• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2181-2202
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• 2016

In Wireless Sensor Networks (WSNs) and even in the Internet of Things (IoT) ecosystem, the reconfiguration of sensor variables is an important problem when the role of a system (or application) program's sensor nodes needs to be adjusted in a particular situation. For example, the outdoor temperature in a volcanic zone, which is usually updated in a system every 10 s, should be updated every 1 s during an emergency situation. To solve this problem, this paper proposes a novel approach based on changing only a set of sensor variables in a part of a program, rather than modifying the entire program, in order to reduce both network congestion and the sensor nodes' battery consumption. To validate our approach, we demonstrate an implementation of a proof-of-concept prototype system and also present results of comparative studies showing the performance and effectiveness of our proposed method.

• Journal of Communications and Networks
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• 제15권2호
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• pp.164-172
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• 2013

We consider the problem of secure and robust clustering for quantized target tracking in wireless sensor networks (WSN) where the observed system is assumed to evolve according to a probabilistic state space model. We propose a new method for jointly activating the best group of candidate sensors that participate in data aggregation, detecting the malicious sensors and estimating the target position. Firstly, we select the appropriate group in order to balance the energy dissipation and to provide the required data of the target in the WSN. This selection is also based on the transmission power between a sensor node and a cluster head. Secondly, we detect the malicious sensor nodes based on the information relevance of their measurements. Then, we estimate the target position using quantized variational filtering (QVF) algorithm. The selection of the candidate sensors group is based on multi-criteria function, which is computed by using the predicted target position provided by the QVF algorithm, while the malicious sensor nodes detection is based on Kullback-Leibler distance between the current target position distribution and the predicted sensor observation. The performance of the proposed method is validated by simulation results in target tracking for WSN.

• 한국정밀공학회지
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• 제24권10호
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• pp.83-90
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• 2007

The vehicle dynamic control system needs to detect the yaw rate of vehicle and a yaw rate sensor is required as a central component. Therefore, A sensor on the basic of the "tuning fork method" for automotive controls is being developed. The sensor was fabricated by the surface micro machining process to miniaturize its size. The sensor output offset is ${\pm}0.37^{\circ}/sec$ in the room temperature. The resonance frequency of the fabricated yaw rate sensor is measured to 5.29kHz for the drive mode. Tests of the sensor demonstrate that its performance is equivalent to that required for implementation of a yaw control system. Vehicle handling and safety are substantially improved using the sensor to implement yaw control.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1361-1368
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• 2005

In this paper, the theoretical method of measuring the tunnel convergence and underground displacement, the objective indices of assessing safety for tunnel construction, using the fiber optic sensor is studied by developing the program to automatically measure them. The model test of Con'c beam is conducted to evaluate reliability of the fiber optic sensor. Furthermore, using the RS232 communication protocol as well as Visual C# and Visual C++, the programming tools, the program was developed to detect automatically the measured value of the fiber optic sensor, calculate the tunnel convergence and underground displacement, predict the deformed shape of the tunnel, and evaluate loosening zone due to the tunnel excavation.

• 센서학회지
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• 제14권5호
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• pp.302-307
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• 2005

Precision displacement of less than a few nm resolution was measured in real-time using fiber optic EFPI sensor. The novel method for real-time processing of analyzing EFPI output signal was developed and verified. Linearity in the mean values of interferometric light intensity among adjacent fringes was shown and verified the sinusoidal approximation algorithm that estimates past and coming fringe values. Real-time signal processing program was developed and the intensity signal of the EFPI sensor was transformed to the phase shift with this program. The resolution below $0.36{\sim}8.6$ nm in the displacement range of $0{\sim}300{\mu}m$ was obtained. The nano-positioner with a piezoelectric actuator and the EFPI sensor system was designed and tested. The positioner successfully reached to the desired destination within 1 nm accuracy.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.231-236
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• 2007

In this paper, we studied the possibility of non-contact bill counting method using optical fiber sensor instead of traditionally used friction counting method. To implement non-contact counting, we designed and made optical fiber sensor and related parts. optical fiber sensor is made of optical fiber of 1mm diameter, photo diode and laser diode. Based on the conclusion which derived from preliminary experiment, instrument part is designed to make unevenness on the surface of bill paper and to stay parallel with optical fiber section. By analyzing the signal of optical sensor, we made counting program. Experimental instrument is composed of sensor part, instrument part, signal handling part. We checked the possibility of non-contact counting method after implementing experiment by using optical fiber sensor and instrument part.

