• International Journal of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.54-59
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• 2019

The parametrization of the surface plays an important role in the 3D computer graphics and computer vision. Especially, it is essential in 3D mesh editing that manipulates the position of 3D objects on a computer monitor. Because computer monitors are two-dimensional, while vertices of objects that actually want to change are in a three-dimensional virtual space. In this study, we propose a new type of parametrization method that takes advantage of the special properties of circles that are common to local parameterization. Experimental results show that our parameterization method is more efficient in terms of time and space than the standard parameterization method that was designed by Floater et al.

• Atmosphere
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• v.18 no.2
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• pp.121-136
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• 2008

We investigate effects of vertical resolution on a parameterization of convective gravity waves (SGWDC) developed in Song and Chun (2005) through offline and online tests of the SGWDC parameterization. For offline tests, numerical simulations of the SGWDC parameterization with different number of vertical levels (L66, L117, L168, L219 and L270) from the surface to 120 km are performed for two different saturation methods. It is found that the wave momentum forcing is overestimated or underestimated in the SGWDC parameterization with different vertical resolutions, depending on the saturation methods. The increase of the vertical resolution modifies the magnitude and distribution of the wave momentum forcing in the parameterization, and this is mainly due to modification of wave saturation levels in the wave saturation processes. However the wave momentum forcing converges in the parameterizations with vertical resolutions higher than L168. For online test, the SGWDC parameterizations with vertical resolutions of L66 and L164 are implemented into a climate model with vertical resolution of L66, separately. In the L164 experiment, the wave momentum forcing decreases in the mid-latitude winter mesosphere in July and zonal mean flows are more realistically reproduced in the tropical regions compared with those in the L66 experiment. These results demonstrate that the wave momentum forcing calculated in the parameterization is sensitive to the vertical resolution, and the implementation of the SGWDC parameterization into high resolution models is required for realistic representation of the gravity wave momentum forcing in large-scale numerical models.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.12
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• pp.641-655
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• 2007

Parameterization has been one of very important research subjects in several application areas including computer graphics. In the parameterization research, the problem of mapping 3D polygonal model to 2D plane has been studied frequently, but the previous methods often fail to handle complicated shapes of polygonal surfaces effectively as well as entail distortion between the 3D and 2D spaces. Several attempts have been made especially to reduce such distortion, but they often suffer from the problem when an arbitrary rectangular surface region on 3D model is locally parameterized. In this paper, we propose a new local parameterization scheme based on the projection level set method. This technique generates a series of equi-distanced curves on the surface region of interest, which are then used to generate effective local parameterization information. In this paper, we explain the new technique in detail and show its effectiveness by demonstrating experimental results.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.106-114
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• 2010

Mesh parameterization is the process of finding one-to-one mapping between an input mesh and a parametric domain. It has been considered as a fundamental tool for digital geometric processing which is required to develop several applications of digital geometries. In this paper, we propose a novel 3D volume parameterization by means that a harmonic mapping is established between a 3D volume mesh and a unit solid cube. To do that, we firstly partition the boundary of the given 3D volume mesh into the six different rectangular patches whose adjacencies are topologically identical to those of a surface cube. Based on the partitioning result, we compute the boundary condition as a precondition for computing a volume mesh parameterization. Finally, the volume mesh parameterization with a low-distortion can be accomplished by performing a harmonic mapping, which minimizes the harmonic energy, with satisfying the boundary condition. Experimental results show that our method is efficient enough to compute 3D volume mesh parameterization for several models, each of whose topology is identical to a solid sphere.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.59-64
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• 2006

A new method to obtain explicit re-parameterization that preserves the curve degree and parametric domain is presented in this paper. The re-parameterization brings a curve very close to the arc length parameterization under $L_2$ norm but with less segmentation. The re-parameterization functions we used are $C^1$ continuous piecewise rational linear functions, which provide more flexibility and can be easily identified by solving a quadratic equation. Based on the outstanding performance of Mobius transformation on modifying pieces with monotonic parametric speed, we first create a partition of the original curve, in which the parametric speed of each segment is of monotonic variation. The values of new parameters corresponding to the subdivision points are specified a priori as the ratio of its cumulative arc length and its total arc length. $C^1$ continuity conditions are imposed to each segment, thus, with respect to the new parameters, the objective function is linear and admits a closed-form optimization. Illustrative examples are also given to assess the performance of our new method.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.692-699
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• 2017

