• 한국해양공학회지
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• 제34권2호
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• pp.89-96
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• 2020

In this study, the Norbury-Fraenkel family of vortex rings is analyzed using a contour dynamics method for the stream function, which significantly reduces the numerical burden in the calculation. The stream function is formulated as the integral along the contour of the vorticity core. The integration over the logarithmic-singular segment is evaluated analytically, and the positions of the nodal points of the contour are calculated directly. The shapes of the cores and the dividing stream surfaces are found based on the mean core radius. Compared with other studies, the proposed method is verified and found to be more efficient.

• Communications for Statistical Applications and Methods
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• 제21권5호
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• pp.461-469
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• 2014

Characteristic functions play an important role in probability and statistics; however, a rigorous derivation of these functions requires contour integration, which is unfamiliar to most statistics students. Without resorting to contour integration, Datta and Ghosh (2007) derived the characteristic functions of normal, Cauchy, and double exponential distributions. Here, we derive the characteristic functions of t, truncated normal, skew-normal, and skew-t distributions. The characteristic functions of normal, cauchy distributions are obtained as a byproduct. The derivations are straightforward and can be presented in statistics masters theory classes.

• Communications for Statistical Applications and Methods
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• 제21권1호
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• pp.81-91
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• 2014

This study derives the characteristic functions of (multivariate/generalized) t distributions without contour integration. We extended Hursts method (1995) to (multivariate/generalized) t distributions based on the principle of randomization and mixtures. The derivation methods are relatively straightforward and are appropriate for graduate level statistics theory courses.

• 한국해양공학회지
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• 제36권2호
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• pp.108-114
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• 2022

Most studies on the shape of the steady vortex ring have been based on the Stokes stream function approach. In this study, the velocity approach is introduced as a trial approach. A contour dynamics method for fluid velocity is used to analyze the Norbury-Fraenkel family of vortex rings. Analytic integration is performed over the logarithmic-singular segment. A system of nonlinear equations for the discretized shape of the vortex core is formulated using the material boundary condition of the core. An additional condition for the velocities of the vortical and impulse centers is introduced to complete the system of equations. Numerical solutions are successfully obtained for the system of nonlinear equations using the iterative scheme. Specifically, the evaluation of the kinetic energy in terms of line integrals is examined closely. The results of the proposed method are compared with those of the stream function approaches. The results show good agreement, and thereby, confirm the validity of the proposed method.

• 비파괴검사학회지
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• 제31권6호
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• pp.665-670
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• 2011

In this paper, a new approach to detect surface cracks from a noisy thermal image in the infrared thermography is presented using an holomorphic characteristic of temperature field in a thin plate under steady-state thermal condition. The holomorphic function for 2-D heat flow field in the plate was derived from Cauchy Riemann conditions to define a contour integral that varies according to the existence and strength of a singularity in the domain of integration. The contour integral at each point of thermal image eliminated the temperature variation due to heat conduction and suppressed the noise, so that its image emphasized and highlighted the singularity such as crack. This feature of holomorphic function was also investigated numerically using a simple thermal field in the thin plate satisfying the Laplace equation. The simulation results showed that the integral image selected and detected the crack embedded artificially in the plate very well in a noisy environment.

• 한국정보과학회논문지:소프트웨어및응용
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• 제34권1호
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• pp.1-10
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• 2007

본 논문에서는 MPEG-7 시각 정보 기술자인 Dominant Color와 Contour Shape 기술자에 대한 새로운 인덱싱 알고리즘을 제안한다. Dominant Color 기술자에서 사용되는 비교 연산 식은 가우스 혼합 모델에 기초하고 있기 때문에 기술자의 각 속성들을 하나의 칼라 히스토그램 형태로 변형시켜서 인덱스로 사용한다. Contour Shape 기술자는 두 단계 형태의 알고리즘을 사용하는데, 첫 번째 단계에서는 글로벌 변수인 Eccentricity와 Circularity를 사용한 대략적인 비교를 통해서 비슷하지 않은 이미지 오브젝트를 배제시키고 두 번째 단계에서 남겨진 오브젝트들과 질의 오브젝트들간의 Peak 변수를 사용한 비교 연산을 통해 인덱싱을 수행한다. 또한 본 논문은 효율적인 멀티미디어 데이타 검색을 위해서 두 가지의 MPEG-7 시각 정보 기술자 결합 알고리즘을 제안한다. 첫 번째 결합 알고리즘은 가중치를 확률로 변환해서 반영하는 것이고 두 번째는 가중치를 각 비교 연산 결과값의 중요도로 간주하는 방법이다. 실험을 통해서 결과를 분석해 보면 근사화를 통한 인덱스 생성으로 100%의 정확도를 유지 할 수는 없지만 논문에서 제안된 각 기술자의 인덱싱 알고리즘과 기술자들의 결합 알고리즘은 기본 검색 알고리즘과 비교했을 때 매우 빠른 속도 향상을 보여주었다. 본 논문에서 제안된 알고리즘은 MPEG-7을 사용하는 검색 시스템의 데이타베이스 구축에 효율적으로 사용될 수 있다.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 봄 학술발표논문집 Vol.31 No.1 (B)
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• pp.148-150
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• 2004

