Dissertations / Theses: 'ABSORPTION TECHNIQUE'

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Davidson, Stephen John. "Absorption spectroscopy in near LTE plasmas." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241501.

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Miller, Steven A. (Steven Alan). "Ultrasensitive Technique for Measurement of Two-Photon Absorption." Thesis, University of North Texas, 1991. https://digital.library.unt.edu/ark:/67531/metadc935773/.

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Intensive demands have arisen to characterize nonlinear optical properties of materials for applications involving optical limiters, waveguide switches and bistable light switches. The technique of Pulse Delay Modulation is described which can monitor nonlinear changes in transmission with shot noise limited signal-to-noise ratios even in the presence of large background signals. The theoretical foundations of the experiment are presented followed by actual measurements of beam depletion due to second harmonic generation in a LiIO3 crystal and two-photon absorption in the semiconductor ZnSe. Sensitivity to polarization rotation arising from the Kerr Effect in carbon disulfide, saturable absorber relaxation in modelocking dyes and photorefractive effects in ZnSe are demonstrated. The sensitivity of Pulse Delay Modulation is combined with Fabry-Perot enhancement to allow the measurement of two-photon absorption in a 0.46pm thick interference filter spacer layer. Also included is a study of nonlinear optical limiting arising from dielectric breakdown in gases.

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Tontiwachwuthikul, Paitoon. "New pilot plant technique for designing gas absorbers with chemical reactions." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/32182.

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Gas absorption with chemical reaction is an important unit operation in the chemical and petroleum industries for the selective removal of components from industrial gas streams. Apart from choosing absorption media, the most difficult problems facing the design engineer are the sizing and performance prediction of the absorption tower due to the scarcity of fundamental design data, especially when novel absorption media and/or packings are used. The solubility of carbon dioxide in 2 and 3 M solutions of 2-amino-2-methyl-1-propanol (AMP), which is a newly introduced absorbent, was determined at 20, 40, 60 and 80 °C and for CO₂ partial pressures ranging from approximately 1 to 100 kPa. The results were interpreted with a modified Kent-Eisenberg model which predicted the present and previous experimental results well. The absorption capacities of AMP and monoethanolamine (MEA) solutions were also compared. Detailed concentration and temperature measurements were reported for the absorption of carbon dioxide from air into NaOH, MEA and AMP solutions. A full-length absorber (0.1 m ID, packed with 12.7 mm Berl Saddles up to heights of 6.55 m) was used. It was operated in countercurrent mode and at 30 to 75 % flooding velocities which are typical for gas absorber operations. The following ranges of operating conditions were employed: superficial gas flow rate 11.1 to 14.8 mol/m² s; superficial liquid flow rate 9.5 to 13.5 m³/m² h; feed CO₂ concentration 11.5 to 19.8 %; total absorbent concentration 1.2 to 3.8 kmol/m³; liquid feed temperature 14 to 20 °C; total pressure 103 kPa. The measurements for the CO₂-NaOH and CO₂-MEA systems were compared with predictions from a previously developed mathematical model. Generally good agreement was obtained except at high CO₂ loadings of MEA solutions. Compared with MEA, AMP was found to have superior CO₂ absorption capacities and inferior mass transfer rates. A new procedure, called the Pilot Plant Technique (PPT), for designing gas absorbers with chemical reactions has been developed. The PPT is primarily intended for designing absorbers for which fundamental design information is lacking. It is based on the premise that full-length absorption columns can be sized by making a minimum number of tests using a small-scale pilot plant. Two special features of the PPT are (i) the details of hydrodynamic parameters (i.e. mass transfer coefficients, effective interfacial area and liquid hold-up) and the physico-chemical information of the system (e.g. reaction mechanism, reaction rate constants) need not be known and (ii) complex calculations are avoided. Using the PPT to size the height or to predict the performance of a given full-length absorber, the specific absorption rate, which is the essential information, can be measured directly using the pilot plant model (PPM) column if both columns have the same hydrodynamic conditions. This can be achieved by using the same type and size of packing in the PPM and the full-length columns and ensuring that the end and wall effects are negligible. The PPM column must also be operated at the same superficial fluid velocities as those of the full-length column. The specific absorption rate was then obtained from the gradient of the fluid composition profile along the PPM column. The validity of the PPT was demonstrated by determining the height and predicting the performance of the full-length column in which carbon dioxide was absorbed from air by aqueous solutions of NaOH and AMP at various operating conditions; good agreement was obtained.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

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Mercier, Xavier. "Mesure de concentrations absolues d'espèces réactives minoritaires dans les flammes par la technique d'absorption Cavity Ring Down Spectroscopy (CRDS)." Lille 1, 2000. http://www.theses.fr/2000LIL10154.

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Les processus de combustion, qui representent aujourd'hui notre principal source d'energie, suscitent encore de nombreuses interrogations. Cela tient essentiellement a la complexite des mecanismes chimiques mis en jeu ainsi qu'a la difficulte inherente a l'etude d'un milieu qui est le sein de plusieurs milliers de reactions simultanees. Or, meme si des modeles performants permettent la simulation de systemes chimiques complexes, ils ne peuvent predire n'importe quels processus de combustion et l'approche experimentale de ceux-ci reste essentielle pour l'amelioration des modeles existant. En particulier, la mesure quantitative d'especes minoritaires dans les flammes constitue une etape fondamentale dans la validation des mecanismes chimiques a haute temperature. C'est dans cette optique que nous avons developpe une nouvelle technique pour l'etude de flamme, le cavity ring-down spectroscopy (crds). Cette technique, qui s'apparente a une methode d'absorption de tres haute sensibilite et dont le principe est base sur la mesure du temps de vie d'une impulsion laser injectee dans une cavite optique dans laquelle se trouve un echantillon absorbant, est apparue a la fin des annees 80 (o'keefe et deacon 1988) dans le cadre d'une etude spectroscopique
Dans ce memoire, nous montrons l'interet et les potentialites du crds pour l'etude de flammes homogenes. Pour ce faire, nous explicitons dans le detail le principe du crds et les precautions a prendre pour la mesure de concentrations absolues. Par ailleurs, une comparaison des profils de concentration absolue obtenus par crds (de cn et ch notamment) dans une flamme de ch 4/o 2 dopee en no, avec ceux issus de la modelisation au moyen du logiciel premix est egalement presentee. Le tres bon accord de cette comparaison montre que le crds, de part sa haute sensibilite et son caractere quantitatif direct, se revele etre une methode des plus efficaces pour la mesure de concentrations absolues d'especes dans des flammes homogenes

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Tynell, Åsa. "Microbial Growth on Pall-rings : A problem when upgrading biogas with the technique water absorption." Thesis, Linköping University, The Tema Institute, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-212.

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Upgradering av biogas med tekniken vattenabsorption är vanligt i Sverige. Elva biogasanläggningar med tillsammans fjorton uppgraderingsanläggningar använder sig av tekniken. Problem med igensättning av fyllkroppar i absorptionskolonnen, samt i ett fall i desorptionskolonnen är vanligt förekommande och har en negativ effekt på uppgraderingen av rågas till fordonsgas. Fem av de nio anläggningarna i denna studie har problem med mikrobiell tillväxt på fyllkropparna. Syftet med denna rapport var att identifiera den mikrobiella tillväxten och avgöra vilka faktorer som reglerar den för att kunna rådge driftsansvariga hur man motverkar tillväxt.

En enkät skickades ut och studiebesök gjordes för att samla information om anläggningarna. Fosfolipidfettsyra (PLFA)-analyser utfördes för att bestämma mikrobiell biomassa och de organismer, som kan indikeras av de PLFA som är s.k. biomarkörer.

Prover samlades in från fyra uppgraderingsanläggningar: Jönköping, Kristianstad, Linköping och Uppsala. Proverna som samlades in var till utseendet olika, allt från gult slem från Linköping till röd-brun gegga som liknade kaffe-sump från Uppsala. I proverna från Linköping och Uppsala detekterades biomarkörer för metanoxiderande bakterier (metanotrofer) av typ I. Metanotrofer finns i jord, vatten och luft i miljöer med tillgång till metan och syre. I Jönköpingsproverna detekterades biomarkörer actinomyceter som är en vanligt förekommande bakterie i avloppsreningsverkens luftningsbassänger. Den mikrobiella tillväxten som samlades in från Kristianstad räckte enbart till ett prov och därför är det resultatet ej tillförlitligt.

I samtliga prover detekterades svamp (fungi) som förmodligen etablerats efter andra organismer.

Faktorer som kan anses påverka den mikrobiella tillväxten är processvattnets kvalitet, pH och temperatur. Rent vatten (dricksvatten) innehåller mindre mängd organiskt material, samtliga anläggningar som använder sig av avloppsvatten upplever problem. Lågt pH är gynnsamt för att minska den mikrobiella tillväxten eftersom de flesta organismer trivs bäst vid neutralt pH. Låg temperatur är gynnsam eftersom lösligheten för koldioxid och divätesulfid är större vid lägre temperaturer, vilket gynnar uppgraderingen av biogas.

Upgrading of biogas performed using the technique absorption with water wash is common in Sweden where eleven biogas plants, comprising a total of fourteen upgrading plants use this technique. However problems with microbial growth on the pall-rings in the absorption column, and in one case in the desorption column, have negative impact on upgrading the raw gas to vehicle gas. Five of the nine biogas plants studied here have experienced problems with microbial growth. The objective of this report was to identify the microbial growth and determine possible factors regulating microbial growth in order to give advice to process management.

A questionnaire was sent out and visits were made to the upgrading plants to collect information about the plants. A phospholipid fatty acid (PLFA) analysis was performed to determine microbial biomass and community structure, for which PLFA biomarkers are one type of indicator.