The determination of the shape and rising velocity of gas bubbles in a liquid pool is of great importance in analyzing the radioactive aerosol emissions from nuclear power plant accidents in terms of the fission product release rate and the pool scrubbing efficiency of radioactive aerosols. This article suggests a simple parameterization for the gas bubble rising velocity as a function of the volume-equivalent bubble diameter; this parameterization does not require prior knowledge of bubble shape. This is more convenient than previously suggested parameterizations because it is given as a single explicit formula. It is also shown that a bubble shape diagram, which is very similar to the Grace's diagram, can be easily generated using the parameterization suggested in this article. Furthermore, the boundaries among the three bubble shape regimes in the $E_o-R_e$ plane and the condition for the bypass of the spheroidal regime can be delineated directly from the parameterization formula. Therefore, the parameterization suggested in this article appears to be useful not only in easily determining the bubble rising velocity (e.g., in postulated severe accident analysis codes) but also in understanding the trend of bubble shape change due to bubble growth.

• Atmosphere
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• v.23 no.1
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• pp.39-45
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• 2013

A parameterization for the scattering of longwave radiation by ice clouds has been developed based on spectral scattering property calculations with shapes and sizes of ice crystals. For this parameterization, the size distribution data by Fu (1996) and by Michell and Arnott (1994) are used. The shapes of ice crystal considered in this study are plate, solid column, hollow column, bullet-rosette, droxtal, aggregate, and spheroid. The properties of longwave scattering by ice crystals are presented as a function of the extinction coefficient, single-scattering albedo, and asymmetry factor. The heating rate and flux by the radiative parameterization model are calculated for wide range of ice crystal sizes, shapes, and optical thickness. The results are compared with the calculated results using a six-stream discrete ordinate scattering algorithm and Chou's method. The new method (with various habits and size distributions) provides a good simulation of the scattering properties and cooling rate in optically thin clouds (optical thickness < 5). Depending on the inclusion of scattering by ice clouds, the errors in the calculation of the cooling rates are significantly different.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.25 no.4
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• pp.196-220
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• 2021

This study formulates a new geometric parameterization scheme to effectively address numerical analysis subject to the variation of the fiber radius of a square unit cell. In particular, the proposed mesh-morphing approach may lead to a parameterized weak form whose bilinear and linear forms are affine in the geometric parameter of interest, i.e. the fiber radius. As a result, we may certify the reduced basis analysis of a square unit cell model for any parameters in a predetermined parameter domain with a rigorous a posteriori error bound. To demonstrate the utility of the proposed geometric parameterization, we consider a two-dimensional, steady-state heat conduction analysis dependent on two parameters: a fiber radius and a thermal conductivity. For rapid yet rigorous a posteriori error evaluation, we estimate a lower bound of a coercivity constant via the min-θ method as well as the successive constraint method. Compared to the corresponding finite element analysis, the constructed reduced basis analysis may yield nearly the same solution at a computational speed about 29 times faster on average. In conclusion, the proposed geometric parameterization scheme is conducive for accurate yet efficient reduced basis analysis.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2003.09a
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• pp.58-61
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• 2003

A land surface parameterization has been used to simulate influences of the terrestrial surface on the atmosphere. A simple biosphere model (SiB2), one of land surface parameterization, calculates exchange of radiation, sensible heat, latent heat, and momentum between the surface and the atmosphere (Sellers, et al., 1996).(omitted)

• Journal of Ocean Engineering and Technology
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• v.16 no.2
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• pp.10-20
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• 2002

본 논문에서는 바다의 자유표면에서 생성되는 항력에 대한 물리적 특성에 대한 연구가 기술되었다. 2차원 파장(Wave Field) 매개변수해석기법(Parametric Analyzing Technique)을 근거로 한 파경계층(Wave Boundary Layer : WBL)의 1차원 모델로서 항력계산과 파경계층의 특성을 추정하였으며 이론의 간략화(Simplifying)에 대한 연구에 주력하였다.