• Journal of KIISE:Computer Systems and Theory
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• v.29 no.8
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• pp.440-444
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• 2002

This paper presents an efficient and robust algorithm to compute the isophote of a surface of revolution. A surface of revolution can be decomposed to a set of cross-sectional circles. The surface normals along each cross-sectional circle form a cone. Using the characteristics of the normal vectors and the symmetric property of the surface of revolution, we propose a method to find the connected components of an isophote, which requires intersecting a planar curve(and its reflection) with two rays. Moreover, we propose a closed-form representation of an isophote as a parametric curve.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04c
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• pp.202-204
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• 2003

본 논문은 isophote 제약조건을 사용한 유전자 알고리즘(Genetic Algorithms) 기반의 효율적인 오류 은닉 방법을 제안한다. 제안된 방법은 먼저 오류 블록을 경계선 정합 알고리즘(Boundary Matching Algorithm)을 사용하여 오류 블록의 주변과 가장 유사한 블록을 이전 프레임에서 찾아 교체한 후, isophote를 제약조건으로 가진 유전자 알고리즘을 사용하여 교체된 오류 블록을 재구성하는 것이다. Isophote들은 영상에서 일정한 밝기 값을 가지는 곡선들로, 본 논문에서는 비디오 통신 시 화질을 개선하기 위해, 전송 오류에 의한 끊어진 isophote들을 부드럽게 연결한다. 끊어진 isophote들을 연결하기 위해, isophote를 제약조건으로 가진 적합도 함수를 최소화하는 픽셀 값을 유전자 알고리즘을 사용하여 추정하고, 그 값을 isephote 방향으로 투영한다. 실험 결과, 제안된 방법이 다른 오류 은닉 방법 보다 좀 더 화질을 개선시킬 수 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.643-645
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• 2002

본 논문은 영상의 isophote정보를 constraint로 사용만 유전자 알고리즘 (Genetic Algorithms) 기반의 컬러 영상 복원방법을 제안한다. 제안만 방법은 오염된 관측 영상으로부터 원 영상으로 복원하기 위해. 영상 복원 문제인 illposed 문제를 유전자 알고리즘을 이용하여 비용함수(cost funcition)가 최소가 되도록 하는 최적화 문제로 모델링 한다. 본 논문에서 제안만 방법은 영상에서 같은 밝기 값을 가진 영역의 경계선을 나타내는 isophole 를 비용함수의 정칙화(regularization) 연산자로 사용하여 영상을 복원한다. 사용자가 복원할 영역을 지정만 후, 유전자 알고리즘을 사용하여 복원될 영역치 isophote 를 자연스럽게 유지하도록 복원한다. 제안한 방법은 디지털 비디오에서 상업적인 광고나, 자막 측은 로고등을 제거하는데 사용될 수 있으며, 실험 결과, 일반적으로 영상 복원에 많이 사용하는 Constraint 로 라플라시안(Laplaoian) 연산자보다 isophote를 정칙화 연산자로 사용함으로써 효율적으로 영상이 복원됨을 알 수 있다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.1-8
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• 2004

In this paper, we propose a method for restoring trademark and caption areas using an isophote. In our method, the image restoration problem is modeled as an optimization problem, which in our case, is solved by a cost function with isophote constraint that is minimized using a GA The technique creates an optimal connection of all pairs of isophotes disconnected by a caption in the frame. For connecting the disconnected isophotes, we estimate the value of the smoothness, given by the best chromosomes of the GA and project this value in the isophote direction. Experimental results show that the isophote operator worked better than Laplacian operator for image restoration, and the proposed method has a great possibility for automatic restoration of a region in an advertisement scene.

• Journal of Astronomy and Space Sciences
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• v.9 no.1
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• pp.1-10
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• 1992

Isophote map and luminosity profile of the barred spiral galaxy NGC 7755 are obtained from PDS scanning of PAL 0-471 plate. From the isophote map, NGC 7755 can be classified SBbc(r) with asymmetric bar ring. We get several physical parameters $({M_T}^\circ,U(R)_{CB},U(R)_{CD},D/B,C_{jj},M/L)$ of NGC 7755 from the analysis of the luminosity distribution.

