• International Journal of High-Rise Buildings
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• v.12 no.4
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• pp.299-306
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• 2023

An overview of seismic isolation and structural control in Japan is presented. The paper includes a mention of the history of aseismic technology and the earthquake threat in Japan, summarizes the merits of seismic isolation and response control, and discusses the types of devices used and some recent project examples. The projects presented are mostly examples of response control used for high-rise buildings. These types of buildings are not amendable to seismic isolation, and are a challenge to applying damping devices, as their high aspect ratio means that their dominant deformation mode is bending. Japanese engineers have developed a range of unique techniques to apply response control to these types of structures. Concluding remarks discuss some of the current challenges to expanding the use of seismic isolation and response control technologies.

• Journal of the Semiconductor & Display Technology
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• v.22 no.1
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• pp.59-63
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• 2023

Various devices have been emerging as a means of measuring indoor air quality, and among them, there are devices that support real-time remote monitoring through IoT technology and a cloud environment. To improve indoor air quality, based on the results determined by measuring devices, air purifiers or ventilation systems may need to be operated, and temperature and humidity control may be required. In this paper, we propose a design of indoor air quality measuring devices required for indoor air quality evaluation, and of the system needed to control relevant devices to improve indoor air quality through the interaction with the measuring devices. Currently, the servers for the interaction of indoor air quality devices and IoT devices are divided into conventional server type and serverless type, comparing the differences in response time of IoT devices to changes of indoor air quality.

• Smart Structures and Systems
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• v.8 no.5
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• pp.449-470
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• 2011

During the last thirty years many structural control concepts have been proposed for the reduction of the structural response caused by earthquake excitations. Their research and implementation in practice have shown that seismic control of structures has a lot of potential but also many limitations. In this paper the importance of two practical issues, time delay and saturation effect, on the performance of controlled structures, is discussed. Their influence, both separately and in interaction, on the response of structures controlled by a modified pole placement algorithm is investigated. Characteristic buildings controlled by this algorithm and subjected to dynamic loads, such as harmonic signals and actual seismic events, are analyzed for a range of levels of time delay and saturation capacity of the control devices. The response reduction surfaces for the combined influence of time delay and force saturation of the controlled buildings are obtained. Conclusions regarding the choice of the control system and the desired properties of the control devices are drawn.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1865-1867
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• 2005

Film bulk acoustic resonator (FBAR) devices which adopt an air-gap type (metai/AlN/metal/air/substrate) configuration are fabricated by a novel process. The newly fabricated resonator doesn't employ any supporting layer below it. FBAR devices with the air-gap type are also fabricated using the conventional method. The frequency response characteristics of all the devices fabricated are measured and compared, in terms of the kinds of top and bottom electrode materials. The results show that the better device performance of FBAR devices can be achieved by employing the proposed process.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.672-680
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• 2012

This paper proposes the control strategy of the shunt Flexible AC Transmission System (FACTS) devices to improve transient stability in multimachine power system. The multimachine power system has high nonlinear response after severe disturbance. The concept of Lyapunov energy function is applied to derive nonlinear control strategy and it was found that the time derivative of line voltage is not only can apply to control the shunt FACTS devices in multimachine system but also is locally measurable signal. The fuzzy logic control is also applied to overcome the uncertainty of various disturbances in multimachine power system. This paper presents the method of investigating the effect of the shunt FACTS devices on transient stability improvement. The proposed control strategy and the method of simulation are tested on the new England power system. It was found that the shunt FACTS devices based on the proposed nonlinear control strategy can improve transient stability of multimachine power system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.375-380
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• 2004

Seismic Isolation and Shock/vibration Control Laboratory has performed the National Research Laboratory(NRL) project, 'Design and Application of Control Devices against Earthquake/Shock/Vibration'. In this project, the prototypes of the vibration control devices for structural control against earthquake and wind were developed and verified their performances. And also, the computer programs were developed for the seismic response analysis and the optimum design of the base-isolated structures with vibration control devices. This paper introduces the developed vibration control devices and computer programs.

• Smart Structures and Systems
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• v.12 no.6
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• pp.595-617
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• 2013

Semi-active control equipments are used to effectually enhance the seismic behavior of structures. Magneto-rheological (MR) dampers are semi-active devices that can be utilized to control the response of structures during seismic loads and have received voracious attention for response suppression. They supply the adaptability of active devices and stability and reliability of passive devices. This paper presents an optimal fuzzy logic control scheme for vibration mitigation of buildings using magneto-rheological dampers subjected to near-fault ground motions. Near-fault features including a directivity pulse in the fault-normal direction and a fling step in the fault-parallel direction are considered in the requisite ground motion records. The membership functions and fuzzy rules of fuzzy controller were optimized by genetic algorithm (GA). Numerical study is performed to analyze the influences of near-fault ground motions on a building that is equipped with MR dampers. Considering the uncontrolled system response as the base line, the proposed method is scrutinized by analogy with that of a conventional maximum dissipation energy (MED) controller to accentuate the effectiveness of the fuzzy logic algorithm. Results reveal that the fuzzy logic controllers can efficiently improve the structural responses and MR dampers are quite promising for reducing seismic responses during near-fault earthquakes.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1594-1596
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• 2004

Film bulk acoustic resonator (FBAR) devices which adopt a membrane-type configuration are fabricated by a novel process. In contrast to the conventional FBAR structure, the newly fabricated resonator doesn't employ any supporting layer below or above it, so that the properties of piezoelectric layer are not influenced by the bottom electrode material. FBAR devices with Mo/AlN/Metal configuration are also fabricated. The frequency response characteristics ($S_{11}$) of the devices fabricated using the proposed process are compared with those of the conventional devices. The return losses are also estimated, in terms of the kind and thickness of bottom electrode materials.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1843-1847
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• 2012

Piezo devices have large power density and simple structure. They can generate larger force than the conventional actuators. It has also wide bandwidth with fast response in a compact size. Thus the piezo devices are expected to be used widely in the future for small actuators with fast response time and large actuating force. However, the piezo actuators need high voltage with high driving current due to their large capacitive property. In this paper, we propose a simple method to drive piezo devices using voltage inversion circuit with coil inductance. Experiments with real circuit demonstrates that the proposed scheme can improve the energy efficiency very much.

• Smart Structures and Systems
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• v.18 no.6
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• pp.1111-1123
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• 2016

The present study aims at proposing an analytical method for semi-active structural control by using block pulse functions. The performance of the resulting controlled system and the requirements of the control devices are highly dependent on the control algorithm employed. In control problems, it is important to devise an accurate analytical method with less computational expenses. Block pulse functions (BPFs) set proved to be the most fundamental and it enjoyed immense popularity in different applications in the area of numerical analysis in systems science and control. This work focused on the application of BPFs in the control algorithm concerning decrease the computational expenses. Variable orifice dampers (VODs) are one of the common semi-active devices that can be used to control the response of civil Structures during seismic loads. To prove the efficiency of the proposed method, numerical simulations for a 10-story shear building frame equipped with VODs are presented. The controlled response of the frame was compared with results obtained by controlling the frame by the classical clipped-optimal control method based on linear quadratic regulator theory. The simulation results of this investigation indicated the proposed method had an acceptable accuracy with minor computational expenses and it can be advantageous in reducing seismic responses.