• Journal of the Society of Naval Architects of Korea
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• v.43 no.6 s.150
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• pp.647-655
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• 2006

In this paper, submerged body dynamics model in vertical plane which can include the effect of free surface and wave is suggested to simulate the motions of submerged body moving beneath free surface precisely. A controller is designed, which can maintain a constant depth below the mean sea level and minimize the pitch angle. Numerical simulations show that the designed controller is effective on depth keeping and minimizing pitch angle in regular waves and irregular waves.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.454-461
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• 1997

Heat transfer and pressure drop for single phase flow of water in circular smooth and micro-fin tubes are measured. Copper tubes of 9.52 and 7mm outer diameter were used. The internal roughness in micro-fin tubes was formed by spiral grooves having $25^{\circ}$ helx angle, 0. 12mm fin height and 0.454mm pitch in 9.52mm tubes; $18^{\circ}$ helix angle, 0.15mm fin height and 0.322mm pitch in 7mm tubes. The measured friction factor and heat transfer coefficient are compared with relevant previous works, and the correlations for micro-fin tube are developed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.654-659
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• 2013

This paper presents a numerical optimization of louvered fins to enhance the JF factor in terms of the design parameters, including the fin pitch, the number of louvers, the louver angle, the fin thickness, and the re-direction louver length. We carried out a parametric study to select the three most important parameters affecting the JF factor, which were the fin pitch, number of louvers, and the louver angle. We optimally designed the louvered fin by using 3rd-order full factorial design, the kriging method, and a micro genetic algorithm. Consequently, the JF factor of the optimum model increased by 16% compared to that of the base model. Moreover, the optimum model reduced the pressure drop by 17% with a comparable heat transfer rate.

• The Journal of the Korean dental association
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• v.51 no.10
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• pp.551-555
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• 2013

The purpose of this study was to give a guideline for selecting the nickel-titanium (NiTi) file by review from many studies. Since the early 1990s, several instrument systems manufactured from NiTi have been introduced into endodontic practice. The specific design characteristics vary, such as tip shape and size, cross sectional view, helix angle, and pitch space. Some of the early systems have been removed from the market or play only minor roles; others are still widely used. New designs continually are produced, but the extent to which clinical outcomes will depend on design characteristics is difficult to forecast. In this study, I have reviewed the different design characteristics in respect of the safety and efficiency. With the review from many studies, I concluded that the clinicians must be understand the specific design characteristics for selecting the ideal NiTi rotary instruments.

• Proceedings of the Korean Society of Computer Information Conference
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• 2014.07a
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• pp.249-252
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• 2014

본 논문에서는 IMU를 이용한 6자유도 모바일 로봇을 설계하고 성능을 평가해 보았다. IMU를 이용하여 로봇의 Roll과 Pitch 각을 측정하여 모바일 로봇의 이동경로 경사각을 측정하여 지면이 수평 일 때 모바일 로봇의 6바퀴 모두 항상 지면과 닿아 있는 상태를 유지한다. 또한 오르막과 내리막일 경우 로봇의 동역학에 의한 최소한의 에너지를 유지하여 이동이 가능하도록 하기위한 로봇의 제어기를 설계하고 그 성능을 평가해 보았다.

• Journal of Aerospace System Engineering
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• v.8 no.4
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• pp.32-38
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• 2014

Sufficient energy charging during a day is essential for a solar-powered long-endurance aircraft. Variations of flight path that is superior to a basic circle path are sought in this study for more efficient charging. Flight path associated with roll and pitch attitudes are investigated. It seems that the pitch angle can play more important role than the roll angle for the solar charging efficiency. Thus, more energy charging is observed when the entire flight path is tilted toward the direction of the sun.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.617-624
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• 2008

This paper proposes design and implementation of wind turbine simulators which incorporate the turbine dynamic characteristics. At first, the turbine output characteristic in steady state is modelled as a function of wind speed and then dynamic characteristics are modelled such as pitch angle control, torsional vibration, tower shadow effect, wind shear effect, and inertia effect. In addition, a wind speed simulator is developed which can generate the real wind speed pattern. The wind turbine simulator is implemented with 3[kW] M-G set(cage-type induction motor coupled with doubly-fed induction generator) at laboratory.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.192-194
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• 2007

This paper proposes a new wind turbine simulator using a squirrel cage induction for control performance test of DFIG (doubly-fed induction generator). The turbine static characteristics are modeled using the relation between the turbine torque versus the wind speed and the blade pitch angle. The turbine performance is subjected to a real wind speed pattern by modeling the wind speed as a sum of harmonics with a wide range of frequency. The turbine model includes the effect of the tower shadow and wind shear. A pitch angle controller is designed and used to protect the coupled generator by limiting the turbine speed to the maximum value. Experimental results are provided for a 3[kW] wind turbine simulator at laboratory.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.33-42
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• 1998

If a ship diesel engine is operated by consolidated control with Controllable Pitch Propeller(CPP), the minimum fuel consumption is achieved together with the demanded ship speed. For this, it is necessary that the ship is operated on the ideal operating line which satisfies the minimum fuel consumption and that the pitch angle of CPP and throtle valve angle are controlled simultaneously. In this point of view, this paper presents a controller design method for a ship propulsion system with CPP based on the decoupling control theory. To do this, Linear Matrix Inequality(LMI) approach is introduced for the control system to satisfy the given $H_\infty$ control performance and robust stability in the presence of physical parameter perturbations. The validity and applicability of this approach are illustrated by simulation in the all operating ranges.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.94-104
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• 2013

A numerical analysis has been conducted to determine the pitch thrust vectoring characteristics of a two-dimensional convergent divergent exhaust nozzle for supersonic aircraft application. The numerical analysis was done by using Fluent and verified by the experimental test results. Analysis was performed with pitch angle of $0^{\circ}$ and $20^{\circ}$ each at the ambient temperature condition. To see the effect of a ratio of pitch flap length and pitch flap height, the ratio was varied from 0.5 to 2.5. The numerical analysis shows that pitch thrust is changed greatly with pitch flap length. The big difference of the pitch thrust with pitch flap length is due to the shock interactions in the nozzle.