• Journal of The Korean Astronomical Society
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• v.34 no.2
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• pp.59-66
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• 2001

In this paper, we investigate the correlation between the radial ultraviolet color distribution and the shapes of the ultraviolet isophote for elliptical galaxies (M32, NGC 1399) and spiral bulges (of M31, M81) by using their archival UIT images. For M31, M81, and NGC 1399, the radial ultraviolet color distributions show a two-component trend; as the distance from the galactic center increase the color becomes redder in the inner region while it becomes bluer in the outer region. On the other hand, the color of M32 continues to become bluer with the increasing galactocentric distance. We also find, unlike the optical/IR images, significant variations of the position angle and the ellipticity in the ultraviolet isophotes of M31, M81, and NGC 1399 through the inner regions. For M32, the variation is significant in the outer region. Since these variation implies the triaxiality of their intrinsic shapes, we suggest that the early-type galaxies and spiral bulges with a radial color gradient in ultraviolet tend to have a triaxiality. On the other hand, the shape parameter characterized by the fourth order cosine Fourier coefficient of the isophote, a(4)/a, indicates that the systematic deviations of the ultraviolet isophotes of the four galaxies are smaller than $\~0.2\%$ in units of the semi-major axis. The latter result implies that the ultraviolet isophotes of the galaxies have a pure elliptical shape rather than the boxy or disky shapes. Therefore, there is no clear evidence of correlation between the radial ultra-violet color gradient and the boxy/disky shapes of isophotes.

• Nonlinear Functional Analysis and Applications
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• v.26 no.2
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• pp.225-236
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• 2021

In this paper, we determine position vector of a line of curvature of a regular surface which is relatively normal-slant helix, with respect to Darboux frame. Then, a vector differential equation is established by means Darboux formulas, in the case of the geodesic torsion is vanishes. In terms of solution, we determine the parametric representation of a line of curvature which is relatively normal-slant helix, with respect to standard frame in Euclidean 3-space. Thereafter, we apply this result to find the position vector of a line of curvature which is isophote curve.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.63.1-63.1
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• 2014

The galaxy disk warp is a common phenomenon, yet their properties and formation mechanism(s) are still unclear. Here, we introduce a new automatic measurement method for the warp properties of stellar disks in nearby edge-on galaxies, including warp's angle, shape, and asymmetry. We obtain isophotal maps of edge-on galaxies and express each of isophote contours in polar coordinates (${\Phi}$, R) centered on the galaxy centers. Two peaks in the ${\Phi}$-R diagram correspond to the outermost tips of each isophote. The locations of peaks, in turn, inform us of the misalignment between their inner and outer galactic planes, i.e., the warp. We apply this method to SDSS Stripe 82 co-added data and discuss its reliability and validity. Based on the measurement of warp properties, we also investigate their correlations with both intrinsic and environmental properties of warped galaxies.

• Journal of The Korean Astronomical Society
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• v.19 no.2
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• pp.69-89
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• 1986

The global morphology and geometric parameters of 39 barred galaxies are investigated, by using isophote map and isodensity tracings obtained from detailed surface photometry with the Kiso V-band plates. The observed results are as follows: i) There is no strong indication that the ratio of bar length to disk size is correlated with Hubble type, except that the largest bars appear in the SBb galaxies. ii) The mean value of axial ratios of bars is $2.0{\pm}0.4$ and there is a trend that early type galaxies have smaller axial ratios than late type galaxies. iii) About 15% of early type barred galaxies(Sb0-SBb) have triaxial bulges.

• Journal of The Korean Astronomical Society
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• v.17 no.1
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• pp.23-36
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• 1984

From the PDS scanning, isophote maps and surface luminosity distributions for the late type spiral galaxy NGC 6946 were obtained. Surface luminosity distribution showed that this galaxy can be classified as the Freeman's type II, and the deep spheroidal component was caused as a result of the ring structure in the central part of NGC 6946. Physical parameters-total magnitude ($M_T^B$), effective radius ($R_e^*$), central surface magnitude $U(0)_{CD}$, length scale (${\alpha}^{-1}$), disk-to-bulge ratio (D/B) and mass-to-luminosity ratio (M/L)-were also calculated, and the results show that NGC 6946 belongs to Sc I type galaxy according to the DDO classification, and is to be a fair sample of classification statge T=6.