• Smart Structures and Systems
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• v.6 no.5_6
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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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.860-863
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• 2010

Wireless sensor networks consist of small, autonomous devices with wireless networking capabilities. In order to further increase the applicability in real world applications, minimizing energy consumption is one of the most critical issues. Therefore, accurate energy model is required for the evaluation of wireless sensor networks. In this paper, we analyze the energy consumption for wireless sensor networks. To estimate the lifetime of sensor node, we have measured the energy characteristics of sensor node based on Telosb platforms running TinyOS. Based on the proposed model, the estimated lifetime of a battery powered sensor node can use about 6.925 months for 10 times motion detection per hour.

• Smart Media Journal
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• v.12 no.3
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• pp.60-67
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• 2023

Hyperledger Indy is an open-source implementation of DID, a decentralized identity verification technology. Hyperledger Indy uses the RBFT consensus algorithm, and if there is a lack of consensus with more than a certain number of problem nodes in the pool, data is not added. This problem can be prevented in advance by adding a node, and a node monitoring system was implemented to operate automatically. The node monitoring system continuously checks the status of the pool and automatically adds nodes when there are more than a certain number of problematic nodes to prevent consensus problems from occurring. This proposed method can increase the availability of Hyperledger Indy and is a study that can be referenced in various blockchain services that use consensus algorithms.

• IEMEK Journal of Embedded Systems and Applications
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• v.9 no.4
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• pp.229-235
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• 2014

This paper presents an environmental navigation system which provides a guidance to the users of smart bicycle for a pollution-free route during their travel. The smart bicycle operates as a sensor node being composed of a distributed wireless sensor network over the whole urban area. Several environmental sensors measuring the amount of dust, CO, $CO_2$, $NO_2$ in the air are built into the smart bicycle to estimate the level of air pollution in the located area. Each smart bicycle sends/receives the measured sensor data and the city pollution map to/from the centralized server, which leads the bike-riders to a healthy route by providing the environmental navigation information. The proposed idea and its implementation give a useful insight on various application services with the distributed smart bicycles.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.606-608
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• 2005

In this paper, we introduce localization server system calculated real location of objects using raw data of location-awareness from sensor node gateway. The software architecture of localization server system consists of location calculation and actuator control based on location. Also, this system supports for collecting raw data, calculating location of real objects using raw data, correcting error from outer environment, and server for applications based on location.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.128-130
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• 2021

Smart cities collect data from thousands of IoT-based sensor devices for intelligent application-based services. Centralized cloud servers support application tasks with higher computation resources but introduce network latency. Fog layer-based data centers bring data processing at the edge, but fewer available computation resources and poor task allocation strategy prevent real-time data analysis. In this paper, tasks generated from devices are distributed as high resource and low resource intensity tasks. The novelty of this research lies in deploying a virtual node assigned to each cluster of IoT sensor machines serving a joint application. The node allocates tasks based on the task intensity to either cloud-computing or fog computing resources. The proposed Task Allocation Strategy provides seamless allocation of jobs based on process requirements.

• Proceedings of the Korean Society of Computer Information Conference
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• 2022.01a
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• pp.145-148
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• 2022

본 논문은 스마트 팜 교육용 시스템을 IoT 기반으로 임베디드 환경에서 설계 및 구현하였다. 시스템 환경은 라즈베리파이 기반에서 노드-레드(Node-RED) 프로그램을 적용하였고 생육재배에 필요한 환경 센서와 구동장치를 연동하여 구축하였다. 센싱 정보는 유. 무선통신으로 서버로 전달되며, 데이터베이스를 근간으로 한 웹 설계는 PHP, MySQL을 사용하고, 스마트 폰 앱은 안드로이드 스튜디오를 사용하였다. 시스템 동작 과정은 센서값 인지 및 비주얼한 표시, 연동 구동장치 제어 프로그래밍, 서버 및 스마트 폰을 이용한 원격제어와 모니터링 과정을 수행할 수 있도록 설계하였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.6
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• pp.616-625
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• 2011

Ensuring the designed prestress force is very important for the safety of prestressed concrete bridge. The loss of prestress force in tendon could significantly reduce load carrying capacity of the structure. In this study, an automated prestress-loss monitoring system for prestressed concrete girder using PZT-interface and wireless impedance sensor node is presented. The following approaches are carried out to achieve the objective. Firstly, wireless impedance sensor nodes are designed for automated impedance-based monitoring technique. The sensor node is mounted on the high-performance Imote2 sensor platform to fulfill high operating speed, low power requirement and large storage memory. Secondly, a smart PZT-interface designed for monitoring prestress force is described. A linear regression model is established to predict prestress-loss. Finally, a system of the PZT-interface interacted with the wireless sensor node is evaluated from a lab-scale tendon-anchorage connection of a prestressed concrete girder.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5556-5573
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• 2017

As a main component of Internet of Things (IoTs), the wireless sensor networks (WSNs) have been widely applied to various areas, including environment monitoring, health monitoring of human body, farming, commercial manufacture, reconnaissance mission in military, and calamity alert etc. Meanwhile, the privacy concerns also arise when the users are required to get the real-time data from the sensor nodes directly. To solve this problem, several user authentication and key agreement schemes with a smart card and a password have been proposed in the past years. However, these schemes are vulnerable to some attacks such as offline password guessing attack, user impersonation attack by using attacker's own smart card, sensor node impersonation attack and gateway node bypassing attack. In this paper, we propose an improved scheme which can resist a wide variety of attacks in WSNs. Cryptanalysis and performance analysis show that our scheme can solve the weaknesses of previously proposed schemes and enhance security requirements while maintaining low computational cost.

• Journal of Electrical Engineering and Technology
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• v.7 no.1
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• pp.75-80
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• 2012

In this paper, a new energy harvesting technology using stray electric field of an electric power line is presented. It is found that energy can be harvested and stored in the storage capacitor that is connected to a cylindrical aluminum foil wrapped around a commercial insulated 220 V power line. The average current flowing into 47 ${\mu}F$ storage capacitor is about 4.53 ${\mu}A$ with 60 cm long cylindrical aluminum foil, and it is possible to operate wireless sensor node to transmit RF data every 42 seconds. The harvested average power is about 47 ${\mu}W$ in this case. Since the energy can be harvested without removing insulating sheath, it is believed that the proposed harvesting technology can be applied to power the sensor nodes in wireless ubiquitous sensor network and smart grid system.