• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.75-78
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• 2004

A mesh generation algorithm adapted to the mesh density map using the Delaunay mesh generation technique is developed. In the finite element analyses of the forging processes, the numerical error increases as the process goes on because of discrete property of the finite elements or severe distortion of elements. Especially, in the region where stresses and strains are concentrated, the numerical discretization error will be highly increased. However, it is too time consuming to use a uniformly fine mesh in the whole domain to reduce the expected numerical error. Therefore, it is necessary to construct locally refined mesh at the region where the error is concentrated such as at the die corner. In this study, the point insertion algorithm is used and the mesh size is controlled by moving nodes to optimized positions according to a mesh density map constructed with a posteriori error estimation. An optimization technique is adopted to obtain a good position of nodes. And optimized smoothing techniques are also adopted to have smooth distribution of the mesh and improve the mesh element quality.

• 산업경영시스템학회지
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• 제34권3호
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• pp.24-34
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• 2011

An Unmanned Aerial Vehicle (UAV) is a powered pilotless aircraft, which is controlled remotely or autonomously. UAVs are an attractive alternative for many scientific and military organizations. UAVs can perform operations that are considered to be risky or uninhabitable for human. UA V s are currently employed in many military missions such as reconnaissance, surveillance, enemy radar jamming, decoying, suppression of enemy air defense (SEAD), fixed and moving target attack, and air-to-air combat. UAVs also are employed in a number of civilian applications such as monitoring ozone depletion, inclement weather, traffic congestion, and taking images of dangerous territory. For accomplishing the UAV's missions, guarantee of survivability should be preceded. The main objective of this study is to suggest a mathematical programming model and a $A^*PS$-PGA (A-star with Post Smoothing-Parallel Genetic Algorithm) for an UAV's path planning to maximize survivability. A mathematical programming model is composed by using MRPP (Most Reliable Path Problem) and TSP (Traveling Salesman Problem). A path planning algorithm for UAV is applied by transforming MRPP into SPP (Shortest Path Problem).

• 한국CDE학회논문집
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• 제10권3호
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• pp.162-167
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• 2005

A 3D solid element mesh generation algorithm was newly developed. 3D surface points of global rectangular coordinates were supplied by a 3D laser scanner. The algorithm is strait forward and simple but it generates hexahedral solid elements. Then, the surface rectangular elements were generated from the solid elements. The key of the algorithm is elimination of unnecessary elements and 3D boundary surface fitting using given 3D surface point data.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1998년도 학술대회
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• pp.33-36
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• 1998

Most image restoration problems are ill-posed and need to e regularized. A difficult task in image regularization is to avoid smoothing of image edges. In this paper, were proposed an edge-preserving image restoration algorithm using block-based edge classification. In order to exploit the local image characteristics, we classify image blocks into edge and no-edge blocks. We then apply an adaptive constrained least squares (CLS) algorithm to eliminate noise around the edges. Experimental results demonstrate that the proposed algorithm can preserve image edges during the regularization process.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.418-418
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• 2000

This paper proposes a path planning algorithm for mobile robot. To generate an optimal path and minimum time path for a mobile robot, we use the Genetic Algorithm(GA) and Visibility Graph. After finding a minimum-distance between start and goal point, the path is revised to find the minimum time path by path-smoothing algorithm. Simulation results show that the proposed algorithms are more effective.

• 대한산업공학회지
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• 제26권3호
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• pp.289-295
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• 2000

The triangulation problem is to make triangles using the given points on the space. The Minimum Weight Triangulation(MWT) is the problem of finding a set of triangles with the minimum weight among possible set of the triangles. In this paper, a modified genetic algorithm(GA) based on an existing genetic algorithm and multispace smoothing technique is proposed. Through the computational results, we can find the tendency that the proposed GA finds good solutions though it needs longer time than the existing GA does as the problem size increases.

