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Relevant bibliographies by topics / Lewis structure

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Academic literature on the topic 'Lewis structure'

Author: Grafiati

Published: 4 June 2021

Last updated: 5 February 2022

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Journal articles on the topic "Lewis structure"

1

Purser, Gordon H. "Lewis Structures Are Models for Predicting Molecular Structure, Not Electronic Structure." Journal of Chemical Education 76, no. 7 (July 1999): 1013. http://dx.doi.org/10.1021/ed076p1013.

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Reed, James L. "The Lewis Structure: An Expanded Perspective." Journal of Chemical Education 71, no. 2 (February 1994): 98. http://dx.doi.org/10.1021/ed071p98.

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Mois�s, Bonilla E., and Michel Malabre. "Geometric characterization of Lewis Structure Algorithm." Circuits, Systems, and Signal Processing 13, no. 2-3 (June 1994): 255–72. http://dx.doi.org/10.1007/bf01188110.

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Harcourta, Richard D., and Thomas M. Klapötkeb. "Valence Bond Studies of N5+." Zeitschrift für Naturforschung B 57, no. 9 (September 1, 2002): 983–92. http://dx.doi.org/10.1515/znb-2002-0903.

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The results of STO-6G valence-bond studies are reported for the six π-electrons of C2v symmetry N5+, with π-electron core charges determined from the valence bond structures. Important types of canonical Lewis structures are calculated to carry either three atomic formal charges, arranged spatially as (+), (-) and (+) , as in or a single (+) atomic formal charge, as in the “long-bond” structure When localized molecular orbitals are used to accommodate bonding electrons between pairs of adjacent atoms, each of these types of Lewis structures, and others, are components of the increased-valence structure whose bond properties are in qualitative accord with experimental estimates of the bond lengths for N5+. Consideration is also given to other types of valence bond representations for N5+, and the results of MP2 molecular orbital calculations for the hypothetical N82+ are reported. For the latter species, a stable energy minimum with C2 symmetry is obtained. Its bond lengths are related to those implied by a Lewis-type valence-bond structure

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Möricke, Jennifer, Birgit Wibbeling, Constantin G. Daniliuc, Gerald Kehr, and Gerhard Erker. "Design and reactions of a carbon Lewis base/boron Lewis acid frustrated Lewis pair." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2101 (July 24, 2017): 20170015. http://dx.doi.org/10.1098/rsta.2017.0015.

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The conjugated dienamine 4 selectively adds Piers' borane [HB(C 6 F 5 ) 2 ] to give the enamine/borane system 5 , which features a boratirane structure by internal enamine carbon Lewis base to boron Lewis acid interaction. Compound 5 behaves as a C/B frustrated Lewis pair and undergoes typical addition reactions to benzaldehyde, several nitriles and to sulfur dioxide. This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.

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Justyniak, Iwona, Daniel Prochowicz, Adam Tulewicz, Wojciech Bury, Piotr Goś, and Janusz Lewiński. "Structure investigations of group 13 organometallic carboxylates." Dalton Transactions 46, no. 3 (2017): 669–77. http://dx.doi.org/10.1039/c6dt03958h.

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The effect of both the relative magnitude of electrophilicity of metal centres and the character of a Lewis base on the molecular structure of the electron-precise [R₂M(μ-O₂CPh)]₂-type carboxylates and their Lewis acid–base adducts [(R₂M)(μ-O₂CPh)(py-Me)] is reported.

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Brady, Joseph A., John N. Milbury-Steen, and John L. Burmeister. "Lewis structure skills: Taxonomy and difficulty levels." Journal of Chemical Education 67, no. 6 (June 1990): 491. http://dx.doi.org/10.1021/ed067p491.

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Miburo, Barnabe B. "Simplified Lewis Structure Drawing for Nonscience Majors." Journal of Chemical Education 75, no. 3 (March 1998): 317. http://dx.doi.org/10.1021/ed075p317.

