• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.52
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• pp.109-116
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• 1999

Flow Shop with Multiple Processors(FSMP) scheduling involves sequencing jobs in a flow shop where, at any processing stage, there exists one or more identical processors. Any methodology to determine the optimal mean flow time for this type of problem is NP-complete. This necessitates the use of sub-optimal heuristic methods to address problems of moderate to large scale. This paper presents global lower bounds on FSMP mean flow time problems which may be used to assess the quality of heuristic solutions when the optimal solution is unknown.

• Journal of Korean Society for Quality Management
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• v.17 no.2
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• pp.121-141
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• 1989

This paper is concerned with a development and evaluation of heuristics for the multi-stage sequence dependent flowshop sequencing. Eighteen heuristics, CAM1, CAM2, and etc., are proposed. The performance measure is a makespan which is to be minimized. The experiment for each algorithm is designed for a 4*3*3 factorial design with 360 observations. The experimental factors are PS(ratio of processing times to setup times), M(number of machines), N(number of jobs). The makespan of the proposed heuristics is compared with the optimal makespan obtained by the complete enumeration of schedules. This yardstick of comparison is called a relative error. The mean relative errors of the eighteen heuristics are from 2.048% to 8.717%. The computational results are analysed using SPSS. The experimental results show that the three factors are statistically significant at 5% level. The simulation for the large size problems is conducted to show having the similar computational results like the small size problems.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.354-356
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• 2011

Renewable energy resources such as wind, wave, solar, micro hydro, tidal and biomass etc. are becoming importance stage by stage because of considering effect of the environment. Solar energy is one of the most successful sources of renewable energy for the production of electrical energy following solar energy. And, the solar/photovoltaic cell generators depend on the solar radiation, which is a random variable so this poses difficulty in the system scheduling and energy dispatching, as the schedule of the photovoltaic cell generators availability is not known in advance. This paper proposes to use the two-layered artificial neural networks for predicting the actual solar radiation from the previous values of the same variable.

• IE interfaces
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• v.7 no.2
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• pp.75-85
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• 1994

This paper presents a production scheduling model in a block assembly shop in shipbuilding industry. In a block assembly shop, the most important performance criterion is load leveling, which balances manpower and work area utilization through the planning horizon. The problem is formulated as a mixed-integer nonlinear programming(MINLP) problem of which objective function is to optimize load leveling. The developed MINLP problem can not be solvable due to computational complexity. The MINLP problem is decomposed into two stage mixed-integer linear programming (MILP) problems to obtain a good solution, but the decomposed MILP problems are still computationally intractable because of combinatorial complexity. Therfore, a heuristic method using linear programming is proposed to solve two stage MILP problems sequentially. The proposed heuristic generates a good production schedule within a reasonable computation time, and it is easily applicable for establishing the production schedule in a block assembly shop in shipbuilding industry.

• ETRI Journal
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• v.26 no.4
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• pp.351-359
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• 2004

Flow aggregation is a scalable method to provide quality of service (QoS) guarantees to a large number of flows economically. A round-robin scheduler is an efficient scheduling algorithm. We investigate flow aggregation using a round-robin scheduler and propose the use of periodic timer interrupts for rate control of the round-robin scheduler. The proposed flow aggregator is a single-stage scheduler compared to Cobb's two-stage flow aggregator consisting of an aggregator and non-aggregating scheduler. It is possible to implement flow aggregation in the existing routers with only a software upgrade. We also present a simulation study showing the delay behaviors of the proposed algorithm.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.1
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• pp.79-86
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• 2022

In general, since the types and types of ships, so complex and various variables are included to measure the amount of construction work. In addition, it is mot easy to predict the schedule or the number of working hours before ship construction, and it is also mostly inaccurate. As a result, the master plan is manually drawn up by the expert's experience, but there are limitations due to various factors. Medium and large shipyards are operating APS(Advanced Planning and Scheduling) system that reflects industrial characteristics to improve productivity in the planning stage, and utilize information from systems such as ERP(Enterprise Resource Planning) system and MES (Manufacturing Execution System). On the other hand, small shipyards rely mostly on manual work such as Excel work based on the experience of the workers. Therefore, this study intends to develop a master plan management system that can efficiently manage the production process from the business planning stage in consideration of the characteristics of small shipyards.

• Journal of Construction Engineering and Project Management
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• v.3 no.3
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• pp.10-16
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• 2013

The annual expenditure on diesel oil and heavy oil in the construction sector is the second largest among all industrial sectors. According to the greenhouse reduction scheme of Korean Government, construction sector targeted 7.1% reduction by 2020. Although this target is not higher than other industrial sectors, it is not easy to achieve the reduction target without radical advance in technology, which cannot be expected to happen soon, considering the conservative characteristics of construction industry. Most researches on environmental issues focus on the issues related to energy saving matters during material production stage or maintenance stage, such as heating and insulation, and few deal with the issues directly related to the energy use in the construction sites. This research regards the operation of equipment for the on-site construction processes as a system and attempts to model the energy use processes related to the activities in construction sites, and provides simulation results of earth excavation and hauling processes. The result of this research is expected to aid construction planners estimating the time-based patterns of energy use and assessing greenhouse gas emission and to help selecting more energy efficient alternatives at the planning stage.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.287-293
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• 2013

The annual expenditure on diesel oil and heavy oil in the construction sector is the second largest among all industrial sectors. According to the greenhouse reduction scheme of Korean Government, construction sector targeted 7.1% reduction by 2020. Although this target is not higher than other industrial sectors, it is not easy to achieve the reduction target without radical advance in technology, which cannot be expected to happen soon, considering the conservative characteristics of construction industry. Most researches on environmental issues focus on the issues related to energy saving matters during material production stage or maintenance stage, such as heating and insulation, and few deal with the issues directly related to the energy use in the construction sites. This research regards the operation of equipment for the on-site construction processes as a system and attempts to model the energy use processes related to the activities in construction sites, and provides simulation results of earth excavation and hauling processes. The result of this research is expected to aid construction planners estimating the time-based patterns of energy use and assessing greenhouse gas emission and to help selecting more energy efficient alternatives at the planning stage.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.390-393
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• 2003

In this paper, we study on an implementation of cell scheduler which arbitrates the ATM exchange efficiently and swiftly. The designed ATM cell scheduler of this paper is based on iSLIP scheduling algorithm. It is aimed at the high-speed implementation. The implemented cell scheduler approximately provides 100% throughput for cell scheduling. We present a basic structure for cell scheduler and describe by using the HDL and perform behavior level and timing simulation. The cell scheduler of this paper is designed to support 8-port switch fabric and can expand in 32-port switch fabric. The cell scheduler for supporting the 8-port switch fabric is designed in 2-stage pipelines for the grant and accept stages respectively.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2227-2235
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• 2018

Under the current policies and compensation rules in South Korea, Photovoltaic (PV) generation supplier can maximize the profit by combining PV generation with Energy Storage System (ESS). However, the existing operational strategy of ESS is not able to maximize the profit due to the limitation of ESS capacity. In this paper, new ESS scheduling algorithm is introduced by utilizing the System Marginal Price (SMP) and PV generation forecasting to maximize the profits of PV generation supplier. The proposed algorithm determines the charging time of ESS by ranking the charging schedule from low to high SMP when PV generation is more than enough to charge ESS. The discharging time of ESS is determined by ranking the discharging schedule from high to low SMP when ESS energy is not enough to maintain the discharging. To compensate forecasting error, the algorithm is updated every hour to apply the up-to-date information. The simulation is performed to verify the effectiveness of the proposed algorithm by using actual PV generation and ESS information.