• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1459-1474
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• 2006

The present study is focused on the development of the RIF (Representative Interactive Flamelet) model which can overcome the shortcomings of conventional approach based on the steady flamelet library. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the RIF model can effectively account for the detailed mechanisms of $NO_x$ formation including thermal NO path, prompt and nitrous $NO_x$ formation, and reburning process by hydrocarbon radical without any ad-hoc procedure. The flamelet time of RIFs within a stationary turbulent flame may be thought to be Lagrangian flight time. In context with the RIF approach, this study adopts the Eulerian Particle Flamelet Model (EPFM) with mutiple flamelets which can realistically account for the spatial inhomogeneity of scalar dissipation rate. In order to systematically evaluate the capability of Eulerian particle flamelet model to predict the precise flame structure and NO formation in the multi-dimensional elliptic flames, two methanol bluffbody flames with two different injection velocities are chosen as the validation cases. Numerical results suggest that the present EPFM model has the predicative capability to realistically capture the essential features of flame structure and $NO_x$ formation in the bluff-body stabilized flames.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.61-69
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• 2018

In this paper, we propose a method for recognizing ground target using dual polarization channels in millimeter waveband air-to-surface radar. First, the Push-Broom target detection method is described and the received signal is modeled considering flight-path scenario of air-to-surface radar. The scattering centers were extracted using the RELAX algorithm, which is a time domain spectral estimation technique, and the feature vector of the target was generated. Based on this, a DB for 4 targets is constructed. As a result of the proposed method, it is confirmed that the target classification rates is improved by more than 15% than the single channel using the data of the dual polarization channel.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.12 no.3
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• pp.1-12
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• 2004

When a straight-in landing from an instrument approach using ILS or VOR/DME is not possible or desirable because of topographical reason or bad weather, a circling approach maneuver is initiated by the pilot to align the aircraft with a runway for landing. Visual contact with the runway is necessary while conducting a circle to land maneuver. This research is to develop a new warning system based on a conventional marker system which alerts pilots to watch out for exceeding the circling approach area. The airborne system also uses the same receiver unit without any new installations. The objective of this research is to design and develop a Yagi antenna in a special form. The research includes computer simulations to determine the size of antenna radiation pattern and to compute an expected flight path in case of alarm to validate effectiveness of the system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.1 s.94
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• pp.53-62
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• 2005

This study presents the NDE (non-destructive evaluation) technique for detecting the loosened bolts on joint steel structures on the basis of TOF (time of flight) and amplitudes of Lamb waves. Probabilistic neural network (PNN) technique which is an effective tool for pattern classification problem was applied to the damage estimation using PZT induced Lamb waves. Two kinds of damages were introduced by dominant damages (DD) which mean loosened bolts within the Lamb waves beam width and minor damages (MD) which mean loosened bolts out of the Lamb waves beam width. They were investigated for the establishment of the optimal decision boundaries which divide each damage class's region including the intact class. In this study, the applicability of the probabilistic neural networks was identified through the test results for the damage cases within and out of wave beam path. It has been found that the present methods are very efficient and reasonable in predicting the loosened bolts on the joint steel structures probabilistically.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.1027-1030
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• 2015

In the airborne SAR, the motion errors induced by atmospheric turbulence decrease the resolution and increase the sidelobes. If the sidelobes are not properly compensated, the image quality is degraded. Thus, in this paper, we have introduced the sidelobe reduction method to increase the image quality. After we calculate the scene center based on the estimated squint angle for the flight path partitioned by the subaperture technique, we perform the motion compensation for the scene center. Then, after we perform the recursive sidelobe reduction for the region of interest in the reconstructed SAR image, we extend it for the full image.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.4
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• pp.316-319
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• 2018

To detect the ground moving target, forward-looking SAR images obtained from the FMCW radar can be exploited. However, the quality of the SAR image is deteriorated due to the turbulence or fluctuation because of the flight path condition during the missile movement. We herein propose an entropy-minimizing autofocus method to compensate the motion error of forward-looking SAR. In particular, owing to the geometry of the forward-looking SAR, the motion error affects the SAR image in the two-dimensional (2D) form (azimuth and time axis). Therefore, we suggest a 2D autofocus method for the motion compensation.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.49.3-49.3
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• 2009

