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Literatura académica sobre el tema "Fractional obstacle"

Autor: Grafiati

Publicado: 10 de marzo de 2023

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Artículos de revistas sobre el tema "Fractional obstacle"

Focardi, Matteo. "Aperiodic fractional obstacle problems". Advances in Mathematics 225, n.º 6 (diciembre de 2010): 3502–44. http://dx.doi.org/10.1016/j.aim.2010.06.014.

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Allen, Mark y Mariana Smit Vega Garcia. "The fractional unstable obstacle problem". Nonlinear Analysis 193 (abril de 2020): 111459. http://dx.doi.org/10.1016/j.na.2019.02.012.

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Caffarelli, Luis y Antoine Mellet. "Random homogenization of fractional obstacle problems". Networks & Heterogeneous Media 3, n.º 3 (2008): 523–54. http://dx.doi.org/10.3934/nhm.2008.3.523.

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Allen, Mark, Erik Lindgren y Arshak Petrosyan. "The Two-Phase Fractional Obstacle Problem". SIAM Journal on Mathematical Analysis 47, n.º 3 (enero de 2015): 1879–905. http://dx.doi.org/10.1137/140974195.

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Bonder, Julián Fernández, Zhiwei Cheng y Hayk Mikayelyan. "Fractional optimal maximization problem and the unstable fractional obstacle problem". Journal of Mathematical Analysis and Applications 495, n.º 1 (marzo de 2021): 124686. http://dx.doi.org/10.1016/j.jmaa.2020.124686.

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Wen, Shuhuan, Xueheng Hu, Zhen Li, Hak Keung Lam, Fuchun Sun y Bin Fang. "NAO robot obstacle avoidance based on fuzzy Q-learning". Industrial Robot: the international journal of robotics research and application 47, n.º 6 (16 de octubre de 2019): 801–11. http://dx.doi.org/10.1108/ir-01-2019-0002.

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Purpose This paper aims to propose a novel active SLAM framework to realize avoid obstacles and finish the autonomous navigation in indoor environment. Design/methodology/approach The improved fuzzy optimized Q-Learning (FOQL) algorithm is used to solve the avoidance obstacles problem of the robot in the environment. To reduce the motion deviation of the robot, fractional controller is designed. The localization of the robot is based on FastSLAM algorithm. Findings Simulation results of avoiding obstacles using traditional Q-learning algorithm, optimized Q-learning algorithm and FOQL algorithm are compared. The simulation results show that the improved FOQL algorithm has a faster learning speed than other two algorithms. To verify the simulation result, the FOQL algorithm is implemented on a NAO robot and the experimental results demonstrate that the improved fuzzy optimized Q-Learning obstacle avoidance algorithm is feasible and effective. Originality/value The improved fuzzy optimized Q-Learning (FOQL) algorithm is used to solve the avoidance obstacles problem of the robot in the environment. To reduce the motion deviation of the robot, fractional controller is designed. To verify the simulation result, the FOQL algorithm is implemented on a NAO robot and the experimental results demonstrate that the improved fuzzy optimized Q-Learning obstacle avoidance algorithm is feasible and effective.

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Jeon, S. y A. Petrosyan. "Almost minimizers for certain fractional variational problems". St. Petersburg Mathematical Journal 32, n.º 4 (9 de julio de 2021): 729–51. http://dx.doi.org/10.1090/spmj/1667.

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A notion of almost minimizers is introduced for certain variational problems governed by the fractional Laplacian, with the help of the Caffarelli–Silvestre extension. In particular, almost fractional harmonic functions and almost minimizers for the fractional obstacle problem with zero obstacle are treated. It is shown that for a certain range of parameters, almost minimizers are almost Lipschitz or C 1 , β C^{1,\beta } -regular.

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Moreno Mérida, Lourdes y Raúl Emilio Vidal. "The obstacle problem for the infinity fractional laplacian". Rendiconti del Circolo Matematico di Palermo Series 2 67, n.º 1 (8 de noviembre de 2016): 7–15. http://dx.doi.org/10.1007/s12215-016-0286-2.

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Duhé, Jean-François, Stéphane Victor, Kendric Ruiz y Pierre Melchior. "Study on obstacle avoidance for fractional artificial potential fields". IFAC-PapersOnLine 53, n.º 2 (2020): 3725–30. http://dx.doi.org/10.1016/j.ifacol.2020.12.2059.

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Bonafini, M., V. P. C. Le, M. Novaga y G. Orlandi. "On the obstacle problem for fractional semilinear wave equations". Nonlinear Analysis 210 (septiembre de 2021): 112368. http://dx.doi.org/10.1016/j.na.2021.112368.

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Más fuentes

Tesis sobre el tema "Fractional obstacle"

OGNIBENE, ROBERTO. "Monotonicity formulas and blow-up methods for the study of spectral stability and fractional obstacle problems". Doctoral thesis, Università degli studi di Pavia, 2021. http://hdl.handle.net/11571/1431735.

