• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.6
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• pp.246-251
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• 2014

Recent studies have shown methods of improving solar cell efficiency. Especially on single crystalline silicon wafer which is high-efficiency solar cell material that has been widely studied. Interstitial oxygen (Oi) is the main impurity in the Czochralski (Cz) growing method, and excess of this can form precipitates during cell fabrication. We have demonstrated the effect of Oi impurity and oxygen precipitation concentration of the wafer on Cz-silicon solar cell efficiency. The result showed a decrease in cell efficiency as Oi and oxygen precipitation increase. Moreover, we have found that the critical point of [Oi] to bring higher cell efficiency is at 14.5 ppma in non-existent Bulk Micro Defect (BMD).

• Polymer(Korea)
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• v.38 no.6
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• pp.767-773
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• 2014

Rheological and electrical properties of polystyrene (PS)/carbon nanotube (CNT) nanocomposites via coagulated precipitation were investigated. Chemical modification and surfactant wrapping of CNT to improve the dispersion of CNTs may reduce the intrinsic properties of pristine CNT. To avoid this problem, PS and CNTs were dissolved and dispersed in dimethylformamide and then PS/CNT nanocomposites were prepared by the coagulated precipitation of CNT-dispersed PS solution in water. The coagulated precipitation method was highly effective enhancing the electrical conductivity of nanocomposites. Furthermore, the effect of adding poly(styrene-co-divinylbenzene) crosslinked particles to PS matrix on the rheological and electrical properties was investigated. With the addition of the crosslinked particles, the electrical percolation threshold of CNT reduced to 0.25 wt% and electrical conductivity increased further. It is speculated that CNTs in the volume occupied by crosslinked particles helped electrical pathway formation.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.631-646
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• 2021

Increasing incidences of landslides in Korea are endangering life and damaging property. To ascertain the cause of the rapid increase in landslides in 2020, this study analyzed the correlation between frequency of their occurrence and persistence of rainfall. The study area comprised seven areas in Gangwon-do, Gyeonggi-do, Gyeongsangnam-do, Gyeongsangbuk-do, Jeollanam-do, Jeollabuk-do, and Chungcheongnam-do. The used rainfall factors were monthly rainfall in June, July, and August, rainfall during the summer (June-August), rainfall during the monsoon season, and number of precipitation days during the summer and during the monsoon season. The effect of these factors on landslides was identified by comparing them with the occurrence of landslides in the year of increased landslide occurrence in each area. The results confirmed that not only rainfall but also the number of precipitation days during the monsoon season affect the occurrence of landslides. The rapid increase in landslide occurrence in 2020 was attributed to increases in both the number of precipitation days during the monsoon season and rainfall during the monsoon season in 2020. These results are expected to be used as basic data for future landslide warning standards that consider the effect of the persistence of rainfall.

• Korean Journal of Remote Sensing
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• v.32 no.3
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• pp.331-337
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• 2016

Water vapor is main absorption factor of outgoing longwave radiation. So, it is essential to monitoring the changes in the amount of water vapor and to understanding the causes of such changes. In this study, we monitor temporal variability of Total Precipitable Water (TPW) which observed by satellite. Among climate variables, precipitation play an important part to analyze temporal variability of water vapor because it is produced by water vapor. And El $Ni{\tilde{n}}o$ is one of climate variables which appear regularly in comparison with the others. Through them, we analyze relationship between temporal variability of TPW and climate variable. In this study, we analyzed long-term change of TPW from Moderate-Resolution Imaging Spectroadiometer (MODIS) data and change of precipitation in middle area of Korea peninsula quantitatively. After these analysis, we compared relation of TPW and precipitation with El $Ni{\tilde{n}}o$. The aim of study is to research El $Ni{\tilde{n}}o$ has an impact on TPW and precipitation change in middle area of Korea peninsula. First of all, we calculated TPW and precipitation from time series analysis quantitatively, and anomaly analysis is performed to analyze their correlation. As a result, TPW and precipitation has correlation mostly but the part had inverse correlation was found. This was compared with El $Ni{\tilde{n}}o$ of anomaly results. As a result, TPW and precipitation had inverse correlation after El $Ni{\tilde{n}}o$ occurred. It was found that El $Ni{\tilde{n}}o$ have a decisive effect on change of TPW and precipitation.

