Orientador : Artur Zaghini Francesconi / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Quimica / Made available in DSpace on 2018-07-16T17:50:40Z (GMT). No. of bitstreams: 1 Zemp_RogerJosef_M.pdf: 2975260 bytes, checksum: 2981ef34797c721c113592c27bf0622f (MD5) Previous issue date: 1989 / Resumo: O objetivo deste trabalho consiste no desenvolvimento, construção e teste de um ebuliômetro para estudos do comportamento de equilíbrio líquido-vapor de sistemas salinos (efeito salino). O ebuliômetro proposto possui a característica de permitir a recirculação de ambas as fases, líquido e vapor condensado, por apresentar um dispositivo denominado de bomba COTTRELL. Uma revisão da literatura pertinente mostrou que entre os equipamentos normalmante utilizados no estudo do efeito salino nenhum apresenta tal dispositivo, nem a recirculação da fase líquida. O equipamento é totalmente construído em vidro, possibilitando o estudo do comportamento de equilíbrio de fases em condições de pressão de 0,10 a 1,5 Bar, e temperaturas variando de 300 a 450 K. O desempenho do ebuliômetro foi testado com a determinação da curva de pressão de vapor do etanol (0,12 a 1,40 Bar), e da coleta de dados de equilíbrio para oa sistema ciclohexano/tolueno, sob condições isobáricas (1,0133 Bar) e isotérmicas (323,15 K). Os resultados foram comparados com dados da literatura. Como sistema salino foi escolhido o sistema etanol/água/acetato de potássio, devido principalmente ao número de publicações com dados a respeito deste sistema. Os dados de equilíbrio foram obtidos a 1,0133 Bar, em toda a faixa de composição dos solventes, para diferentes composi~ões fixas de sal. Os resultados foram comparados com os dados encontrados na literatura, e mostram um pequeno desvio negativo na composição da fase vapor, mas um desvio significante nas temperaturas, cujos valores na literatura estão acima dos determinados experimentalmente Esta diferença pode ser explicada devida à presença de uma bomba Cottrell, que possibilita a determinação exata da temperatura de equilíbrio. O desempenho do ebuliômetro foi considerado como satisfatório. / Abstract: The purpose of this work concerns with the development, construction and testing of a liquid-vapor equilibrium still, in order to study the Iiquid-vapor equilibrium behavior of salt solutions (salt effect) The proposed still has the caracteristic of permitting the recirculation of both the liquid phase and the condensed vapor phase, due to the existence of a Cottrell pump. A review of the pertinent literature shows that none of the usually employed equilibrium stills for salt effect measurements possesses such a device, there for not making impossible the recirculation of the liquid phase. The still is alI made of g1ass, permitting operational conditions from 0,10 to 1,5 Bar, and from 300 to 450 K. The performance of the still was tested -with the measurement of the vapor pressure curve of etanol (from 0,12 to 1,40 Bar), and the measurement of the liquid-vapor equilibrium curve of the system cyclohexane/toluene, at isobaric (1,0133 Bar) and isotermic (323,15 K) conditions. The results were compared to literature data. The system ethanol/water/potassium acetate was choosen as the salt system due to the number of available literature data. Salt solution liquid-vapor data was collected at 1,0133 Bar, in the whole range of solvent composition, for different salt concentrations. The results were. Compared with literature data, and they show a slight negative deviation in the vapor composition, but a significant difference in the temperature measurement, as the literature data reports them higher than those measured experimentally. These differences may be accounted by the Cottrell Pump measurement. The performance of the proposed still was considered satisfactory. / Mestrado / Mestre em Engenharia Química

Orientador : Isaias de Carvalho Macedo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Campinas / Made available in DSpace on 2018-07-17T18:02:48Z (GMT). No. of bitstreams: 1 HernandezMendoza_OscarSaul_D.pdf: 14723627 bytes, checksum: 41090d87e984ba2964bf54fbff696205 (MD5) Previous issue date: 1982 / Resumo: Foi desenvolvido, construído e testado, um protótipo gerador de água quente e vapor para uso industrial, com características apropriadas para testes de operação manual ou automática. Estuda-se o efeito que materiais, dimensões e fluxos de massa tem sobre o comportamento transiente dos componentes de um sistema indireto solar de geração de água quente ou vapor para usos na indústria. Desenvolve-se uma metodologia para a análise da operação transiente deste tipo de sistemas, utilizando um modelo matemático que simula com precisão aceitável o comportamento real do sistema simulando o comportamento do sistema minuto a minuto. Os resultados deste estudo fornecem relações gerais entre o tamanho do campo coletor, a massa necessária no armazenador e o fluxo de massa especifica através do campo coletor / Abstract: Not informed. / Doutorado / Doutor em Engenharia Mecânica

