• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.418-423
• /
• 2008

Among various sensitivity evaluation techniques, semi-analytical method is quite popular since this method is more advantageous than analytical method and global finite difference method. However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified for individual elements. Such errors result from the numerical differentiation of the pseudo load vector calculated by the finite difference scheme. In the present study, the adjoint variable method combined with complex variable is proposed to obtain the shape and size sensitivity for structural optimization. The complex variable can present accurate results regardless of the perturbation size as well as easy to be implemented. Through a few numerical examples of the static problem for the structural sensitivity, the efficiency and reliability of the adjoint variable method combined with complex variable is demonstrated.

• Steel and Composite Structures
• /
• 제21권4호
• /
• pp.755-773
• /
• 2016

In the present paper, a new high-order simple-input analytical method is used to study thick laminated composite straight tubes subjected to combined axial force, torque and bending moment. The most general displacement field of elasticity for an arbitrary laminated composite straight tube is obtained to analytically calculate stresses under combined loadings based on a layerwise method. The accuracy of the proposed method is subsequently verified by comparing the numerical results obtained using the proposed method with finite element method (FEM) and experimental data. The results show good corresponded. The proposed method provides advantages in terms of computational time compared to FEM.

• 한국환경농학회지
• /
• 제13권1호
• /
• pp.90-97
• /
• 1994

Tricyclazole 및 IBP 혼합분제의 공정분석법에 의한 주성분함량의 분석시에 문제점으로 나타나는 각 성분의 분리분석에 의한 비효율성 및 tricyclazole의 회수율 저하요인 등을 규명하여 효율적인 품질관리가 되도록 공정분석법을 개선하고자 하였다. Tricyclazole 및 IBP를 공정분석법에 의하여 주성분함량을 분석하면 IBP는 100% 회수되나 tricyclazole은 89.5% 정도 밖에 회수되지 않는데 그 원인은 증량제로 사용된 kaoline과 talc에 미량으로 함유된 무기물질인 $Al_2O_3$, $Fe_2O_3$, CaO, MgO 등과 tricyclazole이 강하게 결합되기 때문으로 나타났다. Tricyclazole의 회수율을 향상시키기 위하여 tricyclazole보다 염기도가 큰 dimethylamine을 첨가한 결과 tricyclazole은 100% 회수되는 것으로 나타났다. 따라서 tricyclazole과 IBP 혼합분제의 주성분 분석은 각 성분별로 분석하는 것보다 DAP를 내부표준물질로 사용하고 DMA를 첨가한 후 비극성 column을 이용하여 온도를 승온하면서 동시에 tricyclazole과 IBP를 분석하는 것이 효율적인 것으로 나타났다.

• Structural Engineering and Mechanics
• /
• 제42권6호
• /
• pp.867-882
• /
• 2012

Analytical (Rayleigh-Ritz method) and numerical studies are carried out and buckling interaction curves are developed for simply supported plates of varying aspect ratios ranging from 1 to 5, under the combined action of in-plane shear and tension. A multi-step buckling procedure is employed in the Finite Element (FE) model instead of a regular single step analysis in view of obtaining the buckling load under the combined forces. Both the analytical (classical) and FE studies confirm the delayed shear buckling characteristics of thin plate under the combined action of shear and tension. The interaction curves are found to be linear and are found to vary with plate aspect ratio. The interaction curve developed using Rayleigh-Ritz method is found to deviate in an increasing trend from that of validated FE model as plate aspect ratio is increased beyond value of 1. It is found that the observed deviation is due to the insufficient number of terms that is been considered in the assumed deflection function of Rayleigh-Ritz method and a convergence study is suggested as a solution.

• Structural Engineering and Mechanics
• /
• 제16권3호
• /
• pp.341-360
• /
• 2003

The goal of this paper is to determine the eigenvalues of a uniform rectangular plate carrying any number of spring-damper-mass systems using an analytical-and-numerical-combined method (ANCM). To this end, a technique was presented to replace each "spring-damper-mass" system by a massless equivalent "spring-damper" system with the specified effective spring constant and effective damping coefficient. Then, the mode superposition approach was used to transform the partial differential equation of motion into the matrix equation, and the eigenvalues of the complete system were determined from the associated characteristic equation. To verify the reliability of the presented theory, all numerical results obtained from the ANCM were compared with those obtained from the conventional finite element method (FEM) and good agreement was achieved. Since the order of the property matrices for the equation of motion obtained from the ANCM is much lower than that obtained from the FEM, the CPU time required by the ANCM is much less than that by the FEM.

• 보건행정학회지
• /
• 제10권2호
• /
• pp.1-21
• /
• 2000

This study reviewde various parametic and nonparametic method for forexasting hospital closures in Korea. We compared multivariate discriminant analysis, multivartiate logistic regression, classfication and regression tree, and neural network method based on hit ratio of each model for forecasting hospital closure. Like other studies in the literture, neural metwork analysis showed highest average hit ratio. For policy and business purposes, we combined the four analytical method and constructed a foreasting model that can be easily used to predict the probabolity of hospital closure given financial information of a hospital.

• 대한기계학회논문집A
• /
• 제27권4호
• /
• pp.585-592
• /
• 2003

Among various sensitivity evaluation techniques, semi-analytical method(SAM) is quite popular since this method is more advantageous than analytical method(AM) and global finite difference method(FDM). However, SAM reveals severe inaccuracy problem when relatively large rigid body motions are identified fur individual elements. Such errors result from the numerical differentiation of the pseudo load vector calculated by the finite difference scheme. In the present study, an iterative method combined with mode decomposition technique is proposed to compute reliable semi-analytical design sensitivities. The improvement of design sensitivities corresponding to the rigid body mode is evaluated by exact differentiation of the rigid body modes and the error of SAM caused by numerical difference scheme is alleviated by using a Von Neumann series approximation considering the higher order terms for the sensitivity derivatives.

• Bulletin of the Korean Chemical Society
• /
• 제28권3호
• /
• pp.408-412
• /
• 2007

Combining the analytical transfer matrix method with supersymmetry algebra, a new quantization condition is suggested. To demonstrate the efficiency of the new quantization condition, the eigenenergies of the Coulomb potential are analytically derived. The scattering-led phase shifts are also determined and they are the same for all Coulomb potential states. It is found that the new quantization condition is mathematically simple and exact.

• Structural Engineering and Mechanics
• /
• 제52권6호
• /
• pp.1273-1287
• /
• 2014

Plates are most widely used in the hulls of floating concrete structures, bridge decks, walls of off-shore structures and liquid storage tanks. A method of analysis is presented for the determination of load-deflection response and ultimate strength of high-strength steel fiber reinforced concrete (HSSFRC) plates simply supported on all four edges and subjected to combined action of external compressive in-plane and transverse loads. The behavior of HSSFRC plate specimens subjected to combined uniaxial in-plane and transverse loads was investigated. The proposed analytical method is compared to the physical test results, and shows good agreement. To predict the constitutive behavior of HSSFRC in compression, a non-dimensional characteristic equation was proposed and found to give reasonable accuracy.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.684-689
• /
• 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.