• Title/Summary/Keyword: computational models

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A Study on Digital Synectics for The Recomposition of Architectural space (공간 재구성을 위한 Digital Synectics에 관한 연구)

  • 이철재
    • Korean Institute of Interior Design Journal
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    • no.41
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    • pp.266-274
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    • 2003
  • Synectics is one of several techniques used to enhance brainstorming by taking a more active role and introducing metaphor and structure into the process. It is unclear at what level of specificity this should be formulated as a pattern. This thesis reviews recent computational as well as experimental work on analogical reasoning based on synectics. New results regarding information processing of analogical reasoning stages, major computational models and recent attempts to compare these models are reviewed. Computational models are also discussed in the computational as well as cognitive psychology perspectives. Future directions in analogical reasoning research are proposed. The following import is the need to accommodate the typology and normal assessment in the concrete circumstances where actual reasoning and problem solving take place. In order to get to this end, we used computational models by Thagard who take the stand of ‘Computational Philosophy of Science’, which assumes ‘Weak AI’ to explicate what constitute the very pecularity of Analogical Reasoning.

Statistical models and computational tools for predicting complex traits and diseases

  • Chung, Wonil
    • Genomics & Informatics
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    • v.19 no.4
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    • pp.36.1-36.11
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    • 2021
  • Predicting individual traits and diseases from genetic variants is critical to fulfilling the promise of personalized medicine. The genetic variants from genome-wide association studies (GWAS), including variants well below GWAS significance, can be aggregated into highly significant predictions across a wide range of complex traits and diseases. The recent arrival of large-sample public biobanks enables highly accurate polygenic predictions based on genetic variants across the whole genome. Various statistical methodologies and diverse computational tools have been introduced and developed to computed the polygenic risk score (PRS) more accurately. However, many researchers utilize PRS tools without a thorough understanding of the underlying model and how to specify the parameters for the best performance. It is advantageous to study the statistical models implemented in computational tools for PRS estimation and the formulas of parameters to be specified. Here, we review a variety of recent statistical methodologies and computational tools for PRS computation.

Computational modeling of the atmospheric boundary layer using various two-equation turbulence models

  • Juretic, Franjo;Kozmar, Hrvoje
    • Wind and Structures
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    • v.19 no.6
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    • pp.687-708
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    • 2014
  • The performance of the $k-{\varepsilon}$ and $k-{\omega}$ two-equation turbulence models was investigated in computational simulations of the neutrally stratified atmospheric boundary layer developing above various terrain types. This was achieved by using a proposed methodology that mimics the experimental setup in the boundary layer wind tunnel and accounts for a decrease in turbulence parameters with height, as observed in the atmosphere. An important feature of this approach is pressure regulation along the computational domain that is additionally supported by the nearly constant turbulent kinetic energy to Reynolds shear stress ratio at all heights. In addition to the mean velocity and turbulent kinetic energy commonly simulated in previous relevant studies, this approach focuses on the appropriate prediction of Reynolds shear stress as well. The computational results agree very well with experimental results. In particular, the difference between the calculated and measured mean velocity, turbulent kinetic energy and Reynolds shear stress profiles is less than ${\pm}10%$ in most parts of the computational domain.

Computational Modeling and Analysis of Ablative Composites Using Micro-tomographic Images (미세 단층 영상을 이용한 삭마 복합재료의 전산 모델링 및 해석)

  • Cheon, Jae Hee;Roh, Kyung Uk;Shin, Eui Sup
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.47 no.9
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    • pp.642-648
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    • 2019
  • In this study, Image-based computational analysis using the developed models was performed to predict the degradation of effective properties by ablation. The ablation tests of carbon/phenolic composites were performed using a 0.4 MW arc-heated wind tunnel. The carbon/phenolic composite samples were scanned using the micro-computed tomography (Micro-CT) to analyze the ablation characteristics according to a duration time of the ablation test. By calibrating the scanned images, computational models were developed that reflect the actual microstructure of the ablation composites. Also, nine computational models that reflect the actual pore shape were developed using the created cross-sectional images. Image-based computational analysis using the developed models was performed to predict the degradation of effective properties by ablation and the decrease of effective properties was confirmed with increase of porosity.

