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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Studium rozkladu těkavých uhlovodíků v nerovnovážném plazmatu povrchového výboje za atmosférického tlaku / Study of volatile hydrocarbon decomposition in non-thermal plasma of surface discharge at atmoapheric pressure

Věrná, Jana January 2008 (has links)
The main goal of this thesis was to study plasma generated by surface discharge and its application in volatile organic compound destruction. Introduction of this thesis deals with the issue of volatile organic compound. The term of volatile organic compound was defined and explained. Summary of the most important sources of volatile organic compound emissions and possible technics for their elimination was presented. This thesis drew attention on negative aspects of volatile organic compounds on human organism and on the whole environment. The problems of surface discharge and its possible application in various branches are known only few years therefore construction of plasma reactor itself was the first independent step of this work. The plasma reactor was consisted of electrode, which was created from the series of metal stripes each other separated by dielectric barrier. On the surface of the electrode, discharge was regulated and distributed. For the reason of technical limits experiment time was limited up to one minute. The experimental part describes reactor for surface discharge and other parts of apparatus in which degradation volatile organic compound was carried out. Nitrogen was used as carrier gas and it was mixed with air before entering into the reactor. Samples of compounds after degradation process were taken from reactor for the subsequent analysis. Analysis of the products proceeded in a gas chromatogram linked to mass spectrometer. The decomposition products were adsorbed in the SPME filaments or in sorption tubes. The decomposition products were analysed also through the mean of Testo 350 M/XL. This apparatus provided the information on the concentration of small molecules such as CO, H2, NO, NO2 and CxHy Hexane, cyclohexane and xylene were used as VOC examples. Analysis of GC-MS showed decomposition products of hexane, cyclohexane and xylene. The decomposition products were especially various alcohols, ketones, aldehydes and benzene compounds. The apparatus Testo 350 M/XL was unable to detect any CxHy, only large quantity of NO2. This thesis was further focused on possible factors which could have an influence on degradation of compounds, for example input power or different flow of oxygen. It was found that increasing power declined the removal efficiency. The maximum removal efficiency was 87 % for degradation of hexane at the lowest input power. Next part of this thesis was focused on diagnostics of plasma generated in the surface discharge form. The optical emission spectroscopy has been chosen as the best method for plasma characterisation. By this method, various important discharge parameters can be determined, e.g. vibration and rotation temperature. The obtained numeric value of rotation temperature was 840±80 K and vibration temperature was 1880±140 K. The obtained results may be used as a fundament for further study of VOC decomposition in surface discharge.
82

Studium rozkladu těkavých uhlovodíků v nerovnovážném plazmatu klouzavého obloukového výboje za atmosférického tlaku / Study of volatile hydrocarbon decomposition in non-thermal plasma of gliding arc at atmospheric pressure

Töröková, Lucie January 2008 (has links)
Diploma thesis deals with gliding arc discharge in non-equilibrium plasma, its properties and usage for dissociation of volatile organic compounds. Plasma techniques create a perspective alternative to classical methods such as adsorption, biofilters, thermal processes, freezing and condensation. The method used for analysis of dissociation products is described in the theoretical part as well. Method is gas chromatography and it is combined with mass spectroscopy. The experimental part contains the overall description of GlidArc reactor where volatile organic compounds were dissociated. The volatile organic compound is brought into the reactor from the reservoir by carrier gas (nitrogen); synthetic air was used as working gas. The reactor is connected to the device for sampling. This device has several openings for sampling by SPME fibre method, sorption tubes method and a special opening for probe entry from the device Testo 350 M/XL, which enables instant analysis of low-molecular compounds. GC-MS was used for determination of high-molecular products of dissociation. Products sorbed on SPME fibres were analysed directly, compounds sorbed by active carbon were extracted by carbon disulphide. Samples obtained using SPME fibres were analysed. The major products of the dissociaton were found due to this analysis, those major products are in the case of hexane: pentanal, 4 methyl-3-pentanal, 2-butoxy-ethanol, pentane a 2-hexene. Major products detected when dissociating cyclohexane were: l,3-dimethyl-butane, propanal, cyklohexanone, 5-hexenal a 2-pentyn-1-ol. Major products of xylene dissociation were methyl-benzene, benzaldehyde, 4-methyl-benzaldehyde, 1-nitroethyl-benzene a benzenmethanol. After analysis obtained using sorption tubes showed that mainly the dissociated compound was sorbed, but the products of the dissociation were presented in too low concentration for an adequate analysis. For that reason the sorption tubes were used only for quantitative determination of the compounds depending on the power supply. The dependence of the dissociation of the compounds on the power supply was observed using SPME fibres which were used for quantitative determination. The Results obtained by both obtained techniques were almost in accordance. Speaking of low-molecular compounds, dissociation of all compounds gave the same products, i.e. carbon dioxide, hydrogen, nitrogen oxide, nitrogen dioxide and water. The results show that the dissociation of VOC gives - besides many potentially dangerous dissociation products - significant amounts of nitrogen oxides which is harmful to the environment. Hence it is necessary to be concerned with problems studied in the future mainly with respect to limitation of NOx generation. It will be possible to optimalize the conditions of the VOC dissociation on the basis of future kinetic analysis.
83

