Dissertations / Theses: 'Absorbans'

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Nilsson, Sarah, and Sofia Wängdahl. "Reducering av DOC beroende av karaktär med fyra dricksvattenberedningstekniker : Jämförelse mellan fällning (FeCl3 och Al2(SO4)3), membranfiltrering och jonbyte med MIEX®." Thesis, Sveriges lantbruksuniversitet, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-231565.

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Halten löst organiskt material (DOC) har under de senaste 20 åren ökat i våra sjöar. Det har också skett förändringar i karaktären. DOC ställer till problem för vattenverk som använder ytvatten som dricksvattenkälla genom att det kan ge lukt, smak och färg till vattnet. Det ger också ett ökat behov av fällningskemikalier, större slambildning och större bildning av potentiellt skadliga desinfektionsprodukter. I och med förändringarna i halt och karaktär av DOC behöver nuvarande reningstekniker förbättras och nya tekniker utvecklas. I den här studien undersöktes två konventionella reningstekniker; fällning med järnklorid och fällning med aluminiumsulfat, samt två modernare tekniker; jonbyte med MIEX® och membranteknik. Sex olika vatten med extrema typer av DOC användes, såsom algogent vatten, avloppsvatten och myrvatten, för att få en stor spridning i SUVA (specifik UV254-absorbans). SUVA är kvoten mellan absorbansen vid 254 nm och DOC-halten och ger en indikation på fördelningen mellan alloktont och autoktont material. Analys av DOC, absorbans, fluorescensparametrar, anjoner och järn utfördes för att få en uppfattning av hur mycket och vilken typ av DOC som renades för respektive teknik. Membrantekniken hade generellt högre reducering av DOC än övriga reningstekniker. Genomgående renades alloktont material i högre utsträckning än autoktont material. Vatten med högt SUVA-värde (>3), alltså större andel alloktont material, var mer lättbehandlat än ett med lågt värde, men sambandet var inte linjärt. Algogent vatten renades dåligt med MIEX® och fällning men bättre med membran. Det fanns ett tydligt samband mellan absorbans (245 nm) och DOC-halt som gör det möjligt att med online-mätning av absorbans få fram tillräckligt noggranna värden på DOC-halter.
The amount of dissolved organic carbon (DOC) has risen in our lakes during the past 20 years and it has also changed in character. DOC causes problems for water treatment plants that are using surface water as a drinking water source. It gives the water odour, taste and colour. It also leads to a higher need of precipitation chemicals, more sludging, and larger formation of potentially harmful disinfection products. With the changes in both amount and character in DOC, current water treatment techniques need to be improved and new techniques developed. In this study, two conventional water treatment techniques; precipitation with iron chloride and precipitation with aluminium sulphate, and two more modern techniques; ion exchange with MIEX® and membrane filtration, were examined. Six waters with extreme types of DOC were used, including algogenic water, wastewater, and water from mire, in order to have a wide range of SUVA-values (specific UV254-absorbance). SUVA is the ratio between absorbance at 254 nm and the content of DOC. SUVA gives an indication about the distribution of allochthonous and autochthonous matter. In each water treatment technique analysis of DOC, absorbance, fluorescence parameters, anions, and iron were performed to gather information regarding how much and which type of DOC were reduced, in each water treatment technique. Membrane filtration had generally higher reduction of DOC compared to the other techniques. Allochthonous matter was reduced to a higher extent than autochthonous matter. Waters with a high value of SUVA (>3), which means a larger proportion of allochthonous matter, was more easily treated than water with lower values, but the relation was not linear. DOC in algogenic water was poorly reduced with MIEX® and the precipitation techniques, but better reduced with the membrane filtration. There was a correlation between absorbance (254 nm) and the amount of DOC, which makes it possible to do online reading of absorbance and translate the values into amount of DOC.

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Lundstedt, Evert. "Adsorption av Sb på zeolit." Thesis, Växjö University, School of Technology and Design, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-1591.

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Detta examensarbete är en förundersökning till Glafos undersökning angående rening av glasbrukens processvatten från antimon med zeolit.

Förundersökningen gick ut på att via experiment ta reda på hur mycket antimon som adsorberas av behandlad (för optimering: dels med NaNO3 och dels med NaCl) och obehandlad zeolit (porstorlek 0.4 nm). pH mättes och ställdes eftersom det har betydelse för adsorptionen, åtminstone vid väldigt lågt pH. När lösningarna hade filtrerats mättes den kvarvarande antimonhalten med atomabsorptionsspektrofotometri. Mätningarna visade att i genomsnitt 53 % av Sb-halten i lösningarna hade adsorberats av zeoliten. Förundersökningen visade att det inte blir någon adsorption då pH är väldigt lågt (under 1). Den visade också att när pH är över 4 verkar det inte ha någon betydelse om zeoliten är behandlad eller inte.

Zeoliten bör behandlas med NaCl först i en tank med omrörning, sedan blandas i processvattnet (vars pH justerats till pH 4) i en tank eller bassäng och därefter filtreras.

Tidsfaktorn för hur lång tid det tar för zeoliten att nå jämvikt och temperaturens inverkan bör även undersökas.

The aim of this diploma work is to study the removal of antimony from glassworks process water using zeolites.

The experimental part of the studies were carried out to find the quantity of antimony adsorbed by the zeolite. The studies included treated (for optimization: partly with NaNO3 and partly with NaCl) and untreated zeolite. The pore size is 0.4 nm. pH was measured and adjusted because it is important for the antimony adsorption. When the solutions were filtrated the content of antimony left was measured with atomic absorption spectrophotometry. The measurements showed an average uptake of antimony by the zeolite of 53 %.The preinvestigation indicates that with a very low pH (below 1) there is no antimony adsorption. It also indicates that with pH above 4 it does not matter if the zeolite are treated or not.

In further investigations the zeolite should be treated with NaCl in a stirred tank, then be mixed in the process water (pH is set to 4) in a tank or basin and then be filtrated.

The time to reach equilibrium and the influence of temperature should also be investigated.

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Tirén, Ström Julia. "Utvärdering av processen vid Hofors vattenverk med avseende på avskiljning av NOM – fällning och membranfilterteknik." Thesis, Institutionen för vatten och miljö, Geokemi och hydrologi, Sveriges lantbruksuniversitet, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-292673.

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De senaste årtiondena har en ökning av naturligt organiskt material (NOM) observerats i ytvatten i norra Europa och Nordamerika. NOM i vattnet innebär utmaningar för vattenverk som använder ytvatten i dricksvattenproduktionen då det kan ge upphov till lukt, smak och färg och svårigheter i driften. För att åtgärda och förebygga problemen behövs mer kunskap om NOM samt hur kvantiteten och sammansättningen förändras i olika reningsprocesser. Vid Hofors vattenverk används råvatten från sjön Hyen i dricksvattenproduktionen. Driftstörningar upplevs i perioder då råvattnets färgtal (mått på halten NOM) är högt. Därför undersöktes det hur väl den nuvarande reningsprocessen vid Hofors vattenverk fungerar med avseende på avskiljning av NOM samt vilken typ av NOM som avskiljs. Resultaten jämfördes med pilotförsök med direktfällning på ultrafiltermembran för att se om detta kan ge bättre avskiljning. Olika analysmetoder, absorbans, fluorescens och mätning av löst organiskt kol (DOC), användes för att avgöra kvantitet och karaktär på NOM i vattenproverna. Även eventuell förekomst av trend i råvattnets färgtal undersöktes. Likt i många andra ytvatten har färgtalet i Hyen har ökat de senaste åren (1997-2015). Råvattnet är svårfällt och innehåller en blandning av olika NOM-fraktioner. Huvudsakligen avskiljs humuslikt, alloktont NOM i Hofors vattenverk. Avskiljningen var störst i första reningssteget, direktfällning på sandfilter. Förändringen i efterföljande reningssteg, kolfilter samt desinfektions- och pH-höjande steg, var dock svår att bestämma till följd av mycket små förändringar och motsägande analysresultat. Tre ultrafiltermembranförsök gav liknande avskiljningsresultat som sandfilter, men i två av fallen är det troligt att igensättning av membranen spelade in. Det krävs ytterligare försök för att säkert uttala sig om huruvida ultrafiltermembran är en teknik som är lämplig att använda vid Hofors vattenverk i framtiden för avskiljning av NOM.
In recent decades, an increase in natural organic matter (NOM) has been observed in surface waters in Northern Europe and North America. NOM in the water poses challenges for water treatment plants (WTP) using surface water in the drinking water production. It can cause odor, taste and color of the water and cause difficulties in the treatment process. To prevent all these problems, more information about NOM and how the quantity and composition changes in various treatment processes is needed. At Hofors WTP, raw water from the lake Hyen is used in the production of drinking water. Disruptions in running the process have been experienced in periods when the raw water color (measure of the NOM content) has been high. In this thesis, it was investigated how well the current treatment process at Hofors WTP works with respect to the separation of NOM and what type of NOM that is separated. The results were compared with pilot tests with direct filtration using an ultrafilter membrane to see if this can provide better separation. Various analytical methods as absorbance, fluorescence and measurement of dissolved organic carbon (DOC) were used to quantify and determine the composition of NOM in the water samples. It was also examined whether there is a trend in the raw water color. As in many other surface waters the color of the water has increased in Hyen in recent years (1997-2015). The raw water contains a mixture of different NOM fractions and the character indicates difficulties in removing DOC by coagulation and flocculation. It is primarily the humic like, allochtonous NOM that is separated in the treatment process with the greatest separation in the first treatment step, direct filtration with sand filter. What happens in the subsequent treatment steps, carbon filter, disinfection and pH-raising step, was however unclear due to small changes and inconsistent analysis results. Three experiments with ultrafilter membrane yielded similar results as sand filters, but in two of the cases it is likely that clogging of the membranes contributed. Further membrane pilot tests are needed to be sure whether ultrafilter membrane is a is suitable technique to use at Hofors WTP in the future for separation of NOM.

