• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.2
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• pp.76-80
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• 2005

In this paper, a miniaturized ring hybrid circuit is characterized based on a thin film microstrip (TFMS) on low-resistivity silicon. In order to obtain low-loss characteristics, a polyimide layer with 50 $\mu$m thickness is spin-coated onto the silicon to be used for the substrate. First, propagation characteristics of TFMS lines consisting of the ring hybrid circuit are presented. Then, a ring hybrid circuit based on TFMS is featured by employing the triple concentric circle approach for miniaturization. Triple concentric circle lines with $\lambda$$_{g}$/4 or 3$\lambda$$_{g}$/4 line lengths are implemented on the surface of the polyimide by circularly meandering to reduce the circuit size of the designed ring hybrid. Good agreement between measured and simulated results is obtained.

• Journal of computational fluids engineering
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• v.17 no.1
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• pp.23-28
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• 2012

The pressure transient inside the passenger cabin of high-speed train has been simulated using computational fluid dynamics(CFD) based on the axi-symmetric Navier-Stokes equation. The pressure change inside a train have been calculated using first order difference approximation based on a linear equation between the pressure change ratio inside a train and the pressure difference of inside and outside of the train. The numerical results have been assessed for the KTX train passing through a 9km long tunnel of Wonju-Kangneung line at the speed of 250km/h assuming that the train is satisfying the train specification for airtightness required by the regulation.

• Journal of the Korea Society of Computer and Information
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• v.22 no.8
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• pp.93-100
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• 2017

After the fourth industrial revolution came along, SW education to improve creativity and problem-solving ability began in elementary, middle, and high schools first and then in universities as well positively; however, research on the curriculum or what it has to pursue is not yet enough. Here, this study will investigate the current status of SW education provided in software-oriented schools operated in universities and also given as cultural studies in general universities and examines the curriculum or the standard plan for education. In most schools, it is operated as similar subject names, and diverse methods are tried on- and off-line to cultivate computing thinking skills. Also, to study SW education programs that can be operated in the general cultural courses of universities and find out how to utilize them, this author suggests the goal setting, educational contents, and teaching methods for SW education. As follow-up tasks, it will be needed to apply the suggested programs to the field and find out new evaluation methods in order to cultivate creative and convergent persons of ability.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.2
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• pp.122-128
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• 2010

This paper presents vibration control performance of active engine mount system installed with the magneto-rheological(MR) mount and the piezostack mount. The performance is evaluated via hardware-in-the-loop-simulation(HILS) method. As a first step, six degrees-of freedom dynamic model of an in-line four-cylinder engine which has three point mounting system is derived by considering the dynamic behaviors of MR mount and piezostack mount. As a second step, sliding mode controller(SMC) is synthesized to actively control the imposed vibration. In order to demonstrate the effectiveness of the proposed active engine mount, vibration control performances are evaluated under various engine operating speeds(wide frequency range) using HILS method and presented in time and frequency domain.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.175-181
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• 2001

An investigation into the response statistics of a spring-pendulum system whose base oscillates randomly along vertical and horizontal line is made. The spring-pendulum system with internal resonance examined is known to be a good model for a variety of engineering systems, including ship motions with nonlinear coupling between pitching and rolling motions. The Fokker-Planck equation is used to generate a general first-order differential equations for the random responses of the system are reduced to a system of autonomous ordinary differential equations. In view of equilibrium solutions of this system and their stability, the response statistics is examined. It is seen that increase in horizontal excitation level leads to a decreased width of the internal resonance region.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2311-2315
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• 2009

This paper presents a method to apply energy margin for assesment of total transfer capability (TTC). In order to calculate energy margin, two values of the transient energy function have to be computed. The first value is transient energy that is the sum of kinetic and potential energy at the end of fault. The second is critical energy that is potential energy at controlling UEP(Unstable Equilibrium Point). It is seen that TTC level is determined by not only bus voltage magnitudes and line thermal limits but also transient stability. TTC assessment is compared by the repeated power flow(RPF) method and optimization method.

• Journal of the Korean Home Economics Association
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• v.42 no.5
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• pp.107-126
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• 2004

As the information society matures, an analysis on possible outputs of internet usage is needed. Thus, this study was peformed in order to understand the utility cognition and negative outputs of internet users. The method used in this study was a web-based questionnaire that was administered to the internet users. Five hundred married men and women were analyzed with a factor and a multiple regression analysis. Results were as follows: First, many kinds of internet usages - information searching, internet shopping, electronic mail, instant messaging, and decision-making dependent on internet information - were differentiated with age. Second, the altitude about the internet was an important explanatory variable in the types of internet usage. Third, negative outputs of internet usage were great in terms of information resource management and unbalanced scheduling in daily time spent. Fourth, utility cognition was affected by qualitative elements on internet usage more than the quantitative ones.

• Journal of the Korean Home Economics Association
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• v.48 no.5
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• pp.129-143
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• 2010

In order to improve the quality of student teachers' practicum, this study analysed the current situation of student teachers' field practice in child care centers. The study also assessed the practicum implementation case of H Cyber University. First, this research examined the characteristics of practicum implementation in universities. Second, a variety of strategies based on a blended model, on/off-line lectures, professor-student interaction, university-daycare centers collaboration, e-mentoring, and student teachers' portfolios that reduce the problems of student teachers' training, were explored. Finally, the practicum implementation case that adopted these factors was assessed. The results from this case study implied that student teachers' practicums based on a blended model can be an alternative method for problem-solving in existing student teachers' training in universities.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.337-342
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• 2011

The pressure transient inside the passenger cabin of high-speed train has been simulated using computational fluid dynamics(CFD) based on the axi-symmetric Navier-Stokes equation. The pressure change inside a train have been calculated using first order difference approximation based on a linear equation between the pressure change ratio inside a train and the pressure difference of inside and outside of the train. The numerical results have been assessed for the KTX train passing through a 9km long tunnel of Wonju-Kangneung line at the speed of 250km/h assuming that the train is satisfying the train specification for airtightness required by the regulation.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.684-689
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• 2000

In this paper, the equations of motion about vehicle, powertrain and brake system were derived. The vehicle has eight degrees of freedom with nonlinear tire model and the powertrain has two degrees of freedom containing engine, torque converter and four speed automatic transmission. The brake system has two states about front and rear brake line pressures. The transient tire model with first order time lag is also subjoined for low speed or stop-and-go simulation. The modeling was derived considering two points - the fidelity and the simplicity. The simulation using this model is similar with real vehicle dynamic behavior and the model is made as simple as possible far fast simulation. It is validated that the derived vehicle model can be applicable to the real time simulation.