• Proceedings of the KWS Conference
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• 2002.10a
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• pp.244-249
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• 2002

The purpose of this study is to develope the prediction method of liquation crack initiation in HAZ of laser weldment. Thermal two dimensional strain analyses were performed by FEM for bead-on-plate welding in order to obtain the plastic strain at elevated temperature in HAZ of the laser weldment. From these results, it became clear that the plastic strain at elevated temperature affected liquation crack initiation in HAZ, and it could be proposed that the critical strain, which controlled liquation crack initiation, existed. Moreover, an attempt was made to develop thermal and dynamic three dimensional strain analysis method for the laser weldment in order to obtain the plastic strain at elevated temperature in HAZ of the laser weldment in more detail and precisely.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.1-10
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• 2009

An experimental investigation was conducted to evaluate the performance of mortars with and without Metakaolin (MK) exposed to elevated temperatures $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$ for two hours. The binder to sand ratio was kept constant (1:5.23). The ordinary Portland cement (OPC) was replaced with MK at 0%, 5%, 10% 20% and 30%. All mixtures were designed to have a flow of $94{\pm}5%$. The compressive strength of mortars before and after exposure to elevated temperature was determined. The formation of various decomposition phases were identified using X-ray diffractometry (XRD) and differential thermal analysis (DTA). The microstructure of the mortars was examined using scanning electron microscope (SEM). Test results indicated that MK improves the compressive strength before and after exposure to elevated temperature and that the 20% cement replacement of MK is the optimum percentage.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.2
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• pp.154-159
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• 2014

The increasing of atmospheric $CO_2$ are changing the pH (ocean acidification) and temperature of the sea. Although the effects of ocean acidification on calcifying organisms have well-documented, only a few studies have examined the combined effects of ocean acidification and elevated temperature. This study investigated the effects of ocean acidification and elevated temperature for 2100 on survival and growth of juvenile abalone, Haliotis discus hannai. Ocean acidification was simulated by bubbling $CO_2$ into seawater at concentrations of 1,000 and 1,500 ppm, and temperature was set at room temperature $+2^{\circ}C$. Neither $CO_2$ nor temperature had a significant effect on survival of abalone, while both significantly affected growth. There was no significant interaction between the two factors. Shell length can be used as a growth index of abalone to access the impacts of ocean acidification and elevated temperature.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.564-571
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• 2003

This research investigates how characteristics of ball bearing affect non-repeatable runout(NRRO) in a HDD spindle system at elevated temperature. It shows that the elevated temperature results in the increase of bearing contact angle and the decrease of bearing deformation due to the different thermal expansion rate of the components of the HDD spindle system. The increase of contact angle at elevated temperature is so small that the variation of bearing frequencies is negligible. On the other hand, the decrease of bearing deformation at elevated temperature reduces the stiffness of ball bearing and the natural frequencies of HDD spindle system consequently, which changes the amplitude and the frequency distribution of NRRO.

• Journal of Korean Association for Spatial Structures
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• v.4 no.1 s.11
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• pp.87-95
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• 2004

This paper shows the study on the capacity of H-shape column at elevated temperature in fire. The main parameters are temperatures, slenderness ratios and load ratios. The physical properties of steel material at elevated temperatures are according to EC3 Part 1.2. The critical temperature of local buckling at elevated temperatures are lower when the yield strength of the material is higher, and when the ratios of width-thickness of plates are larger. The evaluation capacity of uniformly heated steel cloumns were considered to axial forces, moments of strong axis and weak axis to the LRFD.

• Earthquakes and Structures
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• v.2 no.4
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• pp.397-412
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• 2011

In this paper, the seismic response of elevated broad and slender liquid storage tanks isolated by elastomeric or sliding bearings was investigated. The accuracy of predictions of SAP2000 vs. 3D-BASIS-ME programs was examined. A comparative study of the performance of base isolated tanks when isolation bearings are placed at the top or at the bottom of the supporting tower structure was conducted. It was found that base isolation is quite effective in reducing the earthquake response of elevated liquid storage tanks in which high reductions of base shear and shaft displacement were achieved. Modeling the isolated tanks in SAP2000 was very successful in producing results that are nearly identical to those of program 3D-BASIS-ME. Placing the isolators at the top of the shaft in elevated tanks proved to be much better than placing them at the bottom.

