Academic literature on the topic 'PTT Fluid'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'PTT Fluid.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "PTT Fluid"
1
OLIVEIRA, PAULO J., and FERNANDO T. PINHO. "Analytical solution for fully developed channel and pipe flow of Phan-Thien–Tanner fluids." Journal of Fluid Mechanics 387 (May 25, 1999): 271–80. http://dx.doi.org/10.1017/s002211209900453x.
Full textAbstract:
Analytical expressions are derived for the velocity vector, the stress components and the viscosity function in fully developed channel and pipe flow of Phan-Thien–Tanner (PTT) fluids; both the linearized and the exponential forms of the PTT equation are considered. The solution shows that the wall shear stress of a PTT fluid is substantially smaller than the corresponding value for a Newtonian or upper-convected Maxwell fluid, with implications for comparing predicted and measured values in a non-dimensional form.
2
Bariteau, Jason, Douglas Robertson, and William Carpenter. "Posterior Tibial Tendon Dysfunction." Foot & Ankle Orthopaedics 2, no. 3 (2017): 2473011417S0000. http://dx.doi.org/10.1177/2473011417s000023.
Full textAbstract:
Category: Hindfoot Introduction/Purpose: Stage 1 posterior tibial tendon dysfunction (PTTD) may be present without intra-substance tendon pathology. We hypothesize that in individuals with the clinical diagnosis of Stage 1 PTTD, with no MRI-detectable intra-substance tendon pathology, that sheath fluid amount is a confirmatory finding of PTTD. This purpose of this study was to quantify the amount of PTT sheath fluid in 1) individuals with the clinical diagnosis of Stage 1 PTTD and no MRI-detectable intra-substance tendon pathology and compare to controls with medial ankle pain (causes other) also without MRI-detectable intra-substance PTT pathology, and 2) test if there was a sheath fluid measurement predictive of the clinical diagnosis of PTTD. Methods: 326 individuals with medial ankle pain, no intra-substance PTT pathology, were studied, 48 with the clinical diagnosis of Stage 1 PTT dysfunction and 278 with medial ankle pain, causes other. Geometric methods defined MRI-based sheath fluid volume, maximum cross-sectional fluid area, and maximum fluid width. Fluid measurements were compared between groups and a predictive measurement calculated to identify individuals with PTTD. Measurement reliability was tested. Results: Individuals with PTT dysfunction had larger PTT sheath fluid volume, area, and width than controls (p’s < 0.001). An 9 mm threshold maximum fluid width was associated with PTTD (sensitivity 84%, specificity 85%). Measurements were reliable (p’s <0.03). Conclusion: The amount of PTT sheath fluid, in individuals with medial ankle pain and no intra-substance PTT pathology, was associated with Stage 1 PTTD and a maximum PTT sheath fluid width of > 9 mm predicted PTTD. This is clinically significance as MRI-detected sheath fluid can now be used as a confirmatory finding in individuals with the clinical diagnosis of Stage 1 PTTD who do not have MRI-detectable intra-substance pathology
3
Siddiqui, Abdul, Muhammad Zeb, Tahira Haroon, and Qurat-ul-Ain Azim. "Exact Solution for the Heat Transfer of Two Immiscible PTT Fluids Flowing in Concentric Layers through a Pipe." Mathematics 7, no. 1 (2019): 81. http://dx.doi.org/10.3390/math7010081.
Full textAbstract:
This article investigates the heat transfer flow of two layers of Phan-Thien-Tanner (PTT) fluids though a cylindrical pipe. The flow is assumed to be steady, incompressible, and stable and the fluid layers do not mix with each other. The fluid flow and heat transfer equations are modeled using the linear PTT fluid model. Exact solutions for the velocity, flow rates, temperature profiles, and stress distributions are obtained. It has also been shown that one can recover the Newtonian fluid results from the obtained results by putting the non-Newtonian parameters to zero. These results match with the corresponding results for Newtonian fluids already present in the literature. Graphical analysis of the behavior of the fluid velocities, temperatures, and stresses is also presented at the end. It is also shown that maximum velocity occurs in the inner fluid layer.
4
Lim, Philip S., Mark E. Schweitzer, Diane M. Deely, et al. "Posterior Tibial Tendon Dysfunction: Secondary MR Signs." Foot & Ankle International 18, no. 10 (1997): 658–63. http://dx.doi.org/10.1177/107110079701801011.
Full textAbstract:
We evaluated four potential secondary magnetic resonance imaging signs to aid in clinical diagnosis of posterior tibial tendon (PTT) tears. Seventy-one ankles (25 PTT tears and 46 controls) were evaluated for the following secondary signs: (1) PTT sheath fluid, (2) a distal tibial spur located just anterior to the PTT, (3) unroofing of the talus, and (4) “bone bruise”-like medullary lesions. Two musculoskeletal radiologists rated their confidence using a scale and were compared for level of agreement. The presence of PTT sheath fluid had modest specificity and fair to moderate sensitivity. Tibial spurring and unroofing of the talus had excellent specificity and fair sensitivity. Bone bruise-like lesions were commonly seen in cases and controls. Examination of divergence of opinion between the two radiologists revealed pitfalls in interpretation of PTT sheath fluid and bone bruise-like lesions, which were commonly the result of adjacent vessels and inhomogeneous fat saturation, respectively. We conclude that secondary signs of PTT tears with high specificities include unroofing of the talus, tibial spurring, and PTT sheath fluid.
5
Akyildiz, F. Talay, and Hamid Bellout. "Viscoelastic Lubrication With Phan-Thein-Tanner Fluid (PTT)." Journal of Tribology 126, no. 2 (2004): 288–91. http://dx.doi.org/10.1115/1.1651536.
Full textAbstract:
We analyze the lubrication flow of a viscoelastic fluid to account for the time dependent nature of the lubricant. The material obeys the constitutive equation for Phan-Thein-Tanner fluid (PTT). An explicit expression of the velocity field is obtained. This expression shows the effect of the Deborah number (De=λU/L, λ is the relaxation time). Using this velocity field, we derive the generalized Reynolds equation for PTT fluids. This equation reduces to the Newtonian case as De→0. Finally, the effect of the Deborah number on the pressure field is explored numerically in detail and the results are documented graphically.
6
Siddiqui, A. M., Q. A. Azim, and M. Imran. "Exact solutions for n-layer concentric flow of PTT fluids through a cylindrical pipe." Canadian Journal of Physics 98, no. 2 (2020): 134–41. http://dx.doi.org/10.1139/cjp-2019-0068.
Full textAbstract:
Flows of multiple layers of fluids are encountered in many industrial and manufacturing processes. This paper investigates the concentric n-layer flow for Phan–Thien–Tanner (PTT) fluids through a cylindrical pipe. Finitely many immiscible non-Newtonian fluids are considered to be flowing concentrically in a tube. The flow is modelled using the exponential PTT fluid model and exact solutions for velocity fields and volume flow rates are computed. It has been shown that the corresponding results for linear PTT fluid model as well as Newtonian fluids can be deduced from the obtained expressions, and that they match with the present literature. It has also been observed that for such layered flow, the non-Newtonian parameters significantly affect the flow of fluids in adjacent layers. The effects of involved parameters on the velocity profiles are also shown graphically. We show that a unique velocity maximum exists along the axis of the pipe. Moreover, it is observed with the help of an example that layer thickness can be adjusted to obtain maximal flow rate with a given pressure gradient.
7
AFONSO, A. M., P. J. OLIVEIRA, F. T. PINHO, and M. A. ALVES. "Dynamics of high-Deborah-number entry flows: a numerical study." Journal of Fluid Mechanics 677 (April 13, 2011): 272–304. http://dx.doi.org/10.1017/jfm.2011.84.
Full textAbstract:
High-elasticity simulations of flows through a two-dimensional (2D) 4 : 1 abrupt contraction and a 4 : 1 three-dimensional square–square abrupt contraction were performed with a finite-volume method implementing the log-conformation formulation, proposed by Fattal & Kupferman (J. Non-Newtonian Fluid Mech., vol. 123, 2004, p. 281) to alleviate the high-Weissenberg-number problem. For the 2D simulations of Boger fluids, modelled by the Oldroyd-B constitutive equation, local flow unsteadiness appears at a relatively low Deborah number (De) of 2.5. Predictions at higher De were possible only with the log-conformation technique and showed that the periodic unsteadiness grows with De leading to an asymmetric flow with alternate back-shedding of vorticity from pulsating upstream recirculating eddies. This is accompanied by a frequency doubling mechanism deteriorating to a chaotic regime at high De. The log-conformation technique provides solutions of accuracy similar to the thoroughly tested standard finite-volume method under steady flow conditions and the onset of a time-dependent solution occurred approximately at the same Deborah number for both formulations. Nevertheless, for Deborah numbers higher than the critical Deborah number, and for which the standard iterative technique diverges, the log-conformation technique continues to provide stable solutions up to quite (impressively) high Deborah numbers, demonstrating its advantages relative to the standard methodology. For the 3D contraction, calculations were restricted to steady flows of Oldroyd-B and Phan-Thien–Tanner (PTT) fluids and very high De were attained (De ≈ 20 for PTT with ϵ = 0.02 and De ≈ 10000 for PTT with ϵ = 0.25), with prediction of strong vortex enhancement. For the Boger fluid calculations, there was inversion of the secondary flow at high De, as observed experimentally by Sousa et al. (J. Non-Newtonian Fluid Mech., vol. 160, 2009, p. 122).
