• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.79-84
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• 1993

This paper describes the development of lithium rechargeable cell. $LiCoO_2$ is recently recognized as a suitable cathode active material of a high voltage, high energy lithium rechargeable batteries because $Li^+$ ion can be electrochemically deintercalated/intercalated from/to $Li_xCoO_2$. The transition metal oxide of $LiCoO_2$ was investigated for using as a cathode active material of 4V class Li rechargeable cell. $LiCoO_2$ cathode was prepared by using a active material of 85 wt%, graphite powder of 12 wt% as a conductor and poly-vinylidene fluoride of 3 wt% as a binder. The electrochemical and charge/discharge properties of $LiCoO_2$ were investigated by cyclic voltammetry and galvanostatic charge/discharge. The open circuit voltage of prepared $LiCoO_2$ electrode exhibited approximately. potential range between 3.32V and 3.42V. During the galvanostatic charge/discharge, $LiCoO_2/Li$ cell showed stable cycling behavior at scan rate of 1mV/sec and potential range between 3.6V and 4.2V. Also its coulombic efficiency as function of cycling was 81%~102%. In this study the $LiCoO_2/Li$ cell showed the available discharge capacity of 90.1 mAh/g at current density of $1mA/cm^2$ and cell discharge voltage range between 3.6V~4.2V.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.159-166
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• 2008

The dental caries can be recovered or worse depending on the velocity of de- and remineralization of tooth. It is possible to remineralize the lesions by fluoride agent, but the results can be distinguished according to one's salivary flow rate, quantity of ion contents, and pH of the saliva. This article presents good results after applying the CPP-ACP paste for the patients who have incipient enamel caries. We instructed the patients to apply the paste everyday in the customed tray. We observed the white spot lesions without getting worse and reducing the size of lesions. After applying the CPP-ACP paste for 6 weeks, we concluded that; 1. It was possible to remineralize the incipient caries without preparation of the teeth. 2. CPP-ACP paste was successful for recovery of the demineralized lesions, especially for mild and moderate caries lesions, not for the severe developemental defects or chronic lesions. 3. CPP-ACP paste was efficient for pediatric patients, and the custumed tray was very useful for patients to apply the paste. 4. The ability of the patients for caring their oral hygiene was improved by routine check up and instructions.

• Journal of the Korean Electrochemical Society
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• v.4 no.1
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• pp.6-9
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• 2001

[ $SiO_2$ ] effect on the electrochemical properties of polymeric gel electrolytes(PGEs) reinforced with glass fiber cloth(GFC) was investigated . PGEs were composed of polyacrylronitrile(PAN), poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)), $LiClO_4$ and three kind of plasticizer(ethylene carbonate, dietyl carbonate, propylene carbonate). $SiO_2$ was added to PGEs in the weight fraction of 10, 20, $30\%$ respectively. PGEs containing $SiO_2$ showed conductivity of over $10^{-3}S/cm\;at\;23^{\circ}C$ and electrochemical stability window to 4.8V. In the impedance spectra of the cells, which were constructed by lithium metals as electrodes, interfacial resistance increased due to growth of passivation layer during storage time and remarkable difference was not observed with content of $SiO_2$. In the impedance spectra of the lithium ion polymer batteries consisted of $LiClO_2$ and mesophase pitch-based carbon fiber(MCF), ohmic cell resistance of $SiO_2-free$ PGE was changed continuously with number of cycle, but those of $SiO_2-dispersed$ PGEs were not. Discharge capacity of the PGE containing $20wt\%\;SiO_2$ showed 132 mAh/g at 0.2C rate and $85\%$ of discharge capacity was retained at 2C rate.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.145-149
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• 2004

