• 한국군사과학기술학회지
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• 제11권2호
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• pp.144-151
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• 2008

An experimental study has been conducted to investigate the effects of circular damage hole on the characteristics of airfoil performance. The damage on a wing created from a hit by anti-air artillery was modeled as a circular hole. Force balance measurements and static pressure measurements on the wing surface were carried out for the cases of having damage holes of 10% chord size at quarter chord and/or half chord positions. All experiments were conducted at Reynolds number of $2.85\times10^5$ based on the chord length. The surface pressure data show big pressure alterations near the circular damage holes. This abnormal surface pressure distribution produces shear stress that could lead to the acceleration of the structural degradation of the wing around the circular damage hole. However, in spite of the existence of circular damage holes, the measured force data indicated the only a slight decrease in lift accompanied by increase in drag compared to the results of undamaged one. The influence of damage hole on the aerodynamic performance was increased as the location of damage moved to the leading edge. The effect on the control force was insignificant when the damaged size was not large.

• 터널과지하공간
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• 제19권6호
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• pp.567-582
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• 2009

일본의 기후현의 카미오카광산은 지하 약 1,000 m의 대심도에, 우주에서 도래하는 소립자의 관측과 양자의 붕괴현상 등을 연구하기 위한 실험시설 SUPER-KAMIOKANDE가 건설되었다. 이 시설 설계를 위한 기초 자료의 하나로, 초기지압 측정을 실시하여 건설 예정지의 암반 응력 상태를 파악했다. 측정 방법은, 일본 전력중앙연구소(Central Research Institute of the Electric Power Industry)에서 개발한 ８성분 변형률 게이지를 이용한 공경변화법, Sugahara와 Obara가 개발한 16성분 구면 게이지를 이용한 구면 공저변형법, 오스트레일리아의 CSIRO에 의해 개발된 Hollow Inclusion Cell을 이용한 공벽변형률법이다. ３종류의 방법에 의해 얻어진 결과가 일치하지는 않았지만, ６응력성분의 평균치를 이용하여 주응력 방향 및 크기를 결정하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.20-27
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• 2011

High-speed railway system is exposed to severe aerodynamic problems and has various requirements both on design and operation; 80% of running resistance is composed of aerodynamic drag, the cross-sectional area and portal shape of tunnel should be designed under aerodynamic consideration, and natural wind velocity should always be monitored to prevent the overturning of train by crosswinds. In addition, most of the aerodynamic problems are proportional to the running speed or square of the running speed. Thus, when the running speed of a high-speed railway system either on operation or under construction is to be increased, the aerodynamic problems should be assessed in advance and the countermeasures should be prepared to alleviate the aerodynamic problems to meet certain requirements. In this study, aerodynamic problems that could occur at speed up of high-speed line have been investigated and aerodynamic requirements to meet the increased operational speed have been studied referring the international and domestic rules, guidance, and recommendations.

• 전기학회논문지
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• 제67권3호
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• pp.467-473
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• 2018

R-Bar(Overhead Rigid Conductor system) is being developed for the high-speed in Europe because it has an advantage of cross section area reduction of tunnel compared with OCS (Overhead Catenary Line). Because there are lots of underground sections and mountains in korea, it is necessary to develop the R-Bar for a high-speed line. In this study, a method on speed-up of transition section between OCS and R-Bar is proposed. The commercial program, DAFUL, is used to predict a dynamic characteristics between Overhead Line and pantograph. The program is evaluated according to EN 50318 which is the European Norm for evaluation of the program. Using the evaluated modeling and method, a method for the max. speed of 250 km/h of transition section is proposed.

• 한국추진공학회지
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• 제8권1호
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• pp.61-69
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• 2004

본 연구는 극초음속 모델 스크램제트 엔진 연소기의 화염지지와 연료-공기 혼합과정의 특성을 살펴보기 위하여 수치해석을 이용하여 수행되었다. 연료분사 방법으로 수소연료가 초음속 유동장에 수직분사되는 경우와 공동내부에 분사되는 두 가지 경우를 채택하였으며 각각 UQ(University of Queensland, Australia)와 ANU(Australian National University, Australia)의 충격파 풍동을 이용하여 실험이 수행되었다. 수치해석을 통하여 수직분사 상류의 박리영역과 공동주변에서 연소현상이 관찰되었다. 수직분사의 박리영역과 공동내부분사의 공동은 재순환 영역을 발생시키며, 이 재순환 영역은 연료-공기의 혼합을 촉진시킨다. 또한 자발점화가 박리영역-자유류, 공동-자유류 경계면에서 발생함을 알 수 있었다.

