• Journal of the Korean Geographical Society
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• v.39 no.4
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• pp.562-584
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• 2004

This paper intends to identify the structure of homogeneous regions and functional regions in Seoul based on B.J.L. Berry's ‘general field theory of spatial behavior’. The structure of homogeneous regions by using socio-economic variables can explain how the structural elements of the city are arranged. It can be ssid that Seoul has shifted towards more complicated and differentiated features in terms of homogeneous regions. The different patterns are found between the northern part to Han River where old torn areas are located and the southern part to Han River where newly urbanized areas are located. Usually, the concentric pattern and the sectoral pattern coexist, which is enhanced moving from CBD to the outskirt area. The distribution of different social classes shows irregular pattern similar to the variation of living environment. The social gap is expected to be more widening between new towns and old towns. The analysis of spatial movement pattern shows no clear hierarchical order because of current shifts towards both multi-nuclear pattern and spatial dispersion. The functional regions show duplicated structure overlapping their boundaries each other. The ‘general field theory of spatial behavior’ strongly suggests that spatial interactions among sub-areas in the city are differentiated from the basic characteristics and function of each sub-area. The attributes of homogeneous regions and functional regions are interrelated in the characteristics of isomorphic nature.

• Geotechnical Engineering
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• v.14 no.6
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• pp.153-166
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• 1998

This paper shows the results of a series of model tests on the behavior of steel pipe pile which is subjected to lateral and inclined loads in homogeneous and non-homogeneous Nak-dong River sands. Non-homogeneous soil consisted of two layers, upper and lower layer. The purpose of the present paper is to investigate the effect of ratio of lower layer height to embedded pile length, ratio of soil modules of upper layer to lower layer and inclined load on the behavior of single pile. These effects can be quantified only by the results of model tests. As a result. in non-homogeneous sand soil, it is shown that the lateral behavior depends upon the ratio of soil modules of upper layer to lower layer more than other factors. And it was found that the relationship between the deflection ratio of non-homogeneous sand to homogeneous sand and the ratio of lower layer height to embedded pile length can be fitted to exponential function of H/L by model tests results. For the inclined load applied, it is shown that the bending moment-depth relationship is not similar to the case of laterally loaded pile and the depth of maximum bending moment at relative density of 90% increases about 70% more than the pile only loaded laterally.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.75-84
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• 2013

Soil freezing is a phenomenon arising due to temperature difference between atmosphere and ground, and physical properties of soils vary upon the phase change of soil void from liquid to solid (ice). A heat-transfer mechanism for this case can be explained by the conduction in soil layers and the convection on ground surface. Accordingly, the evaluation of proper thermal properties of soils and the convective condition of ground surface is an important task for understanding freezing phenomenon. To describe convection on ground surface, simplified coefficient methods can be applied to deal with various conditions, such as atmospheric temperature, surface vegetation conditions, and soil constituents. In this study, two methods such as n-factor and convection coefficient for the convective ground surface boundary were applied within a commercial numerical program (TEMP/W) for modeling soil freezing phenomenon. Furthermore, the numerical results were compared to laboratory testing results. In the series of the comparison results, the convection coefficient is more appropriate than n-factor method to model the convective boundary condition.

• Journal of Environmental Health Sciences
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• v.46 no.2
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• pp.150-158
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• 2020

Objective: This study is designed to measure the concentration of DBPs (disinfection by-products) in pool water and in air and to estimate the carcinogenic potential through the evaluation of inhalation exposure. Methods: The subjects were six indoor swimming pools with many users in Gwangju. Samples of pool water and indoor air were taken every one month from August 2018 to August 2019 and analyzed for eight swimming pool standards. Three-liter air samples were collected and the VOCs were analyzed using GC/MS directly connected to thermal desorption. Results: pH was 6.8-7.5 and the concentration of free residual chlorine in pool water was 0.40-0.96 ?/ℓ. Physicochemical test items such as KMnO₄ consumption and heavy metal items such as Aluminum met existing pool hygiene standards. No VOC materials were detected except for the DBPs. The concentration of THMs in the pool water was 11.05-41.77 ㎍/L and the THMs mainly consist of Chloroform (63-97%) and BDCM (3-31%). The concentration of indoor air THMs is 13.24-32.48 ㎍/㎥ and consists of Chloroform. The results of carcinogenic assessment of chloroform in the indoor swimming pool via inhalation exposure were 2.0 to 6.4 times higher than the 'acceptable risk level' suggested by the US EPA. Conclusions: The concentration of THMs in the pool water is 11.05-41.77 ㎍/L, most of which is chloroform. In addition, the concentration of indoor air THMs is 13.24-32.48 ㎍/㎥. The result of carcinogenic assessment of chloroform was 2.0 to 6.4 times higher than the 'acceptable risk level' suggested by the US EPA.

