The Experts below are selected from a list of 426204 Experts worldwide ranked by ideXlab platform
Izuru Takewaki - One of the best experts on this subject based on the ideXlab platform.
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Critical Response of elastic plastic sdof systems with nonlinear viscous damping under simulated earthquake ground motions
Heliyon, 2019Co-Authors: Goki Tamura, Kotaro Kojima, Izuru TakewakiAbstract:Abstract Multi impulse with constant time interval is used as a representative of a long-duration earthquake ground motion. An analytical expression is derived for the elastic-plastic Response of a single-degree-of-freedom (SDOF) model with nonlinear viscous damping subjected to the "Critical multi impulse" which maximizes the Response. The fact that only free vibration appears under such multi impulse enables the smart application of an energy approach in deriving the analytical expression for a complicated elastic-plastic Response with nonlinear viscous damping. The nonlinear viscous damping characteristic for deformation is approximated in terms of a quadratic or elliptical function. The Critical timing of the impulses is found to correspond to the zero restoring-force timing or the maximum velocity timing depending on the input level. It is shown that the nonlinearity in viscous damping causes a remarkable influence on the earthquake Response in some cases. The reliability and accuracy of the proposed theory are investigated through the comparison with the results by the time-history Response analysis to the tuned sine wave as a representative of the long-duration earthquake ground motion.
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Critical Response of elastic-plastic SDOF systems with nonlinear viscous damping under simulated earthquake ground motions
Elsevier, 2019Co-Authors: Goki Tamura, Kotaro Kojima, Izuru TakewakiAbstract:Multi impulse with constant time interval is used as a representative of a long-duration earthquake ground motion. An analytical expression is derived for the elastic-plastic Response of a single-degree-of-freedom (SDOF) model with nonlinear viscous damping subjected to the “Critical multi impulse” which maximizes the Response. The fact that only free vibration appears under such multi impulse enables the smart application of an energy approach in deriving the analytical expression for a complicated elastic-plastic Response with nonlinear viscous damping. The nonlinear viscous damping characteristic for deformation is approximated in terms of a quadratic or elliptical function. The Critical timing of the impulses is found to correspond to the zero restoring-force timing or the maximum velocity timing depending on the input level. It is shown that the nonlinearity in viscous damping causes a remarkable influence on the earthquake Response in some cases. The reliability and accuracy of the proposed theory are investigated through the comparison with the results by the time-history Response analysis to the tuned sine wave as a representative of the long-duration earthquake ground motion. Keywords: Civil engineering, Natural hazards, Structural engineerin
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Critical Response evaluation of damped bilinear hysteretic sdof model under long duration ground motion simulated by multi impulse motion
International Journal of Earthquake and Impact Engineering, 2018Co-Authors: Hiroki Akehashi, Kotaro Kojima, Ehsan Noroozinejad Farsangi, Izuru TakewakiAbstract:Multi impulse is used as a representative of a series of many-cycle harmonic waves which substantially simulate the long-duration earthquake event. An analytical formulation is developed for the elastic-plastic Response of a single-degree-of-freedom (SDOF) damped structure with bilinear hysteresis under the Critical multi impulse condition. Following the procedure for elastic-perfectly plastic models, a novel procedure using an energy balance law is introduced. In this procedure, under the multi impulse condition, only the free-vibration exists, hence the energy balance law can be applied easily. An approximate but effective treatment of the energy dissipated by the viscous damping is a new perspective. It is shown that based on an analytical solution, the Critical maximum plastic deformation and the corresponding Critical impulse timing can be determined in the steady state condition depending on the input values. To investigate the reliability and accuracy of the proposed approach, a comparison is made with the Response analysis outcome to the corresponding sine wave as a representative of the long-duration earthquake ground motion (GM).
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Critical Response of single degree of freedom damped bilinear hysteretic system under double impulse as substitute for near fault ground motion
Frontiers in Built Environment, 2018Co-Authors: Hiroki Akehashi, Kotaro Kojima, Izuru TakewakiAbstract:A double impulse input is used as a substitute for near-fault earthquake ground motions. A closed-form expression is derived in the maximum elastic-plastic Response of a single-degree-of-freedom (SDOF) damped structure with bilinear hysteresis under the ‘Critical double impulse input’ which causes the maximum Response for variable impulse interval with the input level kept constant. Since only the free-vibration exists under the double impulse, the energy balance approach for the kinetic energy, hysteretic and strain energies, and damping energy plays a key role in the derivation of the closed-form expression of a complicated damped bilinear hysteretic Response. It is shown that the Critical elastic-plastic deformation and the corresponding Critical impulse timing can be derived depending on the input level. The accuracy of the proposed simplified but smart methodology is confirmed through the comparison with the Response analysis to the Critical double impulse and the corresponding one-cycle sine wave as a representative for the near-fault earthquake ground motion.
