• The Journal of Information Systems
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• v.25 no.4
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• pp.105-119
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• 2016

Purpose The conventional solution methods for production scheduling problems typically focus on the active schedules, which result in short makespans. However, the active schedules are more difficult to generate than the semi active schedules. In other words, semi active schedule based search strategy may help to reduce the computational costs associated with production scheduling. In this context, this paper aims to compare the performances of active schedule based and semi active schedule based search methods for production scheduling problems. Design/methodology/approach Two decoding approaches, active schedule decoding and semi active schedule decoding, are introduced in this paper, and they are used to implement genetic algorithms for classical job shop scheduling problem. The permutation representation is adopted by the genetic algorithms, and the decoding approaches are used to obtain a feasible schedule from a sequence of given operations. Findings The semi active schedule based genetic algorithm requires slightly more iterations in order to find the optimal schedule, while its execution time is quite shorter than active schedule based genetic algorithm. Moreover, the operations of semi active schedule decoding is easy to understand and implement. Consequently, this paper concludes that semi active schedule based search methods also can be useful if effective search strategies are given.

• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.3
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• pp.75-88
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• 1996

This paper presents an efficient heuristic technique for minimizing the objectives related to tardiness such as total tardiness, maximum tardiness and root mean of tardiness in the job shop scheduling. The heuristic technique iteratively improves an active schedule through exploring the schedule's neighborrhood, using operation move methods. The move operatio is defined on an active chain of tardy jobs in the active schedule. To find the move operations which have a high probability of reducing tardiness, we develop move methods by exploiting the properties of active chains. Our technique is compared with the two existing heuristic techniques, that is, MEHA(Modified Exchange Heuristic Algorithm) and GSP(Global Scheduling Procedure) under the various environmental with the three levels of due date tightness and several sized problems. The experimental results show that the proposed technique outperforms the two exissting techiques in terms of solution quality and computation time.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.344-348
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• 2015

The image data of the web camera is used to identify the construction status of the site in a remote office and it can be used for safety management. This study develops a construction schedule simulation system based on the active nD object linked with real image data of web camera from the construction site. The progress control method by 4D object uses a method that the progress of each activity is represented with different colors by progress status. Since this method is still based on a virtual reality object, it is less realistic description for practical engineers. Therefore, in order to take advantage of BIM more realistic, the real image of actual construction status and 4D object of planned schedule in a data date should be compared in a screen simultaneously. Those methodologies and developed system are verified in a case project where a web camera is installed for the verification of the system.

• Korean Journal of Construction Engineering and Management
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• v.14 no.5
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• pp.74-83
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• 2013

Most current BIM systems are focused on the visual information of work status in the design and construction stages. In a passive BIM system, 3D CAD tool can visualize the interference elements of design drawings, however, it cannot suggest a solution to solve the interference status. And 4D CAD tool in the construction stage can simulate the appearance of each activity by construction schedule, however, it cannot suggest an optimized schedule plan considering specified schedule condition of the project. Recently, many organizations need BIM solutions that can improve the work status beyond the level of simple visual information from BIM system. Active BIM system can provide the solutions to the project manager. This study suggests active BIM functions for the solutions and attempts to develop a 4D CAD engine to validate the usability of the functions.

• Korean Journal of Construction Engineering and Management
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• v.17 no.5
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• pp.54-61
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• 2016

The initial planned annual cost is frequently adjusted under the construction process in construction projects. If the annual cost is reduced than the initial planned cost, the number of possible activities is also reduced from initial planned progress schedule. In such cases, project manager need to replan the progress schedule with possible activities within changed annual cost. However, most project manager will proceed as planned schedule without any change. After the project cost has been exhausted, there are many cases to stop the operation of the construction site. This study developed active 5D CAD system that can replan the progress schedule within changed annual cost and simulate the cost status according to the changed schedule for cost visualization. This system can be used as a decision-making tool in the replaning progress schedule and will be able to increase the practical usability of 5D CAD system.

• Korean Journal of Construction Engineering and Management
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• v.8 no.3
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• pp.125-133
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• 2007

If project time extension were required in the construction projects, either liquidated damages or extension costs should be applied according to causation of the schedule delays. However, in actual cases it is not applied so far according to the contract conditions. The reason why this situation happened Is that function of the present planning and scheduling is not working feasibly. The CPM schedule could not provide a proper solution for apportioning responsibility for the schedule delays. This situation could be considered as breach of contract and will cause potential disputes for schedule delay. Therefore, in this research process based contract administration model for construction delay claim is proposed to prevent schedule delay and solve the claims. The model is based on pro-active management for causation of delay to provide apportionment of responsibility and written evidences.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.3
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• pp.191-199
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• 2001

This paper presents a new genetic algorithm for job-shop scheduling problems. When we design a genetic algorithm for difficult ordering problems such as job-shop scheduling problems, it is important to design encoding/crossover that is excellent in characteristic preservation and to maintain a diversity of population. We used Job-based order crossover(JOX). Since the schedules generated by JOX are not always active-schedule, we proposed a method to transform them into active schedulesby using the GT method with c)laracteristic preservation. We introduce strategies for maintaining a diversity of the population by eliminating same individuals in the population. Furthermore, we are not used mutation. Experiments have been done on two examples: Fisher s and Thompson s $lO\timeslO and 20\times5$ benchmark problem.

• Journal of the Korean Solar Energy Society
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• v.38 no.2
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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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• v.21 no.45
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• pp.165-180
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• 1998

To make a scheduling for minimizing the tardiness of delivery, we present an efficient heuristic algorithm for job-shop scheduling problems with due dates. The SDME(Slack Degree Modified Exchange) algorithm, which is the proposed heuristic algorithm, carries out the operation in two phases. In the phase 1, a dispatching rule is employed to generate an active or non-delay initial schedule. In the phase 2, tasks selected from a predetermined set of promising target operations in the initial schedule are tested to ascertain whether, by left-shifting their start times and rearranging some subset of the remaining operations, one can reduce the total tardiness. In the numerical example, the results indicate that the proposed SDME algorithm is capable of yielding notable reductions in the total tardiness for practical size problems.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.12
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• pp.597-602
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• 2005

The introduction of competition in electricity market emphasizes the importance of sufficient transmission capacities to guarantee various electricity transactions. Therefore, when dispatch scheduling, transmission security constraints should be considered for the economic and stable electric power system operation. In this paper, we propose an optimal dispatch scheduling algorithm incorporating transmission security constraints. For solving these constraints, the dispatch scheduling problem is decomposed into a master problem to calculate a general optimal power flow (OPF) without transmission security constraints and several subproblems to inspect the feasibility of OPF solution under various transmission line contingencies. If a dispatch schedule given by the master problem violates transmission security constraints, then an additional constraint is imposed to the master problem. Through these iteration processes between the master problem and subproblems, an optimal dispatch schedule reflecting the post-contingency rescheduling is derived. Moreover, since interruptible loads can positively participate as generators in the competitive electricity market, we consider these interruptible loads active control variables. Numerical example demonstrates efficiency of the proposed algorithm.