• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.465-465
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• 2008

Conjugated polymers have attracted much scientific and technological research interest during the past few decades because of their potential use such as polymer light-emitting diodes (PLEDs).1,2 Particularly, lots of phenylene-based polymers such as polyfluorene and its derivatives have been synthesized because of their high photoluminescence quantum efficiencies and thermal stabilities. However, troublesome long wavelength emission in polymer film of polyfluorenes on heating during device formation or operation has been the crucial problem for practical applications. The source of the long wavelength emission was initially believed to be solely due to excimer emission as a result of polymer aggregation. It has also recently been correlated with emissions from ketonic defects in the fluorene units. Many efforts have been made to reduce the tendency to red-shifted emission. Here, we report for the first time the design and synthesis of novel 9,9-spiro bifluornene-based polymers containing heteroatoms such as N, S in its molecular skeleton. Especially, the 9,9-spiro bifluornene-based polymers containing N atom showed stable blue electroluminescence, which did not show spectral change upon thermal annealing.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.432-436
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• 2006

The $ZnGa_2O_4$ and Mn, Cr-doped $ZnGa_2O_4$ Phosphors were synthesized through conventional solid state reactions. The XRD patterns show that the $ZnGa_2O_4$ has a (3 1 1) main peak and a spinel phase. The emission wavelength of $ZnGa_2O_4$ showed main peak of 420 nm and maximum intensity at the sintering temperature of $1100^{\circ}C$. In the crystalline $ZnGa_2O_4$, the Mn shows green emission (510 nm, $^4T_1-^6A_1$) with a quenching concentration of 0.6 mol%, and the Cr shows red emission (705 nm, $^4T_2-^4A_2$) with a quenching concentration of 2 mol%. These results indicate that $ZnGa_2O_4$ Phosphors hold promise for potential applications in field emission display devices with high brightness operating in full color regions.

• Bulletin of the Korean Chemical Society
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• 제31권4호
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• pp.989-998
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• 2010

The titled dye of DBPI gives amplified spontaneous emission (ASE) with maximum at 580 nm upon pumping by nitrogen laser (${\lambda}_{ex}\;=\;337.1\;nm$). The ground state absorption cross section (${\sigma}_A$) and emission cross section (${\sigma}_E$) as well as effective emission cross section(${\sigma}^*_E$) have been determined. The electronic absorption spectra of DBPI were measured in ethanol and tetrahydrofuran at room and low temperature. DBPI displays molecular aggregation in water. The photochemical reactivity of DBPI was also studied in carbon tetrachloride upon irradiation with 525 nm light. The electrochemical investigation of DBPI dye has been carried out using cyclic voltammetry and convolution deconvolution voltammetry combined with digital simulation technique at a platinum electrode in 0.1 mol/L tetrabutyl ammonium perchlorate (TBAP) in two different solvents acetonitrile ($CH_3CN$) and dimethylformamide (DMF). The species were reduced via consumption of two sequential electrons to form radical anion and dianion (EE mechanism). In switching the potential to positive direction, the compound was oxidized by loss of two sequential electrons, which were followed by a fast dimerization and/or aggregation process i.e $EC_{dim1}EC_{dim2}$ mechanism. The electrode reaction pathway and the chemical and electrochemical parameters of the investigated compound were determined using cyclic and convolutive voltammetry. The extracted electrochemical parameters were verified and confirmed via digital simulation method.

• 한국토양비료학회지
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• 제49권3호
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• pp.259-264
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• 2016

The effect of biochar application on soil physics and nitrous oxide ($N_2O$) emission from upland soil for broccoli cultivation was investigated. Sesame straw biochar (SB) was applied at amounts 0 (IF), 50 (SB50), 100 (SB100), 200 (SB200) kg $10a^{-1}$, respectively. SB addition to the upland soil decreased bulk density, and increased porosity and soil respiration. The $N_2O$ emission rates in all treatments were higher in the order of IF $${\geq_-}$$ SB50 > SB100 $${\geq_-}$$ SB200 treatments. Global warming potential in SB200 treatment decreased by 15.1% compared to IF treatment. Therefore, SB application in upland soil can improve soil physics and reduce $N_2O$ emission.

