The Experts below are selected from a list of 135081 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 Excitation for Earthquake Energy Input Rate
Critical Excitation Methods in Earthquake Engineering, 2013Co-Authors: Izuru TakewakiAbstract:This chapter discusses a critical Excitation Method for earthquake energy input rate. It explores a new probabilistic critical Excitation Method for identifying the critical frequency content of ground motions maximizing the mean earthquake energy input rate to structures. The critical Excitation problem includes a double maximization procedure with respect to time and to the power spectral density (PSD) function. The key to finding the critical frequency content is the order exchange in the double maximization procedure. No mathematical programming technique is required in the proposed Method. It is shown that the proposed technique is systematic and the critical Excitation can be found extremely efficiently within a reasonable accuracy. Extension of the proposed Method is discussed for a more general ground motion model. The chapter discusses the process to derive a new expression on the probabilistic earthquake input energy and its rate in terms of uniformly modulated and nonuniformly modulated ground motion models. The process to formulate a new critical Excitation problem with the probabilistic earthquake energy input rate as the criticality measure is mentioned. A deterministic expression of earthquake energy input rate to a base-isolated building model is also presented in order to capture the properties of earthquake energy input rate in more detail.
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Overview of Seismic Critical Excitation Method
Critical Excitation Methods in Earthquake Engineering, 2013Co-Authors: Izuru TakewakiAbstract:This chapter presents a detailed overview of the seismic critical Excitation Method. It begins by defining critical Excitation. It is natural to imagine that a ground motion input resonant to the natural frequency of the structure is a critical Excitation. The Method of critical Excitation was proposed by Drenick for linear elastic, viscously damped single-degree-of-freedom systems in order to take into account inherent uncertainties in ground motions. This Method is aimed at finding the Excitation producing the maximum response from a class of allowable inputs. It was suggested that the critical Excitation introduced by Drenick is conservative compared to the recorded ground motions. To resolve this problem, the concept of “subcritical Excitation” was introduced. The concept of critical Excitation may enable structural designers to make ordinary buildings more seismic resistant. However, critical Excitation problems for fully nonstationary Excitations and critical Excitation problems for elasto-plastic responses under those Excitations are challenging problems.
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critical Excitation for acceleration response
Critical Excitation Methods in Earthquake Engineering (Second edition), 2013Co-Authors: Izuru TakewakiAbstract:This chapter discusses a probabilistic critical Excitation Method for acceleration responses of nonproportionally damped structural systems to nonstationary inputs. Recently, acceleration responses are considered important from the viewpoint of the protection and maintenance of functionality in buildings. Therefore, it is natural and desirable to develop critical Excitation Methods for acceleration. In contrast to most of the conventional critical Excitation Methods, a stochastic acceleration response at a point is treated as the objective function to be maximized. The power and the intensity of the Excitations are fixed, and the critical Excitation is found under these restrictions. The key to finding the new nonstationary random critical Excitation for nonproportionally damped structural systems is the order exchange in the double maximization procedure with respect to time and to the power spectral density (PSD) function. Various numerical examples have been incorporated in this chapter. These examples demonstrate the effectiveness and validity of the present critical Excitation Method. They also reflect that there exist peculiar time-varying characteristics of the generalized nonstationary transfer function multiplied by the envelope function of the input motion model. It is concluded that the damping installation in upper stories is effective in reducing the acceleration.
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critical envelope function for nonstationary random earthquake input
Critical Excitation Methods in Earthquake Engineering (Second edition), 2013Co-Authors: Izuru TakewakiAbstract:This chapter discusses a new probabilistic critical Excitation Method for identifying the critical envelope function of ground motions. It is well known that the envelope shape of ground motions depends on various factors. These factors include an arrival time and an order of various kinds of waves. The maximum structural responses of models with rather shorter natural periods are often induced by the intensive motions existing mostly in the first half portion of ground motions. It is therefore of practical interest to investigate the most critical envelope shape in ground motions. Time histories of four ground motions have been outlined here to show that a monotonically increasing function may be a candidate for the envelope function in the former half part of the total duration. The chapter assumes the nonstationary ground motion to be expressed as the product of a deterministic envelope function and another probabilistic function representing the frequency content. The former is determined such that the corresponding mean–square drift of a single–degree–of–freedom model attains its maximum under the constraint on mean total energy. The critical Excitation Method is expected to provide useful information for the design of important structures to which functional and structural damages must be absolutely avoided during severe earthquakes.
