• Title/Summary/Keyword: Primary Mirror

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Optical Design of a Reflecting Telescope for CubeSat

  • Jin, Ho;Lim, Juhee;Kim, Youngju;Kim, Sanghyuk
    • Journal of the Optical Society of Korea
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    • v.17 no.6
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    • pp.533-537
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    • 2013
  • Space telescope optics is one of the major parts of any space mission used to observe astronomical targets or the Earth. This kind of space mission typically involves bulky and complex opto-mechanics with a long optical tube, but attempts have been made to observe a target with a small satellite. In this paper, we describe the optical design of a reflecting telescope for use in a CubeSat mission. For this design we adopt the off-axis segmented method for astronomical observation techniques based on a Ritchey-Chr$\acute{e}$tien type telescope. The primary mirror shape is a rectangle with dimensions of $8cm{\times}8cm$, and the secondary mirror has dimensions of $2.4cm{\times}4.1cm$. The focal ratio is 3 which can yield a 0.383 degree diagonal angle in a $1280{\times}800$ CMOS color image sensor with a pixel size of $3{\mu}m{\times}3{\mu}m$. This optical design can capture a ${\sim}4km{\times}{\sim}2.3km$ area of the earth's surface at 700 km altitude operation.

Casting Conditions and Solidification Characteristics of Sn-Zn Alloys (Sn-Zn합금의 주조조건과 응고특성)

  • Song, Tae-Seok;Kim, Myung-Han;Jo, Hyung-Ho;Ji, Tae-Gu
    • Journal of Korea Foundry Society
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    • v.18 no.6
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    • pp.570-577
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    • 1998
  • An investigation has been conducted to describe solidification characteristics in Sn-Zn binary system and Sn-Zn-Ag ternary system added by Ag produced by the continuous casting process using heated mold as a basic study for developing Pb-free solder materials. To obtain the continuous casting rods with mirror surface and near net shape at higher casting speed, water flow rates must be increased and mold temperature must be lowered. However, surface tearing in the casting rods occured at lower continuous casting speed while break out occured at higher continuous casting speed even if optimum conditions such as water flow rate and heated mold temperature are determined. Primary ${\alpha}Sn$ and eutectic structure in unidirectioally solidified Sn-Zn alloys were finer with increased casting speed. But, directionality may not be expected for primary Zn in hypereutectic Sn-Zn alloy. It was found that the addition of $0.2{\sim}0.8%$ Ag promoted the growth of primary ${\alpha}Sn$ dendrites. The changes of tensile strength and elongation in Sn-Zn binary alloys were not observed while the increase of tensile strength and the decrease of elongation in Sn-Zn-Ag ternary alloys were observed with increased casting speed.

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EPIDEMIOLOGICAL STUDY ON DENTAL CARIES IN TWINS. (쌍생아(雙生兒) 치아(齒牙) 우식증(齲蝕症)에 관(關)한 역학적(疫學的)인 연구(硏究))

  • Jung, Tae-Ryun
    • Journal of the korean academy of Pediatric Dentistry
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    • v.1 no.1
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    • pp.57-61
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    • 1974
  • The Study reported here was designed to analyze the prevalence of Dental Caries in the primary teeth of monozygote twins, and to ascertain and compare the intrapair differences with the intrapair differences in control pairs. The prevalence of dental caries in the primary teeth of 40 pairs of presumably monozygote twins, based on phenotypic analysis, was studied. The age range was from 3 to12 years. The control group consisted of pairs that included a twin chosen at random and an unrelated child of the same sex and age, so that for each pair of twins there was a corresponding control pair. The clinical examination was carried out by an operator using an oral mirror and sharp explorers, and with good lighting. 40 pairs of twins were examined with a total of 4,950 primary tooth surfaces (990 primary teeth) and 40 control pairs with a total of 4,935 primary tooth surfaces (987 primary teeth). Five surfaces were considered for each tooth. After the def individual index was determined, the ratio between this index and the number of examined surfaces was established in each case, the cer (Caries experience rate) index. The def and cer averages were determined for the subjects and the controls. All intrapair differences in twin and control groups were compared following the paired sampling method. The following conclusions were made: 1. Intrapair differences in the control group were significantly greater than in twins, when defs, ds, es, fs, and cer were compared. 2. The genotype appeared to be a determining factor in dental caries susceptibility or resistance, although the environment played an important role as well. 3. Intrapair differences in American children were significantly greater than in Korean when defs, es, fs, and cer were compared, but ds was equal.

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Current Status of the GMT Project

  • Park, Byeong-Gon;Seo, Yoon-Kyung;Yoon, Yang-Noh;Hwang, Narae;Kim, Young-Soo;Yuk, In-Soo;Lee, Jae-Joon
    • The Bulletin of The Korean Astronomical Society
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    • v.38 no.1
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    • pp.67.2-67.2
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    • 2013
  • The GMT project is in its final stage of Design Development Phase in 2013, moving toward the Construction Phase planned to begin on Jan. 1st, 2014. In this contribution, we present the current status and progress of the GMT project including selection of the first generation instruments, development of primary mirror segments, site preparation, and science case revision along with plans for 2013 when the preparation of construction phase will be made.

