Academic literature on the topic 'Dispersion de charges'
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Journal articles on the topic "Dispersion de charges"
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Yaakob, Muhamad Kamil, Mohamad Faris M. Taib, and Muhd Zu Azhan Yahya. "First Principle Study of Dynamical Properties of a New Perovskite Material Based on GeTiO3." Advanced Materials Research 501 (April 2012): 352–56. http://dx.doi.org/10.4028/www.scientific.net/amr.501.352.
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The dynamical properties of a new perovskite GeTiO3 materials have been investigated by using first principle calculation based on Density Functional Theory (DFT) within the gradient generalized approximation (GGA). All calculations were performed using the Cambridge Serial Total Energy Package (CASTEP) computer code. The calculations include the structural parameter, Born effective charges, and phonon dispersion. The calculated Born effective charges and phonon dispersion have been analyzed and the possibility of ferroelectric feature in GeTiO3 compounds has been discussed. From the analysis, the calculated Born effective charge ZGe and ZTi showed large anomaly compared to the nominal charge which contributed to the large atomic displacement. The calculated phonon dispersion showed the most unstable mode was at G point and the unstable modes were dominated by Ge branch. The dynamical properties and ferroelectric properties in GeTiO3 are discussed and compared with the ferroelectric feature in PbTiO3.
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Koné, M., P. Courtin, and J. Lemerle. "Colloidal molybdoantimonic acids as ion exchangers." Canadian Journal of Chemistry 69, no. 2 (February 1, 1991): 293–99. http://dx.doi.org/10.1139/v91-045.
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Colloidal particles with a c.c.p. structure were obtained from mixtures of antimonic and molybdic acids through a polymerization process. These particles were octahedral and their sizes fits the log-normal distributions. The mean size decreases and the polydispersity increases with increasing Mo content in the particles. The stability of the aqueous dispersions was due to the surface charge density of the particles which was enhanced when increasing the Mo content. Ion exchange reactions can occur with the dispersions. Two different routes lead to Ag+ fixation: substitution of core H+ without flocculation of the dispersion or cancellation of external charges with flocculation. Key words: inorganic exchangers, colloids, antimonic acid, molybdic acid.
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Mukherjee, Siddhartha, Jayabrata Dhar, Sunando DasGupta, and Suman Chakraborty. "Patterned surface charges coupled with thermal gradients may create giant augmentations of solute dispersion in electro-osmosis of viscoelastic fluids." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 475, no. 2221 (January 2019): 20180522. http://dx.doi.org/10.1098/rspa.2018.0522.
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Augmenting the dispersion of a solute species and fluidic mixing remains a challenging proposition in electrically actuated microfluidic devices, primarily due to an inherent plug-like nature of the velocity profile under uniform surface charge conditions. While a judicious patterning of surface charges may obviate some of the concerning challenges, the consequent improvement in solute dispersion may turn out to be marginal. Here, we show that by exploiting a unique coupling of patterned surface charges with intrinsically induced thermal gradients, it may be possible to realize giant augmentations in solute dispersion in electro-osmotic flows. This is effectively mediated by the phenomena of Joule heating and surface heat dissipation, so as to induce local variations in electrical properties. Combined with the rheological premises of a viscoelastic fluid that are typically reminiscent of common biofluids handled in lab-on-a-chip-based micro-devices, our results demonstrate that the consequent electro-hydrodynamic forcing may open up favourable windows for augmented hydrodynamic dispersion, which has not yet been unveiled.
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Bauer, Rachel, Paul Pitzel, Emily Johnson, and Catherine Johnson. "Water-Cased Kicker Charges for Use in Explosive Demolition." Buildings 13, no. 2 (January 29, 2023): 378. http://dx.doi.org/10.3390/buildings13020378.
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Demolition projects involving explosives often incorporate cutting charges to sever columns in conjunction with kicker charges that “move” the columns out of alignment. Traditional kicker charges use dynamite secured to the column above a linear-shaped cutting charge. This study investigates the use of water-cased kicker charges for use in explosive demolition. The goal is to reduce the fragmentation of steel members and the quantity of explosive needed due to the increased density, incompressibility, and impedance mismatch water provides. Simulations and experimental tests were utilized to determine what type of charges provide the optimal column movement and water placement. Water charges and traditional charges were placed on hanging steel columns that swung freely from a top pivot and analyzed for the fragmentation and velocity of the column. Tests were recorded with high-speed video to calculate velocity and impulse. Simulations showed the same results as experimental tests, with water-cased charges moving the column faster and with more impulse than traditional charges. Experimental testing showed that water-cased charges moved the column 53% faster than traditional in contact charges while simulations showed that water-cased charges moved the column 43% faster than traditional in contact charges. Simulations showed the water tamped behind the charge increased beam velocity 32% while water in front of the charge reduced pressure 38% through dispersion.
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Chen, Lucy Huajing, Jayanthi Krishnan, and Heibatollah Sami. "Goodwill Impairment Charges and Analyst Forecast Properties." Accounting Horizons 29, no. 1 (October 1, 2014): 141–69. http://dx.doi.org/10.2308/acch-50941.
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SYNOPSIS We examine the association between goodwill impairment charges and analysts' forecast accuracy and dispersion. We compare a test sample of firm-quarters with reported goodwill impairment charges during 2003–2007, and two control samples (matched on propensity scores and performance) of firm-quarters that do not report impairment charges. We find that analysts' forecasts are less accurate and more dispersed for the impairment sample than for the control samples. The magnitude of impairment charges is also negatively associated with forecast accuracy and positively associated with forecast dispersion. However, two forms of monitoring, auditor industry specialization and institutional ownership, reduce the adverse effect of goodwill impairments on analyst forecast dispersion. JEL Classifications: G14; M41; M44
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Verheest, F. "On the nonexistence of large amplitude stationary solitary waves in symmetric unmagnetized pair plasmas." Nonlinear Processes in Geophysics 12, no. 5 (June 9, 2005): 569–74. http://dx.doi.org/10.5194/npg-12-569-2005.
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Abstract. Waves in pair plasmas have a fundamentally different dispersion due to the equal charge-to-mass ratios between negative and positive charges. In view of possible applications e.g. to electron-positron and fullerene pair plasmas, it is shown that there are no stationary large amplitude nonlinear structures in symmetric unmagnetized pair plasmas.