Samples were analysed from four upgrading plants: Jönköping, Kristinstad, Linköping and Uppsala. The cultures collected were visually different, varying from yellow and slimy to reddish brown with the consistency of coffee grounds. In the Linköping and Uppsala samples, biomarkers for methane-oxidising bacteria (type I methanotrophs) were detected. Methanotrophs live in environments with access to methane and oxygen and are inhibited by e.g. acetylene. In the Jönköping samples biomarkers indicating the bacteria actinomycetes common in the water of aeration tanks in sewage treatment plants, were detected. In Kristianstad there was only enough culture for one sample, so no reliable result was obtained. Fungi were detected in all samples and probably established after other organisms.

Factors affecting development of microbial growth were found to be water quality, pH and temperature of the process water. Clean water (drinking water) contains less organic material than cleaned water from sewage treatment plants. All plants using water from sewage treatment plants have experienced microbial growth. Low pH is beneficial for reducing microbial growth since most organisms prefer a neutral environment.

Low temperature is beneficial for minimising microbial growth since the solubility of carbon dioxide and hydrogen sulphide increases with decreasing temperature.

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Jiang, Yu. "Studying the local structures of novel materials using the extended x-ray absorption fine structure technique /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.

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Jönsson, Yvette, and Erik Magnusson. "New Possibilities with Old Technique : a Feasibility Study of Absorption Cooling in Örebro District Cooling Network." Thesis, Linköping University, Department of Management and Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11209.

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E.ON Värme in Örebro produces electricity and delivers heat and cooling to customers in the region. The Åby Plant operates as a combined heat and power (CHP) plant and runs mostly on different biofuels. A new boiler and turbine is projected for the plant and will start operating fully during year 2012. This creates new possibilities for the existing small scale district cooling production. The number of cooling subscribers is today low and the power output is approximately 7.7 MW but has a great potential of growing in the future. Higher electricity prices, due to the deregulated electricity market and growing environmental concerns motivate the use of district cooling. Cooling production at E.ON Värme in Örebro today comes from modified heat pumps with low efficiency and free cooling. The idea is to replace the heat pumps with either new compression cooling machines, absorption cooling machines (ACM) or a mixture of both. This thesis analyzes possible benefits with the use of heat driven cooling i.e. absorption cooling compared with conventional compression cooling.

Excess heat from electricity generation in CHP plants is often a problem during the warm period of the year. Normally most of the heat is distributed to industries and households for heating. However, during the summer, the demand for district heating is low which constrain electricity production. The absorption technique utilizes heat as fuel and increases electricity generation during warm periods. This together with a decrease in electricity consumption has positive effects on the environment since it reduces electricity produced in plants controlling margin production. Those plants are most often coal condense plants with high emissions of fossil CO2.

Most scientists believe that CO2 emissions from human activities are the main cause to the increasing greenhouse effect. The importance of reducing CO2 emissions is therefore high and is one of the motives for district cooling based on ACM that replaces small local electricity driven chillers. Since the Åby plant uses mostly biofuels the contribution of fossil CO2 is low.

ACM utilizes heat as fuel, therefore the positive effects related to ACM are fairly obvious when the electricity price and the demand for cooling are high. To analyze and optimize the energy system in Örebro, a model was created in the program MODEST, which is software developed at Linköping Institute of Technology. Optimizations with different cooling demands and electricity prices have been made. The cooling production mix is split up in two scenarios, a visionary scenario where no restrictions are considered and a restricted scenario with restricted ACM capacity. The results have been gathered and analyzed and supports the common statements about absorption cooling.

A simulation of the visionary scenario with unrestricted ACM capacity together with the highest cooling demand (20 MW) and the highest electricity prices (European prices), gave an annual decrease in global CO2 emissions of 9 400 tonnes compared to a scenario with only compression cooling machines. Furthermore, the system running cost was almost 9 MSEK lower on an annual basis. In the restricted scenario, a pay-off analysis shows that the additional costs due to ACM is covered by the lower system cost in less than 3 years when the electricity prices are as forecasted for 2012-2015. All the simulations where absorption cooling was a part of the energy system gave positive results both from an economical and environmental point of view.

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Thorman, Sofia. "Absorption non-uniformity characterisation and its impact on flexographic ink distribution of coated packaging boards." Licentiate thesis, Karlstads universitet, Institutionen för ingenjörs- och kemivetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-34910.

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There are high demands on flexographic print quality to be sufficiently high and consistent in order to create a competitive packaging. At the same time the production efficiency need to be high. Printers thus need to achieve the same quality every time and quickly start-up new printing jobs. To accomplish this, one needs to gain a thorough understanding of how the liquid packaging board interacts with the ink and impacts the print quality. This thesis focuses on water-based ink absorption of liquid packaging boards and particularly on a) how uniformity of ink absorption can be measured and b) to what extent the absorption characteristics contribute to print mottle in flexographic printing. The work encompasses two parts. First, an absorption non-uniformity test method has been developed using a staining technique. This method is unique as it measures how unevenly an aqueous solution is absorbed, in a short time period and without impact from surface roughness. Moreover, the contributions from white-top mottle and absorption non-uniformity can be quantified simultaneously from one single measurement. Second, a method to independently study the effects of absorption non-uniformity on print quality has been established. This is achieved by introducing artificial absorption non-uniformities with well-controlled barrier patterns. A barrier pattern may modify local pore structure and/or surface energy, hence lead to lateral absorption variations. By these means, it is possible to produce a substrate property-matrix; encompassing absorption non-uniformity and for example surface roughness. It was demonstrated that non-uniform absorption indeed has a negative impact on print quality, both on smoother and rougher boards. Low absorption made print density decrease and uneven absorption caused print mottle. This was the case when other properties of the samples were kept within a narrow range; otherwise surface roughness appeared to determine print mottle ranking.

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Le, Halpere Gilles. "Étude d'une machine à absorption fonctionnant en mode climatisation : identification d'un nouveau mélange adapté à un cycle hybride original à hautes performances." Toulouse, INPT, 1998. http://www.theses.fr/1998INPT101G.

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L'étude présentée concerne une machine à absorption fonctionnant en mode climatisation, destinée au secteur de l'habitat et du petit tertiaire. La notion de haute performance et de compacité a necessité l'analyse des divers cycles à absorption déjà existants. Il en ressort que seul un cycle à double-effet est envisageable. Pour améliorer ses performances, il est proposé d'introduire une compression destinée à abaisser la pression au 2ème séparateur pour favoriser la désoption. La recherche d'u couple frigorigène/absorbant performant a conduit à sélectionner le méthanol comme fluide frigogène. La méthode des paramètres de Hansen a alors été utilisée pour rechercher de manière systématique un absorbant adapté. Suite à ce travail, les équilibres liquide/vapeur du couple méthanol/méta-crésol ont été calculés. Un programme modulaire de simulation utilisant divers couples a permis de vérifier les bonnes performances prévisibles avec le couple précédent. On montre aussi que le nouveau cycle favorise la diminution du taux de solution mais que le COP n'augmente que pour les couples à base de méthanol. Le COP en double-effet peut atteindre environ 0. 85, valeur encore améliorée par l'introduction de la compression en terme de puissance et de performances. L'importance des surfaces d'échange a compensé la faiblesse des coefficients d'échange thermique, résultant de la nécessité de fonctionner à petits débits. Malgré des difficultés d'ordre technologique, il apparaît que le cycle et le mélange proposés possèdent un avenir prometteur en matière de climatisation par absorption.

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Lamoureux, Marc Maurice Carleton University Dissertation Chemistry. "A multi-technique strategy for study of some mechanisms of atom formation and dissipation in electrothermal atomic absorption spectrometry." Ottawa, 1993.

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Kundu, Arunabha. "Tree phase reactors : A, Hydrodynamics and partial wetting of trickle beds : B, absorption enhancement in gas-liquid-liquid bublle column." Toulouse, INPT, 2004. http://www.theses.fr/2004INPT003G.

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Two investigations on three phase reactors are reported : liquid flow maldistribution and partial wetting of the catalyst in trickle bed reactors, and effects of adding small amounts of organic phase on gas to aqueous phase mass transfer in a bubble column. Radial distribution of the liquid flow is investigated in a 0. 152 m in diameter fixed bed of 5 successive catalysts of various shape and size, and various trickling liquids (water, water+additives, kerosene). A model has been derived based on force balance on each fluid phase and compared to experimental results including previous works. This model was extended to partial wetting, characterised by tracer analysis. In bubble column, oxygen to water mass transer was shown to be highly influenced by adding only 1% oil fraction. 7 organic liquids were used showing more than 300% mass transfer enhancement with alkanes and conversely 50% reduction with more water soluble components, these effects being mainly relatde to bubble size.

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Li, Dong. "Comparison of an Advanced Mercury Analyzer with the Cold Vapor Atomic Absorption Technique for the Determination of Mercury in Coal." TopSCHOLAR®, 1999. http://digitalcommons.wku.edu/theses/791.

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For over 30 years the industry standard method for mercury analysis has been the cold vapor atomic absorption spectrometric technique (CVAAS). Recent developments in improving this technique have focused on procedures for concentrating mercury in the analyte or materials to improve detection. The LECO Corporation produces an Advanced Mercury Analyzer, the AMA-254, for analysis of the solid and liquid samples. The system allows for the thermal heating of the sample to decompose the sample and release mercury, which is concentrated in a gold amalgam. Thermal desorption of the mercury from the amalgam is detected by atomic absorption spectroscopy. A comparison of the performance of the AMA-254 with CVAAS techniques was made using standard reference materials. The CVAAS method follows the procedure in ASTM Method D 3684. The results of this research indicate that the AMA-254 is very easy to use in the analysis of solid and liquid samples without pretreatment and has a lower detection limit than the CVAAS technique.

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Degrelle, Deborah. "Caractérisation numérique de la technique de spectrométrie gamma par simulation Monte-Carlo. Application à la datation d'échantillons envrionnementaux." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD004/document.

