• 전기전자학회논문지
• /
• 제26권3호
• /
• pp.389-395
• /
• 2022

기술의 진화와 함께, 사이버 물리 시스템(Cyber Physical System)은 향상되고 있고 이에 따라 새로운 유형의 사이버 공격도 발견되고 있다. 사이버 공격에는 여러 가지 형태가 있으며 모든 사이버 공격은 대상 시스템을 조작하기 위해 이루어진다. 사이버 물리시스템 중 대표적인 시스템이 사이버 물리 전력 시스템, 즉 스마트 그리드이다. 스마트 그리드는 신뢰할 수 있고 안전하며 효율적인 에너지 전송 및 분배를 제공하는 새로운 유형의 전력망이다. 본 논문에서는 스마트 그리드의 상태 추정과 에너지 분배를 타깃으로 하는 허위 데이터 주입 공격(False Data Injection Attack)으로 잘 알려진 특정 유형의 사이버 공격 구성 방법과 이러한 공격의 방어를 위한 보호 전략과 탐지를 위한 동적 모니터링 기법을 소개한다.

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

• Smart Structures and Systems
• /
• 제6권5_6호
• /
• pp.461-480
• /
• 2010

This paper analyses the data collected from the $2^{nd}$ Jindo Bridge, a cable-stayed bridge in Korea that is a structural health monitoring (SHM) international test bed for advanced wireless smart sensors network (WSSN) technology. The SHM system consists of a total of 70 wireless smart sensor nodes deployed underneath of the deck, on the pylons, and on the cables to capture the vibration of the bridge excited by traffic and environmental loadings. Analysis of the data is performed in both the time and frequency domains. Modal properties of the bridge are identified using the frequency domain decomposition and the stochastic subspace identification methods based on the output-only measurements, and the results are compared with those obtained from a detailed finite element model. Tension forces for the 10 instrumented stay cables are also estimated from the ambient acceleration data and compared both with those from the initial design and with those obtained during two previous regular inspections. The results of the data analyses demonstrate that the WSSN-based SHM system performs effectively for this cable-stayed bridge, giving direct access to the physical status of the bridge.

• International Journal of Computer Science & Network Security
• /
• 제24권5호
• /
• pp.135-155
• /
• 2024

Urban public health monitoring in smart cities focuses on the control of conditions and health challenges in urban environments. Considering the rapid spread of diseases and pandemics, it is important for health authorities to trace people carrying the virus. In smart cities, this tracing must be interoperable and intelligent, especially in indoor surfaces characterized by small distances between people. Therefore, to fight pandemics, it is necessary to start with the already-existing digital equipment of the Internet of Things, such as connected objects and smartphones. In this study, the developed system is employed to provide a social IoT network and suggest a strategy which allows reliable traceability without threatening the privacy of users. This IoT-based system allows respecting the social distance between persons sharing public services in smart cities without applying smartphone applications or severe confinement. It also permits a return to normal life in case of viral pandemic and ensures the much-desired balance between economy and health. The present study analyses previous proposed social distance systems then, unlike these studies, suggests an intelligent and distributed IoT based strategy for positioning students. Two scenarios of static and dynamic optimization-based placement of Bluetooth Low Energy devices are proposed and an experimental study shows the contribution and complementarity of the introduced contact tracing strategy with the applications on smartphones.

• Smart Structures and Systems
• /
• 제22권1호
• /
• pp.57-70
• /
• 2018

For the long-term structural health monitoring of civil structures, the effect of ambient temperature variation has been regarded as one of the critical issues. In this study, a principal component analysis (PCA)-based algorithm is proposed to filter out temperature effects on electromechanical impedance (EMI) monitoring of prestressed tendon anchorages. Firstly, the EMI monitoring via a piezoelectric interface device is described for prestress-loss detection in the tendon anchorage system. Secondly, the PCA-based temperature filtering algorithm tailored to the EMI monitoring of the prestressed tendon anchorage is outlined. The proposed algorithm utilizes the damage-sensitive features obtained from sub-ranges of the EMI data to establish the PCA-based filter model. Finally, the feasibility of the PCA-based algorithm is experimentally evaluated by distinguishing temperature changes from prestress-loss events in a prestressed concrete girder. The accuracy of the prestress-loss detection results is discussed with respect to the EMI features before and after the temperature filtering.

• Smart Structures and Systems
• /
• 제17권6호
• /
• pp.881-901
• /
• 2016

In this study, a method to compensate the effect of temperature variation on impedance responses which are used for prestress-loss monitoring in prestressed concrete (PSC) girders is presented. Firstly, an impedance-based technique using a mountable lead-zirconate-titanate (PZT) interface is presented for prestress-loss monitoring in the local tendon-anchorage member. Secondly, a cross-correlation-based algorithm to compensate the effect of temperature variation in the impedance signatures is outlined. Thirdly, lab-scale experiments are performed on a PSC girder instrumented with a mountable PZT interface at the tendon-anchorage. A series of temperature variation and prestress-loss events are simulated for the lab-scale PSC girder. Finally, the feasibility of the proposed method is experimentally verified for prestress-loss monitoring in the PSC girder under temperature-varying conditions and prestress-loss events.

