• International Journal of Precision Engineering and Manufacturing
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• v.8 no.3
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• pp.50-53
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• 2007

Improving the reliability or long-term dependability of a system requires a different approach from the previous emphasis on short-term concerns. The purpose of this paper is to present a reliability evaluation method for an oil cooler intended for high-precision machining centers. The oil cooler system in question is a cooling device that minimizes the deformation caused from the heat generated by driving devices. This system is used for machine tools and semiconductor equipment. We predicted the reliability of the system based on the failure rate database and conducted the reliability test using a test-bed to evaluate the life of the oil cooler. The results provided an indication of the reliability of the system in terms of the failure rate and the MTBF of the oil cooler system and its components, as well as a distribution of the failure mode. These results will help increase the reliability of oil cooler systems. The evaluation method can also be used to determine the reliability of other machinery products.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.5
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• pp.330-336
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• 2000

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SM45C steel. The control of heat-treatment deformation must need the progress of production parts for a landing gear. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.249-256
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• 2019

The 9Cr-1Mo ferritic-martensitic ODS steel is a promising structural material for the next generation nuclear power plants including fast reactors for application in reactor vessels and nuclear fuel. The ODS steel was cooled down by furnace cooling, air cooling, oil quenching and water quenching, respectively, after normalizing it at $1150^{\circ}C$ for 1 h and then tempering at $780^{\circ}C$ for 1 h. It is found that grain size, a relative portion of ferrite and martensite, martensitic lath configuration, behaviors of carbide precipitates, and hardness of the ODS steel are strongly dependent on a cooling rate. The grain size and martensitic lath width become smaller with the increase in a cooling rate. The carbides were precipitated at the grain boundaries formed between the ferrite and martensite phases and at the martensitic lath interfaces. In addition, the carbide precipitates become smaller and more widely dispersed with the increase in a cooling rate, resulting in that the faster cooling rate generated the higher hardness of the ODS steel.

• Fire Science and Engineering
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• v.23 no.6
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• pp.57-65
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• 2009

Fire suppression tests are carried out for a train car using water mist systems. Three kinds of fire scenario applied to the real-scale train car are a surface fire representing car combustibles, a oil pool fire pretending an oil spill and a blocked fire for evaluation of space-cooling capacity. Five fixedpressure water mist systems and one self-contained water mist system with nitrogen gas are used for fire suppression experiments. Almost water mist systems can extinguish effectively train car fires, and fire-control capability of the system is seen due to the space cooling.

• Journal of Energy Engineering
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• v.27 no.4
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• pp.98-102
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• 2018

In order to improve the durability of components in the vehicle engine room, an experiment to improve the air cooling effect of components by installing a cooling duct using intake air aiming at four components, such as generator, battery, ECU and power steel oil, Respectively, experimental results show that the overall component temperature has been reduced, and the reduced temperature difference is in the order of generator, ECU, power steel oil and battery. In order to improve the temperature difference due to these components, it is necessary to optimize the design through the flow analysis in the duct in the future.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.668-669
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• 2016

The retarder as a hydraulic brake system in order to assist a service brakes in commercial vehicle is operated by automatic and manual mode due to driver. Braking energy by retarder operation is transmitted to the engine radiator of vehicle cooling system, passing through the retarder oil heat exchanger. At this moment, the retarder ECU performs the function that is controlled a braking torque with consideration for automatic and manual mode, temperature of retarder oil/water, engine coolant temperature, vehicle speed, and etc. In this paper, it deals with the design of retarder control logic and the results of retarder braking performance test regarding a cooling system of retarder and vehicle.

• Journal of Power System Engineering
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• v.4 no.3
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• pp.55-61
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• 2000

In this study, a new design of an one-body type of an unbalanced-fixed- displacement type vane pump combined with an induction type electric motor was suggested. By the application of the new design scheme, it was possible to reduce the number of parts of the pump system and to cut down the volume of power package than that of already-used products. The case in this study enabled efficient heat transfer and electricity insulation of hydraulic fluid. Thus oil moves through the inside of the package for cooling and returns to the reservoir. Because of this design, it was difficult to measure the shaft-input torque. Therefore the package overall efficiency in the paper was evaluated with a ratio of hydraulic power and electric power.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.419-423
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• 1989

The laboratory quench method used in this study is based on plunging a silver cylinder heated to 800.deg. C in to mineral oil and vegetable at given temperature. Experimental apparatus and measuring method followed Korean Industrial Standard. Colling curves at the boundary of the cylinder measured by a silver-alumel thermocouple is recorded throughout the quenching period. Using the cooling curves, the coolingability of the quenching oils at various temperatures were compared and discussed.

• Korean Journal of Food Science and Technology
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• v.11 no.2
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• pp.86-92
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• 1979

Antioxidants. BHA, BHT and PG were added to a commercial soybean oil at a level of 200 ppm, and the antioxidant-treated oils and a control oil were subjected to 30 min. heating at $150{\pm}2^{\circ}C$ and 23.5 hr. cooling at room temperature for 6 times. Variations of % antioxidant retention and some physical and chemical properties of the oils were investigated. The results of the present study were as follows. 1. The % retention of BHA, BHT and PG after the second heating and cooling was respectively 60.5, 55.7 and 40.5 %. That of BHA, BHT and PG after the 6th heating and cooling was respectively 5.7, 3.0 and 1.8 %. 2. The refractive indices and viscosity of the oils, including the control, increased slowly at first. but after 4th heating and cooling, these values increased rapidly. The color indices of the oils, including the control, increased very rapidly, but after the 2nd heating and cooling, the rates of the increase diminished considerably. 3. The efficiency of each antioxidant in suppressing peroxide, thiobarbituric acid, and acid value development decreased rapidly as the antioxidant contents of the oils decreased. After the 6th heating and cooling, the peroxide. thiobarbituric acid and acid values of the oils treated initially with the antioxidants did not differ appreciably from those of the control.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.32-37
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• 2002

High speed machining is one of most effective technologies to improve productivity. It can give great advantage for manufacture of die and Moulds. However, when the high speed machining of materials, especially in machining of micro groove, a severely thermal demage was generated on workpiece and tool. Generally, the cutting fluid is used to improve penetration, lubrication, and cooling effect. In order to rise the performance of lubrication, it contains extreme pressure agents (Cl, S, P). But the environment of work room go bad by those additive Therefore, the compressed chilly air with Oil mist system was developed to replace the conventional cutting fluid system. This paper carried out the tests to evaluate the machinability by the cutting environment in high speed micro groove machining of NAK80 (HRC40). Compressed chilly air with oil mist was ejected on the contact area between cutting edge and workpiece. The effectiveness of this developed compressed chilly air with oil mist system was evaluated in terms of tool life. The results showed that the tool life of carbide tool coated TiAIN with compressed chilly air mist cooling was much longer than with dry and flood coolant when cutting the material.