Academic literature on the topic 'Rare gas matrix'
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Journal articles on the topic "Rare gas matrix"
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Kedzierski, W., A. DiCarlo, and J. W. McConkey. "Rare gas matrix detector for molecular fragmentation studies." Journal of Physics: Conference Series 194, no. 14 (November 1, 2009): 142005. http://dx.doi.org/10.1088/1742-6596/194/14/142005.
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Fraenkel, Ruchama, and Yehuda Haas. "Molecular dynamics simulations of rare gas matrix deposition." Chemical Physics 186, no. 2-3 (September 1994): 185–204. http://dx.doi.org/10.1016/0301-0104(94)00160-x.
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BAER, M., G. BOUSQUET, P. M. DINH, F. FEHRER, P. G. REINHARD, and E. SURAUD. "DYNAMICS OF METAL CLUSTERS IN RARE GAS CLUSTERS." International Journal of Modern Physics B 21, no. 13n14 (May 30, 2007): 2439–48. http://dx.doi.org/10.1142/s0217979207043798.
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We investigate the dynamics of Na clusters embedded in Ar matrices. We use a hierarchical approach, accounting microscopically for the cluster's degrees of freedom and more coarsely for the matrix. The dynamical polarizability of the Ar atoms and the strong Pauli-repulsion exerted by the Ar -electrons are taken into account. We discuss the impact of the matrix on the cluster gross properties and on its optical response. We then consider a realistic case of irradiation by a moderately intense laser and discuss the impact of the matrix on the hindrance of the explosion, as well as a possible pump probe scenario for analyzing dynamical responses.
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Haas, Y., and U. Samuni. "REACTIONS IN RARE GAS MATRICES MATRIX AND SITE EFFECTS." Progress in Reaction Kinetics and Mechanism 23, no. 1 (March 1, 1998): 211–80. http://dx.doi.org/10.3184/007967498103165031.
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Borowski, A., and O. Kühn. "Tailoring model Hamiltonians for dihalogen—rare gas matrix problems." Theoretical Chemistry Accounts 117, no. 4 (November 8, 2006): 521–33. http://dx.doi.org/10.1007/s00214-006-0177-2.
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Crépin, C., and A. Tramer. "Rare-gas matrix as an infinite rare-gas cluster: a spectroscopic study of 9,10-dichloroanthracene in argon matrices." Chemical Physics Letters 170, no. 5-6 (July 1990): 446–50. http://dx.doi.org/10.1016/s0009-2614(90)87082-3.
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Laroui, B., O. Damak, O. Maillard, and C. Girardet. "HCl–rare gas van der Waals dimers trapped in rare gas matrix: Interpretation of the vibration–orientation spectrum." Journal of Chemical Physics 97, no. 4 (August 15, 1992): 2359–71. http://dx.doi.org/10.1063/1.463075.
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NAKATA, Munetaka. "Study of Tunneling Reaction by Rare-Gas Matrix-Isolation Methods." Journal of the Spectroscopical Society of Japan 47, no. 3 (1998): 119–28. http://dx.doi.org/10.5111/bunkou.47.119.
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Neugebauer, F., and V. May. "Photodissociation of rare gas isolated HCl: a density matrix approach." Chemical Physics Letters 289, no. 1-2 (June 1998): 67–75. http://dx.doi.org/10.1016/s0009-2614(98)00390-x.
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Rasanen, M., L. A. Heimbrook, and V. E. Bondybey. "Rare gas matrix studies of the products of vaporization of nickel." Journal of Molecular Structure 157, no. 1-3 (March 1987): 129–40. http://dx.doi.org/10.1016/0022-2860(87)87088-6.
Full textDissertations / Theses on the topic "Rare gas matrix"
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Fridgen, Travis D. "FT-infrared spectroscopic and computational studies of the matrix-isolated products formed following gas-phase electron bombardment of rare-gas/organic molecule mixtures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0004/NQ38307.pdf.
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Putaud, Thomas. "Études infrarouges des isotopes H216O, H217O et H218O de la molécule d'eau à basse température : dynamique de conversion de spin nucléaire en matrice de gaz rare et rapport ortho-para de l'eau dans la Barre d'Orion." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS321.