• 한국지리정보학회지
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• 제12권4호
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• pp.158-168
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• 2009

국가와 도시가 급속히 발전할수록 국민생활에 필요한 기반시설물들과 관리 체계는 날로 복잡해지고, 이를 체계적으로 건설하고 유지하는 비용과 노력이 기하급수적으로 증가한다. 본 연구에서는 국가기반시설물 중 도시지상시설물을 무선 센서 네트워크로 관리하기 위해 센서노드를 설치하는 방법을 제시하였다. 먼저, 1차 분석으로 관리 대상 및 방법을 도출하여 센싱 커버리지를 만든 후, 이를 도시지상시설물에 센서노드 설치에 적용하였다. 그리고 2차 분석을 통하여 중복설치 문제의 해결 방안을 제시하였다. 제시된 방법과 수치지도를 활용하여 GIS 프로그램을 구현하였으며, 항공사진과의 중첩을 통해 관리의 방법에 현실성을 향상시켰다. 개발된 프로그램을 사용하여, 한국건설기술연구원 주변 지형에 대해 센서노드 실험을 실시하였다. 그 결과 중복 설치된 센서노드를 약 50% 제거하였으며, 도로를 따라 센서노드가 골고루 배치된 것을 확인할 수 있었다.

• 한국인터넷방송통신학회논문지
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• 제8권6호
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• pp.141-146
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• 2008

최근 OGC(Open Geospatial Consortium)의 센서 웹에서는 센서 네트워크에서 수집된 센싱 데이터 및 영상 정보를 저장하고 관리하여 인터넷을 통해 사용자들에게 제공하는 연구가 진행되고 있다. 이와 같은 센싱 데이터 및 영상 정보를 실시간적으로 사용자에게 전달하기 위해서는 센싱 데이터를 비롯하여 오디오 및 비디오를 하나로 묶는 데이터 융합에 대한 연구가 필요하다. 이에 본 논문에서는 센서 네트워크에서 수집된 센싱 데이터와 영상을 인덱스를 이용하여 융합하는 방안을 제시한다. 이 방안에서는 동일한 노드에서 수집된 센싱 데이터와 영상의 식별 정보를 통합 인덱스에 함께 표시하고, 이를 통해 사용자가 질의할 경우 통합 인덱스를 참조하여 센싱 데이터와 영상을 동시에 제공한다. 제안된 방안을 검증하기 위해 센서 네트워크와 영상장치를 이용하여 실시간 멀티미디어 서비스 구조를 설계하고 인덱스 기반의 영상과 센서 데이터를 통합한 유비쿼터스 실시간 멀티미디어 시스템을 설계하고 구현한다. 이를 통하여 제안된 데이터 융합 방안이 영상 장치와 무선 센서 네트워크로부터 수집되는 영상과 센싱 데이터를 통합 인덱스를 이용하여 응용 서비스의 정보 요청에 따라 실시간 멀티미디어 서비스를 제공하는 것을 확인하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.154-157
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• 2003

Precision displacement of less than a few nm resolution was measured in real-time using fiber optic EFPI sensor. The novel method for real-time processing of analyzing EFPI output signal was developed and verified. Linearity in the mean values of interferometric light intensity among adjacent fringes was shown, and the sinusoidal approximation algorithm that estimates past and coming fringe values was verified through the linearity. Real-time signal processing program was developed, and the intensity signal of the EFPI sensor was transformed to the phase shift with this program. The resolution below 0.4 ~ 10 nm in the displacement range of $0 ~ 300\mu\textrm{m}$ was obtained by reducing the photodetector noise using low-pass filter and signal averaging. The nano-translation stage with a Piezo-electric actuator and the EFPI sensor system was designed and tested. This stage successfully reached to the desired destination in $15\mu\textrm{m}$ range within 1 nm accuracy.

• 대한의용생체공학회:의공학회지
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• 제35권3호
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• pp.55-61
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• 2014

In sleep monitoring system, polysomnography (PSG) is the gold-standard but previous studies revealed that attaching numerous amount of sensors disturb sleep during the test which is the fundamental disadvantage of PSG. We suggest an unconstrained rapid-eye-movement (REM) sleep monitoring method measured with polyvinylidene (PVDF) film-based sensor for the normal and the obstructive sleep apnea (OSA) patients. Nine normal subjects and seventeen OSA patients have participated in the study. During REM sleep, rate and variability of respiration are known to be greater than in other sleep stages. Based on this phenomena, respiratory signals of participants were unconstrainedly measured using the PVDF-based sensor with the PSG and REM sleep were extracted from the average rate and variability of respiration. In epoch-by-epoch REM sleep detection, proposed method classified REM sleep with an average sensitivity of 72.3%, specificity of 92.5%, accuracy of 88.9%, and kappa statistic of 0.60 compared to the results of PSG. Student's t-test showed no significant difference between the results of normal and OSA group. This method is potentially applicable to REM sleep detection in homing environment or ambulatory monitoring.