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Chun, Byoungjin, and Myung-Suk Chun. "Electrostatic Potential Analysis in Polyelectrolyte Brush-Grafted Microchannels Filled with Polyelectrolyte Dispersion." Micromachines 12, no. 12 (November 29, 2021): 1475. http://dx.doi.org/10.3390/mi12121475.
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In this study, the model framework that includes almost all relevant parameters of interest has been developed to quantify the electrostatic potential and charge density occurring in microchannels grafted with polyelectrolyte brushes and simultaneously filled with polyelectrolyte dispersion. The brush layer is described by the Alexander-de Gennes model incorporated with the monomer distribution function accompanying the quadratic decay. Each ion concentration due to mobile charges in the bulk and fixed charges in the brush layer can be determined by multi-species ion balance. We solved 2-dimensional Poisson–Nernst–Planck equations adopted for simulating electric field with ion transport in the soft channel, by considering anionic polyelectrolyte of polyacrylic acid (PAA). Remarkable results were obtained regarding the brush height, ionization, electrostatic potential, and charge density profiles with conditions of brush, dispersion, and solution pH. The Donnan potential in the brush channel shows several times higher than the surface potential in the bare channel, whereas it becomes lower with increasing PAA concentration. Our framework is fruitful to provide comparative information regarding electrostatic interaction properties, serving as an important bridge between modeling and experiments, and is possible to couple with governing equations for flow field.
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ALÌ, GIUSEPPE, GIOVANNI MASCALI, VITTORIO ROMANO, and ROSA CLAUDIA TORCASIO. "A hydrodynamical model for covalent semiconductors with a generalized energy dispersion relation." European Journal of Applied Mathematics 25, no. 2 (January 31, 2014): 255–76. http://dx.doi.org/10.1017/s0956792514000011.
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We present the first macroscopical model for charge transport in compound semiconductors to make use of analytic ellipsoidal approximations for the energy dispersion relationships in the neighbours of the lowest minima of the conduction bands. The model considers the main scattering mechanisms charges undergo in polar semiconductors, that is the acoustic, polar optical, intervalley non-polar optical phonon interactions and the ionized impurity scattering. Simulations are shown for the cases of bulk 4H and 6H-SiC.
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AGOSTINI, ALESSANDRA. "COVARIANT FORMULATION OF NOETHER'S THEOREM FOR κ-MINKOWSKI TRANSLATIONS." International Journal of Modern Physics A 24, no. 07 (March 20, 2009): 1333–58. http://dx.doi.org/10.1142/s0217751x09042943.
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The problem of finding a formulation of Noether's theorem in noncommutative geometry is very important in order to obtain conserved currents and charges for particles in noncommutative space–times. In this paper, we formulate Noether's theorem for translations of κ-Minkowski noncommutative space–time on the basis of the five-dimensional κ-Poincaré covariant differential calculus. We focus our analysis on the simple case of free scalar theory. We obtain five conserved Noether currents, which give rise to five energy–momentum charges. By applying our result to plane waves it follows that the energy–momentum charges satisfy a special-relativity dispersion relation with a generalized mass given by the fifth charge. In this paper, we provide also a rigorous derivation of the equation of motion from Hamilton's principle in noncommutative space–time, which is necessary for the Noether analysis.
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BURKIN, Viktor V., Aleksey S. D’YACHKOVSKIY, Aleksandr N. ISHCHENKO, Vladimir Z. KASIMOV, Konstantin S. ROGAEV, and Nina M. SAMOROKOVA. "STUDY OF THE PASTE-LIKE PROPELLANT COMBUSTION AT VARIOUS LOADING SCHEMES." Vestnik Tomskogo gosudarstvennogo universiteta. Matematika i mekhanika, no. 67 (2020): 89–101. http://dx.doi.org/10.17223/19988621/67/9.
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The experimental and theoretical studies of the paste-like propellant combustion in a model ballistic installation are implemented. The research is carried out using three masses of projectile assemblies and three types of the propellant charge. The paper presents two versions of the law of dispersion for paste-like propellants which allow accounting for the pressure on the front and acceleration of the projectile assembly with a traveling charge. The coefficients in the laws of dispersion are obtained. Using the mathematical model presented in this work, the gas-dynamic pictures of the shots when the propellants are applied as traveling charges are obtained for each dispersion law. Based on the results, a detailed study of the processes occurring with the traveling charge consisting of a model paste-like propellant is implemented for various shot arrangements. The discrepancy between theoretical results and the results obtained in the set of experiments is no more than 2% for the maximum pressure and no more than 1% for the muzzle velocity. The dispersion law accounting for the projectile assembly acceleration and traveling charge makes it possible to describe accurately the processes in the space behind the projectile for projectile assemblies of various masses and different types of granulated powder charge in terms of the model ballistic installation in the considered pressure range.
Dissertations / Theses on the topic "Dispersion de charges"
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Boudimbou, Innocent. "Mécanismes élémentaires de dispersion de charges de silice dans une matrice élastomère." Phd thesis, École Nationale Supérieure des Mines de Paris, 2011. http://pastel.archives-ouvertes.fr/pastel-00617953.
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Ce travail se rapporte à l'étude par rhéo-optique des mécanismes de dispersion et contraintes critiques de dispersion de charges agglomérées dans une matrice SBR en cisaillement simple. L'objectif du travail était de déterminer des leviers pour améliorer l'étape de dispersion d'une charge renforçante pour des applications pneumatiques. Cette étude a montré que la dispersibilité d'une charge de type noir de carbone ou silice est caractérisée par un niveau de contraintes à atteindre et un mécanisme de dispersion. L'étude de grades de silice de précipitation sous forme microperle et de noir de carbone a permis de montrer que les critères de dispersion des deux charges sont régis par l'organisation interne des granules. La dispersion du noir de carbone est influencée par l'organisation fractale de ses agrégats. Les microperles de silice présentent une organisation interne de type cœur-peau. Le critère de dispersion de la microperle dépend de la cohésion de la peau. Le mécanisme de dispersion observé pour la microperle est lié au chemin de propagation des contraintes au sein de l'agglomérat et donc à la cohésion du cœur de la microperle. Le traitement physico-chimiques des silices avant leur mise en forme permet de modifier la cohésion des microperles et donc le mécanisme et le niveau de contrainte de dispersion.
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Boudimbou, Innocent Judicaël. "Mécanismes élémentaires de dispersion de charges de silice dans une matrice élastomère." Paris, ENMP, 2011. http://pastel.archives-ouvertes.fr/docs/00/61/79/53/PDF/20401_BOUDIMBOU_2011_archivage.pdf.
