Estimation Of Dynamic Characteristics Research Articles

Proposal of New Perturbation Method with Complementary Term for Dynamic Characteristics Prediction of Modified Structure (2nd Report, Application to Practical Model)

Due to the large scale model of the finite element method in these days, a new method, which is available for the optimal analysis, is required to minimize the time for estimate of dynamic characteristics in changing the structure. In the first report, we focused on a perturbation method effective to this purpose. By finding the complementary vector appropriate to the structure change and the input using Ma-Hagiwara modal method, the accuracy is drastically improved even when the lower mode is truncated. In this report, we apply our new method to a practical model and the following 3 points become clear. First, our method is effective to the change of characteristic value of continuous element. Second, the prediction analysis for structure change becomes to be faster dramatically with high accuracy. Finally, our method contributes to the shortening of the design process in changing the design value in response to the target characteristic value.

Estimation of dynamical characteristics of a parallel program on a model

This paper considers a model of a parallel program that can efficiently be interpreted on an instrumental computer, providing a means for a sufficiently accurate prediction of the actual time needed for execution of the parallel program on a given parallel computational system. The model is designed for parallel programs with explicit message passing written in Java with calls to the MPI library and is a part of the ParJava environment. The model is obtained by transforming the program control tree, which, for Java programs, can be constructed by modifying the abstract syntax tree. The communication functions are simulated on the basis of the LogGP model, which makes it possible to take into account specific features of the distributed computational system.

Evolutionary modal identification utilizing coupled shear–flexural response—implication for multistory buildings. Part II : Application

AbstractA novel solution of dynamic response of multistory buildings is utilized in an evolutionary system identification algorithm for rapid and robust estimation of dynamic characteristics of instrumented structures. The method is fully automated such that it can be used virtually without delay in the aftermath of an urban earthquake. The application of the proposed method and its capabilities are exhibited through numerous examples of building structures shaken by multiple earthquakes in their lives; a number of them are amongst the most intensively studied instrumented buildings. The introduction of stiffness ratio into the reduced‐order dynamic response algorithm that is used in this study (Miranda and Taghavi, 2005) makes it possible to monitor any loss of flexural and/or shear stiffness in a structure subject to strong ground shaking. The system identification scheme presented here is part of a comprehensive structural health‐monitoring software system that is developed for the instrumented building structures at the R&D Department of John A. Martin & Associates with collaboration with research universities. Copyright © 2006 John Wiley & Sons, Ltd.

Evolutionary modal identification utilizing coupled shear–flexural response—implication for multistory buildings. Part I : Theory

AbstractA novel solution of dynamic response of multistory buildings is utilized in an evolutionary system identification algorithm for rapid and robust estimation of dynamic characteristics of instrumented building structures. The empirical characteristics obtained can be used for detection of possible seismic damage and for validating design assumptions with actual recorded structural response. Most structural identification procedures proposed to date only provide some estimates of the modal quantities from which inference to commencement of damage may not be trivial. In this proposed method, besides modal properties such as mode shapes and periods, an overall estimate of the participation of shear to flexural deformations in the lateral response of a building structure is examined. Therefore, any alteration in the mode of response between flexural and shear dominated can be monitored in a time‐varying fashion. The method is fully automated such that it can be used virtually without any delay in the aftermath of an urban earthquake. In a companion paper (Alimoradi and Naeim, 2006), the application of the proposed methodology and its capabilities are exhibited through numerous examples on building structures shaken by multiple earthquakes in their lives; many of them are amongst the most intensively studied instrumented building worldwide. The structural identification work presented here is a component of a comprehensive structural health‐monitoring system for instrumented building structures. Copyright © 2006 John Wiley & Sons, Ltd.

1401 大規模モデルの構造変更シミュレーションの高精度・高効率化(CO1 解析コンテスト(I),未来社会を支えるものづくりとひとづくり(設計・システムから))

Because of the large scale model of the finite element method in these days, it is required to find the method, which can be applied to the optimal analysis, to minimize the time for estimate of dynamic characteristics when changing the structure. We develop here a new perturbation method with complimentary term which is effective to this purpose

Proposal of New Perturbation Method with Complementary Term for Dynamic Characteristics Prediction of Modified Structure

Because of the large scale model of the finite element method in these days, it is required to find the method, which can be applied to the optimal analysis, to minimize the time for estimate of dynamic characteristics when changing the structure. We develop here a new perturbation method with complimentary term which is effective to this purpose. Here we show by both numerical and theoretical analysis that the accuracy of the estimate is greatly improved, including the case of without the lower modes, by using the complimentary vector adjusted to the change of structure and input style, which is obtained by Ma-Hagiwara modal method. We can show the possibility by using the method proposed here to reduce the analysis time drastically when the structure is even much changed on a large scale model.

