Academic literature on the topic 'Centrali a vapore'
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Journal articles on the topic "Centrali a vapore"
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Balagizi, Charles M., and Marcello Liotta. "Key Factors of Precipitation Stable Isotope Fractionation in Central-Eastern Africa and Central Mediterranean." Geosciences 9, no. 8 (July 31, 2019): 337. http://dx.doi.org/10.3390/geosciences9080337.
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The processes of isotope fractionation in the hydrological cycle naturally occur during vapor formation, vapor condensation, and moisture transportation. These processes are therefore dependent on local and regional surface and atmospheric physical features such as temperature, pressure, wind speed, and land morphology, and hence on the climate. Because of the strong influence of climate on the isotope fractionation, latitudinal and altitudinal effects on the δ18O and δ2H values of precipitation at a global scale are observed. In this study, we present and compare the processes governing precipitation isotope fractionation from two contrasting climatic regions: Virunga in Central-Eastern Africa and the Central Mediterranean (Stromboli and Sicily, Italy). While Virunga is a forested rainy tropical region located between Central and Eastern Africa, the Mediterranean region is characterized by a rainy mild winter and a dry hot summer. The reported δ18O and δ2H dataset are from precipitation collected on rain gauges sampled either on a monthly or an approximately bimonthly basis and published in previous papers. Both regions show clearly defined temporal and altitudinal variations of δ18O and δ2H, depending on precipitation amounts. The Central Mediterranean shows a clear contribution of local vapor forming at the sea–air interface, and Virunga shows a contribution from both local and regional vapor. The vapor of Virunga is from two competing sources: the first is the continental recycled moisture from soil/plant evaporation that dominates during the rainy season, and the second is from the East African Great Lakes evaporation that dominates during the dry season.
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Langmann, B., K. Sellegri, and E. Freney. "Secondary organic aerosol formation during June 2010 in Central Europe: measurements and modelling studies with a mixed thermodynamic-kinetic approach." Atmospheric Chemistry and Physics Discussions 13, no. 10 (October 15, 2013): 26761–93. http://dx.doi.org/10.5194/acpd-13-26761-2013.
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Abstract. Until recently secondary organic carbon (SOC) aerosol mass concentrations have been systematically underestimated by three-dimensional atmospheric-chemistry-aerosol models. With a newly proposed concept of aging of organic vapours more realistic model results for organic carbon aerosol mass concentrations could be achieved. Applying a mixed thermodynamic-kinetic approach for SOC aerosol formation shifted the aerosol size distribution towards particles in the cloud condensation nuclei size range, thereby emphasising the importance of SOC aerosol formation schemes for modelling realistic cloud and precipitation formation. The additional importance of hetero-molecular nucleation between H2SO4 and organic vapours remains to be evaluated in three-dimensional atmospheric-chemistry-aerosol models. Here a case study is presented focusing on Puy-de-Dôme, France in June 2010. Even though nucleation events at Puy-de-Dôme were rare during the chosen period of investigation a weak event in the boundary layer could be reproduced by the model when nucleation of low-volatile secondary organic vapour is included. Differences in the model results with and without nucleation of organic vapour are visible in the lower free troposphere over several days of the period. Taking into account nucleation of organic vapour leads to an increase in accumulation mode particles due to coagulation of nucleation and aitken mode particles. Moreover, the measurements indicate a considerable increase in SOC aerosol mass concentration during the measurement campaign, which could be reproduced by modelling using a simplified thermodynamic-kinetic approach for SOC aerosol formation and increased biogenic VOC precursor emissions. Comparison with a thermodynamic SOC aerosol formation approach shows a huge improvement in modelled SOC aerosol mass concentration with the thermodynamic-kinetic approach for SOC aerosol formation and a slight improvement of modelled particle size distribution.
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Langmann, B., K. Sellegri, and E. Freney. "Secondary organic aerosol formation during June 2010 in Central Europe: measurements and modelling studies with a mixed thermodynamic-kinetic approach." Atmospheric Chemistry and Physics 14, no. 8 (April 16, 2014): 3831–42. http://dx.doi.org/10.5194/acp-14-3831-2014.
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Abstract. Until recently secondary organic carbon aerosol (SOA) mass concentrations have been systematically underestimated by three-dimensional atmospheric-chemistry-aerosol models. With a newly proposed concept of aging of organic vapours, more realistic model results for organic carbon aerosol mass concentrations can be achieved. Applying a mixed thermodynamic-kinetic approach for SOA formation shifted the aerosol size distribution towards particles in the cloud condensation nuclei size range, thereby emphasising the importance of SOA formation schemes for modelling realistic cloud and precipitation formation. The additional importance of hetero-molecular nucleation between H2SO4 and organic vapours remains to be evaluated in three-dimensional atmospheric-chemistry-aerosol models. Here a case study is presented focusing on Puy-de-Dôme, France in June 2010. The measurements indicate a considerable increase in SOA mass concentration during the measurement campaign, which could be reproduced by modelling using a simplified thermodynamic-kinetic approach for SOA formation and increased biogenic volatile organic compound (VOC) precursor emissions. Comparison with a thermodynamic SOA formation approach shows a huge improvement in modelled SOA mass concentration with the thermodynamic-kinetic approach for SOA formation. SOA mass concentration increases by a factor of up to 6 accompanied by a slight improvement of modelled particle size distribution. Even though nucleation events at Puy-de-Dôme were rare during the chosen period of investigation, a weak event in the boundary layer could be reproduced by the model in a sensitivity study when nucleation of low-volatile secondary organic vapour is included. Differences in the model results with and without nucleation of organic vapour are visible in the lower free troposphere over several days. Taking into account the nucleation of organic vapour leads to an increase in accumulation mode particles due to coagulation and condensational growth of nucleation and Aitken mode particles.
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Ayadi, Houda, Jan Machac, Milan Svanda, Noureddine Boulejfen, and Lassaad Latrach. "Proof of Concept of Reconfigurable Solvent Vapor Sensor Tag with Wireless Power Transfer for IoT Applications." Applied Sciences 12, no. 20 (October 12, 2022): 10266. http://dx.doi.org/10.3390/app122010266.
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In this paper, a concept of a reconfigurable chipless radio frequency identification (RFID) sensor tag for detecting solvent vapors/gas in IoT applications was presented. The concept was based on the authors’ previously published rectangular loop structure equipped with a U-folded dipole loaded with a glide-symmetrical interdigital capacitor coated with a thin layer of tetrasulfonated copper phthalocyanine deposited as a sensing layer to improve the sensing capability in the presence of acetone vapor. In order to further maximize the sensitivity of the designed structure to the desired solvent, a circuit for a central frequency adjustment using a radio frequency varactor diode biased with a wireless power transfer (WPT) was designed. By varying the DC bias of the diode, a continuous tunable range of approximately 200 MHz was achieved. The proposed reconfigurable wireless sensor tag was manufactured and the frequency shift was verified by measurement. The proposed external frequency control can be applied to a wide class of electrical resonators.
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Wang, Weiguo, Hongyi Li, Jian Wang, and Xiaohua Hao. "Water Vapor from Western Eurasia Promotes Precipitation during the Snow Season in Northern Xinjiang, a Typical Arid Region in Central Asia." Water 12, no. 1 (January 2, 2020): 141. http://dx.doi.org/10.3390/w12010141.
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Atmospheric water vapor plays an important role in the water cycle, especially in arid Central Asia, where precipitation is invaluable to water resources. Understanding and quantifying the relationship between water vapor source regions and precipitation is a key problem in water resource research in typical arid Central Asia, Northern Xinjiang. However, the relationship between precipitation and water vapor sources is still unclear of snow season. This paper aimed at studying the role of water vapor source supply in the Northern Xinjiang precipitation trend, which was investigated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. The results showed that the total water vapor contributed from Western Eurasia and the North Polar area presented upward trends similar to the precipitation change trend, which indicated that the water vapor contribution from the two previous water vapor source regions supplied abundant water vapor and maintained the upward precipitation trend from 1980 to 2017 in Northern Xinjiang. From the climatology of water vapor transport, the region was controlled by midlatitude westerlies and major water vapor input from the western boundary, and the net water vapor flux of this region also showed an annual increasing trend. Western Eurasia had the largest moisture percentage contribution to Northern Xinjiang (48.11%) over the past 38 years. Northern Xinjiang precipitation was correlated with water vapor from Western Eurasia, the North Polar area, and Siberia, and the correlation coefficients were 0.66, 0.45, and 0.57, respectively. These results could aid in better understanding the water cycle process and climate change in this typical arid region of Central Asia.
