• Tribology and Lubricants
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• v.36 no.3
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• pp.124-132
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• 2020

The effect of the stoichiometry on the sliding wear properties of NiAl coatings has been investigated. Three different powder mixtures with the compositions of Ni-50at%Al, Ni-54at%Al and Ni-42at%Al were diepressed respectively, and which were subsequently coated on mild steel through combustion synthesis in an induction heating system. Sliding wear behavior of the coatings was examined against an alloyed tool steel using a pin-on-disc type sliding wear test machine. As results, it could be seen that powder mixture(Ni-54at%Al) with displaying Al-rich deviations from the stoichiometry of NiAl(Ni-50at%Al) was promoted the most the synthetic reactivity. The microstructure of the coating layer with the compositions of Ni-54at%Al exhibits the porous NiAl single phase structure. However, the microstructure of the coating layer of the compositions of Ni-42at%Al exhibits the denser multi-phase structure containing several intermediate phases in addition to NiAl. Densification of the coating layer was enhanced by increasing the reacting temperature. On the other hand, the wear properties of the coating layers showed that the wear mode at speeds of around 1 m/s was severe wear, regardless of the stoichiometry and reacting temperature. However, wear properties of coating layer with the compositions of Ni-42at%Al were superior to those of coating layer with the compositions of Ni-54at%Al. This would be attributed by the fact that coating layer with the compositions of Ni-42at%Al develops little void and much intermediate phases with high strength.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.2013-2020
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• 2010

This paper presents a study on the modeling for transparent toaster with a cap of folding type. The toaster was modelled to solve problems of customer's unsatisfaction such as heat loss, input of a piece of dirt, unidentified heating state of sliced toaster. Rapid prototyping was followed by the first modeling, and the second modeling was implemented in order to solve the problems of the first modeling such as interference of holder and door, and the third modeling was developed with a cap of folding type through analysis of assembly and simulation. The 3D modeling tool used in this paper was Pro/Engineer 4.0. The modeling was designed to minimize heat loss and structured with transparent outer case. So the toasting procedure will be identified with the naked eye, and the transparent toaster will improve the customer's aesthetic satisfaction.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1410-1419
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• 2019

In this research, it is to find a method that frost does not form on the outdoor unit to develop a heat pump capable of heating in cold regions. For this reason, we produced an incubator capable of creating an environment of -25℃, and constructed an experimental apparatus so that experiments in the room were possible. However, it is necessary to grasp the characteristics of the air reaching the front of the heat pump outdoor unit installed in the experimental apparatus, and flow analysis was performed using ANSYS CFX, which is general-purpose software. As a result, the flow velocity of the air reaching the front of the outdoor unit in the outdoor unit chamber in the entire region of the simulation conditions (5.0 to 7.5 m/s) has many differences in the upper and lower portions, resulting in a natural state. It turned out that the condition can not be satisfied. Therefore, it is determined that it is necessary to additionally install a frequency divider at the front of the outdoor unit to make the flow velocity constant.

• Korean Journal of Materials Research
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• v.22 no.1
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• pp.42-45
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• 2012

The mechanical behavior and microstructural evolution during high temperature tensile deformation of recrystallized Ni3Al polycrystals doped with boron were investigated as functions of initial grain size, tensile strain rate and temperature. In order to obtain more precise information on the deformation mechanism, tensile specimens were rapidly quenched immediately after deformation at a cooling rate of more than $2000Ks^{-1}$, and were then observed by transmission electron microscopy (TEM). Mechanical tests in the range of 923 K to 1012 K were carried out in a vacuum of less than $3{\times}10^{-4}$ Pa using an Instron-type machine with various but constant cross head speeds corresponding to the initial strain rates from $1.0{\times}10^{-4}$ to $3.1{\times}10^{-5}s^{-1}$. After heating to deformation temperature, the specimen was kept for more than 1.8 ks before testing. The following results were obtained: (1) Flow behavior was affected by initial strain size; with decreasing initial grain size, the level of a stress peak in the true stress-true strain curve decreased, the steady state region was enlarged and elongation increased. (2) On the basis of TEM observation of rapidly quenched specimens, it was confirmed that dynamic recrystallization certainly occurred on deformation of fine-grained ($3.3{\mu}m$) and intermediate-grained ($5.0{\mu}m$) specimens at an initial strain rate of $3.1{\times}10^{-5}s^{-1}$ and at 973 K. (3) There were some dislocation-free grains among the new recrystallized grains. The obtained results suggest that both dynamic recrystallization and grain boundary sliding are operative during high temperature deformation.

