• 한국자동차공학회논문집
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• 제20권4호
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• pp.46-51
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• 2012

Injection pressure, an important factor in filling process, should be minimized to enhance injection molding quality. Injection pressure can be controlled by valve gate open timing. In this work, we decided the valve gate open timing to minimize the injection pressure. To solve this design problem, we integrated MAPS-3D (Mold Analysis and Plastic Solution-3Dimension), a commercial injection molding CAE tool, to PIAnO (Process Integration, Automation and Optimization), a commercial PIDO (Process Integration, and Design Optimization) tool using the file parsing method. In order to reduce computational cost, we performed an approximate optimization using meta-models that replaced expensive computer simulations. At first, we carried out DOE (Design of Experiments) using OLHD (Optimal Latin Hypercube Design) available in PIAnO. Then, we built Kriging models using the simulation results at the sampling points. Finally, we used micro GA (Genetic Algorithm) available in PIAnO. Using the proposed design approach, the injection pressure has been reduced by 13.7% compared to the initial one. This design result clearly shows the validity of the proposed design approach.

• Advances in aircraft and spacecraft science
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• 제4권2호
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• pp.145-167
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• 2017

The presented paper gives an overview of several projects addressing the experimental characterization and control of the buffet phenomenon on 3D turbulent wings in transonic flow conditions. This aerodynamic instability induces strong wall pressure fluctuations and therefore limits flight domain. Consequently, to enlarge the latter but also to provide more flexibility during the design phase, it is interesting to try to delay the buffet onset. This paper summarizes the main investigations leading to the achievement of open and closed-loop buffet control and its experimental demonstration. Several wind tunnel tests campaigns, performed on a 3D half wing/fuselage body, enabled to characterize the buffet aerodynamic instability and to study the efficiency of innovative fluidic control devices designed and manufactured by ONERA. The analysis of the open-loop databases demonstrated the effects on the usual buffet characteristics, especially on the shock location and the separation areas on the wing suction side. Using these results, a closed-loop control methodology based on a quasi-steady approach was defined and several architectures were tested for various parameters such as the input signal, the objective function, the tuning of the feedback gain. All closed-loop methods were implemented on a dSPACE device able to estimate in real time the fluidic actuators command calculated mainly from the unsteady pressure sensors data. The efficiency of delaying the buffet onset or limiting its effects was demonstrated using the quasi-steady closed-loop approach and tested in both research and industrial wind tunnel environments.

• 한국전산구조공학회논문집
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• 제32권4호
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• pp.233-240
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• 2019

인장 강도는 복합 재료를 설계하기 위한 필수 변수이므로 개방 홀 인장 시험을 통해 복합 재료의 인장 강도를 측정한다. 그러나 인장 시험을 올바르게 모델링하는 것은 섬유와 매트릭스 손상, 층간분리 및 섬유와 매트릭스 사이의 손상 같은 다양한 손상을 수반하기 때문에 매우 어려운 과제다. 따라서 섬유와 매트릭스 사이의 면내 파괴 및 층간분리를 평가하기 위해 본 연구에서는 점진적 손상 모델을 개발하였다. 하신 손상 모델과 응집 영역 접근법을 층과 층간분리를 모델링하는데 사용하였다. 현재 모델의 결과를 이전에 발표된 실험 및 수치 결과와 비교하여 검증하였다. 이를 통해 유한요소해석에서 층간분리를 무시하면 인장 강도가 과대평가 된다는 것을 확인할 수 있었다.

• 천문학회지
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• 제50권3호
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• pp.51-59
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• 2017

The presence of blue stragglers pose challenges to standard stellar evolution theory, in the sense that explaining their presence demands a complex interplay between stellar evolution and cluster dynamics. In the meantime, mass transfer in binary systems and stellar collisions are widely studied as a blue straggler formation channel. We explore properties of the Galactic open clusters where blue stragglers are found, in attempting to estimate the relative importance of these two favored processes, by comparing them with those resulting from open clusters in which blue stragglers are absent as of now. Unlike previous studies which require a sophisticated process in understanding the implication of the results, this approach is straightforward and has resulted in a supplementary supporting evidence for the current view on the blue straggler formation mechanism. Our main findings are as follows: (1) Open clusters in which blue stragglers are present have a broader distribution with respect to the Z-axis pointing towards the North Galactic Pole than those in which blue stragglers are absent. The probability that two distributions with respect to the Z-axis are drawn from the same distribution is 0.2%. (2) Average values of $log_10(t)$ of the clusters with blue stragglers and those without blue stragglers are $8.58{\pm}0.232$ and $7.52{\pm}0.285$, respectively. (3) The clusters with blue stragglers tend to be relatively redder than the others, and are distributed broader in colors. (4) The clusters with blue stragglers are likely brighter than those without blue stragglers. (5) Finally, blue stragglers seem to form in condensed clusters rather than simply dense clusters. Hence, we conclude that mass transfer in binaries seems to be a relatively important physical mechanism of the generation of blue stragglers in open clusters, provided they are sufficiently old.