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Brouwers, M. G., and C. W. Ormel. "How planets grow by pebble accretion." Astronomy & Astrophysics 634 (January 30, 2020): A15. http://dx.doi.org/10.1051/0004-6361/201936480.
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Context. Proto-planets embedded in their natal disks acquire hot envelopes as they grow and accrete solids. This ensures that the material they accrete – pebbles, as well as (small) planetesimals – will vaporize to enrich their atmospheres. Enrichment modifies an envelope’s structure and significantly alters its further evolution. Aims. Our aim is to describe the formation of planets with polluted envelopes from the moment that impactors begin to sublimate to beyond the disk’s eventual dissipation. Methods. We constructed an analytical interior structure model, characterized by a hot and uniformly mixed high-Z vapor layer surrounding the core, located below the usual unpolluted radiative-convective regions. Our model assumes an ideal equation of state and focuses on identifying trends rather than precise calculations. The expressions we derived are applicable to all single-species pollutants, but we used SiO2 to visualize our results. Results. The evolution of planets with uniformly mixed polluted envelopes follows four potential phases. Initially, the central core grows directly through impacts and rainout until the envelope becomes hot enough to vaporize and absorb all incoming solids. We find that a planet reaches runaway accretion when the sum of its core and vapor mass exceeds a value that we refer to as the critical metal mass – a criterion that supersedes the traditional critical core mass. The critical metal mass scales positively with both the pollutant’s evaporation temperature and with the planet’s core mass. Hence, planets at shorter orbital separations require the accretion of more solids to reach runaway as they accrete less volatile materials. If the solids accretion rate dries up, we identify the decline of the mean molecular weight – dilution – as a mechanism to limit gas accretion during a polluted planet’s embedded cooling phase. When the disk ultimately dissipates, the envelope’s inner temperature declines and its vapor eventually rains out, augmenting the mass of the core. The energy release that accompanies this does not result in significant mass-loss, as it only occurs after the planet has substantially contracted.
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Michalsky, Joseph J., and Peter W. Kiedron. "Moderate spectral resolution solar irradiance measurements, aerosol optical depth, and solar transmission, from 360 to 1070 nm, using the refurbished rotating shadow band spectroradiometer (RSS)." Atmospheric Measurement Techniques 15, no. 2 (January 24, 2022): 353–64. http://dx.doi.org/10.5194/amt-15-353-2022.
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Abstract. This paper reports on a third-generation rotating shadow band spectroradiometer (RSS) used to measure global and diffuse horizontal plus direct normal irradiances and transmissions at 1002 wavelengths between 360 and 1070 nm. The prism-dispersed spectral data are from the Atmospheric Radiation Measurement (ARM) Southern Great Plains site in north-central Oklahoma (36.605∘ N, 97.486∘ W) and cover dates between August 2009 and February 2014. The refurbished RSS isolates the detector in a vacuum chamber with pressures near 10−7 torr. This prevents the deposition of outgassed vapors from the interior of the spectrometer shell on the cooled detector that affected the operation of the first commercial RSS. Methods for (1) ensuring the correct wavelength registration of the data and (2) deriving extraterrestrial responses over the entire spectrum, including throughout strong water vapor and oxygen bands, are described. The resulting data produced are archived as ARM data records and include cloud-screened aerosol optical depths, spectral irradiances and direct normal solar transmission, as well as normalized diffuse and global irradiances.
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Lamb, Dennis, and Raymond A. Shaw. "Visualizing Vapor Pressure: A Mechanical Demonstration of Liquid–Vapor Phase Equilibrium." Bulletin of the American Meteorological Society 97, no. 8 (August 1, 2016): 1355–62. http://dx.doi.org/10.1175/bams-d-15-00173.1.
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Abstract Water phase transitions are central to climate and weather. Yet it is a common experience that the principles of phase equilibrium are challenging to understand and teach. A simple mechanical analogy has been developed to demonstrate key principles of liquid evaporation and the temperature dependence of equilibrium vapor pressure. The system is composed of a circular plate with a central depression and several hundred metal balls. Mechanical agitation of the plate causes the balls to bounce and interact in much the same statistical way that molecules do in real liquid–vapor systems. The data, consisting of the number of balls escaping the central well at different forcing energies, exhibit a logarithmic dependence on the reciprocal of the applied energy (analogous to thermal energy kBT) that is similar to that given by Boltzmann statistics and the Clausius–Clapeyron equation. These results demonstrate that the enthalpy (i.e., latent heat) of evaporation is well interpreted as the potential energy difference between molecules in the vapor and liquid phases, and it is the fundamental driver of vapor pressure increase with temperature. Consideration of the uncertainties in the measurements shows that the mechanical system is described well by Poisson statistics. The system is simple enough that it can be duplicated for qualitative use in atmospheric science teaching, and an interactive animation based on the mechanical system is available online for instructional use (http://phy.mtu.edu/vpt/).
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Zhou, Yu-shu, Ze-ming Xie, and Xin Liu. "An Analysis of Moisture Sources of Torrential Rainfall Events over Xinjiang, China." Journal of Hydrometeorology 20, no. 10 (October 1, 2019): 2109–22. http://dx.doi.org/10.1175/jhm-d-19-0010.1.
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Abstract Water vapor is a primary rainfall source for the development of torrential rainfall events. By using a Lagrangian flexible particle dispersion model (FLEXPART), the water vapor transports associated with torrential rainfall over Xinjiang, China, during April–September of 2008–15 are examined in this study. The results show that water vapor related to torrential rainfall events is mostly transported by westerly winds. The moisture sources for the development of torrential rainfall over four areas (Altay, Ili Valley, Hami, and Aksu-Kashgar) are mainly from Xinjiang and central Asia. The north Asia area and the Mediterranean/Black/Caspian Sea region are also important contributors to moisture source over the Altay area. Over Ili Valley, both the central Asia area and Xinjiang contribute 40% of water vapor to rainfall sources. Over the Hami area, 70% of the moisture source is from the Xinjiang. Over the Aksu-Kashgar area, the central Asia region is the most important moisture source area.
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Huang, Wei, Song Feng, Jianhui Chen, and Fahu Chen. "Physical Mechanisms of Summer Precipitation Variations in the Tarim Basin in Northwestern China." Journal of Climate 28, no. 9 (May 1, 2015): 3579–91. http://dx.doi.org/10.1175/jcli-d-14-00395.1.
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Abstract The Tarim basin (TB) in northwestern China is one of the most arid regions in the middle latitudes, where water is scarce year-round. This study investigates the variations of summer precipitation in the TB and their association with water vapor fluxes and atmospheric circulation. The results suggest that the variations of summer precipitation in the TB are dominated by the water vapor fluxes from the south and east, although the long-term mean water vapor mostly comes from the west. The anomalous water vapor fluxes are closely associated with the meridional teleconnection pattern around 50°–80°E and the zonal teleconnection pattern along the Asian westerly jet in summer. The meridional teleconnection connects central Asia and the tropical Indian Ocean; the zonal teleconnection resembles the “Silk Road pattern.” The two teleconnections lead to negative height anomalies in central Asia and positive height anomalies in the Arabian Sea and India and in northern central China. The anomalous pressure gradient force, caused by these height anomalies, leads to anomalous ascending motion in the TB and brings low-level moisture along the eastern periphery of the Tibetan Plateau and water vapor from the Arabian Sea passing over the Tibetan Plateau to influence precipitation development in the study region.
Dissertations / Theses on the topic "Centrali a vapore"
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Oliveira, Junior Valter Barbosa de. "Modelagem de central termelétrica a vapor para simulação dinâmica." Universidade Federal do Espírito Santo, 2009. http://repositorio.ufes.br/handle/10/6220.
