The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Axel Brandenburg - One of the best experts on this subject based on the ideXlab platform.
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The effect of a dynamo-Generated field on the Parker wind
Astronomy & Astrophysics, 2020Co-Authors: P. Jakab, Axel BrandenburgAbstract:Stellar winds are an integral part of the underlying dynamo, the motor of stellar activity. The wind controls the star's angular momentum loss, which depends on the magnetic field geometry which, in turn, varies significantly in time and latitude. Here we study basic properties of a self-consistent model that includes simple representations of both the global stellar dynamo in a spherical shell and the exterior in which the wind accelerates and becomes supersonic. We numerically solve an axisymmetric mean-Field model for the induction, momentum, and continuity equations using an isothermal equation of state. The model allows for the simultaneous generation of a mean magnetic field and the development of a Parker wind. The resulting flow is transonic at the critical point, which we arrange to be between the inner and outer radii of the model. The boundary conditions are assumed to be such that the magnetic field is antisymmetric about the equator, i.e., dipolar. At the solar rotation rate, the dynamo is oscillatory and of $\alpha^2$ type. In most of the domain, the magnetic field corresponds to that of a split monopole. The magnetic energy flux is largest between the stellar surface and the critical point. At rapid rotation of up to 50 times the solar value, most of the magnetic field is lost along the axis within the inner tangential cylinder of the model. The model reveals unexpected features that are not generally anticipated from models that are designed to reproduce the solar wind: highly variable angular momentum flux fluxes even from just an $\alpha^2$ dynamo in the star. For rapid rotation, magnetic fields are ejected mostly along the axis, where the wind speed is reduced.
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Dynamo Generated field emergence through recurrent plasmoid ejections
Astronomy & Astrophysics, 2011Co-Authors: Jörn Warnecke, Axel BrandenburgAbstract:Magnetic buoyancy is believed to drive the transport of magnetic flux tubes from the convection zone to the surface of the Sun. The magnetic fields form twisted loop-like structures in the solar atmosphere. In this paper we use helical forcing to produce a large-scale dynamo-Generated magnetic field, which rises even without magnetic buoyancy. A two layer system is used as computational domain where the upper part represents the solar atmosphere. Here, the evolution of the magnetic field is solved with the stress--and--relax method. Below this region a magnetic field is produced by a helical forcing function in the momentum equation, which leads to dynamo action. We find twisted magnetic fields emerging frequently to the outer layer, forming arch-like structures. In addition, recurrent plasmoid ejections can be found by looking at space--time diagrams of the magnetic field. Recent simulations in spherical coordinates show similar results.
Orestes Llanes-santiago - One of the best experts on this subject based on the ideXlab platform.
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MCPR - Novel Leak Location Approach in Water Distribution Networks with Zone Clustering and Classification
Lecture Notes in Computer Science, 2019Co-Authors: Marcos Quiñones-grueiro, Cristina Verde, Orestes Llanes-santiagoAbstract:A novel leak location approach for large-scale water distribution networks (WDNs) is discussed in this paper. The location task is formulated as a classification problem, and it is simplified by applying a clustering strategy. Data from each class are formed by measurements associated with leakages that occur within a specific zone of the WDN. A zone is defined as a set of nodes that share similar topological properties. Therefore, clustering is performed for network partitioning. Sensors are then placed within the network for maximizing leak detection coverage, and data of each class are Generated by using the EPANET hydraulic simulator. The robustness of the proposal is demonstrated for different kinds of uncertainties and measurements’ noise. A real-life network is used as case study with synthetically Generated field data. The proposal achieves an improved performance for the different scenarios in comparison with the node location approach.
Marcos Quiñones-grueiro - One of the best experts on this subject based on the ideXlab platform.
