898 resultados para bubble attraction and coalescence
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El presente trabajo tiene como objetivo mostrar y analizar las relaciones fronterizas entre indígenas, cronistas, viajeros y agentes del gobierno de Buenos Aires en el período de 1870 a 1880. Se prestará especial atención a las vinculaciones entre estos "mundos" a partir de los viajes que realizó Moreno a los toldos del cacique Valentín Sayhueque y su comunidad en las regiones aledañas al Lago Nahuel Huapi. No se descarta la influencia de otros cronistas de época (Cox y Musters) como tampoco la impronta de personajes centrales en el contexto (Zeballos y Roca). Los viajeros que recorrieron la Patagonia dejaron testimonios claves para comprender el proceso que se dio entre las sociedades indígenas y el Estado nacional argentino a fines del siglo XIX. Su análisis a través de una mirada crítica da la pauta de cómo las sociedades nativas fueron observadas y estudiadas desde el gobierno de Buenos Aires y países extranjeros. La actual Patagonia fue un punto de atracción (y lo sigue siendo), para muchos individuos que no conocen el lugar. Su naturaleza, paisaje, vegetación eran únicos y muy atractivos. Sus tierras eran habitadas por sujetos que no tenían las mismas formas de vida que el resto de las regiones del momento. Habían desarrollado costumbres, formas de comunicación, comercio e intercambio, relaciones sociales, festividades. Cronistas como Francisco Moreno son nodales para adentrarnos al mundo nativo desde otro ángulo, ya que nos muestra las relaciones en el espacio de frontera y los propósitos del gobierno de Buenos Aires en el momento de las campañas militares. Desde el punto de vista metodológico se ha recurrido a la Etnohistoria para abordar nuestro problema desde una óptica diferente y alimentando la investigación en curso
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In a previous paper, Hoornaert et al. (Powder Technol. 96 (1998); 116-128) presented data from granulation experiments performed in a 50 L Lodige high shear mixer. In this study that same data was simulated with a population balance model. Based on an analysis of the experimental data, the granulation process was divided into three separate stages: nucleation, induction, and coalescence growth. These three stages were then simulated separately, with promising results. it is possible to derive a kernel that fit both the induction and the coalescence growth stage. Modeling the nucleation stage proved to be more challenging due to the complex mechanism of nucleus formation. From this work some recommendations are made for the improvement of this type of model.
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O marketing de relacionamento como ferramenta para atrair e fidelizar os alunos do ensino superior privado é o tema desta pesquisa. Trata-se de um estudo de caso múltiplo incorporado enfocando a Universidade Metodista de São Paulo (UMESP) e a Universidade Metodista de Piracicaba (UNIMEP) e que tem como objetivos principais apontar fatores que motivam os estudantes a escolher determinadas instituições de ensino superior, identificar a maneira como elas atuam na tarefa de atraí-los com vistas a estabelecer um relacionamento e uma comunicação eficientes com esses públicos de interesse e fidelizálos, bem como analisar a real efetividade das ações desenvolvidas pelas IESs. Propõe-se uma incursão teórica para abordar motivações psicológicas, culturais, econômicas e sociais relacionadas ao ato de consumir e estabelecer uma correlação com o consumidor-aluno . Discutem-se também características do marketing de relacionamento associadas ao contexto educacional e apontam-se dificuldades/desafios vivenciados pelas instituições nos esforços de criar e estreitar os laços com os estudantes com vistas a tornar tais laços duradouros. Foram aplicados 1.400 questionários em ambas as universidades a fim de identificar, entre outros aspectos, atributos desejáveis de uma IES, fatores influenciadores para o abandono dela e características associadas a processos comunicacionais que representam diferenciais. O estudo apontou que, apesar de as dificuldades financeiras serem um componente que interfere na atração e na fidelização dos alunos, outros também são determinantes, como o nível de excelência de ensino, o corpo docente e a qualidade do relacionamento que as instituições de ensino estabelecem com tais públicos. Tal qualidade passa, obrigatoriamente, por atributos como liberdade para expressar ideias, espaço de diálogo e transparência na comunicação, elementos desafiadores ao modelo vigente e estimuladores a um novo fazer educacional.
