• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.152-156
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• 2016

Experimental research on the preparation of photocatalyst for the decomposition of brilliant blue FCF ($C_{37}H_{31}O_9N_2S_3Na_2$) was performed. $TiO_2$ and ZnO powders were prepared from titanium (IV) sulfate and zinc acetate at low reaction temperature and atmospheric pressure by hydrothermal precipitation method without calcination. In addition, $TiO_2$ was prepared with cationic surfactant CTAB (Hexadecyltrimethyl ammonium bromide) at the same conditions. The physical properties of prepared $TiO_2$ and ZnO, such as crystallinity, average particle size and absorbance, were investigated by XRD, Zeta-potential meter and DRS. And, the photocatalytic degradation of brilliant blue FCF has been studied in the batch reactor under UV radiation. For the photocatalysts prepared without CTAB, $TiO_2$ has smaller particle size and larger absorbance and photocatalytic reaction rate than ZnO. And $TiO_2$, prepared with CTAB whose concentration is 1/10 of that of precursor, shows 15% higher than that prepared without CTAB in final photocatalytic degradation ratio of brilliant blue FCF.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.4
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• pp.269-275
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• 2017

$NO_X$ reducing technique such as LNT, LNC, and selective catalytic reduction (SCR) have been developed and applied, especially on heavy-duty vehicles. However, it is expected that $NO_X$ reduction techniques will also be applied to diesel passenger vehicles. The urea-SCR system is receiving attention as the most effective $NO_X$ reduction technology without a fuel penalty. Thus, many advanced countries are developing this technology. The urea-SCR system sprays an aqueous urea solution that separates $NO_X$ into $N_2$ and $H_2O$, which are harmless and emitted into the atmosphere. The urea injected in front of the SCR catalyst should be changed to 100％ $NH_3$, which is required for $NO_X$ reduction in the SCR system to maximize the reduction efficiency. The purpose of this study was to determine the basic data for the urea-SCR system to maximize the $NO_X$ reduction efficiency by understanding the $NO_X$ reduction characteristics in a real passenger vehicle to comply with the post EURO-6 emission regulation.

• Polymer(Korea)
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• v.24 no.3
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• pp.314-325
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• 2000

Thermal degradation of thermoplasitc polyurethane modified polycarbonate has been investigated by means of DSC, GPC and FT-IR techniques. The polyurethanes used in this study are TPU-35 and TPU-53 containing 35.5 and 53.4 wt% of hard segments, respectively. The more content of hard segment, the higher the glass transition temperature (T$_{g}$) of TPU was observed. On the other hand, the T$_{g}$ of the TPU modified PC decreased with the content of TPU and the annealing temperature regardless of the hard segment contents. The latter behavior nay arise from the thermal degradation of TPU upon annealing process: the observed thermal degradation temperatures were at 240 and 25$0^{\circ}C$ for the PC/TPU-35 and PC/TPU-53, respectively. The molecular weight, molecular weight distribution and viscosity agree well with the DSC measurement, which implicates a thermal degradation of TPU. In addition, thermal stability of the TPU modified PC linearly decreased with an incorporation of TPU. Transesterification or any interaction was not observed using FT-IR: the evidence was no frequency shift or any variance betwere the carbonyl stretching and NH group. For the specimens prepared below the degradation temperature, the enhancement of the thickness dependent impact strength of the PC/TPU blend was observed, and the morphology of the two blends was compared.d.

• Journal of Korean Society on Water Environment
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• v.34 no.4
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• pp.423-430
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• 2018

Insomuch as it is important to manage water quality, from the perspective of water management, it is essential to understand the effect of the weirs on water quality and phytoplankton dynamics in various regions. The purpose of this study is to investigate the characteristics of nitro-nutrients, as well as occurrences and succession patterns of phytoplankton, in the river sections of the two weirs in the Yeongsan River for the five years (from 2012 to 2016) after the weir construction. In respect to this data, the average water temperature measured at the representative point in the section of the Seungchon Weir ($17.1^{\circ}C$) was higher than that of the Juksan Weir ($16.6^{\circ}C$) by comparison. By way of an analysis of this data, it was found that the water quality variables such as, organic matter, nitrogen nutrients and phosphorus nutrients were improved gradually during the period, but the degree of the improvement differs as noted and measured between the weirs. Under the circumstances, it is especially noted that the $NH_3-N$ concentration was higher for the point of the Seungchon Weir (2.204 mg/L) than that of the Juksan Weir (1.157 mg/L). This indicates that effluent as seen from sewage treatment plants and hydrological feature near the densely population area, could be the main cause for the incidence of water pollution in the upstream section of the Seungchon Weir. Additionally, the phytoplankton analysis showed that a relative abundance of diatoms and green algae were 56.9 % and 25.8 % respectively. However, it is noted that the cyanobacteria was measured lower as 10.7 %. Also, in the study sites cell density and occurrence frequency of cyanobacteria were relatively lower than compared to the same measurements noted in other rivers.