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Johansson, Oskar. "Avskiljning av naturligt organiskt material vid konstgjord grundvattenbildning i Uppsalaåsen." Thesis, Sveriges Lantbruksuniversitet, Institutionen för Vatten och Miljö, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-269529.

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Uppsalas dricksvattenförsörjning baseras på konstgjord grundvattenbildning som innebär att vatten från Fyrisån får rinna ned till grundvattnet från infiltrationsbassänger. Detta examensarbete syftar till att undersöka vad som händer med naturligt organiskt material (NOM) i Uppsalaåsen vid konstgjord grundvattenbildning. De viktigaste processerna för minskning av NOM är biologisk avskiljning genom nedbrytning, fysikalisk-kemisk avskiljning genom sorption till metalloxider samt utspädning genom inblandning av naturligt grundvatten. Arbetet bestod av tre delar: 1) analys av vattenkemidata från grundvattenprover, 2) analys av extraktion av TOC, Al och Fe från jordprover för att undersöka utfällning av NOM med metalloxider samt 3) ett inkuberingsexperiment för att utvärdera potentialen för biologisk nedbrytning i löst organiskt material (DOC). Jordproverna hämtades från borrkärnor som tagits på fem platser längs åsen under sommaren 2014. Grundvattenprover togs i 19 brunnar minst en gång per månad från november 2014 fram till april 2015. TOC-halten i grundvattnet är som högst vid infiltrationsbassängerna, ca 15 mg/l. TOC- minskar med 30 % de första 200 metrarna i flödesriktningen men minskningen avtar under grundvattentransporten. I den omättade zonen avskiljs mindre än 10 %. Vattnet i Fyrisån har en varierande sammansättning över ett år, vilket också observerades i provtagningspunkter som ligger närmast infiltrationsanläggningarna. Analys av uran och stabila isotoper visar att dispersion i åsen utjämnar dessa variationer. Analys av UV-absorbans och fluorescens tyder på att det organiska materialet i grundvattnet byter karaktär i den mättade zonen och blir hydrofilt. Resultaten från extraktionerna i jordprover visar på god korrelation mellan Fe och TOC. Bidning till järnoxider antas därför vara den viktigaste avskiljningsmekanismen i åsen. Resultaten indikerar på anrikningar av humuskomplex i de ytligaste jordlagren under sandfiltren samt precis under grundvattenytan i närheten av bassängerna. Inkuberingsexperimentet utfördes genom att grundvatten från fem olika provpunkter sterilfiltrerades. 15 vattenprover tillsattes med inockulat innehållande mikroorganismer och övriga 15 sterila prover användes som referenser. TOC undersöktes varannan vecka på samtliga vattenprover under 1,5 månader. Efter två veckor minskade halten TOC i samtliga prover och referenser med cirka 25 % och var därefter relativt konstant. Sammanfattningsvis sker en snabb minskning av NOM i grundvattnet nära infiltrationsbassängerna. Det antas bero på adsorption till metalloxider och fasta partiklar och biologisk nedbrytning. Minskningstakten av NOM avtar med transportsträckan. Längre bort antas inblandning av naturligt grundvatten vara den viktigaste orsaken till att halten NOM minskar.
The drinking water supply in Uppsala is based on this technique which involves surface water from Fyrisån percolating to the ground water through an infiltration basin. This master thesis aims to evaluate the fate of natural organic matter (NOM) in the Uppsala esker during artificial groundwater recharge. The most important processes for the removal of NOM are biological degradation, physical-chemical sorption to metal complexes and dilution by mixing with natural ground water. The work consisted of three parts: 1) analysis of water chemistry data from groundwater samples, 2) analysis of extractions of TOC, Al and Fe from soil samples to evaluate deposition of NOM with metal oxides, and 3) an incubation test to evaluate the potential for biological degradation in dissolved organic carbon (DOC). Soil samples were collected from drill cores taken from five locations along the Uppsala esker in the summer of 2014. Ground water was sampled in 19 wells at least once every month from November 2014 to April 2015. The levels of TOC in ground water are highest at the infiltration basins, about 15 mg/l. The TOC levels drop by 30 % the first 200 meters in the flow direction, but the removal rate decreases during the ground water transport. Less than 10 % is removed in the unsaturated zone. The water in Fyrisån has a variation in composition during a year, which is also observered in sampling points close to the infiltration basins. Analysis of uranium and stable isotopes shows that dispersion in the esker evens these variations. The analysis of absorbance and fluorescence shows that the NOM changes character in the saturated zone and becomes less humificated and becomes hydrophilic. The results from the extractions in the soil samples show a good correlation between Fe and TOC. Complexes of NOM and iron oxides are thought to be the most important complex in the Uppsala esker. The extractions also indicate that enrichments of humus complexes in the uppermost soil of the infiltration basins and right below the ground water table in several locations near the basins. The incubation test was done by sterilization filtering of ground water from five different locations. Inoculate with microorganisms was added to 15 of these samples, while 15 without inoculate was used as reference samples. Analysis of TOC was done every two weeks during 1,5 months. The levels of TOC decreased by 25 % after two weeks in all samples and reference samples, and were stable afterwards. In summary, a quick decrease of NOM occurs in the groundwater close to the infiltration basins. This is mainly caused by sorption and biological degradation. The removal rate of NOM decreases with distance. Further away from the basins, the most important process for decrease of NOM is mixing with local ground water.

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Fneich, Zeinab. "La conception et la réalisation des absorbeurs en utilisant des métamatériaux." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR095.

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Dans cette thèse, nous visons à concevoir des absorbants à larges bandes passantes pouvant fonctionner efficacement même en basses fréquences. Pour atteindre un tel objectif, nous profitons des propriétés des métamatériaux pour réaliser des dispositifs capables de remplacer les technologies actuelles d’absorbants destinés à des utilisations dans les chambres anéchoïques par exemple. Après avoir étudié l'état de l'art de l'absorbant à base de métamatériaux, nous avons choisi la conception pyramidale comme base de notre recherche eu égard à ses propriétés adaptées à notre application. Nous effectuons une étude paramétrique complète pour ajuster ses paramètres géométriques et les propriétés des matériaux afin d'obtenir la meilleure réponse en terme d’absorption. En outre, nous améliorons sa bande passante d'absorption relative en créant une nouvelle conception avec altitude incurvée. Ces optimisations conduisent à une augmentation de la bande passante d'absorption relative (RAB) trouvée dans les littératures récentes de 63,3% à 73,4% avec un niveau d'absorption supérieur à 80%. Dans ce travail, nous nous nous intéressons également aux contraintes de conception en basses fréquences. Pour répondre aux exigences de dimensionnement à ces fréquences nous nous orientons vers des matériaux diélectriques avec des permittivités relatives élevée afin de réduire l’encombrement de ces structures. Après avoir appliqué ces choix de matériaux, nous avons réussi à déplacer la fréquence vers les bandes UHF. Nous avons réalisé des cellules unitaires miniaturisées en appliquant une géométrie de surface minimale en tant que nouvelle méthode de miniaturisation des absorbants. De plus, pour élargir l'absorption de l'absorbant pyramidal conventionnel, nous présentons différents nouveaux prototypes. Nous citons le prototype d'une épaisseur totale de 12,7 cm, composé de 35 couches résonantes incurvées où les simulations numériques montrent une conception améliorée avec une bande d'absorption totale allant de 0,3 GHz à 30 GHz. Concernant le deuxième prototype proposé, ce dernier est composé, dans une maille élémentaire, de l’association d’absorbants opérants sur des bandes complémentaires et à base de la structure pyramidale. Après avoir introduit de nombreux facteurs d'amélioration et avoir réalisé plusieurs étapes d'optimisation, ce dernier prototype nous a permis d’atteindre une bande passante d'absorption relative de 128,69%. Tous ces prototypes sont conçus et étudiés à l'aide du simulateur numérique High-Frequency Structure Simulator (HFSS). Tous les calculs ont été effectués sur un HPC de 24 cœurs avec une mémoire système de 192 Go de RAM. Pour la fiabilité des résultats, le mode d'analyse fréquentielle en mode discret a été paramétré avec de nombreux points de fréquences pour atteindre des résultats de simulation avec un très haut niveau de précision
In this thesis, we aim to design a broadband absorber that can effectively operate at low frequencies. To achieve such an aim, we take advantage of the properties of the metamaterial to reach a stage in which the former is capable of replacing the present bulky anechoic chamber. After studying the state of the art of metamaterial absorber, we choose the pyramidal design to be the basis of our research view of its suitable properties for our application. We perform a complete parametric study to adjust its geometrical parameters and material properties to obtain the best absorption response. Besides, we enhance its relative absorptive bandwidth by making a novel curved altitude design. The latter two modifications lead to an increase in the Relative Absorptive Bandwidth (RAB) from 63.3% in the literature to 73.4% with an absorption level greater than 80%. In addition, we discuss the requirements needed to reach a low-frequency band absorber that can be summarized by the necessary high relative permittivity material dielectric substrate and the need for bigger dimensions. After applying these requirements, we succeeded to shift the frequency to UHF bands. We achieved a miniaturized unit cells by applying minimal surface geometry as a novel way in miniaturizing absorber. Moreover, to widen the broadband absorption of the conventional pyramidal absorber, we present different new absorber prototypes. We cite the prototype with a total thickness of 12.7 cm, consisting of 35 curved resonant layers where numerical simulations show an enhanced design with an absorption band from 0.3 GHz to 30 GHz. Concerning the second proposed prototype, the latter is dedicated to combining complementary bands for different pyramidal structures dimensions in one unit cell. After introducing many enhancement factors and taking into account optimization, this prototype reached a well-combined band with a relative absorptive bandwidth of 128.69%. These prototypes are tested using the numerical simulator High-Frequency Structure Simulator (HFSS). All calculations were performed on an HPC of 24 cores with a system memory of 192 GB RAM. For the reliability of the results, discrete frequency analysis mode was adjusted with numerous data points to reach simulation results with a very high level of precision

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Ahmed, Masud Omar. "Teststation för industriella UV-celler." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-165036.

