouge ou du THz en raison de leur grande énergie pondéromotrice associée à une faible énergie de photon. Ce manuscrit rapporte sur le développementd’un banc de génération et caractérisation d’impulsions THz intenses. Le couplage de ces rayonnements avec une nano-pointe métallique polarisée négativement a permis de caractériser le champ proche induit à la surface de la nano-pointe qui est fortement modifié par l’effet d’antenne de cette dernière. La deuxième partie rapporte sur le développement d’une source laser ultrarapide de haute cadence accordable dans le moyen infrarouge autour de 3 mm en exploitant des fibres en verre fluoréThe atome probe tomography is an instrument for analyzing matter in three dimensions with atomic resolution. This instrument relies on the effect of an electric field generated at the end of a sample cut into the shape of a nanoscale needle to evaporate the surface atoms which are collected by a two-dimensional detector. The measurement of the time of flight of the ions whose evaporation is triggered by an electrical or optical pulse makes it possible to measure the chemical composition in addition to the 3D localization of the atoms. In current atome probes, atomic evaporation is triggered by a high-speed laser emitting in the UV. However, the interaction of UV light with matter induces thermal heating which limits the mass resolution of the instrument and prevents its use for the analysis of fragile materials such as biocompatible components. This thesis work aims to study solutions to promote rapid evaporation while inhibiting unwanted thermal effects of the laser in atome probe. Our approach consists in exploiting ultrashort pulses in the mid-infrared or THz domain due to their high ponderomotive energy associated with low photon energy. This manuscript reports on the development of a bench for the generation and characterization of intense THz pulses. Coupling these radiations with a negatively polarized metallic nanotip has made it possible to characterize the near field induced at the surface of the nanotip, which is strongly modified by the antenna effect. The second part reports on the development of an ultra-fast laser source tunable in the mid-infrared around 3 mm using fluoride glass fibers
3
Copperwheat, C. M. "The optical emission from ultraluminous X-ray sources." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445395/.
Повний текст джерелаАнотація:
Ultraluminous X-ray sources (ULXs) are point-like, non-nuclear sources which exceed the Eddington luminosity for a stellar mass black hole (BH). The emission from these sources might be beamed or super-Eddington, but it has also been pro posed that the compact object in these sources are intermediate mass BHs (IMBHs), which fit in the mass range between the two known populations of BH in the galaxy. The existence of IMBHs is under intense debate, and study of the X-ray data has been unable to resolve this issue. This thesis describes a model I have constructed in order to examine the optical/IR emission from these sources: an alternative channel by which their nature may be understood. I assume a binary model with a black hole accreting matter from a Roche lobe filling companion star. I consider the effects of radiative transport and radiative equilibrium in the irradiated surfaces of both the star and a thin accretion disc. I use current stellar evolutionary models as an input component in this model, and hence determine the mass, radius and age of the donor stars in a range of ULX systems, and in some cases provide limits on the BH mass. In addition I determine the mass transfer rate in these systems from the X-ray luminosity and compare this to transfer rate calculations based on the stellar evolutionary models. Since this method is independent of the optical data it is a powerful additional constraint on the parameter space. For systems where optical observations are available at multiple epochs, I make further determinations of the binary parameters based on the optical variability. Where it is possible to constrain the masses of the BHs, I find them to be consistent with BHs of up to 100A . I find that in general the donor stars are older and less massive than previously thought, and are consistent with being of spectral type B. I discuss how these results affect our understanding of the evolution and history of ULXs. I discuss how future studies of ULX optical counterparts will be even more revealing, and I make predictions for these optical campaigns, estimating binary periods, variability and the results of IR observational campaigns, which my results suggest will be a important tool in future studies of the nature of this class of sources.
4
Xiu, Meng. "Evaluating the emission of air pollutants from different sources." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/235386/1/Meng%2BXiu%2BThesis%284%29.pdf.
Повний текст джерелаАнотація:
This thesis is an evaluative study of air pollution emissions from different sources in Australia and overseas. It investigates indoor and outdoor sources, including indoor combustion, electric equipment, asphalt pavement, forest fires and vehicular traffic. Based on evaluating sources, a simple practical method is proposed to identify pollution sources. This research has important scientific implications and potential for future practical applications, given the paucity of quantitative air quality studies available for pollution control.
5
Domański, Grzegorz. "The contribution of different sources to the total CO2 emission from soils /." Stuttgart : Inst. für Bodenkunde und Standortslehre, 2003. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=012802754&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Повний текст джерела
6
Lohmann, Rainer. "Studies on the atmospheric sources, fate and behaviour of dioxins and furans." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322093.
Повний текст джерела
7
Holt, Joanna. "An observational study of the emission line systems in compact radio sources." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419256.
Повний текст джерела
8
Hunter, Gillian C. "The behaviour of plumes from point sources in stratified flows." Thesis, Open University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315334.
Повний текст джерела
9
Ursini, Francesco. "Constraining the high energy emission sources in the environment of supermassive black holes." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY062/document.
Повний текст джерелаАнотація:
Des trous noirs supermassifs de plusieurs centaines de millions de masses solaires résident au centre de la plupart des galaxies massives. Dans 90% des cas, ces trous noirs sont dans état quiescent, très peu lumineux. Cependant, dans les 10% restant, des processus extrêmement violents sont observés, avec la libération d'énorme quantités d'énergie no- tamment en UV, X et gamma. On observe aussi parfois des jets puissants de matière pouvant s'étendre sur plusieurs centaines de kpc. Le coeur de ces galaxies sont appelés Noyaux Actifs de Galaxie (NAG). Ce sont parmis les objets les plus lumineux de l'univers. L'accrétion de la matière environnante sur le trou noir supermassif central est unanimement reconnue comme la source d'énergie la plus plausible pour expliquer la puissance phénoménale observée. L'énergie gravitationelle serait ainsi en partie libérée dans un disque d'accrétion, sous forme de rayonnement thermique piquant dans l'optique/UV, et en partie rayonnée en X/gamma par une couronne de plasma chaud présente dans l'environnement proche du trou noir.De nombreux phénomènes sont néanmoins encore très mal connus et beaucoup de ques- tions n'ont toujours pas de réponses satisfaisantes: quelles sont la dynamique et la structure des flots d'accrétion et d'éjection dans les NAG? Quels sont les processus radiatifs produisant le rayonnement UV/X? Quelle est l'origine des différentes composantes spectrales présentes dans ces domaines d'énergie? Cette thèse a pour objectif d'apporter de nouvelles contraintes observationnelles pour meux répondre à ces questions. Son originalité réside dans le développement et l'utilisation de modèles réalistes de Comptonisation thermique permettant d'une part de mieux contraindre les propriétés physiques et géométriques des régions d'émission UV/X et d'autre part de mieux comprendre l'origine des différentes composantes spectrales observées. Nous nous sommes notamment intéressés, au cours de cette thèse, à l'excès d'émission X-mou (<2 keV), présent dans un grand nombre de NAG, et dont l'origine est toujours inconnue.Ces travaux s'articulent autour de deux axes principaux. Le premier est l'étude spectrale détaillée de longues campagnes d'observation multi-longueur d'ondes de trois galaxies de Seyfert (NGC 5548, NGC 7213 et NGC 4593). La qualité des données ont ainsi permis de révéler les paramètres physiques (notamment la température et la profondeur optique) et géométriques de la couronne thermique à l'origine du continuum X. Le second axe porte sur l'analyse de données d'archives (en provenance du satellite XMM-Newton) d'un échantillon important de galaxies de Seyfert. Cela a permis d'apporter, cette fois ci, des contraintes plus générales sur les processus d'émission haute énergie observés dans ces objets. Ces deux approches ont notamment montré que l'exces d'émission X-mou pouvait provenir des couches supérieures chaudes du disque d'accrétion, suggérant un chauffage plus efficace en surface plutôt que dans les régions internesSupermassive black holes of several hundred million solar masses lie at the centre of most massive galaxies. In 90% of cases, these black holes are in quiescent, very low luminous states. Nevertheless, in the remaining 10%, extremely violent processes are seen, with the liberation of huge amounts of energy especially in the UV, X-ray and gamma-ray bands. We also sometimes observe powerful jets, extending up to several hundred kpc scales. The cores of these galaxies are called Active Galactic Nuclei (AGNs). These are among the most luminous objects in the Universe. The accretion of surrounding matter onto the central supermassive black hole is generally considered as the most likely energy source to explain the extraordinary observed luminosity. The gravitational energy would be partly liberated into an accretion disc as thermal radiation peaking in the optical/UV band, and partly radiated in the X-ray/gamma-ray band by a corona of hot plasma lying in the environment close to the black hole.However, several phenomena are still poorly understood and a number of questions lacks satisfactory answers: what are the dynamics and the structure of the accretion and ejection flows in AGNs? What are the radiative processes producing the UV/X-ray radiation? What is the origin of the different spectral components present in those energy bands? The goal of this thesis is to derive new observational constraints to better answer to these questions. Its originality resides in the development and application of realistic models of thermal Comptonization, allowing on the one hand to better constrain the physical and geometrical properties of the UV and X-ray-emitting regions, and on the other hand to better understand the origin of the different observed spectral components. In particular, we studied the excess of the soft (<2 keV) X-ray emission, seen in a great number of AGNs, and whose origin is still unknown.This work is structured along two main branches. One is the detailed spectral analysis of long, multiwavelength observational campaigns on three Seyfert galaxies (NGC 5548, NGC 7213 and NGC 4593). The quality of the data permitted to reveal the geometrical and physical parameters (in particular the temperature and optical depth) of the thermal corona producing the X-ray continuum. The second branch is based on the analysis of archival data (from the XMM-newton satellite) of a large sample of Seyfert galaxies. This allowed us to derive more general constraints on the high-energy emission processes observed in these objects. These two approaches have shown, in particular, that the soft X-ray emission excess may arise in the warm upper layers of the accretion disc, suggesting a more effective heating of the surface rather than the inner regions
10
Falcetelli, Francesco. "Modelling of Pencil-Lead Break Acoustic Emission Sources using the Time Reversal Technique." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16554/.
