• Journal of the Korean Electrochemical Society
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• v.2 no.3
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• pp.123-129
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• 1999

Initial electrochemical characteristics of $LiCoO_2$ electrode for lithium ion battery with various content of super s black as conductive material were evaluated through the charge/discharge with the potential range of 4.3V to 2.0V versus $Li^+/Li^+$. The rate of C/4 and C/2 by the 3 electrode test cell composed with an electrolytic solution of 1 mol/l $LiPF_6/EC+DEC(1:3\;by\; weight)$. Lithium was used as reference electrode. High impedance charge behavior was observed at early stage of charge. In the case of $3\%w/w$ of super s black as conductive material, the specific resistance of the high impedance releasing was $3.82\;{\Omega}\;{\cdot}\;g-LiCoCo_2$ at the current density of $0.5 mA/cm^2$, which corresponds 7 times of the specific resistance of electrode $(0.728 g-LiCoO_2)$. At second charge, the specific resistance of the high impedance releasing was 63 mn · g-Lico02, which corresponds 12eio of the specific resistance of electrode and only $1.7\%$ of that of the first charge. The first charge and discharge specific capacities at C/4 rate were 160-161 and $153\~155mAh/g-LiCoO_2$, respectively, to lead $95.4\~96.4\%$ of coulombic efficiencies and ca. $6 mAh/g-LiCoO_2$ of initial irreversible specific capacity. Specific resistance at the end of charge and rest showed low value at content of super s black between 2 and $7\%w/w$, which agreed with characteristics of irreversible specific capacity. Capacity densities were reduced by the increasing the content of conductive material. They were 447 and 431mAh/ml when 2 and $2.9\%w/w$ of super s black were used, respectively, at the rate of C/4.

• Applied Biological Chemistry
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• v.39 no.5
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• pp.368-373
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• 1996

Korean general medicinal herbs-sasam, gilkyung, jakyak, danggwi, hwangki, and chunkung-were added In the normal brewing procedure as a raw material or in the distilling procedure as a packing material. The distillates from the former procedure and those from the latter procedure were compared in quality and distillation properties. As distillation proceeded, pH of the medicinal herb wine distillate and the control(not added herbs) distillates were decreased, whereas that of the herb packing distillate was increased slowely of $0.05{\sim}0.97$ during $1{\sim}4$ fractions and decreased remarkably of $0.92{\sim}0.98$ afterward. Average pH was the highest of 5.70 in jakyak and lowest of 4.37 In gilkyung. Absorbances of the herb Packing distillate were decreased rapidly of $0.60{\sim}1.59$ in the $1{\sim}4$ fractions but slowely of $0.19{\sim}0.54$ in the next fractions. During distillation both fractional alcohol concentration of the distillates and distillation rate were decreased. Their values were decreased more slowly than the control. Distillation rates of medicinal herb wine distillate were varied by medicinal herb varieties and alcohol concentration of fermented wine. Danggwi and control showed the highest average distillation rate as $0.12\;m{\ell}/sec$ and gilkyung the lowest value as $0.073\;m{\ell}/sec$. Maximum concentration of index component, paeoniflorin of jakyak was observed as 293 mg% in the 5th fraction of herb packing distillate and decrusin of danggwi as 3514 mg% In the 1st fraction of herb packing distillate. The extraction rate was 41.3% for paeoniflorin and 20.5% for decrusin. From sensory evaluation, the highest overall Qualify was observed in the medicinal herb wine distillate of hwangki added wine, the next in those of danggwi and jakyak added wine.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.2
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• pp.198-208
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• 2021

