Academic literature on the topic 'FFA alumni'
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Journal articles on the topic "FFA alumni"
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Perná, Ivana, Tomáš Hanzlíček, Monika Šupová, and Martina Novotná. "Phase Transformations in Fly Ash-Based Solids." Minerals 10, no. 9 (September 11, 2020): 804. http://dx.doi.org/10.3390/min10090804.
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The presented article describes the phase transformations in solid bodies based on fluid fly ash (FFA) over eight years from the initial to the final phases. FFA has been selected as a type of industrial waste whose amount has been growing in recent years. This type of ash has self-hardening properties when watered because of the conditions of its origin. The specific temperature of fluid burning and the addition of calcium carbonate into the burning zone create a mixture of phases which are, even when solidified, ready to form new crystal phases, especially alumina-silicates, relicts of coal clay minerals. For experiments, bricks from the mixture of FFA and quartz sand were industrially produced and left outside. Subsequent mineralogical analyses of samples of various ages confirmed differences in phase compositions. It is supposed that the main role in the presented changes is played by the content of the roentgen-amorphous part of alumina-silicates because they are likely to be transformed into a stable form of feldspar. In addition to that, this article presents the hypothesis of a moving agent, which could explain the transformations in the final bodies.
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Becker, Lillian C., Ivan Boyer, Wilma F. Bergfeld, Donald V. Belsito, Ronald A. Hill, Curtis D. Klaassen, Daniel C. Liebler, et al. "Safety Assessment of Alumina and Aluminum Hydroxide as Used in Cosmetics." International Journal of Toxicology 35, no. 3_suppl (November 2016): 16S—33S. http://dx.doi.org/10.1177/1091581816677948.
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This is a safety assessment of alumina and aluminum hydroxide as used in cosmetics. Alumina functions as an abrasive, absorbent, anticaking agent, bulking agent, and opacifying agent. Aluminum hydroxide functions as a buffering agent, corrosion inhibitor, and pH adjuster. The Food and Drug Administration (FDA) evaluated the safe use of alumina in several medical devices and aluminum hydroxide in over-the-counter drugs, which included a review of human and animal safety data. The Cosmetic Ingredient Review (CIR) Expert Panel considered the FDA evaluations as part of the basis for determining the safety of these ingredients as used in cosmetics. Alumina used in cosmetics is essentially the same as that used in medical devices. This safety assessment does not include metallic or elemental aluminum as a cosmetic ingredient. The CIR Expert Panel concluded that alumina and aluminum hydroxide are safe in the present practices of use and concentration described in this safety assessment.
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Zhou, Hangyu, Guangchuan Wang, Xiao-Feng Li, Yaling Li, Shun-Ya Zhu, Cheng-Feng Qin, and Ruikang Tang. "Alumina-encapsulated vaccine formulation with improved thermostability and immunogenicity." Chemical Communications 52, no. 38 (2016): 6447–50. http://dx.doi.org/10.1039/c6cc02595a.
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Wu, Guoyu, Guihua Liu, Xiaobin Li, Zhihong Peng, Qiusheng Zhou, and Tiangui Qi. "A green approach of preparation of fine active alumina with high specific surface area from sodium aluminate solution." RSC Advances 9, no. 10 (2019): 5628–38. http://dx.doi.org/10.1039/c8ra09853k.
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A green preparation of fine active alumina from saturated sodium aluminate solution by phase evolution is presented. High capillary pressure, numerous mesopores, and the inhibition of aggregation produced FAA with an extremely high specific surface area.
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Begand, Sabine, Thomas Oberbach, and Wilfried Glien. "Mechanical Properties of Hip Joint Heads Made of the Dispersion Ceramic - Alumina Toughened Zirconia." Key Engineering Materials 309-311 (May 2006): 1257–60. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.1257.
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For orthopaedic applications an Alumina Toughened Zirconia Ceramic was tested regarding its mechanical behaviour. We observed a marked higher strength compared to the requirements according to FDA guidelines and a significantly higher strength compared to alumina ceramic despite of 15 % decreased fatigue burst strength. The wear resistance after ring-on-disc method is significantly improved comparing to standard Al2O3/Al2O3 pairings. It means the application of endoprosthetic components made of ATZ-ceramic offers more safety and reliability.
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Sharma, Dheeraj Kumar, Mainak Bandyopadhyay, Jaydeep Joshi, and Arun K. Chakraborty. "Determination of Residual Stresses in Ceramic-Metal Brazed Joint using Finite Element Analysis (FEA) and Experimental Validation of the Results." SAMRIDDHI : A Journal of Physical Sciences, Engineering and Technology 12, no. 01 (June 30, 2020): 1–7. http://dx.doi.org/10.18090/samriddhi.v12i01.1.
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Ceramic vacuum feedthroughs are an inevitable requirement for any vacuum system which requires electrical feedlines to be inserted into the vacuum environment. These feedthroughs consist of metal-ceramic-metal transition and, therefore, require the brazing process as a joining technique. This process allows joining two base materials, i.e., Alumina and Kovar, for this case, which manifests different thermo-mechanical response. The difference between the coefficient of thermal expansion (CTE) of these materials causes the development of residual stresses during the cooling phase of the brazing process. Such residual stresses, if not addressed properly, can lead to the failure in the brazed joint even before the design limits. The purpose of this study is to assess these stresses by performing the thermo-mechanical analysis of the brazing process of ceramic-metal assembly through finite element analysis (FEA) technique. This study includes the assessment of non-linear behavior (due to temperature-dependent material properties) of Alumina and Kovar assembly. Further, X-ray diffraction (XRD) based residual stress measurement technique has been utilized to validate the FEA results. The paper shall present the FEA methodology (model, boundary condition, and results) followed by the experimental results and their comparison.
