• Korean Journal of Ecology and Environment
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• v.34 no.2 s.94
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• pp.106-118
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• 2001

The chemistry of porewater and exchangeable nutrients of sediment was determined to define potential influence of sediment nutrients on the water quality and the phytoplankton growth in Taechong Reservoir in March and May of 2000. The sediment-water interface showed almost anoxic state, < 0.5 mg $O_2/l$. Conductivity of the porewater was higher 1.9${\sim}$2.6 fold than that of sediment, and its variation was greater in the shallow water. Eh ranged from -12mV to -148 mV and bulk density from $1.17\;g/cm^3$ to $1.30\;g/cm^3$ and they did not differ among stations. The water content in the sediment ranged from 58% to 72% and organics from 8% to 13%, and they were higher toward the lower part of reservoir. Soil texture was in the order of sand>clay>silt and sandy sediment accounted for 97% of the total sediment. The total bacterial numbers and diatom abundance were high in the downstream of the reservoir. In porewater and exchangeable nutrients of sediment, nitrogen and phosphorus were mostly consist of the particulate form. Inorganic nitrogen was mostly composed of $NH_4$. Nitrogen of porewater was mostly an inorganic form while exchangeable nutrients were composed an organic form. However, phosphorus was composed of dissolved organic fraction in the porewater while inorganic fraction in the exchangeable nutrients. Silicon content of sediment was much exchangeable nutrients with 63%, and it was higher than in the porewater. In summary, the sediments of Taechong Reservoir were mostly composed of organics and assessed to be a eutrophic state.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.285-294
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• 1994

Some supported gold catalysts were prepared by impregnation and coprecipitation methods. Effect of gold addition and active sloe formation were studied by investigating particle sizes of gold, amounts of oxygen adsorbed, adsorption properties of CO and NO, and reduction and oxidation properties, etc.. The gold particles of the catalyst by impregnation were irregular and very large as 30~100 nm, but those by coprecipitation were uniform and ultra-fine as about 4 nm. On $Au/Al_2O_3$ catalyst, the addition of gold to inactive $Al_2O_3$ caused the decomposition of $N_2O$, and CO was not irreversibly adsorbed while $O_2$ was atomically and irreversibly adsorbed. The adsorption sites of oxygen were attributed to the active sites which were restricted to the circumference of hemispherical gold particle-support interface rather than all atoms on the surface of gold particle. Also, CO was reversibly and irreversibly adsorbed on $Al_2O_3$ at low temperature, and the addition of gold weakened both reversible and irreversible adsorptions. The affinity for CO on $Au/Co_3O_4$ catalyst decreased conspicuously compared to $Co_3O_4$. The effect of gold addition did not appear in reduction step but did remarkably in reoxidation step; the added gold promoted the reoxidation of the reduced cobalt atoms.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.3
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• pp.132-139
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• 1997

CTD and current observation were taken to investigate the structure of the cold water in the Western Channel of the Korea Strait in October 1993. Thickness of the cold water in the deep trough of the strait changes from 20 m to 70 m according to the water depth. Thermocline between the Tsushima Warm Water and the cold water deepens from north to south with 0.00057 in slope. Temporal variation of the thickness appears to be related with the tidal current. The maximum variation is 20 m for 48 hours. Mean velocity of the cold water for 72 hours is 17 cm/sec southward. A simple model was used to understand dynamically the southward flow of the cold water and the return flow at the upper part in the lower layer. Calculated maximum southward flow and eddy viscosity coefficient are 7 cm/sec and 0.038 $m^2$/sec respectively in the model. Southward transport is $0.032$\times$10^6㎥/sec$ at the northern part in the trough and decreases from north to south due to the presence of the return flow. Southward transport increases with the increase in the upper layer transport but is not affected by the density of the upper layer or the interface slope.

