• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.1-10
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• 2002

Flow computations around forward sweep wing small aircraft have been conducted in this study. The main-wing of the forward-wing small aircraft is composed of two planforms: the inboard wing section with backward sweep angle which is known as strake and the outboard wing section with forward sweep angle. The geometrical discontinuity or kink generated by the combination of these two different planforms requires detailed flow analysis around wing. Four different solvers were used to calculate aerodynamic data and the accuracy of each method is examined. For the convenience of grid generation over the aircraft geometry, the overset grid method was applied. Through this calculation, the basic aerodynamic data of the forward-wing aircraft were provided and the aerodynamic characteristics of the wing is expounded.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.430-432
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• 2000

시뮬레이션을 구현할 때 대부분의 경우 eventlist 라는 자료구조를 사용하여 사건(event)를 처리하고 시간을 스케쥴링(scheduling)한다. 그러나 eventlist를 사용하는 것은 객체 스스로가 사건을 처리하고 시간 스케쥴링을 하지 않는다는 점에서 객체지향적이지는 못하다. 그래서 본 논문에서는 객체 스스로가 상태를 가지며 사건을 처리하고 시간을 스케쥴링하는 전차대 전차, 전차대 헬기 교전을 위한 시뮬레이션을 설계 및 구현하였다. 설계는 상태변화를 쉽게 하고 시간 전진 문제를 쉽게 처리할 수 있는 Fa$\square$ade Pattern방법을 사용하였으며, 시간전진 방법은 상태변화에는 논리시간(logical time)을 이용한 이산사건(discrete event) 전진방법을 사용하였고 Graphic Visualization에는 실시간(real time)을 이용한 이산(discrete) 전진방법을 사용하여 논리시간과 실시간을 병렬로 동기화시켜 처리하였다. 구현은 Visual C++의 MFC 라이브러리를 사용한 MDI구조로 구현하였다. 논문의 시뮬레이션은 교전모델을 응용하였고 객체지향(Objected-Oriented)으로 설계 및 구현되어 각 객체의 재사용과 확장 및 수정이 용이하다는 장점을 가진다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.2
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• pp.124-129
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• 2007

Prediction methods for a rotor averaged inflow in forward flight are investigated in this study. The investigated methods are Drees linear inflow model, Mangler & Squire model and free vortex wake(FVW) method. Predictions have been performed for a four-blade rotor operating at three different advance ratios i.e. 0.15, 0.23 and 0.30, at which experimental data are available. According to results, Drees model has a limitation for the inflow non-uniformity prediction due to an inherent linear characteristics. Mangler & Squire model has a reasonable accuracy except the disk edge region. KARI FVW method has very good accuracy and has better accuracy than the other FVW method especially in inboard region. However, there are some discrepancies in retreating side due to the dynamic stall effect and in near hub region due to the fuselage upwash effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.3
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• pp.215-223
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• 2009

In this paper, the helicopter aerodynamics is simulated in hovering and forward flight. Also, an overlapped grid technique is applied in this simulation to consider the blade motion and moving effects. The Caradonna & Tung's rotor blade was selected to analyze the unsteady aerodynamics in hovering and non-lift forward flight. Also, the AH-1G rotor blade was selected in forward flight. In forward flight case, the numerical trim was applied to determine the cyclic pitching angles using Newton-Raphson method, and the numerical results were in good agreement with experimental data, especially, the BVI effects were well simulated in advancing side in comparison other numerical results. The governing equation is a three dimensional unsteady Euler equation, and the Riemann invariants condition is used for inflow and outflow at the boundary.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.6
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• pp.498-504
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• 2011

The flapping characteristics and advance ratios at torque equilibrium state of autorotation were investigated when the airspeed, shaft angle, and pitch angle were varied. To simulate the airspeed increase, the aerodynamic data analyzed by using the compressible Navier-Stokes solver and Pitt/Peters inflow theory were used. Transient Simulation Method(TSM) was used to catch the torque equilibrium states. The maximum flapping angles at torque equilibrium state were correlated to the airspeed, shaft angle, and pitch angle. By comparing flapping behavior to the variation of advance ratio, the phenomenon that the extension of reverse flow area of retreating blade affects the characteristics of autorotation was qualitatively considered.

• Journal of Adhesion and Interface
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• v.15 no.2
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• pp.57-62
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• 2014

Pythagolas rule was used for investigation of static contact angle in particular figures. Static contact angle measurement was important to evaluate the wettability between solid and liquid. Optimum measurement method and standardization of calculation for static contact angle were investigated for practical application. Optimum diameter of droplet for static contact angle measurement was confirmed as 1 mm. Contact angle measurement using Pythagolas rule was also used to calculate advancing, receding angle and wettability of different surface condition. At last, it was concluded that the Pythagolas rule method was more accurate than general lineation method for static contact angle measurement.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.7-8
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• 2018

파 중 선박 조종운동시험을 위하여 선박해양플랜트연구소 공학수조 내 자유항주시험 시스템을 구성하였다. 모형선 내에 제어계측 장비와 PC를 탑재하고 육상 관제 PC에서 원격 통제, 모니터링하며, 레이저 추적 방식으로 모형선 실시간 위치를 계측하였다. 준비된 시스템으로 KVLCC2 1/100 축소모형선의 규칙파 중 선회시험을 수행하였다. 파 중 선회성능은 초반의 전진거리, 전술직경, 정상선회 시의 궤적밀림 거리, 각도 등으로 지수화할 수 있다. 각 지수를 추출하여 분석하였고, 동일한 파장 조건에 대한 궤적밀림 경향은 유사함을 보였다.

• Journal of the Korean Data and Information Science Society
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• v.21 no.5
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• pp.901-908
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• 2010

A geometrical description method is proposed to represent the process of the forward selection and backward elimination methods among many variable selection methods for multiple regression models. This graphical method shows the process of the forward selection and backward elimination on the first and second quadrants, respectively, of half circle with a unit radius. At each step, the SSR is represented by the norm of vector and the extra SSR or partial determinant coefficient is represented by the angle between two vectors. Some lines are dotted when the partial F test results are statistically significant, so that statistical analysis could be explored. This geometrical description can be obtained the final regression models based on the forward selection and backward elimination methods. And the goodness-of-fit for the model could be explored.

• The Science & Technology
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• v.1 no.2 s.2
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• pp.107-109
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• 1968

본란은 산하 각학회(협회)의 제반 소식을 전하기 위하여 ①활동상황 ②주요사업계획 ③사업실적 ④학회동정 ⑤건의사항 ⑥학회육성에 대한 고견 ⑦기타 등의 자세한 소식을 받아 전해드립니다. (도착순)

• Journal of the Society of Naval Architects of Korea
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• v.38 no.3
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• pp.41-46
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• 2001

The very large vessels like VLCC and container ship have been built recently and those vessels have smaller structural strength in comparison with the other convectional skips. As a result the fatigue destruction of upper deck occurs a frequently due to the springing phenomenon at the encountering frequencies. In this study, the hydrodynamic loads are calculated by three-dimensional source distribution method with the translating and pulsating Green function. A ship is longitudinally divided into 23 sections and the added mass, damping and hydrodynamic force of each section is calculated. focusing only on the vertical motion. Stiffness matrix is calculated by the Euler beam theory. The calculation is carried out for Esso Osaka.