• Smart Structures and Systems
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• 제4권2호
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• pp.209-220
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• 2008

A methodology for the seismic vulnerability assessment of historical monuments is presented in this paper. The ongoing work has been conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The case study is the five-century-old Zaouia of Sidi Kassem Djilizi, located downtown Tunis, the capital of Tunisia. Ambient vibration tests were conducted on the case study using a number of force-balance accelerometers placed at selected locations. The Enhanced Frequency Domain Decomposition (EFDD) technique was applied to extract the dynamic characteristics of the monument. A 3-D finite element model was developed and updated to obtain reasonable correlation between experimental and numerical modal properties. The set of parameters selected for the updating consists of the modulus of elasticity in each wall element of the finite element model. Seismic vulnerability assessment of the case study was carried out via three-dimensional time-history dynamic analyses of the structure. Dynamic stresses were computed and damage was evaluated according to a masonry specific plane failure criterion. Statistics on the occurrence, location and type of failure provide a general view for the probable damage level and mode. Results indicate a high vulnerability that confirms the need for intervention and retrofit.

• Smart Structures and Systems
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• 제20권2호
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• pp.139-150
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• 2017

The structural strain plays a significant role in structural condition assessment of in-service bridges in terms of structural bearing capacity, structural reliability level and entire safety redundancy. Therefore, it has been one of the most important parameters concerned by researchers and engineers engaged in structural health monitoring (SHM) practices. In this paper, an SHM system instrumented on the Jiubao Bridge located in Hangzhou, China is firstly introduced. This system involves nine subsystems and has been continuously operated for five years since 2012. As part of the SHM system, a total of 166 fiber Bragg grating (FBG) strain sensors are installed on the bridge to measure the dynamic strain responses of key structural components. Based on the strain monitoring data acquired in recent two years, the strain-based structural condition assessment of the Jiubao Bridge is carried out. The wavelet multi-resolution algorithm is applied to separate the temperature effect from the raw strain data. The obtained strain data under the normal traffic and wind condition and under the typhoon condition are examined for structural safety evaluation. The structural condition rating of the bridge in accordance with the AASHTO specification for condition evaluation and load and resistance factor rating of highway bridges is performed by use of the processed strain data in combination with finite element analysis. The analysis framework presented in this study can be used as a reference for facilitating the assessment, inspection and maintenance activities of in-service bridges instrumented with long-term SHM system.

• International journal of advanced smart convergence
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• 제9권1호
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• pp.63-69
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• 2020

The rapid development in modern industrialization pollutant the water and atmospheric air across the globe that have a major impact on the human and livings health. In worldwide, every country government increasing the importance to improve the outdoor air pollution monitoring and control to provide quality of life and prevent the citizens and livings life from hazard disease. We proposed the environmental dust level detection method for outdoor facilities using sensor fusion technology to measure precise micro-dust level and monitor in realtime. In this proposed approach use the camera sensor and commercial dust level sensor data to predict the micro-dust level with data fusion method. The camera sensor based dust level detection uses the optical flow based machine learning method to detect the dust level and then fused with commercial dust level sensor data to predict the precise micro-dust level of the outdoor facilities and send the dust level informations to the outdoor air pollution monitoring system. The proposed method implemented on raspberry pi based open-source hardware with Internet-of-Things (IoT) framework and evaluated the performance of the system in realtime. The experimental results confirm that the proposed micro-dust level detection is precise and reliable in sensing the air dust and pollution, which helps to indicate the change in the air pollution more precisely than the commercial sensor based method in some extent.

• 디지털융복합연구
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• 제13권6호
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• pp.105-111
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• 2015

경쟁이 치열한 세기에 다양한 제품과 서비스를 인터넷과 스마트 폰을 통해 판매하는 기회와 도전이 모두 존재한다. 온라인 서비스들은 더 이상 온라인에만 머물지 않으려 하며, 더 큰 시장이 있는 오프라인 시장으로 영역을 확대하고 있다. 온라인 상거래 시장과 오프라인 상거래 시장이 합쳐지는 교집합 영역을 O2O(Online to Offilne) 시장이라고 볼 때, 모바일과 인터넷 기술의 발전으로 교집합인 O2O영역이 점차 늘고 있다. 이 연구는 사용자와 오프라인 가맹점을 연결하는 인터넷 회사의 성공적인 노력의 모범 사례를 통해서 사례 연구를 진행한다. 중국 Dianping.com 성공 사례를 바탕으로, 오프라인과 온라인 효과적으로 연결된 생태계를 구축하기 위한 프레임 워크를 분석한다. Dianping.com 10년 넘게 싸여있는 성공 경험이 다른 융복합 분야에서 운영하는 온라인 기업들에게 유용한 경험담을 제공 할 수 있다.

