• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.182-186
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• 2011

Ejector-diffuser system has long been used in many diverse fields of engineering applications and it has advantages over other fluid machinery, because of no moving parts and structural simplicity. This system makes use of high-pressure primary stream to entrain the low-pressure secondary stream through pure shear actions between two streams. In general, the flow field in the ejector-diffuser system is highly complicated due to turbulent mixing, compressibility effects and sometimes flow unsteadiness. A fatal drawback of the ejector system is in its low efficiency. Many works have been done to improve the performance of the ejector system, but not yet satisfactory, compared with that of other fluid machinery. In the present study, a mixing guide vane was installed at the inlet of the secondary stream for the purpose of the performance improvement of the ejector system. A CFD method has been applied to simulate the supersonic flows inside the ejector-diffuser system. The present results obtained were validated with existing experimental data. The mixing guide vane effects are discussed in terms of the entrainment ratio, total pressure loss as well as pressure recovery.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.119-122
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• 2002

In general, Liquid Injection Thrust Vector Control(LITVC) is accomplished by injecting a liquid into the supersonic exhaust flow through holes in the wall of the propulsion nozzle. This injection flow field is highly complicated and detailed flow physics associated with the secondary flow injection should be known far the practical design and use of the LITVC system. The present study aims at understanding the LTTVC flow field and obtaining fundamental design parameters for LITVC. The experimentations were performed in a supersonic blow-down wind tunnel. Compressed, dry air was used for both the main exhaust and injection flows but the pressures of these two flows were controlled independently. The location of the injection holes was changed and the pressures of the two streams were also changed between 2.0 and 15.0 bar. The effectiveness of LITVC was discussed in details using the results of the pressure measurements and flow visualizations

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.7
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• pp.781-786
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• 2015

In this paper, we analyzed characteristic of window type current transformer and we performed the optimal design consider to the loss; in order to design the current transformer figured signal of overcurrent warning circuit. The core size of window type current transformer was determined by the secondary coil turns. We analyzed current waveform, which is appeared by the number of coil turns on the core, we made sure the relation of secondary coil turns and load resistance in order to improve the non-sinusoidal wave by the flux saturation of the current transformer core. Additionally, we did improvement of the accuracy and optimal design through the transformation of the inner diameter and the stack length when the outer diameter of core is sustaining.

• Journal of Astronomy and Space Sciences
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• v.1 no.1
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• pp.55-65
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• 1984

A total of 618 photoelectric observations (302 in yellow and 316 in bule) is made in 1982 at the Yonsei University Observatory. Except that of the secondary eclipse the homogeneous coverage of observations successfully secured B, V, and B-V light curves. Enhanced distortions in the light curves are appeared at the phases aroung $0.^P1$, which supports the wave-like migration period of 9.7 years(Rodono 1981). One epoch time of the primary minimum was made by combining the observations in three nights. This minimum time shows that the O-C values are still decreasing and there seems to indication of increasing. B and V light curves of the primary minimum are in strong asymmetry which show less luminous in the third and fourth contacts compared to those of the first and second ones. This asymmetry may be as a result of the reflection of the wave minimum at $0.^P1$, and B-V curve also shows asymmetry, redder at the third contact than the second one by about $0.^m04$. This color difference apperature distribution on the surface of cooler, larger component(KO IV star).

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.932-933
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• 2015

This paper presents methods to achieve and control accurate output voltage. PSR removed secondary output voltage sensing circuit, therefore standby power loss can be decreased. When sensing the auxiliary winding voltage, sensing must be done at accurate branch which has $V_O$ information. For this reason this paper presents the PSR sensing technique using sawtooth wave and peak detector. Circuit verification carried out with Spectre in Cadence corporation and Manga/Hynix $0.35{\mu}m$ 700V process.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.726-739
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• 2003

A multi-dimensioanl model is being increasingly used to predict the thermo-flow field in the gas turbine combustor. This article addresses an integrated survey of modeling of the liquid spray formation and fuel distribution in gas turbine with high-shear nozzle/swirler assembly. The processes of concern include breakup of a liquid jet injected through a hole type orifice into air stream, spray-wall interaction and spray-film interaction, breakup of liquid sheet into ligaments and droplet,5, and secondary droplet breakup. Atomization of liquid through hole nozzle is described using a liquid blobs model and hybrid model of Kelvin-Helmholtz wave and Rayleigh-Taylor wave. The high-speed viscous liquid sheet atomization on the pre-filmer is modeled by a linear stability analysis. Spray-wall interaction model and liquid film model over the wall surface are also considered.

• Journal of Korea Multimedia Society
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• v.18 no.3
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• pp.330-338
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• 2015

Gradually increasing the value of the technology, the techniques of the various security systems to protect the core technology have been developed. The proposed security scheme, which uses both a Password and the various devices, is always open by malicious user. In order to solve that problem, the biometric authentication systems are introduced but they have a problem which is the secondary damage to the user. So, the authentication methods using EEG(Electroencephalography) signals were developed. However, the size of EEG signals is big and it cause a lot of problems for the real-time authentication. And the encryption method is necessary. In this paper, we proposed an efficient real-time authentication system applied encryption scheme with junk data using chaos map on the EEG signals.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.7-10
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• 2002

We designed the flyback planar transformer, which had 8W capacity, with 70V input voltage and 8.2V output voltage for the establishment of design method and the confirmation of application possibility. The numerical value of inductance measured under the switching frequency of 120 kHz was 1650 ${\mu}H$, which was the inductance efficiency of 85~87% against theoretical value. The A.C. resistance of primary and secondary coil was 4.2 ${\Omega}$ and 0.25 ${\Omega}$ respectively. On the other hand, the quality factor for each wound numbers showed quite a high value of 158 and 75 respectively. And the Coupling Factor was 0.96~0.97 under 120 kHz switching frequency. And the shape of the output wave of the planar transformer at 70V input voltage was a stable square wave.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.129-132
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• 2005

Reclamation coal ash, which is generated as a byproduct at a coal thermal power plant is not recycled but dumped into an ash landfill disposal site. Furthermore, various byproducts and wastes have been proposed for use from the point of reduction in the environmental load. Authors have started research to develope manufacturing technology of concrete mixture design method with large amount of land reclamation coal ash. In this study an optimum mix proportion design for utilizing the reclamation coal ash and containing copper slags as an aggregate for secondary concrete products such as a wave dissipating blocks was successfully developed.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1033-1035
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• 2003

Linear induction motor with multilayer region of the single-sided is analyzed considering multi region traveling wave problem. A hybrid method of analysis consisting of field analysis in conjunction with the multilayer transfer matrix concept with adjustment of secondary iron permeability to match the tangential magnetizing field in each layer is developed.