• 한국콘텐츠학회논문지
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• 제11권8호
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• pp.499-511
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• 2011

본 논문은 방과후학교의 유형과 학습몰입 정도에 따른 중학생의 방과후학교 교육만족도의 차이를 분석하면서 방과후학교의 유형과 학습몰입 정도에 상호작용 효과가 있는지를 살펴보는데 그 목적이 있다. 연구의 대상은 중학교 1,2,3학년 382명이며, 조사도구로는 연구대상자의 일반적 특성, 수강한 방과후학교 수업의 일반적 특성, 그리고 학습몰입 척도와 방과후학교 교육만족도 척도로 구성된 질문지를 사용하였다. 구체적인 연구문제를 검증하기 위하여 다변량분산분석(MANOVA)을 사용한 결과 방과후학교 특기 적성수업을 수강한 중학생들이 교과수업을 수강한 중학생들보다 방과후학교 지도교사만족도가 높은 것으로 나타났으며, 학습몰입 정도가 높은 중학생들이 학습몰입 정도가 낮은 중학생들보다 방과후학교 교육과정, 지도교사, 교육시설만족도가 모두 높은 것으로 나타났다. 그리고 학습몰입 정도가 높은 중학생들에 있어서는 특기 적성수업을 수강한 중학생들이 교과수업을 수강한 학생들보다 방과후학교 교육과정과 교육시설만족도가 높았으며, 학습몰입 정도가 낮은 중학생들에 있어서는 교과수업을 수강한 학생들과 특기 적성수업을 수강한 중학생들 간에 방과후학교 교육과정과 교육시설만족도에 유의한 차이가 나타나지 않았다.

• 대한치과재료학회지
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• 제45권4호
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• pp.311-320
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• 2018

본 연구의 목적은 서로 다른 온도 설정을 받았을 때 열가소성 가타퍼차의 흐름성 특성을 평가 해보고자 현재 임상에서 사용되는 가타퍼차 4개 제품을 연질, 중질, 경질로 분류하여 실험하였으며, 실험시편은 24시간 동안 $(23{\pm}2)^{\circ}C$, ($50{\pm}5$) % 상대습도 조건으로 하여 ISO 1133-1:2011의 제시에 따라 레오미터(Melt flow indexer MFI-10, DAVENPORT, England)로 측정했다. 가타퍼차 재료의 열화 온도는 $108^{\circ}C$, $160^{\circ}C$, $200^{\circ}C$의 온도로 하고 하중은 2.16 ㎏, 3.8 ㎏으로 설정했으며 시편은 레오미터 가압과정에 적합하도록 약 5 mm 단위로 잘랐으며, Preheating time 5 분, Cutting time은 5~240초, 샘플은 10 g 으로 하여 실험한 결과 $108^{\circ}C$, $160^{\circ}C$의 온도에서는 흐름성 성질에 변화가 없었으나 $200^{\circ}C$까지 열화하면 흐름성 성질이 변화되는 것으로 나타났다. 가압 하중은 2.16 ㎏과 3.8 ㎏으로 하여 측정한 결과 하중은 흐름성 특성에 영향을 미치지 않았으나 열가소성 가타퍼차의 흐름성 측정의 경우 온도와 Cut-off time의 설정이 매우 중요한 것으로 조사 되었다.

• Wind and Structures
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• 제23권4호
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• pp.301-311
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• 2016

The numerous benefits of Savonius turbine such as simple in structure, has appropriate self-start ability, relatively low operating velocity, water acceptance from any direction and low environmental impact have generated interests among researchers. However, it suffers from a lower efficiency compared to other types of water turbine. To improve its performance, parameters such flow pattern, pressure and velocity in different conditions must be analyzed. For this purpose, a detailed description on the flow field of various types of Savonius rotors is required. This article presents a numerical study on a nonlinear two-dimensional flow over a classic Savonius type rotor and a Benesh type rotor. In this experiment, sliding mesh was used for solving the motion of the bucket. The unsteady Reynolds averaged Navier-Stokes equations were solved for velocity and pressure coupling by using the SIMPLE (Semi-Implicit Method for Pressure linked Equations) algorithm. Other than that, the turbulence model using $k-{\varepsilon}$ standard obtained good results. This simulation demonstrated the method of the flow field characteristics, the behavior of velocity vectors and pressure distribution contours in and around the areas of the bucket.

• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.139-145
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• 2003

Diode laser sensor is conducted to measure the gas temperature in the liquid-gas 2-phase counter flow flame. C$\_$10/H/ sub 22/ and city gas were used as liquid fuel and gas fuel, respectively. Two vibrational overtones of H$_2$O were selected and measurements were carried out in the spray flame region stabilized the above gaseous premixed flame. The path-averaged temperature measurement using diode laser absorption method succeeded in the liquid fuel combustion environment regardless of droplets of wide range diameter. The path-averaged temperature measured in the post flame of liquid-gas 2-phase counter flow flame showed qualitative reliable results. The successful demonstration of time series temperature measurement in the liquid-gas 2-phase counter flow flame gave us motivation of trying to establish the effective control system in practical combustion system. These results demonstrated the ability of real-time feedback from combustor inside using the non-intrusive measurement as well as the possibility of application to practical combustion system. Failure case due to influence of spray flame was also discussed.

• Journal of Ship and Ocean Technology
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• 제8권4호
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• pp.1-9
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• 2004

High lifting devices used for control purposes have received much attention in the marine field. Hydrofoils for supporting the hull, roll stabilizer fins for developing the motion damping performance, rudders for maneuverability are the well-known devices. In the present study, the ability of the rudder with flap to produce high lift was analyzed. The boundary layer control, one of the flow control techniques, was adopted. Especially, to build the blown flap, a typical and representative type of a boundary layer control, a flapped rudder was designed and manufactured so that it could eject the water jet from the gap between the main foil and the flap to the flap surface tangentially. And it was tested in the towing tank. Simultaneously, to know the information about the 2-dimensional flow field, a fin model with similar characteristics as the rudder model applicable for the motion control was made and tested in the cavitation tunnel. In addition, local flow measurements were carried out to obtain physical information, for example, a surface pressure measurement and flow visualization around the flap. And CFD simulation was used to obtain information difficult to collect from the experiment about the 2-dimensional flow.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권2호
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• pp.71-82
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• 2012

In recent practices, a half circular prismatic bar protruding beyond the concave surface of the horn facing the gap has been formed along the centerplane of a rudder to lessen the gap flow between the horn and the movable portion of the rudder system. If a flow through the gap of a rudder is reduced considerably through this approach, previous numerical studies indicate that not only the gap flow but also the rudder cavitation can be noticeably diminished. In the present study, numerical simulations on two-dimensional rudder sections were performed to show that the blocking ability of the single centre bar can be improved by the proper choice of sectional shape. Moreover, a pair of blocking bars attached symmetric to the centerplane on the opposite convex surface of the movable portion is suggested in the study as well, to circumvent the difficulties arising from the practical application of the single centre bars. The bars are placed near the outer edges of the gap easily accessible at the maximum rudder angle to allow simple installation of the device during a maintenance period of a ship. It is found that the pair of blocking bars further improves the blocking effects and application to a practical three-dimensional rudder also backs up the fact.

• International Journal of Oral Biology
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• 제37권2호
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• pp.69-75
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• 2012

Although neutrophils function in both defense and tissue destruction, their defensive roles have rarely been studied in association with periodontitis. We hypothesized that peripheral neutrophils are pre-activated in vivo in periodontitis and that hyperactive neutrophils would show enhanced phagocytic ability as well as an increased production of reactive oxygen species (ROS). Peripheral blood neutrophils from patients with aggressive periodontitis and age/gender-matched healthy subjects (10 pairs) were isolated. The levels of CD11b and CD64 expression on the neutrophils and the level of plasma endotoxin were determined by flow cytometry and a limulus amebocyte lysate test, respectively. In addition, neutrophils were subjected to a flow cytometric phagocytosis assay and luminol-enhanced chemiluminescence for non-opsonized Fusobacterium nucleatum in parallel. The neutrophilsfrom most patients expressed increased levels of both CD11b and CD64. In addition, the plasma from these patients tended to contain a higher level of endotoxin than the healthy controls. In contrast, no differences were found between the two groups with regard to phagocytosis or ROS generation by F. nucleatum. The ability to phagocytose F. nucleatum was found to positively correlate with the ability to produce ROS. In conclusion, peripheral neutrophils from patients with aggressive periodontitis are hyperactive but not hyperreactive to F. nucleatum.