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Caractérisation numérique de la technique de spectrométrie gamma par simulation Monte-Carlo : Application à la datation d'échantillons environnementaux.Résumé :Afin d'optimiser la détermination de l'activité d'échantillons environnementaux, l'étalonnage en efficacité de la chaîne spectrométrique se doit d'être de bonne qualité. Le travail de cette thèse consiste à rassembler les problématiques principales : les phénomènes d'auto-absorption et de coïncidence. Ces effets sont traités par métrologie et simulation Monte-Carlo (MCNP6), impliquant la bonne modélisation préalable de nos détecteurs. Le problème d'auto-absorption est dominant lorsque le standard utilisé pour l'étalonnage en efficacité a des caractéristiques physico-chimiques différentes des échantillons. Un étalonnage numérique semble plus approprié et nous l'appliquons à une archive sédimentaire du lac de Longemer (France). Nous proposons une méthode nouvelle se basant sur une mesure expérimentale ajustée numériquement afin de déterminer le coefficient d'atténuation massique des échantillons. Il est alors possible de remonter à une composition chimique fictive qui permettra d'utiliser la simulation Monte-Carlo pour réaliser l'étalonnage. Ainsi, à 59,54 keV la correction de l'auto-absorption peut atteindre 24 %. Les phénomènes de coïncidence peuvent également être corrigés par simulation. Le logiciel ETNA permet cette correction mais ne permet pas la modélisation d'un détecteur puits. Dans le but de corriger l'efficacité de notre détecteur puits, possédant une géométrie propice aux coïncidences, nous utilisons le transfert de rendement qui lui est adaptable pour n'importe quelle géométrie. Les résultats par cette méthode sont validés par MCNP6 et Génie 2000 sur les énergies principales du 214Bi
In order to improve the determination of environmental samples activity, the detector efficiency calibration must be reliable. These studies deal with the main issues in gamma-ray spectrometry: the self-absorption and the true coincidence summing effects (TCS). These phenomena are studied by metrology and Monte-Carlo simulation (MCNP6) that imply the faithful of our detector models in relation to the experimental device. The self-absorption problem is the main one when the used standard for efficiency calibration has not the same physical and chemical characteristics than samples. A numerical calibration seems to be more suitable and we apply it for Longemer lake archives (France). A new method is proposed where an experimental measurement is processed through numerical simulations to determine the mass attenuation coefficient of the samples. It makes it possible to define a virtual chemical composition to use Monte-Carlo simulation. Then the numerical calibration at 59.54 keV gives a 24% self-absorption correction. The TCS problems can also be corrected by simulation. The ETNA software can determine this correction but it doesn’t make the well type detector model possible, with a geometry conducive to TCS effects. With the aim of correcting the efficiency of our well detector, the efficiency transfer, which can be adjusted to any device, is used. The results with this method are validated by MCNP6 and Genie 2000 software on the main lines of 214Bi

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Castro, Moema Soares de. "Système de pompage de l'eau utilisant une pompe gas-lift et alimenté par énergie solaire." Toulouse, INPT, 1994. http://www.theses.fr/1994INPT060G.

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En zones rurales des pays en developpement, le manque d'eau constitue l'un des problemes les plus urgent a resoudre. La disponibilite de l'energie solaire dans ces pays croit avec les besoins d'eau, alors il nous semble que l'utilisation de cette source d'energie pour le pompage de l'eau est une question rationnelle. Notre etude est portee sur un systeme de pompage d'eau en utilisant l'energie solaire. Il s'agit de la mise en uvre d'un cycle a absorption discontinu fonctionnant avec le melange eau-ammoniac ; l'ammoniac obtenu par chauffage du melange par energie solaire constitue le fluide moteur actionnant une pompe a eau. La circulation du fluide caloporteur est garantie par le fonctionnement gas-lift du capteur solaire. A la sortie du capteur la vapeur d'ammoniac entraine la pompe hydraulique du type diaphragme a double effet. Ce dispositif peut aussi assurer la circulation du melange si le phenomene gas-lift est juge insuffisant, par recuperation de travail sur l'axe moteur de la pompe. Dans l'absorbeur, la phase liquide sortant du capteur absorbe la vapeur d'ammoniac. L'eau pompee du puits est utilisee pour refroidir l'absorbeur duquel sort le melange, riche en ammoniac, retournant au capteur. L'ensemble ainsi obtenu est donc susceptible de s'auto-adapter aux variations journalieres et saisonnieres de l'ensoleillement. Bien que notre etude ait ete centree sur la mise en uvre et l'etude de la performance du capteur solaire, point cle du systeme a absorption, nous avons reconstitue le fonctionnement du systeme de pompage, utilisant la simulation base sur le logiciel trnsys nous avons developpe des elements pour simuler le capteur diphasique, l'absorbeur et la pompe a diaphragme

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Gangwe, Nana Ghislain Yannick. "Etude par imagerie SIMS de l'effet d'une molécule filmogène sur la pénétration de xénobiotiques dans la peau." Rouen, 2013. http://www.theses.fr/2013ROUES011.

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Les molécules odorantes (dont l’eugénol et ses dérivés) sont très souvent ajoutées dans les formulations cosmétiques pour améliorer leurs propriétés sensorielles. Elles constituent l’ingrédient principal utilisé en parfumerie. Cependant, ces composés peuvent pénétrer dans la peau et entrer en contact avec les cellules de Langerhans, premiers médiateurs de la réaction allergique. Le piégeage de ces molécules à la surface de la peau a été proposé comme une approche pratique pour limiter leur pénétration cutanée. La capacité de la zéine (protéine amphiphile) à former un film fait d’elle un agent potentiellement utile pour ce piégeage de molécules à l’extérieur de la peau. Les objectifs de cette recherche étaient donc d'étudier la distribution cutanée de molécules odorantes dérivées de l’eugénol en présence et en absence de film de zéine par une nouvelle technique d’imagerie ionique : le NanoSIMS 50. Ce travail a consisté à étudier la zéine et son effet sur la distribution cutanée des dérivés de l’eugénol. Pour ce faire, il a été important d’optimiser des protocoles de préparation d’échantillons de peau pour les études d’imagerie. L’étude préalable de la zéine a révélé une structure de film assez complexe, discontinu, inégalement réparti à la surface de la peau et très hétérogène. Nous avons observé en absence de zéine, une accumulation plus importante dans la peau des dérivés de l’eugénol qu’en présence de zéine. L’eugénol semble donc avoir été piégé par la zéine. Cette étude a ainsi permis de montrer pour la première fois que la zéine pourrait réduire la pénétration des molécules dérivées de l’eugénol (isoeugénol et dihydroeugénol) dans la peau. Ces résultats obtenus avec les dérivés de l’eugénol, s’ils peuvent être généralisés à d’autres molécules allergéniques, pourraient contribuer à la réduction de nombre de personne développant des réactions allergique lors de l’utilisant des produits cosmétiques et de parfumeries dans lesquels la zéine serait ajoutée.

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Houbloss, Samir. "Detection thermique de l'absorption optique : developpement de la technique, informatisation, etudes d'elements 3d dans des materiaux iii-v." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21078.

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Developpement d'une technique nouvelle de detection de l'absorption optique, tres sensible aux basses temperatures. Construction d'un spectrometre equipe de differents cellules et informatise. L'appareillage a permis la detection des bandes et des raies a zero phonon associees a la presence du chrome, du vanadium et du titane dans les materiaux iii-v

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Mazingue, Thomas. "Conception et élaboration d'un capteur optique à ondes guidées pour la détection d'espèces chimiques." Phd thesis, Aix-Marseille 3, 2005. http://tel.archives-ouvertes.fr/tel-00011293.

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Le travail de thèse a consisté à élaborer un nouveau type de capteur utilisant la technique des "m-lines" pour détecter la variation d'indice de matériaux sensibles aux gaz déposés en couches minces. En effet, la variation de conductivité d'un matériau sensible utilisé dans les capteurs à oxyde métallique s'accompagne d'une modification de son indice de réfraction lorsqu'il est exposé à un gaz. La littérature a permis d'identifier certains matériaux susceptibles d'être sensibles au butane, au propane et à l'ozone. Ces matériaux ont été déposés et caractérisés afin d'optimiser leurs propriétés optiques, morphologiques et leur sensibilité au gaz. Un banc de test a été réalisé pour la mesure de la sensibilité aux gaz en fonction de la concentration de gaz et de la température (jusqu'à 100°C). Un démonstrateur de principe de capteur a été développé à l'aide d'un réseau coupleur. La détection optique du butane et du propane, dans la gamme 100 à 1000 ppm a été validée.

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Shalygin, Maxim. "Réalisation et caractérisation du transport sélectif gazeux de contacteurs gaz-liquide à membrane (Selective transport of gases in gas-liquid membrane system)." Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL022N/document.

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Ce travail rapporte l’étude de systèmes membranaires à valves sélectives (SMV), qui combinent les avantages des techniques de séparation par membrane et par absorption. La 1ère partie du mémoire présente l'étude du transport de matière en régime permanent et transitoire dans les SMV élaborés à partir de membranes polymères denses et de solution aqueuses. Dans la 2ème partie le développement d'un modèle mathématique original pour la simulation des SMV est proposé ainsi que son évaluation expérimentale pour les séparations CO2/CH4/H2, avec des solutions aqueuses confinées de K2CO3. Des améliorations simultanées de la perméabilité (˜ 4 fois) et de la sélectivité (>20 fois) ont été obtenues pour CO2 avec le mélange CO2/H2. Un logiciel basé sur un nouveau modèle de transport de gaz dans ces contacteurs membranaires prenant en compte la sorption physique et chimique dans la phase liquide a été développé pour le calcul de la perméabilité en régime transitoire ou permanent
Combined gas-liquid membrane systems gather the advantages of membrane and absorption separation techniques. Specifically, selective membrane valves (SMV called flowing liquid membranes) were studied, i.e. creation, gas transport experiments, liquid nature and temperature dependences, and modelling. SMV use a flowing layer of liquid supported between two membranes. The 1st part of the dissertation reports the study of steady and non-steady state gas transports in SMV built out dense polymeric membranes. In the 2nd part is given the development of an original mathematical model for SMV simulation and its experimental assessment for CO2/CH4/H2 mixtures with aqueous solutions of K2CO3. From systematic studies of steady and non-steady state processes, both in flow-through and circulating modes, it was found that increasing of temperature and liquid carrier concentration (K2CO3) leads to the simultaneous rise of permeability and selectivity during CO2 recovery from CO2/H2 mixture

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Graves, Rosemarie Rachel. "Can a hemispherical scanning imaging differential optical absorption spectroscopy technique be used to improve understanding of the emissions, dynamics and chemistry of nitrogen dioxide in the urban boundary layer?" Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/28636.