• Journal of Welding and Joining
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• v.28 no.6
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• pp.35-39
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• 2010

Generally, ceramic material is very difficult to machine due to high strength and hardness. However, ceramic material can be machined at high temperature by plastic flow as metallic material due to the deterioration of the grain boundary glassy phase. Recently, a new method was developed to execute cutting process with CBN cutting tool by local heating of surface with laser. There are various parameters in LAM because it is a complex process with laser treatment and machining. During laser assisted machining, high power results in reducing of cutting force and increasing tool life, but excessive power brings oxidation of the surface. The effect of laser power, feed rate, cutting depth and etc. were investigated on the life of cutting tool. Chips were observed to find out suitable machining conditions. Chips of SSN had more flow-types than HIPSN. It means SSN is easier to machining. The life of cutting tool was increased with increasing laser power and decreasing feed rate and cutting depth.

• Journal of the Korean Home Economics Association
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• v.46 no.4
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• pp.47-59
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• 2008

With increasing numbers of immigrant workers in Korea, the supply of socially and culturally acceptable housing has become an important issue. The purpose of this study was to analyze the state of Goryo-in housing and domestic living conditions in metropolitan areas of Korea. This study will present essential information directly relevant to the establishment of practical housing policy for Goryo-in in Korea. Furthermore, data collected and analyzed here will enable comparative investigation with Goryo-ins who live in Russia and Central Asia. Using ethnographic methodologies, we examined 20 Goryo-in households in relation to their usage of domestic space. The following conclusion were established; 1). The most popular L D K(Living Dining Kitchen)type consisted of kitchen plus one or two bedrooms. The majority of households lived in quarters with separated kitchen and living room areas. 2). Most households had a washing machine in the bathroom due to a lack of space, and they regarded the bathtub and the drain hole of the bathroom as very necessary. The Goryo-ins interviewed preferred quarters with separate bathroom and toilet areas, in order to allow simultaneous use. 3). Their most preferred seating style was chairs, while making Kimchi at home was not very popular. 4). All respondents took their shoes off and wore slippers at home, while also indicating a preference for designated shoes space at the entrance to the house. 5) Half of the households had a carpet or mat in the bedroom or living room, both for keeping warm and aesthetic reasons. 6). All households had modified Ondol heating system and demonstrated satisfaction with this. The majority of Goryo-ins interviewed had a different living style compared to households in Russia and Central Asia which were related to less favorable economic conditions in Korea.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.4
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• pp.62-72
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• 2015

Interest in three-dimensional (3D) printing processes has grown significantly, and several types have been developed. These 3D printing processes are classified as Selective Laser Sintering (SLS), Stereo-Lithography Apparatus (SLA), and Fused Deposition Modeling (FDM). SLS can be applied to many materials, but because it uses a laser-based material removal process, it is expensive. SLA enables fast and precise manufacturing, but available materials are limited. FDM printing's benefits are its reasonable price and easy accessibility. However, metal printing using FDM can involve technical problems, such as suitable component supply or the thermal expansion of the heating part. Thus, FDM printing primarily uses materials with low melting points, such as acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) resin. In this study, an FDM process for enabling metal printing is suggested. Particularly, the nozzle and heatsink for this process are focused for stable printing. To design the nozzle and heatsink, multi-physical phenomena, including thermal expansion and heat transfer, had to be considered. Therefore, COMSOL Multiphysics, an FEM analysis program, was used to analyze the maximum temperature, thermal expansion, and principal stress. Finally, its performance was confirmed through an experiment.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1682-1684
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• 1996