It is necessary for managing a perfect process for degasing aluminum molten metal according to the increase of a grade of aluminum and its alloy products. There are some methods that have been used to manage a degasing process in recent years, such as an injection method that uses aluminum molten metal powder and chemicals supplier and input method that supplies argon and nitrogen, or chlorine gas by using a gas blow-tube. However, these methods show some problems, and it shows that it is a difficult process to handle. pollution due to the producing a lot of toxic gases like chlorine and fluoride gas. irregular effects, and lowering work efficiency due to the excessive processing time. The problems that are the most fatal are the producing a lot of sludge due to the reaction of aluminum molten metal with chemicals. loss of metals, and decreasing the life of refractory materials. In order to solve these problems. this paper develops a technology that is related to aluminum continuous casting molten metal and monolithic degasing apparatus. A degasing apparatus developed in this study improved the exist ing methods and prevented environmental pollution wi th smokeless. odor less, and harmlessness by using a new method that applies argon and nitrogen gas in which the methods used in the West and Japan are eliminated. The developed method can significantly reduce product faults that are caused by the production of gas and oxidation because it uses a preprocessed molten metal with chemicals. In addition. the amount of the produced sludge can also be reduced by 60-80% maximum compared with the existing methods. Then. it makes it possible to minimize the loss of metals. Moreover. the molten metal processing and settling time is also shortened by comparing it with the existing methods that are applied by using chemicals. In addition, it does much to improve the workers' health, safety and environment because there is no pollution. The improvement of productivity and prevent ion effects of disaster from the results of the development can be summarized as follows. It will contribute to the process rationalization because it does not have any unnecessary processes that the molten metal will be moved to an agitator by using a ladle and returned to process for degasing like the existing process due to the monolithic configuration. There are no floating impurities due to the oxidation caused by the contact with the air as same as the existing process. In addition. it can protect the blending of precipitation impurities. Because it has a monolithic configuration. it can avoid the use of additional energy to compensate the temperature decreasing about 60t that is caused by the moving of molten metal. It is not necessary to invest an extra facilities in order to discharge the gas generated from a degasing process by using an agitator. The working environment can be improved by the hospitable air in the factory because the molten metal is almost not exposed in the interior of the area.

• Korean Journal of Microbiology
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• v.40 no.4
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• pp.269-274
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• 2004

Serratia proteamaculans isolated from the midgut of a spider formed big halos around the bacterial colonies, indicating that the bacterial strain produces an extracellular protease. Activity staining of the extracellular pro­tein fractions using zymogram also demonstrated that the major protein with an estimated molecular mass of 52 kDa contained a high proteolytic activity. The protease was purified to near electrophoretic homogeneity from the culture supernatant after filtration and ion exchange and size exclusion chromatography. The purified enzyme had a relatively high proteolytic activity between pH 6.0 and 10.0 and at broad temperature range. The proteolytic activity of the enzyme was not inhibited by phenylmethylsulfonyl fluoride but strongly inhibited by 1, 10-phenanthroline and EDTA. The activity also was dependent on the presence of $Ca^{++}\;and\;Zn^{++}$ ions. These observations indicate that the enzyme is a metalloprotease.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.26-31
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• 2023

For durability improvement of polymer electrolyte membrane fuel cell (PEMFC) polymer membrane, accelerated durability evaluation methods that can evaluate durability in a short time have been researched and developed. However, the lifespan of fuel cells for large commercial vehicles such as trucks and buses is more than three times that of passenger cars, and the chemical accelerated stress test (AST) time is also longer, reaching 1,500 hours or more. Therefore, in this study, as a method to evaluate the chemical durability of a membrane within a short time, it was examined whether the durability could be predicted by the pristine membrane characteristics. Hydrogen crossover current density (HCCD) and short resistance (SR) were estimated as initial characteristics, and AST time was predicted through the Fenton experiment, which was possible as an out-of-cell experiment for 3 hours. As the HCCD and fluoride ion emission concentration increased, the AST time tended to be linearly shortened, but there was a deviation (R² ≒0.65). When the SR decreased, the AST time showed a linear increase, and the accuracy was high (R² =0.93), so the AST time could be predicted with the initial SR of the membrane.

