Literatura científica selecionada sobre o tema "Local desorption"
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Artigos de revistas sobre o assunto "Local desorption"
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Barbero, Giovanni, Antonio M. Scarfone e Luiz R. Evangelista. "The Kinetics of Sorption–Desorption Phenomena: Local and Non-Local Kinetic Equations". Molecules 27, n.º 21 (5 de novembro de 2022): 7601. http://dx.doi.org/10.3390/molecules27217601.
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The kinetics of adsorption phenomena are investigated in terms of local and non-local kinetic equations of the Langmuir type. The sample is assumed in the shape of a slab, limited by two homogeneous planar-parallel surfaces, in such a manner that the problem can be considered one-dimensional. The local kinetic equations in time are analyzed when both saturation and non-saturation regimes are considered. These effects result from an extra dependence of the adsorption coefficient on the density of adsorbed particles, which implies the consideration of nonlinear balance equations. Non-local kinetic equations, arising from the existence of a time delay characterizing a type of reaction occurring between a bulk particle and the surface, are analyzed and show the existence of adsorption effects accompanied by temporal oscillations.
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Shen, Maoliang, Zhonggang Huo, Longyong Shu, Qixian Li, Pengxin Zhang e Weihua Wang. "The Pore Structure Multifractal Evolution of Vibration-Affected Tectonic Coal and the Gas Diffusion Response Characteristics". Processes 12, n.º 8 (14 de agosto de 2024): 1701. http://dx.doi.org/10.3390/pr12081701.
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Vibrations caused by downhole operations often induce coal and gas outburst accidents in tectonic zone coal seams. To clarify how vibration affects the pore structure, gas desorption, and diffusion capacity of tectonic coal, isothermal adsorption-desorption experiments under different vibration frequencies were carried out. In this study, high-pressure mercury intrusion experiments and low-pressure liquid nitrogen adsorption experiments were conducted to determine the pore structures of tectonic coal before and after vibration. The pore distribution of vibration-affected tectonic coal, including local concentration, heterogeneity, and connectivity, was analyzed using multifractal theory. Further, a correlation analysis was performed between the desorption diffusion characteristic parameters and the pore fractal characteristic parameters to derive the intrinsic relationship between the pore fractal evolution characteristics and the desorption diffusion characteristics. The results showed that the vibration increased the pore volume of the tectonic coal, and the pore volume increased as the vibration frequency increased in the 50 Hz range. The pore structure of the vibration-affected tectonic coal showed multifractal characteristics, and the multifractal parameters affected the gas desorption and diffusion capacity by reflecting the density, uniformity, and connectivity of the pore distribution in the coal. The increases in the desorption amount (Q), initial desorption velocity (V0), initial diffusion coefficient (D0), and initial effective diffusion coefficient (De) of the tectonic coal due to vibration indicated that the gas desorption and diffusion capacity of the tectonic coal were improved at the initial desorption stage. Q, V0, D0, and De had significant positive correlations with pore volume and the Hurst index, and V0, D0, and De had negative correlations with the Hausdorff dimension. To a certain extent, vibration reduced the local density regarding the pore distribution in the coal. As a result, the pore size distribution was more uniform, and the pore connectivity was improved, thereby enhancing the gas desorption and diffusion capacity of the coal.
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Mori, G., M. Lazzarino, D. Ercolani, L. Sorba, S. Heun e A. Locatelli. "Desorption dynamics of oxide nanostructures fabricated by local anodic oxidation nanolithography". Journal of Applied Physics 97, n.º 11 (junho de 2005): 114324. http://dx.doi.org/10.1063/1.1923165.
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Rosa, Luis G., P. A. Jacobson e P. A. Dowben. "Evidence for an Influence of Local Dipole Excitations in Thermal Desorption". Journal of Physical Chemistry B 110, n.º 15 (abril de 2006): 7944–50. http://dx.doi.org/10.1021/jp054929n.
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Seyedvakili, Farnaz, e Mohammad Samipoorgiri. "Thermo-kinetic investigation of heavy metal ions adsorption onto lignin considering coupled adsorption–desorption mechanisms: Modeling and experimental validation". International Journal of Modeling, Simulation, and Scientific Computing 09, n.º 02 (20 de março de 2018): 1850014. http://dx.doi.org/10.1142/s1793962318500149.
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A coupled adsorption–desorption thermo-kinetic model is developed incorporating both adsorption and desorption reactions. A local pseudo-equilibrium condition at the interface of adsorbent and adsorbate bulk phases was used as isotherm equation which can even be applied for multi-pollutants scenarios. The developed model is then validated using collected experimental data of heavy metal ions (Pb, Cu, Cd, Zn, and Ni). Comparisons were made for a number of isotherm and kinetic models to examine the performance of the proposed model. The developed model revealed desirable accuracy and superiority over other models in predicting the adsorption behavior and can be used for other systems of concern. The model correlates the adsorption kinetic with an [Formula: see text] value of 0.9391 and desorption kinetic with an [Formula: see text] value of 0.9383. By application of the proposed model to any available adsorption datasets, the individual characteristics of adsorption and desorption can be determined.