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The present dissertation is essentially divided into two parts. In the first part, we investigate questions of spectral stability for eigenvalue problems driven by the Laplace operator, under certain specific kinds of singular perturbations. More precisely, we start by considering the spectrum of the Laplacian on a fixed, bounded domain with prescribed homogeneous boundary conditions (of pure Dirichlet or Neumann type); then, we introduce a singular perturbation of the problem, which gives rise to a perturbed sequence of eigenvalues. Our goal is to understand the asymptotic behavior of the perturbed spectrum as long as the perturbation tends to disappear. In particular, we consider two different types of singular perturbation. On one hand, in the case of homogeneous Dirichlet boundary conditions, we consider a perturbation of the domain, which consists in attaching a thin cylindrical tube to the fixed limit domain and let its section shrink to a point. In this framework, we combine energy estimates coming from a tailor-made Almgren type monotonicity formula with the Courant-Fischer min-max characterization and then we perform a careful blow-up analysis for scaled eigenfunctions; with these ingredients, we identify the sharp rate of convergence of a perturbed eigenvalue in the case in which it is approaching a simple eigenvalue of the limit problem. On the other hand, we deal with a perturbation of the boundary conditions. More specifically, we start with the homogeneous Neumann eigenvalue problem for the Laplacian and we perturb it by prescribing zero Dirichlet boundary conditions on a small subset of the boundary. In this context, we describe the sharp asymptotic behavior of a perturbed eigenvalue when it is converging to a simple eigenvalue of the limit Neumann problem. In particular, the first term in the asymptotic expansion turns out to depend on the Sobolev capacity of the subset where the perturbed eigenfunction is vanishing. We also provide a more ‘explicit’ expression for the eigenvalue variation in the particular case of Dirichlet boundary conditions imposed on a subset which is scaling to a point. In the second part of this thesis, we deal with two problems, both governed by the fractional Laplace operator, i.e. the power of order between 0 and 1 of the classical (negative) Laplacian. First, we address the question of positivity of a nonlocal Schrödinger operator, driven by the fractional Laplacian and with singular multipolar Hardy-type potentials. Namely, we provide necessary and sufficient conditions on the coefficients of the potential for the existence of a configuration of poles that ensures the positivity of the corresponding Schrödinger operator. This result is based, in turn, on a criterion in the spirit of the Agmon-Allegretto-Piepenbrink principle and on a tool fitting in the theory of localization of binding. The second topic we investigate in this part concerns geometric properties of the free boundary of solutions of a two-phase penalized obstacle-type problem for the fractional Laplacian. In view of the Caffarelli-Silvestre extension, we can interpret it as a thin obstacle-type problem driven by a second-order differential operator living in one dimension more and with a Muckenhoupt weight, that can be either singular or degenerate on the thin space. Working in this framework, by means of Almgren and Monneau type monotonicity formulas and blow-up analysis, we first prove a classification of the possible vanishing orders on the thin space and, as a consequence, the boundary strong unique continuation principle. We finally establish a stratification result for the nodal set (which coincides with the free boundary) on the thin space and we provide sharp estimates on the Hausdorff dimension of its regular and singular part.

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Ellery, Adam J. "Modelling transport through biological environments that contain obstacles". Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/106798/1/Adam_Ellery_Thesis.pdf.

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Transport through biological environments that are densely crowded with obstacles is often classified as anomalous, rather than Fickian diffusion. Researchers often describe these transport processes using either a random walk model or a fractional order differential equation model. To explore these ideas, we simulate transport through a crowded environment that is populated by impenetrable immobile obstacles. Our work suggests that it may be inappropriate to model transport through a crowded environment using these standard approaches. We develop a new analytical method for modelling the transport of an agent through a crowded environment. Using our new method, we calculate the exact long-time diffusivity as well as the crossover time, which is the time scale required for the transport process to effectively become Fickian. Finally, we extend our new model to include interactions between the motile agent and the obstacles such as adhesion and repulsion.

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Prasser, H. M., M. Beyer, H. Carl, Issa S. Al, P. Schütz y H. Pietruske. "Experiments on two-phase flow in a vertical tube with a moveable obstacle". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28086.

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A novel technique to study the two-phase flow field around an asymmetric diaphragm in a vertical pipe is presented, that enables producing data for CFD code validation in complex geometries. Main feature is a translocation of the diaphragm to scan the 3D void field with a stationary wire-mesh sensor. Besides the measurement of time-averaged void fraction fields, a novel data evaluation method was developed to extract estimated liquid velocity profiles from the wire-mesh sensor data. The flow around an obstacle of the chosen geometry has many topological similarities with complex flow situations in bends, T-junctions, valves, safety valves and other components of power plant equipment and flow phenomena like curved stream lines, which form significant angles with the gravity vector, flow separation at sharp edges and recirculation zones in their wake are present. In order to assess the quality of the CFD code and their underlying multiphase flow and turbulence models pre-test calculations by ANSYS CFX 10.0 were carried out. A comparison between the calculation results and the experimental data shows a good agreement in term of all significant qualitative details of the void fraction and liquid velocity distributions. Furthermore, the report contains a method to assess the lateral components of bubble velocities in the form of a basic theoretical description and visualisation examples. The plots show the deviation of the flow around the obstacle in term of vectors represented the average velocities of the instantaneous cross-sections of all bubbles in the time interval when they pass the measuring plane. A detailed uncertainty analyse of the velocity assessments concludes the presented report. It includes remarks about the comparison with a second method for calculating bubble velocity profiles - the cross-correlation. In addition, this chapter gives an overview about the influence of acceleration and deceleration effects on the velocity estimation.

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Prasser, H. M., M. Beyer, H. Carl, Issa S. Al, P. Schütz y H. Pietruske. "Experiments on two-phase flow in a vertical tube with a moveable obstacle". Forschungszentrum Dresden-Rossendorf, 2007. https://hzdr.qucosa.de/id/qucosa%3A21633.

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Durif, Caroline. "La migration d'avalaison de l'anguille européenne Anguilla anguilla : caractérisation des fractions dévalantes, phénomène de migration et franchissement d'obstacles". Toulouse 3, 2003. http://www.theses.fr/2003TOU30011.