8
Faraz, Naeem, Zhiming Lu, Lei Hou, Yasir Khan, and Ahmed Faisal Siddiqi. "Exact solutions of magnetohydrodynamic flow of PTT fluid." Journal of Physics: Conference Series 1053 (July 2018): 012064. http://dx.doi.org/10.1088/1742-6596/1053/1/012064.
Full text
9
Renardy, Michael. "Re-entrant corner behavior of the PTT fluid." Journal of Non-Newtonian Fluid Mechanics 69, no. 1 (1997): 99–104. http://dx.doi.org/10.1016/s0377-0257(96)01506-6.
Full text
10
Tezel, Guler Bengusu, Kerim Yapici, and Yusuf Uludag. "Flow Characterization of Viscoelastic Fluids around Square Obstacle." Periodica Polytechnica Chemical Engineering 63, no. 1 (2018): 246–57. http://dx.doi.org/10.3311/ppch.12426.
Full textAbstract:
This study focuses on the computational implementation of structured non-uniform finite volume method for the 2-D laminar flow of viscoelastic fluid past a square section of cylinder in a confined channel with a blockage ratio 1/4 for Re = 10-4, 5, 10 and 20. Oldroyd-B model (constant viscosity with elasticity) and the PTT model (shear-thinning with elasticity) are the constitutive models considered. In this study effects of the elasticity and inertia on the drag coefficients and stress fields around the square cylinder are obtained and discussed in detail. With an increase elasticity, drag coefficients get smaller due to stronger shear thinning effects for PTT fluid, however, the drag coefficients show slightly enhancement for the Oldroyd-B fluid.
Dissertations / Theses on the topic "PTT Fluid"
1
Sibley, David N. "Viscoelastic flows of PTT fluid." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518114.
Full text
2
Kelly, Jennifer Christine. "The fluid evolution of the Mount Mica and Irish Pit pegmatites, Maine| Evidence from stable isotopes." California State University, Long Beach, 2013.
Find full text
3
Capron, Marie. "Couplage fluide-structure dans l’embolie gazeuse du peuplier." Phd thesis, Toulouse, INPT, 2014. http://oatao.univ-toulouse.fr/12164/1/Capron.pdf.
Full textAbstract:
Les arbres irriguent leurs organes par un système microfluidique complexe qui permet le transfert d’eau sous des pressions hydrostatiques négatives allant de -0.1 à -13 MPa. Dans ces conditions de métastabilité, les arbres vivent avec le risque d’une vaporisation soudaine de leur sève, qui conduit à l’embolie. Après cavitation, la poche de gaz créée croît ensuite par différence de pression et diffuse dans les vaisseaux du xylème à travers des membranes poreuses appelées “ponctuations”. Ces membranes permettent d’assurer le transfert hydrique vasculaire et de lutter contre la propagation de l’embolie gazeuse pouvant conduire à un état létal de la plante. Pour comprendre les mécanismes d’embolie d’air dans le xylème, nous avons pu étudier la structure des ponctuations du peuplier et caractériser par microscopie à force atomique (AFM) leurs propriétés mécaniques. Nous avons fait des expériences de nano-indentation et de flexion sur des échantillons secs et saturés en eau. Les premières expériences semblent montrer que les propriétés mécaniques sont peu affectées par la sorption d’eau (le module d’Young de la membrane primaire est E 0:40 GPa). Nous avons pu établir que le module des ponctuations était inférieur à celui de la paroi vaisseaux du xylème (E 8 GPa). Des expériences de micromoulages ont montré que les membranes des ponctuations se déforment sous l’effet d’une différence de pression. En tenant compte de la présence des parois secondaires, l’analyse par éléments finis de la déformation des ponctuations permet de calculer le module d’Young des membranes qui est identique à celui déterminé en AFM. Nous avons pu mettre en évidence que les mâchoires constituées par les parois secondaires limitent la déformation de la membrane au niveau de l’encastrement près du bord. Des expériences d’injection d’air ont permis de déterminer la pression critique (Pc = 1:8 MPa) et les diamètres critiques des pores présents sur les valves capillaires (dpore 160 nm). La taille des pores estimée est cohérente avec les données de la littérature. Nous avons proposé une première modélisation de la propagation d’une embolie sur la base de l’écoulement de Darcy dans la membrane. L’ensemble des résultats semble montrer que la diffusion de gaz est rendu possible par l’effet conjoint de la déformation de la membrane qui génère l’ouverture des pores diminuant ainsi la pression critique de passage du gaz et de la rupture des ponts capillaires présents dans les pores de la membrane.
4
Vergel, José Luis Gomez 1985. "Estudo da influência da malha computacional, modelos de turbulência e aspectos numéricos da modelagem CFD em impelidores PBT usando malhas não-estruturadas." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266654.
Full textAbstract:
Orientadores: José Roberto Nunhez, Nicolas Spogis<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química<br>Made available in DSpace on 2018-08-22T07:47:05Z (GMT). No. of bitstreams: 1
Vergel_JoseLuisGomez_M.pdf: 8156840 bytes, checksum: f0b5d7b4b0875d4716285f8ec3ce5fa2 (MD5)
Previous issue date: 2013<br>Resumo: O uso de malhas não estruturadas recentemente tem recebido uma considerável atenção para discretização do domínio computacional em simulações CFD (Vakili & Esfahany, 2009; Cabrales, et al., 2011). A malha não estruturada (comumente tetraédricas) permite uma adequada adaptação em geometrias irregulares e uma geração automática na maioria dos softwares comerciais em CFD. Na literatura constantemente tem sido sugerido que as malhas hexaédricas são preferidas as tetraédricas, porém esta última pode ser usada, desde que alguns cuidados sejam tomados para proporcionar uma boa representação do fenômeno físico do problema. Alguns trabalhos recentemente publicados mostram que as malhas tetraédricas quando utilizadas com cuidado, podem obter resultados satisfatórios (Spogis & Nunhez, 2009). A maioria dos trabalhos desenvolvidos com uso da simulação CFD para processos de mistura utilizam malha hexaédrica, enquanto os resultados obtidos com malhas tetraédricas não possuem a mesma aprovação (Joaquim Junior et al., 2007), parte deste trabalho esta focado em mostrar que elas podem fornecer bons resultados em simulações de processos de mistura. Outro objetivo desse trabalho é mostrar o efeito do refinamento em malhas tetraédricas. Investigou-se a influência dos elementos prismáticos perto da parede sobre parâmetros globais, tais como o número de potência e número de bombeamento. Foi também realizada uma análise inicial da sensibilidade de alguns modelos de turbulência e esquemas de discretização sobre o campo de fluxo produzido. Além disso, simulações com diferentes refinamentos de malha foram feitas usando a abordagem de múltiplos sistemas de referência (MFR); enquanto em outros casos foi proporcionada uma abordagem de malhas deslizantes (SG) no impelidor. Os esquemas de discretização foram limitados aos esquemas Upwind, High resolution e blend fator, uma vez que esquemas diferentes não funcionam adequadamente com elementos tetraédricos. O software comercial de CFD CFX 14.0 foi utilizado para simular os resultados. Um impelidor de pás inclinadas (PBT 45°, com bombeamento para baixo) foi simulado em regime turbulento. Os resultados obtidos pelas simulações CFD para o número de potência e bombeamento, e perfil da componente axial da velocidade são discutidos e comparados com dados experimentais (Machado et al. et al., 2011). A velocidade foi medida usando a técnica PIV (Particle Image Velocimetry). Uma significativa influencia foi observada em alguns parâmetros na determinação de importantes variáveis nos processos de mistura. De forma geral, a predição do perfil da velocidade é influenciada, de alguma forma, pela resolução da malha, pelo modelo de turbulência e pelo esquema de discretização<br>Abstract: The use of non-structured meshes has received recently considerable attention for discretization of the computational domain in CFD simulations (Vakili & Esfahany, 2009; Cabrales et al., 2011). The non-structured meshes (the most common are tetrahedral) allow adequate adaptation of irregular geometries and easy use of automated algorithms for mesh generation in most commercial CFD software. It has been consistently suggested in the literature that hexahedral meshes are preferred over tetrahedral. However, they can be used, provided that some care is taken to provide a good representation of the physical phenomena of the problem. Recently published works have been proving that if they are used with care, satisfactory results are obtained (Spogis & Nunhez, 2009). Most of works developed with the use of CFD simulation for mixing processes use hexahedral and to date tetrahedral do not have the same acceptance of hexahedral (Joaquim Junior et al., 2007) and part of this work is aimed at showing that they can provide good results when simulating mixing processes. Another objective of this work is to show the effect of mesh refinement in tetrahedral meshes. It is investigated the influence of the prismatic elements near wall on global parameters such as the Power and Flow numbers. An initial analysis of the sensitivity of some turbulence models (Standard k-? model, the shear stress transport (SST) and BSL-Reynolds stress model) and the discretization scheme on the flow field produced were also carried out in this work. In addition, simulations with different mesh resolutions were made using the multiple reference frame (MFR) approach; whereas other cases a sliding mesh modeling was provided for the impeller. The discretization schemes were limited to upwind, high resolution and blend factor, since other schemes do not work well with tetrahedral. The commercial CFD software CFX 14.0 was used to simulate the results. A pitched blade turbine (PBT 45°, down-pumping), was simulated in turbulent flow. The results obtained for the Power and Flow numbers, the axial velocity profile component of the model in CFD are discussed and compared with experimental data (Machado et al. et al., 2011). The velocity was measured using the PIV technique (Particle Image Velocimetry). A significant influence of some parameters is observed on the determination of some important variable mixing. In general, the predictions of the velocity profile are influenced in some way by the resolution of the mesh, turbulence model and the discretization scheme<br>Mestrado<br>Desenvolvimento de Processos Químicos<br>Mestre em Engenharia Química
5
Aucejo, Mathieu. "Vibro-acoustique des structures immergées sous écoulement turbulent." Phd thesis, INSA de Lyon, 2010. http://tel.archives-ouvertes.fr/tel-00777773.
