• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2006-2009
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• 2005

This paper presents a method for registering images using phase correlation technique in fourier domain, hough transform and multi-resolution wavelet. To register images, source and input images are transformed to wavelet domain. An angular transition can be obtained by applying hough transform technique followed by phase correlation. Then we apply phase correlation technique to find x-axis and y-axis transition. We apply wavelet transform to reduce processing time and also use its coefficients as edge information instead of canny detector. With multi-resolution property of wavelet transform, registration time can be greatly reduced. After we get all transition parameters, we transform the input images according to these parameters. Then, we compose and blend all images into a new large image with details of all source images. From our experiment, we can find the accurate transition both x-y translation and angular transition with less error.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.865-870
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• 2004

This paper describes the generation of chordal surface for various shell structures, such as automobile bodies, plastic injection mold components and shell metal parts. After one-layered tetrahedral mesh is generated by an advancing front algorithm, the chordal surface is generated by cutting a tetrahedral element. It is generated one or two elements at a tetrahedral element and the chordal surface is composed with triangular or quadrilateral elements. This algorithm has been tested on several models with rib structure.

• Journal of applied mathematics & informatics
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• 제23권1_2호
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• pp.419-433
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• 2007

Medial axis transform (MAT) is very sensitive to noise, in the sense that, even if a shape is perturbed only slightly, the Hausdorff distance between the MATs of the original shape and the perturbed one may be large. Recently, Choi et al.(2002) showed that MAT is stable for a class of 2D domains called weakly injective, if we view this phenomenon with the one-sided Hausdorff distance, rather than with the two-sided Hausdorff distance. In this paper, we extend this result to general 2D domains with natural boundary regularity. We also present explicit bounds for this general one-sided stability of the 2D MAT.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제4권1호
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• pp.49-65
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• 2000

A method for inverting the Laplace transform is presented, using a finite series of the classical Legendre polynomials. The method recovers a real-valued function f(t) in a finite interval of the positive real axis when f(t) belongs to a certain class ${\mathcal{W}}_{\beta}$ and requires the knowledge of its Laplace transform F(s) only at a finite number of discrete points on the real axis s > 0. The choice of these points will be carefully considered so as to improve the approximation error as well as to minimize the number of steps needed in the evaluations. The method is tested on few examples, with particular emphasis on the estimation of the error bounds involved.

• 한국컴퓨터정보학회논문지
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• 제11권2호
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• pp.169-175
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• 2006

본 논문은 고정된 카메라를 수평 이동(panning)시켜 얻어진 영상으로부터 단순화된 변환식을 이용 실린더 파노라마 영상(cylindrical panorama)을 재구성하는 방법을 제안한다. 일반적인 영상간의 사영 변환식(projective transform)은 3차원 공간의 X, Y, Z축에 대한 카메라의 회전 성분을 모두 고려하지만, 실제 파노라마 영상을 구성하기 위해서는 Y축 중심의 카메라 회전만을 고려한다. 이러한 제약은 기존의 8자유도(degree of freedom)를 갖는 사영 변환식을 4자유도를 갖는 사영 변환식으로 단순화시키고, 그 결과 변환식을 유도하기 위해 필요한 대응점의 개수가 절반으로 줄어들어 전체적인 계산량을 크게 감소시킬 수 있다. 모의실험 결과 제안된 알고리즘은 기존의 알고리즘과 계산량을 감소시키면서 유사한 성능을 보이고 있고, 단순화된 사영 변환식을 이용한 영상을 구성하는 것을 보여주었다.

