• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.215-219
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• 2008

The bonding structure and composition of silicon nitride (SiNx) films were investigated by using Fourier transform infrared spectroscopy (FT-IR). SiNx films were deposited on Si substrate at $340^{\circ}C$ using a conventional PECVD system. The compositions of Si and N in SiNx films were confirmed by using Rutherford backscattering spectroscopy (RBS) and photoluminescence (PL) analysis. The surface morphology of SiNx films was also analyzed by using atomic force microscopy (AFM). It was found that the contents of NH(at. %) is the reverse related with those of SiH corresponding to the result of FT-IR. we conclude that a quantitative analysis on SiNx films can be possible through a precise detection of the contents of H in SiNx films with a FT-IR analysis only.

• Journal of the Korean Ceramic Society
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• v.25 no.2
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• pp.143-153
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• 1988

In order to synthesize the partially stabilized $\alpha$-Sialon, A1N and Y2O3 were added to synthesized $\alpha$-Si3N4. The phase composition, mechanical properties, micro structure, etc, of the synthesized $\alpha$-Sialon were investigated. Partially stabilized $\alpha$-Sialon ceramics could be synthesized from the composition which was a little deviated from x=0.4, x=0.6 composition along the Si3N4.0.1Y2O3:0.9AlN tie line at 1750-180$0^{\circ}C$ for 2 hrs in N2 atmosphere. It is assumed that A1N is more closely related than Y2O3 to the formation of $\alpha$-Sialon, and that A1N is more easily dissolved into $\alpha$-structure than into $\beta$-structure. In Ya2O3-rich phase mechanical properties were observed to be poor because of formation of mellilite, grain growth, and thermal decomposition of $\alpha$-Sialon. The maximum values of M.O.R, KIC and hardness are 723 MPa, 4.5MN/㎥/2 and 19.3 GPa, respectively, and they were observed for the $\alpha$-Sialon ceramics sintered at 178$0^{\circ}C$.

• The Korean Journal of Ecology
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• v.25 no.2
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• pp.83-91
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• 2002

This study was carried out to classify forest vegetation of the Mt. Naeyeon with phytosociological analysis of ZM school and to explain ordination of communities with CCA. The research sites were located between the northern part of Pohang-si area and the southern part of Yeongdeok-gun area. The 70 plots consisted of 253 species were investigated. The forest vegetation was classified into Quercus mongolica community, Q. variabilis community, Pinus densiflora community, Carpinus laxiflora community and Zelkova serrata community. Q. mongolica community was divided into 2 groups such asRhododendron schlippenbachii group and Euonymus oxyphyllus group and Q. variabilis community was divided into 3 groups such as Syneilesis palmata group, Lespedeza × tomentilla group and Tilia mandshurica group, and Z. serrata community was divided into 2 groups such as Carpinus cordata group and Diospyros lotus group. According to the results of CCA ordination, Q. mongolica community showed high positive correlation to altitutde and topography, whereas it showed negative correlation to bare rock. Buck Z. serrata community showed the opposite tendency to Q. mongolica community. Altitude was considered as the most important factor among 5 environmental variables in the correlation with axes.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.72-80
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• 2001

In this paper, we present a systematic method of extracting the input parameters of poly-Si TFT(Thin-Film Transistor) for Spice simulations. This method has been applied to two different types of poly-Si TFTs such as ELA (Excimer Laser Annealing) and SMC (Silicide Mediated Crystallization) with good fitting results to experimental data. Among the Spice circuit simulators, the PSpice has the GUI(graphic user interface) feature making the composition of complicated circuits easier. We added successfully the poly-Si TFT model of AIM-Spice to the PSpice simulator, and analyzed easily to compare the electrical characteristics of pixels without or with the line RC delay. In the comparative results, the ELA poly-Si TFT is superior to the SMC poly-Si TFT in the charging time and the kickback voltage for the TFT-LCD (Thin Film Transistor-Liquid Crystal Display).

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.192-194
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• 2006

To elucidate possible challenges for outdoor practical use of dye-sensitized solar cells(DSC), compared with conventional Si solar cells. DSC modules still need the larger area than conventional Si solar modules to attain the same rated output because of lower photoelectron-chemical conversion efficiency. However, using batteries backup systems, the measured data shows that DSCs gathered over 12% more electricity than Si solar cells of the same rated output power in same outdoor condition. Moreover, battery charging time of DSC is about 1 hour faster than same rate of Si solar module. In this paper, 12 single DSC cells prepared for 4 serialized DSC cells was connected in 3 row parallel which have same output power rate of Si solar module. This DSC module was practiced generating characteristic experiment over outdoor daylight condition and applied with PV battery charger by using DC-DC converter. The main advantages of DSC module battery charger as compared with conventional Si solar module one are shorter charge time and lower cost.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2006.05a
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• pp.236-240
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• 2006

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.63.2-63.2
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• 2010