O uso de tu/voc? em cartas baianas pessoais do s?culo XX em rela??es de simetria

Batista, Priscila Starline Estrela Tuy 15 February 2017 (has links)
Submitted by Jadson Francisco de Jesus SILVA (jadson@uefs.br) on 2018-01-31T22:41:03Z No. of bitstreams: 1 Disserta??o - Depois da defesa.pdf: 7121004 bytes, checksum: 2d0c977d69df64f09c7ef5139af54d9c (MD5) / Made available in DSpace on 2018-01-31T22:41:03Z (GMT). No. of bitstreams: 1 Disserta??o - Depois da defesa.pdf: 7121004 bytes, checksum: 2d0c977d69df64f09c7ef5139af54d9c (MD5) Previous issue date: 2017-02-15 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / This paper analyzes the use of the forms tu and voc? in the position of full subject, in personal letters written by poorly and moderately schooled Bahians between the 1930s and 1980s, in more intimate and less intimate contexts (family, close friends, and boyfriends). It was sought to raise the communicative situations in which tu and voc? were produced, in order to identify the factors that possibly influenced the use of such forms. Also, the senders were distributed by the subsystems proposed by Lopes and Cavalcante (2011) to control the behavior of each sender and to identify the most productive subsystem in the sample of missives analyzed. We also present a contrastive study with the Brazilian states of Rio de Janeiro and Minas Gerais. The material analyzed refers to 70 letters, unpublished, that are part of the collection of the Estrela Tuy Family (1930-1980). Regarding the data, after the manual collection, the data search tool E-Corp was used to ensure the accuracy of the data collected. Afterwards, the data was analyzed according to the principles of Quantitative Sociolinguistics (LABOV, 1994), with the support of the Goldvarb X software, also considering Brown and Levinson's Theory of Polity (1987) to identify the types of relationships established between senders and recipients, in order to take into account the preservation of the face between the interactants. Regarding the results, they indicate the majority use of voc? in the epistolary documentation in question, in contexts of greater and lesser intimacy, and the use of tu, only in the letters of greater intimacy. In this way, it is understood that in the sample of analyzed letters, the use of voc? is quite generalized, whereas the tu was not very productive. / Este trabalho analisa o uso das formas de tratamento tu e voc? na posi??o de sujeito pleno, em cartas pessoais escritas por baianos pouco e mediamente escolarizados, entre as d?cadas de 1930 e 1980, em contextos mais e menos ?ntimos (familiares, amigos ?ntimos e noivos). Buscou-se levantar as situa??es comunicativas em que foram produzidos o tu e o voc?, a fim de identificar os fatores que possivelmente influenciaram o uso de tais formas. Os remetentes foram distribu?dos pelos subsistemas propostos por Lopes e Cavalcante (2011) para controlar o comportamento de cada remetente e identificar o subsistema mais produtivo na amostra de missivas analisadas. Apresenta-se tamb?m um estudo contrastivo com os estados brasileiros do Rio de Janeiro e de Minas Gerais. O material analisado refere-se a 70 cartas, in?ditas, que fazem parte do Acervo da Fam?lia Estrela Tuy (1930-1980). No que concerne aos dados, ap?s a coleta manual, foi utiliza a ferramenta de busca de dados E-Corp, para garantir a precis?o dos dados levantados. Depois, foram analisados, de acordo com os princ?pios da Sociolingu?stica Quantitativa (LABOV, 1994), com apoio do software Goldvarb X, considerando tamb?m a Teoria da Polidez de Brown e Levinson (1987) para identificar os tipos de rela??es que se estabeleciam entre os remetentes e destinat?rios, no intuito de se levar em conta a preserva??o da face entre os interactantes. No que tange aos resultados, esses apontam o uso majorit?rio de voc? na documenta??o epistolar em quest?o, em contextos de maior e de menor intimidade, e o emprego de tu, apenas nas cartas de maior intimidade. Dessa forma, compreende-se que na amostra de cartas analisadas, o uso de voc? se encontra bastante generalizado, enquanto o tu se mostrou pouco produtivo.
84

