• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.729-736
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• 2009

In order to understand flow characteristics and flight mechanism of hummingbird's flapping flight, two-dimensional numerical analysis is carried out on the flapping motion of hummingbird, Selasphorus rufus. Hummingbird's flapping wing motion is realistically modeled from wind tunnel experimental data to perform numerical analysis. Numerical simulation shows that, as freestream velocity changes, wing trajectory is also adjusted and it substantially affects lift and thrust generation mechanism. According to this tendency, flight domain is separated as "low speed" and "high speed" regime, and each flight domain is studied for physical understanding. As a result, the lift generation during downstroke can be explained by the well-known effects, such as leading edge vortex effect, delayed stall, wake capture and so on. In addition, the lift generation during upstroke, the unique character of hummingbird, is also examined by detailed flow analysis. The thrust generation mechanism is investigated by examining the hummingbird's wing bone structure, vortex generation pattern and the resulting pressure gradient.

• Journal of the Society of Naval Architects of Korea
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• v.61 no.4
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• pp.267-277
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• 2024

The Sortie Generation Rate (SGR) is a critical performance indicator for carrier-based aircraft and is a key factor for the carrier design process. This study aims to analyze the factors that affect SGR and establish a representative Sortie Generation Process (SGP) along with simulation results to calculate SGR for a naval ship equipped to carry aircraft. Detailed SGR factors are identified from the perspectives of the aircraft, aviation personnel, and aircraft carrier during the flight preparation stage, and the SGP is established accordingly. As a representative, Korean Navy's CVX basic design is chosen for detailed analysis. The physical dimension and spots for the deck design with time and probabilistic data of SGP are considered to develop a queueing network model for SGR calculation. To consider the specific probabilistic features, the model was solved with discrete event simulation tools(SimPy and AnyLogic) where the results show great agreement. Such findings on SGR factors and calculation are expected to be incorporated in the future development of SGR calculation algorithms and also present guidelines for proper design of aircraft carrier based on concrete operation concept.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1436-1443
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• 2013

A variety of studies on imitating the skeletal structure and the gait of legged animals have been done in order to develop walking robots which have an ability to adapt to atypical environments. In this paper, we analyzed the gait of a Bearded dragon lizard using the motion capture system, proposed a calibration scheme of the motion data and generated the trotting gait of a lizard based on the calibrated data. Also, we constructed the dynamic model based on the biometric data of a Bearded dragon lizard and applied the trotting gait of the lizard to the dynamic model. We verified the validity of the gait with the commercial dynamic simulation software.

• Journal of Korean Society for Atmospheric Environment
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• v.19 no.6
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• pp.745-756
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• 2003

An analysis of wind environments using computational fluid dynamics and an evaluation of wind resources using measurement data obtained from meteorological observation sites at Homi-Cape, Pohang have been carrid out for siting a wind farm. It was shown that a numerical simulation using computational fluid dynamics would provide reliable wind resource map in complex terrain with land-sea breeze condition. As a result of this investigation, Homi-Cape wind farm with 11.25 ㎿ capacity has been designed for maximum power generation and 25.7 GWh electricity production is predicted.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.192-195
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• 2000

GSM(Global System for Mobile Communication) system which is being used in Europe is composed A3, A5 and A8 algorithms. In this paper we implement A3 algorithm using VHDL, and verify the design by simulation. The A3 algorithm is divided into 3 parts, the encryption part, in which F-function encrypts 64 bit block data；the key generation part, which produces 32 bit subkeys；the control part, which produces the control code.

• Proceedings of the IEEK Conference
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• 2001.06b
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• pp.277-280
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• 2001

The proposed clock generator lowers the operating frequency in a system core though it keeps data bandwidth high because it has a multiphase clocking architecture. Moreover. it has a dual loop which is comprised of an inner analog phase generation loop and outer digital phase control loop. It has both advantages of DLL's wide operating range and DLL's low jitter The proposed design has been demonstrated in terms of the concept and Hspice simulation. All circuits were designed using a 0.25${\mu}{\textrm}{m}$ CMOS process and simulated with 2.5 V power supply.

• The Bulletin of The Korean Astronomical Society
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• v.26 no.2
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• pp.56-56
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• 2001

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.107-111
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• 2004

자기 유사적인 트래픽 성질이 차세대 고속 통신망의 성능에 미치는 영향을 예측 분석하기 위해서는 자기유사 트래픽을 정확하고 효율적으로 모델링하기 위한 연구 및 분석 결과는 인터넷 망이나 새롭게 구현될 시스템에서 반드시 고려하여야 할 사항이라고 판단된다. 이러한 관점에서 본 논문에서는 인터넷 데이터 트래픽이 갖는 통계적 특성인 자기유사 트래픽을 발생할 수 있는 시뮬레이션 모델을 제시하고 각 방식의 성능을 분석한 후 이를 기초로 데이터 트래픽이 입력되는 모듈들을 실험할 수 있는 트래픽 발생 방식을 제안하고 마지막으로 결론을 맺는다.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2012.07a
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• pp.38-40
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• 2012

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.377-382
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• 2010

In lunar explorer development program, computer simulator is necessary to provide virtual environments that vehicle confronts in lunar transfer, orbit, and landing missions, and to analyze dynamic behavior of the spacecraft under these environments. Objective of simulation differs depending on its application in spacecraft development cycle. Scope of use cases considered in this paper includes simulation of software based, processor and/or hardware in the loop, and support of ground-based flight test of developed vehicle. These use cases represent early phase in development cycle but reusability of modeling results in the next design phase is considered in defining requirements. A simulator architecture in which simulator platform is located in the middle and modules for modeling, analyzing, and three dimensional visualizing are connected to that platform is suggested. Baseline concepts and requirements for simulator development are described. Result of trade study for selecting simulation platform and approaches of defining other simulator components are summarized. Finally, characters of lunar elevation map data which is necessary for lunar terrain generation is described.