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Ce travail s'attache à l'étude de la répartition des populations des isomères de spin nucléaire des isotopes de l'eau dans le milieu interstellaire et en matrice de gaz rare. Les intensités des raies d'émission infrarouge de l'eau dans la Barre d'Orion ont été analysées avec le modèle de transfert radiatif du code PDR de Meudon. L'adsorption des molécules d'eau à la surface des grains interstellaires sur la chimie de l'eau a été étudiée et mène à une augmentation de la production de l'eau en phase gazeuse pour reproduire les observations. Un OPR de 2.8 à l'équilibre thermodynamique à 36 K s'est révélé correspondre aux observations. L'influence du confinement de l'eau en matrice de gaz rare sur les temps de conversion de spin nucléaire a été étudiée. En revisitant l'attribution des transitions de l'eau en matrice de gaz rare dans l'infrarouge lointain, un confinement plus fort en matrice d'argon que de krypton est déduit du modèle de couplage rotation-translation. La structure rotationnelle (énergies et fonctions d'onde) des isotopes de l'eau en matrices d'argon et de krypton est établie révélant des mélanges d'états de rotation et de translation. Les variations des temps de conversion en fonction de la température sont reproduites par des couplages magnétiques intramoléculaire de type spin-rotation. Les canaux de conversion entre les états rotationnels des deux isomères de spin sont discutés. Enfin, la faisabilité d'un enrichissement en un isomère de spin par pompage optique infrarouge est adressée et l'efficacité de cette technique est limitée par une relaxation vibrationnelle rapide en matrice de gaz rareThe purpose of this work is to study the variations of the ortho-to-para ratio of water isotopes in the interstellar medium and rare gas matrix. The intensities of the water infrared emission lines observed in the Orion Bar were analyzed using the radiative transfer model of the Meudon PDR Code. The water chemistry modifications due to the adsorption of water molecules on interstellar grains were investigated and lead to a strong water depletion which has to be balanced by enhancing water gas phase production in order to retrieve the observed water line intensities. An agreement between the observed and predicted intensities is obtained for an OPR of 2.8 at the thermal equilibrium at 36 K. The role of water confinement on the nuclear spin conversion characteristic time is investigated. Considering a new water line assignment in the far infrared and rotation-translation coupling model, water molecules are more confined in argon matrix than in krypton one. The rotational structure of water isotopes in argon and krypton matrices is derived showing perturbations of the asymmetric rotator wave functions with a mixing of rotation and translation states. The variations of the nuclear spin conversion time with the temperature are retrieved by intramolecular magnetic interactions through spin-rotation coupling. Furthermore considering phonon processes, the nuclear spin conversion channels between nuclear spin isomer rotational states are confirmed. Finally, a new nuclear spin isomer enrichment method was attempted. The first results have shown that the efficiency of this method is reduced due to a quick vibrational relaxation of water molecules in rare gas matrix
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Iftner, Christophe. "Modélisation de complexes et agrégats moléculaires en matrice cryogénique." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30160/document.
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Cette thèse présente le développement et les applications d'un formalisme hybride quantique-classique pour décrire la structure électronique d'un système actif avec un environnement cryogénique (agrégat ou matrice d'atomes de gaz rare). La description quantique de la structure électronique du système actif est faite dans le cadre d'une approximation de type Liaisons Fortes de la Théorie de la Fonctionnelle de la Densité, avec charges atomiques autocohérentes (SCC-DFTB). L'environnement de gaz rare est décrit par des potentiels classiques atome-atome (FF). L'interaction entre le sytème actif et les atomes de l'environnement cryogénique est représentée par des opérateurs matriciels locaux anisotropes électron-atome, ainsi que par des contributions de polarisation et de dispersion. La détermination des opérateurs et des paramètres d'interaction est extraite de calculs ab initio post Hartree-Fock (CCSD-T) sur les paires atome actif/atome d'argon. Les applications concernent les interactions entre hydrocarbures, agrégats d'eau isolés ou complexes hydrocarbures/eau avec des agrégats et ou des matrices d'argon. Le modèle est validé sur de petits systèmes (molécule C6H6 , molécule H2O) en interaction avec des atomes et agrégats d'argon. Nous avons ainsi déterminé les données structurales et énergétiques pour les agrégats (C6H6)Arn (n < 55) qui ont été comparées à des données ab initio (DFT, CCSD-T) pour les plus petits agrégats, ou à des calculs de champ de force publiés dans la littérature pour les agrégats de plus grande taille. Le modèle permet également un traitement unifié de différentes situations électroniques permettant ainsi la détermination de l'évolution des potentiels d'ionisation du système actif en fonction de la taille n de l'agrégat solvatant. Le modèle DFTB/FF a ensuite été appliqué à des molécules et nano-agrégats d'eau (H2O)n (n=2-6) insérés dans des matrices d'argon, représentées par des sous-ensembles finis du réseau cristallin cubique faces centrées. Des données structurales et énergétiques ont été obtenues. Des études de dynamique moléculaire ont permis la détermination de spectres infrarouges (IR) à température finie. La comparaison des spectres IR théoriques caractérisant une molécule d'eau en matrice avec les données expérimentales nous a permis de valider l'approche DFTB/FF. Le cas de l'hexamère (H2O)6, plus petit agrégat présentant une structure tri-dimensionnelle et caractérisé par plusieurs isomères stables, a été étudié de façon exhaustive : l'effet de la matrice sur les structures de certains de ces isomères a été mis en évidence, ainsi que des effets différentiels sur leur stabilités respectives. Une influence sur les positions des bandes IR des agrégats a également été montrée. Les résultats obtenus permettent une interprétation satisfaisante des données expérimentales existantes pour les plus petits agrégats. L'assignation des spectres expérimentaux de l'hexamère demeure incertaine. Enfin, des résultats préliminaires sur les structures, l'énergétique et les spectres IR à température finie ont été obtenus pour des complexes d'Hydrocarbures Aromatiques Polycycliques avec