Full textAbstract:
L'objectif de cette thèse est l'étude du bruit propre d'origine hydrodynamique au niveau de l'antenne d'étrave d'un sous-marin pour des fréquences comprises entre 10 Hz et quelques kHz. Dans cette optique, trois problématiques particulières doivent être étudiées : la modélisation du comportement vibro-acoustique des structures en fluide lourd, l'intégration de l'excitation couche limite turbulente (CLT) dans les modèles numériques déterministes et la mesure de la réponse d'une structure sous écoulement turbulent. Le premier chapitre est consacré à la synthèse bibliographique des différentes méthodes existantes pour étudier de tels problèmes. Dans un second chapitre, nous présentons la méthode PTF (Patch Transfer Functions), qui est une approche par sous-structuration de domaines permettant l'étude des problèmes vibro-acoustiques en basses et moyennes fréquences. Cette méthode n'ayant été appliquée qu'en fluide léger, l'un des enjeux de ce chapitre est d'étudier son applicabilité en fluide lourd et de mettre en lumière d'éventuels points de blocage. Nous montrons ainsi que des problèmes de convergence de la méthode apparaissent en fluide lourd. Pour pallier ces difficultés, nous présentons, dans le troisième chapitre, deux stratégies de calcul permettant d'accélérer la convergence globale de la méthode. Le quatrième chapitre propose une application de la méthode PTF pour caractériser la réponse vibro-acoustique en fluide lourd d'une structure soumise à une CLT et couplée à un milieu fluide extérieur et à une cavité acoustique, encombrée par des structures déformables. Pour traiter ce problème, nous complétons, tout d'abord, le modèle PTF par l'introduction de l'excitation CLT dans les modèles déterministes, à partir d'une décomposition de l'interspectre des fluctuations de pression pariétale sur une base d'ondes planes décorrélées. Nous présentons, ensuite, le calcul de l'impédance de rayonnement par pavé pour des surfaces de couplage de géométrie quelconque, ainsi qu'un modèle d'encombrement permettant, à partir de considérations physiques, de tenir compte simplement de la complexité structurale de structures encombrant une cavité acoustique. Cette application nous permet de montrer que l'influence de l'encombrement des cavités sur la réponse vibro-acoustique du système ne peut pas être négligée, lorsque l'on s'intéresse à l'étude du bruit hydrodynamique au niveau d'une antenne d'étrave de sous-marin. Dans le cinquième chapitre, nous développons une technique expérimentale permettant de caractériser le comportement des structures sous écoulement turbulent. Cette technique est basée sur la décomposition en ondes planes décorrélées présentée au chapitre 4 et nécessite la génération de champs de pression pariétale correspondant à ceux que l'on obtiendrait à partir d'ondes propagatives et évanescentes pour tenir compte des caractéristiques spectrales de la CLT. Pour cela, nous utilisons une antenne de monopôles acoustiques, dont nous déterminons numériquement les principaux paramètres (taille, nombre de monopôles et distance antenne paroi). Le nombre de monopôles augmentant avec la fréquence, la mise en oeuvre de cette méthode peut s'avérer délicate. Pour contourner cette difficulté, nous présentons le principe de l'antenne synthétique, dont la validation expérimentale est étudiée dans le dernier chapitre.
6
Wolf, Martin. "Visualisierung und Quantifizierung der Fluiddynamik in Bohrkernen aus dem Salinar und Deckgebirge des Raumes Staßfurt mittels Positronen-Emissions-Tomographie." Doctoral thesis, Universitätsbibliothek Leipzig, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-77160.
Full textAbstract:
Der ehemalige Salzbergbau im Raum Staßfurt führt seit dem 19. Jahrhundert zu Subrosion und teils bruchhaften Deformationen und damit verbundenen Senkungen und Vernässungen im Stadtgebiet. Im Rahmen eines Forschungsverbundvorhabens unter Federführung der BGR sollen in dieser Arbeit die grundlegenden strömungsdynamischen Prozesse im Salinar und Deckgebirge der betroffenen geologischen Formationen aufgeklärt werden. An Bohrkernen aus den entsprechenden Bereichen werden Durchflussexperimente durchgeführt und die Fluiddynamik im Inneren der Proben mittels Positronen-Emissions-Tomographie dreidimensional dargestellt. In Kooperation mit der Bundesanstalt für Materialforschung- und prüfung Berlin und dem Geologischen Institut der Johannes-Gutenberg Universität Mainz werden diese PET-Messungen der Fluiddynamik mit hochauflösenden computertomographischen Messungen der internen Struktur der Proben in Übereinstimmung gebracht. Die beobachteten Fließmuster sollen mittels einer Lattice-Boltzmann-Simulation nachvollzogen und dadurch das grundlegende Verständnis der Strömungsdynamik in diesen Gesteinen erweitert werden. Langfristig soll dies zu einer Verbesserung des Verständnisses der Grundwasserdynamik auf regionaler Ebene führen.
7
Michel, Julien. "Développements numériques de la méthode SPH couplée aux Eléments Finis appliqués au phénomène de l'hydroplanage." Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0013.
Full textAbstract:
Cette thèse s’inscrit dans le projet Fond Unique Interministériel (FUI) HydroSafeTire, dédié à l’étude du phénomène de l’hydroplanage. Au cours d’une précédente thèse sur le sujet au sein du laboratoire, l’étude de ce phénomène a été réalisée via un couplage fluide/structure SPH/FE en utilisant le solveur FE Abaqus développé par Simulia. Des effets tels que la hauteur d’eau, la vitesse du véhicule ou encore l’usure du pneumatique ont ainsi été investigués, montrant que les tendances observées durant les expérimentations étaient retrouvées numériquement. A l’issue de ces travaux, il a donc été décidé d’utiliser le solveur structure FE développé spécifiquement par Michelin (en collaboration avec le GIREF) pour ses applications, afin de tirer profit des avantages de ce solveur pour le problème spécifique de l’hydroplanage. Ainsi dans cette thèse, la première étape est la validation du couplage SPH/FE avec ce code structure sur des cas tests académiques. L’obtention d’un bon compromis précision des résultats / temps de restitution des simulations constitue un enjeu majeur, en particulier dans un contexte industriel. Ainsi, cette thèse s’articule autour de trois axes. Premièrement, un travail sur la consistance des schémas SPH utilisant une méthode de désorganisation particulaire est effectué, en parallèle d’un travail sur la méthode de désorganisation en elle même. Ensuite, un modèle de décollement de jets de surface libre est proposé, compatible avec la prise en compte des effets de succion. Enfin, différents schémas de couplage SPH/FE à pas de temps différés sont étudiés, avec une application à l’hydroplanage<br>This PhD thesis takes place in the Fond Unique Interministériel (FUI) HydroSafeTire project, dedicated to the study of the hydroplaning phenomenon. During a previous PhD thesis regarding this topic in the lab., the hydroplaning phenomenon has been investigated via a fluid/structure SPH/FE coupling, using the FE solver Abaqus developed by Simulia. Physical effects such as the water height, the velocity of the vehicle and the tire wear have been studied, showing that the tendencies experimentally observed were retrieved in the simulations. Therefore, it has been decided to use the FE structure solver specifically developed by Michelin for their tire applications, in order to take benefits of this solver for the specific hydroplaning problem. Then, in the present PhD thesis, the first step is the validation of the SPH/FE coupling, using this FE code, on academic test cases. The compromise between the accuracy of the results and the restitution time of the simulations is of paramount importance, particularly in an industrial context. Thus, three main topics are investigated in this work. Firstly, the consistency of SPH schemes using a Particle Shifting Technique (PST) is studied, in addition to a work on the PST itself. Then, a model of flow separation is proposed, compatible with suction effects. Finally, different coupling schemes SPH/FE using differed time-steps are studied, with an hydroplaning application
8
Vilaplana, Martínez Eduard. "A biphasic model for cortical structural changes in preclinical AD: a multimodal MRI, CSF and PET study." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/456994.