• Computers and Concrete
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• v.27 no.1
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• pp.13-20
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• 2021

In this paper, the elevated temperature on a concrete-galvalume composite beam's flexural strength based on the numerical and experimental methods is investigated. The strategy is to perform modeling and simulation of the flexural test based on finite element method (FEM) at room temperature and validate its results to experimental data at the same temperature. When the numerical model was proven valid, the model was utilized to simulate the effect of elevated temperatures on the composite element. The study concludes that the flexural strength of the beam decreases at higher temperature. Additionally, it was shown that cracking moments is susceptible to temperature fluctuation and the failure modes are sensitive concerning the elevated temperature.

• Advances in materials Research
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• v.5 no.1
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• pp.21-34
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• 2016

Fire is one of the most destructive powers to which a building structure can be subjected, often exposing concrete elements to elevated temperatures. The relative properties of concrete after such an exposure are of significant importance in terms of the serviceability of buildings. Unraveling the heating history of concrete and different cooling regimes is important for forensic research or to determine whether a fire-exposed concrete structure and its components are still structurally sound or not. Assessment of fire-damaged concrete structures usually starts with visual observation of colour change, cracking and spalling. Thus, it is important to know the effect of elevated temperatures on strength retention properties of concrete. This study reports the effect of elevated temperature on the mechanical properties of the concrete specimen with polypropylene fibres and cooled differently under various regimes. In the heating cycle, the specimen were subjected to elevated temperatures ranging from $200^{\circ}C$ to $800^{\circ}C$, in steps of $200^{\circ}C$ with a retention period of 1 hour. Then they were cooled to room temperature differently. The cooling regimes studied include, furnace cooling, air cooling and sudden cooling. After exposure to elevated temperatures and cooled differently, the weight loss, residual compressive and split tensile strengths retention characteristics were studied. Test results indicated that weight and both compressive and tensile strengths significantly reduce, with an increase in temperature and are strongly dependent on cooling regimes adopted.

• Applied Microscopy
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• v.43 no.3
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• pp.110-116
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• 2013

Effects of elevated air temperature and carbon dioxide ($CO_2$) concentration on the leaf surface structures were investigated in Liriodendron tulipifera (yellow poplar) and Populus tomentiglandulosa (Suwon poplar). Cuttings of the two tree species were exposed to elevated air temperatures at $27/22^{\circ}C$ (day/night) and $CO_2$ concentrations at 770/790 ppm for three months. The abaxial leaf surface of yellow poplar under an ambient condition ($22/17^{\circ}C$ and 380/400 ppm) had stomata and epicuticular waxes (transversely ridged rodlets). A prominent increase in the density of epicuticular waxes was found on the leaves under the elevated condition. Meanwhile, the abaxial leaf surface of Suwon poplar under an ambient condition was covered with long trichomes. The leaves under the elevated condition possessed a higher amount of long trichomes than those under the ambient condition. These results suggest that the two poplar species may change their leaf surface structures under the elevated air temperature and $CO_2$ concentration condition for acclimation of increased photosynthesis.

• Journal of the Korean Society of Tobacco Science
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• v.21 no.1
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• pp.17-25
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• 1999

To elucidate the effect of elevated sublethal temperature ($33\pm1^{\circ}C$) on polyamine metabolism and oogenesis, we investigated alterations in the major polyamines and ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), and ovarian development during the pupal-adult development of the tobacco budworm, Helicoverpa assulta. Ovaries ODC activity under the elevated sublethal temperature ($33\pm1^{\circ}C$) were lower than those of the optimal rearing temperature ($25\pm1^{\circ}C$). whereas ovarian ADC activity was consistently higher than the optimal rearing temperature ($25\pm1^{\circ}C$). When the gonads were exposed to the higher temperature, ovarian putrescine showed somewhat suppressed levels throughout development, indicating a relatively high correlationship with the alteration aspects in ODC or ADC activity under elevated sublethal temperature. A somewhat precocious ovary was observed in an early stage of development at $33\pm1^{\circ}C$, but cellular abnormalities occurred in this ovary. The ovary developed under elevated sublethal temperature was observed the inhibitional effect of polyamine metabolism and the abnormal development of ovariole, which seem to be related to the sterility.