Traite des esclaves et commerce néerlandais et français à Madagascar (XVIIè et XVIIIè siècles) / Dutch and French slave trade and commerce on Madagascar (seventeenth and eighteenth centuries)

Thiebaut, Rafaël 21 November 2017 (has links)
La traite des esclaves à Madagascar a provoqué de changements importants tout au long du XVIIe et XVIIIe siècles, aussi bien sur le plan politique, qu’économique et social. Les Néerlandais et les Français, présents à la colonie du Cap et aux Mascareignes étaient des acteurs de taille dans ces interactions commerciales complexes et symboliques. Des transformations sont perceptibles dès les premiers contacts, non seulement au sein des grands royaumes sakalava et betsimisaraka mais également jusqu’aux régions les plus recluses. Pourtant, les relations commerciales se complexifient dans la longue durée. En effet, une certaine continuité est identifiable sur toute la période étudiée. Le commerce maritime qui jouait un rôle primordial dans ces développements, concernait riz, bétail et captifs échangés contre piastres, armes à feu et toiles. Il a bouleversé la balance des pouvoirs et l’économie de la Grande Île. Le volume de la traite, calculé à partir de centaines d’expéditions néerlandaise et française, était déjà très substantiel avant le milieu du XVIIIe siècle. / The slave trade on Madagascar provoked important changes in the seventeenth and eighteenth centuries, both politically, economically and socially. The Dutch and the French, present on Cape Colony and the Mascarene Islands, were important players in these commercial, but complex and symbolic, interactions. The transformations are detectable from the first contact onwards, not only in the great kingdoms of Sakalava and Betsimisaraka but also in the most secluded areas. However, commercial relations complexified in the longue durée. Indeed, a certain continuity is identifiable during this entire period. The maritime commerce, which played a primary role in these developments, concerned rice, cattle and slaves bartered for Spanish dollars, firearms and textiles. The slave trade disturbed the balance of powers and the economy of the Big Island. The volume of the trade, calculated from hundreds expeditions done by the Dutch and the French, was already very substantial before the middle of the eighteenth century.
85

