• 품질경영학회지
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• 제47권4호
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• pp.701-711
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• 2019

Purpose: The problem of optimizing redundancy allocation in multi-level systems is considered when each item in a multi-level system has alternative items with the same function. The number of redundancy of multi-level system is allocated to maximize the reliability of the system under path set and cost limitation constraints. Methods: Based on cost limitation and path set constraints, a mathematical model is established to maximize system reliability. Particle swarm optimization is employed for redundant allocation and verified by numerical experiments. Results: Comparing the particle swarm optimization method and the memetic algorithm for the 3 and 4 level systems, the particle swarm optimization method showed better performance for solution quality and search time. Particularly, the particle swarm optimization showed much less than the memetic algorithm for variation of results. Conclusion: The proposed particle swarm optimization considerably shortens the time to search for a feasible solution in MRAP with path set constraints. PS optimization is expected to reduce search time and propose the better solution for various problems related to MRAP.

• 산업공학
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• 제12권3호
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• pp.395-400
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• 1999

Shipbuilding process is composed of hull construction, in which the structural body of a ship is formed, and outfitting, in which all the non-structural parts such as pipes, derricks, engines, machinery, electrical cable, etc. are manufactured, added and assembled. Hull construction can be classified into parts fabrication, block assembly and hull erection. Among them, the parts fabrication is the first manufacturing stage that produces components or zones needed for block assembly and hull construction. More specifically, the parts fabrication is performed through machining processes including marking, cutting, pressing, and/or forming. When material is entering into the parts fabrication stage, it is important for achieving the total efficiency of production to select one of production division, so-called 'bay,' as well as machine tools on which the part is fabricated. In this paper, given production quantities of parts in the fabrication stage, the problem is to optimally select machine tools and production division, such that the total flow-time is minimized as well as the workload among machines is balanced. Specifically, three mathematical models for flow-time minimization, load balance, and simultaneously considering both objectives, and a numerical example are analyzed and presented.

• 대한기계학회논문집A
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• 제28권1호
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• pp.48-54
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• 2004

Generally, structural optimization is carried out based on external static loads. All forces have dynamic characteristics in the real world. Mathematical optimization with dynamic loads is extremely difficult in a large-scale problem due to the behaviors in the time domain. In practical applications, it is customary to transform the dynamic loads into static loads by dynamic factors, design codes, and etc. But the optimization results with the unreasonably transformed loads cannot give us good solutions. Recently, a systematic transformation has been proposed as an engineering algorithm. Equivalent static loads are made to generate the same displacement field as the one from dynamic loads at each time step of dynamic analysis. Thus, many load cases are used as the multiple loading conditions which are not costly to include in modem structural optimization. In this research, the proposed algorithm is applied to the optimization of flexible multibody dynamic systems. The equivalent static load is derived from the equations of motion of a flexible multibody dynamic system. A few examples that have been solved before are solved to be compared with the results from the proposed algorithm.

• 한국학교수학회논문집
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• 제9권3호
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• pp.363-384
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• 2006

일선학교에서는 방과 후 또는 방학 중 교육으로써 학습부진학생들에 대하여 특별보충과정반이라는 이름으로 따로 학급을 편성하여 운영하고 있다. 그러나 이들 학급 편성에 대한 명확하면서 납득할 만한 기준이 없고, 학교의 여건, 교사 수급 문제, 학생의 정서 문제 등 여러 가지 이유에 의하여 활성화 되지 못하고 있는 것이 사실이다. 따라서 본 연구에서는 학습부진 학생들을 위한 효율적인 지도방안으로서, 특히 특별보충과정반의 편성 운영에 대하여 탐색한다.

• 한국정밀공학회지
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• 제18권4호
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• pp.209-218
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• 2001

Ultrasonic motors are newly developed motors which are expected to be useful as actuators in many practical systems such as robot arms or manipulators because of several advantages against the electromagnetic motors. However, the precise control of the ultrasonic motor is generally difficult due to the absence of appropriate and rigorous mathematical model. Furthermore, owing to heavy nonlinearity, the position control of a pendulum system driven by the ultrasonic motor has a problem that control method using multiple neural network controllers based on a fuzzy inference system that can determine the initial position of the pendulum in the beginning of control operation. In addition, and appropriate neural network controller that has been learned to operate well at the corresponding initial position is adopted by switching schemes. The effectiveness of the proposed method was verified and evaluated from real experiments.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.698-701
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• 2007