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robustness of sdof elastoplastic structure subjected to double impulse input under simultaneous uncertainties of yield deformation and stiffness
International Journal of Non-linear Mechanics, 2017Co-Authors: Yoshihiro Kanno, Kohei Fujita, Keisuke Yasuda, Izuru TakewakiAbstract:Abstract A series of impulse-type inputs has been extensively used to evaluate the Critical Response of an elastoplastic structure subjected to diverse types of pulse-type inputs, including a near-fault ground motion. In this paper, we consider the Critical double-impulse input for a single-degree-of-freedom elastic–perfectly plastic structure, and study effects of structural uncertainties. When the natural frequency (or, equivalently, the stiffness) is fixed, the Critical Response of the structure does not necessarily decrease as the yield deformation (or, equivalently, the yield force) increases. As the first contribution, we give through investigation of this non-monotonicity property. Moreover, we present a systematic method for finding the worst-case scenario when the yield deformation and the stiffness of a structure assumed to be uncertain simultaneously. Numerical examples are presented to illustrate that the robustness of a structure does not necessarily improve when the yield deformation and/or the yield force is increased.
Mark Omalley - One of the best experts on this subject based on the ideXlab platform.
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market designs for the primary frequency Response ancillary service
Power and Energy Society General Meeting, 2014Co-Authors: Erik Ela, Vahan Gevorgian, Aidan Tuohy, Brendan Kirby, Michael Milligan, Mark OmalleyAbstract:The first part of this two-paper series discusses the motivation of implementing a primary frequency Response (PFR) market in restructured pool-based power markets, as well as the market design that would create the right incentives to provide the Response reliably. PFR is the immediate, autonomous Response of generation and demand to system frequency deviations. It is the Critical Response required to avoid triggering under- and over-frequency relays or instability that could lead to machine damage, load-shedding, and in the extreme case, blackouts. Currently, in many restructured power systems throughout the world, ancillary services markets have been developed to incent technologies to provide the services to support power system reliability. However, few ancillary services markets include a market explicitly incentivizing the provision of PFR. Historically, PFR was an inherent feature available in conventional generating technologies, and in most systems, more was available than needed. Yet, recent trends in declining frequency Response, the introduction of emerging technologies, and market behavior may soon require innovative market designs to incent resources to provide this valuable service.
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market designs for the primary frequency Response ancillary service part i motivation and design
IEEE Transactions on Power Systems, 2014Co-Authors: Vahan Gevorgian, Aidan Tuohy, Brendan Kirby, Michael Milligan, Mark OmalleyAbstract:The first part of this two-paper series discusses the motivation of implementing a primary frequency Response (PFR) market in restructured pool-based power markets, as well as the market design that would create the right incentives to provide the Response reliably. PFR is the immediate, autonomous Response of generation and demand to system frequency deviations. It is the Critical Response required to avoid triggering under- and over- frequency relays or instability that could lead to machine damage, load-shedding, and in the extreme case, blackouts. Currently, in many restructured power systems throughout the world, ancillary services markets have been developed to incent technologies to provide the services to support power system reliability. However, few ancillary services markets include a market explicitly incentivizing the provision of PFR. Historically, PFR was an inherent feature available in conventional generating technologies, and in most systems, more was available than needed. Yet, recent trends in declining frequency Response, the introduction of emerging technologies, and market behavior may soon require innovative market designs to incent resources to provide this valuable service.
William Witczakkrempa - One of the best experts on this subject based on the ideXlab platform.
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quantum Critical Response from conformal perturbation theory to holography
Journal of High Energy Physics, 2017Co-Authors: Andrew Lucas, Todd Sierens, William WitczakkrempaAbstract:We discuss dynamical Response functions near quantum Critical points, allowing for both a finite temperature and detuning by a relevant operator. When the quantum Critical point is described by a conformal field theory (CFT), conformal perturbation theory and the operator product expansion can be used to fix the first few leading terms at high frequencies. Knowledge of the high frequency Response allows us then to derive non-perturbative sum rules. We show, via explicit computations, how holography recovers the general results of conformal field theory, and the associated sum rules, for any holographic field theory with a conformal UV completion — regardless of any possible new ordering and/or scaling physics in the IR. We numerically obtain holographic Response functions at all frequencies, allowing us to probe the breakdown of the asymptotic high-frequency regime. Finally, we show that high frequency Response functions in holographic Lifshitz theories are quite similar to their conformal counterparts, even though they are not strongly constrained by symmetry.