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GE Healthcare Bio-Sciences AB in Umeå produce a variety of chromatography systems. One of the main components in chromatography is the UV module, which measure the light absorption of different wavelengths in the liquid being pumped through a cell. Currently at the Umeå site two types of UV-cells are produced; lab cells and industrial cells. The current test station for the industrial UV-cells is outdated, in disrepair and no longer supported. GE has developed a test station for the lab cells that evaluates UV and flow properties, the data is stored in GE’s own production database, Prodas. The aim of this work is to design a test station for industrial UV-cells to improve the quality of the cells. The primary goal is a test station that can measure pressure, flow and absorption. The secondary goal is to discover and if possible, implement solutions that will streamline and automate the test station. A prototype of a test station for industrial UV-cells based on that for lab cells has been developed. The solution consists of an adapter that links the light path from the monitor through the UV-cell to the detector. The test station can measure pressure, flow and absorption but can only perform absorption and leakage tests. Automation and efficiency have been accomplished in the form of scripts used to conduct absorption and leakage tests. The test station requires further development before it can be used in the production line.
GE Healthcare Bio-Sciences AB i Umeå tillverkar ett flertal system, ett av systemen är vätskekromatografen. Vätskekromatografen är en kemisk separationsmetod som använder sig av en UV-monitor, UV-detektor och en UV-cell för att mäta absorptionen av en lösning och framta koncentrationen av det eftersökta ämnet. På anläggningen i Umeå tillverkas två typer av UV-celler; laborationceller och industriceller. För labbcellerna har GE utvecklat en teststation som testar och utvärderar UV och flödesegenskaper samt lagrar data i GE:s egen produktionsdatabas, Prodas. Den befintliga stationen för industriceller är äldre och omodern, en utveckling behövs för att upprätthålla högre kvalité. Syftet med detta projekt är att uppdatera teststationen för industriella UV-celler till samma nivå som stationen för laborationsceller. Det primära målet är att konstruera och designa en teststation för industriella UV-celler som kan mäta tryck, flöde och absorption. Det sekundära målet är att upptäcka och om möjligt verkställa lösningar som kommer effektivisera och automatisera mätningarna. En prototyp av en teststation för industriella UV-celler baserat på den för laborationceller har framtagits, och består av en adapterlösning som används för att sammanlänka ljusbanan från monitorn genom flödescellen till detektorn. Prototypen kan enbart utföra absorption och läckagemätningar. Automatisering och effektivisering har utförts i form av scripts som används för att genomföra absorptions och läckagemätning. Teststationen kräver fortsatt vidareutveckling innan den kan används i produktionslinjen.

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Baccarelli, Isabella. "Photodissociation et association radiative des molécules interstellaires." Paris 6, 2005. http://www.theses.fr/2005PA066181.

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Oyharçabal, Mathieu. "Synthèse, formulation, et mise en oeuvre de nanomatériaux conducteurs base poly(aniline) / nanotubes de carbone pour des applications micro-ondes." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14633.

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Ces travaux de thèse consistent à formuler des nanocomposites électriquement conducteurs pour des applications micro-ondes. L’objectif principal est la mise en œuvre de matériaux absorbant les ondes radar, plus particulièrement sur la bande X (8-12 GHz). La polyaniline et les nanotubes de carbone, dispersés dans une matrice époxyde, ont été sélectionnés pour apporter les propriétés d’absorption aux fréquences visées. Différentes morphologies de polyaniline ont été synthétisées afin d’étudier leur influence sur les propriétés d’absorption des composites. L’utilisation d’une polyaniline à morphologie feuillet, présentant une forte anisotropie et un facteur de forme élevé, permet d’augmenter la conductivité et les pertes diélectriques des composites. De plus, leur association avec des nanotubes de carbone améliore significativement les propriétés d’absorption aux fréquences micro-ondes. Des écrans absorbants radar performants qui présentent des coefficients de réflexion inférieurs à -20 dB ont pu être modélisés et mis en œuvre, confirmant le potentiel de ces matériaux pour des applications de furtivité radar
This thesis deals with the formulation of electrically conductive nanocomposites for microwave applications. The main purpose is to process radar-absorbent materials, more particularly at the X band. (8-12 GHz). Polyaniline and carbon nanotubes, dispersed in an epoxyde matrix, have been selected. Different morphologies of polyaniline have been synthesized to study its impact on the absorption properties of composites. Using flake-like polyaniline showing high anisotropy and aspect ratio increases conductivity and dielectric losses of composites. Moreover, its association with carbon nanotubes significantly improves the absorption properties at microwaves frequencies. Efficient radar absorbing screens, showing reflection losses lower than -20 dB, have been calculated and processed confirming the potential of these materials for stealth applications

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Jung, Woo-Ram. "Absorbing Darkness." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/35395.

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Beams of light can create volumes of darkness that help define an experience. That is an experience of darkness. Light and darkness in the enclosed space make me respond to myself. It is a canyon empty of everything, yet filled with the total absence of light. And the quality of this darkness is uniquely bewildering, what's more, a thick and viscous mass of black air that seems to brush against your face, limitless and seething. It is darkness visible. Darkness forces me to be isolated from the world. Without any external input, I start to talk to and hear from myself. As well as, I start to feel my body from top to toe with all senses except for the sense of sight. It goes slowly, and the interaction with myself, which is experiencing darkness, puts my mind in calm. In that level of calm, the experience of darkness wanes as we adjust to the environment, gradually becoming aware of people and walls and even faint shadows. This project is an attempt at designing spaces that allows a person to be absorbed in darkness.
Master of Architecture

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Diaz, Mendoza Alvaro. "Conception of a fibrous composite material for the retention of heavy metals." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI125.

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La contamination par les métaux lourds est un problème actuel qui affecte les écosystèmes et leurs organismes constitutifs. Ce problème a été reconnu dans le monde entier comme l'un des plus grands défis de notre époque. Depuis le milieu du siècle dernier, les innovations dans le domaine de la science des matériaux ont permis de mettre au point de nouvelles méthodes pour faire face à ce risque, avec des techniques telles que la précipitation chimique ou la flottation. Toutefois, il reste encore beaucoup à faire dans ce domaine. En outre, des recherches récentes ont exploré comment combiner des biomolécules telles que les protéines avec des matériaux tels que les polymères pour créer des solutions plus actives. Ce travail de thèse vise à créer un prototype de matériau adsorbant hybride capable de capturer spécifiquement les ions métalliques divalents Ni(II), Cd(II) et Pb(II) grâce à la présence d'une métalloprotéine synthétique dans sa structure. Pour atteindre cet objectif, le travail de thèse se concentre sur le développement d'une métalloprotéine synthétique capable de capturer spécifiquement les trois ions métalliques cibles, de la conception in silico à sa synthèse in vivo. D'autre part, le support de matériau est traité avec la technique d'électrofilage qui consiste en un matériau membranaire fibreux, étant optimisé pour accueillir la métalloprotéine synthétique dans sa structure. En outre, une méthode permettant d'intégrer la métalloprotéine dans le support polymère est recherchée. Ceci est réalisé au moyen d'une voie de greffage à travers des nanoparticules de silice modifiées en surface. À la fin, l'intégration des deux composants crée le prototype attendu de matériau biosorbant synthétique. Ce matériau a été caractérisé afin d'évaluer sa capacité à adsorber les trois ions métalliques d'intérêt, ce qui permet de dégager certaines tendances des perspectives futures de développement pour créer des matériaux plus efficaces pour l'industrie
Heavy metal contamination is a current problem which affects the ecosystems and their constituent organisms. This problem has been worldwide recognized as one of the biggest challenges of our time. Since the middle of the last century, innovations in the material science field have developed new methods to confront this risk, with techniques such as chemical precipitation or flotation. However, there is still significant room for improvement in this line. Furthermore, recent research has explored how to combine biomolecules such as proteins with materials like polymers to create more active solutions. This thesis work seeks to create a prototype hybrid biosorbent material capable to capture specifically the divalent metal ions Ni(II), Cd(II) and Pb(II) thanks to the presence of a synthetic metalloprotein in its structure. To address this objective, the thesis work focuses on the development of a synthetic metalloprotein capable to specifically capture the three target metal ions, from the in silico conception to its in vivo synthesis. On the other hand, the biosorbent material support is processed with the electrospinning technique that consists of a fibrous membrane material, being optimized to host the synthetic metalloprotein in its structure. Additionally, a method to integrate the metalloprotein into the polymeric support is researched. This is achieved by means of a grafting route through surface modified silica nanoparticles. At the end, the integration of both components creates the expected prototype synthetic biosorbent material. This material has been characterized to evaluate its capacity to adsorb the three metal ions of interest, providing some trends of the future perspectives for further development to create more efficient materials for the industry

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11

Müller-Bierl, Bernd Michael. "Rayonnement et couplage entre les interconnexions dans les circuits hyperfréquences : étude au moyen de la méthode tlm." Grenoble INPG, 1997. http://www.theses.fr/1997INPG0026.

