• Journal of the Korean institute of surface engineering
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• v.40 no.1
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• pp.11-15
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• 2007

Stable metallic Cu/Zn nanoparticles were prepared in the base oil phase by hydrothermal method. The physical properties, such as crystal structure, crystallite size and crystallinity according to synthesis conditions have been investigated by XRD, FT-IR and TEM. In addition, 4-ball test has been performed in order to investigate the frictional wear properties of prepared nanosized Cu/Zn particles. The peaks of the X-ray diffraction pattern indicate that the particle size was very small and crystallinity of Cu/Zn particles was good. The micrographs of TEM showed that nanosized Cu/Zn particles possessed a spherical morphology with a narrow size distribution. The crystallite size of the Cu/Zn particles synthesized in base oils was 23-30 nm. It was found that the antiwear capacity increases with increasing Cu/Zn concentration. When the concentration of Cu/Zn was 5.0 wt%, the wear scar diameters was 0.38 mm.

• Tribology and Lubricants
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• v.25 no.2
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• pp.125-131
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• 2009

Biodiesel produced from triglyceride which is main component of animal fats and vegetable oils by methanolysis was known for excellent lubricity. In this study, the lubricity of 12 kinds of biodiesel come from vegetable oils were analyzed using HFRR(High frequency reciprocating rig). The biodiesel synthesized from soybean oil has best lubricity by $153{\mu}m$ of wear scar in HFRR and used fried oil's biodiesel has slightly low lubricity by $299{\mu}m$. Also we have found that the lubricity of diesel was improved when mixing ratio of soybean biodiesel was increased in base diesel.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.90-99
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• 2000

This report describes the results of analysis, synthesis and evaluation of antimony dithiocarbamates (SbDTC). Sb-DTC were synthesized by reacting antimony oxide with dithiocarbamates whish were prepared by reaction of dialkylamines and carbon disulfide. The chemical structures and properties of synthesized Sb-DTCs in lab. were discussed. The frictional properties of SbDTC were tested with Four-Ball Wear Scar Tester and Four-Ball Extreme Tester by ASTM method.

• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.583-589
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• 2016

Lubricant additives including zinc dialkyldithiophosphate (ZDDP) containing metal have been widely used due to the advantage of very low cost, but they can generate impurities such as ash. In this work, ZDDP containing metals was partially replaced with bis[3-(dialkyloxyphosphorothionyl) thio-2-methylpropanyloxy] butane (BAP4s) which was synthesized conveniently and effectively from alkanediol without any metal components. Also, the wear resistance property of synthesized BAP4s were studied. Wear scar diameter (WSD) values of BAP4s with butyl, octyl, decyl, dodecyl or tetradecyl groups were also measured by four-ball test. As the length of the alkyl group increased from 4 to 8, the WSD value of BAP4s decreased rapidly from 0.59 to 0.45 mm, but from 8 to 14, the value increased very slowly from 0.45 to 0.50 mm. Thus, among all BAP4s, B8P4 having BAP4 with the octyl group, showed the lowest WSD value. Furthermore, the WSD values were measured in a lubricant base oil mixed with a 0.50 percent concentration (w/w) of either BAP4 or ZDDP. The former was 0.55 mm, and the latter was 0.45 mm. The thermal stability and tribofilm formation peroperty were also measured by thermogravimetric analyzer (TGA) and energy-dispersive X-rays spectroscopy (EDS), respectively.

• Tribology and Lubricants
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• v.28 no.2
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• pp.93-98
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• 2012

The engine oil is an oil used for lubrication of various internal combustion engines. Recently, the vehicle and engine oil manufacture usually guarantee for oil change over 15000~20000 km mileage, but the most of driver usually change engine oil every 5000 km driving in Korea. In this case, it is possible to cause environmental contamination by used engine oil and increase the cost of driving by frequently oil change. In this study, we investigate the various physical properties such as flash point, pour point, kinematic viscosity, cold cranking simulator, total acid number, and four-ball test for fresh engine oil and used engine oil after vehicle driving (5000 km, 10000 km). The test result showed that the total acid number and wear scar by four-ball test of used engine oil had increased than fresh engine oil, but 2 kind of used oil (5000 km and 10000 km) had similar physical properties.

