• Polymer(Korea)
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• v.35 no.1
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• pp.40-46
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• 2011

The synthesis of well-defined poly(styrene-b-isobutylene-b-styrene) (SIBS) triblock copolymers was accomplished by cationic sequential block copolymerization of isobutylene (IB) with styrene (St) using 1,4-di(2-chloro-2-propyl) benzene (DCC) /$TiCl_4$/2,6-di-tert-butylpyridine(DtBP) as an initiating system in methyl chloride ($CH_3Cl$)/methylcyclohexane(MeChx) (50/50 v/v) solvent mixture at $-80^{\circ}C$. The triblock copolymers exhibited excellent thermoplastic and elastomeric characteristics. Tensile strengths and Shore hardness increased with increasing polystyrene (PS) content, while elongation at break decreased. The blood-compatibility of SIBS was assessed by SEM observation of the platelet adhesion, blood clotting time and haemolysis ratio. The haemolysis ratios were below 5% which met the medical materials standard. The platelet adhesion test further indicated that SIBS block copolymers had a good blood compatibility.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.870-874
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• 2000

This investigation reports the grinding characteristics of titanium alloy(Ti-6Al-4V). Grinding experiments were performed at various grinding conditions and the grinding forces and specific grinding energies were measured to investigate the grindability of titanium alloy with the three different wheels including Diamond, Green carbide and Alumina. To investigate the grinding characteristics of titanium alloy grinding force, force-ratio, specific grinding energy and grinding -ratio, were measured. Surface roughness was also measured with tracer and the ground surfaces were observed with SEM. Force-ratio of grinding of titanium alloy was very lower than that of grinding of SKD-11. Specific grinding energy are almost five times larger and rougher surface was obtained in titanium grinding.

• Economic and Environmental Geology
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• v.42 no.3
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• pp.177-193
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• 2009

The Samgwang deposit consists of eight massive mesothermal quartz veins that filled NE and NW-striking fractures along fault zones in Precambrian granitic gneiss of the Gyeonggi massif. The mineralogy and paragenesis of the veins allow two separate discrete mineralization episodes(stage I=quartz and calcite stage, stage II-calcite stage) to be recognized, temporally separated by a major faulting event. The ore minerals are contained within quartz and calcite associated with fracturing and healing of veins that occurred during both mineralization episodes. The hydrothermal alteration of stage I is sericitization, chloritization, carbonitization, pyritization, silicification and argillization. Sericitic zone occurs near and at quartz vein and include mainly sericite, quartz, and minor illite, carbonates and chlorite. Chloritic zone occurs far from quartz vein and is composed of mainly chlorite, quartz and minor sericite, carbonates and epidote. Fe/(Fe+Mg) ratios of sericite and chlorite range 0.45 to 0.50(0.48$\pm$0.02) and 0.74 to 0.81(0.77$\pm$0.03), and belong to muscovite-petzite series and brunsvigite, respectiveIy. Calculated $Al_{IV}$-FE/(FE+Mg) diagrams of sericite and chlorite suggest that this can be a reliable indicator of alteration temperature in Au-Ag deposits. Calculated activities of chlorite end member are $a3(Fe_5Al_2Si_3O_{10}(OH)_6$=0.0275${\sim}$0.0413, $a2(Mg_5Al_2Si_3O_{10}(OH)_6$=1.18E-10${\sim}$7.79E-7, $a1(Mg_6Si_4O_{10}(OH)_6$=4.92E-10${\sim}$9.29E-7. It suggest that chlorite from the Samgwang deposit is iron-rich chlorite formed due to decreasing temperature from high temperature(T>450$^{\circ}C$). Calculated ${\alpha}Na^+$, ${\alpha}K^+$, ${\alpha}Ca^{2+}$, ${\alpha}Mg^{2+}$ and pH values during wallrock alteration are 0.0476($400^{\circ}C$), 0.0863($350^{\circ}C$), 0.0154($400^{\circ}C$), 0.0231($350^{\circ}C$), 2.42E-11($400^{\circ}C$), 7.07E-10($350^{\circ}C$), 1.59E-12($400^{\circ}C$), 1.77E-11($350^{\circ}C$), 5.4${\sim}$6.4($400^{\circ}C$), 5.3${\sim}$5.7($350^{\circ}C$)respectively. Gain elements(enrichment elements) during wallrock alteration are $TiO_2$, $Fe_2O_3(T)$,CaO, MnO, MgO, As, Ag, Cu, Zn, Ni, Co, W, V, Br, Cs, Rb, Sc, Bi, Nb, Sb, Se, Sn and Lu. Elements(Ag, As, Zn, Sc, Sb, Rb, S, $CO_2$) represents a potential tools for exploration in mesothermal and epithermal gold-silver deposits.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.589-597
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• 2010

