Literatura académica sobre el tema "Relation n-aire"
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Artículos de revistas sobre el tema "Relation n-aire"
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Bonetto, Fabienne. "Équilibres multiples et poids de l’histoire: Quelle responsabilité pour la politique économique?" Panoeconomicus 54, n.º 2 (2007): 159–84. http://dx.doi.org/10.2298/pan0702159b.
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(francuski) En formalisant une dynamique ? effets de seuil, les mod?les ? ?quilibres multiples enrichissent le paradigme de la croissance endog?ne; l?objectif de cet article est de montrer qu?ils renforcent ?galement la responsabilit? de la politique ?conomique. En effet, d?s lors que les conditions initiales s?lectionnent l??quilibre de long terme, l?histoire de la politique publique d?investissement (au sens large) devient d?terminante. Par ailleurs l?intervention publique peut permettre la sortie de la trappe de pauvret?. Sur la p?riode 1970-1995, nous testons l?hypoth?se d?effets de seuil en liaison avec le niveau initial du stock de capital (au sens large) d?velopp? par l??tat. Nos r?sultats empiriques sugg?rent un r?le pour la politique publique dans la diff?renciation des r?gimes de convergence de sorte que la relation entre la croissance et la politique ?conomique n?est pas n?cessairement lin?aire.
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Maciá Andreu, María José, Javier Sánchez-Sánchez, José Antonio García Córdoba y Ana María Gallardo Guerrero. "Análisis de la seguridad y accesibilidad de los espacios deportivos en Educación Secundaria Obligatoria". Cuadernos de Psicología del Deporte 21, n.º 1 (1 de enero de 2021): 242–57. http://dx.doi.org/10.6018/cpd.395671.
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Las instalaciones deportivas escolares son el marco idóneo donde los alumnos deben de adquirir los hábitos de actividad física, estableciendo el Real Decreto 132/2010, que estas deben de cumplir con las condiciones de seguridad y accesibilidad que determine la legislación vigente. No obstante, varias investigaciones previas alertan del incumplimiento de dichos requisitos, siendo el objetivo del presente estudio el análisis de aquellos relacionados con la seguridad y accesibilidad de los espacios deportivos utilizados para impartir las clases de Educación Física en la etapa de Educación Secundaria Obligatoria (ESO). La investigación se llevó a cabo en n=45 Institutos de ESO de titularidad pública de la Región de Murcia, a través de una observación in situ con dos listas de control ad hoc en función del espacio a analizar, de 71 ítems para espacios cubiertos y 36 ítems para espacios al aire libre, de respuesta dicotómica (SI/NO), elaboradas a partir de la normativa y legislación vigente. Los resultados muestran un porcentaje medio de cumplimiento del 63,05±7,09 en espacios cubiertos (n=51) y del 61,52±8,70 en espacios al aire libre (n=93) detectándose diferencias estadísticamente significativas en los cubiertos (p <0,05) en función de su titularidad, con un cumplimiento mayor en los municipales. Ninguno de los espacios deportivos analizados cumple con todos los requisitos establecidos, detectando numerosas deficiencias respecto a su seguridad que pueden conllevar riesgos, así como en relación a su accesibilidad, apreciando barreras arquitectónicas y un alto incumplimiento de los aspectos relacionados con la accesibilidad cognitiva y limitaciones de tipo visual. School sports facilities are the ideal framework where students must acquire physical activity habits, establishing Royal Decree 132/2010, that they must comply with the safety and accessibility conditions determined by current legislation. However, several previous research warn of non-compliance with these requirements, being the objective of this study the analysis of those related to the safety and accessibility of the sports facilities used in Physical Education classes at the compulsory secondary education stage. This research was carried out in n=45 compulsory secondary education schools of public ownership of the Region of Murcia, through an in situ observation with two ad hoc checklists according to the space to be analyzed, of 71 items for indoor facilities and 36 items for outdoor ones, of dichotomous response (YES/NO), developed from the current regulations and legislation. The results show an average percentage of compliance of 63.05±7.09 in indoor facilities (n=51) and 61.52±8.70 in outdoor spaces (n=93) detecting statistically significant differences in the indoor ones (p <0.05) depending on their ownership, with greater compliance in the municipal. None of the sports facilities analyzed meets all the established requirements, detecting numerous deficiencies regarding their safety that may entail risks, as well as in relation to their accessibility, appreciating architectural barriers and a high breach of the aspects related to cognitive accessibility and visual limitations. Le strutture sportive scolastiche sono il quadro ideale in cui gli studenti devono acquisire abitudini di attività fisica, stabilendo il regio decreto 132/2010, che deve rispettare le condizioni di sicurezza e accessibilità stabilite dalla normativa vigente. Tuttavia, diverse indagini precedenti avvertono della violazione di questi requisiti, essendo l'obiettivo del presente studio l'analisi di quelli relativi alla sicurezza e all'accessibilità degli spazi sportivi utilizzati per insegnare le lezioni di educazione fisica nell'istruzione secondaria obbligatoria (ESO). L'indagine è stata condotta in n=45 istituti ESO di proprietà pubblica della regione di Murcia, attraverso un'osservazione sistematica con due liste di controllo ad hoc a seconda dello spazio da analizzare, di 71 articoli per spazi coperti e 36 articoli per spazi esterni, risposta dicotomica (SÌ/NO), preparati dalle normative e dalla legislazione vigenti. I risultati mostrano una percentuale media di conformità di 63,05±7,09 negli spazi coperti (n=51) e 61,52±8,70 negli spazi esterni (n=93), rilevando differenze statisticamente significative negli spazi coperti (p <0,05) a seconda della proprietà, con una maggiore conformità nei comuni. Nessuna delle aree sportive analizzate soddisfa tutti i requisiti stabiliti, rilevando numerose carenze relative alla loro sicurezza che possono comportare rischi, nonché in relazione alla loro accessibilità, apprezzando le barriere architettoniche e un'alta violazione degli aspetti relativi all'accessibilità e alle limitazioni cognitive tipo visivo. As instalações esportivas escolares são a estrutura ideal onde os estudantes devem adquirir hábitos de atividade física, estabelecendo o Real Decreto 132/2010, que deve obedecer às condições de segurança e acessibilidade determinadas pela legislação vigente. No entanto, várias investigações anteriores alertam para a violação desses requisitos, sendo o objetivo do presente estudo a análise daqueles relacionados à segurança e acessibilidade dos espaços esportivos utilizados para o ensino das aulas de Educação Física no Ensino Médio obrigatório (ESO). A investigação foi realizada em n=45 institutos ESO de propriedade pública da Região de Múrcia, através de uma observação in situ com duas listas de verificação ad hoc, dependendo do espaço a ser analisado, de 71 itens para espaços cobertos e 36 itens para espaços ao ar livre, resposta dicotômica (SIM/NÃO), elaborado a partir da legislação e regulamentação vigentes. Os resultados mostram uma porcentagem média de conformidade de 63,05±7,09 nos espaços cobertos (n=51) e 61,52±8,70 nos espaços ao ar livre (n=93), sendo detectadas diferenças estatisticamente significantes (p <0,05) dependendo de sua propriedade, com maior conformidade nos municípios. Nenhuma das áreas de esportes analisadas atende a todos os requisitos estabelecidos, detectando inúmeras deficiências em relação à sua segurança que podem acarretar riscos, bem como em relação à sua acessibilidade, valorização de barreiras arquitetônicas e alta quebra de aspectos relacionados à acessibilidade cognitiva e limitações tipo visual.
