• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.331-336
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• 2008

Magnetic path direction in the back-iron of a linear induction motor(LIM) is perpendicular to that of the lift-magnet of the MAGLEV which is recently developing in KOREA. In general the back-iron is isolated magnetically in conventional rail in order to eliminate the thrust dependency of the LIM on the lift force. However the magnetic isolation causes some increase in construction and management cost. So a unit-type rail system is considered, which the magnetic circuit of the back-iron is sharing that of the lift-magnet. In this paper 3-dimensional analysis for the lift-magnet is carried out using finite element method. As a result, a new shape of the unit-type rail is presented to reduce the magnetic dependency between thrust force and lift force. Also the distribution of magnetic flux density vectors and current-lift force characteristics are presented.

• 한국재료학회지
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• 제2권1호
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• pp.76-82
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• 1992

$TEOS-O_3$ 산화막은 깔개층 물질에 따라 증착속도가 변하는 특성을 나타낸다. 본 논문에서는 $TEOS-O_3$ 산화막의 깔개층 물질 의존성 이외에도 배선 밀도, 배선 간격에 따라 증착속도가 달라지는 패턴 의존성에 대하여 조사하였다. 또한 $TEOS-O_3$ 산화막의 깔개층 물질 의존성 및 패턴 의존성을 줄이기 위해 다층 배선에서 1차 배선후에 깔개층, 즉 TEOS-base 프라즈마 산화막 및 $SiH_4-base$ 프라즈마 산화막을 증착했을 때 $TEOS-O_3$ 산화막의 증착 특성을 조사하였다. 그리고 그 깔개층 물질에 $N_2$ 프라즈마 처리를 했을 때 $TEOS-O_3$ 산화막의 증착 특성에 대해 조사하였다. 그 결과 $TEOS-O_3$ 산화막에서 기판 위에 배선 밀도와 배선 간격에 따른 의존성은 깔개층물질이 $SiH_4-base$ 일때보다 TEOS-base 프라즈마 산화막인 경우 $N_2$ 프라즈마 처리를 하면 깔개층 물질 표면이 O-Si-N화 되므로써 의존성이 사라지게 된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.879-881
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• 1999

Radical and ion densities in a CF4 plasma have been calculated as a function of input power density. 9as pressure and feed gas flow rate using simple 0 dimensional global model. Fluorine atom is found to be the most abundant neutral particle. Highly fragmented species such as CF and CF+ become dominant neutral and ionic radical at the high power condition. As the pressure increases. ion density increases but ionization rate decreases due to the decrease in electron temperature. The fractional dissociation of CF4 feed gas decreases with pressure after increasing at the low pressure range. Electron density and temperature are almost independent of flow rate within calculation conditions studied. The fractional dissociation of CF4 monotonically decreases with flow rate. which results in increase in CF3 and decrease in CF density. The calculation results show that the SiO2 etch selectivity improvement correlates to the increase in the relative density of fluorocarbon ion and neutral radicals which has high C/F ratio.

• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 하계학술발표회 논문집
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• pp.285-286
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• 2007

Current distributions according to electrode patterns in vertical structured InGaN/GaN LED (light emitting diode) were investigated quantitatively by utilizing three dimensional electrical circuit modeling method. The uniformity of the injected current density in the active layer was compared among different electrode patterns. It was found that the current uniformity was greatly dependent on the electrode pattern in vertical InGaN/GaN LEDs.

• Journal of Ecology and Environment
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• 제33권4호
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• pp.317-323
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• 2010

Nutrient availability is a critical component of agroecosystems, and is relevant to both above- and below- ground interactions. The principal objective of this study was to determine how the cessation of fertilization affects the communities of weeds and soil organisms in a corn/wheat field. Changes in dominant weed species, substrate-induced respiration, and the population density of nematodes and microarthropods were evaluated. Microbial substrate-induced respiration (SIR) and the population density of microarthropods decreased following the cessation of fertilization and were partly correlated with the aboveground weed biomass. The cessation of organic fertilizer application but continuing application of inorganic fertilizer reduced the population density of nematodes. In response to the cessation of fertilization, weed communities were dominated by species with little dependency on fertilization. Amaranthus retroflexus was identified as the most dominant species in the corn field; however, it was replaced by Digitaria ciliaris after the cessation of fertilization. In the wheat field, the cessation of fertilization led to a rapid reduction in the biomass of most weeds, except for Vicia angustifolia, supposedly as the result of symbiotic nitrogen fixation. Additionally, the fact that weed biomass was partially correlated with SIR or the population density of microarthropods may reflect a mutual feedback between soil organisms and weeds. The results indicate that the cessation of fertilization alters communities of weeds and soil organisms through changes in weed biomass and interactions with symbiotic microorganisms.