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A study of the hydrodynamics and mass transfer characteristics of a liquid-liquid extraction process in a 450 mm diameter, 4.30 m high Rotating Disc Contactor (R.D.C.) has been undertaken. The literature relating to this type of extractor and the relevant phenomena, such as droplet break-up and coalescence, drop mass transfer and axial mixing has been revjewed. Experiments were performed using the system C1airsol-350-acetone-water and the effects of drop size, drop size-distribution and dispersed phase hold-up on the performance of the R.D.C. established. The results obtained for the two-phase system C1airso1-water have been compared with published correlations: since most of these correlations are based on data obtained from laboratory scale R.D.C.'s, a wide divergence was found. The hydrodynamics data from this study have therefore been correlated to predict the drop size and the dispersed phase hold-up and agreement has been obtained with the experimental data to within +8% for the drop size and +9% for the dispersed phase hold-up. The correlations obtained were modified to include terms involving column dimensions and the data have been correlated with the results obtained from this study together with published data; agreement was generally within +17% for drop size and within +14% for the dispersed phase hold-up. The experimental drop size distributions obtained were in excellent agreement with the upper limit log-normal distributions which should therefore be used in preference to other distribution functions. In the calculation of the overall experimental mass transfer coefficient the mean driving force was determined from the concentration profile along the column using Simpson's Rule and a novel method was developed to calculate the overall theoretical mass transfer coefficient Kca1, involving the drop size distribution diagram to determine the volume percentage of stagnant, circulating and oscillating drops in the sample population. Individual mass transfer coefficients were determined for the corresponding droplet state using different single drop mass transfer models. Kca1 was then calculated as the fractional sum of these individual coefficients and their proportions in the drop sample population. Very good agreement was found between the experimental and theoretical overall mass transfer coefficients. Drop sizes under mass transfer conditions were strongly dependant upon the direction of mass transfer. Drop Sizes in the absence of mass transfer were generally larger than those with solute transfer from the continuous to the dispersed phase, but smaller than those with solute transfer in the opposite direction at corresponding phase flowrates and rotor speed. Under similar operating conditions hold-up was also affected by mass transfer; it was higher when solute transfered from the continuous to the dispersed phase and lower when direction was reversed compared with non-mass transfer operation.
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The literature relating to the extraction of the aromatics, benzene, toluene and xylene (BTX) using different commercial solvents, and to mixer-settler design and performance, has been reviewed. Liquid-liquid equilibria of the ternary systems: hexane-benzene-sulfolane, n-heptane-toluene-sulfolane, and octane-xylene-sulfolane were determined experimentally at temperatures of 30oC, 35oC, and 40oC. The work was then extended to a multicomponent system. The data were correlated by using Hand's method and were found to be in a good agreement with theoretical predictions using the UNIFAC method. A study was made of the performance of a 10-stage laboratory mixer-settler cascade for the extraction of BTX from a synthetic reformate utilizing sulfolane as a solvent. Murphree stage efficiency decreased with stage number but 99% extraction was achievable within 4 stages. The effects of temperature, phase ratio, and agitator speed were investigated. The efficiency increased with agitator speed but > 1050 rpm resulted in secondary haze formation. An optimum temperature of 30oC was selected from the phase equilibria; the optimum solvent: feed ratio was 3:1 for 4 stages. The experimental overall mass transfer coefficients were compared with those predicted from single drop correlations and were in all cases greater, by a factor of 1.5 to 3, due to the surface renewal associated with drop break-up and coalescence promoted by agitation. A similar investigation was performed using real reformate from the Kuwait Oil Company. The phase ratios were in the range 0.5 to 1 to 3.25 to 1, the agitator speed 1050 rpm, and the operating temperature 30oC. A maximum recovery of 99% aromatics was achieved in 4 stages at a phase ratio of 3.25 to 1. A backflow model was extended to simulate conditions in the mixer-settler cascade with this multicomponent system. Overall mass transfer coefficients were estimated by obtaining the best fit between experimental and predicted concentration profiles. They were up to 10% greater than those with the synthetic feed but close agreement was not possible because the distribution coefficient and phase ratio varied with stage number. Sulfolane was demonstrated to be an excellent solvent for BTX recovery and a mixer-settler cascade was concluded to be a technically viable alternative to agitated columns for this process.
