• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.86-91
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• 1998

Multimode planar waveguides have been fabricated by an electric-field assisted ion exchange in soda-lime glass substrates. Measurements of the mode indices have been made and the index profiles modeled on modified Fermi function are explained by a comparative analysis with the concentration profiles obtained using an electron probe X-ray micro analyzer. The analytical measurements showed that no more than 95% of sodium ions were replaced by the cesium ions. We established formulas for guide depth, mobility, and refractive index change, given the applied electric field, the diffusion temperature, and the time. We have verified the linear relations in the formulas not only between guide and root of diffusion time but also between guide depth and the applied electric filed experimentally.

• Corrosion Science and Technology
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• v.21 no.6
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• pp.514-524
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• 2022

Carbon emissions from fuel consumption have been pointed by scientists as the cause of global warming. In particular, fossil fuels are known to emit more carbon when burned than other types of fuels. In this regard, International Maritime Organization has announced a regulation plan to reduce carbon dioxide emissions. Therefore, recently, Liquefied Natural Gas propulsion ships are responding to such carbon reduction regulation. However, from a long-term perspective, it is necessary to use carbon-free fuels such as hydrogen and ammonia. Nitrogen oxides might be generated during ammonia combustion. There is a possibility that incompletely burned ammonia is discharged. Therefore, rather than being used as a direct fuel, Ammonia is only used to reduce NO_X such as urea solution in diesel vehicle Selective Catalyst Reduction. Currently, LPG vehicle fuel feed system studies have evaluated the durability of combustion injectors and fuel tanks in ammonia environment. However, few studies have been conducted to apply ammonia as a ship fuel. Therefore, this study aims to evaluate corrosion damage that might occur when ammonia is used as a propulsion fuel on ships.

• Journal of The Korean Society of Grassland and Forage Science
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• v.29 no.4
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• pp.337-344
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• 2009

This study was conducted to investigate the effects of various cropping system applied with cattle slurry on productivity of sorghum $\times$ sudangrass hybrid (SSH) and environmental pollution in paddy land. cropping systems used in this study were consisted of two designs, such as double-cropping sorghum $\times$ sudangrass hybrid followed by whole crop barley applied with cattle slurry (DSSCS) and mono-cropping sorghum $\times$ sudangrass hybrid followed by hairy vetch used as green manure (MSSGM). The field experiments were conducted on the clay loam at Backsanmyun, Kimje, Chunlabukdo province in Korea for three years (May 2006 to Apr. 2009). This study was arranged in completely randomized design with three replicates. The yield of dry matter (DM) of SSH in DSSCS increased significantly as compared with that of MSSGM (P<0.05). The contents of crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF) and total digestible nutrients (TDN) of SSH were not influenced by cattle slurry and green manure. The pH, and contents of OM, T-N and $P_2O_5$ in soil samples collected from DSSCS after the end of experiment were higher than those of MSSGM. The pH, and contents of OM in DSSCS treatment were remarkably higher than those at the beginning of the experiment (p<0.05). However, The pH, and contents of OM in MSSGM treatment were hardly influenced, as compared with those at the beginning of the experiment. The contents of T-N in soil samples collected both from DSSCS snd MSSGM treatments were remarkably higher than those at the beginning of the experiment (p<0.05). In addition, the concentrations of CEC in soil samples collected at the end of the experiment were remarkably higher than those at the beginning of the experiment (p<0.05). The concentrations of $NO_3$-N, $NH_3$-N and $PO_4$-P in leaching water were hardly influenced by the cropping system and application of cattle slurry.

• Korean journal of applied entomology
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• v.48 no.3
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• pp.335-345
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• 2009

Effect of four nematicidal herbal extracts (Daphne genkwa, Eugenia caryophyllata, Quisqualis indica and Zingiber officinale) and 3 acricidal herbal extracts (Pharbitis nil, Xanthium strumarium, and Desmodium caudatum) on entomopathobenic nematodes [Steinernema carpocapsae Pocheon strain (ScP) and Heterorhabditis sp. Gyeongsan strain (HG)], silkworm (Bombyx mori), and ground beetles (Synuchus sp.) were investigated in the laboratory and field. D. genkwa was highly toxic to SCP and HG (100% mortality) at the concentration of 5,000 ppm in X-plate. All the infective juveniles of HG were dead after 3 days by E. caryophyllata and Q. indica. The mortality of ScP and HG was below 10% by D. genkwa, D. caudatum, E. caryophyllata, Q. indica and Z. officinale at the concentration of 1,000 ppm two days after treatment while mortality of HG was 62.8% by D. genkwa at the concentration of 1,000 ppm in X-plate. However, 1,000 ppm had not effect on nematode survival and pathogenicity of ScP in sand column. On the contrary, E. caryophyllata had effect on pathogenicity of HG. Mean number of dead Galleria mellonella larva of HG was 0.5 in E. caryophyllata treatment. Q. indica did not effect silkworm reared on mulberry leaves at the treatment of 1,000 ppm in 10 days after treatment. However, there were 20.0 and 100% mortalities in the treatment of D. genkwa 3 and 10 days after treatment, respectively. The weight of silkworm was low in D. genkwa and did not pupate. The weight of pupa and cocoon were not different in E. caryophyllata, P. nil, Q. indica, X. strumarium and Z. officinale. D. genkwa, E. caryophyllata, P. nil, Q. indica and Z. officinale had no effect on ground beetles, Synuchus sp. in forest soil.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.8
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• pp.459-467
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• 2016

