• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.211-218
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• 2012

Two experiment are planed to identify driver's safe driving behaviour by curve radius, road surface condition in curve section. At four-lane and two-lane road, conducted experiments are check on driver's feeling of safety that 30 subjects do not feel discomfort. And using the data from these experiments, this study compare physical speed (not slipping, fall our of the road) with safety driving speed(drivers felt a comfortable and safe speed) each curve radius and fiver road surface condition(drying, wet, rain, snow and ice). As a result, safe driving behaviour factors that are derived to curve radius of 100m units, five road surface conditions enable to represent quantitative analysis of driver's discomfort. This study will develop road design method and evaluation reflected ergonomic aspects.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.753-755
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• 2015

We had a campaign of observing the annular solar eclipse on 2012 May 21 by naked eye through eclipse eyeglasses to determine the limit line of annularity. As a result, we had about 15,000 reports through our website. In addition there were many observation groups for which about 30,000 people in total participated in the observations. The overall result was that the limit we observed by naked eye through eclipse glasses coincided with a prediction that took into account the lunar limb irregularity within the error of ${\pm}500m$. This error of the limit line location corresponds to about ${\pm}200km$ of the radius of the Sun.

• Journal of Astronomy and Space Sciences
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• v.3 no.1
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• pp.15-27
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• 1986

Variation of radius vector was computed by Cowell's method. Perturbations due to the Sun, moon, and earth's asymmetrical potential are considered. We summarize our results as follows : I) $J_2$ term does not affect the equatorial orbit. ii) Large perturbation and secular variation on the above orbit are caused by tesseral harmonics. iii) The other perturbations have small effect and periodicity.

• Journal of The Korean Astronomical Society
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• v.36 no.spc1
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• pp.1-5
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• 2003

In an early paper Skumanich suggested the existence of a scaling law relating the mean sunspot magnetic field with the square-root of the photospheric pressure. This was derived from an analysis of a variety of theoretical spot models including those by Yun (1968). These were based on the Schliiter-Temesvary (S- T) similarity assumption. To answer criticisms that such modeling may have unphysical (non-axial maxima) solutions, the S-T model was revisited, Moon et al. (1998), with an improved vector potential function. We consider here the consequences of this work for the scaling relation. We show that by dimensionalizing the lateral force balance equation for the S- T model one finds that a single parameter enters as a characteristic value of the solution. This parameter yields Skumanich's scaling directly. Using an observed universal flux-radius relation for dark solar magnetic features (spots and pores) for comparison, we find good to fair agreement with Yun's characteristic value, however the Moon et al. values deviate significantly.

• Journal of Korean Clinical Health Science
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• v.4 no.4
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• pp.662-670
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• 2016

Purpose. Because of a recent increase in use of soft contact lens at younger ages, in the present study, the correlation between corneal eccentricity and radius of curvature and fitting types of contact lens was investigated. Methods. The study evaluated the fitting status of targets through lens centration, push-up test, dynamic lag test and static lag test of lenses usually worn by 49 men and women (98eyes) in their 20s to 30s who put on soft contact lenses. After evaluation, the subjects were classified into 3 categories by fitting status(steep, aligment and flat). The radius of corneal curvature in the naked eyes was measured by using keratometer. Moreover the corneal eccentricity in the nasal side, temporal side, superior side and inferior side was measured by using the device capable of measuring the corneal eccentricity. Results. The radius of corneal curvature and corneal eccentricity of soft lenses worn by subjects were higher in the order of steep fitting and flat fitting, and the higher average corneal curvature radius and corneal eccentricity is intend to be more steep fitting(p=0.051, p=0.052). The corneal eccentricity showed a tendency to nasal fitting type at the higher eccentricity and temporal fitting type at the smaller eccentricity, statistically significant difference was observed(p<0.05). The study showed there were low correlation that nasal and temporal side at steep fitting, superior side at normal fitting and 4side(nasal, temporal, superior, inferior) at flat fitting, therefore when the corneal eccentricity changed the radius of corneal curvature also changed. The corneal eccentricity and the radius of corneal curvature showed statistically significant difference at 4side and each fitting types(p<0.05). Conclusions. The results of this study, the fitting status, of wearer are based on radius of corneal curvature and corneal eccentricity, and if lens fitting would be done considering that, it seems to be useful in a soft contact lens prescription.

