Adaptive control of base-isolated buildings using piezoelectric friction dampers against near-field earthquakes

2010 ◽  
Author(s):  
Maryam Bitaraf ◽  
Osman E. Ozbulut ◽  
Stefan Hurlebaus
Keyword(s):  
Adaptive Control ◽  
Near Field ◽  
Friction Dampers

Control of piezoelectric friction dampers in smart base-isolated structures using self-tuning and adaptive fuzzy proportional–derivative controllers

2016 ◽  
Vol 28 (10) ◽  
pp. 1287-1302 ◽  
Author(s):  
Abbas-Ali Zamani ◽  
Saeed Tavakoli ◽  
Sadegh Etedali
Keyword(s):  
Control Strategies ◽  
Near Field ◽  
The Self ◽  
Feedback Signal ◽  
Far Field ◽  
Friction Dampers ◽  
Adaptive Fuzzy ◽  
Self Tuning ◽  
Base Displacement ◽  
Proportional Derivative Controller

To adjust the contact force of piezoelectric friction dampers for a benchmark base-isolated structure, a self-tuning fuzzy proportional–derivative controller and an adaptive fuzzy proportional–derivative controller are developed. Considering three candidate signals, namely, the isolation displacement, isolation velocity, and roof acceleration, the best feedback signal for the self-tuning fuzzy proportional–derivative controller is selected based on the Pareto-optimal front. The performance of the self-tuning fuzzy proportional–derivative controller during both near-field and far-field earthquakes is enhanced using an adaptive fuzzy proportional–derivative controller, in which the output gain of the self-tuning fuzzy proportional–derivative controller is adaptively tuned according to the kind of entering earthquake. The control objective is to reduce the isolation system deformations without significant increase in superstructure accelerations during far-field and near-field earthquake excitations. Membership functions and fuzzy control rules are simultaneously tuned using a multi-objective cuckoo search algorithm. Considering 14 real-data earthquakes, simulation results show that the proposed controllers perform better than other reported control strategies in terms of simultaneous reduction of the maximum base displacement and superstructure accelerations. Also, they provide acceptable responses in terms of the inter-story drifts, root mean squared of base displacement, and the floor acceleration. Opposite to other reported control strategies, piezoelectric friction dampers controlled by the self-tuning fuzzy proportional–derivative controller and adaptive fuzzy proportional–derivative controller never enter the saturation area.

scholarly journals All-optical adaptive control of quantum cascade random lasers

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Schönhuber ◽  
N. Bachelard ◽  
B. Limbacher ◽  
M. A. Kainz ◽  
A. M. Andrews ◽  
...  
Keyword(s):  
Adaptive Control ◽  
Degrees Of Freedom ◽  
Near Infrared ◽  
Quantum Cascade Lasers ◽  
Near Field ◽  
Optimization Procedure ◽  
Light Sources ◽  
Light Modulator ◽  
Random Lasers ◽  
Quantum Cascade

Abstract Spectral fingerprints of molecules are mostly accessible in the terahertz (THz) and mid-infrared ranges, such that efficient molecular-detection technologies rely on broadband coherent light sources at such frequencies. If THz Quantum Cascade Lasers can achieve octave-spanning bandwidth, their tunability and wavelength selectivity are often constrained by the geometry of their cavity. Here we introduce an adaptive control scheme for the generation of THz light in Quantum Cascade Random Lasers, whose emission spectra are reshaped by applying an optical field that restructures the permittivity of the active medium. Using a spatial light modulator combined with an optimization procedure, a beam in the near infrared (NIR) is spatially patterned to transform an initially multi-mode THz random laser into a tunable single-mode source. Moreover, we show that local NIR illumination can be used to spatially sense complex near-field interactions amongst modes. Our approach provides access to new degrees of freedom that can be harnessed to create broadly-tunable sources with interesting potential for applications like self-referenced spectroscopy.

scholarly journals On the Seismic Response of Protected and Unprotected Middle-Rise Steel Frames in Far-Field and Near-Field Areas

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Dora Foti
Keyword(s):  
Seismic Response ◽  
Ground Motions ◽  
Near Field ◽  
Shaking Table ◽  
Far Field ◽  
Base Shear ◽  
Friction Dampers ◽  
Steel Moment Resisting Frames ◽  
Damage Indices ◽  
Moment Resisting

Several steel moment-resisting framed buildings were seriously damaged during Northridge (1994); Kobe (1995); Kocaeli, Turkey (1999), earthquakes. Indeed, for all these cases, the earthquake source was located under the urban area and most victims were in near-field areas. In fact near-field ground motions show velocity and displacement peaks higher than far-field ones. Therefore, the importance of considering near-field ground motion effects in the seismic design of structures is clear. This study analyzes the seismic response of five-story steel moment-resisting frames subjected to Loma Prieta (1989) earthquake—Gilroy (far-field) register and Santa Cruz (near-field) register. The design of the frames verifies all the resistance and stability Eurocodes’ requirements and the first mode has been determined from previous shaking-table tests. In the frames two diagonal braces are installed in different positions. Therefore, ten cases with different periods are considered. Also, friction dampers are installed in substitution of the braces. The behaviour of the braced models under the far-field and the near-field records is analysed. The responses of the aforementioned frames equipped with friction dampers and subjected to the same ground motions are discussed. The maximum response of the examined model structures with and without passive dampers is analysed in terms of damage indices, acceleration amplification, base shear, and interstory drifts.

Near-field scanning optical microscopy

1986 ◽  
Vol 44 ◽  
pp. 642-643
Author(s):  
E. Betzig ◽  
A. Harootunian ◽  
M. Isaacson ◽  
A. Lewis
Keyword(s):  
Near Field ◽  
Optical Microscope ◽  
Visible Radiation ◽  
Field Methods ◽  
Optical Elements ◽  
Optical Region ◽  
Order Of Magnitude ◽  
Nondestructive Imaging ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

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