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La these est constitue de 3 parties principales. Apres une introduction a l'analyse des lignes micro-ruban sous approximation de propagation des signaux en mode tem, la premiere partie traite d'une methode d'anaulyse dynamique valable pour des distributions de champs qui peuvent meme etre eloignees du mode tem, la methode tlm (transmission line matrix method), introduite 1971 par johns et al. La methode tlm est presentee comme un processus de repartition base sur la decomposition des equations de maxwell sous forme matricielle. Dans une deuxieme partie nous traitons de la possibilite d'utiliser la methode tlm dans les problemes dits de l'espace ouvert, c'est a dire des espaces de calcul limites par des parois absorbant toute l'energie quittant le domaine de calcul. Cela est necessaire afin de reduire l'espace memoire necessaire pour calculer par example des effets de rayonnement et de diffraction. Dans la troisieme partie nous appliquons la methode tlm pour calculer les parametres des differents discontinuites micro-ruban, en particulier les effets de couplage et de rayonnement. Au moyen d'une transformation des champs proches en champs lointain nous determinons egalement les diagrammes de rayonnement correspondants. L'ensemble du travail se situe dans le cadre des problemes de compatibilite electromagnetique.

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12

Benzouaa, Rachid. "Purification de l'hexafluorure d'uranium." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22433.

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L’hexafluorure d’uranium (UF6), est le seul composé utilisé à l’état gazeux dans les procédés d’enrichissement pour la production du combustible nucléaire. Pour le bon déroulement de l’étape d’enrichissement, la qualité de UF6 est primordiale. Cette étude s’est intéressée principalement aux impuretés volatiles sous forme de fluorures et oxyfluorures et leur réactivité avec des matériaux en présence ou non de l’UF6. La nature des produits adsorbés et de réactions a été identifiée. Les mécanismes physico-chimiques mis en jeux lors de la sorption ont été investigués. Les performances (capacité de sorption, sélectivité et régénération) de ces matériaux absorbants et adsorbants ont été évaluées en vue de leur utilisation comme filtre UF6 dans les usines de conversion
Uranium hexafluoride (UF6), is the only compound used in the gaseous state in the process of enrichment to produce nuclear fuel. For the success of the enrichment step, the UF6 quality is paramount. This study is mainly concerned with volatile impurities in form of fluorides and oxyfluorides and their reactivity with the materials in presence or not of UF6. The nature of the adsorbed compounds and reactions products was identified. The physico-chemical mechanisms of sorption were investigated. The performances (sorption capacity, selectivity and regeneration) of the absorbent and adsorbent materials have been evaluated to be used as UF6 filters in conversion plants

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13

Bay, Kerem. "Biodiesel : hoch siedendes Absorbens für die Abluftreinigung /." Göttingen : Cuvillier, 2007. http://d-nb.info/987236148/04.

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Sellier, Alexandre. "Absorbants à métamatériaux : étude théorique et expérimentale." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01060182.

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Les matériaux absorbants électromagnétiques, ou " Radar Absorbing Materials " (RAM), ont été créés à la fois aux USA et en Allemagne lors de la seconde guerre mondiale. Les applications des absorbants appartiennent principalement aux domaines de la Compatibilité ElectroMagnétique (CEM) et de la discrétion radar. Ces absorbants sont lourds et encombrants. Au travers de cette thèse, nous cherchons à développer une solution pour pallier à ces inconvénients grâce aux absorbants à métamatériaux. Les métamatériaux sont des composites artificiels présentant des propriétés électromagnétiques que l'on ne retrouve pas dans la nature. En utilisant ce type de matériaux, nous pouvons obtenir des absorbants ultras fins, et par l'optimisation et la conception couvrir des bandes larges en fréquence. Nous proposons donc plusieurs formes basiques d'absorbant à métamatériaux. De ces formes, nous présentons un modèle théorique et développons les techniques pour définir leur fréquence de fonctionnement et les paramètres nécessaires pour obtenir une absorption totale. Puis nous étudions plus en détail nos différents prototypes à travers des simulations et des mesures. Nous étudions aussi le couplage des absorbants à métamatériaux avec des absorbants traditionnels pour créer un type d'absorbant inédit.

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15

GOROG, SYLVIE. "Transmissibilite acoustique en milieu absorbant. Approche energetique." Palaiseau, Ecole polytechnique, 1995. http://www.theses.fr/1995EPXX0021.

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Dans le domaine de recherche pour l'amelioration de l'isolation phonique et vibratoire, ce travail a pour objet l'analyse de phenomenes d'absorption efficaces pour reduire, voire annuler, la propagation des ondes dans un milieu solide. L'etude examine la transmissibilite acoustique des materiaux utilises comme milieux absorbants dans le cadre rigoureux de la thermodynamique des processus irreversibles. Cette approche energetique generale permet d'evaluer la dissipation generee au cours de la propagation pour differents comportements dynamiques. La modelisation de cette propagation dans le materiau etudie s'effectue a une echelle mesoscopique avec une representation continue viscoelastique ou elastoplastique en decrivant le mouvement propage par des ondes harmoniques planes ou sous forme d'une surface de discontinuite mobile d'acceleration. L'analyse explicite les parametres dissipatifs et conduit a la definition d'une dissipation dynamique intrinseque caracterisant l'absorption acoustique. Cette etude identifie les mecanismes dissipatifs preponderants a des mouvements massiques internes et donne une interpretation physique des phenomenes selon la microstructure traversee

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16

Fan, Rong. "Random Walk With Absorbing Barriers Modeled by Telegraph Equation With Absorbing Boundaries." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/dissertations/1588.

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Organisms have movements that are usually modeled by particles’ random walks. Under some mathematical technical assumptions the movements are described by diffusion equations. However, empirical data often show that the movements are not simple random walks. Instead, they are correlated random walks and are described by telegraph equations. This thesis considers telegraph equations with and without bias corresponding to correlated random walks with and without bias. Analytical solutions to the equations with absorbing boundary conditions and their mean passage times are obtained. Numerical simulations of the corresponding correlated random walks are also performed. The simulation results show that the solutions are approximated very well by the corresponding correlated random walks and the mean first passage times are highly consistent with those from simulations on the corresponding random walks. This suggests that telegraph equations can be a good model for organisms with the movement pattern of correlated random walks. Furthermore, utilizing the consistency of mean first passage times, we can estimate the parameters of telegraph equations through the mean first passage time, which can be estimated through experimental observation. This provides biologists an easy way to obtain parameter values. Finally, this thesis analyzes the velocity distribution and correlations of movement steps of amoebas, leaving fitting the movement data to telegraph equations as future work.

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Bastière, Annie. "Elaboration d'une methode d'aide a la decision pour la realisation de materiaux absorbants radar." Paris 6, 1988. http://www.theses.fr/1988PA066044.

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On presente l'elaboration d'une methode d'optimisation multi critere au vue de la realisation de materiaux radar destines a revetir des aeronefs et constitues de plusieurs couches. Elle necessite, d'une part, l'utilisation d'une methode d'optimisation sous contraintes non lineaires, d'autre part la mise en oeuvre theorique et informatique d'un processus d'aide a la decision mettant en jeu plusieurs criteres et lois d'agregation differentes. Ces dernieres sont obtenues grace a deux approches mathematiques : -l'une basee sur la theorie de l'evidence de dempster et shafer; -l'autre inspiree de la theorie des sous-ensemble flous

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18

Bello, K. A. "Near-infrared absorbing dyes." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375504.

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Yuzcelik, Cihangir Kemal. "Radar absorbing material design." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03sep%5FYuzcelik.pdf.

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20

Tsai, Hsin-Yu Sidney. "Absorbance modulation optical lithography." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42253.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 91-94).
In this thesis, the concept of absorbance-modulation optical lithography (AMOL) is described, and the feasibility experimentally verified. AMOL is an implementation of nodal lithography, which is not bounded by the diffraction limit of incident lights. Experimental results showed promising capability of AMOL and matched well with simulation. Several key elements of the AMOL system are discussed: the material systems of AMOL, limitations on the material and optical systems presented, and the design and fabrication of spiral phase elements that generate ring-shaped beams required by AMOL.
by Hsin-Yu Sidney Tsai.
S.M.

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Zilletti, Michele. "Self-tuning vibration absorbers." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/333270/.

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This thesis presents a theoretical and experimental study of self-tuning vibration control. Feedback design is often based on the assumption of time-invariance, which means that the controller has constant coefficients. Self-tuning control takes into account process changes in the response of the system under control by incorporating an adjusting mechanism which monitors the system, compares its status with the required one and adjusts the coefficients of the controller. In this thesis a self-tuning process is analysed for active and semi-active control of broadband vibration based on the maximisation of the power absorbed by the controller. The absorbed power can be locally estimated without using extra sensors to monitor the global response of the system under control. This is particularly advantageous in applications where many actuators are required, in which case each actuator and the collocated sensor can be treated as an independent self-tuneable unit. A theoretical analysis of vibration control using this approach is presented for lumped parameter systems and also for distributed systems, such as beam and panels. Different tuning strategies are compared in terms of the reduction of the global response of the system under control. An algorithm is then discussed that tunes the feedback gains of independent control units to maximise their individual absorbed powers. Experimental studies are then presented of a selftuning control system with two decentralised control units using velocity error signals and electromagnetic reactive actuators installed on an aluminium panel. In the second part of the thesis the analysis is extended to the use of inertial actuators. In this case the implementation of the self-tuning control based on the maximisation of the power absorbed is investigated using simulations of velocity feedback control and shunted inertial actuators.

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Chobeau, Pierre. "Modeling of sound propagation in forests using the transmission line matrix method : study of multiple scattering and ground effects related to forests." Thesis, Le Mans, 2014. http://www.theses.fr/2014LEMA1016/document.