Recently, because diffusion of cordless machine and smart card and so on, and concern of unpolluted materials, one are concerned with Li secondary batteries. Li secondary batteries have high voltage, high energy density and high power density, and heavy metal pollution problems are little. Mn is low price and is distributed much quantity. Therefore, we investigated $MnO_2$. In this study, we worked the electrochemical properties and charge/discharge characteristics of $MnO_2/Li$ cells. In results, the more heating temperature is high, the more ${\gamma}-phase$ varied ${\beta}-phase$, and when $MnO_2$ is heated at $320^{\circ}C$ and super-s-black 20wt% is mixed, characteristics are the best.

• The korean journal of orthodontics
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• v.20 no.2
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• pp.381-390
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• 1990

The purpose of this study was to evaluate the effects of heat treatment on mechanical properties in $0.016^{{\prime}{\prime}}{\times}0.022^{{\prime}{\prime}}$ blue Elgiloy wires and to measure the amounts of nickel and chromium released from the wires in artificial saliva. Ultimate tensile strength, yield strength and elongation were measured with universal testing machine (Instron). and the amounts of nickel and chromium released from the sample were measured with atomic absorption spectrophotometer after one week immersion in the artificial saliva. Ultimate tensile strength and yield strength were progressively increased below $1000^{\circ}F$, but elongation was decreased. And the results were reversed above $1100^{\circ}F$. After heat treatment of the sample for 9 minutes at $1000^{\circ}F$, the maximum tensile strength and yield strength were $213.6kg/mm^2$, $140.1kg/mm^2$, respectively. Both tensile strength and yield strength were decreased progressively above $1100^{\circ}F$. Elongation was appeared the minimum value (8.6%) after heat treatment for 9 minutes and 12 minutes at $1000^{\circ}F$. There was a pronounced increase in nickel and chromium liberation with increasing time and temperature. The maximum amounts of nickel and chromium released form the sample were $4.947{\mu}m/cm^2$, $3.088{\mu}g/cm^2$, respectively after heat treatment for 12 minutes at $1300^{\circ}F$. Heat treatment is applied to orthodontic wires, especially cobalt-chromium alloys, for the purpose of stress-relievning and hardening. When the heat-treatment of orthodontic wires, the heating procedure should be well controlled in order to have no effect on corrosion resistance and mechanical properties.

• Textile Coloration and Finishing
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• v.26 no.2
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• pp.88-98
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• 2014

This study is to assess the photocatalytic degradation of PET and Nylon 6 films containing nano-sized $TiO_2$ powders of anatase and rutile types. The PET and Nylon 6 films containing six kinds of the nanoparticles were prepared by melt casting method using a heating press machine. Reflectance in visible region and water contact angles of the irradiated PET and Nylon 6 composite films decreased with increasing UV/$O_3$ irradiation. Also the enhanced hydrophilicity has a close relationship with the increase in the Lewis base parameter, which indicates more oxidized polymer surfaces. The photocatalytic degradation of the nanocomposite films increased with increasing $TiO_2$ content and UV energy, which is more significant with the anatase types rather than the rutile types. The amide linkages in the Nylon 6 seemed to be more susceptible to the UV light compared to the ester groups in the PET, particularly in the presence of the $TiO_2$ photocatalysts. The photoscission and photodegradation of the polymers in the composites produced more degraded structure assisted by the photocatalytic activity of the $TiO_2$ nanoparticles. Also the composite films can bleach the methylene blue dyes more easily under the UV/$O_3$ irradiation, suggesting the photobleaching activity of the $TiO_2$ nanoparticles.