• Journal of Biosystems Engineering
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• 제42권1호
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• pp.1-11
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• 2017

Purpose: Methods: Three-dimensional CFD modeling was conducted to analyze the flow structure and discharge flow rate corresponding to the variation in the geometry of the flow channel in a microtube. Additionally, experiments were carried out, and the discharge flow rate was measured at various inlet pressures and inclination angles of the microtube. Results: The quantitative data of velocity distribution and discharge flow rate were obtained. As the width and length of the microtip increased, the discharge flow rate decreased significantly because of the increase in the loss of pressure along the microtube. As the depth of the microtip increased, the flow rate also increased because of the reduction in the flow resistance. However, in this analysis, the variation in the angle of the microtip did not influence the flow rate. From the experimental results, it was observed that the flow rate increased linearly with the increase in the inlet pressure, and the effects of the inclination angle were not clearly observed in those test cases. The values of the flow rate obtained from the experiments were significantly lower than that obtained from the CFD analysis. This is because of the distortion of the shape of the flow path inside the microtube during the fabrication process. The distortion of the flow path might decrease the flow cross-sectional area, and it would increase the flow resistance inside the microtube. The variation in the flow rate corresponding to the variation in the inlet pressure showed similar trends. Conclusions: Therefore, the results of the numerical analysis obtained from this study can be efficiently utilized for optimizing the shape of the microtip inside a microtube.

• 천문학회보
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• 제41권1호
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• pp.40.2-41
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• 2016

To understand the observed kinematics in the narrow-line region (NLR) of type 2 AGNs, we construct a model of 3-D biconical outflow combined with a thin dust plane. The model consists of two identical cones whose apex is located at the nucleus, and the cones are axisymmetric with respect to the bicone axis. After we define the properties of the bicone and the dust plane, we calculate a spatially integrated velocity and velocity dispersion along the line-of-sight using various physical parameters. As we test the effect of model parameters, we find three key parameters determining the integrated kinematics: intrinsic outflow velocity, bicone inclination, and the amount of dust extinction. The velocity dispersion increases as the intrinsic outflow velocity or the bicone inclination increases, while the velocity shift increases as the amount of dust extinction increases. We confirm that the integrated velocity dispersion can be a good indicator of the intrinsic outflow velocity unless dust extinction is not very strong (>~80%), while the effect of dust extinction can be alleviated by combining the integrated velocity and the velocity dispersion. Based on the simulated velocity distributions using the 3-D models, the variety of the observed [O $_{III}$] line profiles of type 2 AGNs can be well reproduced. In addition, we perform Monte Carlo simulations based on the different sets of model parameters. By comparing the model results with the observed [O $_{III}$] kinematics of ~39,000 SDSS type 2 AGNs (Woo et al. 2016), we find that the observed [O $_{III}$] velocity-velocity dispersion distribution is well reproduced by the biconical outflow model, enabling us to constrain the intrinsic physical parameters of outflows.

• 한국지반공학회논문집
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• 제31권12호
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• pp.59-69
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• 2015

본 연구는 절리형성 암반지층 굴착벽체에 작용하는 토압에 대한 암반종류 및 절리조건 (전단강도 및 절리경사각)뿐만아니라 절리군의 수에 대한 영향을 조사하였다. 모델실험 및 그에 대한 시뮬레이션결과를 토대로 다양한 수치해석적 매개변수연구가 수행되었다. 해석결과, 굴착벽체에 발생하는 토압은 절리군에 포함된 절리경사각에 큰 영향을 받았지만, 절리군의 수 자체만으로는 토압에 큰 영향을 주지는 않았다. 연구결과는 또한 토사지반에서의 토압인 Peck 토압과 상호 비교되었으며, 이를 통해 절리가 형성된 암반지층 굴착벽체에 발생하는 토압은 토사지반에서 발생하는 토압과 크게 다를 수 있다는 것을 파악하였다. 본 연구를 통해서 향후 암반지층에 설치되는 굴착벽체 설계시 적용하는 토압은 암반종류 및 절리조건과 더불어 절리군에 포함된 절리경사각을 고려하여 산정해야 할 것으로 판단된다.

