• Archives of Plastic Surgery
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• 제35권1호
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• pp.48-55
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• 2008

Purpose: We measured linear distances, angles and inclinations on the cast models of the noses, and compared these indirect measurements with the direct measurements obtained from the nose in order to validate the accuracy of the indirect anthropometry using the cast model. Methods: Subjects were 50 males and 50 females, medical students in twenties(mean 27.1 years). Cast models were made from the alginate impression material and the plaster. In direct anthropometry, 16 linear, 7 angular, and 2 inclination measurements between 11 landmarks on the nose were obtained using sliding caliper, spreading caliper, and fabric tape measure. At the same time, the same measurements were obtained from the cast models of the same people. Total 25 measurements were compared, and tested by the independent t-test of SPSS. Results: The standard values of Korean nose in twenties were obtained. 24 measurements except the columellar labial angle were not statistically different between the indirect anthropometry and the direct anthropometry. Conclusion: Indirect anthropometry on the cast model of the nose revealed no significant difference from the anthropometric measurement statistically, accounting for 24 in 25 measurements(96%). There are two possible reasons that caused the difference of columellar labial angle between direct and indirect anthropometry. First, the columellar labial angle could be decreased by protrusion of the lips which resulted from contracting mouth in which an drinking straw had been applied on the mouth corner for patients' respiration during making cast model. Second, it is generally known that the columellar labial angle could be measured larger when soft tissues were pressed by protractor in direct anthropometry. Using a drinking straw with greater diameter, and scheming respiration through the nostrils that patients don't feel discomfort, the more accurate data would be obtained from the indirect anthropometry using the cast models of the noses.

• 보존과학회지
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• 제28권4호
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• pp.367-376
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• 2012

철기 생산 기술은 당시 사회 발전을 가늠하는 척도로서 과거의 제철 방법을 이해하기 위한 철기 유물의 미세조직과 개재물에 대한 다양한 연구가 진행되고 있다. 본 연구에서는 고려시대로 추정되는 고양 벽제 제철 유구에서 일괄로 수습된 철제 유물의 시편을 채취하여 광학현미경과 미세경도시험기, SEM-EDS를 이용하여 미세 조직의 성분분석을 통해 제철과 제련 기술을 추론하여 보았다. 연구결과 철괴는 주철괴와 탄소강 철괴로 분류되었다. 주철괴의 경우 백주철 조직과 인(P)의 함량이 높은 회주철 조직으로 분류되었으며 회주철 내 높은 P의 함량은 석회질 등의 융제가 첨가되며 혼입된 것으로 판단된다. 따라서 주철 조직의 철괴 및 고탄소강 철괴는 제련공정을 거치지 않은 선철들로 추정된다. 또한 철기 제작에는 크게 두가지 방법이 사용된 것으로 판단된다. 첫번째는 주물에 주철을 부어 제작하는 주철괴 제작 방법이며, 두번째는 선철의 제련 공정을 통하여 생산되는 탄소강을 제작하는 방법이다. 특히 탄소강의 고른 강 조직과 적은 양의 MnS 개재물은 현대 제철 조직과 매우 유사한 특징을 지니나 고양 벽제 제철유구에서 수습된 탄소강 내 Mn의 함유에 대하여 판단하기에는 좀 더 많은 연구가 이루어져야 할 것이며, 주철의 제강공정을 통한 고탄소강의 생산 가능성도 염두에 두어야 할 것으로 사료된다.

• 한국주조공학회지
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• 제11권3호
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• pp.208-216
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• 1991

The solidification behavior of the squeeze cast composites of aluminum alloys reinforced with boron fiber($100{\mu}m$) and silicon carbide fibers($140{\mu}m$ and $15{\mu}m$) were investigated. Al-4.5wt%Cu and Al-l0wt%Mg were chosen for the matrix phase of the composites. In the squeeze cast specimen with high thermal difference between fiber and melt, the average secondary dendrite arm spacing(DAS) in reinforced alloy is smaller than that in unreinforced alloy. It was also observed that primary ${\alpha}$ and non-equilibrium eutectic, which seems to be penetrated and solidified at the final stage of the solidification of the matrix, are irregularly distributed around fibers. It is considered that cold fibers serve as heterogeneous nucleation site. While in the remelted and resolidified specimen without temperature difference, the DAS was not changed with reinforcement and microstructure reveals non-equilibrium eutectic with relatively uniform thickness around fibers. It might be evident the nucleation starts at interfiber region. Microsegregation decreases with the decrease in cooling rate and with reinforcement in the as-squeeze cast specimen. Al-10wt% Mg alloy shows less microsegregation than Al-4.5wt%Cu alloy.

• 한국주조공학회지
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• 제18권5호
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• pp.467-473
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• 1998

For enhancing the mechanical properties of LTE (low thermal expansion) cast steel, systematic researches have been carried out. The effects of alloying elements such as vanadium, molybdenum and carbon on the hardness and linear thermal expansion coefficient were investigated. In the range of $0.5{\sim}2.3\;wt%$ carbon, addition of 1.73 wt% carbon caused hardness increase due to the formation of eutectic carbide having high hardness but over the range of 1.73 wt% carbon, hardness was decreased. Thermal expansion coefficient increases with carbon contents. In the LTE cast steel containing 0.6 wt% carbon, hardness increased up to 1.96 wt% vanadium addition. But over the range of 1.96 wt% vanadium hardness was decreased by coarse eutectic carbide. Thermal expansion coefficient of LTE cast steel containing 0.6 wt%carbon moderately increased with increasing vanadium contents. There was no significant variation of hardness and thermal expansion coefficient according to molybdenum content in LTE cast steel.