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Ce travail se rapporte à l'étude par rhéo-optique des mécanismes de dispersion et contraintes critiques de dispersion de charges agglomérées dans une matrice SBR en cisaillement simple. L'objectif du travail était de déterminer des leviers pour améliorer l'étape de dispersion d'une charge renforçante pour des applications pneumatiques. Cette étude a montré que la dispersibilité d'une charge de type noir de carbone ou silice est caractérisée par un niveau de contraintes à atteindre et un mécanisme de dispersion. L'étude de grades de silice de précipitation sous forme microperle et de noir de carbone a permis de montrer que les critères de dispersion des deux charges sont régis par l'organisation interne des granules. La dispersion du noir de carbone est influencée par l'organisation fractale de ses agrégats. Les microperles de silice présentent une organisation interne de type cœur-peau. Le critère de dispersion de la microperle dépend de la cohésion de la peau. Le mécanisme de dispersion observé pour la microperle est lié au chemin de propagation des contraintes au sein de l'agglomérat et donc à la cohésion du cœur de la microperle. Le traitement physico-chimiques des silices avant leur mise en forme permet de modifier la cohésion des microperles et donc le mécanisme et le niveau de contrainte de dispersionThis work reports the rheo-optical study of dispersion mechanisms of reinforcing fillers in an elastomer matrix under shear. The purpose of this work was to determine key parameters for dispersion in order to improve the filler dispersion step in a rubber for pneumatic application. This study showed that the dispersibility of a filler such as carbon black or silica is characterized by a critical stress to overcome and a dispersion mechanism. The dispersion study of precipitated silica grades in the shape of micropearls and of carbon black showed that the dispersion criteria for the two filler depend on the internal organization of the granules. Carbon black dispersion is dominated by the fractal organization of its aggregates. Silica micropearls present a skin-core-internal organization. The dispersion criterion for silica is linked to the skin cohesion strength. The dispersion mechanism is related to the stress propagation pathway within the micropearl and thus to the cohesion of the core. The chemical-physical treatment of silica surface during their processing enables to modify the cohesion of silica micropearls and consequently the dispersion mechanism and stress level for dispersion
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Descarpentries, Jérémie. "Compréhension et rôle de la dispersion de charges inorganiques dans une matrice thermoplastique." Caen, 2010. http://www.theses.fr/2010CAEN2020.
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L’optimisation des performances des polymères chargés de nanoparticules nécessite de comprendre les relations entre procédé, matrice et particules. Des profilés de polypropylène renforcés par six types de carbonates de calcium précipités sont extrudés, en faisant varier les conditions de mise en œuvre : taux de charge, température, vitesse de vis, surfactant. La morphologie des agglomérats de particules est déterminée par l’analyse d’images obtenues en microscopie électronique à balayage. L’originalité de la méthode consiste en une prise d’images à différents grossissements de la section des profilés pour obtenir la répartition globale en taille des inclusions. La distribution en taille suit une loi Log-Normal et trois paramètres sont utilisés pour la caractériser quantitativement : le diamètre médian, le coefficient d’asymétrie et la distance interparticulaire. L’évolution des propriétés des différents matériaux tant au niveau du comportement rhéologique, thermodynamique que mécanique est étudiée en fonction de la morphologie et de la distribution des particules. Il ressort que le taux de charge utilisé classiquement n’est pas suffisant pour décrire le comportement des polymères chargés. De plus, à l’interface polymère/charge, la formation d’une couche perturbée de polymère dite « interphase » apparaît ; cette interphase dépend de la morphologie des agglomérats et des interactions entre particules et matrice. Le renforcement provient donc de la qualité de la dispersion des particules et de la synergie entre les inclusions et la matrice.
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De, Rancourt Yoann. "Dispersion de charges d'oxydes de terres rares, Er2O3 et Pr6O11, dans une matrice polymère." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20202.
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Ce travail de thèse porte sur l'incorporation de charges minérales d'oxyde d'erbium, Er2O3, et d'oxyde de praséodyme, Pr6O11, dans une matrice polymère de type élastomère, ceci dans le cadre d'un projet industriel de remplacement du plomb dans des équipements de radioprotection. L'objet de cette thèse était d'améliorer la dispersion des charges au sein de la matrice par le biais de procédés de traitements chimiques de ces particules. Divers types de fonctionnalisations de surface ont été employés afin de compatibiliser celles-ci avec une matrice organique, notamment par greffage de composés de type acides phosphoniques. Plusieurs acides phosphoniques ont ainsi pu être utilisés avec succès pour la fonctionnalisation des deux types de charges. La caractérisation de ces différentes fonctionnalisations représente une part importante de ce projet. Des techniques d'analyse innovantes, aussi bien directes qu'indirectes ont été employées dans ce but, à savoir de la Py-GC/MS pour la détection des composés ancrés à la surface des charges, de la fluorescence X et de la spectroscopie infrarouge dans un objectif de quantification, mais aussi des études cinétiques de sédimentation des charges dans un milieu liquide organique. Finalement, des composites ont pu être obtenus par mélange des charges, traitées et non traitées, avec une matrice polyuréthane. Des essais de traction ont permis de montrer clairement une amélioration des propriétés mécaniques de certains des composites, grâce à la fonctionnalisation des charges par les acides phosphoniquesThis thesis focuses on the incorporation of mineral fillers of erbium oxide, Er2O3, and praseodymium oxide, Pr6O11, in an elastomeric polymer matrix, in the context of an industrial project to replace the lead in radiation protection equipment. The actual purpose of this thesis was to improve the dispersion of the fillers in the matrix through chemical treatment processes of these particles. Various types of surface functionalization were used to compatibilize them with an organic matrix, in particular by grafting compounds such as phosphonic acids. Hence, several phosphonic acids have been successfully used for the functionalization of both types of fillers. The characterization of these functionalizations is an important part of this project. Innovative analysis techniques, both direct and indirect have been used for this purpose, namely Py-GC/MS to detect the chemical compounds anchored to the surface of the fillers, X-ray fluorescence and FTIR spectroscopy with a quantification target, but also a study of sedimentation kinetics of the fillers in an organic medium. Finally, composites were obtained by mixing the fillers, untreated and treated, with a polyurethane matrix. Tensile tests have clearly shown an improvement of mechanical properties for some of the composites, due to the functionalization of the fillers by phosphonic acids
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Olalla, Beatriz. "Analyse des mécanismes de dispersion élémentaires et globaux de charges minérales dans les polymères : influence de la rhéologie et de la structure de la matrice." Thesis, Saint-Etienne, 2010. http://www.theses.fr/2010STET4003/document.
