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Статті в журналах з теми "Taille des pores":
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SULLIVAN, JOHN P., and CARL D. HOPKINS. "A new Stomatorhinus (Osteoglossomorpha: Mormyridae) from the Ivindo River, Gabon, West Central Africa." Zootaxa 847, no. 1 (February 1, 2005): 1. http://dx.doi.org/10.11646/zootaxa.847.1.1.
Анотація:
Stomatorhinus ivindoensis n. sp. is described from the basin of the Ivindo River, a tributary of the Ogooué River, in Gabon, West Central Africa. This species is characterized by its very small size which is not known to exceed 56 mm standard length. It is distinguished from S. fuliginosus from the Congo basin, the only described Stomatorhinus for which all members of the type series are within the size range of S. ivindoensis, by a smaller caudal peduncle depth to length ratio, a narrower head, a greater number of lateral line scales with visible tubes and pores and by rounded caudal fin lobes. It is distinguished from the similar S. polli, also from the Congo basin, by a longer snout, a smaller eye and a greater interorbital width relative to head length. It is distinguished from S. walkeri, the only other species described from the Ogooué River basin, by its smaller size, smaller snout to pectoral fin distance (relative to standard length) and by its reduced numbers of pectoral rays, vertebrae, and lateral line scales with visible tubes and pores. Stomatorhinus ivindoensis is endemic to the Ivindo River basin of Gabon and is allopatrically distributed with respect to S. walkeri which, although found elsewhere in the Ogooué River basin, has never been recorded from the Ivindo River. Stomatorhinus ivindoensis may be the smallest species of mormyrid fish yet described.Stomatorhinus ivindoensis n. sp. est décrite de la rivière Ivindo, un affluent du fleuve Ogooué, au Gabon, Afrique Centrale. Cette espèce est caractérisée par sa très petite taille, qui ne dépasse pas 56 mm en longueur standard. Elle se distingue de S. fuliginosus du bassin du Congo, la seule espèce de Stomatorhinus décrite dont l’intervalle de taille des spécimens types est compris dans celui de S. ivindoensis, par un rapport largeur sur longueur du pédoncule caudal plus petit, une tête plus étroite, un nombre d’écailles percées le long de la ligne latérale plus grand et une nageoire caudale aux lobes arrondies. Elle se distingue de S. polli, une autre espèce similaire du bassin du Congo, par un museau plus long, un oeil plus petit, et une distance interorbitale plus grande par rapport à la longueur de la tête. Elle se distingue de S. walkeri, la seule autre espèce de Stomatorhinus décrite du
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Hattab, Mahdia, Soumia Bouziri-Adrouche, and Jean-Marie Fleureau. "Évolution de la microtexture d’une matrice kaolinitique sur chemin triaxial axisymétrique." Canadian Geotechnical Journal 47, no. 1 (January 2010): 34–48. http://dx.doi.org/10.1139/t09-098.
Анотація:
L’objectif de cette recherche est de comprendre comment évolue la microtexture d’une matrice kaolinitique lorsque celle-ci est soumise à un chemin triaxial de révolution. L’approche consiste à réaliser un essai triaxial sur des éprouvettes du matériau saturé faiblement surconsolidé, puis à suivre l’évolution de la microstructure (orientation des particules et porosité) le long du chemin de chargement par des observations au microscope électronique à balayage. À l’état initial, le matériau est consolidé de façon uniaxiale, et les observations montrent une anisotropie microstructurale avec orientation privilégiée des particules suivant le plan horizontal perpendiculaire à la direction du chargement. Sur chemin isotrope, l’analyse montre une réorientation progressive des particules vers une isotropie structurale. Cette évolution se poursuit en début de chargement triaxial pour tendre ensuite vers une orientation privilégiée des particules selon un plan incliné en fin de chargement. L’évolution de la porosité est examinée à partir de mesures par porosimétrie au mercure, illustrées par des images seuillées de photos MEB. Celles-ci suggèrent l’existence d’une double porosité à l’état initial, qui semble se maintenir lors du chargement isotrope, puis évoluer vers une porosité unimodale, avec une légère diminution de la taille des pores, sur le chemin triaxial.
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Fauchille, Anne-Laure, Bram van den Eijnden, Kevin Taylor, and Peter David Lee. "Détermination de la taille et du nombre d’échantillons devant être analysés en laboratoire pour la caractérisation statistique de la microstructure d’une roche argileuse." Revue Française de Géotechnique, no. 165 (2020): 1. http://dx.doi.org/10.1051/geotech/2020024.
Анотація:
À l’échelle du laboratoire, les roches argileuses sont des matériaux hétérogènes dont le comportement thermo-hydromécanique est en grande partie contrôlé par la microstructure. Le choix du nombre et de la taille des échantillons à étudier en laboratoire est déterminant pour appréhender la variabilité des propriétés de la roche argileuse à petite échelle. Cet article présente une méthode statistique permettant de préciser la surface (ou le volume) et le nombre d’échantillons à prendre en compte pour qu’une propriété p choisie caractérisant la microstructure, soit statistiquement représentative. Initialement établie dans un cas général par Kanit et al. (2003. Determination of the size of the representative volume element for random composites: statistical and numerical approach. Int J Solids Struct 40(13–14): 3647–3679), cette méthode consiste à partitionner un échantillon de propriété moyenne [see formula in PDF] connue, en sous-échantillons de surface D × D afin de calculer l’écart-type et l’erreur relative de la mesure de p en fonction de D. Cette méthode permet ainsi de définir des surfaces élémentaires représentatives de p en tenant compte de l’erreur relative par rapport à [see formula in PDF]. La méthode est d’abord présentée dans des cas généraux en 2D et 3D, et un exemple type est ensuite développé en 2D pour caractériser la fraction argileuse d’une lamine sédimentaire de Bowland (Royaume-Uni). La fraction surfacique argileuse est choisie comme propriété p, à partir d’une image grand-champ en microscopie électronique à balayage. La méthode est applicable en 2D et 3D sur les matériaux finement divisés autant sur les roches que sur les sols argileux, tant que l’échantillon considéré contient suffisamment d’éléments figurés (inclusions rigides ou pores dans une matrice par exemple) pour permettre l’utilisation des statistiques. L’apport principal visé pour la communauté des ingénieurs est dans la mesure du possible un meilleur ciblage de la quantité d’échantillons à prélever en forage pour mieux évaluer la variabilité des paramètres macroscopiques des roches argileuses. Les limites de la méthode sont ensuite discutées.
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Zimmermann, Karen, and J. Mark Hipfner. "Egg Size, Eggshell Porosity, and Incubation Period in the Marine Bird Family Alcidae." Auk 124, no. 1 (January 1, 2007): 307–15. http://dx.doi.org/10.1093/auk/124.1.307.
Анотація:
Abstract Although the ultimate factors that influence the duration of avian incubation periods are well known, we know much less about the proximate mechanisms by which birds adjust incubation period in response to selection. We tested the hypothesis that an adjustment in eggshell porosity is one such proximate mechanism (i.e., that avian species with higher ratios of incubation period to egg size lay eggs with less porous shells). Eggshell porosity affects the rate of gaseous exchange between the developing embryo and the external environment; thus, to the extent that embryonic metabolism is diffusion-limited, eggshell porosity could directly determine incubation period. To test that hypothesis, we collected eggs from seven species of Alcidae, a family of marine birds that exhibits an unusual degree of interspecific variation in incubation period, and measured egg mass and eggshell porosity (determined by the number and size of pores and the thickness of the shell). Incubation periods were obtained from the literature. Egg mass and eggshell porosity combined explained 87% of the variation in incubation period among the seven species, which included at least one member of each of the six main alcid lineages. As predicted, eggshell porosity and incubation period were negatively related, after controlling for egg mass. Our results are consistent with the hypothesis that evolutionary changes in avian incubation period may be attributed, at least in part, to adjustments in eggshell porosity. Taille de l’Œuf, Porosité de la Coquille et Période d’Incubation chez les Oiseaux Marins de la Famille des Alcidés
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Didier, Philippe, Dominique Perret, Yves Tardy, and Daniel Nahon. "Equilibres entre kaolinites ferrifères, goethltes alumineuses et hématites alumineuses dans les systèmes cuirassés. Rôle de l'activité de l'eau et de la taille des pores / Equilibria between Fe-kaolinites, Al-goethites and Al-hematltes in ferricretes. Part of water activity and pore size." Sciences Géologiques. Bulletin 38, no. 4 (1985): 383–97. http://dx.doi.org/10.3406/sgeol.1985.1715.
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Ossebi, Walter, Simplice Bosco Ayssiwede, Félix Nimbona, Richard Malou, Augustin Eric Djettin, Mariame Diop, and Ayao Missohou. "Analyse zootechnique et économique des systèmes d’élevage de porcs en Casamance (Sénégal)." Revue d’élevage et de médecine vétérinaire des pays tropicaux 72, no. 1 (May 16, 2019): 13. http://dx.doi.org/10.19182/remvt.31258.
