• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.148-155
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• 1992

For the enhancement of the concrete durability, we developed high - durable portland cement (ACTPC) by physical treatment of ordinary portland cement with asphalt and carbon black. In this research, the hydration reaction characteristics of ACTPC were studied by using SEM, X-Ray, Conduction Micro Calolimeter etc. When the ACTPC is mixed with water, it is believed the asphalt films on cement particles suppress the early stage of hydration reactions of cements, because the films hinder the contact with water and the elusion of soluble ions from particles. But the carbon blacks on the cement particles accelerated the hydration reactions of cement after a while, because the micro particles can be used as seed crystals in $CaO-SiO_2-H_2O$ gel formation.

• 한국해양학회지
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• v.26 no.3
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• pp.278-290
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• 1991

A synoptic survey of chemical properties was carried out at 21 stations in the Ulleung Basin in May 1988 on board T/V HANBADA. Vertical structures of typical profiles are: surface mixedlayer waters in the upper 30∼40 m with depleted nutrients concentrations, thermocline waters with rapid variations in all physical and chemical properties. and deep Waters below 200 m which are nearly homogeneous. Along the northern section at 37$^{\circ}$12'N. The salinity minimum layer was observed at about 190m. which characterize the East Sea Intermediate Water (ESIW). The dissolved oxygen concentration in this layer was about 230∼ 275uM, lower than 290uM (6.5ml/l) which is the previously known characteristics of the ESIW. However, apparent oxygen utilization (AOU), nitrate, phosphate and silicate show systematically low concentration in the salinity-minimum layer. The low values of AOU and all the nutrients associated with the salinity-minimum, may be useful to identify the ESIW and serve as a new tracer in the East Sea.

• Journal of the Korean Geotechnical Society
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• v.40 no.1
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• pp.39-46
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• 2024

Artificial recharge systems have been employed to solve drought problems due to global climate change. Despite the increased usage, the applications of artificial recharge systems are limited by clogging problems, which reduce recharge rates. In this study, the soil texture and mineral characteristics of alluvial soil in a planned artificial recharge system area were investigated to evaluate the possibility of chemical clogging during the injection of stream water. The primary minerals contained in the clastic particles are quartz, K-feldspar, plagioclase, and biotite, and the secondary minerals filling the pore space are illite, kaolinite and Fe-oxide. The fact that carbonate and sulfate are observed as secondary minerals in the pore space suggests that chemical clogging has not occurred by the interaction between the groundwater and surface water in the study area. Thus, monitoring soil properties, e.g., the formation and growth of secondary minerals in the pore space, is required to investigate the possibility of chemical clogging in artificial recharge systems.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.77-82
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• 1998

It was investigated to evaluate the characteristics of cement-flyash paste affected the replacement level, curing method and chemical admixtures. The strength of cement-flyash paste was lower than that of cement paste only and the differences increased with increasing the replacement level. However, in steam curing, the strength of cement-flyash pastes was improved and specially, the early strength was effectively increased. In order to improve the early strength, the use of $Na_2SO_4$ in cement-flyash paste increased the quality of concrete. In addition, the strength of concrete including 30% of fly ash has improved and obtained the highest strength compared to other concrete mix.

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.439-442
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• 2007

A solid state Hg(Au)/HgO reference electrode was prepared utilizing gold amalgam solid particles. Solid fine powder of the gold amalgam was prepared by chemical reduction of Au(III) with NaBH4 followed by reduction of Hg(II) in the presence of gold fine particles. The solid content in the suspension of the gold amalgam particles and fine mercury oxide particles in DMF containing PVC was precipitated by the addition of a large amount of water to give solid Hg(Au)/HgO/PVC mixture. After drying, the mixture was pressure-molded to a physically stable Hg(Au)/HgO composite reference electrode material. The electrochemical characteristics of the electrode as a reference electrode were very similar to an ordinary Hg/HgO reference electrode. The electrode material can be molded and fabricated in any desired shape and size. The surface can be renewed by a simple polishing process whenever contaminated or deactivated. The applicability of the electrode in the electrochemical detection of carbohydrates after anion exchange separation was evaluated.

• Carbon letters
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• v.1 no.1
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• pp.1-5
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• 2000

The effect of surface free energy on the positive temperature coefficient (PTC) of carbon black/thermoplastic resin composites was investigated. The thermoplastic resins such as EVA, LDPE, LLDPE and HDPE were used with the addition of 30 wt.% of the carbon black. The surface free energy of the composites was studied in the context of two-liquid contact angle measurements, i.e., deionized water and diiodomethane. It was observed that the resistivity on PTC composites Was greatly increased near the crystalline melting temperature, due to the thermal expansion of polymeric matrix. From the experimental results, it was proposed that the decrease of surface free energy induced by interactions between carbon black surfaces and polymer chains is an important factor to the fabrication of a PTC composite made of carbon black and polymeric matrix.