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Irez, Alaeddin Burak, Emin Bayraktar, and Ibrahim Miskioglu. "Flexural fatigue damage analyses of recycled rubber- modified epoxy-based composites reinforced with alumina fibres." Fatigue & Fracture of Engineering Materials & Structures 42, no. 4 (January 14, 2019): 959–71. http://dx.doi.org/10.1111/ffe.12964.
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Porto, C. P. S., M. P. L. Parente, R. M. N. Jorge, L. C. Pereira, and S. Griza. "Fracture toughness of the interface between Ni-Cr/ceramic, alumina/ceramic and zirconia/ceramic systems." Fatigue & Fracture of Engineering Materials & Structures 39, no. 7 (February 16, 2016): 817–29. http://dx.doi.org/10.1111/ffe.12394.
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Hattali, M. L., Stéphane Valette, François Ropital, N. Mesrati, and Daniel Treheux. "Fem Calculations and Experimental Determination of Residual Stresses in Alumina/Nickel Alloy Joints. Optimization of Fabrication Parameters." Advanced Materials Research 89-91 (January 2010): 238–43. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.238.
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The study relates to joints fabricated by solid state bonding between alumina and nickel alloy HAYNESTM214®, using an intermediate nickel metallic foil. Experimentally, damages and cracks often are observed close to the metal/ceramics interface. Consequently, the residual stresses distributions in the specimen were characterized experimentally using X-ray diffraction (XRD) and indentation techniques and predicted by Finite Element Analysis (FEA) calculations using an elastic-plastic-creep model. We demonstrate that a good correlation between FEA calculations and experimental results is obtained. Then, the effect of elaboration and geometrical parameters has been studied in order to minimize the residual stresses in alumina close to the metal-ceramics interface. However, the Al2O3/Ni/HAYNESTM214® system always leads to high residual stresses. To solve this problem, we show that the use of a multi-layer Cu/Ni/Cu joint, associated with the Direct Copper Bonding method (DCB), by pre-oxidation of copper, allows reducing significantly the tensile residual stresses in ceramics.
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Santillán Salgado, Roberto Joaquín, Alejandro Fonseca Ramírez, and Francisco Venegas Martínez. "Impacto de los precios de los metales en la estructura de capital de las empresas minero-metalúrgicas en América Latina (2004-2014)." Contaduría y Administración 63, no. 3 (June 6, 2020): 39. http://dx.doi.org/10.22201/fca.24488410e.2018.837.
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<p>Este trabajo examina los efectos de corto y mediano plazo de las fluctuaciones de los precios internacionales de varios productos minerales (oro, plata, cobre, zinc) y metalúrgicos (aluminio, acero) sobre la estructura de capital de las empresas de la industria minera y metalúrgica listadas en los mercados bursátiles de Argentina, Brasil, México y Perú. Se utilizan datos trimestrales para el periodo 2000-2014. Consistente con la teoría del Orden Selectivo de Preferencia Dinámico “<em>Dynamic Pecking Order</em>”, los resultados del análisis econométrico confirman que la rentabilidad y los precios de los productos se relacionan negativamente con en el apalancamiento financiero de las empresas.</p>
Dissertations / Theses on the topic "FFA alumni"
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Gossen, Larry Alan. "A study of the membership of the national FFA alumni association: volunteering, loyalty, and benefits." Diss., Kansas State University, 2011. http://hdl.handle.net/2097/8450.
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Doctor of PhilosophyCurriculum and Instruction Programs
Steven R. Harbstreit
There has been little research conducted related to the National FFA Alumni Association since its establishment in 1971. The purposes of this study were to determine the demographic characteristics of the membership of the National FFA Alumni Association, determine whether differences exist regarding members’ motivation to join and engage themselves in the local FFA Alumni affiliate, and whether differences exist in members’ loyalty to the FFA Alumni at the national and local levels based on their level of engagement. This descriptive study utilized survey research to accomplish the purpose, assessing the motivational functions for volunteering and measuring loyalty to the local FFA Alumni affiliate and the National FFA Alumni Association. The population of this study was the membership of the National FFA Alumni Association for the 2009-2010 membership year (N = 49,589). A proportional stratified random sample (n = 1,000) was used to identify study participants and ensure representation from the four membership regions of the National FFA Alumni Association. Based on a final usable sample (n = 913), the researcher obtained a final response rate of 43.7% (n = 399). The National FFA Alumni Association is comprised of predominantly white, male, college-educated, actively engaged former FFA members with an average age of 49.6 years. The results of independent sample t-tests indicated a significant difference between male and female members in the importance they place on six motivations for volunteering. Female members were considerably higher in the motivational functions of values, understanding, enhancement, social, career, and protective. A correlation analysis also indicated that age of the respondents played a role in the motivation to volunteer. Older members were less motivated in the areas of career, understanding, values, and enhancement. Paired samples t-tests determined members were significantly more loyal to the local FFA Alumni affiliate than the National FFA Alumni Association. There was also a significant difference in the loyalty of members based on their level of engagement with a local FFA Alumni affiliate with more highly engaged members expressing more loyalty to the association.