Анотація:
Afin de mieux cerner les caractéristiques zootechniques et économiques de l’élevage de porc, une étude diagnostique a été conduite de mars à juin 2016 auprès de 324 élevages porcins, sous forme d’enquêtes transversales et rétrospectives dans les trois régions de la Casamance au Sud Sénégal. Les résultats ont montré que l’élevage porcin était pratiqué à la fois par des hommes et des femmes mariés et instruits. Ils étaient majoritairement des ethnies Diola, Mancagne et Balante et associaient l’élevage à l’agriculture, à l’activité privée ou au commerce. Ils évoluaient dans trois systèmes d’élevage différents (traditionnel, semi-intensif ou intensif), avec une nette prédominance du système traditionnel (85,5 % des élevages). Ce dernier était caractérisé par des porcheries traditionnelles améliorées (51,1 %) ou des abris de fortune (28,4 %), où étaient surtout élevés les porcs de race locale (90,4 % des exploitations). La taille moyenne du cheptel était de 19,2 ± 20,1 porcs. Dans 97 % des cas les éleveurs nourrissaient les animaux à partir de déchets de cuisine et de sous-produits agricoles et agro-industriels. L’âge moyen de mise à la reproduction était de 7,6 ± 1,8 mois et la taille moyenne de la portée était de 7,4 ± 2,2 porcelets. Ce sous-secteur d’élevage a un réel potentiel de réduction de la pauvreté car il génère selon les systèmes des revenus nets de 5435 à 7566 FCFA par porc engraissé par an. Néanmoins, le manque de formation des éleveurs, les habitats porcins inadaptés, les contraintes alimentaires et sanitaires restent les principaux facteurs handicapant l’essor de l’élevage porcin dans cette région. Il serait utile de trouver des voies alternatives d’amélioration des conditions d’habitat, d’alimentation et de suivi sanitaire des porcs, accompagnées d’une meilleure organisation et d’un renforcement de capacité des producteurs et des autres acteurs de la filière porcine.
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Sosina, A. O., O. J. Babayemi, and P. A. Adewuyi. "GIS mapping of pig population and distribution in the derived savannah, Oyo state, Nigeria." Nigerian Journal of Animal Production 49, no. 3 (June 9, 2022): 198–205. http://dx.doi.org/10.51791/njap.v49i3.3550.
Анотація:
Pig production in the rural areas has not been adequately linked with urban markets thus negatively affecting pig industry. Many researchers have associated major challenges confronting pig production as a business to inadequate capital, land, labour, environmental degradation and religion belief. However, information on pig population and distribution, which is key in pig production value chain is scanty, thus the need to investigate pig population and distribution in the derived savannah area of Oyo state. A three-stage sampling technique was used to purposively select 180 pig farmers, nine respondents per village, three villages per cell and three cells were randomly selected for derived savannah, Oyo state, were evaluated. Parameters measured were average herd size, distribution pattern of pigs across locations comprised of Oluyole, Ona-ara, Akinyele, Egbeda, Ido and Ibarapa East LGA. The ARC-GIS software processed the Global Positioning Systems (GPS) data of pig population using the ARC-GIS model 10.0. The mapping of the pig farmers' distribution was done using the spatial analytical tool of the GIS. Data were analyzed using descriptive statistics. The farmers' average herd size of pigs ranged from 2 (Ona-ara and Akinyele) to 100 (Egbeda). The average herd sizes were 5, 20 and 40 in Oluyole, Ibarapa East and Ido, respectively. Only Egbeda had piggery capacity of more than 20 piglets on average. The large pig production in Egbeda were probably influenced mainly by abundance of agro-industrial by-product and feed resources. The off-takers of pig production value chain should focus on Egbeda for supply of pigs with advantage of resources and other productions factors.
La production de porc dans les zones rurales n'a pas été suffisamment liée aux marchés urbains ayant une incidence négative sur l'industrie du porc. De nombreux chercheurs ont des défis majeurs associés à des défis majeurs confrontés à la production de porc en tant qu'entreprise de capital inadéquat, de terres, de travail, de dégradation de l'environnement et de religion. Cependant, des informations sur la population de cochons et la distribution, qui est la clé de la chaîne de valeur de la production de porcs est maigre, la nécessité d'étudier la population de cochons et la distribution dans la zone de Savannah dérivée de l'État Oyo. Une technique d'échantillonnage à trois étages a été utilisée pour sélectionner à dessein de 180 porteurs de porcs, neuf répondants par village, trois villages par cellule et trois cellules ont été sélectionnés au hasard pour Savannah dérivé, Oyo State, ont été évaluées. Les paramètres mesurés ont été la taille moyenne du troupeau, le modèle de distribution de porcs à travers les emplacements d'oluyole, Ona-Ara, Akinyele, Egbeda, Ido et Ibarapa East LGA. Le logiciel ARC-SIG a traité les données de la population de cochonsde système de positionnement global (SPG) à l'aide du modèle 10.0 Arc-SIG. La cartographie de la distribution des agriculteurs de porc a été effectuée à l'aide de l'outil analytique spatial de la SIG. Les données ont été analysées à l'aide de statistiques descriptives. La taille moyenne du troupeau des fermiers des porcs allait de 2 (Ona-Ara et Akinyele) à 100 (Egbeda). Les tailles moyennes du troupeau étaient de 5, 20 et 40 à Oluyole, Ibarapa East and Ido, respectivement. Seul Egbeda avait une capacité de porcère de plus de 20 porcelets en moyenne. La grande production de porc à Egbeda a probablement été principalement influencée par l'abondance des ressources agro-industrielles et des ressources alimentaires. Les preneurs de la chaîne de valeur de production de porc devraient se concentrer sur Egbeda pour l'approvisionnement en porcs ayant un avantage des ressources et d'autres facteurs de production.
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Dotché, Ignace Ogoudanan, Serge Gbênagnon Ahounou, Chakirath Folakè Arikè Salifou, Rodrigue Biobou, Pascal Sègbégnon Kiki, Benoit Govoeyi, Nicolas Antoine-Moussiaux, et al. "Critères de choix et de réforme des reproducteurs mâles et femelles dans les élevages de porcs des départements de l’Ouémé et du Plateau au Bénin." Revue d’élevage et de médecine vétérinaire des pays tropicaux 71, no. 1-2 (September 9, 2018): 47. http://dx.doi.org/10.19182/remvt.31224.
Анотація:
L’objectif de l’étude a été de décrire les critères de choix et de réforme des reproducteurs porcins au Bénin. Une enquête a été réalisée auprès de 65 éleveurs porcins. L’analyse factorielle des correspondances a été utilisée pour identifier des groupes d’éleveurs en fonction de leurs pratiques au niveau de chaque sexe. Le groupe 1 était composé en majorité de personnes non scolarisées élevant principalement des porcs locaux en liberté. Le groupe 2 était composé majoritairement d’éleveurs de niveau du primaire ou du secondaire. Le groupe 3 comprenait des éleveurs non scolarisés et de niveau du secondaire. Les éleveurs des groupes 2 et 3 utilisaient des races améliorées et des animaux croisés, en claustration. Les critères les plus utilisés pour le choix des mâles dans les élevages ont été l’état de santé, la conformation et les testicules très développés, le nombre de tétines, l’absence de défaut génétique, et la croissance. L’absence de défaut génétique a été plus utilisée dans les groupes 2 et 3, puis les testicules développés dans le groupe 1. Les critères les plus utilisés pour le choix des femelles dans les trois groupes ont été l’état de santé, la taille de la portée, les liens de parenté et la croissance des porcelets. La plupart de ces critères ont été moins utilisés dans le groupe 1. Les critères les plus utilisés pour la réforme des verrats ont été l’âge et la perte de libido. Les principaux critères de réforme des femelles âgées dans tous les groupes ont été le rang de portée et la baisse de la taille de la portée. Cette dernière a été plus utilisée dans les groupes 2 et 3. Pour conclure, les éleveurs disposaient de bons critères de choix et de réforme des reproducteurs qu’il faudrait améliorer afin d’augmenter leur productivité.
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Aprilia, Dhea, Harliansyah, and Nenden Lilis. "Sleep Pattern Factors on Premature Skin Aging in YARSI University Medical Students, Force of 2021." International Journal of Science and Society 6, no. 1 (January 5, 2024): 82–88. http://dx.doi.org/10.54783/ijsoc.v6i1.997.
