Дисертації з теми "Absorbing materials"
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1
Lisachuk, G. V., R. V. Kryvobok, Y. M. Pitak, O. Lapuzina, N. A. Kryvobok, and N. S. Maystat. "Radio-absorbing materials with adjustable dielectric properties." Thesis, Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/38982.
2
Lanoye, Reinhilde Vermeir Gerrit Lauriks Walter Sgard Franck. "Assessment of the absorption performance of sound absorbing materials." Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=lanoye.
3
Sudhendra, Chandrika. "A Novel Chip Resistor Spacecloth For Radar Absorbing Materials." Thesis, Indian Institute of Science, 2006. https://etd.iisc.ac.in/handle/2005/280.
Анотація:
Spacecloth design and development is vital and crucial in Radar Absorbing Materials (RAM) for achieving Low Observability in an Aircraft or an Unmanned Air Vehicle(UAV). The RAM design translates into the spacecloth design. The spacecloths form the constituent layers in a broadband Jaumann absorber in which case they have to be designed for various values of surface resistivity. The design specifications of spacecloth(s) in RAMS is well understood and documented in literature. But the design of spacecloth hitherto, has been the domain of materials' scientists wherein the specified properties of the spacecloth are achieved by an iterative, trial and error process, by mixing various constituents in different proportions to get the design specified surface resistivity in the final end-product. In an effort to bridge this gap, a novel spacecloth for RAM applications is proposed in the thesis. It is proposed that a repetitive geometrical grid network of chip resistors simulates spacecloth. The sheet resistivity of the spacecloth is derived by analyzing various geometries like square, rectangle, triangle and hexagonal grids. The transmission and reflection loss for the chip resistor spacecloth is derived. The design of chip resistor spacecloths for operation at S and C bands is given followed by experimental verification using waveguide simulator experiments. Numerical study of multilayer RAM has been carried out with exponential taper variation of surface resistivities for constituent spacecloth layers and design curves are given for multilayer RAM both for normal and oblique incidence for TE and TM polarizations.
4
Sudhendra, Chandrika. "A Novel Chip Resistor Spacecloth For Radar Absorbing Materials." Thesis, Indian Institute of Science, 2006. http://hdl.handle.net/2005/280.
Анотація:
Spacecloth design and development is vital and crucial in Radar Absorbing Materials (RAM) for achieving Low Observability in an Aircraft or an Unmanned Air Vehicle(UAV). The RAM design translates into the spacecloth design. The spacecloths form the constituent layers in a broadband Jaumann absorber in which case they have to be designed for various values of surface resistivity. The design specifications of spacecloth(s) in RAMS is well understood and documented in literature. But the design of spacecloth hitherto, has been the domain of materials' scientists wherein the specified properties of the spacecloth are achieved by an iterative, trial and error process, by mixing various constituents in different proportions to get the design specified surface resistivity in the final end-product. In an effort to bridge this gap, a novel spacecloth for RAM applications is proposed in the thesis. It is proposed that a repetitive geometrical grid network of chip resistors simulates spacecloth. The sheet resistivity of the spacecloth is derived by analyzing various geometries like square, rectangle, triangle and hexagonal grids. The transmission and reflection loss for the chip resistor spacecloth is derived. The design of chip resistor spacecloths for operation at S and C bands is given followed by experimental verification using waveguide simulator experiments. Numerical study of multilayer RAM has been carried out with exponential taper variation of surface resistivities for constituent spacecloth layers and design curves are given for multilayer RAM both for normal and oblique incidence for TE and TM polarizations.
5
Lebedev, Andrej. "Theoretical description of the optical response of heterogeneous absorbing materials." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=96177049X.
6
Lebedev, Andrei. "Theoretical description of the optical response of heterogeneous absorbing materials." Doctoral thesis, Universitätsbibliothek Chemnitz, 2000. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200000113.
Анотація:
Die Arbeit befaßt sich mit der Beschreibung
der linearen optischen Eigenschaften von
heterogenen absorbierenden Materialien,
insbesondere von Clustermaterialien. Das Ziel der
Arbeit besteht in der Ausarbeitung einer
analytischen Methode zur Berechnung des optischen
Verlustes (Extinktion) des heterogenen Materials.
Die präsentierte Methode basiert auf der
klassischen Beschreibung der
Licht-Materie-Wechselwirkung mit Hilfe
dielektrischer Funktionen.
Das Modell berücksichtigt eine mögliche Absorption
in der Einbettmatrix, Mehrfachstreungseffekte in
Systemen mit dichtgepackten Clustern und die
Clusterstatistik.
Um die Absorption in der Einbettmatrix beschreiben
zu können, wird die Mie-Theorie der Lichtstreuung
an einem sphärischen Teilchen in einer
nichtabsorbierenden Umgebung erweitert. Die
Clusterstatistik wird dadurch berücksichtigt, daß
die optischen Eigenschaften eines makroskopischen
Clustersystems als eine Mittelung der
Eigenschaften kleinerer Clusteraggregate berechnet
werden. Die zur Berechnung verwendeten
Clusteraggregate, deren statistische Eigenschaften
der Probenherstellungsmethode entsprechen, werden
mit Hilfe von Monte-Carlo-Simulation des
Clusterwachstums auf Oberflächen generiert.
Nach einer Beschreibung des theoretischen Apparats
werden numerische Beispiele dargestellt, die die
Anwendung der Methode demonstrieren.
Die Extinktion von Eisenclustern in Fulleritmatrix
wird in der Einzelteilchennäherung berechnet und
mit experimentellen Daten verglichen.
Die Extinktionskoeffizienten von Silberclustern
in zwei molekularen Matrizen werden mit der
Berücksichtigung der Clusterstatistik und
Mehrfachstreungseffekten berechnet. Der Vergleich
mit den experimentellen Werten läßt auf den
Einfluß der betrachteten Effekte auf
charakteristische Merkmale in den Spektren von
makroskopischen Clustersystemen schlißen.
7
Norindr, Florian. "Study of inorganic transparent materials with near-infrared absorbing properties." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/171095/.
Анотація:
The pigments investigated in this thesis were synthesised and characterised in order to find promising candidates for near-infrared absorbers. The chemical systems were chosen due to their absorbing properties and also their chemical and thermal stability and non-toxicity as well as for economical reasons. Investigations were undertaken on several phosphates and silicates.Within the group of phosphates, first several known copper compounds, i.e.Cu2P2O7, Cu4P2O9, Cu5P2O10, Cu3(PO4)2, Cu(PO3)2 and Cu2P4O12, were tested and the most suitable were chosen for more detailed experiments. The structure types with the general formula M2P2O7 were found to be promising and the metals calcium, strontium and copper were investigated as a starting point. It was confirmed that M2P2O7 (with M = Ca or Sr) and Cu2P2O7 could only form a pigment material for the middle member e.g. MCuP2O7. Better candidates were found in the systems Mg/Cu and Zn/Cu. Here solid solutions occur and the absorption behaviour could be adjusted according to the ratio of the metal cations. A series of different cation ratio compounds were synthesised for both systems. As Zn/Cu shows more favourable absorption properties compared to Mg/Cu, a full investigation of structural parameters including neutron powder diffraction and EXAFS studies was undertaken and the influence of the shape of M–O coordination spheres on the near-infrared absorption properties is discussed in detail. After deriving the successful concept it was investigated in two further chemical systems. First, the cation Fe2+ was used into the Zn3(PO4)2 structure to form a solid solution (Zn,Fe)3(PO4)2 and then Cu2+ was introduced into the Mg2Si2O6 pyroxene structure. Resulting from the studies, three promising systems for transparent near-infrared absorbing pigment applications were isolated: (Zn,Cu)2P2O7, (Zn,Fe)3(PO4)2 and (Mg,Cu)2Si2O6 solid solutions
8
Zheng, Lixin. "Design, synthesis, and characterization of organic and polymeric two-photon absorbing materials /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/10599.
9
Ohira, Shino. "Theoretical evaluation of the nonlinear optical properties of extended and p-conjugated chromophores." Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29717.
Анотація:
Thesis (Ph.D)--Chemistry and Biochemistry, Georgia Institute of Technology, 2009.Committee Chair: Brédas, Jean-Luc; Committee Member: Janata, Jiri; Committee Member: Kippelen, Bernard; Committee Member: Marder, Seth; Committee Member: Sherrill, David. Part of the SMARTech Electronic Thesis and Dissertation Collection.
10
Ford, Lee. "Adaptive radar signature control with the use of radar absorbing materials." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398391.
11
Mayukh, Mayank. "NEAR-IR ABSORBING PHTHALOCYANINE DERIVATIVES AS MATERIALS FOR ORGANIC SOLAR CELLS." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145442.
Анотація:
Phthalocyanines (Pcs) are highly conjugated synthetic porphyrin analogs that exhibit high extinction coefficients and hole mobilities, and strong pi-pi interactions. We have developed a general method for the synthesis of peripherally functionalized Pc chromophores using `click' chemistry, wherein an alkynyl substituted Pc is reacted with an azide, providing an elegant route to the creation of a library of numerous Pcs. We have also developed a simple route to the synthesis of tri- and tetravalent metal Pc derivatives such as titanyl phthalocyanine (TiOPc) involving solvent-free conditions. Solvent-free conditions are environmentally friendly and industrially economical, and in the present context effectively eliminate the formation of non-metallated phthalocyanine (H2Pc), a side product often seen in other routes that interferes with their purification. We have also prepared and characterized thin-films of some of these Pcs, TiOPcs in particular, wherein we have developed an easy route to various TiOPc polymorphs exhibiting different near-IR sensitivities via spin-coating whose optical properties are reminiscent of Phase-I and Phase-II polymorphs of the unmodified TiOPc. Phase-II is particularly interesting as it is photoelectrically active in the near-IR region with a Q-band maximum at ca. 890 nm. We have also fabricated and characterized organic solar cells in both planar heterojunction (PHJ) and bulk heterojunction (BHJ) architectures based on one of these materials, which exhibited good near-IR photoactivity with the absorption spectrum extending up to 1 micrometer in the near-IR. The incident and absorbed photon to current efficiency (IPCE and APCE) spectra showed contributions from the TiOPc in the near-IR region with local maxima around 680 nm and 920 nm, corresponding to the Frenkel and the charge-transfer (CT) bands of the TiOPc, respectively.
12
Meng, Han. "Acoustic properties of novel multifunctional sandwich structures and porous absorbing materials." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC008/document.