• 대한전자공학회논문지SD
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• 제37권3호
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• pp.39-47
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• 2000

본 논문에서는 입력영상에 대한 광학적 Hough변환(HT)의 결과로부터 θ = θo ＋ 90° 떨어진 지점에서 입력영상에 존재하는 직선과 타원의 장축의 길이 정보를 그리고 θ =θо 지점에서 타원의 단축의 길이정보를 추출하는 방법을 제안하였다. 각 지점에서 포락선의 최대점과 최소점 사이의 거리로부터 직선과 타원의 축의 실제길이를 약 98%의 정확도로 구할 수 있음을 시뮬레이션을 통하여 확인 하였다. 시뮬레이션 결과와 실험 결과를 비교하기 위하여 HT CGH 필터를 사용하여 광학적 실험을 행하였다. 실험을 통하여 광학적HT 결과가 이론적인 시뮬레이션 결과와 유사함을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.560-574
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• 2016

This paper presents a novel method for power system harmonic estimation based on the Park transform. The proposed method firstly extends the signal to a group of three-phase signals in a-b-c coordinate. Then, a linear fitting based method is adopted to estimate the fundamental frequency. Afterwards, the Park transform is utilized to convert the three-phase signals from a-b-c coordinate to d-q-0 coordinate. Finally, the amplitude and phase of a harmonic component of interest can be calculated using the d-axis and q-axis components obtained. Simulation studies have been conducted using matrix laboratory (MATLAB) and power system computer aided design/electromagnetic transients including direct current (PSCAD/EMTDC). Simulation studies in MATLAB have considered three scenarios, i.e., no-frequency-deviation scenario, frequency-deviation scenario and the scenario in the presence of inter-harminics. The results have demonstrated that the proposed method achieves very high accuracy in frequency, phase and amplitude estimation under noisy conditions, and suffers little influence of the inter-harmonics. Moreover, comparison studies have proved that the proposed method is superior to FFT and Interpolated FFT with the Hanning Window (IpFFTHW). Finally, a popular case in PSCAD/EMTDC has been employed to further verify the effectiveness of the proposed method.

• Journal of the Optical Society of Korea
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• 제14권2호
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• pp.104-108
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• 2010

We proposed an axis transformation technique which reveals a distance parameter directly from optical scanning holography (OSH). After synthesis of a real-only spectrum hologram and power fringe adjusted filtering, we transform an original frequency axis to a new frequency axis using interpolation. In the new frequency axis, the filtered hologram has a single frequency which is linearly proportional to the distance parameter. Thus, the inverse Fourier transformation of the filtered hologram gives a delta function pair in the new spatial axis. Finally, we extract the distance parameter by detecting the location of the delta function pair.

• 한국멀티미디어학회:학술대회논문집
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• 한국멀티미디어학회 2001년도 추계학술발표논문집
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• pp.111-114
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• 2001

게이트 심근 SPECT 영상은 좌심실 구혈률(EF), 확장기말 부피(end-diastolic volume), 수축기말(end-systolic volume)부피 등의 지표로 심근의 기능을 평가하는데 널리 이용된다. 이러한 지표들을 구하기 위해서는 심근 안팎의 경계선을 추출해야 한다. 본 연구는 좌심실의 SPECT short-axis 영상에서 전처리 과정을 거친 영상을 Hough Transform을 이용하여 초기점 설정한 후 심실 내외벽의 경계선을 추출하기 위해 Williams 가 제안한 Active Contour Model(snakes)을 이용하여 심근의 경계선을 자동으로 추출하였다.

• 반도체디스플레이기술학회지
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• 제23권2호
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• pp.33-37
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• 2024

Recently, wearable virtual reality devices are widely used. These instruments include a 3-axis accelerometer. User's heart rate information in virtual reality contents can be useful for measuring user experience. In this paper, we propose a method to measure the heart rate through a 3-axis accelerometer based on the principle of ballistocardiography without additional sensors. The angular velocity was successively measured in a time series by the 3-axis accelerometer mounted to the head. The frequency of the maximum magnitude is determined as the heart rate through frequency transform and band pass filtering of the time series signal. For verification, the heart rate calculated from photoplethysmography sensors acquired at the same time was compared as ground-truth. In the virtual reality, the user's heart rate information can be extracted without additional heart rate sensor, and the emotional state and fatigue can be measured.