최근 멀티미디어 정보를 기술하기 위한 표준인 MPEG-7이 제안되어 이미지/동영상 검색 시스템과 같은 응용분야에서 사용되기 시작하였다. 그러나 MPEG-7 시각 정보 기술자들은 대부분 고차원으로 표현되고 기술자들이 가지는 각 속성들의 성질이 서로 동일하지 않기 때문에 기존의 인덱싱 방법으로는 효율적인 검색을 할 수 없다. 본 논문에서는 MPEG-7 시각 정보 기술자중에서 많이 사용되는 Dominant Color 기술자와 Contour Shape 기술자에 대한 새로운 인덱싱 알고리즘을 제안한다. Dominant Color 기술자에서 사용되는 비 교 연산 식 은 가우스 혼합 모델에 기초하고 있기 때문에, 기술자의 각 속성들을 하냐의 칼라 히스토그램 형태로 변형시켜서 인덱스로 사용한다. Contour Shape기술자는 2 단계 형태의 알고리즘을 사용한다. 각 단계는 글로벌 파라미터 속성과 비트맵 인덱스를 사용한 인덱싱이 적용된다. 제안된 인덱싱 방법을 사용했을 때 Dominant Color의 경우 90%의 정확도에 120배 이상의 속도 향상을 나타냈고, Contour Shape의 경우 82%의 정확도에 3배 이상의 속도 향상을 나타냈다.

• 한국통신학회논문지
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• 제18권1호
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• pp.143-149
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• 1993

An approach is presented for efficient numerical integration of the Sormnerfeld type integrals pertinent to the microstrip surface Green's function arising in the problem of an electric current point source on an infinite planar grounded dielectric substrate. This approach, valid for both lossless and lossy dielectric substrates, is based on the deformation of the integration contour via a coordinate transformation and Cauchy's residue theory, and identifies clearly the effects of surface waves. I ts useful application is in a rigorous moment method analysis of micros trip antenna arrays and microstrip guided wave structures. The efficiency and the usefulness of the present approach are emphasized through some numerical calculations of the impedance matrix elements with associated CPU times.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권11호
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• pp.2839-2852
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• 2013

Context-awareness is an essential part of ubiquitous computing, and over the past decade video based activity recognition (VAR) has emerged as an important component to identify user's context for automatic service delivery in context-aware applications. The accuracy of VAR significantly depends on the performance of the employed human body segmentation algorithm. Previous human body segmentation algorithms often engage modeling of the human body that normally requires bulky amount of training data and cannot competently handle changes over time. Recently, active contours have emerged as a successful segmentation technique in still images. In this paper, an active contour model with the integration of Chan Vese (CV) energy and Bhattacharya distance functions are adapted for automatic human body segmentation using depth cameras for VAR. The proposed technique not only outperforms existing segmentation methods in normal scenarios but it is also more robust to noise. Moreover, it is unsupervised, i.e., no prior human body model is needed. The performance of the proposed segmentation technique is compared against conventional CV Active Contour (AC) model using a depth-camera and obtained much better performance over it.

• Selected Papers of The Society of Naval Architects of Korea
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• 제2권1호
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• pp.1-17
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• 1994

For a planar curve-sided panel with constant or linear density distributions of source or doublet in the singularity methods, Cantaloube and Rehbach show that the surface integral can be transformed into contour integral by using Stokes'formulas. As an extension of their formulations, this paper deals with a planar polygonal panel for which we derive the closed-forms of the potentials and the velocities induced by the singularity distributions. Test calculations show that the analytical evaluation of the closed-forms is superior to numerical integration (suggested by Cantaloube and Rehbach) of the contour integral. The compact and explicit expressions may produce accurate values of matrix elements of simultaneous linear equations in the singularity methods with much reduced computer time.