• Title, Summary, Keyword: Inhomogeneous

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Modeling of Defects Nucleation in the Inhomogeneous Liquid Crystal Director Field

  • Lee Gi-Dong;Kim Jae Chang
    • Journal of the Optical Society of Korea
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    • v.9 no.2
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    • pp.74-78
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    • 2005
  • With the fast Q-tensor method, which can model the defect dynamics in a liquid crystal director field, the nucleation and dynamical behavior of defects is modeled. In order to model the defect, hormeotropic aligned liquid crystal cell with step inhomogeneous electrode which has a height of $1\;{\mu}m$ is used. From the simulation, we can observe the nucleation and line of the defect from surface inhomogeneity and the experiment is performed for confirmation. The experimental result is compared with numerical modeling in order to verify the simulation of the defect nucleation.

Evolution of bone structure under axial and transverse loads

  • Qu, Chuanyong;Qin, Qing-Hua
    • Structural Engineering and Mechanics
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    • v.24 no.1
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    • pp.19-29
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    • 2006
  • The evolution process of an initially homogeneous bone structure under axial and transverse loads is investigated in this paper. The external loads include axial and external lateral pressure, electric, magnetic and thermal loads. The theoretical predictions of evolution processes are made based on the adaptive elasticity formulation and coupled thermo-magneto-electro-elastic theory. The adaptive elastic body, which is a model for living bone diaphysis, is assumed to be homogeneous in its anisotropic properties and its density. The principal result of this paper is determination of the evolution process of the initially homogeneous body to a transversely inhomogeneous body under the influence of the inhomogeneous stress state.

SH-wave propagation in a heterogeneous layer over an inhomogeneous isotropic elastic half-space

  • Kakar, Rajneesh
    • Earthquakes and Structures
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    • v.9 no.2
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    • pp.305-320
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    • 2015
  • The present paper is devoted to study SH-wave propagation in heterogeneous layer laying over an inhomogeneous isotropic elastic half-space. The dispersion relation for propagation of said waves is derived with Green's function method and Fourier transform. As a special case when the upper layer and lower half-space are homogeneous, our derived equation is in agreement with the general equation of Love wave. Numerically, it is observed that the velocity of SH-wave increases with the increase of inhomogeneity parameter.

Dynamic Stability Analysis of Thick Plates with Varying Thickness and Concentrated Mass on Inhomogeneous Pasternak Foundation (비균질 Pasternak 지반에 놓인 집중질량을 갖는 변단면 후판의 동적안정해석)

  • Lee, Yong-Soo;Kim, Il-Jung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.8
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    • pp.698-707
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    • 2011
  • This paper is to analyze the stability of the thick plate on inhomogeneous Pasternak foundation, with linearly varying thickness and concentrated mass by finite element method. To verify this finite element method, the results of natural frequencies and buckling stresses by the proposed method are compared with the existing solutions. The dynamic instability regions are decided by the dynamic stability analysis of the thick plate on inhomogeneous Pasternak foundation, with linearly varying thickness and concentrated mass. The non-dimensional Winkler foundation parameter is applied as 100, 1000 and non-dimensional shear foundation parameter is applied as 5. The tapered ratios are applied as 0.25 and 1.0, the ratios of concentrated mass to plate mass as 0.25 and 1.0, and the ratio of in-plane force to critical load as 0.4. As the result of numerical analysis of the thick plate on inhomogeneous Pasternak foundation for $u{\times}v=300cm{\times}300cm$ and $a{\times}b=600cm{\times}600cm$, instability areas of the thick plate which has the larger rigidity of inner area are farther from ${\beta}$-axis and narrower than those which has the larger rigidity of outer area.

Numerical Simulation of Ground-Penetrating Radar Signals for Detection of Metal Pipes Buried in Inhomogeneous Grounds (비균일 지하에 매설된 금속관 탐지를 위한 지하탐사레이다 신호의 수치 모의계산)

  • Hyun, Seung-Yeup
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.1
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    • pp.61-67
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    • 2018
  • The effects of subsurface inhomogeneities on the detection of buried metal pipes in ground-penetrating radar(GPR) signals are investigated numerically. To model the electrical properties of the subsurface inhomogeneities, the continuous random media(CRM) generation technique is introduced. For the electromagnetic simulation of GPR signals, the finite-difference time-domain(FDTD) method is implemented. As a function of the standard deviation and the correlation length of the relative permittivity distribution for a randomly inhomogeneous ground, the GPR signals of the buried metal pipes are compared using numerical simulations. As the subsurface inhomogeneities increase, the GPR signals of the buried pipes are distorted because of the effect of the subsurface clutter.