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Previous issue date: 2009-08-28Centrais termelétricas a vapor são capazes de utilizar biomassa e fazer o reaproveitamento de resíduos agrícolas, resíduos urbanos ou subprodutos industriais para produzir energia elétrica, condicionadas aos seus projetos. Este trabalho tem como objetivos representar, por meio de modelos matemáticos, os principais componentes que constituem o circuito de vapor de uma planta de geração termelétrica a vapor, com foco em caldeira aquatubular, e apresentar uma avaliação dos diversos modelos encontrados na literatura de referência, visando dar suporte ao desenvolvimento de aplicações de simulação dinâmica. Os modelos apresentados abrangem a conversão da energia térmica em energia mecânica e a conversão da energia mecânica em energia elétrica. O conhecimento das características das respostas dinâmicas dos componentes de uma central termelétrica é importante para a análise de estabilidade e para o projeto do sistema de controle. A partir dos modelos dinâmicos do processo é possível a realização de testes de estratégias de controle que, interagindo com os modelos da planta, possibilitem identificar previamente o comportamento dinâmico esperado. Este trabalho também pode ser utilizado como uma referência básica para o desenvolvimento de um simulador com finalidade de treinamento de operadores, cuja aplicação possibilita que seja feita a integração total do operador aos procedimentos operacionais, antes mesmo da partida da planta, ampliando a sua capacidade de aprendizagem
Steam power plants are able to utilize biomass and make the recovering of agricultural residues, urban residues or industrial by-products to produce electric energy, conditioned to its projects. This work aims to represent by means of mathematic modeling the main components that constitute the main steam circuit of a steam power plant, with focus in drum boiler, and to present an analysis of the several models founded at the reference literature, aiming to give support to the development of dynamic simulation applications. The models embrace the conversion of thermal energy in mechanical energy and the conversion of mechanical energy in electric energy. The knowledge of the dynamic response characteristics of power plant components is important for the analysis of stability and control system design. From the dynamic model of process is possible to perform tests of control strategies that, having interaction with the plant models, allow the previous indentifying of its hoped dynamic behavior. This work may be used also as a basic reference to the development of a simulator for operators training purpose, whose application allows the operator to be fully integrated to the operational procedures, before the plant start up, increasing his learning ability
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OLIVEIRA, JUNIOR V. B. "Modelagem de Central Termelétrica à Vapor para Simulação Dinâmica." Universidade Federal do Espírito Santo, 2009. http://repositorio.ufes.br/handle/10/9589.
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Previous issue date: 2009-08-28Centrais termelétricas a vapor são capazes de utilizar biomassa e fazer o reaproveitamento de resíduos agrícolas, resíduos urbanos ou subprodutos industriais para produzir energia elétrica, condicionadas aos seus projetos. Este trabalho tem como objetivos representar, por meio de modelos matemáticos, os principais componentes que constituem o circuito de vapor de uma planta de geração termelétrica a vapor, com foco em caldeira aquatubular, e apresentar uma avaliação dos diversos modelos encontrados na literatura de referência, visando dar suporte ao desenvolvimento de aplicações de simulação dinâmica. Os modelos apresentados abrangem a conversão da energia térmica em energia mecânica e a conversão da energia mecânica em energia elétrica. O conhecimento das características das respostas dinâmicas dos componentes de uma central termelétrica é importante para a análise de estabilidade e para o projeto do sistema de controle. A partir dos modelos dinâmicos do processo é possível a realização de testes de estratégias de controle que, interagindo com os modelos da planta, possibilitem identificar previamente o comportamento dinâmico esperado. Este trabalho também pode ser utilizado como uma referência básica para o desenvolvimento de um simulador com finalidade de treinamento de operadores, cuja aplicação possibilita que seja feita a integração total do operador aos procedimentos operacionais, antes mesmo da partida da planta, ampliando a sua capacidade de aprendizagem.
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Huamán, Esteban Máximo Simón. "Diseño de una turbina de vapor múltiple para una central termoeléctrica." Universidad Nacional de Ingeniería. Programa Cybertesis PERÚ, 1999. http://cybertesis.uni.edu.pe/uni/1999/huaman_em/html/index-frames.html.
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Silva, Ana Teresa Oliveira Santos. "Análise termodinâmica de uma central de biomassa lenhosa." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/9932.
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Dissertação para obtenção do Grau de Mestre em
Engenharia MecânicaPortugal é um país deficitário em fontes de energia não renováveis, mas dispõe de potencialidades significativas no domínio das fontes renováveis, que devidamente aproveitadas podem ajudar a colmatar a deficiência apontada. No caso da biomassa, em particular a de origem florestal, o nosso país tem imensos recursos, pois 38% do território nacional é constituído por florestas. Dispondo deste recurso, o número de centrais termoeléctricas tem vindo a aumentar, embora o rendimento energético seja baixo. Urge assim, um estudo aprofundado que permita conhecer melhor os ciclos termodinâmicos das centrais. A queima da biomassa é difícil, pelo que é importante conhecer certos parâmetros de operação e sua variação ao longo do tempo, de forma a melhorar o rendimento da central. Para tal é necessário modelar o ciclo termodinâmico e fazer uma análise de sensibilidade. É neste âmbito que surge o trabalho de dissertação. Foi feita uma pesquisa e um estudo das técnicas actuais de conversão da biomassa, dos problemas existentes e das características do combustível, em particular do seu teor de humidade e dimensão, que influenciam a sua conversão. Através da realização de um estágio numa Central, foi estudado o seu processo de funcionamento, desde a admissão da biomassa à caldeira até à produção de energia eléctrica, com o objectivo de fazer uma análise termodinâmica ao seu ciclo de vapor. Não tendo acesso à memória descritiva da Central, várias foram as condicionantes e dificuldades com que deparamos, mas foi possível fazer a análise termodinâmica. Para tal, decidiu-se recorrer a uma ferramenta computacional, o Cycle-Tempo, para efectuar a simulação do ciclo termodinâmico, após um levantamento de software disponíveis. Dispor-se de uma ferramenta que permita fazer a modelação de uma central, mesmo já em pleno funcionamento, é extremamente vantajoso pois permite descrever a operação da central, diagnosticar avarias, testar hipóteses e melhorar o ciclo. Recolhidos os parâmetros de funcionamento da Central, foi necessário introduzir pequenas modificações, no decurso do trabalho, no Cycle-Tempo. Após a modelação do ciclo, exploraram-se as vantagens atrás referidas, realizando uma análise de sensibilidade a diversos parâmetros de operação: pressão da caldeira, perda de carga na caldeira mantendo a pressão de saída, temperatura do vapor sobreaquecido, pressão no condensador, temperatura da água de arrefecimento, rendimento isentrópico associado às turbomáquinas, pressão de funcionamento do desgaseificador, potência do gerador. Fez-se ainda uma análise simultânea a vários parâmetros de funcionamento. Dado que o Cycle-Tempo também permite fazer balanços exergéticos, e atendendo a que o estudo do conceito de exergia foi recentemente introduzido na unidade curricular de Termodinâmica Aplicada do DEMI, aproveitou-se para concretizar o balanço exergético a uma central completa. Para concretizar o cálculo foi necessário determinar a exergia do Eucalyptus Globulus. No decorrer do trabalho, identificaram-se limitações no software Cycle-Tempo que motivaram o recurso a uma folha de cálculo, associada à base de propriedades termodinâmicas FluidProp, como processo alternativo à modelação do ciclo. Conseguiu-se modelar o ciclo no Cycle-Tempo depois de identificar e simplificar componentes do ciclo que impossibilitavam uma solução numérica. Da análise de sensibilidade, verificou-se que os parâmetros que mais influenciavam o rendimento do ciclo são a temperatura de sobreaquecimento e a pressão de condensação (influenciada pela temperatura da água de arrefecimento). A pressão do desgaseificador também influencia o rendimento do ciclo, mas a encontrada, 13 bar, é demasiado elevada face à actual de 3 bar, para se considerar um aumento. Tal como em outras áreas do conhecimento, na modelação termodinâmica, a informática também permite, num menor espaço de tempo e com menos esforço, estudar um grande número de configurações, de forma a rentabilizar o ciclo.
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JIMENEZ, GARCIA JUAN ANTONIO 789636, and GARCIA JUAN ANTONIO JIMENEZ. "Análisis exergético y termoeconómico de un sistema de generación de energía. Estudio del caso del generador de vapor de 350 MW instalado en la central termoeléctrica “Villa de Reyes”." Tesis de doctorado, Universidad Autonoma del Estado de Mexico, 2015. http://hdl.handle.net/20.500.11799/69009.