• 한국재난정보학회 논문집
• /
• 제20권1호
• /
• pp.147-155
• /
• 2024

연구목적: 본 연구는 재난 안전 사각지대에 있는 소규모의 민간 건축물을 대상으로 건축물의 위험징후를 분석하고 계측기술을 개발하기 위한 건축물 모니터링 시스템 설치 방안을 제시하는 것을 목적으로 한다. 연구방법: 건축물 위험거동의 원인, 모니터링 계측 기기의 구성요소, 계측기기 설치 위치, 관리 방안 등을 제시한다. 연구결과: 계측기기는 필수적으로 가속도센서, 기울기센서, 자이로센서, GPS 등이 포함된다. 계측장치는 기둥의 높이와 단면적을 고려해야 한다. 결론: 본 연구의 결과는 소규모 민간 건축물에서 발생할 수 있는 건축물 붕괴로부터 발생하는 재난을 대비하여 재난 안전 역량 강화를 할 수 있다.

• Smart Structures and Systems
• /
• 제23권3호
• /
• pp.279-293
• /
• 2019

To ensure high quality data being used for data mining or feature extraction in the bridge structural health monitoring (SHM) system, a practical sensor fault diagnosis methodology has been developed based on the similarity of symmetric structure responses. First, the similarity of symmetric response is discussed using field monitoring data from different sensor types. All the sensors are initially paired and sensor faults are then detected pair by pair to achieve the multi-fault diagnosis of sensor systems. To resolve the coupling response issue between structural damage and sensor fault, the similarity for the target zone (where the studied sensor pair is located) is assessed to determine whether the localized structural damage or sensor fault results in the dissimilarity of the studied sensor pair. If the suspected sensor pair is detected with at least one sensor being faulty, field test could be implemented to support the regression analysis based on the monitoring and field test data for sensor fault isolation and reconstruction. Finally, a case study is adopted to demonstrate the effectiveness of the proposed methodology. As a result, Dasarathy's information fusion model is adopted for multi-sensor information fusion. Euclidean distance is selected as the index to assess the similarity. In conclusion, the proposed method is practical for actual engineering which ensures the reliability of further analysis based on monitoring data.

• Physical Therapy Rehabilitation Science
• /
• 제11권1호
• /
• pp.49-57
• /
• 2022

Objective: This study aims to conduct a comprehensive review of monitoring systems to monitor and manage physical function of community-dwelling elderly living alone and suggest future directions of unobtrusive monitoring. Design: Literature review Methods: The importance of health-related monitoring has been emphasized due to the aging population and novel corona virus (COVID-19) outbreak.As the population gets old and because of changes in culture, the number of single-person households among the elderly is expected to continue to increase. Elders are staying home longer and their physical function may decline rapidly,which can be a disturbing factorto successful aging.Therefore, systematic elderly management must be considered. Results: Frequently used technologies to monitor elders at home included red, green, blue (RGB) camera, accelerometer, passive infrared (PIR) sensor, wearable devices, and depth camera. Of them all, considering privacy concerns and easy-to-use features for elders, depth camera possibly can be a technology to be adapted at homes to unobtrusively monitor physical function of elderly living alone.The depth camera has been used to evaluate physical functions during rehabilitation and proven its efficiency. Conclusions: Therefore, physical monitoring system that is unobtrusive should be studied and developed in the future to monitor physical function of community-dwelling elderly living alone for the aging population.

• Smart Structures and Systems
• /
• 제29권4호
• /
• pp.561-576
• /
• 2022

Heritage timber structures represent the history and culture of a nation. These structures have been inherited from previous generations; however, they inevitably exhibit deterioration over time, potentially leading to structural deficiencies. Structural Health Monitoring (SHM) offers the potential to assess operational anomalies, deterioration, and damage through processing and analysis of data collected from transducers and sensors mounted on the structure. This paper reports on the design and implementation of a long-term SHM system on the Feiyun Wooden Pavilion in China, a three-story timber building built more than 500 years ago. The principles and features of the design and implementation of SHM systems for heritage timber buildings are systematically discussed. In total, 104 sensors of 6 different types are deployed on the structure to monitor the environmental effects and structural responses, including air temperature and humidity, wind speed and direction, structural temperatures, strain, inclination, and acceleration. In addition, integrated data acquisition and transmission subsystem using a newly developed software platform are implemented. Selected preliminary statistical and correlation analysis using one year of monitoring data are presented to demonstrate the condition assessment capability of the system based on the monitoring data.