Повний текст джерелаАнотація:
In Acoustic Emissions (AE), Hsu-Nielsen Pencil-Lead Breaks (PLB) are used to generate sound waves enabling the characterization of acoustic wave speed in complex structures. The broadband signal of a PLB represents a repeatable emission, which can be applied at different regions of the structure, and therefore can be used to calibrate the localization algorithms of the AE system. In recent years, the use of Finite Element Method (FEM) has flourished for modelling acoustic Lamb wave propagation, which is present in thin plate-like structures. The primary challenge faced by the AE community is the lack of a well-known mathematical function of a PLB signal that can be applied in numerical simulations. This study makes use of a Time Reversal (TR) approach to identify the emission source of the PLB on a 7075-T651 aluminum plate. An ABAQUS CAETM model with piezoelectric actuators and sensors was developed. In order to avoid edge reflections, absorbing boundaries based on the Stiffness Reduction Method (SRM) were considered. The captured PLB signals were used as input to the FEM and was time-reversed. Furthermore, a band-limited white noise signal was used to calibrate the contribution of the broadband frequencies found in the transmitted wave packet. Preliminary results indicate that the TR approach can be used to understand the shape and function of the original transmitted signal.
11
Hennen, Mark. "Identifying mineral dust emission sources in the Middle East using remote sensing techniques." Thesis, University of Reading, 2017. http://centaur.reading.ac.uk/76801/.
Повний текст джерелаАнотація:
This investigation presents a new high-resolution mineral dust climatology for the Middle East, describing the dust emission source of over 27,000 dust emission events during the period 2006 – 2013. The inventory was derived from the dust RGB product of the Spinning Enhanced Visual and InfraRed Imager (SEVIRI) on-board Meteosat’s second-generation satellite (MSG). Mineral dust emissions were derived from visual inspection of the SEVIRI scenes, which have 4-5 km2 spatial and 15-minute temporal resolution. The location of every emission event was recorded in a database, along with time and trajectory of dust movement. This is an improvement on previous studies, which derive dust source areas from the daily observations of Aerosol Optical Depth whose maxima do not necessarily coincide with sources of emissions, producing more accurate information on the location of the important dust sources in the region. Results showed that dust sources are constrained to relatively small areas, with 23% of dust emissions generated from areas covering just 1% of the total land surface of the Middle East. Important sources include the Tigris-Euphrates flood plains of Iraq and Syria, Western and Northern Saudi Arabia and the Sistan Basin in Eastern Iran. The Tigris-Euphrates flood plain was the most active dust region, producing 37% of all dust events. Here, agricultural surfaces, especially those producing rain-fed wheat and barley appear to be particularly sensitive to drought conditions, with greatest dust emission frequency at the peak of the 2007 – 2009 drought – the most severe drought in instrumental history. Normalised Difference Vegetation Index (NDVI) data was acquired from the Moderate Resolution Imaging Spectrodiometer (MODIS) (MOD13A2) 1km database and correlated with dust emission frequency data in the region of greatest dust activity. These dust emission ‘hotspots’ showed a significant correlation between vegetation cover and dust emission frequency, with increased vegetation cover during non-drought years producing a marked decrease in dust emission frequency. The southern areas of the Arabian Peninsula recorded very few dust emission observations, contrasting directly to many previous studies, which do not use such high temporal resolution data. The activation and frequency of dust emissions are characterised by strong seasonality developing in response to specific synoptic conditions. ERA Interim reanalysis data were used to characterise synoptic conditions on identified dusty days, demonstrating a concurrent increase in dust emission frequency with intensifying summer (JJA) Shamal (northerly) winds over the Arabian Peninsula.
12
Field, Robert Alexander. "The sources and behaviour of selected urban air pollutants." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309084.
Повний текст джерела
13
Perez, Eduardo G. "Analytical solution to the wave equation with discrete pressure sources a model for the Rijke tube /." Morgantown, W. Va. : [West Virginia University Libraries], 2008. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5718.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--West Virginia University, 2008.Title from document title page. Document formatted into pages; contains x, 97 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 84-88).
14
Gomis, Melissa Ines. "From emission sources to human tissues: modelling the exposure to per- and polyfluoroalkyl substances." Doctoral thesis, Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141034.
Повний текст джерелаАнотація:
Produced since the 1950’s, per- and polyfluoroalkyl (PFASs) substances are persistent, bioaccumulative and toxic compounds that are ubiquitous in the environment. Being proteinophilic with a tendency to partition to protein-rich tissues, PFASs have been found in human serum worldwide and in wildlife with a predominance of long-chain perfluoroalkyl carboxilic acids (C7-C14 PFCAs) and perfluoroalkyl sulfonic acids (C6-C9 PFSAs). Due to rising concern regarding their hazardous properties, several regulatory actions and voluntary industrial phase-outs have been conducted since early 2000s, shifting the production towards other fluorinated alternatives. This thesis explores the human exposure to long-chain PFASs and their alternatives using different modelling methods and aims to 1) link comprehensively the past and current industrial production with the human body burden and 2) assess the potential hazardous properties of legacy PFASs replacements, on which information is very limited. In Paper I, the historical daily intakes in Australia and USA were reconstructed from cross-sectional biomonitoring data of perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA) andperfluorohexanesulfonic acid (PFHxS). The results indicate that humans experienced similar exposure levels and trends to PFOS and PFOA in both regions, suggesting a common historical exposure possibly dominated by consumer products. The model could not be fitted to PFHxS concentration in serum. In Paper II, the relative contribution of indirect (i.e. subsequent metabolism of precursors into legacy PFASs) versus direct exposure was evaluated on occupationally exposed ski wax technicians. The indirect exposure contributed by up to 45% to the total body burden of PFOA. In Paper III, the physicochemical properties, the persistence and the long-range transport of fluorinated alternatives were predicted using different in silico tools. Findings suggest that fluorinated alternatives are likely similar to their predecessors, in terms of physicochemical properties and environmental fate. Finally, Paper IV compares the toxic potency of PFOS, PFOA and their alternatives as a function of external and internal dose. While alternatives are less potent than their predecessors when considering the administered dose, they become similarly potent when the assessment is based on levels in the target tissue. This thesis demonstrates that pharmacokinetic models are effective tools to comprehensively reconnect the body burden to the exposure of phased-out chemicals. More importantly, the studies on fluorinated alternatives raise the necessity to provide more information and data on the potential hazard of these novel and emerging products.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.
15
Liu, Horng-Twu. "The use of high frequency stress waves for detecting shaft seal rubbing and source location." Thesis, Cranfield University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309839.
Повний текст джерела
16
Alanezi, Salwa. "Emission inventories from Kuwait petroleum refineries and respective ground level concentration of pollutants in the neighboring residential area." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12544.
Повний текст джерелаАнотація:
The State of Kuwait has three large refineries, namely, Mina Al Ahmadi Refinery, Mina Abdullah Refinery and Shuaiba Refinery. These refineries process and refine Kuwait Crude Oil through different process units. There are many heaters, boilers and flares that form a part of the complicated equipment which enhance the different petroleum processes. Fuel gas is used as a firing fuel for those heaters and boilers. As a result, stack emissions like SO2, NOx, CO are predominantly present in the flue gases and this study focuses on those emissions and their impact on the surrounding residential area. The area of interest will be Umm Al-Hyman residential area. This study accumulates emission inventories from the three refineries and the respective ground level concentration of the pollutants in the neighboring residential area. It also focuses on the impact of emissions from the refinery operations on the ground level concentrations in the surrounding areas by using the inventory model and latest emission factors to provide accurate emission estimates. The models were developed and the results were verified with the actual data from the area of impact. As a result of the findings of the major pollutants, namely SO2, NOx & CO, it is found that SO2 and CO are not exceeding Kuwait EPA Ambient Air Quality Standards for Residential Areas normally. However, NOx is observed to exceed occasionally. Even though, NOx emissions from refineries sources represented by plume models were much less, there is a consistent increase in the measured NOx. Furthermore, in 2007, the measured hourly, daily and annual NOx concentration exceeded the international standard many times. The increasing trend in NOx is attributed to continuous increase in population and the number of motor vehicles. The study will go further step in recommending engineering solutions and best practices to reduce the pollutants concentrations which will help in the reduction of human health risks and protect the environment.