• 보건교육건강증진학회지
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• 제28권5호
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• pp.145-160
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• 2011

Objectives: This study attempted to apply the Intervention mapping and Transtheoretical models to develop a program to promote moderate alcohol drinking in university students. Methods: Surveyed data from 1,137 university students were analyzed to identify personal and environmental determinants for alcohol drinking. Based on these determinants, program objectives were established. Crossing the objectives with related important determinants resulted in matrices of learning objectives for which educational strategies were developed. Subsequently, an intervention program were designed to achieve those objectives. Results: Identified personal determinants included awareness, attitudes, self-efficacy and behavioral skills. Environmental determinants were binge drinking behaviors of family members and peers, and social pressure for drinking. Program, impact and learning objectives were developed to change the identified determinants. Program activities included provision of information on positive and negative consequences of binge drinking, opportunities for assessing one's drinking pattern, increasing outcome expectancies of and skill building for monitoring drinking, resisting peer pressure and managing stress. To facilitate adoption and maintenance of the program, an intervention diffusion plan was suggested. An evaluation plan was developed by utilizing RE-AIM framework. Conclusions: In order to expand evidence bases for effective theory-based programs, the developed program should be tested in diverse university settings.

• 정보보호학회논문지
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• 제23권5호
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• pp.803-813
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• 2013

최근 스마트 기기 및 소셜 네트워크 서비스의 발달로 인해 데이터가 폭증하며 세계는 이른바 빅데이터 시대를 맞고 있다. 이에 이러한 데이터를 처리할 수 있는 새로운 기술인 빅데이터 처리기술은 클라우드 컴퓨팅 기술과 함께 주목받고 있으며, 가장 대표적인 기술이 바로 하둡이다. 하둡 분산 파일 시스템은 상용 리눅스 서버에서 실행되도록 설계된 오픈소스 프레임워크로서 수백 테라바이트 크기의 파일을 저장할 수 있다. 초기 하둡은 빅데이터 처리에 초점을 맞추어 보안이 거의 도입되지 않은 상태였으나 사용자가 빠르게 늘어남에 따라 하둡 분산 파일 시스템에 개인정보를 포함한 민감한 데이터가 많이 저장되면서, 2009년 커버로스와 토큰 시스템을 도입한 새로운 버전을 발표하였다. 그러나 이 시스템은 재전송 공격, 가장 공격 등이 가능하다는 취약점을 가진다. 따라서 본 논문에서는 하둡 분산 파일 시스템 보안 취약점을 분석하고, 이러한 취약점을 보완하면서 하둡의 성능을 유지할 수 있는 새로운 프로토콜을 제안한다.

• Smart Structures and Systems
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• 제14권1호
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• pp.39-54
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• 2014

Node layout optimization of structural wireless systems is investigated as a means to prolong the network lifetime without, if possible, compromising information quality of the measurement data. The trade-off between these antagonistic objectives is studied within a multi-objective layout optimization framework. A Genetic Algorithm is adopted to obtain a set of Pareto-optimal solutions from which the end user can select the final layout. The information quality of the measurement data collected from a heterogeneous WSN is quantified from the placement quality indicators of strain and acceleration sensors. The network lifetime or equivalently the network energy consumption is estimated through WSN simulation that provides realistic results by capturing the dynamics of the wireless communication protocols. A layout optimization study of a monitoring system on the Great Belt Bridge is conducted to evaluate the proposed approach. The placement quality of strain gauges and accelerometers is obtained as a ratio of the Modal Clarity Index and Mode Shape Expansion values that are computed from a Finite Element model of the monitored bridge. To estimate the energy consumption of the WSN platform in a realistic scenario, we use a discrete-event simulator with stochastic communication models. Finally, we compare the optimization results with those obtained in a previous work where the network energy consumption is obtained via deterministic communication models.

