• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.1
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• pp.61-75
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• 2007

The purpose of this paper is to develop a new group classification method based on genetic algorithm and to com-pare its prediction performance with those of existing methods in the area of bond rating. To serve this purpose, we conduct various experiments with pilot and general models. Specifically, we first conduct experiments employing two pilot models : the one searching for the cluster center of each group and the other one searching for both the cluster center and the attribute weights in order to maximize classification accuracy. The results from the pilot experiments show that the performance of the latter in terms of classification accuracy ratio is higher than that of the former which provides the rationale of searching for both the cluster center of each group and the attribute weights to improve classification accuracy. With this lesson in mind, we design two generalized models employing genetic algorithm : the one is to maximize the classification accuracy and the other one is to minimize the total misclassification cost. We compare the performance of these two models with those of existing statistical and artificial intelligent models such as MDA, ANN, and Decision Tree, and conclude that the genetic algorithm-based group classification method that we propose in this paper significantly outperforms the other methods in respect of classification accuracy ratio as well as misclassification cost.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.325-331
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• 2009

In this paper, a simulation approach for the optimum design of cogeneration system is described. For the purpose of the systematic analysis, a simulation tool is developed with which the prediction of the energy load, calculation of operation data according to prime mover or capacity of it, and estimation of economic gains can be carried out. As for the criterion of the optimum design, the economic gains by adopting cogeneration system is taken. Based on the capital, operation, and maintenance costs etc, LCC analysis is to be carried out for the scenarios respectively. In this study, the simulation for the apartment complex is performed and the analysis of the results are described in detail. The effects of the operation parameters such as capital cost, fuel cost, and unit cost for the purchase or sale of heat and electricity on overall economy are also be considered by sensitivity study.

• Health Policy and Management
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• v.13 no.4
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• pp.28-47
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• 2003

The purpose of this study was to assess the user's satisfaction of health care service in public health centers in Busan. The study respondents were 212, those who visited health centers for health care service. Data were collected in July 2002 by using SERVQUAL(comprehensive service quality measurement scale) and 3 open questions for more details about service satisfaction and the needs for health care service. SERVQUAL has 5 dimensions； tangibles, reliability, responsiveness, assurance and empathy. The results were as follows ： 1. The users reported more satisfaction at 'just service cost', 'convenient service procedure' and 'clean physical environment' at SERVQUAL. Among them the highest rated item was 'service cost'. And the less satisfaction items were 'understanding and individual concerns about service users', 'medical equipment' and 'health center facilities'. 2. There were no statistical differences by general characteristics except for the kind of services rendered. Those who visited for physical examinations and laboratory tests reported lower satisfaction than any other groups. 3. At the open questions, the respondents expressed that they were satisfied with the low service cost, kindness of employee and clean environment. But they criticized the old facilities and worn medical equipment, in addition to the less than kind attitudes. These strengths and weaknesses of health center's service could be applied for planning of customer­centered health care service.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.470-480
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• 2016

The reversal of a silicon chip to find out its security structure is common and possible at the present time. Thanks to reversing, it is possible to use a probing attack to obtain useful information such as personal information or a cryptographic key. For this reason, security-related blocks such as DES (Data Encryption Standard), AES (Advanced Encryption Standard), and RSA (Rivest Shamir Adleman) engines should be located in the lower layer of the chip to guard against a probing attack; in this regard, the addition of a silicon-surface-protection layer onto the chip surface is a crucial protective measure. But, for manufacturers, the implementation of an additional silicon layer is burdensome, because the addition of just one layer to a chip significantly increases the overall production cost; furthermore, the chip size is increased due to the bulk of the secure logic part and routing area of the silicon protection layer. To resolve this issue, this paper proposes a practical silicon-surface-protection method using a metal layer that increases the security level of the chip while minimizing its size and cost. The proposed method uses a shift register for the alternation and variation of the metal-layer data, and the inter-connection area is removed to minimize the size and cost of the chip in a more extensive manner than related methods.