Анотація:
La mise en oeuvre de matériaux acoustiques est une méthode efficace et très utilisée pour réduire le bruit le long de sa propagation. Les propriétés acoustiques de nouvelles structures sandwich multifonctionnelles et de matériaux absorbants poreux sont étudiées dans la thèse. Les principales contributions de la thèse sont les suivantes: Les panneaux sandwich ont généralement d'excellentes propriétés mécaniques et un bon indice de perte en transmission sonore (STL), mais aucune capacité d'absorption acoustique. De nouvelles structures sandwich multifonctionnelles sont développées en intégrant des microperforations et des matériaux absorbants poreux aux panneaux sandwich ondulés et en nid d’abeilles conventionnels, structurellement efficaces pour obtenir de bons STL et de bonnes absorptions en basses fréquences. Le coefficient d'absorption acoustique (SAC) et la perte en transmission (STL) des panneaux sandwich ondulés sont évalués numériquement et expérimentalement en basse fréquence pour différentes configurations de perforations. Les modèles éléments finis (EF) sont construits en tenant compte des interactions vibro-acoustiques sur les structures et des dissipations d'énergie, visqueuse et thermique, à l'intérieur des perforations. La validité des calculs FE est vérifiée par des mesures expérimentales avec les échantillons testés obtenus par fabrication additive. Par rapport aux panneaux sandwich ondulés classiques sans perforation, les panneaux sandwich perforés (PCSPs) avec des perforations dans leur plaque avant présentent non seulement un SAC plus élevé aux basses fréquences, mais aussi un meilleur STL, qui en est la conséquence directe. L'élargissement des courbes des indices d’absorption et de transmission doit être attribué à la résonance acoustique induite par les micro-perforations. Il est également constaté que les PCSPs avec des perforations dans les plaques avant et les parois internes onduleés ont les fréquences de résonance les plus basses de tous les PCSPs. En outre, les performances acoustiques des panneaux sandwich en nid d'abeilles avec une plaque avant microperforée sont également examinées. Un modèle analytique est présenté avec l'hypothèse que les déplacements des deux plaques sont identiques aux fréquences inférieures à la fréquence de résonance des plaques. Le modèle analytique est ensuite validé par des modèles d'éléments finis et des résultats expérimentaux existants. Contrairement aux panneaux sandwich en nid d'abeilles classiques qui sont de piètres absorbeurs de bruit, les sandwichs en nid d'abeilles perforés (PHSPs) conduisent à un SAC élevé aux basses fréquences, ce qui entraîne en conséquence un incrément dans le STL basse fréquence. Les influences de la configuration du noyau sont étudiées en comparant les PHSPs avec différentes configurations de noyaux en nids d'abeilles. […]Implementation of acoustic materials is an effective and popular noise reduction method during propagation. Acoustic properties of novel multifunctional sandwich structures and porous absorbing materials are studied in the dissertation. The main contributions of the dissertation are given as, Sandwich panels generally have excellent mechanical properties and good sound transmission loss (STL), but no sound absorption ability. Novel multifunctional sandwich structures are developed by integrating micro perforations and porous absorbing materials to the conventional structurally-efficient corrugated and honeycomb sandwich panels to achieve good SAC and STL at low frequencies. Low frequency sound absorption and sound transmission loss (STL) of corrugated sandwich panels with different perforation configurations are evaluated both numerically and experimentally. Finite element (FE) models are constructed with considerations of acousticstructure interactions and viscous and thermal energy dissipations inside the perforations. The validity of FE calculations is checked against experimental measurements with the tested samples provided by additive manufacturing. Compared with the classical corrugated sandwich panels without perforation, the perforated corrugated sandwich panels (PCSPs) with perforations in its face plate not only exhibits a higher SAC at low frequencies but also a better STL as a consequence of the enlarged SAC. The enlargement of SAC and STL should be attributed to the acoustical resonance induced by the micro perforations. It is also found that the PCSPs with perforations in both the face plates and corrugated cores have the lowest resonance frequencies of all the PCSPs. Besides, the acoustic properties of honeycomb sandwich panels with microperforated faceplate are also explored. An analytical model is presented with the assumption that displacements of the two faceplates are identical at frequencies below the faceplate resonance frequency. The analytical model is subsequently verified by finite element models and existing experimental results. Unlike classical honeycomb sandwich panels which are poor sound absorbers, perforated honeycomb sandwiches (PHSPs) lead to high SAC at low frequencies, which in turn brings about increment in the low frequency STL. Influences of core configuration are investigated by comparing PHSPs with different honeycomb core configurations. In order to enlarge the SAC bandwidth of perforated sandwich panels, porous absorbing materials are added to the cores of novel perforated sandwich panels. FE models are set up to estimate the SAC and STL of perforated sandwich panels with porous materials. Results show that perforated sandwich panels with porous material can provide SAC with broader bandwidth and lower resonance frequency than that without porous materials. Whereas the peak values in the SAC and STL curves are reduced due to the weakened acoustical resonance by the porous materials. […]
13
Farajzadeh, Khosroshahi Siamak. "New Energy Absorbing Materials and their Use in Personal Protective Equipment." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3426669.
Анотація:
Personal Protective Equipment (PPE) indicates protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury, in particular they are used to dissipate the energy of the impact in case of accidents. Most of PPE items should pass certain standard criteria before being introduced into the market. Moreover, beside standards, biomechanical injury criteria can be used to compare different PPE items according to the human body tolerance against external loading.
Energy absorbing materials with higher capacity of energy dissipation can improve the injury mitigation capability of PPE items. Therefore, this thesis aims at studying the possibility of using new energy absorbing materials to optimize the protection level of protective devices, especially for motorcycle riders. The Finite Element Method (FEM) was mainly used to assess and compare the energy absorption capability of different materials and structures. However, experimental tests were carried out whenever possible for validation of FE models.
A computational method has been developed for partial optimization of the composite-shell of an helmet to mitigate the induced neck axial force due to the facial impact. The results of this optimization show that by varying the orientation of the chin bar plies, thus keeping the helmet mass constant, the neck axial force can be reduced by approximately 30% while ensuring that the helmet complies with the impact attenuation requirements prescribed in helmet standards adopted in Europe.
Moreover, the possibility of using addictively manufactured structures as the helmet liner has been studied. The results show that using a hierarchical lattice liner could reduce the risk of head injury significantly by comparison to a helmet with EPS liner and could potentially be considered as the new generation of energy absorbing liners for advanced helmets.
Furthermore, experimental tests were carried out to study the feasibility of using new polymeric fibres to make helmets lighter. The results of these tests show that such polymeric fibres may be used in conjunction with carbon fibres to mold hybrid laminates to build lighter helmets.
Finally, since there is no standard to design and test neck protective devices, the response of cervical vertebrae to direct impacts to the helmets in case of using such a device was studied numerically. The findings of this work show that using a neck brace designed to restrain the head-neck motion might increase the induced load in the neck and therefore the risk of cervical injuries, therefore the design of such devices needs more investigations and their assessment requires the introduction of the relevant standards.I termini ‘Dispositivi di protezione individuale’ (DPI) indicano indumenti protettivi, caschi, occhiali di protezione o altri indumenti o attrezzature progettati per proteggere il corpo dell'utilizzatore da lesioni, in particolare i DPI sono utilizzati per dissipare l'energia dell'impatto in caso di incidenti. La maggior parte dei DPI dovrebbe superare determinati test standard prima di essere introdotta nel mercato. Inoltre, accanto alle prove di normativa, anche criteri di lesioni biomeccaniche possono essere utilizzati per confrontare diversi articoli di DPI in base alla tolleranza del corpo umano rispetto al carico esterno. I materiali che assorbono energia con maggiore capacità di dissipazione di energia possono migliorare la capacità di mitigazione degli infortuni degli articoli di DPI. Pertanto, questa tesi mira a studiare la possibilità di utilizzare nuovi materiali che assorbono energia per ottimizzare il livello di protezione dei DPI, in particolare per i motociclisti. Il metodo degli elementi finiti (FEM) è stato utilizzato principalmente per valutare la capacità di assorbimento di energia diversi materiali e strutture. Tuttavia anche test sperimentali sono stati effettuati, quando possibile, per la convalida dei modelli FE. È stato sviluppato un metodo computazionale per l'ottimizzazione parziale del guscio composito di un casco per ridurre la forza assiale indotta nel collo dall'impatto sulla testa. I risultati di questa ottimizzazione dimostrano che variando l'orientamento degli strati della mentoniera, mantenendo così la massa del casco inalterata, la forza assiale nel collo può essere ridotta di circa il 30%, mentre si assicura che il casco sia conforme ai requisiti di attenuazione dell'impatto prescritti negli standard del casco adottati in Europa. Inoltre, è stata studiata la possibilità di utilizzare strutture prodotte in modo additivo come imbottitura del casco. I risultati mostrano che l'utilizzo di un rivestimento reticolare gerarchico potrebbe ridurre significativamente il rischio di trauma cranico rispetto a un casco con tradizionale imbottitura in polistirolo, tanto che l’ imbottitura reticolare gerarchica potrebbe essere considerata come la nuova generazione di rivestimenti per l'assorbimento dell’energia in caschi avanzati. Inoltre, sono stati effettuati test sperimentali per studiare la fattibilità dell'uso di nuove fibre polimeriche per rendere i caschi più leggeri. I risultati di questi test mostrano che tali fibre polimeriche possono essere usate in congiunzione con fibre di carbonio per modellare i laminati ibridi per costruire caschi più leggeri. Infine, poiché non esiste una normativa standard per progettare e testare i dispositivi di protezione del collo, è stata studiata numericamente la risposta delle vertebre cervicali ad impatti sul casco in caso di uso di un dispositivo di protezione del collo (neck brace). I risultati di questo lavoro suggeriscono che l'uso di un collare progettato per limitare il movimento dell’insieme testa-collo potrebbe aumentare il carico indotto nel collo e quindi il rischio di lesioni cervicali. Si conclude che la progettazione di tali dispositivi richiede più indagini e la loro valutazione richiede l'introduzione di standard pertinenti.
14
Youh, Meng-Jey. "Development of microwave absorbing diamond coated fibres." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326038.
15
Tkachov, Igor Ivanovich. "Millimeter wave complex dielectric permittivity and complex magnetic permeability measurements of absorbing materials /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2000.
Анотація:
Thesis (Ph.D.)--Tufts University, 2000.Adviser: Mohammed Nurul Afsar. Submitted to the Dept. of Electrical Engineering. Includes bibliographical references (leaves 183-192). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
16
Jaouen, Kévin. "Backside absorbing layer microscopy : a new tool for the investigation of 2D materials." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS296/document.
