• Smart Structures and Systems
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• 제24권4호
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• pp.435-446
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• 2019

The existing piezoelectric spherical transducers with fixed prescribed dynamic characteristics limit their application in scenarios with multi-frequency or frequency variation requirement. To address this issue, this work proposes an improved design of piezoelectric spherical transducers using the resistance tuning method. Two piezoceramic shells are the functional elements with one for actuation and the other for tuning through the variation of load resistance. The theoretical model of the proposed design is given based on our previous work. The effects of the resistance, the middle surface radius and the thickness of the epoxy adhesive layer on the dynamic characteristics of the transducer are explored by numerical analysis. The numerical results show that the multi-frequency characteristics of the transducer can be obtained by tuning the resistance, and its electromechanical coupling coefficient can be optimized by a matching resistance. The proposed design and derived theoretical solution are validated by comparing with the literature given special examples as well as an experimental study. The present study demonstrates the feasibility of using the proposed design to realize the multi-frequency characteristics, which is helpful to improve the performance of piezoelectric spherical transducers used in underwater acoustic detection, hydrophones, and the spherical smart aggregate (SSA) used in civil structural health monitoring, enhancing their operation at the multiple working frequencies to meet different application requirements.

• 한국인터넷방송통신학회논문지
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• 제20권6호
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• pp.59-64
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• 2020

최근 노인 인구가 급격하게 증가하면서 의료시설 내외에서 환자의 안전을 모니터링하는 시스템에 대한 요구가 증가하고 있다. 센서 및 정보통신기술의 발달로 치매 환자를 위한 다양한 모니터링 시스템이 제안되고 있지만 치매 환자에게 부착되는 장치에 의존하여 단편적인 기능을 제공하는 것에 그치고 있다. 본 논문에서는 환자의 상태를 모니터링하는 스마트 기기에서부터 사용자 편의적인 UI/UX, 병원정보시스템 연동까지 포함하는 통합시스템을 설계한다. 제안된 시스템을 통해서 의료진과 보호자는 환자의 상태와 관련된 정보를 실시간으로 전달받을 수 있으며 실내외에서도 치매 환자의 위치를 추적할 수 있다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.504-506
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• 2022

기존의 루프탑 태양광 발전 시스템들은 안전성 문제와 더불어 시스템상의 오류 때문에 주로 고정형 시스템 개발 초점이 맞추어져 있었다. 이에 기존 고정식 루프탑 태양광 발전 기술에 태양광 추적 시스템과 모니터링 시스템을 추가하여 루프탑 설치형 스마트 태양광 발전 시스템을 개발하고자 한다. 이는 태양광 추적시스템 접목, 안전진단 및 대처시스템 접목, 이상진단 및 알람 시스템 접목, 외부기기 제어 및 모니터링 시스템 접목으로 "루프탑 설치형 스마트 태양광 발전시스템" 개발 및 사업화에 활용 계획이다.

• 국제초고층학회논문집
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• 제11권2호
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• pp.125-135
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• 2022

While buildings in recent days become taller and larger, many problems occur during the management of construction. Particularly, as the vertical movement of manpower and materials during construction has become longer while the lifting frequency and load increase, the need for a good lifting management practice is also increasing. Therefore, this study presents a real-time lifting performance monitoring system that can store and manage lifting records for construction management. Through review of literature and preceding studies related to construction lift, the concept of lift planning and operation management was understood, leading to the development of a system to monitor lifting operation and performance information. This system enabled quick measurement of the lifting performance during construction phase while responding to changes in the project schedule. To verify this system, a case study was conducted in which the current status and characteristics of the sensing-based lifting performance were derived.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.264-267
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• 2004

Cure monitoring and nondestructive characteristics of carbon fiber/epoxy composites were evaluated by the measurements of electrical resistance and acoustic emission (AE). Logarithmic electrical resistivity of the untreated single-carbon fiber composite increased suddenly to infinity when the fiber fracture occurred, whereas that of the electrodeposited composite increased relatively broadly up to infinity. As curing temperature increased. logarithmic electrical resistivity of steel fiber increased. On the other hand, electrical resistance of carbon fiber decreased due to the intrinsic electrical properties based on the band theory. The apparent modulus of the electrodeposited composite was higher than that of the untreated composite due to the improved interfacial shear strength (IFSS).