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L’objectif de cette étude est d’analyser la dispersion de charges minérales dans une matrice polymère. Ce travail concerne la dispersion d’une charge minérale hydroxyde de magnésium pour améliorer la résistance au feu d’une matrice polyoléfine. De forts taux de charge sont nécessaires pour une amélioration significative de la résistance au feu. Ces quantités vont provoquer une perte de propriétés mécaniques. Afin d’améliorer l’état de dispersion et de limiter la perte de propriétés mécaniques, une matrice très visqueuse peut être utilisée, cependant la mise en œuvre du matériauva être difficile. Pour résoudre ce problème, il est possible d’utiliser une matrice de viscosité inférieure pour faciliter le procédé de mise en œuvre par extrusion.Deux matrices avec des propriétés physico chimiques identiques mais des viscosités très différentes ont été utilisées pour disperser la charge. Une première partie de l’étude concerne l’identification et l’analyse des mécanismes de dispersion élémentaires, c’est-à-dire la dispersion d'un agglomérat individuel de charge. Ensuite, une extrapolation aux forts taux de charges sera réalisée. Cette partie, correspondant au mécanisme global de dispersion, a été réalisée en mélangeur interne et des techniques de caractérisation tels que la microscopie électronique à balayage avec détection derayons X, les tests mécaniques, la dimension fractale et la rhéométrie dynamique à l’état fondu ont été utilisées. Un modèle rhéologique pour corréler les mesures par rhéométrie dynamique avec l’état de dispersion a été proposé. La dernière partie de l’étude, concerne l’optimisation du procédé de mise en œuvre et de l'état de dispersion par extrusion bivisThe objective of this study is the analysis of the dispersion of mineral fillers within a polymer matrix. This work aims is to increase the fire resistance of a polyolefin by dispersing magnesium hydroxide mineral filler. High amounts of magnesium hydroxide are needed to reach a significant performance of the fire resistance. The high loads induce a degradation of the mechanical properties of the material. In order to obtain a good dispersion and to improve the mechanical properties, a high viscosity matrix may be used. However, this causes problems during the manufacturing of the composite by extrusion because high pressures induced by a highly filled viscous matrix might block the machine. To solve this issue a less viscous matrix can be used to facilitate the processing by extrusion. Two matrices having the same physico-chemical properties but very different viscosities have been used to disperse the filler. The first part of the study concerns the identification and analysis of the elementary mechanism of dispersion, i.e. how an individual agglomerate is dispersed. Then, extrapolation to highly filled systems is carried out. The global mechanism of dispersion has been conducted in an internal mixer and characterization techniques such as scanning electronic microscopy with X-ray detection, tensile test, fractal dimension and dynamic rheometry in the melt have been used. A rheological model relating dynamic rheological measurements and the state of dispersion has been developed. The last part of the study is concerned with the optimization of the fabrication process and the dispersion of filers by twin screw extruder
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Bouty, Adrien. "Influence de la dispersion des charges et de la conformation des chaines sur les propriétés mécaniques de systèmes nanocomposites SBR/Silice." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00925836.
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Dans l'industrie du pneumatique, l'incorporation de nanoparticules de silice dans les élastomères permet d'obtenir des pneumatiques avec des propriétés mécaniques améliorées. D'un point de vue fondamental, deux contributions sont communément invoquées pour expliquer ces changements : (i) une contribution du réseau de charges, fortement dépendante de leur état de dispersion, (ii) une contribution des chaines dont la conformation est potentiellement modifiée en présence du réseau de charges. Cependant, les mécanismes permettant de relier cette structure nanométrique aux propriétés macroscopiques du matériau sont encore mal compris. Dans ce contexte, nous avons synthétisé des systèmes SBR/Silice modèles constituant une première approche de systèmes industriels plus complexes. En modifiant les conditions de dispersion au moyen d'agent de greffage, nous avons obtenu des nanocomposites avec des dispersions variées et reproductibles, avec des organisations multi-échelle. Celles-ci ont été caractérisées finement par l'utilisation combinée de la Diffusion de Rayons X aux Petits Angles (DXPA) et de la Microscopie Electronique en Transmission (MET). La conformation des chaines, déterminée expérimentalement par Diffusion de Neutrons aux Petits Angles (DNPA), n'est pas affectée par un effet à longue distance des charges. La caractérisation quantitative de la dispersion a permis de mettre en évidence le rôle prépondérant de la compacité des agrégats de silice et de la densité de leur réseau sur le renforcement dans le régime élastique.
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Azouz, Niramson. "Modélisation des flux d'ammoniac aux échelles locale et régionale dans des paysages hétérogènes : application à l’évaluation des dépassements des charges critiques." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066030/document.