A implementa??o do voc? em cartas pessoais norte-riograndenses do s?culo XX

Moura, K?ssia Kamilla de 14 March 2013 (has links)
Made available in DSpace on 2014-12-17T15:07:04Z (GMT). No. of bitstreams: 1 KassiaKM_DISSERT.pdf: 954540 bytes, checksum: 24a8f4e968370a7ecb3897bf1b2e5f9f (MD5) Previous issue date: 2013-03-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Considering the theoretical and methodological presuppositions of Variationist Sociolinguistics (cf. WEINREICH; LABOV; HERZOG, 2006; LABOV, [1972] 2008), in this dissertation, we describe and analyze the process of variation/change involving the personal pronouns tu and voc?, and its extension in the pronominal paradigm in Brazilian Portuguese (BP), in three sets of personal letters written by people from Rio Grande do Norte (RN) along the 20th century. The discursive universe of those letters is news from the cities in which the informers lived and the themes from their everyday life (trade, jobs, trips, family and politics). Part of the analyzed letters integrate the written by hand minimum corpus of the Projeto de Hist?ria do Portugu?s Brasileiro no Rio Grande do Norte (PHPB-RN). We are based on previous studies about the pronominal system in BP Menon (1995), Faraco (1996), Lopes e Machado (2005), Rumeu (2008), Lopes (2009), Lopes, Rumeu e Marcotulio (2011), Lopes e Marcotulio (2011) e Martins e Moura (2012) , which register the form voc? replaces tu from the end of the first half of 20th century and attest the following situation: while (a) the imperative verbal forms, (b) the explicit subjects and (c) prepositional complement pronouns are favorable contexts for voc?, the (d) non imperative verbal forms (with null subject), (e) the non prepositional complement pronoun and (f) the possessive pronoun are contexts of resistance of tu. The results got in this dissertation confirm, partially, the statements defended by the previous studies regarding the favorable contexts for the implementation of voc? in BP: (i) there are, in the letters from the first two decades of 20th century (1916 to 1925), high frequency of the usage of the form voc? (98%); (ii) in the personal letters of RN especially in the love letters, in which there are higher recurrence of intimate subjects the discursive universe proved to be itself very relevant in the determination/conditions of the forms of tu; (iii) the unique feminine informer of our sample uses, almost categorically, the forms of tu in letters of the period from 1946 to 1972; (iv) the letters corresponding to the period from 1992 to 1994 present a significant usage of the forms associated to the innovating voc?, letting appear the change is already implemented in the system of BP and there are, in that set of letters, strong evidences that make us state the pronominal forms of non prepositional complement (accusative/ dative) related to tu are also implemented in a system with an almost categorical usage of voc? / Tendo em vista os pressupostos te?ricos metodol?gicos da Sociolingu?stica Variacionista (cf. WEINREICH; LABOV; HERZOG, 2006; LABOV, [1972] 2008), nesta disserta??o, descrevemos e analisamos o processo de varia??o/mudan?a envolvendo os pronomes pessoais tu e voc?, e sua extens?o no paradigma pronominal no Portugu?s Brasileiro (PB), em tr?s conjuntos de cartas pessoais escritas por norte-riograndenses no curso do s?culo XX. O universo discursivo dessas cartas ? basicamente not?cias da cidade em que viviam os informantes e assuntos do cotidiano (com?rcio, trabalho, viagens, fam?lia e pol?tica). Parte das cartas analisadas integram o c?rpus m?nimo manuscrito do Projeto de Hist?ria do Portugu?s Brasileiro no Rio Grande do Norte (PHPB-RN). Tomamos por base estudos anteriores sobre o sistema pronominal no PB Menon (1995), Faraco (1996), Lopes e Machado (2005), Rumeu (2008), Lopes (2009), Lopes, Rumeu e Marcotulio (2011), Lopes e Marcotulio (2011) e Martins e Moura (2012) , os quais registram que a forma voc? suplanta o tu a partir do fim da primeira metade do s?culo XX e atestam o seguinte quadro: enquanto (a) as formas verbais imperativas, (b) os sujeitos plenos e (c) os pronomes complementos preposicionados s?o contextos favorecedores do voc?, as (d) formas verbais n?o imperativas (com sujeito nulo), (e) os pronomes complementos n?o preposicionados e (f) os pronomes possessivos s?o contextos de resist?ncia do tu. Os resultados obtidos nesta disserta??o confirmam, em parte, as asser??es defendidas pelos estudos anteriores sobre os contextos favor?veis ? implementa??o do voc? no PB: (i) h? nas cartas das duas primeiras d?cadas do s?culo XX (1916 a 1925) alta frequ?ncia de uso de formas do voc? (98%); (ii) nas cartas pessoais do RN, especialmente nas cartas de amor em que h? maior recorr?ncia de assuntos ?ntimos, o universo discursivo mostrou-se bastante relevante no condicionamento das formas de tu; (iii) a ?nica informante do sexo feminino da nossa amostra faz uso, quase categ?rico, das formas de tu, em cartas do per?odo que corresponde aos anos de 1946 a 1972; (iv) as cartas correspondentes ao per?odo de 1992 a 1994 apresentam um uso significativo das formas associadas ao inovador voc?, deixando transparecer que a mudan?a j? est? implementada no sistema do PB e h?, nesse mesmo conjunto de cartas, fortes evid?ncias que nos possibilitam afirmar que as formas pronominais de complemento n?o preposicionadas (acusativo/dativo) associadas ao tu est?o resistindo em um sistema com uso quase categ?rico de voc?
86

Characterization of Cu2ZnSnSe4 kesterite thin film solar cells : understanding of the fundamental material properties and quality control for process optimization and monitoring / Caractérisation des cellules solaires à base de couches minces kesterite Cu2ZnSnSe4 : compréhension des propriétés fondamentales des matériaux et contrôle de la qualité pour l'optimisation et le suivi des procédés de fabrication

