• Journal of Astronomy and Space Sciences
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• v.36 no.4
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• pp.265-281
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• 2019

We present new BVRI light curves of UY UMa with no O'Connell effect and a flat bottom secondary eclipse. Light curve synthesis with the Wilson-Devinney code gives a new solution, which is quite different from the previous study: UY UMa is an A-subtype over-contact binary with a small mass ratio of q = 0.21, a high inclination of 81°.4, a small temperature difference of ΔT=18°, a large fill-out factor of f = 0.61, and a third light of approximately 10% of the total systemic light. The absolute dimensions were newly determined. Seventeen new times of minimum light have been calculated from our observations. The period study indicates that the orbital period has intricately varied in a secular period increase in which two cyclical terms with periods of 12^y.0 and 46^y.3 are superposed. The secular period increase was interpreted to be due to a conservative mass transfer of 2.68 × 10^-8 M_⊙/yr from the less massive to the more massive star. The cyclical components are discussed in terms of double-light time contributions from two additional bound stars. The statistical relations of Yang & Qian (2015) among the physical parameters of 45 deep, low mass ratio contact binaries were revisited by using the physical parameters of UY UMa and 25 Kepler contact binaries provided by Şenavci et al. (2016).

• Applied Microscopy
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• v.43 no.1
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• pp.34-39
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• 2013

Glandular and nonglandular trichomes on the leaf surface of Plectranthus tomentosa were investigated by variable pressure field emission scanning electron microscopy (VP-FESEM). The segments of the plant's leaves were directly mounted without any specimen preparation, and examined at ambient temperature using a variable pressure secondary electron (SE) detector under ca. 15 Pa. Foliar trichomes maintained their shapes and structures without severe surface collapse or charging. The adaxial leaf surface was abundantly covered with different types of trichome. Nonglandular trichomes consisted of a basal cell and a long (up to ca. $300{\mu}m$) stalk. Meanwhile, capitate glandular trichomes had a secretory head and a short or long stalk. Peltate glandular trichomes with globose secretory heads were observed in close contact with the leaf epidermis. Spherical projections on the secretory head showed the secretion process of glandular trichomes. In addition to the trichomes, oval stomata were distributed on the abaxial leaf surface. These results suggest that ambient VP-FESEM can be used to classify the dehydration-sensitive foliar trichomes of succulent plants by SE imaging. At the FESEM resolution, this approach facilitates the rapid and detailed morphological analysis of a variety of trichomes in diverse plant taxa with reduced labor and preparation.

• Research in Mathematical Education
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• v.12 no.4
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• pp.283-291
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• 2008

The extension to a wide population of secondary education in many advanced countries seems to have led to a weakening of the mathematics curriculum. In response, many students have been classified as "gifted" so that they can access a stronger program. Apart from the difficulties that might arise in actually determining which students are gifted (Is it always clear what the term means?), there are dangers inherent in programs that might be devised even for those that are truly talented. Sometimes students are moved ahead to more advanced mathematics. Elementary students might be taught algebra or even subjects like trigonometry and vectors, and secondary students might be taught calculus, differential equations and linear algebra. It is my experience over thirty-five years of contact with bright students that acceleration to higher level mathematics is often not a good idea. In this paper, I will articulate some of the factors that have led me to this opinion and suggest alternatives. First, I would like to emphasize that in matters of education, almost every statement that can be made to admit counterexamples; my opinion on acceleration is no exception. Occasionally, a young Gauss or Euler walks in the door, and one has no choice but to offer the maximum encouragement and allow the student to go to the limit of his capabilities. A young genius can demonstrate an incredible amount of mathematical insight, maturity and mastery of technique. A classical example is probably the teen-age Euler, who in the 1720s was allowed regular audiences with Jean Bernoulli, the foremost mathematician of his day.

• Journal of the Korean Home Economics Association
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• v.47 no.2
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• pp.81-95
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• 2009

The purpose of this study is to examine gender equity in the quantity and flow experience of leisure time of urban dual-earner couples having preschool children. The quantity of leisure time is measured by primary activity and the flow experience of leisure time is measured by primary and secondary activities. The data collected by Korean National Statistical Office in 2004 is used. The sample for this study consists of 255 couples, and the statistical methods are frequency, percentage, paired t-test, and one-way ANOVA. The following is a summary of the major findings. The first, the pattern of the leisure time was different between husbands and wives. The quantity of leisure time of husbands was longer than that of wives. The husbands spent more time to perform social activities, media contact, sports and outdoor activities, while women did more in religious activities. The second, husband's leisure flow experience was higher than that of wives. The pure leisure time of wives was shorter than that of husbands and wives experienced more contaminated leisure time by a secondary activity. In other words, wives's leisure is more likely to be interrupted, to involve episodes of shorter duration, and to be associated with personal care and unpaid work.

