• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.314-322
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• 2021

A reflecting telescope consists of a concave primary mirror and a convex secondary mirror. The primary mirror is easy to measure, because it converges the beam from an interferometer, while the secondary mirror diverges the beam and so is not easy to measure, even though it is smaller than the primary mirror. In addition, the Korsch-type telescope uses the central area of the secondary mirror, so that the entire area of the secondary mirror needs to be measured, which the classical Hindle test cannot do. In this paper, we propose a double-stitching method that combines two separate area measurements: the annular area, measured using the Hindle stitching method, and the central area, measured using a spherical wave from the interferometer. We test the surface error of a convex asphere that is 202 mm in diameter, with 499 mm for its radius of curvature and -4.613 for its conic constant. The surface error is calculated to be 19.5±1.3 nm rms, which is only 0.7 nm rms different from the commercial stitching interferometer, ASI. Also, the two results show a similar 45° astigmatism aberration. Therefore, our proposed method is found to be valuable for testing the whole area of a convex asphere.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.61.1-61.1
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• 2010

한국천문연구원의 대형광학망원경 개발사업(K-GMT)은 거대마젤란망원경(GMT; Giant Magellan Telescope)의 지분 10% 확보를 목표로 2009년부터 2018년까지 수행하고 있는 사업이다. 2009년 GMT사업에 공식 참여한 한국천문연구원은 GMT 이사회와 과학자문위원회 등에 적극적으로 참여하여 활동하였다. 본 사업의 2차년도에 해당하는 2010년에는 K-GMT 과학기기워킹그룹을 중심으로 거대망원경 여름학교와 국제워크숍을 개최할 예정이며 GMT 이사회 한국 개최, GMT 부경 시험 모델 개발, GMT 1세대 관측기기 후보로 선정된 GMTNIRS 개념설계연구 등이 수행될 예정이다. 본 발표에서는 GMT 및 K-GMT의 2010년 주요 활동 계획을 보고한다.

• Publications of The Korean Astronomical Society
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• v.11 no.1
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• pp.163-175
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• 1996

We propose the development and test result of new optical axis alignment system for the interchangeable F/8 secondary mirror of the BOAO 1.8m telescope system. Since the original system was not equipped with a suitable optical alignment facility, the whole alignment process was performed by hand. It was necessary at least three persons working more than 2 nights and the altitude of the telescope could not exceed 10 degrees, in such altitude the alignment quality was not so good by atmospheric effect. The new system adopts position readable motorized system and remote control operation by the computer installed in observation room, which reduces the number of workers to only one and eliminates the altitude restriction. The defocused CCD image pair obtained at higher altitude makes the aberration estimates more accurately and the number of required alignment loops is reduced from 10 to 4. The system has been installed on September 1, and performed alignment three times. The test results show that the system is stable and accurate, gives better optical performance of the telescope under F/8 focus. We hope to emphasize the fact that the new system will increase observation time of the telescope by about 20 nights per year assuming one alignment in every month.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.26.3-26.3
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• 2010

한국천문연구원의 대형광학망원경 개발사업(K-GMT)은 거대마젤란망원경(GMT; Giant Magellan Telescope)의 지분 10% 확보를 목표로 2009년부터 2018년까지 수행하고 있는 사업이다. 2009년 GMT사업에 공식 참여한 한국천문연구원은 GMT 이사회와 과학자문위원회 등에 적극적으로 참여하여 활동하였다. 본 사업의 2차년도에 해당하는 2010년에는 K-GMT 과학기기워킹그룹을 중심으로 거대망원경 여름학교와 국제워크숍을 개최할 예정이며 GMT 이사회 한국 개최, GMT 부경 시험 모델 개발, GMT 1세대 관측기기 후보로 선정된 GMTNIRS 개념설계연구 등이 수행될 예정이다. 이 발표에서는 GMT 및 K-GMT의 2010년 주요 활동 계획을 보고한다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.14 no.3
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• pp.145-153
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• 2004

Digital fingerprinting schemes are cryptographic methods that a seller can identify a traitor who illegally redistributed digital contents by embedding it into buyer's information. Recently, Josep Domingo-Ferrer suggested an anonymous digital fingerprinting scheme based on committed oblivious transfer protocol. It is significant in the sense that it is completely specified from a computation point of view and is thus readily implementable. But this scheme has the serious problem that it cannot provide the security of buyers. In this paper, we first show how to break the existing committed oblivious transfer-based fingerprinting schemes and then suggest secure fingerprinting scheme by introducing oblivious transfer protocol with two-lock cryptosystem based on discrete logarithm. All computations are performed efficiently and the security degree is strengthened in our proposal.

