• Journal of The Korean Astronomical Society
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• v.39 no.4
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• pp.129-138
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• 2006

A period study of the semi-detached eclipsing binary system W Delphini based on the extensive series of minimum timings covering more than a century(109 years) indicates a cyclic(O-C) variation of the system. This variation can be explained as due either to (1) stellar magnetic activity cycles of the cool subgiant G5 secondary component of the binary with a subsurface magnetic field equals to 3 kG, or (2) a long-term orbital period increases with a rate of $1.68{\times}10^{-8}$ day/cycle caused by a mass transfer rate of $4.9{\times}10^{-8}M_{\odot}yr^{-1}$ from the less to more massive component modulated by a light time effect due to a hypothetical third body with period of $53.4{\pm}1.06$ years. The former explanation is more recommended than the later one since the obtained third body mass value($M_3=1.58\;M_{\odot}$) is quite large but it can not manifest itself observationally and also it cannot be a white dwarf. In the contrary, from the magnetic activity point of view, the obtained characteristics are in good consistent when applying Applegate(1992) mechanism. However, further precise photometric and CCD observations for minima timings with brightness determinations are needed to confirm the present solution.

• Journal of The Korean Astronomical Society
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• v.39 no.1
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• pp.25-30
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• 2006

We completed four color light curves of the near-contact binary CN And during three nights from September to December 2004 using the 61-cm reflector and BV RI filters at Sobaeksan Observatory. We determined four new times of minimum light (two timings for primary eclipse, two for secondary). Newly obtained BV RI light curves and the radial velocity curves from Rucinski et a1. (2000) were simultaneously analyzed to derive the system parameters of CN And. We used the semi-detached mode 4 of the 2003-version of the Wilson-Devinney binary model, and interpreted the asymmetry of the light curve by introducing two spots; a cool spot on the primary component and a hot spot on the secondary component. New photometric parameters are not much different from those of Cicek et a1. (2005), and it is considered that the system is in the era of broken contact. From the orbital period study with all available timings including our data, we found a continous period decrease with a rate of $P_{obs}=--1.82{\times}10^{-7}\;d\;yr^{-1}$ that can be explained with two possible mechanisms. We think the most likely cause of the period decrease is a thermal mass transfer from the primary to the secondary component, rather than angular momentum loss due to a magnetic stellar wind.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.213-221
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• 2013

We present the first BVRI CCD photometric observations of V345 Cas made on 22 nights during the observing seasons in 2007-2008. Our light curves, resembling those of EB-type binary stars, are analyzed with the 2003 version of the Wilson-Devinney binary code. The photometric study shows that V345 Cas is a typical semi-detached binary system with the primary star being about ${\Delta}T$ = 2400 K hotter, two times more massive, but only 17% larger than the secondary star being filled with it's Roche-lobe. The orbit has a relatively large inclination of about $88^{\circ}$. A cool spot on the secondary component is modeled to explain a small light curve asymmetry. Absolute dimensions and related radiometric parameters of the eclipsing pair are calculated and their evolutionary states are discussed with the HR diagrams of mass-radius and temperature-luminosity. A period analysis of all available times of minima, including our measurements, indicates that the orbital period may vary in a cyclical way, unfortunately the secondary period for the variation can not be uniquely determined because of lack of present timing data.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.7
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• pp.8-13
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• 2019

As increasing demand for precise machining in advanced disciplines, especially in semi-conductor, aeronautical and automotive industries, the magnetic abrasive deburring(MAD) which is able to eliminate micro-sized burr on complex surface in less time has drawn the attention in the last decades. However, the performance of MAD is subject to shape and size of a tool. Therefore, this study aim to identify deburring behavior of MAD in U-type flow channel by measuring the length rate of burr removal in radial distance of the cylindrical tool under four process factors. In order to evaluate the deburring effect of MAD on the surface, finishing regions are divided based on center of the circular cutting tool. As a results, it was defined that the amount of burr removal in a downward direction moving toward flow channel from the top surface was higher than upward direction. This is because the magnetic abrasives were detached from magnetic lines of force due to geometrical shape.

• Journal of Digital Convergence
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• v.11 no.2
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• pp.375-383
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• 2013

The aim of this study is to explore fathers' own expectations and experiences of fatherhood along with their views of what it meant to be a 'good' father. Qualitative methodologies were used; semi-structured in-depth interviews with 10 dual-earner fathers with young children. Interviewees overwhelmingly welcomed the opportunities offered to them by the new fatherhood model and supported a perceived cultural shift towards men and fathers being involved in, rather than detached from, family life. However tension and difficulty in living the ideal were also reported: gaps between perceptions and behaviors; struggle for traditional breadwinning role and caring; conflicts between selflessness and career and uninvolved in family decisions. Political and practical considerations are discussed, and the implications of this study for future research are identified.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2004.11a
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• pp.111-116
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• 2004

This study is aimed to be used as basic data to plan Korean style cohousing for double-income families in the future by studying their lifestyle, housing needs and housing awareness on cohousing. The results of the study are as follows. 1) As for the life style of the subject families, it was a housewife that mainly does the household affairs despite of the status of double-income family. Also, as for the social activity, almost half of the respondents said that the spending in child-care facilities was not sufficient and wanted to send their children to ones within their neighborhood. 2) As far as housing awareness on cohousing concerned, among specific items, the child care area, the household affairs division area, and participatory awareness of residents in housing planning and management got higher scores, while as for awareness on utilizing common space, using the common hobby rooms, promenades and benches, exercise facilities, common yard, and study rooms got higher scores. When asked about the necessity for cohousing in Korea, they gave very positive answers, but the answer to their willingness to reside in it was less positive. 3) Summarizing the housing needs on cohousing, it turned out that more people wanted to reside in suburban area with others having common grounds with them as for a desirable residence environment. They wanted the neighborhood to be composed of 10${\sim}$29 families, and medium-density semi-detached house occupied by owners. They wanted a mixture of independent management and entrust management for managing common facilities, and common meal once a week. They wanted indoor exercise facilities to be more extended than other common facilities, and the house of $100m^{2}{\sim}130m^{2}$ with 3 bedrooms, 2 bath rooms, and a large living room and dining room.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.86-86
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• 2019

