The Experts below are selected from a list of 35241 Experts worldwide ranked by ideXlab platform
Anil K. Chopra - One of the best experts on this subject based on the ideXlab platform.
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linear analysis of concrete arch dams including dam water foundation Rock Interaction considering spatially varying ground motions
Earthquake Engineering & Structural Dynamics, 2010Co-Authors: Jin-ting Wang, Anil K. ChopraAbstract:The available substructure method and computer program for earthquake response analysis of arch dams, including the effects of dam–water–foundation Rock Interaction and recognizing the semi-unbounded size of the foundation Rock and fluid domains, are extended to consider spatial variations in ground motions around the canyon. The response of Mauvoisin Dam in Switzerland to spatially varying ground motion recorded during a small earthquake is analyzed to illustrate the results from this analysis procedure. Copyright © 2009 John Wiley & Sons, Ltd.
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earthquake analysis of arch dams including dam water foundation Rock Interaction
Earthquake Engineering & Structural Dynamics, 1995Co-Authors: Hanchen Tan, Anil K. ChopraAbstract:The available substructure method and computer program for the earthquake response analysis of arch dams, including the effects of dam-water Interaction, reservoir boundary absorption, and foundation Rock flexibility, is extended to include the effects of dam-foundation Rock Interaction with inertia and damping of the foundation Rock considered. Efficient techniques are developed for evaluating the foundation impedance terms, computationally the most demanding part of the procedure.
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dam foundation Rock Interaction effects in frequency response functions of arch dams
Earthquake Engineering & Structural Dynamics, 1995Co-Authors: Hanchen Tan, Anil K. ChopraAbstract:The linear response of a selected arch dam to harmonic upstream, vertical or cross-stream ground motion is presented for a wide range of the important system parameters characterizing the properties of the dam, foundation Rock, impounded water and reservoir boundary materials. Based on these frequency-response functions, the dam-foundation Rock Interaction effects in the dynamic response of arch dams are investigated.
T.g. Ritto - One of the best experts on this subject based on the ideXlab platform.
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stochastic modeling for hysteretic bit Rock Interaction of a drill string under torsional vibrations
Journal of Vibration and Control, 2019Co-Authors: F F Real, Anas Batou, T.g. Ritto, Christophe DesceliersAbstract:This paper aims at constructing a stochastic model for the hysteretic behavior of the nonlinear bit–Rock Interaction of a drill string under torsional vibrations. The proposed model takes into acco...
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hysteretic bit Rock Interaction model to analyze the torsional dynamics of a drill string
Mechanical Systems and Signal Processing, 2018Co-Authors: F F Real, Anas Batou, Christophe Desceliers, T.g. Ritto, R R AguiarAbstract:Abstract The present paper proposes a novel hysteretic (non-reversible) bit/Rock Interaction model for the torsional dynamics of a drill string. Non-reversible means that the torque-on-bit depends not only on the bit speed, but also on the bit acceleration, producing a type of hysteretic cycle. The continuous drill string system is discretized by means of the finite element method and a reduced-order model is constructed using the normal modes of the associated conservative system. The parameters of the proposed hysteretic bit/Rock Interaction model is fitted with field data. The non-linear torsional vibration and the stability map of the drill string system are analyzed employing the proposed bit/Rock Interaction model and also a commonly used reversible model (without hysteresis). It turns out that the hysteretic model affects the stability region of the system.
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bayesian approach to identify the bit Rock Interaction parameters of a drill string dynamical model
Journal of The Brazilian Society of Mechanical Sciences and Engineering, 2015Co-Authors: T.g. RittoAbstract:A drill string is a slender structure used to search for oil and gas. Many works have tackled the problem of modeling the drill-string dynamics in a vertical well. One important aspect in this dynamics is the bit–Rock Interaction, and, therefore, an identification of the parameters of the bit–Rock Interaction model becomes crucial. Few works related to this identification problem have been published. The present paper applies the Bayesian approach to identify the parameters of the bit–Rock Interaction model considering a simplified drill-string dynamical model which takes into account only torsional vibrations. It is assumed an additive Gaussian noise model, and the Metropolis–Hasting algorithm is used to approximate the posterior distribution of the variables analyzed.
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probabilistic model identification of the bit Rock Interaction model uncertainties in nonlinear dynamics of a drill string
Mechanics Research Communications, 2010Co-Authors: T.g. Ritto, Christian Soize, R. SampaioAbstract:Abstract This paper deals with a procedure to perform the identification of the probabilistic model of uncertainties in a bit–Rock Interaction model for the nonlinear dynamics of a drill-string. The bit–Rock Interaction model is represented by a nonlinear constitutive equation, whose uncertainties are modeled using the nonparametric probabilistic approach. The identification of the parameter of this probabilistic model is carried out using the maximum likelihood method together with a statistical reduction in the frequency domain using the Principal Component Analysis.