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Les trois principaux phénomènes acoustiques propres au milieu forestier nécessitant d'être pris en compte sont (1) l'absorption due à la présence d'un sol multi-couche, (2) la diffusion multiple due à la présence d'obstacles tels que les troncs, (3) les effets micro-météorologiques rattachés aux variations des gradients de vitesse de vent et de température. Parmi les méthodes numériques de référence, la méthode des lignes de transmission (TLM), semble particulièrement adaptée pour la modélisation de la propagation acoustique en présence de forêt, à condition de procéder à de nouveaux développements. La première nécessité pour l'adaptation de la méthode TLM aux simulations acoustiques sur de grandes distances est la définition de couches absorbantes, permettant de tronquer efficacement le domaine d'étude, sans introduire de réflexions parasites. La formulation ainsi développée dans le cadre de la thèse est rigoureusement équivalente à l'équation de propagation des ondes amorties, et se traduit dans la méthode TLM par l'introduction et l'optimisation d'un terme de dissipation. L'étape suivante a consisté à vérifier la capacité de la méthode TLM à modéliser les phénomènes de diffusion par des cylindres. L’une des originalités introduites dans cette thèse réside dans le placement des éléments diffuseurs, à partir de lois de distribution aléatoire et de Gibbs, permettant ainsi de définir des répartitions proches de celles rencontrées en forêt. À titre d'application de la méthode développée dans le cadre de la thèse, une étude paramétrique a été réalisée afin de définir les conditions pour lesquelles une forêt peut également être considérée comme un dispositif de protection
The prediction of sound propagation in presence of forest remains a major challenge for the outdoor sound propagation community. Reference numerical models such as the Transmission Line Matrix (TLM) method can be developed in order to accurately predict each acoustical phenomenon that takes place inside forest. The first need for the TLM method is an efficient theory-based absorbing layer formulation that enables the truncation of the numerical domain. The two proposed absorbing layer formulations are based on the approximation of the perfectly matched layer theory. The most efficient proposed formulation is shown to be equivalent to wave propagation in a lossy media, which, in the TLM method formulation, is introduced using an additional dissipation term. Then, the ability of the TLM method for the simulation of scattering is studied comparing the numerical results to both analytical solutions and measurements on scale models. Lastly, the attenuation of acoustic levels by a simplified forest is numerically studied using several arrangements of cylinders placed normal to either reflecting or absorbing ground. It is observed that randomly spaced arrangements are more inclined to attenuate acoustic waves than periodic arrangements. Moreover, the sensitivity to the density, the length of the array and the ground absorption is tested. The main trend shows that the density and the distribution are two important parameters for the attenuation. In future work, it can be interesting to look at the sensitivity of each parameter. This study could then be used to relate the morphology (i.e. distribution, density, length) of a forest to the acoustical properties of the forest

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Lei, Ya-Jie. "Élaboration de matériaux hautement stable thermiquement par modification et fonctionnalisation de la résine bisphthalonitrile." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0265.

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Les polymères de phtalonitrile sont obtenus par des réactions d'addition des groupements cyano à haute température et pour un temps long à partir de dérivés de phtalonitrile. Ils trouvent de nombreuses applications dans les domaines de pointe comme l'aérospatiale et la marine. Cependant, leurs performances sont limitées par les inconvénients suivants : (1) fragilité liée intrinsèquement à leur réseau structural, (2) température de fusion élevée, fenêtre de conditions de mise en forme étroite, température de cuisson élevée, cinétique de cuisson faible, (3) Selon la litérature, le traitement du bisphthalonitrile pour obtenir la résine correspondante s'effectue souvent à des températures inférieures à 500°C. Il y a peu d'études sur les matériaux formés à des températures supérieures à celle-ci, (4) Il n'y a pas beaucoup d'études sur la fonctionnalisation de la résine bisphthalonitrile et son domaine d'application doit être élargis. Cette thèse porte sur le dévelopement de méthodes permettant la modification et la fonctionnalisation de la résine bisphthalonitrile conduisant à une amelioration des propriétés mécaniques de celle-ci. De plus, des nanotubes de carbone ayant une morphologie différente et des matériaux capables d'absorber les hyperfréquences ont été obtenus par pyrolyse de la résine bisphthalonitrile en présence de différents catalyseurs de fer et sur une plage de température allant de 600 a 900°C
Bisphthalonitrile polymers are obtained by addition curing reaction of cyano groups upon heating phthalonitrile derivatives at elevated temperature and for an extended period of time. They have found many applications in advanced technologies such as aerospace and marine. However, their performances are limited by the following disadvantages: (1) high brittleness of the inherent network structure; (2) high melting temperature, narrow processing window, high curing temperature, low curing rate and long curing time; (3) according to the literature, the processing temperature of bisphthalonitrile resin-based composites is controlled at 500°C or less, whereas there are few studies on materials formed above 500°C; (4) studies on the functionalization of bisphthalonitrile resins are not abundant and its application range needs to be expanded. Based on the above statement, this thesis is focused on the modification and functionalization of bisphthalonitrile resins. The latter were modified by a variety of methods, resulting in improved mechanical properties. Moreover, carbon nanotubes with different morphologies and microwave absorbing materials were obtained by pyrolysing bisphthalonitrile resins with different metal iron catalysts in the range of 600 to 900°C

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Jeanmaire, Alain. "Transfert thermique dans les milieux semi-transparents : application aux milieux diffusants et peu absorbants." Vandoeuvre-les-Nancy, INPL, 1993. http://docnum.univ-lorraine.fr/public/INPL_T_1993_JEANMAIRE_A.pdf.

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Les matériaux utilisés pour l'isolation thermique des bâtiments sont en général poreux. Les mousses expansées et les différentes laines de verre en constituent la grande majorité. La conductivité phonique et le transfert radiatif sont les deux modes du transfert. Il s'agit de milieux semi-transparents présentant les phénomènes d'absorption, d'émission et de diffusion de la luminance. Après avoir passé en revue les différentes méthodes expérimentales permettant de caractériser ces matériaux, le mémoire développe une technique d'identification nouvelle adaptée aux milieux semi-transparents diffusants et peu absorbants

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Pertreux, Etienne. "Spectroscopie optique de nano-objets individuels : effets d’environnement, de forme et d’orientation." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10215/document.

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La réponse optique de nano-objets métalliques et semi-conducteurs a été étudiée par spectroscopie par modulation spatiale (SMS), une technique permettant de détecter des nano-objets individuels et d'en mesurer quantitativement la section efficace d'extinction. Dans le cadre de ce travail, nous avons systématiquement corrélé ces mesures optiques à une caractérisation bi- voire tridimensionnelle de leur morphologie, permettant une comparaison précise des mesures avec des simulations numériques. Le premier volet de cette thèse décrit une étude détaillée de l'effet de la déposition de nano-objets métalliques de forme allongée (nanobâtonnets et nanobipyramides) sur un substrat absorbant. Nos expériences montrent qu'elle conduit à un élargissement de la résonance plasmon de surface, dont l'ampleur dépend fortement de la forme et de l'encapsulation des nano objets. En combinant la SMS avec une approche pompe-sonde, nous avons pu mesurer la réponse ultrarapide de nano-bipyramides d'or individuelles, qui contient une contribution de plusieurs de leurs modes de vibration, permettant d'accéder à leur fréquence et taux d'amortissement, en s’attachant en particulier à l'effet d'une encapsulation diélectrique des bipyramides. Au cours de cette thèse, nous avons étendu l'application de la SMS à des nano-objets très allongés avec une dimension micrométrique (nanofils et nanopointes), dans le but notamment d'étudier leur réponse optique, leur interaction avec une nanoparticule d’or et d’obtenir des informations sur leur profil d'absorption, une information essentielle pour l'interprétation d'expériences d'émission électronique (effet de champ) ou ionique (tomographie de sonde atomique)
The optical response of metallic and semi-conductor nano-objects has been studied by spatial modulation spectroscopy (SMS), a technique allowing to detect single nano-objects and to quantitatively measure their extinction cross-sections. During my thesis, we have systematically correlated these optical measurements with the 2D or 3D characterization of their morphology, allowing a precise comparison of the measurements with numerical simulations. The first part of my PhD thesis describes a detailed study of the effect of the deposition of elongated nano-objects on an absorbing substrate. Our experiments show a spectral broadening of the surface plasmon resonance, whose extent highly depends on the shape and the encapsulation of the nano-objects. By combining SMS with a pump-probe approach, we were able to measure the ultrafast response of single gold nano-bipyramids. This response contains a contribution from several vibration modes, allowing extraction of their frequencies and damping times. In particular, we have addressed the effect of a dielectric encapsulation of bipyramids on their vibrational quality factors. During this thesis, we extended the use of SMS to very elongated nano-objects with a micrometric dimension (nanowires and nanotips), with the goal of studying their optical response, their interaction with a gold nanosphere and obtaining information on their absorption profile, as required to interpret electronic (field effect) or ionic (atom-probe tomography) emission experiments

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Crowley, Sarah. "Absorbing energy using coupled resonances." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.629003.

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This thesis is concerned with the small amplitude response of coupled resonant systems which are subject to forcing. In particular, we consider systems consisting of a primary body with a fixed secondary, internal or external, component that each exhibit resonance. Motivated by the potential to exploit the coupled resonances we consider the effect of tuning the secondary component on the displacement or energy absorption characteristics of the system. Problems are studied in which the entire system is submerged in fluid of finite depth or in which the secondary system consists of a fluid-filled tank, fitted with some mechanism to provide damping, or both, all under the assumptions of linear water wave theory. In Chapter 1 a condition is derived which applies to submerged vertical slatted barriers and its adequacy tested in five model problems. This condition is then implemented in Chapter 2, in which sloshing in a horizontally-forced fluid-filled rectangular tank fitted with multiple screens is analysed. We proceed by fixing the tank to an externally-forced sprung mass and tuning the tank to minimise response amplitudes across all frequencies. The remainder of this thesis is concerned with the extraction of energy from ocean waves by coupled resonant absorbers. Chapter 3 gives a brief introduction and describes the existing power absorption theory for devices constrained to a single mode of motion. A submerged horizontal cylindrical wave energy converter (WEC) is used to illustrate the application of this theory. This analysis is extended to devices of the same geometry containing an internal power take-off system; in Chapter 4 the device contains a system of pendulums and in Chapters 5 and 6 a water tank. Chapter 7 continues this theme, now for a vertical cylindrical WEC containing an internal water tank. In each example, the focus is on determining the best device configuration to obtain a broad-banded response.