• Journal of the Korean Chemical Society
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• v.67 no.1
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• pp.33-41
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• 2023

Nanocrystallne WO₃ and MoO₃ with several different sizes and crystal structures were prepared by simple acid precipitation and subsequent heat treatment. The photochromic (PC) properties of these samples were comparatively investigated in powder state by monitoring diffuse reflectance spectral changes after bandgap irradiation. The PC effect of hexagonal WO₃ and monoclinic WO₃ strongly depended upon crystallite size rather than crystal structure. The smaller the crystallite size, the better the PC effect. However, orthorhombic WO·H₂O and MoO₃ having hexagonal and orthorhombic structures did not follow this trend. One consistent result for all WO₃ and MoO₃ samples is that the heat treatment in air, which changes crystallinity, whether it changes the crystal structure or only the crystallite size, reduces the PC effect. Since the thermal treatment reduces the surface oxygen defect sites, we believe that the PC effect of WO₃ and MoO₃ depends critically on the surface oxygen defect sites that serve as deep trap sites for photogenerated electrons and oxygen radical holes. We also found that the proton insertion claimed by double charge injection model is not critical for the PC effect.

• Journal of Korea Water Resources Association
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• v.40 no.7
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• pp.555-570
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• 2007

The effects of climatic changes owing to urbanization on annual water balance have been studied. In this study, 56 meteorological stations including Seoul metropolis in South Korea have been selected, and the area of study site is $314\;km^2$. The meteorological station is centrally located in the study area with a 10 km radius. Land use status of study area was examined to estimate the urbanization extent, so that annual actual evapotranspiration could be estimated. Annual runoff was estimated by annual water balance approach using the estimated annual actual evapotranspiration and measured annual precipitation. Annual actual evapotranspiration was estimated by applying experimental equation suggested by Zhang et al, (2001) which was evaluated from 250 watersheds all over the world. Study results show that reference evapotranspiration is tending upwards due to urbanization; therefore, it seems that climatic change due to urbanization may increase the amount of annual actual evapotranspiration. However, the increase of residential area due to urbanization in study area may decrease the amount of annual actual evapotranspiration. The study results indicate that urbanization effect on annual trend of precipitation was not significant. In urban area, annual runoff is directly affected by annual precipitation, and compared with annual precipitation, annual variation of actual evapotranspiration was not significant even though it was estimated by using annual precipitation. It seems that the effect of urbanization on annual actual evapotranspiration does not influence on annual runoff significantly, and that urbanization effect on annual runoff Is not significant.

• Journal of the Korean Chemical Society
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• v.68 no.3
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• pp.135-138
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• 2024

• Macromolecular Research
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• v.11 no.4
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• pp.241-249
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• 2003

A molecular-thermodynamic model to describe the salt-induced protein precipitation is developed based on the perturbation theory. We employed the modified perturbed hard-sphere-chain (PHSC) equation of state for copolymer mixtures to take into account the pre-aggregation effect among protein particles. Hypothetical pressure-composition diagrams are computed with various size differences and salt concentrations. The precipitation behaviors are also studied for various types of pre-aggregation effect for the given systems.

• Transactions of Materials Processing
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• v.9 no.1
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• pp.66-71
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• 2000

The present study tackles the metallurgical subjects involving the thin slab-direct hot rolling process, i.e. mini-mill process. In order to clarify the effect of chemical composition of steel and MnS precipitation behaviors on the development of edge cracking during hot rolling, the content of manganese and sulfur in low carbon steel was varied and the isothermal treatment prior to roughing was applied. Edge cracking during roughing in the hot-rolling process of mini-mill was effectively prevented by means of the isothermal treatment at 115$0^{\circ}C$ for 5 minutes in the 0.4% manganese steel containing sulfur lower than 0.013%. With the increase in manganese content in low carbon steel, coarser MnS developed. The edge cracking index which denotes the total length of edge crack per unit edge-length of rolled specimens was proposed in this paper. It was found that the edge cracking index linearly decreased with the increase in the ratio of MnS.

• Geomechanics and Engineering
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• v.4 no.2
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• pp.135-150
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• 2012

This paper presents the study of the effect of microorganism Bacillus pasteurii on the properties such as Atterbergs' limit and unconfined compressive strength of cohesive soils. The results of this study reveal that the liquid limit and plasticity index for all clay soils decreased and the unconfined compressive strength increased. Decrease in plasticity index is very high for Kuttanad clay followed by bentonite and laterite. The unconfined compressive strength increased for all the soils. The increase was high for Kuttanad soil and low for laterite soil. After 24 h of treatment the improvement in the soil properties is comparatively less. Besides the specific bacteria selected Bacillus pasteurii, other microorganisms may also be taking part in calcite precipitation thereby causing soil cementation. But the naturally present microorganisms alone cannot work on the calcite precipitation.