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La dispersion et le transport atmosphérique d'ammoniac (NH3) émis par les sources agricoles et son dépôt sec sur le sol et la végétation peuvent entraîner la dégradation des écosystèmes sensibles, ainsi que l'acidification des sols. Les concentrations atmosphériques et les dépôts secs de NH3 sont généralement plus élevés à côté des sources d'émission, et les impacts environnementaux sur les écosystèmes sensibles sont souvent les plus importants à ces endroits. Pour mieux évaluer les impacts et leur étendue à l’échelle de paysages agricoles, des revues scientifiques sur les méthodes d'évaluation des impacts de NH3 ont recommandé une comparaison entre différents types de modèles à différentes échelles spatiales. Dans ce contexte, nous avons comparé les flux de NH3 simulés par deux modèles de dispersion, de transport et de dépôt par voie atmosphérique (CHIMERE et OPS-ST), pour différents scénarios théoriques et semi-réels et pour différentes tailles de maille des modèles. Les résultats de simulations montrent que les dépôts secs annuels de NH3, moyennés sur le domaine d’étude, sont comparables pour des tailles de maille correspondant aux tailles pour lesquelles les modèles ont été conçus. Cela implique que les modèles eulériens fonctionnant à des résolutions kilométriques peuvent être utilisés pour simuler l’impact du NH3 sur la composition chimique de l’atmosphère. Les résultats divergent entre les modèles à proximité des sources. Les conditions météorologiques et la taille des mailles sont les facteurs ayant les effets les plus marqués sur les résultats des deux modèles. Enfin, nos résultats montrent que la détection des dépassements de charges critiques à proximité des sources est mieux représentée avec OPS-ST qu’avec CHIMERE, avec lequel on observe une surestimation des surfaces dépassant les charges critiquesShort-range atmospheric dispersion of ammonia emitted by agricultural sources and its subsequent deposition to soil and vegetation can lead to the degradation of sensitive ecosystems as well as soil acidification. Atmospheric concentrations and dry depositions rates of NH3 are generally higher near the emission source and environmental impacts on sensitive ecosystems are often largest at these locations. To better evaluate the impacts and their extent at the agricultural landscapes scale, scientific reviews of NH3 assessment methods recommended a comparison between different types of models at different spatial scales. In this context, we compared NH3 fluxes simulated by two atmospheric dispersion, transport and deposition models (CHIMERE and OPS-ST) for different theoretical and semi-real scenarios and for different grid cell sizes. The simulation results show that the averaged NH3 dry deposition over the investigated domains is comparable for grid cell sizes for which the models were designed. This implies that eulerian models with a km scale horizontal resolution can be used for studying the larger scale impact of NH3 on atmospheric composition despite an inadequate treatment of near source dry deposition, for which the models diverge. Meteorological conditions and grid cell size are the factors having the strongest effects on the results of the two models. NH3 dry deposition predictions can be used to map critical load exceedances, our results show that the detection of these exceedances near to the sources is better represented with OPS-ST than with CHIMERE, the latter showing an overestimation of the surfaces exceeding critical loads
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Olalla, Béatriz. "Analyse des mécanismes de dispersion élémentaires et globaux de charges minérales dans les polymères : influence de la rhéologie et de la structure de la matrice." Phd thesis, Université Jean Monnet - Saint-Etienne, 2010. http://tel.archives-ouvertes.fr/tel-00673116.
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L'objectif de cette étude est d'analyser la dispersion de charges minérales dans une matrice polymère. Ce travail concerne la dispersion d'une charge minérale hydroxyde de magnésium pour améliorer la résistance au feu d'une matrice polyoléfine. De forts taux de charge sont nécessaires pour une amélioration significative de la résistance au feu. Ces quantités vont provoquer une perte de propriétés mécaniques. Afin d'améliorer l'état de dispersion et de limiter la perte de propriétés mécaniques, une matrice très visqueuse peut être utilisée, cependant la mise en œuvre du matériauva être difficile. Pour résoudre ce problème, il est possible d'utiliser une matrice de viscosité inférieure pour faciliter le procédé de mise en œuvre par extrusion.Deux matrices avec des propriétés physico chimiques identiques mais des viscosités très différentes ont été utilisées pour disperser la charge. Une première partie de l'étude concerne l'identification et l'analyse des mécanismes de dispersion élémentaires, c'est-à-dire la dispersion d'un agglomérat individuel de charge. Ensuite, une extrapolation aux forts taux de charges sera réalisée. Cette partie, correspondant au mécanisme global de dispersion, a été réalisée en mélangeur interne et des techniques de caractérisation tels que la microscopie électronique à balayage avec détection derayons X, les tests mécaniques, la dimension fractale et la rhéométrie dynamique à l'état fondu ont été utilisées. Un modèle rhéologique pour corréler les mesures par rhéométrie dynamique avec l'état de dispersion a été proposé. La dernière partie de l'étude, concerne l'optimisation du procédé de mise en œuvre et de l'état de dispersion par extrusion bivis
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Diawara, Bassidi. "Propriétés barrières de films de polycarbonate modifiés par plasma froid, par dispersion de charges et par mélanges de polymères." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR057.
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L’objectif de ce travail de thèse a été d’améliorer les propriétés barrière du polycarbonate (PC), polymère rigide et transparent utilisé dans l’industrie automobile comme matériau pour phares de voiture. Le PC est le siège de transferts de molécules de gaz et vapeurs provenant de l’intérieur et/ou de l’extérieur des optiques et également de migration de petites espèces (monomères, additifs) au sein de la matière elle-même. Ces phénomènes amènent souvent une perte de transparence du PC et d’autant plus avec la technologie LED qui ne dissipe pas la condensation. Pour y remédier, nous avons utilisé trois approches différentes permettant d’accroître la résistance au transfert des matériaux, à commencer par le traitement de surface par plasma froid afin de déposer sur le substrat de PC une couche barrière organosiliciée. La polymérisation de cette couche est effectuée en mélangeant du dioxygène avec un précurseur organosilicié : l’hexaméthyldisiloxane (HMDSO), le 2,4,6,8-tétraméthylcyclotétrasiloxane (TMCTS) ou le triéthoxyfluorosilane (TEOFS). Les autres approches axées sur les mélanges et l’incorporation de charges ont consisté à élaborer d’une part des micr/nano composites de PC/mica et de l’autre des mélanges de polymères PC/poly(m-xylène adipamide) (MXD6) et enfin le mélange chargéPC/MXD6/mica. Ces films ont été préparés à l’aide d’une extrudeuse bis-vis équipée d’éléments mélangeurs ayant pour but d’améliorer la qualité de mélange de dispersion de la matière. L’ensemble des matériaux obtenus a été caractérisé afin d’établir des relations de structure/morphologie/propriétés. Le dépôt par plasma a permis non seulement d’augmenter la résistance thermique du PC, mais aussi d’accroître son effet barrière à l’eau mais surtout aux gaz (N₂, O₂ et CO₂). L’efficacité du traitement plasma vis-à-vis de l’eau est fortement dépendante du caractère hydrophile du dépôt et de sa densité. Si les composites PC/mica élaborés avec les mélangeurs sont plus barrière à l’eau qu’aux gaz, les mélanges PC/MXD6 sont au contraire bien plus efficaces vis-à-vis des gaz que de l’eau. Ainsi l’ajout du mica à faible taux dans le mélange PC/MXD6 