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Whitehead, Timothy David. "The design of resonant absorbers." Thesis, University of Canterbury. Mechanical Engineering, 2005. http://hdl.handle.net/10092/6627.

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The purpose of this project was to investigate the acoustic performance of a range of resonant absorbers as typically used in automotive applications. A literature review considering sources of exhaust noise, muffler types and components, sound measurement, and prediction techniques was undertaken. Test facilities were constructed that allowed testing of muffler systems with either an engine or a speaker as the source of excitation. This enabled measurements made with a speaker to be compared to those made with an engine, the latter including flow, temperature and pressure effects. A number of different muffler systems were tested and their acoustic performance predicted using a scattering matrix technique. Comparing measured and predicted results allowed assessment of the accuracy of the predictions, the performance of various muffler components and the reliability of measurements. The model adequately predicted muffler performance for all muffler systems tested apart from those containing Helmholtz resonators. This was attributed to pressure and flow effects not included in the model. Using the modelling procedure presented, muffler systems can be quickly designed and optimised.

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McMahan, Michael T. "Metamaterial absorbers for microwave detection." Thesis, Monterey, California: Naval Postgraduate School, 2015. http://hdl.handle.net/10945/45904.

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Approved for public release; distribution is unlimited
The development of high-power microwave weapons and dependence on electronics in modern weapon systems presents a high-power microwave weapons threat in future military conflicts. This study experimentally determines the absorption characteristics of simple metamaterial devices to potentially be used as protection and identification mechanisms, constructed through standard printed circuit board manufacturing processes, in the microwave region. Experimental results and analysis techniques are presented confirming absorption peaks in the anticipated microwave frequency range. The experimental results are compared to a finite-element model of these metamaterials confirming the ability to accurately model and predict absorption characteristics of similar metamaterial structures. Utilization of the absorption characteristics of these types of metamaterial structures to develop a microwave detector and/or equipment shielding is discussed. Several applications for such type of a detector are presented.

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Singleton, Toby Mark. "Characterisation of impact absorbing asphalt." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342071.

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Chuasiripattana, Katawut. "Absorbate induced semiconductor surface reconstructions." Thesis, University of Exeter, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426158.

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Frank, Stephan. "OVI Absorbers in SDSS Spectra." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1222116379.

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Corns, Stephen Nigel. "Novel near-infrared absorbing dyes." Thesis, University of Leeds, 1990. http://etheses.whiterose.ac.uk/981/.

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New near-infrared absorbing donor-acceptor chromophores have been investigated by varying the electron donating and accepting strength of the two halves of the molecule within wide limits. The dihydroperimidine, perimidine, Michler's ethylene and 1-decyl-2(1H)- methyl-benz[c, d]indolium iodide residues were examined as donor residues, and these were coupled to 4-nitrobenzenediazonium chloride to give monoazo dyes. The λmax values of these gave a qualitative indication of relative electron donor strengths, and the 1-ethyl-2-methylperimidine azo dyes proved to be the most bathochromic, being blue in colour. The dyes were amongst the most bathochromic monoazo dyes yet prepared containing the 4-nitrophenylazo residue. The N-alkyl-3-cyano-6-hydroxy-4-methyl-2-pyridone system was investigated as a potentially powerful electron acceptor system, and the 5-formyl and 5-nitroso derivatives were condensed with Michler's ethylene and 1-decyl-2(1H)-methyl-benz[c, d]indolium iodide to give new donor-acceptor dyes. The aza dyes prepared from the nitroso compounds proved to be the most bathochromic in accord with PMO theory and many were near-infrared absorbing. A series of near-infrared absorbing squarylium dyes with narrow, intense absorption bands at about 800nm were obtained by reacting squaric acid with 2,2-disubstituted dihydroperimidines. The first dyes of this type possessed poor organic solvent solubilities but, through modification of the 2,2-substituents of the dihydroperimidines it was possible to obtain squarylium dyes with good organic solvent solubility, this being a much sought after property of infrared dyes. Other squarylium dyes were obtained by the reaction of squaric acid with 1-ethyl-2-methylperimidine, Michler's ethylene and 1-decyl-2(1H)-methyl-benz[c, djindolium iodide. The latter two dyes absorbed in the infrared region at 809 and 900nm respectively in toluene. A modified procedure for the synthesis of croconic acid was developed, which enables the acid to be obtained in the anhydrous form readily. Reaction of croconic acid with 3-hydroxy-N, N-dialkylanilines afforded highly bathochromic dyes (λ max ca. 830nm). Reaction with 1- decyl-2(1H)-methyl benz[c, d]indolium iodide gave a croconium dye that absorbed beyond 1000nm. The reaction of 8-hydroxyjulolidine with croconic acid was particularly interesting as it occurred readily at room temperature. Thus it was possible to undertake a kinetic study of mechanistic aspects of the condensation reaction between croconic acid and arylamines. The results indicated that the optimum reaction conditions involved using a low proportion of an alcohol in a nonpolar aprotic solvent in the presence of a weak acid catalyst. Dyes were also obtained from the reaction of various electrophilic chlorine-substituted compounds with electron-donor aromatic residues, thus giving new donor-acceptor dyes, several of which were nearinfrared absorbing with low molecular masses and good organic solvent solubilities. The dyes were, however, strongly coloured due to their broad absorption bands which extended well into the visible region. The thermal and photochemical stabilities of representative examples of all the infrared dye classes prepared in this work have been examined, using standard procedures.

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Yang, Shuqi. "Synthesis and stabilisation of novel UV absorbers." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/24559.

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Plants can respond differently to different wavelengths in sunlight's spectral range, and crop covers containing additives have a great effect on the growth of crops. This research focuses on synthesising new hydroxybenzophenones bearing long alkyl chains to confer polymer solubility, and to measure their UV absorption and photochemical stability. Compounds substituted with fluorine atoms or different amino groups in particular were under investigated, as these groups may impart stability towards oxidative degradation, or alter the absorption maximum. Related naphthalene analogues were substituted with different amine groups for comparing UV absorption and photostability. Modification of Uvinul A Plus was carried out to improve UV absorption maximum wavelength and light fastness.

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Biboud, Julien. "Développement d'un absorbant acoustique écologique à base de polymère." Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6152.

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L'objectif principale [i.e. principal] de ce travail était de proposer un matériau acoustique absorbant issu de recyclage et/ou recyclé pouvant être une alternative à la laine minérale encore très largement utilisée. Ce projet découlait initialement d'un besoin du Ministère des Transports du Québec (MTQ) qui souhaitait concevoir de nouveaux écrans acoustiques routiers selon les principes du développement durable définis par le gouvernement du Québec [1]. En d'autres termes, ce matériau devait être fait de matériaux recyclés et/ou recyclables, sa fabrication et sa récupération peu énergivores et ses distances de transports faibles; sous-entendant une fabrication locale [2]. Ainsi, dans cette étude nous avons clairement mis en évidence que les fibres de nylon recyclées, largement disponible [i.e. disponibles] au Québec, sont tout aussi efficaces voire supérieure [i.e. supérieures] à la traditionnelle laine minérale dont la fabrication est très énergivore et est difficilement recyclable [3-4]. Enfin un modèle simple prédictif basé sur la masse volumique de panneaux de fibres compactées a été proposé, validé et discuté.

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Méjean, Chloé. "Élaboration de nouveaux matériaux absorbants : application en chambres anéchoïques." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S153.

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Ces travaux de thèse ont porté sur l’étude de nouveaux matériaux pour l’absorption électromagnétique en chambre anéchoïque. Ce sujet a été imaginé à partir de l’étude d’une nouvelle matrice jusqu’alors jamais utilisée pour les absorbants électromagnétiques : la mousse époxy. Cette dernière présente en effet de nombreux avantages par rapport aux matrices habituellement utilisées dans le commerce : possibilité de réaliser des formes complexes, piégeage de la charge au cœur du matériau… Nous avons associé cette matrice avec différentes charges carbonées (noir de carbone, graphite et des fibres longues de carbone). L’association de la mousse époxy avec des fibres de carbone millimétriques a montré d’excellentes performances d’absorption pour un taux de charge très faibles : 0,5 %wt (S11 ≈ -40 dB entre 4 et 18 GHz en incidences normale et oblique). En variant la longueur des fibres de carbone, nous avons mis en évidence qu’il était possible d’améliorer les performances d’absorption en basses fréquences en utilisant des fibres plus longues. Enfin, nous avons dirigé nos recherches sur la réalisation d’un matériau absorbant ‘Vert’ à partir d’une matrice de liège. Ces nouveaux matériaux, réalisés à partir de matières biosourcées, ont montré de meilleures performances d’absorption qu’un absorbant du commerce de mêmes dimensions en incidence normale (S11 = -53 dB et S11 = - 27 dB respectivement à 4,2 GHz) et en incidence oblique (S11 = -50 dB et S11 = -30 dB respectivement à 4,2 GHz) et constituent donc des candidats potentiels pour le remplacement des matériaux absorbants du commerce actuels
This thesis work focused on the study of new materials for electromagnetic absorption in anechoic chambers. This subject arose from the study of a new matrix which was never used for electromagnetic absorbers until then: the epoxy foam. This foam has many advantages compared to the matrices usually used in the trade like the possibility of cutting complex shapes out of them or trapping the charge in the core of the absorber...This matrix was associated to different carbonaceous load (carbon black, graphite and carbon fibers). The combination of epoxy foam with millimeter carbon fibers has shown better absorption performance at very low loading rates: 0.5 %wt (S11 ≈ -40 dB between 4 and 18 GHz under normal and oblique incidences). The use of different fiber lengths showed that it is possible to improve absorption performance at low frequencies using long carbon fibers. Finally, we directed our work on the creation of an absorbent material from a cork matrix. These new materials, made from bio-based materials, have shown better absorption performance than a commercial absorber, with the same dimensions in normal incidence (S11 = -54 dB and S11 = - 27 dB respectively at 4.26 GHz) and oblique incidence (S11 = -51 dB and S11 = -30 dB respectively at 4.26 GHz) and are therefore potential candidates for the replacement of existing commercial absorbent materials

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Grizzi, Ilaria. "Carctérisation de fibres d'alginate de calcium pour pansements absorbants." Montpellier 1, 1995. http://www.theses.fr/1995MON13502.