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chapter 12 critical Excitation for earthquake energy input rate
Critical Excitation Methods in Earthquake Engineering, 2007Co-Authors: Izuru TakewakiAbstract:Publisher Summary This chapter discusses a critical Excitation Method for earthquake energy input rate. It explores a new probabilistic critical Excitation Method for identifying the critical frequency content of ground motions maximizing the mean earthquake energy input rate to structures. The critical Excitation problem includes a double maximization procedure with respect to time and to the power spectral density (PSD) function. The key for finding the critical frequency content is the order interchange in the double maximization procedure. No mathematical programming technique is required in the proposed Method. It is shown that the proposed technique is systematic and the critical Excitation can be found extremely efficiently within a reasonable accuracy. Extension of the proposed Method is discussed to a more general ground motion model. The chapter discusses the process to derive a new expression on the probabilistic earthquake input energy and its rate in terms of uniformly modulated and non-uniformly modulated ground motion models. The process to formulate a new critical Excitation problem with the probabilistic earthquake energy input rate as the criticality measure is mentioned.
L.e. Rickard Petersson - One of the best experts on this subject based on the ideXlab platform.
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Total-and scattered-field decomposition technique for the finite-element time-domain Method
IEEE Transactions on Antennas and Propagation, 2006Co-Authors: D. J. Riley, L.e. Rickard PeterssonAbstract:A new finite-element time-domain (FETD) volumetric plane-wave Excitation Method for use with a total- and scattered-field decomposition (TSFD) is rigorously described. This Method provides an alternative to the traditional Huygens' surface approaches commonly used to impress the incident field into the total-field region. Although both the volumetric and Huygens' surface formulations theoretically provide for zero leakage of the impressed wave into the scattered-field region, the volumetric Method provides a simple path to numerically realize this. In practice, the level of leakage for the volumetric scheme is determined by available computer precision, as well as the residual of the matrix solution. In addition, the volumetric Method exhibits nearly zero dispersion error with regard to the discrete incident field.
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Total- and scattered-field decomposition technique for the finite-element time-domain Method
2005 IEEE Antennas and Propagation Society International Symposium, 2005Co-Authors: D. J. Riley, L.e. Rickard PeterssonAbstract:A total- and scattered-field decomposition (TSFD) technique for the finite-element time-domain (FETD) Method is described. This formulation leads to both a volumetric Excitation Method and a Huygens' surface Excitation Method to impress the incident field in the total-field region. Leakage suppression into the scattered-field region on the order of -250 dB has been obtained, independent of the mesh density and the propagation angle. In addition, in a free-space environment, the relative error between the calculated total field and the discrete incident field is also on the order of -250 dB for the volumetric Excitation scheme. Consequently, this total- and scattered-field approach can provide accuracy that is comparable to a pure scattered-field formulation. Both free space and air-earth interfaces are considered
Santiago D Solares - One of the best experts on this subject based on the ideXlab platform.
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characterization of surface stiffness and probe sample dissipation using the band Excitation Method of atomic force microscopy a numerical analysis
Nanotechnology, 2012Co-Authors: Adam U Kareem, Santiago D SolaresAbstract:Recently Jesse and co-workers introduced the band Excitation atomic force microscopy (BE-AFM) Method (Jesse et al 2007 Nanotechnology 18 435503), in which the cantilever probe is excited in a continuum frequency band in order to measure its response at all frequencies in the band. Analysis of the cantilever response using the damped harmonic oscillator model provides information on the stiffness and level of dissipation at the tip?sample junction as the sample is scanned. Since its introduction, this Method has been used in magnetic, electromechanical, thermal and molecular unfolding applications, among others, and has given rise to a new family of scanning probe microscopy techniques. Additionally, the concept is applicable to any field in which measurement of the frequency response of harmonic oscillators is relevant. In this paper we present an analytical and numerical analysis of the Excitation signals used in BE-AFM, as well as of the cantilever response under different conditions. Our analysis is performed within the context of viscoelastic characterization. We discuss subtleties in the cantilever dynamics, provide guidelines for implementing the Method effectively and illustrate the use of simulation in interpreting the results.
D. J. Riley - One of the best experts on this subject based on the ideXlab platform.
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Total-and scattered-field decomposition technique for the finite-element time-domain Method
IEEE Transactions on Antennas and Propagation, 2006Co-Authors: D. J. Riley, L.e. Rickard PeterssonAbstract:A new finite-element time-domain (FETD) volumetric plane-wave Excitation Method for use with a total- and scattered-field decomposition (TSFD) is rigorously described. This Method provides an alternative to the traditional Huygens' surface approaches commonly used to impress the incident field into the total-field region. Although both the volumetric and Huygens' surface formulations theoretically provide for zero leakage of the impressed wave into the scattered-field region, the volumetric Method provides a simple path to numerically realize this. In practice, the level of leakage for the volumetric scheme is determined by available computer precision, as well as the residual of the matrix solution. In addition, the volumetric Method exhibits nearly zero dispersion error with regard to the discrete incident field.
