• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.839-840
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• 2012

• Journal of Powder Materials
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• v.15 no.1
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• pp.46-52
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• 2008

The restrictor, which is a fluid channel from a reservoir to a chamber inside a thermal micro actuator, has been fabricated using ArF and KrF excimer lasers, Diode-Pumped Solid State Lasers (DPSSL) and femtosecond lasers for a feasibility study. A numerical model of fluid dynamics for the actuator chamber and restrictor is presented. The model includes bubble formation and growth, droplet ejection through nozzle, and dynamics of fluid refill through the restrictor from a reservoir. Since an optimized and well-fabricated restrictor is important for a high frequency actuator, some special beam delivery setups and post processing techniques have been researched and developed. The effects of variations of the restrictor length, diameter, and tapered shapes are simulated and the results are analyzed to determine the optimal design. The numerical results of droplet velocity and volume are compared with the experimental results of a cylindrical-shaped actuator. It is found that the micro actuators having tapered restrictors show better high frequency characteristics than those having a cylindrical shape without any notable decrease of droplet volume. The laser-fabricated restrictors demonstrate initial feasibility for the laser direct ablation technique although more development is required.

• Journal of Drive and Control
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• v.15 no.2
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• pp.32-37
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• 2018

The power plants use turbine output control devices to supply or shut off steam to high pressure and low-pressure steam turbines connected to generators. This turbine output control device is driven by a hydraulic servo actuator. The gas flows into the hydraulic servo actuator during periodic inspection or normal operation, and the resulting adiabatic compression of the gas raises the internal temperature of the actuator to $500^{\circ}C$. This temperature increase causes the seals to burn and show wear and tear, resulting in failure. In this study, an air vent valve was installed to allow gas inside the hydraulic servo actuator to flow large quantities of air at the beginning of the operation and after the periodic inspection. Gas was passed through for only minute flow during normal operation of the power plant. By applying the air vent valve, it improves the reliability of the hydraulic servo actuator by discharge the gas appropriately to improve the life of the seal.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.2
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• pp.418-430
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• 2014

In this paper, a modelling technique for simulating self-propelled ships in waves is presented. The flow is modelled using a RANS solver coupled with an actuator disk model for the propeller. The motion of the ship is taken into consideration in the definition of the actuator disk region as well as the advance ratio of the propeller. The RPM of the propeller is controlled using a PID-controller with constraints added on the maximum permissible RPM increase rate. Results are presented for a freely surging model in regular waves with different constraints put on the PID-controller. The described method shows promising results and allows for the studying of several factors relating to self-propulsion. However, more validation data is needed to judge the accuracy of the model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.297-300
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• 2005

This paper presents vibration control of an engine mount for a passenger vehicle utilizing ER fluid and piezoelectric actuator. The proposed engine mount can be isolated the vibration of wide frequency range with many types of amplitude. The main function of ER fluid is to attenuate vibration for low frequency with large amplitude, while the piezoelectric actuator is activated in hish frequency range with small amplitude. A mathematical model of the engine mount is derived using Hydraulic model and mechanical model. After formulating the governing equation of motion, then field-dependent dynamic stiffness of the engine mount is evaluated for various engine speed and excitation amplitude conditions. Then robust controller is designed to attenuate vibration of wide range frequency component. Computer simulation is undertaken in order to evaluate the vibration control performance such as transmissibility magnitude in frequency domains.

• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.3
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• pp.6-11
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• 2005

A household gas valve is used for flow control of LPG(Liquefied Petroleum Gas) or LNG(Liquefied Natural Gas) of which pressure is about $200mmH_2O(\fallingdotseq\;0.0196[bar])$. Currently, two kinds of valves such as rotary type and button type are widely used in many applications. But, these valves have some problems that they are not controllable and reliable. Piezo actuation combined with modem microelectronics provides a reliable, quiet, low energy, infinitely adjustable gas valve. In this paper, gas valve using piezo actuator which are bimorph and a circle type was studied. Also, Prototype for gas valve was manufactured and characteristics of the prototype gas valve were analyzed.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.10
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• pp.1232-1236
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• 2014

Numerical models of fluid dynamics inside the micro actuator chamber and nozzle are presented. The models include ink flow from reservoir, bubble formation and growth, ejection through the nozzle, and dynamics of refill process. Since high tapered nozzle is one of the very important parameters for overall actuator performance design. The effects of variations of nozzle thickness, diameter, and taper angles are simulated and some results are compared with the experimental results. It is found that the ink droplet ejection through the thinner and high tapered nozzle is more steady, fast, and robust.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.306-308
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• 2006

Numerical simulations were carried out of the effects of momentum and heat produced by a plasma actuator on neutral flow. Momentum and heat generated during plasma discharge were modeled as a body force and heat source using results of experiments and DSMC of particle. These force and heat model were inserted into a Navier-Stokes equation and the flow around the plasma actuator could be explored by solving fluid dynamics only. Fluid simulation showed that force produced in DSMC generated a jet flow in the vicinity of the plasma actuator and heat accounted for density change.

• Transactions of The Korea Fluid Power Systems Society
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• v.4 no.2
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• pp.28-33
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• 2007

In the power plant facility which use soft coal as a power source the fan pitch blade control hydraulic actuator is used to control the inlet and outlet gas to regulate the internal pressure of the furnace and control the frequence. Sometimes malfunctions of this equipment lead to the decline of boiler thermal efficiency and unexpected power plant trip. In order to localize the fan pitch blade control hydraulic actuator specially for the 500MW large scale boiler, Analysis and modelling of the system is carried out mathematically. The responses of the system are examined by using matlab simulation fur the variation of the major parameters in view of reverse engineering. Consequently the validity of the established parameters are examined.

• Transactions of The Korea Fluid Power Systems Society
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• v.8 no.1
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• pp.1-9
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• 2011

The main design factors which effect on operating speed of linear actuator for valve operation are mass of plunger, electromagnetic motive force, inductance, and return spring, and these factors are not independent but related with each other in view point of design and electromagnetic theory. It is impossible to increase the operating speed by only change the value of any one design factor. The change of any one value results in change of any value related it in various design factors. This paper presents a speed increasing method of linear actuator using a solenoid design method by some governing equations which are composed of electromagnetic theory and empirical knowledge and permanent magnets as assistant material, and proved the propriety by experiments.