a permis, par effet de piégeage, d’accroître davantage la résistance à l’eau du mélange tout en maintenant des bonnes propriétés barrière aux gaz. Outre les effets barrière obtenus, nous avons réussi, par l’utilisation des éléments mélangeurs, à augmenter la stabilité thermique du PC et à conserver la transparence des films de PC/mica, PC/MXD6 et PC/MXD6/micaThe aim of the present thesis is to improve the barrier properties of polycarbonate (PC), a stiff and transparent polymer used in automotive industry as material for car headlights. PC represents a place of transfer of gas molecules and vapors coming from inside and/or outside the optics and also of migration of small species (monomers, additives) within the material itself. These phenomena often lead to a loss of the PC transparency, especially with the LED technology which does not allow the condensation dissipation. In order to overcome this limitation, three different approaches allowing the increase of materials transfer resistance were chosen. The first approach consists in the cold plasma surface treatment in order to obtain a barrier organosilicon layer on the PC substrate. This layer is obtained using a mixture of oxygen with an organosilicon precursor : hexamethyldisiloxane (HMDSO), 2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS) or triethoxyfluorosilane (TEOFS). The other approaches focused on the incorporation of fillers and polymer blends permit the elaboration of micro/nano-composites of PC/mica, PC/poly(m-xylene adipamide) (MXD6) polymer blends and charged PC/MXD6/mica blends. These films were prepared using a double-screw extruder equipped with mix elements allowing the improvement of the quality and dispersion of the blend. The physico-chemical characterization of the obtained materials highlights the structure/morphology/properties relationship. The plasma deposition allows an increase of the PC thermal resistance as well as its barrier properties toward water and especially gas (N₂, O₂ and CO₂). The efficiency of the plasma treatment toward water molecules strongly depends on the layer hydrophilicity and density. PC/mica composites elaborated with mix elements are found to be more barrier toward water than toward gas, while PC/MXD6 blends are more efficient toward gas than water. Thus, the addition of low mica contents in the PC/MXD6 blend allowed to further increase the water resistance of the blend by trapping effect, while maintaining its high barrier properties toward gas. In addition, an increase of the PC thermal stability and a presevation of the transparency of PC/mica, PC/MXD6 and PC/MXD6/mica films were revealed using mix elements
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Astruc, Marianne. "Etude rhéo-optique des mécanismes de dispersion de mélanges sous cisaillement simple: Mélanges concentrés de polymères immiscibles: Mélanges polymères-charges poreuse." Paris, ENMP, 2001. http://www.theses.fr/2001ENMP1014.
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Nous avons développé et utilisé des outils rhéo-optiques (microscopie optique) pour étudier in-situ des mécanismes de dispersion dans des mélanges complexes : des mélanges concentrés immiscibles et des mélanges polymeres-charges poreuses. Concernant les mélanges concentrés, nous avons étudié un mécanisme d'inversion de phases induit par un cisaillement simple dans des mélanges polydiméthylsiloxane-solution aqueuse d'hydroxypropylcellulose. L'inversion de phase a été induite par un cisaillement simple en jouant sur le rapport des viscosités de chaque phase. C'est un mécanisme long passant par une succession de morphologies transitoires. L'influence de la concentration, du taux de cisaillement et de l'élasticité sur la durée du régime transitoire et sur la morphologie finale ont été étudiés. La morphologie finale ( inversion de phases ou raffinement de la morphologie initiale) est la résultant d'une compétition entre temps de rupture et coalescence des filaments de chaque phase. Nous avons également étudié la dispersion d'agglomérats de noir de carbone dans des élastomères à l'aide d'un rhéomètre contra-rotatif et d'un mélangeur interne. Les mécanismes de dispersion d'agglomérats isolés sont différents par rapport à ceux identifiés dans des fluides newtoniens : contraintes critiques de dispersion plus élevées, cinétiques plus lentes et nouveaux mécanismes observés (détachement en ruban, décohésion). La cohésion des agglomérats est considérablement renforcée par le caractère viscoélastique du fluide qui les imprègne. Les mécanismes de dispersion dépendent directement du niveau d'imprégnation de ces agglomérats. En jouant à la fois sur les cinétiques d'imprégnations et sur le mécanisme de décohésion, le mouillage de l'élastomère vis-à-vis de la charge a également un rôle prépondérant sur les mécanismes de dispersion. Ces observations réalisées en rhéo-optique permettent d'expliquer certains comportements pendant la phase de malaxage.
Books on the topic "Dispersion de charges"
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Cappellaro, Enrico. IUE-ULDA access guide no. 6: International Ultraviolet Explorer-Uniform Low Dispersion Archive : Supernovae (ESA SP). European Space Agency, 1995.
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Rizzo, Matteo. The Politics of Labour 1. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198794240.003.0004.
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Chapter 4 analyses the barriers that prevented informal bus workers from responding collectively to their criminalization and to the economic squeeze by their employers. Reflecting on the sources of workers’ power, the chapter shows how labour oversupply, its fragmentation amongst different ‘classes of labour’ performing different tasks, and geographical dispersion explain workers’ lack of effective collective response to their plight. The chapter also charts the forms and limits of existing workforce solidarity through a longitudinal study of the rise and fall (1998–2005) of a labour association by transport workers on one bus route. This study sheds light on workers’ strategies to negotiate precariousness and onto the tensions between different categories of workers. Access to the association’s membership records allows some appreciation of the patterns and rhythm of labour circulation within the sector, an important element in understanding both the precariousness faced by transport workers and their political behaviour.
Book chapters on the topic "Dispersion de charges"
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Togashi, F., J. D. Baum, O. A. Soto, R. Löhner, and J. Bell. "A Study of Dispersion, Vaporization, and Combustion of Burnable Liquids Surrounding Charges." In 31st International Symposium on Shock Waves 2, 459–66. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-91017-8_59.
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Santos, Andrea M., Abdelhamid Elaïssari, J. M. G. Martinho, and Christian Pichot. "Preparation of low-size monodisperse carboxylic charged poly(methyl methacrylate) latexes." In Aqueous Polymer Dispersions, 60–63. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b12138.
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Santos, Andrea M., Abdelhamid Elaïssari, J. M. G. Martinho, and Christian Pichot. "Preparation of low-size monodisperse carboxylic charged poly(methyl methacrylate) latexes." In Aqueous Polymer Dispersions, 60–63. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-540-36474-0_12.
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Allison, Wade. "The Dispersion and Absorption of Electromagnetic Waves." In The Flight of a Relativistic Charge in Matter, 59–68. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-23446-0_5.
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Gasser, Ingenuin. "A Review on Small Debye Length and Quasi-Neutral Limits in Macroscopic Models for Charged Fluids." In Dispersive Transport Equations and Multiscale Models, 107–19. New York, NY: Springer New York, 2004. http://dx.doi.org/10.1007/978-1-4419-8935-2_7.