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Chopard, Fabrice. "Etude de la distribution d'un écoulement diphasique et de la condensation d'un fluide réfrigérant dans une conduite à section rectangulaire". Aix-Marseille 1, 1992. http://www.theses.fr/1992AIX11059.

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De nouvelles mesures de la perte de charge diphasique et du taux de vide local ont ete effectuees pour ecoulement diphasique adiabatique ou en condensation dans un canal de section rectangulaire (lisse, arrangement d'obstacles en ligne ou en quinconce). Des correlations du taux de vide et du coefficient diphasique de frottement sont developpees a partir des donnees. Des comparaisons entre la chute de pression et l'intensification du transfert thermique sont presentees. Les points experimentaux sont determines dans des conditions industrielles de fonctionnement. Des cartes experimentales de repartition de taux de vide donnent des informations sur la distribution d'un ecoulement diphasique dans un arrangement d'obstacles. Nous demontrons que l'etude de la fonction densite de probabilite des fluctuations du taux de vide peut etre utilisee comme un indicateur objectif pour determiner le type de l'ecoulement diphasique en presence: ecoulement a bulles, a bouchons ou annulaire

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Ferreira, Edinalva Rodrigues. "Ensino de frações na Educação de Jovens e Adultos: obstáculos didáticos e epistemológicos". Pontifícia Universidade Católica de São Paulo, 2014. https://tede2.pucsp.br/handle/handle/11016.

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Made available in DSpace on 2016-04-27T16:57:34Z (GMT). No. of bitstreams: 1 Edinalva Rodrigues Ferreira.pdf: 3705947 bytes, checksum: ba772663e48a81f8a3029b08d56d4cbd (MD5) Previous issue date: 2014-12-17
This study investigates obstacles to learning that students of the Youth and Adult Education reveal in the study of fractions. This is a qualitative research with analysis of the activities addressed to a sample of four students of high school 2nd grade students of a public school. The study proposed to discover learning obstacles that students have in relation to such content. The theoretical basis of this research follows the assumption of the Theory of Didactic Situations. The procedures of the study sought to design and implement an instructional sequence in order to answer the research question that is whether and to what extent an instructional sequence, whose preparation takes into account the specificities of students of the Youth and Adult Education, contribute to diagnosis obstacles to the construction of conceptions part-whole and operators, related to fractions. The sequence was organized with three activities that consist of similar problems and applied in three consecutive sessions. The results indicate that the sequence of activities applied in the classroom contributed to that were diagnosed pedagogical and epistemological obstacles concerning to the study of fractions which were revealed in learning situations. The data collected showed that although the subjects are young and adults students who, in their experiences, deal with the fractions and their representations, and the content is treated in all previous series, they recognize a fraction, but not understand the concept, representation and conceptions
Este estudo investiga obstáculos à aprendizagem que os alunos da Educação de Jovens e Adultos revelam no estudo das frações. Trata-se de uma pesquisa qualitativa com análise das atividades resolvidas por uma amostra de quatro alunos do 2ª ano do Ensino Médio de uma escola da rede pública estadual. O estudo se propôs a levantar obstáculos à aprendizagem que alunos da Educação de Jovens e Adultos apresentam em relação ao referido conteúdo. A base teórica desta pesquisa segue o pressuposto da Teoria das Situações Didáticas. Procurou-se elaborar e aplicar uma sequência didática a fim de responder a questão de pesquisa que consiste em saber em que medida uma sequência didática, cuja elaboração leva em conta as especificidades dos alunos da Educação de Jovens e Adultos, contribui para o diagnóstico de obstáculos à construção das concepções parte-todo e operadores, referentes às frações. A sequência foi organizada com três atividades compostas por problemas semelhantes e aplicada em três sessões consecutivas. Os resultados indicam que a sequência de atividades aplicadas em sala de aula colaborou para que fossem diagnosticados obstáculos didáticos e epistemológicos, referentes ao estudo de frações, que se revelam em situações de aprendizagem. Os dados coletados mostraram que apesar de os sujeitos da pesquisa serem alunos jovens e adultos que, em suas vivências, lidam com as frações e suas representações e de o conteúdo ser tratado em todas as séries anteriores, os mesmos reconhecem uma fração, mas não compreendem o conceito, a representação e as concepções

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Schmäche, Christopher. "An obstacle problem for a fractional power of the Laplace operator". 2013. https://ul.qucosa.de/id/qucosa%3A16760.

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In dieser Arbeit setzen wir uns mit der Ph.D. Thesis von Luis Silvestre auseinander, in welcher er das Hindernisproblem für den gebrochenen Laplace Operator behandelt hat. Das Ziel war es seine Arbeit nachzuvollziehen und seine Beweise vollständig auszuformulieren. Dabei haben wir uns auf die Existenz der Lösung und erste Regularitätsresultate beschränkt.

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Silvestre, Luis Enrique Caffarelli Luis A. "Regularity of the obstacle problem for a fractional power of the laplace operator". 2005. http://repositories.lib.utexas.edu/bitstream/handle/2152/1727/silvestrel91596.pdf.

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Silvestre, Luis Enrique. "Regularity of the obstacle problem for a fractional power of the laplace operator". Thesis, 2005. http://hdl.handle.net/2152/1727.

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Libros sobre el tema "Fractional obstacle"

Fokin, Sergey. Improvement of technical means for processing waste from logging operations for fuel chips in felling conditions. ru: INFRA-M Academic Publishing LLC., 2017. http://dx.doi.org/10.12737/24135.