• The Korean Journal of Nuclear Medicine Technology
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• v.14 no.2
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• pp.104-109
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• 2010

Purpose: $[^{18}F]$Fallypride plays an effective radiotracer for the study of dopamine $D_2/D_3$ receptor occupancy, neuropsychiatric disorders and aging in humans. This tracer has the potential for clinical use, but automated labeling efficiency showed low radiochemical yields about 5~20% with relatively long labelling time of fluorine-18. In present study, we describe an improved automatic synthesis of [$^{18}F$]Fallypride using different base concentration for routine clinical use. Materials and Methods: Fully automated synthetic process of [$^{18}F$]Fallypride was perform using the TracerLab $FX_{FN}$ synthesizer under various labeling conditions and tosyl-fallypride was used as a precursor. [$^{18}F$]Fluoride was extracted with various concentration of $K_{2.2.2.}/K_2CO_3$ from $^{18}O$-enriched water trapped on the ion exchange cartridge. After azeotropic drying, the labeling reaction proceeded in $CH_3CN$ at $100^{\circ}C$ for 10 or 30 min. The reaction mixture was purified by reverse phase HPLC and collected organic solution was exchanged by tc-18 Sep-Pak for the clinically available solution. Results: The optimal labeling condition of [$^{18}F$]Fallypride in the automatic production was that 2 mg of tosyl-fallypride in acetonitrile (1 mL) was incubated at $100^{\circ}C$ for 10 min with $K_{2.2.2.}/K_2CO_3$ (11/0.8 mg). [$^{18}F$]Fallypride was obtained with high radiochemical yield about $66{\pm}1.4%$ (decay-corrected, n=28) within $51{\pm}1.2$ min including HPLC purification and solid-phase purification for the final formulation. Conclusion: [$^{18}F$]Fallypride was prepared with a significantly improved radiochemical yield with high specific activity and shorten synthetic time. In addition, this automated procedure provides the high reproducibility with no synthesis failures (n=28).

• The Korean Journal of Nuclear Medicine
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• v.33 no.6
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• pp.527-536
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• 1999

Purpose: Radiotracers that bind to the central benzodiazepine receptor are useful for the investigation of various neurological and psychiatric diseases. [C-11]Flumazenil, a benzodiazepine antagonist, is the most widely used radioligand for central benzodiazepine receptor imaging by PET. We synthesized 3-(2-[F-18]fluoro)flumazenil, a new fluorine-18 ($t_{1/2}$= 110 min) labeled analogue of benzodiazepine receptor imaging agent, and evaluated in vivo for biodistribution in mice. Materials and Methods: Flumazenil (Ro 15-1788) was synthesized by a modification of the reported method. Precursor of 3-(2-[F-18]fluoro)flumazenil, the tosylated flumazenil derivative was prepared by the tosylation of the ethyl ester by ditosylethane. [F-18] labeling of tosyl substitued flumazenil precursor was performed by adding F-18 ion at $85^{\circ}C$ in the hot ceil for 20 min. The reaction mixture was trapped by C18 cartridge, washed with 10% ethanol, and eluted by 40% ethanol. Bidistribution in mice was determined after intravenous injection. Results: The total chemical yield of tosylated flumazenil derivative was ${\sim}40%$. The efficiency of labeling 3-(2-[F-18]fluoro)flumazenil was 66% with a total synthesis time of 50 min. Brain uptakes of 3-(2-[F-18]fluoro)flumazenil at 10, 30, 60 min after injection, were $2.5{\pm}0.37,\;2.2{\pm}0.26,\;2.1{\pm}0.11$ and blood activities were $3.7{\pm}0.43,\;3.3{\pm}0.07,\;3.3{\pm}0.09%ID/g$, respectively. Conclusion: We synthesized a tosylated flumazenil derivative which was successfully labeled with no-carrier-added F-18 by nucleophilic substitution.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.2
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• pp.87-94
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• 1979