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Lu, Dongmei, Yijin He, and Chao Wu. "Electronic structure of mono(Lewis base)-stabilized borylenes." Physical Chemistry Chemical Physics 21, no. 42 (2019): 23533–40. http://dx.doi.org/10.1039/c9cp04653d.

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Osmundsen, Christian M., Martin Spangsberg Holm, Søren Dahl, and Esben Taarning. "Tin-containing silicates: structure–activity relations." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, no. 2143 (February 29, 2012): 2000–2016. http://dx.doi.org/10.1098/rspa.2012.0047.

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The selective conversion of biomass-derived substrates is one of the major challenges facing the chemical industry. Recently, stannosilicates have been employed as highly active and selective Lewis acid catalysts for a number of industrially relevant reactions. In the present work, four different stannosilicates have been investigated: Sn-BEA, Sn-MFI, Sn-MCM-41 and Sn-SBA-15. When comparing the properties of tin sites in the structures, substantial differences are observed. Sn-beta displays the highest Lewis acid strength, as measured by probe molecule studies using infrared spectroscopy, which gives it a significantly higher activity at low temperatures than the other structures investigated. Furthermore, the increased acid strength translates into large differences in selectivity between the catalysts, thus demonstrating the influence of the structure on the active site, and pointing the way forward for tailoring the active site to the desired reaction.

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Dissertations / Theses on the topic "Lewis structure"

1

Prickett, Mark Peter. "Probing the structure of Lewis X trisaccharide." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319046.

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Mafra, Lopes Junior Osvaldo. "Retrouver les structures de Lewis à partir des fonctions d'onde." Paris 6, 2010. http://www.theses.fr/2010PA066581.

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La difficulté pour interpréter les résultats issus de la mécanique quantique est toujours un souci pour les chimistes. Plusieurs méthodes ont été proposées pour extraire, à partir de fonctions d'onde, des images permettant au chimiste de mieux comprendre la structure électronique et les propriétés des molécules et des cristaux. C'est dans cette famille des méthodes interprétatives que rentre la méthode MPD développée au cours de cette thèse, qui consiste à chercher des domaines de l'espace pour lesquels la probabilité de trouver un nombre donné d'électrons est maximale. Cette recherche est un problème d'optimisation, qui exige le développement d'algorithmes d'optimisations adaptés. Dans un premiers temps un algorithme simple d'optimisation discrète a été utilisé. Cet algorithme ne s'est pas avéré suffisamment efficace. Un nouvel algorithme, basé sur la définition d'une direction de montée, a alors été implémenté, se montrant beaucoup plus efficace et précis. Le programme écrit a permis d'explorer les potentialités interprétatives de la méthode MPD dans un certain nombre de systèmes modèles, pour des fonctions de type Hartree-Fock. La méthode MPD a fourni des résultats satisfaisants dans la recherche de domaines associés à des liaisons covalentes et aux paires libres des atomes, et a permis de trancher entre les deux principales images proposées pour la liaison à trois électrons. Quelques limites de la méthode et des questions ouvertes ont été mises en évidence lors des applications, et discutées, notamment les questions de multiplicité de solutions et de la répartition de l'espace entre ces solutions.

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Bodensteiner, Michael [Verfasser]. "Lewis Acid-Base-Stabilized Phosphanylalanes : and Crystal Structure Determinations / Michael Bodensteiner." Saarbrücken : Südwestdeutscher Verlag für Hochschulschriften, 2012. https://www.svh-verlag.de.

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Ledoux, Audrey. "Lewis-pair amine-borane polymers as hydrogen reservoirs : structure/reactivity relationship." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1234/document.