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Currently, wood waste in the form of a dissected crown on the ground and the root fraction of the tree's biomass in the ground remain in felling areas, becoming potentially dangerous combustible materials in the event of forest fires, as well as obstacles to reforestation activities, and possible foci of infections. Shredding wood waste into wood chips will solve the problem of their disposal by using fuel chips as an additional source of heat energy. In the present work, the influence of design and operational parameters of milling machines with a modernized hydraulic system and equipped with active working bodies on the process of shredding wood waste is established. The annual economic effect from the introduction of the developed complex of wood waste shredding machines and economic indicators from the use of fuel chips are given. This publication is intended for undergraduates and postgraduates engaged in scientific research in the field of forestry mechanization.

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Capítulos de libros sobre el tema "Fractional obstacle"

Coville, Jèrôme. "A Note on Liouville type results for a fractional obstacle problem". En 2018 MATRIX Annals, 215–28. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-38230-8_14.

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Salsa, Sandro. "The Problems of the Obstacle in Lower Dimension and for the Fractional Laplacian". En Lecture Notes in Mathematics, 153–244. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-27145-8_4.

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Abi Zeid Daou, Roy, Fabio El Samarani, Charles Yaacoub y Xavier Moreau. "Fractional Derivatives for Edge Detection: Application to Road Obstacles". En Smart Cities Performability, Cognition, & Security, 115–37. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-14718-1_6.

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Allen, Scott T., Matthias Sprenger, Gabriel J. Bowen y J. Renée Brooks. "Spatial and Temporal Variations in Plant Source Water: O and H Isotope Ratios from Precipitation to Xylem Water". En Stable Isotopes in Tree Rings, 501–35. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_18.

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AbstractThe water present within trees when sugars and cellulose are formed is the source of hydrogen and oxygen atoms that are incorporated into tree-ring cellulose (see Chaps. 10.1007/978-3-030-92698-4_10 and 10.1007/978-3-030-92698-4_11). However, the isotope composition of relevant water pools is often unknown when trying to interpret δ18O and δ2H isotopic records in tree rings. This chapter focuses on the factors that can influence the O and H isotope ratios of source waters for trees. Trees generally use water that originated as precipitation, but this does not mean that the isotope ratios of water used by trees—predominantly taken up by roots from soils—and incorporated in cellulose exactly matches precipitation isotope ratios. Precipitation isotope ratios vary in space and time, and only a fraction of all precipitation infiltrates soils, reaches roots, and is ultimately taken up by trees. Considering species, soils, and climates may allow for predicting which fraction of water resides in the root-zone during the growing seasons, and how its isotope ratios deviate from that of average precipitation. Here we provide an overview of the terrestrial water cycle and the associated transport and fractionation processes that influence the stable isotope ratios of water used by trees. We highlight obstacles and opportunities to be considered, towards more accurately interpreting the records of O and H isotope ratios in tree cellulose.

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"Obstacle Problems Involving the Fractional Laplacian". En Recent Developments in Nonlocal Theory, 81–164. De Gruyter Open Poland, 2017. http://dx.doi.org/10.1515/9783110571561-005.

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Rahaman, Mostafijur, Sankar Prasad Mondal, Banashree Chatterjee y Shariful Alam. "Application of Fractional Calculus on the Crisp and Uncertain Inventory Control Problem". En Handbook of Research on Advances and Applications of Fuzzy Sets and Logic, 120–48. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-7979-4.ch006.

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This chapter explores the possible application of fractional calculus in the field of operation research, more specifically inventory control problem. The sense of memory can be implemented in a dynamical system with the mathematical manipulation through fractional calculus. In this chapter, some recently published papers on generalized lot-sizing models described by fractional differential equation in crisp as well as uncertain environments are reviewed. The intuitional applicability, obstacles, and challenges for studying the inventory management problems under fractional differential equation (in Riemann-Liouville and Caputo approaches) are discussed in this chapter.

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Hasib, Aziz, Abdellah Ouigmane, Otmane Boudouch, Rida Kacmi, Mustapha Bouzaid y Mohamed Berkani. "Sustainable Solid Waste Management in Morocco: Co-Incineration of RDF as an Alternative Fuel in Cement Kilns". En Solid Waste Management [Working Title]. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.93936.

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The management of municipal solid waste (MSW) is a major obstacle for the majority of municipalities in developing countries because of the impacts related to the landfilling of waste. Garbage is an energy-rich material. As a result, energy recovery is considered to be a sustainable waste management method. In Morocco, 7.4 million tons are produced annually; most of the waste is landfilled without any recovery despite the impacts related to this method of disposal. The objective of this chapter is to characterize combustible fractions (RDF) from household waste in Morocco and to study the economic and environmental benefits of their use as alternative fuels in cement kilns. The results of this research show that the combustible fractions contained in household waste in Morocco constitute a potential sustainable energy source with a high lower calorific value (4454 kcal/kg). The study of the advantages of co-incineration shows that the substitution of pet coke by 15% RDF reduces the pollution linked to gaseous emissions. In addition, the cement plant can make financial savings 389 USD/h by minimizing the use of fossil fuels.

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Cabral-Miramontes, Juan, Pamela Dorantes-Alvarado y Elva Aréchiga-Carvajal. "Standard Analytical Techniques and de novo Proposals for Successfull Soil Biodegradation Process Proposals". En Biodegradation - New Insights [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.109861.