Анотація:
Skin aging does not only occur in older people, but skin aging can appear when entering early adulthood or is called premature skin aging. Skin problems such as the appearance of wrinkles and fine lines on the face, apart from that hyperpigmentation can also occur and large pores, are signs of premature skin aging. Lifestyle factors greatly influence the occurrence of premature skin aging, one of which is poor sleep patterns with poor sleep quality. This study aims to test and show the relationship between sleep patterns and premature skin. Quantitative research methods were applied in this research. The research population was students from the Faculty of Medicine, YARSI University Class of 2021, aged 20-25 years. Data collection methods used questionnaires and Janus skin analyzer examination. This research analysis uses cross sectional observational analytics. Statistical analysis revealed a significant relationship between sleep patterns and premature skin aging with the Asymp value. Sig. (2-tailed) < 0.001. Signs of premature skin aging such as fine wrinkles, large pores, hyperpigmentation begin to appear at the age of 20 years. It can be concluded that insufficient sleep time and quality sleep are factors that influence the occurrence of premature skin aging.
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Perwitasari-Farajallah, Dyah, Hana Intishar Sawitri, Silvy Thiyana, Tommy Langgeng Abimanyu, Entang Iskandar, and Huda Shalahudin Darusman. "Analyses of Vegetation Used by Long-tailed Macaque (<i>Macaca fascicularis</i> Raffles 1821) in Tinjil Island." Journal of Tropical Biodiversity and Biotechnology 8, no. 1 (March 17, 2023): 70739. http://dx.doi.org/10.22146/jtbb.70739.
Анотація:
Tinjil Island is a semi-natural breeding facility for long-tailed macaques (Macaca fascicularis) managed by Primate Research Center, IPB University, located at the southern of Java Island and surrounded by the Indian Ocean. Long-tailed macaques are considered frugivorous even though they are well-known for their flexible diet. This study aims to analyse the vegetation supporting the population of long-tailed macaques. Data were collected from six tracks using square sampling plots with the size of 20 m x 20 m for trees as the main plot, inside the main plot were square subplots consisting of 10 m x 10 m for poles, 5 m x 5 m for saplings, and 2 m x 2 m for seedlings. The Important Value Index (IVI) was calculated for each level of vegetation. Hanjuang (Dracaena elliptica) dominated the seedlings with 29.35%, followed by Kampis (Hernandia peltata) with 18.73%, and Kalapari (Pongamia pinnata) with 13.73%. Hanjuang (Dracaena elliptica) also dominated the saplings with 26.83%, followed by Pancal (Syzygium antisepticum) with 19.19%, and Laban (Vitex pubescens) with 12.30%. The poles were dominated by Ki Cau (Dolichandrone spathacea) as high as 59.28%, while Waru (Thespesia populnea) and Ki Ciat (Ficus septica) dominated at 40.47% and 36.15%, respectively. Kampis (Hernandia peltata) dominated the trees with 39.28%, followed by Ki Ara (Ficus glomerata) with 35.56%, and Ki Langir (Dysoxylum amooroides) with 28.70%. Species found on Tinjil Island are mostly Moraceae (9.84%) and Fabaceae (9.84%), followed by Malvaceae (8.20%), Euphorbiaceae (4.92%), Myrtaceae (4.92%), and Anacardiaceae (4.92%). The vegetation in Tinjil Island supports the livelihood of long-tailed macaques on the island because they have an abundance of food and staple food such as figs to help them fulfil the energy needed to survive and reproduce.
Дисертації з теми "Taille des pores":
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Mihindou-Koumba, Pierre-Claver. "Transformation du méthylcyclohexane sur zeolithes à taille de pores intermediaire." Poitiers, 2007. http://www.theses.fr/2007POIT2280.
Анотація:
Ce travail se situe dans le cadre du craquage catalytique (FCC). L’objectif de cette Thèse a été d’étudier, à 350° C, plus particulièrement la transformation du méthylcyclohexane (molécule modèle représentative des naphtènes) sur zéolithes à taille de pores intermédiaire : MFI, EUO et MWW (Si/Al = 15) afin d’appréhender l’influence de la structure poreuse (présence de canaux, cages, coupes externes) et de l’acidité de la zéolithe. La zéolithe EUO, bien que possédant moins de sites protoniques et des ouvertures de pores plus étroites, est plus active que la MFI. Cette différence d’activité est certainement due à la taille des cristallites de la MFI. Le craquage est la réaction principale sur les deux zéolithes, mais la formation de coke est plus importante sur EUO, ce qui entraîne une plus forte désactivation. La zéolithe MWW est aussi active que la zéolithe MFI, mais la sélectivité en craquage est plus faible. Ceci est certainement dû à la présence de supercages et de coupes externes sur MWW, qui facilitent la diffusion des isomères du méthylcyclohexane et défavorisent légèrement leur craquage. Par contre, un changement très net de sélectivité accompagne la désactivation de la zéolithe. La sélectivité en isomérisation augmente au cours du temps de réaction. L’explication de ce phénomène est liée à la structure poreuse de cette zéolithe, qui possède deux types de systèmes poreux internes qui se désactivent au cours du temps par formation de coke, et un système externe (coupes externes) qui ne se désactive pas et qui défavorise le craquage par une désorption rapide des isomères formésThis work refers to the catalytic cracking (FCC). The objective was to study, at 350° C, the transformation of methylcyclohexane, a model molecule of naphtene compounds over various intermediate pore size zeolites: MFI, EUO et MWW (Si/Al = 15) in order to determine the effect of the pore structure and acidity of zeolites. EUO zeolite is more active than MFI, as EUO possess a low amount of protonic acid sites and narrowest pores. This result can be attributed to a large crystallite size of MFI. Cracking is the predominant reaction of both zeolites, but coke formation is higher over EUO. MWW zeolite is also active than MFI while cracking selectivity is lower. This is certainly due to the presence of supercages and of external cups on MWW which make easier the diffusion of methylcyclohexane isomers and disadvantage this cracking. However, change in selectivity was observed during zeolite deactivation, isomers formation increases with time on stream. The explanation can be related to the particular pore structure of this zeolite. The internal porous system deactivates by coke formation increases the internal cups don’t favorise the retention of coke components. This reaction occurs preferentially in the internal cups when the methylcyclohexane isomers can be rapidly desorbed before their cracking
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Largeot, Céline. "Développement de supercondensateurs carbone/carbone : relation entre la taille des ions de l'électrolyte et la taille des pores de la matière active." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/529/.
Анотація:
L'objectif de cette thèse est d'étudier les interactions ions/carbone poreux afin d'améliorer les performances de supercondensateurs carbone/carbone. Les Carbones Dérivés de Carbures de titane (TiC-CDC) sont des carbones microporeux, dont la porosité est monodisperse. Ils ont permis d'étudier finement les interactions entre la taille des ions de l'électrolyte et la taille des pores de la matière active (carbone) dans la formation de la double couche électrochimique dans deux différents types d'électrolyte (organique et liquide ionique). Contrairement à ce qui était pensé jusqu'à maintenant, afin de maximiser la capacité et donc l'énergie, la taille des pores du carbone doit être voisine de la taille des ions de l'électrolyte. Il a également été montré que les ions adsorbés à la surface du carbone sont partiellement désolvatés. Lorsque la porosité du carbone est adaptée à la taille des ions de l'électrolyte, on observe une augmentation de 40 % de la capacité en milieu acétonitrile et de 60 % en milieu liquide ionique, ce qui correspond respectivement à un doublement et un triplement de l'énergie maximale des supercondensateursThe aim of this work is to study ion/porous carbon interactions in supercapacitor electrodes to improve their electrochemical performances. Titanium Carbide Derived Carbon (TiC-CDC) are microporous carbon with monodisperse porosity. They allowed us to finely study the interactions between electrolyte's ion size and active material pore size during the electrochemical double layer formation in two different kind of electrolyte (organic and ionic liquid). Unlike to traditional views, in order to maximise capacitance, carbon pore size must be close to electrolyte ions size. It was demonstrated that ions adsorbed on carbon's surface are at least partially desolvated. As carbon porosity is well adapted to electrolyte ions size, the capacity is improved of 40 % in acetonitrile and 60 % in ionic liquid. This corresponds respectively to an enhancement by two and by three of the energy of supercapacitors
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Sirijarukul, Suksawat. "Elaboration de membranes à traces en poly(éthylènetéréphtalate) ayant un gradient linéaire de taille de pore et une porosité constante." Montpellier 2, 2007. http://www.theses.fr/2007MON20110.