Full textAbstract:
La enfermedad de Alzheimer (EA) se caracteriza neuropatológicamente por la presencia de depósitos extracelulares de ß-amiloide (Aß) y ovillos neurofibrilares intracelulares (proteína tau fosforilada, p-tau) así como fenómenos inflamatorios. Estos procesos se asocian con atrofia cerebral, pérdida neuronal y alteraciones funcionales que acaban produciendo deterioro cognitivo y eventualmente un síndrome clínico de demencia. El depósito de amiloide comienzan décadas antes de que se pueda hacer un diagnóstico de demencia e incluso de la aparición de los primeros síntomas, y constituyen lo que se conoce como EA preclínica (Sperling et al., 2011).
En la actualidad podemos estudiar los mecanismos fisiopatológicos que ocurren en la EA preclínica a través de biomarcadores (Dubois et al., 2016). Entender las relaciones entre biomarcadores en la EA preclínica es esencial para entender la fisiopatología de la enfermedad y poder desarrollar terapias que ralenticen o frenen su curso. Sin embargo, estas relaciones distan de estar claras, por ejemplo, la relación de la amiloidosis y la estructura cortical dista de es controvertida (Fortea et al., 2014).
El objetivo principal de esta tesis fue estudiar las alteraciones corticales estructurales que ocurren en la enfermedad de Alzheimer preclínica. Concretamente, los objetivos fueron 1) estudiar la relación entre Aß y el grosor cortical y sus posibles interacciones con la proteína p-tau, 2) analizar los cambios estructurales corticales longitudinales de la EA preclínica, 3) investigar la microestructura cortical y entender su relación con la macroestructura en el continuum de la enfermedad y, 4) estudiar el impacto local del depósito de amiloide en la estructura cerebral en la EA preclínica.
Para la realización de esta tesis se ha contado con bases de datos públicas americanas (Alzheimer’s Disease Neuroimaging Initiative, http://adni.loni.usc.edu/) y con bases de datos españolas (proyecto SIGNAL, https://www.signalstudy.es/).
Los resultados de la tesis han conducido a la propuesta de un modelo bifásico de cambios corticales estructurales en la EA preclínica. El depósito de amiloide en ausencia de tau patológico se asocia a un incremento del grosor cortical, una ralentización de la atrofia longitudinal a 2 años y descensos de difusión cortical. Posteriormente, en presencia de tau patológica, y como resultado del efecto tóxico sinérgico o interacción entre procesos patológicos, se produciría una aceleración de la atrofia e incrementos de difusión que se extenderían siguiendo un patrón característico que ha sido definido como la huella cortical de la EA (Dickerson et al., 2009).
Los resultados presentados en esta tesis tienen implicación directa en la investigación y en la práctica clínica. En primer lugar, en relación a los modelos de evolución de biomarcadores de la EA (Jack et al., 2013) ya que esta fase temprana de engrosamiento cortical no está contemplada en los modelos actuales. Nuestro modelo ayudaría a integrar los resultados contradictorios previos en la literatura en relación a los efectos del amiloide sobre la estructura cerebral. Los modelos actuales, no contemplan la interacción/sinergia entre biomarcadores que rigen el mencionado proceso bifásico. En segundo lugar, los resultados tienen implicaciones en el diseño de los ensayos clínicos, tanto en la selección de pacientes como en el uso subrogado de la resonancia como marcador de eficacia, ayudando a entender algunos resultados inesperados de los ensayos clínicos previos con inmunoterapia anti-amiloidea. Finalmente, la difusión cortical podría ser un marcador precoz en el curso de la EA. Futuros estudios multimodales de resonancia magnética y líquido cefalorraquídeo que incorporen PET de inflamación y de Tau con seguimientos longitudinales serán claves para seguir estudiando los procesos fisiopatológicos que subyacen la EA preclínica.<br>The Alzheimer’s disease (AD) neuropathological hallmarks are the presence of extracellular amyloid ß (Aß) deposition and intracellular neurofibrillary tangles (hyperphosphorilated tau protein) as well as inflammation phenomena. These processes are associated with cerebral atrophy, neuronal loss and functional alterations which lead to cognitive dysfunction and, eventually, a clinical syndrome of dementia. These pathophysiological processes begin decades before the diagnosis of the clinical dementia even before the appearance of the first clinical symptoms, and constitute the preclinical AD (Sperling et al, 2011).
Nowadays we can study the pathophysiological mechanisms that occur in preclinical AD through biomarkers (Dubois et al., 2016). It is crucial to understand the relationships between biomarkers in preclinical AD to further understand the disease pathophysiology and be able to develop treatments that could slow down or stop its course. However, these relationships are not clear, for example, the relationship between brain amyloidosis and brain structure is controversial (Fortea et al., 2014).
The objective of this thesis was to study the cortical structural alterations that occur in preclinical AD. Specifically, 1) to study the relationship between Aß and cortical thickness and its potential interactions with p-tau, 2) to analyze the 2-year cortical longitudinal changes in preclinical AD, 3) to investigate cortical microstructure and understand its relationship with brain macrostructure in the disease continuum and, 4) to assess the local impact of amyloid deposition in brain structure in preclinical AD.
In this thesis, we have used data from a public American database (Alzheimer’s Disease Neuroimaging Initiative, http://adni.loni.usc.edu/) and from a Spanish multicentric cohort (proyecto SIGNAL, https://www.signalstudy.es/).
The results of this thesis have conducted to the proposal of a biphasic model of structural cortical changes in preclinical AD. Amyloid deposition in the absence of pathological tau levels would be associated with increased cortical thickness, less 2-year longitudinal cortical thinning and cortical diffusivity decreases. Then, in the presence of pathological tau levels, and as a result of the synergic toxic effect or interaction between pathologic processes, there would be an atrophy acceleration and cortical diffusivity increases that would spread following a pattern that has been described as the AD-signature (Dickerson et al., 2009).
The results presented in this thesis have direct research and clinical implications. First, they impact on the models of biomarker evolution in AD (Jack et al., 2013), as the cortical thickening phase is not contemplated in previous models. Our model would help to understand previous contradictory results in the literature that assessed the effect of amyloid on brain structure. Current models do not take into account the interaction/synergy effect between biomarkers that define the aforementioned biphasic process. Second, our results have relevance in the design of clinical trials, both in the selection of patients and in the use of MRI as a surrogate marker of efficacy, and might help explain some unexpected results in previous anti-amyloid immunotherapy trials. Finally, cortical diffusivity could be an early marker in the AD course. Further multimodal studies that incorporate tau- and inflammation-PET with longitudinal follow-ups are crucial to further investigate the pathophysiological process that underlies preclinical AD.
9
Berkner, Joachim Ernst. "Synthesis and characterization of new organic electrically conducting polymers : part II: Direct carboxylation of sulfolene : part III: Effect of water on PTC systems : part IV: Mechanism of Phase transfer catalytic N-alkylation reactions." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/30715.
Full text
10
Arrieta, Valderrama Gustavo Andrés. "Metodología de optimización numérica multi-objetivo y de simulación numérica de la interacción fluido-estructura del desempeño de un agitador con impulsor PBT variando ángulo, altura y velocidad de rotación utilizando ANSYS CFX, MECHANICAL y DESIGN EXPLORER." Bachelor's thesis, Pontificia Universidad Católica del Perú, 2012. http://tesis.pucp.edu.pe/repositorio/handle/123456789/4770.
Full textAbstract:
Los tanques agitadores son ampliamente utilizados en diferentes industrias, en donde la
eficiencia de las operaciones de mezclado tiene un impacto tanto en los costos como en
la calidad del proceso, si a esto se le añade que para poder mantener la competitividad en
el mercado, el tiempo de desarrollo del producto debe ser el menor posible y a un bajo
costo, por ese motivo es necesario optar por nuevas formas para realizar nuevos diseños.
En muchas empresas fabricantes de gran envergadura, el uso software de optimización
se está convirtiendo en una herramienta ideal para conseguir estos objetivos.