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Probabilistic model identification of uncertainties for the bit-Rock Interaction model (local nonlinearity) of a drill-string system
2010Co-Authors: T.g. Ritto, Christian Soize, R. SampaioAbstract:This paper deals with a procedure to perform the identification of the probabilistic model of uncertainties for the bit-Rock Interaction model of a drill-string system. The bit-Rock Interaction model is represented by a nonlinear constitutive equation, whose uncertainties are modeled using the nonparametric probabilistic approach. The identification of the parameter of this probabilistic model is carried out using the Maximum Likelihood method together with a statistical reduction in the frequency domain using the Principal Component Analysis. This is the first time that a procedure is proposed to identify the probabilistic model, in the context of drill-string dynamics.
Ralf Halama - One of the best experts on this subject based on the ideXlab platform.
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boron isotope record of peak metamorphic ultrahigh pressure and retrograde fluid Rock Interaction in white mica lago di cignana western alps
Contributions to Mineralogy and Petrology, 2020Co-Authors: Ralf Halama, Matthias Konradschmolke, Jan C. M. HoogAbstract:: This study presents boron (B) concentration and isotope data for white mica from (ultra)high-pressure (UHP), subduction-related metamorphic Rocks from Lago di Cignana (Western Alps, Italy). These Rocks are of specific geological interest, because they comprise the most deeply subducted Rocks of oceanic origin worldwide. Boron geochemistry can track fluid-Rock Interaction during their metamorphic evolution and provide important insights into mass transfer processes in subduction zones. The highest B contents (up to 345 μg/g B) occur in peak metamorphic phengite from a garnet-phengite quartzite. The B isotopic composition is variable (δ11B = - 10.3 to - 3.6%) and correlates positively with B concentrations. Based on similar textures and major element mica composition, neither textural differences, prograde growth zoning, diffusion nor a retrograde overprint can explain this correlation. Modelling shows that B devolatilization during metamorphism can explain the general trend, but fails to account for the wide compositional and isotopic variability in a single, well-equilibrated sample. We, therefore, argue that this trend represents fluid-Rock Interaction during peak metamorphic conditions. This interpretation is supported by fluid-Rock Interaction modelling of boron leaching and boron addition that can successfully reproduce the observed spread in δ11B and [B]. Taking into account the local availability of serpentinites as potential source Rocks of the fluids, the temperatures reached during peak metamorphism that allow for serpentine dehydration, and the high positive δ11B values (δ11B = 20 ± 5) modelled for the fluids, an influx of serpentinite-derived fluid appears likely. Paragonite in lawsonite pseudomorphs in an eclogite and phengite from a retrogressed metabasite have B contents between 12 and 68 μg/g and δ11B values that cluster around 0% (δ11B = - 5.0 to + 3.5). White mica in both samples is related to distinct stages of retrograde metamorphism during exhumation of the Rocks. The variable B geochemistry can be successfully modelled as fluid-Rock Interaction with low-to-moderate (< 3) fluid/Rock ratios, where mica equilibrates with a fluid into which B preferentially partitions, causing leaching of B from the Rock. The metamorphic Rocks from Lago di Cignana show variable retention of B in white mica during subduction-related metamorphism and exhumation. The variability in the B geochemical signature in white mica is significant and enhances our understanding of metamorphic processes and their role in element transfer in subduction zones.
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combined thermodynamic geochemical modeling in metamorphic geology boron as tracer of fluid Rock Interaction
Lithos, 2014Co-Authors: Matthias Konradschmolke, Ralf HalamaAbstract:Abstract Quantitative geochemical modeling is today applied in a variety of geological environments from the petrogenesis of igneous Rocks to radioactive waste disposal. In addition, the development of thermodynamic databases and computer programs to calculate equilibrium phase diagrams has greatly advanced our ability to model geodynamic processes. Combined with experimental data on elemental partitioning and isotopic fractionation, thermodynamic forward modeling unfolds enormous capacities that are far from exhausted. In metamorphic petrology the combination of thermodynamic and trace element forward modeling can be used to study and to quantify processes at spatial scales from μm to km. The thermodynamic forward models utilize Gibbs energy minimization to quantify mineralogical changes along a reaction path of a chemically open fluid/Rock system. These results are combined with mass balanced trace element calculations to determine the trace element distribution between Rock and melt/fluid during the metamorphic evolution. Thus, effects of mineral reactions, fluid–Rock Interaction and element transport in metamorphic Rocks on the trace element and isotopic composition of minerals, Rocks and percolating fluids or melts can be predicted. Here we illustrate the capacities of combined thermodynamic–geochemical modeling based on two examples relevant to mass transfer during metamorphism. The first example focuses on fluid–Rock Interaction in and around a blueschist-facies shear zone in felsic gneisses, where fluid-induced mineral reactions and their effects on boron (B) concentrations and isotopic compositions in white mica are modeled. In the second example, fluid release from a subducted slab, the associated transport of B as well as variations in B concentrations and isotopic compositions in liberated fluids and residual Rocks are modeled. We compare the modeled results of both examples to geochemical data of natural minerals and Rocks and demonstrate that the combination of thermodynamic and geochemical models enables quantification of metamorphic processes and insights into element cycling that would have been unattainable if only one model approach was chosen.