• 한국연소학회지
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• 제9권1호
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• pp.11-17
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• 2004

The purposes of this study are to analyze nitrogen oxides(NOx) formation mechanism and to reduce abnormal NOx emissions in gas turbines. Industrial gas turbines emissions have potential to negative affect to the atmosphere in many different ways such as photochemical smog, acid rain and global warming. In conventional gas turbine combustors, one of the main pollutants such as nitrogen oxide(NOx) species, are principally formed from combustion process of fuel with oxygen in the primary combustion zone, and their emission levels are highly depend on peak temperatures in the combustor. In order to examine the characteristics and the effect of NOx formation, we used gas turbine of which commercial operating in Korea. From the examination, it has been found that NOx emissions are relatively high at low load(output) and during combustion mode change. Also, the effect of Air/Fuel ratio was considered. As the Air/Fuel ratio was increased in Lean-Lean mode, the NOx emission was decreased. The results of this study indicated that NOx emission levels are highly depend on peak temperature and pressure of combustion process in the combustor.

• 해양환경안전학회지
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• 제25권3호
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• pp.381-394
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• 2019

The marine industry contributes a large proportion of the air pollutant emissions along coastal regions, and this air pollution has been strongly linked to cardiovascular diseases and other illnesses. To alleviate the problem, many ports have installed alternative maritime power (AMP) facilities that enable onboard marine auxiliary engines with generators (gensets) to be shut down while a ship is at berth. This study compared the emissions from conventional gensets with those from AMP facilities, focusing on four emission types: greenhouse gases (GHG), sulphur oxides (SOX), nitrogen oxides (NOX), and particulate matter (PM). Both direct (combustion / operation) and indirect (upstream) emissions were considered together for the emission comparison. The results showed that AMP has lower emissions than conventional onboard gensets, and this benefit is highly dependent on the electricity generation mix onshore. On average, GHG emissions could be reduced by about 18.3 %, while the other emissions (SOX, NOX, and PM) would decrease more dramatically (88.4 %, 90.1 %, and 91.5 %, respectively). Additionally, future benefits of the AMP would increase due to the expansion of renewable energies. Thus, this study supports the potential of AMP as a promising solution for environmental concerns at ports worldwide.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.688-706
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• 2024

Austenitic stainless steels (ASS) are extensively employed in various sectors such as nuclear, power, petrochemical, oil and gas because of their excellent structural strength and resistance to corrosion. SS304 and SS316 are the predominant choices for piping, pressure vessels, heat exchangers, nuclear reactor core components and support structures, but they are susceptible to stress corrosion cracking (SCC) in chloride-rich environments. Over the course of several decades, extensive research efforts have been directed towards evaluating SCC using diverse methodologies and models, albeit some uncertainties persist regarding the precise progression of cracks. This review paper focuses on the application of Acoustic Emission Technique (AET) for assessing SCC damage mechanism by monitoring the dynamic acoustic emissions or inelastic stress waves generated during the initiation and propagation of cracks. AET serves as a valuable non-destructive technique (NDT) for in-service evaluation of the structural integrity within operational conditions and early detection of critical flaws. By leveraging the time domain and time-frequency domain techniques, various Acoustic Emission (AE) parameters can be characterized and correlated with the multi-stage crack damage phenomena. Further theories of the SCC mechanisms are elucidated, with a focus on both the dissolution-based and cleavage-based damage models. Through the comprehensive insights provided here, this review stands to contribute to an enhanced understanding of SCC damage in stainless steels and the potential AET application in nuclear industry.

