• Title, Summary, Keyword: Homogenization

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One-step Monte Carlo global homogenization based on RMC code

  • Pan, Qingquan;Wang, Kan
    • Nuclear Engineering and Technology
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    • v.51 no.5
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    • pp.1209-1217
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    • 2019
  • Due to the limitation of the computers, the conventional homogenization method is based on many assumptions and approximations, and some tough problems such as energy spectrum and boundary condition are faced. To deal with those problems, the Monte Carlo global homogenization is adopted. The Reactor Monte Carlo code RMC is used to study the global homogenization method, and the one-step global homogenization method is proposed. The superimposed mesh geometry is also used to divide the physical models, leading to better geometric flexibility. A set of multigroup homogenization cross sections is online generated for each mesh under the real neutron energy spectrum and boundary condition, the cross sections are adjusted by the superhomogenization method, and no leakage correction is required. During the process of superhomogenization, the author-developed reactor core program NLSP3 is used for global calculation, so the global flux distribution and equivalent homogenization cross sections could be solved simultaneously. Meanwhile, the calculated homogenization cross section could accurately reconstruct the non-homogenization flux distribution and could also be used for fine calculation. This one-step global homogenization method was tested by a PWR assembly and a small reactor model, and the results show the validity.

A homogenization approach for uncertainty quantification of deflection in reinforced concrete beams considering microstructural variability

  • Kim, Jung J.;Fan, Tai;Reda Taha, Mahmoud M.
    • Structural Engineering and Mechanics
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    • v.38 no.4
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    • pp.503-516
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    • 2011
  • Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.

Comparison of Homogenization Techniques in Magnetostatic Field Problems (정자장 문제의 균질화 기법의 비교)

  • Choi, Jae-Seok;Yoo, Jeong-Hoon;Nishiwaki, Shinji;Terada, Kenjiro
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.3
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    • pp.388-394
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    • 2007
  • Many engineering problems require the calculation of effective material properties of a structure which is composed of repeated micro-structures. The homogenization method has been used to calculate the effective (homogenized) properties of composites and several homogenization procedures for different physical fields have been introduced. This research describes the modified homogenization technique for magnetostatic problems. Assuming that the material is periodically repeated, its effective permeability can be prescribed by calculating the homogenized magnetic reluctivity using the finite element analysis of the micro unit cell. Validity of the suggested method is confirmed by comparing the results by the energy based method as well as the widely known homogenization method.

Determination of Equivalent Thermal Conductivities of Composite Materials Using Homogenization Technique (균질화기법을 이용한 복합재료의 등가 열전도계수의 계산)

  • 이진희;이봉래
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1245-1252
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    • 1994
  • A solution of heat transfer problems of composite materials has been tried using homogenization technique. Homogenization technique, which was derived by applying asymptotic expansion to the standard finite element method, helped compute the equivalent thermal conductivity matrices of base cells which constituted the composite material with repeated patterns. The homogenization technique made it possible to compute the solution of the heat transfer problem of composite materials with lower degrees of freedom compared to those of other numerical methods. The equivalent thermal conductivities computed by computed by homogenization technique are also applicable to other numerical methods such as finite difference method.

A study on the prediction of the mechanical properties of nanoparticulate composites using homogenization method with effect interface concept (유효계면 모델과 균질화 기법을 이용한 나노입자 복합재의 역학적 물성 예측에 관한 연구)

  • Jang, Seong-Min;Yang, Seung-Hwa;Yu, Su-Young;Cho, Maeng-Hyo
    • Proceedings of the KSME Conference
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    • pp.684-689
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    • 2008
  • In this study, homogenization method combined with the effective interface model for the characterization of properties of the nanoparticulate composites is developed. In order to characterize particle size effect of nanocomposites, effective interface model has been developed. The application range of analytical micromechanics approach is limited because a simple analytical approach is valid only for simple and uniform geometry of fiber particles. Therefore this study focuses on the analysis of mechanical properties of the effect interface through the continuum homogenization method instead of using analytical micromechanics approach. Using the homogenization method, elastic stiffness properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. The suggested homogenization method is expected to be applied to optimization problems for nanocomposite design.