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Air quality is an international issue which has been the subject of several European directives on pollution levels as atmospheric pollutants can have significant effects on human health, ecosystems and climate change, especially at high levels. In the UK the largest sources of atmospheric pollutants are products of combustion from power generation and motor vehicles including NO[subscript x] (NO and NO[subscript 2]), CO, VOCs and particulate matter. Hence it is becoming increasingly important to measure changes in these air pollutants especially in urban areas where these pollutants are at the highest levels. Differential Optical Absorption Spectroscopy is now commonly used as an air quality tool; primarily through the measurements of nitrogen dioxide (NO[subscript 2]). CityScan is a Hemispherical Scanning Imaging Differential Optical Absorption Spectrometer (HSI-DOAS) which has been optimised to measure concentrations of NO[subscript 2]. This thesis will describe the development and subsequent deployment of three CityScan instruments and the first results from these deployments. CityScan has a 95° field of view (FOV) between the zenith and 5° below the horizon. Across this FOV there are 128 resolved elements which are measured concurrently, the spectrometer is rotated azimuthally 1° per second providing full hemispherical coverage every 6 minutes. Three CityScan instruments were built between 2009 and 2012 and deployed in various locations, including Leicester, London and Bologna. Data from one of these instruments has been validated with a MAX-DOAS instrument (TROPOGAS) and in situ monitors. The comparison with the TROPOGAS instrument produced gradient values between 0.7 and 1 with R² values rarely lower than 0.7. An NO[subscript 2] detection limit of CityScan has been calculated to be 4 x 10[superscript 15] mol cm[superscript -2]. The extensive field of view of the CityScan instruments has allowed NO[subscript 2] concentrations to be mapped on city-wide scales allowing areas of high and low pollution to be identified with a spatial resolution which has never been possible before without the use of models.

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Colakoglu, Tahir. "The Effects Of Post-annealing Process On The Physical Properties Of Silver-indium-selenium Ternary Semiconductor Thin Films Deposited By Electron Beam Technique." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610974/index.pdf.

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Ternary chalcopyrite compounds are the semiconductors with suitable properties to be used as absorber materials in thin film solar cells. AgInSe2 is a promising candidate with its several advantages over the widely used CuInSe2. The purpose of this study was to optimize the physical properties of the Ag-In-Se (AIS) thin films that were deposited by e-beam evaporation of Ag3In5Se9 single crystal powder for solar cell applications by means of post-annealing process under nitrogen atmosphere. The as-grown AIS thin films were annealed at 200, 300 and 400oC and their structural, optical, electrical and photoelectrical properties were examined to observe the effects of post-annealing process. Structural characterization of the films was performed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) analyses. Optical properties of the films were investigated by optical transmittance measurements. Electrical and photoelectrical properties of the films were examined by temperature dependent conductivity, photoconductivity under different illumination intensities and spectral photoresponse measurements. It was discovered that the annealing of AIS thin films at 200oC resulted in the best physical properties for solar cell applications. The obtained films were polycrystalline with mixed binary and ternary crystalline phases, such as Ag3In5Se9, AgInSe2 and InSe, and showed n-type conductivity with room temperature conductivity value of 2.3x10-6 (Ohm
cm)-1. The band gap energy of the 200oC-annealed films was determined as 1.68 eV from spectral photoresponse measurements. The results of the study revealed that the inadequate Ag incorporation and segregation and/or reevaporation of Se atoms at high annealing temperatures were the major problems encountered in producing single phase polycrystalline AgInSe2 thin films. The required stoichiometry of thin films should be maintained during the growth of the films by means of an alternative deposition procedure and the films should be selenized during post-annealing process.

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Chemat, Farid. "Le chauffage micro-ondes dans les procédés de synthèse organique : application à l'hydrolyse des nitriles et à la pyrolyse de l'urée." Toulouse, INPT, 1994. http://www.theses.fr/1994INPT017G.

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Une premiere partie bibliographique analyse l'etat des connaissances sur le principe, la mise en uvre et la comprehension des reactions chimiques sous chauffage micro-ondes. L'accent est mis sur l'hypothese d'une activation specifique des micro-ondes a l'echelle moleculaire. La deuxieme partie presente une etude sur les effets chimiques et physiques des micro-ondes, effets observes a l'aide d'une reaction modele simple: l'hydrolyse des nitriles en acides carboxyliques. Cette reaction est realisee en milieu homogene en presence de diacides organiques et en milieu heterogene en utilisant des sels mineraux ou de metaux de transition. Une etude sur la surchauffe des liquides sous micro-ondes a ete menee afin d'expliquer les effets thermiques non conventionnels rencontres sous chauffage micro-ondes. Un nouveau procede propre a ete mis au point pour la synthese d'acides et d'amides carboxyliques a partir d'une hydrolyse originale a sec des nitriles par des diacides carboxyliques. Ce procede est simple, ecologique, et de faible cout et pourrait remplacer les techniques traditionnelles. La troisieme partie decrit une etude comparative entre le chauffage conventionnel et micro-ondes sur la reaction de pyrolyse d'uree en acide cyanurique a sec et dans un solvant organique. Ensuite, nous decrivons un dispositif couplant le chauffage par micro-ondes avec le degazage par ultrasons qui sera utilise pour activer la reaction de pyrolyse d'uree. Divers techniques ont ete testes pour essayer de mettre au point un procede de pyrolyse d'uree sous champ micro-ondes

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Le, Meur Loïc. "Etude des propriétés de désintégration bêta de noyaux exotiques d'intérêts pour la physique des réacteurs, la structure nucléaire et l'astrophysique nucléaire, à l'aide de la technique de Spectroscopie Gamma par Absorption Totale (TAGS)." Thesis, Nantes, 2018. http://www.theses.fr/2018NANT4060/document.

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La désintégration bêta est impliquée dans de nombreux domaines de la physique nucléaire : physique des réacteurs, structure nucléaire… De nombreuses expériences ont permis d’étudier les propriétés de la désintégration β d’un certain nombre de noyaux, ces derniers étant de plus en plus exotiques au fur et à mesure des avancées technologiques. Mais une partie de ces données souffre de l’effet « Pandemonium ». Connu depuis les années 70, cet effet est lié à l’utilisation des détecteurs haute résolution au Germanium qui ont une faible efficacité de détection des photons de haute énergie. Il en résulte une sous-estimation de l’alimentation des niveaux de haute énergie lors du calcul de l’intensité de désintégration β. Pour pallier cet effet, on utilise une technique de détection de haute efficacité: la Spectroscopie Gamma par Absorption Totale (TAGS). Dans cette thèse, nous nous sommes focalisés sur l’étude de trois noyaux mesurés auprès de l’accélérateur IGISOL en Finlande avec le détecteur DTAS. Nous présentons les résultats expérimentaux ainsi que l’intensité bêta obtenue, et la comparons aux résultats extraits des bases de données. Cette comparaison montre qu’une quantité non négligeable d’intensité β n’était pas détectée auparavant pour les trois noyaux étudiés. Nous discutons ensuite des impacts de cette différence dans le domaine des réacteurs nucléaires, et étudions l’alimentation β des états de haute énergie dans les noyaux fils qui pourraient constituer des résonances pygmées dans ces noyaux. Des comparaisons de nos résultats expérimentaux avec un modèle microscopique de QRPA sont également présentées afin d’aider à l’interprétation des données
Beta decay is involved in many topics in nuclear physics : reactor physics, nuclear astrophysics, nuclear structure… Many experiments have investigated the properties of beta decay of a number of nuclei, the latter being more and more exotic along with technological advances. But in some cases, data suffer from the “Pandemonium” effect. Known since the seventies, this effect is due to the use of high-resolution germanium detectors which have a very low efficiency to detect high energy photons. This may lead to an underestimation of the beta-intensity feeding the high energy levels. To overcome the problem, we use a technique with high intrinsic and geometric efficiencies: the Total Absorption Gamma-ray Spectroscopy (TAGS). In this work, we will focus on the study of three nuclei, measured at IGISOL in Finland, with the fragmented detector DTAS. We present the experimental results and the associated betaintensities, and compared them with the existing databases. This comparison shows a non-negligeable amount of beta-intensity that was not detected before for the three studied nuclei. Then we discuss the impacts of these new results on the reactor calculations (antineutrino spectra, decay heat), and analyze the β-feeding of the high energy levels in the daughter nuclei to study Pygmy Dipole Resonances (PDR or low lying resonances). Lastly, our experimental β-strengths are compared with the Gamow-Teller strengths obtained with a QRPA model

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23

Vivas, Marcelo Gonçalves. "Relação entre a estrutura molecular e as propriedades de absorção de multi-fótons em compostos orgânicos π-conjugados." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-30092011-150524/.

