• 한국시스템다이내믹스연구
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• 제7권2호
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• pp.215-226
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• 2006

A conceptual system dynamics model is developed to represent the dynamic mechanism between the number of hepatitis B virus and the defense system of the body. The simulation results shows that the model behaves within the reasonable ranges. The developed conceptual model is a first attempt to quantify the dynamic mechanisms of the hepatitis B virus, where only feedback structures are considered without bio-organism data. The next step would be to incorporate the model with bio-organism theory and to carry out case studies to identify personal characteristics. Since the current model is a conceptual model where quantitative results are not based on the sound background, the usage is limited only within the qualitative basis. It could be a effective educational tool for the patients. It also shows what-to-do lists in order to be used for forecast purposes.

• 한국시스템다이내믹스학회:학술대회논문집
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• 한국시스템다이내믹스학회 2002년도 추계학술대회발표논문집
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• pp.103-122
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• 2002

Construct ion sector government policies are targeted towards regulation than facilitation and management. This approach often fails to integrate different segments of the public and private and seems to be inadequate in encouraging the private sector to achieve better quality construction. This situation suggests a need for a better and systematic approach for construct ion policy making. This paper suggests a model-based approach to public policy making using system dynamics approach. Singapore government's policy making efforts to encourage the use of prefabrication are discussed as an application example. This paper presents system models which discuss strengths and weaknesses of the current construction system in Singapore using casual loops, and highlights the feedback processes that would be useful in decision making for the government. Based on these system dynamics models, this paper identifies four major potential policy interventions policy interventions.

• 한국시스템다이내믹스연구
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• 제11권3호
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• pp.5-31
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• 2010

The purpose of this study is to develop a system dynamics model for growth prediction of low birth weight infants(LBWIs) based on nutrition. This growth prediction model consists of 9 modules; body weight, height, carbohydrate, protein, lipid, micronutrient, water, activity and energy module. The results of the model simulation match well with the percentiles of weights and heights of the Korean infants, also with the growth records of 55 LBWIs, under 37 weeks of gestational age, whose weights are appropriate for their gestational age. This model can be used to understand the current growth mode of LBWIs, predict the future growth of LBWIs, and be utilized as a tool for controlling the nutrient intake for the optimal growth of LBWIs in actual practice.

• 한국시스템다이내믹스연구
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• 제7권1호
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• pp.67-90
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• 2006

A series of system dynamics model was developed for forecasting demand and supply of human resource in the electricity industry. To forecast demand of human resource in the electric power industry, BLS (Bureau of Labor Statistics) methodology was used. To forecast supply of human resource in the electric power industry, forecasting on the population of our country and the number of students in the department of electrical engineering were performed. After performing computer simulation with developed system dynamics model, it is discovered that the shortage of human resource in the electric power industry will be 3,000 persons per year from 2006 to 2015, and more than a double of current budget is required to overcome this shortage of human resource.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2008년도 Asian Magnetics Conference
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• pp.259.2-259.2
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• 2008

• Current Applied Physics
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• 제18권11호
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• pp.1352-1358
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• 2018

In recent years, one-dimensional (1D) magnetic nanostructures, such as magnetic nanorods and chains of magnetic nanoparticles have received great attentions due to the breadth of applications. Especially, magnetic nanorods has been opened an area of active research and applications in medicine, sensors, optofluidics, magnetic swimming, and microrheology since they possess the unique magnetic and geometric features. This study focuses on the molecular dynamics (MD) simulations of an infinitely long crystal ${\beta}-Fe_2O_3$ nanorod. To elucidate the structural properties and dynamics behavior of ${\beta}-Fe_2O_3$ nanorods, MD simulation is a powerful technique. The structural properties such as equation of state and radial distribution function of bulk ${\beta}-Fe_2O_3$ are performed by lattice dynamics (LD) simulations. In this work, we consider three main mechanisms affecting on deformation characteristics of a ${\beta}-Fe_2O_3$ nanorod: 1) temperature, 2) the rate of mechanical compression, and 3) the rate of mechanical torsion.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1540-1553
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• 2019