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Almeida, Fernando Luis de. "Desenvolvimento de um sensor eletroquímico planar modificado com 1-2 Diaminobenzeno (DAB) para monitoração de nitrito por FIA-automatizada." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-30092010-105650/.
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A presente dissertação de mestrado tem o propósito de relatar o desenvolvimento de um sensor planar eletroquímico com três eletrodos para o monitoramento de nitrito e seus interferentes (ácido úrico, ácido ascórbico e paracetamol). Para tal, no procedimento experimental é descrito o desenvolvimento do aparato extracorpóreo (mini-bomba compressora, válvulas solenóides e cela de análise). Esse é acoplado a um sistema de Análise por Injeção em Fluxo Automatizada (do inglês, Flow-injection Analysis) FIA-automatizada. Este trabalho também descreve a fabricação dos sensores em substrato de alumina, o processo de limpeza padrão dos eletrodos, o processo de obtenção dos eletrodos de referência em HCl (0,1 mol L-1) e ativação eletroquímica da superfície do eletrodo de trabalho com H2SO4 (0,1 mol L-1). Em seguida, é mostrada a estabilização dos eletrodos de referência Ag/AgCl em solução salina contendo cloretos, o estudo da secagem dos eletrodos em temperatura ambiente com exposição à luz e a caracterização dos mesmos por três métodos distintos, a saber: i) teste de reversibilidade (corrente redox vs. potencial); ii) variação do potencial com o tempo (coeficiente de degradação termodinâmica) e iii) variação do potencial com a concentração de cloretos. Também, apresenta-se a caracterização da área efetiva exposta do eletrodo de medição (trabalho) e os resultados da deposição de 1-2 Diaminobenzeno (DAB) como polímero seletivo. Além disso, são apresentados os resultados e discussões dos pseudo-eletrodos (recoberto ou não com Náfion® 117). Um ponto relacionado, a histerese associada à irreversibilidade dos eletrodos de referência resultou da ordem de 40 mVAg/AgCl Náfion® 117. Os potencias termodinâmicos observados foram da ordem de 100 ± 6 mVAg/AgCl Náfion® 117 para pseudo-eletrodo de referência sem e com Náfion® 117. Depois, foi realizado um estudo criterioso dos potenciais de resposta ao nitrito e aos interferentes por meio da técnica de DPV (do inglês, Differencial Pulse Voltammetry). Para evitar degradação acelerada (corrosão) do polímero sobre o eletrodo de trabalho, optou-se por realizar as medições com potencial igual a 0,50 VAg/AgCl Náfion® 117. Nessa condição, apresenta-se a monitoração de nitrito por FIA-automatizada na faixa de concentração de 50 a 250 mol L-1. Os resultados para a medição de nitrito mostraram que o sensor planar eletroquímico amperométrico desenvolvido é promissor, pois esse apresentou ótimo desempenho de reprodutividade (99,66%), sensibilidade (90 microA mol-1 L mm-2), seletividade (0,32%), repetitividade (91,28%) e estabilidade (15 ± 0,3 pA).In this Master of Science, it has been developed an electrochemical planar sensor defined with three electrodes for nitrite measuring and its interferents (uric acid, ascorbic acid and paracetamol). In the experimental procedure, it is shown the development of an extracorporis set up (mini-pump, solenoid valves and analysis cell) which is coupled to a system of Flow-injection Analysis (FIA). This work also describes the sensor fabrication using alumina substrates, the standard cleaning of the electrodes, the process to obtain Ag/AgCl reference electrodes in HCl (0.1 mol L-1) and electrochemical activation of the working-electrode surface with H2SO4 (0.1 mol L-1). Following, it is shown the study of drying for electrodes at room temperature with exposition to room light and their characterization using three different methods: i) reversibility test (redox current vs. potential); ii) variation of the potential with the time (thermodynamics degradation coefficient) and iii) variation of the potential with the chloride concentration. Also, it is presented the characterization of the effective exposed area of the working electrode and the results of the deposited 1-2 Diaminobenzene (DAB) is presented as a selective polymer. In addition, the results and discussions of the pseudo-reference (recovered or not with Nafion® 117) are presented. Related to irreversibility is the hysteresis associated to the reference electrodes which resulted in the order of 40 mVAg/AgCl Nafion® 117. The observed thermodynamic potentials were of (100 ± 6) mVAg/AgCl Nafion® 117 for pseudo-electrodes recovered with Nafion® 117. Later on, a careful study of the response to nitrite and to its interferents was performed by means of the DPV technique (Differential Pulse Voltammetry). In order to avoid accelerated degradation (corrosion) of the polymer, measurements were performed at a potential of 0,5 VAg/AgCl Nafion® 117. In this condition, nitrite was monitored using the automatized-FIA (Flow Injection Analysis) for concentration in the range of 50 to 250 mol L-1. The results have shown that the planar amperometric sensor for nitrite measuring is usefull since it was observed excellent performance related to reproducibility (99.66%), sensitivity (90 microA mol-1 L mm-2), selectivity (0.32%), repetibility (91.28%) and stability (15.0 ± 0.3 pA).
