• Bulletin of the Korean Space Science Society
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• 2004.04a
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• pp.85-85
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• 2004

다목적 실용위성(KOMPSAT) 시리즈는 전력버스가 위성의 배터리와 직접 연결되어 있어 버스전압이 배터리와 동일하며, 전력조절기(Power Regulator)의 스위칭 듀티 값이 위성 탑재 소프트웨어에 의해 제어되는 소프트웨어 제어방식의 비조절형 버스 시스템 (Unregulated Bus System)을 사용한다. 본 논문에서는 이와 같은 소프트웨어 제어방식 비조절형 버스시스템을 채택하는 위성의 전력조절기 모듈화에 적용 가능한 새로운 전원단 회로를 제안하며 제안된 전원단의 모드별 동작 특성을 해석하고 시뮬레이션 결과와 비교, 검토한다. (중략)

• Journal of Engineering Education Research
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• v.12 no.4
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• pp.150-158
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• 2009

This study deals with the effect of learner's self-regulated learning strategy in the non-real-time online discussion. Based on these research results, it was suggested self-regulated learning strategy should be utilized in order to enhance the cognitive dimension participation and discussion satisfaction quality of non-real-time online discussion.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.96-105
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• 1998

The effects of time-sampling to be considered in digital implementation of a nonlinear output regulator is investigated. It is found that the output regulatability of nonlinear systems is generally not robust with respect to time-sampling although the output regulatedness of nonlinear systems is preserved under time-sampling. Also, a certain class of nonlinear systems is clarified for which the preservation of the output regulatability under time-sampling can be decided without difficulty. These results imply that one needs to seek a better approximate sampled-data nonlinear output regulator since a digital output regulator resulting from discretizing the continuous-time nonlinear output regulator designed based on the underlying continuous-time nonlinear system model is nothing but a 1st order approximate one with respect to sampling-time.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.5
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• pp.35-47
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• 2011

Dynamic characteristics of a flow control valve, which plays an important role in thrust and O/F control of liquid rocket engines, have been analyzed by the AMESim simulator modeling. The speed control method was proposed for the control of the flow valve equipped with a BLDC motor. The experimental results demonstrated the feasibility of systematical application as well as the performance of the speed control method. Moreover, the speed control method for BLDC motor is much simpler than the P control method in complex flow systems. With the speed control method, the control flow characteristics were evaluated according to plunger shapes. Consequently, same plunger shape proved to be more efficient in the mixture ratio control operated by two flow valves. It was also shown that the appropriate modification of plunger shapes could reduce the mixture ratio perturbation by 0.5%.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.115-115
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• 2011

본 연구에서는 자갈사주의 식생 이입 과정을 밝히고, 식생 이입에 영향을 미치는 수리적 특성을 규명하기 위한 현지조사 방안을 제시하였다. 자갈사주의 식생이입은 조절 하천과 비조절 하천에서의 이입 과정이 다르며, 본 연구에서는 비조절 하천을 대상으로 하였다. 따라서 상류에 댐이나 저수지가 없는 자연에 가까운 하천을 고려하였으며, 장기적으로는 조절 하천의 식생이입 과정과의 비교를 위해 임하댐의 반변천과 가까운 길안천의 중류 구간을 선정하였다. 자갈사주의 식생이입 과정을 모니터링하기 위해, 자갈사주를 전구역과 세부구역으로 나누어 같은 지점에서 같은 배율로 사진을 촬영하였다. 전자는 자갈사주 전체를 대상으로 촬영하며, 이를 위한 view point 선정이 중요하고 선정에 적절한 지점을 제시하였다. 후자의 경우 식생의 이입 정도를 왕성, 보통, 미약, 없음(4단계)로 구분하기 위해 대상 지점을 matrix가 50% 이상인 지점 ; 식생이입 왕성 (2개 지점), matrix가 50% 이하인 지점 ; 식생이입 보통, 또는 미약 (2개 지점), matrix가 없는 자갈만의 지점 ; 식생이입 없음 (1개 지점)을 선정하였다. 식생이입에 영향을 미치는 변수로는 하상토의 입경과 흐름의 특성(수심, 유속, 하상 소류력 등)을 들 수 있으며, 이들 조사를 위한 방법을 제시하였다.

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.2
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• pp.119-126
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• 2016

Purpose: To analyze the effect of accommodative control and change values between subjective refraction (SR) and auto-refraction (AR) according to application of fogging after accommodative stimulation depending on ametropia type. Methods: Myopic ametropia 76 eyes and hyperopic ametropia 52 eyes participated for this study. SR and AR values measured by three test conditions (Before accommodative stimulation; Before AS, After accommodative stimulation; After AS, and After application of fogging; After AF) were compared, respectively. Results: In myopic eyes, (-)spherical power by SR and AR in After AS test was significantly increased as compared to Before AS test, (-)spherical power in After AF test was decreased to the level of Before AS test. The differences of spherical power between SR and AR were highly measured by SR in After AS test, and highly measured by AR in After AF test, respectively. In hyperopic eyes, (+)spherical power of SR significantly decreased in After AS test compared to Before AS test, more (+)spherical power was detected in After AF test compared to Before AS test. (+)spherical power of AR have no significant difference between Before AS and After AS test, but more (+)spherical power was detected in After AF test compared to Before AS test. The differences of (+)spherical power between SR and AR were significant in all test conditions. Among 52 eyes which were measured as hyperopic ametropia, 7 eyes were measured as myopia by SR in After AS test. In case of AR, 25 eyes among 52 eyes were mismeasured as myopia of ranges from -0.25 D to -1.25 D in Before AS test, 26 eyes in After AS test, and 19 eyes in After AF test were mismeasured as myopia of ranges from -0.25 D to -1.25 D. Conclusions: Regardless of ametropia type, accommodative control by After AF test was effective on both refraction process. However, in auto-refraction for hyperopic eyes, the misdetermined proportion of refractive error's type was high due to consistent accommodative intervention in all test condition. Therefore, in order to obtain an accurate value of refractive errors, full correction should be determined by subjective refraction process after fogging method.