A nuclear power plant (NPP) is a highly complex system-of-systems as manifested through its internal systems interdependence. The negative impact of such interdependence was demonstrated through the 2011 Fukushima Daiichi nuclear disaster. As such, there is a critical need for new strategies to overcome the limitations of current risk assessment techniques (e.g. the use of static event and fault tree schemes), particularly through simulation of the nonlinear dynamic feedback mechanisms between the different NPP systems/components. As the first and key step towards developing an integrated NPP dynamic probabilistic risk assessment platform that can account for such feedback mechanisms, the current study adopts a system dynamics simulation approach to model the thermal dynamic processes in: the reactor core; the secondary coolant system; and the pressurized water reactor. The reactor core and secondary coolant system parameters used to develop system dynamics models are based on those of the Palo Verde Nuclear Generating Station. These three system dynamics models are subsequently validated, using results from published work, under different system perturbations including the change in reactivity, the steam valve coefficient, the primary coolant flow, and others. Moving forward, the developed system dynamics models can be integrated with other interacting processes within a NPP to form the basis of a dynamic system-level (systemic) risk assessment tool.

• 대한전기학회논문지:전력기술부문A
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• 제48권12호
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• pp.1520-1526
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• 1999

This paper presents a current feedback learning controller for dynamic control of DC motors. The proposed controller uses the full third-order dynamics model of DC motor system to drive stable learning rules for virtual current learning input, voltage learning input, and the coefficient of electromotive force. It is shown that the proposed learning controller drives the state of uncertain DC motor system with unknown system parameters and external load torque to the desired one globally asymptotically. Computer simulation and experimental results are given to demonstrate the effectiveness of the proposed adaptive learning controller.

• Journal of Biosystems Engineering
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• 제39권4호
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• pp.310-317
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• 2014

Purpose: This study was conducted to analyze the air flow characteristics in a plant factory with different inlet and outlet locations using computational fluid dynamics (CFD). Methods: In this study, the flow was assumed to be a steady-state, incompressible, and three-dimensional turbulent flow. A realizable k-${\varepsilon}$ turbulent model was applied to show more reasonable results than the standard model. A CFD software was used to perform the numerical simulation. For validation of the simulation model, a prototype plant factory ($5,900mm{\times}2,800mm{\times}2,400mm$) was constructed with two inlets (${\Phi}250mm$) and one outlet ($710mm{\times}290mm$), located on the top side wall. For the simulation model, the average air current speed at the inlet was $5.11m{\cdot}s^{-1}$. Five cases were simulated to predict the airflow pattern in the plant factory with different inlet and outlet locations. Results: The root mean square error of measured and simulated air current speeds was 13%. The error was attributed to the assumptions applied to mathematical modelling and to the magnitude of the air current speed measured at the inlet. However, the measured and predicted airflow distributions of the plant factory exhibited similar patterns. When the inlets were located at the center of the side wall, the average air current speed in the plant factory was increased but the spatial uniformity was lowered. In contrast, if the inlets were located on the ceiling, the average air current speed was lowered but the uniformity was improved. Conclusions: Based on the results of this study, it was concluded that the airflow pattern in the plant factory with multilayer cultivation shelves was greatly affected by the locations of the inlet and the outlet.

• KIEAE Journal
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• 제8권5호
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• pp.11-16
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• 2008

This research has established CFD model on pit's cool-tube system through heat and air movement simulations, of which data was based on experimental and verification. This research work verified the effectiveness of the cool-tube system by analysing temperature, humidity and air current of the actually installed case. Also, we analysed heat transfer through air current simulation and the results are as followings. Firstly, we experiment on temperature, humidity and speed of air currents of the cool tube system with pit space during the month of May (spring). The average exterior temperature was $16.1^{\circ}C$, and $18.2^{\circ}C$ for the pit, $24.7^{\circ}C$ for the compressor room. Secondly, based on measured data of real case, we have analysed heat transfer through air current simulation and verified our proposed model. The actual measurement of average temperature of exhaust air of the pit's area is $19.7^{\circ}C$ with tolerance of $-0.33^{\circ}C{\sim}-0.6^{\circ}C$ compared to above simulations. Thirdly, having verified air current simulation model with formation of 260,000 and 1,000,000 cells, we could get reasonable near values with 260,000 cells. Lastly, the next step of research would be focused on proposing the best possible pit's cool-tube system after analysis of heat transfer of the air current simulation based on verified CFD model.