17
Elton, Stephen Dennis. "A search for celestial sources of very high energy gamma-ray emission using the atmospheric Cerenkov technique /." Title page, contents and summary only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phe51.pdf.
Повний текст джерела
18
Constantin, Anca. "Linking the Power Sources of Emission-Line Galaxy Nuclei from the Highest to the Lowest Redshifts." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1097611827.
Повний текст джерела
19
White, Sheri N. 1971. "An investigation into the characteristics and sources of light emission at deep-sea hydrothermal vents." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/59093.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences and the Woods Hole Oceanographic Institution), 2000.Vita.
Includes bibliographical references (leaves 179-187).
A spectral camera (ALISS - Ambient Light Imaging and Spectral System) was used to image ambient light from high-temperature vents at 9°N East Pacific Rise and the Juan de Fuca Ridge during 1997 and 1998 Alvin dive cruises. ALISS is a low-light digital camera with custom-designed optics. A set of nine lenses, each covered by an individual bandpass filter (50 and 100 nm nominal bandwidths), allows vents to be imaged in nine wavelength bands simultaneously spanning the range of 400-1000 nm. Thus, both spatial and spectral information are obtained. ALISS was used to image three types of vents: black smokers, flange pools, and beehives. The primary source of light is thermal radiation due to the high temperature of the hydrothermal fluid (~350°C). This light is dominant at wavelengths greater than 700 nm. At flange pools, where the fluid is relatively stable, only thermal radiation is present. Black smokers and beehives, however, are subject to mixing with ambient seawater (2°C) leading to mineral precipitation. Data from these types of vents show the existence of non-thermal, temporally varying light in the 400-700 nm region. This light is probably caused by mechanisms related to mixing and precipitation, such as chemiluminescence, crystalloluminescence and triboluminescence.
by Sheri N. White.
Ph.D.
20
Alroe, Joel. "Emission sources, cloud-relevant properties and variability of aerosol over the Southern and Pacific Oceans." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/209152/1/Joel_Alroe_Thesis.pdf.
Повний текст джерелаАнотація:
Cloud-forming aerosol over the Southern Ocean currently contribute a major source of uncertainty in global atmospheric models. This work presents the seasonal changes in marine aerosol over the Southern Ocean, between the summer and winter months. The observations, obtained during two ship-based voyages south of Australia and New Zealand, revealed the impact of meteorology and marine biological productivity on the concentration and cloud-relevant properties of the marine aerosols. Comparison was made against an array of published empirical models for sea spray production to investigate their relevance for this region.
21
Kukkonen, Jaakko. "Modelling source terms for the atmospheric dispersion of hazardous substances." Helsinki : Societas Scientiarum Fennica, 1990. http://catalog.hathitrust.org/api/volumes/oclc/57930643.html.
Повний текст джерела
22
Brewer, Tim M. "The glow discharge - a multifaceted optical emission source from solids analysis to metalloproteins /." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181251765/.
Повний текст джерела
23
Liška, Ivo. "Coulomb Interactions in Electron Beams in the Vicinity of a Schottky and Cold Field Emission Sources." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233896.
Повний текст джерелаАнотація:
Dizertační práce se zabývá problematikou výpočtu vlivu coulombovských interakcí částic na parametry emitovaného elektronového svazku v blízkosti Schottkyho a studené katody. Práce poskytuje základní předhled o problematice, popisuje vytvořené modely emisních zdrojů a metodu simulace Monte Carlo. Představuje novou metodu generování vstupních dat, která klade větší důraz na přesnou simulaci emisního procesu. Pozornost je zde věnována zejména vlivu interakcí na energiovou šířku, velikost virtuálního zdroje a jas katody v závislosti na velikosti poloměru hrotu a emisním proudu. Sledováním vývoje energiové šířky bylo zjištěno, že naprostá většina interakcí se odehrává v prostoru do několika mikrometrů od hrotu katody. Závislost spočtené celkové energiové šířky na úhlové intenzitě je ve shodě s dostupnými experimentálními daty. Spočtené energiové rozšíření vlivem coulombovských interakcí bylo srovnáno s hodnotami vypočtenými pomocí vzorců založených na analytických přiblíženích. Bylo zjištěno, že některé z nich přijatelně předpovídají trendy ale nemohou být použity pro kvantitativní odhad.
24
Sikdar, Anamika. "An objective method for the assessment of the impacts of odourous emissions from stationary sources." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62284.pdf.
Повний текст джерела
25
Dazeley, Steven Ashton. "A search for very high energy gamma-ray emission from four galactic pulsars : a thesis submitted to the Department of Physics and Mathjematical Physics, University of Adelaide for the degree of Doctor of Philosophy." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phd277.pdf.
Повний текст джерела
26
Partridge, Bruce, Laura Bonavera, Marcos López-Caniego, Rahul Datta, Joaquin Gonzalez-Nuevo, Megan Gralla, Diego Herranz, et al. "Can CMB Surveys Help the AGN Community?" MDPI AG, 2017. http://hdl.handle.net/10150/625998.
Повний текст джерелаАнотація:
Contemporary projects to measure anisotropies in the cosmic microwave background (CMB) are now detecting hundreds to thousands of extragalactic radio sources, most of them blazars. As a member of a group of CMB scientists involved in the construction of catalogues of such sources and their analysis, I wish to point out the potential value of CMB surveys to studies of AGN jets and their polarization. Current CMB projects, for instance, reach mJy sensitivity, offer wide sky coverage, are blind and generally of uniform sensitivity across the sky (hence useful statistically), make essentially simultaneous multi-frequency observations at frequencies from 30 to 857 GHz, routinely offer repeated observations of sources with interesting cadences and now generally provide polarization measurements. The aim here is not to analyze in any depth the AGN science already derived from such projects, but rather to heighten awareness of their promise for the AGN community.
27
Clifford, Johanna Marie. "A 2009 mobile source emissions inventory of the University of Central Florida." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4873.
Повний текст джерелаАнотація:
This thesis reports on the results of a mobile source emissions inventory for the University of Central Florida (UCF). For a large urban university, the majority of volatile organic compounds (VOC), oxides of nitrogen (NOsubscript x]), and carbon dioxide (CO[sub2]) emissions come from on-road sources: personal vehicles and campus shuttles carrying students, faculty, staff, and administrators to and from the university, as well as university business trips. In addition to emissions from daily commutes, non-road equipment such as lawnmowers, leaf blowers, small maintenance vehicles, and other such equipment utilized on campus contributes to a significant portion to the total emissions from the university. UCF has recently become the second largest university in the nation (with over 56,000 students enrolled in the fall 2010 semester), and contributes significantly to VOC, NOsubscript x], and CO[sub2] emissions in Central Florida area. In this project, students, faculty, staff, and administrators were first surveyed to determine their commuting distances and frequencies. Information was also gathered on vehicle type, and age distribution of the personal vehicles of students, faculty, administration, and staff as well as their bus, car-pool, and alternate transportation usage. The EPA approved mobile source emissions model, Motor Vehicle Emissions Simulator (MOVES2010a), was used to calculate the emissions from on-road vehicles, and UCF fleet gasoline consumption records were used to calculate the emissions from non-road equipment and on campus UCF fleet vehicles. The results of the UCF mobile source emissions inventory are reported and compared to a recently completed emissions inventory for the entire three-county area in Central Florida.ID: 030423247; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.Env.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 117-120).
M.S.Env.E.
Masters
Civil, Environmental and Construction Engineering
Engineering and Computer Science
Environmental Engineering
28
Mandaloufas, Melissa. "The use of sugarcane bagasse as power source, according to the clean development mechanism guidelines." Universidade de Taubaté, 2010. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=308.
