• Proceedings of the KSME Conference
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• 2004.04a
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.37-43
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• 2015

A Beta-type Stirling engine is developed and tested on the operation stability and cycle performance. The flow rate for cooling water ranges from 300 to 1500 ml/min, while the temperature of heat source changes from 300 to $500^{\circ}C$. The internal pressure, working temperatures, and operation speed are measured and the engine performance is estimated from them. In the experiment, the rise in the temperature of heat source reduces internal pressure but increases operation speed, and overall, enhances the power output. The faster coolant flow rate contributes to the high temperature limit for stable operation, the cycle efficiency due to the alleviated thermal expansion of power piston, and the heat input to the engine, respectively. The experimental Stirling engine showed the maximum power output of 12.1 W and the cycle efficiency of 3.0 % when the cooling flow is 900 ml/min and the heat source temperature is $500^{\circ}C$.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2819-2827
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• 2022

The disposal area of a deep geological repository (DGR) for the disposal of spent nuclear fuels (SNFs) is estimated considering the spacing between deposition holes and between disposal tunnels, as determined by a thermal analysis using the decay heat of a reference SNF. Given the relatively large amount of decay heat of the reference SNF, the disposal area of the DGR is found to be overestimated. Therefore, we develop a computer program using MATLAB, termed ACom (Assembly Combination), to combine SNFs when stored in canisters such that the decay heat per canister is evenly distributed. The stability of ACom was checked and the overall distribution of the decay heat per canister was analyzed. Finally, ACom was applied to disposal scenarios suggested in the conceptual design of a DGR for SNFs, and it was confirmed that the decay heat per canister could be evenly distributed and that the maximum decay heat of the canister could be much lower than that of a canister estimated using a reference SNF. ACom can be used to improve the disposal efficiency by reducing the disposal area of a DGR for SNFs by ensuringg a relatively even distribution of decay heat per canister.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.7
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• pp.47-59
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• 1993

The thermal stability of "stuffed" TiN/Ti barrier matals with different annealing history has been studied to improve the contact reliability of Al/Si contacts in 16M DRAM. The annealing conditions before the Al deposition such as film thickness, the annealing temperature and the annealing ambient have been varied. For TiN(900A)/Ti(300A) annealed at 450 in nitrogen ambient to form a "stuffed barrier" by inducing oxygen atoms into grain boundaries, there is no observation of Al penetrations into Si substrates after the post heat treatment of up to 700 even though there are massive amounts of Al found in TiN film after the post heat treatment of 600 indicating that TiN has a "sponge-like" function due to its ability to absorb several amounts of aluminum at elevated temperature. The TiN/Ti diffusion barrier annealed at 550 has, however, failed after the post heat treatment at 600. The thinner diffusion barriers with TiN(300A)/Ti(100A) failed after the post heat treatment at 600.he post heat treatment at 600.

• Journal of the Korean Wood Science and Technology
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• v.43 no.3
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• pp.334-343
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• 2015

This study was carried out to evaluate quantitatively some properties (density, equilibrium moisture content, shrinkage, water vapor adsorption, water absorptivity, compressive strength, bending strength, hardness and decay resistance) of Larix kaempferi lumber which was heat-treated by hot air and has been used commercially in Korea. Equilibrium moisture content of the heat-treated wood was decreased with increase of hydrophobicity. Dimensional stability of the wood was improved with decrease of shrinkage, water vapor adsorption and free water absorptivity. Also, with the thermo-chemical changes of wood component and lower equilibrium moisture content, decay resistance and compressive strength of heat-treated wood were increased. But, bending strength and hardness of wood were decreased.

• Tribology and Lubricants
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• v.38 no.5
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• pp.185-190
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• 2022

Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.

