• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.148-154
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• 1999

This study was carried out to verify grinding performance of dental diamond bur and investigate the possibility of AE application in dentistry field. Workpieces were made of acryl and bovine respectively for the experiments in this study. Grinding test was conducted to get the data of grinding resistance and specific grinding energy of four different types of diamond bur by using tool dynamometer. AE signal was acquired to verify grinding process in the AE measuring system. Tool wear was observed to find parameters about grinding characteristics of diamond bur by means of SEM picture. It was found that the wear of dental diamond bur could be detected with polishing of grinding material, removal of adhesive parts, wear of particles neighboring cutting nose, loss of material and elevation of temperature. The wear of B, C, D type diamond bur is due to wear and fracture of grain size. Abnormal state can be found through the behavior of AE signal in the grinding working. As a result, it is expected that forecast of abnormal state is possible using AE equipments under real time process.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.299-303
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• 2007

Dry sliding wear behavior of ultra-fine grained(UFG) plain low carbon dual phase steel, of which microstructure consists of hard martensite in a ductile ferrite matrix, has been investigated. The wear characteristics of the UFG dual phase steel was compared with that of a coarse grained dual phase steel under various applied load conditions. Dry sliding wear test were carried out using a pin-on-disk type tester at various loads of 1N to 100N under a constant sliding speed condition of 0.20m/s against an AISI 52100 bearing steel ball at room temperature. The sliding distance was fixed as 1000m for all wear tests. The wear rate was calculated by dividing the weight loss, measured to the accuracy of 10-5g by the specific gravity and sliding distance. The worn surfaces and wear debris were analyzed by SEM, EDS and profilometer. Micro-vickers hardness of the cross section of worn surfaces were conducted to analyze strain hardening underneath the contact surfaces. The wear mechanism of the UFG dual phase steel was investigated with emphasis on the unstable nature of the grain boundaries of the UFG microstructure.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.83-83
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• 2011

본 연구에서는 p-type Si (100) 위에 분자선 에피택시 성장방법으로 ZnO 완충층이 삽입된 ZnO 박막을 성장시켰다. ZnO 완충층은 Zn 셀 셔터의 열림/닫힘을 반복하는 성장 멈춤법으로 성장되었다. Zn 셀 셔터의 열림 시간은 4분, 2분, 1분이며 닫힘 시간은 2분으로 동일하게 유지하였다. 이러한 과정은 각각 5, 10, 20회로 반복되었으며 ZnO 완충층을 성장한 후 ZnO 박막은 기존의 분자선 에피택시 방법으로 성장되었다. ZnO 박막의 구조적, 광학적 특성은 field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence (PL)로 조사하였다. SEM 측정결과 성장 멈춤 횟수가 증가함에 따라 ZnO 박막의 표면은 섬(island) 구조에서 미로(maze) 구조로 변화하였고, XRD 측정결과 full-width at half-maximum (FWHM) 이 감소하고 결정립 크기(grain size)가 증가하였다. 그리고 PL 측정결과 성장 멈춤 횟수가 증가함에 따라 near-band-edge emission (NBE) 피크의 세기가 증가하였고 deep-level emission (DLE) 피크의 위치는 오렌지 발광에서 녹색 발광으로 청색편이(blue-shift)하였다.

• Korean Journal of Materials Research
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• v.5 no.8
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• pp.921-928
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• 1995

MoSi$_2$heating elements were fabricated using MoSi$_2$, powder prepared by SHS. Their apparent density, electrical resistivity, bending strength and victors hardness were measured as a function of sintering temperature, time and the amount of ceramic additives. The additives were A1$_2$O$_3$, SiO$_2$and bentonite which were added as a plastisizer. The electrical resistivity of MoSi$_2$decreased with the increase in the apparent density as expected. It decreased when the additives were added and the increase was the largest for the case of SiO$_2$. The bending strength and hardness decreased when the grain size becomes larger which is opposite to the expectation from the Hall-Petch type relation. Instead, they showed inverse proportionality with the volume fraction of pores probably in an exponential manner. The strength and hardness also decreased with the additives.