Free vibration analysis of damaged beams via refined models

  • Petrolo, Marco;Carrera, Erasmo;Alawami, Ali Saeghier Ali Saeed
    • Advances in aircraft and spacecraft science
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    • v.3 no.1
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    • pp.95-112
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    • 2016
  • This paper presents the free vibration analysis of damaged beams by means of 1D (beam) advanced finite element models. The present 1D formulation stems from the Carrera Unified Formulation (CUF), and it leads to a Component-Wise (CW) modelling. By means of the CUF, any order 2D and 1D structural models can be developed in a unified and hierarchical manner, and they provide extremely accurate results with very low computational costs. The computational cost reduction in terms of total amount of DOFs ranges from 10 to 100 times less than shell and solid models, respectively. The CW provides a detailed physical description of the real structure since each component can be modelled with its material characteristics, that is, no homogenization techniques are required. Furthermore, although 1D models are exploited, the problem unknown variables can be placed on the physical surfaces of the real 3D model. No artificial surfaces or lines have to be defined to build the structural model. Global and local damages are introduced by decreasing the stiffness properties of the material in the damaged regions. The results show that the proposed 1D models can deal with damaged structures as accurately as a shell or a solid model, but with far lower computational costs. Furthermore, it is shown how the presence of damages can lead to shell-like modal shapes and torsional/bending coupling.

EVELOPMENT OF AXISYMMETRIC MULTI-SPECIES GH EQUATION FOR HYPERSONIC RAREFIED FLOW ANALYSES (극초음속 희박유동 해석을 위한 축대칭 다화학종 GH 방정식의 개발)

  • Ahn, J.W.;Kim, C.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.84-91
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    • 2008
  • Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; O$_2$, N$_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

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EVELOPMENT OF AXISYMMETRIC MULTI-SPECIES GH EQUATION FOR HYPERSONIC RAREFIED FLOW ANALYSES (극초음속 희박유동 해석을 위한 축대칭 다화학종 GH 방정식의 개발)

  • Ahn, J.W.;Kim, C.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.84-91
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    • 2008
  • Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; $O_2,\;N_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

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A Framework for Managing Approximation Models in place of Expensive Simulations in Optimization (최적화에서의 근사모델 관리기법의 활용)

  • 양영순;장범선;연윤석
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2000.04b
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    • pp.159-167
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    • 2000
  • In optimization problems, computationally intensive or expensive simulations hinder the use of standard optimization techniques because the computational expense is too heavy to implement them at each iteration of the optimization algorithm. Therefore, those expensive simulations are often replaced with approximation models which can be evaluated nearly free. However, because of the limited accuracy of the approximation models, it is practically impossible to find an exact optimal point of the original problem. Significant efforts have been made to overcome this problem. The approximation models are sequentially updated during the iterative optimization process such that interesting design points are included. The interesting points have a strong influence on making the approximation model capture an overall trend of the original function or improving the accuracy of the approximation in the vicinity of a minimizer. They are successively determined at each iteration by utilizing the predictive ability of the approximation model. This paper will focuses on those approaches and introduces various approximation methods.

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PERFORMANCE ANALYSIS OF THE TURBULENCE MODELS FOR A TURBULENT FLOW IN A TRIANGULAR ROD BUNDLE

  • In W.K;Chun T.H;Myong H.K
    • Journal of computational fluids engineering
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    • v.10 no.1
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    • pp.63-66
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    • 2005
  • A computational fluid dynamics(CFD) analysis has been made for fully developed turbulent flow in a triangular bare rod bundle with a pitch to diameter ratio (P/D) of 1.123. The nonlinear turbulence models predicted the turbulence-driven secondary flow in the triangular subchannel. The nonlinear quadratic κ-ε models by Speziale[1] and Myong-Kasagi[2] predicted turbulence structure in the rod bundle fairly well. The nonlinear quadratic and cubic k-ε models by Shih et al.[3] and Craft et al.[4] showed somewhat weaker anisotropic turbulence. The differential Reynolds stress model by Launder et al.[5} appeared to over predict the turbulence anisotropy in the rod bundle.

IMPLEMENTATION OF VELOCITY SLIP MODELS IN A FINITE ELEMENT NUMERICAL CODE FOR MICROSCALE FLUID SIMULATIONS (속도 슬립모델 적용을 통한 마이크로 유체 시뮬레이션용 FEM 수치 코드 개발)

  • Hoang, A.D.;Myong, R.S.
    • Journal of computational fluids engineering
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    • v.14 no.2
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    • pp.46-51
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    • 2009
  • The slip effect from the molecular interaction between fluid particles and solid surface atoms plays a key role in microscale fluid transport and heat transfer since the relative importance of surface forces increases as the size of the system decreases to the microscale. There exist two models to describe the slip effect: the Maxwell slip model in which the slip correction is made on the basis of the degree of shear stress near the wall surface and the Langmuir slip model based on a theory of adsorption of gases on solids. In this study, as the first step towards developing a general purpose numerical code of the compressible Navier-Stokes equations for computational simulations of microscale fluid flow and heat transfer, two slip models are implemented into a finite element numerical code of a simplified equation. In addition, a pressure-driven gas flow in a microchannel is investigated by the numerical code in order to validate numerical results.