• Bulletin of the Korean Chemical Society
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• 제19권12호
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• pp.1359-1363
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• 1998

The p-fluorobenzyl radical was generated from the p-fluorotoluene and vibronically excited in a corona excited supersonic expansion with inert buffer gases. The vibronic emission spectra of the jet cooled p-fluorobenzyl radical in the D1 → D0 transition have been observed in the visible region. The spectra exhibit several low frequency sequence bands in the vicinity of the every strong vibronic band. The characteristics of the sequence bands have been examined by varying the experimental conditions such as carrier gas and nozzle size to identify the origin of the transition in the spectra.

• Bulletin of the Korean Chemical Society
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• 제17권8호
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• pp.682-685
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• 1996

Photothermal properties depend on the characteristics of energy transfer processes in solution. In this study, a time-resolved single beam thermal lens experiment in various solvents is employed to investigate the energy coupling effects which govern the energy transfer processes. Interestingly, it is observed that the behaviour of the photothermal propagation in solution depends on the property of solution and the concentration of solute in a single beam thermal lens configuration. These characteristics lead us to consider the solute-solvent coupling effects as well as the solvent-solvent interactions.

• 한국유기농업학회지
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• 제9권1호
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• pp.61-73
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• 2001

This study was conducted to investigate the effect of sewage sludge application on the growth of chinese cabbage and the changes of chemical properties of soil. The experiment were set up with two different place and cultivated from Feb. 10 to June. 20 of 2000. Treatments are 0, 1.25, 2.5, 5, 10 and 20kg/3.3$\m^2$ of sewage sludge applicated into the soil and recorded the growth characteristics. Chemical properties of soil were also analysed before and after treatment. The application of the sewage sludge resulted in increasing the content of EC, cations exchange capacity, available phosphate and organic matter. And increased the growth characteristics in terms of the number of leaves, leaf area, fresh and dry weight regardless of crops experiments. Optimum amount of the sewage sludge depended on chemical properties of soil used. This results demonstrated that application of sewage sludge in the soil attribute to have play an important both improving soil chemical properties and promoting the crop growth. As lowering the soil pH(pH 6) heavy metal content increased compared with higher pH(pH 7). Feasibility was recognized in the application of sewage sludge as a fertilizer for the growth of chinese cabbage. Detrimental effects such as heavy metal in the soil and crop followed by the application of sewage sludge was not observed.

• 한국토양비료학회지
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• 제45권1호
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• pp.98-102
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• 2012

Organic farming has rapidly increased in Gangwon province, but there is a concern about nutrient accumulation and nutrient imbalance in the soil of organic farming. This study was conducted to investigate the impact of continuous application of organic amendments on growth and yield of red pepper and soil characteristics compared with chemical fertilizers application for four years. Treatments of organic amendments including oil cake, rice straw compost, amino acid compost, rice bran compost, and mushroom media (spent substrate) compost resulted in comparable growth and yield of pepper to chemical fertilizers. Organic amendments improved soil physical and chemical characteristics. Especially, rice bran compost and oil cake significantly increased soil organic matter compared with chemical fertilizer application and mushroom media compost and rice straw compost significantly improved soil aggregate stability. On the other hand, available phosphate level in the soil amended with rice bran compost or mushroom media compost was relatively high compared with the other treatments due to relatively high phosphate levels in the composts. It is not easy to adjust nutrient composition in the organic materials. Therefore, the results obtained from the study imply that nutrient imbalance needs to be carefully considered in organic farming without use of chemical fertilizers.

• 지질공학
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• 제27권4호
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• pp.451-462
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• 2017

Physical weathering caused by external forces and chemical weathering caused by the decomposition or alteration of constituent materials are the two factors that dominate the mechanical properties of rocks. In this study, a field investigation was undertaken to identify the physical and chemical weathering characteristics of the biotite granite and granitic weathered soils in Gyeongju, South Korea. Samples were collected according to their grade of weathering and subjected to modal analysis, XRD analysis, XRF analysis, physical property tests, particle size distribution tests, and slake durability tests. Modal and XRD analysis identified these rocks as biotite granite; secondary alteration minerals were not observed. Physical property tests and particle size distribution analyses indicate an average porosity of 41.28% and a sand content of > 90 wt.%. These values are somewhat higher than those of granites in general. The results of the slake durability test and XRF analyses show that the physical and chemical weathering indices of the samples vary with the degree of weathering.