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The contamination of water, air, and soil represent a serious problem worldwide. Therefore, it is a priority to reduce the levels of cytotoxic in the environment caused by human activities that generate chronic degenerative diseases. For example, soil contamination caused by oil and derivatives removed with biotechnological products based on biological systems of microorganisms with physiological and molecular mechanisms that allow them to carry out effective bioremediation processes, reducing the concentration of polluting hydrocarbons. The main obstacle is validating the biodegradation efficiency of chemical compounds by bacterial consortia; therefore, it is vital to adapt or develop analytical strategies to verify heavy-end reduction for each type of biological system used in remediation. This chapter describes the techniques and their adaptations for oil degradation and their derivatives promoted by microorganisms. As the limits of the methods vary within the parameters determined by international norms and laws, we compare conventional and new-generation proposals to adjust to probe biotechnological products based on consortia of biodiverse microorganisms that significantly degrade petroleum fractions.

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Saltzman, W. Mark. "Drug Modification". En Drug Delivery. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195085891.003.0014.

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Previous chapters present the characteristics of drug movement through the body. Diffusion is an essential mode of transport at the microscopic scale; concentration gradients drive a substantial fraction of the molecular movements within cells and the extracellular space. The confinement and regulated passage of molecules within compartments of a tissue or cell is also essential for function; membranes confine molecules to spatial locations and regulate transport between these isolated spaces (Chapter 5). Membranes frequently are the major obstacles to the entry or distribution of therapeutic compounds (Chapter 7). Therefore, much of the effort in drug design and drug delivery is devoted to overcoming these diffusional or membrane barriers. This chapter describes strategies for manipulating agents in order to increase their biological activity. The sections orbit a central assumption: i.e., agents can be modified to make analogous agents (analogs), which are chemically distinct from the original compound, but produce a similar biological effect. Nature uses a similar strategy, called “biotransformation” to assure elimination of many toxic compounds and drugs. Substantial chemical modification is often needed in order to impact physical properties that influence drug distribution such as stability or solubility; the challenge of drug modification is to identify chemical features that can be changed without sacrificing biological activity. Often, our understanding of the relationship between chemical structure and biological function for an agent is incomplete, making the rational production of analogs difficult. Drug modifications are frequently directed at altering properties that influence the concentration of the compound (i.e., its solubility), the duration of action (which is usually related to its stability in tissue), or the ability of drug molecules to move between compartments in tissues (which is often related to its permeability in membranes). A chemical modification can effect multiple properties, so these divisions are frequently not as distinct as the section headings suggest. Many agents are protected from degradation within tissues by binding. Binding provides a mechanism for sequestering an unstable or potent compound within a region of a tissue. Protective binding occurs frequently within the plasma and extracellular matrix (ECM); the complex molecular composition of these tissues provides many potential binding sites.

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Actas de conferencias sobre el tema "Fractional obstacle"

Melchior, Pierre, Brahim Metoui, Alexandre Poty, Slaheddine Najar, Alain Oustaloup y Mohamed Naceur Abdelkrim. "Attractive Force Based on Fractional Potential in Dynamic Motion Planning for Mobile Robot". En ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-35495.

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In path planning, potential fields introduce force constraints to ensure curvature continuity of trajectories and thus to facilitate path-tracking design. In previous work, a path planning design by fractional (or generalized) repulsive potential has been developed to avoid fixed obstacles. A fractional road was determined by taking into account danger of each obstacle. Danger level of each obstacle is characterized by the fractional order of differentiation. Then a new attractive force based on fractional potential was introduced, with the aim to extend the method to dynamic obstacles characterized by fractional potential fields. In this paper a comparison between each classical attractive force is presented. Then the new attractive force based on fractional potential is introduced. Finally, this attractive force is applied on an example and compare with the Ge and Cui method which is the classical potential fields for motion planning of mobile robots in a dynamic environment.

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Discant, Anca, Simina Emerich, Eugen Lupu, Alexandrina Rogozan y Abdelaziz Bensrhair. "Ruttier Obstacle Classification by use of Fractional B-spline Wavelets and Moments". En EUROCON 2007 - The International Conference on "Computer as a Tool". IEEE, 2007. http://dx.doi.org/10.1109/eurcon.2007.4400674.

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Hasan, Shatha, Mohammed Al-Smadi, Asad Freihet, Omar Abu Arqub, Marmon Abu Hammad y Shaher Momani. "Application of Power Series Method for Solving Obstacle Problem of Fractional Order". En 2019 IEEE Jordan International Joint Conference on Electrical Engineering and Information Technology (JEEIT). IEEE, 2019. http://dx.doi.org/10.1109/jeeit.2019.8717520.

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Gregori, Federico, Julia Kapran y Emilie Dressaire. "Filtration of Floating Particles by Collectors: Influence of the System Geometry on the Efficiency". En ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71611.

