• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.251-257
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• 1999

Smart structure that contains sensors, which are either embedded in a composite material or attached to a structure, is currently receiving considerable attention. Fiber Bragg grating sensor, one of the optical fiber sensors, has been widely used to sense strain and temperature for smart structures since both parameters change the resonant frequency of the grating. In this paper, according to the various heating and cooling conditions the thermal behavior of unidirectional composite material was monitored by embedding the fiber Bragg grating sensors in the longitudinal and transverse directions of unidirectional composites. The thermal behavior of unidirectional composite material was monitored for various heating and cooling rates and applied pressure. It was found that the thermal behavior was unaffected by pressure variations and heating and cooling rates applied to the composites. The thermal strains were measured by considering the shift in Bragg wavelength that was generated by the thermal expansion of composite specimen. The longitudinal and transverse C.T.E.'s were also obtained from the corresponding temperature-thermal strain curves.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.3
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• pp.247-252
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• 2014

This paper presents a novel impact sensor which can be fabricated with smart paint made of grapheme. This smart nano paint can be easily installed on structures using a spray-on technique and that can make the sensor low cost and practical. The graphene effectively improves the piezoresistivity of the smart paint and that is available to achieve sensitive impact sensor with high gauge factor. The nano smart-paint can detect sufficient impact to cover the damaged energy range of the composite around 1~3J. The voltage outputs from the sprayed paints show fairly linear responses after signal processing. The impact makes deformation of the structure and it brings change of piezoresistivity of the paint and those converts into voltage output consequently by means of a simple signal processing system. The nano smart paint is lightweight and easily applied to the structural surface, and there is no stress concentration. The nano smart paint is expected to be a cost effective and sensitive multi-functional sensor for composites and other damage monitoring applications in the field of structural health monitoring.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.1
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• pp.37-42
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• 2003

Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained layer damping have been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.262-265
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• 1997

Various polymeric electrolytes were prepared from PEG, PEO and PMMA with LiClO$_4$ to develop lithium conductive electrolytes for smart windows. The complementary electrochromic devices were fabricated with these electrolytes involving cathodically coloring WO$_3$ and anodically coloring V$_2$O$\sub$5/ thin films. The performance of electrochromic device with PMMA/LiCLO$_4$ electrolyte was found to be excellent

• Smart Structures and Systems
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• v.17 no.5
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• pp.691-708
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• 2016

Recently, number of smart material are investigated and widely used in civil construction and other industries. Present study investigates the application of smart semi-active piezoelectric friction damper (PFD) made with piezoelectric material for the seismic control of the horizontally curved bridge isolated with lead rubber bearing (LRB). The main aim of the study is to investigate the effectiveness of hybrid system and to find out the optimum parameters of PFD for seismic control of the curved bridge. The selected curved bridge is a continuous three-span concrete box girder supported on pier and rigid abutment. The PFD is located between the deck and abutments or piers in chord and radial directions. The bridge is excited with four different earthquake ground motions with all three components (i.e. two horizontal and a vertical) having different characteristics. It is observed that the use of semi-active PFD with LRB is quite effective in controlling the response of the curved bridge as compared with passive system. The incorporation of the smart damper requiring small amount of energy in addition with an isolation system can be used for effective control the curved bridge against the dynamic loading.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.4
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• pp.271-275
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• 2020

Smart windows are used as windows and doors to determine the cooling and heating efficiency of a building. They have characteristics that can increase the energy efficiency of a building, which leads to energy savings. In addition, smart windows can control the amount of light transmitted from the external environment of a building to the interior of a building according to the needs of the user. In this study, a 297×210 ㎟ liquid crystal cell capable of controlling light transmittance was fabricated using a liquid crystal device as an optical shutter. The effect of driving voltage on the transmittance and the effect of the thermal environment on the driving stability were analyzed. We confirmed the applicability of using smart windows as exterior building materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.6
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• pp.471-474
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• 2020

In recent years, the challenge of higher energy efficiency has emerged as urban buildings have become taller, and the area of window glasses has increased. To address the problem of energy efficiency in buildings, research on smart windows is being actively conducted. In this study, an accelerated experiment for thermal stability was conducted to fabricate a liquid crystal cell applicable to external windows. It was confirmed from the study that the function is maintained even in a high-temperature external environment through the change in transmittance by voltage. Compared with the initial transmittance, after the passage of time, the smart window cell to which the sealant was applied showed a small change in transmittance of 1~2%. This result confirmed the thermal stability of the liquid crystal-based smart window.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.160-164
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• 2022

In this paper, through the development of a smart panel (LCD kiosk) controller, contents to develop a system that can be operate in a desired environment by operating the window control and ventilation facilities according to the automatic controller operation based on the set values such as temperature, humidity, sunlight, and rainfall. In particular, the MQTT protocol-based sensor module can be directly manufactured and applied at any time based on various communication and power sources such as wireless, wired, and PLC (power line communication) to obtain the desired data, as well as fire, power failure, and intrusion in the house. It is also a system that enables operation and monitoring from a remote location based on the cloud environment by connecting sensors. Kiosks are currently being used in many places, and the demand for them is on the rise, and an active influx of young people can be expected through environmental improvement. It is expected to increase interest and understanding for improvement.

• Smart Structures and Systems
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• v.17 no.5
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• pp.773-793
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• 2016

This work presents a methodology to distribute piezoelectric material for structural vibration active control. The objective is to design controlled structures with actuators which maximizes the system controllability. A topology optimization was formulated in order to distribute two material phases in the domain: a passive linear elastic material and an active linear piezoelectric material. The objective is the maximization of the smallest eigenvalue of the system controllability Gramian. Analytical sensitivities for the finite element model are derived for the objective functions and constraints. Results and comparisons with previous works are presented for the vibration control of a two-dimensional short beam.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.123-123
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• 1993