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Sánchez-Sinencio, F., J. M. Figueroa, R. Ramírez-Bon, O. Zelaya, G. A. González de la Cruz, J. G. Mendoza, G. Contreras-Puente, and A. Díaz-Góngora. "Dispersive Transient Charge Carrier Transport in Polycrystalline Films of CdTe." In Springer Proceedings in Physics, 345–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-76376-2_49.
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Tesnière, Marie-Hélène. "La dispersion de la Librairie de Charles V et Charles VI au xve siècle (après 1424)." In Bibliologia, 17–34. Turnhout, Belgium: Brepols Publishers, 2023. http://dx.doi.org/10.1484/m.bib-eb.5.134403.
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Wang, Yanru, Yi Tian, Xinbo Huang, Haonan Shi, Guixin Zhu, Zhiwei Li, and Shuai Wang. "Study on the Surface Charge Accumulation and Dispersion Process of Polyimide for New Cables." In Lecture Notes in Electrical Engineering, 31–42. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-7401-6_4.
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Kosmulski, M., P. Dahlsten, P. Próchniak, and J. B. Rosenholm. "Surface Charge and Conductance in Dispersions of Titania in Nonaqueous and Mixed Solvents." In Trends in Colloid and Interface Science XXIV, 55–59. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-19038-4_10.
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Wang, Dongxing, Yan Liu, Zhang Ting-an, and Xiaolong Li. "Effects of Blowing Conditions on the Dispersion States of Materials Charged into Bottom Blown Oxygen Smelting Furnace." In The Minerals, Metals & Materials Series, 689–701. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-51340-9_67.
Full textConference papers on the topic "Dispersion de charges"
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Alyami, Noktan Mohammed, Vikrant Wagle, Abdullah Saleh Alyami, and Rajendra Kalgaonkar. "Anionic Nanoparticle Based Formulation to Control and Cure Moderate to Severe Losses." In ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211493-ms.
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Abstract Moderate to severe losses can be treated using the loss circulation composition involving nanomaterial-based dispersion and a chemical activator. The nanomaterial employed is an environmentally friendly type of nanosilica. The composition facilitates delayed gelling of nanomaterial-based dispersion. One key benefit of this technology is that it can place the composition into the target loss circulation zone before the nanomaterial-based dispersion gels up. This ensures that the treatment fluid does not set prematurely before reaching the target zone. It is possible to effectively use the newly developed system up to 300°F. In this study, experiments have been carried out on three different types of nanomaterials that have varying surface charges and particle sizes. Two of the nanomaterials have negatively charged nanomaterial-based dispersions and particles measuring 5nm and 17nm in size, whilst the remaining nanomaterial has a positively charged nanomaterial-based dispersion and particles that are larger than 17nm. Moreover, two different types of chemical activators have been employed, namely organic and inorganic activators, whilst their impacts on gelling times have also been assessed. The gelling time experiments were carried out at four different temperatures starting from 150 °C to 300 °C with increment of 50 °C in each experiment. This research also examined the impacts of activator concentration and different shear rates on the gelling times of the three nanomaterial-based dispersions, whilst permeability plugging tests were carried out using 2mm slotted disks in order to assess their effectiveness in controlling moderate to severe losses.
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Mustafa, A. M., Zhongyu Li, and Lin Shao. "Molecular Dynamics Simulations of Damage Cascades Creation in Oxide-Particle-Embedded Fe." In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-67356.
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Oxide-dispersion-strengthened (ODS)alloys have been identified as one promising candidate alloy type for high temperature reactor applications. Understanding irradiation stability of ODS alloys relies on atomic scale modeling such as molecular dynamics simulations. In this study, yttrium and oxygen charges in Y2O3 oxide particles, which are embedded in pure Fe matrix, are optimized to achieve stabilities observed in experiments. Deviation from the optimized charges causes self-explosion and instability of oxide particles. Molecular dynamics simulations further show that under such optimized charge conditions, damage cascade creation and defect developments can be appropriately modeled.
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Liao, Chen-Ting, Guan Gui, Nathan J. Brooks, Bin Wang, Henry C. Kapteyn, and Margaret M. Murnane. "Single-frame measurement of ultrafast spatiotemporal vortex pulses." In Frontiers in Optics. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/fio.2022.fm4e.3.
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We demonstrated a simple method to quantitatively characterize the spatiotemporal orbital angular momentum (ST-OAM) of light. Our method can measure the presence of ST-OAM, space-time topological charges, OAM helicity, pulse dispersion, and beam divergence.
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Jin, Guodong, Shouxiang Ma, Ryan Antle, and Salah M. Al-Ofi. "Reservoir Characterization for Isolated Porosity from Multi-Frequency Dielectric Measurements." In International Petroleum Technology Conference. IPTC, 2022. http://dx.doi.org/10.2523/iptc-22424-ms.
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Abstract Due to processes of geological diagenesis, pores in rocks can be isolated from the rest of the connected pore networks. The amount and spatial distribution of isolated pores can have direct effect on petrophysical properties and performance of the reservoir. This paper introduces a new methodology to quantify the isolated porosity of heterogeneous reservoirs from multi-frequency (dispersion) dielectric measurements. Based on numerical simulation studies, digital rock physics techniques are used to generate rock models with different isolated porosities. 3D dielectric dispersion modeling is then performed on the models to obtain the dispersion of rock’s dielectric constant. Dielectric dispersion behaves differently as the pore connectivity changes due to increase in isolated porosity. Dielectric constant is sensitive to frequency when pores are isolated, while insensitive to frequency when pores are connected. Variation of dielectric constant is strongly related to the amount of isolated pores. For rocks having the same total porosity, their dielectric constant increases as the isolated porosity increases. This enhancement of dielectric constant is attributed to the increase in pore network tortuosity, resulting in increased accumulations of electric charges at the interfaces between solid and pores. Analytical relationships are developed to correlate isolated porosity with the rate of permittivity change and/or the permittivity ratio, derived from the dispersion of dielectric constants. The validity and applicability of the established method are demonstrated by the agreement of predicted isolated porosity with the true values used in building the rock models. Potentially, this method can be used for enhancing reservoir characterization with modern multifrequency dielectric logs.
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Bondaryeva, Аnna, Maryna Zhaldak, Оlena Mokrousova, and Olena Okhmat. "Nanopigments for Leather Finishing Coatings." In The 9th International Conference on Advanced Materials and Systems. INCDTP - Leather and Footwear Research Institute (ICPI), Bucharest, Romania, 2022. http://dx.doi.org/10.24264/icams-2022.i.4.