Jan C. M. Hoog - One of the best experts on this subject based on the ideXlab platform.
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boron isotope record of peak metamorphic ultrahigh pressure and retrograde fluid Rock Interaction in white mica lago di cignana western alps
Contributions to Mineralogy and Petrology, 2020Co-Authors: Ralf Halama, Matthias Konradschmolke, Jan C. M. HoogAbstract:: This study presents boron (B) concentration and isotope data for white mica from (ultra)high-pressure (UHP), subduction-related metamorphic Rocks from Lago di Cignana (Western Alps, Italy). These Rocks are of specific geological interest, because they comprise the most deeply subducted Rocks of oceanic origin worldwide. Boron geochemistry can track fluid-Rock Interaction during their metamorphic evolution and provide important insights into mass transfer processes in subduction zones. The highest B contents (up to 345 μg/g B) occur in peak metamorphic phengite from a garnet-phengite quartzite. The B isotopic composition is variable (δ11B = - 10.3 to - 3.6%) and correlates positively with B concentrations. Based on similar textures and major element mica composition, neither textural differences, prograde growth zoning, diffusion nor a retrograde overprint can explain this correlation. Modelling shows that B devolatilization during metamorphism can explain the general trend, but fails to account for the wide compositional and isotopic variability in a single, well-equilibrated sample. We, therefore, argue that this trend represents fluid-Rock Interaction during peak metamorphic conditions. This interpretation is supported by fluid-Rock Interaction modelling of boron leaching and boron addition that can successfully reproduce the observed spread in δ11B and [B]. Taking into account the local availability of serpentinites as potential source Rocks of the fluids, the temperatures reached during peak metamorphism that allow for serpentine dehydration, and the high positive δ11B values (δ11B = 20 ± 5) modelled for the fluids, an influx of serpentinite-derived fluid appears likely. Paragonite in lawsonite pseudomorphs in an eclogite and phengite from a retrogressed metabasite have B contents between 12 and 68 μg/g and δ11B values that cluster around 0% (δ11B = - 5.0 to + 3.5). White mica in both samples is related to distinct stages of retrograde metamorphism during exhumation of the Rocks. The variable B geochemistry can be successfully modelled as fluid-Rock Interaction with low-to-moderate (< 3) fluid/Rock ratios, where mica equilibrates with a fluid into which B preferentially partitions, causing leaching of B from the Rock. The metamorphic Rocks from Lago di Cignana show variable retention of B in white mica during subduction-related metamorphism and exhumation. The variability in the B geochemical signature in white mica is significant and enhances our understanding of metamorphic processes and their role in element transfer in subduction zones.
Eysa Salajegheh - One of the best experts on this subject based on the ideXlab platform.
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Shape optimal design of materially nonlinear arch dams including dam-water-foundation Rock Interaction using an improved PSO algorithm
Optimization and Engineering, 2012Co-Authors: S M Seyedpoor, J Salajegheh, Eysa SalajeghehAbstract:An efficient optimization procedure is proposed to find the optimal shape of arch dams including dam-water-foundation Rock Interaction subject to earthquake. The arch dam is treated as a three-dimensional structure involving the material nonlinearity effects. For this purpose, the nonlinear behavior of the dam concrete is idealized as an elasto-plastic material using the Drucker-Prager model. In order to reduce the computational cost of optimization process, a wavelet back propagation (WBP) neural network is designed to approximate the dam response instead of directly evaluating it by a time-consuming finite element analysis (FEA). An improved particle swarm optimization (IPSO) is also presented. In test example, the computational merits of the proposed methodology for optimizing an existing arch dam are demonstrated.
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shape optimal design of arch dams including dam water foundation Rock Interaction using a grading strategy and approximation concepts
Applied Mathematical Modelling, 2010Co-Authors: S M Seyedpoor, J Salajegheh, Eysa SalajeghehAbstract:Abstract Optimal design of arch dams including dam-water–foundation Rock Interaction is achieved using the soft computing techniques. For this, linear dynamic behavior of arch dam-water–foundation Rock system subjected to earthquake ground motion is simulated using the finite element method at first and then, to reduce the computational cost of optimization process, a wavelet back propagation neural network (WBPNN) is designed to predict the arch dam response instead of directly evaluating it by a time-consuming finite-element analysis (FEA). In order to enhance the performance generality of the neural network, a dam grading technique (DGT) is also introduced. To assess the computational efficiency of the proposed methodology for arch dam optimization, an actual arch dam is considered. The optimization is implemented via the simultaneous perturbation stochastic approximation (SPSA) algorithm for the various conditions of the Interaction problem. Numerical results show the merits of the suggested techniques for arch dam optimization. It is also found that considering the dam-water–foundation Rock Interaction has an important role for safely designing an arch dam.
