• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05d
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• pp.100-104
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• 2003

$BaTiO_3$ ceramic thin films were manufactured by rf/dc magnetron sputter technique. We have investigated crystal structure, surface morphology and PTCR(positive-temperature coefficient of resistance) characteristics of the specimen depending on second heat-treatment temperatures. Second heat treatments of the specimen were performed in the temperature range of 400 to $1350^{\circ}C$. X-ray diffraction patterns of $BaTiO_3$ thin films show that the specimen heat treated below $600^{\circ}C$ is an amorphous phase and the one heat treated above $1100^{\circ}C$ forms a poly-crystallization. In the specimen heat-treated at $1300^{\circ}C$, a lattice constant ratio (c/a) was 1.188. Scanning electron microscope(SEM) image of $BaTiO_3$ thin films of the specimen heat treated in between 900 and $1100^{\circ}C$ shows a grain growth. At $1100^{\circ}C$, the specimen stops grain-growing and becomes a poly-crystallization.

• The Korean Journal of Pain
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• v.24 no.1
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• pp.57-60
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• 2011

Pulsed radiofrequency (PRF) treatment of nervous tissue has been proposed as a less neurodestructive technique alternative to continuous RF heat lesioning. Recently, clinical reports using PRF have shown favorable effects in the treatment of a variety of focal pain areas, even in non-nervous tissues; however, the mechanism of effect underlying this treatment to non-nervous tissue remains unclear. We report the case of a 67-year-old male who presented with pain reliving point in the posterior neck. The patient had pain in the posterior neck for 3 years. The pain subsided with pressure applied to a point in the posterior neck. There were no specific abnormal findings on laboratory testing and radiologic examinations. After PRF treatment to the pain-relieving point, he had pain relief which lasted more than 5 months.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.1
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• pp.130-143
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• 1997

A heat-pressed technique(IPS-Empress, Ivoclar) has been described to construct single unit crown, inlay/onlay and veneers using a partially pre-cerammed and pre-colored glass-leucite ingot that has the greateast strength by the combination of heat-pressed procedure through the smalldiameter sprue and heat treatment procedure. The purpose of this study was to evaluate the flexure strength of a heat-pressed ceramic material(IPS-Empress) without simulated firing treatments according to pontic designs. Two groups of 9 disks(1.4mm thick, 14mm in diameter) each using two types of sprues with different diameters($({\Phi}2.8\;,{\Phi}1.8)$) and numbers were prepared. The specimens were mounted in the testing jig. The flexural strengths were determined, by means of the bi-axial bending test, by loading the center of disk to failure using a universal testing machine(Zwick 145141, Zwick, Germany) at a cross-head speed of 1.0 mm/min. The means flexural strength value of one group using a sprue with ${\Phi}2.8$ was $140.4{\pm}8.0Mpa$. That of the other group using two sprues with ${\Phi}1.8$ was $151.8{\pm}10.3Mpa$. After analysis, results showed that there was a statistical difference between groups(t=2.33m p<0.05). No clnical implications were drawn from these data because of absence of simulated firing treatment.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.1
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• pp.17-22
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• 2004

In the present study, newly developed spark plasma sintering(SPS) technique was introduced to refine the grain size of ${\gamma}$-based TiAl intermetallic compounds. Ti-46Al-1.5Mo and Ti-46Al-1.5Mo-0.2C(at%) prealloyed powders were produced by mechanical milling(MM) in high-energy attritor. The mechanically milled powders were characterized by XRD and SEM for the microstructural evolution as a function of milling time. And then, the MMed powders were sintered by both spark plasma sintering and hot pressing in vacuum (HP). After the sintering process, MM-SPSed specimens were heat-treated in a vacuum furnace (SPS-VHT) and in the SPS equipment(MM-SPS) for microstructural control. It was found from microstrutural observation that the microstructure consisting of equiaxed ${\gamma}$-TiAl with a few hundred nanometer in average size and ${\alpha}_2-Ti_3Al$ particles were formed after both sintering processes. It was also revealed from hardness test and three-point bending test that the effect of grain refinement on the hardness and bending strength is much higher than that of carbon addition. The fully lamellar microstructures, which is less than $80{\mu}m$ in average grain size was obtained by SPS-VHT process, and the fully lamellar microstructure which is less than $100{\mu}m$ in average grain size was obtained by MM-SPS for a relatively shorter heat-treatment time.

• Korean Journal of Acupuncture
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• v.34 no.3
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• pp.109-115
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• 2017

Objectives : Many researches have studied warm needling technique to standardize its treatment by temperature measurement and material differences in the effectiveness. The purpose of this study is to compare the temperature changes of the acupuncture needle shaft during the combustion process of the moxa stick to determine the heat transfer pattern of the warn needling. Methods : A moxa stick($7{\times}8mm$) was connected to one side of the needle shaft using a stainless steel needle(ø 0.3 mm, ø 0.5 mm, ø 0.8 mm, shaft length 40 mm) with the needle handle removed. During the warm needling, temperature changes of the needle shaft were observed with an infrared camera(Flir E30) and an infrared thermometer(TESTO 845). Results : In the normal condition, heat transmit of needle shaft increased at spots 10 mm and 25 mm below the moxa stick. The amount of heat transmit increased with the diameter of needle shaft. However, when the heat shield was installed to exclude radiant heat from the moxa stick, heat transfer was less at 10 mm below the moxa stick and no temperature change was observed at 25 mm below the moxa stick. Heat transfer by warm needling does not reach the end of needle shaft even in ø 0.8 mm needle. Conclusions : It is suggested that the radiant heat of moxa stick results in the heat transmit of acupuncture needle shaft. Thus, radiant heat transmit must be considered as one of the heat transfer characteristics of the warm needling.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.319-323
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• 2008

