• Journal of Periodontal and Implant Science
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• v.48 no.4
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• pp.201-201
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• 2018

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.513-514
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• 2006

Recently intradiscal electrothermal therapy is introduced, which is a new and minimally invasive technique fer the treatment of discogenic low back pain. This procedure involves the percutaneous threading of a flexible catheter into the disc under fluoroscopic guidance. The catheter, composed of thermal resistive coil, heats the posterior annulus of the disc, causing contraction of collagen fibers and destruction of afferent nociceptors. This study tries to investigate the effects of the important factors of this procedure such as heat source temperature and heat applying time on the temperature distribution within the intervertebral disc. This study utilized both computer simulation and the experiment for the verification of finite element analysis. FE analysis was carried out with ANSYS v7.0 (ANSYS Inc, USA) using 10,980 number of brick element and 12,551 number of node. The functional spinal units of 5 month old swine were used for the experiment and the temperature was monitored using 10 channel temperature measurement device MV200. Through this study, it was able to analyze the temperature range of inner intervertebral disc by two mechanisms which are known to alleviate pain clinically. The results showed that when the heat source temperature was kept up 80 degree for 1,020 seconds, the temperature of inner annulus reached at 45 degree up to the distance of 15.6mm from heat source, which explains coagulation of inner annulus by heat. When the same heat source was used, the temperature of inner nucleus reached at 60 degree up to the distance of 9mm from heat source, which explains contraction of inner nucleus by heat.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.85-91
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• 2003

Narrow gap welding has many advantages over conventional V-grooved butt welding such as high productivity, small deformation and improved mechanical property of joints. With narrower groove gap, less arc heat input is expected will all the other advantages of narrow gap welding. The main defects of narrow gap welding include the lack of root fusion, convex bead surface and irregular surface, all of which have negative effects on the next welding pass. This paper suggests an up-and-down torch oscillation for ultra narrow gap welding with gap size of 5mm and investigates the proper welding conditions to fulfill the reliable and high welding quality. First, GMA welding model was suggested for ultra narrow gap welding system with Halmoy's model referenced for wire melting modeling. And the arc length in ultra narrow gap was defined. Secondly, based on the experimental results of up-and-down torch oscillation welding, phase shift of current and wire extension length were simulated for varying oscillation frequency to show that weld the bead shape in ultra narrow gap welding can be predicted. As the result, it was confirmed that reliable weld quality in ultra narrow gap welding can be achieved with up-and-down torch oscillation above 15Hz due to its ability to provide uniform heat input along the sidewall of gap.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.107-115
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• 1999

Hydrocarbon emission from spark ignition engines deeply relates with fuel evaporation mechanism. Therefore, fuel evaporation on the back of the intake valve is very important to understand fuel evaporation mechanism during engine warm up period. Intake valve heat transfer model was build up to estimate the amount of fuel evaporation on the intake valve back . Intake valve temperature was measured intake valve temperature is increased rapidly during few seconds right after engine start up and it takes an important role on fuel evaporation. The liquid fuel evaporation rate on the intake valve back proportionally increases as valve temperature increases, however its contribution slightly decreases as intake port wall temperature increases. The fuel evaporation rate on the valve back is about 40∼60% during engine warm-up period and it becomes about 20∼30% as intake port wall temperature increases. The estimation model also makes possible model also makes possible to review the effect of valve design parameters such as the valve mass and seat area on fuel evaporation rate through intake valve heat transfer.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.2
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• pp.8-14
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• 2018

A boiling heat transfer is used in various industry such as power generation systems, heat exchangers, air-conditioning and refrigerations. In the boiling heat transfer system, the critical heat flux (CHF) is the important factor, and it indicated safety of the system. It has kept up studies on the CHF enhancement. Recently, it is reported the CHF enhancement, when working fluid used the nanofluid with excellent thermal properties. Therefore, in this study, we investigated the influence of nano particles coated surface for heat transfer enhancement in pure water, oxidized multi-wall carbon nanotube nanofluid (OMWCNT), and oxidized graphene nanofluid (OGraphene). Nanoparticles were coated for 120 sec on the surface, and we measured the CHF at the flow velocities of 0.5, 1.0, and 1.5 m/sec, respectively. As the results, both of the OMWCNT and OGraphene nanofluids increased up to about 34.0 and 40.0%.

• Solar Energy
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• v.19 no.3
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• pp.43-51
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• 1999

Axisymmetric circular water jet impinges against rectangular heated surface with uniform hear flux and wire-mesh screens are set up in the nozzle-to-heater space to augment heat transfer. In the free jet region to be used them, pressure drop and intensive turbulence flow was brought up. When water jet system is not used wire-mesh screens, maximum heat transfer appears in the stagnation point and the secondary maximum appears X/D=4 but it disappears when they are is used. In the low velocity(Vo<6.0m/s), coarse mesh-screen enhanced heat transfer but fine mesh-screens inpeded heat transfer. In the high velocity(Vo>6m/s), all of them enhanced heat transfer. Average Nusselt number of experimental system to be used wire-mesh screens was promoted $4{\sim}6$times than that of simple water jet system. The stagnation heat transfer of experimental system to be used wire-mesh screens was augmented 6times that of simple water jet system.

• Journal of Korea Foundry Society
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• v.3 no.3
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• pp.159-166
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• 1983

In order to develope domestic carburizers, the experiment was carried out by applying crystallization heat treatment to domestic anthracites and also to foreign products to compare with domestic anthracites.The present work was mainly concerned with the effect of their degree of crystallization of carbon-bearing materials on carbon pick-up in molten iron.Those effects were evaluated by the measurement of density, chemical composition, specific electric resistivity, and X-ray intensity of carbon-bearing materials. Experimental results thus obtained were summurized as follows. 1. The degree of crystallization of domestic anthracites and foreign products was increased with increasing heat treatment temperature. 2. The more degree of crystallization, the shorter the dissolving time of domestic anthracites in molten iron was obtained, while that of foreign products was remained constant. 3. As the degree of crystallization of domestic anthracites and foreign products was increased, the carbon content as well as carbon recovery in molten iron was increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.228-229
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• 2017

MOCK-UP TEST was conducted in the extreme region of the cement which was researched and developed by using the reducing slag Experimental results show that the basic properties (air volume, slump) are improved compared with the specimens using Mongolian cement. The compressive strength achieved the target strength (target strength: age 3day: 7MPa, age 7day 14MPa) and the hydration heat was about 8 ℃ higher than that of Mongolian cement products. Therefore, it is considered that the cement powders developed by our company showed the strength of concrete due to high hydration heat even at extreme temperatures.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.246-247
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• 2005

This study suggested fanless thermal design using CAE technique for the information storage system under the serious thermal problem. At first, main heat flow was controlled by CAE based fanless heat sink design not to influence sensitive optical pick-up sensor. Then, vent parametric studies found a thermal solution about highly concentrated case top heat due to fanless. These CAE results were verified by experimental methods. As a consequence of newly designed thermal path, thermal specification of optical pick-up sensor was satisfied and fanless thermal design for the information storage system was achieved.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.339-345
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• 2006

This these was conducted to investigate tile characteristics of a frozen start up for a VCHP which has water as a working fluid and Nitrogen as a non-condensible gas. The tested heat pipe was made of a copper tube with the outer diameter of 12.7 mm, the length of 340 mm, and the sintered metal wick had the thickness of 0.7 mm. This experiment was conflicted under the thermal load, inclined angle and cooling conditions.