• Industrial Engineering and Management Systems
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• v.7 no.2
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• pp.84-92
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• 2008

Scheduling is one of the most important issues in the planning and operation of production systems. This paper investigates a general job shop scheduling problem with reentrant work flows and sequence dependent setup times. The disjunctive graph representation is used to capture the interactions between machines in job shop. Based on this representation, four two-phase heuristic procedures are proposed to obtain near optimal solutions for this problem. The obtained solutions in the first phase are substantially improved by reversing the direction of some critical disjunctive arcs of the graph in the second phase. A comparative study is conducted to examine the performance of these proposed algorithms.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.4
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• pp.20-26
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• 2018

This study analyzes the economic effect of introducing the arrival duty - free shop at Incheon International Airport. Based on the estimated sales of KRW 127 billion for the duty-free shop at the port of entry, the international balance of payments was estimated at KRW 55.5 billion. Job creation was estimated at 530, including direct and indirect workforce. With the admission of arrival duty-free shops, duty-free shops in the airline are likely to see a decline in sales, helping to improve monopoly structure on the market structure side. It is expected that the rental income generated through the operation of the arrival duty-free shop will be used as a resource for social contribution activities, creating additional social economic effects.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.759-760
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• 2013

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.1
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• pp.33-40
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• 2019

This study focuses on a job-shop scheduling problem with the objective of minimizing total tardiness for the job orders that have different due dates and different process flows. We suggest the dispatching rule based scheduling algorithm to generate fast and efficient schedule. First, we show the delay schedule can be optimal for total tardiness measure in some cases. Based on this observation, we expand search space for selecting the job operation to explore the delay schedules. That means, not only all job operations waiting for process but also job operations not arrived at the machine yet are considered to be scheduled when a machine is available and it is need decision for the next operation to be processed. Assuming each job operation is assigned to the available machine, the expected total tardiness is estimated, and the job operation with the minimum expected total tardiness is selected to be processed in the machine. If this job is being processed in the other machine, then machine should wait until the job arrives at the machine. Simulation experiments are carried out to test the suggested algorithm and compare with the results of other well-known dispatching rules such as EDD, ATC and COVERT, etc. Results show that the proposed algorithm, MET, works better in terms of total tardiness of orders than existing rules without increasing the number of tardy jobs.

• Journal of the Korea Safety Management & Science
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• v.5 no.2
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• pp.87-98
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• 2003

With the development of CNC(Computer Numerical Control) and communication technology, the connotation and functions of Distributed Numerical Control have been greatly enlarged. In this study, we develop and implement a Distributed Numerical Control system that has real time and multi-tasking operation capability for the machining cell with various NC(Numerical Control) and CNC machines. With the consideration of economy, generalization and extension, this system is interfaced with Shop Floor Control System, Machine Control System and Tool Preparation System using advanced networking method. In the implementation phase, we use the ORACLE DBMS (Database Management System) as the DBMS and Microsoft Visual C++ as the programming tools.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1053-1059
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• 2009

Construction system modeling can enhance work performance by following the behaviors of a system. System behaviors may originate from physical aspects of a system, namely operation level variables, or from non-physical aspects of a system known as context level variables. However, construction system modelers usually focus on only one type of system variable (i.e., operation level or context level) which can lead to less accurate results. Hybrid modeling with System Dynamics (SD) and Discrete Event Simulation (DES) is one of the approaches that has been utilized to address this issue. In this research, an SD-DES hybrid model of a steel fabrication shop is developed, and the benefits of capturing context level variables together with operation level variables in the model are discussed.

• Industrial Engineering and Management Systems
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• v.15 no.1
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• pp.32-40
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• 2016

This paper considers a special case of a three machine flow shop scheduling problem in which operation processing time of each job is ordered such that machine 1 has the longest processing time, whereas machine 3, the shortest processing time. The objective of the problem is the minimization of the total completion time. Although the problem is simple, its complexity is yet to be established to our best knowledge. This paper first introduces the problem and presents some optimal properties of the problem. Then, it establishes several special cases in which a polynomial-time optimal solution procedure can be found. In addition, the paper proves that the recognition version of the problem is at least binary NP-complete. The complexity of the problem has been open despite its simple structure and this paper finally establishes its complexity. Finally, a simple and intuitive heuristic is developed and the tight worst case bound on relative error of 6/5 is established.

• Journal of the Korean Operations Research and Management Science Society
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• v.17 no.3
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• pp.47-57
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• 1992

The purpose of this paper is to improve the operation performance of unit-load Automated Guided Vehicles (AGV's) used as a carrier and mobile workstation in a flow-shop type flexible manufacturing system. An algorithm is developed to determine the optimal job sequence which minimizes the vehicle idle time on the line and the production makespan by the use of the entering interval and travel time between workcenters. An entering times of AGV's and the minimum number of AGV's required are calculated by optimal job sequence. When the numbe rof AGV's is limited, enterling times of AGV's are adjusted to maximize the efficient use of vehicles. A numerical example is given to illustrate the application of the algorithm.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.3
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• pp.301-308
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• 2011

International Maritime Organization (IMO) proposed the Energy Efficiency Operation Indicator (EEOI) in 2005 and the Energy Efficiency Design Index (EEDI) in 2008 so as to address emission concern and regulation. Likewise, Ship Energy Efficiency Management Plan (SEEMP) and Greenhouse Gas (GHG) monitoring and management are also becoming an issue lately. This paper introduces the energy efficiency design index (operation indicator) monitoring system (EDiMS) software can continuously monitor $CO_2$, $NO_x$, $SO_x$, and PM values emitted from ship. The accurate inventory of ships GHG can be obtained from base of emission result during the engine shop test trial and the actual monitoring of shaft power and ship speed. In addition, the ability to store all exhaust emission and engine operation data can be applied as the useful tool of the inventory work of air pollution and ship energy management plan for the mitigation or reduction of ship emissions.

• Journal of Korean Institute of Industrial Engineers
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• v.20 no.4
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• pp.181-192
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• 1994

In an order-oriented production system such as mold manufacturing, the production starts with an order acceptance, and the production planning is set up according to the accepted order information. Such a work can be done through a dynamic process management system which can reflect shop floor situation dynamically. In this paper, so called the Quick order acceptance evaluation system that can investigate order confirmation quickly, is discussed. When an order is asked, this system must consider the time constraint to determine whether to accept or not, and must be reliable when the determined results are used in the shop floor. For this system, firstly, we simplified the machines by grouping based on their operation capabilities, secondly, we conducted load analysis to calculate available capacities during given periods using heuristic method instead of mathematical algorithm, thirdly, expert can input his experienced knowledge into the system interactively when simulation results don't meet the required due dates. As a case study, we applied this system to an injection mold manufacturing factory.