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Majima, Yuichi, Kazuhiko Takeuchi, Yukiyoshi Hamaguchi, Atsuhito Morishita, Keisuke Hirata y Yasuo Sakakura. "Hearing Impairment in Relation to Viscoelasticity of Middle Ear Effusions in Children". Annals of Otology, Rhinology & Laryngology 97, n.º 3 (mayo de 1988): 272–74. http://dx.doi.org/10.1177/000348948809700311.
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Both dynamic viscosity (n′) and elasticity (G′) of middle ear effusion were measured with an oscillating sphere magnetic rheometer and compared with the degree of conductive hearing loss in 65 ears of 40 children. There was a significant correlation between n′ and the magnitude of the air-bone gap at 500 and 1,000 Hz, but there was no significant correlation between G′ and the magnitude of the air-bone gap at 2,000 or 4,000 Hz. No significant correlation was noted between G′ and the magnitude of the air-bone gap at 500,1,000, 2,000, or 4,000 Hz. These results indicate that the n′ of middle ear effusion has an effect on the amount of hearing impairment at frequencies below 1,000 Hz.
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Karunaratne, K. C. y C. R. Burn. "Relations between air and surface temperature in discontinuous permafrost terrain near Mayo, Yukon Territory". Canadian Journal of Earth Sciences 41, n.º 12 (1 de diciembre de 2004): 1437–51. http://dx.doi.org/10.1139/e04-082.
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The association of site characteristics with the n-factor, a ratio of air to ground surface temperature, was investigated at five sites in the boreal forest near Mayo, Yukon Territory. Permafrost was in equilibrium with surface conditions at three sites, was degrading at another, and was absent from the fifth. Air and near-surface ground temperatures were recorded by data loggers between September 2000 and April 2002, and mean daily temperatures were accumulated to calculate n-factors for the freezing (nf) and thawing (nt) seasons. Air temperature did not vary between the sites, so inter-site differences in nf and nt were because of variations in surface temperature. Variations in nf between the sites over the two winters were primarily because of differences in snow depth, but at sites with similar snow cover, the surface temperatures were relatively high when the site was underlain by unfrozen ground. During summer, daily mean surface temperatures were initially less than air temperatures. However, once the thawing front had penetrated below the depth of diurnal temperature fluctuation, the air and ground surface temperatures converged. Since the rate of thaw penetration is governed by soil thermal diffusivity, nt varies directly with this property. These results indicate that subsurface conditions, particularly absolute temperature and ground thermal properties, exert considerable influence on n-factors, and, at the Mayo sites, the influence is greater than that of the vegetation.
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Frankel, Mika, Gabriel Bekö, Michael Timm, Sine Gustavsen, Erik Wind Hansen y Anne Mette Madsen. "Seasonal Variations of Indoor Microbial Exposures and Their Relation to Temperature, Relative Humidity, and Air Exchange Rate". Applied and Environmental Microbiology 78, n.º 23 (21 de septiembre de 2012): 8289–97. http://dx.doi.org/10.1128/aem.02069-12.
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ABSTRACTIndoor microbial exposure has been related to adverse pulmonary health effects. Exposure assessment is not standardized, and various factors may affect the measured exposure. The aim of this study was to investigate the seasonal variation of selected microbial exposures and their associations with temperature, relative humidity, and air exchange rates in Danish homes. Airborne inhalable dust was sampled in five Danish homes throughout the four seasons of 1 year (indoors,n= 127; outdoors,n= 37). Measurements included culturable fungi and bacteria, endotoxin,N-acetyl-beta-d-glucosaminidase, total inflammatory potential, particles (0.75 to 15 μm), temperature, relative humidity, and air exchange rates. Significant seasonal variation was found for all indoor microbial exposures, excluding endotoxin. Indoor fungi peaked in summer (median, 235 CFU/m3) and were lowest in winter (median, 26 CFU/m3). Indoor bacteria peaked in spring (median, 2,165 CFU/m3) and were lowest in summer (median, 240 CFU/m3). Concentrations of fungi were predominately higher outdoors than indoors, whereas bacteria, endotoxin, and inhalable dust concentrations were highest indoors. Bacteria and endotoxin correlated with the mass of inhalable dust and number of particles. Temperature and air exchange rates were positively associated with fungi andN-acetyl-beta-d-glucosaminidase and negatively with bacteria and the total inflammatory potential. Although temperature, relative humidity, and air exchange rates were significantly associated with several indoor microbial exposures, they could not fully explain the observed seasonal variations when tested in a mixed statistical model. In conclusion, the season significantly affects indoor microbial exposures, which are influenced by temperature, relative humidity, and air exchange rates.
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Tremblay, Maryse. "Décisions rendues par le Conseil canadien des relations du travail". Articles 46, n.º 1 (12 de abril de 2005): 204–14. http://dx.doi.org/10.7202/050651ar.
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Suite à la déréglementation dans le secteur du transport en 1987, Air Canada a voulu s'allier à des transporteurs régionaux en vue de combattre la concurrence. Elle a conclu des ententes avec eux et investi d'importantes sommes en vue de l'élaboration d'un réseau liaison. Face à cette nouvelle situation, l'Association internationale des machinistes et des travailleurs de l'aérospatiale, district n ° 148, agent négociateur actuel d'environ 8 000 employés d'Air Canada, a décidé d'adresser une demande au Conseil afin qu'il déclare qu'Air Canada, Air BC, Air Nova et Air Ontario constituent un employeur unique pour les fins du Code canadien du travail. Après avoir examiné les critères régissant la question de contrôle ou de la direction en commun des entreprises, le Conseil a décidé que les entreprises remplissaient les cinq critères requis, mais a refusé d'exercer son pouvoir discrétionnaire défaire une telle déclaration.
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Tseng, C. M., C. S. Liu y C. Lamborg. "Seasonal changes in gaseous elemental mercury in relation to monsoon cycling over the northern South China Sea". Atmospheric Chemistry and Physics 12, n.º 16 (16 de agosto de 2012): 7341–50. http://dx.doi.org/10.5194/acp-12-7341-2012.
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Abstract. The distribution of gaseous elemental mercury (GEM) was determined in the surface atmosphere of the northern South China Sea (SCS) during 12 SEATS cruises between May 2003 and December 2005. The sampling and analysis of GEM were performed on board ship by using an on-line mercury analyzer (GEMA). Distinct annual patterns were observed for the GEM with a winter maximum of 5.7 ± 0.2 ng m−3 (n = 3) and minimum in summer (2.8 ± 0.2; n = 3), with concentrations elevated 2–3 times global background values. Source tracking through backward air trajectory analysis demonstrated that during the northeast monsoon (winter), air masses came from Eurasia, bringing continental- and industrial-derived GEM to the SCS. In contrast, during summer southwest monsoon and inter-monsoon, air masses were from the Indochina Peninsula and Indian Ocean and west Pacific Ocean. This demonstrates the impact that long-range transport, as controlled by seasonal monsoons, has on the Hg atmospheric distribution and cycling in the SCS.
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Ghaffar, Zulkifli Abdul, Salmiah Kasolang, Ahmad Hussein Abdul Hamid y Mohd Syazwan Firdaus Mat Rashid. "Effect of Dimensionless Numbers on Air Core Diameter of Pressure-Swirl Atomizer". Applied Mechanics and Materials 899 (junio de 2020): 22–28. http://dx.doi.org/10.4028/www.scientific.net/amm.899.22.