l'eau (HAP-H2O) en matrices d'argon. L'ensemble des données obtenues pour ces complexes est discuté en relation avec les résultats expérimentaux en environnement cryogénique obtenus dans l'équipe de Joëlle Mascetti de l'Institut des Sciences Moléculaires de l'Université Bordeaux I, dans le cadre d'une collaboration ANR (ANR PARCS no 13-BS08-0005). Ce travail a bénéficié d'une allocation de thèse co-financée par l'Institut de Physique du CNRS et le Conseil Régional de la région Midi-PyrénéesThis thesis presents the development and applications of an hybrid quantum-classical formalism in order to describe the electronic structure of an active system in a cryogenic environment (cluster or rare gas matrix). The quantum description of the electronical structure of the active system is based on a a tight-binding approximation of the density functional theory, with self-consistency regarding the charges (SCC-DFTB). The rare gaz environment is described via classical atom-atom potential (FF). The interaction between the active system and the atoms of the cryogenic environment is represented by local anisotropic matricial electron-atom operators, as well as by polarisation and dispersion contributions. Operators and interaction parameters are extracted from post Hartree-Fock \textit{ab initio} calculations (CCSD-T) of active atom/argon atom pairs. The applications involve hydrocarbons, isolated water clusters or hydrocarbon/water complexes in interaction with argon clusters or matrices. The model has been validated on small systems (C6H6 molecule, H2O molecule) in interaction with argon atoms and clusters. We have been able to determine structural and energetic data for (C6H6)Arn (n < 55) clusters which are benchmarked against ab initio results (DFT,CCSD-T) for the smaller sizes, or with respect to FF calculations, available in the literature, for larger sized clusters. The model enables to treat various electronic situations, allows in particular to determine the evolution of the ionization potentials of the active system as a function of the inert cluster size. The SCC-DFTB/FF model has then been applied to water molecules and water nano-clusters (H2O)n (n=2-6) embedded in argon matrices, represented by finite size cristal pieces of the face centered cubic lattice. Structural and energetical data have been obtained. Molecular dynamics studies have enabled the determination of finite temperature infrared (IR) spectra. Comparison between the theoretical and experimental spectra of the water monomer embedded in the matrix validates the SCC-DFTB/FF approach. The case of the water hexamer (H2O)6, the smallest cluster presenting a three-dimensional structure and caracterized by several low-energy isomers, has been investigated exhaustively : the effect of the matrix on the structures of some isomers has been shown as well as differential effects on their respective stabilities. An influence on IR lines positions has also been highlighted. Our theoretical study allows for a satisfactory interpretation of the experimental data for the smallest clusters (n<4). The assignment of the experimental spectra of the hexamer remains in discussion. Finally, preliminary results on structures, energetics and finite temperature IR spectra have been obtained for Polycyclic Aromatic Hydrocarbons (PAH) /water complexes. The results for the complexes are discussed in relation with experimental data obtained in the team of Joëlle Mascetti at the Institute of Molecular Sciences (University of Bordeaux I), in the context of an ANR collaborative project (ANR PARCS no 13-BS08-0005). The thesis has been co-financed by the CNRS Institute of Physics and Conseil Regional of Region Midi-Pyrénées
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GOMES, Natasha Lopes. "Desenvolvimento e produção de compósitos de matriz cerâmica baseado em zircônia-titânia reforçado com óxido de terra-rara para revestimento do sistema de exaustão de turbina aeroespacial." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/17607.
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Dissertação de Mestrado - Natasha Lopes Gomes.pdf: 9410241 bytes, checksum: 569cb64525645737ca47e38f379de72c (MD5)Made available in DSpace on 2016-08-04T12:41:31Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação de Mestrado - Natasha Lopes Gomes.pdf: 9410241 bytes, checksum: 569cb64525645737ca47e38f379de72c (MD5) Previous issue date: 2016-02-26
FACEPE
A indústria aeroespacial é um setor que contribui significativamente para o desenvolvimento econômico e social de alguns países. A confiabilidade e a disponibilidade de seus equipamentos são uma preocupação constante, uma vez que estes operam a temperaturas elevadas. Dentre os equipamentos que mais falham prematuramente devido à temperatura, destacam-se os bocais de exaustão das turbinas a gás, compostos por um conjunto de ligas à base de níquel ou à base de cobalto. No entanto, os fabricantes de turbinas tem demonstrado um maior interesse no uso de compósitos cerâmicos para revestimento nas seções quentes, devido sua maior capacidade de suportar altas temperaturas e exigência de menor refrigeração do ar. Mas a fragilidade intrínseca das cerâmicas é ainda um fator limitante para o uso destes materiais em estruturas mecânicas e aplicações industriais. Para reduzir fragilidade e aumentar resistência mecânica e tenacidade, normalmente as cerâmicas são reforçadas com incorporação de aditivos. Estudos vêm sendo realizados acerca da utilização da zircônia incorporada com outros óxidos, pois em comparação com outros cerâmicos, a zircônia tem propriedades mecânicas superiores, tais como alta resistência mecânica, estabilidade química e boa tenacidade à fratura. Neste trabalho foram produzidos compósitos cerâmicos zircônia-titânia (ZrO2-TiO2) reforçados com um óxido de terra rara, lantânio (La2O3), variando o teor de TiO2 em 5%, 10%, 15% e 20% e o teor de La2O3 em 5%, 7% e 10%. Os compósitos foram produzidos por processo termomecânico e sinterizados à 1385°C. Posteriormente, foram caracterizados quanto à estrutura, microestrutura e propriedades mecânicas através de difração de raios X, densidade relativa, microscopia óptica, microscopia eletrônica de varredura, espectroscopia de energia dispersiva e microdureza Vickers. A microestrutura do material sinterizado revelou uma boa homogeneidade em distribuição e tamanho de partículas, e a microdureza Vickers mostrou que o compósito com 15% de TiO2 e 10% de La2O3 obteve um melhor resultado, indicando que este possui boas propriedades físicas que apontam para uma possível aplicabilidade. No entanto, é necessário avaliar outras propriedades mecânicas a fim de garantir sua utilização como revestimento cerâmico de exaustores de turbinas a gás aeroespaciais.
