• Environmental Engineering Research
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• 제10권2호
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• pp.88-103
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• 2005

In this paper, data-driven modeling and multiresolution analysis (MRA) are applied for a full-scale wastewater treatment plant (WWTP). The proposed method is based on modeling by partial least squares (PLS) and multiscale monitoring by a generic dissimilarity measure (GDM), which is suitable for nonstationary and non-normal process monitoring such as a biological process. Case study in an industrial plant showed that the PLS model could give good modeling performance and analyze the dynamics of a complex plant and MRA was useful to detect and isolate various faults due to its multiscale nature. The proposed method enables us to show the underlying phenomena as well as to filter out unwanted and disturbing phenomena.

• 전기학회논문지
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• 제66권6호
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• pp.968-974
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• 2017

In this paper, modeling of brushless DC motor (BLDC) driving system for platform screen door control applied fuel cell power generation system has been proposed. At first the system configuration and operational principle of the developed fuel cell simulator has been investigated and the design of BLDC motor driving system is studied and the overall performance and dynamics of the proposed system could be effectively examined by simulation. PSIM simulation program is implemented to verify the performance and compatibility of the fuel cell power generation system and BLDC motor control system modeling.

• Computers and Concrete
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• 제33권3호
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• pp.325-340
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• 2024

The growing demands for sustainable and high-performance construction materials necessitate a deep understanding of their physicochemical properties by that of these heterogeneities. This paper presents a comprehensive review of the state-of-the-art hierarchical multiscale modeling approach aimed at predicting the intricate physicochemical characteristics of construction materials. Emphasizing the heterogeneity inherent in these materials, the review briefly introduces single-scale analyses, including the ab initio method, molecular dynamics, and micromechanics, through a scale-bridging technique. Herein, the limitations of these models are also overviewed by that of effectively scale-bridging methods of length or time scales. The hierarchical multiscale model demonstrates these physicochemical properties considering chemical reactions, material defects from nano to macro scale, microscopic properties, and their influence on macroscopic events. Thereby, hierarchical multiscale modeling can facilitate the efficient design and development of next-generation construction.

• 한국시스템다이내믹스연구
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• 제12권2호
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• pp.153-176
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• 2011

This paper is a summary of how we constructed a national R&D investment model. Although a national R&D investment is an important decision making for the government as well as industries, currently there were little efforts on making a model reflecting governmental decision making on the individual size of national R&D. We constructed a simple national R&D model through discussion with 3 researchers who have rich experience of governmental investment of national R&D. In this paper, we tried to show how our simple R&D model can reflect the perception on the R&D efficiency that changes as the industry reach to its saturation level.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권2호
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• pp.323-332
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• 2014

High-speed marine vehicles can take advantage of aerodynamically supported platforms or air wings to increase maximum speed or transportation efficiency. However, this also results in increased complexity of boat dynamics, especially in the presence of waves and wind gusts. In this study, a mathematical model based on the fully unsteady aerodynamic extreme-ground-effect theory and the hydrodynamic added-mass strip theory is applied for simulating vertical-plane motions of a tunnel hull in a disturbed environment, as well as determining its steady states in calm conditions. Calculated responses of the boat to wind gusts and surface waves are demonstrated. The present model can be used as a supplementary method for preliminary estimations of performance of aerodynamically assisted marine craft.

• Tribology and Lubricants
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• 제29권5호
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• pp.318-323
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• 2013

Overheating in electrical motors results in detrimental effects such as degradation of the insulation materials, demagnetization of magnets, increases in Joule losses, and decreases in motor efficiency and lifetime. Thus, it is important to find ways to dissipate heat from the motor and to keep the motor operating at its most efficient temperature. In this study, a new design to guide air flow through a given brushless direct current (BLDC) motor is developed and the design is analyzed, specifically by using computational fluid dynamics (CFD) simulations. The results showed that the temperature distribution in the three proposed models is lower than that in the original model, although the speed of the cooling fan in the original model reaches a very high value of $15{\times}10^3$ rpm. The results also showed that CFD can be effectively used to simulate the heat transfer of BLDC motors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.231-236
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• 1997

We propose the hybrid control for the path control of wheeled mobile robot system. To develop the hybrid control of mobile robot, the continuous dynamics of mobile robot are modeled by the switched systems. The abstract model and digital automata for the path control are developed. This hybrid control system has the 3-layered hierachical structure : digital automata as the higher process, mobile robot system as the lower process, and the interface as the interaction process between the continuous dynamics and the discrete dynamics. The control of following the desired-paths with edges are investigated as the applications by the computer simulation.

• Interaction and multiscale mechanics
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• 제1권2호
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• pp.303-315
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• 2008

In this paper, thermodynamical properties of crystalline silicon under strain are calculated using classical molecular dynamics (MD) simulations based on the Tersoff interatomic potential. The Helmholtz free energy of the silicon crystal under strain is calculated by using the ensemble method developed by Frenkel and Ladd (1984). To account for quantum corrections under strain in the classical MD simulations, we propose an approach where the quantum corrections to the internal energy and the Helmholtz free energy are obtained by using the corresponding energy deviation between the classical and quantum harmonic oscillators. We calculate the variation of thermodynamic properties with temperature and strain and compare them with results obtained by using the quasi-harmonic model in the reciprocal space.

• 상하수도학회지
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• 제20권1호
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• pp.104-114
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• 2006

Recently, the PPP (Public-Private-Participate) program on water and wastewater services in Korea has been under an active debate. However, the controversy has reached the limits of getting more valuable implications from past foreign experience beyond conceptual and/or qualitative case studies. This paper analyze scientifically and quantitatively the Buenos Aires Water Concession Project focused on propriety of the contract using system dynamics modeling. The results show that Buenos Aires's Project has several problems in the contract phase even though Argentina government spent much time to design it. Analysis results suggest that estimation of K factor considering delay effect and future uncertainty, reduction of the first fixed terms of contract, etc., are needed for a proper contract.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.2087-2092
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• 2009

We performed molecular dynamics simulations on dimyristoylphosphatidylcholine lipid bilayer with 50 mol% halothane. The structural properties, electron density profile, segmental order parameter of acyl chains, headgroup orientation distribution, water dipole orientation distribution, have been examined. Overall the effects of the halothane molecules on structural properties of DMPC lipid bilayer were found to be small. The electron density profiles, the segmental order parameter, the headgroup orientation, the water dipole orientation were not affected significantly by the halothane molecules. Pressure tensor calculations shows that the lateral pressure increases at the hydrocarbon tail region and the headgroup region, and decreases at the water-headgroup interfacial region.