Анотація:
Nous avons fabriqué un nouveau type de membrane polymère à traces avec des gradients de taille de pore et de densité de pore le long de la membrane. Ces gradients sont fort bien contrôlés de façon indépendante et par des procédés très simples. Dans une première étape, un gradient de densité de pores est obtenu par un déplacement d'un film de poly(éthylènetéréphtalate) –PET- devant un faisceau d'ions lourds de flux variable. Dans une seconde étape, la taille de pore est contrôlée par le trempage progressif du film préalablement exposé aux ions lourds dans une solution de soude 2N à 50°C. La relation entre densité de pores et taille de pore en chaque point de la membrane est préalablement choisie : nous avons fabriqué des membranes ayant une porosité constante et un gradient linéaire de taille de pore. Des mesures de microscopie électronique à balayage ont permis de contrôler la formation d'un pore cylindrique à travers toute l'épaisseur (13 µm) du film de PET, après exposition à un rayonnement UV centré autour de 312 nm. Un modèle théorique a été proposé pour décrire le phénomène de filtration tangentielle dans un canal ayant une paroi constituée d'une telle membrane : le cas d'une perméabilité constante donne lieu à des expressions analytiques relativement simples, contrairement au cas de la porosité constante. Une cellule a été montée et caractérisée par des mesures électriques et hydrauliques. Le caractère hydrophobe de la membrane est atténué en milieu basique (NaOH 10-2N) par ionisation des groupes carboxyliques. Nous avons montré que la durée variable du traitement à la soude concentrée permettant d'obtenir le gradient de taille de pore n'induisait pas un gradient de mouillabilité du matériau à la condition que celui-ci ait été exposé préalablement au rayonnement UVA new type of polymer track-etch membrane was produced with a gradient of pore size and another gradient of pore density along the large dimension of the membrane. Those gradients are independently very well controlled and obtained by simple procedures. In a first step, the pore density gradient is created by displacing the poly(ethyleneterephthalate) –PET- film in front of a swift heavy ions beam of varying flux. In a second step, the pore size is controlled by dipping progressively the previously ion beam exposed film into an aqueous solution of 2N NaOH at 50°C. The relationship between both gradients at any position along the membrane is predetermined before preparation: we have chosen to maintain porosity constant with a linear gradient of pore size. Scanning electron microscopy measurements allowed verification of the existence of a cylindrical pore through the whole thickness (13 µm) of the PET film after exposure to UV light centred around 312 nm. A theoretical model has been proposed which describes tangential filtration in a channel where one wall is such a membrane: the case of constant permeability leads to relatively simple analytical expressions contrary to the case of constant porosity. One cell was built up and characterized by electrical and hydraulic measurements. The membrane hydrophobic character is attenuated at high pH (10-2N NaOH) by ionization of the carboxylic groups. We showed also that varying etching time to obtain a gradient of pore size did not induce a wettability gradient provided that the material was previously exposed to UV radiation
4
Malvault, Guillaume. "Détermination expérimentale de la distribution de taille de pores d’un milieu poreux par l’injection d’un fluide à seuil ou analyse harmonique." Thesis, Paris, ENSAM, 2013. http://www.theses.fr/2013ENAM0040/document.
Анотація:
Deux approches pour caractériser les milieux poreux en terme de distribution de taille de pores (DTP) sont développées au sein de l'équipe ECPS. Ce travail a pour but de confirmer expérimentalement leurs validités. A l'instar des autres méthodes utilisant l'intrusion du mercure, l'adsorption isotherme ou la thermoporosimétrie, la première méthode consiste à utiliser un fluide à seuil d'écoulement. En effet, l'utilisation de l'écoulement d'un fluide à seuil de type Herschel-Bulkley, au travers d'un poreux, en fonction du gradient de pression permet (en utilisant les solutions analytique et numérique du problème inverse) de déterminer la fonction de distribution de la taille de pores. La seconde méthode utilise l'admittance complexe d'un milieu poreux, mesurée à partir de la réponse en débit à une sollicitation harmonique du gradient de pression. Comme la fréquence de la sollicitation est reliée aux rayons des pores par le biais de la profondeur de pénétration hydrodynamique, l'admittance permet de retrouver la distribution de taille de pores par la résolution numérique du problème inverse associé. Ces deux techniques sont basées sur le modèle de faisceaux de capillaires parallèles employé dans la plupart des autres études qui traitent du même problème. Nos expériences s'appuient sur des milieux poreux calibrés. L'application de ces techniques aux milieux poreux réels se fait actuellement en collaboration avec le TREFLE de Bordeaux. Les résultats expérimentaux obtenus affirment clairement la validité et l'applicabilité de ces deux méthodes pour la caractérisation de la DTP. Il est désormais envisageable de les transférer pour un usage industrielTwo approaches to characterize porous media in terms of pore size distribution (PSD) are developed within our ECPS team. The aim of this study is to experimentally confirm their validity. Like the other methods using mercury intrusion, adsorption isotherm or thermoporometry, the first method consists in the use of a fluid flow threshold. Indeed, the use of flow of a yield-stress fluid like those of Herschel-Bulkley's, through a porous media, versus the pressure gradient, permits (using the analytical and numerical solutions of the inverse problem) to determine the distribution function of its PSD. The second method uses the complex admittance of a porous medium, measured from the flow rate response to a harmonic pressure gradient. As the frequency of the sollicitation is related to the pore radius through the hydrodynamic penetration depth, the admittance allows to determine the PSD using numerical solution of the associated inverse problem. Both techniques are based on the parallel capillaries bundle model, as used in most of similar studies. Our experiments use calibrated porous media. The application of these techniques to real porous media is currently lead in collaboration with the TREFLE (Bordeaux). Our experimental results clearly confirm the validity and the applicability of these methods for the characterization of the PSD. It is now possible to transfer them for an industrial use
5
Gassara, Sana. "Préparation des membranes à base de poly(étherimide) fonctionnalisées et à taille de pores contrôlée : application à la séparation sélective des ions et des acides aminés." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20131.
Анотація:
Des gammes de membranes en poly(étherimide) (PEI) fonctionnalisées avec des tailles de pores contrôlées ont été préparées en se basant sur deux étapes successives : élaboration des membranes UF de seuil de coupure (MWCO) de 120 ± 10 kDa par la technique inversion de phase induite par la coagulation dans l'eau suivie d'un traitement de surface par une solution aqueuse contenant des oligomères aminés. Une modification avec un dérivé monoaminé commercial, le Jeffamine M-2070, a donné des membrane recouvertes de brosses de courtes chaines de poly(éthylèneglycol) (PEG-PEI) qui ont rendu la membrane plus hydrophile et plus résistante au colmatage par le BSA avec un taux de récupération de flux de l'ordre de 80 à 93 % (traitement de 1 à 3 h). Le MWCO des membranes PEG-PEI traitées plus que 3 h augmente progressivement pour atteindre 500 kDa après 5 h de traitement. D'autre part, une réaction avec des oligomères de poly(éthylèneimine) a donné des membranes chargées positivement (Cat-PEI) en rétrécissant la taille des pores pour atteindre des gammes de membranes d'UF serrée et de NF. Des membranes Cat-PEI de NF de MWCO de l'ordre de 300-500 Da sont adaptées au dessalement avec par un ordre de rétention décroissant de sels simples de CaCl2 > NaCl > MgSO4 > Na2SO4. La forte rétention des ions Ca2+ (plus que 90 %) rend ces membranes très efficaces pour l'adoucissement d'eau (diminution de la dureté d'une eau du robinet de 37 à 7°F). Les membranes Cat-PEI ont montré aussi, une bonne rétention des acides aminés basiques (plus que 80 % pour l'Arginine et la Lysine) à un pH entre 3 et 6. Ainsi une sélectivité expérimentale de l'ordre de 20 a été obtenue pour des mélanges d'acide glutamique et d'arginine avec des membranes de MWCO entre 500 et 750 DaFunctionalized poly(etherimide) (PEI) membranes with controlled pore size were prepared based on two steps : preparation of UF membranes with a molecular weight cut-Off (MWCO) of 120 ± 10 kDa by phase inversion induced by coagulation in water followed by a surface treatment with an aqueous solution containing amino oligomers. Modification with a commercial monoamine derivative, Jeffamine M-2070, gave membranes (PEG-PEI) coated with brushes of poly (ethylene glycol) short chains that made the membrane more hydrophilic and more resistant to fouling by BSA with a recovery flow rate of of 80 to 93 % (treatment of 1 to 3 h). The MWCO of PEG-PEI membranes treated more than 3 h became progressively larger and reached 500 kDa after 5 h of treatment. On the other hand, reaction with oligomers of poly (ethyleneimine) gave positively charged membranes (Cat-PEI) by narrowing the pore size yielding tight UF and NF membranes. Cat-PEI NF membranes with MWCO of about 300-500 Da are suitable for desalination with a retention order of decreasing simple salts CaCl2> NaCl> MgSO4> Na2SO4. The high retention of Ca2+ ions (more than 90%) make Cat-PEI effective membranes for softening water (reducing the hardness of tap water from 37 to 7 °F). In addition, Cat-PEI membranes showed a good retention of basic amino acids (more than 80% for arginine and lysine) at pH between 3 and 6. Thus, an experimental selectivity of about 20 was obtained for a glutamic acid and arginine mixture using Cat-PEI membranes with a MWCO between 500 and 750 Da
6
Letellier, Franck. "Influence de la taille des pores du support MCM-41 sur les propriétés catalytiques du platine en hydrogénation et hydrodesalkylation d'aromatiques." Paris 6, 2004. http://www.theses.fr/2004PA066206.
7
Meynard, Joane. "Influence de la taille, de la morphologie et de la distribution spatiale des pores sur la conductivité thermique de céramiques UO2." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0607.