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quantum Critical Response from conformal perturbation theory to holography
arXiv: High Energy Physics - Theory, 2017Co-Authors: Andrew Lucas, Todd Sierens, William WitczakkrempaAbstract:We discuss dynamical Response functions near quantum Critical points, allowing for both a finite temperature and detuning by a relevant operator. When the quantum Critical point is described by a conformal field theory (CFT), conformal perturbation theory and the operator product expansion can be used to fix the first few leading terms at high frequencies. Knowledge of the high frequency Response allows us then to derive non-perturbative sum rules. We show, via explicit computations, how holography recovers the general results of CFT, and the associated sum rules, for any holographic field theory with a conformal UV completion -- regardless of any possible new ordering and/or scaling physics in the IR. We numerically obtain holographic Response functions at all frequencies, allowing us to probe the breakdown of the asymptotic high-frequency regime. Finally, we show that high frequency Response functions in holographic Lifshitz theories are quite similar to their conformal counterparts, even though they are not strongly constrained by symmetry.
Todd Sierens - One of the best experts on this subject based on the ideXlab platform.
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quantum Critical Response from conformal perturbation theory to holography
Journal of High Energy Physics, 2017Co-Authors: Andrew Lucas, Todd Sierens, William WitczakkrempaAbstract:We discuss dynamical Response functions near quantum Critical points, allowing for both a finite temperature and detuning by a relevant operator. When the quantum Critical point is described by a conformal field theory (CFT), conformal perturbation theory and the operator product expansion can be used to fix the first few leading terms at high frequencies. Knowledge of the high frequency Response allows us then to derive non-perturbative sum rules. We show, via explicit computations, how holography recovers the general results of conformal field theory, and the associated sum rules, for any holographic field theory with a conformal UV completion — regardless of any possible new ordering and/or scaling physics in the IR. We numerically obtain holographic Response functions at all frequencies, allowing us to probe the breakdown of the asymptotic high-frequency regime. Finally, we show that high frequency Response functions in holographic Lifshitz theories are quite similar to their conformal counterparts, even though they are not strongly constrained by symmetry.
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quantum Critical Response from conformal perturbation theory to holography
arXiv: High Energy Physics - Theory, 2017Co-Authors: Andrew Lucas, Todd Sierens, William WitczakkrempaAbstract:We discuss dynamical Response functions near quantum Critical points, allowing for both a finite temperature and detuning by a relevant operator. When the quantum Critical point is described by a conformal field theory (CFT), conformal perturbation theory and the operator product expansion can be used to fix the first few leading terms at high frequencies. Knowledge of the high frequency Response allows us then to derive non-perturbative sum rules. We show, via explicit computations, how holography recovers the general results of CFT, and the associated sum rules, for any holographic field theory with a conformal UV completion -- regardless of any possible new ordering and/or scaling physics in the IR. We numerically obtain holographic Response functions at all frequencies, allowing us to probe the breakdown of the asymptotic high-frequency regime. Finally, we show that high frequency Response functions in holographic Lifshitz theories are quite similar to their conformal counterparts, even though they are not strongly constrained by symmetry.
Vahan Gevorgian - One of the best experts on this subject based on the ideXlab platform.
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market designs for the primary frequency Response ancillary service
Power and Energy Society General Meeting, 2014Co-Authors: Erik Ela, Vahan Gevorgian, Aidan Tuohy, Brendan Kirby, Michael Milligan, Mark OmalleyAbstract:The first part of this two-paper series discusses the motivation of implementing a primary frequency Response (PFR) market in restructured pool-based power markets, as well as the market design that would create the right incentives to provide the Response reliably. PFR is the immediate, autonomous Response of generation and demand to system frequency deviations. It is the Critical Response required to avoid triggering under- and over-frequency relays or instability that could lead to machine damage, load-shedding, and in the extreme case, blackouts. Currently, in many restructured power systems throughout the world, ancillary services markets have been developed to incent technologies to provide the services to support power system reliability. However, few ancillary services markets include a market explicitly incentivizing the provision of PFR. Historically, PFR was an inherent feature available in conventional generating technologies, and in most systems, more was available than needed. Yet, recent trends in declining frequency Response, the introduction of emerging technologies, and market behavior may soon require innovative market designs to incent resources to provide this valuable service.
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market designs for the primary frequency Response ancillary service part i motivation and design
IEEE Transactions on Power Systems, 2014Co-Authors: Vahan Gevorgian, Aidan Tuohy, Brendan Kirby, Michael Milligan, Mark OmalleyAbstract:The first part of this two-paper series discusses the motivation of implementing a primary frequency Response (PFR) market in restructured pool-based power markets, as well as the market design that would create the right incentives to provide the Response reliably. PFR is the immediate, autonomous Response of generation and demand to system frequency deviations. It is the Critical Response required to avoid triggering under- and over- frequency relays or instability that could lead to machine damage, load-shedding, and in the extreme case, blackouts. Currently, in many restructured power systems throughout the world, ancillary services markets have been developed to incent technologies to provide the services to support power system reliability. However, few ancillary services markets include a market explicitly incentivizing the provision of PFR. Historically, PFR was an inherent feature available in conventional generating technologies, and in most systems, more was available than needed. Yet, recent trends in declining frequency Response, the introduction of emerging technologies, and market behavior may soon require innovative market designs to incent resources to provide this valuable service.