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Le stockage et le relargage contrôlé du dihydrogène est devenu un domaine important de recherche visant à répondre à une demande énergétique grandissante. Bien que le borazane (NH3-BH3) ait été identifié comme un candidat de choix dû à sa grande capacité de stockage (16.9 wt.% H2), les chercheurs ont mis en évidence certaines limitations telles que des difficultés de mise en forme et des difficultés de régénération du matériau.Nous avons tenté de répondre à ces problématiques en concevant de nouveaux polymères contenant des fonctions de type amine-borane dans leur chaîne principale (polyboramines) et sur les chaînes latérales, afin d’étudier l’influence du squelette polymère sur les propriétés du matériau et sa réactivité associée. Nos objectifs ont visé une facilité de synthèse et de mise en forme mais aussi l'éventualité d'une régénération simple et directe du réservoir après relargage du dihydrogène. Nous avons synthétisé ces polymères en une étape quantitativement et sélectivement à partir de fragments commerciaux ou facilement accessibles. Nous avons observé une influence conséquente de la matrice polymère sur les paramètres cinétiques et thermodynamiques de la déshydrogénation, à la suite de quoi nous avons étudié les paramètres structuraux influençant la réactivité. De plus les polymères obtenus après déshydrogénation ont montré d’intéressantes propriétés mécaniques et chimiques. Ces résultats nous ont encouragés à nous pencher vers le recyclage de ces réservoirs à hydrogène
Dihydrogen storage and controlled release has become an essential area of research aspiring to answer the ever-growing energetic demand. If ammonia-borane (NH3-BH3) was early on identified as a premium candidate to constitute a H2 reservoir, due to its maximum storage capacity (16.9 wt.% H2), researchers have then identified its shortcomings such as poor processability and troublesome material recycling.We have proposed to address these issues through the synthesis of new polymers containing the amine-borane motif in the main-chain (polyboramine) or as pendant moieties, harnessing improvements brought by the polymer backbone on the reactivity and material properties. We aimed at an ease of preparation, an enhanced processability but also an access to recyclable materials via simple re-hydrogenation techniques. We have synthesized these polymers from available organic building blocks by simple treatment of diammonium and bisboronic acids with LiAlH4. We showed that the polymer matrix has a drastic effect on kinetic and thermodynamic parameters of the dehydrogenation process. We investigated the role of structural parameters on the reactivity. Moreover, polymers obtained after dehydrogenation (H2 release) still feature interesting mechanical and chemical properties. These results give us hope regarding the recycling of these hydrogen reservoirs

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Falcon, Bernardo Mechaca. "Structure and properties of PBZT/Nylon 6,6 blends processed via Lewis acid mediated solubilization." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/8522.

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Hair, Gregory Scott. "Synthesis, structure and reactivity of group 13 Lewis acids and group 4 metallocene zwitterions /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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Henry, Heather Marie. "Investigation of a triangle zone structure between Augusta and Bowman's Corners, Lewis and Clark County, Montana." CONNECT TO THIS TITLE ONLINE, 2007. http://etd.lib.umt.edu/theses/available/etd-05212007-104742/.

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Vergnaud, Jérôme. "Ligands ambiphiles pyridine/borane et phosphine/borane : synthèse, structure, coordination et réactivité." Toulouse 3, 2007. http://thesesups.ups-tlse.fr/67/.

