• Journal of Welding and Joining
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• v.21 no.3
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• pp.78-84
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• 2003

The changes of microstructure and hardness of TLP bonds of directionally solidified Ni base superalloy, GTD-111, with variation of homogenizing and aging treatment were investigated. The specimens were bonded at 1403K for 7.2ks using different insert metals such as MBF-50, MBF-80 and MBF-90 and they were homogenized at 1393K with various holding time. At center of bonded interlayer homogenized for hold time 30h, the contents of aluminum and titanium were approximately 90% and 95% of base metal, respectively. In this study, aging was performed at three different kinds : one step aging ; 1113K $\times$ 16h, two step aging ; 1113K $\times$ 10h ⇒ 1103K $\times$ 10h, three step aging ; 1113K $\times$ 10h ⇒ 1103K $\times$ 8h ⇒ 922K $\times$ 24h. ${\gamma}$' volume fraction and hardness of joints were high in the sequence of one step, two step and three step aging, whereas ${\gamma}$' volume fraction and hardness of joints obtained by three step aging treatment were higher than those of raw material. Tensile properties of joints bonded with MBF-80 and MBF-90, homogenized at 1393K for 30h and then three step aged became excellent than those of raw material, however, joint bonded with MBF-50 was poor.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.153-160
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• 2002

A new system identification method based on tunnel deformation data is proposed to find the damage in the lining structure. For this, an inverse problem in which the deformation data and dead load of concrete lining are known a priori is introduced to estimate the degree and location of the damages. Models based on uniform reduction of stiffness and homogenized crack concept are individually employed to compare the applicability and relative advantages of the models. Numerical analyses are peformed for the idealized tunnel structure and the effect of white noise, common in most measurement data, is also included to better understand the suitability of the proposed models. As a result, model 1 based on uniform stiffness reduction method is shown to be relatively insensitive to the noise, while model 2 with the homogenized crack concept is proven to be easily applied to the field situation since the effect of stiffness reduction is rather small.

• Nuclear Engineering and Technology
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• v.16 no.4
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• pp.202-216
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• 1984

The success of coarse-mesh nodal solution methods provides strong motivation for finding homogenized parameters which, when used in global nodal calculation, will reproduce exactly all average nodal reaction rates for large nodes. Two approximate theories for finding these ideal parameters, namely, simplified equivalence theory and approximate node equivalence theory, are described herein and then applied to the PWR benchmark problem. Nodal code, ANM, is used for the global calculation as well as for the homogenization calculation. From the comparative analysis, it is recommended that homogenization be carried out only for the unique type of fuel assemblies and for core boundary color-sets. The use of approximate homogenized cross-sections and approximate discontinuity factors predicts nodal powers with maximum error of 0.8% and criticality within 0.1% error relative to the fine-mesh KIDD calculations.

• Korean Journal of Metals and Materials
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• v.46 no.10
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• pp.691-699
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• 2008

Electrochemical characteristics of Ti-30Ta-xZr alloys coated with HA/TiN by using magnetron sputtering method were studied. The Ti-30Ta containing Zr(3, 7, 10 and 15wt%) were 10 times melted to improve chemical homogeneity by using a vacuum furnace and then homogenized for 24hrs at $1000^{\circ}C$. The specimens were cut and polished for corrosion test and coating, and then coated with HA/TiN, respectively, by using DC and RF-magnetron sputtering method. The analyses of coated surface and coated layer were carried out by using optical microscope(OM), field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD). The electrochemical characteristics were examined using potentiodynamic (-1,500 mV~ + 2,000 mV) and A.C. impedance spectroscopy(100 kHz ~ 10 mHz) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The microstructure of homogenized Ti-30Ta-xZr alloys showed needle-like structure. In case of homogenized Ti-30Ta-xZr alloys, a-peak was increased with increasing Zr content. The thickness of TiN and HA coated layer showed 400 nm and 100 nm, respectively. The corrosion resistance of HA/TiN-coated Ti-30Ta-xZr alloys were higher than that of the non-coated Ti-30TaxZr alloys, whic hindicate better protective effect. The polarization resistance($R_p$) value of HA/TiN coated Ti-30Ta-xZr alloys showed $8.40{\times}10^5{\Omega}cm^2$ which was higher than that of non-coated Ti-30Ta-xZr alloys.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3450-3463
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• 2023