236 実稼動解析によるエレベータ乗りかごの動特性の推定

236 実稼動解析によるエレベータ乗りかごの動特性の推定

Analysis of EEG data using optimization, statistics, and dynamical system techniques

The use of dynamical system techniques, optimization methods and statistical algorithms to estimate the characteristics of brain electrical activity are explored. A system approach for characterizing EEG (electroencephalogram) signals, based on nonlinear estimation of dynamical characteristics and modeling the evolution of dynamical processes over time is applied. The dynamical characteristics can be used to better visualize the “state vector” of epileptic EEG signals and for the purpose of pattern recognition. An optimization method for reconstructing parameter spaces of dynamical systems is applied to systems with one or more hidden variables, and can be used to reconstruct maps or differential equations of the brain dynamics. The methods are illustrated by using numerically generated data and EEG data from epileptic patients.

Seismic behaviour estimation of thin alluvium layers using microtremor recordings

The microtremor spectral ratio proposed by Nakamura (A method for dynamic characteristics estimation of subsurface using microtremor on ground surface. QR of RTRI, 1989, 30(1), 25–33.) developed a new interest on the use of microtremor measurements for the estimation of site effects. The Lisbon region is an earthquake-prone area and several descriptions of destructive earthquakes are reported in the historical data, which suggest the existence of site effects in the town of Lisbon. Several seismic hazard studies were already performed, as well as some microzonation studies based on records from blasts. In order to characterize the seismic behaviour of alluvium layers existing in the town, two sets of microtremor measurements were performed. The data were processed according to the Nakamura technique and the results are presented here. These results were correlated with the thickness of the alluvium deposits and compared with the spectral ratios obtained using records from blasts, as well as with 1D theoretical models and with 2D theoretical simulations obtained by the use of the Aki-Larner technique. These comparisons seem to prove that the use of microtremor measurements could give a good contribution for the microzonation techniques, specially in urban zones, due to the simplicity and rapidity of their acquisition.

Direct estimation of dynamic characteristics and interaction potential of latex particles interacting with a glass surface by evanescent wave light-scattering microscope method

The dynamic and static characteristics of a polystyrene latex particle in dispersion interacting with a glass surface were studied by the evanescent wave light-scattering microscope (EVLSM) technique originally proposed by Prieve et al. for static studies. The dynamic behavior of the thermal vibration of the particle in a potential well created by electrostatic interaction between the particle and glass and gravity was clearly and quantitatively estimated, in addition to the estimation of the potential profile itself. The potential minimum became shallower with increasing added salt concentration. It was also clearly observed that the vibrational motion of the particle in the well became large in amplitude and the probability of the occurrence of the large vibration became large with increasing salt concentration. Such information on the dynamics is essential for the correct under-standing of the interaction potential. The EVLSM method is shown to be a very powerful technique for the estimation of not only the potential profile but also dynamic characteristics.

Analysis of Dynamic Tilt Stiffness and Damping Coefficients of Externally Pressurized Porous Gas Journal Bearings

A theoretical estimate of dynamic characteristics in terms of stiffness and damping of an externally pressurized gas-lubricated porous journal under tilting mode of vibration is made. The governing nonlinear partial differential equations in the porous medium and in the bearing clearance are linearized using a first-order perturbation analysis. The tilt stiffness and damping are then determined from the solution of the resulting linear partial differential equations numerically. The effect of feeding parameter, supply pressure, porosity parameter, L/D ratio and eccentricity ratio on these two above characteristics is shown.

An Improved Displaced Frequency Method for Estimation of Dynamical Characteristics of Mechanical Systems

The “displaced frequency” method is widely used in the aircraft industry for estimating the generalised masses and stiffnesses of aircraft, which are used in response and other aeroelastic calculations. The usual procedure is to measure the natural frequencies, ωi, and the associated normal modes, zi, by standard resonance testing techniques. (The number of frequencies and modes actually measured depends, of course, on the accuracy required in subsequent calculations.) A small mass, or group of masses, is then added to the structure at a convenient point or points and the resulting frequency changes, δωi noted. Now if αi and εi are generalised masses and stiffnesses respectively, then in normal co-ordinates