• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.17-25
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• 2006

In the present study, a 2-D chimera technique for overlapped bodies in relative motion is developed using unstructured triangular meshes. The solid boundary nodes located next to the intersecting point between bodies are merged to the intersecting point to assure accurate representation of the intersecting region. In order to assign proper value of flow variables at the nodes located out of the computational field, interpolation is conducted for non-active nodes. For validation, the motions of a NACA64A006 airfoil and a NACA0012 airfoil with a plane flap are computed and the results are compared with other simulations. The motion of a launching missile ejected from a NACA0012 airfoil is also simulated.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.422-427
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• 2018

The purpose of this study is to investigate the effect of acoustic radiation force on the standing wave acoustic levitation phenomenon, which is the levitation of small objects near the pressure node of the standing wave, using the Bernoulli principle. The source and scheme of the acoustic radiation force, which is the cause of the levitation, are conceptually explained through comparison with the graph of the acoustic radiation force versus the distance from the transducer. A series of experiments supporting this explanation was performed with a BLT(Bolt-clamped Langevin Type) ultrasonic transducer to confirm that the objects are floating near the pressure nodes and that it satisfies the condition for the standing wave formation when the object is levitating. Furthermore, the vertical alignment of floating objects, which is a characteristic of standing wave acoustic levitation phenomenon, could be explained.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.104-117
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• 1991

When a body starts to move, the flow near the intersection point between a body and a free surface changes violently and rapidly in a very short initial time interval. This flow phenomena must be investigated whenever one treats the interaction between a body and a fluid, such as the motion of a floating body, sloshing in a tank, wave maker problem, entry of a body into a fluid etc.. Until Roberts(1987), it was widely accepted that a singularity exists at the intersection point. However, he showed that the singularity does not exist if a body moves non-impulsively. In this paper, an analytical solution cosistent for the case of impulsive motion of a body is obtained by including the effect of surface tension. From the characteristics of the newly obtained solution, a critical value associated with an oscillating phenomenon is found, and further more, it is shown that the oscillating phenomenon does not appear in the region where the distance form the intersection point is less than this critical value.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.433-440
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• 2018

A radar receives reflected signals from various objects to detect a target. Undesired object, called clutter, as well as the target generates reflected signals. The clutter radar cross section(RCS) is dependent on many factors, which are the antenna pattern, distance between the radar and the target, and the height of the target and the radar. Herein, surface clutter RCS for ground-based radar is analyzed, and the effect of the surface clutter RCS on the received signal is investigated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.671-674
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• 2018

In this study, we implement a YOLO driving assistance system using a model car. The YOLO is an object detection and recognition algorithm using deep running which is becoming an issue recently. The system alerts the lane departure by applying the image processing technology to the image acquired through the camera, recognizes the objects using the YOLO, and performs various functions according to the type of the object and the distance between the vehicle. the YOLO, which is superior to the existing object detection and recognition algorithm, improves the performance of the driving assist system without additional equipment. The driving assist system using the YOLO will ensure the safety of the driver with low cost.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.157-158
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• 2011

Golf clubs hit the ball, and golf balls fly with great speed and long distances due to the conflict. In this paper, the size of the momentum after collision of golf clubs and golf balls should seek. Also, the collision times and average force that served of golf clubs and golf balls are obtained. We know that the impulse acting body is equals the change in momentum of a body. And you can see the average force is constant force that the actual strength of a body to give the same impulse instead of force changing by the hour.

• The KIPS Transactions:PartB
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• v.13B no.5 s.108
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• pp.515-524
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• 2006

Background extraction is an important technique to find the moving objects in video surveillance system. This paper proposes a new on-line background extraction method for color video using vector order statistics. In the proposed method, using the fact that background occurs more frequently than objects, the vector median of color pixels in consecutive frames Is treated as background at the position. Also, the objects of current frame are consisted of the set of pixels whose distance from background pixel is larger than threshold. In the paper, the proposed method is compared with the on-line multiple background extraction based on Gaussian mixture model(GMM) in order to evaluate the performance. As the result, its performance is similar or superior to the method based on GMM.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.2
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• pp.75-82
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• 2001

In this paper, a transmitter and a receiver using a Gunn diode and SBD was designed and fabricated in X-band. This system detects Doppler shift signal reflected by moving target through the homodyne detection, which is Doppler radar sensor for the measurement of the velocity of moving target. By the experimental results, the oscillating condition of the transmitter was satisfied at about the half wavelength between the supporting post of the Gunn diode in the waveguide and the waveguide short. And using the fabricated Doppler radar sensor, the velocity measurement deviation of moving target was 1.24%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10B
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• pp.1111-1116
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• 2009

In this paper, we discuss distortion-tolerant pattern recognition using computational integral imaging reconstruction. Three-dimensional object information is captured by the integral imaging pick-up process. The captured information is numerically reconstructed at arbitrary depth-levels by averaging the corresponding pixels. We apply Fisher linear discriminant analysis combined with principal component analysis to computationally reconstructed images for the distortion-tolerant recognition. Fisher linear discriminant analysis maximizes the discrimination capability between classes and principal component analysis reduces the dimensionality with the minimum mean squared errors between the original and the restored images. The presented methods provide the promising results for the classification of out-of-plane rotated objects.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2002.12a
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• pp.313-316
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• 2002

이동 물체의 이동 거리 추적이나 대상 물체의 인식과 판별 물체의 특징 추출과 같은 응용분야에서 컴퓨터(Computer)와 비젼시스템(vision system)을 이용한 영상 데이터 처리 분야에 대한 이용률이 증가하면서, 그에 따른 연구가 활발히 진행되고 있다. 따라서 CCD 카메라(Charge-Couple Device Camera)로부터 입력된 그레이 레벨(Gray Level)의 영상을 입력받아 처리과정을 거쳐 위치정보를 전송하는 과정에서 정확한 정보를 얻기 위한 전처리 과정 방법을 제안하고, 실제 시스템에 적용한 결과를 제시한다. 여기서 영상의 전처리 과정 중 입력 영상에서 불필요한 부분을 제거하거나, 배경과 대상물의 분리, 내포된 잡음을 없애기 위하여 흔히 이진화 방법을 많이 사용한다 특히 이진화 과정에서 그레이 레벨의 입력영상에서 히스토그램(histogram) 정보를 이용하여 영상의 이진화시의 임계값을 찾는 것은 아주 중요한 요인이다 따라서 본 논문에서는 신경회로망을 이용하여 실시간으로 CCD 카메라를 통하여 입력되는 그레이 레벨의 입력 영상에 대하여 동적으로 적당한 임계값을 .찾는 방법을 제안하고자한다. 또한 제안한 신경회로망을 이용한 임계값 추출 알고리즘(algorithms)을 구현한 시스템(system)에 적용하여 일반적인 방법과 비교 검토하고 응용 가능성을 확인한다.