• Journal of the Korean Applied Science and Technology
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• v.15 no.1
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• pp.1-7
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• 1998

Lubricating softner(SOS-2) for permanent press(PP) finish was prepared by blending water, beef tallow hardened oil for improving softness, and the emulsion which was synthesized from N-hexadecanoyl-N,N'-bis(2-hexadecamidoethyl)amine as a softening component and silicone oil KF-96 as a lubricating component. The prepared SOS-2 and the PP finishing resin were applied to PP finishing cotton broad cloth and P/C gingham samples using one bath method. The properties such as tear strength, crease recovery, bending resistance test were tested. The samples treated with SOS-2 and PP finishing resin have improved properties, compared with nontreated samples, those treated only with PP finishing resin, those treated with commercial PP finishing softners and PP finishing resin.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.715-719
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• 1996

Thin films of polyaniline (PANI) salts were in situ deposited on a Pt plate during either chemical polymerization or electrochemical polymerization. The oxidation states of the salt films were controlled by the applied DC potential. AC impedance of the Pt/PANI electrode were measured in monomer-free 1 N HCl solution in order to investigate the electrodic properties of the films at the following applied DC potentials: 0, 0.45 and 0.75 V vs. SCE. Very small differences in film conductivity according to its oxidation state were observed by analysis of the impedance spectra, the reasons of which are complicated by enriched water content in the film and possible decrease in the film thickness during the measurements. The electrochemical activity of the film/solution interface varied with its oxidation state. Stability of the film in 1 N HCl solution was also evaluated by impedance and cyclic voltammetry measurements.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.3
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• pp.77-86
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• 2005

A monitoring study has been conducted to identify hydrologic conditions, water quality and nutrient loading characteristics of small watershed in Juam Lake. Climate data of the watershed were collected; flow rate was measured and water quality sampling was conducted at the watershed outlet for this study. Water quality data revealed that T-P concentrations meet I grade of lake water quality standard during non-storm period, but degraded up to II-III grade of lake water quality standard during storm period. The observed T-N concentrations always exceeded lake water quality standard. Therefore, T-P was identified as limiting chemical constituent for eutrophication of Juam Lake. T-P concentration of non-storm period also revealed that point source pollution is not serious in the watershed. Three year monitoring results showed that the observed T-N losses were $10.85\~18.88$ kg/ha and T-P losses were $0.028\~0.323$ kg/ha during six month (Mar. - Oct.), respectively. Major portion of runoff amount discharged by a few storm events a year and nutrient load showed apparent seasonal variation. Huge runoff amounts were generated by intense storms, which make application of water treatment or detention facilities ineffective. Monitoring results confirmed that water quality improvement by abating nonpoint source pollution in rural watershed of monsoon climate should be focused on source control. T-P losses from paddy field seemed to consist of significant amount of total load from study watershed. Therefore, management of drainage from paddy field is considered to be important for preventing algal blooming problem in Juam Lake.

• Environmental Engineering Research
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• v.10 no.5
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• pp.227-238
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• 2005

The characteristics of nitrogen removal by the free cell and the immobilized cell of R. capsulatus were investigated. Denitrification by R. capsulatus cells resulted in reduction of ORP with the rapid depletion of DO and the increase of pH. Without accumulation of nitrite, the removal efficiencies of ${NO_3}^-$-N for the free cell and the immobilized cell were 99.1 and 99.3%, respectively. During the three-month experiment of goldfish breeding equipped with a water-purification biofilter, the average values of pH and total cell numbers present in an aquarium were not significantly different between water-purification system and the control. The average concentrations of ${NH_4}^+$-N and ${PO_4}^{2-}$-P in water-purification system were relatively low, compared to that in the control. Goldfish died at $11^{th}$, $16^{th}$, $43^{rd}$, and $67^{th}$ days in the control, while goldfish died at $10^{th}$, $20^{th}$, and $39^{th}$ days in the water-purification system. On the days of goldfish's death, the total concentrations of nitrogenous compounds except for ${NO_2}^--N$ were higher than those on the other days of the experiment, especially with the concentrations of ${NH_4}^+$-N ranging from 7.4 to 13.5 mg/L. The water-purification system also showed the less turbidity of water with more active movement of goldfish than the control. PVA gel beads showed almost the full denitrifying ability even after the long-term experiment. As a result, the water-purification system was effective to remove nitrogenous compounds with better survival of goldfish.