• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.711-712
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• 2010

본 논문에서는 가변노즐의 다물체동력학적 특성을 연구하였다. 가변노즐은 다양한 운용고도조건에서 비행체의 효율성을 향상시키기 위하여 사용된다. 플랩을 포함하는 가변노즐 메커니즘의 동적특성을 다물체동력학 소프트웨어인 RecurDyn을 이용하여 분석하였다.

• 대한의용생체공학회:의공학회지
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• 제15권2호
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• pp.151-158
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• 1994

It has been shown that many of physiological systems have nonlinear dynamics. The evidences of these nonlinear behaviors make us analyze physiological systems in the new viewpoint. And, some of these nonlinear dynamics can be represented by chaotic behaviors, which is studied by several methods-correlation dimension, return map, power spectrum analysis, etc. This study is on the analysis of nonlinear characteristics of ECG. After data have been acquired from 20 children (10-13 years old), and 30 students (20-24 years old). We have calculated parameters HR, PR, VAT, TD, TRD, TPD from data, and estimated correlation dimension, return map, power spectrum, time series. Results show the nonlinear and chaotic characteristics of ECG.

• 한국시스템다이내믹스연구
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• 제17권3호
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• pp.91-120
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• 2016

This study explores hedge fund characteristics that affect hedge fund performance, namely, fund size, fund age, and performance fee. Previous studies have examined relationships between hedge fund characteristics and fund performance using singular and static thinking to report inconsistent findings without providing full understanding of the causal relationships among variables. To identify that comprehensive causal relationships between hedge fund characteristics and hedge fund performance, this research applies the system dynamics perspective, which allowed demonstration of the interactions within the overall system beyond the singular causal relationships between hedge fund characteristics and performance found in existing traditional research. This study contributes to existing literature in the following ways. First, it overcomes the limitations of singular research methodologies by looking at the integrated system of hedge fund characteristics and fund performance from a bird's eye view based on their dynamic feedback relationships. Second, policy suggestions in terms of regulation and education are presented as growth strategies for the sustainable development of the Korean hedge fund market.

• 한국수소및신에너지학회논문집
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• 제32권1호
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• pp.1-10
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• 2021

Water electrolysis technology, which generates hydrogen using renewable energy resources, has recently attracted great attention. Especially, the polymer electrolyte membrane water electrolysis system has several advantages over other water electrolysis technologies, such as high efficiency, low operating temperature, and optimal operating point. Since research that analyzes performance characteristics using test bench have high cost and long test time, however, model based approach is very important. Therefore, in this study, a system model for water electrolysis dynamics of a polymer electrolyte membrane was developed based on MATLAB/Simulink®. The water electrolysis system developed in this study can take into account the heat and mass transfer characteristics in the cell with the load variation. In particular, the performance of the system according to the stack temperature control can be analyzed and evaluated. As a result, the developed water electrolysis system can analyze water pump dynamics and hydrogen generation according to temperature dynamics by reflecting the dynamics of temperature.

• Journal of Mechanical Science and Technology
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• 제15권9호
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• pp.1302-1310
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• 2001

This paper introduces modeling and simulation results for pipeline inspection gauge (PIG) with bypass flow control in natural gas pipeline. The dynamic behaviour of the PIG depends on the different pressure across its body and the bypass flow through it. The system dynamics includes: dynamics of driving gas flow behind the PIG, dynamics of expelled gas in front of the PIG, dynamics of bypass flow, and dynamics of the PIG. The bypass flow across the PIG is treated as incompressible flow with the assumption of its Mach number smaller than 0.45. The governing nonlinear hyperbolic partial differential equations for unsteady gas flows are solved by method of characteristics (MOC) with the regular rectangular grid under appropriate initial and boundary conditions. The Runge-Kuta method is used for solving the steady flow equations to get initial flow values and the dynamic equation of the PIG. The sampling time and distance are chosen under Courant-Friedrich-Lewy (CFL) restriction. The simulation is performed with a pipeline segment in the Korea Gas Corporation (KOGAS) low pressure system, Ueijungboo-Sangye line. Simulation results show us that the derived mathematical model and the proposed computational scheme are effective for estimating the position and velocity of the PIG with bypass flow under given operational conditions of pipeline.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.497-500
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• 2002

