• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.82.3-82
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• 2002

This paper designs an integrated navigation system that uses the signals from both GPS satellites and pseudolites. While GPS satellite clocks are synchronized, pseudolite clocks are not exactly synchronized even though pseudolite can use 1PPS signal from the GPS receiver. This can cause large range error and can be solved by transmitting the correction information. Assuming that the positions of pseudolites are known, it is possible to determine the true range between two pseudolites. Also, from the measurement of pseudolite signals, the pseudo range between two pseudolites can be calculated. Using the difference between the true range and the pseudo range, each pesudolite can produce correc...

• 전기학회논문지
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• 제61권11호
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• pp.1695-1699
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• 2012

This paper is proposed all digital wide-range clock and data recovery circuit. The Proposed clock data recovery circuit is possible input data rate which is suggested is wide-range that extends from 100Mb/s to 3Gb/s and used an phase error detector which can use a way of over-sampling a data by using a 1/2-rate multi-phase clock and phase rotator which is regular size per $2{\pi}$/16 and can make a phase rotation. So it could make the phase rotating in range of input data rate. Also all circuit is designed as a digital which has a specificity against a noise. This circuit is designed to 0.13um CMOS process and verified simulation to spectre tool.

• 한국정보통신학회논문지
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• 제26권5호
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• pp.808-811
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• 2022

In this paper, a wide-range microphone system for lectures using dual 3D sensors is proposed. A previous work using a single sensor had lowering the detecting threshold to support wide-area. However it was found that an error occurred when lecturer wears clothes with low reflectivity or has small body size. When multiple sensors are used to expand the coverage it could be cause various problems. Each sensor could show different distance to the same target. We derive the rotation angle and and compensate for lecturing microphone system using sensors on the line. The proposed method shows a little improvement in performance by about 1dB compared to the previous works but the performance is uniform in all areas regardless of reflectivity.

• 한국해양공학회지
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• 제18권4호
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• pp.33-39
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• 2004

This paper presents a hybrid underwater navigation system for unmanned underwater vehicles, using an additional range sonar, where the navigation system is based on inertial and Doppler velocity sensors. Conventional underwater navigation systems are generally based on an inertial measurement unit (IMU) and a Doppler velocity log (DVL), accompanying a magnetic compass and a depth sensor. Although the conventional navigation systems update the bias errors of inertial sensors and the scale effects of DVL, the estimated position slowly drifts as time passes. This paper proposes a measurement model that uses the range sonar to improve the performance of the IMU-DVL navigation system, for extended operation of underwater vehicles. The proposed navigation model includes the bias errors of IMU, the scale effects of VL, and the bias error of the range sonar. An extended Kalman filter was adopted to propagate the error covariance, to update the measurement errors, and to correct the state equation, when the external measurements are available. To illustrate the effectiveness of the hybrid navigation system, simulations were conducted with the 6-d.o.f. equations of motion of an AUV in lawn-mowing survey mode.

• 한국측량학회지
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• 제6권2호
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• pp.10-18
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• 1988

대형구조물의 삼차원위치해석과 변형측정을 하기 위하여 근접사진측량을 이용할 경우 정확도에 가장 큰 영향을 미치는 촬영거리를 접근시켜 다중기법(Multiple Method)에 의해 해석하는 것이 효율적이다. 본 연구에서는 다중방법에서 제기되는 문제점들을 해결하기 위하여 중복도, 기준점 수와 배치, 촬영거리의 변화에 따른 오차의 영향을 분석하여 그 특성을 파악하고자 하였다. 촬영대상으로는 7m$\times$3m의 평면형의 피사체에 총 225점의 말지점을 고르게 배치하고 중복도와 촬영거리를 변화시키면서 총 143교의 사진을 찰영하였다. 이 사진들에 의한 종ㆍ횡스트립과 블럭을 형성, on-line system으로 개발된 프로그램에 의해 해석하였다. 기준점 수를 감소시킴에 따라 기하학적 오차(simulated error)는 계속 증가 하지만 관측오차(a ctual error)는 감소하다가 다시 증가되고 있으며, 촬영거리의 변화에 따른 오차는 Z방향이 X, Y방향보다도 크게 나타났으며 redundancy를 증가시키면 Z도 양호한 결과를 얻을 수 있었다. 그리고 중복도의 증가에 따른 오차는 중복도 70%전후에서 가장 양호한 결과를 얻었다. 본 연구의 결과에 의하면, 피사체의 크기와 형태에 따라 기준점 배치및 중복도를 적절하게 선택하는 것은 대형구조물해석에 무엇보다 중요하며 촬영거리를 가능한 한 피사체에 근접시켜 다중촬영을 실시하여 처리한다면 주요 구조물의 정밀해석은 물론 변형측정에 널리 활용할 수 있을 것으로 기대된다.