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Xia, Qibin, Zhong Li, Hongxia Xi e Kefeng Xu. "Activation Energy for Dibenzofuran Desorption from Fe3+/TiO2 and Ce3+/TiO2 Photocatalysts Coated onto Glass Fibres". Adsorption Science & Technology 23, n.º 5 (junho de 2005): 357–66. http://dx.doi.org/10.1260/026361705774355469.
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In this work, TiO2, Fe3+/TiO2 and Ce3+/TiO2 photocatalytic films were respectively immobilized on glass fibres via the sol—gel technique to prepare supported photocatalysts. Temperature programmed desorption (TPD) experiments were conducted to measure the TPD curves for the removal of dibenzofuran from these photocatalysts, from which the activation energy for dibenzofuran desorption from the photocatalyst surfaces was estimated. The results showed that the activation energies for dibenzofuran desorption from the photocatalysts TiO2, Ce3+/TiO2 and Fe3+/TiO2 coated separately onto the glass fibres were 16.41 kJ/mol, 22.55 kJ/mol and 33.59 kJ/mol, respectively, while the hardness values of the ions Fe3+, Ce3+ and Ti4+ were respectively 13.1 eV, 11.9 eV and 10.6 eV. The data indicated that the use of Fe3+ or Ce3+ ions for doping a TiO2 photo-catalyst increased the local hardness of the doped TiO2 photocatalyst surface. This, in turn, increased the activation energy for the desorption of dibenzofuran from such a TiO2 photocatalyst surface.
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Zavorotynska, O., I. Saldan, S. Hino, T. D. Humphries, S. Deledda e B. C. Hauback. "Hydrogen cycling in γ-Mg(BH4)2 with cobalt-based additives". Journal of Materials Chemistry A 3, n.º 12 (2015): 6592–602. http://dx.doi.org/10.1039/c5ta00511f.
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Hydrogen desorption and absorption properties of magnesium borohydride (Mg(BH4)2) were studied for three cycles. Effect of cobalt additives and their local structure upon cycling were investigated in detail.
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Sonobe, Satoshi, Yosuke Shibata, Yusuke Asakuma, Anita Hyde, Cuong Nguyen e Chi Phan. "A dimensionless number for microwave non-equilibrium local heating through surfactant desorption". Colloids and Surfaces A: Physicochemical and Engineering Aspects 591 (abril de 2020): 124560. http://dx.doi.org/10.1016/j.colsurfa.2020.124560.
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Бернацкий, Дмитрий Петрович, e Виктор Георгиевич Павлов. "FIELD DESORPTION MICROSCOPY OF CARBON-COATED FIELD ELECTRON EMITTERS". Physical and Chemical Aspects of the Study of Clusters, Nanostructures and Nanomaterials, n.º 13 (23 de dezembro de 2021): 25–31. http://dx.doi.org/10.26456/pcascnn/2021.13.025.
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Полевые электронные эмиттеры в форме металлического острия с пленкой углерода на поверхности обладают рядом перспективных эксплуатационных свойств. Характеристики эмиттера зависят от фазового состава, толщины и однородности пленки. Определение параметров пленок толщиной в один или несколько моноатомных слоев представляет определённые трудности. В данной работе образование и характеристики углеродных наноструктур на поверхности полевых эмиттеров из иридия и рения исследуются с помощью полевой десорбционной микроскопии непрерывного режима. На полевых десорбционных изображениях области углеродных наноструктур проявляются в виде локальных вспышек (лавинообразная десорбция). При покадровом анализе видеозаписей вспышек обнаружено несколько стадий формирования вспышек и выявлены различия в протекании десорбции с углеродных наноструктур на иридии и на рении. Обнаруженные различия объясняются образованием на иридии однослойного, а на рении многослойного графена. Десорбционные изображения выявляют неоднородности и локальные различия толщины пленки. Показано, что полевая десорбционная микроскопия непрерывного режима позволяет определять закономерности формирования полевых десорбционных изображений различных углеродных наноструктур, в частности, однослойного и многослойного графена на поверхности полевого эмиттера, и проводить диагностику поверхности после науглероживания и контролировать однородность получаемого покрытия. Получаемые данные полезны для разработки технологии эффективных полевых электронных эмиттеров. Field electron emitters in the form of a metal tip with a carbon film on the surface have a number of promising operational properties. The characteristics of the emitter depend on the phase composition, thickness and uniformity of the film. Determining the parameters of films with a thickness of one or more monoatomic layers presents certain difficulties. In this paper, the formation and characteristics of carbon nanostructures on the surface of field emitters made of iridium and rhenium are studied using continuous-mode field desorption microscopy. In the field desorption images, the regions of carbon nanostructures appear as local flashes (avalanche-like desorption). Frame-by-frame analysis of flash video recordings revealed several stages of the flash formation and revealed differences in the desorption from carbon nanostructures on iridium and rhenium. The found differences are explained by formation of the single-layer graphene on iridium and a multilayer graphene on rhenium. Desorption images reveal inhomogeneities and local differences in the film thickness. It is shown that continuous-mode field desorption microscopy makes it possible to determine the regularities of formation of the field desorption images of various carbon nanostructures, in particular, the single-layer and multilayer graphene on the surface of the field emitter, and to diagnose the surface after carburization. Besides, control the uniformity of the resulting coating is possible. The obtained data are useful for developing technology of the effective field electronic emitters.