• Structural Engineering and Mechanics
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• v.83 no.5
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• pp.681-692
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• 2022

The vibrational response of the two bones in a Volleyball player's arm under ball impact is conducted. The two bones in hand, Ulna and Radius, are modeled as two cylindrical shells. The formulations associated with the shells' vibration are obtained using the energy method. Then, the results are extracted with the aid of the two-dimensional form of DQM in conjunction with Runge-Kutta. The results are validated by means of a published paper. Lastly, the role of parameters in determining vibrational frequency as well as deflection is explored through parametric studies. It was shown that the impactor speed and the time of the impact could be essential factors in determining the vibration behavior of the bones. This work can be used in the further investigation of the behavior of bones and physiological structures.

• Journal of Power Electronics
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• v.9 no.4
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• pp.631-642
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• 2009

The sun is a useful reference direction because of its brightness relative to other astronomical objects and its relatively small apparent radius as viewed by spacecrafts near the Earth. Most satellites use solar power as a source of energy, and so need to make sure that solar panels are oriented correctly with respect to the sun. Also, some satellites have sensitive instruments that must not be exposed to direct sunlight. For all these reasons, sun sensors are important components in spacecraft attitude determination and control systems. To minimize components and structural mass, some components have multiple purposes. The solar cells will provide power and also be used as coarse sun sensors. A coarse Sun sensor is a low-cost attitude determination sensor suitable for a wide range of space missions. The sensor measures the sun angle in two orthogonal axes. The Sun sensor measures the sun angle in both azimuth and elevation. This paper presents the development of a model to determine the attitude of a small cube-shaped satellite in space relative to the sun's direction. This sensor helps small cube-shaped Pico satellites to perform accurate attitude determination without requiring additional hardware.

• Journal of the Korean Geotechnical Society
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• v.31 no.11
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• pp.49-60
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• 2015

Open-water sediment disposal has many applications in costal construction. Dumping of sediment in open water can be divided into descending stage under water and sedimentation stage on the seabed, and retained rate is evaluated from analyzed results of these two successive stages. Descending particle cloud have two distinct thermal and swam phase, and trajectory equations for each phase are derived to describe settling velocity and radius of particle cloud. For sedimentation stage, a numerical simulator is used to calculate growth factors for particle fiction angle and current velocity. Retained rate is defined as a mass rate of remained sediment inside the circle which has a center at dumping point on the sea level and user-defined effective radius. Retained rate map for Singapore coast is presented with water depth of 20 m, current velocity of 0.0~1.5 m/s, and effective radius of 5 m. It will decrease sediment mass loss during disposal operation and minimize surrounding environmental pollution.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2136-2138
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• 1999

In this study, we describe the change of electrical properties of XLPE with electrical-tree degradation. XLPE insulation was used as specimen which was cut off from 22.9kV XLPE insulated cable and made in a type of block. The applying voltages are 8kV, 10kV, 12kV and frequency is 60Hz Ogra needles having tip radius of 10$\mu\textrm{m}$ were inserted in blocks. PD quantity and $tan{\delta}$ and DC current were measured from inception of tree to breakdown and their characteristics were analyzed.

• Journal of The Korean Association For Science Education
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• v.30 no.7
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• pp.901-907
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• 2010

The purpose of this study is to analyze methods for measuring the size of the Earth, put forth in 6 different Korean 8th grade science textbooks. The research questions are as follows: 1) Do they adequately map out the experiments for measuring the size of the earth by using the concept of the sun's altitude? 2) Do they reduce the size of the sun like as the Earth is similarly downsized to the globe? 3) Do they suggest the precise experimental conditions for selecting two equal longitudinal spots for measuring the size of the earth? 4) Do they design adequate experiments for exact measurement? 5) Do they offer a proportional expression for seeking the size of globe which is easily understood by students? 6) Do they develop experiments to measure actual size of the earth? Four graduate students and one researcher took part in this study. All conditions were unanimously agreed upon by the participants. The results are as follows. First, one publishing company must include the concept of the sun's altitude to accurately measure the size of the Earth. However, some textbooks fail to mention this. As such, the concept of the sun's altitude must be introduced to accurately measure the size of the Earth. Second, a reduced size globe is used as the actual earth so; the sun should be factored in with a reduced light value. Third, you have to lay a stress on two points at the same longitude. In other words, a shadow located at the same longitude from two randomly selected points. Most textbooks mention two points at the same longitude but two of them design the experiment with a shadow at the same longitude. Fourth, we need a method to precisely measure the angle between a stick and its shadow. The angle between the stick and the tip of its shadow is the sun's altitude difference. Fifth, we need to present more specific proportional expressions for calculating the size of the globe. Only 3 out of the 6 texts employed a proportional expression. Sixth, we need to calculate the size of the earth by accurately presenting the scale of the globe to attain the goal of the experiment. Two of the texts analyzed, designed the experiment for the purpose of calculating the size of the globe. Three of the texts designed their experiments to calculate the radius of globe which is not even relevant to the purpose of experiment.