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Thieury, Margaux. "Développement de métamatériaux super-absorbants pour l’acoustique sous-marine." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLS004.

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L’évolution constante des performances des sonars nécessite de nouveaux designs de revêtements absorbants pour l’acoustique sous-marine. De tels revêtements sont utilisés pour améliorer la furtivité des sous-marins, mais ils permettent également d’accroître l’efficacité des systèmes de détection embarqués. Les méta-écrans bulleux (lointains descendants des revêtements de type Alberich) représentent une solution possible pour répondre à cet enjeu. Ils sont constitués d’une distribution périodique bi-dimensionnelle de cavités d’air de taille sub-longueur d’onde emprisonnées dans une matrice viscoélastique. Lorsqu’elles sont excitées par une onde acoustique, les cavités se comportent comme des bulles d’air, et présentent une résonance basse fréquence, dite de "Minnaert". Sous certaines conditions, le méta-écran bulleux permet d’atteindre une absorption totale lorsqu’il est placé devant un réflecteur parfait. Ce travail de thèse a permis la mise au point d’un modèle phénoménologique, validé par des simulations numériques et des mesures en cuve, pour prédire les coefficients de réflexion et de transmission d’un méta-écran bulleux en fonction de ses caractéristiques géométriques et rhéologiques. Ce modèle prend en compte l’influence de la température et de la pression statique sur les performances du méta-écran, ainsi que celle de la forme des cavités
The constant evolution of sonar performance requires new designs of absorbent coatings for underwater acoustics. Such coatings are used to improve stealth of submarines but can also improve the efficiency of on-board detection systems. Bubble meta-screens (reminiscent of the so-called Alberich coatings) are a possible solution to tackle this issue. A bubble meta-screen consists of a periodic distribution of sub-wavelength air cavities trapped in a visco-elastic matrix. The cavities acoustically behave as bubbles and exhibit a low frequency resonance, known as the Minnaert resonance. Under certain conditions, the meta-screen can achieve a total absorption when placed in front of a perfect reflector. This doctoral work allowed us to build a phenomenological model, validated by numerical simulations and experiments, which can predict the reflection and transmission coefficients of the meta screen as a function of its geometric and rheological characteristics. Our model takes into account the influence of the temperature and static pressure on the performance of a meta-screen, as well as the role played by the shape of the cavities

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BOS, SANDRA. "Etudes danes : methodologie et application a des echantillons absorbants." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10152.

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Nous avons developpe les procedures experimentales et de traitement de donnees requises dans le cadre d'etudes danes (diffraction anomalous near edge spectroscopy) appliquees a l'etude d'echantillons tres absorbants sous forme de poudres et de monocristaux. Nous avons pour cela considere deux procedures experimentales differentes, en optiques (i) monochromatique et (ii) dispersive en energie, le but ultime etant d'obtenir des donnees de bonne qualite, reproductibles, en un temps de mesure le plus court possible. Nous avons pu montrer que la diffraction dispersive en energie permet d'effectuer des mesures rapides dans des conditions experimentales identiques pour toutes les energies mais la qualite des donnees obtenues est moindre. Aussi afin d'effectuer un traitement quantitatif des donnees, les intensites diffractees doivent etre preferablement mesurees en faisceau monochromatique. Bien que les temps de collecte soient plus longs, les informations obtenues y sont de meilleure qualite, en particulier au niveau de la reproductibilite, du rapport signal / bruit et de la resolution en energie. Les developpements instrumentaux que nous avons effectues ont ete illustres dans le cas limite des echantillons absorbants, sous forme de poudres et de monocristaux. Des oxydes de metaux de transitions, dans lesquels les metaux presentent differents etats de valence en des sites cristallographiques distincts, ont ete choisis. Des spectres de bonne qualite ont ete obtenus lors des diverses mesures sur ces composes et des analyses quantitatives ont pu etre menees dans les differents cas. L'importance d'une correction extremement precise de l'absorption avant tout traitement de donnees est soulignee, le signal anomal etant noye dans celui de l'absorption. Une discussion des possibilites et des limites des analyses danes est egalement effectuee.

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Bioud, Fatma-Zohra. "Fabrication et caractérisation de fantômes optiques absorbants et diffusants." Mémoire, Université de Sherbrooke, 2010. http://savoirs.usherbrooke.ca/handle/11143/1562.

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Depuis son entrée dans le monde de l'imagerie médicale, l'imagerie optique a connu un grand développement. Beaucoup d'intérêt lui est porté car cette modalité est non invasive et permettrait éventuellement de faire de l'imagerie moléculaire. Toutefois, elle doit relever un défi de taille, celui de la reconstruction de l'image. Cette étape est très ardue, car elle fait intervenir des modèles de propagation de la lumière dans les tissus biologiques complexes, qui se traduisent par des équations intégro-différentielles dont il est difficile de dériver des solutions analytiques. Ainsi, une étape essentielle au développement d'appareil d'imagerie, la calibration, devient cruciale. Les fantômes optiques, l'objet de ce travail de recherche, sont les standards de calibration qui servent à la réalisation de cette étape. Ces derniers interviennent pour valider les performances et les algorithmes de recontructions des appareils. Ce sujet de recherche s'inscrit dans le cadre du projet TomOptUS qui développe un appareil de tomographie optique diffuse pour petits animaux. Ce travail a deux objectifs principaux : la fabrication de fantômes aux propriétés optiques contrôlables et pouvant simuler celles des tissus biologiques et le développement de méthodes de caractérisation des milieux utilisés pour ces fantômes. La réalisation du volet fabrication a permis de doter le laboratoire d'un protocole robuste pour la fabrication de fantômes solides (par opposition à liquides). Ce protocole contourne une problématique majeure rencontrée souvent lors de la réalisation de fantômes solides, qui est la formation de bulles indésirables à l'intérieur des milieux fabriqués. Aussi, ce protocole permet la fabrication de fantômes de formes complexes tels que des fantômes de souris. Quant à la caractérisation, le laboratoire a vu l'implantation de deux méthodes de caractérisation qui permettent l'obtention des propriétées optiques de milieux absorbants et/ou diffusants. Ces méthodes s'inscrivent également à l'intérieur d'un protocole de caractérisation adapté aux besoins du laboratoire. L'étude approfondie des méthodes de caractériation a amené le développement d'une expertise qui pourrait être exploitée pour étendre l'utilisation de ces techniques de caractérisation sur des tissus biologiques, une voie d'avenir pour l'imagerie médicale.

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Foulkes, John Edward. "Absorbance Modulation Optical Lithography: Simulating the Performance of an Adaptable Absorbance Mask in the Near-Field." Thesis, University of Canterbury. Electrical and Computer Engineering, 2010. http://hdl.handle.net/10092/5336.

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The challenge for lithography today is to continue the reduction of feature size whilst facing severe theoretical and practical limitations. In 2006 Rajesh Menon and Hank Smith proposed a new lithography system named absorbance modulation optical lithography (AMOL) [Menon 2006]. AMOL proposed replacing the normal metal mask of a lithography system with an absorbance modulation layer (AML), made from a photochromic material. This allows, through the competition between two incident wavelengths, the creation of an adaptive absorbance mask. The AML allows intimate contact to an underlying resist and hence the optical near-field may be used to create sub-diffraction limited exposures. The aim of this thesis is to model AMOL and demonstrate the abilities and the limits of the system, particularly focusing on sub-diffraction limited imaging. This thesis describes the construction of a vector electromagnetic simulation to explore the idea and performance of AMOL, and an exploration of the ability of AMOL to propagate sub-diffraction limited images into a photoresist. A finite element method (FEM) model was constructed to simulate the formation of apertures in the AML and light transmission through the system. Three major areas of interest were explored in this thesis; the effect of polarisation on imaging, using a plasmonic reflector layers (PRLs) to improve the depth of focus (DOF), and introducing a superlens to AMOL. Investigations of polarisation demonstrated strong preference for a transverse magnetic (TM) polarised exposing wavelength for near-field exposures. Associated with polarisation, and supporting work with absorbance gratings, the importance of the material parameters of the AML in allowing sub-diffraction limited exposures was discussed. It was also noted that, in common with all near-field systems, the depth of focus (DOF) was poor, worse than comparable metal systems. This thesis also demonstrates that the introduction of a PRL can improve the DOF and process latitude for resist thicknesses up to 60 nm and, although performance was reduced when using a silver PRL, the substantial improvements to the DOF and process latitude make a PRL valuable for an AMOL system. This thesis also models the superlens to an AMOL system, which theoretically allows propagation of the image in the near-field. It is demonstrated that the superlens can project an AMOL image into an underlying resist, but that this image is degraded, especially for thick and non-ideal superlenses. The superlens does have a second useful effect, as it can act as a dichroic filter; decreasing the intensity ratio in the resist by a factor of ten, overcoming issues of resist sensitivity. The superlens can allow image projection and filtering with AMOL, however improvements to the available superlens materials or changes to the AML will be needed to avoid image deterioration. This thesis has developed the first full-vector model of an absorbance modulation optical lithography (AMOL) system. This model has been used to increase the understanding of the complex effects that go into the creation of sub-diffraction limited features with AMOL. In particular the model has been used to investigate polarisation, PRLs and superlenses in AMOL. This thesis demonstrates the ability of AMOL to create narrow apertures and sub-diffraction limited exposures in a photoresist, and describes the limitations of AMOL, including material parameters and DOF. AMOL is a new and interesting lithography technique; this thesis simulates the abilities and challenges of sub-diffraction lithography using an AMOL system.