• 한국항공운항학회지
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• 제10권1호
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• pp.69-82
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• 2002

최근 항공자유화의 주요 변화는 미국 중심의 양자간 항공자유화와 소지역적 다자간 협정 체제의 성립이다. 소지역적 다자간 항공운송협력은 서로 마음이 맞는 국가들간에 기존의 양자간 항공 협정 체제에 근거하는 것이며 각국은 항공운송산업의 발전을 도모하기 위하여 시장접근 및 운수권에 대한 규제와 제한을 완화하고 역내의 자유로운 항공교통을 실현하기 위해 노력하고 있다. 본 연구에서는 지역적 항공운송협력의 배경과 실태를 살펴보고 항공자유화의 추진 결과 경제적으로 얻을 수 있는 효과를 예상하고자 아시아에 위치하면서 미국과 항공자유화 협정을 체결한 싱가포르를 대상으로 항공자유화 정책의 경제적 효과를 산업연관분석을 통하여 연구를 행하였다.

• 한국수학교육학회지시리즈A:수학교육
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• 제44권2호
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• pp.307-323
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• 2005

The purpose of this study was to develop a program to cultivate mathematical creativity based on open-ended problem and to investigate its effect. The major features of this innovative program are (a) breaking up fixations, (b) multiple answers, (c) various strategies, (d) problem posing, (e) exploring strategies, (f) selecting and estimating, (g) active exploration through open-ended problems. 20 units for 7th grade mathematics were developed. This study hypothesizes that experimental students may develop more divergent thinking abilities than their traditional counterparts. The participants were 7th grade students attending middle schools in Seoul. Instruments were pre and post tests to measure mainly divergent thinking skills through open-ended problems. The results indicated that the experimental students achieved better than the comparison students on overall and each component of fluency, flexibility, and originality of divergent thinking skills, when deleting the effect of covariance of the pretest. The developed program can be a useful resource for teachers to use in enhancing their students' creative thinking skills. Further this open-ended approach can be served as a model to implement in classes. This study suggests that further investigations are needed in order to examine effects on affective domains such as motivation and task perseverance which are also considered as important factors of creativity.

• Journal of Trauma and Injury
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• 제23권2호
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• pp.175-179
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• 2010

Purpose: Sternal fractures after blunt thoracic trauma can cause significant pain and disability. They are relatively uncommon as a result of direct trauma to the sternum and open reduction is reserved for those with debilitating pain and fracture displacement. We reviewed consecutive 11 cases of open reduction and fixation of sternum and tried to find standard approach to the traumatic sternal fractures with severe displacement. Methods: From December 2008 to August 2010, the medical records of 11 patients who underwent surgical reduction and fixation of sternum for sternal fractures with severe displacement were reviewed. We investigated patients' characteristics, chest trauma, associated other injuries, type of open reduction and fixation, combined operations, preoerative ventilator support and postoperative complications. Results: The mean patient age was 59.3years (range, 41~79). The group comprised 6 male and 5 female subjects. Among 11 patients who underwent open reduction and fixation for sternal fracture with severe displacement, 6 cases had isolated sternal fractures and the other 5 patients had associated other injuries. Sternal fractures were caused by car accidents (9/11, 81.8%), falling down (1/11, 9.1%) and direct blunt trauma to the sternum (1/11, 9.1%), respectively. 3 of the 7 patients (42.9%) who underwent sternal plating with longitudinal plates showed loosening of fixation. Otherwise, none of the 4 patients who underwent surgical fixation using T-shaped plate had stable alignment of the fracture. Conclusion: Sternal fractures with severe displacement need to be repaired to prevent chronic pain, instability of the anterior chest wall, deformity of the sternum, and even kyphosis. In the present study, a T-shaped plate with a compression-tension mechanism constitutes the treatment of choice for displaced sternal fractures.