We present BV photometric observations and high-resolution spectra of AO Ser, which were obtained at the Mt. Lemmon Optical Astronomy Observatory (LOAO) and the Bohyunsan Optical Astronomy Observatory (BOAO), respectively, in 2017. The radial velocities (RVs) for both components were measured, and the effective temperature of the primary star was found to be $T_{eff,1}=8,820{\pm}62K$ by a comparison of the observed spectra and the Kurucz models. A unique set of fundamental parameters of AO Ser were derived for the first time by a simultaneous analysis of the light and RV curves. The results indicate that our program target is a semi-detached eclipsing system with values of $M_1=2.06{\pm}0.11M_{\odot}$ and $M_2=0.41{\pm}0.03M_{\odot}$, $R_1=1.54{\pm}0.03R_{\odot}$ and $R_2=1.30{\pm}0.02R_{\odot}$, and $L_1=12.9{\pm}0.2L_{\odot}$ and $L_2=0.9{\pm}0.3L_{\odot}$. We applied multiple frequency analyses to the eclipse-subtracted light residuals. As a result, two frequencies of $f_1=21.85151days^{-1}$ and $f_2=23.48405days^{-1}$ were detected and their pulsation constants were calculated to $Q_1=0.0344days$ and $Q_2=0.0320days$. The pulsational characteristics and the position in the HR diagram demonstrate that the primary star is a ${\delta}$ Sct pulsator.

• Journal of Fashion Business
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• v.26 no.2
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• pp.143-155
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• 2022

The purpose of this study was to develop protective clothing that could alleviate fall impacts. Fall impact protection pants for elderly women were designed, and motion adaptable hip pads and knee pads printed by 3D printing were integrated into the pants and evaluated. First, the design of the fall impact protection pants with variable motion was semi-loose fitting pants that could be worn and detached from the protective pad. A pad pocket was made in the lining inside the pants so that the protective pad could be fixed to the protective area. Second, in the evaluation of the appearance of the fall impact protection pants, the wearer group had a good score of 4.60 or higher for all questions on color, material, ease, and fit. In the evaluation of the insertion method of the protective pad, the flexibility of the pad, and the weight of the pad, the subjects' scores were 4.30~4.80. The fit of the fall impact protection pants was excellent in the texture and elasticity of the outside and inside of the pants. There was no discomfort due to the pad(4.60), and no difficulty in movement during wearing activities was reported. During squatting, it was evaluated as 4.80, indicating that the motion adaptable hip joint and knee pads were highly effective during operation.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.34.4-35
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• 2021

We present the TESS photometry and our high-resolution spectra of the semi-detached Algol EW Boo. For an orbital period study, we collected all available times of minima including ours for the last 30 years. It is found that the eclipse timing variation of the system can be represented by a periodic oscillation of 18.5±1.0 yr plus a secular period increase with a rate of [dP/dt]_orb=-6(±3)×10^-8 d yr^-1. From our observed spectra, the effective temperature of the primary star was determined to be T_eff,1=8560±118 K. From a simultaneous analysis of the TESS light and our double-lined radial velocity curves, the absolute masses, radii, and luminosities are M₁=2.30±0.07M_⊙, M₂=0.38±0.01M_⊙, R₁=1.92±0.02 R_⊙, R₂=1.27±0.01 R_⊙, L₁=1.92±0.02 L_⊙, and L₂=0.752±0.007 L_⊙, respectively. Multiple frequency analyses were carried out for the light residuals after subtracting the binary star model. We detected a total of 75 frequencies in the region of 16.50-104.8 day-1. Our results demonstrate that the more hotter primary star of EW Boo is a δ Sct pulsator by considering its position in the δ Scuti region of the Cepheid instability strip and pulsational characteristics.

• Journal of The Korean Astronomical Society
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• v.49 no.6
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• pp.295-306
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• 2016

We present the results of BV time-series photometry of the globular cluster NGC 288. Observations were carried out to search for variable stars using the Korea Microlensing Telescope Network (KMTNet) 1.6-m telescopes and a 4k pre-science CCD camera during a test observation from August to December, 2014. We found a new SX Phe star and confirmed twelve previously known variable stars in NGC 288. For the semi-regular variable star V1, we newly determined a period of 37.3 days from light curves spanning 137 days. The light-curve solution of the eclipsing binary V10 indicates that the system is probably a detached system. The pulsation properties of nine SX Phe stars were examined by applying multiple frequency analysis to their light curves. We derived a new Period-Luminosity (P-L) relation, ${\langle}M_V{\rangle}=-2.476({\pm}0.300){\log}P-0.354({\pm}0.385)$, from six SX Phe stars showing the fundamental mode. Additionally, the period ratios of three SX Phe stars that probably have a double-radial mode were investigated; $P_{FO}/P_F=0.779$ for V5, $P_{TO}/P_{FO}=0.685$ for V9, $P_{SO}/P_{FO}=0.811$ for V11. This paper is the first contribution in a series assessing the detections and properties of variable stars in six southern globular clusters with the KMTNet system.