Анотація:
Dans un réacteur nucléaire, le comportement des combustibles est piloté par des phénomènes thermiques. C'est pourquoi il est important de modéliser précisément leur comportement thermique.L’objectif de ces travaux est d’évaluer l’impact de la microstructure sur les propriétés thermiques d’un combustible UO2 à 50°C.Des céramiques UO2 ont été fabriquées. Deux familles de porosité ont été identifiées à l’aide de différentes techniques d’imagerie (microscopie optique, MEB-FIB et tomographie X) : la porosité occluse de forme quasi-sphérique et localisée dans les granulats d’UO2 et un réseau de porosité "d'assemblage" localisée à l’interface des granulats. Des paramètres descripteurs ont été déterminés par mesures par immersion et par analyse d’images. Des études par homogénéisation analytique et numérique (calculs par transformée de Fourier rapide) ont été réalisées afin d’évaluer l’impact de ces caractéristiques sur la conductivité thermique. Les calculs numériques ont été réalisés sur des images 2D et 3D obtenues par imagerie et générées avec un modèle morphologique original reproduisant les spécificités des structures poreuses observées. Ces études ont mis en évidence l’impact de la répartition spatiale et de l’interconnexion de la porosité d’assemblage sur la conductivité thermique des céramiques UO2. Finalement, le modèle proposé a été comparé à des mesures expérimentales de diffusivité thermique obtenues par méthode Flash. Cette comparaison a permis de montrer que le modèle reproduit les tendances associées à la dégradation de la conductivité thermique mesurée sur les céramiques étudiéesInside a nuclear reactor core, the behavior of fuels is largely controlled by thermal phenomena. That is why it is very important to model the thermal behavior of fuels very precisely.The objective of this study is to develop a model that indicates the influence of porosity on thermal conductivity at 50° that is representative of the thermal behavior of the UO2 fuels. UO2 fuels were manufactured and their microstructures were studied using optical microscopy, SEM-FIB and X-ray tomography. Two types of porosity were identified: 1) sealed and near-spherical pores which are located in UO2 aggregates, and 2) an interconnected "assembly" porosity located at the interfaces of aggregates. Several descriptive parameters were estimated by immersion measurements and image analysis. Studies based on analytical and numerical homogenization were conducted. Numerical calculations using the Fast Fourier Transform method were performed on images of slice planes obtained with imaging technologies or 3D simulated microstructures generated with an original morphological model reproducing some characteristics of the observed porosity networks. The significant impact of the spatial distribution and the interconnection of the assembly porosity on the thermal conductivity of manufactured UO2 fuels were highlighted. Finally, the proposed model was compared with experimental thermal diffusivity measurements obtained by the Flash method.Discrepancies between the model and the experimental measurements have been largely reduced with the proposed model compared with the standard models, which means that the developed model is more representative of the UO2 thermal behavior
8
Altinier, Maria Victoria. "Etude de la composition isotopique des eaux porales de l'argilite de Tournemire : inter-comparaison des méthodes de mesure et relations avec les paramètres pétrophysiques." Paris 11, 2006. http://www.theses.fr/2006PA112065.
9
Rodriguez, de Castro Antonio. "Flow experiments of yield stress fluids in porous media as a new porosimetry method." Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0021/document.
Анотація:
Les méthodes expérimentales utilisées actuellement pour déterminer la distribution de taille des pores (DTP) dans les milieux poreux présentent des inconvénients, tels que par exemple, la toxicité des fluides employés (porosimétrie à mercure). La base théoriques d'une nouvelle méthode pour obtenir la DTP a été proposée dans la littérature. Celle-ci est fondée sur l'injection de fluides à seuil, caractérisés par une contrainte de cisaillement en deçà de laquelle ils ne s'écoulent pas. L'idée principale de ces travaux théoriques est que l'écoulement de fluides à seuil à travers un milieu poreux permet d'obtenir sa DTP à partir de la mesure des débits correspondant à différents gradients de pression Q(∇P). L'objectif du travail proposé ici est de présenter une nouvelle méthode d'exploitation des données expérimentales Q(∇P) permettant d'obtenir de façon simple, robuste et reproductible les DTPs des milieux poreux analysés. La démarche consiste à évaluer la contribution au débit total des nouveaux pores qui s'incorporent à l'écoulement entre deux valeurs de ∇P. Ces nouveaux pores sont caractérisés par un rayon représentatif qui est fonction de la contrainte seuil du fluide et de ∇P. L'importance de leur contribution au débit total par rapport à celle d'un seul pore donne le nombre de pores dans l'échantillon ayant ce rayon représentatif. Cette méthode est d'abord testée et validée avec des expériences générées numériquement. Ensuite, elle est utilisée pour exploiter des données provenant d'expériences de laboratoire réalisées avec de différents milieux poreux. Les résultats obtenus en termes de DTPs sont comparés avec ceux fournis par d'autres techniques: porosimétrie à mercure et microtomographieCurrent experimental methods used to determine pore size distributions (PSD)of porous media present several drawbacks such as toxicity of the employed fluids (e.g., mercury porosimetry). The theoretical basis of a new method to obtain the PSD by injecting yield stress fluids through porous media and measuring the flow rate Q at several pressure gradients ∇P was proposed in the literature. On the basis of these theoretical considerations,an intuitive approach to obtain PSD from Q(∇P) is presented in this work. It relies on considering the extra increment of Q when ∇P is increased, as a consequence of the pores of smaller radius newly incorporated to the flow. This procedure is first tested and validated on numerically generated experiments. Then, it is applied to exploit data coming from laboratory experiments and the obtained PSDs are compared to those deduced by mercury porosimetry and micro tomography
10
Ali, Imtiaz. "Contribution à l'étude du comportement mécanique des fibres recyclées. Applications aux supports fibreux." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00872112.
Анотація:
Les objectifs principaux des travaux de recherche réalisés sont de caractériser, quantifier et corréler les changements induits lors du recyclage sur les fibres, la pâte et le papier. Pour ce faire, des techniques de caractérisation spécifique ont été utilisées telles que la chromatographie inverse d'exclusion stérique (ISEC), l'analyse mécanique dynamique (DMA), la microscopie électronique à balayage environnementale (ESEM), la microscopie à force atomique (AFM) et la tomographie à rayons X. Le racornissement des fibres à elle seule ne peut pas expliquer totalement la perte de résistance des fibres. Lors du recyclage la largeur des fibres, l'épaisseur des parois fibreuses, la courbure, le nombre de coudes et d'irrégularité diminuent. Les points faibles à l'intérieur de la paroi augmentent dans les premiers et les derniers cycles de recyclage. Les fibres deviennent plus dures et cassantes à l'état sec. Les forces capillaires et la friction de surface augmentent à l'état humide. La surface de liaison entre fibres dans le réseau fibreux diminue initialement à cause de la perte de la flexibilité des fibres à l'état humide et des éléments fins alors que l'augmentation qui suit peut être reliée au collapse du lumen. Comme la solidité des fibres de diminue pas, la baisse des caractéristiques mécaniques du papier pourrait être attribuée à la dégradation de la qualité des liaisons et plus particulièrement à une délamination partielle de la couche P/S1.
Книги з теми "Taille des pores":
1
Baltet, Charles. Culture du poirier: Comprenant la plantation, la taille, la mise à fruit et la description abrégée des cent meilleures poires. Adamant Media Corporation, 2001.
Частини книг з теми "Taille des pores":
1
Qi, Yue, Ruqing Zhong, Benjamin Kaiser, Long Nguyen, Hans Jakob Wagner, Alexander Verl, and Achim Menges. "Working with Uncertainties: An Adaptive Fabrication Workflow for Bamboo Structures." In Proceedings of the 2020 DigitalFUTURES, 265–79. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4400-6_25.
Анотація:
AbstractThis paper presents and investigates a cyber-physical fabrication workflow, which can respond to the deviations between built- and designed form in real-time with vision augmentation. We apply this method for large scale structures built from natural bamboo poles. Raw bamboo poles obtain evolutionarily optimized fibrous layouts ideally suitable for lightweight and sustainable building construction. Nevertheless, their intrinsically imprecise geometries pose a challenge for reliable, automated construction processes. Despite recent digital advancements, building with bamboo poles is still a labor-intensive task and restricted to building typologies where accuracy is of minor importance. The integration of structural bamboo poles with other building layers is often limited by tolerance issues at the interfaces, especially for large scale structures where deviations accumulate incrementally. To address these challenges, an adaptive fabrication process is developed, in which existing deviations can be compensated by changing the geometry of subsequent joints to iteratively correct the pose of further elements. A vision-based sensing system is employed to three-dimensionally scan the bamboo elements before and during construction. Computer vision algorithms are used to process and interpret the sensory data. The updated conditions are streamed to the computational model which computes tailor-made bending stiff joint geometries that can then be directly fabricated on-the-fly. In this paper, we contextualize our research and investigate the performance domains of the proposed workflow through initial fabrication tests. Several application scenarios are further proposed for full scale vision-augmented bamboo construction systems.
