• Management Science and Financial Engineering
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• v.20 no.2
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• pp.33-37
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• 2014

A flow shop scheduling problem involves scheduling jobs on multiple machines in series in order to optimize a given criterion. The flow time of a job is the amount of time the job spent before its completion and the stretch of the job is the ratio of its flow time to its processing time. In this paper, a hybrid genetic algorithm (HGA) approach is proposed for minimizing the total stretch in flow shop scheduling. HGA adopts the idea of seed selection and development in order to reduce the chance of premature convergence that may cause the loss of search power. The performance of HGA is compared with that of genetic algorithms (GAs).

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.2
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• pp.156-160
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• 2012

In this paper, we investigate the effect of asynchronous haptic and video feedback on the performance of teleoperation. To analyze the effect, a tele-manipulation experiment is specially designed, which operator moves square objects from one place to another place by using master/slave telerobotic system. Task completion time and total number of falling of the object are used for evaluating the performance. Subjective study was conducted with 10 subjects in 16 different combinations of video and haptic feedback while participants didn't have any prior information about the amount of each delay. Initially we assume that synchronized haptic and video feedback would give best performance. However as a result, we found that the accuracy was increased when haptic and video feedback was synchronized, and the completion time was decreased when one of the feedback (either haptic or video) was decreased. Another interesting fact that we found in this experiment is that it showed even better accuracy when haptic information arrives little bit earlier than video information, than the case when those are synchronized.

• Journal of the Korean Operations Research and Management Science Society
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• v.33 no.2
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• pp.87-101
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• 2008

This paper considers an order scheduling model to minimize the total weighted tardiness of orders. Each order requires different types of products. Each type of product is manufactured on its dedicated machine specified in advance. The completion time of each order is represented by the time when all the products belonging to the order are completed. The objective of this paper is to find the optimal production schedule minimizing the total weighted tardiness of a finite number of orders. In the problem analysis, we first derive a powerful solution property to determine the sequence of two consecutive orders. Moreover, two lower bounds of objective are derived and tested along with the derived property within a branch-and-bound scheme. Two efficient heuristic algorithms are also developed. The overall performances of the proposed property, branch-and-bound and heuristic algorithms are evaluated through various numerical experiments.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.78-79
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• 2019

A construction project with a total construction cost of over 10 billion KRW should be evaluated whether construction works are appropriately executed. The evaluation is carried out on quality management, process management, construction management, safety management, environmental management. The implementation period is within 60 days after completion of construction of the construction, from the time when the construction rate of the construction work has progressed by more than 90% to the construction cost. However, the participating construction engineers should prepare the evaluation within the period according to the evaluation criteria, but there are difficulties in preparation for the evaluation due to the reasons such as the change of engineers in charge and loss of data. Therefore, this study proposes the procedure of construction evaluation and adjusts timing of construction evaluation.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.3
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• pp.169-180
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• 2015

Recently, scheduling problems with position-dependent processing times have received considerable attention in the literature, where the processing times of jobs are dependent on the processing sequences. However, they did not consider cases in which each processed job has different learning or aging ratios. This means that the actual processing time for a job can be determined not only by the processing sequence, but also by the learning/aging ratio, which can reflect the degree of processing difficulties in subsequent jobs. Motivated by these remarks, in this paper, we consider a two-agent single-machine scheduling problem with linear job-dependent position-based learning effects, where two agents compete to use a common single machine and each job has a different learning ratio. Specifically, we take into account two different objective functions for two agents: one agent minimizes the total weighted completion time, and the other restricts the makespan to less than an upper bound. After formally defining the problem by developing a mixed integer non-linear programming formulation, we devise a branch-and-bound (B&B) algorithm to give optimal solutions by developing four dominance properties based on a pairwise interchange comparison and four properties regarding the feasibility of a considered sequence. We suggest a lower bound to speed up the search procedure in the B&B algorithm by fathoming any non-prominent nodes. As this problem is at least NP-hard, we suggest efficient genetic algorithms using different methods to generate the initial population and two crossover operations. Computational results show that the proposed algorithms are efficient to obtain near-optimal solutions.