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Li, Chun, Zejun Zhang e Lars Heinke. "Mass transfer of toluene in a series of metal–organic frameworks: molecular clusters inside the nanopores cause slow and step-like release". Physical Chemistry Chemical Physics 24, n.º 6 (2022): 3994–4001. http://dx.doi.org/10.1039/d1cp05560g.
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Toluene forms dimers in sufficiently large pores of MOFs of UiO-type. During the release process, the dimer break-up rather than the diffusion is rate limiting, causing a step-like desorption kinetics with a local maximum of the release rate.
Teses / dissertações sobre o assunto "Local desorption"
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Sato, K. "Local Molecular Structures Induced by Water Adsorption/Desorption in Smectite Minerals". Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35185.
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Positronium (Ps) annihilation spectroscopy and thermogravimetry and differential thermal analysis
(TG-DTA) were conducted for synthetic smectite clay minerals to investigate local molecular structures induced
by water adsorption and desorption. The TG curves indicate the weight loss of ~ 3.5 wt %, ~ 2.5 wt %,
and ~ 2.0 wt % for saponite, hectorite, and stevensite due to dehydration, in accordance with DTA endothermic
peaks around 332 K, 350 K, and 345 K. It is found based on the results of Ps lifetime spectroscopy
that the presence of angstrom-scale open space is sensitively dependent on water adsorption and desorption
in smectite clay minerals.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35185
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Denis, Julien. "Dynamic modelling of local fuel desorption and retention in the wall of nuclear fusion reactors for auto-consistent plasma-wall interaction simulations". Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0682.
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Dans les réacteurs à fusion nucléaire, un échange constant de particules se développe entre le plasma et la paroi. Ce phénomène, appelé recyclage, présente un intérêt crucial pour ces réacteurs car, une fois le plasma établi, le recyclage représente la principale source de particules pour le plasma. Une connaissance complète du recyclage est donc essentielle pour assurer un contrôle fiable de la densité plasma ainsi qu'une performance optimale du réacteur. Cependant, les études in-situ du recyclage demeurent complexes. La modélisation numérique peut assister dans la compréhension de ce phénomène. Les codes de transport de plasma de bord présentent la description la plus avancée de l’interaction plasma-paroi. La description du recyclage reste néanmoins partielle : la réflexion atomique est déjà traitée tandis que la désorption moléculaire est fixée ad-hoc par l’utilisateur. Cette thèse de doctorat se concentre sur le développement d’une extension au code de transport SolEdge2D-EIRENE, dénommée D-WEE, dont l’objectif est de modéliser la dynamique de la désorption. Afin d’initialiser D-WEE, une séquence de décharges plasma est simulée pour modéliser l’opération d’un tokamak. La dynamique simulée pendant ces décharges est étudiée, révélant des comportements intéressants qui pourraient impacter l’opération du réacteur. Pour évaluer la pertinence de la simulation, une confrontation avec l'expérience est effectuée et révèle un accord qualitatif entre la chute de pression post-décharge simulée (avec une tendance en t^{-0.8}) et celle observée expérimentalement. Le taux de rétention simulé pendant la décharge est étudié et présente un accord qualitatif avec l'expérienceIn all plasma devices, a constant exchange of particle develops between the plasma and the wall. This phenomenon, referred to as recycling, is of critical interest for those reactors as, once the plasma is established, particle recycling represents the main particle source for the plasma. A complete understanding of the recycling phenomenon is therefore essential to ensure a reliable plasma density control and optimum performance. However, the in-situ experimental study of recycling remains challenging. Modelling can assist in the understanding of this phenomenon.The edge-plasma transport codes present the most-advanced description of the plasma-wall interaction. However, the description of recycling remains partial: atomic reflection is already handled while molecular desorption is set ad-hoc by the code user. This PhD focuses on the development of an extension of the SolEdge2D-EIRENE transport code, named D-WEE, whose goal is to model the dynamics of desorption.To initialise D-WEE, a sequence of plasma discharges is simulated with D-WEE to model a tokamak operation. The simulated wall dynamics during those discharges is studied, reveling some interesting behaviours that could impact the reactor operation. To assess the relevance of the simulated wall dynamics, a confrontation to post-pulse experimental pressure measurement is performed which reveals a qualitative agreement between the temporal pressure drop obtained in the simulation (with a t^{-0.8} trend) and the one observed experimentally under ILW configuration. The retention rate during the discharge is also studied and reproduces qualitatively the experimental trends
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Duportal, Malo. "Impact de la concentration en hydrogène sur les processus de dissolution et de passivation d’un acier inoxydable austénitique". Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS024.