Orientador: Saul Gonçalves D'Avila / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-07-18T08:51:33Z (GMT). No. of bitstreams: 1 CardozoFilho_Lucio_M.pdf: 2811103 bytes, checksum: 47a69ac6d61b82683922d94e0fb1ed9b (MD5) Previous issue date: 1993 / Resumo: Neste trabalho foi explorada a potencialidade do método de contribuição de grupos ASOG aplicado ao equilíbrio de fases, abordando-se três tópicos: Estudo comparativo dos desempenos dos métodos ASOG/ELV e INIFAC/ELV aplicando ao equilíbrio líquido-vapor (ELV); Obtenção de novos parâmetros ASOG/ELV contribuindo para diminuir as lacunas na atual matriz; Extensão da aplicabilidade do método ASOG/ELV ao equilíbrio líquido-líquido (ELL). Usando as versões mais recentes das matrizes ELV dos métodos ASOG e UNIFAC, verificou-se que ambos apresentarem desempenhos equivalentes em cálculos de ponto de bolha e orvalho de misturas binárias. A potencialidade do método ASOG/ELL na predição de dados de equilíbrio líquido-líquido foi demonstrada, determinando-se parâmetros de interação entre sete grupos estruturais, incluindo o grupo H2O. Foi verificada a adequação do método na predição de sistemas comumente encontrados em equipamentos industriais envolvendo água, hidrocarbonetos, álcoois e ésteres. Foi observado que o método ASOG/ELL apresenta resultados equivalentes aos do método ASOG/ELL em cálculos de equilíbrio de misturas binárias, ternárias e quaternárias / Abstract: In this work the potentially of the ASOG group contribution method was explores when applied to phase equilibrium comprehending three topics: A comparative study of the performace of the ASOG/VLE and UNIFAC/VLE methods apllied to liquid-vapor equilibrium (VLE); Acquisition of news ASOG/VLE parameters helping to reduce the gaps in the present parameter matrix; Extension of the applicability of the ASOG/VLE method liquid-liquid equilibrium (LLE). Using more recent versions of the VLE matrix of the ASOG and UNIFAC methods, both showed equivalent performances concerning the prediction of the bubble and dew points for binary mixtures. The potentiality of the ASOG/LLE method to predict liquid-liquid equilibrium data was demonstrated determining interaction parameters among seven structural groups, including the H2O group. The metod adequacy for prediction of system usually found in industries was verified, covering water, hydrocarbon, alcohol end ester. It was observed, that the ASOG/LLE gives results equivalent to those of the UNIFAC/LLE method for equilibrium calculations of binary, ternary and quaternary mixtures / Mestrado / Mestre em Engenharia Química

Orientador : Saul G. d'Avila / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-07-18T11:57:42Z (GMT). No. of bitstreams: 1 Medeiros_SilvioDinizde_M.pdf: 3157996 bytes, checksum: 875685e0d9a4ea8ccee8b2dd4ef8c77e (MD5) Previous issue date: 1993 / Resumo: Uma nova relação P-V-T do tipo cúbica é proposta para o cálculo de propriedades termodinâmicas de substâncias puras e de sistemas multicomponentes em condições de equilíbrio líquido-vapor, na faisã de baixa e alta pressão, incluindo a região critica. A forma genérica da nova relação, assim como a equação de van der Waals, é expressa em termos da soma de um termo repulsivo e de um termo atrativo. P = 'P IND. rep¿ + 'P IND. at¿ . A correlação foi desenvolvida substituindo-se o termo repulsivo da equação de van der Waals (1873), por outro oriundo da aplicação do Modelo de Esferas Rígidas. A aplicação da nova correlação em cálculos computacionais é bastante prática, devido a sua estrutura simples e ao pequeno tempo envolvido em resolução numérica. Nas aplicações envolvendo componentes puros, por exemplo, basta que se disponha dos valores de suas temperatura e pressão críticas, além dos parâmetros ajustáveis par a cálculo das constantes 'alfa¿ e 'beta¿. Nos problemas envolvendo misturas, adicionalmente são necessárias duas constantes de interação binária. A nova correlação se aplica a sistemas com componentes subscríticos ou supercríticos, polares ou não polares. A equação apresentou bons resultados na predição de propriedades termodinâmicas, tais como pressão de vapor, volume molares de líquido e de vapor, e entalpias de substâncias puras ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital / Abstract: A new cubic P-V-T relation is proposed in order to calculate thermodynamic properties of purê components and multicomponent system in conditions of vapor-liquid equilibria,. The ralation is suitable for applicatios to system involving non-polar and polar compounds. The new equation also predicts both the low and high prossure ranges of the equilibrium diagram, including the critical region. The general form of the new ralation, as in the van der Waals equation is expressed in terms of the summation of a repulsive term and an attractive term. P = 'P IND. rep¿ + 'P IND. att¿. The correlation was develop changing the repulsive term of van der Waals equation (1873) for another derived from the Hard Sphere Model. The application of the proposed correlation to computer calculations proved to be specially useful due to its simplicity, short cmputation time and reliability. In applications envolving pure components, only critical temperature, pressure, and fitted interactions are necessary. For mixture calculations, two binary interactions constant are also required. The new equation can be applied to system with polar or non-polar component, in subcritical conditions. Its has been shown that good results are obtained in prediction thermodynamic properties such as vapor pressure, liquid and vapor densities, and enthalpies of pure compnent ...Note: The complete abstract is available with the full electronic digital thesis or dissertations / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Memoria para optar al título de Ingeniero Civil Mecánico / En el año 2017, las energías renovables mostraron un crecimiento del 49% en la matriz energética mundial, siendo la tecnología solar fotovoltaica la tecnología con mayor crecimiento en el año. Con respecto a la tecnología solar térmica, el crecimiento se ha visto estancado desde el año 2013. De la capacidad instalada a nivel mundial, 99% corresponde a sistemas térmicos para uso domiciliario y calentamiento de piscinas, siendo prácticamente nula su participación en procesos industriales, a baja o mediana temperatura. Dentro de los esfuerzos por desarrollar colectores más eficientes, en 2008, Gerardo Diaz presentó un nuevo diseño de colector solar utilizando tubos de minicanales como absorbedor solar. Diversos estudios han demostrado que este colector presenta una eficiencia superior que los colectores utilizados comúnmente a baja temperatura. Van Doung en 2015 investigó la aplicación a mediana temperatura de estos colectores para su integración con procesos industriales, encontrando resultados poco alentadores para un diseño sin concentración solar. En este trabajo se presenta un nuevo diseño de colector solar de minicanales, integrando los tubos de minicanales con un sistema de concentración solar tipo lineal Fresnel para su aplicación a mediana temperatura. En el trabajo se describe el proceso de diseño del concentrador, receptor y el absorbedor de minicanales, y se desarrolla un modelo óptico y un modelo termodinámico para estudiar la operación del colector. Ambos modelos fueron validados utilizando referencias comerciales o resultados experimentales en la literatura. Dentro de los principales resultados, se observa que bajo las mismas condiciones de operación que los colectores Fresnel comerciales, el colector Fresnel con minicanales produce un 26% más de potencia térmica por unidad de área de captación, alcanzando 702,2 W/m^2. Debido a la mayor superficie de absorción del absorbedor y la geometría del receptor, la eficiencia óptica alcanza un valor de 0,934, siendo un 50% mayor que los colectores Fresnel comerciales. Sin embargo, ya que el absorbedor de minicanales no se encuentra al vacío, las pérdidas térmicas son 12 veces mayores que en un tubo evacuado convencional. Con respecto a la generación de vapor, un módulo del colector de 6 metros de largo, con una radiación de 900 W/m^2, alcanza un título de vapor de 0,12, produciendo 31,7 kg. de vapor por hora. Se concluye que integrar un absorbedor de tubos de minicanales a un colector lineal Fresnel mejora la eficiencia óptica del colector, alcanzando una potencia térmica superior que los modelos comerciales. Adicionalmente, gracias a la concentración solar se demuestra la factibilidad de utilizar tubos de minicanales para la generación de calor a mediana temperatura, incluyendo la generación directa de vapor.