• Journal of the Korean Society for Heat Treatment
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• v.4 no.1
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• pp.1-12
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• 1991

This study has been performed to find out the effect of austenitizing temperature, austempering temperature and its holding time, and tempering cycle on the mechanical properties such as impact resistance, hardness etc. of AISI $M_2$ Mo series high speed tool steel austempered or tempered after austempering treatment. The results obtained from the experiment are as follows ; (1) Optical micrograph has revealed that the transformation rate of bainite is delayed as the austenitizing temperature increases and that bainite is most apparently transformed at an austempering temperature of $290^{\circ}C$. (2) The amount of retained austenite during austempering has been analysed to be increased by the X-ray diffraction technique as the transformation product of bainite is increased. It has also been shown that the longer the holding time of austempering, the more the transformation quantity of bainite is formed, exhibiting, however, that the rate of bainitic transformation is considerably retarded after a certain period of holding time elapses. (3) Hardness measurement has shown that hardness values obtained after austempering increase with decreasing the amount of retained austenite. (4) The austempering and then tempering cycle has been formed to give hardness values which are more greatly improved as austenitizing temperature is increased. (5) The mechanical property of the specimen primary-tempered for 1 hour at $550^{\circ}C$ after austempering for 2 hours at $290^{\circ}C$ from the austenitizing temperature range of $1180^{\circ}C$ to $1210^{\circ}C$ have been estimated to be good values.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.228-234
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• 2001

A methodology is developed and used to evaluate the response sensitivity of the thermal systems to variations in their design parameters. Technique for computing the sensitivity of temperature distributions to changes in processing parameters needed to decide the more effective laser input parameters for laser surface hardening treatment is considered. In this study, a state equation governing the heat flow in laser surface treatment is analyzed using a three-dimensional finite element method and sensitivity data of the processing parameter obtained using a direct differentiation method is applied to the sensitivity analysis. The interesting processing parameters are taken as the laser scan velocity and laser beam radius ( $r_{ b}$), and the sensitivities of the temperature T versus v and $r_{b}$ are analyzed. These sensitivity results are obtained with another parameters fixed. To verify the numerical analysis results, hardened layer dimensions (width and depth) of the numerical analysis are compared with the experimental ones.nes.

• The Journal of Advanced Prosthodontics
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• v.2 no.3
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• pp.65-70
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• 2010

Large oro-facial defects result from cancer treatment consequences in serious functional as well as cosmetic deformities. Acceptable cosmetic results usually can be obtained with a facial prosthesis. However, retention of a large facial prosthesis can be challenging because of its size and weight. This article describes prosthetic rehabilitation of a 57-year-old man having a right lateral mid-facial defect with intraoral-extraoral combination prosthesis. A modified technique to fabricate a hollow substructure in heat-polymerizing polymethyl-methacrylate to support silicone facial prosthesis was illustrated. The resultant facial prosthesis was structurally durable and light in weight facilitating the retention with magnets satisfactorily. This technique is advantageous as there is no need to fabricate the whole prosthesis again in case of damage of the silicone layer because the outer silicone layer can be removed and re-packed on the substructure if the gypsum-mold is preserved.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1181-1184
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• 2008

$GeO_2$/ormosil organic-inorganic hybrid films doped with neodymium ions and $TiO_2$/Ormosil organic-inorganic hybrid films dispersed with neodymium oxide nanocrystals are prepared by combining an inverse microemulsion technique and a low-temperature sol-gel technique. The effects of $Nd^{3+}$ concentration, $Nd_2O_3$ nanocrystal content, and heat treatment temperature on up-conversion and photoluminescence luminescence properties of the hybrid films are studied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.373-379
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• 2009

Presented in this paper is a new experimental technique to measure material properties of lock plate of gas turbine plants by using ultrasonic guided wave. In comparison with the mechanical destructive testings, material characterization of the Inconel x-750 was nondestructively carried out in a more efficient manner to discriminate the change in elastic moduli and the poisson's ratio attributed to the variation of heat treatment condition. The proposed technique shows a satisfactory feasibility via the comparative experiments with the imported lock plate specimens. It is also expected that the guided wave technique can cover a longer and wider range as a new cost-&-time-saving inspection tool due to the interaction with a greater part of specimen, compared to a conventional local point-by-point scheme.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.98-106
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• 1999

