• Steel and Composite Structures
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• v.49 no.5
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• pp.533-546
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• 2023

Cost-effective solutions provided by composite construction are gaining popularity which, in turn, promotes the appearance on the market of new types of composite sections that allow not only to take advantage of the synergy of steel and concrete working together at room temperature, but also to improve their behaviour at high temperatures. When combined with high performance materials, significant load-bearing capacities can be achieved even with reduced cross-sectional dimensions. Steel-reinforced concrete-filled steel tubular (SR-CFST) columns are one of these innovative composite sections, where an open steel profile is embedded into a CFST section. Besides the renowned benefits of these typologies at room temperature, the fire protection offered by the surrounding concrete to the inner steel profile, gives them an enhanced fire performance which delays its loss of mechanical capacity in a fire scenario. The experimental evidence on the fire behaviour of SR-CFST columns is still scarce, particularly when combined with high performance materials. However, it is being much needed for the development of specific design provisions that consider the use of the inner steel profile in CFST columns. In this work, a new experimental program on the thermo-mechanical behaviour of SR-CFST columns is presented to extend the available experimental database. Ten SR-CFST stub columns, with circular and square geometries, combining high strength steel and concrete were tested. It was seen that the circular specimens reached higher failure times than the square columns, with the failure time increasing both when high strength steel was used at the embedded steel profile and high strength concrete was used as infill. Finally, different proposals for the reduction coefficients of high performance materials were assessed in the prediction of the cross-sectional fire resistance of the SR-CFST columns.

• Korean Journal of Materials Research
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• v.14 no.8
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• pp.547-551
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• 2004

The sulfidation behaviour of Fe-XAl-0.3Y(X=5, 10, 14, 25 $wt.\%$) alloys was investigated at 1123 K in $H_2/H_{2}S$ gas atmosphere for $1\sim24$ hrs using SEM/EDX, XRD and EPMA. The weight changes of Fe-XAl-0.3Y alloys followed the parabolic rate law, Sulfidation rates of iron aluminide alloys with high Al content were one-twentieth lower than that of 5Al alloys. This is due to the formation of protective $Al_{2}O_3$ oxides on the surface of 10Al, 14Al and 25Al alloys. By calculating partial pressure of impurity oxygen contained $H_2/H_{2}S$ gas, the $Al_{2}O_3$ oxides formation could be explained using Fe-Al-S-O thermodynamic stability diagram. The sulfidation product scales of the 5Al alloy showed that thick iron sulfide scale(FeS) containing porosities formed during early stages of sulfidation. With continued sulfidation, aluminum sulfide was formed at the alloy/scale interface.

• Asian-Australasian Journal of Animal Sciences
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• v.1 no.3
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• pp.157-161
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• 1988

To study the effect of moisture content of the diet on drinking behaviour and the amount of water drunk, observations were made on 8 Holstein steers fed either fresh cut forage or first cut hay. The observations were made in a barn with a mean temperature of about $13^{\circ}C$. Drinking occurred mainly within 3 hours after feeding for the steers fed hay, while those fed soilage drank casually. Frequency of drinking (F) was related to the dry-matter concentration (DMC, %) of herbage: F = 0.47 (${\pm}0.09$) DMC - 6.5, $SE={\pm}0.4$, r = 0.86, P<0.01. Intake of drinking water for each 100 kg of live weight (IDW/100kg) for steers fed soilage was related to the dry-matter concentration: IDW/100kg = 0.55 (${\pm}0.06$) DMC - 8.7, $SE={\pm}0.3$, r = 0.94, P<0.01. The intake of water in each drinking period for animals fed fresh forage was curvilinearly related to the drinking frequency; for the hay-fed steers there was a negative linear relationship. When the drinking frequency for steers fed the fresh forage increased to the same as that observed for the hay, water intake in each drinking period was the same as found for the hay-fed steers.

• Journal of the Korean Ceramic Society
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• v.30 no.6
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• pp.449-456
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• 1993

Sintering behaviour of zirconia powders prepared by different processing treatment was discussed. About >99% densities of theoretical were obtaiend on sintering at 140$0^{\circ}C$ for 2h in case of 300MPa uniaxially cold-pressed compact. But the lower densities were obtained on sintering above this temperature due to abnormal grain growth enabling the tetragonal to monoclinic phase transformation during cooling resulted in microcracks. All kinds of different dried powders exhibited nearly the same shrinkage behaviour with end-point shrinkage between 19 and 20%, and had maximum shrinkage rate (0.99~1.27%/min) around 120$0^{\circ}C$. During whole sintering process densification was mainly governed by grain growth and rearrangement of agglomerates. Heterogeneous abnormal grain growth and abrupt decrease in shrinkage were observed when continuous interagglomerate pore collapsed into isolated pores.

