• 대한조선학회논문집
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• 제56권6호
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• pp.550-558
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• 2019

The roll motion of a general vessel, which is more influenced by resonance as compared to other motions, adversely affects the passenger and hull. Therefore, reducing the roll motion through an anti-rolling system is critical, and most ships use various devices such as anti-rolling tanks, bilge keels, and fin stabilizers to accomplish this. In this study, a simplified model is developed for the application of an anti-rolling device for unmanned semi-submersible vessels. The applied anti-rolling device is installed on the stern and stem of a ship using a pair of servo motors with added weight, and the motor is controlled through the Arduino. The moment of the motor is designed and implemented based on a mathematical model such that it is calculated through the restoring force according to the heel angle of the ship. The performance of the proposed system was verified by utilizing the roll damping coefficient calculated by the free-roll decay test and logarithmic decrement method and was validated by a towing tank test. The system is expected to be used for unmanned vessels to perform sustainable missions.

• 분석과학
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• 제34권3호
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• pp.115-121
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• 2021

에탄올 대사체인 에틸글루쿠로나이드(ethyl glucuronide, EtG)와 에틸설페이트(ethyl sulfate, EtS)는 에탄올 섭취의 직접적인 지표물질로서 여러 생체 시료에서 법과학적으로 다양하게 연구되고 있다. 부검 변사자에게서 검출된 에탄올이 사망 전 음주에 의한 것인지 사후 부패에 의해 생성된 에탄올인지 판단하기 위해서는 에탄올 대사체를 분석할 필요가 있다. 일반적으로 혈액에서 에탄올과 함께 EtG, EtS를 검출하고 있지만 부패 상황에 따라 혈액을 확보하는 것이 어려우므로 조직 생체시료를 이용해 에탄올 대사체를 검출함으로써 이를 대체해야 한다. 본 연구에서는 조직 중에서 비장을 선택하여 LC-MS/MS를 이용해 EtG, EtS를 검출하였으며 시험법이 적합한 방법인지를 증명하기 위해 밸리데이션을 수행하여 법과학적 감정에 사용할 수 있는 분석법을 완성하고 실제 부검 사례에 적용하였다.

• 한국소음진동공학회논문집
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• 제21권3호
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• pp.248-257
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• 2011

It was reported recently that railpads can be included as a continuous elastic support of the rail and the model was justified from experiments. In general, however, railpads are installed discretely on sleepers with a regular span. The effect of the discrete railpad was not clearly examined so far in such a high frequency range. In this paper, the effect of the railpads in track modelling for high frequencies is investigated by means of the finite element analysis. To do that, the railpads are regarded as 'a continuous elastic support' and 'a discrete elastic support' in this paper. The dispersion relations and decaying features are predicted and compared between the two models up to 80 kHz.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 추계 학술대회논문집
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• pp.134-140
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• 2007

Nonlinear parabolized stability equations for compressible flow in general curvilinear coordinate system are derived to deal with a broad range of transition prediction problems on complex geometry. A highly accurate finite difference PSE code has been developed using an implicit marching procedure. Blasius flow is tested. The results of the present computation show good agreement with DNS data. Nonlinear interaction can make the T-S fundamental wave more unstable and the onset of its amplitude decay is shifted downstream relative to linear case. For nonlinear calculations, rather small difference in initial amplitude can produce large change during nonlinear region. Compressible secondary instability at Mach number 1.6 is also simulated and showed that 1.1% initial amplitude for primary mode is enough to trigger the secondary growth.

• 대한기계학회논문집B
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• 제27권4호
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• pp.504-510
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• 2003

Simultaneous measurements of turbulent velocity and concentration field in a stirred mixer tank are carried out by using PIV/LIF technique. Instantaneous velocity fields are measured with a 1K$\times$1K CCD camera adopting the frame straddle method while the concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by the second pulse of Nd:Yag laser light. Image distortion due to the camera view-angle is compensated by a mapping function. It is found that the general features of the mixing pattern are quite dependent on the local flow characteristics during the rapid decay of mean concentration. However, the small scale mixing seems to be independent on the local turbulent velocity fluctuation.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
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• pp.83-83
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• 2002