Анотація:
La microscopie optique sur substrats antireflets est un outil de caractérisation simple et puissant qui a notamment permis l'isolation du graphène en 2004. Depuis, le domaine d'étude des matériaux bidimensionnels (2D) s'est rapidement développé, tant au niveau fondamental qu'appliqué. Ces matériaux ultraminces présentent des inhomogénéités (bords, joints de grains, multicouches, etc.) qui impactent fortement leurs propriétés physiques et chimiques. Ainsi leur caractérisation à l'échelle locale est primordiale. Cette thèse s'intéresse à une technique récente de microscopie optique à fort contraste, nommée BALM, basée sur l'utilisation originale de couches antireflets très minces (2-5 nm) et fortement absorbantes (métalliques). Elle a notamment pour but d'évaluer les mérites de cette technique pour l'étude des matériaux 2D et de leur réactivité chimique. Ainsi, les différents leviers permettant d'améliorer les conditions d'observation des matériaux 2D ont tout d'abord été étudiés et optimisés pour deux matériaux modèles : l'oxyde de graphène et les monocouches de MoS₂. L'étude de la dynamique de dépôt de couches moléculaires a notamment permis de montrer à la fois l'extrême sensibilité de BALM pour ce type de mesures et l'apport significatif des multicouches antireflets pour l'augmentation du contraste lors de l'observation des matériaux 2D. L'un des atouts principaux de BALM venant de sa combinaison à d'autres techniques, nous nous sommes particulièrement intéressés au couplage de mesures optiques et électrochimiques pour lesquelles le revêtement antireflet sert d'électrode de travail. Nous avons ainsi pu étudier optiquement la dynamique de réduction électrochimique de l'oxyde de graphène (GO), l'électro-greffage de couches minces organiques par réduction de sels de diazonium sur le GO et sa forme réduite (r-GO), ainsi que l'intercalation d'ions métalliques entre feuillets de GO. En combinant versatilité et fort-contraste, BALM est ainsi établi comme un outil prometteur pour l'étude des matériaux 2D et en particulier pour la caractérisation locale et in situ de leur réactivité chimique et électrochimiqueOptical microscopy based on anti-reflective coatings is a simple yet powerful characterization tool which notably allowed the first observation of graphene in 2004. Since then, the field of two-dimensional (2D) materials has developed rapidly both at the fundamental and applied levels. These ultrathin materials present inhomogeneities (edges, grain boundaries, multilayers, etc.) which strongly impact their physical and chemical properties. Thus their local characterization is essential. This thesis focuses on a recent enhanced-contrast optical microscopy technique, named BALM, based on ultrathin (2-5 nm) and strongly light-absorbing (metallic) anti-reflective layers. The goal is notably to evaluate the benefits of this technique for the study of 2D materials and their chemical reactivity. The various levers to improve 2D materials observation were investigated and optimized for two model materials: graphene oxide and MoS₂ monolayers. The investigation of molecular layer deposition dynamic notably showed the extreme sensitivity of BALM for such measurements and the significant contribution of multilayers anti-reflective coatings to enhance contrast during the observation of 2D materials. One of the main assets of BALM comes from its combination to other techniques. We particularly considered the coupling between optical measurements and electrochemistry for which the anti-reflective layer serves as working electrode. We investigated optically the dynamic of electrochemical reduction of Graphene Oxide (GO), the electrografting of organic layers by diazonium salts reduction on GO and its reduced form (rGO), as well as the intercalation of metallic ions within GO sheets. By combining versatility and high-contrast, BALM is established as a promising tool for the study of 2D materials, especially for the local and in situ characterization of their chemical and electrochemical reactivity
17
Makarov, Nikolay Sergeevich. "Ultrafast two-photon absorption in organic molecules quantitative spectroscopy and applications /." Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/makarov/MakarovN0510.pdf.
Анотація:
This dissertation explores quantitative two-photon absorption spectroscopy to relate molecular structure with optical properties of organic chromophores. The dissertation describes an advanced fluorescence-based technique for reliable measurements of the two-photon spectra and cross sections. To facilitate the measurements it establishes a set of reference compounds measured with a 15% absolute accuracy covering a broad range of excitation and fluorescence wavelengths. The dissertation shows that in many cases the few-essential-levels model can be successfully applied for the description and interpretation of two-photon absorption spectra and cross sections, at least for the low-energy transitions. The dissertation presents examples of applications of two-photon absorption for volumetric optical storage and cancer tumor detection. It describes the basic principles of the two-photon absorption-based optical memory and limitations imposed on two-photon sensitivity of photochromic materials by a necessity of fast access to the data. It also proposes a novel technique for sensitive detection of cancer cells by using two-photon excitation of near-IR fluorescence of a commercial dye and discusses the mechanisms responsible for differentiation between the normal and the cancer cells. The methods described in this dissertation can be applied to understanding the relations between structure and two-photon absorption strength of individual transitions of organic and biological chromophores, which can be used for design of new materials, maximally adapted for particular applications.
18
Zhao, Shuxi. "Spectrally Selective Solar Absorbing Coatings Prepared by dc Magnetron Sputtering." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7530.
19
Sharma, Hrishikesh. "Design of a bridge bumper to protect bridge girders against collisions of overheight vehicles." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1467.
20
Zhao, Ying. "Design of energy absorbing materials and composite structures based on porous shape memory alloys (SE) /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/7148.
21
Lavoie, J. André. "Design and application of a quasistatic crush test fixture for investigating scale effects in energy absorbing composite plates /." This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-03172010-020104/.
22
Odevik, William, and Nyberg Viktor Wästersved. "Modular Sound Absorbing Unit : A system solution for implementation of noise abatement appliance in indoor environments." Thesis, Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-80784.
Анотація:
There is a rising concern about the effects of noise on human health. The noise from our technologies and comforts that evokes a negative physiological response as a response, effects like cardiovascular disease, cognitive and hearing impairments are all examples of critical health results stemming from prolonged noise exposure (WHO, 2004 & 2018). A reaction to the insight of the effects of noise pollution is directives and policies to fight noise pollution, both at a European union level but also member state level (EU, 2002). The applied Swedish policy is enforced by the Swedish work environment authority which has given the following provision for indoor environments and workplace design (AFS 2009:2) which states “4 § Work should be planned, conducted and be followed up so that noise exposure is reduced through eliminating noise from its source or is reduced as much as possible. Consideration should also be taken into the technological advancements and the possibilities to reduce noise.”. This is where this master thesis project comes in to develop a modular sound absorbing unit that could help in the fight against noise pollution and reduce the negative effects of prolonged noise exposure. The master thesis is performed as a part of our final master’s degree course in the program- me of industrial design engineering at the Luleå University of Technology. The company Sontech International AB served as client and collaborator for the master thesis. The objective for the project was to develop a modular sound absorbing unit that uses Sontech’s unique sound absorbing materials to break into a new market, diverging from their previous focus on industrial applications. The project was based in the product design specification developed in the inspiration phase of our project, stemming from the data gathered in needfinding and current state analysis, in conjunction with Sontech. The product design specification was split into three segments of need, function and design which was used in the remaining phases of ideation and implementation. From there the ideation phase consisted of different types of brainstorming methods and explorative prototyping to cre- ate a large sum of ideas to later be analysed through a design space evaluation process which resulted in five distinct concepts. The ideation phase was concluded in a selection of the final concepts to be brought into the implementation phase. The implementation phase entailed refinement of the concepts through testing and detail design. The final design concluded in a modular sound absorbing system called Unison which consist of two modes of thinking, vertical aligned units called Acustibrick for building sound absorbing walls. The other is horizontally aligned units called Acustitile made for creating sound absorbing & deflecting roofs. For each of unit there is the option two pick two types of material, acustimet which is an aluminium sheet with micro perforations which gives it its sound absorbing properties. The second material is acustiboard which is a cardboard sheet made of paper honeycomb and two thin outer layers of paper, this outer layer is perforated to give the material its sound absorbing properties. The units are constructed with stamped holes, called interface, which are aligned to allow mounting on different objects depending on the user’s choice. These objects, called the architecture, can be rods, pipes, wires, ropes etc. depending on how the user chooses to implement the system in their environment. This modular system will allow the user to construct their own arrays of units, with their own resources, to shape and better their noise environment.Det finns en ökande oro över effekterna av buller på människors hälsa. Bullret från vår teknik och bekvämligheter som framkallar en negativ fysiologisk respons som svar, effekter som hjärt-kärlsjukdom, kognitiva och hörselnedsättningar är alla exempel på kritiska hälsoresultat som härrör från långvarig bullerexponering (WHO, 2004 & 2018). En reaktion på insikten om effekterna av bullerföroreningar är direktiv och politik för att bekämpa bullerföroreningar, både på EU-nivå men också på medlemsstatsnivå (EU, 2002). Den tillämpade svenska policyn upprätthålls av Arbetsmiljöverket som har gett följande bestämmelser för inomhusmiljöer och arbetsplatsdesign (AFS 2009:2) där det står “4 § arbete bör planeras, genomföras och följas upp så att bullerexponeringen reduceras genom att eliminera buller från dess källa eller minskas så mycket som möjligt. Hänsyn bör också tas till de tekniska framstegen och möjligheterna att minska bullret. “. Det är här detta examensarbete kommer in för att utveckla en modulär ljudabsorberande enhet som kan hjälpa till i kampen mot buller och minska de negativa effekterna av långvarig bullerexponering. Examensarbetet utförs som en del av vår slutgiltiga magisterkurs i programmet industriell design Engineering vid Luleå tekniska universitet. Företaget Sontech International AB verkade som klient och samarbetspartner för examensarbetet. Målet för projektet var att utveckla en modulär ljudabsorberande enhet som använder Sontechs unika ljudabsorberande material för att bryta sig in i en ny marknad och avvika från deras tidigare fokus på industriella tillämpningar. Projektet baserades på produktdesign specifikationen som utvecklades i inspirations fasen av vårt projekt, som härrör från de data som samlats in i needfinding och current state analys, tillsammans med Sontech. Produktdesign specifikationen delades upp i tre segment av behov, funktion och design som användes i de återstående faserna av ideation och implementation. Ideationsfasen bestod av olika typer av brainstorming-metoder och utforskande prototyper för att skapa en stor summa idéer som senare kunde analyseras genom en utvärderingsprocess som resulterade i fem distinkta koncept. Ideationfasen avslutades i ett urval av de slutgiltiga koncepten som skulle föras in i implementation fasen. Implementeringsfasen innebar förfining av koncepten genom testning och detaljdesign. Den slutliga utformningen slutade med ett modulärt ljudabsorberande system som kallas unison som består av två sätt att tänka, vertikala justerade enheter kallas Acustibrick för att bygga ljudabsorberande väggar. Den andra är horisontellt anpassade enheter kallas Acustitile gjort för att skapa ljudabsorberande & reflekterande tak. För varje enhet finns alternativet att plocka två typer av material, acustimet som är en aluminiumplåt med mikroperforeringar som ger den dess ljudabsorberande egenskaper. Det andra materialet är acustiboard som är en pappskiva gjord av en kärna av papper i ett honeycomb mönster och två tunna yttre lager av papper, detta yttre skikt är perforerad för att ge materialet dess ljudabsorberande egenskaper. Enheterna är konstruerade med stämplade hål, kallas Interface, som är justerade för att tillåta montering på olika objekt beroende på användarnas val. Dessa objekt, som kallas arkitektur, kan vara stavar, rör, ledningar, rep etc. beroende på hur användaren väljer att implementera systemet i sin omgivning. Detta modulära system gör det möjligt för användaren att konstruera sina egna matriser av enheter, med sina egna resurser, för att forma och förbättra sin bullermiljö.
23
Rumpler, Romain. "Efficient Finite Element Approach for Structural-Acoustic Applications including 3D modelling of Sound Absorbing Porous Materials." Doctoral thesis, KTH, MWL Numerisk akustik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-90335.