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Wang, Haisheng. "Modélisation Morphologique et Propriétés de Transport d'Alumines Mésoporeuses." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM045/document.
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Dans ce travail réalisé au Centre de Morphologie Mathématique and IFPEN, on s'intéresse à la microstructure et aux propriétés physiques d'alumines mésoporeuses. Il s'agit d'un supporte de catalyseur utilisés notamment dans les processus industriels de raffinage du pétrole. Fortement poreux, ce matériau est formé de ''plaquettes'' distribuées de manière désordonnée à l'échelle de la dizaine de nanomètres. Les propriétés de transport de masse du support de catalyseur sont fortement influencées par la morphologie de la microstructure poreuse. Ce travail porte sur la modélisation de la microstructure et des propriétés de transport des alumines mésoporeuses, à l'aide d'outils numériques et théoriques dérivés de l'analyse d'image et de la théorie des ensembles aléatoires. D'une part, on met en place des méthodes de caractérisation et de modélisation des microstructures, qui s'appuient sur, entre autre, des images obtenues par microscopie électronique en transmission (MET) et des courbes de porosimétrie azote. D'autre part, on utilise des méthodes d'homogénéisation numérique à champs complets par transformées de Fourier rapide (FFT).Dans un premier temps, le matériau est caractérisé expérimentalement par porosimétrie azote et résonance magnétique nucléaire à gradient de champ pulsé (RMN-GCP). Les images MET sont obtenus sur des échantillons d'épaisseur variable, filtrées et caractérisés par des fonctions de corrélation, notamment. Le bruit à haute fréquence issu de la membrane de carbone est identifié et pris en compte dans la modélisation de l'imagerie MET. À partir des images MET 2D, un modèle aléatoire à deux échelles est proposé pour représenter la microstructure 3D. Il prend en compte la forme des plaquettes d'alumines, leurs tailles, les effets d'alignement locaux et d'agrégation, qui sont identifiés numériquement. La procédure est validée à l'aide de comparaisons entre modèle et images expérimentales, en terme notamment de fonctions de corrélation et de surface spécifique, mesurées par porosimétrie azote.Dans un deuxième temps, une méthode de simulation des courbes d'isothermes de porosimétrie dans des milieux poreux périodiques ou aléatoires est développée. Basée sur des opérations morphologiques simples, elle étend un travail antérieur sur la porosimétrie au mercure. L'adsorption multicouche à basse pression est simulée à l'aide d'une dilatation tandis que les ménisques de l'interface vapeur-liquide intervenant pendant l'adsorption sont simulés à l'aide de fermetures de la phase solide par des éléments structurants sphériques. Pour simuler la désorption, une combinaison de fermetures et de bouchages de trou est utilisée. Le seuil de désorption est obtenu par une analyse de la percolation de la phase gazeuse. La méthode, d'abord validée sur des géométries simples, est comparée à des résultats antérieurs. Elle prédit une hystérésis et les distributions de pores associées à la porosimétrie. Nous l'appliquons aux modèles de microstructures 3D d'alumines mésoporeuses et proposons un modèle à trois échelles afin de rendre compte du seuil de pression pendant la désorption. En plus de la courbe de désorption, ce modèle reproduit les fonctions de corrélation mesurées sur les images MET.Dans un troisième temps, la diffusion de Fick, la perméabilité de Darcy, et les propriétés élastiques sont prédits à l'aide de calculs de champs complets par FFT sur des réalisations des modèles d'alumines mésoporeuses à deux et trois échelles. Les coefficients de diffusion effectifs et les facteurs de tortuosité sont prédits à partir de l'estimation du flux. Sont étudiés les effets de forme, d'alignement et d'agrégation des plaquettes sur les propriétés de diffusion à grande échelle. Les prédictions numériques sont validées au moyen des résultats expérimentaux obtenus par méthode RMN-GCPIn a work made at Centre de Morphologie Mathématique and IFPEN, we study the microstructure and physical properties of mesoporous alumina. This is a catalyst carrier used in the petroleum refining industry. Highly porous, it contains disordered ''platelets'' at the nanoscale. The mass transport properties of the catalyst carrier are strongly influenced by the morphology of the porous microstructure. We focus on the modeling of the microstructure and of transport properties of mesoporous alumina, using numerical and theoretical tools derived from image analysis and random sets models. On the one hand, methods are developed to characterize and model the microstructure, by extracting and combining information from transmission electron microscope (TEM) images and nitrogen porosimetry curves, among others. On the other hand, the numerical homogenization relies on full-field Fourier transform computations (FFT).The material is first characterized experimentally by nitrogen porosimetry and pulse-field gradient nuclear magnetic resonance (PFG-NMR). TEM images, obtained on samples of various thicknesses are filtered and measured in terms of correlation function. The high-frequency noise caused by carbon membrane support is identified and integrated in the TEM image model. Based on the 2D TEM images, a two-scale random set model of 3D microstructure is developed. It takes into account the platelet shape, platelet size, local alignments and aggregations effects which are numerically identified. The procedure is validated by comparing the model and experimental images in terms of correlation function and specific surface area estimated by nitrogen porosimetry.Next, a procedure is proposed to simulate porosimetry isotherms in general porous media, including random microstructures. Based on simple morphological operations, it extends an earlier approach of mercury porosimetry. Multilayer adsorption at low pressure is simulated by a dilation operation whereas the menisci of the vapor-liquid interface occurring during adsorption are simulated by closing the solid phase with spherical structuring elements. To simulate desorption, a combination of closing and hole-filling operations is used. The desorption threshold is obtained from a percolation analysis of the gaseous phase. The method, validated first on simple geometries, is compared to previous results of the literature, allowing us to predict the hysteresis and pore size distribution associated to porosimetry. It is applied on 3D microstructures of mesoporous alumina. To account for the pressure threshold during desorption, we propose a refined three-scale model for mesoporous alumina, that reproduces the correlation function and the desorption branch of porosimetry isotherms.Finally, Fick diffusion, Darcy permeability, and elastic moduli are numerically predicted using the FFT method and the two-scale and three-scale models of mesoporous alumina. The hindering effects in diffusion are estimated by the Renkin's equation. The effective diffusion coefficients and the tortuosity factors are estimated from the flux field, taking into account hindering effects. The effects of platelet shape, alignment and aggregation on the diffusion property are studied. The numerical estimation is validated from experimental PFG-NMR results
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Staub, Déborah. "Étude du comportement mécanique à rupture des alumines de forte porosité : Application aux supports de catalyseurs d'hydrotraitement des résidus." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0089/document.