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Air core is an important parameter in pressure swirl atomizer since formation of air core determines the thickness of the discharged liquid sheet and the effective flow area of nozzle discharge. This consequently will affect the coefficient of discharge and the spray angle. This study conducted for the investigation of the relation between dimensionless numbers on the air core diameter. Dimensionless numbers are helpful aid for the quantification of independent parameters involving atomizer design and operating conditions simultaneously. Reynolds number, Re and orifice-to-swirl chamber diameter ratio, N are the dimensionless numbers selected for this study. Despite of the availability of study on the effect of dimensionless numbers on air core diameter, more study requires especially for smaller N. An experimental test-rig was constructed to conduct the performance test of the atomizer. Acquired images were analyzed using image-processing software. It was found that N has more significant effect on the change of air core diameter compared to Re. However, it is observed that at Re = 40000, N = 0.07 produces almost similar air core diameter with N = 0.25 at Re < 20000. In contrast, with N = 0.5, air core diameter produces are larger even at Re < 20000. Hence, it can be concluded that both Re and N are important parameters in characterizing the air core diameter in pressure-swirl atomizer.
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LI, Y. T. y R. WONG. "GLOBAL ASYMPTOTICS OF STIELTJES–WIGERT POLYNOMIALS". Analysis and Applications 11, n.º 05 (septiembre de 2013): 1350028. http://dx.doi.org/10.1142/s0219530513500280.
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Asymptotic formulas are derived for the Stieltjes–Wigert polynomials Sn(z; q) in the complex plane as the degree n grows to infinity. One formula holds in any disc centered at the origin, and the other holds outside any smaller disc centered at the origin; the two regions together cover the whole plane. In each region, the q-Airy function Aq(z) is used as the approximant. For real x > 1/4, a limiting relation is also established between the q-Airy function Aq(x) and the ordinary Airy function Ai (x) as q → 1.
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Tseng, C. M., C. S. Liu y C. Lamborg. "Seasonal changes in gaseous elemental mercury in relation to monsoon cycling over the Northern South China Sea". Atmospheric Chemistry and Physics Discussions 12, n.º 5 (11 de mayo de 2012): 12203–27. http://dx.doi.org/10.5194/acpd-12-12203-2012.
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Abstract. The distribution of gaseous elemental mercury (GEM) was determined in the surface atmosphere of the Northern South China Sea (SCS) during 12 SEATS cruises between May 2003 and December 2005. The sampling and analysis of GEM were performed on board ship by using an on-line mercury analyzer (GEMA). Distinct annual patterns were observed for the GEM with a winter maximum of 5.7 ± 0.2 ng m−3 (n = 3) and low in summer (2.8 ± 0.2) (n = 3), with concentrations elevated 2 ∼ 3 times global background values. Source tracking through backward trajectory analysis demonstrated air masses during the northeast monsoon in winter came from Eurasia, bringing continental- and industrial-derived GEM to the SCS. In contrast, during summer southwest monsoon and inter-monsoon, air masses were from the Indochina peninsula and Indian Ocean and West Pacific Ocean. This demonstrates the impact that long-range transport, as controlled by seasonal monsoons, has on the Hg atmospheric distribution and cycling in the SCS.
Tesis sobre el tema "Relation n-aire"
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Touhami, Rim. "Construction et évolution d'une ressource termino-ontologique dédiée à la représentation de relations n-aires". Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20131.
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Les ontologies sont devenues incontournables pour définir des vocabulaires standardisés ainsi qu'une représentation partagée d'un domaine d'intérêt. La notion de Ressource Termino-Ontologique (RTO) permet d'associer une partie terminologique et/ou linguistique aux ontologies afin d'établir une distinction claire entre la manifestation linguistique (le terme) et la notion qu'elle dénote (le concept). Les RTOs sont actuellement au cœur de nombreuses méthodes, outils et applications de l'Ingénierie des Connaissances (IC), discipline de l'Intelligence Artificielle permettant en particulier de développer des méthodes et des outils de capitalisation de connaissances.L'objectif de cette thèse, qui s'inscrit dans les problématiques de l'IC, est de capitaliser des données expérimentales issues de documents textuels (articles scientifiques, rapports de projet, etc.) afin de pouvoir les réutiliser dans des outils d'aide à la décision. Nous avons d'abord défini la notion de relation n-aire permettant de relier plusieurs arguments et l'avons modélisée dans une nouvelle RTO, baptisée naRyQ. Cette notion de relation n-aire nous a permis de modéliser des mesures expérimentales (e.g. diffusivité de l'oxygène dans un aliment, perméabilité à l'oxygène d'un emballage, broyage d'une biomasse, etc.) réalisées sur différents objets d'études (produit alimentaire, emballage, procédé de transformation, etc.). Afin d'implémenter la plateforme de capitalisation, nommée @Web, nous avons modélisé la RTO naRyQ en OWL/SKOS et défini l'ensemble des contraintes de cohérence qu'elle doit respecter. Enfin, une RTO étant amenée à évoluer pour répondre aux besoins de changement, nous avons proposé une méthode de gestion de l'évolution de cette RTO qui permet de maintenir sa cohérence de manière préventive. Cette méthode est implémentée dans le plug-in Protégé, nommé DynarOntoThis PhD thesis in Artificial Intelligence deals with knowledge engineering. Ontology, which can be defined as a controlled vocabulary allowing a community to share a common representation of a given area, is one of the key elements of knowledge engineering. Our framework is the capitalization of experimental data extracted from scientific documents (scientific articles, project reports, etc.), in order to feed decision support systems. The capitalization is guided by an ontological and terminological resource (OTR). An OTR associates an ontology with a terminological and/or a linguistic part in order to establish a clear distinction between the term and the notion it denotes (the concept). Experimental data can be represented by n-ary relations linking arguments of the experimentation, i.e. experimental measurements (e.g. oxygen diffusivity in food, oxygen permeability in packaging, biomass grinding, etc.), with studied objects (food, packaging, transformation process, etc.). We have defined the n-ary relation concept and a nary Relation between Quantitative experimental data OTR, called naRyQ. Our modeling relies on OWL2-DL and SKOS, W3C languages. Moreover, we have studied the evolution of such an OTR, extending the existing works taking into account i) the specificity of our OTR which deals with interdependent concepts and ii) its language representation. For that, we have proposed a preventive ontology evolution methodology defining elementary and composed changes based on a set of consistency constraints defined for our naRyQ OTR. Our contributions are implemented in two systems : our naRyQ OTR is nowadays the core of the existing capitalization system @Web and our evolution method is implemented in a Protégé plug-in called DynarOnto
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Minard, Anne-Lyse. "Extraction de relations en domaine de spécialité". Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00777749.
