• Structural Engineering and Mechanics
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• v.58 no.3
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• pp.443-458
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• 2016

In this paper, we propose a method for taking into account uncertainties based on the projection on polynomial chaos. Due to the manufacturing and assembly errors, uncertainties in material and geometric properties, the system parameters including assembly defect, damping coefficients, bending stiffness and traction-compression stiffness are uncertain. The proposed method is used to determine the dynamic response of a one-stage spur gear system with uncertainty associated to gear system parameters. An analysis of the effect of these parameters on the one stage gear system dynamic behavior is then treated. The simulation results are obtained by the polynomial chaos method for dynamic analysis under uncertainty. The proposed method is an efficient probabilistic tool for uncertainty propagation. The polynomial chaos results are compared with Monte Carlo simulations.

• ETRI Journal
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• v.40 no.2
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• pp.246-256
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• 2018

A spatial augmented reality (SAR) system enables a virtual image to be projected onto the surface of a real-world object and the user to intuitively control the image using a tangible interface. However, occlusions frequently occur, such as a sudden change in the lighting environment or the generation of obstacles. We propose a robust object tracker based on a multithreaded system, which can track an object robustly through occlusions. Our multithreaded tracker is divided into two threads: the detection thread detects distinctive features in a frame-to-frame manner, and the tracking thread tracks features periodically using an optical-flow-based tracking method. Consequently, although the speed of the detection thread is considerably slow, we achieve real-time performance owing to the multithreaded configuration. Moreover, the proposed outlier filtering automatically updates a random sample consensus distance threshold for eliminating outliers according to environmental changes. Experimental results show that our approach tracks an object robustly in real-time in an SAR environment where there are frequent occlusions occurring from augmented projection images.

• Structural Engineering and Mechanics
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• v.53 no.4
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• pp.819-831
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• 2015

In this paper, we propose a new method for taking into account uncertainties based on the projection on polynomial chaos. The new approach is used to determine the dynamic response of a spur gear system with uncertainty associated to gear system parameters and this uncertainty must be considered in the analysis of the dynamic behavior of this system. The simulation results are obtained by the polynomial chaos approach for dynamic analysis under uncertainty. The proposed method is an efficient probabilistic tool for uncertainty propagation. It was found to be an interesting alternative to the parametric studies. The polynomial chaos results are compared with Monte Carlo simulations.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.959-960
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• 2008

Recently, biometric authentication mechanism has been used to provide high level of security in cryptographic systems. In this paper, we propose an efficient method of generating invariant iris key to be applied in cryptographic systems. In order to generate iris key and improve the performance at the stolen token scenario, multiple random projection technique was combined with multiple linear transformation methods. From the experimental results, we proved that invariant iris keys were generated and the proposed method was robust to stolen token scenario.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.2
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• pp.118-126
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• 2008

Statistical image reconstruction methods have played an important role in emission computed tomography (ECT) since they accurately model the statistical noise associated with gamma-ray projection data. Although the use of statistical methods in clinical practice in early days was of a difficult problem due to high per-iteration costs and large numbers of iterations, with the development of fast algorithms and dramatically improved speed of computers, it is now inevitably becoming more practical. Some statistical methods are indeed commonly available from nuclear medicine equipment suppliers. In this paper, we first describe a mathematical background for statistical reconstruction methods, which includes assumptions underlying the Poisson statistical model, maximum likelihood and maximum a posteriori approaches, and prior models in the context of a Bayesian framework. We then review a recent progress in developing fast iterative algorithms.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.269-274
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• 1999

As the semiconductor industry enters the next century, we are facing to the technological changes and challenges. Optical lithography has driven by the miniaturisation of semiconductor devices and has been accompanied by an increase in wafer productivity and performance through the reduction of the IC image geometries. In the last decade, DRAM(Dynamic Random Access Memories) have been quadrupoling in level of integration every two years. Korean chip makers have been produced the memory devices, mainly DRAM, which are the driving force of IC＇s(Integrated Circuits) development and are the technology indicator for advanced manufacturing. Therefore, Korean chip makers have an important position to predict and lead the patterning technology. In this paper, we will be discussed the limitations of the optical lithography, such as KrF and ArF. And, post optical lithography technology, such as E-beam lithography, EUV and E-beam Projection Lithography shall be introduced.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.11a
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• pp.242-244
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• 2014

