• Structural Engineering and Mechanics
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• 제71권2호
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• pp.197-210
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• 2019

Probabilistic buckling behavior of sandwich panel considering random system parameters using a radial basis function (RBF) approach is presented in this paper. The random system properties result in an uncertain response of the sandwich structure. The buckling load of laminated sandwich panel is obtained by employing higher-order-zigzag theory (HOZT) coupled with RBF and probabilistic finite element (FE) model. The in-plane displacement variation of core as well as facesheet is considered to be cubic while transverse displacement is considered to be quadratic within the core and constant in the facesheets. Individual and combined stochasticity in all elemental input parameters (like facesheets thickness, ply-orientation angle, core thickness and properties of material) are considered to know the effect of different degree of stochasticity, ply- orientation angle, boundary conditions, core thickness, number of laminates, and material properties on global response of the structure. In order to achieve the computational efficiency, RBF model is employed as a surrogate to the original finite element model. The stiffness matrix of global response is stored in a single array using skyline technique and simultaneous iteration technique is used to solve the stochastic buckling equations.

• Steel and Composite Structures
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• 제47권5호
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• pp.569-585
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• 2023

This paper proposes an efficient approach for the structural topology optimization of bi-directional functionally graded structures by incorporating popular radial basis functions (RBFs) into an implicit level set (ILS) method. Compared to traditional element density-based methods, a level set (LS) description of material boundaries produces a smoother boundary description of the design. The paper develops RBF implicit modeling with multiquadric (MQ) splines, thin-plate spline (TPS), exponential spline (ES), and Gaussians (GS) to define the ILS function with high accuracy and smoothness. The optimization problem is formulated by considering RBF-based nodal densities as design variables and minimizing the compliance objective function. A LS-RBF optimization method is proposed to transform a Hamilton-Jacobi partial differential equation (PDE) into a system of coupled non-linear ordinary differential equations (ODEs) over the entire design domain using a collocation formulation of the method of lines design variables. The paper presents detailed mathematical expressions for BiDFG beams topology optimization with two different material models: continuum functionally graded (CFG) and mechanical functionally graded (MFG). Several numerical examples are presented to verify the method's efficiency, reliability, and success in accuracy, convergence speed, and insensitivity to initial designs in the topology optimization of two-dimensional (2D) structures. Overall, the paper presents a novel and efficient approach to topology optimization that can handle bi-directional functionally graded structures with complex geometries.

• Structural Engineering and Mechanics
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• 제88권3호
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• pp.239-249
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• 2023

The Radial Point Interpolation Method (RPIM) has been proposed to overcome the difficulties associated with the use of the Radial Basis Functions (RBFs). The RPIM has the following properties: Simple implementation in terms of boundary conditions as in the Finite Element Method (FEM). A less expensive CPU time compared to other collocation meshless methods such as the Moving Least Square (MLS) collocation method. In this work, we propose an adaptive high-order numerical algorithm based on RPIM to simulate the thermoviscoplastic behavior of a material mixing observed in the Friction Stir Welding (FSW) process. The proposed adaptive meshfree RPIM algorithm adapts well to the geometric and physical data by choosing a good shape parameter with a good precision. Our numerical approach combines the RPIM and the Asymptotic Numerical Method (ANM). A numerical procedure is also proposed in this work to automatically determine an improved shape parameter for the RBFs. The efficiency of the proposed algorithm is analyzed in comparison with an iterative algorithm.

• Journal of Radiation Protection and Research
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• 제38권4호
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• pp.172-178
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• 2013

본 연구에서는 미래 파이로 시설에서의 핵물질 계량 연구를 위하여 개발하고 있는 통합비파괴측정장치(Unified Non-Destructive Assay, UNDA)의 중성자 검출 효율을 MCNPX 코드를 이용하여 평가하였다. 검출 효율 평가는 두 개의 다른 설계안의 UNDA에 대하여 수행되었으며, $^{252}Cf$ 중성자 발생 선원 위치에 따른 검출 효율 평가와 감손우라늄의 용기 두께 및 위치에 따른 검출 효율 평가를 수행하였다. $^{252}Cf$ 중성자 선원의 위치에 따른 UNDA의 검출 효율 결과는 6.83%부터 13.35%까지 분포로 나타났으며, $^{252}Cf$ 선원이 장치 내부의 상단에 위치할수록 검출 효율은 증가 후 감소하는 경향을 나타냈고, 선원이 외각에 위치될수록 효율이 증가하는 경향을 보였다. 감손우라늄 용기의 두께 및 위치에 따른 검출 효율 평가에서는 용기 두께가 증가할수록 검출 효율은 낮아지는 경향을 보이며, 용기 위치가 장치 상부에 위치될수록 효율은 감소하고, 외각에 위치할수록 효율은 증가하였다. 검출 효율은 $^{252}Cf$ 선원의 경우보다 약간 높게 나타났다(10.31~13.61%). 또한, 장치 상단에 고밀도 폴리에틸렌 덮개가 있는 설계안이 덮개가 없는 설계안 보다 평균적으로 약 2% 정도 중성자 검출 효율이 높은 것으로 평가되었다.