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La quantité d'information disponible dans le domaine biomédical ne cesse d'augmenter. Pour que cette information soit facilement utilisable par les experts d'un domaine, il est nécessaire de l'extraire et de la structurer. Pour avoir des données structurées, il convient de détecter les relations existantes entre les entités dans les textes. Nos recherches se sont focalisées sur la question de l'extraction de relations complexes représentant des résultats expérimentaux, et sur la détection et la catégorisation de relations binaires entre des entités biomédicales. Nous nous sommes intéressée aux résultats expérimentaux présentés dans les articles scientifiques. Nous appelons résultat expérimental, un résultat quantitatif obtenu suite à une expérience et mis en relation avec les informations permettant de décrire cette expérience. Ces résultats sont importants pour les experts en biologie, par exemple pour faire de la modélisation. Dans le domaine de la physiologie rénale, une base de données a été créée pour centraliser ces résultats d'expérimentation, mais l'alimentation de la base est manuelle et de ce fait longue. Nous proposons une solution pour extraire automatiquement des articles scientifiques les connaissances pertinentes pour la base de données, c'est-à-dire des résultats expérimentaux que nous représentons par une relation n-aire. La méthode procède en deux étapes : extraction automatique des documents et proposition de celles-ci pour validation ou modification par l'expert via une interface. Nous avons également proposé une méthode à base d'apprentissage automatique pour l'extraction et la classification de relations binaires en domaine de spécialité. Nous nous sommes intéressée aux caractéristiques et variétés d'expressions des relations, et à la prise en compte de ces caractéristiques dans un système à base d'apprentissage. Nous avons étudié la prise en compte de la structure syntaxique de la phrase et la simplification de phrases dirigée pour la tâche d'extraction de relations. Nous avons en particulier développé une méthode de simplification à base d'apprentissage automatique, qui utilise en cascade plusieurs classifieurs.
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Cerf, Loïc. "Fouille Sous Contraintes de Motifs Fermés dans des Relations n-aires Bruitées". Phd thesis, INSA de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00508534.
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Les jeux de données décrivant des objets par des propriétés Booléennes sont des relations binaires, c'est à dire des matrices 0/1. Dans une telle relation, un ensemble fermé est un sous-ensemble maximal d'objets partageant le même sous-ensemble maximal de propriétés. L'extraction de ces motifs, satisfaisant des contraintes de pertinences définies par l'utilisateur, a été étudiée en profondeur. Néanmoins, beaucoup de jeux de données sont des relations n-aires, c'est à dire des tenseurs 0/1. Réduire leur analyse à deux dimensions revient à en ignorer d'autres qui sont potentiellement intéressantes. Par ailleurs, la présence de bruit dans les jeux de données réelles conduit à la fragmentation des motifs à découvrir. On généralise facilement la définition d'un ensemble fermé aux relations de plus grande arité et à la tolérance au bruit. Au contraire, généraliser leur extraction est très difficile. Notre extracteur parcourt l'espace des motifs candidats d'une façon originale qui ne favorise aucune dimension. Cette recherche peut être guidée par une très grande classe de contraintes de pertinence que les motifs doivent satisfaire. En particulier, cette thèse étudie des contraintes spécifiques à la fouille de graphes dynamiques. Notre extracteur est plusieurs ordres de grandeurs plus efficace que les algorithmes existants, pourtant plus restreints dans leurs applications. Malgré ces résultats, une approche exhaustive ne peut souvent pas, en un temps raisonnable, lister des motifs tolérants beaucoup de bruit. Dans ce cas, compléter l'extraction avec une agglomération hiérarchique des motifs permet d'arriver à ses fins.
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Berrahou, Soumia Lilia. "Extraction d'arguments de relations n-aires dans les textes guidée par une RTO de domaine". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS019/document.
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Aujourd'hui, la communauté scientifique a l'opportunité de partager des connaissances et d'accéder à de nouvelles informations à travers les documents publiés et stockés dans les bases en ligne du web. Dans ce contexte, la valorisation des données disponibles reste un défi majeur pour permettre aux experts de les réutiliser et les analyser afin de produire de la connaissance du domaine. Pour être valorisées, les données pertinentes doivent être extraites des documents puis structurées. Nos travaux s'inscrivent dans la problématique de la capitalisation des données expérimentales issues des articles scientifiques, sélectionnés dans des bases en ligne, afin de les réutiliser dans des outils d'aide à la décision. Les mesures expérimentales (par exemple, la perméabilité à l'oxygène d'un emballage ou le broyage d'une biomasse) réalisées sur différents objets d'études (par exemple, emballage ou procédé de bioraffinerie) sont représentées sous forme de relations n-aires dans une Ressource Termino-Ontologique (RTO). La RTO est modélisée pour représenter les relations n-aires en associant une partie terminologique et/ou linguistique aux ontologies afin d'établir une distinction claire entre la manifestation linguistique (le terme) et la notion qu'elle dénote (le concept). La thèse a pour objectif de proposer une contribution méthodologique d'extraction automatique ou semi-automatique d'arguments de relations n-aires provenant de documents textuels afin de peupler la RTO avec de nouvelles instances. Les méthodologies proposées exploitent et adaptent conjointement des approches de Traitement automatique de la Langue (TAL) et de fouille de données, le tout s'appuyant sur le support sémantique apporté par la RTO de domaine. De manière précise, nous cherchons, dans un premier temps, à extraire des termes, dénotant les concepts d'unités de mesure, réputés difficiles à identifier du fait de leur forte variation typographique dans les textes. Après la localisation de ces derniers par des méthodes de classification automatique, les variants d'unités sont identifiés en utilisant des mesures d'édition originales. La seconde contribution méthodologique de nos travaux repose sur l'adaptation et la combinaison de méthodes de fouille de données (extraction de motifs et règles séquentiels) et d'analyse syntaxique pour identifier les instances d'arguments de la relation n-aire recherchéeToday, a huge amount of data is made available to the research community through several web-based libraries. Enhancing data collected from scientific documents is a major challenge in order to analyze and reuse efficiently domain knowledge. To be enhanced, data need to be extracted from documents and structured in a common representation using a controlled vocabulary as in ontologies. Our research deals with knowledge engineering issues of experimental data, extracted from scientific articles, in order to reuse them in decision support systems. Experimental data can be represented by n-ary relations which link a studied object (e.g. food packaging, transformation process) with its features (e.g. oxygen permeability in packaging, biomass grinding) and capitalized in an Ontological and Terminological Ressource (OTR). An OTR associates an ontology with a terminological and/or a linguistic part in order to establish a clear distinction between the term and the notion it denotes (the concept). Our work focuses on n-ary relation extraction from scientific documents in order to populate a domain OTR with new instances. Our contributions are based on Natural Language Processing (NLP) together with data mining approaches guided by the domain OTR. More precisely, firstly, we propose to focus on unit of measure extraction which are known to be difficult to identify because of their typographic variations. We propose to rely on automatic classification of texts, using supervised learning methods, to reduce the search space of variants of units, and then, we propose a new similarity measure that identifies them, taking into account their syntactic properties. Secondly, we propose to adapt and combine data mining methods (sequential patterns and rules mining) and syntactic analysis in order to overcome the challenging process of identifying and extracting n-ary relation instances drowned in unstructured texts
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Pierre, Manuelle. "Relations propriétés - structure - composition - distribution de mélanges n-aires de normal-alcanes synthétiques et industriels". Vandoeuvre-les-Nancy, INPL, 2002. http://www.theses.fr/2002INPL056N.