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention owing to their unique electrical, optical, mechanical, and thermal properties not found in their 3D counterparts. They can be obtained by mechanical, chemical, or electrochemical exfoliation. However, these strategies lack uniformity and produce defect-rich samples, making it impossible for large-scale device fabrication. Chemical vapor deposition (CVD) method emerges as the viable candidate to create atomically thin specimens at the technologically relevant scale. However, the large-scale growth of monolayer TMD films with spatial homogeneity and high electrical performance remains an unsolved challenge. The spatial inhomogeneity and the associated grain boundaries between randomly oriented domains culminate to the deleterious quality of TMDs, breaking of the long-range crystalline periodicity and introduction of insidious strain. Recent research efforts have therefore dedicated to obtaining the single crystallinity of 2D materials by controlling the orientation and dimensionality to obtain a large-scale and grain boundary-free monolayer films for Si-comparable electron mobility and overcoming the scaling limitation of traditional Si-based microelectronics,. In the first part of this thesis, orientation and dimensionality controlling of TMDs are discussed. To this end, we systematically study the growth of stereotypical molybdenum disulfide (MoS2) monolayer on a c-plane sapphire with CVD to elucidate the factors controlling their orientation. We have arrived at the conclusion that the concentration of precursors- that is, the ratio between sulfur and molybdenum oxide, plays a key role in the size and orientation of seeds, subsequently controlling the orientation of MoS2 monolayers. Later, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer, and single-crystalline MoS2 nanoribbons on β-gallium (iii) oxide (β-Ga2O3) (100) substrates. LDE MoS2 nanoribbons have spatial uniformity over a long-range and transport characteristics on par with those seen in exfoliated benchmarks. In the second part, we theoretically reveal and experimentally determine the origin of resonant modulation of contrast as a result of the residual 3-fold astigmatism in modern scanning transmission electron microscopy (STEM) and its unintended impact on violating the power-law dependence of contrast on coordination modes between the transition metal and chalcogenide atoms.

Ingeniero Civil Mecánico / Los sistemas de calefacción representan una de las principales fuentes de consumo energético a nivel doméstico. Por ello surge la necesidad de buscar sistemas de elevada eficiencia y que no estén asociados a la generación de gases contaminantes. Una bomba de calor resulta una opción favorable pues su alta eficiencia se basa en un funcionamiento como transportador de calor, y no a través de una conversión directa. En particular, durante el invierno, las temperaturas máximas que se presentan en Santiago no superan los 20 $[^\circ C]$ y las temperaturas mínimas llegan a ser menores a los 4 $[^\circ C]$, presentando una alta demanda de calefacción durante este periodo. A su vez, debido a las bajas temperaturas, el uso que se hace de una piscina es casi nulo. En este contexto, el objetivo de la presente Memoria fue evaluar, en términos termodinámicos y económicos, la configuración de un sistema de calefacción a través de una bomba de calor, considerando una piscina como fuente de calor. Dentro de la literatura, se han investigado extensamente este tipo de sistemas, tanto a nivel de modelación del ciclo de compresión de vapor como de instalaciones térmicas de bombas de calor. Sin embargo, no se han presentando investigaciones que cuantifiquen el desempeño ni factibilidad económica de una instalación de características similares y que, además, considere las fluctuaciones de las condiciones ambientales a lo largo del periodo de invierno. Un modelo que captura este comportamiento transiente fue desarrollado utilizando la plataforma TRNSYS, para las localidades de Concepción, Santiago y Valparaíso. Por su parte, se empleó el programa EES para modelar el comportamiento en estado estacionario de la bomba de calor. Se propone un análisis termodinámico y económico para evaluar el desempeño termodinámico y los potenciales beneficios, en términos de ahorro, de la configuración. Los resultados muestran un rendimiento bajo de la configuración, en términos del COP, respecto a su valor nominal, debido a las bajas temperaturas que alcanza la piscina. Debido a esto, la configuración presenta ahorros cuando la demanda de calefacción es alta, la cual depende del área superficial de la vivienda y las condiciones ambientales de la localidad. Las dimensiones de la piscina, por su parte, influyen principalmente en el ratio de la capacidad de calefacción de la bomba de calor respecto a su valor nominal, pero no en el rendimiento de la configuración. Se concluye que se presentan ahorros a partir de tamaños de vivienda mayores a los 310 $[m^2]$ en las ciudades de Concepción y Santiago, con una capacidad de calefacción nominal de 14 $[kW]$ como la mejor alternativa entre las analizadas. En ese contexto, cabe mencionar que la entalpía de fusión del agua de la piscina no fue considerada y el modelo de vivienda y radiador posee un nivel de modelación simple.

