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rss_1.0 Clasificación por Disciplina

Nomenclatura Unesco > (22) Física > (2213) Termodinámica
(2213.01) Cambios de estado (2213.02) Física de la transmisión del calor
(2213.03) Altas presiones (2213.04) Altas temperaturas
(2213.05) Teoría cinética (2213.06) Bajas temperaturas
(2213.07) Cambio de fase (2213.08) Técnicas de medida del calor
(2213.09) Equilibrios termodinámicos (2213.10) Relaciones termodinámicas
(2213.11) Fenómenos de transporte (2213.99) Otras (especificar)

Mostrando recursos 1 - 20 de 2,279

1. Replanteamiento de la termodinámica energética: estrategias de ingesta de energía para la optimización de la composición corporal y el rendimiento de atletas - Benardot, Dan
A key feature of physical activity is that it results in an increased rate of energy expenditure and, as a result of metabolic inefficiencies that lead to high heat production, an increase in the requirement to dissipate the added heat through sweat.  Nevertheless, surveys commonly find that athletes fail to optimally satisfy both energy and fluid needs, causing them to perform at levels below their conditioned capacities.  To some extent this problem results from an excess reliance on the sensations of ‘hunger’ and ‘thirst’ to guide energy and fluid intakes, but there are also common misunderstandings of the best eating...

2. Nuevos procesos tándem iniciados por transferencias de hidruro desde funciones acetálicas - Marín Luna, Marta
Objetivos: Estudiar la capacidad de funciones acetálicas tales como 1,3-dioxolano, 1,3-ditiolano y sus análogas de seis miembros, para participar en procesos tándem iniciados por una transferencia de hidruro. Se evaluarán como unidades receptoras potenciales de dicho anión agrupaciones cetena, cetenimina, aleno, fulveno y fragmentos benciliden malonato. Metodología: 1) Diseñar y sintetizar acetal compuestos aptos para experimentar dichos procesos tándem. 2) Estudiar su reactividad química mediante inducción térmica y catalítica. 3) Caracterizar los productos de reacción mediante diferentes técnicas espectroscópicas. 4) Postular rutas mecanísticas que expliquen las transformaciones acontecidas en los materiales de partida. 5) Estudiar computacionalmente tales transformaciones. Resultados: 1)...

3. Thermodynamics of stress-induced ferroelastic transitions: Influence of anisotropy and disorder - Lloveras Muntané, Pol Marcel; Castán, Teresa; Porta, Marcel; Planes, Antoni; Saxena, Avadh
Stress-induced stress-strain constitutive behavior has been studied in detail in ferroelastic martensites. It hasbeen found that the weights of the long-range anisotropic interactions and of the disorder are important todetermine the fine structure of the stress-strain curves. As experiments show, a wide variety of behaviors hasbeen observed. A decrease of anisotropy and/or increase in the disorder results in changes in the temperaturerange where pseudoplastic and superelastic regimes are observed. Also, a smoothing of the stress-inducedferroelastic transition, accompanied with a decrease in the transition stress and the hysteresis area, is found.However, Clausius-Clapeyron slope has been observed not to depend on the...

4. Equilibrio entre fases para la aplicación de solventes verdes en tecnología de alimentos - Hernández Ramos, Elvis Judith
[ES]: En este trabajo se presentan los resultados obtenidos del estudio (experimental y teórico) del equilibrio entre fases de compuestos alimentarios y solventes verdes, aportando nuevos resultados a los fundamentos de los procesos de separación por contacto en equilibrio de la tecnología de alimentos. Se obtuvieron nuevos datos de equilibrio entre fases, aplicando métodos experimentales a altas presiones (equilibrio líquido – fluido supercrítico, para el disolvente dióxido de carbono) y a bajas presiones (equilibrio líquido – líquido, para el disolvente lactato de etilo). Se desarrollaron metodologías apropiadas para medir experimentalmente tanto sistemas binarios simples, como en el caso de Escualeno +...

