• 환경영향평가
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• 제27권5호
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• pp.447-474
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• 2018

본 연구의 목적은 다양한 지리통계학적 공간화 기법을 적용한 격자기후자료와 기상청에서 제공하는 국지예보모델(Local Data Assimilation and Prediction System, LDAPS) 격자기후자료를 비교 분석하여 남한 지역의 고해상도 격자기후지도 작성 방안을 모색하는 것이다. 2017년의 595개 기후관측자료 중, 80%의 지점자료를 이용하여 순간 온도와 1시간 누적강수량에 대한 격자기후자료를 생성하였고 나머지 117개의 지점자료를 검증에 이용하였다. ArcGIS10.3.1과 Python3.6.4을 이용하여 관측자료 및 DEM을 IDW, 공동크리깅, 크리깅에 적용한 후, 공간보간 결과를 3개 군집으로 나누어 검증하였으며 LDAPS 격자기후자료를 바탕으로 유역 별 패턴 비교를 수행하였다. 결과적으로 순간 온도의 공간화에는 고도를 부변수로 추가한 공동크리깅이, 1시간 누적강수량 공간화에는 IDW가 가장 적합하였다.

• 한국농림기상학회지
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• 제3권1호
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• pp.37-43
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• 2001

Crop status monitoring and yield prediction at higher spatial resolution is a valuable tool in various decision making processes including agricultural policy making by the national and local governments. A prototype crop forecasting system was developed to project the size of rice crop across geographic areas nationwide, based on daily weather pattern. The system consists of crop models and the input data for 1,455 cultivation zone units (the smallest administrative unit of local government in South Korea called "Myun") making up the coterminous South Korea. CERES-rice, a rice crop growth simulation model, was tuned to have genetic characteristics pertinent to domestic cultivars. Daily maximum/minimum temperature, solar radiation, and precipitation surface on 1km by 1km grid spacing were prepared by a spatial interpolation of 63 point observations from the Korea Meteorological Administration network. Spatial mean weather data were derived for each Myun and transformed to the model input format. Soil characteristics and management information at each Myun were available from the Rural Development Administration. The system was applied to the forecasting of national rice production for the recent 3 years (1997 to 1999). The model was run with the past weather data as of September 15 each year, which is about a month earlier than the actual harvest date. Simulated yields of 1,455 Myuns were grouped into 162 counties by acreage-weighted summation to enable the validation, since the official production statistics from the Ministry of Agriculture and Forestry is on the county basis. Forecast yields were less sensitive to the changes in annual climate than the reported yields and there was a relatively weak correlation between the forecast and the reported yields. However, the projected size of rice crop at each county, which was obtained by multiplication of the mean yield with the acreage, was close to the reported production with the $r^2$ values higher than 0.97 in all three years.

• 전자공학회논문지
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• 제50권7호
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• pp.205-215
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• 2013

디지털 이미징 장치는 일반적으로 베이어 패턴(Bayer pattern)을 사용하며, 영상 획득 과정에서 광학적 블러(blur)에 의해 영상의 품질이 손상된다. 블러된 베이어 영상에서 고해상도 컬러 영상을 얻기 위하여, 일반적으로 컬러 보간 방법과 디블러링 방법을 독립적으로 수행한다. 하지만, 베이어 샘플링에 의한 에지 정보가 불충분하여 에지를 가로지르는 방향으로 보간 하게 되고, 이에 따라 컬러 보간 과정에서 에러가 발생한다. 이러한 에러는 디블러링 과정에서 강조되어 영상의 품질을 하락시킨다. 따라서 본 논문은 컬러 보간 방법과 결합된 디블러링 알고리즘을 제안한다. 제안하는 방법은 크게 보간 단계와 영역 결정 단계로 나눌 수 있다. 보간 단계에서는 가정된 에지 방향에 따라 보간 및 디블러링 과정을 수행하고, 영역 결정 단계에서는 각 화소 위치에서 국부 영역의 특성을 추정하고, 보간 단계에서 구한 값을 영역 적응적으로 융합한다. 또한 본 논문에서는 디블러링 성능을 향상시키기 위하여 광학적 블러와 유사한 파동 광학에 근거한 블러 모델을 기반으로 하고, 추정한 국부 영역 특성을 반영하여 디블러링 필터를 추정한다. 실험 결과를 통해 제안하는 방법이 컬러 보간 에러가 확대되는 것을 방지함을 확인할 수 있으며, 기존 방법에 비해 수치적인 면과 시각적인 면에서 뛰어난 결과를 보임을 확인 할 수 있다.