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Important industrial processes including oil extraction, mineral processing and wastewater treatment, rely on the separation of buoyant particles from a liquid phase. The capillary attraction between floating particles and fixed collectors can be leveraged to improve the efficiency of the separation process. The capture of an advected floating particle by a fixed cylindrical obstacle is due to direct interception and capillary attraction for sub-millimeter particles. The capillary attraction stems from the local deformation of the air/liquid interface. Previous work has established that floating particles placed on the surface of a still liquid bath, spontaneously move toward or away from one another depending on their surface properties. More recently, a numerical study has considered the competition between hydrodynamic and capillary interactions as floating particles are advected past a fixed cylinder. This seminal work revealed that capillary interactions can enhance the capture of particles at low flow velocity. Building on these results, we develop a numerical approach to study the interactions between advected particles and an array of obstacles. The results are obtained with the finite element modeling of the fluid flow in the channel, in presence of obstacles. Assuming that the particles do not alter the fluid flow, we solve the momentum conservation equation for each advected particle using the Basset Boussineq Oseen equation. If contact occurs, we assume that the particle is captured by the obstacle, thus neglecting inertial effects. We demonstrate that an array of obstacles can capture most of the particles traveling down the channel. First, we show that the efficiency of an array of obstacles, i.e. the fraction of particles captured depends on interfacial and hydrodynamic effects. For example, parameters such as the Reynolds number, capillary length, contact angle and collector size influence the trapping efficiency. Second we vary the geometry of the array and seek to minimize the amount of static material needed to get the maximum efficiency. These results provide guidelines for the design of efficient filters.

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Kashinsky, O. N., P. D. Lobanov, A. S. Kurdyumov y N. A. Pribaturin. "Two-Phase Flow in an Annular Channel With an Obstacle". En 2012 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icone20-power2012-54450.

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Experimental study of gas-liquid two-phase flow in an annular channel is performed. The channel consisted of two coaxial tubes with the diameters of 42 and 20 mm. An obstacle covering a quarter of the channel section was placed in the channel to produce a strong three-dimensional disturbance of the flow. Gas-liquid flow was produced by injecting air bubbles at the channel entrance through a special mixer. Measurements of local wall shear stress are performed using an electrochemical technique. Measurements of time-averaged and fluctuational wall shear stress are performed at various points relative to the obstacle, this allowed to study the field of the hydrodynamic parameters of the flow. Local void fraction is measured using a conductivity probe which traversed across the channel. The distribution of local void fraction in the region downstream the obstacle is obtained. Increased values of local void fraction in the region close to the obstacle are detected. The experimental data obtained can be used for validation of existing and developing computer codes accounting for a 3-D structure of two-phase flows.

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Duarte, Fernando B. M. y J. A. Tenreiro Machado. "Fractional Order Dynamics in the Trajectory Planning of Redundant and Hyper-Redundant Manipulators". En ASME 2003 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/detc2003/vib-48383.

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Redundant manipulators have some advantages when compared with classical arms because they allow the trajectory optimization, both on the free space and on the presence of obstacles, and the resolution of singularities. For this type of arms the proposed kinematic control algorithms adopt generalized inverse matrices but, in general, the corresponding trajectory planning schemes show important limitations. Motivated by these problems this paper studies the pseudoinverse-based trajectory planning algorithms, using the theory of fractional calculus.

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Murai, Yuichi, Toshio Sasaki, Masa-aki Ishikawa y Fujio Yamamoto. "Bubble-Driven Convection Around Cylinders Confined in a Channel". En ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45373.

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This paper concerns with flow visualization and image measurement of bubbly flows around various shapes of cylinders. A coaxial confined double rectangular chamber is constructed in order to provide a wide two-dimensional uniform bubble distribution upstream of the obstacle. The experiment shows that a wide two-phase convection is induced around the obstacle, though such an effect is not observed in research on the single-phase flow around objects. The spatial scale of the two-phase convection depends sensitively on the shape of the obstacle. Dense arrangement of cylinders is also investigated to find the interaction among the convection. The measurement results of void fraction, bubble velocity and liquid phase flow, which are obtained by image processing including particle tracking velocimetry (PTV), explore the detailed mechanism of generating the convection.

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Takase, Kazuyuki, Hiep H. Nguyen, Gaku Takase y Yoshihisa Hiraki. "Behavior of Bubbles Separated by a Cross-Shaped Obstacle Placed in a Circular Flow Channel". En ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71810.

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Clarifying two-phase flow characteristics in a nuclear reactor core is important in particular to enhance the thermo-fluid safety of nuclear reactors. Moreover, bubbly flow data in subchannels with spacers are needed as validation data for current CFD codes like a direct two-phase flow analysis code. In order to investigate the spacer effect on the bubbly flow behavior in a subchannel of the nuclear reactor, bubble dynamics around the simply simulated spacer was visually observed by a high speed camera. Furthermore, the void fraction and interfacial velocity distributions just behind the simulated spacer were measured quantitatively by using a wire-mesh sensor system with three wire-layers in the flow direction. From the present study, bubble separation behavior dependence upon the spacer shape was clarified.

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Karlsson, Natalia y Wiggo Kilborn. ""TEACHERS’ MATHEMATICAL CONTENT KNOWLEDGE AND STUDENTS’ PROGRESSION IN LEARNING OF FRACTION AND PROPORTION"". En International Conference on Education and New Developments. inScience Press, 2022. http://dx.doi.org/10.36315/2022v1end002.