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Effects of Ultra-high Pressure Homogenization on the Emulsifying Properties of Whey Protein Isolates under Various pH

  • Lee, Sang-Ho;Subirade, Muriel;Paquin, Paul
    • Food Science and Biotechnology
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    • v.17 no.2
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    • pp.324-329
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    • 2008
  • The effect of ultra-high pressure homogenization on the emulsifying properties of whey protein was investigated in a model emulsion made with whey protein isolate and soya oil under various pH. The emulsifying properties, the average diameter of the oil droplets ($d_{vs}$), and the protein load, were measured for each emulsion produced at different homogenization pressures (50 to 200 MPa) and pH values (4.6 to 8.0). According to the results of variance analysis and response surface, the pH had more influence on oil droplet size and protein load than homogenization pressure. The model equations, which were obtained by response surface analysis, show that pH and homogenization pressure had the major effect on oil droplet size and protein load. Higher homogenization pressure decreased the average droplet size and the protein load. Homogenization at high pressure, as opposed to low pressure, causes no overprocessing, but the effect was pH-dependent. The average diameter of the oil droplets increased slightly by decreasing the pH from 8.0 to 6.5 and then increased dramatically toward the isoelectric point of whey protein (i.e., at pH 4.6). Moreover associated droplets were found at acidic pH and their size was increased at high temperature.

HOMOGENIZATION OF THE NON-STATIONARY STOKES EQUATIONS WITH PERIODIC VISCOSITY

  • Choe, Hi-Jun;Kim, Hyun-Seok
    • Journal of the Korean Mathematical Society
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    • v.46 no.5
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    • pp.1041-1069
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    • 2009
  • We study the periodic homogenization of the non-stationary Stokes equations. The fundamental homogenization theorem and corrector theorem are proved under a very general assumption on the viscosity coefficients and data. The proofs are based on a weak formulation suitable for an application of classical Tartar's method of oscillating test functions. Such a weak formulation is derived by adapting an argument in Teman's book [Navier-Stokes Equations: Theory and Numerical Analysis, North-Holland, Amsterdam, 1984].

A Study on the Topology Optimization in Magnetic Fields - Comparisons Between the Density Method and the Homogenization Design Method (자기장 내의 위상최적화 방법에 대한 연구 - 밀도법과 균질화법의 비교 -)

  • Yoo, Jeong-Hoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.4
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    • pp.370-377
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    • 2004
  • The density approach and the homogenization design method are representative methods in topology optimization problems. In the topology optimization in magnetic fields, those methods are applied based on the results of the applications In elastic fields. In this study, the density method is modified considering the concept of the homogenization design method. Also, the results of the topology optimization in magnetic fields by the modified density method as well as the homogenization method are compared especially focusing the change of the penalization parameter in the density approach. The effect of the definition of the design domain such as global/local design domain is also discussed.

Influence of pH, Emulsifier Concentration, and Homogenization Condition on the Production of Stable Oil-in-Water Emulsion Droplets Coated with Fish Gelatin

  • Surh, Jeong-Hee
    • Food Science and Biotechnology
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    • v.16 no.6
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    • pp.999-1005
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    • 2007
  • An oil-in-water (O/W) emulsion [20 wt% com oil, 0.5-6.0 wt% fish gelatin (FG), pH 3.0] was produced by high pressure homogenization, and the influence of pH, protein concentration, and homogenization condition on the formation of FG-stabilized emulsions was assessed by measuring particle size distribution, electrical charge, creaming stability, microstructure, and free FG concentration in the emulsions. Optical microscopy indicated that there were some large droplets ($d>10\;{\mu}m$) in all FG-emulsions, nevertheless, the amount of large droplets tended to decrease with increasing FG concentration. More than 90% of FG was present free in the continuous phase of the emulsions. To facilitate droplet disruption and prevent droplet coalescence within the homogenizer, homogenization time was adjusted in O/W emulsions stabilized by 2.0 or 4.0 wt% FG. However, the increase in the number of pass rather promoted droplet coalescence. This study has shown that the FG may have some limited use as a protein emulsifier in O/W emulsions.