• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.11
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• pp.541-546
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• 2006

In a levitation magnet system with large air gap, numerical method is needed because analytic method cannot consider the leakage flux properly. This paper conducted an optimal design of a levitation magnet system with large air gap which was used for an OLED system, where evolution strategy was adopted for optimal design algorithm. Levitation forces near the initial design were calculated first by using finite element method to reduce the computation time. During the optimization process, levitation forces of arbitrary dimension were obtained using the interpolation of the levitation forces which were calculated previously Weight of the maget system was chosen as the object function and it was used minimized.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.4
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• pp.427-433
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• 2013

Stair climbing is one of critical issues for field robots to widen applicable areas. This paper presents optimal design on kinematic parameters of a new robotic platform for stair climbing. The robotic platform climbs various stairs by body-flip locomotion with caterpillar type main platform. Kinematic parameters such as platform length, platform height, and caterpillar rotation speed are optimized to maximize stair-climbing stability. Three types of stairs are used to simulate typical user conditions. The optimal design process is conducted based on Taguchi methodology, and resulting parameters with optimized objective function are presented. In near future, a prototype is assembled for real environment testing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.7
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• pp.650-658
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• 2012

This paper proposes a high performance position controller for a driving system using a time optimal controller which has been widely used to control driving systems to achieve desired reference position or velocity in a minimum response time. The main purpose of this research lies in an improvement of transient response performance rather than that of steady-state response in comparison with other control strategies. In order to refine the scheme of time optimal control, Lyapunov stability proofs are incorporated in a controller of standard second order system model. This scheme is applied to the control of a driving system. In view of the simulation and experiment results, the standard second order system model exhibits better minimum-time control performance and robustness than double integral system model does.

• Journal of Korea Water Resources Association
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• v.35 no.4 s.129
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• pp.367-374
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• 2002

Water supply plan by optimal conjunctive use of surface and ground water is studied to prepare expected water deficit in near future. The optimization model for conjunctive use of surface and ground water is developed using discrete differential dynamic programming technique to maximize net benefit by water supply. As a result of applying the model to Namdaechun river located in Yangyang, it is found that water supply reliability using optimal conjunctive use of surface and ground water is much higher than reliability using surface water alone.

• Structural Engineering and Mechanics
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• v.71 no.2
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• pp.139-151
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• 2019

In a project schedule, it is possible to reduce the time required to complete a project by allocating extra resources for critical activities. However, accelerating a project causes additional expense. This issue is addressed by finding optimal set of time-cost alternatives and is known as the time-cost trade-off problem in the literature. The aim of this study is to identify the optimal set of time-cost alternatives using a multiobjective teaching-learning-based optimization (TLBO) algorithm integrated with the non-dominated sorting concept and is applied to successfully optimize the projects ranging from a small to medium large projects. Numerical simulations indicate that the utilized model searches and identifies optimal / near optimal trade-offs between project time and cost in construction engineering and management. Therefore, it is concluded that the developed TLBO-based multiobjective approach offers satisfactorily solutions for time-cost trade-off optimization problems.

• Journal of applied mathematics & informatics
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• v.42 no.3
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• pp.647-661
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• 2024

This study aims to determine the optimal solution to transportation problems. We proposed a novel approach for tackling the initial basic feasible solution. This is a critical step toward achieving an optimal or near-optimal solution. The transportation issue is an issue of distributing goods from several sources to several destinations. The literature demonstrates many ways to improve IBFS. In this work, to solve the IBFS, we suggested a new method based on the statistical formula called cumulative distribution function (CDF) in exponential distribution, and inverse contra-harmonic mean (ICHM). The spreadsheet converts transportation cost values into exponential cost cell values. The stepping-stone method is used to identify an optimum solution. The results are compared with other existing methodologies, the suggested method incorporates balanced, and unbalanced, maximizing the profits, random values, and case studies which produce more effective outcomes.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.2
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• pp.90-98
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• 1998

The optimal rechlorination in water distribution systems was investigated by incorporating optimization techniques into a numerical water quality model. For a hypothetical system that consists of 10 junctions including a storage tank and 12 links, the bulk ($k_b$) and pipe-wall ($k_w$) decay-rate constants of chlorine residual are assumed to be 2.0 1/day and 1.5 m/day, respectively. It was also assumed that the lower and upper limits of chlorine residual in the network are 0.2 mg/L and 0.6 mg/L. When the chlorine source is only the storage tank (without rechlorination), the high levels of chlorine residual appear near the storage tank to maintain the chlorine residuals above the lower limit over the junctions. On the other hand, the chlorine residuals in the network are distribute within the desirable range (0.2 - 0.6 mg/L) after the optimal rechlorination through five injection sites including the storage tank. In case of a real water distribution system that comprises 28 junctions including a clear well and 27 links, the bulk and pipe-wall decay-rate constants are 0.3 1/day and 0.2 m/day, respectively. Before rechlorination, the required chlorine residual at the clearwell is 5.1 mg/L to keep the chlorine residuals above the minimum level (0.6 mg/L) over the junctions. By the optimal rechlorination at five injection sites, the chlorine residuals are distributed within a desirable range of 0.6 mg/L through 2.0 mg/L, which can avoid the excess of chlorine residuals near the clear well. Consequently, total chlirine doses are decreased by 81% in the hypothetical distribution network and 69 % in the real distribution network for satisfying the minimum chlorine residuals.

• Journal of Korean Institute of Industrial Engineers
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• v.38 no.3
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• pp.173-181
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• 2012

The size and layout of user interface components need to be optimally designed in terms of reachability, visibility, clearance, and compatibility in order for efficient and effective use of products. The present study develops an ergonomic design method which optimizes the size and layout of user interface components using adaptive genetic algorithm. The developed design method determines a near-optimal design which maximizes the aggregated score of 4 ergonomic design criteria (reachability, visibility, clearance, and compatibility). The adaptive genetic algorithm used in the present study finds a near-optimum by automatically adjusting the key parameter (probability of mutation) of traditional genetic algorithm according to the characteristic of current solutions. Since the adaptive mechanism partially helps to overcome the local optimality problem, the probability of finding the near-optimum has been substantially improved. To evaluate the effectiveness of the developed design method, the present study applied it to the user interface design for a portable wireless communication radio.

• Journal of Biomedical Engineering Research
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• v.37 no.1
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• pp.53-60
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• 2016

Monitoring of dermal collagen is important to assess various scar conditions, and many diagnostic methods have been applied to quantify collagen contents in scar tissue. In this study, Monte Carlo simulation was used to evaluate diffuse reflectance distributions in scar condition by a near-infrared laser source. The results showed that the effective distance of the light source and the detector was 2 mm to monitor the various scar conditions using diffuse reflectance spectroscopy. This study may suggest to the optimal design for a near infrared diffuse reflectance spectroscopy during the scar treatment.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.6
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• pp.74-80
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• 2008

Analysis of the electromagnetic environment on topside of a ship is needed for optimal arrangement of all kinds of antennas to be installed on the shipboard in order to minimize the probability of EMI of equipment and subsystems in real ship after construction phase. In this paper we analyze the characteristics of electric-fields such as radiation patterns and near E-fields of V/UHF antennas installed on a shipboard. We compare simulated results with measurements on the real ship for near E-fields to verify the reliability of the computed electromagnetic environment. Although there are various factors causing errors such as cable loss and impedance mismatching etc. when measuring near E-field, both data show similar trends in the range of the acceptable tolerance.