Анотація:
In the context of interior noise reduction, the present work aims at proposing Finite Element (FE) solution strategies for interior structural-acoustic applications including 3D modelling of homogeneous and isotropic poroelastic materials, under timeharmonic excitations, and in the low frequency range. A model based on the Biot-Allard theory is used for the poroelastic materials, which is known to be very costly in terms of computational resources. Reduced models offer the possibility to enhance the resolution of such complex problems. However, their applicability to porous materials remained to be demonstrated.First, this thesis presents FE resolutions of poro-elasto-acoustic coupled problems using modal-based approaches both for the acoustic and porous domains. The original modal approach proposed for porous media, together with a dedicated mode selection and truncation procedure, are validated on 1D to 3D applications.In a second part, modal-reduced models are combined with a Padé approximants reconstruction scheme in order to further improve the efficiency.A concluding chapter presents a comparison and a combination of the proposed methods on a 3D academic application, showing promising performances. Conclusions are then drawn to provide indications for future research and tests to be conducted in order to further enhance the methodologies proposed in this thesis.Dans le contexte de lutte contre les nuisances sonores, cette thèse porte sur le développement de méthodes de résolution efficaces par éléments finis, pour des problèmes de vibroacoustique interne avec interfaces dissipatives, dans le domaine des basses fréquences. L’étude se limite à l’utilisation de solutions passives telles que l’intégration de matériaux poreux homogènes et isotropes, modélisés par une approche fondée sur la théorie de Biot-Allard. Ces modèles étant coûteux en terme de résolution, un des objectifs de cette thèse est de proposer une approche modale pour la réduction du problème poroélastique, bien que l’adéquation d’une telle approche avec le comportement dynamique des matériaux poreux soit à démontrer.Dans un premier temps, la résolution de problèmes couplés élasto-poro-acoustiques par sous-structuration dynamique des domaines acoustiques et poreux est établie. L’approche modale originale proposée pour les milieux poroélastiques, ainsi qu’une procédure de sélection des modes significatifs, sont validées sur des exemples 1D à 3D.Une deuxième partie présente une méthode combinant l’utilisation des modèles réduits précédemment établis avec une procédure d’approximation de solution par approximants de Padé. Il est montré qu’une telle combinaison offre la possibilité d’accroître les performances de la résolution (allocation mémoire et ressources en temps de calcul).Un chapitre dédié aux applications permet d’évaluer et comparer les approches sur un problème académique 3D, mettant en valeur leurs performances encourageantes. Afin d’améliorer les méthodes établies dans cette thèse, des perspectives à ces travaux de recherche sont apportées en conclusion.
QC 20120224
FP6 Marie-Curie Smart Structures
FP7 Marie-Curie Mid-Frequency
24
Rumpler, Romain. "Efficient finite element approach for structural-acoustic applicationns including 3D modelling of sound absorbing porous materials." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2012. http://tel.archives-ouvertes.fr/tel-00726915.
Анотація:
In the context of interior noise reduction, the present work aims at proposing Finite Element (FE) solution strategies for interior structural-acoustic applications including 3D modelling of homogeneous and isotropic poroelastic materials, under timeharmonic excitations, and in the low frequency range. A model based on the Biot-Allard theory is used for the poroelastic materials, which is known to be very costly in terms of computational resources. Reduced models offer the possibility to enhance the resolution of such complex problems. However, their applicability to porous materials remained to be demonstrated.First, this thesis presents FE resolutions of poro-elasto-acoustic coupled problems using modal-based approaches both for the acoustic and porous domains. The original modal approach proposed for porous media, together with a dedicated mode selection and truncation procedure, are validated on 1D to 3D applications.In a second part, modal-reduced models are combined with a Padé approximants reconstruction scheme in order to further improve the efficiency.A concluding chapter presents a comparison and a combination of the proposed methods on a 3D academic application, showing promising performances. Conclusions are then drawn to provide indications for future research and tests to be conducted in order to further enhance the methodologies proposed in this thesis.
25
Anderson, Michele Lynn 1968. "Characterization of organic/organic' and organic/inorganic heterojunctions and their light-absorbing and light-emitting properties." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282555.
Анотація:
Increasing the efficiency and durability of organic light-emitting diodes (OLEDs) has attracted attention recently due to their prospective wide-spread use as flat-panel displays. The performance and efficiency of OLEDs is understood to be critically dependent on the quality of the device heterojunctions, and on matching the ionization potentials (IP) and the electron affinities (EA) of the luminescent material (LM) with those of the hole (HTA) and electron (ETA) transport agents, respectively. The color and bandwidth of OLED emission color is thought to reflect the packing of the molecules in the luminescent layer. Finally, materials stability under OLED operating conditions is a significant concern. LM, HTA, and ETA thin films were grown in ultra-high vacuum using the molecular beam epitaxy technique. Thin film structure was determined in situ using reflection high energy electron diffraction (RHEED) and ex situ using UV-Vis spectroscopy. LM, HTA, and ETA occupied frontier orbitals (IP) were characterized by ultraviolet photoelectron spectroscopy (UPS), and their unoccupied frontier orbitals (EA) estimated from UV-Vis and fluorescence spectroscopies in combination with the UPS results. The stability of the molecules toward vacuum deposition was verified by compositional analysis of thin film X-ray photoelectron spectra. The stability of these materials toward redox processes was evaluated by cyclic voltammetry in nonaqueous media. Electrochemical data provide a more accurate estimation of the EA since the energetics for addition of an electron to a neutral molecule can be probed directly. The energetic barriers to charge injection into each layer of the device has been correlated to OLED turn-on voltage, indicating that these measurements may be used to screen potential combinations of materials for OLEDs. The chemical reversibility of LM voltammetry appears to limit the performance and lifetimes of solid-state OLEDs due to degradation of the organic layers. The role of oxygen as an electron trap in OLEDs has also been verified electrochemically. Finally, a more accurate determination of the offset of the occupied energy levels at the interface between two organic layers has been achieved via in situ monitoring of the UPS spectrum during heterojunction formation.
26
Makoundou, Ngongo Christina Jessie <1994>. "Vulnerable users' protection with advanced recycling paving materials. Design and characterisation of rubber-based impact-absorbing pavement materials for bike lanes and sidewalks." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10411/1/FINAL_THESIS_MAKOUNDOU_MAY_2022.pdf.
Анотація:
Our cities are constantly evolving, and the necessity to improve the condition and safety of the urban infrastructures is fundamental. However, on the roads, the specific needs of cyclists and pedestrians are often neglected.
The Vulnerable Road Users (VRUs), among whom cyclists and pedestrians are, rarely benefit from the most innovative safety measures. Inspired by playgrounds and aiming to reduce VRUs injuries, the Impact-Absorbing Pavements (IAP) developed as novel sidewalks, and bike lanes surface layers may help decrease injuries, fatalities, and the related societal costs. To achieve this goal, the End-of-Life Tyres (ELTs) crumb rubber (CR) is used as a primary resource, bringing its elastic properties into the surface layer.
The thesis is divided into five main chapters. The first concerns the formulation and the definition of a feasible mix. The second explores the mechanical and environmental properties in detail, and the ageing effect is also assessed. The third describes the modelling of the material to simulate accidents and measure the injury reduction, especially on the head. The fourth chapter is reserved for the field trial. The last gives some perspectives on the research and proposes a way to optimize and improve the data and results collected during the doctoral research.
It was observed that the specimens made with cold protocol have noticeable performances and reduce the overall carbon footprint impact of this material. The material modelling and the accident simulation proved the performance of the IAP against head injuries, and the field trial confirmed the good results obtained in the laboratory for the cold-made material.
Finally, the outcomes of this thesis opened many prospective to the IAP development, such as the use of a plant-based binder or recycled aggregates and gave a positive prospect of an innovative material to the urban road infrastructures.
27
Fast, Jonatan. "Investigation of Bismuth Iodine as Light Absorbing Materials for Solar Cell Applications: From Synthesis to XPS Characterisation." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331340.
Анотація:
During the last years perovskite materials have taken the photovoltaic community by storm, bringing promises of solar cells with efficiencies comparable to conventional silicon devices but at a lower price. However perovskite solar cells so far are facing two main obstacles, they are unstable in the presence of air, moisture and heat and they are usually toxic due to being based on lead-halide materials. This has spurred investigations into alternative materials with similar properties but without the mentioned drawbacks. Just next to Pb in the periodic table is bismuth (Bi) with just one more electron in its outer-shell, Bi however is less toxic. In this work the perovskite derived compounds of Ag-Bi-I and Cu-Bi-I are characterized and their properties as light absorbing material in solar cell devices are investigated. Devices are prepared by preparing Ag-Bi-I and Cu-Bi-I solutions which are then spin-coated on top of a mesoporous TiO2. A conducting polymer, P3HT, was then deposited and serve as hole transport material. For Ag-Bi-I, the molar ratios of AgI:BiI3= 1:2 and 2:1 were observed with SEM to form homogeneous crystal films with one dominating crystal phase, which by XRD could be determined to most likely have formed a cubic AgBi2I7 crystal structure for the 1:2 ratio and a hexagonal Ag2BiI5 crystal structure for the 2:1 ratio. The Cu-Bi-I materials were not successfully synthesized to form homogeneous films with a dominating crystal phase, although several molar ratios were investigated. All investigated compositions of both Cu and Ag devices showed to in principle work as light absorbing materials, the best Ag-Bi-I device showing a PCE of 1.92%, for the 2:1 ratio, while the Cu-Bi-I devices at best reached 0.32% for a ratio of 1:1. XPS measurements were carried out with a classical in-house XPS using an Al K X-ray source of 1486.7 eV as well as at the Diamond Light Source (UK) synchrotron facility using photon energies of 758 eV and 2200 eV so that a depth resolution of the composition could be observed. Because of their inhomogeneous crystal formation, XPS couldn’t give much useful quantitative information regarding the Cu devices. For Ag devices it was observed that the stoichiometry at the extreme surface deviated from that predicted by XRD, but deeper into the surface the relative ratio of elements approach the predicted ones, hinting towards a different structure at the outermost surface or a lot of surface defects. For all samples, two types of bismuth atoms were observed, metallic (Bi0) as well as a cationic (Bi+x), the later corresponding to Bi atoms which are partaking in the crystal bond. The ratio of metallic to cationic Bi was observed to decrease notably just a few nm below the extreme surface. The effect of the high presence of metallic Bi on final device performance was not concluded with certainty but not believed to be positive. By varying the annealing temperature, after spin coating the light absorber solution on the TiO2, it was observed that lower temperature resulted in a lower ratio of metallic Bi. As final conclusions, it was said that the synthesis method of Cu-Bi-I needs to be improved before those materials can be studied further. The synthesis of Ag-Bi-I is showing much more promise and one can start looking into further optimizing their final device structure to boost efficiency. Both Cu-Bi-I and Ag-Bi-I devices are relatively simple, cheap and energy efficient (with annealing temperatures around 150C) to produce, great aspects for solar cells. UVVis measurements showed they have band gaps around 1.6-1.7 eV which makes them a great potential material for use in tandem solar cells together with a semiconductor of lower band gap such as silicon.
28
Young, Aaron Cody. "Optical applications of two-photon and microexplosion lithography /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/9780.
29
DeArmond, Fredrick Michael. "Two-Photon Excitation, Fluorescence Microscopy, and Quantitative Measurement of Two-Photon Absorption Cross Sections." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/4036.