5. Determinación de propiedades fisicoquímicas y termodinámicas de dioxinas y furanos por el método de contribución de grupos - García Ubaque, Cesar Augusto; García Vaca, María Camila; Vaca Bohórquez, Martha Lucía

6. Adsorção do corante amarelo crepúsculo (Sunset yelow ins 110) presente em efluente da indústria de refrigerante - Vasques, Érika de Castro
Resumo: A indústria de refrigerantes desperdiça correntes de água provenientes da lavagem de garrafas retornáveis e equipamentos, que somado ao descarte proveniente do processamento da bebida formam o efluente industrial. Os processos convencionais de tratamento biológico não são eficientes para a degradação de corantes recalcitrantes. Desta forma, o objetivo deste trabalho foi avaliar o processo de adsorção do corante amarelo crepúsculo presente em efluente sintético e efluente real, proveniente de indústria de refrigerante, a partir de experimentos em batelada e coluna de leito fixo. O efluente utilizado neste trabalho foi coletado em uma indústria de refrigerantes da região de Curitiba,...

7. Response surface modelling and optimization in pervaporation - Khayet Souhaimi, Mohamed; Cojocaru, C.; Zakrzewska-Trznadel, G.
Both the conventional method of experimentation, in which one of factors is varied maintaining the other factors fixed at constant levels and the statistically designed experimental method, in which all factors are varied simultaneously are carried out for organic removal from water by pervaporation. Binary acetonitrile-water mixtures are considered. The effects of the operating parameters on the pervaporation performance of the membrane system have been investigated. The overall mass transfer coefficients have been determined for different conditions of feed temperature and initial organic concentration. in addition, the activation energy associated to the permeation process has been determined and discussed for...

8. Measurement of the thermal conductivity of nanofluids by the multicurrent hot-wire method - Khayet Souhaimi, Mohamed; Vázquez Peñas, José R.; Ortiz de Zárate Leira, José María
We present experimental results of the thermal conductivity of several nanofluids prepared by dispersing nanoparticles of SiO(2) and CuO in water and ethylene glycol at various concentrations up to approximate to 5% in mass fraction. The measurements have been performed by the multicurrent hot-wire technique. Good agreement, within 2%, is found in recommended and published thermal conductivities of the pure fluids. Our experimental technique allows a very accurate determination of the enhancement in the thermal conductivity of the fluids due to the presence of dispersed nanoparticles. Measured enhancements compare well with some of the values published so far in the...

9. Studies on pervaporation separation of acetone, acetonitrile and ethanol from aqueous solutions - Khayet Souhaimi, Mohamed; Cojocaru, C.; Zakrzewska-Tunadel, G.
Pervaporation is applied for acetone, acetonitrile and ethanol removal from water solutions. The separation of binary acetone-water, acetonitrile-water and ethanol-water mixtures was initially carried out. The effects of feed concentration and feed temperature on the pervaporation performance, total and partial permeate fluxes as well as organic selectivity, have been investigated. The overall mass transfer coefficients have been determined and discussed for each organic-water mixture at different conditions of feed temperature and initial organic feed concentrations. The overall and individual activation energies of water and each organic compound associated to the permeation process have been calculated. Finally, pervaporation was applied to...

10. Preparation and characterization of novel hydrophobic/hydrophilic polyetherimide composite membranes for desalination by direct contact membrane distillation - Khayet Souhaimi, Mohamed; Qtaishat, M.; Rana, D.; Matsuura, T.
Two different types of hydrophobic surface modifying macromolecules (SMMs) were synthesized and characterized for fluorine content, average molecular weight and glass transition temperature. The synthesized SMMs were blended into polyetherimide (PEI) hydrophilic host polymer to form porous hydrophobic/hydrophilic composite membranes by the phase inversion method. The prepared membranes were characterized by the contact angle measurements, X-ray photoelectron spectroscopy test, gas permeation test, liquid entry pressure of water and scanning electron microscopy. Finally, these membranes were tested for desalination by direct contact membrane distillation (DCMD). Different parameters affecting the membrane preparation process were studied and their effects on the membrane morphology...

