• 한국생산제조학회지
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• 제24권3호
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• pp.320-326
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• 2015

Despite the wide industrial applications of planetary gear trains, the relationship between the design parameters (tooth profile, carrier mass, etc.) and performance (strength, vibration, noise, etc.) remains poorly understood. A significant amount of research has focused on transmission errors, which are measurable performance indicators directly related to the design parameters. Herein, an experimental test rig for a single-stage planetary gear set built using digital angular encoders and gap sensors is described. To study the static and dynamic characteristics of this planetary gear train, the transmission errors and sun gear orbit are analyzed from the data measured under various levels of torque and speed. The transmission errors of the gear train decrease 40% when the speed increases from 30 to 600 rpm with an output torque of 39.2 Nm, and increase 22% when the output torque increases from 19.6 to 39.2 Nm with an input speed of 30 rpm.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.637-642
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• 1995

For measuring the error motion of ultra-precision spindle, eliminating the geometric errors is a must. Unless it is achieved, geometric errors will be dominant in data. Here, the roundness error and alignment error between spindle and sensor are to be removed. That's because typical error range of such spindle is muchless than geometric one. A capacitive transducer of cylidricalshape was developed, which takes full advantage of the spatial-averaging effect by using large area compared tpo the geometric error. This idea was first proposed by Chapman and here it is modified for better performance with nomical gap of 50 .mu. m and with newly designed guards which encompass the respective sensor to rectify the electrical field distribution in good shape. The measurement system is made to get the orbit of Ultra-Precision Air Spindle which is supposed to have its runout under 1 .mu. m. The Calibration data of this sensor is presented and the spindle orbit from 2000rpm to 5500rpm is showed. It is quite reasonable to use this sensor in the range of 60 .mu. m with an accuracy of several tens of nm.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.48-48
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• 2003

A precision orbit determination (POD) system of low Earth orbiter using the GPS dual frequency measurements has been developed. It is an option of KOMPSAT-2 POD process system. In this research, the orbit determination using the real dual frequency carrier phase measurements of the SAC-C satellite was conducted to verify KOMPSAT-2 POD system reliability. The SAC-C satellite is an international cooperative mission between NASA, the Argentine Commission on Space Activities (CONAE), Centre National d'Etudes Spatiales (CNES or the French Space Agency), Instituto Nacional De Pesquisas Espaciais (Brazilian Space Agency), Danish Space Research Institute, and Agenzia Spaziale Italiana (Italian Space Agency). The SAC-C was launched at November 21, 2000. The altitude of SAC-C is 702 km and it carries a TurboRogue III GPS and four high gain antennas developed by the JPL. The receiver is able to generate the dual frequency code and carrier phase data. Double-differenced carrier phase measurements were formed using 25 IGS stations. The data were sampled at 30 seconds interval. Fully dynamic approach was adopted for POD. The POD results were compared with those of JPL using GOA n software. The comparison verifies that deci-meter level 3D position accuracy of low Earth orbiting satellite could be achieved. The POD system has been developed successfully.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.77-82
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• 2010

무선주파수를 사용하는 추적안테나의 추적성능은 비행체 추적 및 위치 측정에서 매우 중요한 요소이나, 전기적 물리적으로 매우 큰 안테나의 특성을 정확히 측정하는 것은 쉽지 않다. 특히 우주응용분야에서 사용되는 대형 접시형 추적안테나 시스템과 같이 신호원을 따라 안테나의 지향방향이 변하는 경우에는 안테나 지향방향에 따라 특성이 일정하지 않을 수 있다. 본 논문에서는 대형 추적안테나 시스템의 추적 성능지표인 지향정확도 및 추적정확도에 영향을 주는 오차요인을 검토하고, 나로우주센터에서 원격측정용으로 사용하고 있는 11m 대형 접시형 추적안테나에 대한 추적성능을 효율적으로 측정할 수 있는 저궤도위성(Low Earth Orbit)을 사용한 측정방법 및 그 결과를 기술한다.

• 전기전자학회논문지
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• 제28권1호
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• pp.20-25
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• 2024

This paper presents a new dualband shared-aperture microstrip antenna to operate in the S-Band of 2 GHz and X-Band of 8 GHz, for a Low Earth Orbit satellite antenna system. The proposed antenna incorporates two types of patches those are a rectangular loop-shaped for the S-Band and a square patch for the X-Band. Each patch are optimized for its respective operating band with minimal interference. The proposed antenna achieves a bandwidth of 16 MHz in the S-Band and 572 MHz in the X-Band. The highest gain is measured 7.14 dBi at 1.99 GHz and 7.95 dBi at 7.88 GHz. The proposed antenna exhibits half power beamwidths of 85 degree and 80 degree at 1.99 GHz and 7.88 GHz, respectively. The proposed dualband shared-aperture microstrip antenna may be a good candidate for as a feeding system of a dualband reflectarray antenna With its unidirectional radiation pattern from excellent agreement between simulation and measurement results.