• 한국재료학회지
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• 제18권6호
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• pp.302-306
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• 2008

Polycrystalline germanium (Ge) thin films were grown by metal organic chemical vapor deposition (MOCVD) using tetra-allyl germanium [$Ge(allyl)_4$], and germane ($GeH_4$) as precursors. Ge thin films were grown on a $TiN(50nm)/SiO_2/Si$ substrate by varying the growth conditions of the reactive gas ($H_2$), temperature ($300-700^{\circ}C$) and pressure (1-760Torr). $H_2$ gas helps to remove carbon from Ge film for a $Ge(allyl)_4$ precursor but not for a $GeH_4$ precursor. $Ge(allyl)_4$ exhibits island growth (VW mode) characteristics under conditions of 760Torr at $400-700^{\circ}C$, whereas $GeH_4$ shows a layer growth pattern (FM mode) under conditions of 5Torr at $400-700^{\circ}C$. The activation energies of the two precursors under optimized deposition conditions were 13.4 KJ/mol and 31.0 KJ/mol, respectively.

• 대한화학회지
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• 제6권1호
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• pp.47-53
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• 1962

The "reactivity" of coal is one of the important characteristics of a coal used as a process raw material as well as a fuel. In this study, the reactivity was measured in terms of the magnitude of the reaction rate constant in the reduction of carbon dioxide with coal. A reactivity-testing apparatus was designed and constructed, and its performance characteristics were investigated by using Korean anthracite and hard-wood charcoal. Experiments were carried out at temperatures ranging from 750 to 1100$^{\circ}C$ with pulverized Korean anthracite whose sizes range from 1 to 10mm in diameter. Results showed that the reaction rate constant was not appreciably affected by the particle size investigated, and the reactivities of the anthracite and the charcoal were found to be a function of reaction temperature alone. It was also found that a straight line was produced when the logarithm of the rate constant is plotted against the reciprocal of the absolute temperature. The reactivities of the charcoal were found to be 2 to 10 times higher than those of the anthracite at a temperature ranging from 750 to 1100$^{\circ}C$, and 90% of carbon dioxide was reduced to carbon monoxide by the anthracite at a temperature above 1050$^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4173-4179
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• 2012

From Neungsalli Temple located in Buyeo, ancient glass vessel fragments were discovered along with hundreds of glass beads. In this research, we used SEM-EDS to analyze glass vessel fragments and beads excavated from Neungsalli Temple. Then, we analyzed their chemical composition and examined their characteristics. In particular, we investigated a relationship between glass vessels from Neungsalli temple and Hwangnamdaechong (South tomb). The result of our experiment showed that the glass artifacts from Neungsalli temple were all soda glass. To be specific, the vessel fragments were soda-lime glass and spherical beads were high-alumina soda glass. Then, we compared glass vessel fragments from Neungsalli temple to glass vessels excavated from Hwangnamdaechong. Glass vessels from both sites turned out to be soda lime glass. We classified them further based on raw material used for soda - natron and marine plant ash.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.107-111
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• 2013

A new green-emitting material with donor-acceptor architecture, 3,7-bis(1'-phenylbenzimidazole-2'-yl)-10-phenylphenothiazine (BBPP) was synthesized and its thermal, optical, and electroluminescent characteristics were investigated. Organic light-emitting diodes (OLEDs) with four different multilayer structures were prepared using BBPP as an emitting layer. The optimized device with the structure of [ITO/2-TNATA (40 nm)/BBPP (30 nm)/TPBi (30 nm)/Alq3 (10 nm)/LiF (1 nm)/Al (100 nm)] exhibited efficient green emission. Enhanced charge carrier balance and electron mobility in the organic layers enabled the device to demonstrate a maximum luminance of 31,300 cd/$m^2$, a luminous efficiency of 6.83 cd/A, and an external quantum efficiency of 1.62% with the CIE 1931 chromaticity coordinates of (0.21, 0.53) at a current density of 100 mA/$cm^2$.

• Korean Chemical Engineering Research
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• 제54권2호
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• pp.274-277
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• 2016

녹색 발광다이오드의 다양자우물층과 전자막이층 사이에 p형 중간층 삽입이 소자의 특성에 미치는 영향이 소자 시뮬레이션을 통하여 연구되었다. 중간층의 Mg 도핑 깊이에 따른 발광다이오드의 전류-전압, 발광파장, 누설전류, 광효율 특성이 분석되었으며 최적의 발광 특성을 나타내는 소자 구조가 제시되었다. 중간층 전 영역이 p형으로 도핑된 구조와 30 nm까지 도핑된 구조는 누설전류 억제를 통하여 녹색 발광다이오드의 가장 큰 문제점 중에 하나인 효율 드룹 현상을 효과적으로 완화하였다. 특히, 30 nm까지 도핑된 구조는 전류-전압 및 발광 특성에 있어서 가장 향상된 결과를 보였다.