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Total- and scattered-field decomposition technique for the finite-element time-domain Method
2005 IEEE Antennas and Propagation Society International Symposium, 2005Co-Authors: D. J. Riley, L.e. Rickard PeterssonAbstract:A total- and scattered-field decomposition (TSFD) technique for the finite-element time-domain (FETD) Method is described. This formulation leads to both a volumetric Excitation Method and a Huygens' surface Excitation Method to impress the incident field in the total-field region. Leakage suppression into the scattered-field region on the order of -250 dB has been obtained, independent of the mesh density and the propagation angle. In addition, in a free-space environment, the relative error between the calculated total field and the discrete incident field is also on the order of -250 dB for the volumetric Excitation scheme. Consequently, this total- and scattered-field approach can provide accuracy that is comparable to a pure scattered-field formulation. Both free space and air-earth interfaces are considered
Stephen Jesse - One of the best experts on this subject based on the ideXlab platform.
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probing local bias induced transitions using photothermal Excitation contact resonance atomic force microscopy and voltage spectroscopy
ACS Nano, 2015Co-Authors: Qian Li, Sergei V. Kalinin, Stephen Jesse, Alexander Tselev, Liam Collins, Pu Yu, Ivan I Kravchenko, Nina BalkeAbstract:Nanomechanical properties are closely related to the states of matter, including chemical composition, crystal structure, mesoscopic domain configuration, etc. Investigation of these properties at the nanoscale requires not only static imaging Methods, e.g., contact resonance atomic force microscopy (CR-AFM), but also spectroscopic Methods capable of revealing their dependence on various external stimuli. Here we demonstrate the voltage spectroscopy of CR-AFM, which was realized by combining photothermal Excitation (as opposed to the conventional piezoacoustic Excitation Method) with the band Excitation technique. We applied this spectroscopy to explore local bias-induced phenomena ranging from purely physical to surface electromechanical and electrochemical processes. Our measurements show that the changes in the surface properties associated with these bias-induced transitions can be accurately assessed in a fast and dynamic manner, using resonance frequency as a signature. With many of the advantages o...
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the band Excitation Method in scanning probe microscopy for rapid mapping of energy dissipation on the nanoscale
Nanotechnology, 2007Co-Authors: Stephen Jesse, Sergei V. Kalinin, Roger Proksch, Arthur P Baddorf, Brian J RodriguezAbstract:Mapping energy transformation pathways and dissipation on the nanoscale and understanding the role of local structure in dissipative behavior is a key challenge for imaging in areas ranging from electronics and information technologies to efficient energy production. Here we develop a family of novel scanning probe microscopy (SPM) techniques in which the cantilever is excited and the response is recorded over a band of frequencies simultaneously, rather than at a single frequency as in conventional SPMs. This band Excitation (BE) SPM allows very rapid acquisition of the full frequency response at each point (i.e. transfer function) in an image and in particular enables the direct measurement of energy dissipation through the determination of the Q-factor of the cantilever–sample system. The BE Method is demonstrated for force–distance and voltage spectroscopies and for magnetic dissipation imaging with sensitivity close to the thermomechanical limit. The applicability of BE for various SPMs is analyzed, and the Method is expected to be universally applicable to ambient and liquid SPMs.
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the band Excitation Method in scanning probe microscopy for rapid mapping of energy dissipation on the nanoscale
arXiv: Materials Science, 2007Co-Authors: Stephen Jesse, Sergei V. Kalinin, Roger Proksch, Arthur P Baddorf, Brian J RodriguezAbstract:Mapping energy transformation pathways and dissipation on the nanoscale and understanding the role of local structure on dissipative behavior is a challenge for imaging in areas ranging from electronics and information technologies to efficient energy production. Here we develop a novel Scanning Probe Microscopy (SPM) technique in which the cantilever is excited and the response is recorded over a band of frequencies simultaneously rather than at a single frequency as in conventional SPMs. This band Excitation (BE) SPM allows very rapid acquisition of the full frequency response at each point (i.e. transfer function) in an image and in particular enables the direct measurement of energy dissipation through the determination of the Q-factor of the cantilever-sample system. The BE Method is demonstrated for force-distance and voltage spectroscopies and for magnetic dissipation imaging with sensitivity close to the thermomechanical limit. The applicability of BE for various SPMs is analyzed, and the Method is expected to be universally applicable to all ambient and liquid SPMs.