목적： 현재 임상적으로 사용되고 있는 확산경사자장의 세기 이상( > 1200)의 강한 확산 경사자장이 가해진 경우 뇌구조물들의 확산계수값을 조사하고 고자장(Bo = 3T)에서 이러한 강한 확산 경사자장을 이용하는 경우 1.5T에서 시행하는 경우와의 차이점을 비교 연구해보고자 하였다. 대상 및 방법： 정상 성인 3명을 대상으로 b-value를 0부터 3500까지 변화시키며 확산강조영상을 최대경사자장 40 mT/m, slew rate 150 T/m/s의 경사자장계가 장착된 3T MR scanner (General Electric, USA)에서 획득하였다. 사용한 펄스열은 Stejskal-Tanner type의 확산강조 경사자장이 포함된 single-shot SE EPI를 사용하였으며 영상획득시 사용한 파라미터는 다음과 같다. TR/TE= 10000/95.1, Thickness/space=512mm, FOV=24$\times$21cm, Matrix=128$\times$128, NEX=1 뇌구조물들에 관심 영역을 설정하고 b-value에 따른 신호감소를 측정하였다. 측정된 데이터를 hi-exponential decay 모델을 이용하여 분석하였다.

• 건축역사연구
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• 제3권1호
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• pp.45-55
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• 1994

This study deals with the method of constructing and repairing column, important element of traditional wooden building. Column should have long-lasting strength and resistance to decay and vermin because it is more important in role of structure than in that of ornament. And the rotten or the split part of wooden column should be repaired regularly or irregularly. First of all, this study treats of general character related to the life length and strength of wood. Then it describes the technical method of choosing proper wood for column and that of carpentering, painting, and mending wooden column.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2002년도 추계학술대회 논문집
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• pp.101-104
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• 2002

Simultaneous measurement of turbulent velocity and concentration field in a stirred mixer tank is carried out by using PIV/LIF technique. Instantaneous velocity fields are measured by a $1K\times1K$ CCD camera adopting the frame straddle method while the concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by the second pulse of Nd:Yag laser light. Image distortion due to the camera view-angle is compensated by a mapping function. It is found that the general features of the mixing pattern are quite dependent on the local flow characteristics during the rapid decay of mean concentration. However, the small scale mixing seems to be independent on the local turbulent velocity fluctuation.

• Bulletin of the Korean Chemical Society
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• 제13권3호
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• pp.325-331
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• 1992

By using the general theoretical framework proposed recently for treating the fluorescence quenching kinetics, we investigate the effect of light pulse intensity on the decay of fluorescence which follows excitation of fluorophors by the light pulse of very short but finite duration. It is seen that conventional theory breaks down when the exciting light pulse has a pulse width comparable to the fluorescent lifetime and its intensity is very high. We also find that even when the light intensity is not too high, conventional theory may fail in either of the following cases: (i) when the quencher concentration is high, (ii) when there is an attractive potential of mean force between the fluorophor and quencher, or (iii) when the energy transfer from the fluorophor to the quencher may also occur at a distance, e.g., via dipole-dipole interaction. The validity of the predictions of the present theory may thus be tested by fluorescence quenching experiments performed under such situations.

• 대한소아치과학회지
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• 제24권1호
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• pp.220-234
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• 1997

The purpose of this study was to investigate the knowledge and attitude of a group of mothers who had infants about baby bottle tooth decay(BBTD) and dental caries prevention. The sample consisted of 261 mothers who had infants from 6 to 36 months from certain areas of Dae-jeon city. The mothers were asked to answer a questionnaire which included a series of questions regarding general information cencerning the infant and his mother, knowledge about BBTD and methods of prevention using fluoride, knowledge about behavioral risk factors contributing to caries of the infant, attitude toward oral health care of the infant, opinions regarding the effectiveness of methods to prevent dental caries and sources of oral health information. he results of this study were as follow. 1. 85.4% of the respondents thought that prolonged bottle feeding would harm the teeth of the infant, but 77% of the respondents had never heard of baby bottle tooth decay. 2. Levels of knowledge about methods of prevention using fluoride were relatively low and there were significant relationships between the levels of this knowledge and the educational level of the respondents(P<0.05). 3. Only 7.3% of the respondents thought that prolonged breast feeding would harm the teeth of the infant. 4. Overall oral health care of the infants was relatively insufficient. 5. Only 28.7% of the respondents selected either when the first tooth erupt or deciduous dentition complete as the time a infant should first be seen by a dentist. 6. 64.6% of the respondents thought that toothbrushing should be instituted once the first tooth appears. 7. Among the six methods of preventing caries in infants, respondents ranked the effective of fluoride lower than making regular dental visits and reducing intake of sugared foods. 8. Most frequently cited sources of information about dental health were newspapers, magazines and books(65%), followed by friends, neighborhoods and families (55%).