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La présente étude porte sur le comportement mécanique de deux types de supports de catalyseurs utilisés industriellement en hydrotraitement des résidus. Ces supports extrudés, fabriqués par IFPEN, sont constitués d’alumine de transition γ avec un taux de porosité proche de 70%. La porosité du premier matériau est uniquement constituée de mésopores (< 50 nm). La porosité du second matériau est constituée de mésopores et de macropores (jusqu’à 20 µm). Les niveaux de sollicitation en service étant très peu connus, cette étude s’attache à décrire de manière précise et exhaustive le comportement mécanique de ces supports sous une large gamme de sollicitations, et à identifier les différents mécanismes de ruine possibles. L’objectif final est de mieux comprendre les relations entre les paramètres microstructuraux et les propriétés mécaniques afin d’identifier des leviers d’amélioration de la tenue mécanique des supports. Dans un premier temps, une méthodologie adaptée de caractérisation mécanique est établie. Le comportement des supports est étudié d’une part en traction, à l’aide d’essais de flexion trois points et d’écrasement diamétral, et d’autre part, en compression sous différents taux de triaxialité, à l’aide d’essais de compression uniaxiale et hydrostatique et d’essais de micro-indentation sphérique. Les différents mécanismes responsables de la ruine des supports sont identifiés au moyen de techniques d’imagerie telles que la microscopie électronique à balayage et la micro-tomographie à rayons X. En traction, le comportement est fragile avec l’amorçage de la rupture sur un défaut critique. En compression, une transition fragile / quasi-plastique du comportement est observée avec l’augmentation du taux de confinement. Cette quasi-plasticité s’exprime en particulier à travers un phénomène de densification de la macroporosité. Dans un deuxième temps, un critère de rupture est identifié pour chaque type de matériau en vue de représenter sur une même surface de charge les différents types de comportement et phénomènes physiques observés. Cette identification est réalisée en couplant les essais d’indentation sphérique à une analyse numérique. Des critères faisant intervenir la pression hydrostatique permettent de rendre compte de la forte dissymétrie du comportement des matériaux en traction et en compression. Enfin, dans un souci de se rapprocher des sollicitations subies par les supports de catalyseurs dans un réacteur en service, le comportement d’un empilement de supports est étudié en compression œdométrique. L’analyse de cet essai par tomographie à rayons X permet de déterminer les différents mécanismes de ruine intervenant au sein d’un empilement, en particulier ceux responsables de la génération de fines. Les résultats illustrent la pertinence de la caractérisation en flexion et en indentation des supports de catalyseurs seuls pour prévoir leur comportement au sein d’un empilement en compressionIn this work, we study the mechanical behaviour of two types of catalysts supports produced by IFPEN and industrially used in residues hydrotreating. Those extruded supports are made of transition γ-alumina with about 70% of porous volume. The first material’s porosity is exclusively composed of mesopores (< 50 nm). The porosity of the second material is composed of both mesopores and macropores (up to 20 µm). Because of the limited knowledge of the stress fields in embedded catalysts supports in use in a reactor, this study aims at precisely and exhaustively describing the mechanical behaviour of those supports under a wide range of stresses, and identifying the possible damage mechanisms. The final objective is to better understand the influence of microstructural parameters on the mechanical properties of the supports in order to propose some leads about how to improve their mechanical strength. First, an adequate mechanical characterization methodology is set. On one hand, the tensile mechanical behaviour of the supports is studied with three-point bending and diametrical crushing tests. On the other hand, their compressive behaviour under various triaxiality rates is characterized in uniaxial and hydrostatic compression, and by spherical micro-indentation. The different damaging mechanisms are identified by imaging techniques such as scanning electronic microscopy and X-ray micro-tomography. Under tensile stresses, the supports exhibit a brittle behaviour and fracture initiates at a critical flaw. Under compressive stresses, a brittle/quasi-plastic transition is observed with increasing the triaxiality rate. The quasi-plasticity is mainly due to the densification of the macroporosity. The second part of the study consists in identifying, for each material, a fracture criterion able to represent every types of behaviour and physical phenomena observed on the same yield surface. This identification is achieved by coupling the spherical indentation tests to a numerical analysis. Fracture criteria involving hydrostatic pressure are well suited to describe the highly dissymmetric mechanical behaviour of the materials in tension and in compression. The last part of this work aims at studying the mechanical behaviour of a stack of supports under œdometric compression in order to produce stress fields more representative of those existing within the supports stacked in a reactor. This test is analysed by X-ray tomography, which allows us to determine/acknowledge the different damaging mechanisms involved in fragments and fines generation. The results illustrate the suitability of the bending and indentation tests to characterize the mechanical properties of a single support and relate them to its mechanical behaviour in a stack of supports under compression
Books on the topic "FFA alumni"
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J, Petersilie Erin, and Future Farmers of America, eds. The FFA cookbook: Favorite recipes from FFA members and alumni across America. Minneapolis, Minn: MBI Pub. Company, 2009.