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Nesta tese estudamos a relação entre as propriedades de absorção de multi-fótons e a estrutura molecular de três classes distintas de compostos orgânicos π-conjugados: derivados de vitamina A, complexos de platina acetilada e compostos quirais. Materiais orgânicos emergiram nas últimas décadas como candidatos para aplicações em dispositivos fotônicos, principalmente aqueles envolvendo processos de absorção multifotônica, uma vez que suas propriedades podem ser facilmente otimizadas através de engenharia molecular. Devido às diferenças inerentes entre as estruturas químicas dos compostos aqui investigados, foi possível verificar individualmente a influência do comprimento de conjugação, da presença de grupos doadores e aceitadores de elétrons (estruturas push-pull), da planaridade molecular e de efeitos de comprimento de ligação sobre a seção de choque de absorção multifotônica. Para tanto, foram utilizadas as técnicas de Varredura-Z convencional e com contínuo de luz branca, espectroscopia de fluorescência por absorção de multi-fótons e fluorescência resolvida no tempo. Para correlacionar as propriedades moleculares com os espectros não-lineares, foram utilizados cálculos de química quântica em conjunto com o modelo de soma de estados essenciais. Através desse modelo foi possível associar aspectos puramente moleculares, como o momento de dipolo de transição, o momento de dipolo estático, a força do oscilador e a largura de linha dos estados eletrônicos com a estrutura molecular dos cromóforos, visando futuras aplicações tecnológicas. Resultados de espectroscopia de absorção de dois fótons revelaram que os derivados da vitamina A, como o trans-β-apo-8-carotenal e all-trans β-caroteno, possuem magnitudes da seção de choque extremamente elevadas (~5000 GM), indicando-os como materiais promissores para armazenamento óptico 3D. Os complexos de platina acetilada apresentaram características impares para aplicações em dispositivos de limitação de potência óptica baseados em processos de absorção de dois e três fótons como, elevadas absortividades não-lineares, boa transparência óptica, baixo limiar de limitação, alto intervalo dinâmico e rápido tempo de resposta. Por fim, os compostos quirais abriram possibilidades de explorar novos efeitos em óptica não-linear como, por exemplo, efeito de dipolo magnético e quadrupolo elétrico, apenas modificando o estado de polarização da luz.
In this thesis we studied the relationship between the multi-photon absorption properties and the molecular structure of three distinct classes of π-conjugated organic compounds: derivatives of vitamin A, platinum acetylide complexes and chiral compounds. Organic materials have emerged as potential candidates for applications involving multiphoton absorption, since their properties can be changed through molecular engineering. Because of the inherent differences between the molecular structures of the compounds investigated here, it was possible to verify the influence of conjugation length, electron donor and acceptors groups (push-pull structures), molecular planarity and effects of bond length alternation on the multi-photon absorption cross-section. To investigate such properties, we have employed the conventional and white-light continuum femtosecond Z-scan technique and multi-photon and time-resolved fluorescence spectroscopy. We have also employed quantum chemical calculation and the essential sum-over-states approach to correlate the impact of molecular properties on the nonlinear spectra. It was possible to link pure molecular features such as transition dipole moment, static dipole moment, oscillator strength and states linewidth with the chromophores structures, aiming at future applications. The two-photon absorption spectroscopy results revealed that the derivatives of vitamin A, such as trans-β-apo-8-carotenal and all-trans β-carotene, present cross-sections values extremely high (~ 5000 GM), indicating them as promising materials for 3D optical storage. The platinum acetylide complexes can be applied in optical power limiting devices based on the two- and three-photon absorption process, since they present unique features, such as high nonlinearity, good optical transparency, low threshold limit, high dynamic range and fast response time. Finally, the chiral compounds opened up new possibilities to be explored in nonlinear optics, such as the effect of magnetic dipole and electric quadrupole, only manipulating the polarization state of the light.

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Rodriguez, Ruben Dario Fonseca. "Não linearidades de segunda e terceira ordem de sistemas moleculares ramificados." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-26012017-090852/.

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Compostos orgânicos constituem uma classe interessante de materiais para aplicações em óptica por apresentarem boa processabilidade, relativa facilidade para integração em dispositivos e, principalmente, pela possibilidade de otimização de suas propriedades ópticas através da engenharia molecular. Várias estratégias têm sido empregadas para sintetizar moléculas orgânicas, que exibam singificativos efeitos ópticos não lineares. Nesta direção, nos últimos anos moléculas multi-ramificadas vêm sendo produzidas com o objetivo de intensificar efeitos não lineares, já que estas podem exibir um forte efeito cooperativo entre seus ramos. Nesta tese estudamos a relação da absorção de dois fótons (A2F) e da primeira hiperpolarizabilidade com a estrutura molecular, para um conjunto de nove derivados de trifenilamina com diferentes grupos aceitadores de elétrons arranjadas em geometrias dipolar, quadrupolar e octopolar. O processo A2F foi estudados através da técnica de Varredura-Z, enquanto que a primeira hiperpolarizabilidade foi caracterizada pela técnica de espelhamento hiper Rayleigh. Os dados experimentais para a absorção de dois fótons revelaram espectros bem definidos, com valores razoáveis de seção de choque na região do visível e infravermelho próximo. Observamos ainda um engrandecimento para a seção de choque de A2F para as moléculas quadrupolares. Os resultados obtidos para a primeira hiperpolarizabilidade (β) mostraram que moléculas quadrupolares apresentam maior β do que as dipolares e octopolares, portanto, nossos resultados permitem concluir que o acoplamento eletrônico entre os ramos contribuem fortemente para a seção de choque por A2F e β nas moléculas quadrupolares, não sendo este processo relevante nas moléculas octopolares. Todos os resultados foram interpretados por meio de estudos teóricos empregando a teoria do funcional da densidade (DFT).
Organic compounds constitute an interesting class of materials for optical applications due to their excellent processability, easy integration into devices and, mainly, the possibility of optimizing its optical properties through molecular engineering. Several strategies have been employed to synthesize organic molecules, which exhibit significant nonlinear optical effects. In this direction, in the last few years multi-branched molecules have been obtained aiming at intensifying nonlinear optical effects, since they may exhibit a strong cooperative effect among their branches. On this thesis we have studied the relationship of two-photon absorption (2PA) and first hyperpolarizability with the molecular structure of a group of nine triphenylamine derivatives attached to distinct electron acceptor groups arranged in dipole, quadrupole and octopolar geometries. The 2PA process was studied by Z-scan technique, while the first hyperpolarizability was characterized by the hyper-Rayleigh scattering technique. The experimental data for two-photon absorption revealed well-defined spectra with reasonable cross section magnitude in the visible and near infrared range. We also observed an enhancement of the 2PA cross-section for the quadrupolar molecules in comparison to the dipolar and octopolar ones. The results obtained for the first hyperpolarizability (β) shown that the quadrupolar molecules present higher β than the dipolar and octopolar, suggesting that the electronic coupling between the branches strongly contribute to the 2PA cross-section and β in quadrupolar molecules, being not relevant in the octopolar molecules. All results were interpreted through theoretical studies based on the density functional theory (DFT).

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Keil, Allessandra, and Michael Raupach. "Polymermodifizierte Feinbetone - Untersuchungen zum Feuchtetransport." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-77927.

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Untersuchungen zur Dauerhaftigkeit von ARGlasbewehrung im Textilbeton haben gezeigt, dass durch die Alkalität des Betons in Verbindung mit Feuchtigkeit eine Glaskorrosion hervorgerufen wird, die im Laufe der Zeit zu Festigkeitsverlusten des Glases führt. Eine Möglichkeit, die durch die Glaskorrosion verursachten Festigkeitsverluste zu reduzieren, stellt die Polymermodifikation des Betons dar. Durch die Polymerzugabe wird die Wasseraufnahme der Feinbetonmatrix reduziert, dadurch sinkt der Gehalt an gelösten Alkalien im Bereich der Bewehrung. Um den Einfluss verschiedener Feinbetonmatrices auf die Dauerhaftigkeit von Textilbeton beurteilen zu können, sind u. a. zeit- und tiefenabhängige Informationen zur Feuchteverteilung erforderlich, die durch den Einsatz der NMR-Technik gewonnen werden. Der nachfolgende Artikel beschreibt den Feuchtetransport in einer speziell für den Textilbeton entwickelten Feinbetonmatrix sowie den Einfluss verschiedener Modifikationsstoffe auf das Wasseraufnahmeverhalten des Betons
Durability tests of textile reinforced concrete revealed a loss of strength of the AR-glass reinforcement due to glass corrosion effected by the alkalinity and moisture content of the concrete. In order to reduce this strength loss of AR-glass in cementitious matrices, polymers can be used for concrete modification. The aim of the polymer addition is to reduce the amount of capillary water absorption of the matrix, which reduces the amount of free alkalies closed to the reinforcement. In order to evaluate the effect of the concrete matrix on the durability of TRC, it is necessary to determine the moisture content as functions of time and depth. This data can be obtained by the use of nuclear magnetic resonance (NMR) technique. This paper deals with the moisture transport in a finegrained concrete matrix especially developed for the use in TRC as well as the influence of polymer addition on the water absorption properties of the concrete matrix

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Dairon, Jonathan. "Développement d'une nouvelle technique d'élaboration de mousses d'acier par fonderie et caractérisation mécanique." Phd thesis, Ecole Centrale de Lille, 2008. http://tel.archives-ouvertes.fr/tel-00694478.