The aerospace industry is a sector that contributes significantly to the economic and social development of some countries. The reliability and availability of your equipment is a constant concern, since they operate at high temperatures. Among the equipment more fail prematurely due to temperature, we highlight the exhaust nozzles of gas turbines, comprising a set of nickel based alloys or cobalt-based. However, turbine manufacturers have shown an increased interest in the use of ceramic composite coating on hot sections due to their greater ability to withstand high temperatures and requiring less cooling air. But the intrinsic brittleness of ceramics is still a limiting factor for the use of these materials in mechanical and industrial applications structures. To reduce brittleness and increase strength and toughness, typically ceramics are reinforced by incorporation of additives. Studies have been conducted on the use of zirconia incorporated with other oxides, as compared to other ceramic, zirconia has superior mechanical properties such as high mechanical strength, chemical stability and good fracture toughness. In this work we were produced composite ceramic zirconia-titania (ZrO2-TiO2) reinforced with a rare earth oxide, lanthanum (La2O3), varying the TiO2 content of 5%, 10%, 15% and 20%, and the La2O3 content 5%, 7% and 10%. The composites were produced by thermomechanical process and sintered at 1385 ° C. Later, they were characterized as to structure, microstructure and mechanical properties through X-ray diffraction, relative density, optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and microhardness. The microstructure of the sintered material showed a good homogeneous distribution and particle size, and Vickers microhardness showed that the composite with 15% TiO2 and 10% La2O3 obtained best results, indicating that it has good physical properties which indicate a possible applicability. However, it is necessary to assess other mechanical properties to ensure their use as ceramic coating aerospace gas turbine exhaust.
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Grisolia, Christian. "Etude optique et magnetooptique de depots dilues de metaux de transition en matrice de gaz rare : application a la determination de l'interaction atomemetallique-matrice et a la caracterisation de petits agregats." Paris 6, 1988. http://www.theses.fr/1988PA066272.
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Mesures des spectres d'absorption et des dichroismes lineaire et circulaire. Si les atomes presentent un fort couplage spin-orbite, ils ont, dans la matrice, des etats bien decrits par un modele d'atome libre. Par contre si la constante de couplage spin-orbite est faible, les atomes ont des etats electroniques fortement couples aux vibrations du reseau. Dans la premiere possibilite, c'est le cas du nickel et du fer, et dans la seconde c'est le cas du manganese
Books on the topic "Rare gas matrix"
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Bach, Stephan Bruno Heinrich. Spectroscopic investigations of metal clusters and metal carbonyls in rare gas matrices. 1987.
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Stephens, Vincent L. Rocking the Closet. University of Illinois Press, 2019. http://dx.doi.org/10.5622/illinois/9780252042805.001.0001.
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Rocking the Closet: How Little Richard, Johnnie Ray, Liberace, and Johnny Mathias Queered Pop Music examines the way four popular male musicians who emerged in the 1950s, Johnnie Ray, Little Richard, Johnny Mathis, and Liberace challenged post-World War II masculine conventions. Rocking is a critical close reading that fuses queer literary theory, musicology, and popular music studies frameworks to develop its argument. Recent scholarship in queer theory and literary history constitutes a key strand of the book’s discussion of queer ambivalence regarding identity. Notably, the book explores how the four artists challenged male gender and sexual conventions without overtly identifying their respective sexual orientations or necessarily affiliating with gay activism, identity politics, or community tropes. The book outlines the emergence of postwar social expectations of male figures and employs these expectations to define a unique a set of five “queering” tools the four musicians employed in various combinations, to develop their public personae and build audiences. These tools include self-neutering, self-domesticating, spectacularizing, playing the “freak,” and playing the race card. Despite the prevalence of postwar gender norms, their deft use of these tools enabled each artist to develop sexually ambiguous personae and capitalize on the postwar audiences’ attraction to novelty and difference. These “queering” tools endure among contemporary musicians who challenge masculine conventions in popular music.
Book chapters on the topic "Rare gas matrix"
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Huisken, Friedrich. "Matrix Spectroscopy in Molecular Beams: A Vibrational Study of Hydrogen-Bonded Complexes Embedded in Rare Gas Host Clusters." In Recent Theoretical and Experimental Advances in Hydrogen Bonded Clusters, 229–47. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-015-9434-9_16.
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Raff, Lionel, Ranga Komanduri, Martin Hagan, and Satish Bukkapatnam. "Fitting Potential Energy Hypersurfaces." In Neural Networks in Chemical Reaction Dynamics. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199765652.003.0005.
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Molecular dynamics (MD) and Monte Carlo (MC) simulations are the two most powerful methods for the investigation of dynamic behavior of atomic and molecular motions of complex systems. To date, such studies have been used to investigate chemical reaction mechanisms, energy transfer pathways, reaction rates, and product yields in a wide array of polyatomic systems. In addition, MD/MC methods have been successfully applied for the investigation of gas-surface reactions, diffusion on surfaces and in the bulk, membrane transport, and synthesis of diamond using chemical vapor deposition (CVD) techniques. The structure of vapor deposited rare gas matrices has been studied using trajectories procedures. If the chemical reaction of interest contains three atoms or fewer, various types of quantum and semiclassical calculations can be brought to bear on the problem. These methods include wave packet studies, close-coupling calculations at various levels of accuracy, and S-matrix theory. Several excellent review articles have been published describing the principal techniques and problems involved in conducting MD studies; the reader may wish to consult these as background material for this discussion. With the advent of relatively inexpensive, powerful personal computers, MD/MC simulations have become routine. Once the potential-energy hypersurface for the system has been obtained, the computations are straightforward, though time-consuming. In the majority of cases, the computational time required is on the order of hours to a few days. However, the accuracy of these simulations depends critically on the accuracy of the potential hypersurface used. The major problem associated with MD/MC investigations is the development of a potential-energy hypersurface whose topographical features are sufficiently close to those of the true, but unknown, surface that the results of the calculations are experimentally meaningful. Once the potential surface is chosen or computed, all the results from any quantum mechanical, semiclassical, or classical scattering or equilibrium calculation are determined. The only purpose of the MD calculations is to ascertain what these results are. Therefore, the most critical part of any MD/MC study is the development of the potential-energy hypersurface and the associated force field.