11. Guidelines for preparation of higher flux hydrophobic/hydrophilic composite membranes for membrane distillation - Khayet Souhaimi, Mohamed; Qtaishat, M.; Matsuura, T.
For the first time, a mathematical model is presented to validate the hydrophobic/hydrophilic composite membrane concept in membrane distillation (MD). This mathematical model aims at providing the optimal characteristics of both hydrophobic and hydrophilic layers as well as giving the guidelines to prepare highly efficient MD membranes. The model was tested by the experimental data obtained from four laboratory-made and two commercial membranes. A very good agreement between the experimental and theoretical values for the vapour fluxes was obtained. In addition, the effect of morphological characteristics of both hydrophobic top-layer and hydrophilic sub-layer was studied by simulating the permeate flux,...

12. Structural and performance studies of poly(vinyl chloride) hollow fiber membranes prepared at different air gap lengths - Khayet Souhaimi, Mohamed; García Payo, María del Carmen; Qusay, F. A.; Zubaidy, M. A.
Poly(vinyl chloride) hollow fiber membranes were prepared by the dry/wet and wet/wet spinning technique at different air gap lengths keeping all other spinning parameters constants. Mean pore size, pore size distribution and mean roughness of both the internal and external surfaces of the hollow fibers were determined by atomic force microscopy. Cross-sectional structure was studied by scanning electron microscopy. Ultrafiltration experiments of pure water and aqueous solutions of different solutes having different molecular weights (bovine serum albumin, polyethylene glycol and polyvinyl pyrrolidone) were carried out. It was found that the inner and outer diameters of the PVC fiber membranes decreased...

13. Comparing the desalination performance of SMM blended polyethersulfone to SMM blended polyetherimide membranes by direct contact membrane distillation - Khayet Souhaimi, Mohamed; Qtaishat, M.; Matsuura, T.; Khulbe, K. C.
This study aims to compare the effect of host hydrophilic polymer on novel hydrophobic/hydrophilic composite membrane characteristics and desalination performance by direct contact membrane distillation (DCMD). Two different polymers are used for the host polymer: polyethersulfone (PES) and polyetherimide (PEI). The membranes were prepared by the phase inversion method by blending surface modifying macromolecules (SMM) into the host hydrophilic polymer (PES and PEI). The membranes were characterized using a wide variety of characterization techniques including the gas permeation test, measurement of the liquid entry pressure of water (LEPw), scanning electronic microscopy (SEM), atomic force microscopy (AFM) and contact angle measurement....

14. Modeling and multi-response optimization of pervaporation of organic aqueous solutions using desirability function approach - Khayet Souhaimi, Mohamed; Cojocaru, C.; Zakrzewska-Trznadel, G.; Jaworska, A.
The factorial design of experiments and desirability function approach has been applied for multiresponse optimization in pervaporation separation process. Two organic aqueous solutions were considered as model mixtures, water/acetonitrile and water/ethanol mixtures. Two responses have been employed in multi-response optimization of pervaporation, total permeate flux and organic selectivity. The effects of three experimental factors (feed temperature, initial concentration of organic compound in feed solution, and downstream pressure) on the pervaporation responses have been investigated. The experiments were performed according to a 21 full factorial experimental design. The factorial models have been obtained from experimental design and validated statistically by analysis...

15. Concentration of olive mill wastewater by membrane distillation for polyphenols recovery - Khayet Souhaimi, Mohamed; El-Abbassi, A.; Hafidi, A.; García Payo, María del Carmen
The possibility of olive mill wastewaters (OMW) treatment and concentration by membrane distillation has been investigated. The objective is to obtain pure water and a concentrate containing high amounts of polyphenols, which can be extracted later. Two types of commercial membranes, polytetrafluoroethylene (TF200) and polyvinilydene fluoride (GVHP), were tested and the effects of membrane parameters on direct contact membrane distillation (DCMD) performance (i.e. permeate flux and polyphenols retention) were studied. The effects of different DCMD operating parameters were also investigated. The obtained results demonstrated the efficiency of DCMD for OMW treatment and concentration. The membrane TF200 showed a better separation...