파노라마 영상은 하나의 영상이 가지는 제한된 시점의 한계를 극복하고 폭넓은 시야를 가질 수 있다는 점에서 최근 여러 분야에서 활용되고 있는 기술이다. 본 논문에서는 자연스러운 파노라마 영상 생성을 위해 SURF(speed up robust feature)를 이용한 특징점 기반의 파노라마 영상 생성 기법을 제안한다. SURF 알고리즘을 사용하면 정합할 두 영상에서 특징점들을 추출할 수 있다. 추출된 특징점들을 RANSAC(random sample consensus) 알고리즘을 통해 특징점 간 정합시 오차율을 최소화한다. 또한, 이미지 왜곡을 최소화하기 위해 실린더 투영을 이용하여 영상을 보정한다. 최종적으로, 서로 다른 두 영상을 합성할 때 발생하는 경계 주변의 이질감을 보완하기 위해 블렌딩 기법을 사용함으로써 자연스러운 파노라마 영상을 생성한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.271-273
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• 2002

추천 시스템에서 사용되고 있는 중요한 방법인 협력적 여과는 유사한 사용자들에 기초하여 그 사용자들이 선호하는 아이템을 교차 추천을 해주는 방법이다. 사용자들에 대한 정보는 아이템을 평가한 등급에 기초하며, 그 평가 등급 패턴이 유사한 사용자를 찾게 된다. 협력적 여과는 사용자와 정보의 증가에 따라서 성능이 저하되는 문제점을 가지고 있다. 이러한 문제점을 해결하기 위하여 SVD, PCA, LSI와 같은 차원 감소 방법이 제시되어 왔으나, 이러한 방법은 계산 비용이 크다는 단점을 가지고 있다. 따라서, 계산 비용이 적고, 정확성에 있어서도 충분히 정확한 임시 사상이 최근에 주목을 받고 있다. 본 논문에서는 임의 사상을 이용한 차원 감소 방법이 협력적 여과에 미치는 효과를 실험을 통하여 제시한다. 실험적으로, 임의 사상 방법은 협력적 여과에서 충분히 정확한 성능을 보였다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.2
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• pp.73-79
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• 1987

This paper describes a new algorithm to evaluate the production cost for a generation system including energy-limited hydroelectric plants. The algorithm is based upon the analytical production costing model developed under the assumption of Gaussian probabilistic distribution of random load fluctuations and plant outages. Hydro operation and pumped storage operation have been dealt with in the previous papers using the concept of peak-shaving operation. In this paper, the hydro problem is solved by using a new version of the gradient projection method that treats the upper / lower bounds of variables saparately and uses a specified initial active constraint set. Accuracy and validity of the algorithm are demonstrated by comparing the result with that of the peak-shaving model.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.499-502
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• 2012

문양이나 패턴이 없는 민 무늬의 물체에는 동일점 정합에 의해 3 차원 계측을 하는 스테레오 정합방식을 적용할 수 없다. 본 논문에서는 난수 발생 함수로 제작한 랜덤 칼라 패턴을 대상물체에 투영하여, 대상 물체 표면에 특징적인 문양을 인위적으로 생성시키는 것에 의해 민 무늬의 물체를 스테레오 정합법으로 측정하는 방식을 제안한다. 투사된 패턴으로 자체 문양을 지니게 된 물체를 스테레오 카메라로 촬영하였고, 동일점 정합은 전역 스테레오 정합 방식의 일종인 TRW 방식에 의한 컬러 매칭 방식을 사용하였다. 제안된 방식은 원형의 흰색 석고상 3 차원 계측에 적용되었고, 안정적이고 정확한 스테레오 정합 계측 결과를 보였다.