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Zindani, Divya, Nadeem Faisal, and Kaushik Kumar. "Optimization of Process Parameters for Electro-Chemical Machining of EN19." In Handbook of Research on Green Engineering Techniques for Modern Manufacturing, 127–42. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-5445-5.ch008.
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Electrochemical machining (ECM) is a non-conventional machining process that is used for machining of hard-to-machine materials. The ECM process is widely used for the machining of metal matrix composites. However, it is very essential to select optimum values of input process parameters to maximize the machining performance. However, the optimization of the output process parameters and hence the machining performance is a difficult task. In this chapter an attempt has been made to carry out single and multiple optimization of the material removal rate (MRR) and the surface roughness (SR) for the ECM process of EN19 using the particle swarm optimization (PSO) technique. The input parameter considered for the optimization are electrolyte concentration (%), voltage (V), feed rate (mm/min), and inter-electrode gap (mm). The optimum value of MRR and SR as found using the PSO algorithm are 0.1847 cm3/min and 25.0612, respectively.
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Sivachidambaram, P., Raghuraman Srinivasan, and Venkatraman Ramamoorthy. "Pulsed TIG Welding of Al–SiC Composite: Welding Parameter Optimization." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000275.
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Pulse on time, pulse frequency, peak current, and base current are the important parameters to be optimized in pulsed current tungsten inert gas (PCTIG) welding of Al–SiC metal matrix composite. Experiments were designed and conducted using the L9 orthogonal array technique. The regression equation was developed using Design Expert® statistical software package to predict the weld center’s micro hardness, yield strength, ultimate strength, elongation (%), bending load, weld depth, weld width, cooling rate, and peak temperature near the weld zone of Al-8% SiC composite, welded using PCTIG welding. Correlation coefficient shows 0.9 for all the mechanical properties. This showed that the regression equation and the mathematical model developed were adequate. Analysis of contour plot, interaction effect, signal-to-noise ratio, and mean response were developed, the influence of each pulsed current parameter was evaluated at each level, and the percentage of influence was calculated by using pulsed current parameters. Ultimate tensile strength and bending load values depend on the microstructure. When the cooling rate is higher, fine microstructures are observed due to grain refinement; higher tensile strength and bending load are also observed. Due to the decreased cooling rate, coarse microstructures are observed, which result in poor tensile strength and bending load. PCTIG welding parameters are responsible for the change in the cooling rate of the weld zone. The optimization of the PCTIG welding parameters shows that the peak current and base current should be 160 and 60 A, respectively. Pulse on time is recommended to be 50%–55% and pulse frequency to be 5 Hz.
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Nitzan, Abraham. "Vibrational Energy Relaxation." In Chemical Dynamics in Condensed Phases. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780198529798.003.0020.
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An impurity molecule located as a solute in a condensed solvent, a solid matrix or a liquid, when put in an excited vibrational state will loose its excess energy due to its interaction with the surrounding solvent molecules. Vibrational energy accumulation is a precursor to all thermal chemical reactions. Its release by vibrational relaxation following a reactive barrier crossing or optically induced reaction defines the formation of a product state. The direct observation of this process by, for example, infrared emission or more often laser induced fluorescence teaches us about its characteristic timescales and their energetic (i.e. couplings and frequencies) origin. These issues are discussed in this chapter. Before turning to our main task, which is constructing and analyzing a model for vibrational relaxation in condensed phases, we make some general observations about this process. In particular we will contrast condensed phase relaxation with its gas phase counterpart and will comment on the different relaxation pathways taken by diatomic and polyatomic molecules. First, vibrational relaxation takes place also in low density gases. Collisions involving the vibrationally excited molecule may result in transfer of the excess vibrational energy to rotational and translational degrees of freedom of the overall system. Analysis based on collision theory, with the intermolecular interaction potential as input, then leads to the cross-section for inelastic collisions in which vibrational and translational/rotational energies are exchanged. If C∗ is the concentration of vibrationally excited molecules and ρ is the overall gas density, the relaxation rate coefficient kgas is defined from the bimolecular rate law When comparing this relaxation to its condensed phase counterpart one should note a technical difference between the ways relaxation rates are defined in the two phases.
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Zhang, Weigang, Changming Xie, Xi Wei, and Min Ge. "C/C-ZrB2-ZrC-SiC Composite Derived from Polymeric Precursor Infiltration and Pyrolysis." In MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments, 435–59. IGI Global, 2013. http://dx.doi.org/10.4018/978-1-4666-4066-5.ch014.