• Journal of Environmental Science International
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• v.27 no.4
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• pp.241-250
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• 2018

The objective of this study was to estimate air quality trends in the study area by surveying monthly and seasonal concentration trends. To do this, the mass concentration of $PM_{10}$ samples and the metals, ions, and total carbon in the $PM_{10}$ were analyzed. The mean concentration of $PM_{10}$ was $33.9{\mu}g/m^3$. The composition of $PM_{10}$ was 39.2% ionic species, 5.1% metallic species, and 26.6% carbonic species (EC and OC). Ionic species, especially sulfate, ammonium, and nitrate, were the most abundant in the $PM_{10}$ and had a high correlation coefficient with $PM_{10}$. Seasonal variation of $PM_{10}$ showed a similar pattern to those of ionic and metallic species. with high concentration during the winter and spring seasons. $PM_{10}$ showed high correlation with the ionic species $NO_3{^-}$ and $NH_4{^+}$. In addition, $NH_4{^+}$ was highly correlated with $SO{_4}^{2-}$ and $NO_3{^-}$. We obtained four factors through factor analysis and determined the pollution sources using the United States Environmental Protection Agency(U.S. EPA) pollution profile. The first factor accounted for 51.1% of $PM_{10}$ from complex sources, that is, soil, motor vehicles, and secondary particles: the second factor indicated marine sources; the third factor, industry-related sources; and the last factor, heating-related sources. However, the pollution profile used in this study may be somewhat different from the actual situation in Korea because it was from US EPA. Therefore, to more accurately estimate the pollutants present, it is necessary to create a pollution profile for Korea.

• KSBB Journal
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• v.15 no.1
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• pp.100-105
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• 2000

Optimal medium composition, culture conditions, characteristics of phase variation and activity of insecticidal toxin by Xenorhabdus nematophilus isolated and identified from Korean entomopathogenic nematode Steinernema carpocapsae were examined. Optimal medium composition of this strain was 50-70 g/L yeast extract, 3 g/L $K_{2}HPO_{4}$, 1g/L $NH_{4}H_{2}PO_{4}$, 2g/L ${MgSO}_4$$\cdot$${7H}_{2}O$, 10g/L NaCl and, these, yeast extract was found as a limiting nutrient for cell growth. When Monod equation was applied, maxmum specific growth rate and Monod constant were estimated as 0.13 $hr^{-1}$ and 20g/L, respectively. The pH of culture medium increased up to 8.5-9.5 regardless of initial pH 6-7 as the cells continued to grow. The specific growth rate in a 7 L fermentor was 0.18 $hr^{-1}$, which was enhancement 1.4 fold compared to a flask culture. In case of phase variation, phase I fraction was maintained above 90% at the stationary phase for both flask and fermentor cultures. According to oral toxicity test of Gallena mellonella by Xenorhabdus nematophilus, the addition of cell pellets into feed inhibited normal growth of insect larvae and killed completely then after 20 days cultivation. When culture supernatant of this strain was injected into hemolymph of insect larva, the toxicity was strongest at 24hr cultivation in the early exponential phase and gradually decreased as the culture time proceeded.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1015-1020
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• 2012

