• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.220-228
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• 2008

In this study the aerodynamic characteristics of a canard-controlled missile with freely spinning tailfins were investigated by using a semi-empirical method and a CFD code. The mean aerodynamic coefficients for the rolling and roll damping moments were first calculated and then used to predict the roll-rate of freely spinning tailfins. The calculation of roll-rate in the CFD code was carried out by combining a Chimera overset grid system and 6-DOF analysis module. The predicted roll-rate was in good agreement with the experimental data for the roll and yaw canard control inputs. It was also shown that the results are in good agreement with the prediction by a CFD code. This indicates that the semi-empirical method can be used to predict the roll-rate of a canard-controlled missile with freely spinning tailfins.

• Journal of the Korea Society for Simulation
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• v.28 no.1
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• pp.49-56
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• 2019

In this study aerodynamic characteristics of guided gliding type ammunition were investigated by using a computational analysis and wind tunnel test. Missile DATCOM, a semi-empirical method, and a FLUENT, a computational fluid dynamics analysis program, were used for computational analysis. For a guided gliding type ammunition, aerodynamic characteristics were investigated by calculating lift force, drag force, pitching moment and etc. Aerodynamic characteristics of guided gliding type ammunition are completely different from those of conventional ammunition. The results obtained from the computer analysis are similar to those obtained from the wind tunnel test. Although the pitch moment values obtained by the semi-empirical method were slightly different from the wind tunnel test results, the overall computer analysis results showed trends and values similar to the test results. In this study, aerodynamic characteristics of guided gliding type ammunition were identified and it found that semi-empirical method can be applied to analyze the aerodynamic characteristic in the initial design of guided gliding ammunition.

• Journal of Science Education
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• v.38 no.1
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• pp.144-159
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• 2014

The purpose of this study was to investigate the effects of the elementary students' environmentally friendly attitude and environment literacy through Edward de Bono's Six Thinking Hats in science class. The objects of this study were the sixth grade of both an experimental class (25 students) and a comparative class (24 students) a the S elementary school science class located in Incheon city. The results of this study were as follows: First, the change of environmentally friendly attitude in the experimental group applying the six thinking hats program have statistically meaningful differences (p<.05). Second, the environmental literacy of the experimental group was improved somewhat, but it has no meaningful differences compared the other group statistically. Therefore, the six thinking hats program applied in this study might be useful to improve the students' environmentally friendly attitude in elementary school science class.

• The KIPS Transactions:PartB
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• v.12B no.2 s.98
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• pp.131-136
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• 2005

Motion Estimation (ME) has been developed to remove redundant data contained in a sequence of image. And ME is an important part of video encoding systems, since it can significantly affect the qualify of an encoded sequences. Generally, ME consists of two stages, the integer pixel motion estimation and the half pixel motion estimation. Many methods have been developed to reduce the computational complexity at the integer pixel motion estimation. However, the studies are needed at the half pixel motion estimation to reduce the complexity. In this paper, a method based on the correlations between integer pixel motion vectors and half pixel motion vectors is proposed for the half pixel motion estimation. The proposed method has less computational complexity than the full half pixel search method (FHSM) that needs the bilinear interpolation of half pixels and examines nine half pixel points to the find the half pixel motion vector. Experimental results show that the speedup improvement of the proposed method over FHSM can be up to $2.5\~80$ times faster and the image quality degradation is about to $0.07\~0.69(dB)$.

• Journal of KIISE:Software and Applications
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• v.26 no.1
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• pp.66-79
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• 1999

요약화일 기법은 대규모 데이터베이스 응용에서 효율적인 색인 기법으로 알려져 있으며 최근에는 보다 빠른 검색을 위해 병렬 요약화일 기법이 제안되고 있다. 본 논문에서는 효율적으로 병렬 처리를 할 수 있는 수직 분할 병렬 요약화일(Vertically-partitioned Parallel Signature File, VPSF) 기법을 제안한다. 본 VPSF는 동적인 환경에 잘 적응하도록 신장해싱을 이용하며, 검색의 효율성을 위해 프레임 슬라이스 기법을 사용한다. 실행의 편중을 없애기 위해 요약을 수직으로 분할하여 레코드를 프로세싱노드에 저장함으로써 병렬처리를 수행한다. 뿐만 아니라, 본 논문에서는 VPSF의 효율성을 보이기 위해 성능평가 모델을 제시하고, 실제의 레코드 집합을 가지고 실험을 실시하여 검색시간, 부가저장공간, 삽입시간에 대해 성능을 평가한다. 또한 레코드 집합의 분포에 다른 성능을 평가하기 위해 표준편차를 반으로 줄인 반 정규분포와 두 배로 크게 한 정규분포에 대한 성능평가를 실시한다. VPSF기법은 기존의 병렬 요약화일 기법들과 비교할 때, 실제 레코드 집합의 정규분포에서 기존의 Hamming filter 보다 평균 40% 정도 검색성능이 개선된다. 반 정규분포에서는 Hamming filter 보다 약 50% , HPSF보다 약 20% 정도 개선된 검색 성능을 보인다. 뿐만 아니라, 부가 저장공간 및 삽입시간에도 기존의 방법들보다 좋은 성능을 보인다. 일반적으로 VPSF는 데이터베이스의 레코드 크기가 서로 비슷할 때 그리고 데이터베이스의 크기가 클수록 우수한 검색 성능을 보인다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.3
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• pp.26-31
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• 2005

