• International Journal of Contents
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• 제8권2호
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• pp.19-22
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• 2012

New and handoff calls control mechanisms are the key point to wireless cellular networks. In this paper, we present an adaptive algorithm for dynamic channel allocation scheme with guard channels and also with handoff calls waiting queue ensuring that handoff calls take priority over new calls. Our goal is to find better tradeoff between handoffs and new calls blocking probabilities in order to achieve more efficient channel utilization. Simpy is a Python based discrete event simulation system. We use Simpy to build our simulation models to get analytical data.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2002년도 추계학술대회 논문집
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• pp.79-83
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• 2002

High Level Architecture (HLA)는 이기종 시뮬레이터 간의 연동을 위한 미들웨어이다. 본 논문에서는 Discrete Event System Specification (DEVS) 형식론을 바탕으로 한 DEVS 모델의 시뮬레이션을 HLA 기반에서 수행하는 방법에 대하여 제시한다. DEVS 시뮬레이션 메시지를 HLA의 서비스를 사용하여 변환하여 기존의 시뮬레이션 알고리즘을 그대로 사용하여 분산 시뮬레이션 할 수 있는 방식에 대하여 기술한다. 또한 모델 사이의 연결 정보를 HLA 환경에서 이용하는 방식에 대하여 기술한다. 제안된 방식을 구현한 DEVSimHLA 시뮬레이션 환경의 구조 및 동작 방식에 대하여 알아보고 이를 이용한 간단한 예제를 보인다.

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.360-372
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• 2017

Many advanced reactor designs rely on passive systems to fulfill safety functions during accident sequences. These systems depend heavily on boundary conditions to induce a motive force, meaning the system can fail to operate as intended because of deviations in boundary conditions, rather than as the result of physical failures. Furthermore, passive systems may operate in intermediate or degraded modes. These factors make passive system operation difficult to characterize within a traditional probabilistic framework that only recognizes discrete operating modes and does not allow for the explicit consideration of time-dependent boundary conditions. Argonne National Laboratory has been examining various methodologies for assessing passive system reliability within a probabilistic risk assessment for a station blackout event at an advanced small modular reactor. This paper provides an overview of a passive system reliability demonstration analysis for an external event. Considering an earthquake with the possibility of site flooding, the analysis focuses on the behavior of the passive Reactor Cavity Cooling System following potential physical damage and system flooding. The assessment approach seeks to combine mechanistic and simulation-based methods to leverage the benefits of the simulation-based approach without the need to substantially deviate from conventional probabilistic risk assessment techniques. Although this study is presented as only an example analysis, the results appear to demonstrate a high level of reliability of the Reactor Cavity Cooling System (and the reactor system in general) for the postulated transient event.

• 대한조선학회논문집
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• 제53권2호
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• pp.101-107
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• 2016

Generally, the shipbuilding industry has finite resources and limited workspace. Due to finite resources, limited workspace and state of block preparation, erection process in shipbuilding industry is frequently delayed than erection process scheduling which is planned at long-term plan stage. In this study, considering variability of block reserve ratio, the degree of delay in real erection process is measured and compared to scheduling which is planned at long-term plan stage in shipbuilding industry including finite capacity and variative lead time. Also, the erection process scheduling which has minimum lead time can be checked through simulation. The results of this study could be improved the accuracy of erection process scheduling by checking the main event compliance ratio by block reserve ratio and calculating the optimum erection pitch for the main event compliance.

• 한국건설관리학회논문집
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• 제8권1호
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• pp.141-149
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• 2007

시뮬레이션은 건설관리를 위한 도구로써 많은 잠재력을 가지고 있으나, 국내의 경우 대단히 제한된 범위에서 마이크로 프로세스의 공정 평가에 적용을 시도하고 있는 단계에 있다. 시뮬레이션을 건설 공정에 적용하기 위해서는 현장 특성을 반영한 입력 데이터 수집과 모델 구축에 상당한 노력이 필요하다. 본 연구에서는 시뮬레이션 모델 구축을 위한 장비 운영 데이터 활용과 시뮬레이션 모델 구축 방법론을 소개하고, 현장 측정 데이터와의 검증을 수행하였다. 그리고 버력 처리 시스템의 전체 운행 주기(Cycle Times)를 결정하는 주요 요인을 분석하고 장비운영 계획을 수립하기 위한 시뮬레이션 활용 방안을 제시하였다.

• 산업경영시스템학회지
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• 제41권4호
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• pp.59-69
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• 2018

This study deals with the case study on the pallet quantity determination problem for the flexible manufacturing system producing 32 different types of aircraft wing ribs which are major structures of an aircraft wings. A Korean company has constructed the WFMS (wing rib flexible manufacturing system) that is composed of several automated equipments such as the 5-axis machining centers, the RGV (rail guided vehicles)s, the AS/RS (automated storage and retrieval system), the loading/unloading stations, and so on. Pallets play a critical role in the WFMS to maintain high system utilization and continuous work flow between 5-axis machining machines and automated material handling devices. The discrete event simulation method is used to evaluate the performance of the WFMS under various pallet mix alternatives for wing rib manufacturing processes. Four performance measures including system utilization, throughput, lead-time and work in process inventory level are investigated to determine the best pallet mix alternative. The best pallet mix identified by the simulation study is adopted in setting up and operating a real Korean aircraft parts manufacturing shop. By comparing the real WFMS's performances with those of the simulation study, we discussed the cause of performance difference observed and the necessity of developing the CPS (cyber physical system).

