The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Tasnuva Moutushi - One of the best experts on this subject based on the ideXlab platform.
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fixed bed reactors for exothermic reactions a Qualitative Relation between start up time and traveling waves velocity
Chemical Engineering Science, 2021Co-Authors: Axel Fache, Frederic Marias, Marco J Castaldi, Michael Lugopimentel, Yegor Nikitin, Tasnuva MoutushiAbstract:Abstract An experimental investigation of the reaction front movements upon reacting gas injection in a pre-heated non-adiabatic fixed-bed methanation reactor is conducted. The relocation starts with a backward movement of the front, whose maximal velocity turns out to be a linear function of the temperature setpoint. The front then moves forward in response to the fact that the injected cold gas cools down the bed in the upstream zone. The front stabilizes asymptotically in the downstream (upstream, resp.) zone of the reactor after a characteristic time that is an increasing (decreasing, resp.) function of the temperature setpoint, if the setpoint is below (above, resp.) a certain threshold. This behavior is interpreted in terms of reaction wave velocity.
Kuang-yin Song - One of the best experts on this subject based on the ideXlab platform.
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Calculation Method and Distribution Characteristics of Fracture Hydraulic Aperture from Field Experiments in Fractured Granite Area
Rock Mechanics and Rock Engineering, 2015Co-Authors: Yang-bing Cao, Xia-ting Feng, E-chuan Yan, Gang Chen, Kuang-yin SongAbstract:Knowledge of the fracture hydraulic aperture and its Relation to the mechanical aperture and normal stress is urgently needed in engineering construction and analytical research at the engineering field scale. A new method based on the in situ borehole camera measurement and borehole water-pressure test is proposed for the calculation of the fracture hydraulic aperture. This method comprises six steps. The first step is to obtain the equivalent hydraulic conductivity of the test section from borehole water-pressure tests. The second step is a tentative calculation to obtain the Qualitative Relation between the reduction coefficient and the mechanical aperture obtained from borehole camera measurements. The third step is to choose the preliminary reduction coefficient for obtaining the initial hydraulic aperture. The remaining three steps are to optimize, using the genetic algorithm, the hydraulic apertures of fractures with high uncertainty. The method is then applied to a fractured granite engineering area whose purpose is the construction of an underground water-sealed storage cavern for liquefied petroleum gas. The probability distribution characteristics of the hydraulic aperture, the Relationship between the hydraulic aperture and the mechanical aperture, the hydraulic aperture and the normal stress, and the differences between altered fractures and fresh fractures are all analyzed. Based on the effects of the engineering applications, the method is proved to be feasible and reliable. More importantly, the results of the hydraulic aperture obtained in this paper are different from those results elicited from laboratory tests, and the reasons are discussed in the paper.
Hernández Santana Senaida - One of the best experts on this subject based on the ideXlab platform.
