• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1074-1076
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• 2005

Magnetic Inductance Tomography System은 비투자율이 공기보다 큰 대상물체를 외부에서 자기장을 인가하여 자기장의 변화를 자기센서로 측정하여 대상물체의 형상, 위치, 비투자율을 측정하고 판단하는 시스템이다. Magnetic Inductance Tomog-raphy System은 비투자율이 공기보다 큰 대상물체를 외부에서 자기장을 인가하여 자기장의 변화를 자기센서로 측정하여 대상물체의 형상, 위치, 비투자율을 측정하고 판단하는 시스템이다. Magnetic Inductance To-mography System은 대상물체의 위치, 모양, 크기에 따라 자기장의 변화가 달라게 된다. 대상물체를 실시간으로 측정하기 위하여 Magnetic Inductance To-mography System을 자기장 발생부와 신호변환부, 모니터링 부로 구분하여 구축하였다. 또한 대상물체를 위치를 이동시키거나 크기를 변경하여 대상물체의 신호를 해석, 측정하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.16-16
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• 2021

전자파표면유속계(Microwave Water Surface Current Meter)를 이용한 홍수기 유량측정은 교량과 같은 구조물을 이용하여 안전 및 측정위치의 흐름조건 등의 이유로 측정의 한계가 발생한다. 이런 문제점을 개선하기 위해 전자파표면유속계를 드론(Drone)과 결합하여 하천에서의 유량측정에 이용하였다. 전자파표면유속계는 비접촉식 유속측정 장비로 하천의 표면유속을 측정하고 유량산정을 위해 환산계수 0.85를 적용하여 평균유속을 산정하고 있다. 환산계수 0.85는 하천의 각 횡측선 수심-유속분포를 일반적인 분포로 가정하고 표면유속에 0.85를 곱하여 평균유속을 산정한다(Rantz, 1982). 그러나 하천의 측정위치 및 흐름특성에 따라 유속분포가 변화하기 때문에 국외 많은 연구에서 환산계수의 범위를 0.72에서 1.72까지 제시한 바 있다(Johnson and Cowen, 2017). 따라서 환산계수 0.85의 일률적인 적용은 부정확한 유량산정을 초래할 수 있어 측정위치에 적절한 환산계수 산정이 필요하다. 본 연구에서는 2020년 금강의 지류인 봉황천에 위치한 금산군(황풍교) 관측소에서 드론과 전자파표면유속계를 이용해 측정한 표면유속과 ADCP를 이용하여 동시 측정한 평균유속의 비교를 통해 환산계수를 산정하여 평균유속 산정의 정확도를 높이고자 하였다. 전자파표면유속계로 측정한 6개 성과 중 ADCP와 동시 측정한 4개의 성과를 분석하여 환산계수를 산정하였다. 측정성과별 측선수는 16~17개로 홍수터로 월류하여 비정상흐름이 발생한 측선은 제외하고 측선별 환산계수는 0.66에서 1.09의 범위로 나타났고, 성과별 환산계수의 평균치는 0.90에서 0.93 범위로 산정되었다. 환산계수가 일반적인 수치보다 높게 산정된 것은 측정위치 하류 약 600m에 위치한 콘크리트 고정보의 영향이 홍수 시 흐름의 수위-유속분포에 영향을 미쳐 높게 산정된 것으로 판단된다. 따라서 유량산정에 있어 환산계수는 4개 성과에서 산정된 환산계수의 평균치인 0.92를 적용하여 산정하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.86-97
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• 2009

RTLS is a system for automatically locating and tracking people and objects. The TDOA-based RTLS determines the location of the tag by calculating the time differences of a signal received from the tag. In TDOA-based RTLS, time synchronization is essential to calculate the time difference between readers. This paper presents a precision time synchronization method for TDOA-based RTLS over IEEE 802.15.4. In order to achieve precision time synchronization in IEEE 802.15.4 radio, we analyzed the error factors of delay and jitter. We also deal with the implementation of hardware assisted time stamping and the Kalman filtering method to minimize the error factors. In addition, this paper described the experiments and performance evaluation of the proposed precision time synchronization method in IEEE 802.15.4 radio. The results show that the nodes in a network can maintain their clocks to within 10 nanoseconds offset from the reference clock.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.1
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• pp.97-108
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• 2013

Recently, mobile devices were increased and there was a sharp rise in demand. To exploit the location information of each device, many researcher was studying locating systems. The favorite locating or positioning systems were a GPS using satellites and a RTLS using wireless communication between devices. If some obstacle existed nearby the target device, The system have difference of performance. The obstacles near targets were caused signal disconnection and reflection because of NLOS condition. As the result, the NLOS condition degrade the locating performance. In this paper, we propose a locating system which is cooperated two systems using information reliability estimates from LOS/NLOS condition. We developed proposed system. In addition, we performed fields test and simulation tests at various environment for performance evaluation. As the result, the test showed 97% success rate to estimate NLOS condition. Furthermore, the simulation result of our locating system was increased to 89% compared with a single system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.105-113
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• 2008