An efficient estimation of the aerodynamic characteristics for missile configurations is essential in the preliminary stage of a missile design. In this study, a Missile DATCOM family code based on the semi-empirical method was utilized for this purpose. In order to check the accuracy and reliability of the code several test cases have been considered: subsonic flow with high angles of attack and supersonic flow with moderate angles of attack. It turned out that the code in general provides prediction in qualitative agreement with the experimental data and results by other works. Finally, the code was applied to a more complicated missile configuration with canard and freely spinning tail fin.

• The Journal of the Acoustical Society of Korea
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• v.31 no.6
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• pp.410-418
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• 2012

Parametric stereo(PS) and MPEG surround(MPS) are major spatial audio coding(SAC) tools. In this paper, the problem of the inter-channel correlation(ICC) synthesis in the conventional SAC is analyzed. Conventional methods assume that ambient components mixed to two output channels are anti-phased, while the primary components are assumed to be in-phased. This assumption can cause excessive ambient mixing for a negative-valued ICC. As a remedy to this problem, we propose a new ICC synthesis method based on an assumption that the primary components are anti-phased each other for a negative ICC. The proposed method is also applied to the approximation which works in practice. The performance of the proposed method was evaluated by computer simulations and the subjective listening tests verified that the proposed method is effective in not only headphones but also loudspeakers playback.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.6
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• pp.37-46
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• 2006

It is known to be hard to apply cryptographic one-way functions to the recognition system using bio-information directly. As one of the solutions about that problem there is a permutation transformation scheme. However, they did not show my algorithmic behavior or any performance analysis of the transformation by experiment. In this paper, by showing the recognition ratio of the transformed scheme by experiment, we prove that that scheme is sound. Also, we adopt their transformation to LDA(Linear Discriminant Analysis) to show the experimental results. In the negative side, we introduce a new type of attack against the permutation transformation schemes. finally, we briefly mention a generalization of the permutation transformation for countermeasure of the attack at the end of this paper.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.61-73
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• 2004

Rayleigh wave and Love wave are the major elastic waves belonging to the category of the surface wave. The fact that Love wave is not contaminated by P-wave makes Love wave superior to Rayleish wave and other body waves. Therefore, the information that Love wave carries is more distinct and clearer than the information of Rayleigh wave. In this study, for the purpose of employing Love wave in the SASW method, the dispersion characteristics of the Love wave were extensively investigated by the theoretical, numerical and experimental approaches. The 2-D and 3-D finite element analyses for the half space and two-layer systems were performed to determine the phase velocities from Love wave as well as from both the vertical and the horizontal components of Rayleigh wave. Also, the SASW measurements were performed at the geotechnical sites to verify the results obtained by the numerical analysis. The results of the numerical analysis and the field testing indicated that the dispersion characteristics of Love wave can be an extended information to make better evaluation of the subsurface stiffness structure by SASW method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.79-81
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• 2018

혈관내 초음파(Intravascular Ultrasound, IVUS)는 혈관 내벽의 단면을 보여주는 검사 방법으로 관상 동맥 내의 내강, 죽상 경화반, 그리고 혈관벽의 변화에 관한 직접적이고 구체적인 정보를 제공한다. 본 논문에서는 IVUS 영상에서 내막과 외막을 추출하고 각 막의 지름을 자동적으로 추출하는 방법을 제안한다. 제안된 방법은 IVUS 영상에 Histogram Equalization 기법을 적용하여 명암 대비를 강조한 후에 퍼지 이진화 기법과 평균 이진화 기법을 각각 적용하여 내막과 외막을 추출하기 위해 이진화한다. 이진화된 내막과 외막의 각 영역 중에서 혈관내 초음파 영상 중심에서 가장 큰 영역의 정보를 이용하여 라벨링 기법을 적용하여 내막과 외막 영역을 추출하고 각 막의 지름을 계산한다. 제안된 방법을 IVUS 영상을 대상으로 실험한 결과, 내막과 외막의 지름이 비교적 정확히 추출되는 것을 실험을 통하여 확인하였다.