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La@connaissance du comportement des alcanes linéaires ou n-alcanes et de leurs alliages modèles est nécessaire pour l'étude de leurs mélanges n-aires ou paraffmes, présents naturellement dans le pétrole entre autres. Ces paraffines sont à l' origine de nombreuses applications qui demandent des propriétés physicochimiques spécifiques. Seule la catégorie des mélanges n-aires de distribution en n-alcanes « normale logarithmique » est étudiée dans ce manuscrit. Des études compositionnelles, structurales et calorimétriques sur des paraffines d'origine industrielle, commerciale et synthétique montrent l'existence d'une unique solution solide, isostructurale de celle identifiée dans les alliages modèles. Lis peuvent donc être assimilés à un hypothétique n-alcane de formule brute CnH2n+2 avec n correspondant à la composition moyenne du mélange. Enfin, des propriétés physico-chimiques complètent cette caractérisation : le coefficient de dilatation thermique, la masse volumique et le module d' élasticité. La deuxième partie consiste à étudier deux systèmes ayant un constituant commun, le mélange n-aire d'origine commerciale Prolabo. La compilation des résultats des analyses structurales et calorimétriques permet la construction des diagrammes composition - température: Prolabo-C20(42 et Prolabo-C50H102• Ces systèmes présentent à température ambiante un large domaine de composition dans lequel coexistent les deux phases caractéristiques des constituants initiaux. En température ces systèmes montrent l'existence de transformations invariantes, déjà observées dans les mélanges modèles. Li s' avère que ces mélanges forment des coupes isoplèthes, parties de diagramme de phases n-aire qui peuvent être considérées comme des systèmes pseudo-binaires : Prolabo se comporte en effet comme un pseudo-constituant. L'étude des propriétés physico chimiques des alliages montre l'influence de la modification de la répartition en n-alcanes du mélange sur ses propriétés physicochirniquesThis@ document displays the results on severa! properties of multi-alk:anes mixtures and the effect on structural state and on sorne properties of n-alkanes adding to this type of mixture. First, major results on pure alk:anes and their molecular alloys is presented. Then, severa! multi-alkanes product of "normal logarithmic" distribution were specially studied. It appears that such mixture forms a single solid solution ~ · isostructural to the ordered intermediate phase of the n-alk:anes alloys (binary or ternary). From the crystallographic c-parameter of this solid solution, it is possible to determine the average chain length of the molecules in the crystallographic unit-cell. Finally, the product can be considered as a hypothetical orthorhombic pure n-alkane. Sorne of their chemical and physical properties (thermal dilation coefficient, density and mechanical magnitudes) are also measured. Moreover, the n-alkanes distribution of one mixture was modified by pure component adding. Thus, two systems were studied : commercial multialk: ane product with eicosane or pentacontane. The isopleth section of the both systems were established by means of X-ray diffraction and differentiai thermal analyses on molecular allo ys. Examinations of the results show existence of a large domain where the phase ~ ' and the phase characteristic of the pure alkane added coexist (triclinic phase y0-C20H42 or orthorhombic phase ~0-C50Hto2). In the both case, the solubility limits of the alk:ane added in the commercial multi-alk:ane product were established. Compilation of the X-ray analyses at various temperature and differentiai thermal analyses allowed to propose both isopleth sections, which are of eutectic or peritectic type. The prope1ties of an alloy of each isopleth were also compared to those of the initial product. In conclusion, addition of pure component to multi-alkanes mixtures induces structural transformation and significant modifications to the physico-chemical properties
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Nguyen, Van Tien. "Méthode d’extraction d’informations géographiques à des fins d’enrichissement d’une ontologie de domaine". Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3052/document.
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Notre thèse se situe dans le contexte du projet ANR GEONTO qui porte sur la constitution, l’alignement, la comparaison et l’exploitation d’ontologies géographiques hétérogènes. Dans ce contexte, notre objectif est d'extraire automatiquement des termes topographiques à partir des récits de voyage afin d'enrichir une ontologie géographique initialement conçue par l'IGN. La méthode proposée permet de repérer et d'extraire des termes à connotation topographiques contenus dans un texte. Notre méthode est basée sur le repérage automatique de certaines relations linguistiques afin d'annoter ces termes. Sa mise en œuvre s'appuie sur le principe des relations n-aires et passe par l'utilisation de méthodes ou de techniques de TAL (Traitement Automatique de la Langue). Il s'agit de relations n-aires entre les termes à extraire et d'autres éléments du textes qui peuvent être repérés à l'aide de ressources externes prédéfinies, telles que des lexiques spécifiques: les verbes de récit de voyage (verbes de déplacement, verbes de perceptions, et verbes topographiques), les pré-positions (prépositions de lieu, adverbes, adjectifs), les noms toponymiques, des thésaurus génériques, des ontologies de domaine (ici l'ontologie géographique initialement conçue par l'IGN). Une fois marquées par des patrons linguistiques, les relations proposées nous permettent d'annoter et d'extraire automatiquement des termes dont les différents indices permettent de déduire qu'ils évoquent des concepts topographiques. Les règles de raisonnement qui permettent ces déductions s'appuient sur des connaissances intrinsèques (évocation du spatial dans la langue) et des connaissances externes contenues dans les ressources ci-dessus évoquées, ou leur combinaison. Le point fort de notre approche est que la méthode proposée permet d'extraire non seulement des termes rattachés directement aux noms toponymiques mais également dans des structures de phrase où d'autres termes s'intercalent. L'expérimentation sur un corpus comportant 12 récits de voyage (2419 pages, fournit par la médiathèque de Pau) a montré que notre méthode est robuste. En résultat, elle a permis d'extraire 2173 termes distincts dont 1191 termes valides, soit une précision de 0,55. Cela démontre que l'utilisation des relations proposées est plus efficace que celle des couples (termes, nom toponymique)(qui donne 733 termes distincts valides avec une précision de 0,38). Notre méthode peut également être utilisée pour d'autres applications telles que la reconnaissance des entités nommées géographiques, l'indexation spatiale des documents textuelsThis thesis is in the context of the ANR project GEONTO covering the constitution, alignment, comparison and exploitation of heterogeneous geographic ontologies. The goal is to automatically extract terms from topographic travelogues to enrich a geographical ontology originally designed by IGN. The proposed method allows identification and extraction of terms contained in a text with a topographical connotation. Our method is based on a model that relies on certain grammatical relations to locate these terms. The implementation of this model requires the use of methods or techniques of NLP (Processing of Language). Our model represents the relationships between terms to extract and other elements of the texts that can be identified by using external predefined resources, such as specific lexicons: verbs of travelogue (verbs of displacement, verbs of perceptions, topographical verbs), pre-positions (prepositions of place, adverbs, adjectives), place name, generic thesauri, ontologies of domain (in our case the geographical ontology originally designed by IGN). Once marked by linguistic patterns, the proposed relationships allow us to annotate and automatically retrieve terms. Then various indices help deduce whether the extracted terms evoke topographical concepts. It is through reasoning rules that deductions are made. These rules are based on intrinsic knowledge (evocation of space in the language) and external knowledge contained in external resources mentioned above, or their combination. The advantage of our approach is that the method can extract not only the terms related directly to place name but also those embedded in sentence structure in which other terms coexisted. Experiments on a corpus consisting of 12 travel stories (2419 pages, provided by the library of Pau) showed that our method is robust. As a result, it was used to extract 2173 distinct terms with 1191 valid terms, with a precision of 0.55. This demonstrates that the use of the proposed relationships is more effective than that of couples (term, place name) (which gives 733 distinct terms valid with an accuracy of 0.38). Our method can also be used for other applications such as geographic named entity recognition, spatial indexing of textual documents
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Searle, Rebecca K. "Art, propaganda and the experience of aerial warfare in Britain during the Second World War". Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6919/.
