• Journal of the Korean Operations Research and Management Science Society
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• v.23 no.4
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• pp.87-96
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• 1998

Using the concept of cellular manufacturing systems(CMS) in job shop manufacturing system is one of the most innovative approaches to improving plant productivity. However. several constraints in machine duplication cost, machining capability, cell space capacity, intercell moves and exceptional elements(EEs) are main problems that prevent achieving the goal of maintaining an ideal CMS environment. Minimizing intercell part traffics and EEs are the main objective of the cell formation problem because it is a critical point that improving production efficiency. Because the intercell moves could be changed according to the sequence of operation, it should be considered in assigning parts and machines to machine ceil. This paper presents a method that eliminates EEs under the constraints of machine duplication cost and ceil space capacity attaining two goals of minimizing machine duplications and minimizing intercell moves simultaneously. Developing an algorithm that calculates the machine duplications by cell-machine incidence matrix and part-machine Incidence matrix, and calculates the exact intercell moves considering the sequence of operation. Based on the number of machine duplications and exact intercell moves, the goal programming model which satisfying minimum machine duplications and minimum intercell moves is developed. A linear programming model is suggested that could calculates more effectively without damaging optimal solution. A numerical example is provided to illustrate these methods.

• Korean Management Science Review
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• v.16 no.1
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• pp.157-171
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• 1999

In a increasingly competitive marketplace, the manufacturing companies have no choice but looking for ways to improve productivity to sustain their competitiveness and survive in the industry. Recently cellular manufacturing has been under discussion as an option to be easily implemented without burdensome capital investment. The objective of cellular manufacturing is to realize many aspects of efficiencies associated with mass production in the less repetitive job-shop production systems. The very first step for cellular manufacturing is to group the sets of parts having similar processing requirements into part families, and the equipment needed to process a particular part family into machine cells. The underlying problem to determine the part and machine assignments to each manufacturing cell is called the cell formation. The purpose of this study is to develop a clustering algorithm based on the neural network approach which overcomes the drawbacks of ART1 algorithm for cell formation problems. In this paper, a generalized learning vector quantization(GLVQ) algorithm was devised in order to transform a 0/1 part-machine assignment matrix into the matrix with diagonal blocks in such a way to increase clustering performance. Furthermore, an assignment problem model and a rearrangement procedure has been embedded to increase efficiency. The performance of the proposed algorithm has been evaluated using data sets adopted by prior studies on cell formation. The proposed algorithm dominates almost all the cell formation reported so far, based on the grouping index($\alpha$ = 0.2). Among 27 cell formation problems investigated, the result by the proposed algorithm was superior in 11, equal 15, and inferior only in 1.

• Human Ecology Research
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• v.52 no.3
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• pp.243-253
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• 2014

This qualitative case study examined the experience of middle-aged homemakers with buying and wearing clothes. Clothing benefits and clothing purchase types were observed in the homemakers' daily clothing-related behavior. This study aims to understand clothing consumption values in light of clothing benefits and to determine purchasing methods, purchasing mental states, and personal characteristics according to the clothing purchase types of middle-aged homemakers. The participants of this study were four full-time homemakers and four homemakers with a job outside the home, all in middle age. This study was conducted through in-depth interviews based on an unstructured questionnaire, and the data were collected from January 2010 to October 2010. The results were as follows: first, the clothing benefits were identified as a social stereotype, aesthetic taste, economy, wearing situation, and age perception. The most important clothing consumption values to the middle-aged homemakers based on the observed clothing benefits were, in order: social value, emotional value, epistemic value, functional value, and conditional value. Second, the type of clothing purchase was observed to be planned buying, followed by impulse buying, and compensatory buying. Even when a homemaker planned to shop regularly, when they were exposed to an attractive retailer promotion, they seized on the opportunity on impulse or made a compensatory purchase to divert oneself. Even though homemakers prefer primarily impulse buying, when they went shopping for clothing with their mother-in-law or husband, they made planned purchase also.