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Tesis de Doctorado en Ingeniería, Área Terminal MecánicaEn la presente investigación, se desarrolla el análisis exergético y termoeconómico de la central térmica de vapor de Villa de Reyes, que consta de un recalentamiento y dos regeneraciones. Para dicho análisis se determinan las ecuaciones de transferencia de calor y volúmenes de control que describen el comportamiento físico de cada uno de los componentes de la planta. El estudio se divide en varios módulos, integrados de la siguiente manera: a) Modulo del Cálculo térmico del hogar. En este módulo se caracteriza el proceso de combustión en el hogar del generador de vapor, y se determina la temperatura de los productos de la combustión a la salida de la cámara de combustión, dicho valor es fundamental en el diseño de los sobrecalentadores y recalentadores del generador de vapor, ya que con ayuda de la temperatura, se pueden determinar las propiedades termodinámica del lado de los gases, lo que permite realizar los cálculos de la transferencia de calor en los elementos subsecuentes. b) Módulo de la Transferencia de calor. En este módulo se realizan los cálculos de la transferencia de calor en los elementos de intercambio del generador de vapor. (1er, 2do. y 3er sobrecalentadores, 1er y 2do. recalentadores, economizador y precalentador de aire), se determinan las propiedades termodinámicas del vapor a la salida de cada uno de estos elementos. Con la metodología presentada se determina el coeficiente global de transferencia de calor (U) y de las características de flujo, tanto de vapor, como gases de combustión, finalmente, se determina la temperatura a la salida de los gases de combustión y vapor empleando el método de efectividad- NTU. c) Modulo del ciclo Rankine real. En este apartado se realiza el análisis del ciclo térmico de vapor de la central termoeléctrica con recalentamiento y dos regeneraciones, se estudia la influencia que tienen los parámetros de operación de la planta en el rendimiento total del ciclo y se analiza el comportamiento de los elementos de la central termoeléctrica, como son: la turbina de vapor, las extracciones de baja y alta presión de la turbina, condensador, desgasificador y calentador cerrado de agua de alimentación. Para validar el modelo termodinámico, se comparan los resultados obtenidos en los módulos a), b) y c) directamente contra los datos de operación de la central térmica de vapor conocidos (regímenes: 100%,75%,50% y 25%), y una vez validados, se modifican las variables independientes del modelo y se predicen las condiciones de operación a régimen de carga variable, donde se simula la operación de la central termoeléctrica desde el 25% de carga hasta el 100%, realizando la simulación en dependencia del incremento del flujo de combustibles al hogar del generador de vapor y en las presiones de operación establecidas para la central termoeléctrica. d) Modulo del cálculo exergético y termoeconómico, una vez validado el modelo termodinámico y obtenido resultados del análisis del ciclo térmico de vapor, se integran los módulos a, b y c, para realizar el análisis exergético y termoeconómico del ciclo, con lo que se identifican los regímenes de carga más eficientes, se presentan las irreversibilidades de los elementos participantes en el ciclo. los flujos exergéticos y los costos de las irreversibilidades asociados a la operación de la central térmica de vapor a los regímenes de carga seleccionados por sus altas eficiencias, y se presentan los costos asociados a las irreversibilidades de los procesos y los equipos, e) Análisis de sensibilidad, finalmente se realiza un análisis de sensibilidad, donde se estudia la influencia de las principales variables del modelo sobre los resultados obtenidos en la presenten investigación, con la finalidad de observar su efecto sobre la eficiencia térmica y exergética del ciclo, así como sobre el trabajo útil generado. Así también, este análisis permite evaluar las oportunidades de mejora de la central termoeléctrica, ya que las modificaciones en las principales variables del sistema, permiten identificar, los posibles resultados de implementar acciones de mejora en los elementos de la central o en los parámetros de operación. Debido a la naturaleza no lineal de los procesos térmicos que se llevan a cabo en la central térmica de vapor, la simulación de la central térmica de vapor a carga variable, se realiza empleando el método de sustituciones sucesivas, integrando los módulos a, b, c y d. Donde, la potencia requerida de generación se considera como variable independiente y se realiza el cálculo iterativo con aproximaciones sucesivas desde el límite inferior, e incrementando el flujo de combustible de manera gradual, hasta que el programa alcance la potencia del ciclo térmico requerida. En cada iteración, el programa determina las características de las variables de control en la planta termoeléctrica como son: el flujo de agua de alimentación, el flujo de combustible a la cámara de combustión, la cantidad de gases de recirculación, la presión del domo de vapor, la presión de vapor recalentado, se establece las presiones de extracción de la turbina de alta y baja presión, así como la presión de operación del condensador. En el capítulo I se presenta el estado del arte del diseño de equipo térmico, de los modelos de simulación por primera y segunda ley de la termodinámica y de los modelos exergéticos y Termoeconómicos. En el capítulo II, se plantean las generalidades sobre las instalaciones de producción de ponencia mediante vapor, se analizan las diferentes configuraciones del ciclo Rankine, se muestran las características de construcción y operación de la central térmica de vapor Villa de Reyes conocidas, en especial las características geométricas de los elementos que integran al generador de vapor. En el capitulo III, se presentan las metodologías de los cálculos termodinámicos y de la transferencia de calor de que se llevan a cabo en el hogar y las superficies intercambiadoras del generador de vapor. Metodologías que se emplean para determinar las propiedades termodinámicas de los fluidos de trabajo (vapor, gases de combustión), en cada uno de los En el capítulo IV, se presentan los fundamentos teóricos de los análisis Exergéticos y Termoeconómicos y la metodología del costo nivelado de generación que es la base del análisis termoeconómico realizado a la central termoeléctrica Villa de Reyes. En el capítulo V, se presentan los resultados del analíticos del cálculo térmico del hogar del generador de vapor a cargas parciales (100%, 75%, 50% y 25%), la validación de la transferencia de calor en las superficies intercambiadoras del generador de vapor, el análisis del ciclo termodinámico de la central térmica, obteniendo la eficiencia total del ciclo y finalmente, se presentan los resultados del análisis exergético y termoeconómico a carga variable, del análisis termoeconómico y los resultados del análisis de sensibilidad aplicado al modelo de la central termoeléctrica Villa de Reyes. En el capítulo VI, se presentan las conclusiones y las recomendaciones a la presente investigación, así como los futuros estudios que se desprenden en base a los resultados obtenidos en el presente trabajo. elementos que integran el generador de vapor.
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Cerda, Escobar Daniel Martín. "Análisis mecánico del efecto sísmico en el piping interior de una caldera en una central térmica." Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/146423.
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Ingeniero Civil MecánicoUn estudio reciente de modelación sísmica de una caldera ha detectado posibles colisiones entre sus elementos interiores. En particular, los haces de tubos que operan en la etapa de sobrecalentamiento y recalentamiento, chocan contra las paredes laterales de la caldera, durante un sismo. Dada la envergadura de la estructura y considerando también las condiciones de operación, no se tiene certeza de cuáles serían los efectos que puede originar el impacto de los tubos interiores. Es por este motivo, que el objetivo principal de este trabajo consiste en plantear una estrategia de solución al eventual problema de choque. La metodología utilizada considera un modelo computacional de tubos cuyo diseño se asemeja en mayor medida a aquel indicado en los planos mecánicos de la caldera. Además, su respuesta dinámica obedece a parámetros sísmicos cuyas solicitaciones son más exigentes, de acuerdo a lo establecido por la norma de diseño sísmica chilena. Para determinar el máximo desplazamiento del haz de tubos durante un sismo, estos son excitados mediante una aceleración sinusoidal, cuya amplitud y frecuencia representa el movimiento del techo de la caldera. Sumada a esta respuesta armónica de los tubos, que superpone los máximos modales, se añade el ángulo de rotación que sufren al nivel de su anclaje con el techo de la caldera. Los resultados indican que es altamente probable que ocurra una colisión entre los tubos de agua y las paredes laterales de la caldera, ya que el desplazamiento máximo que sufre la parte inferior del haz de tubos supera la holgura disponible. Para evaluar la magnitud del impacto, se utiliza la teoría desarrollada para el contacto entre superficies sólidas (esféricas). Donde a partir de la energía almacenada como deformación elástica en el haz de tubos, se determina el trabajo de compresión que realiza la fuerza de impacto, de acuerdo al número de tubos en contacto. Los resultados advierten que el daño no es despreciable. Se estima que la fuerza de impacto entre el tubo de agua y el tubo de pared podría alcanzar los 155 [kN], desarrollando un comportamiento en el rango plástico. Sin bien es cierto que difícilmente ocurra una ruptura catastrófica, el daño local puede ser un sitio de inicio de corrosión, causando problemas de mediano a largo plazo. Una posible solución a este problema consiste en evitar el contacto entre tubos, al interponer una placa en la trayectoria de éstos, mitigando la deformación plástica local.