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This thesis examines how artists working for the War Artists' Advisory Committee (WAAC) represented aerial warfare. In contrast to the scholarly attention lavished on wartime films and posters, official war art remains a much neglected aspect of the propaganda war. The few studies that do exist, most notably by Brian Foss, survey the collection as a whole and consider it from an art history perspective. By focusing on the single theme of aviation, a central and defining experience of the Second World War, I embed the WAAC within the economic, social, military and cultural histories of the period and locate it within a longer time frame. Through bringing these usually disparate fields of study into dialogue, I am able to use the art to enrich broader understandings of the period, in particular, the ways in which aerial warfare was represented, how this image evolved during the war and how these cultural products related to economic, military and social factors. This thesis highlights the different roles the WAAC was expected to fulfil. Housed within the Ministry of Information, the WAAC was expected to perform a propagandist function. The committee distanced itself from propaganda and insisted that its primary function was to record for posterity the experience of living through the war. I assess exactly what kind of record the WAAC bequeathed by looking thematically at the key aspects of aerial warfare: aircraft production; the Battle of Britain; the Blitz and the bombing of Germany. I argue that whilst there was broad correlation between war art and propaganda, these images registered aspects of experience that were incongruent with and therefore absent from wartime propaganda, such as the fear of aerial bombardment and the true nature of the bombing of Germany. Moreover, propagandist constructions were not entirely separate to lived experience, rather they both reflected experience and shaped the way that individuals understood and made sense of the world around them. Therefore, in producing images that accorded with propagandist portrayals, the WAAC artists were recording a fundamental part of the experience of living through the war.
Libros sobre el tema "Relation n-aire"
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The N-factor in natural landscapes: Relations between air and soil-surface temperatures in the Kuparuk River Basin, Northern Alaska. Pittsgrove, N.J: C.W. Thornthwaite Associates, Laboratory of Climatology, 2000.
Buscar texto completoCapítulos de libros sobre el tema "Relation n-aire"
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Whiteman, C. David. "Mountain Climates of North America". En Mountain Meteorology. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195132717.003.0008.
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The basic climatic characteristics of the major mountain ranges in the United States—the Appalachians, the Coast Range, the Alaska Range, the Cascade Range, the Sierra Nevada, and the Rocky Mountains—can be described in terms of the four factors discussed in chapter 1. The mountains of North America extend latitudinally all the way from the Arctic Circle (66.5°N) to the tropic of Cancer (23.5°N) (figure 2.1). There are significant differences in day length and angle of solar radiation over this latitude belt that result in large seasonal and diurnal differences in the weather from north to south. Elevations in the contiguous United States extend from below sea level at Death Valley to over 14,000 ft (4270 m) in the Cascade Range, the Sierra Nevada, and the Rocky Mountains. Several prominent peaks along the Coast Range in Alaska and Canada (e.g., Mount St. Elias and Mount Logan) reach elevations above 18,000 ft (5486 m). Denali (20,320 ft or 6194 m) in the Alaska Range is the highest peak in North America. The highest peak in the Canadian Rockies is Mt. Robson, with an elevation of 12,972 ft (3954 m). The climates of the Coast Range, the Cascade Range, and the Sierra Nevada, all near the Pacific Ocean, are primarily maritime. The Appalachian Mountains of the eastern United States are subject to a maritime influence from the Atlantic Ocean and the Gulf of Mexico, but they are also affected by the prevailing westerly winds that bring continental climatic conditions. Only the climate of the Rocky Mountains, far from both the Pacific and Atlantic Oceans, is primarily continental. Each of the mountain ranges is influenced by regional circulations. For example, the Appalachians are exposed to the warm, moist winds brought northward by the Bermuda-Azores High and to the influence of the Gulf Stream. Similarly, the Coast Range feels the impact of the Pacific High, the Aleutian low, and the Japanese Current. A mountain range, depending on its size, shape, orientation, and location relative to air mass source regions, can itself affect the regional climate by acting as a barrier to regional flows.
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María Cerón Bretón, Rosa, Julia Griselda Cerón Bretón, Jonathan Kahl, Evangelina Ramírez Lara, Atl Víctor Córdova Quiroz, Alberto Antonio Espinosa Guzmán, Manuel Muriel García, Gilma Gabriela Arenas Hernández, José Angel Solís Canul y Abril Rodríguez Guzmán. "Atmospheric N and S Deposition Fluxes in the Metropolitan Area of Monterrey, Mexico and Its Relation with Criteria Air Pollutants and Meteorological Conditions". En Air Pollution - Monitoring, Quantification and Removal of Gases and Particles. IntechOpen, 2019. http://dx.doi.org/10.5772/intechopen.79484.
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"RESULTS AND DISCUSSION The olfactometer readings of the measurements are statistically treated as described in /3/. The results for the plants and air cleaning systems, described in table 1, are given in table 2. system chemical biological plant ABCDE rel. odour raw air 65200 14200 26800 41400 95100 concentration Z50 cleaned air 48300 7360 29500 7930 5100 /odour units/ olfactometric efficiency n 26 % 48 % 81 % 95 % Table 2. Results of measurements, obtained during normal performance, cooker closed. Taking the index R for raw air at the cleaner inlet and the index C for cleaned air at the cleaner outlet, the olfactometric efficiency of the cleaner is defined according to /6/: 50 R In the regarded air cleaning systems, the odoriferous pollutants are first seperated from the raw air by sorption and then decomposed by chemicals or by micro-organisms. As long as this decomposition is not yet completed, the pollutants may desorb and repollute the air, when sorption conditions, i.g. the raw gas concentration, change. By the relation of the difference in raw and cleaned gas concentration to the actual raw gas concentration, a negative efficiency may be calcula ted by equation 1, i.g. when a low raw air concentration is preceded by a high one. Table 3 shows peak concentrations and increasing olfactometric efficiency, wherT’in plant A the cooker is opened. rel. odour concentration raw air 627000 Zgg /odour units/ cleaned air 240800 olfactometric efficiency n 62 % Table 3. Results of measurements, obtained in peak load performance when cooker is opened. Although the number of measurements is too small for general assertions, some deductions can be drawn: The results confirm the superiority of the biofilters. And in fact, the number of biofilters in rendering plants increases. Concerning the rel. odour concentration in the cleaned air, a large difference is evident between the presented results and the assertion that a limit value of 100 odour units can be achieved. Two interpretations can be offered:". En Odour Prevention and Control of Organic Sludge and Livestock Farming, 239. CRC Press, 1986. http://dx.doi.org/10.1201/9781482286311-98.
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"Table V: Amounts of odourous constituents in the aerosol phase (M 9 / 9) arid in the settled dust (^ig/g) of swine house air from 1)= HAMMOND et al. (40), 2) = AENGST (33), and 3) = HARTUNG (34). - indicates not reported. quantitative results quantitative results in n g /l aerosol in jug /g settled dust compounds 1) 2 ) 3) CV relative 0.3 62 4 84 9.9 0.2 --- 11 488 40 skatole -- 43.8 54". En Odour Prevention and Control of Organic Sludge and Livestock Farming, 345. CRC Press, 1986. http://dx.doi.org/10.1201/9781482286311-139.
Texto completoActas de conferencias sobre el tema "Relation n-aire"
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Arias, Luis F., Antonio J. Bula Silvera y Marco E. Sanjuan. "A CFD-Based Robust Design of Operating Conditions for an HVAC System". En ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-66431.
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HVAC systems are directly related to comfort (human health, productivity, etc.) and energy consumption. Depending on the application and geographical area, they may become a key disruptive and energy starving system. The research discussed in this paper describes a CFD-based approach for robust HVAC system design aimed at reducing variability in the conditioned area by adjusting operating parameters. Since robust design techniques aim at minimum variance (via S/N ratio), the solutions obtained allow the selection of operating parameters leading to more uniform distribution. Three variables were used: air velocity (to control energy transfer from people to the surrounding air), Unit usage (a ratio to consider the air conditioning system inertia compared to air conditioning requirements), and room temperature set point (representing the relation between the machine and the conditions room). Embedded codes with field functions in the CFD software allow the simulation of a very basic operation strategy, and demonstrate a quasi-dynamic operation for different cooling capacities and air velocity. Results allow allocating operating parameters that lead to a more uniform temperature and relative humidity distributions, therefore, this approach can be adequately combined with statistical design of experiments for better conditions.
