• Industrial Engineering and Management Systems
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• v.8 no.3
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• pp.162-170
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• 2009

This paper deals with a closed-loop remanufacturing system with one manufacturer and one remanufacturer. The manufacturer sells new products bearing the 'Extended Producer Responsibility (EPR).' It is assumed that the manufacturer's collection rate of used products depends only on the buy-back cost, while that of the remanufacturer depends on the minimum allowed quality level of used products in addition to the buy-back cost. Through the development of mathematical models with the objective function of maximizing profit, we study an efficient operation policy of each party. The decision variables are the unit selling price of new products and remanufactured products, the unit buy-back cost of the used products of the manufacturer and remanufacturer, and the minimum allowed quality level. The validity of the model is examined through numerical examples and sensitivity analysis.

• Structural Engineering and Mechanics
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• v.51 no.3
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• pp.361-375
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• 2014

The main aim of this paper is to investigate the relationship between thickness and height of the axially symmetric cylindrical reinforced concrete (RC) walls by the help of a meta-heuristic optimization procedure. The material cost of the wall which includes concrete, reinforcement and formwork, was chosen as objective function of the optimization problem. The wall thickness, compressive strength of concrete and diameter of reinforcement bars were defined as design variables and tank volume, radius and height of the wall, loading condition and unit cost of material were defined as design constants. Numerical analyses of the wall were conducted by using superposition method (SPM) considering ACI 318-Building code requirements for structural concrete. The optimum wall thickness-height relationship was investigated under three main cases related with compressive strength of concrete and density of the stored liquid. According to the results, the proposed method is effective on finding the optimum design with minimum cost.

• Structural Engineering and Mechanics
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• v.45 no.5
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• pp.643-654
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• 2013

Optimum cost design of columns subjected to axial force and uniaxial bending moment is presented in this paper. In the formulation of the optimum design problem, the height and width of the column, diameter and number of reinforcement bars are treated as design variables. The design constraints are implemented according to ACI 318-08 and studies in the literature. The objective function is taken as the cost of unit length of the column consisting the cost of concrete, steel, and shuttering. The solution of the design problem is obtained using the artificial bee colony algorithm which is one of the recent additions to metaheuristic techniques. The Artificial Bee Colony Algorithm is imitated the foraging behaviors of bee swarms. In application of this algorithm to the constraint problem, Deb's constraint handling method is used. Obtained results showed that the optimum value of numerical example is nearly same with the existing values in the literature.

• Journal of Korea Society of Industrial Information Systems
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• v.4 no.2
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• pp.81-87
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• 1999

This paper discusses a bicriterion approach to sequencing with time/cost trade-offs. The first problem is to minimize the total flow time and the maximum tardiness. And second is to the maximum tardiness and resource allocation costs. This approach, which produces an efficient flintier of possible schedules, has the advantage that it does not require the sequencing criteria to be measurable in the same units as the m allocation cost. The basic single machine model is used to treat a class of problems in which the sequencing objective is to minimize the maximum completion penalty. It is further assumed that resource allocation costs can be represented by linear time/cost function.

• Smart Structures and Systems
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• v.15 no.4
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• pp.1041-1062
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• 2015

In this paper a method of finding optimal positions for piezoelectric actuators and sensors on different structures is presented. The genetic algorithm and multi-objective genetic algorithm are selected for optimization and $H_{\infty}$ norm is defined as a cost function for the optimization process. To optimize the placement concerning the selected modes simultaneously, the multi-objective genetic algorithm is used. The optimization is investigated for two different structures: a cantilever beam and a simply supported plate. Vibrating structures are controlled in a closed loop with feedback gains, which are obtained using optimal LQ control strategy. Finally, output of a structure with optimized placement is compared with the output of the structure with an arbitrary, non-optimal placement of piezoelectric patches.

• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2403-2413
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• 1999

There is a strong need to develop a software cost estimation model on economic value perspective. The objective of this research is to improve current software cost estimation method on economic value perspective. We reviewed domestic and foreign researches and practices on software cost estimation with function point method, and derived promising alternative models. Pilot simulation was performed with real project data, and the probable best model was chosen. We collected data from 39 Korean companies, and assesed statistical significance of the model with those data. Empirical data shows that more practical model has better prediction accuracy. That is, the number of input and output modules, the number of tables, and the number of algorithms are chosen to be best set of functions. There exists strong correlation between the calculated function points and project effort. And, the revised set of technical complexity factors and evaluation guidelines show practical usefulness. We suggest that the above result be incorporated in a new improved guideline for software cost estimation. By adopting the results of this research to the guideline, we expect that technology innovation will be expedited, and that overall productivity of software industry will be increased.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.4
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• pp.113-128
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• 2016