• East Asian Economic Review
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• 제27권1호
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• pp.33-60
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• 2023

This paper analyzes the entire distribution of stock market returns/volatility in five emerging markets (ASEAN5) and figures out the conditional distribution of the CHI_EPU index. The aim is to examine the impact of CHI_EPU on the stock returns/volatility density of ASEAN5 markets. It also examined whether changes in CHI_EPU explain returns at higher or lower points (abnormal returns). This paper models the behaviour of stock returns from March 2011 to June 2018 using a non-parametric conditional density estimation approach. The results indicate that CHI_EPU diminishes stock returns and augments volatility in ASEAN5 markets, except for Malaysia, where it affects stock returns positively. The possible reason for this positive impact is that EPU is not the leading factor reducing Malaysian stock returns; but, other forces, such as dependency on other countries' stock markets and global factors, may have a positive impact on stock returns (Bachmann and Bayer, 2013). Thus, the risk of simultaneous investment in Chinese and ASEAN5 stock markets, except Malaysia, is high. Further, the degree of this influence intensifies at extreme high/low intervals (positive/negative tails). The findings of this study have significant implications for investors, policymakers, market agents, and analysts of ASEAN5.

• Communications for Statistical Applications and Methods
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• 제21권2호
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• pp.183-191
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• 2014

We define a multivariate Cauchy distribution using a probability density function; subsequently, a Ferguson's definition of a multivariate Cauchy distribution can be viewed as a characterization theorem using the characteristic function approach. To clarify this characterization theorem, we construct two dependent Cauchy random variables, but their sum is not Cauchy distributed. In doing so the proofs depend on the characteristic function, but we use the cumulative distribution function to obtain the exact density of their sum. The derivation methods are relatively straightforward and appropriate for graduate level statistics theory courses.

• Journal of the Optical Society of Korea
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• 제16권2호
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• pp.181-184
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• 2012

We report, for the first time, operation frequency dependence of current density-voltage ($J_{OLED}-V_{OLED}$) shift for multi-layer organic light-emitting diodes (OLEDs). When the OLEDs were electrically stressed for 21 hours with 50% duty voltage pulses at 60, 120, 240, and 360 Hz, the JOLED-VOLED shifts were suppressed by half for 360 Hz operation compared with 60 Hz operation, but with little change in emission efficiencies. This frequency dependent $J_{OLED}-V_{OLED}$ shift is believed to be commonly observed for typical multi-layer OLEDs and can be used to further improve lifetime of digitally-driven active-matrix OLED displays.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.556-559
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• 1999

In order to investigate the influence on dielectric characteristic due to physical structural change of specimens, we investigated the frequency and temperature dependency of tan $\delta$ for virgin specimen and mixtured specimens in the temperature range of 25[$^{\circ}C$] ~ 120[$^{\circ}C$], frequency range of 300(mv) ~ 1500[mV] An experimenatal specimen is selected as Low Liner Density Polyethylene (LLDPE) and Ethylene Vinyl Acetate(EVA) (thickness 200[$\mu$m]) produced by mixture ratio of 50:50, 60:40, 70:30 and 80:20. From the results of XRD it can be confirmed that the peak of LLDPE and EVA made by mixture ratio of 70:30 at 2$\theta$= 21.4$^{\circ}$is higher and the peak made by amorphous contribution at 2$\theta$= 19.5[$^{\circ}$] is almostly constant without no concern.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.29-32
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• 2000

In this paper, an analytical model for I-V characteristics of a HEMTs is Proposed. The developed model takes into account the temperature dependence of drain current. In high-speed ICs for optical communication systems and mobile communication systems, temperature variation affects performance; for example the gain, efficiency in analog circuits and the delay time, power consumption and noise mrgin in digital circuits. To design such a circuit taking into account the temperature dependence of the current-voltage characteristic is indispensible. This model based on the analytical relation between surface carrier density and Fermi potential including temperature dependent coefficients.