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Cette thèse traite de l'utilisation de molécules dîtes ambiphiles, comportant à la fois un site donneur et accepteur d'électrons, en chimie organométallique, en tant que ligand. Dans le premier chapitre, une étude bibliographique décrit l'utilisation des acides de Lewis du groupe 13 en tant que co-catalyseur en chimie organométallique, afin de mieux comprendre quel rôle pourrait jouer celui-ci au sein d'un ligand ambiphile coordiné sur un métal de transition. Les différents modes de coordination de ces ligands sont examinés. Les rares contributions traitant de la réactivité de ce type de complexes sont également décrites. Le second chapitre décrit la synthèse par couplage bore-carbone d'une nouvelle famille de ligands ambiphiles, 2-picolylboranes. En fonction des substituants du bore, ces composés sont obtenus sous forme dimère ou monomère fermé par interactions datives donneur-accepteur, inter ou intramoléculaires. Le comportement en solution du 2-picolylBCy2 a été examiné attentivement. Un équilibre entre la forme dimère et monomère est mis en évidence. Des calculs théoriques valident nos conclusions. La coordination de ce ligand sur plusieurs précurseurs métalliques est étudiée. Un exemple rare de coordination pontante donneur->Ru-Cl->accepteur a été caractérisé dans le complexe [(p-cym)RuCl2(2-picolylBCy2)]. Dans le troisième chapitre, la synthèse par hydroboration d'une famille de ligands ambiphiles, 1,2-phosphinoethylborane, est décrite. Deux complexes de ruthénium neutres contenant ces ligands, ainsi que leur dérivés cationiques sont caractérisés. Des tests catalytiques préliminaires d'hydrosilylation du benzaldéhyde avec l'un des complexes cationiques ont montré la dégradation rapide du pré-catalyseur en un complexe ruthénacycle original. Sa réactivité avec un chloroborane et un chloroalane est étudiée
The present contribution deals with the use of ambiphilic molecules featuring both a Lewis base and a Lewis acid site, as ligands in organometallic chemistry. In the first chapter, a bibliographic study describes the behaviour of Lewis acids of group 13 in organometallic chemistry. Their role as co-catalysts is examined in order to better understand how the Lewis acid could behave in a complex featuring an ambiphilic ligand. The different coordination modes of those ligands are reviewed. The rare contributions dealing with the reactivity of those complexes are also examined. The second chapter describes the synthesis by carbon-boron coupling of a new family of ambiphilic ligands, namely 2-picolylboranes. Depending on the borane substituents, they are obtained as dimer or closed monomer via inter or intramolecular donor-acceptor dative interaction. The behaviour of 2-picolylBCy2 in solution is examined in details by NMR. An equilibrium between a dimer and a closed monomer form is evidenced. Theoretical calculations ascertain our conclusions. Coordination of this ligand to several transition metal precursors is studied. .

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9

Francke, Loïc. "Préparation et caractérisation d'hydroxy-et d'oxyhydroxyfluorures d'aluminium, de fer ou de chrome : corrélation entre la composition / structure, la stabilité thermique et les propriétés acides." Bordeaux 1, 2002. http://www.theses.fr/2002BOR12567.

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Il s'agissait dans ce travail de préparer des composés fluorés de structure de type HTB ou hollandite au sein desquels la présence d'autres anions tels que OH- ou encore O2- viennent se substituer au fluor. Nous avons voulu dans ce travail mieux comprendre par une approche " chimie du solide " les propriétés de morphologie, de stabilité thermique et d'acidité des ces composés. Des études par diffraction neutronique couplées à une analyse par FTIR nous ont permis de mieux appréhender leurs propriété physico-chimiques. Nos résultats ont mis en avant les rôles joués par les cations, les anions et la structure sur les différentes propriétés et notamment l'importance d'un nouveau paramètre, [khi]/r, qui permet d'expliquer à la fois la force des sites acides et la stabilité thermique de ces composés. L'eau de constitution, le taux et la nature des groupements OH' sont des paramètres clefs qui conditionnent la stabilité thermique et les propriétés acido-basiques de ces composés à anions mixtes.

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Yamashita, Hiroshi, Yoshinori Ogata, and Kazuhiro Yamamoto. "Flame structure and flame spread rate over a solid fuel in partially premixed atmospheres." Elsevier, 2011. http://hdl.handle.net/2237/20040.

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Books on the topic "Lewis structure"

1

Yosemite National Park (Agency : U.S.), ed. Lewis Memorial Hospital historic structure report. [San Francisco, Calif.]: [Architectural Resources Group], 2013.

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United States. National Park Service. Southeast Regional Office. Cultural Resources Division. Cape Lookout National Seashore: Lewis-Davis House : historic structure report. [Atlanta?]: National Park Service, U.S. Department of the Interior, 2004.

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Cox, Richard A. V. The Gaelic place-names of Carloway, Isle of Lewis: Their structure and significance. [Dublin]: School of Celtic Studies, Dublin Institute for Advanced Studies, 2002.