Airborne measurements of the downward spectral solar irradiance were analyzed with differential optical absorption spectroscopy for the integrated water vapor (IWV) in the atmospheric column above the aircraft. The measurements are obtained from two campaigns in 2016, during which the High Altitude and Long Range Research Aircraft (HALO) took measurements of the downward solar irradiance within the upper troposphere and lower stratosphere (UTLS). The feasibility and limitations of the presented method are discussed for the dry conditions, which are typical for the high altitudes of the UTLS and above. Considering the uncertainties encountered in the irradiance measurements and the high sensitivity of the retrieval, the method was unable to provide sound results for the stratosphere, but provided reasonable results in the troposphere. / Flugzeuggetragene Messungen der abwärtsgerichteten spektralen solaren Irradianz wurden mit der Methode der differenziellen optischen Absorptionsspektroskopie auf den integrierten Wasserdampf (IWV) in der Atmosphäre oberhalb des Flugzeuges untersucht. Im Rahmen zweier Messkampagnen im Jahr 2016 führte das High Altitude and Long Range Research Aircraft (HALO) Messungen der spektralen solaren Irradianz in dem Höhenbereich der oberen Troposphäre und unteren Stratosphäre (UTLS) durch. Hier werden das Potential und die Limitierungen eines solchen Verfahrens untersucht, um Wasserdampf in den trockenen Gegebenheiten abzuleiten, die in und oberhalb der UTLS herrschen. Angesichts der Messunsicherheiten und der hohen Sensitivität des Verfahrens, konnten in der Statosphäre nicht aussagekräftige Ergebnisse erreicht werden, aber in der Troposphäre konnte das Verfahren zuverlässige Ergebnisse liefern.

The dangers of secondhand smoke (SHS) exposure on the human body were initially reported in 1972, just eight years after the negative effects of smoking on smokers was reported. The Surgeon General of the United States systematically expanded (and continues to expand) the warnings over time, as new scientific evidence becomes available. Warnings, which began to incorporate youths in 1975, emphasized the need to pay particular attention to fetuses, newborns, infants, children, adolescents, and young adults since they rely on parents, guardians, and other adults to keep them safe. Although fewer in number than adults, the diseases that are causally linked to smoking and exposure to SHS in youths are also complex and can result in death (i.e., sudden infant death syndrome). The introduction of new tobacco products, such as low nicotine cigarettes and electronic cigarettes, prompted the Surgeon General to release additional warnings. In 2016, the Surgeon General advised the nation that more information will become available as the electronic cigarette manufacturers comply with new Tobacco Control Act requirements to report harmful vapor constituents. Physicians need to keep abreast of the vast and growing body of knowledge related to the biological and chemical components of SHS and vapor, as well as the dangers that SHS and vapor cause. To ease the burden on physicians, the federal government and medical professional societies created clinical practice guidelines which summarize the literature related to the dangers of SHS and make recommendations for medical management. Guidelines recommend that physicians and other clinicians should offer smoking cessation advice and intervene to limit youth exposure to SHS. Although the approach recommended for use with patients in a physician’s office is clear and attempts to streamline the processes have been made, the identification and counseling process for smoking cessation and eliminating SHS exposure remains time consuming. Barriers to payment make it difficult for physicians to be adequately reimbursed for their efforts to keep their patients safe from the dangers of SHS and vapor exposure. More work is needed to be able to continue to reduce the percentage of youths exposed to SHS in their environments. Additional attention is needed to address the racial and ethnic disparities that are evident in the scientific literature.