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Part II. Mechanical and ablation properties of the 2D C/C-ZrB2-ZrC-SiC composites with a fiber volume fraction of 17.6%, fabricated by infiltration and co-pyrolysis of blended polymeric precursors, were studied in this Part II. Flexural strength and fracture toughness of the composites were found to be influenced strongly by the thickness of the deposited pyrolytic carbon interphase, a composite with the pyrolytic carbon volume fraction of 22.3% exhibits improved bending strength and fracture toughness of 127.9 MPa and 6.23 MPa·m1/2, respectively. The pseudo-plastic strain to failure of the composite is ascribed to sliding of the interphase and pulling out of carbon fibers from the brittle ceramics matrix. Ablation properties of the composite were investigated with a plasma torch and arc-heated wind tunnel tests at temperatures above 1800~2200°C. The composite exhibits very low ablation rates of 0.18×10-3 mm/s at 1800°C and 0.37×10-3 mm/s at 2000°C in the plasma torch after 1000s testing, as compared to a similar rate of 0.30×10-3 mm/s in the wind tunnel at 1900°C after 600s testing. Ablation rates increase with increasing of temperatures from 1800 to 2200°C. The maximum ablation rate is only 1.67×10-3 mm/s in a plasma torch at 2200°C for 1000s, decreased by 71.0% as compared with the C/C-SiC composite with the same fiber and interphase contents. The 2D C/C-ZrB2-ZrC-SiC composite simultaneously showed excellent thermal shock resistance, on account of no cracks on the surface and breakage of the material being detected after these abrupt temperature increasing and long time ablations. The heating-up rate at the center of the composite specimen was found as high as above 30K/s in the plasma torch tests. Excellent ablation and thermal shock resistances of the composite can be attributed to its architecture of carbon fiber and interphase, as well as its matrix microstructures characterized by nano sized dispersions of ZrB2-Zr-SiC phases inherent formed by co-pyrolysis of three polymeric precursors. These meso- and microstructures make the composites possess very small and steady coefficients of thermal expansion (CTE) around 1.5~2.5×10-6/K and high thermal conductivities around 10~14 W/mK (which increases with increasing of temperature) from room temperature to 1300°C, respectively. Surface products and cross sectional morphologies of the composite after the ablation tests were also investigated using SEM and XRD, it was found that a homogeneous distributed and continuous glass layer composing of ZrO2-SiO2 with zirconia as a skeleton was in-situ formed. These special features of coating benefits from the merits of matrix microstructures, and inhibits the inward diffusion of oxygen and protects the composite from further oxidation and spalled off by strong gas fluid.
Conference papers on the topic "Rare gas matrix"
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van Roode, Mark, Arun K. Bhattacharya, Mattison K. Ferber, and Frank Abdi. "Creep Resistance and Water Vapor Degradation of SiC/SiC Ceramic Matrix Composite Gas Turbine Hot Section Components." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-23012.
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Ceramic Matrix Composites (CMCs) are potentially valuable structural materials for high temperature stationary components in the hot section of advanced gas turbines. Endurance field testing, totaling in excess of 88,000 engine operating hours, conducted since 1997 by Solar Turbines Incorporated has shown promise for SiC/SiC and Oxide/Oxide CMC combustor liners. In support of ongoing development life prediction modeling was used to generate creep rupture strengths for two SiC/SiC CMC model systems, incorporating polycrystalline Hi-Nicalon and stoichiometric Sylramic-iBN fibers, respectively. The creep rupture strengths were combined with water vapor degradation modeling, extrapolated from laboratory studies, to estimate the Upper Use Temperature (UUT) of CMC combustor liners in the hot section of gas turbines of various pressure ratios. In the absence of a protective Environmental Barrier Coating (EBC) the UUT is <1000°C and the advantage of the superior creep rupture strength of the Sylramic-iBN fiber over the Hi-Nicalon fiber is largely lost. The selection of a suitable EBC restores the creep rupture strength of the SiC/SiC CMCs provided the EBC remains functional during the operation of the gas turbine over the expected service life of 30,000 hours. A heat transfer study was conducted to estimate the EBC surface temperature and CMC surface and average temperatures over the Turbine Rotor Inlet Temperature (TRIT) range of 1000–1400°C. A comparison was made with a standard metal combustor liner with Thermal Barrier Coating (TBC) which can be used for TRITs up to ∼1200°C. It was learned that the SiC/SiC CMCs with the standard Si/Mullite/BSAS EBC does not offer an advantage over the metal/TBC systems at a TRIT of 1200°C because of the recession rates of the EBC constituents. Replacing the BSAS top coat with a rare earth disilicate or monosilicate has the the potential for a reduction in surface recession of the EBC by one to two orders of magnitude. It is estimated that rare earth disilicate- and monosilicate-based EBCs may enable adequate SiC/SiC CMC life for gas turbines with TRITs up to ∼1350°C and ∼1400°C, respectively.
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van Roode, Mark, and Arun K. Bhattacharya. "Durability of Oxide/Oxide CMCs in Gas Turbine Combustors." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68974.
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An integrated creep rupture strength degradation and water vapor degradation model for gas turbine oxide-based CMC (Ceramic Matrix Composite) combustor liners was expanded with heat transfer computations to establish maximum TRIT (Turbine Rotor Inlet Temperature) for gas turbines with 10:1 pressure ratio. Recession rates and average CMC operating temperatures were calculated for an existing baseline N720/A (N720/Al2O3) CMC combustor liner system, with and without protective Al2O3 FGI (Friable Graded Insulation) for 30,000-h liner service life. The potential for increasing TRIT by YAG (Y3Al5O12) substitution for the fiber, matrix and FGI constituents of the CMC system was explored, because of the known superior creep and water vapor degradation resistance of YAG compared to Al2O3. It was predicted that uncoated N720/A can be used as a combustor liner material up to a TRIT of ∼1200°C, offering no TRIT advantage over a conventional metal + TBC (Thermal Barrier Coating) combustor liner. A similar conclusion was previously reached for a SiC/SiC CMC liner with BSAS-type EBC (Barium Strontium Aluminum Silicate Environmental Barrier Coating). The existing N720/A + Al2O3 FGI combustor liner system can be used at a maximum TRIT of ∼1350°C, a TRIT increase over metal + TBC and uncoated N720/A of ∼150°C. Replacing the Al2O3 with YAG is predicted to increase the maximum allowable TRIT. Substitution of the fiber or matrix in N720/A increases TRIT by ∼100°C. A YAG FGI improves the TRIT of the 720/A + Al2O3 FGI by ∼50°C, enabling a TRIT of ∼1400°C, similar to that predicted for SiC/SiC CMCs with protective rare earth monosilicate EBCs.
