• 한국재료학회지
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• 제19권1호
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• pp.50-53
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• 2009

Multi-walled carbon nanotubes (MWNTs) were synthesized on different substrates (bare Si and $SiO_2$/Si substrate) to investigate dye-sensitized solar cell (DSSC) applications as counter electrode materials. The synthesis of MWNTs samples used identical conditions of a Fe catalyst created by thermal chemical vapor deposition at $900^{\circ}C$. It was found that the diameter of the MWNTs on the Si substrate sample is approximately $5{\sim}10nm$ larger than that of a $SiO_2$/Si substrate sample. Moreover, MWNTs on a Si substrate sample were well-crystallized in terms of their Raman spectrum. In addition, the MWNTs on Si substrate sample show an enhanced redox reaction, as observed through a smaller interface resistance and faster reaction rates in the EIS spectrum. The results show that DSSCs with a MWNT counter electrode on a bare Si substrate sample demonstrate energy conversion efficiency in excess of 1.4 %.

• Industrial Engineering and Management Systems
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• 제6권1호
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• pp.83-93
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• 2007

This paper gives an attempt to build a decision support tool linked with a simulation software called ARENA for evaluating and comparing the performance of the push and pull material driven strategies operating in the flow shop environment with a bottleneck resource as the shop's constraint. To be fair for such evaluation, the comparison must be made fairly under the optimal setting of both systems' operating parameters. In this study, an optimal-seeking heuristic algorithm, Genetic Algorithm (GA), is employed to suggest a systems' best design based on the economic consideration, which is the profit generated from the system. Results from the study have revealed interesting outcomes, letting us know the strength and weakness of the push and pull mechanisms as well as the effect of each operating parameter to the overall system's financial performance.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제6권2호
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• pp.127-137
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• 2006

This paper presents an $H_{\infty}$ controller synthesis method for discrete time fuzzy dynamic systems based on a piecewise smooth Lyapunov function. The basic idea of the proposed approach is to construct controllers for the fuzzy dynamic systems in such a way that a Piecewise smooth Lyapunov function can be used to establish the global stability with $H_{\infty}$ performance of the resulting closed loop fuzzy control systems. It is shown that the control laws can be obtained by solving a set of Bilinear Matrix Inequalities (BMIs). An example is given to illustrate the application of the proposed method.

• 대한안전경영과학회지
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• 제24권4호
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• pp.149-156
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• 2022

Manufacturing process mining performs various data analyzes of performance on event logs that record production. That is, it analyzes the event log data accumulated in the information system and extracts useful information necessary for business execution. Process data analysis by process mining analyzes actual data extracted from manufacturing execution systems (MES) to enable accurate manufacturing process analysis. In order to continuously manage and improve manufacturing and manufacturing processes, there is a need to structure, monitor and analyze the processes, but there is a lack of suitable technology to use. The purpose of this research is to propose a manufacturing process analysis method using process mining and to establish a manufacturing process mining system by analyzing empirical data. In this research, the manufacturing process was analyzed by process mining technology using transaction data extracted from MES. A relationship model of the manufacturing process and equipment was derived, and various performance analyzes were performed on the derived process model from the viewpoint of work, equipment, and time. The results of this analysis are highly effective in shortening process lead times (bottleneck analysis, time analysis), improving productivity (throughput analysis), and reducing costs (equipment analysis).

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
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• pp.187-190
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• 2003

Many manufacturing companies consider the integrated and concurrent scheduling because they need the global optimization technology that could manufacture various products more responsive to customer needs. In this paper, we propose an advanced scheduling model to generate the schedules considering resource constraints and precedence constraints in make-to-order (MTO) manufacturing environments. Precedence of work- in-process(WIP) and resources constraints have recently emerged as one of the main constraints in advanced scheduling problems. The advanced scheduling problems is formulated as a multiobjective mathematical model for generating operation schedules which are obeyed resources constraints, alternative workstations of operations and the precedence constraints of WIP in MTO manufacturing. For effectively solving the advanced scheduling problem, the multi-objective hybrid genetic algorithm (m-hGA) is proposed in this paper. The m-hGA is to minimize the makespan, total flow time of order, and maximum tardiness for each order, simultaneously. The m-hGA approach with local search-based mutation through swap mutation is developed to solve the advanced scheduling problem. Numerical example is tested and presented for advanced scheduling problems with various orders to describe the performance of the proposed m-hGA.

