• Journal of Advanced Navigation Technology
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• 제14권6호
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• pp.783-790
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• 2010

For safety navigation of ships at sea, ships monitor their location obtained from Global Positioning Satellite System (GNSS). In this study, we computed near-real-time positions of a ship at sea using GPS Precise Point Positioning (PPP) technique and analyzed precision of the near-real-time positions. We conducted ship borne GPS observations in the south sea of Korea. To process the GPS data using PPP technique, GIPSY-OASIS (GPS Inferred Positioning System-Orbit Analysis and Simulation Software) developed by the Jet Propulsion Laboratory was used. Antenna phase center variations, ocean tidal loading displacements, and azimuthal gradients of the atmosphere were corrected or estimated as standard procedures of high-precision GIPSY-OASIS data processing. As a result, the precisions of near-real-time positions was ~1cm.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제24권7호
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• pp.885-890
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• 2020

In the distance measurement system the time-to-digital conversion circuit used measures the distance using the time interval between the start signal and the stop signal. The time interval is generally converted to digital information using a counter circuit considering the response speed. Therefore, a clock signal with a high frequency is required to improve precision, and a clock signal with a high frequency is also required to measure fine distances. In this paper, a counter circuit was designed to increase the accuracy of distance measurement while using the same frequency. The circuit design was performed using a 0.18㎛ CMOS process technology, and the operation of the designed circuit was confirmed through HSPICE simulation. As a result of the simulation, it is possible to obtain an improvement of four times the precision compared to the case of using a general counter circuit.

• Journal of the Korea Institute of Information Security & Cryptology
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• 제33권3호
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• pp.375-381
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• 2023

Fully homomorphic encryption enables algebraic operations on encrypted data, and recently, methods for approximating non-algebraic operations such as the maximum function have been studied. However, precise approximation of max-pooling operations for four or more numbers have not been researched yet. In this study, we propose a precise max-pooling approximation method using the composition of approximate polynomials of the maximum function and theoretically analyze its precision. Experimental results show that the proposed approximate max-pooling has a small amortized runtime of less than 1ms and high precision that matches the theoretical analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제19권8호
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• pp.116-121
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• 2005

To realize the tap coefficient of a finite impulse response(FIR) filter or the twiddle factor of a fast Fourier transform(FFT) using a current-mode analog circuit, a high accurate current-attenuator circuit is needed This paper introduces an accuracy enhancement technique in the current-mode signal processing. First of all, the DC of set-current error in a conventional current-attenuator using a gate-ratioed orient mirror circuit is analyzed and then, the current-attenuator circuit with a negligibly small DC offset-current error is introduced. The circuit consists of N-output current mirrors connected in parallel with me another. The output current of the circuit is attenuated to 1/N of the input current. On the basis of the Kirchhoff current law, the current scale ratio is determined simply by the number of the current mirrors in the N-current mirrors connected in parallel. In the proposed current-attenuator circuit the scale accuracy is limited by the ac gain error of the current mirror. Considering that a current mirror has a negligibly small ac gain error, the attainable maximum scale accuracy is theoretically -80[dB] to the input current.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.1002-1006
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• 2009

본 연구에서는 물리학적인 모형에서 사용되고 있는 토지이용도를 이용하여 공간적인 해상도의 차이에 따른 유출량의 변화를 비교해 보았다. 현재 수문모형에서 주로 사용되고 있는 토지이용도는 국가 수자원관리종합정보 시스템 (WAMIS)에서 제공하고 있는 위성영상을 기반으로 한 토지이용자료이다. 이 토지이용 자료는 공간적으로 30 m ${\times}$ 30 m의 해상도를 갖고 있어 소유역에 대해 세밀한 분석을 위해서는 보다 세밀한 토지이용 자료와의 비교 검토가 필요하다. 이에 본 연구에서는 WAMIS에서 제공하고 있는 2000년도 토지이용도와 개별적으로 제작한 정밀한 토지이용도를 이용하여 학의천 유역의 유출량을 비교해 보았다. 정밀한 토지이용도는 2000년에 작성된 수치지도와 1 m ${\times}$ 1 m의 공간해상도를 갖는 Ikonos 위성영상을 바탕으로 제작되었으며, 유출량 모의는 토지이용도를 반영할 수 있는 HSPF (Hydrological Simulation Program - Fortran) 모형을 이용하였다. 본 연구에서 HSPF 모형을 통하여 모의한 유출량에 있어서는 토지이용의 해상도의 따른 차이는 거의 발견할 수 없었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 1993년도 춘계학술대회 논문집
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• pp.223-227
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• 1993