Повний текст джерелаАнотація:
This work focuses on the actions sought by the authorities to minimize global climate problems that are currently changing the conditions of survival of the planet to mitigate emissions of greenhouse gases (GHG) in the atmosphere. First, it is addressed the Framework Convention to start the discussions on climate changes, then the creation of the Kyoto Protocol, which came, giving nations the opportunity to act, minimizing damage to the environment, thus enabling that developing countries work together through the Clean Development Mechanism (CDM) in creating new and more efficient technologies, replacing the use of fossil fuels by renewable energy sources. The power source focus of this work is the residue of sugar cane bagasse that is more representative biomass of the Brazilian energy matrix. The sector chosen for the research was the sugar-alcohol, through the Usina Santa Candida placed within the State of Sao Paulo. It is shown through data comparison, the current Brazilian situation in the global scenario, both in world energy supply and in the composition of the energy matrix, showing that Brazil is in a privileged position about renewable energy use in comparison to the world, and is the third more significant country that reduces emissions of CO2, which shows its commitment to the Kyoto Protocol. By creating a scenario, it is evaluated the financial performance of Usina Santa Candida (SP), after the implementation of CDM. Scenario 1 shows the financial return without cogeneration system; scenario 2 shows the financial return after installation of cogeneration system; scenario 3 shows the financial return of cogeneration system installation associated to sale of grant guarantee; and the scenario 4 shows the financial return of cogeneration system installation associated to sale of grant guarantees and the receipt obtained with carbon credit market. Briefings for scenario analysis were generated through calculations of net present value (NPV), internal rate of return (IRR) and payback, to demonstrate the financial benefits after the adjustment to the clean development mechanism, demonstrating the gains from the sale of surplus power and the negotiations of certified emission reductions (CERs), the brief return of the investment payback, profitability by the board and monetary return for NPV. The result of the work shows that investment in compliance with the guidelines is very low compared to the financial return in the first auction of CERs, and added that the sale of surplus power, it becomes even more viable.Este trabalho aborda as ações buscadas pelas autoridades mundiais para minimizar os problemas climáticos que atualmente estão mudando as condições de sobrevivência do planeta, mitigando as emissões de gases de efeito estufa (GEE) na atmosfera. Primeiramente, foi abordada a Convenção-Quadro como início das discussões sobre as mudanças do clima, posteriormente, a criação do Protocolo de Kyoto, que surgiu, dando às nações, a oportunidade para que ajam, minimizando os danos causados ao ambiente, possibilitando assim, que os países em desenvolvimento colaborem por meio do mecanismo de desenvolvimento limpo (MDL) na criação de novas e mais eficientes tecnologias, substituindo o uso de fontes de energia fósseis por fontes de energia renováveis. A fonte de energia foco desta pesquisa, o bagaço da cana-de-açúcar que é a biomassa mais representativa da matriz energética brasileira. O setor escolhido para a pesquisa foi o sucroalcooleiro, na Usina Santa Cândida situada no interior do Estado de São Paulo. É demonstrado, por meio de comparação de dados, a atual situação brasileira perante o mundo, tanto na oferta mundial de energia como na composição da matriz energética, mostrando que o Brasil está em uma posição privilegiada na utilização de energias renováveis em relação ao mundo, sendo o terceiro país que mais reduz as emissões de CO2, confirmando seu comprometimento com o Protocolo de Kyoto. Por meio da criação de cenários, foi possível avaliar o desempenho financeiro da Usina Santa Cândida (SP). O cenário 1 demonstra o retorno financeiro sem sistema de cogeração, o cenário 2 demonstra o retorno financeiro após a implementação de sistemas de cogeração, o cenário 3 demonstra o retorno financeiro do sistema de cogeração mais a venda das garantias contratuais, e por fim, o 4 cenário onde e demonstrado o retorno financeiro da implementação do sistema de cogeração mais a venda das garantias contratuais e ainda a receita obtida por meio da negociação dos créditos de carbono. As informações apuradas para análise dos cenários foram geradas a partir dos cálculos de Valor Presente Líquido (VPL), da Taxa Interna de Retorno (TIR) e do Payback para demonstrar os benefícios financeiros após a adequação ao mecanismo de desenvolvimento limpo, comprovando os ganhos obtidos com a venda de energia excedente e com as negociações dos Certificados de Redução de Emissão (RCEs), o retorno breve do investimento pelo payback, sua rentabilidade pela TIR e o retorno monetário pelo VPL. O resultado da pesquisa mostra que o investimento para a adequação às diretrizes é muito baixo se comparado com o retorno financeiro já no primeiro leilão das RCEs e que somado à venda de energia excedente, torna-se financeiramente ainda mais viável.
29
Muhamad, Bunnori Norazura. "Acoustic emission techniques for the damage assessment of reinforced concrete structures." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54633/.
Повний текст джерела
30
Houston, Brian P. "The role of gamma-ray sources in relation to the observed diffuse emission and the cosmic ray origin problem." Thesis, Durham University, 1985. http://etheses.dur.ac.uk/7236/.
Повний текст джерелаАнотація:
Interpretation of the present gamma-ray data above 100 MeV is discussed in relation to cosmic ray interactions with the atomic and molecular hydrogen in the Galactic plane. The SAS II gamma-ray data are analysed for supportive evidence on the 2CG candidate sources identified from the COS B observations. The strongest sources are confirmed. There is good evidence to suggest that many of the weaker sources are not truly discrete. A Monte-Carlo analysis of the discrete source detection efficiencies suggests that many 2CG sources are unresolved giant molecular clouds, irradiated by the ambient cosmic ray flux. An attempt is made to define a genuine source catalogue. Taking account of the detection efficiencies the net source flux (from both resolved and unresolved sources) is estimated to be 11-23% of the Galactic plane emission. Cosmic ray interactions with the Orion molecular cloud complex are investigated through an analysis of the gamma-ray emission above 100 MeV. There is no evidence for cosmic ray exclusion from the clouds. A new derivation of the CO/H (_2) ratio is obtained. N (_H2) / T ((^12) CO) dv = (3.7 ± 0.6) x 10(^20) at cm (^-2) (K kms (^-1)) (^-1) Contributions to the extragalactic gamma-ray flux from radio galaxies and rich clusters are estimated. The flux may be dominated by emission from these objects. With the estimate of the discrete Galactic source flux and the CO→H (_2) ratio, the radial gamma-ray emissivity is compared to the HI, inferred H (_2) and possible cosmic ray radial densities in the inner Galaxy. It is shown that a moderate cosmic ray gradient overestimates the gamma-ray flux, unless the metal abundance gradient reduces the inferred H (_2) mass.
31
Zhou, Jinpeng. "Chemical characterisation and source apportionment study of PM10 in the atmosphere of London." Thesis, King's College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267484.
Повний текст джерела
32
Chowdhury, Muhammed Zohir. "Characterization of Fine Particle Air Pollution in the Indian Subcontinent." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5112.
Повний текст джерелаАнотація:
This thesis characterizes the mass and chemical composition of the fine particle air pollution over several cities in South Asia and quantifies how major sources impact the observed levels by using Chemical Mass Balance modeling with organic compounds as tracers. During February 1999, as part of the INDOEX program, a study was conducted to measure the size distribution and chemical composition of the fine particles in a remote island in Maldives off the coast of India. We found that the fine particle concentrations were comparable to those found in major cities in the United States, and were surprisingly high for a background site. 10-day backwind trajectories pointed the source region towards the Indian subcontinent; other INDOEX studies confirmed the presence of a thick haze layer over the Indian Ocean and the subcontinent during the time of the experiment. Motivated by these findings, a detailed analysis of ambient PM2.5 was carried out in Delhi, Mumbai, Kolkata, and Chandigarhfour cities located upwind of the island in Maldives. Seasonality of the fine particle concentrations was observed in each of these cities with the highest concentrations occurring during the wintertime and the lowest concentrations during the summer. Size distribution and chemical composition of the fine particle emissions from five Bangladeshi biomass (rice straw, coconut leaves, dried cow dung, synthetic biomass log, and jackfruit wood) and three Asian coals (Bangladeshi, Indian, and Chinese) were characterized and important source signatures were identified. Finally, recently developed chemical tracer techniques were applied to the ambient samples from North India to differentiate between the contributions from the many different source types. The emission profiles and source signatures from the source tests conducted previously along with the ones conducted using the Indian Subcontinent fuels were used as inputs to the model.
These results serve several purposes. First, they provide a description of the mass and detailed inorganic and organic chemical characteristics of fine particulate matter conducted for the first time ever in this region. Second, the source apportionment study will help to define the relative importance of those sources that should be included within an air quality control program. Chemical tracer techniques are particularly attractive for application in regions that have not been studied previously because they are able to yield rapid insights into the causes of a local air pollution problem before the completion of an accurate emissions inventory. Third, the source tests results will prove useful in constructing and evaluating regional emission inventory and assessing source impacts on air quality. Fourth, this work has been carried out with collaborations from Georgia Tech and several other Indian research institutions where pollution control personnel in India was trained in the operation of air sampling equipments that were left for continued monitoring, thus contributing to technology transfer and knowledge transfer from the US.
33
Hall, Andrew Jensen. "Identification of Chlorinated Solvent Sources in the Indoor Air of Private Residences around Hill Air Force Base, Utah." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/60.
