• Transactions of Materials Processing
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• v.30 no.3
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• pp.125-133
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• 2021

In this study, response surface method (RSM), back propagation neural network (BPNN), and genetic algorithm (GA) were used for modeling and multi-objective optimization of the parameters of AA5052-H32 in incremental sheet forming (ISF). The goal of optimization is to determine the maximum forming angle and minimum surface roughness, while varying the production process parameters, such as tool diameter, tool spindle speed, step depth, and tool feed rate. A Box-Behnken experimental design (BBD) was used to develop an RSM model and BPNN model to model the variations in the forming angle and surface roughness based on variations in process parameters. Subsequently, the RSM model was used as the fitness function for multi-objective optimization of the ISF process the GA. The results showed that RSM and BPNN can be effectively used to control the forming angle and surface roughness. The optimized Pareto front produced by the GA can be utilized as a rational design guide for practical applications of AA5052 in the ISF process

• Journal of the Korean Society for Library and Information Science
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• v.6
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• pp.53-70
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• 1979

This is to report the objectives, planning and the process of the establishment of an on-line information retrieval system in Korea. The model is the case of the Library of the Korea Institute of Science and Technology (KIST) which is the multi-disciplinary contract research organization in science and technology. The report explains the objectives and the step by step process such as input materials, analysis of the materials, structure of the data base files, indexes, command language, and the process, technique and logic of information retrieval. A brief comparison is made with other systems such as OCLC and BALLOTS and the authors gave various illustrations and samples to clarify the processes. The authors regrets that they could not give any detailed information on the budget or the cost accrued so far.

• Industrial Engineering and Management Systems
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• v.1 no.1
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• pp.93-98
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• 2002

It is important to evaluate the performance of candidates mathematically from various aspects, and reflect it on decision making. In decision making, we judge the candidates through two steps, classification of objects and comparison of objects or candidates with plural elements. In the former step, Analytic Hierarchy Process (AHP) is useful method to evaluate candidates from plural viewpoints, and in the later step, Data Envelopment Analysis (DEA) is also useful method to evaluate candidates with plural categorized data. In fact, each candidate has plural elements, nevertheless it has been more important to evaluate from various aspects in IT society. So, we propose a new procedure complementing AHP with DEA.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.10a
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• pp.167-170
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• 2000

This paper is concerned with development of a performance evaluation model for material handling system in cellular manufacturing system based on multi-attributes analysis method. We used the AHP(analytic hierarchy process) and fuzzy set ranking methodologies to overcome the special decision problems; those of multi -objective, multi-criterion, and multi-attributes. We proposed a 3-step approaches and we developed a systemic and practical computer program to solve the problems in the proposed methods. Computational experiments are then performed to cellular manufacturing system and show the effectiveness of the proposed model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.356-361
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• 2008

Eigenvalue reduction schemes approximate the lower eigenmodes that represent the global behavior of the structures. In the previous study, we proposed a two-level condensation scheme (TLCS) for the construction of a reduced system. And we have improved previous TLCS with combination of the iterated improved reduced system method (IIRS) to increase accuracy of the higher modes intermediate range. In this study, we apply previous improved TLCS to multi-level sub-structuring scheme. In the first step, the global system is recursively partitioned into a hierarchy of sub-domain. In second step, each uncoupled sub-domain is condensed by the improved TLCS. After assembly process of each reduced sub-eigenvalue problem, eigen-solution is calculated by Lanczos method (ARPACK). Finally, Numerical examples demonstrate performance of proposed method.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.471-477
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• 2014

The novel permanent magnetic actuator (PMA) and its optimal design method were proposed in this paper. The proposed PMA is referred to as the separated permanent magnetic actuator (SPMA) and significantly superior in terms of its cost and performance level over a conventional PMA. The proposed optimal design method uses the evolutionary strategy algorithm (ESA), the kriging meta-model (KMM), and the multi-step optimization. The KMM can compensate the slow convergence of the ESA. The proposed multi-step optimization process, which separates the independent variables, can decrease time and increase the reliability for the optimal design result. Briefly, the optimization time and the poor reliability of the optimum are mitigated by the proposed optimization method.