When one is interested in the dynamics of a mechanical system with electric motors, the force generated by the motor is generally considered as only an applied torque or force independent of mechanical state variables such as velocity. For a system operated in non-steady dynamic conditions, however, the usual analysis approach may fail to predict some characteristics in the dynamic behaviors because of electromechanical coupling effects. In this paper, we propose dynamics analysis model in which dc motor dynamics with the electromechanical coupling effects are embedded to mechanical dynamics models. The do motor is modeled based on its equivalent circuit model and included in the dynamics solving algorithm which we developed before, called generalized recursive dynamics formula. The developed dynamic analysis model is effective and realistic for analysis of electromechanical dynamics of a system with do motors. The developed model is evaluated by constructing and simulating the flexible antennas of an artificial satellite driven by do motors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1553-1558
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• 2003

The authors investigate influences of manipulator dynamics on and roles of kinesthetic sensation and visual sensation in a Human-Machine Cooperative System (HMCS). At first, the general structure and essential transfer functions of HMCSs are described based on the previous work. Then, after showing theoretical treatment of manipulator dynamics, this paper analyzes the influences on HMCSs in two cases: one is the control design focusing on tool dynamics and reaction force transfer function, and the other is that specifies maneuver transfer function and transfer function for object dynamics variation. In addition to conventional experiments only employing kinesthetic sensation, other experiments with both kinesthetic and visual sensations are performed to examine difference in the roles of these sensations and the validity of the design without the visual sensation.

• 한국시스템다이내믹스연구
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• 제13권2호
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• pp.73-91
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• 2012

This study aims to comprehensively understand the dynamics between the factors related to service quality, satisfaction and reuse intention. The contents of the study are as follows. First, it draws the limitations of the existing studies by reviewing the literature related to the relationships between service quality, satisfaction and reuse intention. Second, it highlights the characteristics of System Dynamics as a means of overcoming their shortcomings as well as examining the dynamic mechanism of the relevant factors. Third, it explores the feedback loops of the relevant key variables and the feedback structure of the system. Lastly, it concludes with the suggestions and implications of the key research findings. This study is expected to emphasize the importance of the feedback mechanism operating around the service quality, satisfaction, and reuse intention. Further, the causal loop diagram developed can be a basic material for the diverse levels of governments as well as service providers to refer to for improving the service quality of Community Social Service Investment Program.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권2호
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• pp.346-363
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• 2015

We have performed integrated dynamics modeling for a supercavitating vehicle. A 6-DOF equation of motion was constructed by defining the forces and moments acting on the supercavitating body surface that contacted water. The wetted area was obtained by calculating the cavity size and axis. Cavity dynamics were determined to obtain the cavity profile for calculating the wetted area. Subsequently, the forces and moments acting on each wetted part-the cavitator, fins, and vehicle body-were obtained by physical modeling. The planing force-the interaction force between the vehicle transom and cavity wall-was calculated using the apparent mass of the immersed vehicle transom. We integrated each model and constructed an equation of motion for the supercavitating system. We performed numerical simulations using the integrated dynamics model to analyze the characteristics of the supercavitating system and validate the modeling completeness. Our research enables the design of high-quality controllers and optimal supercavitating systems.

• 제어로봇시스템학회논문지
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• 제7권12호
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• pp.993-1000
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• 2001

Configuration-dependent nonlinear coefficient matrices in the dynamic equation of robot manipulator impose computa- tional burden in real-time implementation of tracking control based on the inverse dynamics controller. However, parallel manipulators such as Stewart platform have relatively small workspace compared to serial manipulators. Based on the characteristics of small motion range. nonlinear coefficient matrices can be approxiamted to constant ones. The modeling errors caused by such approximation are compensated for by H-infinity controller that treats the modeling errors disturbance. The proposed inverse dynamics controller with approximate dynamics combined with H-infinity control shows good tracking performance even for fast tracking control in which computation of full inverse dynamics is not easy to implement.