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De nombreux phénomènes sont susceptibles d’occasionner l’adsorption puis l’absorption d’hydrogène à la surface d’un matériau, modifiant ainsi ses propriétés intrinsèques de cœur comme de surface. En particulier, l’hydrogène introduit peut impacter les processus de corrosion, sujet encore que peu exploré et qui reste à interroger. Dans ce cadre, le présent travail a pour objet d’évaluer l’impact de l’absorption d’hydrogène sur les mécanismes de dissolution et passivation d’un acier inoxydable austénitique AISI 316L. Dans un premier temps, une caractérisation fine de la distribution d’hydrogène a été conduite. Les résultats obtenus ont montré un fort gradient de concentration permettant d’estimer le coefficient de diffusion ainsi que la concentration locale d’hydrogène. De plus, des techniques de caractérisation telles que le MET et la nano-indentation ont révélé que cette localisation induit une augmentation de la dureté, la formation de défauts de type dislocations, ainsi qu’une transformation locale de phase (γ→ε). Dans un deuxième temps, l’impact de l’absorption d’hydrogène sur les processus anodiques de l’alliage a été questionné. En particulier, les essais électrochimiques réalisés ont montré une augmentation des cinétiques dans le domaine anodique après absorption d’hydrogène. En présence du soluté le pic d’activité et la densité de courant passif sont sensiblement augmentés, et la résistance à la corrosion par piqûre est nettement altérée. Des analyses XPS ex-situ ont souligné le peu de modifications de la couche passive alors qu’une diminution significative de résistance a été clairement observée par EIS. Une augmentation des cinétiques de dissolution a clairement été établie par de analyses ICP, même si les poids respectifs de la dissolution et de l’oxydation de l’hydrogène n’ont pu être clairement quantifiés. Les modifications observées après chargement semblent en partie réversibles avec la désorption de l’hydrogène. Les résultats démontrent donc que l’hydrogène mobile est majoritairement responsable des effets observés, et que l’hydrogène piégé irréversiblement et les modifications métallurgiques induites par l’hydrogène et n’ont que peu d’effet sur les processus de corrosion même s’ils peuvent expliquer la non-réversibilité totale des effets observésDifferent processes can lead to hydrogen absorption on the surface of the materials and can decrease their inherent materials properties, especially their surface characteristics. Interactions between these modifications and corrosion processes have to be more thoroughly studied. In this context, this work aims to investigate the role of hydrogen absorption on the dissolution and passivation mechanisms of the AISI 316L. First, the total absorbed hydrogen concentration has been quantified after an electrochemical charging process. Then, we evaluated the different hydrogen states in the material and its distribution from surface to the bulk. Results suggest a strong concentration gradient and allows to estimate both an apparent coefficient of diffusion and a local hydrogen concentration. In addition, we observed that the local hydrogen increased hardness enhanced the dislocations density and induced an occasionally phase transformation to martensite (γ→ε). In the second time, the influence of hydrogen on anodic processes on the AISI 316L have been investigated. For that purpose, electrochemical tests have been conducted and show an increase of anodic kinetics after hydrogen absorption. Hydrogen induced an increase of the passive current density while the pitting resistance is widely degraded. XPS analyses attest of a similar passive layer (thickness and composition) before and after H-charging even though EIS results show a decrease of the resistance. Inductively Coupled Plasma showed that hydrogen promotes dissolution processes. The modifications induced by hydrogen are partially reversible with hydrogen desorption. Our results illustrate that mobile hydrogen is mainly responsible for the decrease of the properties and that trapped hydrogen and / or metallurgical modifications induced by electrochemical charging have few effects on the corrosion process even they highlight the partial non-reversibility of the observed effects
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Vega, Marlo. "Étude expérimentale et théorique des effets photo-thermiques ultra-rapides dans des réseaux de nanoparticules - application au contrôle local de la chimie de surface". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPAST081.
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L'excitation de nanoparticules métalliques par des impulsions delumière ultra-brèves génère des effets photo-thermiques localisés capables d'altérer leurchimie de surface. Ce travail de recherche a pour objectif d'étudier et d'utiliser ceseffets dans le but de contrôler localement la distribution de molécules d'intérêt sur lesnanoparticules. Dans un premier temps, l'utilisation conjointe de mesures despectroscopie pompe-sonde et d'un modèle numérique thermo-optique ayant un nombreminimum de paramètres libres ont permis de mettre en évidence l'hétérogénéité deseffets photo-thermiques se produisant dans des nanostructures en forme de croixasymétriques.Par la suite, un protocole permettant de marquer spécifiquement la chimiede surface avec des nanoparticules de silice a été développé. Celui-ci a permis demettre en lumière la dégradation locale de molécules à la surface de nanostructuresilluminées par des impulsions très brèves. Pour une illumination à faible puissance,seules les molécules dans les zones de forts champs électriques sont dégradées. Ainsi,cela permet de marquer et de visualiser expérimentalement la distribution de ce dernierà la surface des structures avec une résolution de quelques dizaines de nanomètres. Cesrésultats ouvrent la voie au développement de capteurs plasmoniques optimisés pour ladétection de molécules en très faible concentrationThe excitation of metal nanoparticles through short pulses of lightinduces localized photo-thermal effects capable of altering their surface chemistry. Thisresearch aims to investigate and harness these effects for the precise manipulation ofmolecule distribution on nanoparticles at a local level. Initially, employing both pumpprobespectroscopy measurements and a thermo-optical numerical model with minimalfree parameters, we outlined the heterogeneous nature of photo-thermal effects withinasymmetric cross-shaped nanostructures. Then, a methodology was developed tospecifically label the surface chemistry using silica nanoparticles. This labelingrevealed the localized degradation of molecules on the nanostructure's surface exposedto very short pulses. Under low-power illumination, only molecules within highelectricfield zones undergo degradation, enabling the experimental delineation andvisualization of electric field intensity distribution on the structure surfaces with a fewtens of nanometers resolution. These findings pave the way for the development ofplasmonic sensors optimized for the detection of molecules at very low concentrations
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Bohra, Lalit Kumar. "Analysis of Binary Fluid Heat and Mass Transfer in Ammonia-Water Absorption". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19780.