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Meng, Xiangyu, Wuqiang Long, Yihui Zhou, Mingshu Bi y Chia-Fon F. Lee. "Effects of N-Butanol Content on the Dual-Fuel Combustion Mode With CNG at Two Engine Speeds". En ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9595.
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Because of the potential to reduce NOx and PM emissions simultaneously and the utilization of biofuel, diesel/compressed natural gas (CNG) dual-fuel combustion mode with port injection of CNG and direct injection of diesel has been widely studied. While in comparison with conventional diesel combustion mode, the dual-fuel combustion mode generally leads lower thermal efficiency, especially at low and medium load, and higher carbon monoxide (CO) and total hydrocarbons (THC) emissions. In this work, n-butanol was blended with diesel as the pilot fuel to explore the possibility to improve the performance and emissions of dual-fuel combustion mode with CNG. Various pilot fuels of B0 (pure diesel), B10 (90% diesel/10% n-butanol by volume basis), B20 (80% diesel/20% n-butanol) and B30 (70% diesel/30% n-butanol) were compared at the CNG substitution rate of 70% by energy basis under the engine speeds of 1400 and 1800 rpm. The experiments were carried out by sweeping a wide range of pilot fuel start of injection timings based on the same total input energy including pilot fuel and CNG. As n-butanol was added into the pilot fuel, the pilot fuel/CNG/air mixture tends to be more homogeneous. The results showed that for the engine speed of 1400 rpm, pilot fuel with n-butanol addition leads to a slightly lower indicated thermal efficiency (ITE). B30 reveals much lower NOx emission and slightly higher THC emissions. For the engine speed of 1800 rpm, B20 can improve ITE and decrease the NOx and THC emissions simultaneously relative to B0.
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Lassen, Tom, Jose L. Arana, Luis Canada, Jan Henriksen y Nina K. Holthe. "Crack Growth in High Strength Chain Steel Subjected to Fatigue Loading in a Corrosive Environment". En ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67242.
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The present article presents the fatigue crack growth behavior of new high strength steels designated R4S grade. Eight Compact Tension (CT) specimens with 25 mm thickness were subjected to constant amplitude loading while exposed to seawater without and with cathodic protection. The Cathodic Potential (CP) was set to −890 mV and −1100 mV relative to an Ag/AgCl reference cell. Rates in air are included as a reference. The crack growth parameters were determined from a linear relation between da/dN and δK for a log-log scale. The derived figures are given in the table below. The figures for dry air and cathodic protection are valid for δK between 15 and 30 MPam0.5. Below this range the slope m of the linear relation will change and further investigations have to be carried out for this region. The figures for free corrosion are valid for δK values from 10 to 30 MPam0.5. The threshold value for δK is close to 5 MPam0.5 in this case. The measured growth rates were compared with the rates for medium strength carbon manganese steels found in rules and regulation, i.e. BS7910. The present growth rates are well within the scatter band given for these steels in air and free corrosion. The present growth rates found in seawater with cathodic protection are however substantially lower than the rates given in BS7910. When a cathodic potential of −1100 mV was applied, crack closure was observed at medium levels of δK. The explanation is the formation of calcareous deposit in the wake of the crack front that gives significantly reduced growth rates and finally leads to crack closure. This finding is a surprise for a high strength steel. The results are promising and should be investigated further. Finally, a linear elastic fracture mechanics model was established to study the fatigue behavior in a stud-less link. The model was used to construct S-N curves that are consistent with experimental fatigue lives and the design curve given in the DNV rules. The present growth parameters were used in conjuction with a crack-like initial flaw with depth in the range from 0.12 to 0.20 mm. The difference found between the growth rates in dry air and in free corrosion are in accordance with tested fatigue lives for these two environments.
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Zhang, Chao, Terrence W. Simon y Perry Y. Li. "Storage Power and Efficiency Analysis Based on CFD for Air Compressors Used for Compressed Air Energy Storage". En ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-88985.
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The compression process in a piston cylinder device in a Compressed Air Energy Storage (CAES) system is studied computationally. Twelve different cases featuring four different compression space length-to-radius aspect ratios and three different Reynolds numbers are studied computationally using the commercial CFD code ANSYS FLUENT. The solutions show that for compression with a constant velocity, the compression can be approximated by a polytropic pressure vs. volume relation. The polytropic exponent, n, characterizes the heat transfer and temperature rise of the air being compressed. For the cases computed, it varies from 1.124 to 1.305 and is found to be more affected by Reynolds number and less by the length-to-radius ratio. Since the efficiency and storage power of the compressor depend on pressure vs. volume trajectory during compression, they are written as functions of the pressure rise ratio and the polytropic exponent, n. The efficiency is high at the beginning of the compression process, and decreases as the compression proceeds. The effect of temperature rise or heat transfer on efficiency and storage power is shown by comparing the efficiency and storage power vs. volume curves having different n values. Smaller temperature rise always results in higher efficiency but lower dimensionless storage power for the same compression pressure ratio. The storage power is used in this study to distinguish the compression process effect (n effect) and the compressor’s size effect on the storage power. The likelihood of flow transitioning into turbulent flow is discussed. A k–ε Reynolds Averaged Navier Stokes (RANS) turbulence model is used to calculate one of the larger Reynolds number cases. The calculated polytropic exponent was only 0.02 different from that of the laminar flow solution. The CFD results show also that during compression, complex vorticity patterns develop, which help mix the cold fluid near the wall with the hot fluid in the inner region, beneficial to achieving a higher efficiency.
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Shafiei, M. y A. T. Alpas. "Friction and Wear Behaviour of Nanocrystalline Nickel". En World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-64315.
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The tribological behaviours of conventional nickel with a grain size of 20±5 μm and nanocrystalline (nc) nickel with a grain size of 15±3 nm were compared. A pin-on-disc tribometer was employed for the friction and wear measurements under unlubricated conditions in ambient air with ∼35% relative humidity. As the grain size was decreased to the nanometer size, a reduction of about 18% was observed in the peak value of coefficient of friction (COF), but the steady-state COF remained almost unchanged. Also it was shown that the wear rate of nc nickel was about 82% lower than that of conventional nickel at 2 N load. This behaviour is mainly attributed to considerable reduction in plastic deformation and microplowing due to increased hardness.
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Gaspar, Pedro Dinis, L. C. Carrilho Gonc¸alves y R. A. Pitarma. "Three-Dimensional CFD Modelling and Analysis of the Thermal Entrainment in Open Refrigerated Display Cabinets". En ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56421.
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This study presents a three-dimensional Computational Fluid Dynamics (CFD) simulation of the air flow pattern and the temperature distribution in a refrigerated display cabinet. The thermal entrainment is evaluated by the variations of the mass flow rate and thermal power along and across the air curtain considering the numerical predictions of abovementioned properties. The evaluation on the ambient air velocity for the three-dimensional (3D) effects in the pattern of this type of turbulent air flow is obtained. Additionally, it is verified that the longitudinal air flow oscillations and the length extremity effects have a considerable influence in the overall thermal performance of the equipment. The non uniform distribution of the air temperature and velocity throughout the re-circulated air curtain determine the temperature differences in the linear display space and inside the food products, affecting the refrigeration power of display cabinets. The numerical predictions have been validated by comparison with experimental tests performed in accordance with the climatic class n.° 3 of EN 441 Standard (Tamb = 25 °C, φamb = 60%; νamb = 0,2 m s−1). These tests were conducted using the point measuring technique for the air temperature, air relative humidity and air velocity throughout the air curtain, the display area of conservation of food products and nearby the inlets/outlets of the air mass flow.