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Les mousses métalliques sont des matériaux intéressants pour fabriquer des absorbeurs d'énergie et des panneaux de faible masse travaillant en flexion. Jusque là, l'aluminium a principalement été employé : sa masse volumique réduite et ses performances mécaniques assez élevées ont fait de lui le candidat idéal pour créer des structures rigides et légères pouvant absorber de grandes quantités d'énergie. Cette thèse étudie la possibilité d'employer de l'acier pour produire des mousses métalliques. L'objectif a été de tirer parti du faible coût et/ou des performances mécaniques très élevées de ce métal pour fabriquer des mousses rivalisant avec les mousses d'aluminium. Pour fabriquer des mousses d'acier, deux types de techniques ont été testés dans le cadre de cette thèse : le moussage d'un métal liquide et l'infiltration d'une préforme. Le premier consiste à former une mousse liquide qui est ensuite solidifiée. Pour cela, nous nous sommes attachés à introduire du gaz dans l'acier et à créer les conditions pour que la mousse formée soit stable. Le second consiste à couler le métal dans un réseau de porosités ayant la forme d'une mousse. Pour mettre en œuvre ce procédé, nous avons mis au point une nouvelle technique de fabrication de préformes. Nous avons également étudié les paramètres conditionnant ses possibilités en termes de taille de pièce. Finalement, les performances des mousses d'acier fabriquées par infiltration ont été évaluées, via des essais de compression uniaxiale, pour les comparer à celles des mousses d'aluminium. Une première modélisation numérique de la mousse d'acier a aussi été effectuée, pour en apprécier la pertinence à prévoir le comportement de ce matériau.

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Woodall, Milton Andrew. "Nonlinear Absorption Techniques and Measurements in Semiconductors." Thesis, North Texas State University, 1985. https://digital.library.unt.edu/ark:/67531/metadc331299/.

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We have conducted a detailed experimental and theoretical study of nonlinear absorption in semiconductors. Experimental measurements were made on a variety of materials at wavelengths of 1.06 and 0.53 microns using a picosecond Nd:YAG laser. Both two- and three-photon processes were investigated. Values of nonlinear absorption coefficients extracted from these measurements show excellent agreement with recent theory and scaling rules. Our theoretical investigation has been carried out for two-, three-,and n-photon absorption, for both continuous and pulsed sources. Expressions are obtained for the transmission of the sample in terms of the incident irradiance for each case. The physical interpretation of these results is discussed. We have also considered the effects of the photogenerated carriers on the measurements. Equations are developed that include linear absorption by these carriers. We have observed severe distortions on the transmitted beam, caused by changes in the refractive index of the material, due to the presence of these carriers. We present a model that accurately describes these effects in terms of the photogenerated carrier density. We have developed several novel techniques for monitoring nonlinear absorption. In particular, we have adapted the photoacoustic technique to the measurement of nonlinear absorption in semiconductors. We have also developed a technique employing irradiance modulation to greatly enhance the sensitivity to nonlinear processes and simultaneously discriminate against linear background signals. A related technique has been used to observe coherent mixing effects in semiconductors with cw, modelocked dye lasers.

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Letellier, Michel. "Etude du comportement microdynamique de l'eau dans les suspensions et gels d'argiles par la technique de resonance magnetique nucleaire : methode de determination d'aires de surfaces et application a la prise des ciments." Orléans, 1988. http://www.theses.fr/1988ORLE2009.

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Etude des temps de relaxation de l'eau normale, de l'eau lourde et des protons en contact avec une surface d'argile, analysant les phenomenes en fonction de la concentration, de la temperature et de la nature de l'argile. Mesure du volume de la couche d'eau absorbee a la surface du solide, deduction de son epaisseur et determination de l'aire de la surface hydratee. Fonde sur le concept de tactoide, ce travail nombre l'existence de forces d'interaction a courte portee entre une molecule d'eau et une surface argileuse. Dans la deuxieme partie, etude du composant principal d'un ciment (silicate tricalcique), mesurant aire d'absorption en fonction du temps de prise; la methode rmo est une technique de surface simple et non destructrice, pouvant mesurer l'effet des adjuvants

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Humphries, Gordon S. "Novel diode laser absorption techniques for combustion diagnostics." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28843.

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In-situ optical techniques offer one of the most attractive options for measuring species concentration and spatial distribution profiles in reacting environments, such as flames. The generally non-intrusive nature and spatial resolution of these techniques are now preferred over on extractive sampling, followed by analysis using techniques such as gas chromatography. In this thesis two laser absorption measurement techniques are applied to measure the soot distribution, and acetylene concentration profiles in a flat-flame burner. The in-situ measurement of the distribution of particulate matter in flames is a key step in understanding the mechanism of its formation. Most in-situ measurement systems for this purpose are based on laser induced incandescence where particles are heated using high power laser sources and the increased incandescence emission of the soot particles is detected. However as the soot cools by heat transfer to the surrounding gas, following laser heating, the pressure of the gas is increased creating an acoustic effect. Photoacoustic detection has been applied to quantify low concentrations of particulate matter in ambient air but there have been few applications of photoacoustic detection to the in-situ measurement of particulate matter formation in combustion processes. A novel simple approach using a modulated continuous wave diode laser is presented in this thesis. The measurements taken using this new technique are compared to measurements of the visible emission from the flame, and previous soot distribution measurements using laser induced incandescence. Absorption spectroscopy using near-infrared tunable diode lasers has been applied to measure species in several harsh environments such as aero-engine exhaust plumes, flames, and other industrial processes. Simple single pass absorption techniques are not always suitable for this purpose due to the low absorption of the target species, either due to low concentration or weak absorption line-strength at high temperatures. One method to increase the sensitivity of such techniques is by using cavity enhanced methods which increase the effective path length of the laser through the absorbing medium. One such cavity enhanced method is Cavity Ring-Down Spectroscopy (CRDS). CRDS uses a cavity constructed of highly reflecting mirrors, laser light is then coupled into this cavity and absorption measurements can be evaluated from the decay rate of light from the cavity. The design and, novel application of continuous wave CRDS to measure the concentration profile of acetylene in the flat-flame burner is presented. Difficulties in deriving an absolute acetylene concentration from the measured ringdown times were encountered due to the large number of interfering features. Serveral fitting and extraction techniques are applied and compared to attempt to overcome these difficulties.

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Paříková, Lucie. "Rtuť v odpadních vodách." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216362.

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In the time period from November to April of the academic year 2007/2008 presence of mercury and its forms was monitored in the waste waters of Faculty of Chemistry, VUT in Brno. The level of mercury was determined as total mercury with help of the atomic absorption spectrometry method and in available forms by diffusive gradient in thin film technique.

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Charles, Therese. "Enhanced e-learning engagement using game absorption techniques ELEGANT." Thesis, University of Ulster, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551593.

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The influence of technology on education is significant and growing. In particular, most students in higher education now work in a learning environment that supports electronic access to course materials and perhaps controls aspects of the learning process. Within such an environment, students have greater choice as to when, where and how they study; unfortunately, however, these advantages are often offset by a reduction in student engagement. This is partly due to the quality of the learning content but equally important is the suitability of the learning environment in which that material is studied. This thesis focuses on that environment, considering, in particular, how student engagement might be improved using techniques common in digital games. In general, games succeed by entertaining players in a way that builds on their natural curiosity and competitiveness, thereby encouraging them to continue to play. Similar encouragement seems desirable in education. The thesis examines the hypothesis that student performance in e-learning can be improved by using engagement techniques from digital games. Essentially, this means enhancing technology-oriented learning environments with engaging features that occur in game design. The thesis considers the general requirements of such environments and identifies relevant engagement techniques. From this understanding, a game-oriented learning framework (GOLF) is proposed. The essence of the framework is that a game setting can promote desirable behaviour in terms of completing basic learning tasks and tackling additional challenges, with engagement further encouraged through regular feedback on performance, measured against others in the same class. It was anticipated at the outset that the design of the framework would require significant experimental evaluation and refinement so it has been produced through action research and evolutionary prototyping. A series of case studies in academia has been used in this development process. Results show that the framework can enhance, student engagement leading to improved performance. Also, as might be expected, however, there are significant soft factors involved that can have a significant impact on the benefit of the game approach and indeed determine whether or not it succeeds at all. These factors are discussed, together with suggestions for future work.

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Paoli, M. P. "Electron-volt neutron spectroscopy of condensed matter." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235080.

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Clinton, Jamie C. "Colloidal Cerium Oxide Nanoparticle: Synthesis and Characterization Techniques." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/31065.

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Fluorescence spectra and UV-Vis absorption spectra are collected on cerium oxide nanocrystalline particles. While CeO2 is the stable form of bulk cerium oxide, ceria nanoparticles exhibit a nonstoichiometric composition, CeO2-Î³, due to the presence of oxygen vacancies and the formation of Ce2O3 at the grain boundaries. The Ce(III) ions, which are more reactive and therefore more desirable for various applications, are created by oxygen vacancies, which act as defects in the CeO2-Î³ crystal lattice. These defects form trap states in the band gap of CeO2, which can be seen in the absorption spectra. Ce(III) is required for fluorescence of the ceria nanoparticles while Ce(IV) is involved in only nonradiative transitions. The optical spectroscopy results show that the ceria samples have different ratios of Ce(III) ions to Ce(IV) ions, which is verified by x-ray photoemission spectroscopy (XPS).
Master of Science

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34

Bradley, Robert Stephen. "Attenuation correction techniques for tissue fluorescence." Thesis, University of Manchester, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488398.

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Fluorescence intensity measurements have the potential to facilitate the diagnoses of many pathological conditions. However, accurate interpretation of the measurements is complicated by the distorting effects of tissue scattering and absorption. Consequently, different techniques have been developed to attempt to compensate for these effects.

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Newman, Stuart Michael. "Electronic spectroscopy of molecules of atmospheric interest using sensitive absorption techniques." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322613.

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Corrêa, Daniel Souza. "Absorção de multi-fótons em polímeros e resinas poliméricas: espectroscopia não linear e microfabricação." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-18032009-101119/.

