• Title/Summary/Keyword: Boundary-Value Problems

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Surface Extraction from Multi-material CT Data

  • Fujimori, Tomoyuki;Suzuki, Hiromasa
    • International Journal of CAD/CAM
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    • v.6 no.1
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    • pp.81-87
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    • 2006
  • This paper describes a method for extracting surfaces from multi-material CT (Computed Tomography) data. Most contouring methods such as Marching Cubes algorithm assume that CT data are composed of only two materials. Some extended methods such as [3, 6] can extract surfaces from the multi-material (non-manifold) implicit representation. However, these methods are not directly applicable to CT data that are composed of three or more materials. There are two major problems that arise from fundamentals of CT. The first problem is that we have to use n(n-1)/2 threshold values for CT data contains n materials and select appropriately one threshold value for each boundary area. The second is that we cannot reconstruct only from CT data in which area three or more materials are adjacent each other. In this paper, we propose a method to solve the problems by using image analysis and demonstrate the effectiveness of the method with application examples construct polygon models from CT data of machine parts.

Numerical Analysis of Violent Sloshing Problems by CCUP Method (CCUP 기법을 이용한 2 차원 슬로싱 문제의 수치해석)

  • Yang, Kyung-Kyu;Kim, Yong-Hwan
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.1
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    • pp.1-10
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    • 2010
  • In the present paper, a numerical method based on the constraint interpolation profile (CIP) method is applied for simulating two-dimensional violent sloshing problems. The free surface boundary value problem is considered as a multiphase problem which includes water and air. A stationary Cartesian grid system is adopted, and an interface capturing method is used to trace the shape of free surface profile. The CIP combined unified procedure (CCUP) scheme is applied for flow solver, and the tangent of hyperbola for interface capturing (THINC) scheme is used for interface capturing. Numerical simulations have been carried out for partially-filled 2D tanks under forced sway and roll motions at various filling depths and frequencies. The computational results are compared with experiments and/or the other numerical results to validate the present numerical method.

PSEUDO-SPECTRAL LEAST-SQUARES METHOD FOR ELLIPTIC INTERFACE PROBLEMS

  • Shin, Byeong-Chun
    • Journal of the Korean Mathematical Society
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    • v.50 no.6
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    • pp.1291-1310
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    • 2013
  • This paper develops least-squares pseudo-spectral collocation methods for elliptic boundary value problems having interface conditions given by discontinuous coefficients and singular source term. From the discontinuities of coefficients and singular source term, we derive the interface conditions and then we impose such interface conditions to solution spaces. We define two types of discrete least-squares functionals summing discontinuous spectral norms of the residual equations over two sub-domains. In this paper, we show that the homogeneous least-squares functionals are equivalent to appropriate product norms and the proposed methods have the spectral convergence. Finally, we present some numerical results to provide evidences for analysis and spectral convergence of the proposed methods.

Finite Element Analysis of Elasto-Plastic Large Deformation considering the Isotropic Damage(the 2nd Report) (등방성손상을 고려한 탄소성 대변형 무제의 유한요소해석(제2보))

  • 이종원
    • Journal of Ocean Engineering and Technology
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    • v.14 no.2
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    • pp.76-83
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    • 2000
  • this paper was concentrated on the finite element formulation to solve boundary value problems by using the isotropic elasto-plastic damage constitutive model proposed previously(Noh, 2000) The plastic damage of ductile materials is generally accompanied by large plasticdeformation and strain. So nonlinearity problems induced by large deformation large rotation and large strain behaviors were dealt with using the nonlinear kinematics of elasto-plastic deformations based on the continuum mechanics. The elasto-plastic damage constitutive model was applied to the nonlinear finite element formulation process of Shin et al(1997) and an improved analysis model considering the all nonlinearities of structural behaviors is proposed. Finally to investigate the applicability and validity of the numerical model some numerial examples were considered.

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SYMMETRIC SOLUTIONS FOR A FOURTH-ORDER MULTI-POINT BOUNDARY VALUE PROBLEMS WITH ONE-DIMENSIONAL $p$-LAPLACIAN AT RESONANCE

  • Yang, Aijun;Wang, Helin
    • Journal of applied mathematics & informatics
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    • v.30 no.1_2
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    • pp.161-171
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    • 2012
  • We consider the fourth-order differential equation with one-dimensional $p$-Laplacian (${\phi}_p(x^{\prime\prime}(t)))^{\prime\prime}=f(t,x(t),x^{\prime}(t),x^{\prime\prime}(t)$) a.e. $t{\in}[0,1]$, subject to the boundary conditions $x^{\prime\prime}}(0)=0$, $({\phi}_p(x^{\prime\prime}(t)))^{\prime}{\mid}_{t=0}=0$, $x(0)={\sum}_{i=1}^n{\mu}_ix({\xi}_i)$, $x(t)=x(1-t)$, $t{\in}[0,1]$, where ${\phi}_p(s)={\mid}s{\mid}^{p-2}s$, $p$ > 1, 0 < ${\xi}_1$ < ${\xi}_2$ < ${\cdots}$ < ${\xi}_n$ < $\frac{1}{2}$, ${\mu}_i{\in}\mathbb{R}$, $i=1$, 2, ${\cdots}$, $n$, ${\sum}_{i=1}^n{\mu}_i=1$ and $f:[0,1]{\times}\mathbb{R}^3{\rightarrow}\mathbb{R}$ is a $L^1$-Carath$\acute{e}$odory function with $f(t,u,v,w)=f(1-t,u,-v,w)$ for $(t,u,v,w){\in}[0,1]{\times}\mathbb{R}^3$. We obtain the existence of at least one nonconstant symmetric solution by applying an extension of Mawhin's continuation theorem due to Ge. Furthermore, an example is given to illustrate the results.

