• International Journal of Naval Architecture and Ocean Engineering
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• 제8권1호
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• pp.83-101
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• 2016

This paper suggests an event-based scenario manager capable of creating and editing a scenario for shipbuilding process simulation based on multibody dynamics. To configure various situation in shipyards and easily connect with multibody dynamics, the proposed method has two main concepts: an Actor and an Action List. The Actor represents the anatomic unit of action in the multibody dynamics and can be connected to a specific component of the dynamics kernel such as the body and joint. The user can make a scenario up by combining the actors. The Action List contains information for arranging and executing the actors. Since the shipbuilding process is a kind of event-based sequence, all simulation models were configured using Discrete EVent System Specification (DEVS) formalism. The proposed method was applied to simulations of various operations in shipyards such as lifting and erection of a block and heavy load lifting operation using multiple cranes.

• Journal of Positioning, Navigation, and Timing
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• 제11권3호
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• pp.209-215
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• 2022

As intelligent autonomous driving vehicle development has become a big topic around the world, accurate reference dynamics estimation has been more important than before. Current systems generally use speed and heading information sensed from a distant point as a vehicle reference dynamic, however, the dynamics between different points are not same especially during rotating motions. In order to estimate properly estimate the reference dynamics from the information such as velocity and heading sensed at a point distant from the reference point such as center of gravity, this study proposes estimating reference dynamics from any location in the vehicle by combining the Bicycle and Ackermann models. A test system was constructed by implementing multiple GNSS/INS equipment on an Robot Operating System (ROS) and an actual car. Angle and speed errors of 10° and 0.2 m/s have been reduced to 0.2° and 0.06 m/s after applying the suggested method.

• 한국시스템다이내믹스연구
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• 제15권2호
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• pp.5-25
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• 2014

The purpose of this study is to analyze the effects of nuclear power plant workers and organizational characteristics on accidents, and seek the combination of policies for reducing accidents. For this purpose, it grasped, by using System Dynamics and Causal Loop Diagram, how various factors that cause accidents in nuclear plants are interrelated, and performed simulations after building simulation models. As a result of the analysis, first, the fundamental cause of safety accidents in nuclear power plants turned out to be the time constraint on the workload. Second, it turned out that as the workload of workers increases, physical and mental stresses increase, thereby increasing accidents due to errors and violations. Third, it turned out that as the levels of educational training and compliance with regulations and procedures are enhanced, accidents are reduced. Lastly, it turned out that as the combination of policies (reliance level + working environment + educational training + compliance with regulations and procedures) is increased, accidents are reduced. Especially, it turned out that if the combination of policies is increased by 30%, more than 10 cases of accidents are reduced.

• 한국ITS학회 논문지
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• 제8권1호
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• pp.1-8
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• 2009

본 연구는 기존의 버스 운영계획모형을 시스템 다이나믹스(System Dynamics : SD) 관점에서 검토하는 것을 주된 목적으로 하고 있다. 결정변수들 간의 선형적 관계에 기초한 교��비용모델에 SD관점을 적용하여 순환적 관계로의 재구성을 시도하였으며, 그 결과물로 최적배차간격모형의 인과지도(Causal Loop Diagram)을 제시하였다. 또한 계량적 시뮬레이션이 가능한 저유량 인과지도(Stock & Flow Diagram)을 작성하여 시뮬레이션 결과의 의미를 논의하였다. 연구결과, 시뮬레이션에 적용한 수식이 기존의 교통비용모형에 토대를 두고 있기 때문에 시뮬레이션 결과가 기존의 연구와 큰 차이를 보이지 않았다.

• 한국시스템다이내믹스연구
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• 제3권1호
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• pp.79-104
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• 2002

A system dynamics project is going on for forecasting automobile market in Korea. The project is made up of three stages, and the first stage has been wrapped up. As the first attempt, most efforts have been focused on the sound foundation rather than the exact forecast. The model consists of three sectors; the supply sector, the demand sector, and the population sector. The supply sector is a simple stock and flow diagrams representing the supply capacities of all automobile types. The major effort is made on the demand sector and the population sector. The demands are divided into three categories; replacement demands, new demands, and additional demands. The model applies “one car per person" concept, and assumes there will be no additional demands for a while. The replacement demands are calculated based on a simple stock and flow diagram. The new demands are calculated via Bass models; each bass model represents a diffusion for each age group. The population is divided into 101 age groups (age 0 to age 100). The model has been calibrated with past 10 year data (1990 - 1999), and tested for the next two years (2000-2001). The results ware acceptable, although a fine tuning is required. Now the second stage is going on, and most of efforts are made how to incorporate the economic and cultural factors.