• Bulletin of the Korean Institute for Industrial Safety
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• v.3 no.1
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• pp.11-17
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• 2003

In recent years, work-related musculoskeletal disorders (WMSDs) are one of major issues in occupational safety and health in Korea, since the number of injured workers has rapidly increased and the related regulation was amended to improve the work conditions. Main risk factors of WMSDs in Korean industries include manual handling of heavy weight loads, awkward postures, repetitive tasks, prolonged static muscle contraction, and so on. in this article, some ergonomics case studies for identifying the risk factors of WMSDs and far their prevention were introduced. They include a biomechanical analysis for the heavy-weight handling task in a machine-repair shop, physiological evaluation of backpack-carrying tasks in a beverage delivery job, and a set of psychophysical studies to evaluate static-postural load. These studies showed that there are several different ergonomic approaches to identifying and evaluating risk factors of WMSDs and to eliminating them or reducing their levels, and that it is important to select proper methods and apply them in improving the work conditions according to the characteristics of the task. In addition, it needs to develop practical and effective ergonomic tools to prevent WMSDs and to provide these tools to the safety managers in the field so that they can improve the tasks by themselves.

• IE interfaces
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• v.12 no.1
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• pp.10-18
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• 1999

Job shop manufacturing environments are using the concept of cellular manufacturing systems(CMS) which has several advantages in reducing production lead times, setup times, work-in-process, etc. Utilizing the similarities between cell-machine, part-machine, and the shape/size of parts, CMS can group machines and parts resulting in improved efficiency of this system. However, when grouping machines and parts in machine cells, there inevitably occurs exceptional elements(EEs), which can not operate in the same machine cell. Minimizing these EEs in CMS is a critical point that improving production efficiency. Constraints in machine duplication cost, machining process technology, machining capability, and factory space limitations are main problems that prevent achiving the goal of maintaining an ideal CMS environment. This paper presents an algorithm that minimizes EEs under the constraints of machine duplication cost and factory space limitation. Developing exceptional operation similarity(EOS) by cell-machine incidence matrix and part-machine incidence matrix, it brings the machine cells that operate the parts or not. A mathematical model to minimize machine duplication is developed by EOS, followed by a heuristic algorithm in order to reflect dynamic situation resulting from minimizing exceptional elements process and the mathematical model. A numerical example is provided to illustrate the algorithm.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.04a
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• pp.53-53
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• 1999

제품에 대한 수요의 다양화에 대응하기 위해서, 다품종소량생산방식이 정착하고 있다. 다품종소량생산을 효율적으로 실현하는 현대의 전형적인 자동화생산시스템으로서, 유연생산시스템(Flexible Manufacturing System : 이하 FMS)이 급속히 보급되어, FMS의 효율적인 운영이 생산현장에 있어서 중요한 과제가 되고 있다. 다수의 품종이 동시에 병행해서 반복적으로 생산되는 실제의 FMS에서는, 품종의 생산에 필요한 일련의 작업의 종류에 대한 우선순서인 "투입우선순서(Dispatching Priority)"를 설정해서, 그것을 기반으로 시스템이 운영되는 것이 보통이다.본 연구에서는 투입우선순서로 제어되는 동일한 품종의 반복이 있는 FMS를 염두에 두고, 생산요건이 확정적인 상태에서 주어진 평가척도를 최적화하는 투입우선순서를 결정하는 문제로써, FMS의 투입우선순서 결정문제 (FMS dispatching priority problem)를 제기하여, 시뮬레이션을 통해서 그 해법을 논한다. 실재하는 많은 FMS에 있어서 투입우선순서를 단기간에 용이하게 정할 수 있는 우선규칙(dispatching rule)이 실용적으로 넓게 이용되고 있다. 종래로부터, ？샵(job shop)을 대상으로 하는 다수의 우선규칙이 제안, 평가되어 왔지만, 그것들은 각 품종이 서로 다른 종류의 일감인 것을 상정하고 있으며, 동일한 품종의 일감의 존재를 의식하고 있지 않다. 본 연구에서는 재래형의 ？샵 환경에 있어서 그 유효성이 검증되어 있는 기존의 표준적인 우선규칙의 성능이, 동일한 품종의 반복이 있는 경우에도 잘 기능하는지 어떤지를 시뮬레이션을 통해 평가한 후에, 오더사이즈(order size)를 고려한 우선규칙을 제안하고, 납기지체의 평가척도에 관한 유효성을 명확히 하고 있다. 시뮬레이션 실험의 결과에서는, 우선규칙의 기본적인 결정요인이 성능에 미치는 영향을 통계적으로 분석하고 있다.로 분석하고 있다.