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An investigation of binary fluid heat and mass transfer in ammonia-water absorption was conducted. Experiments were conducted on a horizontal-tube falling-film absorber consisting of four columns of six 9.5 mm (3/8 in) nominal OD, 0.292 m (11.5 in) long tubes, installed in an absorption heat pump. Measurements were recorded at both system and local levels within the absorber for a wide range of operating conditions (nominally, desorber solution outlet concentrations of 5 - 40% for three nominal absorber pressures of 150, 345 and 500 kPa, for solution flow rates of 0.019 - 0.034 kg/s.). Local measurements were supplemented by high-speed, high-resolution visualization of the flow over the tube banks. Using the measurements and observations from videos, heat and mass transfer rates, heat and vapor mass transfer coefficients for each test condition were determined at the component and local levels.
For the range of experiments conducted, the overall film heat transfer coefficient varied from 923 to 2857 W/m2-K while the vapor and liquid mass transfer coefficients varied from 0.0026 to 0.25 m/s and from 5.51×10-6 to 3.31×10-5 m/s, respectively. Local measurements and insights from the video frames were used to obtain the contributions of falling-film and droplet modes to the total absorption rates. The local heat transfer coefficients varied from 78 to 6116 W/m2-K, while the local vapor and liquid mass transfer coefficients varied from -0.04 to 2.8 m/s and from -3.59×10-5 (indicating local desorption in some cases) to 8.96×10-5 m/s, respectively. The heat transfer coefficient was found to increase with solution Reynolds number, while the mass transfer coefficient was found to be primarily determined by the vapor and solution properties. Based on the observed trends, correlations were developed to predict heat and mass transfer coefficients valid for the range of experimental conditions tested. These correlations can be used to design horizontal tube falling-film absorbers for ammonia-water absorption systems.
Livros sobre o assunto "Local desorption"
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Riley, Peter. The role of the microbiology laboratory in antimicrobial stewardship. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780198758792.003.0010.
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Microbiology laboratories play an important role in antimicrobial stewardship at the level of individual patients and the population as a whole. When empiric therapy has been started, rapid results can lead to earlier targeted treatment. Accumulated results of susceptibility tests can be analysed and used to generate local or national guidelines on empiric treatment and prophylaxis. Several methods can be used to determine microbial identity and antimicrobial susceptibility, including traditional culture-based methods and newer molecular methods such as matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, polymerase chain reaction (PCR), and whole-genome sequencing. These methods and potential advantages are reviewed. Before results are reported, expert rules are applied and results edited. At this point the laboratory can influence prescribing practices.
Capítulos de livros sobre o assunto "Local desorption"
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P. Smith, Daniel, e Nathaniel T. Smith. "Solanum tuberosum Cultivation Using Nitrogen Recovered from Local Wastewater". In Solanum tuberosum - a Promising Crop for Starvation Problem [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98554.
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This chapter presents an approach to recover nitrogen from human waste-water at local-scale for cultivation of Solanum tuberosum (potato) as food crop. Nitrogen capture is by ion exchange of ammonium (NH4+) onto zeolite, a natural low cost mineral which is available worldwide. A coupled process is described in which wastewater ammonium is sorbed to granular zeolite, biologically extracted (desorbed), and used to support Solanum tuberosum growth in fill-and-drain or irrigation cultivation. The system employs separate components to optimize conditions for ammonium sorption (anaerobic ion exchange), desorption (aerobic bioextraction), and cultivation (flexible timing of water and nitrogen supply and nutrient recycle). System architecture provides a low cost and readily implemented system for highly efficient nitrogen capture and incorporation into potato tuber. The nitrogen recycle system enables sustainable local-scale intensification of Solanum tuberosum production and enhanced food security through use of a reliable local nutrient supply. Metrics are presented for per capita tuber production, land area, and productivity. A system design is presented with a path forward for demonstration and development.
