• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1773-1778
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• 2006

Steady-state natural convection heat transfer characteristics from cylinders in a multiply-connected bounded region are clarified. A spectral finite difference scheme (spectral decomposition of the system of partial differential equations, semi-implicit time integration) is applied in numerical analysis, with a boundary-fitted conformal coordinate system through a Jacobian elliptic function with a successive transformation to formulate a system of governing equations in terms of a stream function, vorticity and temperature. Multiplicity of the domain is expressed explicitly.

• 대한수학회지
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• 제58권3호
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• pp.791-797
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• 2021

In this corrigendum, we offer a correction to [J. Korean Math. Soc. 54 (2017), No. 2, 461-477]. We construct a counterexample for the strengthened Cauchy-Schwarz inequality used in the original paper. In addition, we provide a new proof for Lemma 5 of the original paper, an estimate for the extremal eigenvalues of the standard unpreconditioned FETI-DP dual operator.

• 한국컴퓨터그래픽스학회논문지
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• 제22권2호
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• pp.1-10
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• 2016

의상 시뮬레이션과 렌더링 계산 비용은 메쉬의 종류와 그 품질에 크게 좌우 된다. 일반적으로 정확도와 효율성 면에서 삼각메쉬 보다 사각메쉬가 더 선호된다. 본 논문은 재귀 기하 분할법에 기초한 의복 패턴의 사각화 방법을 기술한다. 논문에서는 기존의 방법에서 두 가지 개선점을 제안한다. 첫째, 제안 방법은 기존의 방법보다 향상 된 회귀 기하 분해 알고리즘을 사용한다. 제안된 방법에서 의복패턴의 물리적 도매인은 보다 더 간단하고 맵핑 가능한 형태로 분해된다. 둘째, 본 논문에서는 정점 분류 알고리즘의 유효성 확인작업을 수행한다. 제안 알고리즘을 이용하여 인식 되지 않은 정점 분류에 대한 유효성을 검증 할 수 있다.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.425-434
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• 2020

Practical non-synoptic fluctuating wind often exhibits nonstationary features and should be modeled as nonstationary random processes. Generally, the coherence function of the fluctuating wind field has time-varying characteristics. Some studies have shown that there is a big difference between the fluctuating wind field of the coherent function model with and without time variability. Therefore, it is of significance to simulate nonstationary fluctuating wind field with time-varying coherent function. However, current studies on the numerical simulation of nonstationary fluctuating wind field with time-varying coherence are very limited, and the proposed approaches are usually based on the traditional spectral representation method with low simulation efficiency. Especially, for the simulation of multi-variable wind field of large span structures such as transmission tower-line, not only the simulation is inefficient but also the matrix decomposition may have singularity problem. In this paper, it is proposed to conduct the numerical simulation of nonstationary fluctuating wind field in one-spatial dimension with time-varying coherence based on the wavenumber-frequency spectrum. The simulated multivariable nonstationary wind field with time-varying coherence is transformed into one-dimensional nonstationary random waves in the simulated spatial domain, and the simulation by wavenumber frequency spectrum is derived. So, the proposed simulation method can avoid the complicated Cholesky decomposition. Then, the proper orthogonal decomposition is employed to decompose the time-space dependent evolutionary power spectral density and the Fourier transform of time-varying coherent function, simultaneously, so that the two-dimensional Fast Fourier transform can be applied to further improve the simulation efficiency. Finally, the proposed method is applied to simulate the longitudinal nonstationary fluctuating wind velocity field along the transmission line to illustrate its performances.

• 중소기업융합학회논문지
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• 제6권4호
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• pp.151-156
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• 2016

소프트웨어 생산성을 향상시키고 자동화하기 위한 효과적인 개발방법이 지속적으로 요구되어 왔다. 본 논문에서는 DMI를 기반으로 설계단계에서 도메인 설계정보를 재사용하기 위한 부품자산을 구성하려고 한다. 그리고 설계단계에서 설계정보를 재사용하기 위해서는 개발환경에 독립적인 플랫폼의 추상화된 아키텍처정보가 필요하다. 또한 잘 설계된 아키텍처를 기반으로 응용영역의 설계를 지원할 수 있어야 한다. 그러므로 본 연구에서는 아키텍처 레벨의 플랫폼과 응용 도메인영역의 설계정보를 정형화하여 표현할 수 있는 DMI 구조를 이용하였다. DMI에서 아키텍처 자산은 추상화 레벨이 높은 설계단계에서 설계정보를 자산부품으로 분해하거나 합성이 가능하다. 따라서 아키텍처 자산의 메타 데이터 구성은 도메인 영역의 기반설계구조를 재사용할 수 있는 구조를 지원하게 된다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.513-528
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• 2013

