• Tribology and Lubricants
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• 제20권6호
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• pp.337-342
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• 2004

One of the serious challenges in developing rotary compressor with HFC refrigerant is the prediction of scuffing times and wear amounts between vane and roller surfaces. In this study, the tribological characteristics of sliding surfaces using vane-roller geometry of rotary compressor were investigated. The sliding tests were carried out under various sliding speeds, normal loads and surface roughness. During the test, friction force, wear depth, time to failure and surface temperature were monitored. Because severe wear occurred on vane surface, TiN coating was applied on sliding surfaces to prolong the wear life of vane-roller interfaces. From the sliding test it was found that there was the optimum initial surface roughness to break in and to prolong the wear life of sliding surfaces. Depending on the load and speed, the protective layers, which were composed of metallic oxide and organic compound, were formed on sliding surfaces. Those would play an important role in the amounts of friction and wear between roller and vane surfaces.

• Tribology and Lubricants
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• 제25권1호
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• pp.56-60
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• 2009

A journal bearing is used in a hydrodynamic lubrication state, but it becomes a boundary lubrication state that asperity of a contact part touch each other when pressure is too high and an enough oil film is not formed by viscosity change due to lubricating oil temperature. At this time, abrasion due to contact between a journal and a bearing is unavoidable, and scuffing damage that the journal adheres to the bearing occurs if the process is repeated. Damage of the journal bearing is an important problem because it gives huge damage to a machine and can generate large accidents such as economic loss and human life damage. In this study, method for using the pull-up resistor concept was introduced as the monitoring technology. This monitoring system is important to enhance reliability of the engine.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.133-140
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• 2007

The purpose of this study was to evaluate the effects of gasoline fuel to the LPI engine. Firing test bench was used in order to assess the effect on gasoline-injected LPI engine. Gasoline fuel was supplied into the reverse direction(3-4-2-1 cylinder) at 3.0 bar with commercial gasoline fuel pump. Engine test was performed using the firing test mode at end of line. The deviations of excess air ratio of each cylinder and maximum combustion pressure using gasoline fuel were within 0.1 and $1{\sim}2\;bar$. Engine start time was measured with changing coolant temperature at $20^{\circ}C,\;40^{\circ}C,\;80^{\circ}C$, respectively. Residual gasoline volume in the fuel line was measured about 32 cc after firing test and it was less than 2 cc within 10 seconds purging. To simulate the end of line, the residual gasoline in the fuel line was purged during 5 and 10 seconds. Start time of LPI engine with LPG fuel were 0.61 and 0.58 seconds. This work showed that severe problems such as misfiring and liner scuffing were not occurred applying gasoline fuel to LPI engine.

• Clinics in Shoulder and Elbow
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• 제24권3호
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• pp.135-140
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• 2021

Background: We hypothesized in this study that the characteristics of retear cases vary according to surgeon volume and that surgical outcomes differ between primary and revision arthroscopic rotator cuff repair (revisional ARCR). Methods: Surgeons performing more than 12 rotator cuff repairs (RCRs) per year were defined as high-volume surgeons, and those performing fewer than 12 RCRs were considered low-volume surgeons. Of the 47 patients who underwent revisional ARCR at our clinic enrolled in this study, 21 cases were treated by high-volume surgeons and 26 cases by low-volume surgeons. In all cases, the interval between primary surgery and revisional ARCR, degree of "acromial scuffing," number of anchors, RCR technique, retear pattern, fatty infiltration, retear size, operating time, and clinical outcome were recorded. Results: During primary surgery, significantly more lateral anchors (p=0.004) were used, and the rate of use of the double-row repair technique was significantly higher (p<0.001) in the high- versus low-volume surgeon group. Moreover, the "cut-through pattern" was observed significantly more frequently among the cases treated by high- versus low-volume surgeons (p=0.008). The clinical outcomes after revisional ARCR were not different between the two groups. Conclusions: Double-row repair during primary surgery and the cut-through pattern during revisional ARCR were more frequent in the high- versus low-volume surgeon groups. However, no differences in retear site or size, fatty infiltration grade, or outcomes were observed between the groups.