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The mechanisms by which drops of secondary liquid dispersion ie. <100μ m, are collected, coalesced and transferred have been studied in particulate beds of different sizes and heights of glass ballotini. The apparatus facilitated different coalescer cell arrangements. The liquid-liquid system was toluene/de-ionised water. The inlet drop size distribution was measured by microscopy and using the Malvern Particle Size analyser; the outlet dispersion was sized by photography. The effect of packed height and packing size upon critical velocity, pressure drop and coalescence efficiency have been investigated. Single and two phase flow pressure drops across the packing were correlated by modified Blake-Kozeny equations. Two phase pressure drop was correlated by two equations, one for large ballotini sizes (267μm - 367μm), the other for small ballotini sizes (93μm- 147.5μm). The packings were efficient coalescers up to critical velocities of 3 x 10-2 m/s to 5 x 10-2 m/s. The saturation was measured across the bed using relative permeability and a mathematical model developed which related this profile to measured pressure drops. Filter coefficients for the range of packing studied were found to be accurately predicted from a modified queueing drop model.
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The literature relating to sieve plate liquid extraction columns and relevant hydrodynamic phenomena have been surveyed. Mass transfer characteristics during drop formation, rise and coalescence, and related models were also reviewed. Important design parameters i.e. flooding, dispersed phase hold-up, drop size distribution, mean drop size, coalescence/flocculation zone height beneath a plate and jetting phenomena were investigated under non-mass transfer and mass transfer conditions in a 0.45m diameter, 2.3m high sieve plate column. This column had provision for four different plate designs, and variable plate spacing and downcomer heights, and the system used was Clairsol `350' (dispersed) - acetone - deionised water (continuous) with either direction of mass transfer. Drop size distributions were best described by the functions proposed by Gal-or, and then Mugele-Evans. Using data from this study and the literature, correlations were developed for dispersed phase hold-up, mean drop size in the preferred jetting regime and in the non-jetting regime, and coalescence zone height. A method to calculate the theoretical overall mass transfer coefficient allowing for the range of drop sizes encountered in the column gave the best fit to experimental data. This applied the drop size distribution diagram to estimate the volume percentage of stagnant, circulating and oscillating drops in the drop population. The overall coefficient Kcal was then calculated as the fractional sum of the predicted individual single drop coefficients and their proportion in the drop population. In a comparison between the experimental and calculated overall mass transfer coefficients for cases in which all the drops were in the oscillating regime (i.e. 6.35mm hole size plate), and for transfer from the dispersed(d) to continuous(c) phase, the film coefficient kd predicted from the Rose-Kintner correlation together with kc from that of Garner-Tayeban gave the best representation. Droplets from the 3.175mm hole size plate, were of a size to be mainly circulating and oscillating; a combination of kd from the Kronig-Brink (circulating) and Rose-Kintner (oscillating) correlations with the respective kc gave the best agreement. The optimum operating conditions for the SPC were identified and a procedure proposed for design from basic single drop data.