En este trabajo se utilizó las herramientas computacionales ANSYS CFX, MECHANICAL
y DESIGN EXPLORATION para realizar una metodología que permita realizar la
simulación numérica tanto a nivel de fluidos y estructural como para realizar la
optimización de un modelo de tanque agitador. Para la elaboración de este procedimiento
se optó por variar en un rango determinado ciertos parámetros geométricos y de
funcionamiento.
En el estudio fluido dinámico se trabajó tres fluidos: agua, metanol y aire, en donde los
dos primeros se modelaron como “multicomponentes” es decir como fluidos miscibles,
mientras que la interacción con el aire se modelo como “superficie libre”. Para esto, se
utilizó el modelo de turbulencia SST (Shear Stress Transport), el cual demostró en un
estudio anterior ser el que más se ajusta al ser contrastado con resultados
experimentales, además se empleó los modelos de “marco de referencia móvil (MRF)” y
de “Frozen Rotor” para tratar la interacción entre las partes móviles (rotor) y partes
estáticas (tanque y deflectores). Para el análisis estructural se utilizó la metodología de
interacción fluido-estructura (FSI) del tipo “unidireccional (one-way)” para determinar los
esfuerzos y deformaciones en cada diseño. Finalmente, se utilizó el método de la
superficie de respuesta (RSM) como base para la optimización, donde se utilizó un
algoritmo estocástico (MOGA) como buscador de soluciones óptimas en el modelo del
tanque agitador parametrizado, el cual consta de tres variables de entrada (ángulo de
alabe, altura de impulsor y velocidad de rotación) y dos funciones objetivos: maximizar
grado de mezcla y minimizar la potencia consumida.
El presente estudio demuestra que la velocidad y el ángulo son los parámetros más
incidentes en las funciones objetivas mencionadas anteriormente y que al variar estos
parámetros se pueden obtener mejoras significativas en los resultados. En este estudio en
particular se encontró que el ángulo de 60 grados y una altura de 300mm con respecto al
tanque, mejora en un 8% y 36% el consumo de potencia y grado de mezcla
respectivamente, para las configuraciones del tanque dadas.<br>Tesis
Books on the topic "PTT Fluid"
1
Elaine, Snyder-Conn, ed. Effects of Prudhoe Bay reserve pit fluids on water quality and macroinvertebrates of Arctic tundra ponds in Alaska. Fish and Wildlife Service, U.S. Dept. of Interior, 1987.
Find full text
3
Escudier, Marcel. Bernoulli’s equation. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0007.
Full textAbstract:
In this chapter Newton’s second law of motion is used to derive Euler’s equation for the flow of an inviscid fluid along a streamline. For a fluid of constant density ρ Euler’s equation can be integrated to yield Bernoulli’s equation: p + ρgz′ + ρV2 = pT which shows that the sum of the static pressure p, the hydrostatic pressure ρgz and the dynamic pressure ρV2/2 is equal to the total pressure pT. The combination p + ρV2/2 is an important quantity known as the stagnation pressure. Each of the terms on the left-hand side of Bernoulli’s equation can be regarded as representing different forms of mechanical energy and also equivalent to the hydrostatic pressure due to a vertical column of liquid. The dynamic pressure can be thought of as measuring the intensity or strength of a flow and is frequently combined with other fluid and flow properties to produce non-dimensional (or dimensionless) numbers which characterise various aspects of fluid motion.
4
Bhagavatula, Sharath K., Daniel A. T. Souza, Milana Flusberg, Stuart G. Silverman, and Paul B. Shyn. CT- and PET/CT-Guided Interventional Radiology Procedures. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190495756.003.0011.
Full textAbstract:
Computed tomography (CT) has become a valuable guidance modality for a large number of diagnostic and therapeutic percutaneous interventions. Diagnostic and therapeutic interventions guided by CT are among the most common interventional radiology procedures performed in clinical practice. Common diagnostic CT-guided interventions include tissue biopsies, fluid aspirations, and catheter drainages. Needle biopsies can be used to obtain tissue for cytologic or histologic assessment from almost any anatomical region of the body. Positron emission tomography (PET)/CT–guided diagnostic and therapeutic interventions have emerged recently and are increasing in frequency and number of indications. This chapter discusses common interventional procedures that are performed in both the interventional CT and PET/CT suites and outlines patient issues, procedural techniques, radiation/safety, and other clinical considerations that pertain to both interventionalists and anesthesiologists.
5
Muñoz-Rujas, Natalia, Gabriel Rubio Pérez, Mohamed Lifi, Fatima E. M’Hamdi Alaou, and Eduardo A. Montero. Ingeniería termodinámica. Ecuación de estado térmica de fluidos mediante experimentación / Engineering thermodynamics. Thermal equation of fluids by experimentation / Ingénierie thermodynamique. Équation d'etat thermique par l'expérimentation. Universidad de Burgos, 2021. http://dx.doi.org/10.36443/9788418465048.
Full textAbstract:
En muchas industrias se emplean fluidos en los procesos de producción. Estos fluidos, sean líquidos, gases o mezclas de ambos, se almacenan en depósitos y se transportan por conductos en las instalaciones industriales. El volumen que cada kilogramo de fluido ocupa en estas instalaciones puede variar si también lo hacen su presión y temperatura. Encontrar esta interdependencia entre presión, volumen y temperatura resulta crucial para dimensionar depósitos y conductos. Conocer la relación matemática que expresa la interdependencia física de estas tres propiedades es esencial en ingeniería. En este libro veremos de modo experimental la interdependencia que presentan las propiedades presión, volumen y temperatura en fluidos. Lo haremos a través un caso práctico. En este libro mostraremos: 1) la dependencia mutua de las variables de estado presión-volumen-temperatura (PVT) para el fluido contenido en un volumen variable al modificar la presión y la temperatura. 2 ) la distinción de las propiedades de un fluido en las diferentes zonas de operación. 3 ) la obtención de la curva de vaporización presión-temperatura (P-T) y el diagrama presión-volumen (P-V) de un fluido.
6
Falk, Bareket, and Raffy Dotan. Temperature regulation. Edited by Neil Armstrong and Willem van Mechelen. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780198757672.003.0014.
Full textAbstract:
Under all but the most extreme environmental heat conditions, children control their body temperature (at rest and during exercise) as well as adults. Children, however, use a different thermoregulatory strategy. Compared with adults, children rely more on dry heat dissipation and less on evaporative cooling (sweating). Their larger skin surface-area relative to mass does put children at increasing disadvantage, relative to adults, as ambient temperatures rise above skin temperature. Similarly, they become increasingly disadvantaged upon exposure to decreasing temperatures below the thermo-neutral zone. Like adults, children inadvertently dehydrate while exercising in hot conditions and are often hypohydrated, even before exercise, and their core temperature rises considerably more than adults in response to a given fluid (sweat) loss, which may put them at higher risk for heat-related injury. However, epidemiological data show rates of both heat- and cold-related injuries among children and adolescents as similar or lower than at any other age.
7
Chadwick, David, Alastair Compston, Michael Donaghy, et al. Investigations. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780198569381.003.0100.
Full textAbstract:
This chapter describes the many methods that can be used to investigate neurological disorders. The application and suitability for specific disorder types are outlined, as are contraindications for use. Methods of imaging the central nervous system include computed tomography (CT) imaging, several magnetic resonance (MR) scanning methods, Single photon emission computed tomography (SPECT) and Positron Emission Tomography (PET). Invasive (angiography) and non-invasive methods of imaging the cerebral circulation are also outlined.The standard method of recording electrical activity of the brain is the electroencephalogram (EEG), which is heavily used in epilepsy to investigate regions of epileptogenesis.Other investigations described include evoked potentials, nerve conduction and electromyography studies, the examination of cerebrospinal fluid and the diagnostic use of neurological autoantibodies. Finally, neurogenetics, neuropsychological assessment and the assessment of treatments by randomized trials are discussed.
8
Jacquet, Gabrielle. Pharyngitis, Tonsillitis, and Peritonsillar Abscess. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199976805.003.0010.
Full textAbstract:
Pharyngitis typically presents with sore throat, fever, and pharyngeal inflammation. More serious cases may progress to peritonsillar abscess (PTA). Infection or inflammation of the throat that primarily affects the palantine tonsils is considered tonsillitis, whereas infections involving the posterior pharynx are considered pharyngitis. Weber glands (a group of mucous salivary glands superior to the tonsil in the soft palate) have been implicated in the formation of PTA; one must consider their proximity to the trachea and to the carotid artery when pursuing fine needle aspiration. Treatment for all cases includes supportive care with antipyretics, analgesics, and fluids. Despite the much lower prevalence of group A beta-hemolytic Streptococcus infection (for which antibiotics is indicated), a staggering 49% to 57% of children and 64% of adults evaluated for pharyngitis receive an antibiotic prescription. Up to 90% of primary infections with HIV-1 are associated with acute retroviral syndrome, which can include pharyngitis 2 to 4 weeks after exposure.