• 항공우주기술
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• 제2권2호
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• pp.1-10
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• 2003

비행선은 주익이 없고 미익에 비해 동체 효과가 큰 형상 특성으로 인해 정적으로 불안정한 특성을 지닌다. 따라서 동안정 특성 예측이 매우 중요하다. 본 연구에서는 강제진동 풍동시험을 통한 비행선의 동안정 특성을 확보하였다. 풍동시험은 미국 BAR사의 독일소재 시설인 BAR LAMP 시설을 사용하였으며, 16회의 정적시험과 26회의 강제진동시험을 수행하였다. 시험결과, 비행선의 동안정 특성은 받음각 뿐만 아니라 옆미끄럼각, 각속도 크기와 방향에 비선형적으로 변한다. 전반적으로 세 방향의 모멘트는 댐핑이 있는 것으로 나타났으며, 수직력과 측력, 교차성분은 불안정하게 나타났다. 조종면의 영향은 작은 것으로 나타났으나 옆미끄럼각의 영향은 완전히 비선형적으로 나타났다.

• 오토저널
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• 제12권3호
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• pp.53-62
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• 1990

A wind tunnel experiment for the flow around a 1/5 scale passenger vehicle model has been carried out. A 5-hole Pitot tube is used for measuring velocity distributions around the model and a scanivalve with 48 ports is used for measuring surface pressure distribution at various Reynolds numbers. In order to observe the flow on the surface and in the wake region, a flow visualization experiment has been performed using wool tuft with and without paper cones. In addition, a 2-dimensional viscous calculation considering only the mid-plane section of the model has been performed. A complex wake structure in the immediate rear of the model has been confirmed. The distributions of the surface pressure coefficient are not sensitively dependent on the Reynolds Number. In the first half of the model, they do not seem to vary form section to section. However, in the second half, they do vary from section to section, especially at the bottom surface, which indicates that the cross flow vortex is more affected by the bottom surface than the top surface. The qualitative agreement of the measured and calculated velocity field also explains the usefulness of the 2-dimensional calculation in the limited sense.

• 동력기계공학회지
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• 제10권3호
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• pp.23-31
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• 2006

Mean velocities and turbulent characteristics in the three-dimensional flow fields of a gun-type gas burner were measured by using triple hot-wire probe (T-probe) in order to compare them with the results already presented by X-type hot-wire probe (X-probe). Vectors obtained by the measurement of two kinds of probes in the horizontal plane and in the cross section respectively show more or less difference in magnitude each other, but comparatively similar shape in overall distribution. Axial mean velocity component along the centerline shows that the value by T-probe is about ten times smaller than that by X-probe above the range of X/R=3. Also, the axial component of turbulent intensity along the centerline appears the biggest difference between the two probes. Moreover, axial mean velocity component, axial turbulent intensity component and rotational along the Y-directional distance show a big difference between slits and swirl vanes. On the whole, the values by T-probe appear smaller than those by X-probe.

• 한국생산제조학회지
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• 제25권1호
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• pp.7-13
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• 2016

With the increasing running speed of trains, new railway lines in metropolitan areas, and the rising demand for green transportations, the number of underground and tunnel sections are constantly becoming larger, and installations of overhead rigid conductor systems are becoming wider. However, domestic commercial products for overhead rigid conductors are limited to 120 km/h train speeds. In this study, to develop a high-speed (250 km/h) overhead rigid conductor, R-Bar (Rigid Bar), the electrical and mechanical stability was enhanced through the improvement of the cross sectional shape of the R-Bar; the transition structure was also designed for flexibility and natural frequency isolation. In addition, the evaluation of contact forces between a pantograph and the overhead rigid conductor system for 250 km/h train speeds was performed using dynamic analysis.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.584-587
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• 2011

마하 5 스크램젯 엔진에 대하여 연소 시험에 대한 예비 시험 성격으로서 연료 분사 없이 내부 유동 공력 시험을 수행하였다. 엔진은 흡입구 크기 $70mm{\times}200mm$, 전체 길이 1.7m의 시험용 모델을 대상으로 하였다. 설비는 한국항공우주연구원이 자체 설계 개발하여 보유한 불어내기식 극초음속 시험 설비를 사용하였다. 측정은 엔진 내부 유로를 따라 19개 지점에서 압력을 측정하였다. 시험 결과 본 엔진 모델을 사용하여 설비 시동이 가능하였으며 엔진 내부는 초음속 유동이 유지됨을 확인하였다.