• 한국시스템다이내믹스연구
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• 제1권2호
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• pp.149-174
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• 2000

In recent years, how to promore the Utilization of Internet is a main issue of national information policy. In this study, we focused our approach to find promoting sttategies for Internet utilization on three sector's users, governments, enterprises, and households. Promoting the Internet utilization of these three sector's users is a very difficult problem, because their information levels are different and information gap among them can be regarded as bottleneck. And since the interactions between user's demands and diverse information seccor's factors are very complex, policy leverages can not find easily. By the system dynamics methodology, this paper examines the interrelationships between three user's demand mechanism and information policy sector. Information policy sector consist of four sectors, infrastruccure policy seccor, application-contents sector, governance sector, and access and price policy sector (free access policy, literacy policy, telecommunication price policy, etc.). To find and investigate policy leverage that will help understanding dynamic behavior of users in using Internet we build a causal loop diagrams and SD models by using survey data obtained from three sectors'specialized users, 488 persons.

• 한국해양공학회지
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• 제35권2호
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• pp.121-130
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• 2021

In this study, a computational fluid dynamics (CFD) simulation based on an Eulerian-Eulerian approach was used to evaluate the mixing performance of a mud agitator through the distribution of bulk particles. Firstly, the commercial CFD software Star-CCM+ was verified by performing numerical simulations of single-phase water mixing problems in an agitator with various turbulence models, and the simulation results were compared with an experiment. The standard model was selected as an appropriate turbulence model, and a grid convergence test was performed. Then, a simulation of the liquid-solid multi-phase mixing in an agitator was simulated with different multi-phase interaction models, and lift and drag models were selected. In the case of the lift model, the results were not significantly affected, but Syamlal and O'Brien's drag model showed more reasonable results with respect to the experiment. Finally, with the properly determined simulation conditions, a multi-phase flow simulation of a mud agitator was performed to predict the mixing time and spatial distribution of solid particles. The applicability of the CFD multi-phase simulation for the practical design of a mud agitator was confirmed.

• 농업과학연구
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• 제48권2호
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• pp.311-331
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• 2021

Climate change with extreme hydrological events has become a significant concern for agricultural water systems. Climate change affects not only irrigation availability but also agricultural water requirement. In response, adaptation strategies with soft and hard options have been considered to mitigate the impacts from climate change. However, their implementation has become progressively challenging and complex due to the interconnected impacts of climate change with socio-economic change in agricultural circumstances, and this can generate more uncertainty and complexity in the adaptive management of the agricultural water systems. This study was carried out for the agricultural water supply system in Seongju dam watershed in Seonju-gun, Gyeongbuk in South Korea. The first step is to identify system disturbances. Climate variation and socio-economic components with historical and forecast data were investigated Then, as the second step, problematic trends of the critical performance were identified for the historical and future climate scenarios. As the third step, a system structure was built with a dynamic hypothesis (causal loop diagram) to understand Seongju water system features and interactions with multiple feedbacks across system components in water, agriculture, and socio-economic sectors related to the case study water system. Then, as the fourth step, a mathematical SD (system dynamics) model was developed based on the dynamic hypothesis, including sub-models related to dam reservoir, irrigation channel, irrigation demand, farming income, and labor force, and the fidelity of the SD model to the Seongju water system was checked.

• 멤브레인
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• 제30권6호
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• pp.433-442
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• 2020

본 연구에서는 수전해용 ionomer의 분자동역학 전산모사 모델 제작을 위하여, 과량의 물 분자가 존재하는 수전해 시스템의 특성을 반영한 ionomer 모델을 제작한 후, 기존 연료전지용 전해질막 전산모사 조건에 맞춰 제작한 ionomer 모델과 비교하였다. 최종적으로 얻어진 모델은 과불소계 ionomer의 중요 특징 중 하나인 명확한 상분리 및 수화채널이 관찰되었으며, 과량의 물 및 높은 운전 온도 조건에서도 물에 녹지 않고 안정된 구조를 나타내었다. 제조된 ionomer 모델에서는 과량의 물분자로 인한 이온 희석 효과로 이온 전달 성능 감소가 나타났으며, 반대로 수소 기체의 투과는 더 증가할 것으로 분석되었다. 따라서 이러한 수전해 시스템의 특성을 반영한 수전해용 ionomer 분자 구조 설계 전략이 필요하고, 분자동역학 전산모사 연구 시에도 이를 감안한 수전해용 ionomer 모델 제작이 필요하다.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1015-1022
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• 2009

Currently, Korean real estate market has experienced cooling down of the business because of the global economic crisis which resulted from the subprime mortgage lending practice. In response, the Korean government has enforced various policies at the base of deregulating real estate speculation, such as increasing Loan to value ratio (LTV) in order to stimulate housing demand and supply. However, these policies seemed to result in deep confusion in the Korean housing market. Furthermore, analysis for housing market forecasting, especially international financial crisis on Korean real estate market, has been partial and fragmentary, therefore comprehensive solution and systematical approach is required to analyze the real estate and real estate financial market including causal nexus between market determining factors. In an integrated point of view, applying the system dynamics modeling, the paper aims at proposing Korean Real Estate and Mortgage market dynamics models based on fundamental principles of housing market determined by supply and demand. We also find the impact of deregulation policies focusing on mortgage loan which is the main factors of policies.