Risch, Lisa Carina Mareike 12 December 2016 (has links)
Cette thèse porte sur la caractérisation des cellules solaires à base de couches minces de kesterite Cu2ZnSnSe4 (CZTSe). Au cours des dernières années, une attention croissante a été portée aux cellules solaires kesterite. En effet, Cu, Sn et Zn étant abondants dans la croûte terrestre, les technologies photovoltaïques à base de couches minces absorbantes de kesterite apparaissent comme un candidat prometteur pour la production à grande échelle et à faible coût de cellules solaires. Cependant, les cellules solaires kesterite souffrent d'un sévère déficit de la tension en circuit ouvert (Voc) par rapport aux autres technologies PV, résultant en un écart de performance significatif avec la technologie cousine à base de chalcopyrite (CIGS). Les meilleurs rendements reportés pour la technologie à base de couches minces CIGS sont 22,6%, alors que les cellules solaires kesterite restent en dessous de 13% de rendement. Comprendre les propriétés fondamentales des matériaux et cellules solaires kesterite et résoudre les difficultés liées à leur fabrication sont des points cruciaux pour améliorer les performances de cette technologie.Dans le cadre de cette thèse, différents mécanismes responsables des faibles valeurs de Voc des cellules kesterite ont été identifiés et caractérisés. Deux facteurs principaux y contribuent de manière significative: la recombinaison non radiative et le bandtailing. Ces phénomènes sont liés à la présence de phases secondaires et de défauts impactant l'hétérojonction p-n. Par conséquent, cette thèse se concentre sur la détection des phases secondaires et des défauts et le rôle de la couche tampon de type n. / The present thesis deals with the characterization of Cu2ZnSnSe4 (CZTSe) kesterite thin film solar cells. Over the last years, kesterite based devices have attracted growing attention. As Cu, Sn and Zn are earth-abundant metals, the kesterite compounds are promising candidates as absorber materials for the mass production of low-cost photovoltaic devices. However, kesterite solar cells suffer from a severe open circuit voltage (Voc) deficit in comparison with other PV technologies, resulting in a significant performance gap between thin film kesterite and chalcopyrite (CIGS) based devices. Best reported efficiencies for the related CIGS thin film technology are 22.6% at cell size and 17.9% for a commercial module – very close to the performance of Si solar cells – while kesterite solar cells remain below 13% power conversion efficiency. Understanding the fundamental properties of kesterite materials and devices and solving challenges associated with their fabrication are the key to improve device performances.In the framework of this thesis, different loss mechanisms related to the low Voc values of kesterite solar cells have been identified and characterized. Two major factors are thereby observed to be responsible for the significant Voc deficit: non-radiative recombination and band tailing. These aspects are related to the presence of secondary phases and defects that have a significant impact on the pn-heterojunction. Therefore, this thesis focuses on the detection of secondary phases and defects and the role of the n-type buffer layer.
87

Katalytická oxidace VOC na komerčně dostupných katalyzátorech / Catalytic oxidation of VOC on commercially available catalysts

Osička, Tomáš January 2016 (has links)
The main topic of this thesis is a catalytic oxidation which belongs to a group of modern technologies for removing emission of CO and VOC from waste air. In the introduction of this thesis, the basic concepts are defined. Further the legislative requirements associated with VOC emissions, emission limits and conditions are summarized. Described destructive and non-destructive methods for removing VOCs from waste gases are also briefly described. Increased attention is paid to the catalytic oxidation as the main theme of the thesis. It was searched for industrial applications where the catalytic oxidation is used. Another chapter is devoted to the theoretical analysis of kinetics of catalytic oxidation reactions. Firstly, the basic types of reactors are described and also material balance and reaction rate for the isothermal and adiabatic reactor. In the experimental part results of performed kinetic measurements on a pilot unit for catalytic commonly used organic solvents (VOCs) using commercially available catalysts were summarized. Pre-exponential factors and activation energies for sprinkling catalysts EnviCat VOC-5565 and EnviCat 55068 for substances ethanol, toluene and acetone were determined. "Light-off" curves for these substances and methane were measured and on sprinkled catalyst EnviCat 55068 and on monolithic catalyst Purelyst PH-304.
88