• Geomechanics and Engineering
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• v.7 no.2
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• pp.149-164
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• 2014

One of the most advanced classes of techniques for ground response analysis is based on the use of Transfer Functions. They represent the ratio of Fourier spectrum of amplitude motion at the free surface to the corresponding spectrum of the bedrock motion and they are applied in frequency domain usually by FFT method. However, Fourier spectrum only shows the dominant frequency in each time step and is unable to represent all frequency contents in every time step and this drawback leads to inaccurate results. In this research, this process is optimized by decomposing the input motion into different frequency sub-bands using Wavelet Multi-level Decomposition. Each component is then processed with transfer Function relating to the corresponding component frequency. Taking inverse FFT from all components, the ground motion can be recovered by summing up the results. The nonlinear behavior is approximated using an iterative procedure with nonlinear soil properties. The results of this procedure show better accuracy with respect to field observations than does the Conventional method. The proposed method can also be applied to other engineering disciplines with similar procedure.

• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.482-494
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• 2016

The Feshbache-Kermane-Koonin (FKK) multi-step direct (MSD) theory of pre-equilibrium reactions has been used to compute the single-step cross-sections for some (p,${\alpha}$) reactions using the knock-on and pick-up reaction mechanisms at two incident proton energies. For the knock-on mechanism, the reaction was assumed to have taken place by the direct ejection of a preformed alpha cluster in a shell-model state of the target. But the reaction was assumed to have taken place by the pick-up of a preformed triton cluster (also bound in a shell-model state of the target core) by the incident proton for the pick-up mechanism. The Yukawa forms of potential were used for the proton-alpha (for the knock-on process) and proton-triton (for the pick-up process) interaction and several parameter sets for the proton and alpha-particle optical potentials. The calculated cross-sections for both mechanisms gave satisfactory fits to the experimental data. Furthermore, it has been shown that some combinations of the calculated distorted wave Born approximation cross-sections for the two reaction mechanisms in the FKK MSD theory are able to give better fits to the experimental data, especially in terms of range of agreement. In addition, the theory has been observed to be valid over a wider range of energy.

• Composites Research
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• v.34 no.5
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• pp.269-276
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• 2021

PCM (Prepreg Compression Molding) process is a high-speed molding technology that can manufacture high-quality CFRP (Carbon Fiber Reinforced Plastic) parts. Compared to the autoclave process, it generates less waste and can significantly reduce cycle time, so various studies are being conducted in the aerospace and automobile industries. In this study, in order to improve the quality of the PCM process, a molding method was developed to increase the compression pressure of the press step by step according to the curing behavior of the prepreg. It was confirmed that this multi-stage compression molding technology is a good means to produce high-quality CFRP products and shorten cycle times. And, the laminated prepreg at room temperature was immediately put into the mold and preheated and molded at the same time, so that it could be molded without a separate preheating process. In addition, as a result of applying the same process conditions optimized for flat plate molding to three-dimensional shapes, a product similar to a flat plate in appearance could be made without the process of establishing process conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.199-202
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• 2005

In this paper, the six sigma scheme is employed together with the rigid-viscoplastic finite element method to obtain the optimal metal flow lines in hot press forging. In general, the six sigma process is consisted of following five steps : define, measure, analyze, improve and control. Each step Is investigated in detail to meet customer's requirements through improvement of product quality. A forging simulator, AFDEX-2D, is used for analysis of the metal flow lines of a multi-stage hot forging process under various conditions of major factors, determined at each step of the six sigma process. The analyzed results are examined in order to reveal the effects of major factors on the metal flow lines and the formed shapes. The effects are used to find an optimal process and the optimal process with die is devised and tested. The comparison between required metal flow lines and experiments shows that the approach is effective for optimal process in hot forging design considering metal flow lines.