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Research on the Solar Concentrating Optical System for Solar Energy Utilization

  • Duan, Yimeng;Yang, Huajun;Jiang, Ping;Wang, Ping
    • Journal of the Optical Society of Korea
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    • v.17 no.5
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    • pp.371-375
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    • 2013
  • To improve the utilization efficiency of solar energy, a new solar optical concentrating system composed of a parabolic reflector with a square cross-section, a hyperbolic reflector with a square cross-section and two converging convex lenses has been designed. The proposed method can simultaneously focus and shape sun light into a square pattern on the solar panel. In addition, the total reflection property of photonic crystal within the range of the visible sunlight spectrum has been analyzed. Finally, the relationship between solar concentrating multiples and the diameter of the primary mirror has been discussed.

우주물체 전자광학 감시체계 (OWL) 광학계 개발현황

  • Han, Jeong-Yeol;Han, In-U;Na, Ja-Gyeong;Jang, Jeong-Gyun;Mun, Il-Gwon;Park, Yeong-Sik;Choe, Yeong-Jun;Park, Jang-Hyeon
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.223.1-223.1
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    • 2012
  • 우주물체 전자광학 감시체계(OWL: Optical Wide-field Patrol)는 지구상에서 빠르게 이동하는 우주물체를 신속하고 정확하게 관측할 수 있는 광학 감시체계이다. 이 체계의 임무를 완수하기 위한 광학계는 약 2도 이상의 광시야, 충분한 광량 확보를 위해 직경 500 mm 이상의 주반사경(primary mirror), 광학적 능률향상을 위한 25% 이상의 투과율, 운반 및 진동에 의한 영상성능 저하를 보정하기 위한 부반사경 구동기능, 빠른 경통 회전속도에 의한 광학 및 광기구 구조물의 안전성 확보를 위한 작은 F-수 확보 등 주요 요구조건을 만족해야 한다. 본 논문에서는 OWL 광학계의 요구조건을 만족하는 광학계의 광학 및 광기구 설계 등 개발현황을 소개하고자 한다.

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Preparation of Titanium Microfiltration Membrane by Field-flow Fractionation Deposition

  • Wang, QiangBing;Tang, HuiPing;Zhang, QianCheng;Qiu, QunFeng;Wang, JianYong
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.312-313
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    • 2006
  • The primary aim pursued by the preparation of separation membrane is the preparation of the membrane thin as well as with no defect. The field-flow fractionation deposition is a new molding technology which can overcome the traditional disadvantages such as multi-preparation to the preparation of great area of separation membrane with no defect. Therefor the mainly ingredients which influence the appearance and performance of titanium membrane layer are investigated by scanning electricity mirror (SEM) as well as porous material testing instrument: powder performance prepared and confected; selection of supporting body; sintering system such as temperature and time. It is shown that the membrane thickness can be controlled at $50{\mu}m$ or so; the filtration precision mainly rests with powder performance and selection of supporting body and little sintering system

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Developing an Optical Testing Method for Space Telescopes

  • Kim, Young-Soo
    • Journal of the Optical Society of Korea
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    • v.5 no.3
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    • pp.70-75
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    • 2001
  • Next Generation Space Telescope (NGST) is under design study for proposed launch around 2008. It will take over the task of Hubble Space Telescope (HST) and provide much more detailed information about celestial objects. Present large telescopes both in space and on the ground contain aspheric mirrors, called Ritchey-Chretien type. As the size of the telescope becomes larger and the optical quality is requested to be higher, reaching the diffraction limit, more accurate optical testing methods are required. However, there are few testing methods which can achieve the required accuracy for aspheric optics, and none of them has achieved it with certainty. The failure of producing the primary mirror of the Hubble Space Telescope to meet specification is a good example. Moreover, testing aspheric mirrors of large convex form adds the difficulty to extreme. In this paper, space telescopes and large ground-based telescopes are surveyed and testing methods for aspheric optics are reviewed. a method of testing aspheric convex mirrors is suggested.

Experimental performance investigation of compound parabolic cavity receiver having single absorber tube

  • Omar Al-Nabhani;Saud Al-Kalbani;Azzam Al-Alawi;Afzal Husain
    • Advances in Energy Research
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    • v.8 no.3
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    • pp.155-163
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    • 2022
  • The current study presents experimental research on a parabolic trough collector with tube and cavity receivers. The primary concentrating parabolic reflector is designed for an aperture area of 2×2 m2 with mirror-polished stainless steel sheet reflectors. The cavity receiver consists of a compound parabolic secondary reflector and a copper tube. Both the conventional tube receiver and the cavity receiver tube are coated with black powder. The experiments are carried out to compare the efficiency of the cavity receiver with the tube receiver for fluid temperature rise, thermal efficiency, and overall losses. The experiments showed significantly higher fluid temperature rise and overall efficiency and lower thermal losses for the cavity receiver compared to the tube receiver within the parameters explored in this study.

Next generation spectroscopic facilities: GMACS for the Giant Magellan Telescope and the Maunakea Spectroscopic Explorer

  • Marshall, Jennifer
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.2
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    • pp.35.2-35.2
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    • 2019
  • The next decade will see great advances in ground-based spectroscopic observing capabilities: facilities that are under development today will have larger collecting areas and greater spectroscopic multiplexing capabilities than ever before, and are sure to revolutionize the scientific productivity of our field. In this talk I will review the status of two of these next-generation facilities, the Giant Magellan Telescope's wide-field multiobject optical spectrograph, GMACS, and the Maunakea Spectroscopic Explorer project, a massively multiplexed spectroscopic facility currently under development in Hawaii that features an 11.25m diameter primary mirror which feeds 4,332 fibers and a suite of low- and high-resolution spectrographs. These two projects are scientifically quite complementary and both present exciting instrument development opportunities over the next few years.

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