This paper proposes a Bi-level Genetic Algorithm for the Fixed Charge Transportation Problem with Non-linear Unit Cost. The problem has the property of mixed integer program with non-linear objective function and linear constraints. The bi-level procedure consists of the upper-GA and the lower-GA. While the upper-GA optimize the connectivity between each supply and demand pair, the lower-GA optimize the amount of transportation between the pairs set to be connected by the upper-GA. In the upper-GA, the feasibility of the connectivity are verified, and if a connectivity is not feasible, it is modified so as to be feasible. In the lower-GA, a simple method is used to obtain a pivot feasible solution under the restriction of the connectivity determined by the upper-GA. The obtained pivot feasible solution is utilized to generate the initial generation of chromosomes. The computational experiment is performed on the selected problems with several non-linear objective functions. The performance of the proposed procedure is analyzed with the result of experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1249-1259
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• 2012

This paper proposes a Web Based Online Outage Cost Assessment and Information System(WOOCAIS) for power system outage cost assessment. The proposed WOOCAIS is a kind of web based survey method for outage cost assessment. While conventional survey methods have done outage cost assessment based on survey paper lists collected by post mail or visiting customers, the proposed WOOCAIS is a web based online survey operation and assessment system. Therefore, it can curtail expenditure for survey and also is more convenient than conventional method. It will be set up for actual outage cost assessment system of KEPCO in South Korea in the near future. The WOOCAIS will be applied in various research and actual planning and operation areas. First of all, the assessed results may be not only applied as one of objective function for generation system and grid expansion but also operational planning problems in power system.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.4
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• pp.203-212
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• 2018

Quality requirements of manufactured products or parts are given in the form of specification limits on the quality characteristics of individual units. If a product is to meet the customer's fitness for use criteria, it should be produced by a process which is stable or repeatable. In other words, it must be capable of operating with little variability around the target value or nominal value of the product's quality characteristic. In order to maintain and improve product quality, we need to apply statistical process control techniques such as histogram, check sheet, Pareto chart, cause and effect diagram, or control charts. Among those techniques, the most important one is control charting. The cumulative sum (CUSUM) control charts have been used in statistical process control (SPC) in industries for monitoring process shifts and supporting online measurement. The objective of this research is to apply Taguchi's quality loss function concept to cost based CUSUM control chart design. In this study, a modified quality loss function was developed to reflect quality loss situation where general quadratic loss curve is not appropriate. This research also provided a methodology for the design of CUSUM charts using Taguchi quality loss function concept based on the minimum cost per hour criterion. The new model differs from previous models in that the model assumes that quality loss is incurred even in the incontrol period. This model was compared with other cost based CUSUM models by Wu and Goel, According to numerical sensitivity analysis, the proposed model results in longer average run length in in-control period compared to the other two models.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.3
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• pp.82-94
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• 1988

A growing attention has been paid to the optimum design of structures in recent years. Most studies on the optimum design of reinforced concrete structures has been mainly focussed to the design of structural members such as beams, slabs and columns, and there exist few studies that deal with the optimum design of large-scale concrete shell structures. The purpose of the present investigation is, therefore, to set up an efficient optimum design method for the large-scale reinforced concrete cylindrical shell structures like intake tower of reservoir. The major design variables are the dimensions and steel areas of each member of structures. The construction cost which is compo8ed of the concrete, steel, and form work costs, respectively, is taken as the objective function. The constraint equations for the design of intake-tower are derived on the basis of strength design method. The results obtained are summarized as follows 1. The efficient optimlzation algorithrns which can execute the automatic optimum design of reinforced concrete intake tower based on the strength design method were developed. 2. Since the objective function and design variables were converged to their optimum values within the first or second iteration, the optimization algorithms developed in this study seem to be efficient and stable. 3. When using the strength design method, the construction cost could be saved about 9% compared with working stress design method. Therefore, the reliability of algorithm was proved. 4. The difference in construction cost between the optimum designs with substructures and with entire structure was found to be small and thus the optimum design with substructures may conveniently be used in practical design. 5. The major active constraints of each structural member were found to be the 'bending moment constraint for slab, the minimum longitudinal steel ratio constraint for tower body and the shearing force, bending moment and maximum eccentricity constraints for footing, respectively. 6. The computer program developed in the present study can be effectively used even by an uneiperienced designer for the optimum design of reinforced concrete intake-tower on the basis of strength design method.