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Experiments on drying of moist particles by ambient air were carried out to measure the mass transfer coefficient in a bubbling fluidized bed. Fine glass beads of mean diameter 125?µm were used as the bed material. Throughout the drying process, the dynamic material distribution was recorded by electrical capacitance tomography (ECT) and the exit air condition was recorded by a temperature/humidity probe. The ECT data were used to obtain qualitative and quantitative information on the bubble characteristics. The exit air moisture content was used to determine the water content in the bed. The measured overall mass transfer coefficient was in the range of 0.0145–0.021?m/s. A simple model based on the available correlations for bubble-cloud and cloud-dense interchange (two-region model) was used to predict the overall mass transfer coefficient. Comparison between the measured and predicted mass transfer coefficient have shown reasonable agreement. The results were also used to determine the relative importance of the two transfer regions.
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We have investigated the evolution of radiation damage and changes in hardness of sputter-deposited Cu/V nanolaminates upon room temperature helium ion irradiation. As the individual layer thickness decreases from 200 to 5 nm, helium bubble density and radiation hardening both decrease. The magnitude of radiation hardening becomes negligible for individual layer thickness of 2.5 nm or less. These observations indicate that nearly immiscible Cu/V interface can effectively absorb radiation-induced point defects and reduce their concentrations.
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2000 Mathematics Subject Classification: 62G32, 62G20.
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This manuscript is comprised of three papers that examine the far-reaching and often invisible political outcomes of gender role socialization in the United States. These papers focus primarily on two areas: political confidence amongst girls and women, and the effects of gender on survey measurement and data quality.
Chapter one focuses on political confidence, and the likelihood that women will run for political office. Women continue to be underrepresented at all levels of political leadership, and their lack of political ambition, relative to men, has been identified as a primary cause. In this paper, I explore the relationship between an individual's masculinity and femininity and her development of political ambition. Using original survey data from the 2012 Cooperative Congressional Election Study (CCES), I first empirically demonstrate that gender (masculinity/femininity) and sex (male/female) are unique elements of identity and, moreover, are both independently related to political ambition. I then explore the relevance of gender for the study of candidate emergence, testing whether and how masculinity and femininity might be related to political ambition are supported empirically. While the results suggest that masculinity is positively associated with the development of political ambition, the relationship between femininity and candidate emergence seems to be more complicated and not what prevailing stereotypes might lead us to expect. Moreover, while the relationship between masculinity and political ambition is the same for men and women, the relationship between femininity and political ambition is very different for women than it is for men. This study suggests that gender role socialization is highly related with both men's and women's desire to seek positions of political leadership.
Chapter two continues this exploration of gendered differences in the development of political ambition, this time exploring how social attractiveness and gendered perceptions of political leadership impact the desire to hold political office.Women are persistently underrepresented as candidates for public office and remain underrepresented at all levels of government in the United States. Previous literature suggests that the gendered ambition gap, gender socialization, insufficient recruitment, media scrutiny, family responsibilities, modern campaign strategies, and political opportunity structures all contribute to the gender imbalance in pools of officeholders and candidates. To explain women's reticence to run, scholars have offered explanations addressing structural, institutional, and individual-level factors that deter women from becoming candidates, especially for high positions in the U.S. government. This paper examines a previously unexplored factor: how dating and socialized norms of sexual attraction affect political ambition. This study investigates whether young, single, and heterosexual women's desire for male attention and fear of being perceived as unattractive or "too ambitious" present obstacles to running for office. The results of these experiments suggest that social expectations about gender, attraction and sexuality, and political office-holding may contribute to women's reticence to pursue political leadership. Chapter two is a co-authored work and represents the joint efforts of Laura Lazarus Frankel, Shauna Shames, and Nadia Farjood.