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Kestner, Brian K., Jeff S. Schutte, Jonathan C. Gladin y Dimitri N. Mavris. "Ultra High Bypass Ratio Engine Sizing and Cycle Selection Study for a Subsonic Commercial Aircraft in the N+2 Timeframe". En ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45370.
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This paper presents an engine sizing and cycle selection study of ultra high bypass ratio engines applied to a subsonic commercial aircraft in the N+2 (2020) timeframe. NASA has created the Environmentally Responsible Aviation (ERA) project to serve as a technology transition bridge between fundamental research (TRL 1–4) and potential users (TRL 7). Specifically, ERA is focused on subsonic transport technologies that could reach TRL 6 by 2020 and are capable of integration into an advanced vehicle concept that simultaneously meets the ERA project metrics for noise, emissions, and fuel burn. An important variable in exploring the trade space is the selection of the optimal engine cycle for use on the advanced aircraft. In this paper, two specific ultra high bypass engine cycle options will be explored: advanced direct drive and geared turbofan. The advanced direct drive turbofan is an improved version of conventional turbofans. In terms of both bypass ratio and overall pressure ratio, the advanced direct turbofan benefits from improvements in aerodynamic design of its components, as well as material stress and temperature properties. By putting a gear between the fan and the low pressure turbine, a geared turbo fan allows both components to operate at optimal speeds, thus further improving overall cycle efficiency relative to a conventional turbofan. In this study, sensitivity of cycle design with level of technology will be explored, in terms of both cycle parameters (such as specific thrust consumption (TSFC) and bypass ratio) and aircraft mission parameters (such as fuel burn and noise). To demonstrate this sensitivity, engines will be sized for optimal performance on a 300 passenger class aircraft for a 2010 level technology tube and wing airframe, a N+2 level technology tube and wing air-frame, and finally on a N+2 level technology blended wing body airframe with and without boundary layer ingestion (BLI) engines.
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Lungu, M. V., E. Enescu, M. Lucaci, C. D. Cîrstea, F. Grigore, S. Mitrea, D. Pătroi et al. "TRIBOLOGICAL BEHAVIOR OF ARCING CONTACT MATERIALS BASED ON COPPER INFILTRATED TUNGSTEN COMPOSITES". En BALTTRIB. Aleksandras Stulginskis University, 2017. http://dx.doi.org/10.15544/balttrib.2017.07.
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Tungsten copper composites with 70±3 wt.% W, maximum 1.5 wt.% Ni, and balance Cu were achieved as disks (diameter × height of 50×6 mm) by copper infiltration process of tungsten skeletons. Elemental analysis was assessed by WDXRF spectroscopy. Hydrostatic density was evaluated in ethanol. Vickers hardness and Young’s modulus were determined in ambient air by instrumented indentation technique and Oliver&amp;amp;amp;Pharr computation method. Tribological behavior was investigated under 30 N up to 400 m sliding distance and naphthenic mineral oil lubricant with a standard tribometer of ball-on-disk type. The results yielded highly dense materials with relative density over 96%, Vickers hardness (HVIT) of 244…323, Young’s modulus (EIT) of 156…185 GPa, mean coefficient of friction of 0.11…0.22 and specific wear rate up to 8×10–6 mm3/(Nm). The developed composites with low coefficient of friction and high wear resistance for use as arcing contacts in oil circuit breakers will endow high performance in service.
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Hong, Jeong K. y Thomas P. Forte. "Study on Weld Fatigue Evaluation Under Sour Service Environment Using Battelle Structural Stress Method". En ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10374.
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Risers, pipelines and flowlines for deep water applications are subject to corrosive environments. Especially, in the presence of hydrogen sulfide which makes the field sour, their fatigue performance becomes significantly degraded. In order to quantify the sour degradation effect, a knock-down factor has been introduced. This factor is defined as the fatigue life reduction relative to the in-air fatigue life. Several sets of fatigue test results in sour service environments have been published. These include strip specimens of different sizes, e.g., diameters, wall thicknesses, and arc lengths. Naturally, the knock-down factor must be based upon a statistically valid number of fatigue test results obtained from the same specimen geometry and the same loading conditions tested in air and in sour conditions. Currently, the database available in the open literature is too limited to properly define a knock-down factor. Moreover, there is a great deal of scatter within the database and each test in a sour environment is costly and time consuming. Thus, it is difficult to establish a statistically valid database upon which to base the knock-down factor. A mesh-insensitive structural stress method has been developed by Battelle researchers and has been proven to be highly effective in correlating the fatigue behavior of welded joints. In 2007, the Battelle structural stress based weld fatigue master S-N curve was included in ASME Section VIII Div. 2 because it successfully consolidated more than 800 fatigue test results for weld toe failures onto a single master S-N curve with very little scatter, regardless of specimen shape, size, loading type, and steel alloy [1–2]. A knock-down factor is derived by applying the Battelle structural stress method to the existing database for sour environment tests and by using the current in-air database as the reference condition. This approach will reduce the uncertainty in the knock-down factor because it allows a wider range of sour environment data from specimens of different sizes, types, and loading conditions to be combined, while simultaneously reducing scatter. As such, a unified knock-down factor can be determined with greater statistical validity and wider applicability for design recommendations in sour conditions.
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Rivera, Matthew B. y Randall D. Manteufel. "Exergetic Analysis of a Cross-Flow Microchannel Heat Exchanger for Bleed Air Cooling in Aircraft Gas Turbine Engines". En ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37722.
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A current issue with high-pressure-ratio compressors found in aircraft engines is the temperature of the air exiting the compressor. The exiting air is used as coolant for engine components found in later stages of the engine such as first-stage turbine blades, and afterburner walls. A viable option for reducing outlet temperature of high-pressure-ratio compressors is to “bleed-off” a fraction of the air which is cooled in a heat exchanger by rejecting heat into the liquid fuel stream and then use the air for cooling critical components downstream. Bleeding off air from the outlet of the compressor has two benefits: (1) air temperature is reduced, and (2) fuel temperature is elevated. Along with reduced air temperatures, the fuel will ultimately receive the heat lost from the air, making the fuel more ideal for combustion purposes. The higher temperature the fuel is received in the combustion process, the greater the work output will be according to the basics of thermodynamic combustion. The objective of this case study is to optimize the efficiency of the cross-flow micro channel heat exchanger, with respect to (1) volume (1.75–2.75 mm3) and heat transfer, and (2) weight (0.15–.25 N) and heat transfer. The optimization of the heat exchanger will be evaluated within the bounds of the 2nd law of thermodynamics (exergy). The only effective way to measure the 2nd law of thermodynamics is through exergy destruction or its equivalent form: entropy generation as a factor of dead state temperature. With relations and equations obtained to design an optimal heat exchanger, applications to high performance aircraft gas turbine engines is considered through exergy. The importance of developing an exergetic analysis for a thermal system is highly effective for identifying area’s within the system that have the path of highest resistance to work potential through various modes of heat transfer and pressure loss. Thus, optimization to reduce exergy destruction is sought after through this design method alongside verifying other heat exchanger methods through effectiveness.