In order to study the water pollution in Suyeong Bay, Busan, some chemical constituents were determined at 25 stations in the neap tides on 9 Aug. 1977 and spring tides on 30 Aug. 1977. Range and mean values of the constituents in the spring tides are as follows: $pH\;6.54\~8.06,\;7.54;$ electrical conductivity $0.413\~0.481\times10^5\;\mu\mho/cm,\;0.467\times10^5\;\mu\mho/cm;\;transparency\;0.2\~5.5m,\;2.2m;$ turbidity $1\~60ppm$, 14ppm, chlorosity $15.20\~18.11g/\ell,\;17.67g/\ell;$ fluoride ion $0.94\~1.03ppm$, 0.99ppm; dissolved oxygen $0.17\~7.60ppm$, 4.77ppm; sulfide $0\~0.46ppm$, 0.07ppm; chemical oxygen demand $1.20\~40.74ppm$, 6.11ppm; ammonia-nitrogen $0.060\~0.520ppm$, 0.180ppm; nitrite-nitrogen $0.001\~0.026ppm$, 0.009ppm; nitrate-nitrogen $0\~0.037ppm$, 0.014ppm; phosphate-phosphorus $0.002\~0.261ppm$, 0.050ppm; n-Hexane soluble $0.5\~5.4ppm$, 2.1ppm ; iron $1.0\~104.11\;ppb$, 24.15ppb ; copper $0\~27.45ppb$, 4.19ppb; lead $0\~2.50ppb$, 0.92ppb; zinc $0\~5.15ppb$, 1.47ppb ; cadmium $0\~0.26ppb$, 0.04ppb; and mercury $0.05\~0.37ppb$, 0.11ppb respectively. The variations of the contents of the chemical constituents in the spring tides were larger than in the neap tides. The contents of COD, sulfide, nutrient salts and heavy metals were the highest in the estuary of Suyeong River, and decreased in order of off Kwangan-Ri region, outer Bay and off Haeun-Dae region. The water quality in Suyeong Bay was particularly shown that the concentrations of COO, iron, copper and mercury were higher than those of other coastal aseas and deficiency in dissolved oxygen was observed in some parte of Suyeong Bay. In consideration of the relationship between the chlorosity and the concentrations of nutrient salts, COD and total heavy metals, water pollution of this area is considered due to the inflow of Suyeong River which was extremely polluted by sewage and industrial wastewaters.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.6
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• pp.715-721
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• 2007

Residual calcium concentration is high, in general, at the effluent of the fluoride removal process in the electronics industry manufacturing semiconductor and LCD. To increase the stability of the membrane process incorporated for reuse of wastewater, the residual calcium is required to be pre-removed. Hyperkinetic Vortex Crystallization(HVC) process was installed in the electronics industry manufecturing semi conductor as a pilot scale for accelerating calcification of calcium ion. Compared to the conventional soda ash method, the 31% higher calcium removal efficiency was achieved when HVC was applied at the same sodium carbonate dosage. In order to maintain the economic calcium removal target of 70% preset by manufacturer, the dosing concentration of the soda ash was 530 mg/L based on influent flowrate. The seed concentration in the reactor was one of the critical factors and should be maintained in the range of $800\sim1,200mg$ SS/L to maximize the calcium removal efficiency. The calcite production rate was 0.30 g SS/g $Na_2CO_3$ in the average. The economic HVC passing time of the mixture was in the range of $2\sim5$ times. Relatively, stable calcium concentration was maintained in the range of $30\sim72$ mg/L(average 49 mg/L) although the calcium concentration in the feed was severely fluctuated with $74\sim359$ mg/L(average 173 mg/L). The HVC process was characterized as environment-friendly technology reducing chemical dosage and chemical sludge production and minimizing maintenance cost.