In order to assess the pollution status and distribution characteristics of PM and PM-bound species, PM10 samples were collected using mini-volume air sampler at the subway cabin in Daejeon city. Measurements of about 24 elements including toxic metals (e.g., As, Cr, Mn, V, Zn) in PM10 were made by instrumental neutron activation analysis and X-ray fluorescence. The average PM10 concentration was $59.3{\pm}14.5{\mu}g/m^3$ in the subway cabin with a range of 42.2 to $97.4{\mu}g/m^3$, while the associated elemental concentrations were varied in the range of $10^{-3}$ to $10^5ng/m^3$. It was found that the concentration of Fe ($12.5{\mu}g/m^3$) was substantially higher than any other element. The Fe concentration was apportioned by about 20% of the PM10 concentration. The results of factor analysis indicate that there are no more than six sources in the cabin (e.g., brake-nonferrous metal particle, resuspended rail dust, fuel combustion, vehicle exhaust, black carbon, Cr-related).

• Journal of the Korean earth science society
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• v.22 no.6
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• pp.480-490
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• 2001

The soil-air exchange processes of Hg were investigated from the Hari area of Kang Hwa Island during the late March 2001. In the course of our study, we determined the concentration gradients of Hg and combined these gradient data with micrometeorological components to derive its fluxes. Results of our study indicate that the concentration levels of Hg in the study area are notably lower than those typically found in urbanized areas of Korea. However, the computed fluxes were seen to be significantly larger for relatively remote areas, reaching over 200 ng/m$^2$/hr. Comparison of environmental conditions shows that the concentrations of most pollutant species including NO$_X$ and PM were significantly higher during emission, while meteorological conditions were characterized by high temperature and low humidity. Results of correlation analysis also indicate that such pollutants as hydrocarbons, nitrogen oxides, and PM generally exhibit strong positive correlations with Hg-related parameters during emission events, while such relationships were reversed during dry deposition events. The results of our present study suggest the possibility that the concentrations and fluxes of total gaseous Hg observed during deposition events can be influenced by the processes that are also important for the fine, rather than coarse, size fraction of particles.

• Clean Technology
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• v.23 no.3
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• pp.294-301
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• 2017

Air pollution associated with the $NO_x$ emission from the ship engines is becoming one of the major environmental concerns these days. As the regulations on ship pollutants are strengthened, the wet absorption method, for controlling complex pollutants in a confined space, has the advantage of simultaneously removing various pollutants, but the low solubility of nitrogen monoxide is drawback. In this study, for improving existing denitrification scrubber system, NO oxidation process by hydroxyl radical produced from irradiating UV light on $H_2O_2$ is suggested and the $H_2O_2$ decomposition rates and hydroxyl radical quantum yields were measured to find the optimum condition of $H_2O_2$ photolysis reaction. As a result, the optimum quantum yield and photolysis rate of $H_2O_2$ were 0.8798, $0.6mol\;h^{-1}$ at 8 W, 2 M condition, and oxidation efficiency of 1000 ppm NO gas was 40%. In batch system, NO removal efficiency has a range of 65.0 ~ 67.3% according to input gas concentration of 100 ~ 1500 ppm. This results indicate that the scrubber system using hydrogen peroxide photolysis can be applied as air pollution prevention facility of ship engines.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.746-751
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• 2002