Анотація:
As optical microscopy techniques continue to improve, most notably the development of super-resolution optical microscopy which garnered the Nobel Prize in Chemistry in 2014, renewed emphasis has been placed on the development and use of fluorescence microscopy techniques. Of particular note is a renewed interest in multiphoton excitation due to a number of inherent properties of the technique including simplified optical filtering, increased sample penetration, and inherently confocal operation. With this renewed interest in multiphoton fluorescence microscopy, comes an increased demand for robust non-linear fluorescent markers, and characterization of the associated tool set.
These factors have led to an experimental setup to allow a systematized approach for identifying and characterizing properties of fluorescent probes in the hopes that the tool set will provide researchers with additional information to guide their efforts in developing novel fluorophores suitable for use in advanced optical microscopy techniques as well as identifying trends for their synthesis.
Hardware was setup around a software control system previously developed [1]. Three experimental tool sets were set up, characterized, and applied over the course of this work. These tools include scanning multiphoton fluorescence microscope with single molecule sensitivity, an interferometric autocorrelator for precise determination of the bandwidth and pulse width of the ultrafast Titanium Sapphire excitation source, and a simplified fluorescence microscope for the measurement of two-photon absorption cross sections.
Resulting values for two-photon absorption cross sections and two-photon absorption action cross sections for two standardized fluorophores, four commercially available fluorophores, and ten novel fluorophores are presented as well as absorption and emission spectra.
30
Kiani, Ghaffer I. "Passive, active and absorbing frequency selective surfaces for wireless communication applications." Phd thesis, Australia : Macquarie University, 2008. http://hdl.handle.net/1959.14/76611.
31
Al-Hilo, Naeem A. "Novel Sound Absorbing Materials Made From Elastomeric Waste: Compounding And Structuring Of Elastomeric Waste Crumb And Fibers With Binders Into Innovative Noise Insulation Materials." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/17383.
Анотація:
Elastomeric wastes plague our time, polluting our environment and requiring urgent upcycling solutions. This research contributes to this agenda using an important source of waste, car tyre shred fibre residue (TSFR). It is demonstrated how using binders, non-foaming (SBR) and foaming (PU), we can transform these TSFR into structured porous acoustic-thermal insulation materials, suitable as underlay, cavity wall and pipe insulation. These structures were fabricated in purpose designed moulds and characterised for their porosity, tortuosity, flow resistivity and density. Their acoustic absorption performance was measured using industrial standards and the measurement underpinned with the Johnson-Champoux-Allard (JCA) model. With the under-layer materials, thermal insulation was also measured.
The results were as follows: (i) 40%/60% SBR/TSFR was an optimal composition for the underlay with the addition of 15% w/w bumper crumb of size > 1mm enhancing both impact sound and thermal insulation, (ii) PU was found to produce well performing wall cavity insulation, particularly when vacuum pressure was applied, allowing micro and macro pores to be formed; (iii) PU applied with controlled amount of water to control foaming CO2 formation produced super-performing (compared with Armacell System B) stratified pipe cladding insulation, optimal at porosity stratification of 90%, 83%, and 70%; (iv) Very good agreement was observed with predictions using JCA model, allowing further research to be carried out with these now well characterised sound insulations.
In addition to the developing materials, a novel technique for measuring sound absorption of pipe cladding was developed that could replace the expensive standard using a reverberation chamber.
32
Gapin, Adèle. "Elaboration of functional copolymers absorbing in the near infrared region." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3034.
Анотація:
De nos jours, les matériaux organiques absorbant dans la région du proche infrarouge ont trouvé un terrain fertile dans une variété d'applications et ont contribué de manière significative à l'amélioration des dispositifs optoélectroniques, de la bioimagerie, de la biodétection et des thérapies biomédicales. Le développement de polymères à faible bande interdite retient particulièrement l'attention car leurs bandes interdites réduites conduisent à des propriétés optiques et électroniques intéressantes. La fonctionnalisation de ces polymères conjugués en bout de chaînes ouvre la voie au développement de matériaux hybrides susceptibles d'améliorer les performances des dispositifs optoélectroniques. En outre, les copolymères à blocs rigide-flexible intégrant des polymères à faible bande interdite sont désormais accessibles et pourraient fournir une plus large absorption de la lumière, une meilleure solubilité, ainsi que des propriétés d'auto-assemblage. Dans ce contexte, l'objectif de nos travaux a été de développer des matériaux innovants à base de polymères à faible bande interdite absorbant dans le domaine spectral 650-1000 nm afin d'obtenir des matériaux actifs dans la région proche infrarouge. Nous avons synthétisé un nouveau matériau hybride en greffant un polymère à faible bande interdite sur des nanosphères de ZnO via la technique de grafting onto. Nous avons conçu et préparé des copolymères à blocs rigide-flexible intégrant un bloc à faible bande interdite via deux méthodes de synthèse. Le premier copolymère est composé d'un bloc flexible aux propriétés filmogènes que nous prévoyons d'utiliser comme additif dans l'élaboration de photodétecteurs infrarouges organiques. Le second copolymère présente un bloc flexible biocompatible et hydrophile afin d'obtenir des nano-objets hydrosolubles aux propriétés photothermiquesNowadays, organic materials absorbing in the near infrared region have found fertile ground in a variety of applications and have significantly contributed in improving optoelectronic devices, bioimaging, biosensing, and biomedical therapies. The development of low band-gap polymers draw particular attention since their reduced bandgaps determine interesting optical and electronic properties. The end-functionalization of these conjugated polymers paves the way to the development of hybrid materials which could improve the performances of optoelectronic devices. Furthermore, rod-coil block copolymers incorporating low band-gap polymers are reachable and could provide broader light absorption, better solubility, as well as self-assembly properties. In this context, the objective of our work was to develop innovative materials based on low band-gap polymers absorbing in the spectral range 650-1000 nm in order to obtain active materials in the near infrared region. We synthesized a new hybrid material by grafting a low band-gap polymer onto ZnO nanospheres via the grafting onto technique. We designed and prepared rod-coil block copolymers involving a low band-gap block via two synthetic method. The first copolymer was based on the use of a coil block with filmogenic properties which we plan to employ as additive in the elaboration of organic infrared photodetectors. The second copolymer was based on the use of a hydrophilic biocompatible coil block in order to obtain water soluble nano-objects with photothermal properties
33
Tan, Elvan. "Characterization Of Electromagnetic Wave Absorbing Properties Of Sic-based And Alumina Ceramic Woven Fabrics." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609619/index.pdf.
Анотація:
Electromagnetic wave absorbing properties of SiC-based and alumina ceramic woven fabrics have been investigated. Electrical conductivities of SiC-based ceramic woven fabrics were modified by heat treatment in air resulting in their oxidation. Surface properties of alumina woven fabrics were altered by gold-sputtering resulting in a high conductivity layer on the surface of the wovens. Electromagnetic wave interactions of single layer and double layered combinations of these ceramic woven fabrics were determined in 17-40 GHz frequency range using &ldquofree-space&rdquo
method. Electromagnetic wave absorption potential of ceramic woven fabrics with different chemical compositions and woven types were correlated with their material properties by X-ray diffraction, scanning electron microscopy and electrical conductivity measurements. Effects of modifications and varying woven fabric arrangements in combinations on the electromagnetic wave absorption potential of the ceramic woven fabrics have been discussed. Various double layer combinations of SiC-based and alumina woven fabrics revealed a promising potential in terms of both reduced reflection and transmission resulting in more than ~95% absorption in millimeter wavelength range, which makes them powerful candidate materials for electromagnetic wave absorption applications.
34
Kiani, Ghaffer I. (Ghaffer Iqbal). "Passive, active and absorbing frequency selective surfaces for wireless communication applications." Australia : Macquarie University, 2008. http://hdl.handle.net/1959.14/76611.
Анотація:
"March, 2009".Thesis (PhD)--Macquarie University, Faculty of Science, Dept. of Physics & Engineering, 2008.
Bibliography: p. 145-158.
Introduction -- Frequency selective surfaces -- Absorb/transmit frequency selective surface absorber -- Switchable frequency selective surface for wireless applications -- Energy-saving glass characterisation -- Frequency selective surface solution for energy-saving glass -- Conclusion.
This thesis presents three topics related to frequency selective surfaces (FSSs), namely bsorb/transmit FSSs, active FSSs and passive bandpass FSSs for energy-saving glass used in modern buildings. These three FSSs are unique in their design and functionalities. The absorb/transmit FSS is a novel dual-layer frequency selective surface for 5 GHz WLAN applications. This FSS can stop propagation of specific bands by absorbing as opposed to re ecting, while passing other useful signals. This is in contrast to the conventional Salisbury and Jaumann absorbers, which provide good absorption in the desired band while the out-of-band frequencies are attenuated. The second topic is a single-layer bandpass active FSS that can be switched between ON and OFF states to control the transmission in 2.45 GHz WLAN applications. Previously, researchers have focused on the bandstop and dual-layer versions of the active FSS. This is in contrast to the design presented in this thesis which is single-layer and provides extra advantage in a practical WLAN environment. Also the dc biasing techniques that were used for the active FSS design are easier to implement and provide good frequency stability for different angles of incidence and polarisations in both ON and OFF states. The last topic is on the use of a bandpass FSS in energy-saving glass panels used in building design. The manufacturers of these glass panels apply a very thin metal-oxide coating on one side of the glass panels to provide extra infrared (heat) attenuation. However, due to the presence of the coating, these energy-saving glass panels also attenuate communication signals such as GSM 900, GSM 1800/1900, UMTS and 3G mobile signals etc. This creates a major communication problem when buildings are constructed with windows of this glass. In this thesis, a solution to this problem is presented by designing and etching a cross-dipole bandpass FSS on the coated side of the glass to pass the useful signals while keeping infrared attenuation at an acceptable level. One of the advantages of this FSS design is that measured material values of the metal-oxide coating are used for simulations, which have not been done previously.
Mode of access: World Wide Web.
166 p. ill. (some col.)
35
Pessoa, R?gia Chacon. "Estudo das caracter?sticas magn?ticas e absorvedoras das ferritas de nizn, niznmn, mnzn, nimg, nicuzn e nicuznmg obtidas via m?todo do citrato precursor." Universidade Federal do Rio Grande do Norte, 2009. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17716.