9
Ganciu, Raluca Maria. SAC CU PENE. Editura Universitara, 2021. http://dx.doi.org/10.5682/9786062813529.
Full textAbstract:
De la cele ce nu sunt cu putinta de povestit pana la cele ce pot fi povestite doar in fata oglinzii, este un drum, un traseu de pasare migratoare, de pasare calatoare. Pentru Raluca Maria Ganciu, acesta este un drum al cocorilor. Exista o legenda japoneza, mai mult un fluid real decat o poveste, unde se spune ca pasarile migratoare, cand pleaca spre tarile calde, iau cu ele o scandurica de lemn, si o tin in cioc. Atunci cand sunt deasupra oceanelor, si sunt obosite de-atata zbor, dau drumul acestei scandurici de lemn in apa, se aseaza pe ea, odihnindu-se, si in acelasi timp, plutind mai departe. Raluca Maria Ganciu este o melancolica incurabila, si nu vad de ce ar fi altfel. Este starea ei nativa ca om si poet. Este prima ei sursa de identitate sau in termeni de literatura digitala, aceasta melancolie face parte din datele prin care poate fi identificata.
10
Prud'homme, Alex. Hydrofracking. Oxford University Press, 2013. http://dx.doi.org/10.1093/wentk/9780199311262.001.0001.
Full textAbstract:
Constantly in the news and the subject of much public debate, fracking, as it is known for short, is one of the most promising yet controversial methods of extracting natural gas and oil. Today, 90 percent of natural gas wells use fracking. Though highly effective, the process-which fractures rock with pressurized fluid-has been criticized for polluting land, air, and water, and endangering human health. A timely addition to Oxford's What Everyone Needs to Know series, Hydrofracking tackles this contentious topic, exploring both sides of the debate and providing a clear guide to the science underlying the technique. In concise question-and-answer format, Alex Prud'homme cuts through the maze of opinions and rhetoric to uncover key points, from the economic and political benefits of fracking to the health dangers and negative effects on the environment. Prud'homme offers clear answers to a range of fundamental questions, including: What is fracking fluid? How does it impact water supplies? Who regulates the industry? How much recoverable natural gas exists in the U.S.? What new innovations are on the horizon? Supporters as diverse as President Obama and the conservative billionaire T. Boone Pickens have promoted natural gas as a clean, "21st-century" fuel that will reduce global warming, create jobs, and provide tax revenues, but concerns remain, with environmental activists like Bill McKibben and others leading protests to put an end to fracking as a means of obtaining alternative energy. Prud'homme considers ways to improve methods in the short-term, while also exploring the possibility of transitioning to more sustainable resources-wind, solar, tidal, and perhaps nuclear power-for the long term. Written for general readers, Hydrofracking clearly explains both the complex science of fracking and the equally complex political and economic issues that surround it, giving readers all the information they need to understand what will no doubt remain a contentious issue for years to come.
Book chapters on the topic "PTT Fluid"
1
Swain, B. K., M. Das, and G. C. Dash. "Heat Transfer of MHD Channel Flow of Viscoelastic (PTT) Fluid." In Advances in Intelligent Systems and Computing. Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1402-6_4.
Full text
2
Brattekås, Bergit, Martin Fernø, and Heidi Espedal. "Fluid Flow visualization By PET-CT." In Album of Porous Media. Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-23800-0_83.
Full text
3
Ashena, Rahman. "Drilling Fluids and Pit Management." In The Practical Handbook of Well Control. CRC Press, 2025. https://doi.org/10.1201/9781003473770-3.
Full text
4
Kabaila, Rasa. "Nurses and Bodily Fluids." In Put some Concrete in your Breakfast: Tales from Contemporary Nursing. Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-24393-6_4.
Full text
5
Wu, Jianjun, Jian Li, Yuanzheng Zhao, and Yu Zhang. "Numerical Simulation of the PPT Plume Process Based on Hybrid Particle–Fluid Models." In Numerical Simulation of Pulsed Plasma Thruster. Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-97-7958-1_7.
Full textAbstract:
AbstractPulsed plasma thrusters (PPTs) have advantages in terms of their structural mass and size, operational performance, and power supply requirements, making them widely applicable to tasks such as attitude control, drag compensation, orbit raising, and constellation phase control of microsatellites. With the development of space exploration technology, modern microsatellites are required to have higher functional density, lower manufacturing cost, and longer operational lifespans. However, the PPT plume may cause severe adverse effects (such as sputter erosion, sediment contamination, chemical contamination, thermal loads, and electromagnetic interference) on satellites.
6
Biassoni, Lorenzo, Helen Nadel, and Zvi Bar-Sever. "Central Nervous System: The Brain and Cerebro-Spinal Fluid." In A Practical Guide for Pediatric Nuclear Medicine. Springer Berlin Heidelberg, 2023. http://dx.doi.org/10.1007/978-3-662-67631-8_2.
Full textAbstract:
AbstractNuclear medicine studies of the central nervous system provide unique information on cerebral perfusion and metabolism and the physiology of cerebro-spinal fluid (CSF) fluid. Diagnosis of brain death is based on clinical findings indicating a complete lack of function of the entire brain. Mandatory additional studies supporting the clinical suspicion are required by most countries, such as electroencephalography (EEG), brainstem evoked response audiometry (BERA), transcranial Doppler, and brain scintigraphy. Brain scans following the administration of perfusion agents are considered to represent the most objective assessment tool. FDG PET and possibly ictal-interictal cerebral perfusion SPECT studies are used to identify an epileptogenic focus in drug-resistant epilepsy. The main indication is in patients with likely unifocal seizures at semiology and EEG, and a negative brain MRI, or with MRI findings not corresponding to clinical signs and symptoms and to EEG findings. CSF shunt patency studies involve injection of a radiopharmaceutical into the reservoir of a ventriculo-peritoneal shunt in children with hydrocephalus. The study shows the transit of labelled CSF through the shunt and may detect shunt obstructions. Radionuclide molecular imaging studies on brain tumors are rare and mainly part of research projects and are not performed in routine clinical settings and therefore will not be dealt with in this section.
7
El-Banbi, Ahmed, Ahmed Alzahabi, and Ahmed El-Maraghi. "Reservoir-Fluid Classification." In PVT Property Correlations. Elsevier, 2018. http://dx.doi.org/10.1016/b978-0-12-812572-4.00002-3.
Full text
8
Casas, Juan. "Cryogenic fluid-level indicators." In Handbook of Applied Superconductivity, Volume 2. Taylor & Francis, 1998. http://dx.doi.org/10.1201/9781420050271.pte.
Full text
9
"Supercritical Fluid Extraction Technology." In Functional Food Ingredients and Nutraceuticals. CRC Press, 2006. http://dx.doi.org/10.1201/9781420004076.pt1.
Full text
10
"Fundamentals of Fluid Turbulence." In Series in Plasma Physics. Taylor & Francis, 2002. http://dx.doi.org/10.1201/9781420033694.pt2.
Full textConference papers on the topic "PTT Fluid"
1
Mraied, Hesham, Gray Mullins, Alberto A. Sagüés, and Ivan Lasa. "Mechanism of Corrosion Mitigation of Post-Tensioned Tendons by Impregnation." In CORROSION 2019. NACE International, 2019. https://doi.org/10.5006/c2019-13449.
Full textAbstract:
Abstract Grouting deficiencies of post-tensioned tendons (PTT) have been associated with accelerated corrosion of the strands. A corrosion mitigation method by which a fluid is introduced via the interstitial spaces between the wires of a tendon’s strand has been recently used with promising results. Mechanistic experiments and multiphysics modeling simulation were used to examine the relative importance of alternative corrosion mitigating mechanisms, including oxygen transport limitation, cathodic and anodic inhibition, and ohmic resistance increase. Experimental results yielded a favorable prognosis that impregnating PTT would be successful in mitigating ongoing corrosion of steel strands. Both experiment and modeling pointed to a decrease of surface kinetics - lowered exchange current density for both anodic and cathodic reactions - as the likely main mitigation mechanism. Increasing grout resistivity and concentration polarization of the cathodic reaction did not seem to be dominant factors in mitigating corrosion.
2
Palacios T., Carlos A., and Thais Hernández. "Field Experiences for SRB-MIC Control in Water Injection Plants Having Continuous Pit Recovered Fluids." In CORROSION 2003. NACE International, 2003. https://doi.org/10.5006/c2003-03547.
Full textAbstract:
Abstract This article describes the experiences for SRB-MIC Control in a water plant with fluid recovered from a disposal pit through the use of different biocide treatment strategies, and a comparison of the cost-effectiveness of the different products used to control MIC, such as glutaraldehydes, quaternary ammonium, acrolein and THPS. Results are supported by field experience. The use of a good bio-treatment program shows how the SRB corrosion control can be achieved even in difficult systems such as this one in which there is continuous fluid recovered from a pit.
