• Journal of Korean Library and Information Science Society
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• v.47 no.3
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• pp.187-211
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• 2016

The present study investigates the seventh and the eighth graders' perception of Free Learning Semester Programs offered by libraries by developing a survey questionnaire on students' needs for Free Learning Semester Programs of Libraries. The skills that middle school students want to improve in Free Learning Semesters are career exploration skills, and the type of Free Learning Semester that is most intensively implemented is career exploration activities. Programs are often offered in the form of experiential classes. Regarding the activities that the students want to participate during Free Learning Semester, the most preferred activities included field experience activity in the career exploration domain, cooking class in the student choice program, smartphone app development in club activities, design activity in the art domain, the badminton in the physical education domain, and using iPad in the information use skills. In addition, among the library programs in coordination with Free Learning Semester, the students liked the occupational experience program most. Future studies need to include the development and implementation of Free Learning Semester Programs based on students' opinions, and investigate their satisfaction with the Free Learning Semester Programs offered by libraries.

• Journal of The Korean Association For Science Education
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• v.31 no.2
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• pp.143-152
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• 2011

The purpose of this study is to investigate the contents of open inquiry activities of the newly revised 2007 National curriculum for each grade level and to teach open inquiry activities and selection of rational inquiry activities. For this study, 470 elementary students in Seoul, ranging from 3rd to 6th grades were surveyed. The experiment plans written by students were analyzed based on the analysis criteria. These criteria consisted of the reason for the selection, type, and suitability of open inquiry activities. The reason for selecting open inquiry activities were analyzed according to the reason why they want to conduct the activity, degree of getting help and the object of getting help. The types of the open inquiry activities were analyzed according to the field of inquiry, the inquiry method and the period of inquiry. Suitability of the open inquiry activities were analyzed according to the reason of suitability or unsuitability.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.353-360
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• 2016

Tests of hydraulic rock splitting were conducted using double packer at the 1, 2 free surface in the limestone mining and granodiorite Suksan area, respectively. The method of hydraulic rock splitting was applying hydraulic power in the interval layer using double packer. As a result of tests, a crack occurred. At about 6.5 MPa and 13 MPa, a crack occurred in 2 free surface. Any crack did not occur in the 1 free surface. Rather, used 1 double packer was broken in the 1 free surface. Also, it was confirmed that the water pressure of the interval increased through the existing crack and the new crack in the test areas.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.2
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• pp.69-78
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• 2013

This study is constructed to investigate the sloshing effect on the motions of a two-dimensional rectangular cylinder experimentally and numerically. The modes of motion under consideration are sway and roll, and also experimental cases are divided by two categories; 1-DoF roll motion and 2-DoF motion (Coupling sway and roll). It is found that the sway response is considerably affected by the motion of the fluid, particularly near the sloshing natural frequency, while the roll response changes comparatively small. The dominant mode of motion is analyzed for 2-DoF experiments as well. The measured data for 1-DoF motions is compared with numerical results obtained by the Multi-modal approach. The numerical schemes vary in detail with the number of dominant sloshing modes; i.e. there is a single dominant mode for the Single-dominant method, while the Model 2 method assumes that the first two modes are superior. For the roll motion, numerical results obtained by the two different methods are relatively in good agreement with the experiments, and these two results are similar in most wave frequency range. However, the discrepancies are apparent where the fluid motion is not governed by a single mode. But both of numerical methods over-predict the motion at the vicinity of the sloshing natural frequency. In order to correct the discrepancy, the modal damping needs to be investigated more precisely. Furthermore, another multi-modal approach, such as the Boussinesq-type method, seems to be required in the region of the intermediate liquid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.290-296
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• 2019

Head-up displays for vehicles play an important role in displaying various information about the safety and convenience of driving on the windshield of the vehicle. In this study, ultra-precision machining was performed and evaluated as a method for machining a large-area aspheric free-form mirror that is applicable to augmented reality technology. Precision diamond cutting is highly accurate and suitable for the production of advanced parts with excellent surface integrity, low surface roughness, and low residual stress. By using an aspheric free-form mold, it is possible to improve the optical transfer function, reduce the distortion path, and realize a special image field curvature. To make such a mold, the diamond cutting method was used, and the result was evaluated using an aspherical shape-measuring machine. As a result, it was possible to the mold with shape accuracy (PV) below $1{\mu}m$ and surface roughness (Ra) below $0.02{\mu}m$.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1268-1271
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• 2007