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Bunker, Bruce C., e William H. Casey. "The Colloidal Chemistry of Oxides". In The Aqueous Chemistry of Oxides. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780199384259.003.0014.
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Colloids are defined as suspensions of finely divided particles in a continuous medium that do not settle rapidly and are not readily filtered. To be more specific, the International Union of Pure and Applied Chemistry defines a colloid as any material for which one or more of its three dimensions lies within the size range of 1 to 1000 nm. As the nucleation and growth of oxides from aqueous solutions almost always produces suspensions containing submicron particles (see Chapter 7), typical oxide suspensions fall squarely within the colloidal domain. In this book, we consider colloidal particles to represent oxides or hydroxides that are small enough to stay in aqueous suspensions for more than a few hours, yet are larger and lacking in the specific molecular structures of typical hydrolysis products (see Chapter 5). Given the density range of most oxides (from around 2−10 g/cm3), the sizes of most colloidal oxides fall within the limits of the International Union of Pure and Applied Chemistry (see Section 8.4.5). Colloidal oxide particles suspended in water represent a complex chemical environment. At the molecular level, protons, ions, small molecules, and polymeric species interact with particle surfaces to create charged surface sites and promote adsorption and desorption phenomena (see Chapter 6). These modified surfaces perturb the adjacent liquid, creating ordered solvent layers and strong concentration gradients in ions and other dissolved species. These interfacial phenomena generate a range of forces called interaction potentials. Such forces determine whether particles repel each other (leading to stable suspensions) or are attracted to one another, resulting in agglomeration and sedimentation phenomena. The length scales of those components of the oxide–water interface that influence the interaction potentials to be discussed in this chapter are introduced in Figure 8.1. At the subatomic level, the correlated polarization of electron clouds gives rise to dispersion forces described by quantum mechanics that contribute to van der Waals interactions. At the atomic level, the inherent charge on each exposed oxygen anion that terminates the oxide surface is controlled by local chemical bonds to adjacent cations (see Chapter 6).
Trabalhos de conferências sobre o assunto "Local desorption"
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Matthias, E., H. N. Nielsen, J. Reif, A. Rosén e E. Westin. "Multiphoton-Induced Desorption of Positive Ions from Bariumfluoride". In Microphysics of Surfaces, Beams, and Adsorbates. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/msba.1987.mc3.
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This paper is addressed to the question of surface states on the (111)-surface of BaF2, which can serve as a model for other divalent ionic crystals. The goal is to prove that surface states, which are energetically located in the middle and upper half of the bandgap, play a decisive role in the desorption process. They can either absorb single photons which results in local heating and thermal desorption or, more of interest in this context, they can resonantly enhance multiphoton absorption.
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Tonouchi, Masayoshi, e Iwao Kawayama. "Study on local oxygen absorption/desorption dynamics onto 2D materials probed by potential-sensitive THz radiation". In International Symposium on Ultrafast Phenomena and Terahertz Waves. Washington, D.C.: OSA, 2016. http://dx.doi.org/10.1364/isuptw.2016.it5a.1.
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Cao, Jiming, e Richard N. Christensen. "Modeling an Integral Dual Solar/Gas Fired Generator for a Water-Lithium Bromide Absorption Chiller". In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0823.
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Abstract This paper presents a design process for a dual solar/gas fired generator. A generator fired by solar energy and/or natural gas for a water-lithium bromide absorption chiller of 25 refrigeration tons (RT) was modeled. The natural gas is considered as the backup heat when the solar energy is unavailable or insufficient. The flue gas and the water-lithium bromide solution are in co-current flow, while the solar fluid and the water-lithium bromide solution are in counter-current flow. Fifty fluted tubes were installed vertically between two concentric cylindrical tubes. A solid ceramic insert was used to enhance heat transfer on the gas side that is considered as having the dominant heat transfer resistance. The burner is installed inside the smaller cylindrical tube. The solar fluid from the solar collector enters the generator through the fluted tubes while the water-lithium bromide mixture flows in the annular channel around the fluted tubes as a subcooled liquid. The generator is divided into two regions according to the heat transfer mechanism: subcooled liquid region and desorption region. In this model, a simultaneous solar and gas fired desorption process was investigated. The amount of makeup heat needed from natural gas was determined as a function of the solar fluid flow rate. Local temperature profiles were predicted by the model.
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Zhang, Juntao, e Raj M. Manglik. "Numerical Investigation of Single Bubble Dynamics During Nucleate Boiling in Aqueous Surfactant Solutions". In ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47047.
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The dynamics of a single growing and departing bubble during nucleate boiling from a horizontal heated surface in an aqueous surfactant solution has been numerically simulated. The full Navier-Stokes equations together with the bulk transport and adsorption-desorption-controlled surfactant interfacial transport equations are solved. A PDE-based fast local level-set method is used to computationally capture the vapor-liquid interface, and the dynamic surface tension is modeled as a body force on the interface. A second-order projection method along with a third-order ENO (essentially non-oscillatory) scheme for differencing the convection terms are applied for solving the momentum equation. The time discretization is dealt with a high order Runge-Kutta method. The multigrid preconditioned conjugate method (MPCG) is employed to solve the projection, which has strongly discontinuous coefficients caused by the physical properties jump across the vapor-liquid interface. The results illustrate the altered bubble dynamics in aqueous surfactant solutions, and their role in enhancing heat transfer.