• Tribology and Lubricants
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• v.28 no.6
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• pp.321-327
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• 2012

Paraffin bio-based hydrotreated biodiesel(HBD) is originated from vegetable oil(the process can also be applied to animal fat) with the the chemical structure $C_nH_{2n+2}$. In the number of process of the oil or fat, the hydrogenation is significantly important to create a bio-based diesel fuel. This study is focused on lubricity characteristics of BTL diesel blends to use alternative diesel fuel in Korea. The BTL diesel are blended the different volume ratios (HBD 5(5 vol.% HBD - 95 vol.% diesel), HBD 10, HBD 20, HBD 30, HBD 40 and HBD 50. HBD with paraffin compounds showed a very high centane number, low sulfur content and free aromatic compound. Especially, the wear scar of HBD showed poor lubricity compared to automotive diesel due to the fuel composition, low sulfur content and free aromatic compound. Also, the lubricity specification of automotive diesel with different six HBD blends is within the limit by the Korean standards. Finally, HBD as an alternative diesel fuel is challengeable in transportation sector of Korea.

• Archives of Plastic Surgery
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• v.50 no.6
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• pp.563-567
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• 2023

Ear keloids are challenging lesions to treat due to high recurrence rates postexcision. Conservative compression techniques as adjunct treatment have been reported to be effective. An innovative technique of using computer-aided design/computed-aided manufacturing to print a customized auricular splint improves efficiency and comfort level for patients compared with conventional methods. The ear is scanned using an intraoral scanning 2 weeks postsurgery. A two-piece auricular splint is designed on the digital model, incorporating perforated projections for three nylon screws for retention of the splint. The splint is printed with clear acrylic material, postprocessed, and finished. The patient is taught to assemble the components of the splint and instructed to wear for at least 8 hours daily. The surgery site reviewed for any ulceration, pain, or recurrence of keloid for 6 months. During the 6-month review, the excision scar remained flat and pink. The patient also reports unrestricted daily activities. The digital workflow increases comfort for the patient and reduces the number of hours required to produce a customized auricular splint compared with conventional methods. A fully digital workflow for a printed auricular splint should be considered for adjunctive treatment to excision of ear keloids.

• Journal of the Korean Society of Costume
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• v.22
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• pp.205-224
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• 1994