In the present study, the effect of variation in alloying elements on the carbide formation behavior during casting and homogenization treatment of M2 high speed steels was investigated. M2 high speed steels of various compositions were produced by vacuum induction melting. Contents of C, Cr, W, Mo, and V were varied from the basic composition of 0.8C, 0.3Si, 0.2Mn, 4.0Cr, 6.0W, 5.0Mo, and 2.0V in weight percent. Homogenization treatment at $1150^{\circ}C$ for 1.5 hr followed by furnace cooling was performed on the ingots. Area fraction and chemical compositions of eutectic carbide in as-cast and homogenized ingots were analyzed. Area fraction of eutectic carbide appeared to be higher in the ingots with higher contents of alloying elements the area fraction of eutectic carbide also appeared to be higher on the surface regions than in the center regions of ingots. As a result of the homogenization treatment, $M_2C$ carbide, which was the primary eutectic carbide in the as-cast ingots, decomposed into thermodynamically stable carbides, MC and $M_6C$. The latter carbide was found to be the main one after homogenization. Fine carbides uniformly distributed in the matrix was found to be MC type carbide and coarsened by homogenization.

• The Journal of the Petrological Society of Korea
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• v.16 no.4
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• pp.217-232
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• 2007

The Puu Oo eruption in Hawaii since 1983 is one of the largest eruptions on Hawaii's volcanic history with prominent compositional variation ($5.6{\sim}10.1wt.%$ in MgO content). Although intense researches of Hawaiian eruption have been conducted for recent years, there is no up-to-date study on Puu Oo lavas that is erupting hot lavas today. in oder to obtain basic information on the geological characteristics of the eruption including any noticeable change in its petrological trend and magma dynamics, we applied several geological approaches such as field survey, systematic sampling, petrography, mineralogy, and geochemistry. Clinopyroxene and Plagioclase phenocrysts are rarely observed on the thin section, however Olivine crysts are much more obvious in the study area. It indicates that Puu Oo is early stage of magma differentiation. Variation diagram of whole rock composition shows that the elements such as $TiO_2,\;Al_2O_3,\;SiO_2$ and $Na_2O$ decrease with increasing MgO. In the trace element Sr, Y Zr and V versus $K_2O$, P18, P19 samples are plotted in primitive area. Variations of the Ni contents during $2003{\sim}2006$ may suggest a sudden change in magma composition probably caused by new magma injection.

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.429-447
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• 1995

This study was designed to determine the most effective concentration of fluoride and levels of laser irradiation for the remineralization of decayed teeth. After irradiation with a pulsed Nd:YAG laser and the topical application of fluoride, phosphate and fluoride concentration in enamel were measured. And then the changes on surface enamel using an scanning electron microscope were observed. Samples by extraction healthy, permanent, mandibular bovine teeth with no caries were obtained. Among them 371 healthy samples were selected and artificial carious lesions were made. 20 samples were assigned to each experimental group. After irradiation with a pulsed Nd:YAG laser with total energy densities of 10J/$\textrm{cm}^2$, 20J/$\textrm{cm}^2$ for each group. On the teeth, 2% NaF, 1.9% NH4F, 1.6% TiF4 Elmex gel(amine fluoride) and 1.23% APF gel were applied. After pH circulatory procedures, concentrations of fluoride with and Ionalyzer (Orion Research, Model 901, USA) and phosphates with an Uv/V is spectrophotometer (Uvikon 860, Kontrom Co, Switzerland) were measured. By etching the teeth in layers and measuring fluoride concentrations, a profile of fluoride penetration according to depth could be developed. And also the changes on the surface of the enamel using an electron scanning microscope were observed. The comparative analysis yielded the following results : 1. Phosphate concentration was low in all groups compared with the control group except for teeth treated Elmex gel, irradiated with 10J/$\textrm{cm}^2$ and 30J/$\textrm{cm}^2$ energy densities. Teeth treated with APF gel and 30J/$\textrm{cm}^2$ irradiation gad the lowest phosphate concentration. 2. Among all groups, fluoride concentrations in tooth enamel were highest in APF gel and NaF groups irradiated at 30J/$\textrm{cm}^2$. The APF gel group had the highest fluoride concentrations across all energy densities. 3. In the APF gel group, and the NaF group, the greater the energy density of the laser, the higher the fluoride concentrations in the enamel. 4. In all groups, the concentration of fluoride in the enamel by depth tended to decrease with depth. 5. Under the scanning electron microscope, under the condition of irradiation with 20J/$\textrm{cm}^2$, enamel crack was detected for the first time. In the NH4F group, spherical deposits were found on the surface of the enamel, and in the TiF4 group the surface of enamel was covered with an irregular, thin membranous mass in places. In the APF gel and NaF groups irradiated with 10J/$\textrm{cm}^2$, spherical and irregular particles covered the teeth. When these groups were irradiated at 20J/cm2, they were covered with amorphous crystals. These results suggest that one could obtain more effective anticariogenic effects without damage to teeth when less than 20J/$\textrm{cm}^2$ energy densities and APF gel are used.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.72-78
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• 2004