Evaluation of Homogeneous Ultra-fine Grain Refinements via Equal Channel Angler Pressing Process (등통로각압축공정을 통한 결정립의 균질한 초미세립화에 대한 고찰)

  • Kim, W.;Lee, H.H.;Seo, S.J.;Lee, J.K.;Yoon, T.S.;Kim, H.S.
    • Transactions of Materials Processing
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    • v.27 no.4
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    • pp.222-226
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    • 2018
  • Severe plastic deformation (SPD) is a promising method for drastically enhancing the mechanical properties of the materials by grain refinement of metallic materials. However, inhomogeneous deformation during the SPD process results in the inhomogeneous microstructure of the SPD-processed material. We manufactured cylindrical copper specimens of 42 mm in diameter with ultrafine grains (UFG) using an equal channel angular pressing (ECAP) to figure out the relationship between homogeneous microstructure and the number of the processing passes. Two specimens, which are ECAP-processed 4 times (4pass) and 6 times (6pass) each with Route Bc, are prepared for comparison of mechanical properties and microstructure. The results show that the mechanical properties of the two specimens (4pass and 6pass) are similar. Moreover, both the specimens show highly enhanced mechanical properties. The 4pass specimen, however, shows inhomogeneity in hardness distribution, while the 6pass specimen shows a homogeneous distribution. Microstructure analysis reveals that the 4pass specimen has an inhomogeneous microstructure with incompletely refined grain structure. This inhomogeneity of the 4pass specimen could be explained by the circumferential rotation during ECAP process.

Free Vibration Analysis of Thick Plates on Inhomogeneous Pasternak Foundation (비균질 Pasternak지반 위에 놓여진 후판의 자유진동해석)

  • 김일중;오숙경;이효진;이용수
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.852-857
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    • 2003
  • This paper has the object of investigating natural frequencies of thick plates on inhomogeneous Pasternak foundation by means of finite element method and providing kinematic design data lot mat of building structures. This analysis was applied for design of substructure on elastic foundation. Mat of building structure may be consisdered as a thick plate on elastic foundation. Recently, as size of building structure becomes larger, mat area of building structure also tend to become target and building structure is supported on inhomogeneous foundation. In this paper, vibration analysis or rectangular thick plate is done by use or serendipity finite element with 8 nodes by considering shearing strain of plate. The solutions of this paper are compared with existing solutions and finite element solutions with 4${\times}$4 meshes of this analysis are shown the error of maximum 0.083% about the existing solutions. It is shown that natrural frequencies depend on not only Winkler foundation parameter but also shear foundation parameter.

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Photon dose calculation of pencil beam kernel based treatment planning system compared to the Monte Carlo simulation

  • Cheong, Kwang-Ho;Suh, Tae-Suk;Kim, Hoi-Nam;Lee, Hyoung-Koo;Choe, Bo-Young;Yoon, Sei-Chul
    • Proceedings of the Korean Society of Medical Physics Conference
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    • pp.291-293
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    • 2002
  • Accurate dose calculation in radiation treatment planning is most important for successful treatment. Since human body is composed of various materials and not an ideal shape, it is not easy to calculate the accurate effective dose in the patients. Many methods have been proposed to solve the inhomogeneity and surface contour problems. Monte Carlo simulations are regarded as the most accurate method, but it is not appropriate for routine planning because it takes so much time. Pencil beam kernel based convolution/superposition methods were also proposed to correct those effects. Nowadays, many commercial treatment planning systems, including Pinnacle and Helax-TMS, have adopted this algorithm as a dose calculation engine. The purpose of this study is to verify the accuracy of the dose calculated from pencil beam kernel based treatment planning system Helax-TMS comparing to Monte Carlo simulations and measurements especially in inhomogeneous region. Home-made inhomogeneous phantom, Helax-TMS ver. 6.0 and Monte Carlo code BEAMnrc and DOSXYZnrc were used in this study. Dose calculation results from TPS and Monte Carlo simulation were verified by measurements. In homogeneous media, the accuracy was acceptable but in inhomogeneous media, the errors were more significant.

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A Thermal Conductivity Model for LWR MOX Fuel and Its Verification Using In-pile Data

  • Byung-Ho Lee;Yang-Hyun Koo;Jin-Silk Cheon;Je-Yong Oh;Hyung-Koo Joo;Dong-Seong Sohn
    • Nuclear Engineering and Technology
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    • v.34 no.5
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    • pp.482-493
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    • 2002
  • The MOX fuel for LWR is fabricated either by direct mechanical blending of UO$_2$ and PuO$_2$ or by two stage mixing. Hence Pu-rich particles, whose Pu concentrations are higher than pellet average one and whose size distribution depends on a specific fabrication method, are inevitably dispersed in MOX pellet. Due to the inhomogeneous microstructure of MOX fuel, the thermal conductivity of LWR MOX fuel scatters from 80 to 100 % of UO$_2$ fuel. This paper describes a mechanistic thermal conductivity model for MOX fuel by considering this inhomogeneous microstructure and presents an explanation for the wide scattering of measured MOX fuel's thermal conductivity. The developed model has been incorporated into a KAERI's fuel performance code, COSMOS, and then evaluated using the measured in-pile data for MOX fuel. The database used for verification consists of homogeneous MOX fuel at beginning-of-life and inhomogeneous MOX fuel at high turnup. The COSMOS code predicts the thermal behavior of MOX fuel well except for the irradiation test accompanying substantial fission gas release. The over-prediction with substantial fission gas release seems to suggest the need for the introduction of a recovery factor to a term that considers the burnup effect on thermal conductivity.