• Journal of Information Technology Applications and Management
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• v.18 no.1
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• pp.125-141
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• 2011

As the sales volume of online shops increases, the job burden in the back-offices of the online shops also increases. Order picking is the most labor-intensive operation among the jobs in a back-office and mid-size pure click online shops are experiencing the time delay and complexity in order picking nowadays while fulfilling their customers' orders. Those warehouses of the mid-size shops are based on manual systems, and as order pickings are repeated, the warehouses get a mess and lots of products in those warehouses are getting missing, which results in severe delay in order picking. To overcome this kind of problem in online clothing shops, we research a methodology to locate warehousing products. When products arrive at a warehouse, they are packed into a box and located on a rack in the warehouse. At this point, the operator should determine the box to be put in and the location on the rack for the box to be put on. This problem could be formulated as an Integer Programming model, but the branch-and bound algorithm to solve the IP model requires enormous computation, and sometimes it is even impossible to get a solution in a proper time. So, we relaxed the problem, developed a set of heuristics as a methodology to get a semi-optimum in an acceptable time, and proved by an experiment that the solutions by our methodology are satisfactory and acceptable by field managers.

• Industrial Engineering and Management Systems
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• v.11 no.4
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• pp.310-330
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• 2012

Scheduling is an important tool for a manufacturing system, where it can have a major impact on the productivity of a production process. In manufacturing systems, the purpose of scheduling is to minimize the production time and costs, by assigning a production facility when to make, with which staff, and on which equipment. Production scheduling aims to maximize the efficiency of the operation and reduce the costs. In order to find an optimal solution to manufacturing scheduling problems, it attempts to solve complex combinatorial optimization problems. Unfortunately, most of them fall into the class of NP-hard combinatorial problems. Genetic algorithm (GA) is one of the generic population-based metaheuristic optimization algorithms and the best one for finding a satisfactory solution in an acceptable time for the NP-hard scheduling problems. GA is the most popular type of evolutionary algorithm. In this survey paper, we address firstly multiobjective hybrid GA combined with adaptive fuzzy logic controller which gives fitness assignment mechanism and performance measures for solving multiple objective optimization problems, and four crucial issues in the manufacturing scheduling including a mathematical model, GA-based solution method and case study in flexible job-shop scheduling problem (fJSP), automatic guided vehicle (AGV) dispatching models in flexible manufacturing system (FMS) combined with priority-based GA, recent advanced planning and scheduling (APS) models and integrated systems for manufacturing.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.20-37
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• 2020

In this paper, we propose a simulation method based on backward simulation and process-oriented simulation to take into account the characteristics of shipbuilding production, which is an order-based industry with a job shop production environment. The shipyard production planning process was investigated to analyze the detailed process, variables and constraints of mid-term production planning. Backward and process-centric simulation methods were applied to the mid-term production planning process and an improved planning process, which considers the shipbuilding characteristics, was proposed. Based on the problem defined by applying backward process-centric simulation, a system which can conduct Discrete Event Simulation (DES) was developed. The developed mid-term planning system can be linked with the existing shipyard Advanced Planning System (APS). Verification of the system was performed with the actual shipyard mid-term production data for the four ships corresponding to a one-year period.

• Journal of Korean Clinical Health Science
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• v.2 no.4
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• pp.216-222
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• 2014

Purpose. The purpose of this study was to investigate career awareness of the students majoring in optometry in Gyeongnam area so that it could be used as a database to educate them on their career. Methods. The graduates of the Department of Optometry in 6 universities of Gyeongnam area were surveyed through a questionnaire. Results. Most of their motive for entering Department of Optometry was for 'finding a job(38%), while at the time of entrance, most of them (55%) thought 'optician' as their job after graduation. Now most of them are the expectant graduate and they still think 'optician' as their job(54%). The biggest reason why they think of this career was 'aptitude(34%),' and most of them wanted their first monthly wage as less than '1.5 million won (46%).' For the desired work time, most of them said 'less than 10 hours a day (73%),' and they have been figured out to want '2 days off a week and monthly paid holiday (35%).' For the questions asking any improvements that are needed for department of Optometry, they (32%) answered 'equipments that are old or in short.' For the question asking if they are willing to choose optical task even if they entered a company that is irrelevant with it, most of them (37%) said they will if the conditions work, and the other 37% said they didn't know. Conclusions. The cooperation among universities and the field and their interest are required so that the students of the Department of Optometry would be able to work with pride as a professional to improve social welfare.