• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.6
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• pp.1-10
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• 2013

In this paper, the main cause on excitation of the combustion instability which may occur in the hybrid rocket motor with a diaphragm was studied. Hybrid rocket motor propulsion tests considering various experimental conditions such as with a diaphragm or not, a diameter of diaphragm, oxidizer mass flow rate, fuel length, etc were performed, and the combustion visualization for the inside of a hybrid rocket motor with a diaphragm was performed. With these experimental results, it was confirmed that the main cause of a large excitation was the hole-tone, and it was shown that the hole-tone model can be predicted experimental primary pressure oscillation frequency quite well.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.978-983
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• 2017

Ammonium dinitramide(ADN) is currently under inder investigation as a replacement for ammonium perchlorate, both for environmental and toxicological reasons. Another promising application is ADN-based liquid monopropellant as a replacement for hydarzine, which is highly toxic and carcinogenic. Production of ADN is today normally performed via guanylurea dinitramide(GUDN) by reaction with potassium hydroxide to yiela potassium dinitramide(KDN). In a second reaction step, KDN is reacted with ammonium sulfate to give ADN. In our new improved process, ADN is synthesized from GUDN in one single reaction step. The simplified process improves purity, reduces the amount of by-products and allows production of ADN at a potentially lower cost, which is crucial to favour the use of ADN.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.139-141
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• 2017

By modulating the flow rate of $N_2O$ into a HR motor assembly, a control valve of a hybrid rocket engine plays a role to increase or decrease the thrust. In this study, the control valve has been designed to meet the requirements which are response speed(${\leq}$ about 1 second) and torque(${\geq}$ about $36N{\cdot}m$). Then, when analog signal 0~10V is applied, the situation where the valve is opened and closed has to be realized. To do this, the data values have to be entered into the actuator. Finally, the performance evaluation of the control valve has been performed to validate this product.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1084-1087
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• 2017

When a liquid rocket engine is started the oxidizer and fuel must be flowed into combustion chamber and gas generator with time differences. The wrong time difference between propellants or malfunction of ignition device can occur the explosion of combustion chamber due to detonation by energized premixed-propellants. Therefore it is important to observe the transient characteristic of propellants or to measure the inflow time of propellants into combustion chamber and gas generator. The measurement of static pressure is not enough to observe the propellants inflow time into combustion chamber and gas generator. By measuring dynamic pressure of main flow passage of propellants the accurate propellants inflow time could be investigated.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.9-16
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• 2020

A performance evaluation of the 200 N-class GCH₄/LOx small rocket engine was performed through ground hot-firing test. As a result, the combustion pressure and thrust raised with the increase of the oxidizer supply pressure, and thus the specific impulse, characteristic velocity, and their efficiency increased. The characteristic velocity was measured at about 90% performance efficiency. The change of chamber aspect ratio did not affect the performance of the rocket engine in the test condition specified. In addition, uncertainty evaluation was conducted to ensure the reliability of the test results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.517-527
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• 1989

A theoretical analysis for the characteristics of pyrolysis and combustion of solid fuel was carried out in the present study. The hollow cylindrical combustion model including gas phase and solid fuel at inside and outside respectively was developed for the numerical analysis and parametric studies. The effects of volatile contents in the porous solid fuel and Reynolds number at inlet of gas phase on the characteristics of pyrolysis and combustion such as the radial, axial and time variations of volatile mass flux through porous solid fuel, temperature, mass fractions of gaseous fuel and oxidizer, and flame shape were investigated in the parametric studies. The results of the present study show that the flame produced by the volatiles moves to the downstream of fuel with accelerating velocity with time until extinction is occurred resulting from the completion of pyrolysis. When flame is employed with smaller amount of volatiles content in the solid fuel, the flame sheet exists closer to the inner wall of solid fuel. As Reynolds number at inlet increases, the flame sheet moves to the inner wall due to effect of convection even though the volatiles by pyrolysis increases.