• Journal of Haehwa Medicine
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• v.5 no.2
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• pp.473-484
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• 1997

This study was performed to survey the specific information about the time of onset, frequency, duration, and severity of the side effect of radiation therapy following breast cancer surgery, and identify the difference of these data according to the type of breast cancer surgery : modified radical mastectomy(MRM) vs. breast consevative operation(BCO). 38 breast cancer patients were interviewed with side effect profile about radiation therapy. Interview was done weekley from the start of radiation therapy through 6 weeks and 3 month follow-up interview was done at 3 month after completion of the treatment. The results are as follow : 1. Total score of side effect experienced by the breast cancer patients was rapidly increased at 2-3 week after intiating treatement and continousely raised maintaing high score until completion of the treatement. Some problems like cough, dyspnea and pain were more experienced after treatment. 2. Patients with modified radical mastectomy showed more total score of side effects than patients with breast conservative operation. And both patients with MRM and BCO experienced similar pattern of side effect to radiation therapy. Through these data we concluded that side effect to radiation therapy was not ended at completion of treatement. Patents will continously experiend various problems and suffer from not only acute side effects like skin problem, sore throat and swollowing difficulty but also late effect of the radiation therapy. Clinically these data can be used for oncologic nurse to provide informational interventions to prepare breast cancer patients for the radiation therapy.

• Journal of the Korea Society for Simulation
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• v.24 no.4
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• pp.77-88
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• 2015

In this paper, we consider a two-agent single-machine scheduling problem with exponential job-dependent position-based learning effects. The objective is to minimize the total weighted completion time of one agent with the restriction that the makespan of the other agent cannot exceed an upper bound. First, we propose a branch-and-bound algorithm by developing some dominance /feasibility properties and a lower bound to find an optimal solution. Second, we design an efficient simulated annealing (SA) algorithm to search a near optimal solution by considering six different SAs to generate initial solutions. We show the performance superiority of the suggested SA using a numerical experiment. Specifically, we verify that there is no significant difference in the performance of %errors between different considered SAs using the paired t-test. Furthermore, we testify that random generation method is better than the others for agent A, whereas the initial solution method for agent B did not affect the performance of %errors.

• Journal of Gastric Cancer
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• v.22 no.3
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• pp.210-219
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• 2022

Purpose: Completion total gastrectomy (CTG) for remnant gastric cancer (RGC) is a technically demanding procedure and associated with increased morbidity. The present study aimed to evaluate postoperative complications and their risk factors following surgery for RGC after initial partial gastrectomy due to gastric cancer excluding peptic ulcer. Materials and Methods: We retrospectively reviewed the data of 107 patients who had previously undergone an initial gastric cancer surgery and subsequently underwent CTG for RGC between March 2002 and December 2020. The postoperative complications were graded using the Clavien-Dindo classification. Logistic regression analyses were used to determine the risk factors for complications. Results: Postoperative complications occurred in 34.6% (37/107) of the patients. Intra-abdominal abscess was the most common complication. The significant risk factors for overall complications were multi-visceral resections, longer operation time, and high estimated blood loss in the univariate analysis. The independent risk factors were multi-visceral resection (odds ratio [OR], 2.832; 95% confidence interval [CI], 1.094-7.333; P=0.032) and longer operation time (OR, 1.005; 95% CI, 1.001-1.011; P=0.036) in the multivariate analysis. Previous reconstruction type, minimally invasive approach, and current stage were not associated with the overall complications. Conclusions: Multi-visceral resection and long operation time were significant risk factors for the occurrence of complications following CTG rather than the RGC stage or surgical approach. When multi-visceral resection is required, a more meticulous surgical procedure is warranted to improve the postoperative complications during CTG for RGC after an initial gastric cancer surgery.

• Journal of the Korean Operations Research and Management Science Society
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• v.38 no.2
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• pp.25-42
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• 2013

We consider a project time-cost tradeoff problem with two milestones, where one of the jobs has an uncertain processing time. Unless each milestone is completed on time, some penalty cost may be imposed. However, the penalty costs can be avoided by compressing the processing times of some jobs, which requires additional resources or costs. The objective is to minimize the expected total costs subject to the constraint on the expected project completion time. We show that the problem can be solved in polynomial time if the precedence graph of a project is a chain.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.29 no.2
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• pp.7-12
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• 2006

This study considers the problem of scheduling jobs on uniform parallel machines with a common due date. The objective is to minimize the total absolute deviation of job completion times about the common due date. This problem is motivated by the fact that a certain phase of printed circuit board manufacturing is bottleneck and the processing speeds of parallel machines in this phase are uniformly different for all jobs. Optimal properties are proved and a simple polynomial time optimal algorithm is developed.