삼중접합 태양전지에 상부전지로 이용되는 a-SiO:H 태양전지는 PECVD(Plasma Enhanced Chemical Vapour Deposition)을 이용하여 증착하였다. i a-SiO:H는 $CO_2/SiH_4$ 비율을 변화하여 밴드갭을 조절하였다. $CO_2/SiH_4$가 0에서 0.43으로 증가 할수록 밴드갭이 1.74 eV에서 1.94 eV로 증가하는 경향을 보였다. 이는 FTIR에서 나타난 결과인 Si-O-Si 결합의 증가 때문인 것으로 판단한다. 그에 반해서 광 전도도는 감소하는 경향을 보였다.그러나 암전도도와 광전도도의 비율인 광민감도는 $10^5$에서 $10^4$의 값으로 비정질 태양전지에 적용가능한 값을 보였다. 이러한 박막 특성을 가진 i a-SiO:H를 이용하여 비정질 실리콘 태양전지를 제작한 결과 $CO_2/SiH_4$의 비율이 증가함에 따라 태양전지의 $V_{oc}$가 0.8 V에서 0.5 V로 현저하게 감소하였고, $J_{sc}$와 FF 역시 11 $mA/cm^2$에서 4 $mA/cm^2$, 69%에서 50%로 감소하였다. 단위박막 결함을 측정하는 CPM(Constant Photocurrent Method)을 이용하여 i a-SiO:H 내부에 $10^{16}cm^{-3}$ 정도의 내부 결함을 관찰하였고 이는 태양전지의 특성 감소와 관련이 있는 것으로 판단한다.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.3
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• pp.40-53
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• 2013

Most of the existing domestic studies to identify the distribution of longevity population and influencing factors oriented confirmatory approach. Furthermore, most of the studies in this research topic simply have used their own definition of spatial unit of analysis or employed arbitrary spatial units of analysis according to data availability. These research approaches can not sufficiently reflect the spatial characteristic of longevity phenomenon and exposed to the Modifiable Aerial Unit Problem(MAUP). This research performed the Exploratory Spatial Data Analysis(ESDA) to identify the spatial autocorrelation of the distribution of longevity population and investigated whether the modifiable areal unit problem in the aspect of scale effect using spatial population data in Korea. We used Si_Gun_Gu and Eup_Myeon_Dong as two different spatial units of regional longevity indicators measured. Then, we applied Getis-Ord Gi* to investigate the existence of spatial hot spots and cold spots. The results from our analysis show that there exist statistically significant spatial autocorrelation and spatial hot spots and cold spots of regional longevity at both Si_Gun_Gu and Eup_Myeon_Dong levels. This result implies that the modifiable areal unit problem does exist in the studies of spatial patterns of longevity population distribution. The demand for longevity researches would be increased inevitably. In addition, there were apparent differences for the global spatial autocorrelation and local spatial cluster which calculated different spatial units such as Si_Gun_Gu and Eup_Myeon_Dong and this can be seen as scale effect of MAUP. The findings from our analysis show that any study in this topic can mislead results when the modifiable areal unit problem and spatial autocorrelation are not explicitly considered.

• Journal of the Korean Geographical Society
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• v.50 no.5
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• pp.485-503
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• 2015

This study aims at evaluating geomorphological classification systems to predict the occurrence of landslides in mountainous region in Korea. Geomorphological classification systems used in this study are Catena, TPI, and Geomorphons. Study sites are Gapyeong-gun, Hoengseong-gun, Gimcheon-si, Yeoju-si/Yicheon-si in which landslide occurrence data were collected by local governments from 2001-2014. Catena method has objective classification standard to compare among regions objectively and understand the result intuitively. However, its procedure is complicated and hard to be automated for the general public to use it. Both TPI and Geomorphons have simple procedure and GIS-extension, therefore it has high accessibility. However, the results of both systems are highly dependent on the scale, and have low relevance to geomorphological formation process because focusing on shape of terrain. Three systems have low compatibility, therefore unified concept are required for broad use of landform classification. To assess the effectiveness of prediction on landslide by each geomorphological classification system, 50% of geomorphological classes with higher landslide occurrence are selected and the total landslide occurrence in selected classes are calculated and defined as 'predictive ability'. The ratio of terrain categorized by 'predictive ability' to whole region is defined as 'vulnerable area ratio'. An indicator to compare three systems which is predictive ability divided by vulnerable area ratio was developed to make a comprehensive judgment. As a result, Catena ranked the highest in suitability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.222-223
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• 2006

고전압 전기기기의 열화는 여러 가지 요인에 의해 발생한다. 따라서 여러 환경 요인에 영향을 비교적 적게 맡는 절연재료 개발에 의한 절연성능 항상은 그동안 많은 연구자들의 관심의 대상이 되어왔다. 최근 고분자 수지 내에 나노 크기의 충진제를 혼합하여 절연성능 및 기계적, 열적 특성을 향상시키는 연구가 점차 활성화되고 있다. 그러나 나노 크기 입자의 활용은 분자단위 크기의 입자가 가지는 Van der Waals력의 문제로 인하여 전기기기의 절연재료로 활용하기에는 어려운 점이 나타나고 있다. 본 논문에서는 에폭시/$SiO_2$ 나노복합재료를 제조하여 분산시간에 따른 입자의 문산 상태를 살펴보았다.