Повний текст джерелаАнотація:
Volatile chlorinated solvents such as trichloroethylene (TCE), 1,2 dichloroethane (1,2 DCA), and perchloroethylene (PCE) have been identified in the indoor air of residences located near Hill Air Force Base (AFB), Utah. These vapors can originate from either volatilization of contaminates from shallow contaminated groundwater and transport into residences or from sources within the residence. The focus of the thesis was the development of a testing strategy for determining sources of TCE, 1,2 DCA, and PCE in the indoor air of residences near Hill AFB. Eight residences were selected for this study by Hill AFB based on prior detections of TCE, 1,2 DCA, and PCE in indoor air. Residents were asked to turn off the heating, ventilation, and air conditioning (HVAC) system and keep windows and doors closed for at least 3 hours prior to the sampling visit to reduce mixing of residence air. Indoor air samples were collected on Tenax© sorbent tubes from various locations within the residences to determine the location of the potential source(s). Sampling tubes were analyzed by thermal desorption gas chromatography/mass spectrometry (GC/MS). Results from a tracer experiment using sulfur hexafluoride gas confirmed the effectiveness of sampling approach. In cases where elevated levels of chlorinated solvents were found, the suspected source materials(s) were removed and the room air was re-sampled. If removal of the materials reduced or eliminated indoor air contamination, an emission chamber was used to determine contaminant emission from the materials. Sources were identified in three of the sampled residences. Sampling in two of the residences was discontinued due to scheduling problems. Sources were not located in the remaining residences. The emission of contaminants from items identified as sources in two of the residences was measured using an emission chamber developed for this project. An ornament from residence U8-8452 emitted 36.4 ng/min/cm2 of 1,2 DCA. The emission of 1,2 DCA from a wedding dress located at residence U8-8211 was below the method detection limit of 1.99 pg/min/cm2 but the emission of PCE was 18.9 ng/min/cm2 and decreased by a factor of 7 during repeated measurements.
34
Hastings, Astley St John. "The potential of bio-energy crops to meet Europe's energy needs and reduce greenhouse emissions." Thesis, University of Aberdeen, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=26255.
Повний текст джерелаАнотація:
This thesis focuses on determining the potential of bio-energy crops to contribute to Europe’s future energy needs and to reduce future greenhouse gas emissions. This requires an end-to-end (seed to exhaust gas) analysis of the crop production and enabling technology in terms of energy use and greenhouse gas emissions. The starting point of this research was to consider which energy crops had the potential to grow in future European climate scenarios and to determine those for which models did not exist to make this prediction. Miscanthus was identified as a relatively new crop with 15 years of European growing experience but with limited previous model development. MISCANMOD, a simple model of Miscanthus crop growth, was improved and rewritten in FORTRAN so that it could be interfaced to use climate scenario, soil property and land use data bases to predict energy yields for current and future climate scenarios. A greenhouse gas emissions and energy balance model was added to investigate the sustainability of Miscanthus as a bio-energy crop. This model was combined with data from other energy crop predictions to determine the energy yields and GHG mitigation of different crops for the various scenarios of future climate, each considering the soil conditions, land available and climatic conditions. We conclude that Miscanthus is the crop with the highest energy yield and largest carbon mitigation potential of all the available energy crops, and that the maximum amount of primary energy that could be produced by bio-energy crops in Europe would represent only 12% of EU 25’s primary energy needs. The carbon intensity of such energy is estimated to be 24% of that for gas. To achieve this level of energy production we show that it is necessary to develop drought and frost resistant hybrids to increase the range of the Miscanthus crop for current and future climate scenarios. This demonstrates that bio-energy is not a panacea but must be considered as part of the strategy to achieve sustainable energy whilst mitigating greenhouse gas emissions.
35
Cheung, Soe Hoo. "Development of models for the atmospheric dispersion of odours from different source types." Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268226.
Повний текст джерела
36
Engle, Mark Alan. "The influence of tropospheric ozone, hydrothermal systems, and fires on atmospheric mercury emissions from natural sources /." abstract and full text PDF (free order & download UNR users only), 2005. http://0-wwwlib.umi.com.innopac.library.unr.edu/dissertations/fullcit/3209132.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of Nevada, Reno, 2005."December 2005." Includes bibliographical references. Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2005]. 1 microfilm reel ; 35 mm.
37
TURRION, R. GONZALEZ. "IDENTIFICATION AND QUANTIFICATION OF MOLECULAR MARKERS TO INDIVIDUATE THE CONTRIBUTION OF SOURCES IN PARTICULATE MATTER EMISSIONS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/331041.
Повний текст джерелаАнотація:
Nowadays, the atmospheric pollution entails a huge problem of public health and environmental conservation, increasing the necessity of creating new policies to regulate the emissions and to reduce the impact of this in the global climate. These characteristics make the aerosols the central topic of research in the current years. The composition of the particulate matter present in the atmosphere is so varied, being difficult to determine all the species present, and so, relate the pollution with precise sources.
Aerosol particles are involved in several atmospheric processes, such as cloud formation, precipitation and in the change of the optical properties, enhancing the absorbing and scattering by the particles. They have an effect in the distribution and abundance of the trace gases due to the participation in heterogeneous chemical reactions
In this work, we have direct the aim of the project to the development of extraction methods in order to improve the recovery of the different components and use new analytical techniques to obtain a more detailed characterization of molecular markers, molecules that can be linked to one emission source which help to identify them. The developed analytical techniques have been further applied to three different cases of study:
- A full characterization of the components in an urban background site, with a special interest on the organic fraction and the characterization of single molecules that act as markers of specific sources of emission.
- Analysis of the water soluble organic fraction in a rural site in the frame of the quantification of the contribution to the atmospheric pollution of biological aerosol.
- Analysis of water soluble organic compounds in a marine environment to identify the effect of harbour activities in the air quality of the cities.
38
Akinshipe, Oladapo Bola. "The development of an ‘emission inventory tool’ for brickmaking clamp kilns." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/40846.
Повний текст джерелаАнотація:
An emission inventory tool for estimating SO2, NO2, and PM10 emissions from brick clamp kiln sites
was developed from investigations performed on three representative South African clamp kiln
sites in order to facilitate application for Atmospheric Emission Licenses (AELs) from these sources.
The tool utilizes readily available site-specific parameters to generate emission factors for
significant activities that emit the aforementioned pollutants. PM10 emission factors for significant
processes were developed using empirical expressions from the Compilation of Air Pollutant
Emission Factors (AP-42) documents.
SO2 emission factor for clamp kiln firing was obtained from “reverse-modelling”, a technique that
integrates ambient monitoring and dispersion modelling (using Atmospheric Dispersion Modelling
System software) to “standardize” actual emission rate from an assumed rate of 1 g/s. The use of
multiple point sources proved to improve the simulation of the buoyancy-induced plume rise;
therefore, a “bi-point” source configuration was adopted for the kiln. The “reverse-modelling”
technique and “bi-point” source configuration produced SO2 emission rates differing from -9 % to
+22 % from mass balance results, indicating that the “reverse-modelling” calculations provide
reliable emission estimates for SO2.
An NO2 emission factor could not be obtained from the “reverse-modelling” technique due to
experimental errors and the significant effect of NO2 emissions from other onsite air emission
sources such as internal combustion engines. The NO2 emission factor was obtained from previous
comprehensive study on a similar clamp kiln site.
The emission factors obtained from this study were utilized in developing an “emission inventory
tool” which is utilized by clay brick manufacturers in quantifying air emissions from their sites.
Emissions quantification is a requirement for brick manufacturers to obtain an AEL which is
regulated under South African environmental laws.
It is suggested that the technique used here for SO2 emission confirmation could be used to
estimate emissions from a volume or area source where combustion occurs and where knowledge
of the source parameters is limited.Dissertation (MSc)--University of Pretoria, 2013.
gm2014
Chemical Engineering
unrestricted
39
Nygren, Anton. "Investigation of Emission Source Heights in FLEXPART 10.02 for the Wildfire in Pedrógão Grande, Portugal, 2017." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-383457.