16. X-Ray diffraction study of polyethersulfone polymer, flat-sheet and hollow fibers prepared from the same under different gas-gaps - Khayet Souhaimi, Mohamed; García Payo, María del Carmen
Polyethersulfone (PES) hollow fiber membranes were prepared by both wet spinning technique, without gas-gap, and dry/wet spinning technique under different gas-gaps, namely, air, oxygen, nitrogen, carbon dioxide, argon and humid air. All spinning parameters were maintained the same except the type of the gas-gap used. Flat-sheets were prepared by the phase-inversion method using the same polymer solution and water as coagulant. The X-ray diffraction pattern of virgin PES indicated that this polymer is mainly amorphous in nature and X-ray diffraction study revealed quite similar structure for flat-sheets and hollow fibers prepared from the PES polymer. It was observed that the...

17. Thermodynamic and dynamic anomalies for dumbbell molecules interacting with a repulsive ramplike potential - Netz, Paulo Augusto; Buldyrev, Sergey V.; Barbosa, Marcia Cristina Bernardes; Stanley, H. Eugene
Using collision driven discrete molecular dynamics, we investigate the thermodynamics and dynamics of systems of 500 dumbbell molecules interacting by a purely repulsive ramplike discretized potential, consisting of n steps of equal size. We compare the behavior of the two systems, with n=18 and n=144 steps. Each system exhibits both thermodynamic and dynamic anomalies, a density maximum and the translational and rotational mobilities show anomalous behavior. Starting with very dense systems and decreasing the density, both mobilities first increase, reach a maximum, then decrease, reach a minimum, and finally increase; this behavior is similar to the behavior of SPC/E Simple...

18. Método dos modelos termodinâmicos simplificados (MMTS) : uma abordagem eficiente para descrever o equilíbrio líquido-vapor - Paranhos, Juliana Feldens
O estudo e a compreensão da termodinâmica é extremamente importante para todos os processos que envolvam equilíbrio de fases. A determinação das propriedades termodinâmicas de uma mistura pode ser obtida por diferentes formas de cálculo, que podem consumir um grande tempo computacional e apresentar difícil solução. Para casos que envolvam controle e simulações online, otimizações em tempo real e até simuladores de treinamento de operadores (OTS) isso pode ser um fator decisivo no emprego da aplicação. Esta dissertação propõe uma nova formulação denominada de Método dos Modelos Termodinâmico Simplificado (MTS) em lugar da utilização dos modelos termodinâmicos locais (MTL), os...

19. Thermodynamics of stress-induced ferroelastic transitions: Influence of anisotropy and disorder - Lloveras Muntané, Pol Marcel; Castán, Teresa; Porta, Marcel; Planes, Antoni; Saxena, Avadh
Stress-induced stress-strain constitutive behavior has been studied in detail in ferroelastic martensites. It has been found that the weights of the long-range anisotropic interactions and of the disorder are important to determine the fine structure of the stress-strain curves. As experiments show, a wide variety of behaviors has been observed. A decrease of anisotropy and/or increase in the disorder results in changes in the temperature range where pseudoplastic and superelastic regimes are observed. Also, a smoothing of the stress-induced ferroelastic transition, accompanied with a decrease in the transition stress and the hysteresis area, is found. However, Clausius-Clapeyron slope has been observed not to depend on the...

20. Bose e Einstein : do nascimento da estatística quântica à condensação sem interação I - Dahmen, Silvio Renato
Em 1924, motivado por um trabalho de S. Bose sobre a radia,c˜ao do corpo negro, A. Einstein escreveu uma série de três artigos acerca das propriedades termodinâmicas de um gás ideal quântico. No segundo destes artigos, publicado em janeiro de 1925, ele previu o fenômeno da “condensação” dos átomos não interagentes no estado fundamental a partir de uma certa densidade crítica do gás, fenômeno este que veio a ser posteriormente conhecido como Condensação de Bose-Einstein (CBE). Neste primeiro artigo discuto detalhadamente o trabalho de Bose e as implicações do método por ele desenvolvido sobre o trabalho de Einstein. Em um...

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