• 천문학회보
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• 제25권2호
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• pp.90-90
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• 2000

• 천문학회지
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• 제47권6호
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• pp.215-218
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• 2014

One-dimensional (1-D) microlens parallaxes can be combined with heliocentric lens-source relative proper motion measurements to derive the lens mass and distance, as suggested by Ghosh et al. (2004). Here I present the first mathematical anlysis of this procedure, which I show can be represented as a quadratic equation. Hence, it is formally subject to a two-fold degeneracy. I show that this degeneracy can be broken in many cases using the relatively crude 2-D parallax information that is often available for microlensing events. I also develop an explicit formula for the region of parameter space where it is more difficult to break this degeneracy. Although no mass/distance measurements have yet been made using this technique, it is likely to become quite common over the next decade.

• 천문학회지
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• 제34권2호
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• pp.99-109
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• 2001

In the present study we have determined the distance moduli for seven globular clusters M2, M3, Ml0, M12, NGC 2808, NGC 6229, and NGC 6752, whose metallicities are in the range -1.54 < [Fe/H] < -1.10. We have derived distances for them by the main-sequence fitting method using a sample of local subdwarfs, whose accurate parallaxes are taken from the Hipparcos Catalog. The derived distance moduli are 15.52 for M2, 14.98 for M3, 14.23 for Ml0, 14.03 for M12, 15.56 for NGC 2808, 17.34 for NGC 6229, and 13.29 for NGC 6752.

• 천문학회지
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• 제50권1호
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• pp.1-5
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• 2017

Like Hipparcos, Gaia is designed to give absolute parallaxes, independent of any astrophysical reference system. And indeed, Gaia's internal zero-point error for parallaxes is likely to be smaller than any individual parallax error. Nevertheless, due in part to mechanical issues of unknown origin, there are many astrophysical questions for which the parallax zero-point error ${\sigma}({\pi}_0)$ will be the fundamentally limiting constraint. These include the distance to the Large Magellanic Cloud and the Galactic Center. We show that by using the photometric parallax estimates for RR Lyrae stars (RRL) within 8kpc, via the ultra-precise infrared period-luminosity relation, one can independently determine a hyper-precise value for ${\pi}_0$. Despite their paucity relative to bright quasars, we show that RRL are competitive due to their order-of-magnitude improved parallax precision for each individual object relative to bright quasars. We show that this method is mathematically robust and well-approximated by analytic formulae over a wide range of relevant distances.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2000년도 한국우주과학회보 제9권2호
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• pp.90-90
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• 2000

No Abstract, See Full Text

• 한국광학회지
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• 제31권2호
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• pp.88-95
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• 2020

본 연구에서는 헤드업 디스플레이에서 발생하는 왜곡수차와 양안시차를 정량적으로 분석 및 보정하는 방법을 제시한다. 비대칭적인 왜곡수차를 분석하기 위해 다섯 종류의 왜곡수차를 제시하고, 이를 아이박스의 중심부에서 측정된 왜곡수차로부터 다른 4개의 가장자리에서 측정된 왜곡수차의 변화량을 상대적인 왜곡으로 정의하였다. 또한 아이박스 내 6개의 양안 위치에서 수렴 양안시차 및 발산 양안시차에 대해 정의하고 평가하였다. 이런 분석 방법을 이용하여 아이박스 내 눈의 위치에 따른 양안시차 및 왜곡수차 변화량을 제한조건으로 두어 최적설계를 진행하여 왜곡수차 및 양안시차가 보정 된 헤드업 디스플레이용 광학계를 구성하였다.

• 천문학논총
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• 제30권2호
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• pp.189-191
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• 2015

The calibration of the period luminosity relation (PLR) for Galactic Mira variables is one of the principle aims of the VERA project. We observe $H_2O$ maser emission at 22 GHz associated with Mira variables in order to determine their distances based on annual parallaxes. We conduct multi-epoch VLBI observations over 1-2 years with a typical interval of one month using VERA in order to obtain annual parallaxes with an accuracy of better than than 10%. Recently, the annnual parallax of T Lep was determined to be $3.06{\pm}0.04$ mas corresponding to a distance of $327{\pm}4pc$ (Nakagawa et al., 2014). The circumstellar distribution and kinematics of $H_2O$ masers was also revealed. With accurate distances to the sources, calibrations of K-band absolute magnitudes ($M_K$) can be improved compared to conventional studies. By compiling Mira variables whose distances were determined with astrometric VLBI, we obtained a PLR of $M_K=3.51logP+1.37{\pm}0.07$.

• 한국광학회:학술대회논문집
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• 한국광학회 2005년도 하계학술발표회
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• pp.150-151
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• 2005

Integral imaging is one of the three-dimensional(3D) display methods, which is an autostereoscopic method. The integral imaging system can provide volumetric 3D image which has both vertical and horizontal parallaxes. The elemental image which is obtained in the pickup process by lens array has the 3D information of the object and can be used for the depth perception and the 3D correlation. Moreover, the elemental image which represents a cyber-space can be generated by computer process.

• 천문학회보
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• 제46권2호
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• pp.80.3-81
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• 2021

RR Lyrae variables are excellent distance indicators thanks to their visual magnitude-metallicity relation and well-defined Period-Luminosity Relations (PLRs) at infrared wavelengths. These population II variables together with the tip of the red giant branch provide primary calibration for the first-rung of the population II distance ladder. We will present new empirical calibration of RR Lyrae PLRs at near-infrared wavelengths using our data from the ongoing CFHT-WIRCam RR Lyrae program. We will discuss the systematic uncertainties involved in the calibration of these relations based on the latest Gaia EDR3 parallaxes and the implication for the cosmic distance scale.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2663-2678
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• 2012

Due to sharp depth transition, big holes may be found in the novel view that is synthesized by depth-image-based rendering (DIBR). A hole-filling method based on disparity map is proposed. One important aspect of the method is that the disparity map of destination image is used for hole-filling, instead of the depth image of reference image. Firstly, the big hole detection based on disparity map is conducted, and the start point and the end point of the hole are recorded. Then foreground pixels and background pixels are distinguished for hole-dilating according to disparity map, so that areas with matching errors can be determined and eliminated. In addition, parallaxes of pixels in the area with holes and matching errors are changed to new values. Finally, holes are filled with background pixels from reference image according to these new parallaxes. Experimental results show that the quality of the new view after hole-filling is quite well; and geometric distortions are avoided in destination image, in contrast to the virtual view generated by depth-smoothing methods and image inpainting methods. Moreover, this method is easy for hardware implementation.