• Electrical & Electronic Materials
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• v.9 no.9
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• pp.942-948
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• 1996

Electrical properties such as surface flashover discharge and discharge degradations of insulating materials for superconducting cable have been investigated. It is found that the surface voltage is proportional to $l^{0.7}$ (l: discharge length) in liquid helium (LHe). V-t characteristic in LHe was a n=5.5 that was less than liquid nitrogen (L $N_{2}$). After applied AC voltage, the surface condition of polymer films was observed non-eroded areas and eroded areas. The eroded area is depending on the applied voltage. In case of LHe, the crack was observed.d.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.525-531
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• 2002

The effects of different surface hydrophilicity on frosting and defrosting characteristic were experimentally investigated. Mass of frost and water hold-up was measured. Results showed that no significant difference in the frost mass was found between the two different surfaces while the water hold-up of heat exchanger court be reduced by the enhancement of surface hydrophilicity. Also, the defrosting efficiency m hydrophilic surface was improved by 76%. It was expected that hydrophilic heat exchanger could provide the improvements in both thermal-hydraulic performances and system reliability during frost/defrost operating in refrigeration systems.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.735-740
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• 2001

With the development of micro-technology, the demand for micro actuator is increasing. But, it is difficult to achieve high resolution and long travel range simultaneously with the conventional actuators. So, the noncontact surface actuator was proposed. This actuator can realize high dynamic range and the planar motion without complex cross-axis linear slides. This paper describes a magnetically suspended linear actuator for developing a non-contact surface actuator. The operating principle and the structure of the proposed linear actuator are similar to switched reluctance motor, but the proposed linear actuator utilizes normal force and propulsion force simultaneously. With this characteristic, the system can be simpler than other non-contact surface actuator.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.100-106
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• 2013

Stainless steel has some excellent properties as the material for the mechanical component. Purpose of this study is carried out to obtain mirror surface on the surperfinishing of stainless steel with high efficiency. To achieve this, we have conducted a series of polishing experiment for stainless steel using abrasive film from the perspective of oscillation speed, the rotational speed of workpiece, contact roller hardness, contact pressure and feed rate. Abrasive film used this study is a micro-finishing film and a lapping film. Furthermore, the polishing characteristics and efficiency of stainless steel is discussed through measuring optimal polishing time and surface roughness. From the obtained results, it was confirmed that efficient superfinishing conditions and polishing characteristic of Stainless steel can be determined.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.6
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• pp.921-927
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• 1999

In this study, the defrosting behaviors according to the surface characteristics in the fin-tube heat exchanger is experimentally examined. It is found that the draining rate of the hydrophilic and hydrophobic heat exchangers are evenly dispersed during defrosting, compared with that of the bare one. It is caused by the high density frost for the hydrophilic heat exchanger, and surface characteristic for the hydrophobic heat exchanger, respectively. The rest period of the hydrophilic and hydrophobic heat exchangers are shorter and their weight of residual water are smaller than those of the bare heat exchanger The hydrophilic and hydrophobic heat exchangers are more effective than the bare one in terms of defrosting efficiency, and the hydrophobic heat exchanger is better than the hydrophilic one.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.221-224
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• 1997

In this study we investigated the acting characteristics of Polymers for electrical insulation by UV radiation and salt water spray treatment. We used the Polymers such as EPDM, SR. PTFE. EVA. We measured contact angle and surface resistance to know the aging characteristic of Polymer surface. And we use SEM to observe the change of the surface shape. Dry flashover voltage test impulse voltage test were carried for the polymer insulator(EVA) . Through this experiment and the analysis we could know the polymers have a good resistance to weathering conditions like as salt spray UV irradiation and mix of them. And we can compare the aging characteristics between Polymers. As a result, we could know that the surface characteristics of PTFE is better than the other. And the degree, electrical characteristics is affected by change of surface shape is not big.

• Journal of the Korean Vacuum Society
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• v.9 no.3
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• pp.279-284
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• 2000

In order to analysis the degradation process of epoxy/glass fiber for outdoor condition, FRP laminate was exposed to high temperature and water. Then the degradation process was evaluated by comparing contact angle, surface potential decay, and surface resistivity. For the change of wettability, the contact angle of thermal-treated specimen with the high temperature of $200^{\circ}C$ increased. But that of water-treated specimen decreased. The characteristic of surface potential decay shows the tendency of the remarkable decrease on water-treated specimens, but increase on thermal-treated specimen compared with untreated one. Also, for the surface resistivity, it shows the same trend compared with the change of contact angle.

• Journal of the Korean institute of surface engineering
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• v.47 no.6
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• pp.282-286
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• 2014

Wear characteristic of the nitrided SKD61 which is a typical mold material using for the extrusion of Al6061 alloy was investigated. The surface of SKD61 was nitrided by salt bath and plasma processes. The thickness of surface nitride layer was about $8.9{\mu}m{\sim}21.3{\mu}m$. Reciprocating friction wear test conducted using pin on disk type indicated the plasma treatment followed salt bath has a lower friction coefficient and a smaller adhesive wear with Al6061 alloy. That was identified by the $Fe_4N$ which has a better wear resistance than FeN mainly formed by plasma nitriding.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.510-513
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• 2004

This paper represents the response surface model for the cell gap on the flexible liquid crystal display (LCD) process. Using response surface methodology (RSM). D-optimal design is carried out to build the design space and the cell gap is characterized by the quadratic model. The statistical analysis is used to verify the response surface model. This modeling technique can predict the characteristics of the desired response, cell gap, varying with process conditions.

• Journal of the Korean Society of Visualization
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• v.21 no.2
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• pp.55-62
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• 2023

The characteristic of jet impinging on the concave surface were analyzed through thermographic phosphor thermometry (TPT) and numerical investigation. Under a jet Reynolds number of 6600, nozzle diameters and nozzle-to-surface distances (H/d) were changed 5mm and 10mm and H/d=2 and 5. The RNG k-ε turbulence model can accurately predict the distribution of Nusselt number, compared to other models (SST k-ω, realizable k-ε). Heat transfer characteristics varied with the nozzle diameter and H/d, with a secondary peak noted at H/d =2, due to vortex-induced flow detachment and reattachment. An increase in nozzle diameter enhanced jet momentum, turbulence strength, and heat transfer.