• Journal of Oral Medicine and Pain
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• 제44권2호
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• pp.59-64
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• 2019

Purpose: The aim of this study was to analyse and evaluate the morphology of the articular eminence of temporomandibular joint in young Korean adults using cone-beam computed tomography (CBCT). Methods: One hundred seventy-one subjects (59 males, 112 females) in the 20s were examined using CBCT. Width and height of articular eminence, top-roof line angle, best-fit line angle, joint space were measured. For the group comparisons, independent t-test was used with the level of significance established at $p{\leq}0.05$. Results: In asymptomatic young Korean adults, average eminence width was $9.49{\pm}1.62mm$ in males and $9.33{\pm}1.36mm$ in females. Average eminence height was $7.23{\pm}1.81mm$ in males and $6.82{\pm}1.31mm$ in females. Average eminence inclination of measured by top-roof line angle was $37.09^{\circ}{\pm}7.74^{\circ}$ in males and $36.12^{\circ}{\pm}5.65^{\circ}$ in females. Average eminence inclination measured by best-fit line angle was $50.79^{\circ}{\pm}11.49^{\circ}$ in males and $48.43^{\circ}{\pm}9.05^{\circ}$ in females. Average joint space was $3.03{\pm}0.67mm$ in males and $2.63{\pm}0.68mm$ in females. Conclusions: Increasing age did not affect the morphology of the articular eminence in asymptomatic young Korean adults. Males had slightly larger eminence width, height, top-roof line angle, best-fit line angle and joint space, but no statistical significance (p>0.05) was observed only in the joint space (p=0.001). There was no side-to-side difference in morphology (p>0.05).

• Journal of Positioning, Navigation, and Timing
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• 제8권2호
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• pp.79-85
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• 2019

The mission tasks of polar exploration utilizing unmanned systems such as glacier monitoring, ecosystem research, and inland exploration have been expanded. To facilitate unmanned exploration mission tasks, precise and robust navigation systems are required. However, limitations on the utilization of satellite navigation system are present due to satellite orbital characteristics at the polar region located in a high latitude. The orbital inclination of global positioning system (GPS), which was developed to be utilized in mid-latitude sites, was designed at $55^{\circ}$. This means that as the user is located in higher latitudes, the satellite visibility and vertical precision become worse. In addition, the use of satellite-based wide-area augmentation system (SBAS) is also limited in higher latitude regions than the maximum latitude of signal reception by stationary satellites, which is $70^{\circ}$. This study proposes a local-area augmentation system that additionally utilizes Global Navigation Satellite System (GLONASS) considering satellite navigation system environment in Polar Regions. The orbital inclination of GLONASS is $64.8^{\circ}$, which is suitable in order to ensure satellite visibility in high-latitude regions. In contrast, GLONASS has different system operation elements such as configuration elements of navigation message and update cycle and has a statistically different signal error level around 4 m, which is larger than that of GPS. Thus, such system characteristics must be taken into consideration to ensure data integrity and monitor GLONASS signal fault. This study took GLONASS system characteristics and performance into consideration to improve previously developed fault detection algorithm in the local-area augmentation system based on GPS. In addition, real GNSS observation data were acquired from the receivers installed at the Antarctic King Sejong Station to analyze positioning accuracy and calculate test statistics of the fault monitors. Finally, this study analyzed the satellite visibility of GPS/GLONASS-based local-area augmentation system in Polar Regions and conducted performance evaluations through simulations.

• Geomechanics and Engineering
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• 제29권5호
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• pp.567-582
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• 2022

In the present study, a series of physical experiments and numerical simulations were conducted to investigate the effects of mode I and mixed-mode I/II cracks on the fracture modes and stability of roadway tunnel models. The experiments and simulations incorporated different inclination angle flaws under both static and dynamic loads. The quasi-static and dynamic testing were conducted by using an electro-hydraulic servo control device and drop weight impact system (DWIS), and the failure process was simulated by using rock failure process analysis (RFPA) and AUTODYN software. The stress intensity factor was also calculated to evaluate the stability of the flawed roadway tunnel models by using ABAQUS software. According to comparisons between the test and numerical results, it is observed that for flawed roadways with a single radical crack and inclination angle of 45°, the static and dynamic stability are the lowest relative to other angles of fractured rock masses. For mixed-mode I/II cracks in flawed roadway tunnel models under dynamic loading, a wing crack is produced and the pre-existing cracks increase the stress concentration factor in the right part of the specimen, but this factor will not be larger than the maximum principal stress region in the roadway tunnel models. Additionally, damage to the sidewalls will be involved in the flawed roadway tunnel models under static loads.