Geostationary Ocean Colour Imager (GOCI) is the first ocean color instrument that will be operating in a geostationary orbit from 2010. GOCI will provide the crucial information of ocean environment around the Korean peninsula in high spatial and temporal resolutions at eight visible bands. We report an on-going development of imaging and radiometric performance prediction model for GOCI with realistic data for reflectance, transmittance, absorption, wave-front error and scattering properties for its optical elements. For performance simulation, Monte Carlo based ray tracing technique was used along the optical path starting from the Sun to the final detector plane for a fixed solar zenith angle. This was then followed by simulation of red-tide evolution detection and their radiance estimation, following the in-orbit operational sequence. The simulation results proves the GOCI flight model is capable of detecting both image and radiance originated from the key ocean phenomena including red tide. The model details and computational process are discussed with implications to other earth observation instruments.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.3
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• pp.492-500
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• 2011

The airborne backbone network(ABN) provides communication transport services between airborne nodes, surface nodes and satellite nodes. Such ABN is generally constructed with wide-body and high-capacity planes such as AWACS, which can fly long-term along pre-defined flight paths. In this paper, we propose an efficient method to improve routing performances by reconfiguring routing path before link failure based on the prediction of link state with the information of pre-defined backbone nodes' trajectories. Since the proposed method does not need additional information exchange between airborne nodes in order to acknowledge the link failure, it can be effectively used for airborne backbone network with limited bandwidths.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.625-632
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• 2004

This study presents the NDE (non-destructive evaluation) technique for detecting the loosened bolts on joint steel structures on the basis of TOF (time of flight) and amplitudes of Lamb waves. Probabilistic neural network (PNN) technique which is an effective tool for pattern classification problem was applied to the damage estimation using PZT induced Lamb waves. Two kinds of damages were introduced by dominant damages (DD) which mean loosened bolts within the Lamb waves beam width and minor damages (MD) which mean loosened bolts out of the Lamb waves beam width. They were investigated for the establishment of the optimal decision boundaries which divide each damage class's region including the intact class. In this study, the applicability of the probabilistic neural networks was identified through the test results for the damage cases within and out of wave beam path. It has been found that the present methods are very efficient and reasonable in predicting the loosened bolts on the joint steel structures probabilistically.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10b
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• pp.172-177
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• 2007

공중공간은 평면에 비해 넓고 많은 항공기들이 고속으로 비행하고 있다. 더불어 항공사고는 바로 대형사고로 이어지므로 공중상황 통제의 중요성은 항상 강조되고 있다. 그러나 항공기는 3차원 공간에서 복잡한 패턴으로 비행하기 때문에 통제하기가 매우 어렵다. 통제를 위한 공중상황 정보는 시각화 시스템을 통해 제공되고 있으나, 이를 운영하는 통제요원의 경험, 인지능력이 공중상황판단의 결정적 역할을 하고 있다. 그래서 정확한 상황판단을 위한 정보제공이 매우 중요하다. 본 논문에서는 공중상황에 대한 정확한 정보제공을 위해 비행경로를 이용한 시각화 기법을 제안한다. 대부분의 항공기는 정지하지 않고, 급격한 상태전이 없이 이동하므로 과거 비행자료를 통해 미래의 비행상태를 예측할 수 있다. 즉 과거 상태정보와 현재 상황정보를 통합하여 시각화하면 비행패턴을 예측할 수 있어 정확한 공중상황 판단이 가능하다. 이를 위해 실시간 자료를 분석하여 동적자료를 구분한다. 동적자료만으로 상태전이자료를 생성하고 비행경로 상에서 색상과 도형 및 기호화를 통해 시각화한다. 비행경로와 색상 및 기호화로 제공된 상태전이 시각화 정보는 항공기의 상승/하강, 가속/감속, 직진/선회, 기타 상태전이정보와 바람의 방향과 같은 공중 공간의 상황정보 둥을 제공할 것이다. 이를 통해 운용요원은 공중상황을 정확히 인식하고 신속하게 판다하여 통제함으로서 공중안전을 도모하고 통제업무를 효과적으로 수행할 수 있을 것이다.