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PEREIRA, Adriano Fernandes. "Procedimentos de avaliação de esforços torcionais em centrais termelétricas que operam em ciclo combinado gás-vapor." reponame:Repositório Institucional da UNIFEI, 2010. http://repositorio.unifei.edu.br/xmlui/handle/123456789/1413.
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Manobras em sistemas elétricos de potência, especialmente relacionadas a linhas de transmissão, são frequentes e importantes para manter um grau de confiabilidade e uma adequada condição de operação para os mesmos. Quando se trata de sistemas interligados com a presença de geração termelétrica, tais manobras podem acarretar severos esforços torcionais nos eixos de suas unidades geradoras e, consequentemente causar danos irreversíveis por estresse mecânico, como fadiga e perda de vida útil. O presente trabalho propõe procedimentos de avaliação de esforços torcionais nos eixos de centrais termelétricas que operam em ciclo combinado gás vapor, decorrentes da prática de religamentos automáticos de linhas de transmissão, através da utilização de técnicas complementares como técnicas de análise modal, critérios simplificados e critérios mais aprofundados com programas de transitórios eletromagnéticos. Com esses procedimentos e uma ação conjunta com os fabricantes dos turbogeradores pretende-se apresentar uma forma de avaliar os esforços torcionais nos eixos das unidades geradoras com o intuito de permitir a utilização de religamentos automáticos de linhas de transmissão sem ocasionar danos aos equipamentos.
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Caruso, Roberto. "Propagation of Hydrogen Air Vapor Flame in presence of Water Droplets." Thesis, Orléans, 2019. http://www.theses.fr/2019ORLE2002.
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L'accident de Fukushima en 2011 a remis en évidence les graves conséquences qu'une explosion d’un mélange gazeux à base d'hydrogène induit sur les installations et l'environnement. Lors de cet accident, la destruction complète du réacteur 2 a entraîné un rejet important de poussières radioactives dans l'atmosphère avec de graves conséquences environnementales qui sont encore à l'étude. Une connaissance approfondie de la propagation d'une flamme d'hydrogène dans un environnement confiné est essentielle pour comprendre les conditions de transition entre les régimes de déflagration et de détonation de la flamme qui peuvent compromettre l'intégrité du bâtiment réacteur. Un aspect des aspects qui a été très peu étudié concerne l'impact que l'activation des jets d'eau de refroidissement peut avoir sur la gravité d'une explosion. Le but de ce travail de thèse est de mieux comprendre le rôle de l'injection d'eau pulvérisée sur les régimes de combustion de mélanges hydrogène-air (vitesses de propagation et chargement en pression) dans un espace confiné. Ce travail de recherche a débuté par une étude préliminaire afin d'évaluer l'impact de la présence de vapeur d'eau sur la vitesse laminaire et sur l'épaisseur de flamme. Par la suite, une étude expérimentale a été menée, au laboratoire ICARE-CNRS Orléans, dans un tube d'accélération vertical ENACCEF 1 (volume interne 720 l). Pour mener cette étude, différents mélanges hydrogène/air ont été choisis, représentatifs de différents régimes de combustion, afin d'investiguer l'impact de la pulvérisation d'eau sur une flamme ascendante et descendante. L'ensemble du travail constitue une base de données expérimentale utile pour la validation de codes CFD utilisés dans l'évaluation de la sureté des installations nucléairesThe Fukushima accident in 2011 highlighted the serious consequences that an explosion of a hydrogen-based gas mixture has on installations and the environment. In this accident, the complete destruction of Reactor 2 resulted in a significant release of radioactive dust into the atmosphere with serious environmental consequences that are still under investigation. A thorough knowledge of the propagation of a hydrogen flame in a confined environment is essential to understand the transition conditions between deflagration and flame detonation regimes that can compromise the integrity of the reactor building. One aspect of the aspects that has been little studied concerns the impact that the activation of cooling water jets can have on the severity of an explosion. The purpose of this thesis work is to better understand the role of water spray injection on the combustion regimes of hydrogen-air mixtures (propagation rates and pressure loading) in a confined space. This research work began with a preliminary study to evaluate the impact of the presence of water vapour on laminar velocity and flame thickness. Subsequently, an experimental study was carried out at the ICARE-CNRS Orléans laboratory in an ENACCEF 1 vertical acceleration tube (internal volume 720 l). To conduct this study, different hydrogen/air mixtures were selected, representative of different combustion regimes, to investigate the impact of water spray on an ascending and descending flame. All the work constitutes a useful experimental database for the validation of CFD codes used in the safety assessment of nuclear installations
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Marques, Frederico Augusto Spolidorio. "Implementação e validação pratica de modelos multidisciolinares abordados em uma central de co-geração de energia eletrica." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259510.
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Orientador: Luiz Carlos Pereira da SilvaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Este projeto busca relacionar diversos aspectos interdisciplinares envolvidos em uma central de co-geração de energia elétrica. Motivado pela crescente inserção de centrais de geração distribuída operando de forma ilhada ou paralela ao sistema, foram desenvolvidos modelos mecânicos (térmicos e dinâmicos) e elétricos buscando representar os diversos equipamentos envolvidos em uma central de geração em um nível industrial. Baseado nesta concepção, optou-se pela geração de energia através de máquinas térmicas (turbinas a vapor) impulsionadas pela energia proveniente da queima de biomassa restante de diferentes processos industriais. Os modelos teóricos aqui representados foram numericamente simulados com parâmetros obtidos em um estudo de caso real. Seus resultados foram então comparados qualitativamente e quantitativamente contra as variáveis reais do processo analisado. Ao consolidar esta ferramenta de estudo, o simulador mostrou-se eficiente no treinamento de operadores de casas de forças, sendo capaz de esclarecer as interferências entre o nível de carga com as demais variáveis envolvidas em seu processo
Abstract: This project intends to gather several interdisciplinary aspects common to a co-generation power plant. Driven by the increasing amount of distributed generation units operating on island or parallel mode with the network, some mechanical (thermo and dynamic) and electrical models were developed in order to represent the equipments usually installed on an industrial size power station. Based on this concept, the more convenient option was to proceed the evaluation through turbo machinery (steam turbine) driven by the energy acquired from the heat power on burning byproducts of industrial processes. The theoretical models were simulated with parameters obtained from a real case study. The results were then finally compared with real process information acquired from field research. In order to consolidate this computational tool, the simulator has shown efficient results on training power station operators on clarifying the impacts of load level on the other relevant variables on their processes
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica
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LOPEZ, LUIZ A. N. M. "Transformadas de Wavelets e logica Fuzzi na inspecao por Eddy-Current em tubos de geradores de vapor de centrais nucleares." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11012.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
Books on the topic "Centrali a vapore"
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Temazcalli: Higiene, terapéutica, obstetricia y ritual en el Nuevo Mundo. Sevilla: Escuela de Estudios Hispano-Americanos de Sevilla, Consejo Superior de Investigaciones Científicas, 2000.
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Castelán, Guillermo Mendoza. Temazcalli: Higiénico, terapéutico y ritual. Chapingo, Texcoco, México]: Programa Universitario de Medicina Tradicional y Terapéutica Naturista, Departamento de Fitotecnia,Universidad Autónoma de Chapingo, 2009.
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3
United States. National Transportation Safety Board. Railroad accident report: Denver and Rio Grande Western Railroad Company train yard accident involving punctured tank car, nitric acid and vapor cloud, and evacuation, Denver, Colorado, April 3, 1983. Washington, D.C: The Board, 1985.
