• Structural Engineering and Mechanics
• /
• v.16 no.5
• /
• pp.597-612
• /
• 2003

In this paper, multi-story buildings with shear-wall structures and with narrow rectangular plane configuration are modeled as a multi-step flexural-shear plate with varying cross-section for buckling analysis. The governing differential equation of such a plate is established. Using appropriate transformations, the equation is reduced to analytically solvable equations by selecting suitable expressions of the distribution of stiffness. The exact solutions for buckling of such a one-step flexural-shear plate with variable stiffness are derived for several cases. A new exact approach that combines the transfer matrix method and closed from solution of one-step flexural-shear plate with continuously varying stiffness is presented for stability analysis of multi-step non-uniform flexural-shear plate. A numerical example shows that the present methods are easy to implement and efficient.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.4
• /
• pp.574-582
• /
• 1999

This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.379-384
• /
• 2000

High-Tc superconducting current leads with multi-step and continually varied cross-sectional area are studied to reduce heat leak into cryostat and material use. Assuming conduction-cooled lead the cross-sectional area is reduced along the heat flow direction according to the increase of critical current density which increases with decreasing temperature. In this study, we also analyze the multi-step cross-sectional area High-Tc current leads. The multi-st데 current leads changes the cross-sectional area to have constant safety-factor at changed section. The heat leak into cryostat, total voume, safety-factor and the temperature profiles are compared to those of the constant safety-factor current leads. The developed methods are applied to the Bi-2223 superconductor sheathed with Ag-Au alloy.

• Journal of the Korea Society for Simulation
• /
• v.9 no.3
• /
• pp.91-102
• /
• 2000

The distribution routing problem is one of the important problems in distribution and supply center management. This research is concerned with an integrated distribution routing problem for multi-supply centers based on improved genetic algorithm and GUI-type programming. In this research, we used a three-step approach; in step 1 a sector clustering model is developed to transfer the multi-supply center problem to single supply center problems which are more easy to be solved, in step 2 we developed a vehicle routing model with time and vehicle capacity constraints and in step 3, we developed a GA-TSP model which can improve the vehicle routing schedules by simulation. For the computational purpose, we developed a GUI-type computer program according to the proposed methods and the sample outputs show that the proposed method is very effective on a set of standard test problems, and it could be potentially useful in solving the distribution routing problems in multi-supply center problem.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.36 no.8
• /
• pp.539-546
• /
• 1987

In case of operating at Variable speed the induction motor by a frequency transformer, it will cause ripples in motor torque and considerably bad effects on the machines because the output side of the frequency transformer involves a great number of harmonics. This paper Presents the methods of decreasing torque ripples in induction motor and of improving current waveform, by means of forming the waveforms of output current into multi-step waveforms similiar to sinusoid, and also by means of eliminating the harmonic components maximally, in case of operating a 18-phase multi-inverter combining 3-step current source inverter.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.24 no.3
• /
• pp.243-291
• /
• 2020

In this paper, multi-block generalized backward differentiation methods for numerical solutions of ordinary differential and differential algebraic equations are introduced. This class of linear multi-block methods is implemented as multi-block boundary value methods (MB₂ VMs). The root distribution of the stability polynomial of the new class of methods are determined using the Wiener-Hopf factorization of a matrix polynomial for the purpose of their correct implementation. Numerical tests, showing the potential of such methods for output of multi-block of solutions of the ordinary differential equations in the new approach are also reported herein. The methods which output multi-block of solutions of the ordinary differential equations on application, are unlike the conventional linear multistep methods which output a solution at a point or the conventional boundary value methods and multi-block methods which output only a block of solutions per step. The MB₂ VMs introduced herein is a novel approach at developing very large scale integration methods (VLSIM) in the numerical solution of differential equations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.05a
• /
• pp.278-282
• /
• 2003

There is a strong industrial demands for the development of light-vehicle to improve fuel efficiency. It is more effective to reduce weight of the parts directly driven by an automobile engine. So the saving in weight of wheels which is operated by an automobile engine improve fuel efficiency more than other parts. There are many step of sheet metal forming in fabricating automotive wheel, so that it is difficult to design process and tools of multi-stage stamping. Traditionally, design process and tools have depended on the experience of skilled workers and it has done by trial and error methods. However, it needs too much costs and time. Taguchi methods has an advantage of the number of required experiments and reliability compared with trial and error method. In this study, Taguchi methods and response surface methods are applied to design process and tools of automotive wheel. As a result, the principal variables are selected and process conditions are optimized.

• Journal of the Korea Society of Computer and Information
• /
• v.28 no.2
• /
• pp.201-207
• /
• 2023

In this paper, we propose an optimal model for mid to long-term price prediction of agricultural products using LGBM, MLP, LSTM, and GRU to compare and analyze the three strategies of the Multi-Step Time Series. The proposed model is designed to find the optimal combination between the models by selecting methods from various angles. Prior agricultural product price prediction studies have mainly adopted traditional econometric models such as ARIMA and LSTM-type models. In contrast, agricultural product price prediction studies related to Multi-Step Time Series were minimal. In this study, the experiment was conducted by dividing it into two periods according to the degree of volatility of agricultural product prices. As a result of the mid-to-long-term price prediction of three strategies, namely direct, hybrid, and multiple outputs, the hybrid approach showed relatively superior performance. This study academically and practically contributes to mid-to-long term daily price prediction by proposing an effective alternative.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.4
• /
• pp.458-465
• /
• 2003

The main objective of the research is to develop a research code solving transient incompressible Navier-Stokes equation. In this research code, Adams-Bashforth method was applied to the convective terms of the navier stokes equation and the splitted equations were discretized spatially by finite element methods to solve the complex geometry problems easily. To reduce the divergence on the boundaries of pressure poisson equation due to the unsuitable pressure boundary conditions, multi step approximation pressure boundary conditions derived from the boundary linear momentum equations were used. Simulations of Lid Driven Flow and Flow over Cylinder were conducted to prove the accuracy by means of the comparison with results of the previous workers.

• The Pure and Applied Mathematics
• /
• v.20 no.4
• /
• pp.277-286
• /
• 2013

In this paper, we suggest and analyze a family of multi-step iterative methods which do not involve the high-order differentials of the function for solving nonlinear equations using a different type of decomposition (mainly due to Noor and Noor [15]). We also discuss the convergence of the new proposed methods. Several numerical examples are given to illustrate the efficiency and the performance of the new iterative method. Our results can be considered as an improvement and refinement of the previous results.