• Wind and Structures
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• 제7권6호
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• pp.373-392
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• 2004

This paper presents a methodology for spatial extrapolation of wind-induced pressure time series from a corner bay to roof locations on a low building away from the corner through the application of proper orthogonal decomposition (POD). The approach is based on the concept that pressure time series in the far field can be approximated as a linear combination of a series of modes and principal coordinates, where the modes are extracted from the full roof pressure field of an aerodynamically similar building and the principal coordinates are calculated from data at the leading corner bay only. The reliability of the extrapolation for uplift time series in nine bays for a cornering wind direction was examined. It is shown that POD can extrapolate reasonably accurately to bays near the leading corner, given the first three modes, but the extrapolation degrades further from the corner bay as the spatial correlations decrease.

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.64-72
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• 2016

The coverage area of a GNSS regional ionospheric delay model is mainly determined by the distribution of GNSS ground monitoring stations. Extrapolation of the ionospheric model data can extend the coverage area. An extrapolation algorithm, which combines observed ionospheric delay with the environmental parameters, is proposed. Neural network and least square regression algorithms are developed to utilize the combined input data. The bi-harmonic spline method is also tested for comparison. The IGS ionosphere map data is used to simulate the delays and to compute the extrapolation error statistics. The neural network method outperforms the other methods and demonstrates a high extrapolation accuracy. In order to determine the directional characteristics, the estimation error is classified into four direction components. The South extrapolation area yields the largest estimation error followed by North area, which yields the second-largest error.

• 한국항공운항학회지
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• 제22권3호
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• pp.74-81
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• 2014

The coverage area of GNSS regional ionospheric correction model is mainly determined by the disribution of GNSS ground monitoring stations. Outside the coverage area, GNSS users may receive ionospheric correction signals but the correction does not contain valid correction information. Extrapolation of the correction information can extend the coverage area to some extent. Three interpolation methods, Kriging, biharmonic spline and cubic spline, are tested to evaluate the extrapolation accuracy of the ionospheric delay corrections outside the correction coverage area. IGS (International GNSS Service) ionosphere map data is used to simulate the corrections and to compute the extrapolation error statistics. Among the three methods, biharmonic method yields the best accuracy. The estimation error has a high value during Spring and Fall. The error has a high value in South and East sides and has a low value in North side.

• 방송공학회논문지
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• 제20권4호
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• pp.533-544
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• 2015

최근에 대부분의 비디오 서비스는 무선 네트워크를 통해서 전송된다. 하지만 무선 네트워크 환경에서 비디오 패킷은 전송되는 동안 오류에 노출되기 쉽다. 이러한 문제를 해결하기 위해 본 논문에서는 새로운 오류 은닉 (Error Concealment : EC) 알고리즘을 제안한다. 제안하는 알고리즘에서는 High Efficiency Video Coding (HEVC) 환경에서 시간적 상관도를 이용한 적응적인 예측 단위 기반의 움직임 벡터 외삽 (Adaptive Prediction Unit-based Motion Vector Extrapolation : APMVE)과 공간적 상관도를 이용한 경계 정합(Boundary Matching : BM) 알고리즘을 이용한다. APMVE는 시간적 상관도를 기반으로 손실 프레임 이전 프레임의 예측 단위(Prediction Unit : PU)를 이용하여 오류 은닉 기본 단위 (Error Concealment Basic Unit : ECBU)를 적응적으로 결정하고 BM은 공간적 상관도를 이용하여 비신뢰 블록 (Unreliable Block)들에 한하여 수행한다. 제안하는 알고리즘은 기존 알고리즘에서 나타나는 블록킹 열화를 효과적으로 제거하여 높은 주관적 화질을 보여준다.

• 오토저널
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• 제7권3호
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• pp.94-101
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• 1985

The flame temperature of LPG-air premixture flame was measured by extrapolation of limiting case corresponding to the infinitely thin diameter of Platinum-resistance-hot-wire. LPG-air premixture flame, initially under atmospheric pressure and room temperature, propagates downward from top of the model combustion chamber maintained at constant pressure through the whole combustion process. Analytical calculation technique was also applied to determine full temperature history or spatial temperature distribution from flame reaction zone to burnt gas region.

