• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.77-82
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• 2003

The ac loss is an important issue in the design of high-Tc superconducting power devices such as transformers and cables. In these devices many Bi-2223 tapes are closely stacked together and exposed to alternating magnetic fields that can have different orientations with respect to a tape. In such arrangement the magnetization loss is influenced by the screening current induced in adjacent tapes and thus different from that in a single tape. This stacking effect was experimentally investigated by measuring the magnetization loss in a stack, which consists of a number of tapes. First the magnetization loss in the single tape was measured in order to confirm the reliability of the loss data measured in the stack. The results for the single tape coincide well will the loss characteristics described in other previous works. For the stack In parallel and longitudinal magnetic fields the measured loss is Independent of both the number of tapes and stacking type. The longitudinal magnetization loss Is well explained rather by the slab model for decoupled filaments. For the tall stack in perpendicular field the measured loss at low fields is greatly decreased, compared to the loss of the single tape. However the loss at high fields is unaffected. These loss behaviors in the tall stack are well described by the slab model for full coupling.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.267-270
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• 2005

We investigate the spectral energy distributions (SEDs) of low mass-loss rate O-rich asymptotic giant branch (AGB) stars using the infrared observational data including the Infrared Space Observatory (ISO) data. Comparing the results of detailed radiative transfer model calculations with observations, we find that the dust formation temperature is much lower than 1000 K for standard dust shell models. We find that the superwind model with a density-enhanced region can be a possible alternative dust shell model for LMOA stars.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.163-165
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• 2012

Korea is now the country with shortage of electric power because of limits on power usage of businesses to prevent a possible blackout during the summer and winter. This is due to the failure to predict the total power usage. And the futhermore several accidents in the power plant during the overhaul maintenance threaten the stable power supply. Accidents were due to the combustion of low calorific coal and the shortage of the maintenance time. We should not incur a future great loss by pursuing a present small profit.

• Macromolecular Research
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• v.12 no.3
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• pp.290-292
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• 2004

Multimode channel waveguides were fabricated using a direct UV patterning technology from thick films deposited by the one-step dip-coating of an organic/inorganic hybrid material (ORMOCER(equation omitted). The core size of the covered ridge waveguide was 43${\times}$51 $\mu\textrm{m}$$^2$; the waveguides can be readily prepared for multimode applications by direct UV patterning. The waveguides exhibited smooth surface profiles and a low optical loss of 0.07 ㏈/cm at the most important wavelength (850nm) used for optical interconnects.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.153-155
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• 1994

This paper presents a new low loss snubber including the overvoltage snubber for three-level GTO inverters. The proposed snubber can not only minimizes the snubber loss and the number of components but also improve blocking voltage balancing problem between the inner and the outer GTOs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1287-1293
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• 2008

Antenna switch module(ASM) for quad-band was developed. This module was integrated by RFIPD(RF integrated passive device) and transistor switch instead of LTCC-type device using low pass filters, diodes and passive elements in RF front end module for cellular phone. This module leads to low cost and miniaturization(The area is $5{\times}5\;mm$ and the thickness is 0.8 mm). The insertion loss and the return loss of each band were averagely measured as 1.0 dB(insertion loss), 15.1 dB(GSM/EGSM return loss) and 19 dB(DCS/PCS return loss), respectively.

• Journal of KSNVE
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• v.4 no.3
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• pp.377-384
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• 1994

This paper is an investigation of the performance of absorption diffusers to suppress the vent noise emitted when high pressure gas is throttled. First, experiment for the static performance is carried out. When there is no through-flow, the insertion loss has been obtained in terms of 1/3 octave band spectrum and the effect of the number of diffusers and the thickness of the absorption material on the static performance has been obtained. And the similarity in the spectrum of the static insertion loss is confirmed by comparing two similar models with different size. Second, the dynamic performance has been obtained by experiment using blow-down of compressed air from a storage tank through an orifice of diameter 10 mm. The back pressure by the diffuser is measured and compared with that of a single diffuser. It is found that the insertion loss of asingle diffuser is very low around 3 dB at high frequencies with negative value at low frequencies. By absorption material between the diffuser tubes, however, the performance is increased considerably. Without flow the static insertion loss increases by 3 - 4 dB by doubling the thickness or the density of the absorptionmaterial. With flow, however, the dynamic insertion loss increases. While, the back pressure by the diffuser is small enough to be neglected.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.133-138
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• 2014

This paper proposes a low power-loss averaging current mode control using a resistor and bypass switch. Generally, current sensing method using a resistor has a disadvantage of power loss which degrades the efficiency of the entire systems. On the other hand, proposed measurement technique operating with bypass-switch connected in parallel with sensing resistor can reduce power loss significantly the current sensor. An analog-circuited bypass driver is implemented and used along with an average-circuit mode controller. The bypass switch bypasses the sensing current with a small amount of power loss. In this paper, a 50[W] prototype average current mode boost converter has been implemented for the experimental verification.

• Korean Journal of Materials Research
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• v.13 no.8
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• pp.531-536
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• 2003

The electromagnetic properties and microstructures of the ferrites based on ($Ni_{0.2}$ $Cu_{0.2}$ $Zn_{0.6}$)$_{1.085}$($Fe_2$$O_3$)$_{0.915}$ were investigated by changing the amount of additive SnO$_2$and CaO and the sintering temperatures. Addition of $SnO_2$caused pores in the specimen. There was no variation of grain size by changing the amount of additives. Total loss was reduced when ($Ni_{0.2} $Cu_{0.2}$ $Zn_{ 0.6}$)$_{1.085}$ ($Fe_2$$O_3$)$_{0.915}$ composition was sintered at $1150^{\circ}C$ rather than $1300^{\circ}C$. Addition of CaO was useful to reduce the total loss because it increased the sintering density. The lowest total loss was obtained when 0.06 wt% $SnO_2$and 0.4 wt% CaO were added at the same time.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.1
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• pp.9-14
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• 2012

In this study, the diplexer used a separator or a combine of signals was designed and its characteristics were investigated. The diplexer consists of two fixed tuned bandpass filter such as low pass filter(LPF) and high pass filter(HPF) sharing a common part and was simulated. The diplexer with micro-strip structure was fabricated. The LPF of diplexer has insertion loss of -0.4 dB, return loss of -30 dB and 1.6 GHz cut-off frequency and HPF has insertion loss of -0.8 dB, return loss of -30 dB and 1.9 GHz cut-off frequency, respectively.