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Local temperature and corRelations in quantum many-body systems
Universitat Politècnica de Catalunya, 2019Co-Authors: Hernández Santana SenaidaAbstract:Quantum Mechanics was established as the theory of the microscopic world, which allowed to understand processes in atoms and molecules. Its emergence led to a new scientific paradigm that quickly spread to different research fields. Two relevant examples are Quantum Thermodynamics and Quantum Many-Body Theory, where the former aims to characterize thermodynamic processes in quantum systems and the latter intends to understand the properties of quantum many-body systems. In this thesis, we tackle some of the questions in the overlap between these disciplines, focusing on the concepts of temperature and corRelations. Specifically, it contains results on the following topics: locality of temperature, corRelations in long-range interacting systems and thermometry at low temperature. The problem of locality of temperature is considered for a system at thermal equilibrium and consists in studying whether it is possible to assign a temperature to any of the subsystems of the global system such that both local and global temperatures are equal. We tackle this problem in two different settings, for generic one-dimensional spin chains and for a bosonic system with a phase transition at non-zero temperature. In the first case, we consider generic one-dimensional translation-invariant spin systems with short-range interactions and prove that it is always possible to assign a local temperature equal to the global one for any temperature, including at criticality. For the second case, we consider a three-dimensional discretized version of the Bose-Einstein model at the grand canonical ensemble for some temperature and particle density, and characterize its non-zero-temperature phase transition. Then, we show that temperature is locally well-defined at any temperature and at any particle density, including at the phase transition. Additionally, we observe a Qualitative Relation between corRelations and locality of temperature in the system. Moving to corRelations, we consider fermionic two-site long-range interacting systems at thermal equilibrium. We show that corRelations between anti-commutative operators at non-zero temperature are upper bounded by a function that decays polynomially with the distance and with an exponent that is equal to the interaction exponent, which characterizes the interactions in the Hamiltonian. Moreover, we show that our bound is asymptotically tight and that the results extend to density-density corRelations as well as other types of corRelations for quadratic and fermionic Hamiltonians with long-range interactions. Regarding the results on thermometry, we consider a bosonic model and prove that strong coupling between the probe and the system can boost the thermal sensitivity for low temperature. Furthermore, we provide a feasible measurement scheme capable of producing optimal estimates at the considered regime.La Mecánica Cuántica fue establecida como la teoría del mundo microscópico, el cual permitió entender los procesos en átomos y moléculas. Su nacimiento llevo a un nuevo paradigma científico que se propagó rápidamente a otros campos de investigación. Dos ejemplos relevantes son la Termodinámica Cuántica y la Teoría Cuántica de muchos cuerpos, donde la primera pretende caracterizar los procesos termodinamicos en sistemas cuántico y la segunda intenta entender las propiedades de los sistemas cuánticos de muchos cuerpos. En esta tesis, atacamos algunas de las preguntas en la intersección entre estas disciplinas, enfocandonos en los conceptos de la temperatura y las correlaciones. Específicamente, contiene resutlados en os siguientes temas: localidad de la temperature, correlaciones en sistemas interactuantes de largo alcance y termometría a baja temperature. El problema de localidad de la temperatura es considerado para un sistema a equilibrio térmico y consiste en estudiar si es posible asignar temperature a cualquiera de los subsistemas del sistema global tal que la temperature local y global sean equivalentes. Atacamos este problemas en dos casos diferentes, for cadenas de spines genéricas y para un sistema de bosones con una transición de fase a temperature distinta a cero. En el primer caso, consideramos sistemas de espines invarantes traslacional y de una dimensión con interactions de corto alcance y provamos que siempre es posible asignar una temperature local igual a la global para cualquier temperature, incluyendo en la criticalidad. Para el segundo caso, consideramos una versión 3D y discretizada del modelo de Bose-Einstein en el estado gran canónico para alguna temperature y densidad de partículas, y caracterizamos su transición a temperatura distinta a cero. Luego, mostramos que la temperature esta localmente bien definida a cualquier temperature y cualquier densidad de partículas, incluyendo en la transición de fase. Adicionalment, observamos una relación cualitativa entre las correlaciones y la localidad de la temperature en el sistema. Moviéndonos a las correlaciones, consideramos sistemas fermiónicos