• 한국지열·수열에너지학회논문집
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• 제8권2호
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• pp.1-8
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• 2012

The G-class cement is usually used for geothermal well grouting to protect a steel casing which is equipped in a geothermal well to transfer geothermal water from deep subsurface to ground surface. In geothermal grouting process, obtaining appropriate fluidity is extremely important in order to fill cement grout flawlessly. In this paper, a series of the V-funnel and Slump Flow test was performed on both of the Portland cement and the G-class cement in order to compare fluidity and filling ability of those kind of cements. In the result of V-funnel test, the fluidity of G-class cement was evaluated much better than the Portland cement at the water/cement ratio of 0.8. In the case of Slump Flow test, the fluidity of G- class cement was estimated slightly better than the Portland cement at both the water/cement ratio of 0.55 and 0.8. Even though the initial fluidity and filling ability of G-class cement were relatively higher than the Portland cement, the results could be considerably changed with time. The results show that the fluidity and filling ability for geothermal well cementation can be properly controlled with water content and additives for adverse geothermal well environment.

• 한국치위생학회지
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• 제16권5호
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• pp.687-693
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• 2016

Objectives: The purpose of the study was to investigate the influence of instructor trust on learning flow and academic achievement in dental hygiene students. Methods: A self-reported questionnaire was completed by 202 dental hygiene students in Gyeongnam from July to August, 2016. A five point Likert scale questionnaire consisted of intimacy (8 items), professionalism (8 items), teaching ability (5 items), and leadership (6 items). Measurement of learning flow was adapted and modified by Kim et al. Academic achievement was adapted and modified by Noe and Schmitt. Cronbach's ${\alpha}$ of learning flow was 0.77 and that of academic achievement was 0.78 in the study. Data wee analyzed by t-test, one way ANOVA, $Scheff{\acute{e}}$ test, and Pearson's correlation using SPSS 23.0 program. Results: The scores of instructor trust, learning flow, and academic achievement were 4.37, 3.46, and 3.23, respectively. Academic achievement had a close positive correlation with instructor trust (r=0.46, p<0.001) and learning flow (r=0.63, p<0.001). Instructor trust had a positive correlation with learning flow (r=0.50, p<0.001). Learning flow took mediating effects on instructor trust and academic achievement. Conclusions: The trust between students and instructors had a great influence on learning flow and academic achievement. So the instructor should try to make the students concentrate on learning.

• 한국지반환경공학회 논문집
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• 제16권3호
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• pp.49-55
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• 2015

토석류가 발생할 때는 강우패턴, 강우강도 및 해석을 위한 지형여건에 따라 토석류의 발생량과 흐름의 속도가 달라진다. 지형여건의 고려는 일정규모의 격자로 지형을 구분하고 구분된 격자 내의 지형경사는 평균경사로 가정하여 계산하므로 굴곡이 심한 지형에서는 분할되는 격자를 세분할수록 실제와 근접한 결과를 얻을 수 있게 된다. 그러나 지금까지는 해석알고리즘 및 컴퓨터 계산능력, 해석수행 시간 등의 한계로 인해 지형분할 격자를 상당히 크게 구분하여 수행하고 있다. 그러나 토석류 해석의 정확도를 위해서는 지형구분 격자크기를 가급적 작게 하여야 하므로, 실무적 접근을 위한 적절한 격자규모의 제안이 필요하게 된다. 따라서 본 논문에서는 기존 연구에서 논의되었던 누가 강우량, 강우강도, 강우지속시간 및 선행 강우량 등의 강우 특성 이외에 지형분할 격자크기가 토석류 흐름에 미치는 영향을 평가하고 이로부터 합리적이고 현실성 있는 지형분할규모를 제시하였다.