• 제어로봇시스템학회지
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• 제4권1호
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• pp.19-21
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• 1998

• 한국생산제조학회지
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• 제22권2호
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• pp.281-286
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• 2013

As the product lifecycle is getting shorter and various models should be released to respond to the needs of customers and markets, automation-based flexible production line has been recognized as the core competitiveness. According to these trends, system vendors supply cell-level systems such as FMC(Flexible Manufacturing Cell) that is integration of core functions of FMS(Flexible Manufacturing System) and RMC(Reconfigurable Manufacturing Cell) that can easily extend components of FMC. In the cell-based environment, flexible management for shop floor composed of existing job shop, FMCs and RMCs from various system vendors has emerged as an important issue. However, there could be some problems on integrated operation between heterogeneous cells to use vendor-specific cell controllers and on seamless information flow with high level systems such as ERP(Enterprise Resource Planning). In this context, this paper proposes process management systems supporting integrated shop operation of heterogeneous multi-cell based flexible manufacturing environment: First of all, (1) Integrated Shop Operation System to apply the process management system is introduced, and (2) Multi-Layer BOP(Bill-Of-Process) model, a backbone of the process management system, is derived with its data structure. Finally, application of the proposed model is illustrated through system implementation results.

• Industrial Engineering and Management Systems
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• 제3권1호
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• pp.52-58
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• 2004

This report examines the issue of designing an efficient production system by increasing several types of flexibility. Increasing manufacturing flexibility is a key strategy for efficiently improving market responsiveness in the face of uncertain market demand for final products. The manufacturing system comprises multiple plants, of which individual plants have multiple manufacturing lines that are designed to produce limited types of products in accordance with their size and materials. Imbalance in the workload occurs among plants as well as among manufacturing lines because of fluctuations in market demand for final products. Thereby, idleness of some manufacturing lines and longer lead times in some manufacturing lines occur as a result of the high workload. We clarify how these types of flexibility affect manufacturing performance by improving only one type of flexibility or by improving multiple types of flexibility simultaneously. The average lead time and the imbalance in workload are adopted as measures of manufacturing performance. Three types of manufacturing flexibility are interrelated: machine flexibility, routing flexibility, and process flexibility. Machine flexibility refers to the various types of operations that a machine can perform without requiring the prohibitive effort of switching from one order to another. Routing flexibility is the capability of processing a given set of part types using more than one line (alternative line) in the plant. Process flexibility results from being able to build different types of final products at the same plant.

• 대한조선학회논문집
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• 제39권3호
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• pp.75-80
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• 2002

오늘날 세계는 글로벌, 디지털 시대를 향해 눈부신 변화를 거듭하고 있으며 제조업 기반의 기업은 이러한 변화에 대응하기 위하여 새로운 경영기법과 생산시스템을 도입하고자 노력하고 있다. 그러나 기업이 빠른 변화에 대응하기 위해 제조시스템에 대한 명확한 분석도 없이 새로운 기술만 적용한다면 실패는 필연적으로 존재하게 된다. 그러므로 기업은 제조 시스템에 대한 명확한 분석이 필요하고, 공정개선에 대한 위험성을 줄이는 새로운 방법이 필요하게 된다. 따라서 본 논문은 공장 시스템의 공정개선에 대한 새로운 접근 방법인 시스템 접근 방법을 시스템 분석, 시스템 진단, 시스템 검증으로 체계화하여 제시하고자 한다. 시스템 분석은 객체지향 분석법인 UML로 시스템의 제품(Product), 자원(Resource)과, 공정(Process)관점에서 시스템을 분석한다. 시스템 진단은 제약이론(Theory of constraints)으로 시스템 향상을 위한 핵심요인을 확인한다. 시스템 검증은 가상 생산 기술(Virtual Manufacturing Technique)을 적용하여 핵심 제약요인에 대한 해결 방안을 제시한다. 위와 같은 방법론을 조선소 가공공장에 적용하여 생산성 향상을 위한 새로운 대안들을 제공한다. 가공공장에서 UML 모델은 가공공장에 대한 명확한 분석방법과 외부환경에 쉽게 적응하기 위한 재사용성을 나타내고, 제약이론의 논리나무(logical tree)는 가공공장을 최적하기위한 논리적 도구를 제공하며. 이산 사건 시뮬레이터-QUEST는 최적화된 가공공장을 검증하는 의사결정 도구를 제공한다.

• 산업공학
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• 제23권2호
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• pp.182-192
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• 2010

Customer needs for final products are very unpredictable because product specifications and technologies are being improved very quickly thereby their requirement level is also elevated correspondingly. In order to survive and to enhance competitiveness in the global market, many manufacturing companies are trying to find a breakthrough from collaborization. Even though they want to collaborate with others, however, they do not exactly know what kind of system they have to develop or which technology they have to use. In this paper, therefore, we first investigate status and trend of information systems and infrastructure that are essential for collaboration. We then clearly describe definition and classification of collaboration with various point of views considering collaboration pattern, timing condition of collaborative activities, organizational structure, etc. With web-based collaboration systems already developed by i-Manufacturing (Korean-style Manufacturing Innovation) project, led by Korean government from 2004, we introduce main functions and analyze collaboration types of each system. Strategically important technologies for supporting collaboration will also be illustrated by reorganizing collaborization technologies after evaluating them with respect to emergency and importance of each technology. We hope this research will provide a guideline on collaboration especially for small and medium sized manufacturing companies.