• 한국CDE학회논문집
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• 제18권1호
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• pp.21-27
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• 2013

Presented in the paper is a log data based modeling method for effective construction of a virtual plant model which can be used for the virtual PLC (Programmable Logic Controller) simulation. For the PLC simulation, the corresponding virtual plant, consisting of virtual devices, is required to interact with the input and output symbols of a PLC. In other words, the behavior of a virtual device should be the same as that of the real device. Conventionally, the DEVS (Discrete Event Systems Specifications) formalism has been used to represent the behavior a virtual device. The modeling using DEVS formalism, however, requires in-depth knowledge in the simulation area, as well as the significant amount of time and efforts. One of the key ideas of the proposed method is to generate a plant model based on the log data obtained from the production system. The proposed method is very intuitive, and it can be used to generate the full behavior model of a virtual device. The proposed approach was applied to an AGV (Automated Guided Vehicle).

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.879-884
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• 2004

This paper describes the development of a synthetic multi-agent called KMITL Cadence 2003. KMITL Cadence 2003 is a robotic soccer simulation team consisting of eleven autonomous software agents. Each agent operates in a physical soccer simulation model called Robocup Soccer Server which provides fully distributed and real-time multi-agent system environment. All teammates have to cooperate to achieve the common goal of winning the game. The simulation models many aspects of the football field such as noise in ball movements, noisy sensors, unreliable communication channel between teammates and actuators, limited physical abilities and restricted communication. This paper addresses the algorithm to develop the soccer agents to perform basic actions which are scoring, passing ball and blocking the opponents effectively. The result of this development is satisfactory because the successful scoring attempts is increased from 11.1% to 33.3%, successful passing ball attempts is increased from 22.08% to 63.64%, and also, successful intercepting attempts is increased from 88% to 97.73%.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2012년도 추계 학술논문 발표대회
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• pp.115-117
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• 2012

Task based modeling is essential in a construction operation simulation modeling. It allows dealing with local variables or delay factors that affect productivity and improves the reusability of existing operation models. An operation model can secure reality only if it reflects the real construction processes by effectively dealing with zoning issue. However, system users have some difficulties in modeling a construction operation that is consisted of several processes having different production units. Zoning is a major modeling issue when the task based modeling method is implemented using the existing discrete event simulation systems. This paper highlights the difficulty and presents a new method that complements the zoning issues attributed to different production units. The method is described in detail by presenting the flow of entities. It is confirmed that the zoning method effectively deals with the unbalance of production units between processes and facilitates to model an operation model having processes with different production units. The "Zoning module" contributes to increasing accuracy of simulation result.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권2호
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• pp.579-603
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• 2018

In this paper we propose a QoS-enhanced intelligent stochastic optimal fair real-time packet scheduler, QUEST, for 4G LTE traffic in routers. The objective of this research is to maximize the system QoS subject to the constraint that the processor utilization is kept nearly at 100 percent. The QUEST has following unique advantages. First, it solves the challenging problem of starvation for low priority process - buffered streaming video and TCP based; second, it solves the major bottleneck of the scheduler Earliest Deadline First's failure at heavy loads. Finally, QUEST offers the benefit of arbitrarily pre-programming the process utilization ratio.Three classes of multimedia 4G LTE QCI traffic, conversational voice, live streaming video, buffered streaming video and TCP based applications have been considered. We analyse two most important QoS metrics, packet loss rate (PLR) and mean waiting time. All claims are supported by discrete event and Monte Carlo simulations. The simulation results show that the QUEST scheduler outperforms current state-of-the-art benchmark schedulers. The proposed scheduler offers 37 percent improvement in PLR and 23 percent improvement in mean waiting time over the best competing current scheduler Accuracy-aware EDF.

• 한국정보과학회논문지:시스템및이론
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• 제36권2호
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• pp.53-59
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• 2009

국방 획득업무에 있어 통합적 협력에 의한 M&S의 활용을 지향하는 SBA가 적용 중에 있다. 이를 효율적으로 수행하기 위해서는 공통하부기반을 통해 M&S 구성요소의 재사용성, 재구성, 확장성 등의 제고가 요구된다. PlugIn-Based Architecture(PBA)는 컴포넌트 간 상호독립적인 인터페이스 및 상호작용이 가능함으로써 기존 아키텍처에 비해 컴포넌트의 추가 및 조합이 용이하고 재사용을 높일 수 있는 공통하부기반을 제공할 수 있도록 설계되었다. 또한, 이러한 PBA를 적용한 시뮬레이터 개발을 지원할 수 있도록 PBA Framework을 구현하였다. PBA Framework은 공통하부기반으로서 M&S 업무 적용 시 효율성을 제고시킬 수 있을 것으로 기대된다.