2
Elahi, Sepideh Hakim, and Isabel C. Escobar. "Investigation of the Effects of Thickness and Presence of Pore Formers on Tailor-Made Ultrafiltration Polysulfone Membranes." In ACS Symposium Series, 271–83. Washington, DC: American Chemical Society, 2011. http://dx.doi.org/10.1021/bk-2011-1078.ch016.
3
Bouwmeester –, W., E. Schlangen, and van den Bos. "Influence of curing on the pore structure of concrete." In Tailor Made Concrete Structures, 40. CRC Press, 2008. http://dx.doi.org/10.1201/9781439828410.ch16.
4
Swastic and Jegatha Nambi Krishnan. "Nanoporous Metallic Films." In Nanopores [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95933.
Анотація:
Nanoporous metallic films are known to have high surface to volume ratio due to the presence of pores. The presence of pores and ligaments make them suitable for various critical applications like sensing, catalysis, electrodes for energy applications etc. Additionally, they also combine properties of metals like good electrical and thermal conductivity and ductility. They can be fabricated using top-down or bottom-up approaches also known as dealloying and templating which give the fabricator room to tailor properties according to need. In addition, they could find potential applications in many relevant fields in current scenario like drug delivery vehicles. However, there is a long way to go to extract its whole potential.
5
Wang, Chang Jiang, Kevin Hazlehurst, Arun Arjunan, and Lida Shen. "Analysis of the Porous Structures from Laser Powder Bed Fusion Additive Manufacturing." In Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210019.
Анотація:
Open and closed porous structures with lattice and honeycomb geometry can be built using laser powder bed fusion additive manufacturing processes. The porous structures can be used to tailor the mechanical properties of a component or provide other functionality, such as for bone ingrowth in medical implants. Porous structures were created and analysed in this paper both physically and using finite element modelling. It was found that the accuracy of the built parts was reasonable and within the manufacturing processes general tolerance of +/- 50 μm. However, it was noticeable that the corners of the square shape pores were naturally filleted by the manufacturing process. The finite element model was developed using ANSYS software, stress concentrations were observed in the porous structures under loading. In addition to this, fragments of the material were present on the internal surfaces of the pores, which were formed from partially melted powder particles.
6
Eimeleus, K. B. E. E. "Skis as a Brake." In Skis in the Art of War, translated by William D. Frank and E. John B. Allen, 70–72. Cornell University Press, 2019. http://dx.doi.org/10.7591/cornell/9781501747403.003.0020.
Анотація:
This chapter discusses using skis as a brake. For a skier-sportsman, braking with skis is a more suitable solution, but it requires better command over one's equipment than braking with poles. A skier can brake with both skis, or just one (in two distinct styles). When braking with two skis, the tips draw together while the tails tend to split apart. This method works well on hard snow; in soft snow, one must employ it gradually, otherwise a large pile of snow accumulates in front of the skis, movement stops abruptly, and a skier tumbles forward from their momentum. A variation of this is braking with one ski, which offers two possibilities: both of them are twisting motions.
7
Maraddi, A. S. "Polymer-Based Membranes." In Advanced Functional Membranes, 1–42. Materials Research Forum LLC, 2022. http://dx.doi.org/10.21741/9781644901816-1.
Анотація:
Membrane science and technology is increasingly playing an important role in maintaining environmental health. Polymer based membranes in particular show great potential in removing environmentally hazardous pollutants from the wastewater. Membrane technology has also been widely used for ground, surface and seawater desalination which is serving the humanity by providing high quality drinking water. Polymeric membranes have been categorized based on their pore size and their distribution which make them tailor made and innovative separation media namely, reverse osmosis, nanofiltration, ultrafiltration, microfiltration and forward osmosis. All these membrane process require high performing membranes as separation media. This chapter give detailed account of membrane preparation techniques, membrane modules and their applications in different fields. Further, the ideas covered in this chapter are fundamental to all membrane processes. Transport processes, membrane preparation, and flow separation effects are just few of the topics that have been studied.
8
Ripmeester, John A., and L. S. Kotlyar. "2H NMR and Gel Formation of the Ultrafine Solids Fraction Associated with the Athabasca Oil Sands Fine Tails." In Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0017.
Анотація:
The two oil sands plants operated by Syncrude Canada Ltd. and Suncor Canada Ltd. near Fort MacMurray, Alberta, use a hot water process for the separation of bitumen from oil sands. In brief, hot water and oil sands, with caustic soda as dispersing agent, are mixed thoroughly, and bitumen is floated to the top of the resulting slurry by streams of air. After secondary bitumen recovery, the remaining tailings are carried to ponds, where the coarse sands are used to form dikes, the fine tails are left to settle, and freed water is recycled. Typical production figures for the Syncrude plant are 390 000 barrels of diluted bitumen per day produced from 325 000 tonnes of oil sand. One complicating factor is that the fine tails dewater only to a solids content of ~30%, requiring ponds of ever increasing size (the Syncrude pond is 22km2) to store the resulting sludge. As the ponded material is toxic to wildlife, it poses a considerable local environmental hazard. In addition, there is the potential hazard of contamination of surface water and a major river system as a result of seepage or potential dike failure. The work reported here was carried out as part of a major project initiated to address the problem of the existing tailings ponds, and also to modify the currently used separation process so as not to produce sludge. Starting with the recognition that the very stable fine tails, consisting of water, silt, clay and residual bitumen, have gel-like properties, we employed the strategy of fractionating the fine tails with the hope of identifying a specific fraction which might show gel-forming propensity. This was done by breaking the gel, and collecting fractions according to sedimentation behavior during centrifugation. Fractions consisting of the coarser solids (>0.5μm) settled rapidly, whereas fractions with smaller particle sizes (termed ultrafines) gave suspensions which set into stiff, thixotropic gels on standing. Gel formation and the sol-gel transition in colloidal clay suspensions are classical problems which have received much attention over the years; however, much remains to be learned. NMR techniques have shown considerable promise in understanding clay-water interactions at a microscopic level.
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Peterson, Janine Larmon. "Methods of Contesting Authority." In Suspect Saints and Holy Heretics, 196–217. Cornell University Press, 2019. http://dx.doi.org/10.7591/cornell/9781501742347.003.0009.
Анотація:
This chapter studies the methods that individuals and communities used to thwart popes and their agents. Bishops, civic officials, and devotees often fought hard to keep a saint's cult viable once a majority reached consensus that the person was holy. In some notable cases, they did not fear inquisitors and rejected their authority. Muzio di Francesco of Assisi, an antipapal rebel in the early fourteenth century, purportedly remarked, “I would not fear sentences of excommunication and interdict, any more than I would fear the tail of a donkey.” This evidently was a popular saying in late medieval Italy, for it echoed testimony from inquisitorial deponents in Bologna given twenty years prior. This blasé attitude toward papal authority was expressed through citizens routinely contesting inquisitors, who represented papal authority. Sometimes it took the form of riots and physical violence. In cases of disputed saints who were facing possible condemnation, individuals often sought legal means to beat the system instead, in a process which can be defined as oppositional inquisitorial culture. The chapter also considers two other methods, canonization inquiries and questioning legitimacy, through which various members of a community colluded to challenge inquisitorial authority on a larger scale and protect local saints' cults.
10
Rosell, Frank, and Róisín Campbell-Palmer. "Territoriality, communication, and populations." In Beavers, 221–60. Oxford University Press, 2022. http://dx.doi.org/10.1093/oso/9780198835042.003.0007.
Анотація:
Beavers are highly territorial and actively defend a territory that includes nutritional resources, one or more rest sites, a family overwintering site, and a reproduction site. New territories are normally established during early autumn when dispersing subadults settle down in a new area of their own, but this can vary considerably. Each family group scent marks its territories with castoreum and/or anal gland secretion. Territory size is generally measured as the length of shoreline but can also be expressed as a combination of terrestrial and aquatic patches used by the beavers in a two-dimensional space. The territorial size depends on many factors such as habitat quality and quantity, habitat type (stream, river, or pond), density of beavers, social factors (sex and age), time of year (season), and settlement pattern. Beavers patrol their territory to look out for intruders and potential predators and scent mark their territory with fluid from their castor sacs and/or secretions from their anal glands. Territorial defence can include direct fighting or even more unusual warning behaviours such as boundary stick displays. The duration of territory occupancy and its importance for the fitness of beavers are also discussed. Further, this chapter explores beaver communication using odours, sounds, tail slapping, poses, and other movements. Beavers predominantly communicate via odours, but the importance of all these modalities is explored. Lastly, population estimations, growth, fluctuations, and densities of beaver populations are discussed.
Тези доповідей конференцій з теми "Taille des pores":
1
Xie, H., G. J. Yang, C. X. Li, and C. J. Li. "Multi-Scale Multi-Points Inter-Splat Connection Enhanced Sintering Model for Plasma-Sprayed Lamellar TBCs." In ITSC 2014, edited by R. S. Lima, A. Agarwal, M. M. Hyland, Y. C. Lau, G. Mauer, A. McDonald, and F. L. Toma. DVS Media GmbH, 2014. http://dx.doi.org/10.31399/asm.cp.itsc2014p0774.