• 정보관리연구
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• 제39권4호
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• pp.1-20
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• 2008

최근 학술커뮤니케이션에 나타난 변화 중 괄목할 만한 것이 '오픈액세스(Open Access)인데, 세계적으로 정보공유를 위한 연구자들의 참여와 학계와 정부에서의 지원 정책 발표가 이어면서 서구를 중심으로 급속히 확산되고 있다. 정보공유에 있어서 가장 중요한 것은 정보의 생산자이면서 소비자인 연구자들의 참여의지와 인식이다. 따라서 연구성과 정보의 공유에 대한 인식 조사는 대단히 긴요하다. 본 조사는 특정 주제 분야의 연구자들을 대상으로 오픈액세스 환경에 대한 인식도를 조사하였다. 이 조사를 바탕으로 오픈액세스 환경에서 이슈가 되고 있는 저작권 문제를 조명하였다. 결과적으로 국내 연구자들에게 있어서 '오픈액세스'에 대한 인식은 아직은 미비한 것으로 나타난 반면, 저작권이 침해되지 않는 범위 내에서 명확한 출처를 밝히고 합법적인 목적으로 연구물을 사용한다면 오픈액세스 활동에 참여할 의사를 가지고 있는 것으로 조사되었다. 이러한 결과를 바탕으로 이 논문에서는 저작권과 라이선스의 마련, 그리고 산재한 연구성과물의 원활한 관리와 접근 및 활용을 극대화시킬 수 있는 연구정보관리 체제의 구축이 필요함을 밝혔다.

• 대한치과교정학회지
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• 제44권4호
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• pp.203-216
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• 2014

The purpose of the current report is to present 6-year long-term stability and 10-year follow-up data for an adult patient who was treated with a tongue elevator for relapsed anterior open-bite. The 19-year-old male patient presented with the chief complaint of difficulty in chewing his food. Collectively, clinical and radiographic examinations revealed an anterior open-bite, low tongue posture, and tongue-tie. The patient opted for orthodontic treatment alone, without any surgical procedure. A lingual frenectomy was recommended to avoid the risk of relapse, but the patient declined because he was not experiencing tongue discomfort. Initial treatment of the anterior open-bite with molar intrusion and tongue exercises was successful, but relapse occurred during the retention period. A tongue elevator was used for retreatment, because the approach was minimally invasive and suited the patient's requirements regarding discomfort, cost, and time. The appliance changed the tongue posture and generated an altered tongue force, which ultimately resulted in intrusive dentoalveolar effects, and a subsequent counterclockwise rotation of the mandible. The results showed long-term stability and were maintained for six years through continual use of the tongue elevator. The results of this case indicated that a tongue elevator could be used not only as an alternative treatment for open-bite, but also as an active retainer.

• 한국과학교육학회지
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• 제21권2호
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• pp.255-263
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• 2001

중학교 '전기와 자기' 에 대한 개방적 탐구 과제는 관찰을 통한 서술적인 결과 처리가 특징인 정성적 과제와, 변인통제를 통한 정량적 결과 처리가 특징인 정량적 과제로 나눌 수 있다. 본 연구의 목적은 두 종류의 과제에 대한 중학교 2학년 학생들의 탐구 수행 특징을 탐구 과정을 중심으로 분석하는 것이다. 학생이 작성한 '탐구 보고서' 및 '탐구 활동 평가서' 그리고 연구자의 관찰 및 면담 자료를 분석하였다. 정성적인 과제에 대한 탐구에서는 자신의 생각과 다른 뜻밖의 관찰을 인지하고 처리하는 것이 어려운 점이었고, 정량적인 과제에 대한 탐구에서는 여러 개의 변인을 다루고, 신뢰롭고 타당한 측정을 하며, 정량적으로 결과를 처리하는 것이 어려운 점이었다. 정성적인 과제에 대한 탐구에서는 자신이 제시한 탐구 방법 및 결과의 부족한 점을 인지하고 있었는데 반해, 정량적인 과제에 대한 탐구에서는 부족한 점을 거의 인지하지 못했다. 이러한 결과는 기존의 실험실습과는 다른 개방적인 탐구를 지도할 때, 정성적인 과제의 경우 뜻밖의 관찰 결과를 신뢰롭고 타당하게 처리하도록 지도하는 것이 중요하며, 정량적인 과제의 경우 여러 개의 변인을 다루는 방법 및 신뢰롭고 타당한 측정 방법을 지도하는 것이 중요하다는 것을 시사한다.