• Korean Journal of Microbiology
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• v.33 no.4
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• pp.267-273
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• 1997

Various physico-chemical and microbiological parameters of a composting system were compared with respect to their potential use for the monitoring and evaluation of composting processes for cattle manure. The temperature changed within a range of $30-65^{\circ}C$ during the whole composting process, and the period of active composting (>$40^{\circ}C$) persisted for 16 days. The concentrations of total carbon, total nitrogen, and organic matter decreased by 15% during active composting, but significant changes in C/N ratio were not observed. The decrease of temperature in the latter period of active composting caused a decrease of $NH_4^+-N$ and an increase of $NO_3^--N$ in the composting pile. When temperature exceeded $50^{\circ}C$, the population of thermophiles was higher than that of mesophiles by more than 1 or 2 orders of magnitude. Correlation analyses showed that amylase activity correlated positively with the population of mesophiles and reducing sugar content, but negatively with the population of thermophiles. Amylase activity was higher at the beginning of active composting, whereas cellulase, xylanase and ligninase activities which showed close relationship with each other, increased continually during active cornposting, suggesting the distinction of temporal niches between amylose-degrading and lignocellulose-degrading bacteria in the same habitat.

• 한국해양학회지
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• v.7 no.1
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• pp.24-45
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• 1972

The Han River is an important water source in Seoul and neighbouring districts, for public and industrial supply, and for agriculture and fishery. Nowadays, more than six million inhabitants are supplied withe water from this river. The total length of the river is 470km, and has 17 10$\^$9/㎥ an average annual flow. The hydrographic characteristics at Seoul are 653㎥/sec in an average flow, 4,608㎥/sec in the maximum average flow, and 201㎥/sec in the minimum average flow. These are influenced in some degree by snowmelt in early spring, and greatly by the flood during summer. For the pollution problems, the periods of low flow are critical ones. As a rule they occur around the months November through June. Nowadays, most of the sewage from towns and industries is discharged untreated. Apart from domestic and industrial sewages, there are some discharges of mineral matter by mines in the upriver region. In general, water quality of the Han River is kept very clean and healthy until Kwangnaru of the upper region of Seoul. A large pollution, however, is received in the downstream by the domestic and industrial sewages of Seoul. It can be seen that dissolved oxygen, COD and BOD$\sub$5/ diminish markedly, and the intensity of almost every water parameter of the river continues to increase. Comparison of the figures for 1971 derived from a sampling point 40km downstream of Kwangnaru leads to the conclusion that hardness, Ca and Mg were no changed; alkalinity, Si and soluble- Fe were slightly increased; CO$\sub$2/, acidity, Cl, NO$\sub$2/-N, Cu, Zn and Al were increased in 2 and 3 times; total residue, total ignitious residue, COD, BOD$\sub$5/, NH$\sub$4/-N, PO$\sub$4/-P, Mn, Pb and total-Fe were increased in 4 to 7 times; and SO$\sub$4/, particulate-Fe and Cd were increased in 10 to 11 times. On the other hand, coliforms were increased in 650 times; fecal coliforms in 365 times; enterococci and total plate counts in 30 times, respectively. In view points of water quality standards, the down Han River water is now leveling out in Cd, coliforms and fecal coliforms for the agricultural use; in dissolved oxygen and some trace elements (Cu, Zn, Pb and Cd) for the fishery use; in ammonia, COD, BOD$\sub$5/, and Cd for the drinking use.

• Journal of Life Science
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• v.13 no.4
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• pp.473-480
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• 2003

We analyzed the patterns of mineral ions and growth responses among symbiotic nitrogen fixing legumes by external nitrogen applications under salt gradients. Glycine max, Phaseolus angularis and Albizzia julibrissin showed remarkable growth inhibition above 40 mM NaCl treatments, but Cassia tora did not exhibit any visible injury symptom up to 100 mM NaCl treatments. As to ionic pattern, the $Na^+$ and $Cl^-$contents in leaves of G. max, P. angularis and A. julibrissin progressively increased with higher contents of external salinity. Compared to other plants, C. tora excluded $Na^+$more efficiently and maintained rather constant ionic contents in spite of high salt levels. With a few exception, these 4 legume plants exhibited better growth by the external nitrogen supply rather than the contribution of symbiotic nitrogen fixation only under saline condition.