Анотація:
Abstract Plasma-sprayed thermal barrier coatings are highly insulating due to intersplat pores. High-temperature exposure, however, leads to pore healing and a loss of thermal insulating capability. Previous sintering models based on the healing of iso-thick pores cannot explain the ultrafast sintering kinetics observed during the initial sintering stage. To better understand the sintering process and the kinetics of pore healing, a study was conducted on the changes that occur at the interfaces between lamellae at high temperatures. It was found that splat surfaces develop multiscale convexes, forming bridges between adjacent splats that significantly accelerate pore healing. This model explains the fast sintering kinetics of the initial sintering stage and presents new opportunities to further tailor the sintering kinetics of YSZ coatings and thereby improve TBC performance.
2
Schondel, J. Patrick, and Michael R. Robinson. "VECTOR Program Background and Plan." In ASME 1998 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/98-gt-145.
Анотація:
The U.S. Navy in cooperation with the Ministries of Defense of Germany and Sweden are initiating a 3-year demonstration program in 1998 to evaluate and define the benefits of thrust vectoring beyond those already understood for Close-in-Combat (CiC). The VECTOR (Vectoring ESTOL Control and Tailless Operational Research) program will capitalize on the X-31 airframe and a contractor team that includes Boeing, G.E., DASA, Volvo, and SAAB to demonstrate the following technologies: • AVEN® Nozzle - a G.E. designed vectoring nozzle applicable to the F404 family of engines • Extremely Short Takeoff and Landing (ESTOL) - employ thrust vectoring and precision control for poststall flight in approach to landing and during take off • Reduced Tail/Tailless - rely on thrust vectoring for primary aircraft stability and control • Advanced Air Data System (AADS) - flush air data ports or optical air data system integrated with the control system to handle the extensive angle-of-attack and sideslip envelope. The flight test activity will be conducted in the United States. However, technical development activities will be conducted in all three countries. Germany and Sweden will contribute technical expertise primarily related to flight control and propulsion system integration, respectively.
3
Ekberg, J., U. Klement, S. Creci, and L. Nordstierna. "Porosity Measurements on Heat Treated Suspension Plasma Sprayed YSZ Coatings Using NMR Cryoporometry." In ITSC2017, edited by A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen, and C. A. Widener. DVS Media GmbH, 2017. http://dx.doi.org/10.31399/asm.cp.itsc2017p0308.
Анотація:
Abstract Suspension plasma sprayed (SPS) coatings can be produced with fine powder particles and tailor-made porosity. This allows to achieve low thermal conductivity which makes the coatings attractive as e.g. topcoats in thermal barrier coatings (TBCs). Used in gas turbine applications, the TBCs are exposed to high temperatures which leads to alterations of the microstructure. To obtain coatings with optimized properties, possible microstructure alterations like closing of pores and opening of cracks have to be taken into account. Hence, in this study, TBC topcoats consisting of 8 wt.% yttria-stabilized zirconia (YSZ) were heat treated in air at 1150°C and thereafter investigated using scanning electron microscopy, X-ray diffraction, and nuclear magnetic resonance (NMR) cryoporometry. For all investigated samples, the porosity decreased as a result of the heat treatment. The finer pores and cracks disappeared and the larger pores grew slightly and achieved a more distinct shape as the material seemed to become more compact.
4
Jandhyala, Siva Rama Krishna, and Walmy Cuello Jimenez. "Design Tool to Tailor Properties of Cement for P&A Applications." In Offshore Technology Conference. OTC, 2023. http://dx.doi.org/10.4043/32624-ms.
Анотація:
Abstract As oil and gas wells approach the end of their productive lifetime, they must be permanently abandoned. In recent years, there has been a lot of emphasis on creating modeling tools for design tailoring and placement of abandonment plugs. Moreover, it is of equal significance to devise a process and design tool for achieving long-term integrity of abandonment plugs. Such a design tool will help understand and mitigate the risks of thermo-mechanical damage or flow through plugs. A sound underlying design process should demonstrate the following attributes - (i) be flexible to accommodate different load types: structural, thermal, pore fluid, and strain loads that can be rapid or gradual in nature, (ii) communicate stresses, deformation and temperature information between load stages, (iii) allow load application on the top, bottom, and radial directions of the plug, (iv) evaluate risk of mechanical failure and permeable flow, and (v) allow tailoring of cement properties to minimize the risks. As a result, this work presents a design tool that complies with all the attributes described. The design tool has been used to model a cement plug interacting with its near wellbore environment. It has the necessary geomechanical and transient features to model rapid or gradual changes in pore pressure and stress to subsequently assess the risk of fluid flow, mechanical failure in shear, tension and/or debonding. The design tool is verified by simulating the construction phases and operational loads of a representative plug job and then comparing its outcome to the expected and/or actual behavior. The effect of plug in-situ stresses and stress anisotropy of the rock are demonstrated. Further, the response of formation's permeability changes from 50 nano Darcy to 5000 μDarcy is used to highlight the impact of fluid communication between the adjacent formation and the abandonment plug. Interestingly, the verification results align with the expected behavior. Pore pressure buildup is found to increase or decrease the risk of plug failure in shear mode depending on whether the plug is cured in compression or tension, respectively. An increase in formation permeability shows a flow diversion from the plug into the rock, thus, limiting the stress build-up in the plug. For the case analyzed herein, the encountered impact of rock stress anisotropy is minimal. Ultimately, the design tool demonstrates how a typical abandonment construction and operation process can be simulated to assess the risk of failure and fluid flow through an abandonment plug. It also highlights the critical factors that govern a plug's response, which in some cases includes the role of formation and casing.
5
Broughton, Justin, and Yogendra Joshi. "A Numerical Investigation of Additive Manufactured Foam Structures for Single Phase Hotspot Thermal Management." In ASME 2019 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ipack2019-6519.
Анотація:
Abstract Wide band-gap (WBG) power devices have been investigated for their higher power densities, efficiencies, and operating temperatures. However, implementation of WBG devices may cause increased volumetric heat generation despite efficiency increases due to a significant decrease in volume. To fully take advantage of the benefits offered by these devices, the packaging, including cooling infrastructure, must also be addressed. Additive manufactured (AM) structures, based on unit cells seen in stochastic foams, have been investigated as an improvement in thermal management for electric vehicle power electronics. Metal foams have a high specific surface area, high thermal conductivity, and low relative density, which makes them excellent for heat transfer applications as demonstrated extensively in prior literature. Additionally, additive manufacturing offers the ability to print directly on a substrate which eliminates a thermal interface layer and make complex structures for little to no increase in cost. Designed foams were examined specifically for their ability to locally control relevant parameters to tailor the heat transfer performance. The design of the AM foam samples, as well as discussion of relevant parameters for proper characterization with respect to thermohydraulic performance, were discussed. Two geometries — one with local, spanwise densification with decreased pore size and another with uniform density and pore size throughout — were investigated for thermal management of several discrete heaters. Pore-scale models with decreased computational domains were used to obtain closure terms for volume-averaged (VA) modeling. The VA models were then used for full-scale modeling of five chip heaters cooled with the designed metal foams.
6
Gordeev, E. I. "Detecting near-tail current sheet formation using isotropic boundaries: lessons from global MHD." In Physics of Auroral Phenomena. FRC KSC RAS, 2020. http://dx.doi.org/10.37614/2588-0039.2020.43.002.
Анотація:
A number of recent studies suggests an existence of magnetotail current sheet configurations with tailward Bz gradient during the growth phase of the substorm. Such configurations are especially interesting since they are potentially unstable for different types of instabilities and can lead to explosive reconfiguration of the magnetosphere. However, the observations are rare and ability to observe tailward gradients is very limited. Here we use the global MHD configuration with near-tail Bz minimum to investigate the regions with adiabatic and non-adiabatic behavior of energetic particles. Thus we estimate the locations of the isotropic boundaries for the modelled POES-type spacecraft flybys. We expect that the lessons learned from global MHD simulation may become helpful in exploration of non-monotonic tail current sheet configuration using observations on low-orbiting spacecraft.
7
Hassaine Daoudji, Doriane Ibtissam, Quentin Struss, Amrid Amnache, Étienne Léveillé, Mahmood Reza Salim Shirazy, and Luc G. Fréchette. "Impact of Micropillar Density Distribution on the Capillary Limit of Heat Pipes." In ASME 2020 Heat Transfer Summer Conference collocated with the ASME 2020 Fluids Engineering Division Summer Meeting and the ASME 2020 18th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/ht2020-9001.