• Corrosion Science and Technology
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• 제7권2호
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• pp.134-137
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• 2008

Cold arc welding of cast iron has been widely used with repair welding of metal structures. However its welding is often resulted in the galvanic corrosion between weld metal zone and heat affected zone(HAZ) due to increasing of hardness. In this study, corrosion properties such as hardness, corrosion potential, surface microstructures, and variation of corrosion current density of welding zone with parameters of used electrodes for cast iron welding were investigated with an electrochemical evaluation. Hardness of HAZ showed the highest value compared to other welding zone regardless of kinds of used electrodes for cast iron welding. And its corrosion potential was also shifted to more negative direction than other welding zone. In addition, corrosion current density of WM in polarization curves was qualitatively smaller than that of HAZ. Therefore galvanic corrosion may be apparently observed at HAZ. However galvanic corrosion may be somewhat controlled by using an optimum welding electrode.

• 한국압력기기공학회 논문집
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• 제6권1호
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• pp.16-22
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• 2010

Cast austenitic stainless steel(CASS) is used in the primary cooling piping system of nuclear power plant for it's relative low cost, corrosion resistance and easy of welding. However, the coarse-grain structure of cast austenitic stainless steel can strongly affect the inspectability of ultrasonic testing. The major problems encountered during inspection are beam skewing, high attenuation and high background noise of CASS component. So far, the best inspection performance involving CASS components have been achieved using low frequency TRL(Transmitter/Receiver side-by-side L wave) angle beam probe. But TRL technique could not detect shallow defect and it contains an uncertainty for sizing capability. Currently, most of researchers are studying to overcome these challenge issue. In this study, low-frequency phased array TRL technique used to detect and sizing the flaws in CF8A cast austenitic stainless steel.As conclusion, we could detect and size not only axial flaw but also circumferential flaw using low frequency phased array technique.

• 한국해양공학회지
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• 제17권5호
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• pp.76-81
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• 2003

Friction welding of GCD45 spheroidal graphite cast iron and 2024 aluminum alloy has been studied, especially in terms of the joint faces and strength of friction welding. For appropriate results of the friction welding of GCD45 graphite cast iron and 2024 aluminum alloy, an insert of A1050 pure aluminum metal was used. The joint strength of the A1050 pure aluminum insert approached the maximum strength of 165.7Mpa, compared to 128MPa for the joint between GCD45 graphite cast iron and A1050 pure aluminum without the insert metal. Maximum strength, 165.7Mpa, was possible for the following optimum conditions: 20MPa for the friction pressure, P1, 60MPa for the upsetting pressure, P2, 1 second for the friction time, t1, 3000rpm for the rotation, N, and 0.3 seconds for the brake time, tB.

• 분석과학
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• 제6권3호
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• pp.297-305
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• 1993

글로우 방전 방출원을 다색화장치에 연결시켜 개발된 글로우방전/방출분광법으로 탄소의 농도가 수 퍼센트에 이르러 스파크방출분광법으로서는 분석이 곤란한 주철시료를 분석하고 정확성을 검토하고자 하였다. 알곤가스 압력, 전압, 방전시간 등 glow discharge lamp(GDL)의 방전조건을 최적화시키고 이 조건에서 두 종류의 주철 표준시료(BAS, LECO)에 대해 원소별 방출 복사선의 세기와 농도의 상관관계를 조사하였다. Mn, Si, P, S 등 대부분 원소의 검정곡선이 양호한 직선성을 보여 주었고 탄소의 경우에는 표준시료의 종류에 따라 절편과 기울기값이 미소하게 계통적인 차이를 나타내었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 제35회 춘계학술대회
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• pp.235-239
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• 2002

The objective of the experiment is to investigate the effect of microstructures of gray cast iron oil wear characteristics of automotive disc brakes. Six different gray cast iron rotors were manufactured by changing carbon equivalent and cooling rate. The change of DTV (disc thickness variation) before and after wear tests was measured to examine the wear properties according to the microstructures of gray iron discs since the DTV generation is caused by the circumferential uneven wear. Experimental results showed that the morphology of graphite flake and hardness in gray cast iron were crucially associated with the change of DTV. In particular, the DTV changes of rotor decrease when the length and area fraction of graphite flake in brake rotors increase and hardness of brake discs reduces.

• 동력기계공학회지
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• 제21권6호
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• pp.13-20
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• 2017

Ni-base superalloy Haynes 282 was developed as a gas turbine material for use in the ultra-super-critical stage (USC) of next-generation coal-fired power plants. Temperatures in the USC stage exceed $700^{\circ}C$ during operation. In spite of its important role Haynes 282 in increasing the performance of high-pressure turbines, as a result of its high-temperature capability, there is little information on the microstructure, deformation mechanism, or mechanical properties of the cast condition of this alloy. The aim of present study is to examine the creep properties of cast alloy and compare with wrought alloy. The ${\gamma}^{\prime}-precipitates$ were coarsen with the increase of aging time ranging from 8 to 48 hrs. A creep test performed at $750^{\circ}C$ showed faster minimum creep rate and shorter rupture lifetime with the aging time. A creep test performed showed only a slight difference in the rupture life between cast and wrought products. Based on the creep test results, the deformation mechanism is discussed using fractographs.