• Corrosion Science and Technology
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• 제12권1호
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• pp.40-49
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• 2013

Effects of magnesium and pH on corrosion of aluminum galvanically coupled to iron have studied by using potentio- dynamic and static tests for polarization curves, Mott-Schottky test for analysis of semiconductor property, and GD-AES and XPS for film analysis. Pitting potential was sensitive to magnesium as an alloying element but not to pH, while passive current was sensitive to pH but not to magnesium. It was explained with, instead of point defect model (PDM), surface charge model describing that the ingression of chloride depends on the state of surface charge and passive film at film/solution interface is affected by pH. In addition, galvanic current of aluminum electrically coupled to iron was not affected by magnesium in pH 8.4, 0.2M citrate solution but was increased by magnesium at the solution of pH 9.1. The galvanic current at pH 9.1 increased with time at the initial stage and after the exposure of about 200 minute, decreased and stabilized. The behavior of the galvanic current was related with the concentration of magnesium at the surface. It agreed with the depletion of magnesium at the oxide surface by using glow discharge atomic emission spectroscopy (GD-AES). In addition, pitting potential of pure aluminum was reduced in neutral pH solution where chloride ion maybe are competitively adsorbed on pure aluminum. It was confirmed by the exponential decrease of pitting potential with log of [$Cl^-$] around 0.025 M of [$Cl^-$] and linear decrease of the pitting potential. From the above results, unlike magnesium, alloying elements with higher electron negativity, lowering isoelectric point (ISE), are recommended to be added to improve pitting corrosion resistance of aluminum and its alloys in neutral solutions as well as their galvanic corrosion resistance in weakly basic solutions.

• 한국물환경학회지
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• 제38권2호
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• pp.63-71
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• 2022

This study aimed to maximize the potential of fluorescence 3D excitation-emission matrix (EEM) for predicting the trihalomethane formation potential (THMFP) of DOM with various sources. Fluorescence spectroscopy is a useful tool for characterizing dissolved organic matter (DOM). In this study, differential spectroscopy was applied to EEM for the prediction of THMFP, in which the difference between the EEM before and after chlorination was taken into account to obtain the differential EEM (DEEM). For characterization of the original EEM or the DEEM, the maximum intensities of several different fluorescence regions in EEM, fluorescence EEM regional integration (FRI), and humification index (HIX) were calculated and used for the surrogates for THMFP prediction. After chlorination, the fluorescence intensity decreased by 77% to 93%. In leaf-derived and effluent DOM, there was a significant decrease in the protein-like peak, while a more pronounced decrease was observed in the humic-like peak of river DOM. In general, leaf-derived and effluent DOM exhibited a relatively lower THMFP than the river DOM. Our results were consistent with the high correlations between humic-like fluorescence and THMFP previously reported. In this study, HIX (r= 0.815, p<0.001), FRI region V (r=0.727, p<0.001), humic-like peak (r= 0.827, p<0.001) from DEEM presented very high correlations with THMF P. When the humic-like peak intensity was converted to a logarithmic scale, a higher correlation was obtained (r= 0.928, p<0.001). This finding suggests that the humic-like peak in DEEM can serve as a universal predictor for THM formation of DOM with various origins.

• 자원리싸이클링
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• 제22권6호
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• pp.3-11
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• 2013

본 연구는 사용종료매립지 정비를 위한 폐기물 처리과정에서 가연성폐기물의 처리 방법별 온실가스 발생량을 IPCC에서 제시하고 있는 기본배출계수(default emission factor)를 활용하여 산정하고 그 결과 비교를 통해 온실가스 감축량을 산정하였다. 대상 매립지로부터 굴착한 폐기물의 성상을 조사한 결과 토사류가 64.96%로 가장 많은 비율을 차지하고 있었으며, 다음으로 비닐/플라스틱류가 19.18%의 비율을 차지하고 있어 전체 폐기물 중 토사류의 비율이 매우 높은 것으로 나타났다. 음식물류, 목초류, 종이류와 같이 생분해가 용이한 폐기물이 거의 발견되지 않은 점 등이 일반적인 비위생매립지의 굴착폐기물과 성상이 유사하였다. 전체 폐기물의 겉보기 밀도는 평균 $0.74t/m^3$으로 확인되었다. 폐기물을 매립으로 처리하는 경우 약 60,542 $tCO_2$, 소각을 통해 폐기물 처리 시 9,933 $tCO_2$의 온실가스가 배출되며 폐기물 고형연료 생산 시에는 33,738 $tCO_2$의 온실가스가 감축되는 것으로 산정되어 폐기물 고형연료 생산이 온실가스 감축에 도움이 되는 것으로 확인되었다.