Анотація:
Abstract This paper shows the performance enhancement of heat pipes by tailoring the density distribution of micropillar wicks to minimize viscous pressure loss while maintaining sufficient capillary pumping. In a heat pipe, capillarity and permeability are linked, since small pores create higher capillary pumping while unfortunately inducing more pressure drop along the heat pipe. This pressure loss accumulates along the heat pipe, leading to a non-uniform pressure difference between the liquid and vapor. Therefore, we do not need a uniform capillary pressure to withstand this difference. This provides the opportunity to spatially tailor the wick structure, aiming for a high capillarity to pump the liquid, but a low permeability to induce less pressure loss. Our study offers a compromise between capillarity and permeability by designing the density distribution of the pillar wick structure. This density distribution, which was not studied before, will be shown to enhance the heat pipe performance. The theoretical models show that a tailored density distribution can enhance the heat pipe performance by a factor of 1.5. To support this result, ‘rate of rise’ measurements along a pillar array demonstrate that the liquid pressure loss in a tailored density array are less compared to a constant pillar density.
8
Zhang, Yanna, Liangchuan Li, Fei Yan, and Yucai Wang. "The Study and Application of Seepage Reconstruction for Water Plugging in High Permeability Sandstone Reservoirs." In SPE International Conference on Oilfield Chemistry. SPE, 2023. http://dx.doi.org/10.2118/213865-ms.
Анотація:
Abstract In the medium/high permeability sandstone reservoirs, long-term water flooding led to large pore channels formed in the reservoir, and the injected water quickly breaks into oil wells along the large pore channels, resulting in water cut increase rapidly and a significant reduction in water flooding efficiency. The traditional water shut-off by chemical or cement squeeze cannot reduce water cut for a long time and cannot increase oil production because they don't change the existing seepage characteristics of the reservoir. The seepage reconstruction is a combination of chemical water shut-off and fracturing technology. It involves innovation on intelligent water control materials and fracturing injection process. There are three plugging slugs, a strong plugging slug, a seepage reconstruction slug, and a tail plugging slug, should be filled into reservoir one by one. The strong plugging slug adopts inorganic polymer to shut-off the large pore by low speed injection. The seepage reconstruction slug is composed of 70-140 mesh quartz sand, 50-80um ceramist and intelligent water control materials with a ratio of 6:3:1, which is carried by low-concentration guar. The tail plugging slug is made of self-consolidated material to prevent sand returning from formation. The technology is used in G111-6 located in J oil field, which is successful in increasing oil production from 3.08bopd to 56.28bopd and reducing the water cut from 96.64% to 78%. The validity period was 492d, and the total oil production was 22624bbls. The technology of seepage reconstruction for water shut-off could effectively reduce the water cut and greatly increase the daily oil production. It effectively improves waterflood development efficiency of medium/high permeability sandstone reservoirs in high water cut stage. The innovation of this technology is the effective combination of fracturing technology and traditional chemical water shut off technology. The goals of water shut-off and oil increase are realized by innovative design of three plugging slugs. It provides a new approach for water shut-off in medium/high permeability sandstone reservoirs with high water cut.
9
Loghin, Adrian, Al Cerrone, Anjali Singhal, and Ying Zhou. "Connecting Computed-Tomography-Assisted Discontinuity Detection in Ni-Base Superalloys to Engineering Simulation." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-65087.
Анотація:
The impact of non-metallic inclusions on fatigue life of various materials (steel alloys, Ni-base) has been studied extensively for more than fifty years. Specimen test procedures at various conditions (temperature, air or vacuum, LCF, HCF, VHCF) have been used to quantify the impact of inherent manufacturing induced discontinuities (ceramic inclusions, pores, carbides) on the fatigue capability of the material. Frequently, the fatigue data shows large scatter, leading to a large set of test specimens that has to be considered to quantify the lower tail of the fatigue life distribution. To understand the specimen recorded fatigue lives, assessment of the discontinuity population is usually conducted post-mortem by fractography wherein the origin of crack nucleation, size of the eventual inclusion on fracture surface, and distance from the free surface are identified. 3D characterization techniques can be leveraged to extract previously unobtainable information out of the testing specimens non-destructively. In this study, samples of different Powder Metallurgy (PM) Ni-base superalloys with different inclusion content and size were scanned to identify the Computed Tomography (CT) test setup that would provide adequate contrast to discriminate between matrix and eventual discontinuities (inclusions, pores). To further validate the capability to identify discontinuities within the matrix (Ni base alloy) using the CT technique, a set of LCF specimens were scanned prior to the test procedure. Post-failure fractography analysis showed that one of the CT indications is correlated with the failure-inducing inclusion. Volume reconstruction and finite element meshing conclude this study to: a) further provide a size distribution of inclusions in the scanned volume as well as location of these inclusions relative to the surface of the specimen and b) connect direct measurement with engineering simulation.
10
Donald A., Anschutz, Wildt Patrick J., Stribling K. Michelle, Craig Jim, Curimbaba Luiz R., Silva Pedro, and Abou-sayed Ibrahim S. "An Advanced Proppant Depositional Study with Post-Production Flow Evaluation in a 10' X 20', Transverse Fracture, Slot Flow Configuration." In SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206212-ms.
Анотація:
Abstract While the shale revolution flourished prior to the pandemic, the increased supply bubble had already taken a toll on the profitability of horizontal wells with multiple transverse fractures. A significant shift previously occurred to reduce proppant costs by utilizing cheaper, smaller grained, lower strength, and broadly diverse grain sized sands. Due to the extremely low matrix permeability in active unconventional plays, the use of regional 40/70 and 100 mesh sands (50/140, 70/140, etc.) has become commonplace with adequate results. What remains is the need for enhanced conductivity near the wellbore to handle the radial flow convergence loss when the well is brought on-line. Research is being conducted to better understand how to efficiently increase near-wellbore conductivity using lead and tail-in stages with higher permeability (ceramic) proppant when frac sand is the majority of the material pumped into the well. A 10’x20’ Large Slot Flow (LSF) apparatus, equipped with multiple injection points, side-panel ports for leak-off and/or post-test injection, with the ability to be disassembled for sample analysis after testing, was utilized for this project. For this data, the inlet was moved to the centerline of the wall to allow for proppant and fluid to transport into an environment similar to a horizontal wellbore connecting with a transverse fracture. Various tests were conducted to study the depositional characteristics of lead and tail-in stages with ceramic proppant (15% BW-Lead, 5% BW-Tail) and a main stage of 100 mesh sand (80%). Three inlet positions were established in the lower, middle, and upper portion of the apparatus. Tests were recorded to visually capture the efficiency of placing the premium proppants near the wellbore for increased conductivity. A key addition to the study was the innovative, post-production analysis through the side-panel ports. Fluid was injected into the proppant pack to observe the effect of increased near-wellbore conductivity. To improve visibility, the fluid was colored with a fluorescent dye and observed under black lights. The injection front geometry was radial initially, but typically elongated toward the exit point after contacting the ceramic proppant. The amount of time and distance for the fluid to travel through the sand pack, as well as that for the fluid to reach the offtake point once the ceramic bed was reached, were monitored and recorded. The ratio of the velocities should represent a valid qualitative indication of the conductivity contrast of the two proppants. This paper will describe the unique experimental configuration, outline the testing program for both deposition and post-production assessments performed on the deposits, along with results that could provide better design practices leading to improved transverse fracture performance.
Звіти організацій з теми "Taille des pores":
1
Peitz, David, and Naomi Reibold. White-tailed deer monitoring at Arkansas Post National Memorial, Arkansas: 2005–2020 trend report. Edited by Tani Hubbard. National Park Service, April 2021. http://dx.doi.org/10.36967/nrr-2285087.
Анотація:
From 16 years (2005–2020) of monitoring trends in white-tailed deer within a defined survey area of Arkansas Post National Memorial, we have been able to demonstrate both population declines and recoveries. The adjusted count of deer had a seven-fold increase between 2007 and 2011 following a two-year decline and a three-fold increase between 2017 and 2019 following a six-year decline. Overall, the deer population has declined slightly, averaging a 0.5% reduction in herd size annually. The number of deer in the survey area ranged from 16.77 ± 21.26 (mean + 95% CI) individuals/km2 in 2007 to 118.95 ± 39.03 individuals/km2 in 2011. The amount of visible area surveyed each year varied between 0.25 and 0.47 km2 (coefficient of variation = 16.47%). If the white-tailed deer population becomes too large, this poses several problems for Arkansas Post National Memorial. First, it adds a level of complexity to implementing active natural resource management critical to preventing the cultural landscapes of Arkansas Post National Memorial from changing into something that has little resemblance to the historical character of the park. Deer deferentially browse native vegetation over exotic vegetation, thus promoting the spread of exotic species, and the success of tree planting can be curtailed by heavy deer browsing. Second, controlling deer related disease, some of which can affect domestic livestock and human health in and around the park, becomes increasingly difficult when there are more deer. Third, as additional ancillary data suggests, the largely unreported and costly deer-vehicle collisions in and around Arkansas Post National Memorial have the potential to increase if the deer populations grow.