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Mumford, Lewis. Sidewalk critic: Lewis Mumford's writings on New York. New York: Princeton Architectural Press, 1998.

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Mumford, Lewis. Sidewalk critic: Lewis Mumford's writings on New York. New York: Princeton Architectural Press, 2000.

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Marlitt, Richard. Matters of proportion: The Portland residential architecture of Whidden & Lewis. [Portland, Or.]: Oregon Historical Society Press, 1989.

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Center, Lewis Research. Lewis Structures Technology - 1988: Proceedings of an exposition and symposium of structures technology developed under the auspices of NASA Lewis Research Center's Structures Division, Cleveland, Ohio, May 24-25, 1988. Cleveland, Ohio: Lewis Research Center, 1988.

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Center, Lewis Research. Engine structures: A bibliography of Lewis Research Center's research for 1980-1987. Cleveland, Ohio: Lewis Research Center, 1988.

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Kostura, William. William F. Lewis: A San Francisco house builder. San Francisco: Book Club of California, 1993.

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NASA Lewis Research Center Workshop on Forced Response in Turbomachinery (1993). NASA Lewis Research Center Workshop on Forced Response in Turbomachinery: Proceedings of a conference. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Program, 1994.

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Book chapters on the topic "Lewis structure"

1

Gooch, Jan W. "Lewis Structure." In Encyclopedic Dictionary of Polymers, 425. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_6885.

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Chen, Hui-Li. "Lewis Glyco-Epitopes: Structure, Biosynthesis, and Functions." In Advances in Experimental Medicine and Biology, 53–80. Boston, MA: Springer US, 2011. http://dx.doi.org/10.1007/978-1-4419-7877-6_4.

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Winter, Charles H., and Xiao-Xing Zhou. "Synthesis, Structure, and Reactivity of Highly Soluble Organotitanium Lewis Acids." In ACS Symposium Series, 366–82. Washington, DC: American Chemical Society, 1994. http://dx.doi.org/10.1021/bk-1994-0555.ch023.

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Weinhold, Frank, and John E. Carpenter. "The Natural Bond Orbital Lewis Structure Concept for Molecules, Radicals, and Radical Ions." In The Structure of Small Molecules and Ions, 227–36. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4684-7424-4_24.

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Haaland, Arne, and Mats Tilset. "Lewis and Kossel’s Legacy: Structure and Bonding in Main-Group Compounds." In The Chemical Bond II, 1–70. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/430_2015_192.

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Sinclair, John McH. "Sense and structure in lexis." In Linguistics in a Systemic Perspective, 73. Amsterdam: John Benjamins Publishing Company, 1988. http://dx.doi.org/10.1075/cilt.39.05sin.

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Patterson, Christopher, Robert Dunsire, and Steven Hillier. "Development of Wave Energy Breakwater at Siadar, Isle of Lewis." In Coasts, marine structures and breakwaters: Adapting to change, 1: 738–749. London: Thomas Telford Ltd, 2010. http://dx.doi.org/10.1680/cmsb.41301.0065.

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Islam, Rizwanul. "Structural Transformation and Alternative Pathways to the Lewis Turning Point." In Rural Labour Mobility in Times of Structural Transformation, 15–34. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-5628-4_2.

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Hayashi, Shun. "Effect of Local Structures on Lewis Base Catalysis of [Nb10O28]6−." In Key Structural Factors of Group 5 Metal Oxide Clusters for Base Catalytic Application, 55–67. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-7348-4_4.

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Landis, Clark R., and Frank Weinhold. "Natural Bond Orbitals and Lewis-Like Structures of Copper Blue Proteins." In Modeling of Molecular Properties, 77–89. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527636402.ch6.

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Conference papers on the topic "Lewis structure"

1

Weiher, Norbert, Anna Makarowicz, Angela M. Beesley, Erhard Kemnitz, and Sven L. M. Schroeder. "Structure-Property Relationships in Solid AlF3 Lewis Acids." In X-RAY ABSORPTION FINE STRUCTURE - XAFS13: 13th International Conference. AIP, 2007. http://dx.doi.org/10.1063/1.2644677.