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Celata, G. P., M. Cumo, S. McPhail e G. Zummo. "Hydrodynamic Behaviour and Influence of Channel Wall Roughness and Hydrophobicity in Microchannels". In ASME 2004 2nd International Conference on Microchannels and Minichannels. ASMEDC, 2004. http://dx.doi.org/10.1115/icmm2004-2340.
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The sometimes contradictory results available for fluid flow in micropipes show that much is yet to be verified in micro fluid dynamics. In this study the influence of channel wall roughness and of channel wall roughness and of channel wall hydrophobicity on adiabatic flow in circular microchannels is investigated, varying in diameter from 70 μm to 326 μm. The hydrodynamic behaviour of water in smooth tubes down to 30 μm inner diameter (ID) is also ascertained. Within the current experimental accuracy it is found that the classical Hagen-Poiseuille law for friction factor vs. Reynolds number is respected for all diameters measured and Re > 300. With degassed water, no effect of slip flow conditions due to hydrophobic channel walls even at 70 μm ID was noted, which might suggest that the slip flow phenomenon is associated with local desorption of dissolved gases on the hydrophobic surface, as reported elsewhere in the literature. For roughened glass channels, an increase in friction factor above 64/Re was observed only at the smallest diameter measured, 126 μm. For all experiments, no anticipated transition to turbulent flow was observed (2000 < Retr < 3000).
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Pakseresht, A., e A. Shahbazkhan. "The Effect of Splats Morphology and Post-Treatment on the Microstructure of Sprayed Coating". In ITSC2017, editado por A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen e C. A. Widener. DVS Media GmbH, 2017. http://dx.doi.org/10.31399/asm.cp.itsc2017p0879.
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Abstract In the thermal spray process, particulate materials can be melted by plasma atmosphere due to its high local temperature from 8700 °C to 15,000 °C. Therefore, the material powders turn into droplets after being melted by injection into the hot flame. Molten droplets are accelerated toward a substrate and form the splats which quickly solidify; finally, the film is formed by pile-up splats. Splat morphology and post treatment can determine the microstructure, mechanical and physical properties of the coating. In this study, BaTiO3 films were deposited onto a mirror polished stainless steel substrates kept at room temperature and 500 °C. At the elevated temperatures, the desorption of adsorbates and condensate at the substrate surface are the most important factor which change the morphology of the splats, from irregular- splash morphology to disk-like shape. Splat morphology can determine deposit microstructure and improve the coating properties. The morphology of individual splats and the post treated films were studied using scanning electron microscopy. Results indicated that the porosity in the film produced at room temperature was higher than that in the film deposited on the heated substrates. Also, post heat treatment can improve coating properties
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N. Premnath, Kannan, Farzaneh Hajabdollahi e Samuel W. J. Welch. "A Computational Approach to Study Heat Transfer Enhancement in Film Boiling due to the Addition of Surfactants". In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-1003.
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Two-phase flows involving phase change are ubiquitous in a diverse range of scientific and technological applications. There has been great recent interest in the enhancement of boiling heat transfer processes by means of additives such as surfactants. Surfactants can influence boiling through convection currents in the bulk fluids as a result of changes in the surface tension caused by local surfactant concentration due their adsorption/desorption from the bulk regions. This can result in changes in bubble release patterns and higher heat transfer rates if such changes lead to higher rate of vapor formation. We intend to study this effect in the context of film boiling. Our computational approach augments the CLSVOF method with bulk energy and diffusion equations along with a phase change model and an interface surfactant model. The challenge here is to accurately calculate the tangential gradients of the interfacial surfactant concentration in the presence of discontinuous bulk concentration gradients near the interface. We discuss a simplified model in which the interfacial surfactant concentration is always in equilibrium with the changing bulk concentrations and then present validation results to assess the accuracy of this approach. Finally, initial studies of surfactant enhanced film boiling will be presented and interpreted.
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Jia, Fuming, Feng Xie, Hong Li e Jianzhu Cao. "Generation and Distribution of Tritium in HTGRs and Review on the Tritiated Water Treatment Technologies". In 2017 25th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/icone25-66417.