In this study cold rolling process for the irregular cross-sectional shape has been investigated. The product analyzed in present study is the steel cutter, which is frequently used to cut the desired shape on leather. Because steel cutter always has a irregular cross-section, after rolling process the workpiece is severely bended to every direction. The bending of the workpiece affects the processed performed after rolling such as heat treatment and grinding, then that of the workpiece becomes more severe. In this study, therefore, to prevent the bending of the workpiece to the left and right sides. rigid-plastic finite element method has been utilized and in order to find optimal roll geometry rapidly, one dimensional equal interval search technique has been also introduced. By using both rigid plastic finite element method and optimum technique, cold rolling process for the irregular cross-sectional shape has been successfully investigated.

• Korean Journal of Heritage: History & Science
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• v.53 no.1
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• pp.168-183
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• 2020

Efforts had been made to eliminate the brittleness unique to cast ironware from 5 BC up until the time that cast ironware became widely used. One of the techniques used to this end was to produce the cast ironware in one kiln and then anneal it in another kiln. This technique condensed or removed the carbon in the structure to eliminate the brittleness of cast ironware and enable forging. To clarify the nature of this technique, this study examined cast ironware made of malleable cast iron, which manifests the characteristics of the annealing technique for cast ironware excavated on the Korean peninsula, based on current steelmaking technology and research results from China and Japan. Results confirmed that all cast ironware made of malleable cast iron had been imported into Korea until the Proto-Three Kingdoms Period. Also, since the Chiljido (Seven-Branched Sword), which is housed at the Ishigami Shrine in Japan, appears to have been produced in the Korean peninsula, it is determined that Baekje in the 4^th century must have possessed such an annealing technique. At that time, however, iron was produced mainly with an iron bloom, and a large amount of forged iron was produced with a steel bloom smelted from an iron bloom. In addition, most of the cast ironware that was used previously, except for cast iron hoes, had been replaced by forged ironware. In other words, this annealing technique was not used frequently until the Three Kingdoms Period. However, it spread broadly during the Unified Silla Period in so much as it was identified in the Jangan-ri remains, which represented the regional hub of iron production and distribution.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.381-389
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• 2000

Metal matrix composite(MMCs) have been rapidly becoming one of the strongest candidates for structural materials for high temperature application. It is well recognized that MMCs always experience at least one large cool-down from processing temperature before my significant applied service loading. Due to the large difference in thermal expansion coefficient between the fiber and matrix, large thermal residual stresses generally develop in composites. It was reported from many previous studies that the effects of thermal residual stress on mechanical properties and fracture behavior were much more complex and dramatic than conventional engineering materials. Therefore it is crucial to evaluate the effect of heat treatment which changes the characteristic of distribution of thermal residual stress in MMCs. Single fiber composite(SFC) test based on the balance in a micromechanical model is a quite convenient method to evaluate interfacial shear strength(IFSS) and the failure mode of composite. In this study the effect of heat treatment on IFSS and the microscopic failure mechanism of MMC is investigated by combining acoustic emission(AE) technique with SFC test. The characteristic of AE signal, IFSS and microscopic failure mechanism due to heat treatment condition is discussed.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.113-118
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• 2005

Small form factor optical disks for near-field optics using solid immersion lens were developed. Disk durability properties in terms of head-disk interface (HDI) properties were investigated by drag test, diamond like carbon film and lubricant film were coated on the small form factor disk to enhance HDI. Disks with glass substrates and lubricant films after heat treatment showed more durable characteristics. Coverlayers made of UV resin were uniformly coated by spin coating In which the ski-jump could not be formed by adopting outer ring technique.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.26-31
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• 2006

Small form factor optical disks for near-field optics using solid immersion lens were developed. Diamond like carbon film and lubricant film were coated on the small form factor optical disk to enhance the head-disk interface(HDI) characteristics. The disk durability properties in terms of HDI phenomena were investigated by drag test. Disks with glass substrates and the lubricant films experienced heat treatment showed more durable characteristics. Coverlayers made of UV resin were uniformly coated by spin coating in which the ski-jump could be removed by adopting outer ring technique