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"Proportional reasoning causes considerable difficulty for students. One reason for this is, that a lack of basic understanding of fractions in earlier years, causes difficulties in the middle years. Moreover, learning of fractions and proportion is a long-term process and students encounter it continuously from grade 1 to 9. It is also difficult to teach, and teachers’ mathematical content knowledge plays a crucial role in students’ learning of mathematics. The purpose of this study is to analyse the effects of teaching, and the influence of teachers’ mathematical content knowledge about fractions and proportion on students learning in progression from grade 4 and 5 to grade 8. The method contains pre- and post-tests for 86 students, classroom observations, checking students’ written solutions and interviews of 35 selected students after the post-test. The intervention includes construction of educational materials (EM), teachers participating in seminars-training related to EM and teacher’s implementation of EM. The EM contains tasks for students and a teachers’ guide with aims and goals for teaching and a theoretical background. Tools for analysis were a methodological design, Variation theory, and a theoretical approach, Mathematical Content Knowledge for Teaching. In focus of the analysis was students learning in progression, related to variation and crucial aspects of learning. Findings from this study shows that teachers’ mathematical content knowledge and their ability to identify the objects of learning and apply this in teaching is very important for students’ learning and progression in their learning. Most students showed an ability to learn, but their performance was intimately linked to teachers’ perception of the crucial aspects in teaching, and variation. Moreover, anomalies in students’ perceptions of basic concepts caused obstacles in their learning. Some anomalies seem to have followed students from middle School to grade 8. Finally, the study illustrated how anomalies arise if misconceptions are not noticed by teachers. The outcome of the study can explain more about crucial steps in teaching and learning of fraction and proportion. The study pay attention to challenges in mathematics teaching."

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Kang, Hyung Seok, Sang Baik Kim, Min-Hwan Kim y Hee Cheon No. "CFD Prediction for an Overpressure Buildup Phenomenon of SRI Hydrogen Test in an Open Space". En ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-18002.

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A computational fluid dynamics (CFD) calculation for a hydrogen explosion test with a complicated obstacle tube geometry of pitch 21.3mm and diameter 99.1mm at a stoichiometric condition was performed to establish a CFD analysis method for a hypothetical hydrogen explosion accident between a very high temperature reactor (VHTR) and a hydrogen production facility. We developed a spark ignition model to simulate high ignition energy of 40J induced by an electric device for 2 ms in the hydrogen explosion based on an energy conservation law. We performed a sensitivity calculation by varying a constant value of the eddy dissipation model (EDM), a time step size, and a cell length size around the obstacle tube to evaluate an effect of each factor on the flame propagation and overpressure buildup phenomenon. The CFD results of the flame front time of arrival (TOA) and overpressure were compared with those of the test data. The comparison results showed that the spark ignition model with a radius of 6 cm, a pressure of 105.7 kPa, a temperature of 1000 K, a turbulent mixing time of 2 ms, and an assumption of the 10% product mass fraction can reasonably initiate the hydrogen flame propagation in the CFD calculation. As for the CFD analysis method, the EDM constants of A = 10 and B = 0.8, the time step size of 0.01 ms, the cell length of 1 cm around the obstacle tube predicted the measured flame front TOA and peak overpressure with an error range of about 27.8% and 53.3%, respectively. Therefore, it is known that the CFD analysis with the EDM may be used as an accurate evaluation tool to provide the 3-dimesnional information of the flame front TOA and overpressure buildup phenomenon if the CFD analysis method is properly chosen.

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Informes sobre el tema "Fractional obstacle"

Cohen, Shabtai, Melvin Tyree, Amos Naor, Alan N. Lakso, Terence L. Robinson y Yehezkiel Cohen. Influence of hydraulic properties of rootstocks and the rootstock-scion graft on water use and productivity of apple trees. United States Department of Agriculture, 2001. http://dx.doi.org/10.32747/2001.7587219.bard.

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This one year exploratory project investigated hydraulic architecture of apple dwarfing rootstocks. The hypothesis was that hydraulic conductance is correlated with rootstock vigor. A previous study of trees on three rootstocks in Israel showed that dwarfed trees used less water than un-dwarfed trees. Analysis showed that if the tree maintains leaf water potentials above minimum values, then this implies that the dwarfed trees have lower leaf conductance, which may also be the cause of dwarfing. The current project studied small 2-year old unworked rootstock trees, and full sized trees bearing commercial yields. In both cases hydraulic conductance was determined with two methods - the non-destructive evaporative flux (EF)-leaf water potential (L WP) method, and a destructive method in which water was forced through the plant at known pressure using the "high pressure flow meter" (HPFM). Detailed work allowed measurement of conductance of the rootstock-scion union. This was achieved both with the HPFM and with the EF-LWP methods, the former in the US and the latter in Israel. Direct measurements of leaf conductance were made, and carbon isotope ratios ( d ¹³ C) were determined for leaves sampled at the end of the season. The latter can indicate sustained differences in leaf conductance behavior. HPFM and EF-LWP methods did not give the same results. In the small plants results were similar in magnitude, but not significantly correlated. In large trees, EF- L WP measurements were a fraction of those obtained with the HPFM. The latter indicates that some of the xylem is not normally functional but transports water when pressurized. Additional experimental work targeted this result. Xylem was stained before and after perfusion with water at high pressure. This showed that at least for one rootstock a significant amount of xylem was blocked before perfusion. The "air method" for determining xylem vessel properties was improved and employed. Length, radius and density of xylem vessels of different rootstocks were found to be similar, and significant differences found were not clearly related to rootstock vigor. Measurements in the commercial orchard in Israel showed that the graft union in a dwarfing rootstock was a large obstacle for water transport (i.e. had a high resistance). This apparently led to low leaf conductance to water vapor, as indicated by lower d ¹³ C, which implies low internal CO ₂ concentrations. In the US orchard, d ¹³ C in 2001 was correlated with rootstock vigor, and significant differences were found in leaf conductance. However, the d ¹³ C differences were not observed in 2002, were opposite to those found in the Israeli orchard, and measurements of the graft union with the HPFM did not find large resistances. We speculate that the graft union is not necessarily a large impediment to water transport unless the scion starts to separate from the rootstock. It was concluded that significant differences in hydraulic conductance exist between different dwarfing rootstocks. These differences may be caused by differences in xylem properties and in the degree of cavitation, as well as resistance in the graft union. However, no general relationship to rootstock vigor was found. Therefore, hydraulic conductance alone cannot explain dwarfing, but may be one of two or more factors that lead to dwarfing. Future work should integrate more factors with hydraulic relations, e.g. nutrient and solute transport and production of hormones.