최근 생산성 향상을 위해 용접 자동화가 실용 분야, 특히 GMAW 공정에서 활발히 진행되고있다. 그러 나, 현 수준의 용접 자동화는 완전 자동화에는 이르지 못하고 단지 주어진 용접 조건과 용접 경로로 용 접을 실행하는 로보트 시스템의 채용으로 인간의 작업을 대체하는 정도이다. 이와 같은 로보트 시스템 을 이용한 자동화에 있어서는 예기치못한 공정의 변동에 대처하기 위한 공정 중 용접질 모니터링이 더욱 중요해지고 있다. 본 연구에서는 이 목적으로 표면의 다점 온도를 측정하여 이 중 한점의 온도와 이점 이점 부근의 온도 구배로써 용융지 크기 추정 지수를 구성하였다. 이 지수는 온도 변수들과 대응 용융지 크기 간에 다중 회귀 방법을 이용하여 최소 추정 오차가 발생하도록 설정된 수학적 모델이다. 제안된 지 수의 추정 성능을 평가하기 위해 용접 열전도 모델로 부터 얻은 용융지 크기와 표면 온도분포 data를 이용 하여 일련의 시뮬레이션 연구를 실시하였다. 이 과정에서 지수 구성 온도 변수들의 차수가 추정 성능에 미치는 영향과 온도 측정 위치에 따른 추정 성능의 민감도를 추정 오차와 오차 분산을 통해 분석하고, 지수를 사용하였을 때의 추정성능을 한점 온도를 이용하는 경우와 비교 평가하였다.

• The Journal of Korean Institute for Practical Engineering Education
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• 제3권1호
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• pp.193-199
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• 2011

In this paper, we propose a novel manipulator intended for the needs of telerobotic micromanipulation. We designed an original manipulator capable of performing fine motion with an accuracy greater than $2{\mu}m$, while remaining simple in design and easy in control. Preliminary calculations of manipulator accuracy have been conducted, and the device has been designed and manufactured accordingly. The accuracy of the proposed manipulator has been verified during the series micro-positioning experiments under different types of controllers, and the results proved that the manipulator is suitable for micromanipulation applications as a part of telerobotic system. The proposed manipulator has been compared to existing analogues by several parameters, and both its advantages and disadvantages have been discussed.

• Journal of the Korean Magnetics Society
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• 제2권2호
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• pp.150-155
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• 1992

The low magnetic field standard below 1 mT with resolution of 100 nT has been established for the calibration and testing of low field magnetometers. A precision single layered solenoid, which is made of quartz tube and bare copper wire, was constructed in order to generate a precise magnetic field. To improve the field homogeneity in the solenoid, three-current method was employed. The injected current and injection points on the solenoid were optimized by computer simulation. The magnetic field uncertainty in the solenoid was 0.1 % and 0.01 % in the range of ${\pm}5\;cm$ from the center for a single and three-current methods respectively. We also constructed a testing system for the dynamic properties of low field magnetometers.

• Journal of the Korean GEO-environmental Society
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• 제18권4호
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• pp.5-12
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• 2017

Since 2000, the national geotechnical information DB has been constructed by Transport and Maritime Affairs (present Ministry of Land) and recently, it provides more than 210 thousands borehole informations through the geotechnical information DB portal systems. The initial project of underground space information computerization was begun in 2007, focusing on collecting the informations after then additional studies had been conducted to verify the precision and accuracy of collected informations in 2013~2014. In accordance with the recent initiation of the 3D integrated underground space mapping project, it is necessary to construct 3D image of the geotechnical information and evaluate the accuracy and precision of the information. Therefore, in this research, the basic information regarding the precision of the geotechnical DB is provided by kriging method and analysis of RMSE for the systematic 3D construction of geotechnical information. In addition, the elevation data errors of boring information are verified by analysis of elevation data such as boring information data and DEM data.

• Journal of KIISE
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• 제44권6호
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• pp.643-648
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• 2017

Among Wi-Fi based indoor positioning systems, fingerprinting localization is the most common technique with high precision. However, construction of the initial radio map and the update process require considerable labor and time effort. To address this problem, we propose an efficient method that constructs the initial radio map at each vertex based on a graph. In addition, we introduce a method to update the radio map automatically by mapping signal data acquired from users to the reference point created on each edge. Since the proposed method collects signal data manually only at the vertex of the graph to build the initial radio map and updates it automatically, our proposed method can dramatically reduce labor and time effort, which are the disadvantages of the conventional fingerprinting method. In our experimental study, we show validity of our radio map update method by comparing with the actual reference point data. We also show that our proposed method is able to construct the radio map with an accuracy of about 3.5m by automatically updating the radio map.