Повний текст джерелаАнотація:
One of the worst wildfires in Portugal in 2017 on June17- 21 started at the central part of Pedrógão Grande and spread fast to the surrounding areas Góis, Pampilhosa da Serra and Arganil. The wildfire took 64 lives and a large smoke plume was observed. The interest in smoke plumes from wildfires is partly due to their emitting of greenhouse gases (CO2), a large source of aerosols, CO, oxides of nitrogen and other trace gases that can affect the air quality at local and regional scale. The regional scale can be affected because the smoke from wildfires can get elevated and be transported into the free troposphere and the lower stratosphere by either pyro convection or radiative driven convection and can be transported long distances, for example from Canada to Germany. This thesis investigates how the emission source height in a model affects the transport of the smoke plume and compares the simulations with observations. Observations of transport of emissions from wildfires are often done with satellites and in this thesis data from the second modern-era retrospective analysis for research and applications (MERRA2) is used as the observations. In this thesis the numerical model FLEXPART 10.02 is used to calculate the transportation of CO from the wildfire in Pedrógão Grande. The altitude of the emission source top height and bottom height in FLEXPART was changed to see how it affected the smoke plume in the simulation. The agreement between plumes from the observations and the simulation plumes were calculated with the structural similarity (SSIM) index and the change of SSIM index was investigated. The results were that the best similarity for horizontal images was with an emission source height of 100- 300 m, for vertical images at 40°N with an emission source height 0- 1500 m and for vertical images at 41°N with an emission source height 100- 1200. The overall best simulation was the simulation with emission source height 100- 1200 m (average of the three similarity calculations). Some uncertainty occurs in the results due to for example differences in resolutions between MERRA2 and FLEXPART and the weather condition may have contributed. To improve the results there is a need to compare simulations with more wildfires to see that the SSIM index behaves the same.En av de värsta skogsbränderna i Portugal 2017 var den 17–21 juni och började i centrala Pedrógão Grande och spred sig snabbt till de omgivande områdena Góis, Pampilhosa da Serra och Arganil. Skogsbranden tog 64 liv och stora rökplymer observerades. Rökplymer från skogsbränder är intressanta därför att de bland annat är en källa av växthusgaser till exempel koldioxid (CO2), aerosoler, kolmonoxid (CO) och andra spårgaser som kan påverka luftkvaliteten på lokal och regional skala. Den regionala skalan kan påverkas eftersom rök från skogsbränder kan sprida sig upp till den fria troposfären och den nedre stratosfären med konvektion. Konvektion är när luften blir varm av olika skäl och stiger, luften kyls av när den stiger och blir då tyngre och till slut sjunker luften. Det som kan driva konvektion vid en brand är branden själv och strålning och kan transportera röken från branden långa avstånd, till exempel från Kanada till Tyskland. Den här uppsatsen undersöker hur utsläppshöjden (mellan vilka höjder röken släpps ut från) påverkar transporten av rök och jämför beräkningarna med observationer. Observationer av transport av utsläpp från bränder sker ofta med satelliter och i denna uppsats används data från en återanalys av en samling observationer från MERRA2 (the second modern-era retrospective analysis for research and applications) som observationer. En återanalys är ett dataset som räknas med en modell från i tid och rum oregelbundna observationer från historiska och nutida data. I denna uppsats används den numeriska transportmodellen FLEXPART 10.02 för att beräkna transport av kolmonoxid från skogsbranden i Pedrógão Grande. Höjden av utsläppskällans topphöjd och bottenhöjd i FLEXPART ändrades för att se hur det påverkat rökplymen i simuleringen. Likheten mellan rökplymen från observationerna och simuleringarna beräknades sedan med ett test kallat SSIM och förändringen av SSIM indexet undersöktes. Resultaten var att den bästa simuleringen för de horisontella bilderna med en utsläppshöjd på 100– 300 m, för de vertikala bilderna på 40°N en utsläppshöjd på 0– 1500 m och för de vertikala bilderna på 41°N en utsläppshöjd på 100– 1200 m. Totalt sett (medelvärde från de tre simuleringarna) hade emissions höjden 100- 1200 m den bästa likheten med observationerna. Det finns en osäkerhet i resultaten på grund av tillexempel att det är olika upplösning i MERRA2 och FLEXPART och att väderförhållanden kan ha påverkat beräkningarna. För att förbättra resultatet så kan man göra simuleringar av fler skogsbränder för att se om SSIM indexet uppför sig densamma.
40
Jones, Derek. "Evaluation of Arrayed-Field Concentration Measurements and U. S. EPA-Regulatory Models for the Determination of Mixed-source Particulate Matter Emissions." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/156.
Повний текст джерелаАнотація:
With the continued population growth and the blurring of the urban and rural interface, air quality impacts associated with agricultural particle-producing processes are becoming increasingly important. There is a lack of emission rate data from these source types and no prescribed measurement technique available to the agricultural and regulatory communities. One technique that has shown promise is combining field measurements with inverse modeling. This approach was used herein to examine particulate emissions from an almond harvesting operation, a cotton ginning facility, and comparative emissions from conservation versus conventional tillage practices. EPAapproved models ISCST3 and AERMOD were used with AirMetrics samplers. With error representing the standard deviation for all values, for ISCST3, the almond harvesting operation found PM10 emissions for shaking were 3.4 kilograms per hectare; PM2.5, PM10, and TSP emissions for sweeping were 0.81 ± 0.76, 4.8 ± 3.7, and 7.5 ± 5.1 kg ha-1, respectively; PM2.5, PM10, and TSP emissions for pickup were 1.7 ± 1.5, 6.1 ± iii 1.9, and 10.3 ± 3.8 kg ha-1, respectively. Using AERMOD, the almond harvesting operation found PM10 emissions for shaking were 4.4 kg ha-1; PM2.5, PM10, and TSP emissions for sweeping were 1.3 ± 1.5, 8.3 ± 9.4, and 27.0 ± 41.2 kg ha-1, respectively; PM2.5, PM10, and TSP emissions for pickup were 2.7 ± 1.3, 15.7 ± 14.1, and 42.3 ± 20.7 kg ha-1, respectively. PM2.5, PM10, and TSP emissions from the cotton gin were determined to be 1.7 ± 1.4, 14.3 ± 17.0, and 27.9 ± 41.1 g s-1 using ISCST3 and 0.9 ± 0.9, 10.5 ± 18.8, and 43.0 ± 79.9 g s-1 using AERMOD, respectively. ISCST3 emission rates for the combined tillage operations for PM2.5, PM10, and TSP were 0.15 ± 0.24, 0.44 ± 0.17, and 1.4 kg acre-1, while AERMOD rates were 0.17 ± 0.27, 0.66 ± 0.25, and 2.1 kg acre-1, respectively. ISCST3 emissions for the conventional tillage operations for PM2.5, PM10, and TSP were 0.47 ± 2.1, 1.1 ± 0.23, and 3.4 kg acre-1, and the AERMOD rates were 0.18 ± 0.26, 1.2 ± 0.24, and 5.1 kg acre-1, respectively.
41
Mainord, Jacinda L. "Investigation of Ambient Reactive Nitrogen Emissions Sources and Deposition in the Columbia River Gorge National Scenic Area." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3621.
Повний текст джерелаАнотація:
Anthropogenic reactive nitrogen is emitted into the atmosphere from fossil fuel combustion (nitrogen oxides) and agricultural activities (nitrogen oxides and ammonia). Nitrogen oxide emissions have long been controlled for their role in ambient air pollution and human health effects. However, reactive nitrogen deposition is less understood even though it can play a significant role in altering biodiversity, impairing ecosystem and biogeochemical function and degrading cultural artifacts. Although nitrogen deposition is a natural part of biogeochemical cycling, many ecosystems across the United States are at risk of exceeding the critical nitrogen deposition load. While nitrogen oxides are routinely measured in urban areas, far less is known in non-urban landscapes where ecosystems may be especially sensitive. Regional chemical transport models have been used to predict the impacts of ambient reactive nitrogen deposition in non-urban areas, but models have difficulty simulating reactive nitrogen due to poorly quantified emissions, especially from the agricultural sector.
My research explores the speciated deposition of reactive nitrogen through monitoring and modeling in the unique field setting of the 150 mile Columbia River Gorge (CRG) located along the border of Oregon and Washington. This site is ideally suited for this investigation due to the large sources of reactive nitrogen at either end of the CRG and unique seasonally driven channel wind flow. Seasonally driven wind allowed us to look at the reactive nitrogen emissions flowing through the CRG to assess ambient the reactive nitrogen partitioning and deposition gradient. Using data collected by the United States Forest Service to control ambient haze in the CRG and our co-located nitrogen oxides (NOx) gas analyzer, we first characterized the influence of seasonal, bimodal wind distributions on the spatial distribution of reactive nitrogen. We found that during winter months with predominantly easterly winds, particulate nitrate and ammonium and gas-phase nitrogen dioxide levels create a gradient from the eastern end to the western end. Particulate nitrate and sulfate mass concentrations influence the CRG gradient during summer months with predominantly western winds. We also found that the magnitude of the impact from east is greater than the magnitude of impact from the west. When we compared our observations to regional chemistry transport models, we found that models are significantly under-predicting levels of reactive nitrogen in the CRG. This bias is not isolated to a single station within the Gorge, but throughout the whole Columbia Basin. Our results indicate that there are under-represented emissions in the region leading to this bias.
Partly due to the bias in reactive N gas-phase species in the CRG, regional models have been underestimating the impact of gas-phase reactive N on dry N deposition. We conducted field studies at two sites within the CRG monitoring reactive nitrogen species (nitric oxide, nitrogen dioxide, ammonia, nitric acid, particulate nitrate, particulate ammonium, and particulate sulfate) as well as ozone and meteorological parameters. These measurements allowed us to conduct the first comprehensive analysis of reactive nitrogen partitioning and deposition in the CRG.