Carbon nanotubes exhibit excellent field emission properties and will likely be prime candidates as electron sources in future vacuum electronic applications. Recent research has focused on enhancing field emission from traditional diode-type emitters by adding a gate electrode between the anode and the cathode. Since the gate to cathode (emitter) distance in this triode-type structure is small relative to the anode to cathode distance, this structure allows relatively small gate voltages to significantly enhance or dampen field emission. The key challenge for this research is: synthesizing vertically aligned carbon nanotube field emitters inside arrays of triode-type devices. The most common "top-down", etch-deposit-synthesis method of synthesizing carbon nanotubes inside gated cavities is discussed here, and a novel "bottom-up" method is presented. This new approach bypasses the lithography and wet chemistry essential to the etch-deposit-synthesis method, instead using a dual-beam focused ion beam (FIB) system to mill cavities into a multi-layered substrate. Here the substrate is designed such that the act of milling a hole simultaneously creates the gate structure and exposes the catalyst from which carbon nanotubes can then be grown. Carbon nanotubes are synthesized using plasma enhanced chemical vapor deposition (PECVD) rather than thermal chemical vapor deposition, due to the superior alignment of the PECVD growth. As dual-beam FIB and PECVD can both be largely computerized, this synthesis method is highly reproducible. The dual-beam FIB also permits a high degree of controllability in gate radius, cavity depth and emitter spacing. The effects of a host of PECVD growth parameters (initial catalyst thickness, gas concentration, growth temperature, temperature ramping rate, chamber pressure, and plasma voltage) were characterized so that the morphology of the carbon nanotube emitters could be controlled as well. This "bottom-up" method is employed to construct functional, large area carbon nanotube field emitter arrays (CNT FEAs). The role of the gate layer in field emission is examined experimentally as well as through theoretical models. Field emission testing revealed that increasing gate voltage by as little as 0.3 V had significant impact on the local electric fields, lowering the turn-on and threshold fields by 3.6 and 3.0 V/µm, respectively, and increasing the field enhancement factor from 149 to 222. A quantum mechanical model of such triode-type field emission indicates that the local electric field generated by a negatively or positively biased gate directly impacts the tunneling barrier thickness and thus the achievable emission current. However, the geometry of triode-type devices (gate height, gate radius, emitter density) can influence the degree to which the gate voltage influences field emission. I demonstrate here an effective method of analytically calculating the effect of various such geometric parameters on the field emission. Results show that gate type (the height of the gate relative the emitter tip) can significantly impact the local electric field and hence the type of applications a device is suitable for. Side gates (gate height < emitter height) induced the highest local electric field, while top gates (gate height > emitter height) provided the greatest controllability. For all gate types, increasing the size of the gate opening increased the local electric field by diminishing the gate-emitter screening effect. However, gate voltages were able to enhance or inhibit the local electric field much more readily with smaller gate radii. Due to the strength of gate-emitter field screening in the triode-type structure, the spacing between emitters had virtually no impact on the local electric field, allowing relatively high emitter densities. These theoretical results, combined with a highly controllable synthesis method, provide valuable information and methodology for those designing and optimizing triode-type devices targeted at specific applications.