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Tritium (H-3) can discharge mainly in the form of HT and/or HTO as gaseous and/or liquid waste into the environment from the nuclear power plant, and participate in the cycle among hydrosphere, atmosphere and biosphere, which would lead to the long-term radiological effects on organisms. Thus, in the daily operation of the nuclear power station, tritium became one of the most concerned nuclides in the source term analysis. In high temperature gas-cooled reactors (HTGRs), tritium was mainly generated by the ternary fission reaction of heavy nuclei in the fuel and neutron activation reaction of impurities like lithium-6 (Li-6), lithium-7 (Li-7) and boron-10 (B-10) in the graphite matrix, carbon bricks, etc. Tritium would be resorted completely in the intact tristructural-isotropic (TRISO) coated particles, while tritium in the graphite can diffuse into the primary loop depending on the local temperature. In the helium purification system of a typical HTGR, the molecular adsorber can adsorb the tritium in the primary coolant, and then the tritiated water was formed from the regeneration and desorption process of the molecular adsorber. Meanwhile, since the high permeability of tritium at a high temperature, it can permeate into the secondary loop through stainless steel heat exchange tube from the primary loop, and entered into the environment with leakage of the secondary water. Therefore, it was very important to analyze the production, transport and release mechanism of tritium for the estimation of the inventory and distribution of tritium in a nuclear power plant. With the rapid development of nuclear energy and the commercial application of HTGRs, tritiated water treatment technologies attracted more attention in the field of radioactive nuclear waste. Current paper will introduce and summarize general tritiated water treatment technologies, including water distillation, tritium sorbent process, palladium membrane reaction (PMR), and combined electrolysis catalytic exchange (CECE).
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Sumerling, Trevor, Paul Fish, George Towler, James Penfold, John Shevelan e Richard Cummings. "An Assessment of the Radiological Impact of Coastal Erosion of the UK Low-Level Waste Repository". In ASME 2011 14th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2011. http://dx.doi.org/10.1115/icem2011-59137.
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The UK Low Level Waste Repository Ltd submitted an Environmental Safety Case for the disposal of low-level waste to our regulator, the Environment Agency, on the 1st of May 2011. This includes assessments of the long-term radiological safety of past and future disposals. A particular feature of the Low Level Waste Repository (LLWR) is that, because of its proximity to the coast, the site is vulnerable to coastal erosion. Our present understanding is that the site will be eroded on a timescale of a few hundred to a few thousand years, with consequent disruption of the repository, and dispersal of the wastes. We have undertaken a programme of scientific research and monitoring to characterise the evolution and function of the current coastal system that provides a basis for forecasting its future evolution. This has included modelling of contemporary hydrodynamics, geomorphological mapping, repeat LiDAR and aerial photographic surveys to detect patterns and rates of change, coastal inspections and reconstructions of post-glacial (i.e. last 15,000 years) sea levels and sediment budgets. Estimates of future sea-level rise have been derived from international sources and consideration given to the impact of such on the local coastline. Two alternative models of coastal recession have then been applied, one empirical and one physical-process based, taking account of the composition of Quaternary-age sediments between the coast and the site and uncertainties in future local sea level change. Comparison of the ranges of calculated times to site contact with sea-level rise indicate that the repository is most likely to be disrupted by undercutting of the engineered vaults and of the trenches. A novel and flexible radiological assessment model has been developed to analyse the impacts of the erosion of the repository and subsequent dispersal of wastes. The model represents the spatial layout of the site and distribution of radionuclides within the repository and is able to take account of a range of uncertainties. These include uncertainties related to the rate of erosion through the facility, amounts of co-erosion of geological and cap materials, alternative assumptions for residence of waste materials on the beach, alternative waste form associations, the wider dispersion of the eroded materials and marine sorption/desorption processes. Results indicate assessed annual doses and risks that are consistent with regulatory guidance levels.
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Adhikary, D. P., e H. Guo. "A Continuum Model for Simulating Mine Water Inflow and Gas Emission". In ASME 2008 Fluids Engineering Division Summer Meeting collocated with the Heat Transfer, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/fedsm2008-55044.
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This paper describes a three-dimensional numerical model, called COSFLOW. It uses a Cosserat continuum approach for the efficient description of mechanical stress changes and deformation in weak layered rock, typical of coal measures. This mechanical model is coupled with a two-phase dual porosity fluid flow model to describe flow of water and gas through porous rock, desorption of gas from the matrix and subsequent flow of water and gas through the fracture network. The coupling includes simulation of permeability and porosity changes with rock deformation. Further the rock mass consisting of many interconnected fractures is idealized as an equivalent porous continuum using an equivalent anisotropic hydraulic conductivity matrix defined in terms of mean fracture spacing and mean aperture. This formulation is amenable to easy evaluation of modifications to the hydraulic conductivities as a function of stress induced changes in fracture aperture. The numerical code is used to simulate water inflow and gas emission in two Australian coal mines. The models at the two mine sites require significant geotechnical and hydrogeological data for adequate calibration. Many parameters in the model are not directly measurable and must be inferred by back-analysis of existing deformation, stress and hydrological data obtained during previous mining. The calibrated model is then used to make predictions for future mining panels. Water inflows at Mine A were predicted to increase significantly as mining progressed and this was supported by later measurements. This increase was attributed to wider longwall panels and increased roof rock permeability as more panels are mined. At Mine B, the model used measurements of gas production from predrainage boreholes for calibration and provided accurate predictions of average gas emissions into the longwall panel and post-drainage boreholes, although transient fluctuations were seen in the measurements. These were probably caused by local variations in geology or gas content or other factors not incorporated in the model.