• Journal of the Korean Society of Combustion
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• v.21 no.2
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• pp.22-28
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• 2016

High efficient and environment friendly combustion technologies are used to be operated an extreme condition, which results in unintended flame instability such as extinction and oscillation. The use of electromagnetic energy is one of methods to enhance the combustion stability and a microwave as electromagnetic wave is receiving increased attention recently because of its high performance and low-cost system. In this study, an experiment was performed with jet diffusion flames induced by microwave. Micro jet was introduced to simulate the high velocity of industrial combustor. The results show that micro jet flames had three different modes with increasing oxidizer velocity; attached yellow flame, lifted flame, and lifted partially premixed flame. As a microwave was induced to flames, the overall flame stability and blowout limit were extended with the higher microwave power. Especially the interaction between a flame and a microwave was shown clearly in the partially premixed flame, in which the lift-off height decreased and NOx emission measured in post flame region increased with increasing microwave power. It might be attributed to increase of reactivity due to the abundance of radical pool and the enhanced absorption to thermal energy.

• Journal of the Korean Society of Combustion
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• v.19 no.3
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• pp.44-52
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• 2014

Solid oxide fuel cell(SOFC) makes electric power using hydrogen or reformed from methane and emits high temperature products that contain flammable species like hydrogen, carbon monoxide and methane which varies with operation condition. SOFC/gas turbine integrated system which uses thermal and chemical energy of the discharges is more efficient than SOFC itself. Burning character of the SOFC products will affect the efficiency and stability of the system. Experiments were conducted to know the characteristics of the flame for two typical composition of SOFC products, i.e. start-up and steady state composition. When coflowing air temperature was higher than $600^{\circ}C$, auto-ignitin occurred for both fuels. Though start-up fuel has higher contents of hydrogen, it makes longer flame than steady state composition. It was inferred that the amount of oxidizer necessary to burn makes this phenomenon. Steady state composition fuel was unstable since it contains lots of water. Nozzle that had 6 holes, distance between each hole was 16.7 times of hole diameter, improved the stability of the flame.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.252-255
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• 2004

반도체는 high integrated, high speed, low power를 위하여 design 뿐만 아니라 재료 측면에서도 많은 변화를 가져오고 있으며, RC delay time을 줄이기 위하여 Al 배선보다 비저항이 낮은 Cu와 low-k material 적용이 그 대표적인 예이다. 그러나, Cu 배선의 경우 dry etching이 어려우므로, 기존의 공정으로는 그 한계를 가지므로 damascene 또는 dual damascene 공정이 소개, 적용되고 있다. Damascene 공정은 절연막에 photo와 RIE 공정을 이용하여 trench를 형성시킨 후 electrochemical plating 공정을 이용하여 trench에 Cu를 filling 시킨다. 이후 CMP 공정을 이용하여 절연막 위의 Cu와 barrier material을 제거함으로서 Cu 배선을 형성하게 된다. Dual damascene 공정은 trench와 via를 동시에 형성시키는 기술로 현재 대부분의 Cu 배선 공정에 적용되고 있다. Cu CMP는 기존의 metal CMP와 마찬가지로 oxidizer를 이용한 Cu film의 화학반응과 연마 입자의 기계가공이 기본 메커니즘이다. Cu CMP에서 backside pressure 영향이 uniformity에 미치는 영향을 살펴보았으며, electrochemical plating 공정에서 발생하는 hump가 CMP 결과에 미치는 영향과 dishing 결과를 통하여 그 영향을 평가하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.78-78
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• 2007

In semiconductor devices, Cu has been used for the formation of multilevel metal interconnects by the damascene technique. Also lower dielectric constant materials is needed for the below 65 nm technology node. However, the low-k materials has porous structure and they can be easily damaged by high down pressure during conventional CMP. Also, Cu surface are vulnerable to have surface scratches by abrasive particles in CMP slurry. In order to overcome these technical difficulties in CMP, electro-chemical mechanical planarization (ECMP) has been introduced. ECMP uses abrasive free electrolyte, soft pad and low down-force. Especially, electrolyte is an important process factor in ECMP. The purpose of this study was to characterize KOH and $KNO_3$ based electrolytes on electro-chemical mechanical. planarization. Also, the effect of additives such as an organic acid and oxidizer on ECMP behavior was investigated. The removal rate and static etch rate were measured to evaluate the effect of electro chemical reaction.