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United States. National Transportation Safety Board. Railroad accident report: Denver and Rio Grande Western Railroad Company train yard accident involving punctured tank car, nitric acid and vapor cloud, and evacuation, Denver, Colorado, April 3, 1983. Washington, D.C: The Board, 1985.
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Sherwood, Dennis, and Paul Dalby. Phase equilibria. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198782957.003.0015.
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This chapter extends the discussion of gas phase equilibria to phase equilibria. The central concept is the vapour pressure, and the key proof is that the criterion for phase equilibrium is the equality of the molar Gibbs free energies, or chemical potentials, of each phase. This then leads to the Clapeyron and Clausius-Clapeyron equations. A notable feature of this chapter is the discussion of non-ideal gases, answering the question “Given that, by definition, an ideal gas can never liquefy, what is it about a real gas that enables the gas to change phase into a liquid?”. A unique feature of this discussion is the rigorous analysis of the Gibbs free energy of a van der Waals gas under compression, and the proof of the ‘Maxwell construction’.
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The World Market for Auxiliary Plant for Use with Steam Generating and Central Heating Boilers and Condensers for Steam or Other Vapor Power Units: A 2004 Global Trade Perspective. Icon Group International, Inc., 2005.
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Parker, Philip M. The 2007 Import and Export Market for Auxiliary Plant for Use with Steam Generating and Central Heating Boilers and Condensers for Steam or Other Vapor Power Units in India. ICON Group International, Inc., 2006.
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dos Santos Chaves, Lígia Gizely, and Ricardo Figueiredo Pinto. Estudo do perfil socioeconômico, estado nutricional, nível de mercúrio e desenvolvimento motor em crianças da Ilha de Cotijuba, Pará / Brasil. Edited by Robson Antonio Tavares Costa, Carlos Gomes de Carvalho Leitão, and Carla Sandra Carneiro Afonso. Conhecimento e ciência, 2019. http://dx.doi.org/10.20872/estudodoperfilsocieconomico.
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Este estudo objetiva avaliar o desenvolvimento motor, estado nutricional, nível de mercúrio e perfil socioeconômico de crianças residentes na Ilha de Cotijuba, Pará, Brasil, na faixa etária de 5 a 10 anos. Metodologicamente, o desenvolvimento motor foi avaliado através do protocolo TGMD – 2 (Test of Gross Motor Development, Secunde Edition). A avaliação do estado nutricional da amostra, utilizou o software WHO AntroPlus. A análise de mercúrio foi realizada através da metodologia de redução e espectrometria de absorção atômica por vapor frio (CVAAS) (sistema aberto de circulação do fluxo de ar), utilizando um detector de mercúrio automático, o Automatic Mercury analyzer Model HG-201 da Sanso Seisakusho Co. Ltd., Tokyo, Japan. Para a avaliação socioeconômica da amostra, foi utilizado o instrumento CCEB 2014 (Critério de Classificação Econômica Brasil 2014) da ABEP. A análise dos dados foi realizada pelo programa SPSS 22.0, em que se adotou a estatística descritiva de tendência central, não central e dispersão e para a estatística inferencial primeiramente foi realizado o teste de Kolmogorov-Smirnov para normalidade da amostra, e o Teste t independente para comparar as médias da amostra de acordo com o sexo e grupo etário. O teste de correlação de Pearson foi utilizado para analisar o grau de associação entre as variáveis. Foi adotado um nível de significância p≤0,05. O desenvolvimento motor encontrou-se na média em sua maioria, seguido por abaixo da média e, posteriormente, acima da média. Quanto ao estado nutricional, a maioria apresentou peso adequado para a idade, estatura adequada para idade e eutrofia com o aparecimento de alguns casos de sobrepeso e obesidade com o avançar da idade. O nível de exposição ao mercúrio encontrou-se abaixo do limite de tolerância biológico, com diferença significativa entre sexo. O perfil socioeconômico das famílias, na sua maioria, perteceu às classes C2 e D. A renda média bruta das famílias, majoritariamente, apresentou-se entre R$ 1277,00 e R$ 895,00. Conclui-se que a avaliação do desenvolvimento motor e os fatores intervenientes a este estão na normalidade. Análises similares devem ocorrer periodicamente para planejamento legislativo e projetos de intervenção em educação e saúde.
Book chapters on the topic "Centrali a vapore"
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Churakova, Olga V., Trevor J. Porter, Alexander V. Kirdyanov, Vladimir S. Myglan, Marina V. Fonti, and Eugene A. Vaganov. "Stable Isotopes in Tree Rings of Boreal Forests." In Stable Isotopes in Tree Rings, 581–603. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92698-4_20.
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AbstractThe boreal forests are widely expanded from subarctic forest to tundra, and from taigato forest-steppe zone (from 50 °N to 70 °N). We reviewed available stable isotope chronologies in tree-ring cellulose (δ13C, δ18O and δ2H) from 16 sites located in the Russian Federation; 4 research sites from Fennoscandia (Finland, Sweden and Norway); 5 sites from Canada, and 1 site from Alaska (USA) to evaluate impact of climatic changes from seasonal to annual scale across boreal forest ecosystems. Results of our review of carbon isotope data showed that droughtconditions (mainly high vapour pressure deficit) are prevalent for western and central regions of Eurasia, Alaska and Canada, while northeastern and eastern sites of Eurasian subarctic are showing water shortage developments resulting from decreasing precipitation. Oxygen isotopechronologies show increasing trends towards the end of the twentieth century mainly for all chronologies, except for the Siberian northern and southern sites. The application of the multiple stable isotope proxies (δ13C, δ18O, δ2H) is beneficial to study responses of boreal forests to climate change in temperature-limited environments. However, a deeper knowledge of hydrogen isotope fractionation processes at the tree-ring cellulose level is needed for a sound interpretation and application of δ2H for climate reconstructions, especially for the boreal forest zone where forest ecosystems are more sensitive to climatic and environmental changes.
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Hadley, Julian L., and William K. Smith. "Effect of Elevation and Foliar Age on Maximum Leaf Resistance to Water Vapor Diffusion in Conifers of the Central Rocky Mountains, U.S.A." In Air Pollutants and the Leaf Cuticle, 261–68. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-79081-2_22.
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Menin, Marco. "Pathological Tears." In Thinking About Tears, 255—C10.P70. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/oso/9780192864277.003.0011.
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Abstract This chapter shows how tears were cast into doubt on the physiological level in the first decades of the nineteenth century, with lachrymal secretions increasingly considered to represent a pathological degeneration of sensibility that had to be ‘cured’ by both physicians and philosophers. The epistemological conviction underlying the idea of a link between tears and pathology was fairly simple: disease, by virtue of the fact that it modifies the element of physique, makes it possible to grasp with greater clarity the repercussions that emotions have on morals, thus allowing scientists to analyse both of sensibility’s twofold facets. This investigative method can be seen particularly vividly in descriptions of the pathology of ‘vapours’ (vapeurs), one of the most curious and fascinating expressions of the synergy between medicine, literature, and philosophy in French culture. While ‘vapours’ involved an excess of tears, early nineteenth-century physicians were more concerned with the absence of lachrymal secretions. Particularly, the emerging field of psychiatry—which found fertile ground for its development in the philosophical environment of the Idéologues—took as one of its great challenges the task of providing a medical and scientific explanation for the inability to cry. This issue was central to the ‘moral therapy’ theorized by Jean-Étienne Dominique Esquirol, one of the founding fathers of modern psychiatry.
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Zhang, Yiming, Yuanfeng Xu, Yujie Xia, Juan Zhang, Hao Zhang, and Desheng Fu. "Photo-Induced Displacive Phase Transition in Two-dimensional MoTe2 from First-Principle Calculations." In Phase Change Materials - Technology and Applications [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108460.
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The discovery and control of new phases of matter are a central endeavor in materials research. Phase transition in two-dimensional (2D) materials has been achieved through laser irradiation, strain engineering, electrostatic doping, and controlled chemical vapor deposition growth, and laser irradiation is considered as a fast and clean technique for triggering phase transition. By using first-principles calculations, we predict that the monolayer MoTe2 exhibits a photo-induced phase transition (PIPT) from the semiconducting 2H phase to the topological 1T′ phase. The purely electronic excitations by photon soften multiple lattice vibrational modes and lead to structural symmetry breaking within sub-picosecond timescales, which is shorter than the timescale of a thermally driven phase transition, enabling a controllable phase transition by means of photons. This finding provides deep insight into the underlying physics of the phase transition in 2D transition-metal ditellurides and show an ultrafast phase-transition mechanism for manipulation of the topological properties of 2D systems. More importantly, our finding opens a new avenue to discover the new families of PIPT materials that are very limited at present but are essential to design the next generation of devices operated at ultrafast speed.