• Wind and Structures
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• v.36 no.6
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• pp.423-434
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• 2023

Aerodynamic force coefficients are generally obtained from traditional wind tunnel tests or computational fluid dynamics (CFD). Unfortunately, the techniques mentioned above can sometimes be cumbersome because of the cost involved, such as the computational cost and the use of heavy equipment, to name only two examples. This study proposed to build a deep neural network model to predict the aerodynamic force coefficients based on data collected from CFD simulations to overcome these drawbacks. Therefore, a series of CFD simulations were conducted using different geometric parameters to obtain the aerodynamic force coefficients, validated with wind tunnel tests. The results obtained from CFD simulations were used to create a dataset to train a multilayer perceptron artificial neural network (ANN) model. The models were obtained using three optimization algorithms: scaled conjugate gradient (SCG), Bayesian regularization (BR), and Levenberg-Marquardt algorithms (LM). Furthermore, the performance of each neural network was verified using two performance metrics, including the mean square error and the R-squared coefficient of determination. Finally, the ANN model proved to be highly accurate in predicting the force coefficients of similar bridge sections, thus circumventing the computational burden associated with CFD simulation and the cost of traditional wind tunnel tests.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.309-312
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• 2007

We consider a proportionate flow shop problem with controllable processing times. The objective is to minimize the sum of total completion time and total compression cost, in which the cost function of compressing the processing times is non-decreasing concave. We show that the problem can be solved in polynomial time by reducing it to a polynomially solvable 0-1 unconstrained quadratic program.

• Corrosion Science and Technology
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• v.5 no.5
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• pp.173-176
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• 2006

Previous national studies on costs of corrosion are reviewed and brief explanations are given of the Uhlig method, Hoar method and Input-output method that are employed for corrosion cost estimation. Total costs of corrosion of 11 countries are summarized and the results by Uhlig methods are compared especially for the recent studies from the U.S, Japan and China.

• Journal of the Korean Institute of Landscape Architecture International Edition
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• no.1
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• pp.213-218
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• 2001

To many developing countries like China, the practical way to constant development of city construction is low consuming. The basic methods of low-cunsuming landscape construction: 1) Low building consumption: Decreasing construction quantity. Using low-costing material. Designing low-consuming landscape. Reusing of building material. 2) Low energy consumption: Decreasing water consumption. Consuming and enrichment of earth fertilizer. Decreasing electrical consumption. 3) Low maintenance: Adapting natural material. Using local plants. Special design to decrease maintaining. Because of many reasons, China has not yet adapting Low-consuming Landscape Construction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.633-636
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• 2005

Imprint lithography is a promising method for high-resolution and high-throughput lithography using low-cost equipment. As with other nanoimprint methods, ultraviolet-nanoimprint lithography (UV-NIL) resolution appears to be limited only by template resolution, and offers a significant cost of ownership reduction when compared to other next generation lithography (NGL) methods such as EUVL and 157 nm lithography. The purpose of this paper is to suggest optimum values of control parameters of Imprio 100 manufactured by Molecular Imprint, Inc., which is the first commercially available UV-NIL tool, for sound nanoimprint. UV-NIL experiments were performed on Imprio 100 to find dispensing recipe for avoiding air entrapment. Dispensing recipe related to residual layer thickness and uniformity was optimized and 40 nm thick residual layer was achieved.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.130-145
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• 2019

Widespread commercialization of solid oxide fuel cells (SOFCs) is expected to be realized in various application fields with the advent of cost-effective fabrication of cells and stacks in high volumes. Cost-reduction efforts have focused on production yield, power density, operation temperature, and continuous manufacturing. In this article, we examine several issues associated with processing for SOFCs from the standpoint of the bimodal packing model, considering the external constraints imposed by rigid substrates. Optimum compositions of composite cathode materials with high volume fractions of the second phase (particles dispersed in matrix) have been analyzed using the bimodal packing model. Constrained sintering of thin electrolyte layers is also discussed in terms of bimodal packing, with emphasis on the clustering of dispersed particles during anisotropic shrinkage. Finally, the structural transition of dispersed particle clusters during constrained sintering has been correlated with the structural stability of thin-film electrolyte layers deposited on porous solid substrates.