• Tribology and Lubricants
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• v.25 no.2
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• pp.96-101
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• 2009

In order to improve leakage characteristic, angled-circumferential-groove pump seal is suggested. CFD analysis using FLUENT has been performed to predict leakage and determine an optimum slanted-groove angle $\alpha$ which yields the best leakage reduction. The optimum value of $\alpha$ ranges from $45^{\circ}$ to $60^{\circ}$ and depends on the pressure difference of seal and number of grooves for the same groove geometry. The maximum leakage reduction ratio increases as increasing the pressure difference of angled-circumferential-groove pump seal with the optimum value of $\alpha$.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.118-125
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• 1992

The ground deformation due to the tunnel excavation is dependent on various factors such as ground condition, geometry of the tunnel, excavation method, installation of support members, construction condition of each excavation stage, etc. And the distance from the facing effects significantly the stress conditions of the supported and unsupported ground due to the 3-dimensional structural nature of the excavated tunnel. The concept of ground characteristic line has been applied to properly consider the loading condition given by staged tunnel excavation so that the imaginary supporting pressure is applied against the surface of excavated ground. Discussions on the results of the performed finite element analysis were mainly made with respect to the ground settlement, tunnel displacement, earth pressure, stress mobilized in supporting members.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.599-606
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• 2010

It has been reported that many slope failures in unsaturated soils are mainly caused by downward infiltration due to rainfall. The rainfall characteristics could be an important factor, and more predictable slope failures can be achieved by considering more reasonable rainfall conditions. So, a need exists that these trends of infiltration in weathered soils, which is commonly found in Korea, are assessed by considering rainfall conditions based on phenomenological approach. In this paper, numerical analyses of unsaturated soil slope under rainfall conditions are presented based on the soil-water characteristic curve in the laboratory and huff method. Then the performance of unsaturated weathered soil slopes was evaluated under various conditions after applying the effect of overburden pressure on SWCCs and fines contents. The results demonstrated that the rainfall conditions using Huff method can be very effective and the proper application on analysis is very important to enhance the prediction on unsaturated slope stability.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.82-97
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• 2009

In this study, a linearlized model of liquid rocket engine specifically for the gasgenerator cycle one was developed to serve as a basic control model. A commercial software Simulink was used for the modeling. Using this tool we studied the throttling characteristic of engine around its nominal mode. To obtain the effect of the throttle valve design on the engine's control characteristic, we included mathematical model of the control valve with driving motor and the pressure stabilizer which installed on the gas-generator fed line to sustain the mixture ratio of the gas-generator.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1439-1447
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• 1994

Test results of friction-factor for the flow of air in a narrow channel lined with various honeycomb geometries show that, generally, the friction-factor is nearly constant or slightly decreases as the Reynolds number(or Mach number) increases, a characteristic common to turbulent flow in pipes. However, in some test geometries this trend is remarkably different. The friction factor dramatically drops and then rises as the Mach number increases. This phenomenon can be characterized as a "friction-factor jump." Further investigations of the acoustic spectrum indicate that the "friction-factor jump" phenomenon is accompanied by an onset of a normal mode resonance excited coherent flow fluctuation structure, which occurs at Reynolds number of the order of $10^4$. New empirical friction-factor model for "friction-factor jump" cases is developed as a function of Mach number and local pressure.ach number and local pressure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.154-159
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• 2012

For numerical analysis of the plate heat exchanger, a lot of time are required in modeling work and calculation. Whereas, this paper was purposed to identify characteristic of the plate heat exchanger through simplification of modeling by interpreting the numerical analysis proximity with the actual model. This study was also examined temperature difference between inlet side and outlet side, inner pressure drop, heat transfer area of plate and change of heat transfer coefficient on the plate depending on the inner corrugation angle and corrugation pitch of a herring bon pattern of the plate heat exchanger among chevron types of the plate exchanger.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.262-265
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• 2003

This Study is focused on the instrumenting Hybrid Rocket Motor of ACPL at Konkuk University and researching combustion instability by measuring regression rate versus oxidizer mass flux. In the result of experiment, test fire was moderate and we could acquire data of pressure, thrust, and temperature of combustion chamber. In the future, studying unsteady change of regression rate and pressure characteristic analysis of combustion chamber through hundreds of experiments should be performed. furthermore, researching characteristic velocity by taking a measurement of combustion temperature will be inevitable.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.311-315
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• 2012

In these days, promising renewable energy, wind turbine is clean energy but has an environmental pollutant which is noise. Noise assessment is one of the major performance evaluations for wind turbine and nowadays, developing and research for measurement and method of the assessment considering environmental pollutants is being important. Object in this study is that figuring out sound power characteristic of the gearbox for wind turbine through measuring sound intensity. In back-to-back test, we can figure out the noise characteristic of the gearbox for wind turbine through comparing and measuring sound pressure level, sound power level in operating at the each load condition respectively.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.162-167
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• 2006

Hot embossing lithography(HEL) has the production advantage of comparatively few process step, simple operation, a relatively low cost for embossing tools(Si), and high replication accuracy for small features. In this paper, we considered the nano-molding characteristic according to molding parameters(temperature, pressure, times, etc) and induced a optimal molding condition using HEL. High precision nano-patter master with various shapes were designed and manufactured using the DRIE(Deep Reactive ion Etching), LPCVD(Low Pressure Chemical Vapor Deposition) and thermal oxidation process, and we investigated the molding characteristic of DVD and Blu-ray nickel stamp. We induced flow behaviors of polymer, rheology by shapes and sizes of the pattern through various molding experiments. Finally, with achieving nano-structure molding with high aspect ratio, we will secure a basic technology about the molding of large-area nano-pattern media.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2000.04a
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• pp.97-102
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• 2000

We have studied etching characteristic of Ta film using Electron Cyclotron Resonance (ECR) etcher system. Microwave source power. RF bias power. and working pressure were varied to investigate the etch Profile. And we have used two step etching method to acquire the goWe have studied etching characteristic of Ta film using Electron Cyclotron Resonance (ECR) etcher system. Microwave source power. RF bias power. and working pressure were varied to investigate the etch Profile. And we have used two step etching method to acquire the good etch profile preventing the microloading effect.od etch profile preventing the microloading effect.