In Ubiquitous Society, accurate Location Calculation of user's device is required to achieve the need of users. As the location calculation is processed by ranging between transceivers, if some obstacles exist between transceivers, NLoS(Non-line-of-Sight) components of received signal increase along with the reduction of LoS(Line-of-Sight) components. Therefore the location calculation error will increase due to the NLoS effect. The conventional location calculation algorithm has the original ranging error because there is no transformation of ranging information which degrades the ranging accuracy. The Iterative Calculation method which minimizes the location calculation error relys on accurately identifying NLoS or LoS condition of the tested channel. We employ Kurtosis, Mean Excess Delay and RMS Delay spread of the received signal to identify whether the tested channel is LoS or NLoS firstly. Thereafter, to minimize location calculation error, the proposed Iterative Calculation method iteratively select random range and finds the averaged target location which has high probability. The simulation results confirm the enhancement of the proposed method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10A
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• pp.938-948
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• 2005

Localization in wireless sensor networks is to determine the positions of all nodes based on the Down positions of several nodes. Much previous work for localization use multilateration or triangulation based on measurement of angles or distances to the fixed nodes. In this paper, we propose a new centralized algorithm for localization using weights of adjacent nodes. The algorithm, having the advantage of simplicity, shows that the localization problem can be formulated to a linear matrix equalities. We mathematically show that the equalities have a unique solution. The unique solution indicates the locations of unknown nodes are capable of being uniquely determined. Three kinds of weights proposed for practical use are compared in simulation analysis.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.2056-2063
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• 2012

In a port terminal, containers are stored and transshipped by yard tractors and crane vehicles. For operation efficiency of the terminal, location information of these vehicles is an essential factor. However, most of port terminals try to estimate location of these assets using indirect methods such as event tracking of shipping or unshipping containers. Because these kinds of events are rarely occurred, location of the event includes seriously locating error compared to a real location of vehicle. In this paper, we propose a real-time asset tracking system to obtain accurate and reliable location of terminal assets. The proposed system overcomes a location estimation error caused by container stacks which interrupt wireless communication. In order to mitigate uncertainty and increase accuracy of location estimation, we designed hardwares and multi-step locating system to resolve additional preblems. We implemented system components, and installed these at a port environment for evaluation. The result shows superiority of the system that the accuracy is approximately 5.87 meters (CEP).

• Water for future
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• v.29 no.2
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• pp.167-178
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• 1996

In designing automatic water quality monitoring networks for a river basin, determination of measurement locations and items is critical to the effectiveness of the total system. In this paper we studied how to decide these two design factors when a monitoring network is designed for the purposse of water quality surveillance and emergency alarm. For measurement locations, candidate sites are chosen based on the intake amount for water supply and the point sources of contamination. Then, detailed locations are decided according to the contaminant flow distance. As for measurement items, characteristics and the accident history of water pollution in the basin must be taken into account. Considering economic aspects, we proposed a two-stage measurement plan: basic components for all locations and selective ones variable for different locations. Proposed methodology is demonstrated through a case study for Nak-dong River Basin.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1238-1244
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• 2011

This paper presents the matching method of reflectors for localization of laser navigation. The laser navigation is a device that measures distance and angle of reflector. The conventional major matching using the laser navigation is method that moves position of measured reflectors to position of installed reflectors and than rotate moved reflectors. However, it is difficult to use the industry because it has high computational complexity and high errors. To solve those problem, The proposed matching is method that create position of measured reflectors to assume that the position of installed reflectors is position of AGV and than rotate the position of installed reflectors. For experiment, we used AGV which was designed by ourselves, and compared positioning accuracy when AGV moves according to varying steering angle and driving speed.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.5
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• pp.80-85
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• 1997

Preventive diagnosis technique of power transforms is very important for highly reliable operation of power systems, and especially that of online transformer is needed in view of economy. Acoustic methods for partial discharge points have been studied abroad since 1960's in earnest. Electric-ultrasonic locating method by which partial discharges are found through detecting the electric and ultrasonic signal generated in partial discharge and ultrasonic-ultrasonic locating method by which partial discharges are found through detecting two ultrasonic signal with two ultrasonic sensor have been researched in our country. By using this ultrasonic-ultrasonic locating method, it was proposed of graphical determination technique of partial discharge points one dimension, two dimension, three dimension. But in locating partial discharges, they have assumed that the number of signal origin is one. So in this study we suggests a method of locating and knowing the number of signal origins when there are several origins by using ultrasonic-ultrasonic method.