The aim of this study was to evaluate the antibacterial effect on Enterococcus Faecalis and physical properties of chitosan added calcium hydroxide canal filling material. Low, medium, high molecular weights of chitosan powder were mixed with calcium hydroxide canal filling material. Also, for each molecular weight group, 1.0, 2.0, 5.0 wt% of chitosan powder were added. An overnight culture of E. faecalis was adjusted to 1 × 10⁶ CFU/ml. For test of antibacterial effect, three different molecular weights of 2.0 wt% chitosan and three different concentrations of high molecular weight chitosan were mixed with calcium hydroxide canal filling material. The absorbance of plates was analyzed using spectrophotometer at 570 nm with a reference wavelength of 600 nm. Physical properties such as flow, film thickness and radiopacity were examined according to ISO 6876 : 2012. All molecular weight type of chitosan containing material showed inhibitory effect against E. faecalis growth compared to non-chitosan added calcium hydroxide canal filling material group (p < 0.05). High molecular weight chitosan containing material showed the most antibacterial effect. Also, the antibacterial effect decreased as the incorporated amount of chitosan decreased (p < 0.05). Every molecular weight group of material containing chitosan had a tendency for reduced flow and radiopacity, increased film thickness according to amount of chitosan. Low molecular weight of 1.0 wt% chitosan addition did not show any significant difference of physical properties compared to conventional calcium hydroxide canal filling material. In conclusion, for reinforcement of antibacterial effect against E. faecalis and for favorable physical properties, 2.0 wt% of chitosan adding is recommended. Considering its antibacterial effect of chitosan, further studies are required for clinical application of chitosan in endodontics and pediatric dentistry.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.21-27
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• 2016

Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

• Journal of the Korean Institute of Gas
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• v.7 no.1 s.18
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• pp.19-23
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• 2003

The purpose of this thesis is to investigate the BLEVE probability of LP gas storage tanks which are relatively more dangerous, by the deductive calculating method using the results of Birk's pilot tank test and the required heat capacity of BLEVE. The result that BLEVEs can occur in only above 43.68 percent of liquid filling level under $600^{\circ}C$ of tank pate temperature and $53^{\circ}C$ of inner liquid temperature, was obtained and will be useful for preventing the BLEVE of LP gas storage tanks in fire sites. In addition, this research showed conditions of external leak and fire causing BLEVE, based on 15ton capacity of LP gas tank which has the same specifications as those in Puchon LP gas filling station accident. The result of the calculation is that the minimum pool fire conditions of BLEVE are above 7.2mm equivalent diameter under a liquid release condition and above 17.6mm equivalent diameter under a two-phase release condition. In the end, the result of calculating the pool size corresponding the above conditions using EFFECTS version 2.1, concludes that a minimum of 3.3 meters of diameter and 10.4 meters of height should be needed for BLEVE outbreak.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.1
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• pp.369-377
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• 2013

This paper deals with the state of charge(SOC) and life cycle evaluation algorithm for lead-acid battery, which is essential factor of the electric vehicle(EV) and the stabilization of renewable energy in the smart grid. In order to perform the effective operation of the lead-acid battery, SOC and life cycle evaluation algorithm is required. Specific gravity with the change of electrolyte temperature inside battery case should be obtained to evaluate the SOC of lead-acid battery, however it is difficult to measure the electrolyte temperature of sealed type lead-acid battery. To overcome this problem, this paper proposes the equation of thermal transmission to compensate internal temperature of the lead-acid battery. Also, it is difficult to exactly evaluate the life cycle of battery, depending on the operation conditions of lead-acid battery such as charging and discharging state, self discharging rate and environmental issue. In order to solve the problem, this paper presents the concept for gravity accumulation of charge and discharge cycle, which is the value converted at $20^{\circ}C$. By using the proposed algorithm, this paper propose the test device based on the Labview software. The simulation results show that it is a practical tool for the maintenance of lead-acid battery in the field of industry.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.703-708
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• 2015

In order to improve the dispersity of nanofiller, polyurethane (PU) nanocomposites were manufactured via poly(propylene gylcol) (PPG) dispersion with MWCNTs prepared by using a ball mill shaker. MWCNTs could be functionalized by treating with the hydrogen peroxide ($H_2O_2$). Tensile strengths and elongations at break of $PU/H_2O_2$ treated MWCNTs nanocomposites were enhanced compared to those of the PU/pristine MWCNTs nanocomposites. The good dispersion of MWCNTs shown in SEM images was obtained by the functionalization of MWCNTs surface. PU/carbon black (CB) composites showed no significant change in the tensile properties. The tensile properties of PU nanocomposites containing pristine MWCNTs or $H_2O_2$ treated MWCNTs were enhanced with increasing dispersion time. As a result, it was certified that the enhanced dispersity of nanofiller brought the improvement of the tensile properties of the MWCNTs based PU nanocomposites.

