• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.780-789
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• 2008

A new method for measuring the performance of a micro-thruster is suggested in this paper. A few thrust stands have been developed for measuring micro-level thrusts. This paper describes a different measurement method that can minimize the calibration involved in the measurements, while providing the capability of directly measuring the produced minimum impulse bit directly. The underlying theory and the theoretical background for the measurement mechanism are described here. The theory and method is verified using a computer simulation, and the result is given in this paper. The theory has also been tested on an actual hardware. Although this hardware is a prototype, developed for proof-of-concept analysis, satisfactory results have been obtained.

• Journal of Advanced Navigation Technology
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• v.18 no.3
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• pp.201-208
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• 2014

Due to diversification of ships and limited space of pier, when ships come alongside the shallow water or narrow pier, sea area with small mooring facilities and floating matter is frequently applied. Through these, coming alongside the various space is capable and cost effectiveness is enhanced. However, when ships, applying small mooring facilities and floating matter, come alongside, there can be some impulse by waves between the floating things and ships which possibly leads to mass disaster. Therefore, there should be forecasts and analysis of the movement caused by waves. On this study, we develop measuring system for movement analysis of mooring and floating matters which provides base data with movement traits by measuring 3-D exercise information and acceleration at mokpo maritime university marina facility. Also, the composition and principles of the developed system is explained.

• The Journal of Advanced Prosthodontics
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• v.13 no.4
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• pp.191-204
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• 2021

PURPOSE. The purpose of this study is to present a methodology to evaluate the accuracy of intraoral scanners (IOS) used in vivo. MATERIALS AND METHODS. A specific feature-based gauge was designed, manufactured, and measured in a coordinate measuring machine (CMM), obtaining reference distances and angles. Then, 10 scans were taken by an IOS with the gauge in the patient's mouth and from the obtained stereolithography (STL) files, a total of 40 distances and 150 angles were measured and compared with the gauge's reference values. In order to provide a comparison, there were defined distance and angle groups in accordance with the increasing scanning area: from a short span area to a complete-arch scanning extension. Data was analyzed using software for statistical analysis. RESULTS. Deviations in measured distances showed that accuracy worsened as the scanning area increased: trueness varied from 0.018 ± 0.021 mm in a distance equivalent to the space spanning a four-unit bridge to 0.106 ± 0.08 mm in a space equivalent to a complete arch. Precision ranged from 0.015 ± 0.03 mm to 0.077 ± 0.073 mm in the same two areas. When analyzing angles, deviations did not show such a worsening pattern. In addition, deviations in angle measurement values were low and there were no calculated significant differences among angle groups. CONCLUSION. Currently, there is no standardized procedure to assess the accuracy of IOS in vivo, and the results show that the proposed methodology can contribute to this purpose. The deviations measured in the study show a worsening accuracy when increasing the length of the scanning area.

• Journal of Astronomy and Space Sciences
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• v.40 no.4
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• pp.199-215
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• 2023

The Korea Pathfinder Lunar Orbiter (KPLO), the first South Korea lunar exploration probe, successfully arrived at the Moon on December, 2022 (UTC), following a 4.5-month ballistic lunar transfer (BLT) trajectory. Since the launch (4 August, 2022), the KPLO magnetometer (KMAG) has carried out various observations during the trans-lunar cruise phase and a 100 km altitude lunar polar orbit. KMAG consists of three fluxgate magnetometers capable of measuring magnetic fields within a ± 1,000 nT range with a resolution of 0.2 nT. The sampling rate is 10 Hz. During the originally planned lifetime of one year, KMAG has been operating successfully while performing observations of lunar crustal magnetic fields, magnetic fields induced in the lunar interior, and various solar wind events. The calibration and offset processes were performed during the TLC phase. In addition, reliabilities of the KMAG lunar magnetic field observations have been verified by comparing them with the surface vector mapping (SVM) data. If the KPLO's mission orbit during the extended mission phase is close enough to the lunar surface, KMAG will contribute to updating the lunar surface magnetic field map and will provide insights into the lunar interior structure and lunar space environment.

