• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.149-155
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• 2001

New semi-fluorinated polyol esters were synthesized by condensation reaction of polyols (NPG and TMP) and carboxylic acids such as 2-ethylhexanoic acid, stearic acid and perfluorooctanoic acid. The structures of polyol esters were confirmed by FT-IR and H-NMR etc. And, the fluorinated polyol esters were insoluble in several oils, however, the semi-fluorinated polyol esters were soluble in several oils depended on the structure of polyol esters. The physical properties such as 4-ball wear property and extreme-pressure (EP) properties were characterized by measuring wear scar diameter through ASTM D2266 and by determining the load-carrying through ASTM D2783 method, respectively. As the results, wear scar diameters of oils in which the semi-fluorinated polyol esters were added were not changed compared to those of not added oils. While extreme-pressure properties remarkably Increased with fluorine contents of the esters depended on the structure of acid moiety and polyol moiety. Also, the extreme-pressure property of semi-fluorinated NPG polyol ester in gasoline engine oil was better than that of commercial Teflon coating additive.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1363-1372
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• 1992

The effects on lubricity and the anti-seizure property of lubricant according to base oils and extreme pressure additives of sulfur type and phosphorous type in cold rolling were evaluated by a laboratory scale rolling mill, where the contact conditions between work roll and strip are very close to actual cold rolling mill. The important results were obtained as follows : (1) synthetic oil has better effect on lubricity than tallow, (2) lubricant with extreme pressure additives of sulfur type of phosphorous type has better effect than base oil noly, (3) the more amount of extreme pressure additives is, the better effect on lubricity is, (4) sulfur type has better effect on lubricity than phosphorous type and (6) phosphorous type has better effect on anti-seizure property than sulfur type.

• Tribology and Lubricants
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• v.11 no.1
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• pp.50-57
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• 1995

When engine oil is used under severe running condition, the Lubricational characteristics is very important. I have studied the Lubricational characteristics with Compound Additives of engine oil for the Falex wear test machine. Adding detergent (Ca-phenate) to engine oil, the seizure is more improved than in case of non-adding, and adding Zn-DTP (Zinc dialkyl dithio phosphate), the extreme pressure property is excellent at the high load. But when the PTFE (Polytetra Fluoro Ethylene) and MoS$_{2}$ (Molybdenum disulfide) are added, the temperature characteristics and the anti-wear property become excellent because the stability can be maintained in a high temperature. The result are as follows, it can be improved that when the compound of the Ca-phenate and Zn-DTP, MoS$_{2}$, PTFE, etc. was added to engine oil, the lubrication characteristics become better. It is argued that it is improved because of excellence of the anti-wear, the extreame pressure properties and the heat stability.

• Tribology and Lubricants
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• v.1 no.1
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• pp.80-87
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• 1985

Lithium dual complex grease was prepared through the second continuous saponification reaction of a complex gellant system whose essential components comprised of a selected hydroxy fatty acid, lithium hydroxide monohydrate and boric acid to have a fiber structure of chemical, thermal and mechanical stability at high temperatures. An optimum amount of complex gellant was found to be 14% (NLGI #2), and an addition of castor wax of 1.5% provided an excellent performance properties, especially. The oil separation, oxidation stability, water wash-out property, shear stability, extreme pressure and wear property of thus prepared were tested by the ASTM and KS methods, and a characteristic result was obtained.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.1
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• pp.62-68
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• 2014

Recently, MRI(magnetic resonance imager) scanner is continually used for medical diagnosis and many biomedical researches. When it operates, however, intense noise is generated. The SPL(sound pressure level) of the noise approaches 130 dB especially in 3 T(Tesla) MRI. Meanwhile, more than 3 T MRI scanners have been developed to get higher-resolution images, so louder noise is expected in the future. The intense noise makes patients feel nervous and uncomfortable. Moreover, it could possibly cause hearing loss to patient in extreme cases. For this reason, some active noise control systems have been researched. One of them used feedback Filtered-X LMS(FXLMS) algorithm which is able to control only narrowband noises and possible to diverge in severe case. In this paper, we determine the property of MRI noise. Using the property, we applied a method of open-loop and adaptive control for reducing MRI noise at target point inside bore. We verified performance of the method with computer simulation and preliminary experiment. The results demonstrate that the method can effectively reduce MRI noise at target point.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.4
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• pp.576-582
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• 2015