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Alonso, Mariela, and Ely V. Di Croce, eds. Escribir para las artes. Editorial de la Universidad Nacional de La Plata (EDULP), 2017. http://dx.doi.org/10.35537/10915/63644.
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La formación superior del estudiante universitario en relación con el análisis, la comprensión y la producción de textos resulta fundamental, tanto para su etapa de formación como para su posterior trabajo como profesional, y en ese sentido, es destacable que sea la propia institución la que proporcione las herramientas necesarias para su desarrollo a través de las materias de cursada obligatoria que conforman los planes de estudio. <i>Escribir para las Artes</i> surgió como respuesta a la convocatoria de la colección Libros de Cátedra con la idea de reunir en un libro algunos escritos sobre los contenidos abordados en la asignatura Producción de Textos (FBA-UNLP), con el fin de ponerlos a disposición de los alumnos y así complementar la bibliografía teórica que se aborda durante las clases. Producción de Textos para las Artes, como nos gusta llamar a nuestra propuesta de cátedra, comenzó mucho antes.
Book chapters on the topic "FFA alumni"
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Hashemi, Ray R., Louis A. Le Blanc, Azita A. Bahrami, Mahmood Bahar, and Bryan Traywick. "Association Analysis of Alumni Giving." In Intelligent, Adaptive and Reasoning Technologies, 262–74. IGI Global, 2011. http://dx.doi.org/10.4018/978-1-60960-595-7.ch014.
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A large sample (initially 33,000 cases representing a ten percent trial) of university alumni giving records for a large public university in the southwestern United States is analyzed by Formal Concept Analysis. This likely represents the initial attempt to perform analysis of such data by means of a machine learning technique. The variables employed include the gift amount to the university foundation as well as traditional demographic variables such as year of graduation, gender, ethnicity, marital status, etc. The foundation serves as one of the institution’s non-profit, fund-raising organizations. It pursues substantial gifts that are designated for the educational or leadership programs of the giver’s choice. Although they process gifts of all sizes, the foundation’s focus is on major gifts and endowments. Association Analysis of the given dataset is a two-step process. In the first step, FCA is applied to identify concepts and their relationships and in the second step, the association rules are defined for each concept. The hypothesis examined in this paper is that the generosity of alumni toward his/her alma mater can be predicted using association rules obtained by applying the Formal Concept Analysis approach.
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Onutai, Sujitra, Sirithan Jiemsirilers, and Takaomi Kobayashi. "Geopolymer Sourced with Fly Ash and Industrial Aluminum Waste for Sustainable Materials." In Applied Environmental Materials Science for Sustainability, 165–85. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-1971-3.ch008.
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Geopolymer is alumino-silicate material which can apply for many applications due to that geopolymers have several attractive properties of high strength, low permeability, high acid resistance, hazardous materials, and immobilization of toxic materials. This chapter presents synthesis of the dense and the porous structures of geopolymer by using fly ash and industrial waste as the raw materials. Aluminum hydroxide waste (Al-waste) and fly ash (FA) were used to synthesis the dense geopolymers for cement materials. The Al-waste based geopolymer influenced the geopolymer strength, when sodium hydroxide (NaOH) concentration was changed at different curing temperatures. As preliminary microwave oven was exposed in the lower NaOH paste of geopolymer, the successful synthesis of geopolymer cement was obtained. In addition, porous fly ash geopolymers was achieved using a household microwave oven. The geopolymer paste was cured within 1 min by using a microwave oven at different output power. Porous geopolymers were formed immediately as ued at 850 W power of the microwave oven.
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Onutai, Sujitra, Sirithan Jiemsirilers, and Takaomi Kobayashi. "Geopolymer Sourced with Fly Ash and Industrial Aluminum Waste for Sustainable Materials." In Waste Management, 676–96. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1210-4.ch032.