In this paper, mechanical behaviors of developed pedicle screw system, made of bio-mechanical materials(Ti-6Al-4V, Grade 5), ale predicted using FEM analysis. As a first step, morphologic construction of normal Korean spines and surgical operation convenience are considered to design optimum pedicle screw system. In this step, various design variables are considered as design parameters to develop optimized models. As a next step, tension and bending tests are performed to improve the structural performance of the developed system using finite element method. In this step, required Static compression and bending test specifications by ASTM F-04 25 04 01 are applied to understand the bio-mechanical behaviors of the designed spinal implant system under various load types. As the results of this research, it is possible to develop efficient pedicle screw system, having enough rigidity and fixation to stand any spinal damage under allowable stress conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.4
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• pp.111-120
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• 2014

The aim of this study is to develop an integrated urea-SCR catalytic filter system for reducing soot and $NO_X$ emissions simultaneously in diesel engines. In this study, the characteristics of exhaust emissions relative to reactive activation temperature under four kinds of engine loads are experimentally investigated by using a four-cycle, four-cylinder, direct injection type, water-cooled turbo intercooler ECU common-rail diesel engine with the integrated urea-SCR $MnO_2-V_2O_5-WO_3/TiO_2/SiC$ catalytic filter system operating at three kinds of engine speeds. The urea-SCR reactor is used to reduce $NO_X$ emissions, and the catalytic filter system is used to reduce soot emissions. The reactive activation temperature is very important for reacting a reducing agent with exhaust emissions. The reactive activation temperatures in this experiment is applied to 523, 573 and 623 K. The fuel is sprayed by the pilot and main injections at the variable injection timing between BTDC $15^{\circ}$ and ATDC $1^{\circ}$ according to experimental conditions. It is found that the $NO_X$ conversion rate is the highest as 83.9% at the reactive activation temperature of 523 K in all experimental conditions of engine speed and load, and the soot emissions shown by the average reduction rate of approximately 93.3% are almost decreased below 0.6% in all experimental conditions regardless of reactive activation temperatures. Also, the THC and CO emissions by oxidation reaction of Mn, V and Ti are shown in the average reduction rates of 70.3% and 38% regardless of all experimental conditions.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.117-117
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• 2016

Total ankle replacement (TAR) is a visible option in the surgical treatment of degenerative or inflammatory diseases of ankle joint. it is attributed to the current TAR which has improvements in surgical technique, uncemented implant fixation and minimally constrained articulation. In the clinical result, they can show promised surgical result when compared to earlier attempts in TAR. However, TAR is still not as successful as total knee replacement (TKR) or total hip replacement (THR), it needs to be note that there are limitations in concerning of long term performance of TAR, the high failure rate still associated with wear of the PE (polyethylene) component that has related with their material property and surface roughness. The aim of this study was to introduce the tribology characteristics of total ankle joint prosthesis with one of TDR model which was fabricated to try multi-axis wear test as a region of motion in ankle joint. The wear specimen of TDR was prepared with Ti-6Al-4V alloy and UHMWPE (ultra-high molecular weight polyethylene) for tibia-talus and bearing component, respectively. A wear test was carried out using a Force 5 (AMTI, Massachusetts, US) wear simulator which can be allowed to move in three axis to flexion-extension ($+3^{\circ}{\sim}-6^{\circ}$), internal-external axial rotation (${\pm}5^{\circ}$), as well as sinusoidal compressive load (1.6 kN, R=10). All tests were performed following standard ISO 14243, wear rate was calculated with weight loss of UHMWPE bearing while the specimen has tested at certain cycles. As based on the preliminary results, wear rate of UHMWPE bearing was $7.9{\times}10^{-6}mg/cycles$ ($R^2=0.86$), calculated loss weight until $10^7cycles$ was 79 mg, respectively.

• Analytical Science and Technology
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• v.13 no.6
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• pp.766-774
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• 2000

The major and trace constituents of Mongolian chromite were analyzed by ICP-AES. The dissolution procedures, mixed acid ($HClO_4+H_3PO_4$) digestion and fusion with $Na_2O_2$ flux, have been studied to dissolve the chromite. The optimum dissolution method was found to be a fusion with $Na_2O_2$ flux. The effect of large amount of Na on major and trace constituents was examined when these elements were determined by ICP-AES. There was no effect on major elements at a concentration of Na 250 mg/L solution. The emission intensity of trace constituents containing Na 1,250 mg/L decreased to 1.0-5.2% according to elements and wavelengths. The result of this method was compared with that of neutron activation analysis (NAA) to confirm the accuracy of this procedure. The results between two methods were in a good agreement within less than 5% for $Al_2O_3$, $Cr_2O_3$, MgO and -20 to 8% for Co, Mn, V, Zn, respectively.