• 대한산업공학회지
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• 제39권6호
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• pp.473-479
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• 2013

This paper introduces user intervention to control simulation states during the execution of a simulation for military engagements. In an engagement simulation, it covers both a discrete event system and a continuous state system. Thus a system for the engagement simulation can have numerous simulation states, because there are lots of factors to decide states of an engagement that are derived during an execution of the simulation (e. g. detection probability, moving speed, moving path, and so on). It means both a result and progression of simulations are important outputs. Configuration of an engagement simulation scenario and expectation of simulation states, though, is hindered by the number of generate-able states. In order to solve the obstacle, the engagement simulation system should be controllable by user intervention during a simulation execution. This paper is to define objects of user intervention, and to design control processes of defined objects.

• 한국시뮬레이션학회논문지
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• 제21권3호
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• pp.1-9
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• 2012

본 논문에서는 공항 정밀접근 항공기의 안전성을 증대시키기 위한 방법으로 S/W 패킷모뎀을 이용한 PAR 관제 자동화 방안을 제안하고, DEVS 형식론을 이용하여 제안하는 시스템의 기능을 검증하였다. 기존의 PAR 관제는 음성으로 항공기를 통제함으로써 조종사의 정보 획득 능력이 떨어질 수 있다. 이를 해결하기 위하여 디지털 신호에 의한 자동 관제 시스템을 제안하고, 공항의 PAR이 추적하고 있는 항공기의 비행경로, 강하각, 거리를 조종사에게 실시간으로 전송해 주고 일반화함으로서 관제사의 숙련도와 관제 특성에 기인하는 요소를 배제할 수 있다. 제안된 시스템의 동작을 검증하기 위하여 확장된 DEVS 형식론인 C-DEVS 형식론을 사용하고, 하나의 모델로 합성된 원자 모델을 통해 시스템의 전체 상태 시퀀스를 검색하여 시스템의 안전성(Safeness)과 필연성(Liveness)을 검증할 수 있다. 제안하는 시스템의 C-DEVS 모델을 기존의 음성 관제 시스템과 비교하여 두 시스템이 동일한 상태 시퀀스를 가짐을 확인하였으며, 모든 상태를 검증함으로써 실제 상황에 적용할 수 있을 것으로 생각된다.

• 한국시뮬레이션학회논문지
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• 제22권4호
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• pp.109-118
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• 2013

전통적으로 신뢰도 분석에 사용되는 Fault Tree Analysis의 경우 관련 분야의 전문가가 필요하고 작성자의 판단에 따라 신뢰도 분석 결과가 달라진다. 반면, Reliability Block Diagram의 경우 시스템 구성도나 Process Flow Diagram (PFD), Piping and Instrument Diagram (P&ID)을 기반으로 하기에 작성에 필요한 비용과 시간이 절감되는 장점이 있다. 본 논문에서는 Dynamic Reliability Block Diagram과 이산 사건 시뮬레이션에 널리 사용되는 DEVS 형식론을 이용하는 신뢰도 분석 방법을 제안한다. 또한 시스템 모델링 방법론 중 하나인 System Entity Structure/Model Base의 개념을 도입함으로써 다양한 설계 대안에 대한 신뢰도 분석 모델을 자동으로 생성할 수 있도록 하였다. 그리고 Reliability Block Diagram을 이용한 신뢰도 분석 시 오래 소요되는 계산 시간을 단축시키기 위해 GPU 가속 기술을 신뢰도 분석 시뮬레이션에 접목하였다.

• 한국멀티미디어학회논문지
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• 제23권10호
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• pp.1270-1285
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• 2020

As a representative concept of the fourth industrial revolution era where everything is digitized, digital twin means analyzing and optimizing a complex system using a simulation model synchronized with the system. In this paper, we propose a digital twin simulation model for the efficient operation of urban railways in Busan. Due to the geopolitical nature of Busan, where there are many mountains and narrow roads, the railways are more useful than other public transportation. However, this inversely results in a high level of congestion, which is an inconvenience to citizens and may be fatal to the spread of the virus, such as COVID19. Considering these characteristics, the proposed model analyzes the congestion level of the railways in Busan. The model is developed based on a mathematical formalism called discrete-event system specification and deduces the congestion level and the average waiting time of passengers depending on the train schedule. In addition, a new schedule to reduce the congestion level is derived through particle swarm optimization, which helps the efficient operation of the railways. Although the model is developed for the railways in Busan, it can also be used for railways in other cities where a high level of congestion is a problem.