• Journal of the Korean Society of Safety
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• v.35 no.6
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• pp.9-14
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• 2020

This study was to compare the sampling efficiencies for monitoring of diesel particulate matter (DPM) using two different sampling methods; In-House PVC cyclone sampling heads and commercial airborne DPM (EC) sampling heads mounted on Dorr-Oliver cyclone heads. Personal exposure levels of DPM, analysed for elemental carbon (EC) were 0.004 - 0.2 mg/m³ for the loader drivers and 0.005 - 0.34 mg/m³ for the specialised mining vehicle (SMV) drivers were similar to previous study results. The highest result (0.34 mg/m³) might be from an irregular production schedule and multiple job tasks requested. The results using the two sampling heads were not significantly different and it is thought that the In-House PVC cyclone with 37 mm quartz filter could be used in place of the commercial sampler as a preliminary screen in place of using the commercial sampler.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.537-550
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• 2023

This study investigates the impact of Hallyu human brands on consumer behavior, given the increasing influence of Hallyu human brands due to their global spread and the limited academic discussions surrounding this topic. The research examines the role of self-congruity, human brand attachment, and brand equity factors. An online survey was conducted, targeting Chinese consumers who are highly engaged with the Korean Wave. Data from 403 respondents were analyzed. The results reveal that both ideal and actual self-congruity with the Hallyu human brand significantly affected attachment to the brand, while social self-congruity was found to be insignificant. Furthermore, attachment to Hallyu human brands positively influenced brand recognition, perceived quality, brand image, and brand loyalty.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.557-567
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• 2023

The rapidly evolving social platform marketing landscape has led businesses to increasingly rely on social platform influencers for brand and service promotion. Despite growing interest in these influencers, there remains a dearth of empirical research examining the impact of their characteristics on consumer attachment and brand loyalty. This study, therefore, investigates the relationships between social platform influencer characteristics, consumer attachment, and brand loyalty. An online survey targeting Chinese consumers was conducted, and a total of 360 responses were analyzed using SPSS and AMOS software. The findings reveal that among the various social platform influencer characteristics, reliability, professionalism, and intimacy significantly influence consumer attachment. Furthermore, it was confirmed that higher attachment to a social platform influencer leads to increased brand loyalty.

• Journal of Aerospace System Engineering
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• v.12 no.3
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• pp.9-17
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• 2018

For Earth observation, a small satellite camera has relatively weak structural stability compared to medium-sized satellite, resulting in misalignment of optical components due to severe launching and space environments. These alignment errors can deteriorate the optical performance of satellite cameras. In this study, we proposed a 3-axis focus mechanism to compensate misalignment in a small satellite camera. This mechanism consists of three piezo-electric actuators to perform x-axis and y-axis tilt with de-space compensation. Design requirements for the focus mechanism were derived from the design of the Schmidt-Cassegrain target optical system. To compensate the misalignment of the secondary mirror (M2), the focus mechanism was installed just behind the M2 to control the 3-axis movement of M2. In this case, flexure design with Box-Behnken test plan was used to minimize optical degradation due to wave front error. The wave front error was analyzed using ANSYS. The fabricated focus mechanism demonstrated excellent servo performance in experiments with PID servo control.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.327-338
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• 2003

The aim of this paper is to describe the results of the study on the extreme-ultra-violet (EUV) solar telescope, which is designed to. a possible satellite mission. Since the EUV band can not be observed on the ground, the observation in EUV should be performed in space using a satellite or a rocket. Design of the Extreme-Ultra-Violet solar Telescope (BUVT) in this study is based on "Designing a small-sized engineering model of solar EUV telescope for a Korean satellite" (Han et al. 2001). Our EUVT design is satisfied with the requirements for a satellite in size and input voltage. The major goal of the study is to confirm if we can detect the specific wavelength (58.4nm to 62.9nm) with the EUVT. We describe re-designing of the EUVT to decrease a shelter ratio. Also we describe the technics in the optic system and the detector, which were used to manufacture the EUVT. We explain the detective program, which is to calculate the amount of the solar radiation, and the image data processing system.ng system.