Through our measurements, we found reactive nitrogen was higher in the spring than the summer. We found concentrations ranging from 0-15 ppbv ammonia, 0-7 ppbv nitric acid, 0-2 µg/m3 ammonium nitrate and 0-1 µg/m3 ammonium sulfate at the sites. Through the measurements of all these species, we evaluated the limiting gas-phase precursor to inorganic nitrogen particle formation. In the springtime, ammonia limits the formation of particulate reactive nitrogen; while in the summer, nitric acid and oxidized sulfur limit the formation of inorganic nitrogen particles. This suggests that there may be more sources of ammonia in the spring with fertilizer application or perhaps reactive nitrogen reservoirs are renoxified through thermal dissociation during warmer summer months.
Our estimated deposition from gas and particle phase reactive nitrogen ranged from 0-0.14 kg N/ha per day. We also found that gas-phase reactive nitrogen plays the largest role in dry N deposition in the CRG with particle-phase contributing less than 15% of total dry N deposition. These results are important for land managers to understand the total impact of reactive nitrogen to non-urban areas. This research can inform mitigation strategies for haze formation, identify the major species and sources involved in dry N deposition and assess the potential impacts to ecosystems and cultural artifacts.
42
Douce, David Stewart. "Air quality assessment and the use of specific markers to apportion pollutants to source." Thesis, Sheffield Hallam University, 1998. http://shura.shu.ac.uk/19672/.
Повний текст джерелаАнотація:
The contributions of specific polluting sources to both indoor and outdoor atmospheric pollution are difficult to determine, as solid and gaseous products from different combustion sources are often similar. Sometimes, however, a marker compound can be identified that is unique to a pollution source (or at least not present in most other local combustion sources) and which will allow assessment of the contribution of that source to total atmospheric pollution. The aim of this study was to identify suitable marker compounds and methods for the apportionment (assessment of percentage contribution) of specific sources to atmospheric pollution. The sources selected were diesel exhaust emissions in outdoor, and environmental tobacco smoke (ETS) in indoor environments. Studies with controlled (laboratory) atmospheres would be followed by field studies using these methods and markers to produce apportionments for these sources to air pollution in selected environments. Initial analysis of such polluting sources was therefore the qualitative analysis of volatile compounds and particulate associated material, both organic and inorganic. Volatile organic compounds were adsorbed onto various resins, while particulate material was sampled onto various filter paper types. Organics were determined by GC-AED and GC-MS, and elements by ICP-MS.1-Nitropyrene was identified as a suitable marker for diesel particulate emissions (< 5um). A large volume air sample from Sheffield city centre using 1-nitropyrene as a marker suggested that 63% of atmospheric particulate material (< 5um) might be of diesel origin. However the concentration of 1-nitropyrene is low in atmospheric samples, and in the volumes used in routine sampling the amount of 1-nitropyrene was below the limit of detection on the instrument used. In an alternative approach the aliphatic alkane tetracosane (C24) was used as a diesel marker for urban air, with a 1-nitropyrene:tetracosane ratio derived from the average results from laboratory experiments with a diesel engine running at various speeds and loads. This approach yielded apportionment values ranging from 5-85% for the diesel contribution to particulate material (< 5mum) in the urban air of Sheffield. No volatile marker compound was found for diesel apportionment. The contribution of ETS to atmospheric pollution has previously been estimated from the measurement of respirable suspended particulates (RSP), which was superseded by total UV absorbance and total fluorescence of a methanol extract. More recent work has suggested the use of solanesol or scopoletin as marker compounds. This thesis shows that the non specific methods overestimated the particulate contribution of ETS in some atmospheres, and that solanesol is a better marker compound than scopoletin. Preliminary studies from a small number of smokers homes and offices, with solanesol as a marker compound for particulate ETS, indicated that ETS contributions to total particulate material (< 5mum) ranged from 6 to 49% in homes and 11 to 28% in offices. Pyrrole was used as a marker for ETS contribution to volatile organic pollution, and studies with controlled atmospheres with a smoking machine allowed calculation of the ratios of pyrrole to other volatile organic compounds (VOC's) in ETS. Samples from the field study were used to produce apportionment percentage levels of benzene, toluene, o-xylene and p+m-xylene associated with ETS.In addition the use of tree bark as a atmospheric sink for airborne particulates was investigated. Six nitrated polycyclic aromatic hydrocarbons associated with diesel emissions were quantified in bark extracts and levels of these were found to be highest during winter months.
43
Pemberton, Robin Douglas. "The fate of naphthalene and n-alkylnaphthalenes during combustion, and an evaluation of the sources of these compounds in diesel exhaust emissions." Thesis, University of Plymouth, 1996. http://hdl.handle.net/10026.1/2684.
Повний текст джерелаАнотація:
The main objective of this research was to understand the fate of naphthalene and n-alkylnaphthalenes during diesel combustion, and an evaluation of their sources in diesel exhaust emissions. This was achieved by the use of a procedure which employed a [14C]radiolabelled PAH technique and a diesel enriched fuel technique (DEFT). The combustion of diesel fuel spiked with [14C]naphthalene has shown unequivocally that 0.5% of the naphthalene contained in diesel fuel survives combustion under the engine conditions studied (2500 rpm and 50 Nm). The survived naphthalene represented 22.8% of the total recovered naphthalene, the other 77.2% was presumably pyrosynthetic in nature. The sources of the pyrosynthesised naphthalene in the emissions was investigated at 2500 rpm and 50 Nm. The previously unreported input of n-methylnaphthalenes to the pyrosynthesised naphthalene was demonstrated by combusting fuel spiked with [14C]2-methylnaphthalene. Radiolabelled 2- methylnaphthalene (0.53% of the original [14C]2-methylnaphthalene) which had survived combustion, and radiolabelled naphthalene (0.02% of the original [14C]2-methylnaphthalene), were recovered in the exhaust extracts. This showed unequivocally that 2-methylnaphthalene was converted to naphthalene in the combustion chamber. The first enrichment experiments (DEFT), in which 1- and 2-methylnaphthalene were added separately to fuel prior to combustion confirmed that demethylation of both species produced naphthalene in small yields (1.9% and 6.1% respectively). The contribution of n-alkylnaphthalenes with the alkyl group greater than methyl in length, to pyrosynthesised naphthalene contained in exhaust emissions was investigated using fuel spiked with non-radiolabelled alkyl-PAH. The major product of combustion of these compounds was 2- vinylnaphthalene, with a 0.08% conversion for 2-butylnaphthalene and a 0.01% conversion for 2- ethylnaphthalene. No dealkylated products were detected in the exhaust emissions. A mechanism for the formation of 2-vinylnaphthalene was proposed. The effect of engine speed and load on the recovery of naphthalene and the contribution of pyrosynthesised and survived naphthalene to recovered naphthalene were established using [14C]naphthalene. At all speeds and loads investigated the pyrosynthesised fraction of recovered naphthalene was shown to be dominant.
44
Wenger, Daniela. "Endocrine-disrupting chemicals in the air : investigation of emission sources and ambient concentrations with reporter gene assays and chemical analysis /." Zürich : ETH, 2008. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18004.
Повний текст джерела
45
Yukita, M., A. Ptak, A. E. Hornschemeier, D. Wik, T. J. Maccarone, K. Pottschmidt, A. Zezas, et al. "Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623858.
Повний текст джерелаАнотація:
We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR-Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5-10 keV band, the source had been classified as an X-ray Binary candidate in various Chandra and XMM-Newton studies; however, since it was not clearly associated with Swift J0042.6+4112, the previous E < 10 keV observations did not generate much attention. This source has a spectrum with a soft X-ray excess (kT similar to 0.2 keV) plus a hard spectrum with a power law of Gamma similar to 1 and a cutoff around 15-20 keV, typical of the spectral characteristics of accreting pulsars. Unfortunately, any potential pulsation was undetected in the NuSTAR data, possibly due to insufficient photon statistics. The existing deep HST images exclude high-mass (> 3 M-circle dot) donors at the location of this source. The best interpretation for the nature of this source is an X-ray pulsar with an intermediate-mass (< 3 M-circle dot) companion or a symbiotic X-ray binary. We discuss other possibilities in more detail.
46
Lim, Guo Quan. "Evaluation of the Influence of Non-Conventional Sources of Emissions on Ambient Air Pollutant Concentrations in North Texas." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc804841/.