de con interaction entre dos cuerpos y de largo alcance a equilibrio térmico. Mostramos que las corRelations entre los operadores anti-comutativos at temperatura distinta a cero estan acotadas por arriba por una función que decae polinomiamente con la distancia y con un exponent que es igual al exponente de interacción, el cual caracteriza las interacciones en el Hamiltoniano. Además, mostrado que nuestro límite es "ajustado" asintoticamente y que los resultados se extiense a corRelations entre operadores de densidad y a otros tipos de correlaciones para Hamiltonianos cuadráticos y fermiónicos con interacciones de largo alcance. Sobre los resultados en termometría, consideramos un modelo bosónico y provamos que el acoplamiento fuerte entre el termómetro y el sistema pueda incrementar la sensibilidad térmica para baja temperatura. Además, explicamos un esquema de medida accesible y capaz de producir estimación óptimas en el régimen que consideramosPostprint (published version
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Local temperature and corRelations in quantum many-body systems
Universitat Politècnica de Catalunya, 2019Co-Authors: Hernández Santana SenaidaAbstract:Quantum Mechanics was established as the theory of the microscopic world, which allowed to understand processes in atoms and molecules. Its emergence led to a new scientific paradigm that quickly spread to different research fields. Two relevant examples are Quantum Thermodynamics and Quantum Many-Body Theory, where the former aims to characterize thermodynamic processes in quantum systems and the latter intends to understand the properties of quantum many-body systems. In this thesis, we tackle some of the questions in the overlap between these disciplines, focusing on the concepts of temperature and corRelations. Specifically, it contains results on the following topics: locality of temperature, corRelations in long-range interacting systems and thermometry at low temperature. The problem of locality of temperature is considered for a system at thermal equilibrium and consists in studying whether it is possible to assign a temperature to any of the subsystems of the global system such that both local and global temperatures are equal. We tackle this problem in two different settings, for generic one-dimensional spin chains and for a bosonic system with a phase transition at non-zero temperature. In the first case, we consider generic one-dimensional translation-invariant spin systems with short-range interactions and prove that it is always possible to assign a local temperature equal to the global one for any temperature, including at criticality. For the second case, we consider a three-dimensional discretized version of the Bose-Einstein model at the grand canonical ensemble for some temperature and particle density, and characterize its non-zero-temperature phase transition. Then, we show that temperature is locally well-defined at any temperature and at any particle density, including at the phase transition. Additionally, we observe a Qualitative Relation between corRelations and locality of temperature in the system. Moving to corRelations, we consider fermionic two-site long-range interacting systems at thermal equilibrium. We show that corRelations between anti-commutative operators at non-zero temperature are upper bounded by a function that decays polynomially with the distance and with an exponent that is equal to the interaction exponent, which characterizes the interactions in the Hamiltonian. Moreover, we show that our bound is asymptotically tight and that the results extend to density-density corRelations as well as other types of corRelations for quadratic and fermionic Hamiltonians with long-range interactions. Regarding the results on thermometry, we consider a bosonic model and prove that strong coupling between the probe and the system can boost the thermal sensitivity for low temperature. Furthermore, we provide a feasible measurement scheme capable of producing optimal estimates at the considered regime.La Mecánica Cuántica fue establecida como la teoría del mundo microscópico, el cual permitió entender los procesos en átomos y moléculas. Su nacimiento llevo a un nuevo paradigma científico que se propagó rápidamente a otros campos de investigación. Dos ejemplos relevantes son la Termodinámica Cuántica y la Teoría Cuántica de muchos cuerpos, donde la primera pretende caracterizar los procesos termodinamicos en sistemas cuántico y la segunda intenta entender las propiedades de los sistemas cuánticos de muchos cuerpos. En esta tesis, atacamos algunas de las preguntas en la intersección entre estas disciplinas, enfocandonos en los conceptos de la temperatura y las correlaciones. Específicamente, contiene resutlados en os siguientes temas: localidad de la temperature, correlaciones en sistemas interactuantes de largo alcance y termometría a baja temperature. El problema de localidad de la temperatura es considerado para un sistema a equilibrio térmico y consiste en estudiar si es posible asignar temperature a cualquiera de los subsistemas del sistema global tal que la temperature local y global sean equivalentes. Atacamos este problemas en dos