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Ma, L., R. T. Johns, D. Zhu, and A. D. Hill. "Fast Method for Real-Time Interpretation of Variable-Rate Wells with Changing Skin: Application to Matrix Acidizing." In International Oil and Gas Conference and Exhibition in China. Society of Petroleum Engineers, 2000. http://dx.doi.org/10.2118/64651-ms.
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Kedir, N., C. Gong, L. Sanchez, M. J. Presby, S. Kane, D. C. Faucett, and S. R. Choi. "Erosion in Gas-Turbine Grade Ceramic Matrix Composites (CMCs)." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75827.
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Erosion behavior of a large number of gas-turbine grade ceramic matrix composites (CMCs) was assessed using fine to medium grain garnet erodents at velocities of 200 and 300 m/s at ambient temperature. The CMCs used in the current work were comprised of nine different SiC/SiCs, one SiC/C, one C/SiC, one SiC/MAS, and one oxide/oxide. Erosion damage was quantified with respect to erosion rate and the damage morphology was assessed via SEM and optical microscopy in conjunction with 3-D image mapping. The CMCs response to erosion appeared to be very complicated due to their architectural complexity, multiple material constituents, and presence of pores. Effects of architecture, material constituents, density, matrix hardness, and elastic modulus of the CMCs were taken into account and correlated to overall erosion behavior. The erosion of monolithic ceramics such as silicon carbide and silicon nitrides was also examined to gain a better understanding of the governing damage mechanisms for the CMC material systems used in this work.
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Chandraker, S., and H. Roy. "A Balanced IIRS Model for Investigating the Dynamics of Damped Rotor Bearing System." In ASME 2014 Gas Turbine India Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gtindia2014-8279.
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In this paper the application of the balanced Iterative Improved Reduction model techniques to complex rotor-bearing systems is investigated. It is demonstrated that, Iterative Improved Reduction System (IIRS) improves the matrix reductions by ensuring that the transformation matrix for each reduction is optimized. This reduction technique also benefices the problem due to skew symmetric matrices, which arises for inclusion of gyroscopic effect and internal damping. Numerical examples are solved to demonstrate the validity and efficiency of the reduced order model in representing the dynamics of the actual rotor system. Under these conditions, the complex behaviour of the rotor-shaft is studied to get an insight of the dynamic characteristics of the system, in terms of Campbell Diagram, Decay rate plot and Unbalance Response. Many researchers adopted different methodology for obtaining the model reduction but their work is limited up to undamped system. This work is started by motivation of the absentia of work for damped rotor bearing system.
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Óttarsson, Gísli, and Christophe Pierre. "A Transfer Matrix Approach to Vibration Localization in Mistuned Blade Assemblies." In ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/93-gt-115.
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A study of mode localization in mistuned bladed disks is performed using transfer matrices. The transfer matrix approach yields the free response of a general, mono-coupled, perfectly cyclic assembly in closed form. A mistuned structure is represented by random transfer matrices, and the expansion of these matrices in terms of the small mistuning parameter leads to the definition of a measure of sensitivity to mistuning. An approximation of the localization factor, the spatially averaged rate of exponential attenuation per blade-disk sector, is obtained through perturbation techniques in the limits of high and low sensitivity. The methodology is applied to a common model of a bladed disk and the results verified by Monte Carlo simulations. The easily calculated sensitivity measure may prove to be a valuable design tool due to its system-independent quantification of mistuning effects such as mode localization.
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Chamis, C. C., P. L. N. Murthy, S. N. Singhal, and J. J. Lackney. "Hitcan for Actively Cooled Hot-Composite Thermostructural Analysis." In ASME 1991 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1991. http://dx.doi.org/10.1115/91-gt-116.
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A computer code, HITCAN (HIgh Temperature Composite ANalyzer) has been developed to analyze/design hot metal matrix composite structures. HITCAN is a general purpose code for predicting the global structural and local stress-strain response of multilayered (arbitrarily oriented) metal matrix structures both at the constituent (fiber, matrix, and interphase) and the structure level and including the fabrication process effects. The thermomechanical properties of the constituents are considered to be nonlinearly dependent on several parameters including temperature, stress, and stress rate. The computational procedure employs an incremental iterative nonlinear approach utilizing a multifactor-interaction material behavior model, i.e., the material properties are expressed in terms of a product of several factors that affect the properties. HITCAN structural analysis capabilities (static, load stepping - a multistep static analysis with material properties updated at each step-modal, and buckling) for cooled hot structures are demonstrated through a specific example problem.
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Crandall, Dustin, Goodarz Ahmadi, and Duane H. Smith. "Modeling of Gas-Liquid Flow Through an Interconnected Channel Matrix." In ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78092.
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The motion of a less viscous, non-wetting gas into a liquid-saturated porous medium is known as drainage. Drainage is an important process in environmental applications, such as enhanced oil recovery and geologic CO2 sequestration. Understanding what conditions will increase the volume of gas that can saturate an initially water-saturated porous medium is of importance for predictions of the total CO2 volume that can be sequestered in known geologic formations. To further the understanding of how drainage flow properties are related to different injection flow-rates, a porous medium consisting of interconnected channels and pores was manufactured to perform bench-top experiments of drainage. Additionally, a finite-volume model of this interconnected channel matrix was constructed. Numerical simulations of constant-rate injection into the model porous medium are first shown to compare favorably to the bench-top experiments. The fluid and injection properties of the drainage process were then varied to evaluate the flow conditions which would maximize the volume of gas trapped within the porous medium. In particular, CO2 displacing brine within the porous medium was modeled, with representative subsurface temperatures and fluid properties. It was shown with these fluid conditions a higher final saturation of the invading less-viscous CO2 was obtained, as compared to air into water experiments at similar injection rates.