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Nesta tese, estudamos o processo de absorção multifotônica em polímeros e resinas poliméricas, abordando tanto aspectos fundamentais quanto aplicados. Com relação aos aspectos fundamentais, estudamos processos de absorção multifotônica (absorção de dois, três e quatro fótons) no polímero conjugado MEH-PPV (poly(2-methoxy-5-(2´-ethylhexyloxy)-1,4- phenylenevinylene)), utilizando a técnica de Varredura-Z com pulsos ultracurtos. Através desta técnica, determinamos o espectro da absorção de dois, três e quatro fótons do MEHPPV. As seções de choque de absorção de multi-fótons correspondentes a cada processo foram determinadas através do ajuste das curvas experimentais com um conjunto de equações desenvolvidas neste trabalho. Os resultados obtidos permitiram traçar relações entre os espectros não lineares e os níveis de energia do polímero. Na vertente mais aplicada do projeto, estudamos a fotopolimerização de resinas acrílicas através do processo de absorção de dois fótons. Devido ao confinamento espacial da polimerização, graças à absorção de dois fótons, este método permite a confecção de micro-estruturas complexas para diversas aplicações tecnológicas. Além da fabricação de microestruturas convencionais não dopadas, neste trabalho desenvolvemos uma metodologia que possibilita a fabricação de microestruturas dopadas com MEH-PPV, visando a produção de micro-elementos fluorescentes para dispositivos fotônicos, e microestruturas dopadas com quitosana, um polímero biocompatível que pode ser utilizado em aplicações médicas e biológicas.
In this thesis we have studied the multi-photon absorption process in polymers and polymeric resins, exploiting its fundamental as well as technological aspects. Regarding the fundamental aspects, we have studied the multi-photon absorption (two-, three- and four-photon absorption) in the conjugated polymer MEH-PPV (poly(2-methoxy-5-(2´-ethylhexyloxy)-1,4-phenylenevinylene)), by using the Z-scan technique with ultrashort laser pulses. Through this technique, we determined the two-, three- and four-photon absorption spectra of MEH-PPV. The multi-photon absorption cross-sections, corresponding to each specific process, have been determined by fitting the experimental data with a set of equations developed in this work. The results allowed us to correlate the nonlinear absorption spectra to the energy level of the polymer. On the technological side of this thesis, we have investigated the photopolymerization of acrylic resins by two-photon absorption. Because of the spatial confinement of the polymerization, resulting from the two-photon excitation, this method allows the fabrication of complex microstructures which can be used for several technological applications. In addition to the fabrication of undoped microstructures, in this work we have developed a methodology that allows the fabrication of microstructures doped with MEHPPV, aiming the production of fluorescent micro-elements for photonics applications, and microstructures doped with chitosan, a biocompatible polymer, that can be used for medical and biological applications.

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Zhao, Ming. "In situ reflection absorption spectroscopic techniques for the study of electrogenerated species." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1057154581.

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Scarpa, Roberta. "Mécanisme d’accélération d’une flamme de prémélange hydrogène/air et effets sur les structures." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2046/document.

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Le risque d’explosion des mélanges H2/air revêt toujours une importance cruciale pour la gestion des accidents graves dans les centrales nucléaires. Des critères expérimentaux ont été proposés dans les années 2000 par Dorofeev et al. afin de déterminer les conditions nécessaires à l’accélération de flamme et à la TDD. Ce travail de thèse a l’objectif de mieux comprendre les mécanismes d’accélération des flammes de prémélange H2/air et de fournir une solide base de données expérimentales pour la validation des codes utilisés pour les études de sûreté. Les expériences ont été menées dans un tube muni d’obstacles (taux de blocage entre 0.3 et 0.6) avec un diamètre interne de 12 cm et une longueur d’environ 5 m. Les effets de la pression initiale et de la dilution en azote sur des mélanges pauvres en H2 ont été étudiés. Les résultats montrent que la pression favorise l’accélération seulement pour les mélanges les plus réactifs et que la surpression induite par la combustion est directement proportionnelle à la pression initiale. Les interactions flamme-choc ainsi que les instabilités thermo-diffusives jouent un rôle important sur la propagation de flamme. Une nouvelle technique a été développée dans le but d’obtenir une représentation plus fine du profil de vitesse de flamme. Des mesures d’absorption IR résolues dans le temps ont été effectuées en dopant le mélange avec un alcane. Le profil de vitesse a été obtenu en mesurant la variation d’extension du gaz frais pendant l’avancement de la flamme. Enfin, des analyses préliminaires ont été menées pour la conception d’un nouveau dispositif expérimental pour l’étude des effets de la combustion sur des structures en acier inox
Flame acceleration and explosion of hydrogen/air mixtures remain key issues for severe accident management in nuclear power plants. Empirical criteria were developed in the early 2000s by Dorofeev and colleagues providing effective tools to discern possible FA or DDT scenarios. The objectives of the present work are to better understand the mechanisms of acceleration for premixed H2/air flames and to provide a solid base of experimental data for the validation of the codes used for safety analyses. The experiments were performed in an obstacles-laden tube (blockage ratio between 0.3 and 0.6) with 120 mm internal diameter and about 5 m length. The effects of the initial pressure and the nitrogen dilution on lean H2 mixtures have been studied. The results show that pressure promote flame acceleration only for highly reactive mixtures. Moreover, the overpressure induced by the combustion is directly proportional to the initial pressure. Besides, flame-shock interactions and thermo-diffusive instabilities play an important role in flame acceleration. A new technique to track the flame position along the tube has been developed in order to obtain a finer representation of the flame velocity profile. The method consists in performing time-resolved IR absorption measurements by doping the mixture with an alkane. The velocity profile is then derivedby measuring the variation of the extension in depth of the unburnt gas along the tube axis. Finally, analyses on the effects of combustion generated loads on stainless steel structures were performed in order to provide preliminary results for the design of a new experimental device

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39

Souza, Amadeu Bandeira de. "Conversão ascendente de frequências e absorção não linear de salicilaldeido azina." Universidade Federal de Alagoas, 2013. http://www.repositorio.ufal.br/handle/riufal/1658.

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Two-photon absorption and two-photon excitation fluorescence of salicylaldehyde azine crystals were investigated. It was observed an intense visible fiuorescence when this material was excited with a laser tuned at the near infrared region. Varying the laser intensity we identified this phenomenon as a simultaneous two-photon laser absorption process. Using open aperture Z-scan measurements we characterized this two-photon absorption phenomenon and measured the value of the two-photon absorption crosssection of this molecule to be equal to 87 GM. Our results indicate that this is a promising organic material aiming nonlinear photonics applications.
Fundação de Amparo a Pesquisa do Estado de Alagoas
Neste trabalho foram investigados os efeitos físicos de Absorção não linear de dois fótons e fluorescência assistida por absoção de dois fótons em cristais orgânicos de salicilaldeído azina. Observou-se uma intensa fluorescência na região visível do espectro, quando este material foi excitado com um laser sintonizado na região do infravermelho próximo. Variando a intensidade do laser, esse fenômeno foi identificado como um processo de absorção simultânea de dois fótons do laser. Usando a técnica de varredura Z fenda aberta, esse efeito de absorção de dois fótons foi caracterizado e a seção de choque de absorção de dois fótons medida para esta molécula foi igual a 87 GM. Esses resultados indicam que essa molécula é um material orgânico promissor para o desenvolvimento de aplicações fotônicas.

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Erdem, Arzu Eroğlu Ahmet E. "Use Of Different Gold Amalgamation Techniques In Mercury Determination By Cold Vapor Atomic Absorption Spectrometry/." [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/kimya/T000354.pdf.

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Thesis (Master)--İzmir Institute of Technology, İzmir, 2005.
Keywords: Mercury, atomic absorption spectrometry, gold, amalgamation, cold vapor. Includes bibliographical references (leaves 48-51).

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41

Rotava, Oscar. "Implementation of linear and nonlinear optimal control techniques in carbon dioxide absorption/desorption plant." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/7341.

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42

Jenkin, Lance. "Application of cepstral techniques to the automated determination of the sound power absorption coefficient." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/16913.

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Includes bibliographical references.
This thesis builds on research by Bolton and Gold, who developed the theory of using cepstral analysis to determine the absorption coefficient of elastic porous materials. Jongens, in his Masters thesis, applied this technique to determine the absorption coefficient of asphalt samples mounted in a sample holder at the end of a tube. Jongens and others identified numerous factors that introduced uncertainties into the measurement. These uncertainties fall into two main categories. The first deals with the influences that the links of the measurement chain have on the ability to separate the incident and reflected signal. The second deals with the influence of the air leakage between the tube and the surface under measurement in-situ. This thesis deals with the first category. The objectives of this project are to continue the work of Jongens, to produce an apparatus that can rapidly determine the sound power absorption coefficient by a non-skilled operator in a noisy environment. The results should correlate closely with the standardised impedance tube method, within 0.05 over the range 200 Hz to 2000 Hz. The constraint that the apparatus be usable by a non-skilled operator means that little or no calibration should be required, nor should the microphone need to be handled. This thesis presents a survey of related methods used to determine the sound power absorption coefficient. Theory of the cepstral technique is discussed, along with methods that could be used to improve the accuracy of the technique. Excitation signals that could be used with the cepstral method are put forward. The Inverse Repeat Sequence (IRS) was used to excite the system. It was chosen for its high noise immunity, as well as its complete odd-order non-linearity immunity. Sources of uncertainties from the links of the measurement chain are considered and methods to overcome them are presented. Issues that arise from liftering - cepstral equivalent of windowing - are then highlighted. The apparatus for the cepstral technique and method of standing wave ratios used to determine the absorption coefficient is given. The results obtained using the cepstral technique are correlated with the impedance tube results. It was found that the cepstral method correlates closely with the impedance tube over the range of 200 Hz to 2000 Hz for a wide variety of samples. The apparatus was developed to be used by a non-skilled operator, only requiring the press of a button to perform the measurement. With the high noise immunity of the IRS signal, the measurement could be carried out in a noisy environment.

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43

Von, Laue Lukas. "Transferts de protons par effet tunnel dans l'acide benzoique : le rôle des vibrations moléculaires." Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10060.