Fluidized bed combustion is a coal combustion technology that can reduce both SOx and NOx emission; SOx is removed by limestone that is fed into the combustion chamber and the NOx is reduced by low temperature combustion in a fluidized bed combustor and air stepping, but $N_2O$ generation is quite high. $N_2O$ is not only a greenhouse gas but also an agent of ozone destruction in the stratosphere. The calcium oxide(CaO) is known to be a catalyst of $N_2O$ decomposition. This study of $N_2O$ decomposition reaction in fixed bed reactor packed over CaO bed has been conducted. Effects of parameters such as concentration of inlet $N_2O$ gas, reaction temperature, CaO bed height and effect of $CO_2$, NO, $O_2$ gas on the decomposition reaction have been investigated. As a result of the experiment, it has been shown that $N_2O$ decomposition reaction increased with the increasing fixed bed temperature. While conversion of the reaction was decreased with increasing $CO_2$ concentration. Also, under the present of NO, the conversion of $N_2O$ decomposition is decreased. From the result of kinetic study gained the heterogeneous reaction rate on $N_2O$ decomposition. In the case of $N_2O$ decomposition over CaO, heterogeneous reaction rate is. $\frac{d[N_2O]}{dt}=\frac{3.86{\times}10^9{\exp}(-15841/R)K_{N_2O}[N_2O]}{(1+K_{N_2O}[N_2O]+K_{CO_2}[CO_2])}$. In this study, it is found that the calcium oxide is a good catalyst of $N_2O$ decomposition.

• Journal of the Mineralogical Society of Korea
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• v.31 no.4
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• pp.235-248
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• 2018

The present work was performed in order to study the effect of competing cation of $Ca^{2+}$ ion on ion exchange of $Cs^+$ on zeolite Y (Si/Al = 1.56). Three single-crystals of fully dehydrated and partially $Cs^+$-exchanged zeolites Y (Si/Al = 1.56) were prepared by the flow method using mixed ion-exchange solutions. The $CsNO_3:Ca(NO_3)_2$ molar ratios of the ion exchange solution were 1 : 1 (crystal 1), 1 : 100 (crystal 2), and 1 : 250 (crystal 3) with a total concentration of 0.05 M. The single-crystals were then vacuum dehydrated at 723 K and $1{\times}10^{-4}Pa$ for 2 days. The structures of the crystals were determined by single-crystal synchrotron X-ray diffraction technique in the cubic space group $Fd{\bar{3}}m$, at 100(1) K. The unit-cell formulas of crystals 1, 2, and 3 were ${\mid}Cs_{21}Ca_{27}{\mid}[Si_{117}Al_{75}O_{384}]-FAU$, ${\mid}Cs_2Ca_{36.5}{\mid}[Si_{117}Al_{75}O_{384}]-FAU$, and ${\mid}Cs_1Ca_{37}{\mid}[Si_{117}Al_{75}O_{384}]-FAU$, respectively. In all three crystals, the $Ca^{2+}$ ions preferred to occupy site I in the D6Rs, with the remainder occupying sites I', II', and II. On the other hand, the significant differences in the fractional distribution of $Cs^+$ ions are observed depending on the intial $Cs^+$ concentrations in given ion exchange solution. In Crystal 1, $Cs^+$ ion are located at sites II', II, III, and III', and in crystal 2, at sites II, IIIa, and IIIb. In crystal 3, $Cs^+$ ions are only located at sites IIIa and IIIb. The degree of $Cs^+$ ion exchange decreased sharply from 28.0 to 2.7 to 1.3 % as the initial $Ca^{2+}$ concentration increases and the $Cs^+$ content decreases.

• Clinical and Experimental Pediatrics
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• v.48 no.5
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• pp.534-538
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• 2005

Purpose : Kawasaki disease(KD) is a multisystemic inflammatory vasculitis of unknown etiology. Many complications other than cardiovascular involvement have been recognized in KD. However, there have been few reports published concerning involvement of the lungs in this disease. The purpose of this study was to examine the relationship between serum TNF-${\alpha}$, the degree of coronary artery dilatation and chest X-ray(CXR) findings. In addition, we have investigated serum anti-Mycoplasma antibody(AMA) titers in patients with KD who have abnormal CXR findings. Methods : Eighty four patients with KD were included in this study(group I; 41 patients with normal CXR fndings, group II; 43 patients with abnormal CXR findings). Serum levels of TNF-${\alpha}$ and AMA titer were measured. Results : We reviewed the CXR findings and clinical courses of 84 patients with Kawasaki disease and found abnormal CXR findings in 43 patients(51.2 percent). Peribronchial cuffing was the most frequent abnormality(22.4 percent). In the group with abnormal CXR findings(group II), a statistical difference was not noted in age, sex, duration of fever, hemoglobin, WBC, platelet, ESR, and CRP levels and incidence of coronary arterial lesions as compared with the group having normal CXR findings(group I). No difference was noted in serum TNF-${\alpha}$ level between group I and group II. 2 patients(12.5 percent) of 16 KD patients with abnormal CXR findings have positive AMA titer(above 1 : 320). Conclusion : Most of the abnormal CXR findings in KD patients were peribronchial cuffing. The abnormal CXR findings in KD patients did not mean severe inflammations. It is difficult to consider that CXR abnormalities are related to coronary arterial lesions. In addition, further study on the relationship between Mycoplasma infection and Kawasaki disease is needed.