• International Journal of Advanced Culture Technology
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• v.6 no.3
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• pp.1-11
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• 2018

The purpose of this study is to develop and analyze the meaning and contents of the "H-STEAM teaching & learning model" which combines Science, Technology, Engineering, Arts & Mathematics (STEAM) with the elements of Humanities. We developed this model based on the key competencies linked with career path for middle school students in Korea, with the recognition of two issues. First, the existing Korean STEAM education lacks the elements of humanities, thus failing to achieve an authentic convergence education. Second, it is necessary to develop a program that might correspond to the Free Semester Program that was first introduced in 2013, and implemented at full scale in 2016 for middle school students in Korea. The advantages of H-STEAM are as follows: First, H-STEAM enables students to flexibly think while traversing the physical world and the symbolic world in the process of dealing with the daily problems. Second, it combines advanced technology with human sensibility and imagination, and enables students to derive creative outcomes that stimulate their minds. Third, it makes students feel and realize a point of contact between the subject that students learn, and jobs of the real world.

• Journal of Korean Society on Water Environment
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• v.21 no.2
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• pp.190-195
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• 2005

The laboratory and pilot scale BAFs (biological aerated filters) were operated with 0.3 hr to 1.1 hr EBCT(empty bed contact time) at a maximum filtration rate of $472m^3/m^2/day$ as a treatment method for reuse of secondary effluent and by-pass flow in this study. The effluent BOD and SS were generally 3.5 to 5 mg/L and 2 to 3 mg/L, respectively with 2ndary effluent, but the SS concentrations increased to 4 to 8 mg/L with the increased flow rates of by-pass flow. Potential nitrification rates were very high, but the nitrogen removal efficiencies were low due to the limited carbon sources. Bypass of a part of primary effluent seemed to be desirable to increase the nitrogen removal. Disinfection must be furnished for the reuse of BAF effluent.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.31.2-31.2
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• 2013

We use grid-based hydrodynamic simulations to study star formation in nuclear rings in barred galaxies. The gaseous medium is assumed to be infinitesimally thin, isothermal, and unmagnetized. To investigate various situations, we vary the total gas content in the bar regions and the bar growth time. We find that star formation rate (SFR) in a nuclear ring is determined by the mass inflow rate to the ring rather than the total gas mass in the ring. The SFR shows a strong primary burst and weak secondary bursts at early time, and declines to small values at late time. The primary burst is caused by the rapid gas infall to the ring due to the bar growth, with its duration and peak depending on the bar growth time. The secondary bursts result from re-infall of the ejected gas by star formation feedback of the primary burst. When the SFR is low, ages of young star clusters exhibit an azimuthal gradient along the ring since star formation takes place mostly near the contact points between the dust lanes and the nuclear ring. When the SFR is large, on the other hand, star formation is widely distributed throughout the whole length of the ring, with no apparent age gradient of star clusters. Regardless of SFR, star clusters have a positive radial age gradient, with younger clusters located closer to the ring, since the ring shrinks in size over time.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.112-118
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• 2003

The friction coefficients of the rubber for clutch master cylinder were experimentally measured in this study. The cylindrical rubber samples for primary cup-seal and secondary cup-seal were tested against the aluminum or the steel plates of master cylinder housing under the various conditions of brake oil temperatures and normal loads. Dry sliding friction coefficients were also measured under various load conditions. The test revealed following results. First, the friction coefficient under fluid lubrication condition in general decreases, as the oil temperature or normal load increases. Second, the steel plate of low surface roughness yielded comparatively low friction coefficient on the range of 0.30∼0.67. On the other hand, the aluminum plate of high surface roughness yielded high friction coefficient on the range of 0.31∼1.15. Third, the friction coefficient of dry surface contact decreases as the normal load increases. This is contrary to the general principle of friction coefficient between metal plates.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.2
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• pp.162-169
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• 2016

A new concept of membrane type LNG CCS was proposed. Also, its static behavior was numerically analyzed considering the interaction between primary and secondary barrier together with securing device. Hull deflection was taken into account as an external load, together with temperature distribution across the barriers. The suggested numerical model considers both sliding and contact between the two mating surfaces of both the primary and secondary barrier, and anisotropic material behavior of plywood, R-PUF was also taken into account. Furthermore, detailed local strength was evaluated for the securing device, which is arranged between two barriers to hold the primary barrier. It was confirmed through the numerical analysis that the new concept of membrane type CCS was structurally safe under static loading condition and securing concept was structurally reliable.

• English Language & Literature Teaching
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• no.1
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• pp.1-20
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• 1995

Nowadays in Korea the subject of English education has been rising as one of the essential matters which need to be emphasized, reorganized, and thus refined. From the history of about one century to the current, English education may be compared to an adolescent who should be paid much more attention to grow as an independent adult. Although we recognize that there was much improvement in the past age of English education, a lot of assignments to solve await us. This study aims to suggest a recipe for optimal learning in English classes by linking theory with practice: First, the nation-wide academic associations of English teaching should act more energetically and cooperatively than ever. They need further specialization, dynamic participation, and systematic organization. At the same time the academic journals of their own should be publicized broadly, internationally as well as nationally. Second, there should be close contact and discussion between professors and secondary-school teachers. To achieve better learning in English classes, an effective cycle of equilibrium ought to be maintained by combining theory with practice. For example, language institute in universities/colleges can serve instructional programs such as lectures, colloquiums, and intensive courses for conversation. Third, native speakers of English should be positively utilized. Teachers had better keep close contact with native speakers as frequently as possible if they want to become fluent or at least acceptable speakers in English. Teachers may also use native speakers as aides in their classes.