Real-Time Virtual-View Image Synthesis Algorithm Using Kinect Camera (키넥트 카메라를 이용한 실시간 가상 시점 영상 생성 기법)

  • Lee, Gyu-Cheol;Yoo, Jisang
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38C no.5
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    • pp.409-419
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    • 2013
  • Kinect released by Microsoft in November 2010 is a motion sensing camera in xbox360 and gives depth and color images. However, Kinect camera also generates holes and noise around object boundaries in the obtained images because it uses infrared pattern. Also, boundary flickering phenomenon occurs. Therefore, we propose a real-time virtual-view video synthesis algorithm which results in a high-quality virtual view by solving these problems. In the proposed algorithm, holes around the boundary are filled by using the joint bilateral filter. Color image is converted into intensity image and then flickering pixels are searched by analyzing the variation of intensity and depth images. Finally, boundary flickering phenomenon can be reduced by converting values of flickering pixels into the maximum pixel value of a previous depth image and virtual views are generated by applying 3D warping technique. Holes existing on regions that are not part of occlusion region are also filled with a center pixel value of the highest reliability block after the final block reliability is calculated by using a block based gradient searching algorithm with block reliability. The experimental results show that the proposed algorithm generated the virtual view image in real-time.

A Study on TE Scattering by a Resistive Strip Grating Between a Double Dielectric Layer Using PMM (PMM을 이용한 2중 유전체층 사이의 저항띠 격자구조에 의한 TE 산란에 관한 연구)

  • Yoon, Uei-Joong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.19 no.4
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    • pp.21-26
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    • 2019
  • In this paper, TE(transverse electric) scattering problems by a resistive strip grating between a double dielectric layer are analyzed by using the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients, the scattered electromagnetic fields are expanded in a series of Floquet mode functions, and the resistive boundary condition is applied to analysis of the resistive strip. The numerical results for the normalized reflected and transmitted power are analyzed by according as the width and spacing of resistive strip, the relative permittivity and thickness of the double dielectric layers, incident angles, and uniform resisitivity. Typically, the reflected power for the conductive strip increased as the value of the relative dielectric constant increased, the reflected power for the resistive strip with uniform resistivity decreased as the value of the resisvivity increased. The numerical results for the presented structure of this paper are shown in good agreement compared to those of the existing papers.

Numerical Analysis of Tapered Circular Arch with Fixed Ends (양단고정 변단면 도호아-치의 수치해석에 관한 연구)

  • 박문호;이병구
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.19 no.3
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    • pp.4462-4471
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    • 1977
  • The governing differential equations for the tapered circular arch with fixed ends have been derived, and a numerical procedure for the solution of these equations have been developed. The governing differential equations were solved numerically by an initial value integration procedure and Shooting Methods for boundary value problems. The Rungekutta fourth order integration technique was used. The methods was programmed for a Cyber 73-18 computer System, and all esults were obtained on this computer. A detailed study has been made for a fixed arch with an angle of opening equal to 0.7 radian, and the results are presented in detail in tables and curves. It is hoped that the results presented herein is applied to the deformations of gives point from the tri-axial direction of tapered circular arch with fixed ends, bending moment, and torsional moment, and that at the same time results to be used for archwise structures in steel structure.

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Computer Simulation of the Computational Method in Fuel Optimal Control

  • Lee, B.J.
    • Nuclear Engineering and Technology
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    • v.4 no.1
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    • pp.11-22
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    • 1972
  • Determination of a two-point boundary value problem is the key of finding the control function u(t) with the application of the fundamental idea of Minimum principle. The late development shows the discovery of the initial costate vector for the solution of a two-point value problem. As a new technique of determining the optimal control function, Newton's Sequential method is examined about a number of engineering problems and found available.

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Developing a new mutation operator to solve the RC deep beam problems by aid of genetic algorithm

  • Kaya, Mustafa
    • Computers and Concrete
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    • v.22 no.5
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    • pp.493-500
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    • 2018
  • Due to the fact that the ratio of their height to their openings is very large compared to normal beams, there are difficulties in the design and analysis of deep beams, which differ in behavior. In this study, the optimum horizontal and vertical reinforcement diameters of 5 different beams were determined by using genetic algorithms (GA) due to the openness/height ratio (L/h), loading condition and the presence of spaces in the body. In this study, the effect of different mutation operators and improved double times sensitive mutation (DTM) operator on GA's performance was investigated. In the study following random mutation (RM), boundary mutation (BM), non-uniform random mutation (NRM), Makinen, Periaux and Toivanen (MPT) mutation, power mutation (PM), polynomial mutation (PNM), and developed DTM mutation operators were applied to five deep beam problems were used to determine the minimum reinforcement diameter. The fitness values obtained using developed DTM mutation operator was higher than obtained from existing mutation operators. Moreover; obtained reinforcement weight of the deep beams using the developed DTM mutation operator lower than obtained from the existing mutation operators. As a result of the analyzes, the highest fitness value was obtained from the applied double times sensitive mutation (DTM) operator. In addition, it was found that this study, which was carried out using GAs, contributed to the solution of the problems experienced in the design of deep beams.