A floating Oscillating Water Column (OWC) wave energy converter, a Backward Bent Duct Buoy (BBDB), was simulated using a state-of-the-art, two-dimensional, fully-nonlinear Numerical Wave Tank (NWT) technique. The hydrodynamic performance of the floating OWC device was evaluated in the time domain. The acceleration potential method, with a full-updated kernel matrix calculation associated with a mode decomposition scheme, was implemented to obtain accurate estimates of the hydrodynamic force and displacement of a freely floating BBDB. The developed NWT was based on the potential theory and the boundary element method with constant panels on the boundaries. The mixed Eulerian-Lagrangian (MEL) approach was employed to capture the nonlinear free surfaces inside the chamber that interacted with a pneumatic pressure, induced by the time-varying airflow velocity at the air duct. A special viscous damping was applied to the chamber free surface to represent the viscous energy loss due to the BBDB's shape and motions. The viscous damping coefficient was properly selected using a comparison of the experimental data. The calculated surface elevation, inside and outside the chamber, with a tuned viscous damping correlated reasonably well with the experimental data for various incident wave conditions. The conservation of the total wave energy in the computational domain was confirmed over the entire range of wave frequencies.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.55-58
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• 1997

In this paper, we study a signal processing method which extracts each MUAP(motor unit action potential) from EMG(Electromyogram) interference pattern or clinical diagnostic purposes. First of all, differential digital filtering is selected or eliminating the spike components of the MUAP's from the background noise. And, the algorithm identifies the spikes over the certanin threshold by template matching in frequency domain. After missing or false firing actor is cut off at the IPI(inter pulse interval) histogram, we averages the MUAP waveforms from the raw signal using the identified spikes as triggers, and Finally, measures their amplitudes, durations, and numbers of phases. Specially, We introduce algorithm performed by template matching in the frequency domain. A typical 3-s signal recorded from the biceps brachii muscle using a conventional needle electrode during a isometric contraction is used. Finally, the method decomposed five simultaneous active MUAP's from original EMG signal.

• 한국음향학회지
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• 제31권5호
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• pp.317-331
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• 2012

본 논문에서는 다채널 음향 신호의 음원 분리를 수행하기 위하여, 빔공간-영역에서 다채널 비음수 행렬 분해 기법을 이용하는 음원 분리 시스템을 제안한다. 비음수 행렬 분해(NMF) 기법은 음원 분리에서 최근 널리 쓰이는 알고리즘이며, 특히 최근에는 다채널 비음수 행렬 분해(MC-NMF) 기법으로 발전하여 다채널 음향 신호에 대해서 적용되고 있다. 본 논문에서 제안하는 다채널 비음수 행렬 분해 기법은 빔공간-영역에서 수행되어, 기존의 다채널 비음수 행렬 분해 기법에 비해 좋은 성능을 가진다. 제안되는 비음수 행렬 분해 기법은 SiSEC 2010의 데이터셋을 이용하여 검증되었다.

• Journal of Information Processing Systems
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• 제16권6호
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• pp.1391-1406
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• 2020

A zero-watermarking algorithm in transform domain based on RGB channel and voting strategy is proposed. The registration and identification of ownership have achieved copyright protection for color images. In the ownership registration, discrete wavelet transform (DWT), discrete cosine transform (DCT), and singular value decomposition (SVD) are used comprehensively because they have the characteristics of multi-resolution, energy concentration and stability, which is conducive to improving the robustness of the proposed algorithm. In order to take full advantage of the characteristics of the image, we use three channels of R, G, and B of a color image to construct three master shares, instead of using data from only one channel. Then, in order to improve security, the master share is superimposed with the copyright watermark encrypted by the owner's key to generate an ownership share. When the ownership is authenticated, copyright watermarks are extracted from the three channels of the disputed image. Then using voting decisions, the final copyright information is determined by comparing the extracted three watermarks bit by bit. Experimental results show that the proposed zero watermarking scheme is robust to conventional attacks such as JPEG compression, noise addition, filtering and tampering, and has higher stability in various common color images.

• 대한전자공학회논문지SP
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• 제48권4호
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• pp.160-168
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• 2011

주파수 영역 빔형성기 (frequency domain beamformer)는 시간 영역 빔형성기에 비해 연산량 측면에서 효율성이 높아 다수의 빔과 센서가 요구되는 수동 소나 시스템에서 널리 사용되고 있다. 주파수 영역 빔형성기에서는 푸리에 변환을 통한 입력 신호의 스펙트럼 분석 과정이 필수적이며, 이 과정의 효율성에 따라 전체 시스템의 성능이 결정된다. 또한 기본적으로 실시간 신호처리가 요구되는 실제 전장 환경에서 이러한 스펙트럼 연산 과정 최적화의 중요성이 더욱 부각되고 있다. 따라서 본 논문에서는 실시간으로 수신되는 협대역 신호의 효율적인 국부 스펙트럼 분석 (partial spectrum analysis)을 위해, TD (transform decomposition) 기법과 GSFFT (generalized sliding fast Fourier transform) 기법의 장점을 모두 적용한 pruned-GSFFT 기법을 제안한다. 또한 제안된 기법의 구현상의 특성을 분석하고 요구되는 연산량을 기존 기법들과 비교한다.