• Journal of Sensor Science and Technology
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• v.4 no.3
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• pp.15-21
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• 1995

In this paper, $TiO_{2}-V_{2}O_{5}$ humidity sensors are fabricated by Sol-Gel method. For the establishment of optimum processing condition which is good humidity sensitive characteristics for specimens, their microstructures and crystalline-structures are analysed. Grain size increases with substitution rate of $V^{5+}$ on $Ti^{4+}$ site. From the analysis of XRD, $V^{5+}$ peak can't confirm with $V_{2}O_{5}$ rate. Their humidity sensitive characteristics is good at 1mol% of $V_{2}O_{5}$ rate and heat-treated at $700^{\circ}C$. The capacitance of specimens decreases with frequency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.4
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• pp.294-299
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• 2000

For practical application as a humidity sensor SnO$_2$thick films devices were fabricated on the refresh type electrode by screen printing method and their material and humidity sensing properties were investigated. As a function of Sb$_{2}$/O$_{3}$ addition rate grain size was increased while porosity and initial resistance were rapidly decreased. And the area of resistance variation according to relative humidity was decreased with increasing heat treatment temperature. SnO$_2$thick film device heat treated at 95$0^{\circ}C$ and contained 0.05mole% Sb$_{2}$/O$_{3}$ had a best humidity sensing properties. From this result it is conformed that humidity sensing properties of SnO$_2$thick film devices could be approved by very small amount of Sb$_{2}$/O$_{3}$ addition.

• Journal of Welding and Joining
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• v.23 no.4
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• pp.27-33
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• 2005

Quantitative evaluation was performed on the microstructure of flux-cored arc(FCA) weld metal using a method blown as IIW scheme. It was mainly intended to figure out any practical difficulties in applying this method and also to provide the consumable makers with basic guide line in developing FCA welding consumables far better properties. Assessment of the experimental results showed IIW scheme was quite reliable in the low heat input range where the acicular ferrite was a major constituent. However, in the high heat input range, some scatter was noticed as the other phases like grain boundary ferrite and Widmansttaten ferrite become dominant. It implies that the accuracy of IIW scheme depends on the faction of microstructural constituents and it become worse as the fraction of latter two phases increases. This tendency was discussed in terms of the characteristics of those two phases. In addition, base line microstructure of rutile type FCA weld metal was addressed for developing new FCA welding consumables intended for higher heat input welding.

• Food Science of Animal Resources
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• v.36 no.6
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• pp.709-718
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• 2016

This review addresses the characteristics and health benefit of highly marbled Wagyu and Hanwoo beef. Marbling of Wagyu and Hanwoo beef has been increased in Japan and Korea to meet domestic consumer preferences. Wagyu and Hanwoo cattle have high potential of accumulating intramuscular fat (IMF) and producing highly marbled beef. The IMF content varies depending on the feeding of time, finishing diet, and breed type. IMF increases when feeding time is increased. The rate of IMF increase in grain-fed cattle is faster than that in pasture-fed cattle. Fatty acid composition are also different depending on breeds. Highly marbled Wagyu and Hanwoo beef have higher proportions of monounsaturated fatty acid (MUFA) due to higher concentrations of oleic acid. MUFAs have little effect on total cholesterol. They are heart-healthy dietary fat because they can lower low-density lipoprotein (LDL)-cholesterol while increasing high-density lipoprotein (HDL)-cholesterol. Clinical trials have indicated that highly marbled beef does not increase LDL-cholesterol. This review also emphasizes that high oleic acid beef such as Wagyu and Hanwoo beef might be able to reduce risk factors for cardiovascular disease.

• Journal of Korea Foundry Society
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• v.14 no.1
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• pp.28-34
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• 1994

Metallurgical-grade polycrystalline silicon was directionally solidified at growth rates of $0.2{\sim}1.0mm/min$ by using split type, reusable graphite molds which were coated with $Si_3N_4$ powder. The resultant grain sizes of the silicon ingots and the shapes of the solid/liquid(S/L) interfaces were investigated. X-ray diffraction was used to determine the preferred orientation in each of the silicon ingots. The impurity content of the silicon was analyzed and the resistivities of the ingots were measured. During the growth of an ingot, the shape of the S/L interface was concave to the silicon melt, and the resistivity decreased. The presence of Al which can be acting as a carrier, is thought to be the main factor causing such a decrease in resistivity. When a growth rate of 0.2㎜/min was used, the preferred orientation was found to be (111).

• Journal of Ocean Engineering and Technology
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• v.2 no.2
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• pp.104-111
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• 1988

This paper deals with the micro-surface-cracks behavior on the unnotched smooth specimens of Type 304 stainless steel at $593^{\circ}C$ in air under creep and creep-fatigue conditions that have 10 mim and 1 min load holding times respectively. The behaviors of the micro-surface-cracks have been visualized by means of surface replica method and optical micro-photography. The quantitative characteristics of initiation, growth and coalescence of micro-surface-cracks have been investigated by observing and measuring the crack growth behaviors. some of the important results are as follows: Main crack initiates at grain boundary in the early stage(10 to 20%)of its life time and grows through coalescence and finally leads to fracture. The distribution of micro-surface-crack length, 2a, can be plotted against the composite Weibull distribution. The growth rate of the main crack can be plotted against the stress intensity factor, crack tip opering displacement and J integral.