In the two-step analysis of Pebble-Bed type High-Temperature Gas-Cooled Reactor (PB-HTGR), the lattice physics calculation for the generation of homogenized cross-sections is based on the fuel pebble. However, the randomly-dispersed fuel particles in the fuel pebble introduce double heterogeneity and randomness. Compared to the deterministic method, the Monte Carlo method which is flexible in geometry modeling provides a high-fidelity treatment. Therefore, the Monte Carlo code NECP-MCX is extended in this study to perform the lattice physics calculation of the PB-HTGR. Firstly, the capability for the simulation of randomly-dispersed media, using the explicit modeling approach, is developed in NECP-MCX. Secondly, the capability for the generation of the homogenized cross-section is also developed in NECP-MCX. Finally, simplified PB-HTGR problems are calculated by a two-step neutronics analysis tool based on Monte Carlo homogenization. For the pebble beds mixed by fuel pebble and graphite pebble, the bias is less than 100 pcm when compared to the high-fidelity model, and the bias is increased to 269 pcm for pebble bed mixed by depleted fuel pebble. Numerical results show that the Monte Carlo lattice physics calculation for the two-step analysis of PB-HTGR is feasible.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.173-179
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• 2023

In this study, the age-hardening behavior and tensile properties of a cast AZ91-0.3Ca-0.2Y (SEN9) alloy are investigated and compared with those of a commercial AZ91 alloy. Even after homogenization heat treatment, the SEN9 alloy contains numerous undissolved secondary phases, Al₈Mn₄Y, Al₂Y, and Al₂Ca, which results in a higher hardness value than the homogenized AZ91 alloy. Under aging condition at 200 ℃, both the AZ91 and SEN9 alloys exhibit the same peak-aging time of 8 h, but the peak hardness of the latter (86.8 Hv) is higher than that of the former (83.9 Hv). The precipitation behavior of Mg₁₇Al₁₂ phase during aging significantly differs in the two alloys. In the AZ91 alloy, the area fraction of Mg₁₇Al₁₂ discontinuous precipitates (DPs) increases up to ~50% as the aging time increases. In contrast, in the SEN9 alloy, the formation and growth of DPs during aging are substantially suppressed by the Ca- or Y-containing particles, which leads to the formation of only a small amount of DPs with an area fraction of ~4% after peak aging. Moreover, the size and interparticle spacing of Mg₁₇Al₁₂ precipitates of the peak-aged SEN9 alloy are smaller than those of the peak-aged AZ91 alloy. The homogenized AZ91 alloy exhibits a higher tensile strength than the homogenized SEN9 alloy due to the finer grains of the former. However, the peak-aged SEN9 alloy has a higher tensile elongation than the peak-aged AZ91 alloy due to the smaller amount of brittle DPs in the former.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.6
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• pp.359-366
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• 2023

Changes in microstructure and mechanical properties of Mg-1.0Al-1.0Zn-0.2Mn-0.5Ca (AZMX1100) alloy sheet manufactured by normal casting and twin roll casting process, were studied according to process and heat treatment. Non-uniform microstructure was observed in the initial sheet produced through both processes, and in particular, tilted dendrites and shifted central segregation were observed in the twin roll casting sheet. It was homogenized through hot rolling and heat treatment, and heat treated at 350℃ and 400℃ to compare the effect of heat treatment temperature. Both sheets were homogenized by the hot rolling process, and the grain size increased as the heat treatment temperature and time increased. It was confirmed that the grain size, deviation, and distribution of the second phase were finer and more homogenized in the TRC sheet. Accordingly, mechanical properties such as hardness, formability, and tensile strength also showed better values. However, unlike other previously reported AZMX alloy systems, it showed low formability (Erichsen value), which was judged by the influence of Al2Ca present in the microstructure.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2002.11a
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• pp.179-179
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• 2002

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 1997.06a
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• pp.103-103
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• 1997

• Journal of Nutrition and Health
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• v.17 no.1
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• pp.60-67
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• 1984

Inhibiting action of sulfur dioxide $(SO_{2})$ on enzymatic discoloration was investigated with crude enzyme preparations from homogenized tissues or sliced disks of raw potato tubers. $SO_{2}$ appeared to inhibit the formation of dopachrome in a competitive manner. At insufficient concentrations of $SO_{2}, the formation of dopachrome was reinitiated as time elapsed. The present results suggested that $SO_{2}$ would form an additional compounds with certain intermediate during the course of enzymatic browning and delay the enzymatic discoloration. To inhibit the production of dopachrome in sliced disks of raw potato tubers, much higher concentrations of $SO_{2}$ were required than homogenized tissues.