• Composites Research
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• v.24 no.5
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• pp.34-38
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• 2011

Carbon nanotubes (CNTs) have been widely investigated as reinforcements of CNT/polymer nanocomposites to enhance mechanical and electrical properties of polymer matrices since their discovery in the early 90's. Furthermore, the number of studies about incorporating CNTs into carbon fiber reinforced plastics (CFRP) to reinforce their polymer matrices is increasing recently. In this study, single-walled carbon nanotubes (SWNT) were dispersed in epoxy with 0.2 wt.% and 0.5 wt.%. Then, the SWNT/epoxy mixtures were processed to carbon fiber composites by a vacuum assisted resin transfer molding (VARTM) and a wet lay up method. The processed composite samples were tested for the interlaminar shear strength (ILSS). The relationship between the interlaminar shear strengths and processing, and the reinforcement mechanism of carbon nanotubes were investigated. CNT/epoxy nanocomposite specimens showed the increased tensile properties. However, the ILSS of carbon fiber composites was not enhanced by reinforcing the matrix with CNTs because of processing issues caused by increased viscosity of the matrix due to addition of CNTs particularly for a VARTM method.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.822-827
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• 1999

The specific capacitance characteristics which were of the electric double layer capacitors(ELDC) made of phenol based activated carbon fiber(ACF) electrodes and organic electrolytes has been investigated with respect to different specific surface area of electrodes and different kinds of organic electrolytes. Throughout charge-discharge cell tests, it has been found that larger surface area and larger pore diameter of electrodes contribute to increase the specific capacitance. Binary mixture of organic solvent with propylene cabonate(PC) and tetrahydrofuran(THF) for 1 M-$LiClO_4$ electrolyte has a higher specific capacitance than single solvent of PC or mixed solvent with PC and diethyl cabonate(DEC). Also, even though 1 M-tetraethylamonium perchlorate(TEAPC) of organic electrolyte shows higher specific capacitance, it has longer charge time because of its lower ion mobility.

• Journal of Chest Surgery
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• v.25 no.5
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• pp.469-479
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• 1992

Searching for the clinical effects of colloid solutions that used to increasing the oncotic pressure of priming solutions at the cardiopulmonary bypass, 29 patients [who were diagnosised as simple VSD around 10kg of body weight and scheduled to be operated from June 1990 to December 1990 at Sejong General Hospital] were divided randomly and prospectively to the two groups: A group [15] was received 4gm% albumin as addition to the priming solutions and B Group [14] the same amount of Ringer`s lactated solution. 34 clinical parameters [Body weight, sex, age, body surface area, Qp/Qs, pulmonary arterial pressure, cardiopulmonary bypass time, anesthetic time, intraoperatively infused crystalloid and colloid amount, hemoglobin, hematocrit, serum sodium concentration, serum osmolarity, urine osmolarity, urine specific gravity, serum concentration, serum osmolarity, urine osmolarity, urine specific gravity, serum protein, serum albumin concentration, urine output, central venous pressure, postoperatively infused colloid amount, immedediate post-operative peak inspiratory pressure, cardiac index, blood pressure and pump flow during cardiopulmonary bypass, inotro-pic assist, diuretics, extubation period, total drain amount, duration of ICU] were measured and compaired between the two groups. There were no differences of preoperative and operative clinical parameters. And postoper-atively, practically there were no nearly differences at the clinical outcomes between the two groups, but some parameters [cardiac index, PIP, BP and pumpflow during CPB, etc] contributed to being preferable to the Group A at certain times [P<0.05]. Conclusively, it might be thought that the priming solution of cardiopulmonary bypass added by colloid solution had some beneficial effects on the patients, especially younger and associated with complex anomaly to be expected taken longer time of cardiopulmonary bypass, and more studies about the neonatal and complex anomaly cases were needed in that points.