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Une description quantitative des transferts de protons inter- et intramoleculaires, qui sont parmi les reactions chimiques les plus fondamentales, demande une connaissance de la surface d'energie potentielle. Le present travail contribue a la caracterisation de cette surface pour un systeme modele, le monocristal d'acide benzoique. Proche des positions d'equilibre, la spectroscopie vibrationnelle apporte des informations, tandis que la barriere de potentiel est caracterisee par des mesures d'effet tunnel. Ces mesures, par spectroscopie optique (raman, absorption, emission) et diffusion quasi-elastique de neutrons, sont faites en combinaison avec des substitutions isotopiques (#1#8o) et sous pression hydrostatique. Une nouvelle methode permettant de calculer la dynamique sur la surface d'energie potentielle multidimensionnelle est presentee. Elle repose sur une approche perturbative qui utilise la technique des instantons et evite la reduction habituelle a 2 ou 3 dimensions. Cette theorie peut etre appliquee dans le but d'evaluer l'effet tunnel de facon generale : inversion de l'ammoniac, rotation des groupements methyles, etc. . Pour les transferts de protons dans des dimeres d'acides carboxyliques, on fait une comparaison avec les resultats experimentaux.

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44

Lathdavong, Lemthong. "Development of diode laser-based absorption and dispersion spectroscopic techniques for sensitive and selective detection of gaseous species and temperature." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43799.

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The main aim of this thesis has been to contribute to the ongoing work with development of new diode-laser-based spectroscopic techniques and methodologies for sensitive detection of molecules in gas phase. The techniques under scrutiny are tunable diode laser absorption spectrometry (TDLAS) and Faraday modulation spectrometry (FAMOS). Conventional distributed-feedback (DFB) telecommunication diode lasers working in the near-infrared (NIR) region have been used for detection of carbon monoxide (CO) and temperature in hot humid media whereas a unique frequency-quadrupled external-cavity diode laser producing mW powers of continuous-wave (cw) light in the ultra violet (UV) region have been used for detection of nitric oxide (NO). A methodology for assessment of CO in hot humid media by DFB-TDLAS has been developed. By addressing a particular transition in its 2nd overtone band, and by use of a dual-fitting methodology with a single reference water spectrum for background correction, % concentrations of CO can be detected in media with tens of percent of H2O (≤40%) at T≤1000 °C with an accuracy of a few %. Moreover, using an ordinary DFB laser working in the C-band, a technique for assessment of the temperature in hot humid gases (T≤1000 °C) to within a fraction of a percent has been developed. The technique addresses two groups of lines in H2O that have a favorable temperature dependence and are easily accessed in a single scan, which makes it sturdy and useful for industrial applications. A technique for detection of NO on its strong electronic transitions by direct absorption spectrometry (DAS) using cw UV diode laser light has been developed. Since the electronic transitions are ca. two or several orders of magnitude stronger than of those at various rotational-vibrational bands, the system is capable of detecting NO down to low ppb∙m concentrations solely using DAS. Also the FAMOS technique has been further developed. A new theoretical description expressed in terms of both the integrated line strength of the transition and 1st Fourier coefficients of a magnetic-field-modulated dispersive lineshape functions is presented. The description has been applied to both ro-vib Q-transitions and electronic transitions in NO. Simulations under different pressures and magnetic field conditions have been made that provide the optimum conditions for both cases. A first demonstration and characterization of FAMOS of NO addressing its electronic transitions in the UV-region has been made, resulting in a detection limit of 10 ppb∙m. The characterization indicates that the technique can be significantly improved if optimum conditions can be obtained, which demonstrates the high potential of the UV-FAMOS technique.

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Gao, Du Yang. "Engineering of protein-based multifunctional nanoparticles with near-infrared absorption as photoacoustic contrast agents for biological applications." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3953810.

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Devaraj, Kiruthika. "The centimeter- and millimeter-wavelength ammonia absorption spectra under jovian conditions." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42806.

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Accurate knowledge of the centimeter- and millimeter-wavelength absorptivity of ammonia is necessary for the interpretation of the emission spectra of the jovian planets. The objective of this research has been to advance the understanding of the centimeter- and millimeter-wavelength opacity spectra of ammonia under jovian conditions using a combination of laboratory measurements and theoretical formulations. As part of this research, over 1000 laboratory measurements of the 2-4 mm-wavelength properties of ammonia under simulated upper and middle tropospheric conditions of the jovian planets, and approximately 1200 laboratory measurements of the 5-20 cm-wavelength properties of ammonia under simulated deep tropospheric conditions of the jovian planets have been performed. Using these and pre-existing measurements, a consistent mathematical formalism has been developed to reconcile the centimeter- and millimeter-wavelength opacity spectra of ammonia. This formalism can be used to estimate the opacity of ammonia in a hydrogen/helium atmosphere in the centimeter-wavelength range at pressures up to 100 bar and temperatures in the 200 to 500 K range and in the millimeter-wavelength range at pressures up to 3 bar and temperatures in the 200 to 300 K range. In addition, a preliminary investigation of the influence of water vapor on the centimeter-wavelength ammonia absorptivity spectra has been conducted. This work addresses the areas of high-sensitivity centimeter- and millimeter-wavelength laboratory measurements, and planetary science, and contributes to the body of knowledge that provides clues into the origin of our solar system. The laboratory measurements and the model developed as part of this doctoral research work can be used for interpreting the emission spectra of jovian atmospheres obtained from ground-based and spacecraft-based observations. The results of the high-pressure ammonia opacity measurements will also be used to support the interpretation of the microwave radiometer (MWR) measurements on board the NASA Juno spacecraft at Jupiter.

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Savic, Radojka. "Improved pharmacometric model building techniques." Doctoral thesis, Uppsala University, Department of Pharmaceutical Biosciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9272.

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Pharmacometric modelling is an increasingly used method for analysing the outcome from clinical trials in drug development. The model building process is complex and involves testing, evaluating and diagnosing a range of plausible models aiming to make an adequate inference from the observed data and predictions for future studies and therapy.

The aim of this thesis was to advance the approaches used in pharmacometrics by introducing improved models and methods for application in essential parts of model building procedure: (i) structural model development, (ii) stochastic model development and (iii) model diagnostics.

As a contribution to the structural model development, a novel flexible structural model for drug absorption, a transit compartment model, was introduced and evaluated. This model is capable of describing various drug absorption profiles and yet simple enough to be estimable from data available from a typical trial. As a contribution to the stochastic model development, three novel methods for parameter distribution estimation were developed and evaluated; a default NONMEM nonparametric method, an extended grid method and a semiparametric method with estimated shape parameters. All these methods are useful in circumstances when standard assumptions of parameter distributions in the population do not hold. The new methods provide less biased parameter estimates, better description of variability and better simulation properties of the model. As a contribution to model diagnostics, the most commonly used diagnostics were evaluated for their usefulness. In particular, diagnostics based on individual parameter estimates were systematically investigated and circumstances which are likely to misguide modelers towards making erroneous decisions in model development, relating to choice of structural, covariate and stochastic model components were identified.

In conclusion, novel approaches, insights and models have been provided to the pharmacometrics community.

Implementation of these advances to make model building more efficient and robust has been facilitated by development of diagnostic tools and automated routines.

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Heuvel, Elisabeth Gertruda Hendrika Maria van den. "Application of dual stable isotope techniques to measure absorption of calcium, magnesium and iron in man." [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Maastricht University [Host], 1998. http://arno.unimaas.nl/show.cgi?fid=8251.

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Dick, Ian Peter. "Factors affecting the dermal absorption of lindane : the use of in vitro and in vivo techniques." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261320.

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Al, Rais Masood. "Effects of hydrogen in an aluminium-magnesium-silicon alloy during the production of extrusion ingots." Thesis, Brunel University, 1995. http://bura.brunel.ac.uk/handle/2438/5020.

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Hydrogen causes defects, for which aluminiurn alloy products are rejected. The behaviour of hydrogen in aluminium-magnesium-silicon alloy extrusion ingots, has been studied throughout the course of manufacture from freshly reduced aluminium. It is shown that hydrogen in the liquid metal is produced by temperature-dependent reaction between the metal and water vapour in the atmosphere. As the metal is received from the reduction cells, its temperature is -850 'C and its hydrogen content, >0.4 cm3/100 g, is too high for casting sound ingots. The metal is transferred first to a so-called melting furnace, where it is alloyed and stirred, thence to a holding furnace, where the composition is adjusted, the metal is degassed by gas sparging and allowed to settle before casting. The metal cools throughout these operations and as the temperature falls, the calculated value for the hydrogen content in equilibrium with the atmosphere falls in response to the reduced hydrogen solubility. The actual hydrogen content of the metal exhibited marked hysteresis in following the equilibrium value. Significant reduction of the hydrogen content occurred only when the metal was agitated. The hydrogen content never fell below the equilibrium value even during the nominal degassing operation, leading to the conclusion that gas sparging in a furnace does not positively remove hydrogen but only assists the equilibration. The hot-top DC casting process yielded a 8 m x 0.18 m diameter ingot with a virtually uniform hydrogen content. When this ingot was homogenised by heating it to 590˚C in a 7h cycle, a significant proportion of the hydrogen content was lost from the surface zone. By matching the loss to a theoretical model assuming diffusion control, it was shown that the loss of hydrogen is attenuated by trapping in micropores. The effects of simulated industrial atmospheres on the loss or absorption of hydrogen by the solid alloy were investigated in an extended series of laboratory heat-treatments. The interaction of the metal with these atmospheres was found to be determined by the nature of the oxide films formed and therefore the films were investigated by XPS and SIMS surface analysis techniques. In clean atmospheres the absorption or loss of hydrogen was determined by the balance between inward migration of protons and outward diffusion of hydrogen atoms through the oxide. Pollution of the air by chlorine or especially sulphur stimulated hydrogen absorption to a degree which seriously damaged the metal by pore growth. These effects are explained by modified compositions and structures in the surface oxide.

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Dissertations / Theses on the topic 'ABSORPTION TECHNIQUE'

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