• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1121-1136
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• 2002

The flow characteristics of film coolant issuing into turbulent boundary layer developing on a convex surface have been investigated by means of flow visualization and three-dimensional velocity measurement. The Schlieren optical system with a spark light source was adopted to visualize the jet trajectory injected at 35° and 90° inclination angles. A five-hole directional pressure probe was used to measure three-dimensional mean velocity components at the injection angle of 35°. Flow visualization shows that at the 90° injection, the jet flow is greatly changed near the jet exit due to strong interaction with the crossflow. On the other hand, the balance between radial pressure gradient and centrifugal force plays an important role to govern the jet flow at the 35° injection. The velocity measurement shows that at a velocity ratio of 0.5, the curvature stabilizes downstream flow, which results in weakening of the bound vortex structure. However, the injectant flow is separated from the convex wall gradually, and the bound vortex maintains its structure far downstream at a velocity ratio of 1.98 with two pairs of counter rotating vortices.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
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• pp.55-60
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• 2008

This study is on the analysis of power output of transparent thin-film PV windows which are integrated into the building envelope instead of traditional windows. 3 installation angles of vertical, horizontal and $30^{\circ}C$ inclination are investigated. To measure power output of PV windows, full scale mock-up house was designed and constructed. The power performance of PV window system was analyzed for horizontal angle, declination angle and vertical angle according to incline angle. Monitoring data are gathered from November 2006 to August 2007 and statistical analysis is performed to analysis a characteristics of power performance of transparent PV windows. Results show that annual power output of PV window with horizontal angle is 844.4kWh/kWp/year, declination angle 1,060kWh/kWp/year and vertical angle 431.6 kWh/kWp/year.

• 치위생과학회지
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• 제20권2호
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• pp.118-124
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• 2020

The purpose of this comparison of case reports is to introduce the results of the application of new devices for the management of growing Class III malocclusions in children. Two 8-year-old boys had a chief complaint of anterior crossbite. Anterior crossbite correction using a tandem traction bow appliance (TTBA) or a Carriere Motion 3D Class III appliance with a Transforce appliance was planned. By comparing cephalometric radiographs before and after treatment, changes in skeletal growth and incisor inclination to the Frankfort horizontal (FH) plane could be measured. Both devices increased SNA and ANB angles, N-I Pg-A, U1 to SN, and U1 to FH. Both appliances improved facial features and resolution of anterior crossbite. The TTBA and Carriere Motion 3D Class III appliance had similar effects when applied as early treatment for growing mesio-occlusions and anterior crossbite in two boys. However, long-term outcome assessments and well-designed comparative studies are still required.

• 대한치과교정학회지
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• 제8권1호
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• pp.59-71
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• 1978

The author compared and analysed the roentgenocephalograms of one hundred Korean adults with the normal occlusion (50 males and 50 females), which were taken on the centric occlusion and the rest position of the mandible respectively for every subject, and then researched the relations among the relaxed muscle of the mandible, lightly touched of the lips, and the position just after the swallowing of saliva, of which 38 among 50 males had the rest position of the mandible. The results are as followings: 1. The anterior facial height increases more at the rest position of the mandible than at the centric occlusion, while the posterior facial height decreases. 2. The mandible moves more backward and downward at the rest position of the mandible than at the centric occlusion. 3. The facial procumbency and the incisor tooth inclination increases more at the rest position of the mandible than the centric occlusion in terms of the facial plane. 4. There are no differences between males and females at the rest position of the mandible and the centric occlusion in the meaning of variation. 5. There are no differences among the three methods from the view of lines and angles of the roentgenocephalogram.

• 한국산림과학회지
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• 제95권4호
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• pp.495-500
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• 2006

자주식 반송기를 이용한 가선집재작업의 안정성을 이론적인 계산과 현장 계측을 통해 검토하였다. 가선집재 시스템의 이론적 안정성 평가의 유용성을 입증하기 위하여 스카이라인의 장력과 근주의 저항력을 측정하여 이론 계산값과 비교평가하였다. 그 결과 측정된 스카이라인의 장력과 계산값이 유사하였으며, 이를 통해 전체적인 안정성 검토가 가능하였다. 또한 근주의 저항력은 근주의 직경과 밀접한 관계가 있으며 근주변의 각도가 $5-10^{\circ}$일 때 가장 큰 저항력을 나타내었으며, 그 이상의 각도에서는 지주목으로서의 기능을 잃어버리는 것으로 판단되었다.