Chapter 3 bridges survey methodology and gender socialization, focusing on how interviewer sex affects survey measurement and data quality. Specifically, this paper examines whether and how matching interviewer and respondent sex affects panel attrition--respondents dropping out of the study after participating in the first wave. While the majority of research on interviewer effects suggests that matching interviewer and respondent characteristics (homophily) yields higher quality data, little work has examined whether this pattern holds true in the area of panel attrition. Using paradata from the General Social Survey (GSS), I explore this question. My analysis reveals that, despite its broader positive effects on data quality, matching interviewer and respondent sex increases likelihood to attrit. Interestingly, this phenomenon only emerges amongst male respondents. However, while assigning female interviewers to male respondents decreases their propensity to attrit, it also increases the likelihood of biased responses on gender related items. These conflicting outcomes represent a tradeoff for scholars and survey researchers, requiring careful consideration of mode, content, and study goals when designing surveys and/or analyzing survey data. The implications of these patterns and areas for further research are discussed.
Together, these papers illustrate two ways that gender norms are related to political outcomes: they contribute to patterns of candidate emergence and affect the measurement of political attitudes and behaviors.
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We report a method of growing site controlled InGaN multiple quantum discs (QDs) at uniform wafer scale on coalescence free ultra-high density (>80%) nanorod templates by metal organic chemical vapour deposition (MOCVD). The dislocation and coalescence free nature of the GaN space filling nanorod arrays eliminates the well-known emission problems seen in InGaN based visible light sources that these types of crystallographic defects cause. Correlative scanning transmission electron microscopy (STEM), energy-dispersive X-ray (EDX) mapping and cathodoluminescence (CL) hyperspectral imaging illustrates the controlled site selection of the red, yellow and green (RYG) emission at these nano tips. This article reveals that the nanorod tips' broad emission in the RYG visible range is in fact achieved by manipulating the InGaN QD's confinement dimensions, rather than significantly increasing the In%. This article details the easily controlled method of manipulating the QDs dimensions producing high crystal quality InGaN without complicated growth conditions needed for strain relaxation and alloy compositional changes seen for bulk planar GaN templates.
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We present measurements of pCO2, O2 concentration, biological oxygen saturation (Delta O2/Ar) and N2 saturation (Delta N2) in Southern Ocean surface waters during austral summer, 2010-2011. Phytoplankton biomass varied strongly across distinct hydrographic zones, with high chlorophyll a (Chla) concentrations in regions of frontal mixing and sea-ice melt. pCO2 and Delta O2 /Ar exhibited large spatial gradients (range 90 to 450 µatm and -10 to 60%, respectively) and co-varied strongly with Chla. However, the ratio of biological O2 accumulation to dissolved inorganic carbon (DIC) drawdown was significantly lower than expected from photosynthetic stoichiometry, reflecting the differential time-scales of O2 and CO2 air-sea equilibration. We measured significant oceanic CO2 uptake, with a mean air-sea flux (~ -20 mmol m-2 d-1) that significantly exceeded regional climatological values. N2 was mostly supersaturated in surface waters (mean Delta N2 of +2.5 %), while physical processes resulted in both supersaturation and undersaturation of mixed layer O2 (mean Delta O2phys = 2.1 %). Box model calculations were able to reproduce much of the spatial variability of Delta N2 and Delta O2phys along the cruise track, demonstrating significant effects of air-sea exchange processes (e.g. atmospheric pressure changes and bubble injection) and mixed layer entrainment on surface gas disequilibria. Net community production (NCP) derived from entrainment-corrected surface Delta O2 /Ar data, ranged from ~ -40 to > 300 mmol O2 m-2 d-1 and showed good coherence with independent NCP estimates based on seasonal mixed layer DIC deficits. Elevated NCP was observed in hydrographic frontal zones and regions of sea-ice melt with shallow mixed layer depths, reflecting the importance of mixing in controlling surface water light and nutrient availability.