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Mizera, Jiří, and Zdeněk Řanda. "Geochemical indicators of a biogenic component in source materials of moldavites." In In the Footsteps of Warren B. Hamilton: New Ideas in Earth Science. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2553(26).
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ABSTRACT Formation of the Central European tektites, known as moldavites, has been associated with a large meteorite impact in southern Germany 14.8 m.y. ago. The geochemical link between moldavites and their source materials, and the processes of their possible chemical differentiation still remain uncertain. Some differences in chemical composition between moldavites and sediments of corresponding age from the surroundings of the Ries crater could be explained by a hypothesis according to which biomass covering the pre-impact area contributed to the source materials. In a comparison of the geochemical compositions of a large representative set of moldavites and suitable Ries sediments, enrichment in elements K, Ca, Mg, and Mn and depletion of Na in moldavites, similar to redistribution of these elements during their transfer from soil to plants, could indicate the unconventional biogenic component in moldavite source materials. Simple mixing calculations of the most suitable Ries sediments and a model biogenic component represented by burned biomass residue are presented. The plausibility of the estimated biomass contribution considering reconstructions of the middle Miocene paleoenvironment in the pre-impact Ries area is discussed. No significant vapor fractionation is required to explain the observed variability of moldavite chemical composition.
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Gonçalves, N. F., T. T. S. Santos, L. C. Paixão, M. C. S. Sant’Anna, D. A. Luz, J. G. M. Silva, and A. A. Santana. "BIOPOLÍMEROS DE ALGINATO ADITIVADO COM RESÍDUO DE CENOURA: CARACTERIZAÇÃO FÍSICO-QUÍMCA E ANTIOXIDANTE." In Ciência e Tecnologia de Alimentos: Pesquisas e Avanços. Agron Food Academy, 2022. http://dx.doi.org/10.53934/9786599539664-36.
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Atualmente, um dos grandes problemas enfrentados pela sociedade mundial é o descarte indevido de embalagens não biodegradáveis no meio ambiente. Para minimizar esse grave problema, novas tecnologias e produtos vêm sendo desenvolvidos, isto é, a elaboração de materiais biodegradáveis quando descartados no meio ambiente. A utilização de biopolímeros formados por polímeros incorporados de compostos naturais, que conservam o alimento, mantendo a qualidade, aumentando a vida útil do produto, a proteção e inibição de compostos indesejáveis, vêm ganhando destaque como materiais de grande potencial para aplicação como revestimentos protetores comestíveis. O objetivo deste trabalho foi caracterizar físicoquimicamente biopolímeros de alginato aditivados com extrato de cenoura (Daucus carota, L.), conferindo-lhes atividade antioxidante. Estes foram obtidos pelo método casting utilizando a proporção de 1:1 (água:cenoura). Na obtenção dos filmes utilizou-se Delineamento Composto Central Rotacional, com 11 ensaios, variando a concentração de alginato e extrato de cenoura, tendo como respostas, umidade, espessura, solubilidade, permeabilidade ao vapor de água e carotenoides totais. A incorporação do extrato de cenoura aos filmes de alginato proporcionou um aumento na capacidade antioxidante destes, sem significantes alterações das características físico-químicas, tendo assim, potencial para utilização como filme com característica antioxidante.
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Aveyard, Bob. "Capillarity, wetting, and surface (interfacial) tension." In Surfactants, 25–52. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198828600.003.0003.
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Capillarity reflects the action of interfacial tension and has been central to understanding intermolecular forces. When a liquid meets a solid surface (with contact angle θ) it forms a meniscus which is associated with the rise/depression of liquid in a capillary tube, hence the term capillarity. Interfacial tensions also determine how a liquid wets and adheres to a solid or another liquid. Liquid menisci are curved, and Young, Laplace, and Kelvin have all thrown light upon the properties of curved liquid surfaces. The Young–Laplace equation relates the pressure difference across a curved liquid interface to both the interfacial tension and curvature of the interface. Interfacial tension also gives rise to a dependence of the vapour pressure (and solubility) of a liquid on the curvature of its surface (e.g. drop radius), as expressed in the Kelvin equation. Common methods for measurement of interfacial tensions are described in an Appendix.
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Tuck, Adrian F. "Radiative and Chemical Kinetic Implications." In Atmospheric Turbulence. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780199236534.003.0009.
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The laws governing the dynamical behaviour of atoms and molecules are quantum mechanical, and specify that their internal energy states are discrete, with only definite photon energies inducing transitions between them, subject to selection rules. These energy levels appear as spectra in different regions of the electromagnetic spectrum: pure rotational lines in the microwave or far infrared, ‘rovibrational’ (rotation + vibration) lines in the middle and near infrared, while electronic transitions, sometimes with associated rotational and vibrational structure (‘rovibronic’) occur from the near infrared through the visible to the ultraviolet. An important feature of these spectra in the atmosphere is that they do not appear as single sharp lines, but are collisionally broadened about the central energy into ‘line shapes’ which frequently overlap with other transitions, both from the same molecule and from others. One of the primary dynamical quantities involved in the processes broadening these line shapes is the relative velocity of the molecules with which the photon absorbing and emitting molecules are colliding. These are primarily N2 and O2 in the atmosphere; if they have an overpopulation of fast moving molecules relative to a Maxwell–Boltzmann distribution, as we have suggested, the line shapes will be affected. Molecules such as carbon dioxide, water vapour, and ozone are all active in the infrared via rovibrational transitions, with water vapour being light enough and so having sufficiently rapid rotation that it has rotational bands appearing in the far infrared rather than the microwave. Nitrous oxide, N2O, and methane, CH4, are also active, but make smaller contributions because of their lower abundances. Molecular nitrogen and molecular oxygen, because they are homonuclear diatomic molecules, do not absorb or emit via electric dipole allowed transitions in the atmospherically important regions of the electromagnetic spectrum. Molecular oxygen, having a triplet ground state, does have weak forbidden and magnetic dipole transitions which, however, play only a very small role in the radiative balance. It should be noted that the translational energy of molecules in a large system like the atmosphere is effectively continuous rather than quantized.
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"The Chemical Study of Metals—the Medieval and Later Brass Industry in Europe." In Archaeological Chemistry, 245–95. 3rd ed. The Royal Society of Chemistry, 2016. http://dx.doi.org/10.1039/bk9781782624264-00245.
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This chapter reviews one particular aspect of the history of copper alloys, which is the use of brass, an alloy primarily of copper and zinc. This alloy is different from all other alloys of copper because of the volatility of zinc, which means that metallic zinc could not be directly smelted from its ore, and was therefore largely unknown in Europe until the 17th century AD. In turn, this means that brass could not be made by the direct mixing of metallic copper and zinc. The Romans employed an indirect method of manufacturing brass called the calamine process, in which metallic copper is heated with zinc ore in a closed crucible. Between about 900 and 1000 °C, the zinc vapour enters the hot copper by diffusion, to produce brass, the zinc content of which is practically limited by the process. This method appears to have its origins somewhere in Anatolia, Iran or Central Asia during the 2nd millennium BC. The bulk of this chapter focuses on the production of brass in Medieval and later England and Europe, with examples given of the analysis of jettons (tokens similar to coinage) and scientific instruments. The chapter ends with a discussion of the identification of imported copper and brass in early contact North America.
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Stephens, Graeme. "Cirrus, Climate, and Global Change." In Cirrus. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780195130720.003.0024.