• Nuclear Engineering and Technology
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• 제44권1호
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• pp.71-78
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• 2012

In many semi-empirical analyses of flow boiling heat transfer, an annular flow is often assumed as a model flow and the local liquid film thickness is a key parameter in the analysis. This work considers a simple electrical conductance technique to estimate the local liquid film thickness in two-phase annular flows. In this approach, many electrodes are mounted flush with the inner wall of the pipe. Voltage differences between two neighboring electrodes for concentric annular flows with various liquid film thicknesses are obtained before the main experiments and logged in a look-up table. For an actual application in the annual flow, voltage differences of neighboring electrodes are measured and then corresponding local film thicknesses are determined by the interpolation of the look-up table. Even though the proposed technique is quite simple and straightforward, the numerical and static phantom experiments support its usefulness.

• 한국통신학회논문지
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• 제32권5C호
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• pp.487-495
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• 2007

에러가 존재하는 전송 환경에서 압축된 영상을 전송하는 경우, 일정한 화질을 유지하기 위해서는 에러 은닉 기법이 필요하다. 본 논문에서는 블록 기반의 영상 압축에 있어서 공간적 에러 은닉 기법을 제안한다. 제안된 기법은 공간 영역에서 슬라이스 단위의 에러가 발생했을 경우, 에러가 발생한 블록에 이웃하는 상 하 블록의 경계 화소를 이용하여 손상된 블록의 상 하 외곽 영역의 세밀한 에지 방향성을 찾아 각각 부분 복원을 한다. 그리고 복원되지 않은 내부 영역은 이웃한 경계 화소를 이용하여 블록 내의 전체적인 에지 방향성을 찾아 적응적으로 최종 복원 영상을 만들어 내는 2단계의 경계 정합 기법이다. 이 기법은 기존의 에러 은닉 방식보다 복잡도가 낮을 뿐만 아니라 에지를 흐름을 잘 복원하여 객관적 주관적으로 우수한 복원 영상을 얻게 해준다.

• 한국항만학회지
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• 제13권1호
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• pp.167-174
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• 1999

Numerical analysis of two-fluid flows for both water and air is carried out. Free-Surface flows with an arbitrary deformation have been simulated around two dimensional submerged hydrofoil. The computation is performed using a finite volume method with unstructured meshes and an interface capturing scheme to determine the shape of the free surface. The method uses control volumes with an arbitrary number of faces and allows cell-wise local mesh refinement. the integration in space is of second order based on midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation in time through three time levels The linear equation systems are solved by conjugate gradient type solvers and the non-linearity of equations is accounted for through picard iterations. The solution method is of pressure-correction type and solves sequentially the linearized momentum equations the continuity equation the conservation equation of one species and the equations or two turbulence quantities.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.172-176
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• 2008

In this paper, three dimensional linear conforming variable-finite elements are presented with the aid of a smoothed integration (a class of stabilized conforming nodal integration), for mnltiscale mechanics problems. These elements meet the desirable properties of an interpolation such as the Kronecker delta condition, the partition of unity condition and the positiveness of interpolation function. The necessary condition of linear exactness is fully relaxed by employing the smoothed integration, which renders us to meet the linear exactness in a straightforward manner. This novel element description extend the category of the conventional finite elements space to ration type function space and give the flexibility on the number of nodes of element which are fixed in the conventional finite elements. Several examples are provided to show the convergence and the accuracy of the proposed elements, and to demonstrate their potential with emphasis on the multiscale mechanics problems such as global/local analysis, nonmatching contact problems, and modeling of composite material with defects.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.8-13
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• 2008

In this study, an adaptive node generation procedure in the radial point interpolation method is proposed. Since we set the initial configuration of nodes by subdivision of background cell, abrupt changes of inter-nodal distance between higher and lower error regions are unavoidable. This unpreferable nodal spacing induces additional errors. To obtain the smoothy nodal configuration, it's regenerated by local Delaunay triangulation algorithm This technique was originally developed to generate a set of well-shaped triangles and tetrahedra. To demonstrate the performance of proposed scheme, the results of making optimal nodal configuration with adaptive refinement method are investigated for stress concentration problems.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1215-1220
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• 2008

To obtain the shape of the free surface more accurately, computations are carried out by a finite volume method using unstructured meshes and an interface capturing method. Free-surface flow, which is very important in the fields of ship and marine engineering, is numerically simulated for flows of both water and air. Control volumes are used with an arbitrary number of faces and allows a local mesh refinement. The integration is of second order, with a midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation. The solution method of pressure-correction type solves sequentially equations of momentum, continuity, conservation, and two-equations turbulence model. Comparison are quantitatively made between the computation and experiment in order to confirm the solution method.

• 전자공학회논문지A
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• 제32A권9호
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• pp.106-113
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• 1995

The radiation characteristics of the subreflector of a shaped dual offset reflector antenna are analyzed by the uniform theory of diffraction(UTD). The discrete shaped subreflector profile is transformed into an analytic function by the global interpolation. To obtain the first and the second derivative terms on the surface, the local interpolation method is used. The reflection point needed for the geometrical optics(GO) is found by using the multi-dimensional function minimizing algorithm. The radiation pattern of a Gregorian type shaped subreflector is presented. The characteristics of the radiation patterns for various feed edge taperings and frequencies are examined.