• Smart Structures and Systems
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• 제26권2호
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• pp.227-239
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• 2020

Despite proven effectiveness and accuracy in laboratories, the existing damage assessment based on guided ultrasonic waves (GUWs) or acoustic emission (AE) confronts challenges when extended to real-world structural health monitoring (SHM) for railway tracks. Central to the concerns are the extremely complex signal appearance due to highly dispersive and multimodal wave features, restriction on transducer installations, and severe contaminations of ambient noise. It remains a critical yet unsolved problem along with recent attempts to implement SHM in bourgeoning high-speed railway (HSR). By leveraging authors' continued endeavours, an SHM framework, based on actively generated diffuse ultrasonic waves (DUWs) and a benchmark-free condition contrast algorithm, has been developed and deployed via an all-in-one SHM system. Miniaturized lead zirconate titanate (PZT) wafers are utilized to generate and acquire DUWs in long-range railway tracks. Fatigue cracks in the tracks show unique contact behaviours under different conditions of external loads and further disturb DUW propagation. By contrast DUW propagation traits, fatigue cracks in railway tracks can be characterised quantitatively and the holistic health status of the tracks can be evaluated in a real-time manner. Compared with GUW- or AE-based methods, the DUW-driven inspection philosophy exhibits immunity to ambient noise and measurement uncertainty, less dependence on baseline signals, use of significantly reduced number of transducers, and high robustness in atrocious engineering conditions. Conformance tests are performed on HSR tracks, in which the evolution of fatigue damage is monitored continuously and quantitatively, demonstrating effectiveness, adaptability, reliability and robustness of DUW-driven SHM towards HSR applications.

• Smart Structures and Systems
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• 제26권5호
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• pp.657-666
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• 2020

A rotational pulse-echo ultrasonic propagation imager that can inspect cylindrical specimens for material nondestructive evaluations is proposed herein. In this system, a laser-generated ultrasonic bulk wave is used for inspection, which enables a clear visualization of subsurface defects with a precise reproduction of the damage shape and size. The ultrasonic waves are generated by a Q-switched laser that impinges on the outer surface of the specimen walls. The generated waves travel through the walls and their echo is detected by a Laser Doppler Vibrometer (LDV) at the same point. To obtain the optimal Signal-to-Noise Ratio (SNR) of the measured signal, the LDV requires the sensed surface to be at a right angle to the laser beam and at a predefined constant standoff distance from the laser head. For flat specimens, these constraints can be easily satisfied by performing a raster scan using a dual-axis linear stage. However, this arrangement cannot be used for cylindrical specimens owing to their curved nature. To inspect the cylindrical specimens, a circular scan technology is newly proposed for pulse-echo laser ultrasound. A rotational stage is coupled with a single-axis linear stage to inspect the desired area of the specimen. This system arrangement ensures that the standoff distance and beam incidence angle are maintained while the cylindrical specimen is being inspected. This enables the inspection of a curved specimen while maintaining the optimal SNR. The measurement result is displayed in parallel with the on-going inspection. The inspection data used in scanning are mapped from rotational coordinates to linear coordinates for visualization and post-processing of results. A graphical user interface software is implemented in C++ using a QT framework and controls all the individual blocks of the system and implements the necessary image processing, scan calculations, data acquisition, signal processing and result visualization.

• 대한공간정보학회지
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• 제20권1호
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• pp.73-81
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• 2012

본 연구는 U-City 경쟁력의 개념 및 U-City 관련 지수의 연구동향을 파악하여 U-City 경쟁력 지수의 개발방향을 제시하는데 목적이 있다. 이를 위해 먼저 정보화시대, 미래도시, U-City의 개념을 관련문헌을 토대로 파악하고, U-City경쟁력의 개념을 제시하였다. 다음으로 U-City를 비롯한 미래도시 관련 지수의 연구동향을 파악하여 U-City 경쟁력 지수 개발에의 시사점을 도출하였다. 마지막으로 U-City 경쟁력지수 개발 절차와 각 단계에서의 유의점을 제시하였다. 연구결과 U-City 경쟁력은 거주민의 요구사항에 대한 신속한 대응 및 도시공간 관리의 효율성을 극대화할 수 있는 ICT, U-City 인프라, U-City 서비스, U-City 관리 능력을 의미하며, 이를 측정하기 위해 평가체계의 마련, 평가지표의 선정, 표준화, 지표별 가중치 산정, 평가모형 설정의 개발절차가 필요한 것으로 파악되었다.