• Smart Structures and Systems
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• 제12권3_4호
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• pp.415-426
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• 2013

Condition assessment and monitoring of bridges is critical for safe passenger travel, public transportation, and efficient freight. In monitoring, displacement measurement capability is important to keep track of performance of bridge, in part or as whole. One of the most important parts of a bridge is the expansion joint, which accommodates continuous cyclic thermal expansion of the whole bridge. Though expansion joint is critical for bridge performance, its inspection and monitoring has not been considered significantly because the monitoring requires long-term data using cost intensive equipment. Recently, a wireless smart sensor network (WSSN) has drawn significant attention for transportation infrastructure monitoring because of its merits in low cost, easy installation, and versatile on-board computation capability. In this paper, a rapid wireless displacement monitoring system, wireless hybrid sensor (WHS), has been developed to monitor displacement of expansion joints of bridges. The WHS has been calibrated for both static and dynamic displacement measurement in laboratory environment, and deployed on an in-service highway bridge to demonstrate rapid expansion joint monitoring. The test-bed is a continuous steel girder bridge, the Founders Bridge, in East Hartford, Connecticut. Using the WHS system, the static and dynamic displacement of the expansion joint has been measured. The short-term displacement trend in terms of temperature is calculated. With the WHS system, approximately 6% of the time has been spent for installation, and 94% of time for the measurement showing strong potential of the developed system for rapid displacement monitoring.

• 한국인터넷방송통신학회논문지
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• 제19권6호
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• pp.9-13
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• 2019

본 논문에서는 IoT 기반 열상 센서와 영상 센서 일체형 IP CCTV 설계에 관하여 연구하였으며 Full HD IP 카메라 영상과 열상모듈에서 전송되어지는 열상 데이터를 동시에 인지하여 가공 및 전송 할 수 있는 모니터링 시스템에 사용할 수 있도록 하였다. 열상 센서에서 감지하는 신호를 디지털로 변환하여 영상에 중첩시켜 실제 주변 온도에 대한 정보를 영상과 함께 실시간 제공하고, 영상 카메라에 열상이 추가됨으로 온도 변화를 예측하여 기존 장비에서 불가능한 화재 예측이 가능하게 하였다. 따라서 열상 센서와 영상센서 일체형 감시 장비를 통하여 환경 모니터링 시스템에서 전송되는 온도 데이터와 영상 신호를 송신하여 모니터링 시스템에 적용 가능하도록 하였다.

• ETRI Journal
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• 제35권4호
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• pp.617-624
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• 2013

Low power consuming and highly responsive semiconductor-type microelectromechanical systems (MEMS) gas sensors are fabricated for real-time environmental monitoring applications. This subsystem is developed using a gas sensor module, a Bluetooth module, and a personal digital assistant (PDA) phone. The gas sensor module consists of a $NO_2$ or CO gas sensor and signal processing chips. The MEMS gas sensor is composed of a microheater, a sensing electrode, and sensing material. Metal oxide nanopowder is drop-coated onto a substrate using a microheater and integrated into the gas sensor module. The change in resistance of the metal oxide nanopowder from exposure to oxidizing or deoxidizing gases is utilized as the principle mechanism of this gas sensor operation. The variation detected in the gas sensor module is transferred to the PDA phone by way of the Bluetooth module.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제8권1호
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• pp.11-17
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• 2008

Typical wireless sensor networks used in structural monitoring are continuous types wherein data transmission is progressive at all time that may include irrelevant and insignificant data and information. Continuous types of wireless monitoring systems often pose problems of handling large-sized data that may deteriorate the performance of the system. The proposed method is to suggest an event-triggered monitoring system that captures and transmits relevant data only. An error signal generated by the Principal Components Analysis (PCA) is utilized as an index for event detection and selective data transmission. With this new monitoring scheme, the remote server is relieved of unwanted data by receiving only relevant information from the wireless sensor networks. The performance of the proposed scheme was verified with simulation studies.

• 한국전자통신학회논문지
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• 제7권1호
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• pp.195-201
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• 2012

센서노드와 관제시스템으로 구성된 환경정보모니터링시스템은 센서노드에서 실시간 정보를 수집하고 원격지의 관제시스템으로 수집된 데이터를 실시간 전송한다. 센서 노드에 설치되는 센서의 종류, 센서의 개수, 센서노드와 관제시스템 사이의 통신환경, 관제시스템 데이터 운영 환경에 따라 관제시스템의 운용성이 크게 저하될 수 있다. 따라서 본 연구에서는 운영 효율성을 증대하기 위하여 운용환경에 따라 적절한 컴포넌트를 이용하는 컴포넌트 기반 환경정보모니터링시스템을 제안하고 구현하였다.

