• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.05a
• /
• pp.163-166
• /
• 2002

For the development of an all composite unmanned aerial vehicle (UAV), manufacturing consideration in design phase, works for composite parts fabrication, subassembly and final assembly are summarized. In design phase, to maximize the advantage of composite material, manufacturing processes such as cocuring, cobonding and secondary bonding are introduced. For the curing of designed parts, composite tools are designed and manufactured. Assembly jigs are designed to satisfy dimensional tolerance of the structure. Inspection criteria are established and applied to the manufacturing. Technical data about inspection items and methods are summarized as manufacturing specifications for the mass production of the UAV structure.

• Proceedings of the KIPE Conference
• /
• 2004.07a
• /
• pp.335-340
• /
• 2004

Recently, multilevel H-bridge inverters have become more popular in medium to high power ac drive applications. One of significant advantages of them is low harmonic contents in their input line currents thanks to the transformer with multiple phase-shifted secondary windings. This paper attempts to provide basic guidelines for the design of the phase shifting transformer windings and theoretical analysis of input line current harmonics.

• Proceedings of the KIPE Conference
• /
• 1999.07a
• /
• pp.643-645
• /
• 1999

The conventional high frequency phase-shifted full bridge dc/dc converter has a disadvantage that a circulating current flows through transformer and switching devices during the freewheeling interval. Due to this circulating current, RMS current stress, conduction losses of transformer and switching devices are increased. To alleviate this problem, this paper provides a circulating current free type high frequency soft switching phase-shifted full bridge (FB) dc/dc converter with the modified energy recovery snubber (ERS) attached at the secondary side of transforemr.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.35 no.2
• /
• pp.184-189
• /
• 2022

In this paper, the fault current limiting operations of three-phase transformer type superconducting fault current limiter (SFCL) using double quench, which consisted of E-I iron core with three legs wound by primary and secondary windings and two superconducting modules (SCMs), were analyzed according to three-phase ground fault types. To verify the effective operation of the three-phase transformer type SFCL using double quench, the test circuit for three-phase ground faults was constructed, and the fault current tests were carried out. Through analysis on the fault current test results, the different fault current limiting characteristics of three-phase transformer type SFCL using double quench from three-phase transformer type SFCL using three SCMs were discussed.

• Journal of the Korean Ceramic Society
• /
• v.35 no.9
• /
• pp.995-1001
• /
• 1998

As a basic study for cathode materials of {{{{ { {LiMn }_{2 }O }_{4 } }}-based lithium-ion secondary batteries Li({{{{ { { { {Mn }_{1-$\delta$ }Nb }_{$\delta$} )}_{2 }O }_{4 } }} ($\delta$=0.05, 0.1, 0.2) materials which Nb is substituted for Mn were synthesized by the solid state reaction at 80$0^{\circ}C$ and 110$0^{\circ}C$ respectively. The second phase {{{{ { LiNbO}_{3 } }} appeared above $\delta$=0.1 As the result of im-pedance analysis as the amount of substituted Nb increased the resistivity of grain boundary increased greatly. Compared to undoped-{{{{ { {LiMn }_{2 }O }_{4 } }} the electrical conductivity of Li({{{{ { { { {Mn }_{1-$\delta$ }Nb }_{$\delta$} )}_{2 }O }_{4 } }} decreased slightly but is charging capacity and potential plateau increased.

• Journal of Korean Society for Atmospheric Environment
• /
• v.32 no.4
• /
• pp.349-359
• /
• 2016

Researchers have traditionally assumed that aerosol particles containing secondary organic aerosols (SOAs) are to be in liquid state with low viscosity even at low relative humidity. However, recent measurements showed that SOAs can have high viscosity under certain conditions. Herein, new different techniques for measurements of viscosities of SOA particles are introduced. Moreover, laboratory studies for the viscosities and the phases of biogenic SOAs produced by ${\alpha}$-pinene, isoprene, limonene, and ${\beta}$-caryophyllene of atmospheric relevance are reviewed. Future studies for determination of the phases of atmospheric aerosol particles are also suggested.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.846-848
• /
• 2001

In this paper, electromagnetic fields of a linear induction motor with cage-type secondary are analyzed by the finite element method. Contact resistances between end-bars and secondary conductors are considered in the finite element analysis. The field quantify is a magnetic vector potential transformed into a phasor form. As a result, the sensitivities of a phase current thrust and normal force are presented according to the variation of the contact resistance.

• Journal of the Korean Ceramic Society
• /
• v.22 no.3
• /
• pp.41-45
• /
• 1985

An experimental study has been carried out to investigate the effect of growth rate V and time on secondary dendrite arm spacing of cristobalite dendrites in $14.6K_2O-85.4SiO_2$ glass by means of x-ray diffractormetry optical microscopy and scanning electron microscopy The scanning lectron microscopy reveals a two-phase layer of dendritic crystals and interstitial melt which grow from the surface at a constant rate. Based on this experiment secondary arm spacing is proportional to V-0.24 and dendrite coarsening during isothermal holding shows that the secondary arm spacing increases with increasing heat-treatment time.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.926-927
• /
• 2008

This paper presents the ZVZCS(Zero- Voltage and Zero-Current-Switching) Full-Bridge converter using the secondary coupled inductor and auxiliary capacitor. The converter with phase-shift control is proposed to reduce the circulating loss in primary and the voltage stress in secondary side. Using a coupled winding of the output inductor, two auxiliary capacitors are generated to reset the primary current at circulating interval.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2000.11a
• /
• pp.30-36
• /
• 2000

A numerical study was conducted to investigate the effects of flow parameters in a entrained flow combustor on the flow characteristics. The computational model was based on the gas phase Eulerian equations of mass, momentum and energy. The code was formulated with RNG k-$\varepsilon$ model for turbulent flow. The calculation parameters were the magnitude of primary and secondary jet velocity and the height difference between primary and secondary jet. As the secondary jet velocity increased, the upper recirculation zone of the primary jet was strengthened. It was found that as the primary jet velocity increased, there was a critical jet velocity at which the size of upper and lower recirculation zone was changed.