casos diferentes, for cadenas de spines genéricas y para un sistema de bosones con una transición de fase a temperature distinta a cero. En el primer caso, consideramos sistemas de espines invarantes traslacional y de una dimensión con interactions de corto alcance y provamos que siempre es posible asignar una temperature local igual a la global para cualquier temperature, incluyendo en la criticalidad. Para el segundo caso, consideramos una versión 3D y discretizada del modelo de Bose-Einstein en el estado gran canónico para alguna temperature y densidad de partículas, y caracterizamos su transición a temperatura distinta a cero. Luego, mostramos que la temperature esta localmente bien definida a cualquier temperature y cualquier densidad de partículas, incluyendo en la transición de fase. Adicionalment, observamos una relación cualitativa entre las correlaciones y la localidad de la temperature en el sistema. Moviéndonos a las correlaciones, consideramos sistemas fermiónicos de con interaction entre dos cuerpos y de largo alcance a equilibrio térmico. Mostramos que las corRelations entre los operadores anti-comutativos at temperatura distinta a cero estan acotadas por arriba por una función que decae polinomiamente con la distancia y con un exponent que es igual al exponente de interacción, el cual caracteriza las interacciones en el Hamiltoniano. Además, mostrado que nuestro límite es "ajustado" asintoticamente y que los resultados se extiense a corRelations entre operadores de densidad y a otros tipos de correlaciones para Hamiltonianos cuadráticos y fermiónicos con interacciones de largo alcance. Sobre los resultados en termometría, consideramos un modelo bosónico y provamos que el acoplamiento fuerte entre el termómetro y el sistema pueda incrementar la sensibilidad térmica para baja temperatura. Además, explicamos un esquema de medida accesible y capaz de producir estimación óptimas en el régimen que consideramo
Axel Fache - One of the best experts on this subject based on the ideXlab platform.
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fixed bed reactors for exothermic reactions a Qualitative Relation between start up time and traveling waves velocity
Chemical Engineering Science, 2021Co-Authors: Axel Fache, Frederic Marias, Marco J Castaldi, Michael Lugopimentel, Yegor Nikitin, Tasnuva MoutushiAbstract:Abstract An experimental investigation of the reaction front movements upon reacting gas injection in a pre-heated non-adiabatic fixed-bed methanation reactor is conducted. The relocation starts with a backward movement of the front, whose maximal velocity turns out to be a linear function of the temperature setpoint. The front then moves forward in response to the fact that the injected cold gas cools down the bed in the upstream zone. The front stabilizes asymptotically in the downstream (upstream, resp.) zone of the reactor after a characteristic time that is an increasing (decreasing, resp.) function of the temperature setpoint, if the setpoint is below (above, resp.) a certain threshold. This behavior is interpreted in terms of reaction wave velocity.
Yang-bing Cao - One of the best experts on this subject based on the ideXlab platform.
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Calculation Method and Distribution Characteristics of Fracture Hydraulic Aperture from Field Experiments in Fractured Granite Area
Rock Mechanics and Rock Engineering, 2015Co-Authors: Yang-bing Cao, Xia-ting Feng, E-chuan Yan, Gang Chen, Kuang-yin SongAbstract:Knowledge of the fracture hydraulic aperture and its Relation to the mechanical aperture and normal stress is urgently needed in engineering construction and analytical research at the engineering field scale. A new method based on the in situ borehole camera measurement and borehole water-pressure test is proposed for the calculation of the fracture hydraulic aperture. This method comprises six steps. The first step is to obtain the equivalent hydraulic conductivity of the test section from borehole water-pressure tests. The second step is a tentative calculation to obtain the Qualitative Relation between the reduction coefficient and the mechanical aperture obtained from borehole camera measurements. The third step is to choose the preliminary reduction coefficient for obtaining the initial hydraulic aperture. The remaining three steps are to optimize, using the genetic algorithm, the hydraulic apertures of fractures with high uncertainty. The method is then applied to a fractured granite engineering area whose purpose is the construction of an underground water-sealed storage cavern for liquefied petroleum gas. The probability distribution characteristics of the hydraulic aperture, the Relationship between the hydraulic aperture and the mechanical aperture, the hydraulic aperture and the normal stress, and the differences between altered fractures and fresh fractures are all analyzed. Based on the effects of the engineering applications, the method is proved to be feasible and reliable. More importantly, the results of the hydraulic aperture obtained in this paper are different from those results elicited from laboratory tests, and the reasons are discussed in the paper.