• Journal of Nutrition and Health
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• v.43 no.6
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• pp.607-619
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• 2010

The purpose of this study was to identify the concepts of body image, weight control and food behavior in 520 Korean high school seniors from Seoul and Gyeonggi Province. A questionnaire survey was conducted to investigate body image, concern of weight control, experience of weight control, the first time to try weight control, plan for weight control, reasons of weight control and food behaviors related with weight control. Anthropometric parameters such as weight and height were measured. Finally, data from 497 high school seniors were used for statistical analysis. The results were as follows. Many subjects had misperceptions. Among the subjects who perceived themselves as 'fat', 57.8% were normal weight and 0.5% underweight. Among the subjects who perceived themselves as 'thin', 59.5% were normal weight, 0.9% overweight and 0.9% obese. Girls were more concerned about weight control than boys (4.20 vs. 3.66). Weight loss had been experienced by 61.5% of the subjects and weight gain by 12.8%. First weight control was attempted by 71.3% of the subject at high school and by 28.7% at middle school. The majority of subjects planned for weight control before their freshman year. The boys choose 'health' as the primary reason for weight control, whereas the girls chose 'good appearance'. The total score of food behaviors varied significantly according to BMI. Overweight and obese subjects had more desirable food behaviors than normal weight and underweight subjects (24.00, 24.06 vs. 21.92, 21.52). However, total scores of food behaviors showed no variation according to sex, weight control attempt and body image. In conclusion, the high school seniors had misconceptions about body image and weight control. They were exposed to a high risk of inappropriate weight control and food behaviors. Therefore, proper nutritional education programs need to be developed for high school seniors to prevent nutrition problems related to weight control and to maintain desirable food behaviors.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.1
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• pp.73-78
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• 2010

Purpose: The purpose of this study was to examine diurnal variation of accommodation on people whose age are between 35 and 50 years old with frequent alternation of accommodation at period 1 (8:00-10:00), period 2(13:00-15:00) and period 3 (18:00-20:00). Methods: All \04 subjects were separated to nonpresbyopia and incipient presbyopia. Tests were done for amplitude of accommodation, accommodative facility and relative amplitude of accommodation. Results: Both nonpresbyopia and incipient presbyopia had the highest amplitude of accommodation in oculus dexter, oculus sinister and oculus uterque at period 2. In addition, the incipient presbyopia showed the statistical significance of daily change. The nonpresbyopia had the most accommodative facility at period 3 and incipient presbyopia had the most accommodative facility at period 2. Their daily variations were statistically significant. Both nonpresbyopia and incipient presbyopia had the most negative relative accommodation of daily change at period I. Both of them had the most positive relative accommodation at period 2. Conclusions: The incipient presbyopia had the highest amplitude of accommodation, accommodative facility. and positive relative accommodation (except the negative relative accommodation) at period 2.

• 한국벤처창업학회:학술대회논문집
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• 2020.06a
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• pp.155-160
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• 2020

본 연구는 농업경영체 종사자를 대상으로 SNS 활용을 조절변수로 하여 내부마케팅요인이 기업성과에 미치는 영향에 관하여 분석하였다. 내부마케팅요인을 교육훈련, 커뮤니케이션으로 및 보상시스템으로 구분하고 기업성과를 재무적성과와 비재무적성과의 하위변수로 설정하였다. 농업경영체 종사자들로부터 수집한 설문지 349부를 실증분석에 사용하였다. SPSS v22.0과 Process macro v3.4를 사용한 분석결과는 첫째, 커뮤니케이션과 보상시스템은 재무적성과에 유의한 영향을 미치고 교육훈련은 재무적성과에 유의한 영향을 미치지 않는 것으로 나타났다. 둘째, 커뮤니케이션은 비재무적성과에 유의한 영향을 미치며 교육훈련은 비재무적성과에 부(-)의 유의한 영향을 미치고 보상시스템은 비재무적성과에 유의한 영향을 미치지 않는 것으로 나타났다. 셋째, SNS 활용은 내부 마케팅요인과 재무적성과 간의 관계를 유의하게 조절하는 것으로 나타났다. 넷째, SNS 활용은 내부마케팅요인과 비재무적성과 간의 관계를 유의하게 조절하는 것으로 나타났다. 본 연구는 농업경영체의 성과에 영향을 미치는 내부마케팅요인을 발굴했다는 의의를 가진다. 후속 연구로는 매개변수의 발굴로 형성된 매개모형에 대한 연구와 추가로 매개변수가 도입된 조건부과정 모형을 통한 조절된 매개분석을 위한 연구가 필요할 것으로 보인다.

• Journal of Astronomy and Space Sciences
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• v.16 no.2
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• pp.265-272
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• 1999

A thrusters modulation method is suggested for spacecraft attitude control with asymmetric configured thrusters during orbit adjustment maneuvers. Attitude is controlled by thrusters off-modulation during orbit maneuvers. Usual control method for symmetric configured thrusters cam not be applied for asymmetric configured thrusters. Disturbance induced from thrusters asymmetricity shall be compensated during pulsing. In this paper, a thrusters control method using null solution is suggested, which is shown working well without inducing disturbance.