3
Meng, Q., and V. Jovancicevic. "Electrochemical Evaluation of CO2 Corrosion Inhibitors in High Turbulence Multiphase Fluid Flow." In CORROSION 2008. NACE International, 2008. https://doi.org/10.5006/c2008-08625.
Full textAbstract:
Abstract Inhibition effectiveness of two CO2 corrosion inhibitors was evaluated at 93 °C (200 °F) and 0.55 MPa (80 psi) CO2 partial pressure under high turbulence multiphase fluid flow condition using the jet impingement technique. Electrochemical methods including linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) were employed to determine the general corrosion rate and obtain mechanistic information about flow induced pitting corrosion and film capacitance in the corrosion tests. The occurrence of pitting resulted in two time constants found in the EIS data compared to only one time constant found for the pit-free surface. The results demonstrate that high shear stress corrosion inhibitors not only offer general corrosion inhibition but also prevent carbon steels from pitting under aggressive multiphase flow conditions.
4
Kojima, Y., and S. Tsujikawa. "Corrosion of Steels in Absorption Heating and Refrigeration Fluid." In CORROSION 1995. NACE International, 1995. https://doi.org/10.5006/c1995-95599.
Full textAbstract:
Abstract Pitting corrosion of carbon steel and crevice corrosion of Type 304 stainless steel in a newly developed working fluid for absorption heating and refrigeration systems were studied. The fluid was a concentrated aqueous solution of mixed lithium salts consisting of LiBr, LiCl, LiI and LiNO3. This solution contained NO3− and a small amount of I2, the oxidized species of I−, both of which were able to act as the oxidizing agent for steels. The spontaneous electrode potential of Platinum, ESP(Pt), in the 60% solution kept at 150 C was + 120 mV vs SCE, and when the I2 was reduced by the addition of NaHSO3 the ESP(Pt) was approximately -120 mV. Thus, the fluid forms an oxidizing halide environment that tends to induce localized corrosion on steels. The critical pitting potential, VC,PIT, of the carbon steel and the critical crevice corrosion potential, ER,CREV, of Type 304 stainless steel were measured to be -340 ~ -310 mV and -180 ~ -160 mV respectively. It became apparent that in solutions containing I2, the ESP's of the steels were nobler than the critical potentials, and that pitting corrosion of carbon steel and crevice corrosion of Type 304 stainless steel occurred violently. However, it became also apparent that both localized corrosions ceased when I2 was reduced by adding NaHSO3. Resistance of the steels to localized corrosion increased with higher concentration of NaHSO3 and less concentration of NO3−.
5
Choi, H. J. "Sweet Corrosion Mechanism of Dynamic Oil-Brine Two-Phase Flows." In CORROSION 1990. NACE International, 1990. https://doi.org/10.5006/c1990-90031.
Full textAbstract:
Abstract A study in the mechanism of sweet corrosion below 75°C was conducted in order to gain a better understanding of the initiation stage of sweet corrosion on low alloy tubular materials, L-80 and X-52, in flowing crude oil, and brine two-phase fluids. Wettability of a steel surface by an aqueous phase is critical to initiation of mesa-type corrosion. This localized corrosion appears to be governed by local turbulence of a moving fluid in conjunction with existing surface heterogeneities (physical discontinuities) of the steels rather than metallurgical heterogeneities such as second phase inclusions or anisotropy. Local turbulence and wetting time of the aqueous phase at an active corrosion site on the steel surface controls pit propagation.
6
Ariyaratna, Thenuka, Nihal Obeyesekere, and Jonathan Wylde. "Development of Novel Inhibitor Chemistries to Protect Metal Surfaces from Saturated Completion Fluid." In CORROSION 2016. NACE International, 2016. https://doi.org/10.5006/c2016-07802.
Full textAbstract:
Abstract The use of completion fluids or heavy brines in drilling environments can prove to be corrosive on completion equipment and production tubing. A range of tests has been undertaken to identify suitable corrosion inhibitor products for application in various completion fluids under these corrosive conditions. The initial inhibitor selections were focused on calcium nitrate heavy brines, followed by inhibitor selections for other heavy brines such as calcium chloride and mixtures of calcium nitrate and calcium chloride. Chemicals were initially screened for superior solubility in these heavy brines and tested using rotating cylinder electrode linear polarization resistivity. Inhibitors that passed initial screening were further tested at high temperature/high pressure in static autoclaves. Surface analysis of the coupons was essential to determine the presence of localized corrosion. Static autoclave tests were conducted to confirm performing chemicals. Poor performing products demonstrated metal surface morphology with high pit density and deep pits, while the new chemistries with a novel approach yielded performance of either no pitting at all, or very limited pits and low general corrosion. This paper details the testing criteria and gives insight into the mechanism of corrosion attack.
7
Achour, Mohsen H., Juri Kelts, A. H. Johannes, and Guahai Liu. "Mechanistic Modeling of Pit Propagation in CO2 Environment under High Turbulence Effects." In CORROSION 1993. NACE International, 1993. https://doi.org/10.5006/c1993-93087.
Full textAbstract:
Abstract Pitting corrosion of carbon steel in CO2 environments occurs mostly in high turbulence regimes. Several experimental investigations have been conducted to achieve a better understanding of the complex phenomenon of flow induced localized attack. In this work, a theoretical model is developed to predict the extent of pit propagation under the effects of high turbulence regimes. Given the flow conditions in the main stream and an initial shape of a pit along the pipe wall, the model predicts the hydrodynamics inside the cavity and its extent of propagation or repassivation. It takes into account the equilibrium conditions, the surface kinetics, the electrochemical process at the surface, and the fluid flow inside the pit. The hydrodynamics of the model have been based on flow separation and reattachment for shallow and medium size pits, whereas the skimming flow analysis has been applied to deep pits. The criterion of pit passivation or propagation is evaluated, depending on the iron carbonate supersaturation kinetics and the concentration of Fe++ at the surface of the pit walls. The former is influenced by both the iron dissociation and the mass transfer rates. The model, as developed, has been used to study the effect of velocity on the pit wall shear stress, the surface concentration of ferrous ion, the mass transfer coefficient in and out of the cavity, and, hence, the overall propagation rate of an existing pit.
8
Musayev, Kudrat, Silvio Baldino, and Evren M. Ozbayoglu. "Accelerating Pressure Transmission Test Analysis to Quantify Shale-Fluid Interactions." In SPE Oklahoma City Oil and Gas Symposium. SPE, 2025. https://doi.org/10.2118/224356-ms.
Full textAbstract:
Abstract Drilling shale formations using water-based fluid is challenging due to unfavorable interactions. Designing optimal fluid formulation requires laboratory tests such as pressure transmission test (PTT) to evaluate shale-fluid interactions. However, the requirement of complex lab equipment and a long testing time can make it difficult to use this technique. In this study, integration of the analytical solution to PTT was explored through adaptive procedure to reduce experimental time. By applying the proposed adaptive procedure, we achieved up to a 90% reduction in experimental time consumption. This procedure offers a promising solution for conserving time and resources traditionally consumed by PTT. Keywords Pressure transmission test, Shale, Shale-fluid interactions, Analytical solution, Adaptive procedure
9
Evans, J. D., Theodore E. Simos, George Psihoyios, and Ch Tsitouras. "Re-Entrant Corner Singularity of the PTT Fluid." In ICNAAM 2010: International Conference of Numerical Analysis and Applied Mathematics 2010. AIP, 2010. http://dx.doi.org/10.1063/1.3498161.
Full text
10
Khodadadi Yazdi, M., A. Ramazani S. A., H. Hosseini Amoli, A. Behrang, and A. Kamyabi. "Flow of a PTT Fluid Through Planar Contractions: Vortex Inhibition Using Rounded Corners." In ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-40267.
Full textAbstract:
Contraction flow is one of important geometries in fluid flow both in Newtonian and non-Newtonian fluids. In this study, flow of a viscoelastic fluid through a planar 4:1 contraction with rounded corners was investigated. Six different rounding ratios (RR = 0, 0.125, 0.25, 0.375, 0.438, 0.475, 0.488) was examined using the linear PTT constitutive equation at creeping flow and isothermal condition. Then the resulting PDE set including continuity, momentum, and PTT constitutive equations were implemented to the OpenFOAM software. The results clearly show vortex deterioration with increasing rounding diameter, so that when rounding corner exceeds a critical value, the vortex disappears completely. This phenomenon was also observed at different upstream widths. Furthermore, by increasing rounding diameter, the diminishing vortex approaches to the re-entrant corner.
Reports on the topic "PTT Fluid"
1
Hadorn, JC, M. Lämmle, K. Kramer, et al. Design guidelines for PVT collectors. IEA SHC Task 60, 2020. http://dx.doi.org/10.18777/ieashc-task60-2020-0003.