• 디지털콘텐츠학회 논문지
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• 제6권1호
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• pp.85-88
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• 2005

분산 멀티미디어 응용에 대한 요구는 정교한 QoS 관리를 위해서 필요하다. 분산 멀티미디어 시스템 견지에서 보면, QoS의 가장 중요한 범주는 시간성, 볼륨, 신뢰성이다. 본 논문에서는 결함 허용을 통해서 신뢰성을 향상시키는 방법에 대해서 기술한다. ERA는 분산 멀티미디어에서 하나의 소프트웨어 오류를 자동적으로 복구할 수 있는 시스템이다. 본 논문은 규칙-기반 DEVS 모델링과 시뮬레이션 기법을 사용하면서 분산 멀티미디어 상에서의 오류 복구 시스템의 성능 분석을 설명한다. DEVS에서 하나의 시스템은 시간 입력, 상태, 출력 및 함수들을 가지고 있다.

• 한국시뮬레이션학회논문지
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• 제18권1호
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• pp.9-16
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• 2009

본 연구에서는 교착상태 확인 알고리즘의 성능분석을 위하여 사이폰(siphon) 알고리즘, DAPN알고리즘과 추이적 행렬 알고리즘을 상호 비교한다. 이를 위하여 비교 모델을 설정하여 각 알고리즘을 활용한 결과를 복잡도, 이해도 그리고 신속성 등의 3가지 함수를 이용하여 성능을 분석한다. 서로 다른 개념의 알고리즘을 비교분석에 한계성이 있으나, 동일한 모델에 적용하여 그 효율성을 비교 분석하여 각 알고리즘의 특성들을 분석한다.

• 산업경영시스템학회지
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• 제46권1호
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• pp.68-75
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• 2023

In an automotive plant, an automated storage and retrieval system (ASRS) synchronizes material handling flows from a part production line to an auto-assembly line. The part production line transfers parts on small-/large-sized pallets. The products on pallets are temporarily stored on the ASRS, and the ASRS retrieves the products upon request from the auto-assembly line. Each ASRS aisle is equipped with narrow-/wide-width racks for two pallet sizes. An ASRS aisle with narrow-/wide-width racks improves both storage space utilization and crane utilization while requiring delicate ASRS aisle design, i.e., the locations of the narrow-/wide-width racks in an ASRS aisle, and proper operation policies affect the ASRS performance over demand fluctuations. We focus on operation policies involving a common storage zone using wide-width racks for two pallet sizes and a storage-retrieval job-change for a crane based on assembly-line batch size. We model a discrete-event simulation model and conduct extensive experiments to evaluate operation policies. The simulation results address the best ASRS aisle design and suggest the most effective operation policies for the aisle design.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권8호
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• pp.2399-2416
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• 2024

The current automotive industry is transitioning from Internal Combustion Engine (ICE) vehicles to Electric Vehicles (EVs), adopting a mixed assembly production approach to respond to fluctuating demand. While mixed assembly production offers the advantages of lower investment costs and flexibility in responding to changing demands, the supply of EV components requires more extensive provisioning compared to ICE vehicle components, potentially leading to unexpected issues such as congestion of transport vehicles. This study proposes a digital twin system architecture that uses Discrete Event Simulation (DES) and Business Intelligence (BI) tools to specifically address logistics challenges. The proposed architecture facilitates real-time, data-driven decision making across three layers; Data source, Simulation, and BI. It was implemented in factories engaged in the mixed assembly production of ICE and EV vehicles. The simulation challenges involve a tier 1 vendor supplying parts to Korean automobile manufacturers that produce both ICE and EV parts. A total of 240 scenarios were created to run the simulations. The deployment of the proposed architecture demonstrates its capability to quickly respond to diverse experimental situations and promptly identify potential issues.

• 산업경영시스템학회지
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• 제40권4호
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• pp.211-220
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• 2017

The application of the theoretical model to real assembly lines has been one of the biggest challenges for researchers and industrial engineers. There should be some realistic approach to achieve the conflicting objectives on real systems. Therefore, in this paper, a model is developed to synchronize a real system (A discrete event simulation model) with a theoretical model (An optimization model). This synchronization will enable the realistic optimization of systems. A job assignment model of the assembly line is formulated for the evaluation of proposed realistic optimization to achieve multiple conflicting objectives. The objectives, fluctuation in cycle time, throughput, labor cost, energy cost, teamwork and deviation in the skill level of operators have been modeled mathematically. To solve the formulated mathematical model, a multi-objective simulation integrated hybrid genetic algorithm (MO-SHGA) is proposed. In MO-SHGA each individual in each population acts as an input scenario of simulation. Also, it is very difficult to assign weights to the objective function in the traditional multi-objective GA because of pareto fronts. Therefore, we have proposed a probabilistic based linearization and multi-objective to single objective conversion method at population evolution phase. The performance of MO-SHGA is evaluated with the standard multi-objective genetic algorithm (MO-GA) with both deterministic and stochastic data settings. A case study of the goalkeeping gloves assembly line is also presented as a numerical example which is solved using MO-SHGA and MO-GA. The proposed research is useful for the development of synchronized human based assembly lines for real time monitoring, optimization, and control.