• Journal of the Korean Magnetics Society
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• v.16 no.6
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• pp.279-282
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• 2006

Magnetic tunnel junctions (MTJs), which consisted of amorphous ferromagnetic NiFeSiB free layers, were investigated. The NiFeSiB layers were used to substitute for the traditionally used CoFe and/or NiFe layers with the emphasis being given to obtaining an understanding of the effect of the amorphous free layer on the switching characteristics of the MTJs. $Ni_{16}Fe_{62}Si_{8}B_{14}$ has a lower saturation magnetization ($M_{s}:\;800\;emu/cm^{3}$) than $Co_{90}Fe_{10}$ and a higher anisotropy constant ($K_{u}:\;2700\;erg/cm^{3}$) than $Ni_{80}Fe_{20}$. The $Si/SiO_{2}/Ta$ 45/Ru 9.5/IrMn 10/CoFe $7/AlO_{x}/CoFeSiB\;(t)/Ru\;60\;(in\;nanometers)$structure was found to be beneficial for the switching characteristics of the MTJ, leading to a reduction in the coercivity ($H_{c}$) and an increase in the sensitivity resulted from its lower saturation magnetization and higher uniaxial anisotropy. Furthermore, by inserting a very thin CoFe layer at the tunnel barrier/NiFeSiB interface, the TMR ratio and switching squareness were improved more with the increase of NiFeSiB layer thickness up to 11 nm.

• Journal of the Korean Chemical Society
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• v.39 no.11
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• pp.869-877
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• 1995

Carbonation process of Jung sun slake lime$(Sr(OH)_2=0.053 wt%)$ suspension with $CO_2$ gas at 30∼80$^{\circ}C$ has been studied to investigate the formation process of aragonite. The reaction temperature at above $50^{\circ}C$, rhombic nuclei of $SrCO_3$ has been grown with the interaction of $CO_3^{2-}$(aq) which is profitable to growth the nuclei at the liquid film of gas-liquid interface to form pillar aragonite crystal. At $40^{\circ}C$, the controlling of concentration of $CO_2$(aq) at the beginning of the reaction has been made the nuclei to growth to be an aragonite crystal. Addition of some $Sr(OH)_2$ to Yi Lee slake lime $(Sr(OH)_2=0.011 wt%)$ suspension and controlling the concentration of $OH^-$(aq) and $CO_2$(aq), the carbonation reaction produced pillar aragonite crystal with the short side of 0.1∼0.2 ${\mu}m$ and long side of 1∼2 ${\mu}m.$

• Journal of Energy Engineering
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• v.22 no.3
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• pp.270-282
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• 2013

Combustible waste into energy policy is an effective method to respond to climate change and depletion of fossil fuels. Combustible waste into energy is the process of generating energy in the form of electricity and/or heat from the combustible waste such as vinyl, paper and plastic. This study tries to estimate the external benefit of enhancing the ratio of combustible waste into energy to primary energy from 1.89% to 5% using contingent valuation(CV) method. To this end, we report the results from a CV survey to elicit the willingness to pay (WTP) for combustible waste into energy. A CV survey of 500 households was conducted in the Seoul by using person-to-person interviews. Thus, the procedures of applying and the findings from the one-and-one-half bounded dichotomous choice spike model used to deal with the zero WTP responses are provided in the paper. The results show that the average WTP is estimated to be 2,724 won per household per month and statistically significant at the 5% level. Expanding the value to the Seoul gives us an aggregate value of 13.7 billion won per year.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.

• Korean Journal of Remote Sensing
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• v.37 no.5_2
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• pp.1317-1328
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• 2021

This study analyzes the early satellite mission marine fog detection results from Geostationary Ocean Color Imager-II (GOCI-II). We investigate optical characteristics of the GOCI-II spectral bands for marine fog between October 2020 and March 2021 during the overlapping mission period of Geostationary Ocean Color Imager (GOCI) and GOCI-II. For Rayleigh-corrected reflection (R_rc) at 412 nm band available for the input of the GOCI-II marine fog algorithm, the inter-comparison between GOCI and GOCI-II data showed a small Root Mean Square Error (RMSE) value (0.01) with a high correlation coefficient (0.988). Another input variable, Normalized Localization Standard (NLSD), also shows a reasonable correlation (0.798) between the GOCI and GOCI-II data with a small RMSE value (0.007). We also found distinctive optical characteristics between marine fog and clouds by the GOCI-II observations, showing the narrower distribution of all bands' R_rc values centered at high values for cloud compared to marine fog. The GOCI-II marine fog detection distribution for actual cases is similar to the GOCI but more detailed due to the improved spatial resolution from 500 m to 250 m. The validation with the automated synoptic observing system (ASOS) visibility data confirms the initial reliability of the GOCI-II marine fog detection. Also, it is expected to improve the performance of the GOCI-II marine fog detection algorithm by adding sufficient samples to verify stable performance, improving the post-processing process by replacing real-time available cloud input data and reducing false alarm by adding aerosol information.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.3
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• pp.169-189
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• 2024

