• Journal of Astronomy and Space Sciences
• /
• v.22 no.1
• /
• pp.21-34
• /
• 2005

The initial conditions that generate bounded motion in eccentric reference orbit are determined for satellite formation flying. Because Hill's equations cannot describe the relative motion between two satellites in eccentric orbit, a new relative dynamics utilizing the nonlinearity and eccentricity correction for Hill's initial conditions is implemented. The constraint that matches angular rates of chief and deputy satellites is used to obtain the bounded motion between them. The constraint can be applied to satellite formation motions in eccentric orbit, since it implicates J2 perturbation due to the central body's aspherical gravitational forces. The periodic bounded motions are analyzed for the orbit with the eccentricity of less than 0.05 and about 0.5 km relative distance between chief and deputy satellites. It is mainly illustrated that the satellite formations in small eccentric orbits can have hounded motions; consequently, the formation can be kept by matching angular rates of the satellites. These results demonstrate an useful method that reduces the cost for operating satellites by providing effective initial conditions for satellite formation flying in eccentric orbit.

• Science of Emotion and Sensibility
• /
• v.20 no.1
• /
• pp.115-132
• /
• 2017

Differences in reaction time and accuracy were compared among driver groups of middle-, old-, and stroke old-age drivers using various reaction time tasks including simple reaction task, 2-choice task, 4-choice task with different stimuli eccentricity, search task, and moving target detection task. The results can be summarized as followings. First, although overall reaction time tended to be slowed with age and stroke, stroke old drivers showed significantly slower reaction time than the other driver groups when the stimuli were presented in a large eccentricity. Second, differences in reaction time for 2-choice task and moving target detection task seemed to be determined mainly by participants' simple reaction time. Third, the search task which required temporary retention of previously presented stimuli was found to be more sensitive in discriminating difference in reaction time between middle-age drivers and old-age drivers (including stroke old drivers). Fourth, reaction accuracy of old (and stroke old) drivers decreased when more stimuli alternatives were presented and temporary retention for stimuli was required. Altogether, memory demand in reaction time task can be sensitive to evaluate performance for different age groups, whereas size of useful field of view for brain stroke.

• Proceedings of the KSCN Conference
• /
• 2003.05a
• /
• pp.107-107
• /
• 2003

초등 학교 시기에 바람직한 식습관을 형성하는 것이 반드시 필요하며, 특히 현대인의 만성질환 예방 및 건강증진을 위한 바람직한 식습관 형성을 위하여 영양교육의 실시는 절실히 요구된다. 이에 본 연구는 영양교육실시 여부가 초등학생들의 영양상태에 미치는 영향을 파악하고, 앞으로 성장기 아동들이 올바른 식습관을 형성할 수 있도록 구체적인 영양교육 방법을 제시하고자 실시되었다. (중략)

• Proceedings of the KSCN Conference
• /
• 2003.05a
• /
• pp.109-109
• /
• 2003

본 연구는 학교급식이 교육의 일환으로 이루어질 수 있도록 하는 기초 자료를 제공하고자 가정의 식생활 관리자로서 자녀들의 식습관에 가장 큰 영향을 주는 어머니를 대상으로 하여 가정에서의 식생활 관리와 학교급식과 영양교육에 대한 인식 및 요구도를 알아보아, 자녀와 어머니에게 필요한 교육과 학교에서 제공할 수 있는 교육방안을 제시하고자 하였다. 대상자는 서울시 강서교육청 소속 57개 초등학교 중 지역차이를 고려하여 4개 학교 3,4 학년 학부모 400명을 대상으로 설문지를 이용하여 조사하였으며, 이 중 362부를 분석에 이용하였다. (중략)