Full textAbstract:
Geopolymer is alumino-silicate material which can apply for many applications due to that geopolymers have several attractive properties of high strength, low permeability, high acid resistance, hazardous materials, and immobilization of toxic materials. This chapter presents synthesis of the dense and the porous structures of geopolymer by using fly ash and industrial waste as the raw materials. Aluminum hydroxide waste (Al-waste) and fly ash (FA) were used to synthesis the dense geopolymers for cement materials. The Al-waste based geopolymer influenced the geopolymer strength, when sodium hydroxide (NaOH) concentration was changed at different curing temperatures. As preliminary microwave oven was exposed in the lower NaOH paste of geopolymer, the successful synthesis of geopolymer cement was obtained. In addition, porous fly ash geopolymers was achieved using a household microwave oven. The geopolymer paste was cured within 1 min by using a microwave oven at different output power. Porous geopolymers were formed immediately as ued at 850 W power of the microwave oven.
Conference papers on the topic "FFA alumni"
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Kreiner, Jesa H., and David J. Miles. "Maintaining Currency and Staying at the Cutting Edge of the Profession." In ASME 2008 9th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2008. http://dx.doi.org/10.1115/esda2008-59597.
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Educators and employers have traditionally worked together to identify engineering skills which require ongoing updating and upgrading in order to avoid obsolescence. That, along with the need to work successfully in multidisciplinary environments, has become increasingly critical in staying competitive in the face of rapidly changing technology and current trends toward outsourcing of engineering jobs. Mechanical engineers, specifically, are continuously confronted with the requirement to maintain proficiency in CAD and FEA tools, evolving multiplicity of design materials and fabrication processes and increased sophistication of design components. Another aspect of a successful engineer entails the ability to communicate with both engineers and non-engineers who frequently are in positions to approve or cancel projects which may affect success and/or survival of the company where engineers work. A recent survey was conducted of engineering alumni of the mechanical engineering program at California State University, Fullerton spanning a period of close to four decades to assess if and how these graduates managed to stay current and the degree of success achieved in this continuing endeavor. The survey evaluated ways and means of these efforts and the employers’ attitudes and support, or lack thereof, towards such efforts. Also the surveys examined alumni experiences of working in multidisciplinary and multinational teams. Relationships between continued education and success in pursuit of the career of alumni were examined. Implications of these findings to engineers, academic institutions and industry were discussed with particular interest in the roles that educational institutions and professional societies play in the career of engineers.
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Feng, Jie, Bongsuk Kim, and Jun Ni. "Modeling of Ceramic Microgrinding by Cohesive Zone Based Finite Element Method." In ASME 2009 International Manufacturing Science and Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/msec2009-84108.
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This study investigates modeling of microgrinding of ceramic materials by cohesive zone method (CZM) and Finite element analysis (FEA). A maximum grinding chip thickness model, which considers detail diamond profile and tool deflection, is developed in this study. The chip thickness model is then implemented in FEA to predict peak grinding force in grinding alumina. The simulation result is compared with experimental result for a specific diamond on the microgrinding tool. The feasibility of modeling ceramic microgrinding by CZM based FEA is then discussed.
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Rinaldy, Dina Ramadhini, Agus Setyo Budi, and Widyaningrum Indrasari. "PENGARUH PENAMBAHAN MATERIAL ALUMINA DAN KARBON AKTIF TERHADAP KEKERASAN DAN MUTU AIR PADA TEKO TEH POCI." In SEMINAR NASIONAL FISIKA 2016 UNJ. PRODI Pendidikan Fisika dan Fisika UNJ, 2020. http://dx.doi.org/10.21009/03.snf2020.01.fa.17.
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Miles, David J., and Jesa H. Kreiner. "Efforts in Maintaining Currency in Engineering and Avoiding Obsolescence." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43841.
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Updating ones professional skills, continuing education and the ability to work successfully in multidisciplinary environments have become increasingly critical to staying competitive in the face of rapid advances in technology and the current trends toward outsourcing of engineering jobs. Mechanical engineers, specifically, are continuously confronted with staying current with proficiency in CAD and FEA tools, evolving multiplicity of design materials and increased sophistication of design components, as are their capabilities in communicating with both engineers and non-engineers. A survey conducted of engineering alumni of the California State University, Fullerton indicates how its graduates pursue the complex task of staying current and the degree of successes achieved in this never ending endeavor. The survey evaluated ways and means of these efforts and the employers’ attitudes and support, or lack thereof, towards such efforts, experiences of working in multidisciplinary and multi national teams and attitudes towards community service. Relationships between continued education and career are examined. Implications of the findings to engineers, education and industry are discussed. Roles that educational institutions and professional societies play in this process are carefully examined and discussed.
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Jiang, Hao, Jy-An John Wang, and Hong Wang. "Potential Impact of Interfacial Bonding Efficiency on Used Nuclear Fuel Vibration Integrity During Normal Transportation." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-29067.
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Finite element analysis (FEA) was used to investigate the impacts of interfacial bonding efficiency at pellet–pellet and pellet–clad interfaces on surrogate of used nuclear fuel (UNF) vibration integrity. The FEA simulation results were also validated and benchmarked with reversible bending fatigue test results on surrogate rods consisting of stainless steel (SS) tubes with alumina-pellet inserts. Bending moments (M) are applied to the FEA models to evaluate the system responses of the surrogate rods. From the induced curvature, κ, the flexural rigidity EI can be estimated as EI=M/κ. The impacts of interfacial bonding efficiency include the moment carrying capacity distribution between pellets and clad and cohesion influence on the flexural rigidity of the surrogate rod system. The result also indicates that the immediate consequences of interfacial de-bonding are a load carrying capacity shift from the fuel pellets to the clad and a reduction of the composite rod flexural rigidity. Therefore, the flexural rigidity of the surrogate rod and the bending moment bearing capacity between the clad and fuel pellets are strongly dependent on the efficiency of interfacial bonding at the pellet–pellet and pellet–clad interfaces. FEA models will be further used to study UNF vibration integrity.