• 한국작물학회지
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• 제51권spc1호
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• pp.283-291
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• 2006

To investigate seed non destructive and fast determination technique utilizing near infrared reflectance spectroscopy (NIRs) for screening ultra high oleic (C18:1) and linoleic (C18:2) fatty acid content sesame varieties among genetic resources and lines of pedigree generations of cross and mutation breeding were carried out in National Institute of Crop Science (NICS). 150 among 378 landraces and introduced cultivars were released to analyse fatty acids by NIRs and gas chromatography (GC). Average content of each fatty acid was 9.64% in palmitic acid (C16:0), 4.73% in stearic acid (C18:0), 42.26% in oleic acid and 43.38% in linoleic acid by GC. The content range of each fatty acid was from 7.29 to 12.27% in palmitic, 6.49% from 2.39 to 8.88% in stearic, 12.59% of wider range compared to that of stearic and palmitic from 37.36 to 49.95% in oleic and of the widest from 30.60 to 47.40% in linoleic acid. Spectrums analyzed by NIRs were distributed from 400 to 2,500 nm wavelengths and varietal distribution of fatty acids were appeared as regular distribution. Varietal differences of oleic acid content good for food processing and human health by NIRs was 14.08% of which 1.49% wider range than that of GC from 38.31 to 52.39%. Varietal differences of linoleic acid content by NIRs was 16.41% of which 0.39% narrower range than that of GC from 30.60 to 47.01%. Varietal differences of oleic and linoleic acid content in NIRs analysis were appeared relatively similar inclination compared with those of GC. Partial least square regression (PLSR) among multiple variant regression (MVR) in NIRs calibration statistics was carried out in spectrum characteristics on the wavelength from 700 to 2,500 nm with oleic and linoleic acids. Correlation coefficient of root square (RSQ) in oleic acid content was 0.724 of which 72.4 percent of sample varieties among all distributed in the range of 0.570 percent of standard error when calibrated (SEC) which were considerably acceptable in statistic confidence significantly for analysis between NIRs and GC. Standard error of cross validation (SECV) of oleic acid was 0.725 of which distributed in the range of 0.725 percent standard error among the samples of mother population between analyzed value by NIRs analysis and analyzed value by GC. RSQ of linoleic acid content was 0.735 of which 73.5 percent of sample varieties among all distributed in the range of 0.643 percent of SEC. SECV of linoleic acid was 0.711 of which distributed in the range of 0.711 percent standard error among the samples of mother population between NIRs analysis and GC analysis. Consequently, adoption NIR analysis for fatty acids of oleic and linoleic instead that of GC was recognized statistically significant between NIRs and GC analysis through not only majority of samples distributed in the range of negligible SEC but also SECV. For enlarging and increasing statistic significance of NIRs analysis, wider range of fatty acids contented sesame germplasm should be kept on releasing additionally for increasing correlation coefficient of RSQ and reducing SEC and SECV in the future.

• 한국수자원학회논문집
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• 제54권7호
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• pp.485-493
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• 2021