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MCPR - Novel Leak Location Approach in Water Distribution Networks with Zone Clustering and Classification
Lecture Notes in Computer Science, 2019Co-Authors: Marcos Quiñones-grueiro, Cristina Verde, Orestes Llanes-santiagoAbstract:A novel leak location approach for large-scale water distribution networks (WDNs) is discussed in this paper. The location task is formulated as a classification problem, and it is simplified by applying a clustering strategy. Data from each class are formed by measurements associated with leakages that occur within a specific zone of the WDN. A zone is defined as a set of nodes that share similar topological properties. Therefore, clustering is performed for network partitioning. Sensors are then placed within the network for maximizing leak detection coverage, and data of each class are Generated by using the EPANET hydraulic simulator. The robustness of the proposal is demonstrated for different kinds of uncertainties and measurements’ noise. A real-life network is used as case study with synthetically Generated field data. The proposal achieves an improved performance for the different scenarios in comparison with the node location approach.
Cristina Verde - One of the best experts on this subject based on the ideXlab platform.
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novel leak location approach in water distribution networks with zone clustering and classification
Mexican Conference on Pattern Recognition, 2019Co-Authors: Marcos Quinonesgrueiro, Cristina Verde, Orestes LlanessantiagoAbstract:A novel leak location approach for large-scale water distribution networks (WDNs) is discussed in this paper. The location task is formulated as a classification problem, and it is simplified by applying a clustering strategy. Data from each class are formed by measurements associated with leakages that occur within a specific zone of the WDN. A zone is defined as a set of nodes that share similar topological properties. Therefore, clustering is performed for network partitioning. Sensors are then placed within the network for maximizing leak detection coverage, and data of each class are Generated by using the EPANET hydraulic simulator. The robustness of the proposal is demonstrated for different kinds of uncertainties and measurements’ noise. A real-life network is used as case study with synthetically Generated field data. The proposal achieves an improved performance for the different scenarios in comparison with the node location approach.
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MCPR - Novel Leak Location Approach in Water Distribution Networks with Zone Clustering and Classification
Lecture Notes in Computer Science, 2019Co-Authors: Marcos Quiñones-grueiro, Cristina Verde, Orestes Llanes-santiagoAbstract:A novel leak location approach for large-scale water distribution networks (WDNs) is discussed in this paper. The location task is formulated as a classification problem, and it is simplified by applying a clustering strategy. Data from each class are formed by measurements associated with leakages that occur within a specific zone of the WDN. A zone is defined as a set of nodes that share similar topological properties. Therefore, clustering is performed for network partitioning. Sensors are then placed within the network for maximizing leak detection coverage, and data of each class are Generated by using the EPANET hydraulic simulator. The robustness of the proposal is demonstrated for different kinds of uncertainties and measurements’ noise. A real-life network is used as case study with synthetically Generated field data. The proposal achieves an improved performance for the different scenarios in comparison with the node location approach.
P. Jakab - One of the best experts on this subject based on the ideXlab platform.
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The effect of a dynamo-Generated field on the Parker wind
Astronomy & Astrophysics, 2020Co-Authors: P. Jakab, Axel BrandenburgAbstract:Stellar winds are an integral part of the underlying dynamo, the motor of stellar activity. The wind controls the star's angular momentum loss, which depends on the magnetic field geometry which, in turn, varies significantly in time and latitude. Here we study basic properties of a self-consistent model that includes simple representations of both the global stellar dynamo in a spherical shell and the exterior in which the wind accelerates and becomes supersonic. We numerically solve an axisymmetric mean-Field model for the induction, momentum, and continuity equations using an isothermal equation of state. The model allows for the simultaneous generation of a mean magnetic field and the development of a Parker wind. The resulting flow is transonic at the critical point, which we arrange to be between the inner and outer radii of the model. The boundary conditions are assumed to be such that the magnetic field is antisymmetric about the equator, i.e., dipolar. At the solar rotation rate, the dynamo is oscillatory and of $\alpha^2$ type. In most of the domain, the magnetic field corresponds to that of a split monopole. The magnetic energy flux is largest between the stellar surface and the critical point. At rapid rotation of up to 50 times the solar value, most of the magnetic field is lost along the axis within the inner tangential cylinder of the model. The model reveals unexpected features that are not generally anticipated from models that are designed to reproduce the solar wind: highly variable angular momentum flux fluxes even from just an $\alpha^2$ dynamo in the star. For rapid rotation, magnetic fields are ejected mostly along the axis, where the wind speed is reduced.