Einfluss der Exposition mit flüchtigen organischen Verbindungen im Innenraum auf akute Bronchitis und allergische Erkrankungen von Kindern im 4. Lebensjahr – LISA-Studie

Hoffmann, Stefanie 08 April 2011 (has links)
Flüchtige organische Verbindungen (Volatile organic compounds (VOC)) sind ubiquitär vorkommende kohlenstoffhaltige Substanzen. Untersuchungen haben relevante VOC-Konzentrationen im Inneren von Gebäuden nachgewiesen. Da der Innenraum zum typischen Aufenthaltsort des modernen Menschen geworden ist, sind diese Schadstoffe in das Interesse der Forschung gerückt. Kinder reagieren unter Schadstoffexposition besonders sensibel, denn viele wichtige Organsysteme befinden sich noch in ihrer Entwicklung. In der vorliegenden Arbeit wurden Leipziger Daten der LISA-Studie („Einfluss von Lebensbedingungen und Verhaltensweisen auf die Entwicklung von Immunsystem und Allergien im Ost-West-Vergleich“) hinsichtlich möglicher Effekte einer VOC-Exposition auf Erkrankungen der Kinder im 4. Lebensjahr analysiert. Bei der LISA-Studie handelt es sich um eine multizentrische prospektive Geburts-Kohortenstudie, in die von November 1997 bis Januar 1999 insgesamt 3097 gesunde und reife Neugeborene deutscher Herkunft mit einem Geburtsgewicht > 2500 g rekrutiert wurden. Die Berechnungen der vorliegenden Arbeit erfolgten mit VOC-Messwerten um den 3. Geburtstag der Kinder. Die jeweiligen logistischen Regressionsmodelle wurden auf das Geschlecht, die atopische Familienanamnese, eine passive Tabakrauchexposition, das Aufstellen neuer Möbel im Kinderzimmer, Renovierungen und die Erneuerung des Fußbodenbelags in der Wohnung adjustiert. Es ließen sich VOC bestimmen, die bei Konzentrationserhöhungen eine erhöhte Chance für eine akute Bronchitis zur Folge hatten. Als Risikofaktor einer akuten Bronchitis ließ sich außerdem die Erneuerung des Fußbodenbelags in der Wohnung ermitteln. Während sich für eine akute Bronchitis in Abhängigkeit der VOC-Konzentration erstmals eine Dosis-Wirkungs-Kurve ableiten ließ, war dies für allergische Erkrankungen nicht möglich. Weitere Untersuchungen sind notwendig um Pathomechanismen der VOC-Einwirkungen auf den kindlichen Organismus aufzuklären.
89

A Comparison of Solvent and Water-Borne Alkyd Coatings and the History of VOC Regulations in the United States

Burns, Molly Elise 01 September 2016 (has links) (PDF)
A Comparison of Solvent and Water-Borne Alkyd Coatings Abstract Conventional solvent based alkyd coatings have gone out of favor due to concerns over volatile organic compound (VOC) content. However, due to recent focus on renewable raw materials, alkyds are making a comeback in waterborne form. Water based alkyd coatings are known to have poor shelf stability and corrosion resistance, as well as other problems during the formulation process. This project focused on comparing solvent borne to two types of water-borne alkyds, water reducible alkyds and alkyds emulsions. The purpose was to understand the differences between the three types of alkyds in terms of their production and final properties. It was ultimately hoped that the formulations used for this project would prove to solve the problems normally experienced by waterborne alkyds. After testing several chemical and physical properties, it was determined that the solvent borne alkyd coatings performed better than both water based systems in corrosion resistance, accelerated weathering, and shelf stability but the water reducible and emulsion alkyd coatings performed similarly to the solvent borne alkyd in gloss, contrast ratio, and durability. The VOC emissions for all three alkyd types were as expected; the solvent borne had the highest emission at 253 g/L, followed by water reducible with 166 g/L, and emulsion with 34 g/L. The History of VOC Regulations in the United States Abstract In another solvent based alkyd coating focused project within my research group, the question of the how volatile organic compound (VOC) regulation in the United States (U.S.) evolved came up. It quickly became apparent that no comprehensive answer to this question existed. Part two of this project is an attempt to answer this question in a comprehensive manner. VOC regulations started in California in the late 1970s, and paints and coatings became a nationally regulated emission source by the 1990s. The U.S. government limited harmful emissions, such as smog and compounds contributing to ozone depletion, through Clean Air Acts. The first Clean Air Act was enacted in 1965, but it wasn’t until the Clean Air Act of 1990 that VOC emissions became a focus. VOCs are not inherently hazardous but are a source of concern because they serve as a precursor to the formation of damaging ground level ozone. The Environmental Protection Agency (EPA) has established the minimum VOC emission limits in the Architectural and Industrial Maintenance (AIM) federal rule, but each state or state subdivision can enforce stricter limits within their borders. The strictest limits are set by the South Coast Air Quality Management District (SCAQMD) in Southern California, but other entities exist. This report thoroughly documents the history of VOC regulation in the United States by collecting, combining, organizing, and summarizing information gathered from various industries and government publications, agency members, and industrial and academic professionals.
90