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The work is focused on obtaining nanopigments by adsorption of anionic dyes on positively charged montmorillonite. The effect of sequential modification of aqueous dispersions of montmorillonite with cationic and anionic compounds on the structural and charge characteristics of mineral dispersions was studied. The effect of chemical dispersion of agglomerates of aqueous montmorillonite dispersions after adding carbonate solutions was shown. The treatment of dispersions of original montmorillonite with sodium carbonate provides maximum dispersion of mineral aggregates by penetrating into the interstructural space of aluminosilicate packets, moving them apart and separating them. It was found that the modification of montmorillonite dispersed by sodium carbonate by adding basic chromium sulfate is accompanied by a change in the surface chemistry of the mineral and structural transformations. Structural changes are manifested by the formation of a developed structure of cationic montmorillonite. The cationic surface charge of montmorillonite and high specific surface of montmorillonite are important factors for ensuring effective adsorption of anionic dyes on the surface of the mineral. The efficiency of adsorption of anionic dyes on cationic montmorillonite is investigated. It was shown that the adsorption of dyes depended on the pH of the medium. The scheme of obtaining nanopigments, which were characterized by good сovering power, saturated and intense colour was proposed.
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De Leebeeck, Angela, and David A. Sinton. "Taylor-Like Dispersion of Charged Species in Electrokinetically-Driven Nanoflows." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-81852.
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In this paper, electrokinetic dispersion of charged and uncharged species in nanochannels with finite electric double layers is modelled numerically. The relatively thick electrical double layers in these flows influence dispersion through the coupled effects of both cross-stream electromigration and advection in the presence of cross-stream velocity gradients. It is found that valence charge has a significant effect on axial dispersion in these flows, in addition to other established dependencies. Effective diffusion coefficients were found to vary over 30% from the case of neutral species for single charged ions. An effective diffusion coefficient similar to Taylor dispersion is calculated and a relationship between effective diffusion coefficient, Peclet number, relative electric double layer thickness, and valence charge is plotted.
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Mattsson, Rosa, Johan Sterte, and Lars Ödberg. "Colloidal Stability of Alkyl Ketene Dimer (AKD) Dispersions. Influence of Shear, Electrolyte Concentration, Poly-electrolytes and Surfactants." In The Science of Papermaking, edited by C. F. Baker. Fundamental Research Committee (FRC), Manchester, 2001. http://dx.doi.org/10.15376/frc.2001.1.393.
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The influence of shear, electrolytes, polyelectrolytes (anionic trash), and surfactants on the colloidal stability of differently formulated AKD dispersions was investigated. The stability was tested under shear in a Britt Dynamic Drainage Jar by measuring particle size distributions and microelectrophoretic mobilities. Three cationic dispersions were used, stabilised with (1) starch with low charge density, (2) starch with medium charge density and a polyaluminum salt, (3) synthetic polymer with high charge density. All dispersions showed good to excellent stability to high levels of shear and electrolytes. All tested dispersions were influenced by carboxymethylcellulose, CMC, and flocculation was induced at a CMC addition giving a z-potential around zero. Dispersions with a higher charge density formed larger flocs and the floc size was a function of the ratio dispersion/CMC. The presence of xylan and sodium oleate only affected the dispersions with high charge density. Experimental results and theoretical calculations of the rate of AKD flocculation are in good agreement. The theoretical calculations are based on Smoluchowski’s equation for collisions between spherical particles in a uniform shear with a correction for hydrodynamic and van der Waals forces between the particles. Calculations indicate that AKD flocculation can compete with deposition on fines and fibres under papermaking conditions.
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Venturini, Marco, Rami A. Kishek, and Martin Reiser. "Dispersion and space charge." In Workshop on space charge physics in high intensity hadron rings. American Institute of Physics, 1998. http://dx.doi.org/10.1063/1.56748.
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Brown, Nicholas A., Yaqun Zhu, Ao Li, Mingfei Zhao, Xin Yong, and Paul R. Chiarot. "Structure of Electrospray Printed Deposits for Short Spray Times." In ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-3032.
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In electrospray printing, a plume of highly charged droplets is created from a conductive ink. Printing occurs by positioning a target substrate in the path of the emitted material. Here, the ink used is a colloidal dispersion consisting of nanoparticles suspended in a volatile solvent. The selection of a volatile solvent allows for rapid evaporation of the droplets in-flight to produce dry nanoparticles. An excess electric charge is imparted on the emitted particles during electrospray. The interaction of this charge with the global electric field and with other charged particles/droplets governs the particles trajectory and determines the microstructure of the printed deposit. In this study, we characterized the structure of nanoparticle deposits printed using electrospray for short spray times. Electrospray printing is capable of exerting much finer control over microstructure compared to other printing techniques. This has significant implications for the manufacturing of thin-films.
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Baghaei Lakeh, Reza, and Majid Molki. "Patterns of Secondary Flow Field in a Circular Tube Caused by Corona Wind Using the Method of Characteristics." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12611.
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Corona discharge is widely known as an effective method for improving the characteristics of the flow field and enhancing heat transfer. Distribution of charge density and electric field form a Coulomb body force which acts on the charged particles within the fluid and generates a secondary flow field. The thermal enhancing effects of corona wind are normally dominant in low Reynolds numbers or free convection problems. Although the governing differential equations of corona discharge are relatively simple, solving these equations by conventional computational methods does not yield a smooth solution for charge density and electric field. In particular, the results obtained from finite-volume method suffer from dispersion errors and fluctuations which lead to distorted values of electric body force, and consequently a distorted secondary flow. In this study, the corona discharge in a circular tube with the electrode positioned at the tube centerline is considered. An exact solution for charge density, electric field, and potential distribution along the radius of the tube has been derived analytically using a Lagrangian formulation for the charge density and the Method of Characteristics. It was found that the results of this method do not show any fluctuations or dispersion effects on charge density and electric field. The solution of the electric field provided a body force which was used in the Navier-Stokes equations to obtain the secondary flow in the cross section of the tube. In this paper, the electric and fluid flow fields are presented. The results are compared with those obtained by other computational methods and the differences are discussed.
Reports on the topic "Dispersion de charges"
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Stevens, David E. A New Approach to Charged Particle Slowing Down and Dispersion. Office of Scientific and Technical Information (OSTI), March 2016. http://dx.doi.org/10.2172/1248284.
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