• 한국유체기계학회 논문집
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• 제10권2호
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• pp.22-31
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• 2007

This paper describes the shape optimization of rotor blade in a transonic axial compressor rotor. Three surrogate models, Kriging, radial basis neural network and response surface methods, are introduced to find optimum blade shape and to compare the characteristics of object function at each optimal design condition. Blade sweep, lean and skew are considered as design variables and adiabatic efficiency is selected as an objective function. Throughout the shape optimization of the compressor rotor, the predicted adiabatic efficiency has almost same value for three surrogate models. Among the three design variables, a blade sweep is the most sensitive on the object function. It is noted that the blade swept to backward and skewed to the blade pressure side is more effective to increase the adiabatic efficiency in the axial compressor Flow characteristics of an optimum blade are also compared with the results of reference blade.

• 한국경영과학회지
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• 제24권2호
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• pp.53-68
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• 1999

This paper presents a nonparametric method to test if the mean difference of DEA efficiency estimates between two groups statistically exists. A proposed method employs a bootstrapping approach to generation BCC efficiency estimates through Monte Carlo simulation resampling process. For the purpose of demonstration, we empirically apply the proposed method to the korean bank industry and compare its result with the result by the traditional deterministic DEA method. The nonparametric statistical hypothesis testing procedure in this study, which considers not only stochastic variability of the DEA data, but also random radial deviations off the efficient frontier, serves as a useful tool for dbjectively evaluating whether the mean difference of DEA efficiency estimates between groups is statistically significant.

• 한국유체기계학회 논문집
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• 제11권2호
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• pp.46-54
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• 2008

This study presents a numerical optimization to optimize an axial flow fan blade to increase the efficiency. The radial basis neural network is used as an optimization method with the numerical analysis by Reynolds-averaged Navier-Stokes equations using SST model as turbulence closure. Four design variables related to airfoil maximum camber, maximum camber location, leading edge radius and trailing edge radius, respectively, are selected, and efficiency is considered as objective function which is to be maximized. Thirty designs are evaluated to get the objective function values of each design used to train the neural network. Optimum shape shows the efficiency increased by 1.0%.

• 산경연구논집
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• 제10권2호
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• pp.7-15
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• 2019

Purpose - The industrial structure upgrading can play an important role in promoting the carbon emission efficiency. Thus, this paper attempts to study the impact of industrial structure upgrading on carbon emission efficiency in order to reduce carbon emissions. Research design, data, and methodology - This paper selects panel data of 30 provinces and municipalities (autonomous regions) in China from 2001 to 2016, and divides them into three regions. The Moore index is used to measure the industrial structure upgrading, the non-radial SBM model based on undesired output is used to measure the slack variable to calculate the total factor carbon emission efficiency. Finally the impact of industrial structure upgrading on the carbon emission efficiency are analyzed. Results - It is found that the Moore index and the carbon emission efficiency in the eastern region is the highest in the three regions. Conclusions - The influence of various influencing factors on carbon emission efficiency is different between regions. The Moore index has a positive effect on the carbon emission efficiency in the eastern region, and has a negative influence coefficient on the central region. The effect on the western region is not obvious.

• 대한정형외과스포츠의학회지
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• 제5권1호
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• pp.75-80
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• 2006

목적: 해부학적 정복이 가능한 요골두 골절에 대하여 Acutrak 나사를 이용한 고정술의 치료 결과와 유용성에 대해 알아보고자 하였다. 대상 및 방법: 2001 년 5월부터 2003년 2월까지 본원에서 요골두 골절에 대해 수술한 12 예중 Acutrak 나사 고정술로 치료한 7 예를 대상으로 하였다. 추시 기간은 최소 6개월부터 최장 30개월로 평균 1.2년이었고, 평균 나이는 47세였다 손상의 원인은 낙상이 4예, 교통사고가 3예이었다. 치료 결과 평가 방법은 Mayo Clinic에서 발표한 Functional Rating index를 이용하였다 결과: Mayo Clinic의 Functional Rating Index를 이용한 기능적 평가상 우수가 2예, 양호가 5예였다 방사선학적 소견 상 모든 예에서 골유합 소견을 보였고, 부정 유합이나 나사 이완, 이소성 골형성, 감염, 외상 후 퇴행성 변화 등의 합병증은 없었고 수술 후 건측과 비교하여 운동장애도 보이지 않았다. 결론: 본원에서 시행한 요골두 골절의 Acutrak 나사 고정은 요골두 부분의 안전지대에 대한 고려없이 시행 가능하며 방사선학적 및 임상적 평가에서 만족할 만한 결과를 보였고, Acutrak 나사의 형태학적 특성상 골절의 선상 형태에 대하여 근위 요척골관절에 영향을 주지 않으며, 강한 고정력을 얻을 수 있는 술식으로 사료된다.

• 제어로봇시스템학회논문지
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• 제10권2호
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• pp.185-191
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• 2004

Partial least squares(PLS) is one of multiplicate statistical process methods and has been developed in various algorithms with the characteristics of principal component analysis, dimensionality reduction, and analysis of the relationship between input variables and output variables. But it has been limited somewhat by their dependency on linear mathematics. The algorithm is proposed to classify for the non-linear data using PLS and the residual compensator(RC) based on radial basis function network (RBFN). It compensates for the error of the non-linear data using the RC based on RBFN. The experimental result is given to verify its efficiency compared with those of previous works.