• 한국CDE학회논문집
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• 제15권5호
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• pp.354-361
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• 2010

The paper presents an efficient computation of optimal tool length for 5-axis mold & die machining. The implemented procedure processes an NC file as an initial input, where the NC data is generated by another commercial CAM system. A commercial CAM system generates 5-axis machining NC data which, in its own way, is optimal based on pre-defined machining condition such as tool-path pattern, tool-axis control via inclination angles, etc. The proper tool-length should also be provided. The tool-length should be as small as possible in order to enhance machinability as well as surface finish. A feasible tool-length at each NC block can be obtained by checking interference between workpiece and tool components, usually when the tool-axis is not modified at this stage for most CAM systems. Then the minimum feasible tool-length for an NC file consisting of N blocks is the maximum of N tool-length values. However, it can be noted that slight modification of tool-axis at each block may reduce the minimum feasible tool-length in mold & die machining. This approach can effectively be applied in machining feature regions such as steep wall or deep cavity. It has been implemented and is used at a molding die manufacturing company in Korea.

• Journal of Astronomy and Space Sciences
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• 제32권3호
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• pp.257-268
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• 2015

Characteristics of delta-V requirements for deploying an impactor from a mother-ship at different orbital altitudes are analyzed in order to prepare for a future lunar CubeSat impactor mission. A mother-ship is assumed to be orbiting the moon with a circular orbit at a 90 deg inclination and having 50, 100, 150, 200 km altitudes. Critical design parameters that are directly related to the success of the impactor mission are also analyzed including deploy directions, CubeSat flight time, impact velocity, and associated impact angles. Based on derived delta-V requirements, required thruster burn time and fuel mass are analyzed by adapting four different miniaturized commercial onboard thrusters currently developed for CubeSat applications. As a result, CubeSat impact trajectories as well as thruster burn characteristics deployed at different orbital altitudes are found to satisfy the mission objectives. It is concluded that thrust burn time should considered as the more critical design parameter than the required fuel mass when deducing the onboard propulsion system requirements. Results provided through this work will be helpful in further detailed system definition and design activities for future lunar missions with a CubeSat-based payload.

• Korean Journal of Geomatics
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• 제1권1호
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• pp.69-74
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• 2001

In conventional photogrammetry, three-dimensional coordinates are obtained from two consecutive images of a stationary object photographed from two exposure stations, separated by a certain distance. However, it is impossible to photograph moving objects from two stations with one camera at the same time. Various methods to overcome this obstacle were devised e. g. taking the left and right scenes simultaneously with one camera using a beam splitter attached to the front, thus creating a stereo scene in one image. A beam splitter consists of two outer mirrors and two inner mirrors. This paper deals with research where the optical principles of the beam splitter were evaluated based on light path phenomena between the outer mirrors and the inner mirrors. A mathematical model of the geometric configuration was derived for the beam splitter. This allows us to design and control a beam splitter to obtain maximum scale and maximum base-height ratio by stepwise application of the mathematical model. The results show that the beam splitter is a very useful tool for stereophotography with one camera. The optimum geometric configurations ensuring maximum scale and base-height ratio are closely related to inner and outer reflector sizes, their inclination angles and the offsets between the outer mirrors.

• 한국항공우주학회지
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• 제33권9호
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• pp.97-103
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• 2005

본 연구에서는 소형 동-소결윅 히트파이프를 대상으로 소결윅의 구조적 인자들이 히트파이프의 열수송 한계에 미치는 영향을 이론적으로 분석하였다. 소결윅의 입자 크기의 균일성과 소결 조건이 전체적인 기공분포와 기공률을 포함한 물리적 특성에 지배적인 요소로 작용했으며, 윅 두께 및 기공의 작은 편차가 히트파이프의 열수송 한계에 대체로 큰 영향을 미치는 것으로 나타났다. 특히, 증기온도와 경사각에 따라서 윅 두께와 평균 입자 반경, 그리고 모세관반경의 미세한 변화가 히트파이프의 모세관한계를 현저하게 변화시켰다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.43-50
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• 1998

The current design equations for ultimate strength of tubular joints are based on a limited number of experimental results performed on simple joints with simple loading conditions and depend on value of the branch to the chord diameter- ratio $\beta$ too much. Therefore, the purpose of this study is to estimate the ultimate strength of CHS tilbular joints considering the effects of branch inclination angles $\theta$, chord length to diametel ratio $\alpha$ and chord end conditions by finite element analysis. The analyses are performed using finite element software ADINA that is capable of modeling elasto-plastic material behavior as well as geometric nonlinearities. The results show that the current use of sin $\theta$ in normalized design equations for inclined branches is reasonable, but somewhat conservative. When compared with the previous experimental database, the close numerical results are obtained from the parametric studies on the static strength of T-, Y-, DT- and X-joints. Also, a new design equation for ultimate stregth of CHS tubular joints is derived using a modified version of the ring model which can include the effects of $\alpha$ and chord end condtion.