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This study addresses the question of attraction and retention of talent in companies that produce engineering projects in the area of oil and natural gas in the city of Natal. The objectives were to identify the mechanisms that these companies use to attract and retain talented professionals and what the relationship between these practices and performance of these organizations in the market. This is a case study of a qualitative nature which were included in the fullness of companies that work in that class in the capital Potiguar. Have been applied to the managers of these companies structured questionnaires with eleven issues orientativas based on theoretical reference adopted. The research finds that managers understand the word "talent", recognize the importance of the appreciation of its employees and the development of their innate abilities to better organizational performance, much due to the fact they are acting in a market of fierce competition. His companies - though not submit the formal procedures related to the subject in question - have mechanisms that can be characterized as the attraction and retention of talent. The relationships identified in this study are consistent with the results found in other studies and put the information here can serve as the basis for that other managers, including other areas, to reach excellence in their respective industries
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A Teoria da Mente (TM) é uma competência cognitiva que permite ao individuo reconhecer os seus próprios estados mentais bem como o das outras pessoas. Trata-se de uma capacidade que se desenvolve desde os primeiros meses de vida até à idade escolar e que faz com que sejamos capazes de compreender e antecipar o comportamento do outro: compreender os sentimentos, pensamentos, crenças, desejos e intenções (ver glossário). É a TM que permite ao indivíduo compreender o contexto social em que está inserido, demonstrando comportamentos sociais adequados. A linguagem está intimamente relacionada com a TM, nomeadamente com a capacidade de compreender falsas crenças, expressões idiomáticas, duplos sentidos e ironias (marcadores ao nível do seu desenvolvimento). A semântica e a sintaxe (sob ponto de vista expressivo e recetivo) têm um papel fulcral na compreensão dos estados mentais. É nesta relação entre TM, Competências Sociais (CS) e linguagem que se enquadra a presente investigação. Esta teve como objetivos analisar a relação existente entre TM e CS em crianças com desenvolvimento neurotípico, bem como a sua relação existente entre fatores sociais e demográficos, comparar a perceção dos pais e professores sobre as CS e analisar algumas variáveis preditoras da TM. Para isso, constituiu-se uma amostra de 103 crianças de ambos os sexos (54 do sexo feminino e 49 do sexo masculino) com idades compreendidas entre os 6 e os 9 anos com desenvolvimento neurotípico que frequentassem o 1º ciclo do ensino básico. Para a recolha de dados, os encarregados de educação preencheram um questionário sobre dados socio – demográficos e o questionário de CS (também preenchidos pelo professores). As competências de TM foram avaliadas através duas sequências do Teste Doctor Martin – Brune. Esta investigação encontrou correlações efetivas entre competências de TM e CS, nomeadamente nos domínios do altruísmo, iniciação e orientação pró – social bem como na reciprocidade. Tal como se esperava após a revisão bibliográfica, encontraram-se correlações entre alguns fatores sociais e demográficos, TM e CS ainda que alguns resultados tenham sido inconclusivos. De qualquer forma, verificou-se a existência de relações com a idade, escolaridade, número de irmãos, idade dos irmãos, escolaridade e idade dos pais. Os resultados acerca da perceção de pais e professores acerca das CS da criança foram igualmente curiosos e passiveis de nova investigação: as CS nos diferentes contextos em que a criança se insere e a avaliação que diferentes interlocutores fazem das suas competências. Foram encontradas correlações positivas entre CS e alguns fatores socio – demográficos anteriormente referidos pela investigação (escolaridade da mãe, número de irmãos, idade, anos de escolaridade). No entanto, outros fatores surgiram como estando relacionados (fatores relacionados com o pai) sem que exista mais informação acerca destes dados. Os resultados demonstraram também que os pais avaliam as CS dos filhos de modo superior aos professores no que se refere à orientação pró – social e iniciação social, mas inferior no domínio do altruísmo. De acordo com o Teste de Pearson, existem correlações positivas entre a avaliação realizada pelos pais e professores no que diz respeito à orientação pró – social, iniciação social e altruísmo bem como no total do Questionário. Todavia, é fundamental continuar a desenvolver estudos nesta área de investigação tendo em consideração a pouca informação existente acerca de algumas variáveis, nomeadamente, em relação ao papel do pai no desenvolvimento da TM.