The efficiencies of thermal power system using fossil fuel depend on heat exchangers which extract energy from the exhaust gas before it is expelled to the atmosphere. To increase heat transfer efficiency it is very important to maintain the surface of heat exchanger as clean condition. The accepted skill of cleaning of fouled surface of heat exchanger is soot blowing. A high pressure jet of air is forced through the flat surface of plate to remove the deposit of fouling. There is, however, little knowledge of the fundamental principles of how the jet behave on the surface and how the jet actually removes the deposit. Therefore, the study focuses on the measuring of cleaning area and cleaning dwell time after accumulating the simulated deposit on the flat surface. The deposit test rig was built for the study and simulated deposit material is used after measuring the physical property of the each material by shearing stress test. Much data was obtained for the analysis by the parameters change such as the different jet speed, different inner pressure and variable distance of the jet from the test rig surface. The experimental data was compared with the theoretical equation and most of the data matches well except some extreme cases.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.3
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• pp.369-380
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• 2019

When a extreme loading such as blast is applied to prestressed concrete (PSC) structures and infrastructures for an instantaneous time, serious property damages and human casualties occur. However, a existing design procedure for PSC structures such as prestressed containment vessel (PCCV) and gas storage tank do not consider a protective design for extreme internal blast scenario. Particularly, an internal blast is much more dangerous than that of external blast. Therefore, verification of the internal blast loading is required. In this paper, the internal blast resistance capacity of PSC member is evaluated by performing internal blast tests on RC and bi-directional PSC scaled down specimens. The applied internal blast loads were 22.68, 27.22, and 31.75 kg (50, 60, and 70 lbs) ANFO explosive charge at 1,000 mm standoff distance. The data acquisitions include blast pressure, deflection, strain, crack patterns, and prestressing force. The test results showed that it is possible to predict the damage area to the structure when internal blast loading occurs in PCCV structures.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.2
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• pp.1-7
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• 2005

In order to determine the wear Properties of PECVD ceramic coatings, wear process was evaluated using the coated pin of Falex Tribosystem. Coating materials deposited wear the TiC, TiN and Ti(CN). An experimental process was established to determine the tribological characteristics of friction and wear behavior under the variation of applied load, temperature and sliding distance by the Falex test machine. The experimental results indicate that TiN coating compared with TiC coating on e materials have e excellent friction and wear characteristics. However TiC coating compared i친 TiN coatings have a low friction coefficient with steel and good thermal stability, and Ti(CN) has the excellent anti-wear properly as well as the superiority of extreme pressure property. Compound coating compared wi simple coatings show improved tribological characteristics.

• Elastomers and Composites
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• v.53 no.1
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• pp.13-18
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• 2018

A face seal comprising a metal ring and acrylonitrile butadiene rubber (NBR) was installed in the driving part and suspension unit. The seal serves as a bearing and simultaneously prevents entry of foreign matter from external environment as well as internal oil leakage. Subsequently, the rubber-rod ring generates axial pressure owing to rubber elasticity (hardness), performs static sealing function between housing details and outer diameter of seal, and transmits rotational torque to the rotating support ring. In order to improve the durability of NBR, which performs the above tasks, and to effectively use it in tracked-vehicle applications at extreme temperatures, this study reports a mixing design approach to enhance cold and oil resistances of NBR.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.262.1-262.1
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• 2014

Lipid peroxidation induces functional deterioration of cell membrane and induces cell death in extreme cases. These phenomena are known to be related generally to the change of physical properties of lipid membrane such as decreased lipid order or increased water penetration. Even though the electric property of lipid membrane is important, there has been no report about the change of electric properties after lipid peroxidation. Herein, we demonstrate the molecular energy band change in red blood cell membrane through peroxidation by air-based atmospheric pressure DBD plasma treatment. Ion-induced secondary electron emission coefficient (${\gamma}$ value) was measured by using home-made gamma-focused ion beam (${\gamma}$-FIB) system and electron energy band was calculated based on the quantum mechanical Auger neutralization theory. The oxidized lipids showed higher gamma values and lower electron work functions, which implies the change of surface charging or electrical conductance. This result suggests that modified electrical properties should play a role in cell signaling under oxidative stress.