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"Effects of anthocyanin-rich grain diet on growth and metastasis of Lewis lung carcinoma in mice." In Bioinformatics of Genome Regulation and Structure/ Systems Biology. institute of cytology and genetics siberian branch of the russian academy of science, Novosibirsk State University, 2020. http://dx.doi.org/10.18699/bgrs/sb-2020-223.

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Ramadan, Bassem H. "Effect of Damkohler Number and Non-Unity Lewis Number on a Laminar Diffusion Flame." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45434.

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The effect of the Damkohler number (Da) and non-unity Lewis number on a two-dimensional, steady, laminar diffusion flame anchored by a dividing plate in a rectangular channel was considered. The governing equations were solved numerically, using the SIMPLE and ADI schemes. The results for non-unity Lewis number were compared with those for a unity Lewis number, and Da a was also varied in order to determine their effect on the flame structure. The results show that an increase in the Da causes the flame to exist closer to the trailing edge of the divider and to increase the reactivity. A non-unity Lewis number creates a non-symmetrical flame by forcing the flame to exist on the fuel side.

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Phan, Hung, Thomas Kelly, Hieu Huynh, An Nguyen, Andriy Zhugayevych, Sergei Tretiak, Thuc-Quyen Nguyen, and Emily Jarvis. "Tuning optical properties of conjugated molecules by Lewis acids: Insights from electronic structure modeling and machine learning." In Organic and Hybrid Sensors and Bioelectronics XIV, edited by Ruth Shinar, Ioannis Kymissis, and Emil J. List-Kratochvil. SPIE, 2021. http://dx.doi.org/10.1117/12.2594321.

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Li, Lei, Paul M. Jones, Alexei G. Merzlikine, and Yiao-Tee Hsia. "Effect of Molecular Weight (MW) and End-Groups on the Thermal and Lewis-Acid Catalyzed Decomposition of Fomblin Z-Type Lubricants." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63823.

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The high-temperature stability of disk lubricants has attracted a lot of interest in recent years because smaller head-media spacing may cause head-media contact and thus a local temperature rise. At elevated temperatures, the lubricant may either evaporate or decompose, leading to the eventual failure of the head-media interface. The decomposition might result from heating and/or may be catalyzed by the presence of a Lewis acid site at the head-disk interface (HDI). In this paper, we study how the chemical structure, namely, molecular weight (MW) and end-groups (see Fig. 1), of disk lubricants will affect the thermal and Lewis-acid catalyzed decomposition of the lubricant.

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Ronney, Paul, Ming-Shin Wu, Howard Pearlman, and Karen Weiland. "Structure of Flame Balls At Low Lewis-number (SOFBALL) - Preliminary results from the STS-83 and STS-94 space flight experiments." In 36th AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1998. http://dx.doi.org/10.2514/6.1998-463.

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Cossentine, Jay A., Jere J. Matty, and Robert J. Shaw. "The NPARC Alliance." In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-277.

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The Arnold Engineering Development Center (AEDC) and the NASA Lewis Research Center (LeRC) have formed a government alliance aimed at establishing and supporting a national, application-oriented computational fluid dynamics (CFD) capability, centered around the NPARC flow simulation software. The Alliance is supported by and responsive to an association made up of more that 100 active users at over 60 government, industry, and academic institutions. This paper discusses the history, structure, and philosophy of the NPARC Alliance.

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López-Juárez, Marcos, Xiaoxiao Sun, Bobby Sethi, Pierre Gauthier, and David Abbott. "Characterising Hydrogen Micromix Flames: Combustion Model Calibration and Evaluation." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14893.