Full textAbstract:
Report B2: Here is a one page fact sheet providing many design guidelines for PVT collectors, for covers, encapsulant, rear covers, absorbers, heat transfer medium, insulation, casing, air vents, fluid outlets, sealing, and junction boxes.
2
Evens, Tim, Pol Vanwersch, Sylvie Castagne, and Albert Van Bael. Material selection for injection molding hollow microneedles. Universidad de los Andes, 2024. https://doi.org/10.51573/andes.pps39.gs.im.4.
Full textAbstract:
Hollow microneedles are designed to perform intradermal medical substance delivery or fluid extraction, with polymers standing out as cost-effective materials for mass production via injection molding. However, existing research lacks a comparative analysis of different polymers in terms of processability and performance in skin penetration tests. This study addresses this gap by evaluating hollow microneedles fabricated from five biocompatible thermoplastic materials: polycarbonate (PC), polybutylene terephthalate (PBT), polylactic acid (PLA), polyamide 12 (PA12), and glass-fiber reinforced polyarylamide (PARA). Significant dif ferences in replication fidelity were found among the thermoplastics, with a higher calculated solidification time resulting in better replication fidelity due to extended deformability during the packing phase. PBT microneedles deformed during demolding and were excluded from penetration tests. Penetration tests on piglet ears showed no penetration for PA12 and PLA microneedles due to deformation of the needles. PARA demonstrated consistent penetration results, while PC exhibited an inconsistent penetration behavior, with some needles success fully penetrating while others deformed. High mechanical properties were found to be critical for achieving consistent and successful penetration.
3
Limtrakul, Sunun, and Wiwut Tanthapanichakoon. Modeling and simulation of flows in two-phase fluidized systems. The Thailand Research Fund, 1999. https://doi.org/10.58837/chula.res.1999.57.
Full textAbstract:
This present work aims to investigate the solids motion and fluid flow in a two phase fluidized bed via a discrete particle modeling and simulation. The motion of individual particle is based on the fluid force acting on the particle and the contact force between particles. The contact force is models by using the same analogy of spring, dash-pot and friction slider. In addition, the mixing and segregation in beds containing two types of particles with different densities and different size are also studies. Moreover, the effects of superficial gas velocity and bad geometry on the solids movements are also investigated. A solids circulation cell is found when the bed reaches at steady state. The solids ascend at the center with high velocity and descend with low velocity near the wall. The simulation solids flow pattern agrees well with the experimental result obtain by Moslemian (1987). The solids distributions in the bed containing the particles with the density ratios of 1.4 and 1.25 show good mixing. On the other hand the bed with the particle density ratio of 2.5 shows segregating behavior. Similarly, the beds containing the particles with the size ratios of 1.33 and 2.0 show mixing behavior and segregating behavior, respectively. These results obtained from simulation were found to follow the mixing/degregation criteria obtained experimentally by Tanaka et al. (1996). The solids mixing and segregation are not significantly dependent on the superficial gas velocity. The findings of the simulation i.e., solids movement and distribution will be information for understanding the hydrodynamics, mass and heat transfer leading to successfully design and operation of the system. The knowledge of this modeling and simulation is applicable to study the phenomena in the system concerned with granular materials such as multiphase flow reactor and dryer.
4
Torrijos, Ivan Dario Pinerez, Tina Puntervold, Skule Strand, Panagiotis Aslanidis, Ingebret Fjelde, and Aleksandr Mamonov. Core restoration: A guide for improved wettability assessments. University of Stavanger, 2021. http://dx.doi.org/10.31265/usps.198.
Full textAbstract:
The initial wetting of a reservoir sets a limit for the EOR potential during water-based recovery operations and “Smart Water” injection. For this reason, an improved understanding of the factors influencing the wetting can help to control and better forecast oil production during water-based floods. To preserve and reproduce the original reservoir wettability is a challenging task and wrong cleaning and core restoration procedures can lead to incorrect wettability estimations and thus induce serious errors when evaluating the initial wettability of a reservoir system or its EOR potential by water-based methods. Thereby, there is a need to improve the chemical knowledge on interactions among the rock, brine and fluids present in reservoir systems. This will help to understanding the influence of the parameters affecting wettability during cleaning and core restoration processes. Understanding which are the main parameters influencing oil recovery processes is of great relevance. The objective of this document is to provide suggestions for added-value experiments, complementing and challenging the standard RCA and SCAL procedures, prior to performing experimental research in which wettability and wettability alteration processes are important. Lessons learned will be highlighted and new ideas to optimize core restoration protocols to preserve and closely reproduce wettability are put forward. These recommended practices target core restoration procedures after the core material has been received in the laboratory. The target audience for this document is engineers and scientists with an interest in core preparation for wettability studies.
5
Harris, L. B., P. Adiban, and E. Gloaguen. The role of enigmatic deep crustal and upper mantle structures on Au and magmatic Ni-Cu-PGE-Cr mineralization in the Superior Province. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328984.
Full textAbstract:
Aeromagnetic and ground gravity data for the Canadian Superior Province, filtered to extract long wavelength components and converted to pseudo-gravity, highlight deep, N-S trending regional-scale, rectilinear faults and margins to discrete, competent mafic or felsic granulite blocks (i.e. at high angles to most regional mapped structures and sub-province boundaries) with little to no surface expression that are spatially associated with lode ('orogenic') Au and Ni-Cu-PGE-Cr occurrences. Statistical and machine learning analysis of the Red Lake-Stormy Lake region in the W Superior Province confirms visual inspection for a greater correlation between Au deposits and these deep N-S structures than with mapped surface to upper crustal, generally E-W trending, faults and shear zones. Porphyry Au, Ni, Mo and U-Th showings are also located above these deep transverse faults. Several well defined concentric circular to elliptical structures identified in the Oxford Stull and Island Lake domains along the S boundary of the N Superior proto-craton, intersected by N- to NNW striking extensional fractures and/or faults that transect the W Superior Province, again with little to no direct surface or upper crustal expression, are spatially associated with magmatic Ni-Cu-PGE-Cr and related mineralization and Au occurrences. The McFaulds Lake greenstone belt, aka. 'Ring of Fire', constitutes only a small, crescent-shaped belt within one of these concentric features above which 2736-2733 Ma mafic-ultramafic intrusions bodies were intruded. The Big Trout Lake igneous complex that hosts Cr-Pt-Pd-Rh mineralization west of the Ring of Fire lies within a smaller concentrically ringed feature at depth and, near the Ontario-Manitoba border, the Lingman Lake Au deposit, numerous Au occurrences and minor Ni showings, are similarly located on concentric structures. Preliminary magnetotelluric (MT) interpretations suggest that these concentric structures appear to also have an expression in the subcontinental lithospheric mantle (SCLM) and that lithospheric mantle resistivity features trend N-S as well as E-W. With diameters between ca. 90 km to 185 km, elliptical structures are similar in size and internal geometry to coronae on Venus which geomorphological, radar, and gravity interpretations suggest formed above mantle upwellings. Emplacement of mafic-ultramafic bodies hosting Ni-Cr-PGE mineralization along these ringlike structures at their intersection with coeval deep transverse, ca. N-S faults (viz. phi structures), along with their location along the margin to the N Superior proto-craton, are consistent with secondary mantle upwellings portrayed in numerical models of a mantle plume beneath a craton with a deep lithospheric keel within a regional N-S compressional regime. Early, regional ca. N-S faults in the W Superior were reactivated as dilatational antithetic (secondary Riedel/R') sinistral shears during dextral transpression and as extensional fractures and/or normal faults during N-S shortening. The Kapuskasing structural zone or uplift likely represents Proterozoic reactivation of a similar deep transverse structure. Preservation of discrete faults in the deep crust beneath zones of distributed Neoarchean dextral transcurrent to transpressional shear zones in the present-day upper crust suggests a 'millefeuille' lithospheric strength profile, with competent SCLM, mid- to deep, and upper crustal layers. Mechanically strong deep crustal felsic and mafic granulite layers are attributed to dehydration and melt extraction. Intra-crustal decoupling along a ductile décollement in the W Superior led to the preservation of early-formed deep structures that acted as conduits for magma transport into the overlying crust and focussed hydrothermal fluid flow during regional deformation. Increase in the thickness of semi-brittle layers in the lower crust during regional metamorphism would result in an increase in fracturing and faulting in the lower crust, facilitating hydrothermal and carbonic fluid flow in pathways linking SCLM to the upper crust, a factor explaining the late timing for most orogenic Au. Results provide an important new dataset for regional prospectively mapping, especially with machine learning, and exploration targeting for Au and Ni-Cr-Cu-PGE mineralization. Results also furnish evidence for parautochthonous development of the S Superior Province during plume-related rifting and cannot be explained by conventional subduction and arc-accretion models.