• 대한전자공학회논문지SP
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• 제44권2호
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• pp.55-62
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• 2007

본 논문에서는 카메라 자동 교정을 통한 3차원 재구성 과정에서 생기는 오차로 인해 포함되는 잡음을 특성에 따라 효과적으로 제거하여 정교한 3차원 데이터를 얻기 위한 방법을 제안한다. 기존의 잡음 평활화 과정은 잡음 때문에 면적이 큰 메쉬는 3차원으로 재구성하는데 문제점이 존재한다. 제안한 알고리즘은 메쉬의 면적이 중요하기 때문에 취득된 3차원 데이터는 불필요한 삼각형 메쉬들을 사전에 제거하는 전처리 과정이 필요하다. 본 연구는 3차원 메쉬의 면적 정보를 이용하여 잡음의 특성을 분석하고, 그 특성에 따라 피크 잡음과 가우스 잡음을 분리하여 효과적으로 잡음을 제거한다. 본 알고리즘의 성능은 재구성 데이터에 대한 정량적인 비교 분석을 통해 기존의 메쉬 평활화 방법보다 더 정교한 3차원 데이터를 얻음을 확인하였다.

• 자동차안전학회지
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• 제13권2호
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• pp.35-41
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• 2021

In this study, improved path tracking control algorithm based on pure pursuit algorithm is newly proposed by using improved lane detection algorithm through real time post-processing with interpolation methodology. Since the original pure pursuit works well only at speeds below 20 km/h, the look-ahead distance is implemented as a sigmoid function to work well at an average speed of 45 km/h to improve tracking performance. In addition, a smoothing filter was added to reduce the steering angle vibration of the original algorithm, and the stability of the steering angle was improved. The post-processing algorithm presented has implemented more robust lane recognition system using real-time pre/post processing method with deep learning and estimated interpolation. Real time processing is more cost-effective than the method using lots of computing resources and building abundant datasets for improving the performance of deep learning networks. Therefore, this paper also presents improved lane detection performance by using the final results with naive computer vision codes and pre/post processing. Firstly, the pre-processing was newly designed for real-time processing and robust recognition performance of augmentation. Secondly, the post-processing was designed to detect lanes by receiving the segmentation results based on the estimated interpolation in consideration of the properties of the continuous lanes. Consequently, experimental results by utilizing driving guidance line information from processing parts show that the improved lane detection algorithm is effective to minimize the lateral offset error in the diverse maneuvering roads.

• 정보처리학회논문지C
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• 제14C권3호
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• pp.285-292
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• 2007

적응형 대역폭 할당 방법에서는 가변 비트율로 저장된 비디오 데이터에 대한 전송 계획을 세우고 네트워크 트래픽을 고려하여 전송하는데, 전송 계획으로 CBA 알고리즘이 사용된다 그러나, CBA 알고리즘에서는 전송률 증가 구간의 크기가 감소 구간의 크기보다 일반적으로 크며, 전송률이 증가될 때에 오버플로우 경계선에서 전송률이 변화되므로 가용 전송률이 작은 경우에는 폐기되는 프레임의 양이 많아지게 된다. 본 논문에서는 이를 개선하기 위하여 언더플로우 경계선과 오버플로우 경계선의 중간에서 전송률이 변화되지만, 전송률의 증가가 필요한 경우에는 증가 양을 최소로 하는 스무딩 알고리즘을 제안한다. 제안 알고리즘과 CBA 알고리즘을 적응형 대역폭 할당 방법의 전송 계획으로 사용하였을 때, 최소 재생률, 평균 재생률, 재생률 변화량, 그리고 폐기되는 프레임 양을 비교하여 제안 알고리즘의 성능이 우수함을 보였다.

• 한국음향학회지
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• 제30권7호
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• pp.383-389
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• 2011

본 논문에서는 음성향상을 위하여 환경잡음분류를 적용한 향상된 음성부재확률 추정방법을 제안한다. 기존의 음성부재확률 추정방법에서는 마이크로폰 입력신호와 추정된 잡음신호 기반의 a posteriori SNR값에 문턱값을 적용하여 음성부재확률을 구하는데 필요한 음성부재의 a priori 확률을 도출하였다. 본 논문에서 제안된 알고리즘은 보다 효과적인 음성부재확률 추정을 위하여 고정된 문턱값과 스무딩 (smoothing)파라미터를 사용하는 기존의 방법과는 달리 잡음분류 알고리즘인 가우시안 혼합 모델 (Gaussian mixture model)을 사용하여 잡음마다 최적화된 파라미터를 적용한다. 제안된 음성 향상 기법은 ITU-T P.862 PESQ (perceptual evaluation of speech quality)와 composite measure를 이용하여 다양한 환경에서 평가하였으며, 제안된 알고리즘이 기존의 음성부재확률 추정방법보다 향상된 결과를 보였다.