• Journal of The Korean Astronomical Society
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• v.56 no.2
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• pp.169-185
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• 2023

The GMT-Consortium Large Earth Finder (G-CLEF) is the first instrument for the Giant Magellan Telescope (GMT). G-CLEF is a fiber feed, optical band echelle spectrograph that is capable of extremely precise radial velocity measurement. G-CLEF Flexure Control Camera (FCC) is included as a part in G-CLEF Front End Assembly (GCFEA), which monitors the field images focused on a fiber mirror to control the flexure and the focus errors within GCFEA. FCC consists of an optical bench on which five optical components are installed. The order of the optical train is: a collimator, neutral density filters, a focus analyzer, a reimager and a detector (Andor iKon-L 936 CCD camera). The collimator consists of a triplet lens and receives the beam reflected by a fiber mirror. The neutral density filters make it possible a broad range star brightness as a target or a guide. The focus analyzer is used to measure a focus offset. The reimager focuses the beam from the collimator onto the CCD detector focal plane. The detector module includes a linear translator and a field de-rotator. We performed thermoelastic stress analysis for lenses and their mounts to confirm the physical safety of the lens materials. We also conducted the global structure analysis for various gravitational orientations to verify the image stability requirement during the operation of the telescope and the instrument. In this article, we present the opto-mechanical detailed design of G-CLEF FCC and describe the consequence of the numerical finite element analyses for the design.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.167-175
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• 2015

Purpose: The new-type rangefinder, which is using the biprism principle, is introduced to develop the range finder which can be easily carried by soldiers, and in order to realize those technologies specifically, we try to develop a scope for military rangefinder by doing optical design which can secure enough space to move the biprism. Methods: After setting up the verious initial condition to realize two kinds of goals, that are the securement of enough space to move the biprism and the easy-exchangeability of two kinds of biprisms, and then the optical system was optimized by using optical design program CodeV in order to minimize the finite ray aberrations. Results: We designed the biprism housing to makes it possible to swap the two kinds of biprisms. It was appeared that the Schmidt prism is suitable as erecting prism which can make sure the space to move the biprism. 16.5 mm was good for the face length of Schmidt prism. The optical system with a Schmidt prism and a biprism was designed, and the finite ray aberrations was minimized. Conclusions: We developed a 5X scope for an optical rangefinder using a biprism and a Schmidt prism with 16.5 mm face length. This scope is valid for the optical system which has the effective field angle of ${\pm}3.6^{\circ}$, and the finite ray aberrations are well controlled within the ${\pm}8.95^{\prime}$.

• Korean Journal of Environment and Ecology
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• v.25 no.4
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• pp.516-525
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• 2011

We studied the influence certain environmental factors (proximity of roosting site, roads, and residential areas) have on the spatial distribution of cranes in the Cheorwon, Korea. Using a range finder and GPS, data were collected from January to February 2007 and were subsequently evaluated with ArcGIS. The size of the cranes' wintering habitat was estimated to be 7$76.9km^2$. Five hundred and fifty-five flocks of cranes were observed and detailed distributions were collected. Feeding distribution of the cranes showed clustered distribution, however, no tendencies of spatial autocorrelation were apparent. Adjacent regions with paved roads and residences showed lower densities than other areas. Distances at which paved roads and residential areas induced changes in feeding flock densities were 1500m and 1750m, respectively. Feeding flock density decreased with increased distance from roosting site. Feeding flock density of the two crane species did not increase as distance from roads increased, however, the density of individuals showed a significant increasing tendency with increased distance from roads. In both species, density of feeding flocks and individuals significantly increased with increasing distance from residential areas. In Red-crowned Cranes, the density of feeding flocks and individuals significantly decreased with increasing distance from roosting site, however, in the case of White-naped Cranes, there was an even distribution in density of feeding flocks and individuals.