The polarization resistance of mild steel in 0.5M hydrochloric acid has been evaluated by using impedance (Z) and linear polarization (LPR) techniques and compared to the noise resistance obtained from electrochemical noise data. The degree of localization of this general corrosion has also been discussed by evaluating localization index and power spectral density. Polarization resistance obtained by LPR technique ($28\Omega$) was higher than that obtained by impedance technique ($15\Omega$). Noise resistance ($11\Omega$) was much lower than polarization resistance measured by both of above techniques. Higher polarization resistance obtained by LPR technique is generally caused by passivation effect in the presence of scales or deposits which can introduce an increased resistance as can low conductivity electrolytes. The reason why noise resistance is lower than polarization resistance is the effect of background noise detected by using three platinum electrodes cell in 0.5M hydrochloric acid. Slope($-\beta$) of power spectral density (PSD) obtained from analysis of noise data ($-\beta$ = 3.3) was much higher than 2 which indicates mild steel corroded uniformly. Localization index (LI) calculated from statistical analysis (LI=0.08) is much lower than 1 which indicates that mild steel did not corroded locally. However, LI value is still higher than $1x10^{-3}$ and this indicates that mild steel corroded locally in microscopic point of view.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.40 no.2
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• pp.43-56
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• 2008

The purpose of the experiment was to evaluate the material stability of the paper of the annals of Joseon Dynasty for the conservation purpose and the categories were as listed below : 1. Procuring traditional Hanji and semi-Hanji from different regional hanji paper mill. 2. Artificial accelerated aging treatment to examination its stability (UV irradiation, dry heat) 3. Analysis of optical, physical characteristic. The suitable Hanji for categories would be used as a reconstruction material for the waxel paper in the papers of the annals of Joseon Dynasty.

• Journal of the Korean Society for Heat Treatment
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• v.3 no.2
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• pp.10-19
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• 1990

The tempering behavoirs of 0.45% carbon steel treated by automatic progressive high frequency induction hardening equipment have been investigated. In order to examine the correlation of hardness with both tempering temperature and time, simple regression analysis has been made using the statistical quality control package. The maximum surface hardness value of induction hardened zone and its effective hardening depth have been determined to be Hv 810 and 0.76mm, respectively. The hardness obtained after tempering has been shown to vary lineary with tempering time at six different temperatures. The activation energies during tempering have been calculated to be 25.34kcal/mole, 32.73kcal/mole and 49.24kcal/mole for HRcs 60, 50 and 40, respectively, showing that tempering process occurs by a complex mechanism, The tempering hardness equation of $H=90.113{\sim}4.531{\times}10^{-3}$ [T(11.996+log t)] has proved to be in a reasonably good agreement with experimently determined data and it is also expected to be useful for the determination of tempering treatment conditions to obtain a required hardness value.

• Geomechanics and Engineering
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• v.32 no.3
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• pp.293-305
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• 2023

To ensure the safety of underground infrastructures, ground can sometimes be first treated by cement slurry and then stabilized using artificial ground freezing (AGF) technique before excavation. The hydration heat produced by cement slurry increases the soil temperature before freezing and results in an extension of the active freezing time (AFT), especially when the Metro Jet System (MJS) treatment is adopted due to a high cement-soil ratio. In this paper, by taking advantage of an on-going project, a case study was performed to evaluate the influence of MJS and AGF on the ground temperature variation through on-site measurement and numerical simulation. Both on-site measurement and simulation results reveal that MJS resulted in a significant increase in the soil temperature after treatment. The ground temperature gradually decreases and then stabilized after completion of MJS. The initiation of AGF resulted in a quick decrease in ground temperature. The ground temperature then slowly decreased and stabilized at later freezing. A slight difference in ground temperature exists between the on-site measurements and simulation results due to limitations of numerical simulation. For the AGF system, numerical simulation is still strongly recommended because it is proven to be cost-effective for predicting the ground temperature variation with reasonable accuracy.

• Journal of the Korean institute of surface engineering
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• v.54 no.2
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• pp.90-95
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• 2021

Surface modification technique enabling the control of condensation provides various benefit in various engineering systems, such as heat transfer, desalination, power plants, and so on. In this study, lubricant oil-impregnation into Teflon-coated nanoporous anodic oxide layer of aluminum to enhance a de-wetting and mobility of water droplet on surface. Due to the surface treatment improving water-repellency, the condensation mode is changed to dropwise, thus the frequency of sliding condensed water droplet on surface is increased. For these reasons, the surface of oil-impregnated Teflon-coated nanoporous anodic aluminum oxide shows significantly enhanced condensation heat transfer compared to bare aluminum surface. In addition, the porosity of anodic aluminum oxide affected the mobility of water droplet even with oil-impregnation and Teflon-coating, indicating that the optimization of porous structure of anodic oxide is required for maximizing the condensation heat transfer.