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Understanding the climate of Earth and the way climate varies in time requires a quantitative understanding of the way water cycles back and forth between the atmosphere and at the Earth's surface. The exchanges of water between the surface and atmosphere establish the hydrological cycle, and it is the influence of this cycle on the energy budget of Earth that is central not only to understanding present climate but also to the prediction of climate change. Processes relating to the smallest of the reservoirs of water—namely, the atmospheric branch of the hydrological cycle—play an especially critical role in climate change. Water in vapor phase is the critical greenhouse gas (e.g., Chahine 1992) providing much studied feedbacks on climate forcing (Lindzen 1990; Rind et al. 1991; Stephens and Greenwald 1991; Inamdar and Ramanathan 1998; Hall and Manabe 1999). Water in the form of condensed, precipitation-sized particles is an important source of energy fueling circulation systems and is the fundamental supply of fresh water to life on Earth. Liquid water cloud droplets significantly modulate the radiative budget of the planet (e.g., Wielicki et al. 1995). Water that exists as ice particles suspended in the atmosphere is perhaps the smallest of the water reservoirs of the atmosphere, yet these ice crystals when distributed as part of large-scale cirrus clouds exert a disproportionate influence on the energy and water budgets of the planet. This chapter briefly speculates on the important ways cirrus clouds affect the Earth's climate. The topics discussed are central to what is referred to as the cloud-climate problem, which might be schematically represented in terms of the coupled processes represented in figure 20.1. The two most critical scientific questions associated with the cloud-climate problem are also stated in figure 20.1. Answers to these questions require a clearer understanding of how the large-scale circulation of the atmosphere governs cloud formation and evolution, how these clouds heat and moisten the atmosphere, and how this heating and moistening effect in turn feeds back to influence the dynamical and thermodynamical properties of the atmosphere.
Conference papers on the topic "Centrali a vapore"
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Vuchkov, Nikolay K., Nikola V. Sabotinov, and Krasimir A. Temelkov. "CuBr vapor laser with a central electrode." In XI International Symposium on Gas Flow and Chemical Lasers and High Power Laser Conference. SPIE, 1997. http://dx.doi.org/10.1117/12.270167.
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Beran, Pavel, and Jiří Maděra. "Condensation of water vapor in baroque church." In CENTRAL EUROPEAN SYMPOSIUM ON THERMOPHYSICS 2019 (CEST). AIP Publishing, 2019. http://dx.doi.org/10.1063/1.5114141.
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Mánik, Marek, and Igor Medveď. "Transmission of water vapor through expanded polystyrene." In CENTRAL EUROPEAN SYMPOSIUM ON THERMOPHYSICS 2020 (CEST 2020). AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0025754.
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Shapley, Sarah, Joshua J. Ehlich, Mark R. Frank, and Robert J. Bodnar. "GOLD AND COPPER PARTITIONING BETWEEN VAPOR AND BRINE AT MODERATE TO HIGH TEMPERATURES." In 52nd Annual North-Central GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018nc-312661.
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Esquivel-Hernández, Germain. "Análisis de vapor de agua precipitable sobre Costa Rica: una comparación entre diferentes técnicas de análisis basadas en GPS, sondeo atmosférico y productos satelitales MODIS." In I Congreso Internacional de Ciencias Exactas y Naturales. Universidad Nacional, 2019. http://dx.doi.org/10.15359/cicen.1.41.
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La cuantificación del vapor de agua en regiones tropicales como América Central es necesaria para estimar la influencia del cambio climático en su distribución y la formación de precipitaciones. Este trabajo analiza las estimaciones diarias de vapor de agua precipitable (PWV) utilizando los datos de retardo zenital del Sistema de Posicionamiento Global (GPS) en la región del Pacífico de Costa Rica durante 2017. Las mediciones del PWV con GPS se compararon contra los datos del sondeo atmosférico y del espectrómetro de imágenes de resolución moderada (MODIS). Se encontraron sesgos relativamente pequeños entre las temperaturas atmosféricas medias (Tm) del sondeo atmosférico y la ecuación de Bevis. Las variaciones estacionales de PWV fueron controladas por dos de los principales procesos de circulación en América Central: los vientos alisios del noreste y la migración latitudinal de la Zona de Convergencia Intertropical (ZCIT). No se encontraron diferencias estadísticas significativas para los cálculos de MODIS Terra durante la estación seca con respecto a los cálculos basados en GPS (p> 0.05). Un modelo de regresión lineal múltiple estimado con base en variables meteorológicas de superficie pudo predecir las mediciones basadas en GPS con un sesgo relativo promedio de -0.02 ± 0.19 mm/día (R2=0.597). Estos primeros resultados son prometedores para incorporar aplicaciones meteorológicas basadas en GPS en América Central, donde las condiciones climáticas prevalecientes ofrecen un escenario único para estudiar la influencia de los aportes de humedad marítimos en la distribución estacional de vapor de agua.
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Sadek, H., J. Cotton, and C. Y. Ching. "Horizontal Tube Side Convective Condensation Under an Applied DC Voltage." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22158.
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An experimental study was performed to investigate the tube side convective condensation under an applied DC high voltage. Experiments were performed in a horizontal, single-pass, counter-current heat exchanger with a rod electrode placed along the centre of the tube. A 8 kV DC voltage was applied across the annular gap between the central electrode and the pipe wall. The experiments were performed for mass flux in the range 45 to 156 kg/m2s and average quality of 45 percent. The application of the high voltage electric field results in electric body forces at the liquid-vapor interface which extracts the liquid from the bottom stratum towards the vapour core. The application of the 8 KV DC voltage increased heat transfer and pressure drop by factor 3 and 4.5 respectively at the lowest mass flux of 45 kg/m2s. The results show that liquid extraction from the bottom liquid stratum changed the mode of heat transfer at the bottom of the tube from convective condensation into film condensation.
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Fantozzi, Francesco, Bruno D’Alessandro, and Umberto Desideri. "An IPRP (Integrated Pyrolysis Regenerated Plant) Microscale Demonstrative Unit in Central Italy." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-28000.
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The Integrated Pyrolysis Regenerated Plant (IPRP) concept is based on a Gas Turbine (GT) fuelled by pyrogas produced in a rotary kiln slow pyrolysis reactor; pyrolysis process by-product, char, is used to provide the thermal energy required for pyrolysis. An IPRP demonstration unit based on an 80 kWE microturbine was built at the Terni facility of the University of Perugia. The plant is made of a slow pyrolysis rotary kiln pyrolyzer, a wet scrubbing section for tar and water vapor removal, a micro gas turbine and a treatment section for the exhaust gases. This paper describes the plant layout and expected performance with different options for waste heat recovery.
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Kinder, Katherine M., Christopher A. Gellasch, James S. Dusenbury, Thomas C. Timmes, and Thomas M. Hughes. "EVALUATING THE IMPACT OF AIR TEMPERATURE AND AMBIENT BENZENE VAPOR CONCENTRATIONS ON CONDENSATION WATER FROM AIR TECHNOLOGY PRODUCT WATER." In Joint 52nd Northeastern Annual Section and 51st North-Central Annual GSA Section Meeting - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017ne-291019.
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Lu, Yuanwei, Hongchang Yang, and Chongfang Ma. "Study on a Cascade Utilization of Liquid Natural Gas (LNG) Cold Energy for Power Generation." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22411.
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Liquefied natural gas (LNG) is known as a clean energy source which is widely used in electricity generation and daily living for its friendly environment performance. The global LNG trade has increased rapidly during recent years. Liquid natural gas delivered by sea-ships contains considerable cryogenic exergy which can be utilized for electricity production before its evaporation and introduction into the system of pipelines. Because the need to vaporize LNG offers a thermal sink at a very much lower temperature than seawater, using this thermal sink both power and gas can be produced. So it is possible to recover power from the vaporization of LNG. Based on the exergy analysis of normal Rankine power cycle and LNG gasification characteristics at a different pressure, this paper proposed a cascading power cycle with LNG cold energy recovery, in which a three-tier Rankine cycle system was established to recovery the liquid heat and latent heat of LNG, and the residual sensible heat of LNG vapor can be used to prepare the cold water of central air-conditioning in plant area. The simulating results showed that the cascade power system can improve the LNG cold energy recovery efficiency.
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Drake, Daniel A., Jutima Simsiriwong, Rani W. Sullivan, Hossein Toghiani, Sasan Nouranian, Janis DuBien, Thomas E. Lacy, and Charles U. Pittman. "Creep Compliance Characterization of Vapor-Grown Carbon Nanofiber/Vinyl Ester Nanocomposites Using a Central Composite Design of Experiments." In 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-1585.
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