Lignite of low rank coal and petroleum coke of high sulfur content can be high potential energy sources for coal gasification process because of their plentiful supply. The steam gasification of lignite, anthracite, and pet coke has been carried out in both an atmospheric thermobalance reactor and a lab-scale fludized bed reactor (0.02 m i.d. ${\times}$ 0.6 m height). The effects of gasification temperature ($600{\sim}900^{\circ}C$) and partial pressure of steam (0.15~0.95 atm) on the gasification rate and on the heating value of product gas have been investigated. The modified volumetric reaction model was applied to the experimental data to describe the behavior of carbon conversion, and to evaluate kinetic parameters of char gasification. The results shows that higher temperature bring more hydrogen in the product syngas, and thus increased gas heating value. The feed rate of steam is needed to be optimized because an excess steam input would lower the gasification temperature which results in a degradation of fuel quality. The rank of calorific value of the product gas was anthracite > lignite > pet coke. Their obtained calorific value at $900^{\circ}C$ with 95% steam feed were 10.0 > 6.9 > 5.7 $MJ/m^3$. This study indicates that lignite and pet coke has a potential in fuel gas production.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.6
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• pp.922-927
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• 1996

In order to investigate heat-induced gelation properties of $\alpha-lactalbumin(\alpha-La),$ total free SH groups, half-cystine, and disulfide bond contents of $\alpha-La$ gels prepared in 0.1M Tris-HCI buffer(pH 8.0) were measured. The samples were heated at $90^{\circ}C$ for 40 minutes under different PH and concentrations of NaCl, $CaCl_2,$ $\alpha-La,$ N-ethylrnaleirnide(NEM), and dithiothreitol(DTT). Total free SH groups were low at high concentrations of $\alpha-La$ and at pH 6.5~8.5, and were $14.72~18.58\mu\textrm{m}ol/g$ and $14.17~16.11\mu\textrm{m}ol/g,$ respectively. Half-cystine contents of NEM-induced gels decreased with increasing concentration of NEM, and were $1.03~39.17\mu\textrm{m}ol/g.$ Disulfide bonds of DTT-induced gels increased with increasing concentration of DTT, and were $70.04~71.80\mu\textrm{m}ol/g$.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.293-298
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• 2005

Lab scale experimental study was carried out for SBR process, to investigate the effects of influent ship sewage organic compound removal and Bacillus sp. state on design parameters. This process was able to remove nitrogen and phosphorus as well as organic matter efficiently. More than 95% of chemical oxygen demand(COD) were removed. In addition, about 97% of total nitrogen (T-N) was reduced. The total phosphorus(T-P) reduction averaged 93%. The performance load of SBR process was shown to be 0.095kg ${\cdot}$ TOC/$m^{3}$ ${\cdot}$ day. The pH was decreased from 8.1 to 7.0 within 30 min and increased to 7.3 at the end of anoxic stage, and these phenomena were explained. The sluge produced in the SBR process is characterized by low generation rate (about 0.36kg ${\cdot}$ MLSS/kg ${\cdot}$ TOC) and excellent settleability. The number of Bacillus sp. in the SBR was 24.2%, indicating that Bacillus sp. was a predominant species in the reactor.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.261-271
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• 2003

A condition evaluation procedure for the pavement foundations using multi-load level Falling Weight Deflectometer(FWD) deflections is presented in this paper. A dynamic finite element program incorporating a stress-dependent material model, was used to generate the synthetic deflection database. Based on this synthetic database, the relationships between surface deflections and critical responses, such as stresses and strains in base and subgrade layers, have been established. FWD deflection data, Dynamic Cone Penetrometer(UP) data, and repeated load resilient modulus testing results used in developing this procedure were collected from the Long Term Pavement Performance (LTPP) and North Carolina Department of Transportation (NCDOT) database. Research effort focused on investigation of the effect of the FWD load level on the condition evaluation procedures. The results indicate that the proposed procedure can estimate the pavement foundation conditions. It is also found that structurally adjusted Base Damage Index (BDI) and Base Curvature Index (BCI) are good indicators for the prediction of stiffness characteristics of aggregate base and subgrade respectively. A FWD test with a load of 66.7 kN or less does not improve the accuracy of this procedure. Results from the study for the nonlinear behavior of a pavement foundations indicate that the deflection ratio obtained from multi-load level deflections can predict the type and quality of the pavement foundation materials.