Анотація:
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Previous issue date: 2009-12-22Universidade Estadual de Roraima
Were synthesized systems Ni0,5Zn0,5Fe2O4, i0,2Zn0,5Mn0,3Fe2O4, Mn0,5Zn0,5Fe2O4, Ni0,5Mg0,5Fe2O4, Ni0,2Cu0,3Zn0,5Fe2O4 and Ni0,2Cu0,3Zn0,5Mg0,08Fe2O4, the precursors citrate method. The decomposition of the precursors was studied by thermogravimetric analysis and spectroscopy in the infrared region, the temperature of 350?C/3h. The evolution of the phases formed after calcinations at 350, 500, 900 and 1100?C/3h was accompanied by X-ray diffraction using the Rietveld refinement to better identify the structures formed. The materials were also analyzed by scanning electron microscopy, magnetic measurements and analysis of the reflectivity of the material. The samples calcined at different temperatures showed an increase of crystallinity with increasing calcination temperature, verifying that for some compositions at temperatures above 500?C precipitates of second phase such as hematite and CuO. The compositions of manganese present in the structure diffusion processes slower due to the ionic radius of manganese is greater than for other ions substitutes, a fact that delays the stabilization of spinel structure and promotes the precipitation of second phase. The compositions presented with copper precipitation CuO phase at a temperature of 900 and 1100?C/3h This occurs according to the literature because the concentration of copper in the structure is greater than 0.25 mol%. The magnetic measurements revealed features of a soft ferrimagnetic material, resulting in better magnetic properties for the NiZn ferrite and NiCuZnMg at high temperatures. The reflectivity measurements showed greater absorption of electromagnetic radiation in the microwave band for the samples calcined at 1100?C/3h, which has higher crystallite size and consequently the formation of multi-domain, increasing the magnetization of the material. The results of absorption agreed with the magnetic measurements, indicating among the ferrites studied, those of NiZn and NiCuZnMg as better absorbing the incident radiation.
Foram sintetizados os sistemas Ni0,5Zn0,5Fe2O4, Ni0,2Zn0,5Mn0,3Fe2O4, Mn0,5Zn0,5Fe2O4, Ni0,5Mg0,5Fe2O4, Ni0,2Cu0,3Zn0,5Fe2O4 e Ni0,2Cu0,3Zn0,5Mg0,08Fe2O4, pelo m?todo dos citratos precursores. A decomposi??o dos precursores foi estudada por an?lise termogravim?trica e espectroscopia na regi?o do infravermelho, na temperatura de 350?C/3h. A evolu??o das fases formadas ap?s as calcina??es a 350, 500, 900 e 1100?C/3h foi acompanhada por difra??o de raios X utilizando o refinamento de Rietveld, para melhor identifica??o das estruturas formadas. Os materiais foram tamb?m analisados por microscopia eletr?nica de varredura, medidas magn?ticas e an?lise da refletividade do material. As amostras calcinadas em diferentes temperaturas indicaram um aumento da cristalinidade com o aumento da temperatura de calcina??o, verificando-se que, para algumas composi??es, em temperaturas acima de 500?C ocorre a precipita??o de segunda fase, como hematita e CuO. As composi??es com mangan?s na estrutura apresentaram processos de difus?o mais lentos devido ao raio i?nico do mangan?s ser maior em rela??o aos outros ?ons substituintes, fato que retarda a estabiliza??o da estrutura espin?lio e favorece a precipita??o de segunda fase. As composi??es com cobre apresentaram precipita??o da fase CuO na temperatura de 900 e 1100?C/3h, fato que ocorre segundo a literatura porque a concentra??o de cobre na estrutura ? maior que 0,25 mol%. As medidas magn?ticas revelaram racter?sticas de um material ferrimagn?tico macio, obtendo-se melhores ar?metros magn?ticos para as ferritas de NiZn e NiCuZnMg em altas temperaturas. As medidas de refletividade mostraram maior absor??o da radia??o eletromagn?tica na faixa de microondas para as amostras calcinadas a 1100?C/3h, que tem maior tamanho do cristalito e em conseq??ncia forma??o de multidom?nios, aumentando a magnetiza??o do material. Os resultados de absor??o concordaram com as medidas magn?ticas, indicando dentre as ferritas estudadas, as de NiZn e NiCuZnMg como melhores absorvedoras da radia??o incidente.
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Wu, Ruimeng. "UTILIZATION OF EMPIRICAL MODELS TO DETERMINE THE BULK PROPERTIES OF COMPRESSED SOUND ABSORPTIVE MATERIALS." UKnowledge, 2017. https://uknowledge.uky.edu/me_etds/106.
Анотація:
Empirical models based on flow resistivity are commonly used to determine the bulk properties of porous sound absorbing materials. The bulk properties include the complex wavenumber and complex characteristic impedance which can be used directly in simulation models. Moreover, the bulk properties can also be utilized to determine the normal incidence sound absorption and specific acoustic impedance for sound absorbing materials of any thickness and for design of layered materials. The sound absorption coefficient of sound absorbing materials is measured in an impedance tube using wave decomposition and the measured data is used to determine the flow resistivity of the materials by least squares curve fitting to empirical equations. Results for several commonly used foams and fibers are tabulated to form a rudimentary materials database. The same approach is then used to determine the flow resistivity of compressed sound absorbing materials. The flow resistivities of the compressed materials are determined as a function of the compression ratio. Results are then used in conjunction with transfer matrix theory to predict the sound absorptive performance of layered compressed absorbers with good agreement to measurement.
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Ohira, Shino. "Theoretical evaluation of the nonlinear optical properties of extended and π-conjugated chromophores". Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29717.
Анотація:
The nonlinear optical (NLO) properties were investigated in various extended π-conjugated chromophores: cyanine and alkyne carbocations; porphyrin dimers; and squaraine compounds that possess electronic, double resonance, and vibronic based NLO properties. In summary: (i) It was demonstrated that the alkyne carbocations have very similar optical properties to traditional cyanine dyes. Our theoretical results establish that the alkyne carbocations, in spite of their significant degree of bond-length alternation, behave in the same way as cyanine dyes. (ii) The nature of the -bridge in porphyrin dimers tunes the electronic coupling strength, which in turn determines the splitting of the energy levels and the (non)linear optical properties. (iii) We have shown that the origin of the lowest TPA-active states in squaraines is dependent on the nature of substituent donor moiety, changing from predominantly electronic to vibronic in character. For all squaraines containing indolinylidenemethyl donors, a vibronic origin for the TPA peak, and the energy and lineshape of the experimentally observed lowest TPA peak in these compounds were confirmed.
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Li, Li. "Detection of Proteins by Two-Photon Excitation of Native Fluorescence." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1548.pdf.
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Parra, Martinez Juan Pablo. "On the ECO2 multifunctional design paradigm and tools for acoustic tailoring." Licentiate thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-161209.
Анотація:
Nowadays vehicle design paradigm influences not only the effectiveness of the different means of transport, but also the environment and economy in a critical way. The assessment of the consequences that design choices have on society at large are necessary to understand the limits of the methods and techniques currently employed. One of the mechanisms set in motion is the planned obsolescence of products and services. This has affected vehicle design paradigm in such a way that the variety in the market has shadowed the primary function of vehicle systems: the transport of persons and goods. Amongst the consequences of the expansion of such market is the exponential rise on combustion emissions to the atmosphere, which has become a great hindrance for humans health and survival of ecosystems. The development of evaluation tools for such consequences and their piloting mechanisms is needed so as to implement an ECO2 (Ecological and Economical) vehicle design paradigm. Moreover, the multifunctional design paradigm that drives aeronautical and vehicle engineering is an ever-growing demand of smart materials and structures, able to fulfil multiple requirements in an effective way. The understanding of certain phenomena intrinsic to the introduction of novel materials has found certain limits due to the complexity of the models needed. This work presents as a first step an assessment of the causes and consequences of the vehicle exponential market growth based on the analysis of the planned obsolescence within. Furthermore, a method for the acoustic response analysis of multilayered structures including anisotropic poroelastic materials is introduced. The methodology consists in a plane wave approach as a base for introducing the complex mechanic and acoustic equations governing anisotropic homogeneous media, e.g. open-celled foams, into an alternative mathematical tool manipulating physical wave amplitudes propagation within the studied media. In addition, this method is coupled to a power partitioning and energetic assessment tool so as to understand the phenomena present in complex multilayered designs.QC 20150323
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Jamois, Alexis. "Modélisation et réalisation d'absorbants acoustiques par impression 3D : étude en incidence normale et application au traitement d'un conduit." Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0010.
Анотація:
Au cours des dernières années, il est devenu possible de réaliser des absorbants acoustiques dont la géométrie était difficile à produire auparavant, grâce au perfectionnement des techniques d’impression 3D. La facilité d’utilisation et les prix abordables de ces techniques permettent d’imaginer la conception de dispositifs absorbants sur mesure pour répondre à une demande spécifique très rapidement. Cela nécessite d’une part de pouvoir imprimer précisément les géométries conçues et d’autre part de pouvoir prédire la performance acoustique des matériaux imprimés dans la configuration souhaitée. Les objectifs de cette thèse sont d’étudier l’effet de la variabilité des dimensions d’échantillons produits par impression 3D sur la performance acoustique et d’examiner différentes méthodes pour prédire la performance acoustique allant d’approches microscopiques complètes mais coûteuses, à des approches macroscopiques rapides mais simplifiées. La stéréolithographie a été choisie pour imprimer les échantillons à la suite d’une revue des moyens d’impression évalués dans la littérature. Les géométries étudiées consistent en un empilement de volumes (sphériques ou cubiques), reliés dans les trois directions de l’espace par des canaux à l’image de cristaux cubiques. Une variante à double réseau permet également d’ouvrir quelques pistes en vue d’une optimisation des performances acoustiques. Pour étudier l’effet de la variabilité, un grand nombre d’échantillons a été fabriqué avec différents jeux de paramètres d’impression et les dimensions caractéristiques des échantillons produits ont été mesurées. Un choix judicieux des paramètres permet de réduire la dispersion. La pertinence d’une approche fluide équivalent est montrée : elle permet de reproduire fidèlement et à coût réduit les résultats d’une approche directe résolvant les équations de Navier-Stokes linéarisées dans les pores des échantillons. Dans cette approche, les paramètres JCAPL des fonctions du fluide équivalent sont identifiés à partir d’un volume élémentaire représentatif de l’échantillon. Les échantillons sont d’abord étudiés en incidence normale. Le caractère très résonnant des matériaux rend le coefficient d’absorption très sensible à tout écart entre les dimensions cibles et les dimensions effectivement réalisées. Il en est ainsi pour les dimensions intérieures (diamètre des sphères ou des canaux) et pour le diamètre propre de l’échantillon. La nature rigide des échantillons produits par impression 3D rend très délicate leur adaptation stricte au diamètre du tube de Kundt. Les résultats de la mesure et les prédictions sont cependant globalement en bon accord et confirment dans ce cas classiquement traité dans la littérature, la validité du modèle de fluide équivalent. Des échantillons ont été ensuite réalisés spécifiquement pour être testés en paroi de conduit, par mesure de la perte par transmission. Les résultats expérimentaux confirment là aussi la pertinence de l’utilisation de l’approche fluide équivalent pour prédire les performances de ce type de matériau dans des conditions moins classiquesConventional rigid porous materials such as wools or foams do not provide effective absorption at low frequencies in complex industrial environments. For these applications, the structures developed are generally quarter-wave resonators or Helmholtz resonators. In recent years, 3D printing techniques have made it possible to produce resonator geometries that were previously difficult to produce. The ease of use and affordability of these techniques means that it is now possible to create tailor-made absorbing devices to meet specific requirements very quickly. This long-term objective requires, on the one hand, validation of the reliability of the dimensions obtained during the production of absorbent structures and, on the other hand, the ability to effectively model a variety of geometries in different contexts. In this thesis, stereolithography was chosen to print the samples based on literature results. Studies have concluded that it is more accurate for acoustic devices than other techniques. The geometry chosen for this study consists in a stack of volumes (spherical or cubic), connected in the three directions of space by channels in the image of cubic crystals. A large number of samples were manufactured varying the production parameters in order to measure the variability of the characteristic dimensions of the samples. Among the various modelling approaches presented, the numerical tests carried out led to the choice of equivalent fluid modelling based on the identification of JCAPL parameters. They are identified in a representative volume homogenised throughout the sample. This homogenisation of behaviour is suited to the geometries studied because of their periodic nature. The reaction of the geometries we are considering makes impedance modelling impossible. The samples are first studied at normal incidence, in order to link the variability of realisation to the measured acoustic behaviour. The measurement results and the predictions are in good agreement. Some samples were made specifically for duct wall measurement, in order to validate the use of the equivalent fluid approach. These tests were also used to confirm the conclusions drawn for normal incidence. The variability of the geometry has a real impact on the acoustic behaviour, but the main problem with rigid 3D printed samples is their adaptation to the measurement benches
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Lanoye, Reinhilde. "Assessment of the absorption performance of sound absorbing materials : use of the Trefftz's method and of a new dual particle velocity-pressure sensor." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0031/these.pdf.
