• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1999.11a
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• pp.269-275
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• 1999

This paper presents the results of thermoelastic wear phenomena in ventilated disk brakes for a high-speed train using finite element method. The computed results show that the sinusoidal distortions due to non-uniform distributions of temperature profiles may lead to thermoelastic wears at the rubbing surface. This may decrease the life of a disk brake and produce micro-cracks, noise and squeals between two rubbing surfaces.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1425-1427
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• 1994

Laser ablation of glass substrates (8K-7 and synthetic quartz) using a transversely excited atmospheric (TEA) $CO_2$ laser has been inverstigated to obtain high speed etching. The ablation occurs by local heating of a substrate with a focused TEA-$CO_2$ laser beam. The dependence of ablation rate on pulse count and repetition-rate of laser has been discussed.

• Fire Science and Engineering
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• v.7 no.2
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• pp.24-28
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• 1993

The flash point for flammable liquids (alcohol, aromatic compounds) were measured by Penskt-Martens's measuring apparatus with closed cup. As a result, it was observed that the flash points had the regular tendency according to the carbon number and the molecular structure. Consequently, the flash point for the alcohols were increased in proportion to the increase of the carbon number and branch number. The differences between the literature and experimental data are 14.6% for the relative error and 3.46$^{\circ}C$ in average for the measuring temperature.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.1
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• pp.67-74
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• 2000

One of the important application of a contact melting process is a latent thermal energy storage owing to its high heat flux. In some previous works, the split fins have been employed in order to enhance the melting speed. In the present work, the close contact melting was experimentally investigated using an ice as specimen for both split and non-split fins. It was shown that the contact melting by split fins increases the melting rate compared to that of non-split ones.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.50.4-50.4
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• 2019

We detect a new population of chromospheric jets in a polar coronal hole observed by Hinode/SOT. The propagating speed of the jets ranges in 30 - 490 km/s whose duration time is 3 - 52 s. The recurrent rate is approximately 3/min for a give segment of 1 arc-second horizontal interval. These jets are seemed to be more transient and faster than type II spicules at chromosphere, while the properties are compatible with the network jets seen in emission lines of transition region. We will discuss the implication of these jets for a coronal heating.

• Journal of Energy Engineering
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• v.20 no.2
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• pp.163-169
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• 2011

This research is to decide the possibility of using RM50(reformulated methanol fuel) without any modification of engine by the method of numerical analysis. Comparing the heat release rate, the difference among each fuel was decreased according to the increase of the engine speed, and the maximum heat release rate was higher in the order of RM50 and gasoline fuel. Also, this order corresponds to the order of burning speed. RM50 had the higher turbulent burning speed, and the curve of turbulent intensity was showed similar tendency to the curve of turbulent burning speed. RM50 had relatively high burning speed, short quenching length, high temperature in cylinder, so that it might increase NO emission, but owing to chemical reaction dynamics, it was decreased NO emission. Therefore, in order to predict the possibility of using RM50, it is needed to consider not only the temperature in cylinder by low heating value, but also combustion characteristics including burning speed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.8
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• pp.1478-1485
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• 2007

In this paper, a meteorological system including a wind speed & direction module and the DSP(Digital Signal Processor) sensor interface circuit board are proposed. This DSP system accepts and process the informations from a wind speed & direction module, the atmospheric pressure sensor, the ambient air temperature sensor and transfers it to the PC monitoring system. Especially, a wind speed & direction module and a DSP hardware are directly designed and applied. A wind speed & direction module have a construction that it have four film type RID(Resistive Temperature Detectors) resistive sensor adhered around the circular metal body heated constantly by heating coil for obtaining vector informations about wind. By this structure, the module is enabled precise measurement having a robustness about vibration, humidity, corrosion. A sensor signal processing circuit is using TMS320F2812 TI(Texas Instrument) Corporation high speed DSP. An economical meteorological system could be constructed through the data from wind speed & direction module and by the fast processing of DSP interface circuit board.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.6
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• pp.285-291
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• 2002

In general, utility voltage is maintained at a relatively low level of Phase unbalance since a low level of unbalance can cause a significant power supply ripple and heating effects on the power system equipment. Voltage unbalance more commonly emerges in individual customer loads due to phase load unbalanced, especially where single phase power loads are used. Under unbalanced input voltages large lower order harmonics appears at the input and output ports of Power conversion devices. As the application of adjustable -speed drives (ASDs) and their integration with complex industrial processes increase, so does the need to understand how ASDs perform during voltage This paper describes a real load test to investigate the performance of 3-HP adjustable speed drives by an unbalanced voltage at the low-voltage system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.5
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• pp.446-475
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• 2000

Performance of a water-to-water multi-type heat pump system using R22 has been experimentally investigated. Total refrigerant flow rate was adjusted with a variable speed compressor and the refrigerant flow rate for two indoor units were controlled by electronic expansion valves. Evaporator outlet pressure of refrigerant and indoor unit outlet temperatures of secondary fluid were selected as controlled variables. Experiments were carried out for both cooling and heating modes using PID control method. Results show that the multi-type heat pump system can be adequately controlled by keeping control gains at certain levels for various operating conditions.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.184-191
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• 2002

This paper presents the thermal behavior of a synchronous linear motor with high speed and force. Such a linear motor can successfully replace ball lead screw in machine tools because it has a high velocity, acceleration and good positioning accuracy. On the other hand, low efficiency and high heating up during operation are disadvantage of linear motors. For the application of linear motors to machine tools a water-cooling system is often used. In this research, structure of the linear motor and water cooler is changed to improve the thermal behavior of the linear motor. Some important effects of an integrated cooler, an U-cooler and a thermally symmetrical cooler are presented.