Повний текст джерелаАнотація:
Emissions of air pollutants from non-conventional sources have been on the rise in the North Texas area over the past decade. These include primary pollutants such as volatile organic compound (VOC) and oxides of nitrogen (NOx) which also act as precursors in the formation of ozone. Most of these have been attributed to a significant increase in oil and gas production activities since 2000 within the Barnett Shale region adjacent to the Dallas-Fort Worth metroplex region. In this study, air quality concentrations measured at the Denton Airport and Dallas Hinton monitoring sites operated by the Texas Commission on Environmental Quality (TCEQ) were evaluated. VOC concentration data from canister-based sampling along with continuous measurement of oxides of nitrogen (NOx), ozone (O3), particulate matter (PM2.5), and meteorological conditions at these two sites spanning from 2000 through 2014 were employed in this study. The Dallas site is located within the urban core of one of the fastest growing cities in the United States, while the Denton site is an exurban site with rural characteristics to it. The Denton Airport site was influenced by natural gas pads surrounding it while there are very few natural gas production facilities within close proximity to the Dallas Hinton site. As of 2013, there were 1362 gas pads within a 10 mile radius to the Denton Airport site but there were only 2 within a 10 mile radius to Dallas Hinton site. The Dallas site displayed higher concentrations of NOx and much lower concentrations of VOC than the Denton site. Extremely high levels of VOC measured at the Denton site corresponded with the increase in oil and gas production activities in close proximity to the monitoring site. Ethane and propane are two major contributors to the measured VOC concentration, suggesting the influence of fugitive emissions of natural gas. In Dallas, the mean and maximum values of ozone had decreased since 2000 by about 2% and 25%, respectively. Similarly NOx decreased by 50% and 18% in the mean and maximum values. However, the mean VOC value showed a 21% decrease while the maximum value increased by about 46%. In Denton, the change in percentage of ozone and NOx were similar to Dallas but the mean VOC concentration increased by about 620% while the max value increased 1960%. Source apportionment analysis confirmed the findings by identifying the production of natural gas to be the primary source of VOC emissions in Denton, while traffic sources were more influential near the Dallas site. In light of the recent proposal by EPA to revise the ozone standard, the influence of these new unconventional sources should be further evaluated.
47
Wu, Weiliang. "The detection of incipient faults in small multi-cylinder diesel engines using multiple acoustic emission sensors." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/65649/1/Weiliang_Wu_Thesis.pdf.
Повний текст джерелаАнотація:
This thesis investigates condition monitoring (CM) of diesel engines using acoustic emission (AE) techniques. The AE signals recorded from a small size diesel engine are mixtures of multiple sources from multiple cylinders. Thus, it is difficult to interpret the information conveyed in the signals for CM purposes. This thesis develops a series of practical signal processing techniques to overcome this problem. Various experimental studies conducted to assess the CM capabilities of AE analysis for diesel engines. A series of modified signal processing techniques were proposed. These techniques showed promising results of capability for CM of multiple cylinders diesel engine using multiple AE sensors.
48
Panopoulou, Anastasia. "VOC source apportionment and emission inventory evaluation over the great Athens, comparison with other cities of the Mediterranean basin." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2019. http://www.theses.fr/2019MTLD0024.
Повний текст джерелаАнотація:
Les COV (Composés Organiques Volatils) jouent un rôle majeur dans la problématique de pollution atmosphérique, puisqu’ils interviennent en tant que précurseurs des composés secondaires comme l’ozone troposphérique (O3) et l’Aérosols Organiques Secondaires (AOS) qui ont des impacts sur la santé et le climat. Afin de mettre en place des stratégies efficaces de réduction de la pollution de l’air, il est crucial de caractériser et quantifier la contribution des principales sources d’émission de COV.Le bassin méditerranéen constitue un environnement complexe, favorisant le développement des épisodes de pollution. Cependant, les mesures de COV dans les zones urbaines de la région restent limitées et les études existantes ont montré des incertitudes significatives quant à la contribution des différentes sources d’émission. Dans ce contexte, Athènes (Grèce) est un cas d’étude intéressant notamment pour les COV. Cette zone urbaine fait face à des dépassements des valeurs limites européennes en d’O3 et d’AOS ainsi qu’une augmentation des émissions de polluants pour des sources spécifiques (par exemple, le chauffage résidentiel au bois).Les travaux présentés dans ce manuscrit portent sur l’étude des COV à Athènes, réalisée dans le cadre du projet international ChArMEX (The Chemistry – Aerosol Mediterranean Experiment). La méthodologie s’appuie sur une campagne de mesure de 17 mois (d’octobre 2015 à février 2017) sur un site représentatif proche du centre-ville, sur deux campagnes intensives d’un mois chacune réalisées à la même station ainsi que sur deux campagnes réalisées en champ proche des sources (en tunnel et en station trafic).Plus de 40 COV de 2 à 16 atomes de carbone (C2 à C16) ont été mesurés, permettant la caractérisation détaillée de leur variabilité temporelle et spatiale sur une base annuelle, suivie de la détermination des facteurs d’influence. Les COV de C2 à C3 étaient mesurés pour la première fois à Athènes. La comparaison aux autres études de COV en zones urbaines a mis en évidence la typologie des sources ainsi que l’importance de la pollution atmosphérique en hiver à Athènes. Concernant les monoterpènes et l’isoprène, composés en général d’origine biogénique, l’analyse a mis en évidence des sources anthropiques dans cette atmosphère urbaine, ce qui fournit des informations intéressantes pour l’évaluation de leur impact sur la qualité de l’air en tant que précurseurs des polluants secondaires. L’application du modèle orienté récepteur « Positive Matrix Factorization » (PMF) sur la base de données annuelles, a permis d’identifier et quantifier les contributions des principaux facteurs associés aux sources de COV. Les émissions liées au transport routier et au chauffage résidentiel ont été déterminées comme les sources de COV dominantes. Une seconde analyse PMF sur la base de donnes des campagnes intensives à d’une part corroboré les résultats et, d’autre part, a conduit à l’identification de sources supplément aires comme l’évaporation de carburants des points stationnairesVOC (Volatile Organic Compounds) are key constituents of atmospheric chemistry and pollution as precursors of harmful compounds like ground ozone and secondary organic aerosols, which in turn have a strong impact on local/regional air quality, climate, vegetation and human health. For that reason and in order to design and implement efficient air pollution control measures, there is a growing interest for their better characterization, as well as the identification, speciation and quantification of their respective sources.Mediterranean basin is a complex environment, favoring the development of severe air pollution events. Despite that, there is a lack of VOC studies in the urban areas of the region, while the existing ones have shown significant uncertainties associated with compounds speciation and the contribution from the different emission sources. Considering this, Athens (Greece) is the ideal place for VOC measurements due to the lack of reported levels for NMHCs the last 15 years, the continuous exceedances of O3 and aerosol concentrations and the increasing emissions from specific pollutant sources (e.g. wood burning for residential heating). In this work, we report the results of an 17-mounth field campaign for NMHCs in Athens (October 2015 – February 2017), under the frame of the international project ChArmEX (The Chemistry – Aerosol Mediterranean Experiment). This was supported by two one-month intensive observation periods (winter and summer) at the same station, and two additional near-source campaigns (tunnel and traffic station). More than 40 VOC with 2 to 16 carbon atoms have been measured giving for the first time a detailed characterization of their temporal and spatial variability on an annual basis, especially for C2 – C3 NMHCs, followed by the determination of its driving parameters. The comparison with other VOC studies in cities worldwide highlighted the role of sources to the observed levels, with significant air pollution for Athens in winter. Furthermore, the analysis indicated that monoterpenes and isoprene, known compounds of biogenic origin, presented a complex variability propably influenced by emissions other than biogenic. The latter provides interesting insights for the assessment of their impact on air quality, as precursors of secondary pollutants. Moreover, the application of the receptor-oriented model Positive Matrix Factorization (PMF) allowed the identification of the main factors related to VOC sources and the quantification of their contribution. Traffic-related emissions and residential heating were determined as the major VOC sources in the city, whereas a second PMF simulation to the intensive observation period gave additional information about sources such as the fuel evaporation from stationary points
49
Mizukami, Taku. "Study of Very High Energy Gamma-ray Emission from the Unidentified Source HESS J1614-518 with CANGAROO-III." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/175121.
Повний текст джерела
50
Katushkina, O. A., E. Quémerais, V. V. Izmodenov, R. Lallement та B. R. Sandel. "Voyager 1/UVS Lyman α Measurements at the Distant Heliosphere (90-130 AU): Unknown Source of Additional Emission". AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626567.
Повний текст джерелаАнотація:
In this work, we present for the first time the Lyman alpha intensities measured by Voyager 1/UVS in 2003-2014 (at 90-130 AU from the Sun). During this period Voyager 1 measured the Lyman alpha emission in the outer heliosphere at an almost fixed direction close to the upwind (i.e."toward the interstellar flow). The data show an unexpected behavior in 2003-2009: the ratio of observed intensity to the solar Lyman alpha flux is almost constant. Numerical modeling of these data is performed in the frame of a state-of-the-art self-consistent kinetic-MHD model of the heliospheric interface. The model results, for various interstellar parameters, predict a monotonic decrease of intensity not seen in the data. We propose two possible scenarios that explain the data qualitatively. The first is the formation of a dense layer of hydrogen atoms near the heliopause. Such a layer would provide an additional backscattered Doppler-shifted Lyman alpha emission, which is not absorbed inside the heliosphere and may be observed by Voyager. About 35 R of intensity from the layer is needed. The second scenario is an external nonheliospheric Lyman alpha component, which could be galactic or extragalactic. Our parametric study shows that similar to 25 R of additional emission leads to a good qualitative agreement between the Voyager 1 data and the model results.