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Momtahan, Kian. "Active galactic nuclei and warm absorbers." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601104.

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We present a study into the existence of the broad Fe Ka line, the hot nature of the ionised gas surrounding Active Galactic Nuclei, most commonly referred to as 'warm absorbers', and the AGN environment. We begin with an investigation of the Seyfert 1.5 galaxy NGC 3516. In our analysis, we use the Chandra telescope to explore the environment around the black hole, utilising the high resolution of the spectrometer to constrain the physical parameters. In conjunction with this we use the large effective area of Suzaku in order to detect subtle features such as the broad KO' feature. In this work we come to the conclusion that the effects of partial covering are insufficient to explain the existence of a broad Fe Ka feature. Interestingly enough however, they are required in order to provide an understanding of the soft X-ray region; although other models may provide an adequate explanation without the requirement for invoking partial covering. We go 011 to perform an analysis of 18 different Seyfert galaxies observed with the Chandra HETG, using an in-house pipeline. The purpose of the pipeline is to enable the automised fitting of phenomenological models to AGN, to aid with the diagnosis and study of warm absorbers. From this, we have determined that Seyfert 1 galaxies have negligible effect on the hard X-ray band, and that no correlation exists between the other Seyfert classifications and possible effects on the hard X-ray. We further identify a number of emission lines features throughout these AGN. Finally we investigate numerous possible relationships among the parameters of the warm absorbers in an attempt to understand the mechanism by which they are created. While this is inconclusive, we demonstrate that the mass ejection rate of the warm absorbers is low in comparison to the mass accretion rate and bolometric luminosity of the sources.

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Ellison, S. L. "The chemical evolution of QSO absorbers." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598835.

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Using quasar absorption lines as a probe of the high redshift universe is a powerful tool in the field of chemical evolution. In this thesis, I consider the elemental abundances in absorbers that correspond to a variety of environments, ranging from high redshift galaxies to the low density intergalactic medium. I firstly address the question of abundances in intermediate redshift (z_abs < 1.5) damped Lyα systems (DLAs), objects believed to correspond to the progenitors of present day massive galaxies. I present Hubble Space Telescope (HST) spectra of six intermediate redshift DLAs which have been supplemented with high resolution spectroscopy obtained with the high resolution echelle spectrograph (HIRES) on the Keck telescope. The chemical abundances of a range of elements are investigated and compared with local Galactic values in order to gain an insight into the metallicities, dust-to-gas ratios and star formation histories of these systems. The results from this work have inspired a new survey for DLAs based on a radio-selected sample of QSOs. The motivation for this endeavour has been to determine the extent to which our current view of distant galaxies is obscured by dust. I present intermediate resolution spectra obtained at the Anglo-Australian Telescope (AAT) from which DLAs may be identified. The number statistics of the newly discovered DLAs are analysed in order to determine whether obscuration by dust of background QSOs causes a significant observational bias. Finally, I consider the metallicity of the IGM by studying C IV systems associated with the Lyα forest at z ~ 3. The extent to which the IGM has been polluted with metals will provide important clues to the enrichment mechanism. I firstly investigate the column density distribution function of strong C IV absorbers associated with high column density Lyα clouds. This work is then extended to consider the C IV/H 1 ratio in low column density absorbers which are associated with physically less dense material. The spectra of two high redshift QSOs are analysed using two different techniques, both of which are critically assessed using synthetic spectra.

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Wu, Tao. "Profiled absorbers : theory, measurement and design." Thesis, University of Salford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400825.

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44

Landeryou, Mark Anthony. "Liquid uptake by fibrous absorbent materials." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398854.

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Zhang, Xiaowei. "Conceptual study of adaptive energy absorbers /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?MECH%202009%20ZHANG.

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46

Frank, Stephan. "O VI absorbers in SDSS spectra." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1222116379.

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Schairer, Kim S. "Acoustic Reflex Measurement Using Wideband Absorbance." Digital Commons @ East Tennessee State University, 2012. https://dc.etsu.edu/etsu-works/1811.

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48

Liu, Xianliang. "Infrared Metamaterial Absorbers: Fundamentals and Applications." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3829.

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Thesis advisor: Willie J. Padilla
Realization of an ideal electromagnetic absorber has long been a goal of engineers and is highly desired for frequencies above the microwave regime. On the other hand, the desire to control the blackbody radiation has long been a research topic of interest for scientists--one particular theme being the construction of a selective emitter whose thermal radiation is much narrower than that of a blackbody at the same temperature. In this talk, I will present the computational and experimental work that was used to demonstrate infrared metamaterial absorbers and selective thermal emitters. Based on these work, we further demonstrate an electrically tunable infrared metamaterial absorber in the mid-infrared wavelength range. A voltage potential applied between the metallic portion of metamaterial array and the bottom ground plane layer permits adjustment of the distance between them thus altering the electromagnetic response from the array. Our device experimentally demonstrates absorption tunability of 46.2% at two operational wavelengths. Parts of this thesis are based on unpublished and published articles by me in collaboration with others. The dissertation author is the primary researcher and author in these publications. The text of chapter two, chapter five, and chapter seven is, in part, a reprint of manuscript being prepared for publication. The text of chapter three is, in part, a reprint of material as it appears in Physical review letters 104 (20), 207403. The text of chapter four is, in part, a reprint of material as it appears in Physical Review Letters 107 (4), 45901. The text of chapter six is, in part, a reprint of material as it appears in Applied Physics Letters 96, 011906
Thesis (PhD) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics

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49

Maude, Sarah. "Characterisation of UV-absorbent nanoceramic powders." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/34145.

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Nanoceramic powders were produced via a plasma processing route by QinetiQ Nanomaterials Ltd. The powders were characterised in terms of agglomerate size, morphology, phase analysis and surface chemistry. The powders were made into suspensions and the UV absorbency properties were investigated. It was found that the mixtures produced different products depending on the concentration of titania in the starting material. Powders containing less than 30% titania were solid mixtures of zinc oxide and titania; these powders absorbed UV radiation as well and in some cases better than the individual powders. The powders containing more than 30% titania were shown to have titanium ions incorporated into the zinc oxide structure. This reduced the band gap of the powder which meant that the powders did not absorb UV radiation. For all the powders that absorbed UV radiation, it was found that particles around 100 nm absorbed large amounts of UV radiation and did not interact with visible radiation, producing a clear, transparent suspension which gives ideal characteristics for a sunscreen formulation. The suspensions were found to absorb the most UV radiation above 3 wt %. The powder containing 95 % zinc oxide 5 % titania was shown to absorb more UV radiation and scatter less visible radiation than the individual powders, showing the potential to provide an improvement to the properties of sunscreen formulations.

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Hao, Jianping. "Broad band electromagnetic perfect metamaterial absorbers." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10076/document.

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Ce travail de thèse concerne les structures artificielles à base de métamatériaux permettant la réalisation d’absorbants parfaits. Après une brève introduction des métamatériaux, de leur fonctionnement en tant qu’absorbants et de l’état de l’art, quatre types de structures fonctionnant en bandes centimétrique ou millimétrique ont été conçus puis fabriqués à savoir (i) des réseaux de cubes BaSrTiO3 (BST) basés sur les résonances de Mie, (ii) des réseaux désordonnés composés d’anneaux métalliques mettant en jeu des effets de résonance semblables aux systèmes plasmoniques (iii) des absorbants à quatre résonateurs élémentaires sur substrat flexible et (iv) des réseaux multicouches métal-diélectrique de forme pyramidale. Pour l’ensemble, des simulations numériques, corroborées par l’expérience en guide d’onde ou en espace libre, montrent l’existence d’un moment magnétique. Celui-ci est induit par une boucle des courants de déplacement et de conduction. Pour les structures périodiques, les conditions de grande largeur de bande d’absorption ont été établies sur la base du piégeage et de la dissipation de l’énergie incidente. Pour les réseaux désordonnés, il est montré le rôle capital des couplages entre résonateurs. Des structures périodiques à base de ferroélectrique de dimensions sous longueur d’onde ont été assemblées avec succès tandis que des absorbants flexibles ont été réalisés par technique d’impression jet d’encre montrant l’amélioration d’un facteur quatre de la bande d’absorption. Des améliorations comparables ont été obtenues à l’aide de réseaux d’anneaux, dont les positions dans le plan sont désordonnées, résultant de la distribution des fréquences de résonance par effet de couplage fort entre les résonateurs
In this thesis broadband Metamaterial Perfect Absorbers (MPAs) have been investigated. Following a brief introduction of metamaterials, operating mechanisms and state of the art of MPA, four absorber types operating either at centimeter or millimeter wavelengths have been designed and fabricated namely :(i) Mie-resonance based BaSrTiO3 (BST) arrays operating at microwaves, (ii) plasmonic-type disordered ring-shaped MPA, (iii) four patches millimeter wave flexible absorbers (iv) Pyramidal metal/dielectric stacked resonator arrays. For all the structures, it was demonstrated, through numerical simulations, assessed by characterization in a waveguide configuration or in free space, that unit absorbance relies on magnetic resonances induced by a current loop combining displacement and conduction currents. For periodic arrays, the condition for a broad band operation was established via the optimization of dissipation and trapping of electromagnetic energy in the resonators. For disordered metamaterials, it was shown the major role played by the magnetic dipole-dipole interaction. From the technological side, Ferroelectrics cube arrays with subwavelength dimensions were assembled onto a metal plate while flexible multi-resonators periodic arrays were successfully fabricated by ink-jet printing showing a fourfold enhancement of the absorbance bandwidth thanks to the overlapping of resonance frequencies. Comparable improvement in the bandwidth was also pointed out with randomly position metal ring arrays due to the distribution of resonance frequencies that result from tight in-plane resonator coupling

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Dissertations / Theses on the topic 'Absorbans'

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