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Gupta, Suresh. "Erosion Characteristics of Ceramic Particulate and Whisker Reinforced Aluminum Composites." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-369.
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Advanced composite materials are one of the key enabling technologies for achieving the planned revolutionary improvements in the next generation of aero gas turbine engines. For example the thrust to weight ratio of advanced military engines is targeted to double (to 20:1) within the next 10 to 15 years. A number of families of advanced composites are being developed, and metal matrix composites is one significant member of these. These can be either ceramic fiber or ceramic particulate/whiskers embedded in matrixes of aluminum, titanium or superalloys. Silicon carbide particulate/whisker reinforced aluminum has been under consideration for the cold section of front end engine components such as compressor blades, compressor stator vanes and casings. One potentially serious problem anticipated in using these composites for such application is its behavior in particulate erosion, as may happen in sandy environments and runways. This paper describes the test program undertaken to study this problem, and discusses the results obtained. It was found that the erosion rate of such composites can be considerably higher than that of non-reinforced aluminum alloys. Further, the characteristic erosion behavior is modified significantly. Also identified were new mechanisms of material removal coming into play. These are also discussed.
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Pati, Pravat Ranjan, and Alok Satapathy. "A Study on Tribological Behavior of Linz-Donawitz Slag Filled Polypropylene Composites Using Experimental Design and Neural Networks." In ASME 2017 Gas Turbine India Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gtindia2017-4514.
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Short fiber-reinforced polymer composites are used in numerous tribological applications. In the present work, an attempt has been made to improve the wear resistance of short glass fiber (SGF) reinforced polypropylene composites by incorporation of micro-sized Linz-Donawitz slag (LDS) particles. Composites with different LDS content (0, 7.5, 15 and 22.5 wt%) in a polypropylene matrix base with 20 wt% SGF reinforcement are prepared by injection molding technique. Solid particle erosion trials, as per ASTM G76 test standards, are conducted on the composite samples following a well-planned experimental schedule based on Taguchi design-of-experiments. Significant process parameters predominantly influencing the rate of erosion are identified. The study reveals that the LDS content and impact velocity are the most significant among various factors influencing the wear rate of these composites. Further, a prediction model based on artificial neural network (ANN) is proposed to predict the erosion performance of the composites under a wide range of erosive wear conditions. This work shows that an ANN model is quite helpful in saving time and resources that are required for a large number of experimental trials and thus, successfully predicts the erosion rate of composites both within and beyond the experimental domain.
Reports on the topic "Rare gas matrix"
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Angulo Rodríguez, Emilio, and Ariel Yépez-García. The Role of Natural Gas in Energy Transition. Inter-American Development Bank, November 2020. http://dx.doi.org/10.18235/0002868.
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As of 2004 and continuously to this day, the annual growth rate of renewable sources has been greater than that of all fossil fuels combined. In the midst of this transition to cleaner energy, natural gas is the only fossil fuel that has increased its share in the global energy matrix. Technological changes in the LNG supply chain, as well as transformations in the global natural gas market, largely explain this growth. This publication provides evidence on the fundamental role that natural gas plays in the energy transition, given that: (i) its greenhouse gas emissions are substantially lower than those of oil and coal; (ii) it provides the firm power necessary to complement intermittent renewable energies; (iii) it is particularly safe compared to other fossil fuels. In line with these attributes, the International Energy Agency projects that the share of natural gas in the global energy matrix by 2040 will remain stable (around 24%), even in its Sustainable Development Scenario, which would allow to meet the goals established in the Paris Agreement.
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Hsueh, Gary, David Czerwinski, Cristian Poliziani, Terris Becker, Alexandre Hughes, Peter Chen, and Melissa Benn. Using BEAM Software to Simulate the Introduction of On-Demand, Automated, and Electric Shuttles for Last Mile Connectivity in Santa Clara County. Mineta Transportation Institute, January 2021. http://dx.doi.org/10.31979/mti.2021.1822.
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Despite growing interest in low-speed automated shuttles, pilot deployments have only just begun in a few places in the U.S., and there is a lack of studies that estimate the impacts of a widespread deployment of automated shuttles designed to supplement existing transit networks. This project estimated the potential impacts of automated shuttles based on a deployment scenario generated for a sample geographic area: Santa Clara County, California. The project identified sample deployment markets within Santa Clara County using a GIS screening exercise; tested the mode share changes of an automated shuttle deployment scenario using BEAM, an open-source beta software developed at the Lawrence Berkeley National Laboratory to run traffic simulations with MATSim; elaborated the model outputs within the R environment; and then estimated the related impacts. The main findings have been that the BEAM software, despite still being in its beta version, was able to model a scenario with the automated shuttle service: this report illustrates the potential of the software and the lessons learned. Regarding transportation aspects, the model estimated automated shuttle use throughout the county, with a higher rate of use in the downtown San José area. The shuttles would be preferred mainly by people who had been using gasoline-powered ride hail vehicles for A-to-B trips or going to the bus stop, as well as walking trips and a few car trips directed to public transport stops. As a result, the shuttles contributed to a small decrease in emissions of air pollutants, provided a competitive solution for short trips, and increased the overall use of the public transport system. The shuttles also presented a solution for short night trips—mainly between midnight and 2 am—when there are not many options for moving between points A and B. The conclusion is that the automated shuttle service is a good solution in certain contexts and can increase public transit ridership overall.