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Lahav, Ori, Albert Heber y David Broday. Elimination of emissions of ammonia and hydrogen sulfide from confined animal and feeding operations (CAFO) using an adsorption/liquid-redox process with biological regeneration. United States Department of Agriculture, marzo de 2008. http://dx.doi.org/10.32747/2008.7695589.bard.

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The project was originally aimed at investigating and developing new efficient methods for cost effective removal of ammonia (NH₃) and hydrogen sulfide (H₂S) from Concentrated Animal Feeding Operations (CAFO), in particular broiler and laying houses (NH₃) and hog houses (H₂S). In both cases, the principal idea was to design and operate a dedicated air collection system that would be used for the treatment of the gases, and that would work independently from the general ventilation system. The advantages envisaged: (1) if collected at a point close to the source of generation, pollutants would arrive at the treatment system at higher concentrations; (2) the air in the vicinity of the animals would be cleaner, a fact that would promote animal growth rates; and (3) collection efficiency would be improved and adverse environmental impact reduced. For practical reasons, the project was divided in two: one effort concentrated on NH₃₍g₎ removal from chicken houses and another on H₂S₍g₎ removal from hog houses. NH₃₍g₎ removal: a novel approach was developed to reduce ammonia emissions from CAFOs in general, and poultry houses in particular. Air sucked by the dedicated air capturing system from close to the litter was shown to have NH₃₍g₎ concentrations an order of magnitude higher than at the vents of the ventilation system. The NH₃₍g₎ rich waste air was conveyed to an acidic (0<pH<~5) bubble column reactor where NH₃ was converted to NH₄⁺. The reactor operated in batch mode, starting at pH 0 and was switched to a new acidic absorption solution just before NH₃₍g₎ breakthrough occurred, at pH ~5. Experiments with a wide range of NH₃₍g₎ concentrations showed that the absorption efficiency was practically 100% throughout the process as long as the face velocity was below 4 cm/s. The potential advantages of the method include high absorption efficiency, lower NH₃₍g₎ concentrations in the vicinity of the birds, generation of a valuable product and the separation between the ventilation and ammonia treatment systems. A small scale pilot operation conducted for 5 weeks in a broiler house showed the approach to be technically feasible. H₂S₍g₎ removal: The main goal of this part was to develop a specific treatment process for minimizing H₂S₍g₎ emissions from hog houses. The proposed process consists of three units: In the 1ˢᵗ H₂S₍g₎ is absorbed into an acidic (pH<2) ferric iron solution and oxidized by Fe(III) to S⁰ in a bubble column reactor. In parallel, Fe(III) is reduced to Fe(II). In the 2ⁿᵈ unit Fe(II) is bio-oxidized back to Fe(III) by Acidithiobacillus ferrooxidans (AF).In the 3ʳᵈ unit S⁰ is separated from solution in a gravity settler. The work focused on three sub-processes: the kinetics of H₂S absorption into a ferric solution at low pH, the kinetics of Fe²⁺ oxidation by AF and the factors that affect ferric iron precipitation (a main obstacle for a continuous operation of the process) under the operational conditions. H₂S removal efficiency was found higher at a higher Fe(III) concentration and also higher for higher H₂S₍g₎ concentrations and lower flow rates of the treated air. The rate limiting step of the H₂S reactive absorption was found to be the chemical reaction rather than the transition from gas to liquid phase. H₂S₍g₎ removal efficiency of >95% was recorded with Fe(III) concentration of 9 g/L using typical AFO air compositions. The 2ⁿᵈ part of the work focused on kinetics of Fe(II) oxidation by AF. A new lab technique was developed for determining the kinetic equation and kinetic parameters (KS, Kₚ and mₘₐₓ) for the bacteria. The 3ʳᵈ part focused on iron oxide precipitation under the operational conditions. It was found that at lower pH (1.5) jarosite accumulation is slower and that the performance of the AF at this pH was sufficient for successive operation of the proposed process at the H₂S fluxes predicted from AFOs. A laboratory-scale test was carried out at Purdue University on the use of the integrated system for simultaneous hydrogen sulfide removal from a H₂S bubble column filled with ferric sulfate solution and biological regeneration of ferric ions in a packed column immobilized with enriched AFbacteria. Results demonstrated the technical feasibility of the integrated system for H₂S removal and simultaneous biological regeneration of Fe(III) for potential continuous treatment of H₂S released from CAFO. NH₃ and H₂S gradient measurements at egg layer and swine barns were conducted in winter and summer at Purdue. Results showed high potential to concentrate NH₃ and H₂S in hog buildings, and NH₃ in layer houses. H₂S emissions from layer houses were too low for a significant gradient. An NH₃ capturing system was designed and tested in a 100-chicken broiler room. Five bell-type collecting devices were installed over the litter to collect NH₃ emissions. While the air extraction system moved only 10% of the total room ventilation airflow rate, the fraction of total ammonia removed was 18%, because of the higher concentration air taken from near the litter. The system demonstrated the potential to reduce emissions from broiler facilities and to concentrate the NH₃ effluent for use in an emission control system. In summary, the project laid a solid foundation for the implementation of both processes, and also resulted in a significant scientific contribution related to AF kinetic studies and ferrous analytical measurements.

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