트렌치 수로에서 동수압을 고려한 자유수면 흐름을 해석하고 난류 모형의 적용성을 제시하였다. 본 연구에 사용된 지배방정식으로 비정상 상태의 비압축성 유체에 대한 연속방정식과 비점성 Navier-Stokes 방정식을 사용하였다. 난류완결문제를 해결하기 위해서 $\kappa-\varepsilon$방정식을 사용하여서 난류 와점성을 구할 수 있다. 자유수면과 동수압을 고려하기 위하여 3단계로 나누어서 해석하였다. 제 1단계에서는 운동량방정식을 연직방향에 대해 음해적으로 차분하였다. 제2단계에서는 유속과 동수압 보정항으로 이루어진 식을 연속방정식에 대입하여 타원형 방정식인 동수압-포와송 방정식을 해석하여 얻어지는 유속은 질량보존법칙을 만족하게 된다. 마지막으로 자유수면과 최종유속을 보정 및 계산하였다. 본 연구에서 제시한 수치모형을 검증하기 위해서, 트렌치 수로에서 난류의 흐름에 변화를 고려하기 위해 수치모의를 하였다. 전반적으로 수치모의에 의한 결과와 실험 자료가 일치하는 경향을 보였다.

• Journal of Korean Port Research
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• v.12 no.1
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• pp.87-93
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• 1998

For the calculation of the free-surface elevation, a new finite difference scheme is studied where the third derivative term for the wave elevation is artificially added in the Eulerian expression of the free-surface boundary condition. The paper presents a comparative analysis with simulations performed by the classical MAC method. More schematic computations are carried out by changing the submergence-depth and angle-of-attack. The present study shows that this new method is very efficient for the simulation of free-surface elevation around the trailing edge.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.1 s.94
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• pp.46-52
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• 2005

This paper is concerned with the application of perturbation method to the dynamic analysis of free-free beam. In general, the rigid-body motions and elastic vibrations are analyzed separately. However, the rigid-body motions cause vibrations and elastic vibrations also affect rigid-body motions in turn, which indicates that the rigid-body motions and elastic vibrations are coupled in nature. The resulting equations of motion are hybrid and nonlinear. We can discretize the equations of motion by means of admissible functions but still we have to cope with nonlinear equations. In this paper, we propose the use of perturbation method to the coupled equations of motion. The resulting equations consist of zero-order equations of motion which depict the rigid-body motions and first-order equations of motion which depict the perturbed rigid-body motions and elastic vibrations. Numerical results show the efficacy of the proposed method.

• The Korean Journal of Applied Statistics
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• v.8 no.1
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• pp.119-131
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• 1995

Based on Monte-Carlo simulation results we propose a robust analysis of variance procedure by utilizing trimmed mean and Winsorized variance. We deal with mainly the one-way classification case. We evaluate the empirical distribution of a pseudo-F statistic based on symmetrically Winsorized sum of squares when the population is normally distributed.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.3
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• pp.1-1
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• 2001

본 논문에서는 복잡 배경으로부터 임의의 다중물체를 효과적으로 검출함과 동시에 고속 분할할 수 있는 문맥자유 마커제어 분수계 변환 (context-free marker controlled watershed transform)을 제안하였다. 먼저 잡음에 강건한 주목 연산자 (attention operator)를 써서 복잡 배경 속의 여러 물체 별로 그 위치를 검출하여 문맥자유 마커를 추출하고, 이를 마커로 한정된 레이블링 (marker constrained labeling)을 하여 최소값 부과과정이 필요 없는 문맥자유 마커제어 분수계 변환을 제안함으로써 과분할없이 신속하게 분할할 수 있도록 하였다. 다중 물체가 포함된 복잡 영상에 적용 실험하여, 대상 물체에 대한 사전정보 없이도 과분할과 처리시간을 대폭 줄여 효과적으로 다중 물체를 검출함과 동시에 고속 분할이 가능함을 확인 할 수 있었다.