• Journal of the Korean Society of Radiology
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• v.17 no.3
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• pp.367-373
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• 2023

Aircrews and passengers are exposed to radiation from cosmic rays and secondary scattered rays generated by reactions with air or aircraft. For aircrews, radiation safety management is based on the exposure dose calculated using a space-weather environment simulation. However, the exposure dose varies depending on solar activity, altitude, flight path, etc., so measuring by route is more suggestive than the calculation. In this study, we developed an instrument to measure the cosmic radiation dose using a general-purpose Si sensor and a multichannel analyzer. The dose calculation applied the algorithm of CRaTER (Cosmic Ray Telescope for the Effects of Radiation), a space radiation measuring device of NASA. Energy and dose calibration was performed with Cs-137 662 keV gamma rays at a standard calibration facility, and good dose rate dependence was confirmed in the experimental range. Using the instrument, the dose was directly measured on the international line between Dubai and Incheon in May 2023, and it was similar to the result calculated by KREAM (Korean Radiation Exposure Assessment Model for Aviation Route Dose) within 12%. It was confirmed that the dose increased as the altitude and latitude increased, consistent with the calculation results by KREAM. Some limitations require more verification experiments. However, we confirmed it has sufficient utilization potential as a cost-effective measuring instrument for monitoring exposure dose inside or on personal aircraft.

• Korean Institute of Interior Design Journal
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• no.36
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• pp.128-135
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• 2003

The purpose of this study was to analyze the perception of wayfinding in public interior space. According to this study, a virtual reality simulation test was conducted to examine the effect of wayfinding. Theoretical research was used to explain the psycho-physiological effect of visual perception and case study was carried out to evaluate the physiological response of the subjects. For the physiological evaluation, two simulations with sign and color sample were chosen and the EEG was Used. Data were collected from May 15th. to June 15th. The subjects were 20 students of architecture department and frequency, percentage, ANOVA, T-test, multiple comparisons were used for data analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.41-46
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• 2007

Surface potential properties at the interface of pentacene thin films on gold (Au) and aluminum (Al) surfaces were investigated by using a near-field scanning microwave microprobe (NSMM). The surface potential formed across the pentacene film was observed by measuring the microwave reflection coefficient $S_{11}$ and compared with the result of a Kelvin-probe method. The obtained reflection coefficient ${\Delta}S_{11}$ of the pentacene thin films on Al was decreased as the pentacene film thickness increased due to the increased accumulation of negative space charges, while for Au ${\Delta}S_{11}$ was essentially constant.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.7
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• pp.350-353
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• 2001

In general, the Least Square Error method is used for signal classification to measure distance in the $l^2$ metric or the $L^2$ metric space. A defect of the Least Square Error method is that it does not classify properly some waveforms, which is due to the property of the Least Square Error method: the global analysis. This paper proposes a new linear operator, the Integra-Normalizer, that removes the problem. The Integra-Normalizer possesses excellent property that measures the degree of relative similarity between signals by expanding the functional space with removing the restriction on the functional space inherited by the Least Square Error method. The Integra-Normalizer shows superiority to the Least Square Error method in measuring the relative similarity among one dimensional waveforms.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.109.1-109.1
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• 2014

다이아몬드 선삭 기계(DTM)를 이용한 렌즈 및 반사경 가공은 제작시간 단축 및 비용 절감의 장점을 가지고 있다. 그러나 알루미늄과 같은 무른 금속을 가공하여 반사경을 제작하는 경우에는 반사경 표면에 가공오차가 발생한다. 오차는 크기에 따라 고주파 오차(High Frequency Error, HFE), 중주파 오차(Mid Frequency Error, MFE), 저주파 오차(Low Frequency Error, LFE)로 분류 할 수 있다. LFE는 가공한 반사경 표면이 설계된 형상과 얼마나 다른지를 표현하는 값으로 광학 수차와 같이 해상도를 저하시킨다. MFE는 반사경 표면에 수십 마이크로미터 크기로 나타난다. 회전하는 반사경 시료에 다이아몬드 툴의 홈이 동심원으로 생기면서 회절격자와 같이 회절 및 간섭 현상을 만든다. HFE는 표면의 거친 정도를 나타내며 반사율과 관련되고 수 나노미터 크기로 나타난다. 본 연구에서는 광학 레이저를 사용하여 MFE가 광학 성능에 미치는 영향을 분석하였다. 유리 반사경과 MFE를 제거한 반사경, 제거하지 않은 반사경에 대하여 실험을 진행하였다. 본 실험 결과는 반사경 가공 표면을 평가할 수 있는 유용한 자료가 될 것이다.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.293-296
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• 2002

This paper presents an implementation of Direct torque control(DTC) of Reluctance Synchronous Motor(RSM) drives for an industrial servo drive system with stator current space vector. The estimation of the stator flux magnitude are obtained by using the neural network from measuring the modulus and angle of the stator current space vector. The develolled digitally high-performance control system are shown a good response characteristic of control results and high performance features using 1.0kW RSM.