• Smart Structures and Systems
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• 제13권6호
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• pp.891-899
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• 2014

Over the past several decades, substantial amounts of sensors and sensing systems have been developed for civil infrastructure systems. This special issue focuses on state-of-the-art robotics and automation technologies, including construction automation, robotics, instrumentation, monitoring, inspection, control, and rehabilitation for civil infrastructure. The issue also covers construction informatics supporting sensing, analysis and design activities needed to operate smart and sustainable civil infrastructure. Examples include robotic systems applied to civil infrastructure and equipped with various sensing technologies, such as optical sensors, laser sensors, wireless sensors, multi-sensor fusion, etc. This special issue is published in an effort to disseminate current advances of various robotics and automation technologies for civil infrastructure and built environment.

• Smart Structures and Systems
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• 제16권3호
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• pp.435-457
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• 2015

The most widely known form of multifunctional aircraft structure is smart structures for structural health monitoring (SHM). The aim is to provide automated systems whose purposes are to identify and to characterize possible damage within structures by using a network of actuators and sensors. Unfortunately, environmental and operational variability render many of the proposed damage detection methods difficult to successfully be applied. In this paper, an original robust damage detection approach using output-only vibration data is proposed. It is based on independent component analysis and matrix perturbation analysis, where an analytical threshold is proposed to get rid of statistical assumptions usually performed in damage detection approach. The effectiveness of the proposed SHM method is demonstrated numerically using finite element simulations and experimentally through a conformal load-bearing antenna structure and composite plates instrumented with piezoelectric ceramic materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.47-50
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• 2005

Fiber Bragg Grating (FBG) Sensors as advanced measuring system are introduced and actively being applied to establish a smart monitoring system for bridge maintenance. This study develops FBG sensors and suggests a smart monitoring system. As for its first step, to verify the reliability of FBG sensors that developed, a specimen is made FBG sensors and electric sensor are attached. Then, Static test is conducted on the specimen on the specimens to check reliability. In addition, this study estimates the optimum deflection curve that converts strain curve data measured by FBG sensors into deflection.

• Smart Structures and Systems
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• 제2권1호
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• pp.25-46
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• 2006

Aging wiring in buildings, aircraft and transportation systems, consumer products, industrial machinery, etc. is among the most significant potential causes of catastrophic failure and maintenance cost in these structures. Smart wire health monitoring can therefore have a substantial impact on the overall health monitoring of the system. Reflectometry is commonly used for locating faults on wire and cables. This paper compares Time domain reflectometry (TDR), frequency domain reflectometry (FDR), mixed signal reflectometry (MSR), sequence time domain reflectometry (STDR), spread spectrum time domain reflectometry (SSTDR) and capacitance sensors in terms of their accuracy, convenience, cost, size, and ease of use. Advantages and limitations of each method are outlined and evaluated for several types of aircraft cables. The results in this paper can be extrapolated to other types of wire and cable systems.

• Smart Structures and Systems
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• 제7권1호
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• pp.27-40
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• 2011

Geopolymer concrete is finding a growing number of niche applications in the field of civil engineering due to its high compressive strength and strength gain rate, retainage of structural properties in elevated temperature environments, chemical stability in highly acidic conditions and environmental benefits. Combining the above mentioned characteristics with induced electrical conductivity, could enable geopolymer cement to serve as a smart and sustainable cementitious material suitable for health monitoring of civil structures. Carbon fibers were added to fresh geopolymer and OPC (ordinary Portland cement) mixes to enhance their electrical conductivities. AC-impedance spectroscopy analysis was performed on the specimens with fiber fraction ranging from 0.008 to 0.8 with respect to the weight of cementitious binder, to measure their electrical resistivity values and to determine the maximum beneficial fiber content required to attain electrical percolation. Experimental observations suggest that CFR-geopolymer cement exhibits superior performance to CFR-OPC in terms of conducting electrical current.