• 한국정보통신학회논문지
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• 제21권12호
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• pp.2341-2346
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• 2017

안와 내에서 안구의 상대적 위치는 여러 병적인 상태를 짐작할 수 있는 하나의 기준이 될 수 있다. 특히 안와골절, 갑상선 안질환, 안와 종양 등의 진단과 이에 약물 및 수술적 치료의 결과를 판단하는데 유용하다. 현재 안구 돌출 값을 측정하기 위해 주로 사용되는 대표적 측정 기기인 Hertel과 Naugle 안구돌출계 등은 검사자가 다를 경우, 같은 검사자가 반복적으로 측정하더라도 검사할 때마다 안와의 고정부위가 달라지는 등 측정자에 의한 오차가 필연적이다. 또한 동일한 안구 돌출 계라고 하더라도 제조 회사가 다르다면 안와의 고정부위 디자인이 달라 검사자에의한 측정 오차가 발생한다. 본 논문에서는 안구돌출값의 측정을 3차원 영상 측정기술인 백색광 간섭계를 이용하여 검사 정밀도 및 반복 정도를 크게 올릴 수 있는 자동 측정 방법에 대한 연구를 제안하고자 한다.

• Journal of Astronomy and Space Sciences
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• 제36권1호
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• pp.35-43
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• 2019

The Optical Wide-field patroL-Network (OWL-Net) is a global optical network for Space Situational Awareness in Korea. The primary operational goal of the OWL-Net is to track Low Earth Orbit (LEO) satellites operated by Korea and to monitor the Geostationary Earth Orbit (GEO) region near the Korean peninsula. To obtain dense measurements on LEO tracking, the chopper system was adopted in the OWL-Net's back-end system. Dozens of angle-only measurements can be obtained for a single shot with the observation mode for LEO tracking. In previous work, the reduction process of the LEO tracking data was presented, along with the mechanical specification of the back-end system of the OWL-Net. In this research, we describe an integrity assessment method of time-position matching and verification of results from real observations of LEO satellites. The change rate of the angle of each streak in the shot was checked to assess the results of the matching process. The time error due to the chopper rotation motion was corrected after re-matching of time and position. The corrected measurements were compared with the simulated observation data, which were taken from the Consolidated Prediction File from the International Laser Ranging Service. The comparison results are presented in the In-track and Cross-track frame.

• Journal of Positioning, Navigation, and Timing
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• 제3권1호
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• pp.31-36
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• 2014

Precise Point Positioning (PPP) is a stand-alone precise positioning approach. As the quality of satellite orbit and clock products from analysis centers has been improved, PPP can provide more precise positioning accuracy and reliability. A combined use of Global Positioning System (GPS) and Global Orbiting Navigation Satellite System (GLONASS) in PPP is now available. In this paper, we explained about an approach for combined GPS and GLONASS PPP measurement processing, and validated the performance through the comparison with GPS-only PPP results. We also used the measurement obtained from the GRAS reference station for the performance validation. As a result, we found that the combined GPS/GLONASS PPP can yield a more precise positioning than the GPS-only PPP.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.2055-2058
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• 2004

This paper formulates a yaw angle determination algorithm for earth-point satellite. The algorithm based on vector observation, is implemented with the limited vector measurements. The proposed algorithm doesn't require gyro measurement data but magnetic sensor measurement data. In order to confirm the usefulness of the proposed method, we investigate the simulated telemetry data of the KOMPSAT-2, a satellite that is scheduled to be launched into a 685km altitude sun synchronous circular orbit in 2005.

• 항공우주시스템공학회지
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• 제10권2호
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• pp.34-40
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• 2016

A satellite is exposed to various impact environment until orbit entry. It is particularly undergoing the biggest impact by pyro shock, which is generated when the launch vehicle stages are separated or the satellite is separated from the launch vehicle. In this paper, due to the fact that the pyro shock is prerequisite for performing the test and verification on the ground, we developed an air-gun type shock tester for NEXTSat-1 shock test at the KAIST SaTReC along with the development of program introduced by LabVIEW software. The program operated in shock tester is consist of data measurement and analysis with the convenient implementation of user interface and its easy modification of the code.