지하수는 지표수와 함께 용수로 사용가능한 중요한 수자원이며 특히 섬 지역의 경우 전체 수자원 중 지하수의 이용 비율이 상대적으로 높기 때문에 안정적인 이용을 위해 지하수위 변동성에 대한 연구는 필수적이다. 지하수위 변동성의 예측 및 분석을 위해 인공지능 모델을 활용한 연구들이 지속적으로 증가하고 있으나 지하수위 예측결과의 적절성을 판단할 수 있는 평가기준을 제시한 연구는 충분하지 않다. 본 연구에서는 허용가능한 지하수위 예측오차의 범위를 제시하기 위해 과거 20년 동안 전 세계 다양한 지역을 대상으로 인공지능 모델을 활용하여 지하수위를 예측한 연구결과들을 종합적으로 분석하였다. 그 결과 관측지하수위의 변동성이 커질수록 인공지능 모델에 의한 지하수위 예측오차는 증가하였다. 따라서 관측지하수위 최대변동폭과 예측오차 간의 상관성과 기존 연구들에서 제시한 평가지수들을 고려하여 평가기준을 산정하였으며, 인공지능 모델에 의한 지하수위 예측결과의 적절한 평가기준은 도출된 선형회귀식에 의한 평균제곱근오차 또는 최대오차 이하이거나, NSE ≥ 0.849 또는 R² ≥ 0.880 이다. 이 허용가능한 오차범위는 인공지능 모델을 활용한 지하수위 예측결과의 적절성 판단을 위한 참고자료로 사용할 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.2090-2092
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• 2004

In this paper, the new measurement methodology of characteristics of the vibratory micro gyroscope using Quality factor and the resonant displacement was proposed. Because the Quality factor has a large error under the high Quality factor condition, it is difficult to analyze the characteristics of the vacuum packaged vibratory micro gyroscopes with the Quality factor. We analyzed mechanical characteristics of gyroscope with the value of Quality factor. We described measurement errors of mechanical characteristics of micro gyroscopes. The measured value of Quality factor is 47532 and error range of Quality factor is from -29.8 % to 73.9 %. The value of resonant displacement is 3.4${\mu}m$ and the measurement error is 2.9 %. From the result of Quality factor degradation and resonant displacement degradation, 1698 days and 1503 days were estimated as Time To Failure (TTF), respectively. The range of estimation error of Quality factor degradation and resonant displacement degradation is calculated from 1246 days to 1832 days and from 1456 days to 1537 days, respectively. We can analyze the characteristics of the vibratory gyroscope using the quality factor when the Quality factor is smaller than 10,000. Also we can analyze that using the resonant displacement when the Quality factor is larger than 10,000.

• 제어로봇시스템학회논문지
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• 제13권10호
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• pp.1025-1031
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• 2007

GPS is widely used for positioning applications and attitude of a vehicle can be found also with multiple antennas. However, extremely weak signal level prevents GPS from indoor operation. DR with accelerometers and gyros and landmark based localization method used for indoor applications increase complexity and cost. In this paper, a simple but very efficient ultrasound based attitude determination system which determines both position and attitude in WSN is given. The range between transmitter and receivers are measured using the arrival time difference between ultrasound and RF signal. The 3 dimensional positions can be found using more than 3 range measurements. Furthermore, if more than 2 transmitters are used, the attitude can be determined using the baseline vectors obtained by differencing transmitter and receiver positions. The prototype system is implemented to evaluate the performance of the proposed method. In addition, an error analysis shows the relation between the attitude error and basel me length, quality of measurement and orientation of a vehicle. The static and dynamic experiments performed by micro mobile robot shows accurate position with less than 1.5cm error and attitude with less than 1 degree error can be obtained continuously with 20cm baseline. It is expected that these results can be adapted without modification to indoor applications such as home cleaning robot and autonomous wheelchair maneuvering.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1733-1736
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• 2005

Many studies have been carried out to produce 3D features in the size range between $10{\mu}m\~10,000{\mu}m$, called Meso-scale. If these miniaturized systems have high relative accuracy and good volumetric utilization, it is possible to manufacture more complex and accurate shapes with various materials as well as there are advantages of reducing energy, space and resources. Due to imperfect components and misalignment in assembly, it is necessary to assess the accuracy of the miniaturized system itself to obtain high relative accuracy. Laser interferometers are widely used to measure geometric errors called as quasi-static errors. For miniaturized system, however, it is difficult to install the required accessories such as optics and the measuring range is limited because of the size of the system and also this method is very expensive. Moreover, it is impossible to measure each error component simultaneously. A new system to measure simultaneously multiple geometric errors is proposed using capacitance sensors. Each error was measured using capacitance sensors and a measurement algorithm was mathematically derived. The experiments show that the proposed measurement system can be used effectively to assess the accuracy of miniaturized system at a low cost.