• 한국산학기술학회논문지
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• 제18권5호
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• pp.120-124
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• 2017

시간적 초해상도 기법은 일반 카메라로 찍은 영상을 고속카메라로 찍은 영상과 같이 보일 수 있도록 프레임률을 증가시키는 방법이다. 전자광학 센서는 다양한 감시정찰 무기체계에 탑재되는데, 각 무기체계별 작전요구성능에 따라 필요로 하는 전자광학 센서의 공간적 해상도와 시간적 해상도가 달라진다. 대부분의 영상센서가 30~60 프레임/초로 영상을 촬영하기 때문에, 표적의 이동 및 변화가 이보다 더 빠른 경우 프레임률의 증가가 필요하다. 본 논문은 채널별 색상정보 외삽법을 활용하여 프레임률을 증가시키는 기법을 제안한다. DMD의 각 화소를 카메라 센서의 각 화소와 정합한 후, 카메라 센서의 베이어 패턴에 맞추어 각 채널별로 화소 그룹을 분리한다. DMD를 이용해 일반 카메라의 한 프레임이 채널별로 서로 다른 연속된 노출 시간을 가지도록 조절하여, 촬영한 영상을 프레임률이 증가한 단일채널 영상으로 변환한다. 옵티컬 플로우 기법을 활용하여 각 채널별로 시점에 맞는 가상의 영상을 생성하여, 프레임률이 증가한 단일채널 영상을 컬러채널 영상으로 만들었다. 시뮬레이션을 통해 제안된 시간적 초해상도 기법의 성능을 확인하였다.

• Ocean Systems Engineering
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• 제12권2호
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• pp.143-157
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• 2022

In this study, the nominal wake field of a semi-displacement type high-speed vessel was computed at full scale by using CFD (Computational Fluid Dynamics) and GEOSIM-based approaches. A scale effect investigation on nominal wake field of benchmark Athena vessel was performed with two models which have different model lengths. The members of the model family have the same Fr number but different Re numbers. The spatial components of nominal wake field have been analyzed by considering the axial, radial and tangential velocities for models at different scales. A linear feature has been found for radial and tangential components while a nonlinear change has been obtained for axial velocity. Taylor wake fraction formulation was also computed by using the axial wake velocities and an extrapolation technique was carried out to get the nonlinear fit of nominal wake fraction. This provides not only to observe the change of nominal wake fraction versus scale ratios but also to estimate accurately the wake fraction at full-scale. Extrapolated full-scale nominal wake fractions by GEOSIM-based approach were compared with the full-scale CFD result, and a very good agreement was achieved. It can be noted that the GEOSIM-based extrapolation method can be applied for estimation of the nominal wake fraction of semi-displacement type high-speed vessels.

• Journal of applied mathematics & informatics
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• 제4권1호
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• pp.17-30
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• 1997

In this work we approximate the solution of initialboun-dary value problem using a Galerkin-finite element method for the spatial discretization and Implicit Runge-Kutta method for the spatial discretization and implicit Runge-Kutta methods for the time stepping. To deal with the nonlinear term f(x, t, u), we introduce the well-known extrapolation sheme which was used widely to prove the convergence in $L_2$-norm. We present computational results showing that the optimal order of convergence arising under $L_2$-norm will be preserved in $L_{\infty}$-norm.

• 대한토목학회논문집
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• 제29권6B호
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• pp.543-550
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• 2009

선형외삽법에 기초한 전형적인 단시간 강우예측모형은 호우를 발생하는 강우시스템의 발달과정을 모의하지 못하는 한계를 내포하고 있다. 본 연구에서는 이러한 한계를 극복하기 위하여 기상레이더로 획득할 수 있는 여러 시간대의 반사도 정보로부터 획득한 정보변화 과정과 다항 회귀식을 이용하여 x방향과 y방향의 전파속도의 성장과정과 레이더 반사도의 성장과정 모의에 기초한 단시간 강우예측 모형을 개발하였다. 검정통계량이 제시한 결과는 2-CAPPI를 이용한 기존의 단시간 강우예측모형보다 개선된 결과를 보여주었다. 그럼에도 불구하고 본 모형이 완전한 물리적 모형이 아니라 자료사이의 상관성과 다항 회귀식을 이용한 통계적인 방법에 기초하였으므로 강우의 성장과 소멸과정을 구현과 예측성 개선에도 한계가 있음을 보였다.

• 한국실내디자인학회논문집
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• 제18권2호
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• pp.3-15
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• 2009

In the swirl of change in the world, Media, the development of information technology, and the enterprise-oriented capitalism have tied the world as one unit, and have entered the period of adaptation. With the view of introspection of these concepts, this paper is mainly written by the theory of "matter as the content" with exploration of the design of essence and scientific approach. The design process is the condensational process which is developed by the exchange of reason and sensibility. This process, which is characterized by the objective manipulation of a given condition and the intervention of extrapolation, is the new way of thinking and approach rather than the concept of the way and means. The research of this paper is based on paintings and the analysis of essential experiments in design, the definition of the terms of content in the view of philosophy and design, and the analysis of the cases in architecture and spacial design. As a result, this paper shows that these designs are not just "Simulacre" but the essential eidos, and "content" is the core of these designs which can produce prototype as machine. Also, these designs can relatively be the persuasive methodology for the reflexive modernization.