Анотація:
Porous absorbing materials are applied in various fields of sound and noise control. The presented work wants to deliver a numerical simulation tool to predict the acoustical behavior of geometrically complex sound absorbing media under various excitations. To achieve this goal, a deterministic method, which is based on the indirect Trefftz's method and which makes use of solution functions of the governing equations to describe the field variables int he region of interest, is extented to analyze the sound field in and above porous absorbers. The model is experimentally validated and used to analyze the sound field in some real-life configurations. Afterwards, an initial impetus is given towards the further analysis of the absorption performance of various kinds of patchworks under different angles of sound incidence and the study of sound propagation over impedance jumps, with the aid of a model applicable to unbounded problems. Besides the development of the simulation tool, a new dual particle velocity-pressure measurement technique is presentedLes matériaux poreux absorbants constituent une solution avantageuse pour contrôler la qualité du son dans un espace. Le travail présenté propose un outil numérique de simulation en état de prévoir le comportement acoustique des matériaux absorbants géométriquement complexes sous des excitations diverses. Dans ce but, une méthode déterministe est développée pour analyser le champ sonore dans et au-dessus des poreux. La méthode est basée sur la méthode indirecte de Trefftz et se sert de fonctions qui vérifient les équations du problème pour décrire les variables dans la région d'intérêt. Le modèle est expérimentalement validé et employé pour analyser le champ sonore dans quelques configurations réelles. Ensuite, une première impulsion est donnée vers l'analyse du comportement absorbant de matériaux de genres divers à plusieurs angles d'incidence et vers l'étude de la propagation du son proche d'un changement brusque d'impédance, à l'aide d'un modèle applicable aux problèmes infinis. Après le développement de l'outil de simulation, un nouveau capteur mixte de vitesse particulaire et de pression est présenté
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Siegel, Nisan Naftali. "Two-photon absorption in cruciform and dipolar chromophores: excitonic interactions and response to metal ions." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41127.
Анотація:
Structure-property relationships for two-photon absorption (2PA) in branched organic chromophores is a topic of current interest, as is the design of chromophores with advantageous properties for two-photon laser scanning microscopy (2PLSM). The main goals of this dissertation were to study and explain the one-photon absorption (1PA) and 2PA properties of cruciform chromophores based on 1,4-distyryl-2,5-bis(phenylethynyl)benzene with varying electron donor (D) and acceptor (A) groups, and to characterize the 2PLSM-relevant response of some of these chromophores and a set of dipolar chromophores to binding with zinc ions. The compounds were studied by 1PA, fluorescence and 2PA spectroscopy. A ππ* exciton model was developed to explain the spectral properties of the 1,4-distyryl-2,5-bis(phenylethynyl)benzene cruciform with no D or A groups or with four identical D groups at the termini of the linear arms of the chromophore. This model indicated that there is some coupling and mixing of the lowest excited states e of the linear arms, leading to splitting of the 1PA spectrum of the cruciform. There was little coupling or mixing of the higher excited states e′ accessed in 2PA, leading to a two-band 2PA spectrum for the chromophore, in contrast to cruciform compounds in the literature with identical conjugated arms, which have one visible 2PA band. For cruciforms with D groups on the styryl arm and A character on the terminal phenyls of the phenylethynyl arms (D/A cruciforms), the ππ* exciton model was complemented with a charge-transfer (CT) exciton model describing interactions of charge-transfer pathways between the D and A groups. This model explained the broadness of the 1PA band of D/A cruciforms as well as the two 2PA bands observed for these chromophores.
The fluorescence and 2PA spectral responses to binding of Zn²⁺ ions to the D or A groups of some cruciform compounds were also assessed, to provide insight into the design of new analyte-sensing cruciforms for 2PLSM that take advantage of enhancement or reduction of D/A character upon analyte binding. It was found that canceling charge donation from the D groups in differing D/A cruciforms resulted in fluorescence and 2PA spectra nearly indistinguishable from each other, suggesting that turn-off of D groups is not an optimal modality of 2PLSM analyte sensing in cruciforms. Binding Zn²⁺ to A groups was shown to result in an increase in the D/A character of the cruciform, with fluorescence peak energies that changed depending on the location of the A group. It is suggested that the use of non-binding donors and analyte-binding A groups in differing patterns on the arms could be a valuable design motif to achieve 2PLSM sensor compounds based on this cruciform structure.
The 2PA spectra of a set of dipolar Zn²⁺ sensing dyes designed for ratiometric imaging in 2PLSM were also studied. These dyes had moderate 2PA strength, with redshifts of fluorescence 2PA spectra on Zn²⁺ binding. The isosbestic point of 2PA of most chromophores was within the range of 2PLSM excitation sources commonly used, rendering these dyes good candidates for use in ratiometric sensing in 2PLSM.
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Nootz, Gero. "Experimental and theoretical study of the optical properties of semiconductor quantum dots." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4581.
Анотація:
The aim of this dissertation is to gain a better understanding of the unique electronic structure of lead salt quantum dots (QDs) and its influences on the nonlinear optical (NLO) properties as well as the time dynamics of the photogenerated charge carriers. A variety of optical techniques such as Z-scan, two-photon excited fluorescence and time-resolved pump probe spectroscopy are used to measure these properties. The one-photon as well as the degenerate and nondegenerate two-photon absorption (2PA) spectra are measured and the electronic wave functions from a four-band envelope function formalism are used to model the results. We observe local maxima in the 2PA spectra for QD samples of many different sizes at energies where only 1PA is predicted by the model. This is similar to the previously measured transitions in the 1PA spectra which are not predicted by the model but accrue at the energies of the two-photon allowed transitions. Most importantly we observe 2PA peaks for all samples at the energy of the first one-photon allowed transition. This result can only be understood in terms of symmetry breaking and therefore is strong evidence that other transitions, not predicted by the model if the selection rules are left intact, also have the origin in the lifted spatial symmetry of the wave functions. On the other hand, the uniquely symmetric eigenenergies of these quantum-confined energy states in the conduction and valance bands explain the observed trend toward larger two-photon cross-sections as the quantum confinement is increased in smaller QDs. Moreover, this unique feature is shown to reduce the possible relaxation channels for photoexcited carriers, which is confirmed experimentally by the reduced carrier relaxation rate as compared to CdSe QDs which lack this symmetry. Carrier multiplication (CM), a process in which several electrons are excited by the absorption of a single photon is studied in PbS QDs.; We show that for PbS QDs with radius smaller than 2.5 nm the parameters of CM get very close to the theoretical optimum. Next-generation solar cells operating under these ideal conditions could potentially have conversion efficiency of up to 42%. This compares favorably to the 30% efficiency limit of a single junction silicon solar cell.ID: 029051098; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references (p. 106-112).
Ph.D.
Doctorate
Department of Physics
Sciences
44
Andrade, Carolina D. "Design, synthesis and characterization of new two-photon absorbing (2PA) fluorescent dyes and bioconjugates, and their applications in bioimaging." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4553.
Анотація:
The development of new multiphoton absorbing materials has attracted the attention of researchers for the last two decades. The advantages that multiphoton absorbing materials offer, versus their one-photon absorbing counterparts, rely on the nature of the nonlinearity of the absorption process, where two photons are absorbed simultaneously offering increased 3D resolution, deeper penetration, and less photobleaching and photodamage as a result of a more confined excitation. The applications of efficient two-photon absorbing materials have been extensively expanding into the fields of photodynamic therapy, microscopy, and optical data storage. One of the fields where an increased interest in multiphoton absorbing materials has been most evident is in bioimaging, in particular, when different cellular processes and organelles need to be studied by fluorescence microscopy. The goal of this research was to develop efficient two-photon absorption (2PA) compounds to be used in fluorescence bioimaging, meaning that such compounds need to posses good optical properties, such as high fluorescence quantum yield, 2PA cross section, and photostability. In the first chapter of this dissertation, we describe the synthesis and structural characterization of a new series of fluorescent donor-acceptor and acceptor-acceptor molecules based on the fluorenyl ring system that incorporated functionalities such as alkynes and thiophene rings, through efficient Pd-catalyzed Sonogashira and Stille coupling reactions, in order to increase the length of the conjugation in our systems. These new molecules proved to have high two-photon absorption (2PA), and the effect of these functionalities on their 2PA cross section values was evaluated. Finally, their use in two-photon fluorescence microscopy (2PFM) imaging was demonstrated. One of the limitations of the compounds described in Chapter 1 was their poor water solubility; this issue was addressed in Chapter 2.; The use of micelles in drug delivery has been shown to be an area of increasing interest over the last decade. In the bioimaging field, it is key to have dye molecules with a high degree of water solubility to enable cells to uptake the dye. By enclosing a hydrophobic dye in Pluronic F-127 micelles, we developed a system that facilitates the use of 2PA molecules (typically hydrophobic) in biological systems for nonlinear biophotonic applications, specifically to image the lysosomes. Furthermore, we report in this chapter the efficient microwave-assisted synthesis of the dye used in this study. In addition, linear photophysical and photochemical parameters, two-photon absorption (2PA), and superfluorescence properties of the dye studied in Chapter 2, were investigated in Chapter 3. The steady-state absorption, fluorescence, and excitation anisotropy spectra of this dye were measured in several organic solvents and aqueous media. In Chapter 4, we describe the preparation and the use of an efficient and novel two-photon absorbing fluorescent probe conjugated to an antibody that confers selectivity towards the vascular endothelial growth factor receptor 2 (VEGFR-2) in porcine aortic endothelial cells that express this receptor (PAE-KDR). It is known that this receptor is overexpressed in certain cancer processes. Thus, targeting of this receptor will be useful to image the tumor vasculature. It was observed that when the dye was incubated with cells that do not express the receptor, no effective binding between the bioconjugate and the cells took place, resulting in very poor, nonspecific fluorescence images by both one and two-photon excitation. On the other hand, when the dye was incubated with cells that expressed VEGFR-2, efficient imaging of the cells was obtained, even at very low concentrations (0.4micrometer]). Moreover, incubation of the bioconjugate with tissue facilitated successful imaging of vasculature in mouse embryonic tissue.ID: 030422918; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2010.; Includes bibliographical references (p. 145-158).