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Abstract Hydrogen micromix combustion is a promising concept to reduce the environmental impact of both aero and land-based gas turbines by delivering carbon-free and ultra-low-NOx combustion without the risk of autoignition or flashback. The ENABLEH2 project aims to demonstrate the feasibility of such a switch to hydrogen for civil aviation, within which the micromix combustion, as a key enabling technology, will be matured to TRL3. The micromix combustor comprises thousands of small diffusion flames for which air and fuel are mixed in a cross-flow pattern. This technology is based on the idea of minimizing the scale of mixing to maximize mixing intensity. The high-reactivity and wide flammability limits of hydrogen in a micromix combustor can produce short and low-temperature small diffusion flames in lean overall equivalence ratios. For hydrogen-air mixtures there is a need to further characterise the physical importance and calibration process of the laminar Schmidt (Sc), Lewis (Le) and Prandtl (Pr) and turbulent Schmidt (Sc) numbers. In addition, there is limited numerical and experimental data about flame characteristics and emissions of hydrogen micromix combustor at high pressure and temperature conditions. In this paper, the CFD software STAR-CCM+ was used with the FGM (Kinetic Rate) combustion model to simulate and calibrate hydrogen micromix flames. The research was divided into two parts. In the first part, the values of laminar Schmidt, Lewis and Prandtl numbers for H2 and air, non-reactive, flow mixtures were estimated as 0.22, 0.3 and 0.75 from correlations obtained in the literature. The typical Borghi diagram has been modified to represent this type of diffusion flame, since the assumption of Sc = Le = Pr = 1 can not be applied to hydrogen micromix flames and it is only for premixed flames. This diagram characterizes flame regime based on Damköhler (Da), Karlovitz (Ka) and turbulent Reynolds (Ret) numbers that were calculated from preliminary CFD simulations. In the second part, the value of laminar Schmidt number was set as constant while laminar Lewis and Prandtl numbers were obtained from the flamelet tables. A Turbulent Schmidt number was then obtained by comparing RANS and LES simulations of a single injector. If Sct > 0.2, the predicted NOx production of RANS simulations approaches that of LES; while Sct < 0.2 provides similar overall flame structure between RANS and LES. It is concluded that, for the current simulations, Sct = 0.2 is a good compromise between flame structure and emissions prediction. Flame characteristics and NOx emissions given by Thickened Flame and FGM Kinetic Rate models in a single injector geometry were also compared.

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Chamis, C. C., and D. A. Hopkins. "Probabilistic Structural Analysis Methods of Hot Engine Structures." In ASME 1989 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1989. http://dx.doi.org/10.1115/89-gt-122.

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Development of probabilistic structural analysis methods for hot engine structures is a major activity at Lewis Research Center. It consists of three program elements: (1) composite load spectra methodology, (2) probabilistic structural analysis methodology, and (3) probabilistic structural analysis application. Recent progress includes: (1) quantification of the effects of uncertainties for several variables on High Pressure Fuel Turbopump (HPFT) turbine blade temperature, pressure, and torque of the Space Shuttle Main Engine (SSME), (2) the evaluation of the cumulative distribution function for various structural response variables based on assumed uncertainties in primitive structural variables, and (3) evaluation of the failure probability. Collectively, the results demonstrate that the structural durability of hot engine structural components can be effectively evaluated in a formal probabilistic/reliability framework.

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Chamis, Christos C. "NASA Lewis Research Center/University Graduate Research Program on Engine Structures." In ASME 1985 International Gas Turbine Conference and Exhibit. American Society of Mechanical Engineers, 1985. http://dx.doi.org/10.1115/85-gt-159.

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NASA Lewis Research Center established a graduate research program in support of the Engine Structures Research activities. This graduate research program focuses mainly on structural and dynamics analyses, computational mechanics, mechanics of composites and structural optimization. The broad objectives of the program, the specific program, the participating universities and the program status are briefly described.

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Reports on the topic "Lewis structure"

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Storesletten, Kjetil, Bo Zhao, and Fabrizio Zilibotti. Business Cycle during Structural Change: Arthur Lewis' Theory from a Neoclassical Perspective. Cambridge, MA: National Bureau of Economic Research, August 2019. http://dx.doi.org/10.3386/w26181.

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