• 대한수학회지
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• 제48권6호
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• pp.1285-1325
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• 2011

We solve the isoperimetric problem, the least-perimeter way to enclose a given area, on various Euclidean, spherical, and hyperbolic surfaces, sometimes with cusps or free boundary. On hyperbolic genus-two surfaces, Adams and Morgan characterized the four possible types of isoperimetric regions. We prove that all four types actually occur and that on every hyperbolic genus-two surface, one of the isoperimetric regions must be an annulus. In a planar annulus bounded by two circles, we show that the leastperimeter way to enclose a given area is an arc against the outer boundary or a pair of spokes. We generalize this result to spherical and hyperbolic surfaces bounded by circles, horocycles, and other constant-curvature curves. In one case the solution alternates back and forth between two types, a phenomenon we have yet to see in the literature. We also examine non-orientable surfaces such as spherical M$\ddot{o}$obius bands and hyperbolic twisted chimney spaces.

• 한국환경과학회지
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• 제21권2호
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• pp.203-215
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• 2012

In order to clarify the impacts of thermal difference in atmospheric boundary layer due to the different sophistication of building information in Busan metropolitan areas, several numerical simulations were carried out. ACM (Albedo Calculation Model) and WRF (Weather Research and Forecasting) was applied for estimating albedo and meteorological elements in urban area, respectively. In comparison with coarse aggregated and small buildings, diurnal variation of albedo is highly frequent and its total value tend to be smaller in densely aggregated and tall buildings. Estimated TKE and sensible heat flux with sophisticatedly urban building parameterization is more resonable and valid values are mainly induced by urban building sophistication. The simulation results suggest that decreased albedo and increased roughness due to skyscraper plays an important role in the result of thermal change in atmospheric boundary layer.

• Wind and Structures
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• 제12권3호
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• pp.281-283
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• 2009

Marquardt method is used to estimate the aerodynamic parameters in urban area of Beijing City, China, including displacement length (d), roughness length ($z_0$) and friction velocity (u*) and drag coefficient. The surface drag coefficient defined as the ratio between friction velocity and mean wind speed is 0.125 in our research, which is close to typical urban area value. The averaged d and $z_0$ are 1.2 m and 7.6 m. d and $z_0$ change with direction because of the surface heterogeneity over urban surface and reach their maximum values at S-SW sector, this tendency agrees with the surface rough element distribution around the observation tower.

• 한국통신학회논문지
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• 제33권11C호
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• pp.898-904
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• 2008

본 논문에서는 컴퓨터적으로 생성하는 집적영상 시스템에서 요소영상 배열을 생성하기 위한 새로운 fast 알고리즘을 제안한다. 이 알고리즘은 깊이 정보를 사용해서 요소영상 배열을 생성하며, 경계 영역 개념을 도입하여 경계영역 내에 있는 복셀에 대해서만 연산을 수행하여 알고리즘의 계산 속도를 개선하였다. 제안된 알고리즘과 기존 알고리즘의 계산 시간을 이론적 및 실험적으로 비교한 결과 제안된 알고리즘이 더 효율적임을 증명하였다.

• 한국전기전자재료학회논문지
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• 제15권4호
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• pp.332-337
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• 2002

The applicability of models based on fractal geometry to characterize the surface of the EL devices was investigated. Insulating layer and phosphor layer of EL devices were deposited on ITO glass using e-beam method. The images of phosphor layer by scanning electron microscope(SEM) were transformed to binary coded data. The relations between fractal geometry and electrical characteristics of EL devices were investigated. When the fractal dimension of $Cas:EuF_3$ EL device was 1.82 and its grain boundary area was 19%, the brightness of $Cas:EuF_3$ EL device was 261 cd/$\textrm{m}^2$.

• Korean Journal of Hydrosciences
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• 제5권
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• pp.45-55
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• 1994

A new method to estimate the mean areal precipitation using kriging is developed. Urlike the conventional approach, points for double and quadruple numerical integrations in the kriging equation are selected randomly, given the boundary of area of interest. This feature eliminates the conventional approach's necessity of dividing the area into subareas and calculating the center of each subarea, which in turn makes the developed method more powerful in the case of complex boundaries. The algorithm to select random points within an arbitrary boundary, based on the theory of complex variables, is described. The results of Monte Carlo simulation showed that the error associated with estimation using randomly selected points is inversely proportional to the square root of the number of sampling points.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2003년도 춘계학술발표회 논문집
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• pp.277-281
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• 2003

We fused RADARSAT image and SPOT panchromatic image by wavelet transform in order to improve the accuracy of classification on the water area. Fused image in water not only maintained the characteristic of SAR image (low pixel value)but also had boundary information improved. This leads to accurate method to classify water areas.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제1권1호
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• pp.35-43
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• 1997

Handling the emergency problems such as Chemobyl accident require real time prediction of pollutants dispersion. One-point real time sounding at pollutant source and simple model including turbulent-radiation process are very important to predict dispersion at real time. The stability categories obtained by one-dimensional numerical model (including PBL dynamics and radiative process) are good agreement with observational data (Golder, 1972). Therefore, the meteorological parameters (thermal, moisture and momentum fluxes; sensible and latent heat; Monin-Obukhov length and bulk Richardson number; vertical diffusion coefficient and TKE; mixing height) calculated by this model will be useful to understand the structure of stable boundary layer and to handling the emergency problems such as dangerous gasses accident. Especially, this simple model has strong merit for practical dispersion models which require turbulence process but does not takes long time to real predictions. According to the results of this model, the urban area has stronger vertical dispersion and weaker horizontal dispersion than rural area during daytime in summer season. The maximum stability class of urban area and rural area are 'A' and 'B' at 14 LST, respectively. After 20 LST, both urban and rural area have weak vertical dispersion, but they have strong horizontal dispersion. Generally, the urban area have larger radius of horizontal dispersion than rural area. Considering the resolution and time consuming problems of three dimensional grid model, one-dimensional model with one-point real sounding have strong merit for practical dispersion model.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2002년도 추계학술발표회 논문집
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• pp.71-74
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• 2002

• 전자공학회논문지A
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• 제30A권3호
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• pp.104-113
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• 1993

A new switchbox router, called CONQUEROR, is proposed in this paper. The proposed CONQUEROR efficiently routes large switchbox routing area using divide-and-conquer technique. The CONQUEROR consists of three phases` namely, partition of large routing area and assignment of optimal pins of sub-area, detailed routing of each sub-ared, reassignment of pins after rip-up. First, large switchbox routing area is partitioned into several sub-areas and each sub-area contains 4-6 detailed grids. Then pins are assigned on boundary of sub-area by the estimated weight. Secondly, when global pin assignment is completed on all sub-areas, each sub-area is routed using detailed router. Also, detailed routing consists of three pases` layerless maze routing, assignment of layer using coloring, and rip-up and reroute. Lastly, if detailed routing of any sub-area fails,reassignment of pins after rip-up is invoked. Detailed routing is performed for the failed sub-area again. Benchmark test cases have been run, and on all the benchmark data known in the literature CONQUEROR has performed as well as or better than existing switchbox routers.