• 한국컴퓨터정보학회논문지
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• 제11권5호
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• pp.259-265
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• 2006

유비쿼터스 센서 네트워크 기술은 새로운 컴퓨팅 패러다임인 유비쿼터스 컴퓨팅의 핵심 분야로서, 무선 센서 네트워크를 이용한 상황정보 모니터링 시스템에 적합한 기술이다. 이 기술을 모니터링 시스템에 적용하면 열악한 환경에 간편하고 저렴한 비용으로 실시간으로 발생된 상황데이터를 수집 및 분석하여 즉각적인 상황대처와 사용자가 원하는 환경의 조건을 효율적으로 수행할 수 있다. 본 논문에서는 유비쿼터스 센서 네트워크 기반에서 무선 노드의 센싱 기술을 이용하여 상황 정보 모니터링 시스템을 구축한다. 제안된 시스템은 수집될 데이터의 양이 적고 지속적인 모니터링이 불필요하고 일정한 간격으로 특정 지역에서 발생되는 상황을 감지하는 작업에 기존 유선 통신을 이용한 상황감시보다는 효율적이다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2021년도 학술발표회
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• pp.427-427
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• 2021

During the rainy season, heavy downpours are always a source of concern for the world. Flooding and heavy rains can devastate communities, disrupt agriculture, and contribute to traffic accidents.. Weir and flow hall effect sensors are the conventional analytical methods for measuring flow rate; in this paper, we analyzed manhole flowrate statistics. The measurement of the flow rate of a notch/weir is a time-consuming task that necessitates continuous mathematical analysis. . We created three types of IoT sensors in this study: (HC-SR04 ultrasonic, YF-S201 magnetic, and HB100 radar), which take the sensor's real-time input signal and estimate the flow using a notch equation and a previously calibrated optimized coefficient of discharge. The proposed systems are cost-effective, but in terms of accuracy, we found that the HC-SR04 ultrasonic sensor is the best of the three systems

• Smart Structures and Systems
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• 제6권5_6호
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• pp.689-709
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• 2010

In this paper, a low cost, low power but multifunctional wireless sensor node is presented for the impedance-based SHM using piezoelectric sensors. Firstly, a miniaturized impedance measuring chip device is utilized for low cost and low power structural excitation/sensing. Then, structural damage detection/sensor self-diagnosis algorithms are embedded on the on-board microcontroller. This sensor node uses the power harvested from the solar energy to measure and analyze the impedance data. Simultaneously it monitors temperature on the structure near the piezoelectric sensor and battery power consumption. The wireless sensor node is based on the TinyOS platform for operation, and users can take MATLAB$^{(R)}$ interface for the control of the sensor node through serial communication. In order to validate the performance of this multifunctional wireless impedance sensor node, a series of experimental studies have been carried out for detecting loose bolts and crack damages on lab-scale steel structural members as well as on real steel bridge and building structures. It has been found that the proposed sensor nodes can be effectively used for local wireless health monitoring of structural components and for constructing a low-cost and multifunctional SHM system as "place and forget" wireless sensors.

• Smart Structures and Systems
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• 제15권6호
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• pp.1543-1567
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• 2015

In this study, a wireless crack sensor is developed for monitoring cracks propagating in two dimensions. This sensor is developed by incorporating a laser-based optical navigation sensor board (ADNS-9500) into a smart wireless platform (Imote2). To measure crack propagation, the Imote2 sends a signal to the ADNS-9500 to collect a sequence of images reflected from the concrete surface. These acquired images can be processed in the ADNS-9500 directly (the navigation mode) or sent to Imote2 for processing (the frame capture mode). The computed crack displacement can then be transmitted wirelessly to a base station. The design and the construction of this sensor are reported herein followed by some calibration tests on one prototype sensor. Test results show that the sensor can provide sub-millimeter accuracy under sinusoidal and step movement. Also, the two modes of operation offer complementary performance as the navigation mode is more accurate in tracking large amplitude and fast crack movement while the frame capture mode is more accurate for small and slow crack movement. These results illustrate the feasibility of developing such a crack sensor as well as point out directions of further research before its actual implementation.

• Smart Structures and Systems
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• 제30권6호
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• pp.583-599
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• 2022

In this paper, a multi-objective wireless sensor network configuration optimization method is proposed. The proposed method aims to determine the optimal information and lifespan wireless sensor network for structural health monitoring of large-scale infrastructures. In particular, cluster-based wireless sensor networks with multi-type of sensors are considered. To optimize the lifetime of the wireless sensor network, a cluster-based network optimization algorithm that optimizes the arrangement of cluster heads and base station is developed. On the other hand, based on the Bayesian inference, the uncertainty of the estimated parameters can be quantified. The coefficient of variance of the estimated parameters can be obtained, which is utilized as a holistic measure to evaluate the estimation accuracy of sensor configurations with multi-type of sensors. The proposed method provides the optimal wireless sensor network configuration that satisfies the required estimation accuracy with the longest lifetime. The proposed method is illustrated by designing the optimal wireless sensor network configuration of a cable-stayed bridge and a space truss.