• Journal of Korean Medical classics
• /
• v.21 no.3
• /
• pp.259-271
• /
• 2008

對人體上說, 喫的東西和進行消化作用是維持生命過程當中很重要過程之一. 這樣吸收水穀之物質一定須要水穀之消化而吸收, 然後能産成人體須要物質的精氣神血. 所以稱爲脾胃是'後天之本'. 還有胃就匯聚水穀而腐熟之處, 所以稱爲'水穀之海'. 在五行上脾胃是配列屬土, 消化過程換言之'火生土'的過程. 體內生理方面的火有兩種一爲君火和還有一個是相火. 已往韓醫學理論之消化是宋代許叔微主張的'命門火'理論. 他提到腎之'命門火'能腐熟水穀, 所以命門之火功能減少的話必導致消化功能也減少. 淸代醫家張錫淳在"醫學衷中參書錄"中說道'心君火'主消化而助'命門相火'的. 本論文是心的君火在消化過程中關於脾胃部分爲重點, 次之火生土之方面論述, 還有在心與消化之互相關係上討論.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.837-841
• /
• 1996

It is the eccentricity that determines most of the characteristics of the elliptic gears. Accoding to the theoretical tooth profiles, two pairs of the elliptic gears were manufactured by using CNC wire cutting machine. For harmonious rotating motion, it is necessaryto consider operating pressure angle and module not to generate undercut. The characteristics of vibration were investigated by analyzer.

• TTA Journal
• /
• s.102
• /
• pp.161-166
• /
• 2005

TTA(한국정보통신기술협회)는 2005년 4월 21일자 산업자원부 고시(제2005-45호)에 따라 대기전력저감프로그램 지정시험기관으로 인정받아 공인인증 시험서비스를 제공하고 있다. 최근 산업자원부는 'Standby Korea 2010'을 발표하면서 전기에너지 저감을 위한 정책 기조를 제시하였다. 이에 발맞춰 TTA는 2005년 11월 KOLAS 시험분야 추가 인증을 시작으로 관련 시험분야의 확대를 추진할 예정이기에 이를 소개하고자 한다.

• Journal of Astronomy and Space Sciences
• /
• v.24 no.4
• /
• pp.315-326
• /
• 2007

Recently introduced, several explicit solutions of relative motion between neighboring elliptic satellite orbits are reviewed. The performance of these solutions is compared with an analytic solution of the general linearized equation of motion. The inversion solution by the Hill-Clohessy-Wiltshire equations is used to produce the initial condition of numerical results. Despite the difference of the reference orbit, the relative motion with the relatively small eccentricity shows the similar results on elliptic case and circular case. In case of the 'chief' satellite with the relatively large eccentricity, HCW equation with the circular reference orbit has relatively larger error than other elliptic equation of motion does.

• School Mathematics
• /
• v.15 no.4
• /
• pp.995-1013
• /
• 2013

The purpose of this paper was to investigate mathematics teachers' mathematical content knowledge about quadratic curves. Three components of mathematical knowledge are needed for teaching: (i) knowing school mathematics, (ii) knowing process of school mathematics, (iii) making connections between school mathematics and advanced mathematics. 24 mathematics teachers were asked to perform 10 questions based on mathematics curriculum. The results showed that mathematics teachers had some difficulties in conic section definitions and eccentricity definitions of ellipse and hyperbola. And they also got difficulty in Dandellin sphere proof of the equivalence of conic section definitions and quadratic curve definitions. Especially, no one answered correctly to the question about the definition of eccentricity. The ratio of correct answer for the question about constructing tangent lines of quadratic curves is less than that for the question about the applications of the properties of tangent lines. These findings suggests that it is needed that to provide plenty of opportunities to learn mathematical content knowledge in teacher education programs.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.3
• /
• pp.317-328
• /
• 2009

Relative dynamic models of satellites which describe the relative motion between two satellites is fundamental for research on the formation flying. The accuracy of various linearized or nonlinear models of relative motion is analyzed and compared. A 'Modeling Error Index (MEI)' is defined for evaluating the accuracy of models. The accuracy of the relative dynamic models in various orbit circumstance are obtained by calculating the modeling error with various eccentricities of the chief orbit and distances between the chief and the deputy. It is found that the modeling errors of the relative dynamic models have different values according to the eccentricity, J2 perturbation, and the distance between satellites. Since the evaluated accuracy of various models in this paper means the error of dynamic models of the formation flying, the results of this paper are very useful for choosing the appropriate relative model of the formation flying mission.