• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.416-417
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• 2011

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.119-120
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• 2012

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.2
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• pp.115-120
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• 2018

This paper introduces a magnetic hysteresis monitoring result to apply an EM sensing technique for estimating tensile force of PSC girder to various class of PS tendon. The tensile force of PS tendon is a very important factor in the performance evaluation of PSC bridges. However, in this time, the tensile force was just measured only during construction and it does not monitored after construction. To measure the tensile force of PS tendons, the EM sensing based NDT method was developed but the proposed method cannot be applied to various class of PS tendons. Thus this study performed the magnetic hysteresis measurement according to the tensile force for class B, C and D PS tendons through experimental study. The specific tensile forces(50, 100, 150, 180kN) were induced to the each specimens and the magnetic hysteresis curve was measured at each point. The permeability of specimens were gradually decreased according to increase of tensile force. Especially, the slopes of permeability variation of class B and C were similar while that of class D was different.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.2
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• pp.87-92
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• 2019

In this paper, we have verified a low-voltage EM(elasto-magnetic) sensing technique for tensile force management of PSC(prestressed concrete) internal tendon in order to apply the technique to actual construction sites where stable power supply is difficult. From observation of past domestic and overseas PSC structural accident cases, it was found that PS tension is very important to maintain structural stability. In this paper, we have tried to measure the tensile force from a magnetic hysteresis curve through EM sensors according to voltage value by using relation between magnetostriction and stress of ferromagnetic material based on elastic-magnetic theory. For this purpose, EM sensor of double cylindrical coil type was fabricated and tensile force test equipment for PS tendon using hydraulic tensioning device was constructed. The experiment was conducted to confirm relationship between changes of permeability and tensile force from the measurement results of the maximum / minimum voltage amount. The change of magnetic hysteresis curve with magnitude of tensile force was also measured by reducing amount of voltage step by step. As a result, the slope of estimation equation in accordance with magnitude of magnetic field decreases with the voltage reduction. But it was confirmed a similar pattern of change of magnetic permeability for the magnetic hysteresis loop. So, in this study, it is considered that it is possible to manage the tensions of PSC internal tendon using EM sensing technique in low-voltage state.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.715-722
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• 2015

The prestressing force has not been managed after construction nevertheless it is one of the importrant factors that maintain the structural safety of PSC girder bridges. The prestressing force is just measured during construction using jacking device and after that, it can not be managed practically. For this reason, this study investigated the measurements of prestress using embedded sensors that can be available now with an ultimate goal to propose smart prestressed girders that can measure the prestress from the birth to the end of service life. 4 types of sensors were installed on the small prestressed girders, and the applicability and the accuracy of those sensors were tested while the prestress was applied to the girders. The results show that a center-hole type loadcell has a tendency to measure a prestressing force higher than a reference value, especially when it is loaded with an eccentricity. a EM sensor shows several advantages that has a good practical accuracy, that can be installed anyplace along the tendons.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.1026-1029
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• 2009

Efficient Power consumption is important in sensor networks because charging of deployed sensor nodes is too difficult. So this paper focused on Modified-CBPER reduces energy consumption by reducing CBPER's data announcement ragne, and propose an algorithm to reduce power consumption by additional reduction of data announcement range. Proposed EM-CBPER(Enhanced Modified CBPER) somewhat increases power consumption of data request and data forwarding but it reduces total power consumption by reducing data announcement transmission of account for large quantity on total packet transmission.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.905-912
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• 2011

Interaocular pressure (IOP) sensor and external coil to detect the resonance frequency of the IOP sensor are designed and implemented using MEMS technology. The IOP sensor is designed using 3-D electromagnetic (EM) simulation. The resonance frequency of IOP sensor needs to be lower than that of the external coil. Additionally, the resonance frequency of the IOP sensor needs to be located near the resonance frequency of the coil to get the sufficient amplitude of phase variation. The frequency where the phase peak appears must be constant according to the distance between the IOP sensor and the external coil. From the measurement results, we demonstrated that the designed IOP sensor has the same resonance frequency with various distances between the IOP sensor and the coil.

• Journal of KIISE
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• v.42 no.8
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• pp.1031-1038
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• 2015

The recent emergence of smart phones, wearable devices, and even the IoT concept made it possible for various objects to interact one another anytime and anywhere. Among many of such smart services, a smart home service typically requires a large number of sensors to recognize the residents' activities. For this reason, the ideas on activity recognition using the data obtained from those sensors are actively discussed and studied these days. Furthermore, plenty of sensors are installed in order to recognize activities and analyze their patterns via data mining techniques. However, if many of these sensors should be installed for IoT smart home service, it raises the issue of cost and energy consumption. In this paper, we proposed a new method for reducing the number of sensors for activity recognition in a smart environment, which utilizes the principal component analysis and clustering techniques, and also show the effect of improvement in terms of the activity recognition by the proposed method.

• Korean Journal of Remote Sensing
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• v.19 no.4
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• pp.329-339
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• 2003

In this study, an approach of image fusion in decision level has been proposed for unsupervised image classification using the images acquired from multiple sensors with different characteristics. The proposed method applies separately for each sensor the unsupervised image classification scheme based on spatial region growing segmentation, which makes use of hierarchical clustering, and computes iteratively the maximum likelihood estimates of fuzzy class vectors for the segmented regions by EM(expected maximization) algorithm. The fuzzy class vector is considered as an indicator vector whose elements represent the probabilities that the region belongs to the classes existed. Then, it combines the classification results of each sensor using the fuzzy class vectors. This approach does not require such a high precision in spatial coregistration between the images of different sensors as the image fusion scheme of pixel level does. In this study, the proposed method has been applied to multispectral SPOT and AIRSAR data observed over north-eastern area of Jeollabuk-do, and the experimental results show that it provides more correct information for the classification than the scheme using an augmented vector technique, which is the most conventional approach of image fusion in pixel level.

• Information and Communications Magazine
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• v.30 no.6
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• pp.40-46
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• 2013

본고에서는 무선인체센서내트워크의 개념을 정립하고, WBAN (Wireless Body Network)의 표준화 동향, 문제점 그리고 향후 지속 가능한 연구 방향에 대하여 고찰하였다. 클라우드 컴퓨팅 환경은 인체센서 노드에서 고성능 슈퍼 컴퓨터에 이르는 다양한 범위의 서로 다른 장치를 연결하여 컨텐트 중심의 서비스를 제공하게 될 것이며 이에 대한 이슈와 연구방향을 진단하였다. 나노기술로 인하여 나노미터 수준의 장치를 개발할 수 있을 것으로 예상되며, 이러한 나노장치 간 정보교환은 의료, 환경 및 군사 분야에서 떠오르는 나노 응용기술로 발전하게 되었다. 나노장치 사이의 정보전송을 전기자기학적(EM) 나노통신 및 분자레벨 나노통신으로 구분할 수 있으며 이들의 연구 방향을 통신 이론적 관점에서 고찰하고 분석하였다.