• The Journal of the Acoustical Society of Korea
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• v.12 no.2
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• pp.28-36
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• 1993

임의의 형상을 갖는 진동체에 의한 방사 음장해석은 경계요소법에 의하여 이미 많은 해석이 시도되었다. 그러나, 진동체의 형상이 매우 복잡한 경우에는 겉표면의 요소수가 크게 증가할 뿐만 아니라 각 요소에서의 경계조건을 모두 알아내어야 하므로, 저주파에 국한된 해석일지라도 엄청난 시간과 노력이 필요하게 된다. 이러한 어려움을 극복하기 위하여 경계요소법을 사용하되, 복잡한 형상의 진동체를 둘러싸는 가상적인 표면을 매우 간단하게 설정한 후 그 표면상의 경계조건인 음압을 측정한다. 임의의 형상에 대한 파수 영역에서의 감쇠파의여파작업을 위하여 특이값 분리를 사용하였다. 특이값 분리에 의하여 음압분포를 측정위치에서 설정된 일반 좌표계에서의 고유모드로 분해한다. 각 고유모드의 원거리 음장의 기여도에 해당하는 각 특이벡터에 대한 특이값의 크기를 비교하여, 유한개의 고유모드만을 포함시킴으로써 원거리 음장을 예측한다. 몇 개의 예제를 통하여 해석적 방법의 기존의 경계요소법에 의한 결과를 본 연구 방법의 결과와 비교하여 잘 일치함을 확인하였다.

• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.161-172
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• 2000

자연암석절리 및 인공 절리에 대하여 일정수직응력제어, 일정 수직하중제어 그리고 무한 강성제어가 가능한 암석 절리면 전단기 시험기를 개발하였다. 이 시험기는 전단변위에 의한 첩촉면적의 변화량을 계산하여 하중변화량을 조절하여 일정수직응력상태를 유지한다. 수직하중에 따른 시험기 강성에 의한 변화향이 제어 프로그램 내에서 제어되어 순수한 시편의 변위량을 출력하도록 하였다. 전단하중에 따른 시험기 강성에 의한 변위량은 상, 하부 전단상자의 상대변위 측정으로 최소화하였다. 전단거동 중의 자유도는 전당방향에 대하여 수평이도, 연직이동, 피칭, 롤링이 가능하도록 하였다. 자연절리면을 모사한 석고시편에 대하여 일정 수직응력 제어, 일정수직하중제어 그리고 무한 강성제어 조건으로 시험하여 제어상태 검증 및 비교를 하였다. 또한 경사각이 16.7˚와 22.6˚인 톱니형 시편에 대하여 시험한 결과 경사각 16.7˚와 22.6˚는 JRC로 10과 15를 나타내었으며, 첨두팽창각이 첨두전단강도에서 발생되며, Barton의 모델과 잘 일치함을 보였다.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.392-393
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• 2018

BLDC 전동기는 역기전력이 사다리꼴이며 운전은 전기각 $60^{\circ}$로 구분되어 상전환이 이루어진다. 이와 같은 $60^{\circ}$ 구간에서 전압은 균일하게 인가되어야 하며, 이를 위하여 시비율을 조절하고 각 구간마다 균일한 전압이 출력될 수 있도록 한다. 그러나 $60^{\circ}$의 상전환 시점과 PWM의 인가시점이 일치하지 않으며, 이에 따라 시비율을 일정하게 제어하더라도 각 $60^{\circ}$구간의 전압이 균일하지 않게 될 수 있다. 이와 같은 현상은 $60^{\circ}$ 구간의 시간이 짧아져서 PWM 펄스개수가 줄어드는 고속 구간에서 오차가 더 크게 반영될 수 있다. 이를 보완하기 위하여 본 논문에서는 PWM의 주기 시점과 상전환 시점을 동기화하여 제어하는 방안을 제안하고, 시험을 통하여 검증하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05d
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• pp.346-351
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• 1996

현재 원전의 내진해석 절차에는 수직방향의 동적해석모델을 집중질량-보요소 모델로 나타내고 있으나, 층슬래브이 동적유연성을 합리적으로 고려할 수 있는 기준이 마련되어 있지 않다. 본 연구에서는 벽체로 지지된 4변고정 슬래브를 유한요소모델 및 집중질량모델로 이상화한 후 고유치해석 및 시간이력해석을 수행한 결과, 현재 층슬래브의 수직응답을 얻기 위해 통상적으로 사용되는 일련의 단자유도계 모델은 이에 상응하는 유한요소모델의 각 모드에 대한 평균응답밖에 주지 못함을 확인하였고, 각 모드 층슬래브의 최대응답을 얻기 위해서는 각 고유진동수가 최소한 이자유도계로 모델링되어야 하며, 이때 이자유도계에 분배할 질량 및 연결보의 강성크기가 각각 1:5와 1:6일때 잘 일치함을 확인하였다. 또한 이렇게 결정된 모델링 방법은 실제 전단벽 구조물의 해석을 통해 그 적용성이 입증되었다.