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Segall, A. E., J. R. Hellmann, and R. E. Tressler. "Thermal Shock and Fatigue Behavior of Ceramic Tubes." In ASME 1993 Design Technical Conferences. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/detc1993-0064.
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Abstract A narrow circumferential helium quench was used to thermally shock and fatigue internally heated alumina, reaction bonded, and sintered alpha silicon carbide tubes at 500°C and 1000°C. During these tests, transient temperature measurements required for thermal and stress-profile calculations were obtained through the use of micro-thermocouples positioned along the internal surface of the tubes. Acoustic emissions were also employed for in situ monitoring of crack initiation and propagation of the resident flaw populations during the single and repeated (up to 5) thermal shocks. Post-quench inspections and destructive burst tests were used to correlate the existence, extent, and statistical (Weibull) nature of the damage induced by the cycling. Results indicated progressive strength degradation in alumina tubes with repeated thermal cycles. In contrast, the thermally-cycled silicon carbide samples either showed no damage at all, or suffered minimal progressive strength degradation after the first cycle. In any case, the complex stress distributions computed from an FEA-based inverse heat transfer analysis were required to understand the observed damage (crack paths) and apparent fatigue behavior.
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Hall, Harris J., Bradley D. Davidson, Steven M. George, and Victor M. Bright. "ALD Enabled Nickel MEMS Switches for Digital Logic." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63763.
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CMOS transistor based digital logic technology has delivered spectacular levels of device integration and processing capability since its advent. However, traditional CMOS device performance remains limited in harsh environments, such as high temperature or irradiated environments. Electrostatically actuated MEMS/NEMS switches offer improved performance in these environments. In this work, out-of-plane three terminal microswitches suitable for digital logic are presented. Each switch consists of a suspended fixed-fixed bowtie shaped electroplated nickel beam (300μm × 250μm × ∼2μm) buckled out-of-plane over a 10μm wide gold electrode on a LPCVD nitride coated low resistance Si substrate, which acts as a common gate electrode. Atomic layer deposited (ALD) alumina (100nm thick) is incorporated as a sacrificial layer to keep the fabrication processing low temperature and provide precise gap uniformity across chip. Steady-state I-V performance results are presented showing contact voltages between 17–36V. Mechanical modeling of the beam deformation is performed using commercial FEA software and compared to the actual measured beam response. These devices offer a valid approach for simple MEMS based logic circuitry with proper film stress management and geometry scaling.
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Zhang, Martin Y., Qiong Nian, and Gary J. Cheng. "Deposition of Al-Doped Zinc Oxide by Direct Pulsed Laser Recrystallization at Room Temperature on Various Substrates for Solar Cell Applications." In ASME 2012 International Manufacturing Science and Engineering Conference collocated with the 40th North American Manufacturing Research Conference and in participation with the International Conference on Tribology Materials and Processing. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/msec2012-7381.
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In this study, a method combining room temperature pulsed laser deposition (PLD) and direct pulsed laser recrystallization (DPLR) are introduced to deposit superior transparent conductive oxide (TCO) layer on low melting point flexible substrates. As an indispensable component of thin film solar cell, TCO layer with a higher quality will improve the overall performance of solar cells. Alumina-doped zinc oxide (AZO), as one of the most promising TCO candidates, has now been widely used in solar cells. However, to achieve optimal electrical and optical properties of AZO on low melting point flexible substrate is challenging. Recently developed direct pulsed laser recrystallization (DPLR) technique is a scalable, economic and fast process for point defects elimination and recrystallization at room temperature. It features selective processing by only heating up the TCO thin film and preserve the underlying substrate at low temperature. In this study, 250 nm AZO thin film is pre-deposited by pulsed laser deposition (PLD) on flexible and rigid substrates. Then DPLR is introduced to achieve a uniform TCO layer on low melting point flexible substrates, i.e. commercialized Kapton polyimide film and micron-thick Al-foil. Both finite element analysis (FEA) simulation and designed experiments are carried out to demonstrate that DPLR is promising in manufacturing high quality AZO layers without any damage to the underlying flexible substrates. Under appropriate experiment conditions, such as 248 nm in laser wavelength, 25 ns in laser pulse duration, 15 laser pulses at laser fluence of 25 mJ/cm2, desired temperature would result in the AZO thin film and activate the grain growth and recrystallization. Besides laser conditions, the thermal conductivity and crystallinity of the substrate serve as additional factors in the DPLR process. It is found that the substrate’s thermal conductivity correlates positively with the AZO crystal size; the substrate’s crystallinity correlates positively with the AZO film’s crystallinity. The thermal expansion of substrate would also contribute to the film tensile stress after processed by DPLR technique. The overall results indicate that DPLR technique is useful and scalable for flexible solar cell manufacturing.