• The Korean Journal of Community Living Science
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• v.21 no.3
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• pp.395-410
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• 2010

This qualitative research on women in multi-cultural families aims to analyze their clothing weight, habit, management and purchasing of clothing as well as their children's in order to provide fundamental data or literature for their adjustment in Korean clothing culture and health management. The research was conducted by interviews to eleven married foreign women with nationality of various climates, and subsequently by categorical analysis and subject analysis. The final outcome in terms of subjects included 'heating/cooling system as to environmental temperature', 'scope of climate adaptation differences in the amount of clothing', 'sleepwear and bedding' and 'clothing purchasing behaviour'. The empirical survey showed that those who came from colder regions or warmer regions had difficulties adjusting to the climate. And their clothing weight & clothing habits, originated from their home countries, were found to be kept stable and to be systematically transferred to their children as well. When it comes to sleepwear and bedding, the women seemed to be less interested in them than normal outerwear, but they tended to like to cover the belly of their babies while they didn't have sufficient nightwear for themselves. And shopping and management of clothing were another area with differences between those women and Korean ones. These results imply that further research on the multicultural families, in particular on their clothing behavior, and on changeability of the behaviour through education or through evolution is needed.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.791-795
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• 2003

The oxidation behaviour of Fe-XAl-0.1Y(X= 5, 10, 14 wt.%) alloys were investigated at 1073, 1173 and 1273 K in oxygen/ nitrogen gas atmosphere for 1∼24 hrs using SEM/EDX, XRD and EPMA. The weight changes of Fe-XAl-0.1Y alloys followed the parabolic rate law. Oxidation rates of 10Al and 14Al alloys were ten times lower than that of 5Al alloys. This is attributed to the formations of protective $A1_2$$O_3$oxides on the surface of 10Al and 14Al alloys. The oxidation product scales of the 5Al alloy showed that thick iron oxide scales($Fe_2$$O_3$, $Fe_3$$O_4$) containing porosities formed during early stages of oxidation. With continued oxidation, aluminum oxide was formed at the alloy/scale interface.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.41-49
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• 2003

Tube oscillation behaviour is experimentally investigated for the study on the fuel rod fretting that is caused by the flow-induced vibration in nuclear reactor. The experiment was conducted in all at room temperature. The specimen of tube assembly was supported by plate springs which simulated the spacer grids and fuel rods of a fuel assembly. To investigate the influence of contact condition between the grids and rods, normal load of 10 and 5 N, gaps of 0.1 and 0.3 mm were applied. The range of the oscillation at the center of the fuel rod specimen was varied as 0.2, 0.3 and 0.4 mm to simulate the fuel rod vibration due to flow. Displacements near the contact were measured with four displacement sensors during the tube oscillation. As results, the shape of oscillation (phase) varied depending on the contact condition. The oscillation displacement increased considerably from the contact to gap condition. The displacement increased further as the gap size increased. It is regarded that the spring shape influences the tube oscillation behaviour. Simple calculation showed that the slip displacement was very small. Therefore, cumulative damage concept is necessary for the fuel rod wear. The mechanism of plowing is thought required to explain the severe wear in the case of gap existence.

• Journal of the Korean Ceramic Society
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• v.36 no.5
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• pp.471-477
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• 1999

Fe and Fe-Mo binder were used to produce TiB2 based cermet by a pressureless sintering. The densification behaviour of TiB2-Fe-Mo cermet during liquid-phase sintering in argon was studied in relation to binder phase charactertics. The effects of Mo addition and sintering condition on the sintering behaviour and mechanical properties were also investigated. TiB2-based cermets with Fe-Mo binder composition showed a better sinterability than the cermets with only Fe binder. In TiB2-Fe-Mo cermet higher densities in the wide temperature range were obtained and also fully densified sintered cermet were obtained at 1873K The enhancement in the densification phenomenon of TiB2-Fe-Mo system can be explained by improved liquid phase wettability associated with the roles of Mo components as solute atoms. When Fe-Mo binders were used cermets with a finer grain size and enhanced mechanical properties wereproduced and new phases such as Fe2B and Mo2FeB2 were observed in the sintered cermet. The highest bending strength was obtained from the 20vol% Fe-Mo cermet and these hardness-fracture toughness combination in the wide binder compositions is better than that of TiB2-Fe cermet. In order to improve mechanical properties microstructure control with high purity powders is desirable because high purity powders prevent the formation of Fe2B and Mo2FeB2 phase which comsume the ductile binder phase.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.928-933
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• 1998

The temperature and stress behaviour of mass concrete pier at early ages was analysed based on the finite element method. The pier investigated is a three-dimensional structure of which the cross-sectional shape varies from a circle to an ellipsoid along the longitudinal axis. In order to obtain the transient temperature and stress distributions in the structure, a three dimensional method was adopted, because the structure of this type cannot be modeled accurately by a two-dimensional method. Temperature analysis was performed by taking into consideration of the cement type and content, boundary and environment conditions including the variations of atmospheric temperature and wind velocity. The results of this study may be useful for the temperature control to restrain thermal cracking and the construction management to design the resonable curing method of mass concrete structure.

• Structural Engineering and Mechanics
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• v.6 no.3
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• pp.275-289
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• 1998

The objective of the paper is to present a method whereby the time required for a steel structure to sustain the effects of a prescribed temperature rise according to real fire curves can be calculated. The method is divided into two parts. The first part deals with the post-yield behaviour of steel structures at elevated temperatures. It takes into account the variation of the properties of steel material with temperature in an incremental elastoplastic analysis so that the safety factor of the structure under certain fire conditions can be assessed. The second part deals with the heat transfer problem of bare steel members in real fire. Factors affecting the heat transfer process are examined and a model for predicting the temperature variation with time under real fire conditions is proposed. This model results in more accurate temperature predictions for steel members than those obtained from previously adopted model.