• International conference on construction engineering and project management
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.114-116
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• 2015

This paper presents a Stochastic Time-Cost Tradeoff analysis system (STCT) that identifies optimal construction methods for activities, hence reducing the project completion time and cost simultaneously. It makes use of schedule information obtained from critical path method (CPM), applies alternative construction methods data obtained from estimators to respective activities, computes an optimal set of genetic algorithm (GA) parameters, executes simulation based GA experiments, and identifies near optimal solution(s). A test case verifies the usability of STCT.

• Journal of the Korea Society for Simulation
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• 제15권3호
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• pp.1-9
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• 2006

As an effective solution to resolve complex computing problems and to handle geographically dispersed data sets, grid computing has been noticed. Grid computing separates an application to several parts and executes on heterogeneous computing platforms simultaneously. The most important problem in grid computing environments is to manage grid resources and to schedule grid resources. This paper proposes a grid transaction network model that is applicable for resource management and scheduling in grid computing environment and presents a grid resource bidding algorithm for grid users and grid resource providers. Using DEVSJAVA modeling and simulation, this paper evaluates usefulness and efficiency of the proposed model.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제38권3호
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• pp.249-257
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• 2010

Full authority digital engine control systems for gas turbine engines are replacing conventional mechanical control units rapidly. However, setting up design processes of controllers for high performance helicopter engines are not well known because of the complexity of the total system. This paper presents a high fidelity helicopter and engine simulation for control system design and analysis. Using this environment, a feedforward schedule was set up for a utility helicopter. The total engine simulation with the new controller showed better or equal performance compared to the total engine simulation with the pre-existing controller.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제19권1호
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• pp.60-67
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• 2007

The purpose of this study is to evaluate indoor air quality at the stage of building construction. To check the IAQ at the stage of construction IAQX simulation program developed by EPA was used and the values of TVOC were analyzed with time-series. The Simulation conditions are as follows. 1) Ventilation rate, 2) Time schedule of works, 3) Material change. Through this simulation, the major factors which affect the IAQ were analyzed and the importance of empirical data about the time-series emission rate of concerned material could be confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제19권6호
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• pp.567-574
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• 2018

Risk management is a method to 1) identify risks that can adversely affect the cost, schedule, and target achievement performance of a system development project, and 2) manage the identified risks based on the severity and likelihood assigned to each risk item. Risk management is applicable to various fields, since it can manage the cost/schedule and effectively guides accomplishing the target performance by identifying and managing the risks in advance, which necessitates many concurrent studies. This paper proposes a procedure to estimate the severity value for a risk item using a Kalman filter. It is assumed that the severity can be expressed as an equation consisting of cost/schedule loss during the risk event. A linear Kalman filter is used to reduce the error between the true and estimated values, which can eventually save resources spent on the risk management procedure. A simulation test case was conducted to demonstrate the validity of the proposed method.

• Journal of the Korean Solar Energy Society
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• 제38권2호
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• pp.15-31
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• 2018

A program to design a small capacity wind turbine blade is proposed in this study. The program is based on a matlab GUI environment and designed to perform blade design based on the blade element momentum theory. The program is different from other simulation tools available in a point that it can analyze the side-furling power regulation mechanism and also has an algorithm to find out optimal torque schedule above the rated wind speed region. The side-furling power regulation is used for small-capacity horizontal axis wind turbines because they cannot use active pitch control due to high cost which is commonly used for large-capacity wind turbine. Also, the torque schedule above the rated wind speed region should be different from that of the large capacity wind turbines because active pitching is not used. The program developed in this study was validated with the results with FAST which is the only program that can analyze the performance of side-furled wind turbines. For the validation a commercial 10 kW wind turbine data which is available in the literature was used. From the validation, it was found that the performance prediction from the proposed simple program is close to those from FAST. It was also found that the optimal torque scheduling from the proposed program was found to increase the turbine power substantially. Further experimental validation will be performed as a future work.

• Journal of Korean Society of Industrial and Systems Engineering
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• 제42권1호
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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.

• ETRI Journal
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• 제37권1호
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• pp.147-156
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• 2015

A typical solid-state drive contains several independent channels that can be operated in parallel. To exploit this channel-level parallelism, a variety of works proposed to split consecutive write sequences into small segments and schedule them to different channels. This scheme exploits the parallelism but breaks the spatial locality of write traffic; thus, it is able to significantly degrade the efficiency of garbage collection. This paper proposes a channel-aware write reordering (CAWR) mechanism to schedule write requests to different channels more intelligently. The novel mechanism encapsulates correlated pages into a cluster beforehand. All pages belonging to a cluster are scheduled to the same channels to exploit spatial locality, while different clusters are scheduled to different channels to exploit the parallelism. As CAWR covers both garbage collection and I/O performance, it outperforms existing schemes significantly. Trace-driven simulation results demonstrate that the CAWR mechanism reduces the average response time by 26% on average and decreases the valid page copies by 10% on average, while achieving a similar hit ratio to that of existing mechanisms.

• Journal of the Korea Society of Computer and Information
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• 제9권3호
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• pp.189-194
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• 2004

This paper proposes a Simulated Annealing(SA) algorithm for cluster-based Multicast Routing problems. Multicasting, the transmission of data to a group, can be solved from constructing multicast tree, that is. the whole network is partitioned to some clusters and the clusters are constructed by multicast tree. Multicast tree can be constructed by minimum-cost Steiner tree. In this paper, an SA algorithm is used in the minimum-cost Steiner tree. Especially, in SA, the cooling schedule is an important factor for the algorithm. Hence, in this paper, a cooling schedule is proposed for SA for multicast routing problems and analyzed the simulation results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제16권5호
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• pp.75-82
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• 2002

This paper propose a new mathematical modelling method about optimum operational schedule for cogeneration systems. Proposed algorithm solving the energy product cost function in this paper is very similar to the real model that is, proposed algorithm solve nonlinear type of real model using mixed integer programming based on the piecewise linear function while the conventional algorithms used before could not solve that kind of problems. The effectiveness of the proposed method is ascertained by the simulation results with varius case studies which are similar to real operation circumstances.