In the current work, a series of three-dimensional finite element analyses have been carried out to understand the behaviour of pre-existing single piles and pile groups to adjacent Shield TBM tunnelling by considering various reinforcement conditions. The numerical modelling has analysed the effect of the pile cutting, ground reinforcement and pile cap reinforcement. The analyses concentrate on the ground settlements, the pile head settlements, the axial pile forces and the shear stress transfer mechanism at the pile-soil interface. In all cases of the pile tips supported by weathered rock, the distributions of shear stresses presented a similar trend. Also, when the pile tips were cut, tensile forces or compressive forces were induced on the piles depending on the relative positions of the piles. Furthermore, when the pile tips are supported by weathered rock, approximately 70% of the load is supported by surface friction, and only the remaining 30% is supported by the pile tip. Furthermore the final settlement of the piles without reinforcement showed approximately 70% more settlement than the piles for which ground reinforcement is considered. It has been found that the ground settlements and the pile settlements are heavily affected by the pile cutting and reinforcement conditions. The behaviour of the single pile and group piles, depending on the pile cutting, conditions of ground and pile cap reinforcement, has been extensively examined and analysed by considering the key features in great details.

• Radiation Oncology Journal
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• v.20 no.4
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• pp.316-322
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• 2002

Objective : A retrospective study was peformed to evaluate whether postoperative adjuvant radiotherapy can improve survival and decrease recurrence as compared with surgery alone in resected esophageal cancer. Materials and Methods : From Jan. 1985 to Dec. 1993, among 94 esophageal cancer Patients treated with surgery, fifty-one patients were included in this study. Transthoracic esophagectomy was peformed in 35 patients and transhiatal esophagectomy in 16. Postoperative adjuvant radiotherapy was peformed 4 weeks after surgery in 26 among 38 patients in stage II and III. A total dose of $30\~60\;Gy$ in 1.8 Gy daily fraction, median 54 Gy over 6 weeks, was delivered in the mediastinum+both supraclavicular lymph nodes or celiac lymph nodes according to the tumor location. Forty-seven patients$(92\%)$ had squamous histology. The median follow-up period was 38 months. Results : The overall 2-year and 5-year survival and median survival were $56.4\%,\;36.8\%$ and 45 months. Two-year and 5-year survival and median survival by stage were $92\%,\;60.3\%$ for stage I, $63\%,\;42\%$ and 51 months for stage II and $34\%,\;23\%$ and 19 months for stage III (p=0.04). For stage II and III patients, 5-year survival and median survival were $22.8\%$, 45 months for the surgery alone group and $37.8\%$, 22 months for the postoperative RT group (p=0.89). For stage III patients, 2-year survival and median survival were $0\%$, 11 months for the surgery alone group and $36.5\%$, 20 months for the postoperative RT group (p=0.14). Local and distant failure rates for stage II and III were $50\%,\;16\%$ for the surgery alone and $39\%,\;31\%$ for the postoperative RT group. For N1 patients, local failure rate was $71\%$ for the surgery alone group and $37\%$ for the postoperative RT group (p=0.19). Among 10 local failures in the postoperative RT group, in-field failures were 2, marginal failures 1, out-field 5 and anastomotic site failures 2. Conclusion : There were no statistically significant differences in either the overall survival or the patterns of failure between the surgery alone group and the postoperative RT group for resected stage II and III esophageal cancer. But this study showed a tendency of survival improvement and decrease in local failure when postoperative RT was peformed for stage III or N1 though statistically not significant. To decrease local failure, a more generous radiation field encompassing the supraclavicular, mediastinal, and celiac lymph nodes and anastomotic site in postoperative adjuvant treatment should be considered.