It was aimed to study the costume of Koryo dynasty based upon the thirty pictures of Bud-dha to hang on the wall among the existing Buddist paintings. The costume to study were made about 64 years during the King Chung-yol(1286) to the King Chung-jong(1350) which style was mostly related in Won Dynasty. 가) Men's wear ; 1. Hair style and hair dress ; Man tied up a top knot and they put on the hat such as a Kuan Kun and Mo. The young boys binds his hair up one, two, and three knot-s, and tied up with a hair ribbon, A kinds of Kuan-mo were Mine-lu-kuan Yuan-yu-kuan, Nong-kuan, Hae-chi-kuan Pok-du Yun-wha-kuan Yip-mo- and Tu-ku(Helmeto) 2. clothes ; 1) Colour of Koryo King's Mien-ku Kuan costume was not agree with blue and reddish black colour which was used in Yo, Song, Kum and Won Dynasty, however black and greenhish blue colour was agreed with. 2) The king wore T'ung-t'ien-kuan(Yuan-yu-kuan) and the government officials wore Chin-hien-kuan Hae-chi-kuan and Nong-kuan as a court dress. In general the king and the Crown Prince wore a hats which was used in T'ung-t'ien system however sometimes they wore small hats which was cited in literature. 3) Gate guard and upper garment wore colourful costume figured gold colour pattern which was distin-gtive costume system of Koryo. 4) A monk wore big sleeve long skirt big sleeve long jacket long skirt and shoulder scar-f full shoulder scarf or right hand shoulder opened scarf. 5) The Soldiers wore helmet shoulder or scarf pee-back hung-kap, pok-kap, yang-dan-g-kap we-yu-kap kun-kap, and boots and they carried arms. 6) The young boys wore scarf, loin cloth, long skirt, belt neckless, wan-silk, boots and foots wear and wristless. 나) Women's wear ; 1. Hair style and hairs and tied up with a hair ribbon and wore precious ston decorated hair dress wheel shape hair dress pan shaped head dress handkerchif covered hair dress decorated precious stone hair pin silk chippon made of head dress muf-fler shaped hairdress. Boots mocasin hae lee, suk and sandle wored as a shoes depends on the classes. They wore neckless, earing wres-tless and wan-pu-sik. 2. Closthe 1) High rank lade's wore un-kyun attached jacket and jacket sleeves decorated pleats and pleats decorated long skirt apron back apron knot belt, scarf this type is the same with Dang Dynasty five dynasty of china Song, Kum Won, Myung Dynasty and our cos-tume of Poe-hae, and Shilla Dynasty.

• Tribology and Lubricants
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• v.33 no.2
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• pp.45-51
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• 2017

Engine oil is a substance used for the lubrication of internal combustion systems. However, in some case, defects in engine systems may contaminate engine oil with fuel. Contaminated engine oil can cause problems in the normal functioning of a vehicle. In this study, we investigate the functional properties of engine oil contaminated with diesel fuel. The test results indicate that the engine oil contaminated with diesel fuel has low flash point, pour point, density, kinematic viscosity and cold cranking simulator value. The contaminated engine oil which has low plash point can cause fire and explosion accident. Furthermore, a four ball test indicates that the contaminated engine oil increases wear scar to poor lubricity. Moreover, we investigate the GC pattern using SIMDIST (simulated distillation) for determination of diesel in engine oil. The SIMDIST analytic result, diesel was detected at earlier retention time than engine oil in chromatogram. Thus the SIMDIST method can define whether engine oil is contaminated by diesel fuel or not. We can use the SIMDIST method for the diagnosis of oil condition instead of analyzing other physical properties that require many analytic instruments, large volume of oil sample and long analysis time.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.44-44
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• 1998

It was observed that the friction coefficient decreased with increasing Si concentration in the l ilms. Furthermore, the friction behavior became more s때ble even when very small amount of S Si of less than 0.5 at. % was incorporatA:회 By analyzing the composition of the debris f formed, we could show that the low and stabilized friction coefficient is in마nately relatA:었 w with the formation of the Si rich oxide debris. These result supports the mechanism that the h hydrated silica debris is the reason for low friction coefficient in humid environment. Second e evidence of the role of Si rich oxide debris could be found in the triOO-chemical reactions d during initial stage of triho-test. When the Si concen$\sigma$ation was less than 5 at.%, initial t transient period of high friction coefficient was commonly observed. Mter the transient period, m the friction coefficient becomes lower with increasing contact cycles. The initial $\sigma$ansient p peri여 becomes shorter and the starting and maximum friction coefficients in $\sigma$ansient 야,riod d decreased with increasing Si concentration. Composition of the debris on the wear scar s surface was analyzed by Auger spe따'Oscopy at v뼈ous stages in the initial transient period. W We observed that when the friction coefficient increased in earlier stage of the $\sigma$'ansient p period, iron and oxygen was observed in the debris. However, decrease in the 당iction c coefficient in the later stage of the transient period was associated with the formation of s silicon rich oxide debris. This result also supports the friction mechanism of Si-DLC films t that the formation of Si rich oxide debris results in low friction coefficient in ambient a atmosphere. atmosphere.