• Journal of Soil and Groundwater Environment
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• v.21 no.1
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• pp.28-39
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• 2016

Struvite (MgNH₄PO₄ ⋅ 6H₂O) and hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂) precipitation in urine-separating toilets (NoMix toilets) causes severe maintenance problems and also reduce the phosphate and calcium content. Application of urine separating technique and extraction of by-products from human urine is a cost effective technique in waste water treatment. In this study, we extract urine calcite from human urine by batch scale method, using urease producing microbes to trigger the precipitation and calcite formation process. Extracted urine calcite (calcining at 800℃) is a potential adsorbent for removal of heavy metal(loid)s like (Cd²⁺, Cu²⁺, Ni²⁺, Pb²⁺, Zn²⁺ and As³⁺) along with additional leaching analysis of total nitrogen (T-N), phosphate (T-P) and chemical oxygen demand (COD). The transformations of calcite during synthesis were confirm by characterization using XRD, SEM-EDAX and FT-IR techniques. In additional, the phosphate leaching potential and adsorbate (nitrate) efficiency in aqueous solution was investigated using the calcinedurine calcite. The results indicate that the calcite was effectively remove heavy metal(loid)s lead up to 96.8%. In addition, the adsorption capacity (q_e) of calcite was calculated and it was found to be 203.64 Pb, 110.96 Cd, 96.02 Zn, 104.2 As, 149.54 Cu and 162.68 Ni mg/g, respectively. Hence, we suggest that the calcite obtain from the human urine will be a suitable absorbent for heavy metal(loid)s removal from aqueous solution.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1207-1213
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• 2011

This study was conducted to assess $N_2O$ emissions in agricultural soils of Korea. According to 1996 and 2006 IPCC (Intergovernmental Panel on Climate Change) methodology, $N_2O$ emission was calculated the sum of direct emission ($N_2O_{DIRECT}$) and indirect emission ($N_2O_{INDIRECT}$). To calculate $N_2O$ emissions, emission factor was used default of IPCC and activity data was used the food, agricultural, forestry and fisheries statistical yearbook of MIFAFF (Ministry for Food, Agriculture, Forestry and Fisheries). It was emitted 8,608 $N_2O$ Mg resulted from direct emission by application of chemical fertilizer and animal manure, input in n-fixation crops and input of crop residues and emissions converted $N_2O$ into $CO_2$ equivalent was 2,668 $CO_2$-eq Gg. Indirect emission as $N_2O_{(G)}$ (atmospheric deposition of $NH_3$ and $NO_X$) and $N_2O_{(L)}$ (leaching and runoffs) were 4,567 and 6,013 $N_2O$ Mg and emissions converted $N_2O$ into $CO_2$ equivalent were 1,416 and 1,864 $CO_2$-eq Gg, respectively. Total $N_2O$ emission in Korea agricultural soil in 2009 was 5,948 $CO_2$-eq Gg.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.864-871
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• 2010

At the current situation of continuous utilization of heavy metal contaminated upland for agricultural purpose in Korea, minimizing transport of heavy metals from soil to crops is important for securing safety of human health. The present study (in field scale) examined the efficiency of several soil amendments (dolomite, steel slag, lime, zeolite, and compost) on reduction of phytoavailable heavy metals (Cd, Cu, Pb, and Zn) in soil through comparison with no amendment treatment and clean soil cover treatment. For determination of the phytoavailability, 1 M $NH_4NO_3$ extraction and red pepper cultivation were introduced. Among the amendments, in general, dolomite and steel slag were the most effective in reduction of metal (Cd, Pb, and Zn) phytoavailability resulting in less accumulation of these metals in shoot and fruit of red pepper. However, dolomite and steel slag treatment was not as effective as clean soil cover treatment which showed the least metal accumulation in red pepper fruit. Nevertheless, with taking into account the cost, treatment of dolomite or steel slag can be competitive method because the current study showed that dolomite or steel slag treatment reduced accumulated heavy metal concentration effectively in both shoot and fruit of red pepper compared to those from control soil and the concentration in fruit was within the standard value (<0.2 mg $kg^{-1}$ for both Cd and Pb).