DAHAN, the first 1 MWe Solar Power Tower system locates north to Beijing where nearby The Great Wall is now under construction with cooperation between China and Korea. Results in predicting the preliminary performance of this central receiver system are presented in this paper. Operating cycles under some typical weather condition days are simulated and commented. These results can be used to assess the impact of alternative plant designs or operating strategies on annual energy production, with the final objective being to optimize the design of central receiver power plants. Two subsystems are considered in the system simulation: the solar field and the power block. Mathematic models are used to represent physical phenomena and relationships so that the characteristics of physical processes involving these phenomena can be predicted. Decisions regarding the best position for locating heliostats relative to the receiver and how high to place the receiver above the field constitute a multifaceted problem. Four different kinds of field layout are designed and analyzed by the use of ray tracing and mathematical simulation techniques to determine the overall optical performance ${\eta}_{field}$ and the spillage ${\eta}_{spill}$.The power block including a Rankine cycle is analyzed by conventional energy balance methods.

• 경영과학
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• 제21권3호
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• pp.101-113
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• 2004

In the rapidly propagating Internet based electronic transaction environment. the importance of real time order confirmation has been more emphasized, In this paper, using data mining techniques, we develop intelligent operations decision model to allow real time order confirmation at the time the customer places an order with required delivery terms. Among various operation plannings used for order fulfillment. mill routing is the first interface decision point to link the order receiving at the marketing with the production planning for order fulfillment. Though linear programming based mathematical optimization techniques are mostly used for mill routing problems, some early orders should wait until sufficient orders are gathered for optimization. And that could effect longer order fulfillment lead-time, and prevent instant order confirmation of delivery terms. To cope with this problem, we provide the intelligent decision model to allow instant order based mill routing decisions. Data mining techniques of decision trees and neural networks. which are more popular in marketing and financial applications, are used to develop the model. Through diverse computational trials with the industrial data from the steel company. we have reported that the performance of the proposed approach is effective compared to the present heuristic only mill routing results. Various issues of data mining techniques application to the mill routing problems having linear programming characteristics are also discussed.

• 대한수학교육학회지:수학교육학연구
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• 제15권2호
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• pp.215-232
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• 2005

컴퓨터 대수 체계(CAS) 계산기는 점차 학교와 대학에서 보편화되어가고 있다 이 계산기는 교사와 학생들에게 꽤 정교한 수학적 기능을 제공하지만, 현재로서는 어떻게 잘 활용될 수 있는지에 대해서 명확하지 않다. 특히 학생들의 학습과 문제 해결의 통합은 문제로 남아있다. 본 논문에서 우리는 TI-89 CAS 계산기를 대학에 입학하려는 학생들에게 도입하는 연구에서 이러한 문제를 제기하고 학생들이 그들의 학습에서 CAS 계산기를 조작하면서 형성하는 협력 관계의 여러 측면을 기술하였다.

• 대한수학교육학회지:학교수학
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• 제15권1호
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• pp.1-14
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• 2013

본 연구는 현행 초등학교 교과서에 제시되는 각뿔 관련 내용을 분석하여 문제점을 확인하고 그 개선방안을 제안하는 데 목적이 있다. 교과서에서는 각뿔의 정의를 일반적으로 제시하고 있지만, 학생의 수준을 고려하여 실질적으로는 옆면의 모양이 이등변삼각형인 각뿔만을 의도적으로 다루고 있다. 그러나 그러한 각뿔은 직각뿔의 정의에 맞지 않으며, 기울어지지 않은 안정적인 각뿔이라는 직관에도 부합하지 않는다. 이러한 결과를 바탕으로 각뿔 지도의 개선방안을 제안하고 분석결과가 교사 교육에 주는 시사점을 논의하였다.

• Wind and Structures
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• 제11권2호
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• pp.97-120
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• 2008

Wind and wave loadings have a predominant role in the design of offshore structures in general, and articulated tower in particular for a successful service and survival during normal and extreme environmental conditions. Such towers are very sensitive to the dynamic effects of wind and wind generated waves. The exposed superstructure is subjected to aerodynamic loads while the submerged substructure is subjected to hydrodynamic loads. Articulated towers are designed such that their fundamental frequency is well below the wave frequency to avoid dynamic amplification. Dynamic interaction of these towers with environmental loads (wind, waves and currents) acts to impart a lesser overall shear and overturning moment due to compliance to such forces. This compliancy introduces geometric nonlinearity due to large displacements, which becomes an important consideration in the analysis of articulated towers. Prediction of the nonlinear behaviour of these towers in the harsh ocean environment is difficult. However, simplified realistic mathematical models are employed to gain an important insight into the problem and to explore the dynamic behaviour. In this paper, various modeling approaches and solution methods for articulated towers adopted by past researchers are reviewed. Besides, reliability of articulation system, the paper also discussed the design, installation and performance of articulated towers around the world oceans.