Ph.D.
Doctorate
Department of Chemistry
Sciences
45
Li, Wanlu. "EXPERIMENTAL STUDIES ON THE DETERMINATION OF ACOUSTIC BULK MATERIAL PROPERTIES AND TRANSFER IMPEDANCE." UKnowledge, 2014. http://uknowledge.uky.edu/me_etds/48.
Анотація:
Soft trim absorbing parts (i.e., headliners, backwalls, side panels, etc.) are normally comprised of different layers including films, adhesives, foams and fibers. Several approaches to determine the complex wavenumber and characteristic impedance for porous sound absorbing materials are surveyed and the advantages and disadvantages of each approach are discussed. It is concluded that the recently documented three-point method produces the smoothest results. It is also shown that measurement of the flow resistance and the use of empirical equations is sufficient for many common materials. Following this, the transfer impedance of covers, adhesives, and densified layers are measured using an impedance difference approach. The transfer matrix method was then used to predict the sound absorption of a multi-layered materal which included a perforated cover, fiber layers, and an adhesive. The predicted results agree well with measurement.
46
Goetz, Lee Ann. "Preparation and analysis of crosslinked lignocellulosic fibers and cellulose nanowhiskers with poly(methyl-vinyl ether co maleic acid) â " polyethylene glycol to create novel water absorbing materials." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45893.
Анотація:
The search for cellulosic based products as a viable alternative for petroleum-based products was the impetus for covalently crosslinking lignocellulosic fibers and nanocellulose whiskers with poly(methyl vinyl ether) co maleic acid (PMVEMA) - polyethylene glycol (PEG). The lignocellulosics used were ECF bleached softwood (pine) and ECF bleached birch kraft pulp. This thesis also tests the hypothesis that water absorption and retention can be improved by grafting PMVEMA-PEG to the surface of ECF bleached kraft pulp hardwood and softwood fibers via microwave initiated crosslinking. The crosslinking of the PMVEMA to hardwood and softwood kraft ECF bleached pulp fibers resulted in enhanced water absorbing pulp fibers where the PMVEMA is grafted onto the surface of the fibers. The crosslinking was initiated both thermally and via microwave irradiation and the water absorption and water retention was measured as the percent of grafted PMVEMA. This was the first application of microwave crosslinking of pulp fibers with the goal of creating water absorbing pulp fibers. Ultimately, the water absorption values ranged from 28.70 g water per g dry crosslinked pulp fiber (g/g) to 230.10 g/g and the water retention values ranged from 26% to 71% of the water retained that was absorbed by the crosslinked pulp fibers. The microwave initiated crosslinked fibers had comparable results to the thermally crosslinked fibers with a decreased reaction time, from 6.50 min (thermal) to 1 min 45 sec (microwave).
Cellulose nanowhiskers, crystalline rods of cellulose, have been investigated due to their unique properties, such as nanoscale dimensions, low density, high surface area, mechanical strength, and surface morphology and available surface chemistry. Prior to this study, the crosslinking of cellulose whiskers with the matrix via solution casting of liquid suspensions of whiskers and matrix had not been explored. The hypothesis to be investigated was that incorporating cellulosic whiskers with the PMVEMA-PEG matrix and crosslinking the whiskers with the matrix would yield films that demonstrate unique properties when compared to prior work of crosslinking of PMVEMA-PEG to macroscopic ECF bleached kraft pulp fibers.
Solution cast composites of cellulose nanowhiskers-PMVEMA-PEG were crosslinked at 135 °C for 6.5 min and analyzed for crosslinking, thermal stability, strength and mechanical properties, whisker dispersion, and water absorption and uptake rates. The whisker-composites demonstrated unique properties upon crosslinking the whiskers with PMVEMA-PEG, especially the elongation at break and tensile strength upon conditioning of the final materials at various relative humidities. In addition, the whiskers improved the thermal stability of the PMVEMA-PEG matrix. This is significant as methods of improving processing thermal stability are key to developing new materials that utilize cellulose whiskers, PMVEMA, and PEG. This thesis addresses the hypothesis that cellulose nanowhiskers that are crosslinked with a matrix can create new whisker-matrix composites that behave differently after crosslinking.
47
Shi, Yanrong. "Squaraine dyes for non-linear optics and organic electronics." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44720.
Анотація:
This dissertation describes the investigation of the synthesis and characterization of new squaraine-based photonic and electronic materials. In the first part of this thesis, squaraine dyes with large conjugation systems, including extended squaraines consisting of bis(donor)substituted vinylene-heterocycles and bis(indolinylenemethyl)squaraine-based oligomers linking through different π-bridges were designed, synthesized and characterized to exhibit strong two-photon absorption (2PA) for femotosecond and nanosecond optical-power limiting applications in the near-infrared (NIR). One of the dendronized squaraine forms smooth and high optical quality films with large NIR transparency window. In the second part, a series of squaraine- and phthalocyanine-based metal complexes were studied. Those dyes did not show large triplet quantum yield but significantly improved photovoltaic performance compared to the metal-free compounds. In the last part, an effective approach on optimizing bis(indolinylenemethyl)-based squaraine sensitizers with various surface anchor groups and π-linkers, achieved high power conversion efficiencies (PCEs) of 6.7% in liquid dye-sensitized solar cells (DSSCs) and 2.7% in solid-state DSSCs, which stand out all the previous reported squaraine-based sensitizers.
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Rodrigues, Manuella Karla da Cruz. "Estudo da viabiliza??o do uso da mistura h?brida ferrocarbonila / ferrita de NI0,5Zn0,5Fe2o4 como material absorvedor de radia??o eletromagn?tica." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17652.
Анотація:
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Were synthesized ferrites of NiZn on systems Ni0,5Zn0,5Fe2O4, the precursors citrate method. The decomposition of the precursors was studied by thermogravimetric analysis and spectroscopy in the infrared region, the temperature of 350?C/3h. The evolution of the phases formed after calcinations at 350?C/3h, 600, 1000 and 1100?C/2h was accompanied by X-ray diffraction using the Rietveld refinement method for better identification os structures formed. Was observed for samples calcined at different temperatures increased crystallinity with increasing calcination temperature, being observed for the samples calcined at 900 and 1100 ? C/2h was the precipitation of a secondary phase, the phase hematite. The ferrocarbonila of industrial origin was analyzed by X-ray diffraction and Rietveld for the identification of its structure. The carbonyl iron was added NiZn ferrite calcined at 350?C/3h, 600, 900, 1000 and 1100?C/2h to the formation of hybrid mixtures. They were then analyzed by Xray diffraction and Rietveld. The NiZn ferrite and ferrocarbonila as well as the hybrid mixtures were subjected to analysis of scanning electron microscopy, magnetic measurements and reflectivity. The magnetic measurements indicated that the ferrite, the ferrocarbonila, as well as hybrid mixtures showed characteristics of soft magnetic material. The addition of ferrocarbonila in all compositions showed an increase in the results of magnetic measurements and reflectivity. Best result was observed in the increase of the magnetization for the hybrid mixture of Ferrocarbonila / ferrite of NiZn calcined at 600?C/2h. The mixture Ferrocarbonila / ferrite calcined 1000?C/2h presented better absorption of electromagnetic radiation in the microwave
Foram sintetizadas ferritas de NiZn no sistema Ni0,5Zn0,5Fe2O4, pelo m?todo dos citratos precursores. A decomposi??o dos precursores foi estudada por an?lise termogravim?trica e espectroscopia na regi?o do infravermelho na temperatura de 350?C/3h. A evolu??o das fases formadas ap?s calcina??es a 350?C/3h, 600, 1000 e 1100?C/2h foi acompanhada por difra??o de raios X utilizando o refinamento de Rietveld para melhor identifica??o das estruturas formadas. Foi observado para as amostras calcinadas em diferentes temperaturas o aumento da cristalinidade com o aumento da temperatura de calcina??o, sendo verificado que para as amostras calcinadas a 900 e 1100?C/2h ocorreu a precipita??o de uma fase secund?ria, a fase hematita. A ferrocarbonila de proced?ncia industrial foi analisada por Difra??o de raios X e por Rietveld para a identifica??o de sua estrutura. A ferrocarbonila foi adicionada ? ferrita de NiZn calcinada a 350?C/3h, 600, 1000 e 1100?C/2h para a forma??o das misturas h?bridas. Em seguida foram analisadas por difra??o de raios X e por Rietveld. A ferrita de NiZn, a ferrocarbonila, assim como as misturas h?bridas foram submetidas ? an?lises de Microscopia Eletr?nica de Varredura, medidas magn?ticas e refletividade. As medidas magn?ticas indicaram que a ferrita, a ferrocarbonila, como tamb?m as misturas h?bridas apresentaram caracter?sticas de material magn?tico macios. A adi??o de ferrocarbonila em todas as composi??es indicou um aumento nos resultados de medidas magn?ticas e de refletividade. Foi verificado melhor resultado no aumento da magnetiza??o para a mistura h?brida de Ferrocarbonila/ferrita de NiZn calcinada 600?C/2h. A mistura Ferrocarbonila/ferrita calcinada 1000?C/2h apresentou melhor resultado absor??o da radia??o eletromagn?tica na faixa de microondas em rela??o ?s outras misturas
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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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He, Ying-Hsien, and 何應賢. "The study of Radar absorbing materials." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/64956476451386367298.
Анотація:
碩士國防大學中正理工學院
兵器系統工程研究所
94
In this study, the electromagnetic wave absorbing (EMA) properties of graphite/epoxy sheets were investigated. The hybrid graphite/epoxy sheets were fabricated with the addition of graphite into epoxy resin. The graphite size, thickness of sheets, and weight amount varied for optimizing absorbing sheets. The corresponding EMAs of graphite sheets were measured by a free space vector network analyzer in the frequency range of 3~18 GHz. The experimental results have demonstrated that the graphite/epoxy sheets effectively absorb the electromagnetic wave, especially for the frequency of X-band range. The demand of light for EMA is therefore reached for further applications. The dispersion of graphites in the epoxy resin affects the microwave absorbing characteristics. The value of F*D decreases with the addition of ED211 up to 10 wt%. Nevertheless, the value increases when the weight amount higher than 10 wt%. With increasing the graphite particle size, the dielectric constant of the hybrid sheets increases and causes the microwave absorbing frequency shifts to lower frequency. As a usual, the value of F*D keeps the same for materials. In this case, the absorbing frequency also decreases with increasing the thickness. The dielectric constant increases with increasing the weight percentage of graphite, and, as a result, the absorbing frequency shifts to low frequency. The hybrid sheets mixed with G30 graphite powder absorb the loss more than 20 dB at a thickness of less than 1.0 mm with a density of 1.3kg/m2. The EMA of G30 sheets slightly modulates with the additions of carbonyl-iron, NG300, and G01 particles. The addition of ferrite could extend the 3 % lossy at the refection loss of 10 dB.