• The Journal of Korean Academy of Sensory Integration
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• v.14 no.1
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• pp.1-8
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• 2016

Objective : The purpose of this study was to determine the reliability of Test of Playfulness (ToP) in Attention Deficit Hyperactivity Disorder (ADHD) children. Methods : Twenty ADHD children participated in this study. To determine inter-rater reliability, two raters was evaluated by Test of Playfulness scores and analyzed Kappa coefficient and total agreement and intraclass correlation coefficient (ICC). Results : Total agreement was the range of 75%~95% and the Kappa coefficients was the range of. 45~1.00. Analyzing inter-rater reliability by ICC showed very high reliability: Intrinsic motivation was .96, internal control was .98, suspension of reality was .90, framing was .98, total score was .99. Conclusion : A reliability of Test of Playflness of children with ADHD showed that high. On the basis of this study, it will provide availability for clinical evaluation of children with ADHD, and basic study on the play of children with ADHD.

• Korean Journal of Psychosomatic Medicine
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• v.19 no.1
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• pp.34-40
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• 2011

Objectives: The purpose of this study is to test the reliability of the Korean version of self-compassion scale (K-SCS). Methods: The total of 484 participants were included in this study. Reliability studies were conducted and internal consistency were examined. Results: The internal consistency of the K-SCS was 0.76, and test-retest reliability was 0.53. Conclusion: The K-SCS appeared to be a reliable instrument for assessing self-compassion in Korean population. If supplements further studies of the validity, this scale may be applicable in clinical trials, research, clinical practice.

• Journal of the Korean GEO-environmental Society
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• v.9 no.5
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• pp.71-81
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• 2008

Active earth pressure formula, which can consider the effects of ground surface inclination, inclination of inside retaining wall face, wall friction, line load, uniform load, soil cohesion and adhesion, was derived based on the force equilibrium principle. In order to verify the accuracy of this proposed formula, the calculated active earth pressures by the proposed formula were compared with those of graphical solutions. Also, the active earth pressures determined by the proposed formula were compared with those by Coulomb's, Rankine's and Mazindrani's solution under specific conditions. The results matched quite well not only with the graphical solutions but also with those by three other methods. Also, the trend of active earth pressures by the proposed formula were corresponded with results of experimental study by Fang, et al. It can be concluded that this generalized formula not only can overcome the limitations of Rankine's, Coulomb's and Mazindrani's active earth pressure formula but also can consider the external loading conditions.

• Korean Business Review
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• v.18 no.1
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• pp.43-57
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• 2005

This paper investigate to test the validity of the basic assumptions of strategic trading models with the broker and informed trader using daily closing data of KOSPI 200 stock index futures for the year 2001-2003. Major results are summarized as follows: (i) For these years, while foreign investors and brokerage companies traded for the directions consistent with the model, brokerage companies and individual investors traded for inconsistent directions. (ii) Cross correlation function (CCF) analysis shows no systematic dependency in the trading between all three participants(foreign investor, brokerage companies and individual investors) for these years. (iii) Chi-square validity test for the 30 days of the largest unexpected trading volume shows some systematic dependency in the trading between three participants for these years. Finally, some limitations of this paper and direction for further research were suggested.

• Journal of The Geomorphological Association of Korea
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• v.21 no.4
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• pp.19-40
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• 2014

Rock rebound values and chemical compositions of Gamak island at Sangha, Gochang, Jeollabuk do are analysed as a part of geomorphic survey of that area. Some corestones are formed by deep weathering found from the summit of rock mass of Gamak island, while the rocks a part of weathering front are exposed at the foot of the island. Rebound values of rock increase toward coastal plain, so summit would be weak in resistance to erosion. It can be assumed that chemical weathering is more active at the summit by the chemical index of alteration and changes in chemical composition ratio. However it should be mentioned that the samples are taken from the surface of the rock mass that more fresh part will be exposed when the weathered parts are removed. The chemical composition and CIA values of the polygonal cracks found from on the surface of weathering rind showed that this part has values between those of the summit and the footslope. The bottom of weathering rind with polygonal cracks has higher CIA value than those of the surface. Though it supports the result from the Bisul Mt., there also difference in the ratio of SiO2. It looks caused by the difference in weathering environment and chemical difference in parent rock. In summary Gamak island is the remnants of weathering front after removal of weathered material. The removal processes are more active at the footslope where the coastal processes are stronger than the summit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.5
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• pp.1319-1324
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• 1998

The phase and frequency commands of a ratating radar system that utilizes frequency scanning to steer the beam in the azimuth direction and phase shifters in the elevation direction are derived in terms of the angles of the groung based coordinate system. The antenna type considered is slotted arrays that are easy to construct at such high microwave frequency as the X band. The frequency that has non-linear characteristics as a functio ofthe elevation angle is plotted and the derived frequency equation is aproximated to be a simple form to reduce the calculation time for real time multi-function radar systems. It is shown that the approximated frequency command is in good agreement with the exact one if the range of azimuth scanning is limited by ${\pm}10^{\circ}$.