Chemical emissions from building structures : emission sources and their impact on indoor air / Kemiska emissioner från byggnadskonstruktioner : källor till emissioner och deras påverkan på inomhusluften

Glader, Annika January 2012 (has links)
Chemical compounds in indoor air can adversely affect our comfort and health. However, in most cases there is only a limited amount of information available that can be used to assess their health risk. Instead the precautionary principle is often applied, i.e. efforts are made to ensure that the concentrations of pollutants are kept at a minimum when constructing new buildings or conducting renovations by using low-emitting building materials. Today, when investigating buildings in order to solve indoor air quality problems, volatile organic compounds (VOCs) are sampled in the air within rooms. The chemical composition of indoor air is complex and there are many sources for the chemicals present. The potential for emissions from sources in hidden spaces such as wall cavities is poorly understood and little information exists on the toxic potential of chemical releases resulting from moisture-related degradation of building materials. Most of the non-reactive VOCs that have been detected in indoor air in field studies and from building products are not believed to cause health problems. However, reactive compounds and chemical reaction products have the potential to negatively influence our comfort and health even at low concentrations. Even though the impact of chemical compounds on health is unclear in many cases, they can be used to identify technical problems in buildings. When a building is investigated, the air inside building structures could be sampled. This method would eliminate emissions from sources other than the construction materials and the samples would contain higher levels of individual compounds. The aims of this work was to identify emissions profiles for different types of building structures, to see if the emission profiles for moisture damaged and undamaged structures differed, and to determine whether any of the emissions profiles for specific structures also could be found in indoor air. Technical investigations and VOC sampling were performed in 21 different buildings with and without previous moisture damage. Seven of the buildings were investigated in the years 2005-2006 (study 1) and fourteen in the years 2009-2010 (study 2). In study 1, sixty samples were analyzed by PCA at the chemical group level (18 chemical groups, i.e. aldehydes, ketones etc). 41 % of all identified chemical compounds belonged to the hydrocarbon chemical group. The second largest chemical groups, each of which accounted for 5-10 % of all identified compounds, were alcohols, aldehydes, ketones, polyaromatic hydrocarbons (PAHs) and terpenes. The results indicated that one of the main factors that determined the emissions profile of a building structure was the materials used in its construction. Notably, concrete and wooden structures were found to have different emissions profiles. The sum of VOC (TVOC) concentrations for all 241 samples from both study 1 and study 2 was used to compare total emissions between different building elements (ground and higher floors, external walls and roof spaces). Most building elements exhibited relatively low emissions compared to concrete ground floors, which generally had higher TVOC emissions. Emissions from both polystyrene insulation and PVC flooring could be identified in concrete ground floors and were the main cause for the higher emissions found in these structures. Profiles for wood preservatives such as creosote and pentachlorophenol were also identified in external walls. The emission profiles found in the structures could not be identified in the indoor air in the adjacent rooms, although individual compounds were sometimes detected at low concentrations. Our results showed that the main factors influencing emissions in building structures were the construction materials and the nature of the building element in question. Because of difficulties with finding active water damage at the times of sampling and because of sampling inside closed building structures with old dried-out moisture damages, the field method used in this work was unsuitable for identifying differences in emission profiles between moisture damaged and undamaged structures. It will thus be necessary to investigate this difference in a laboratory where the precise composition of all tested structures is known, a range of RH values can be tested and the accumulation of emissions can be followed. / Kompetenscentrum Byggnad - Luftkvalitet - Hälsa 2 (KLUCK 2)

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