• 해양환경안전학회지
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• 제22권6호
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• pp.654-659
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• 2016

정기적으로 운행하던 여객선 세월호가 소각도 변침 중에 급격히 횡경사되면서 전복하는 사고가 최근 발생하였다. 선박의 횡경사가 발생 원인에 따라 Heel, List, Loll로 구분되어 그 원인에 따라 적절히 대응해야 함에도 불구하고 음의 복원력에 의한 횡경사(Loll)에 대한 항해사들의 인식이 매우 부족하다. 이에 본 연구에서는 음의 복원력에 의한 횡경사에 대한 개념, 발생과정 및 횡경사각 산정법을 고찰하고, 박스형 모형선을 이용한 수조 실험을 통해 실제 횡경사각의 발생과 음의 복원력 정도에 따른 횡경사각의 크기를 이론식과 비교 검증하였다. 그 결과, 실험값은 이론식에 의한 횡경사각 계산값과 잘 일치하였으며, 음의 복원력에 의한 횡경사의 특성으로서 좌현과 우현에서 동일한 각도의 횡경사가 발생하였다. 본 연구를 통하여 음의 복원력을 가진 선박의 거동에 관한 인식이 확대되고 과거 원인이 불명확한 전복사고의 원인분석에 참조되길 기대한다. 향후 음의 복원력에 의한 횡경사에서의 부적절한 대응으로 전개될 수 있는 선박의 거동에 관한 실험연구 및 사례연구가 필요하다고 사료된다.

• 한국초등수학교육학회지
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• 제14권1호
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• pp.23-41
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• 2010

본 연구는 일본의 제등승(齊藤昇)(Saito Noboru) 교수에 의해 실천 연구되었던 등산학습법을 초등학교 4, 6학년 학생들에게 적용하여 수학적 창의성과 수학적 창의성 태도, 수학 학업성취도에 미치는 효과를 분석함으로써 수학적 창의성을 신장시킬 수 있는 방안을 모색하는데 그 목적을 두었다. 본 논문에서는 실험집단과 비교집단을 형성하여 t-검증한 결과, 등산학습법이 수학적 창의성 및 수학적 창의성 태도에는 긍정적인 영향을 주었으나 학업성취에서는 유의미한 차이를 나타내지 못했다는 결과와 함께 이러한 결과에 대한 논의와 수업전략을 언급한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.368-373
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• 1997

The transition from a statified wavy to a slug flow has been analyzed considering the mechanistic forces acting on the wave crest in a nearly horizontal air-water countercurrent flow. To verify the results of the analysis, a series of experiments have been performed changing the inclination angle of the test section. Comparisons of the theoretical predictions with experimental data show a good agreement and the results show that the present model gives similar results of Taitel and Dukler's in the case of inclined pipes. However, at high superficial liquid velocity, the results of present work agree more closely with data than that of Taitel and Dukler's. Also, predictions of the present model gives a very close agreement with the experimental data for various tube sizes obtained by others.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.80-83
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• 2004

The FRP plate or sheet bonding technology was widely used for strengthening deficient RC structures. The strengthened structure using FRP bonding scheme, however, experience the complex interfacial behaviour which is difficult to predict. Therefore, the unbonded scheme using some anchorage device can be is an alternative for more reliable design. In this study, wedge-type anchor for FRP plate is developed for the unbonded flexural strengthening scheme. Some parameter study using 2D finite element method is performed. The analysis parameters are taken as wedge-guide friction coefficients, wedge- FRP ,.friction coefficient and wedge inclination angle. Based on the parameter study, more efficient anchors are designed and tested. The test result show that the developed anchor assure about $80\%$ FRP strength, which is higher performance than typical bonding scheme. Last, 3D finite element analysis is performed.