• Transactions on Electrical and Electronic Materials
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• v.10 no.2
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• pp.58-61
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• 2009

The electrical stability of ZnO: Al thin films deposited on glass substrate by the RF magnetron sputtering method have been modified by a hydrogen annealing treatment and $SiO_2$ protection layer. AZO thin films were deposited at room temperature and different RF powers of 50, 100, 150, and 200 W to optimize the AZO film growth condition. The lowest value of resistivity of $9.44{\times}10^{-4}{\Omega}cm$ was obtained at 2 mtorr, room temperature, and a power level of 150 W. Then, the AZO thin films were annealed at $250-400^{\circ}C$ for 1 h in hydrogen ambient. The minimum resistivity obtained was $8.32{\times}10^{-4}{\Omega}cm$ as-annealed at $300^{\circ}C$. The electrical properties were enhanced by the hydrogen annealing treatment. After a 72 h damp-heat treatment in harsh conditions of a water steam at $110^{\circ}C$ for four representative samples, a degradation of electrical properties was observed. The sample of hydrogen-annealed AZO thin films with $SiO_2$ protection layer showed a slight degradation ratio(17%) of electrical properties and a preferable transmittance of 90%. The electrical stability of AZO thin films had been modified by hydrogen annealing treatment and $SiO_2$ protection layer.

• The korean journal of orthodontics
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• v.44 no.5
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• pp.246-253
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• 2014

Objective: To evaluate the bioactivity, and the biomechanical and bone-regenerative properties of Ti6Al4V miniscrews subjected to anodization, cyclic precalcification, and heat treatment (APH treatment) and their potential clinical use. Methods: The surfaces of Ti6Al4V alloys were modified by APH treatment. Bioactivity was assessed after immersion in simulated body fluid for 3 days. The hydrophilicity and the roughness of APH-treated surfaces were compared with those of untreated (UT) and anodized and heat-treated (AH) samples. For in vivo tests, 32 miniscrews (16 UT and 16 APH) were inserted into 16 Wistar rats, one UT and one APH-treated miniscrew in either tibia. The miniscrews were extracted after 3 and 6 weeks and their osseointegration (n = 8 for each time point and group) was investigated by surface and histological analyses and removal torque measurements. Results: APH treatment formed a dense surface array of nanotubular TiO2 layer covered with a compact apatite-like film. APH-treated samples showed better bioactivity and biocompatibility compared with UT and AH samples. In vivo, APH-treated miniscrews showed higher removal torque and bone-to-implant contact than did UT miniscrews, after both 3 and 6 weeks (p < 0.05). Also, early deposition of densely mineralized bone around APH-treated miniscrews was observed, implying good bonding to the treated surface. Conclusions: APH treatment enhanced the bioactivity, and the biomechanical and bone regenerative properties of the Ti6Al4V alloy miniscrews. The enhanced initial stability afforded should be valuable in orthodontic applications.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.583-587
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• 2020

Imitation fish roe (IFR) based on calcium alginate hydrogels (CAG) can be heat treated for sterilization and salted to prolong the shelf life. However, these processes change the physical properties of IFR, and it is necessary to minimize these changes. In this study, we investigated the effects of xanthan gum (XG) treatment on the quality and stability of IFR. Both non-XG and XG-treated IFRs were treated with boiling water (95℃), sodium chloride (0.5-2.0%, w/v), and autoclaving. The non-XG treated IFR shrunk slightly after the boiling water and autoclaving processes. By comparison, shrinkage of the XG-treated IFR after autoclaving was significantly reduced. The sphericity of the non-XG treated IFR was reduced by the boiling water, sodium chloride, and autoclaving treatment. However, the sphericity of the XG-treated IFR was maintained by 90% or more, preserving the IFR shape at a level visually recognized as spherical. In addition, unlike the non-XG treated IFR, the XG-treated IFR showed high rupture strength even after the salt and heat treatments. Our findings provide useful information for the industrialization of IFR based on CAG with heat and salt treatments.

• Korean Journal of Materials Research
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• v.11 no.5
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• pp.431-437
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• 2001

This research was examined the effect of intercritical heat treatment on the mechanical Properties and retained austenite formation in 0.1C-6.5Mn steels for the development of a high strength high ductility steel. using of transformation induced plasticity due to retained austenite. The stability of retained austenite is very important for the good ductility and it depend on diffusion of carbon and manganese during reverse transformation. It is effective to heat treat at$ 645^{\circ}C$ in order to obtain over 30 vol.% of retained austenite. However, it is more desirable to heat treat at $620^{\circ}C$, considering the volume fraction and mechanical stability of retained austenite. The strength-elongation combination in cold rolled steel sheets after reverse transformed at $620^{\circ}C$ for 1hr was about 4000k9/mm7, but it decreased rapidly with increasing holding time at high temperature due to the decrease of ductility. The addition of 1.1%Si in 0.14C-6.5Mn TRIP steel does not improve the mechanical properties and retained austenite formation.