• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.264-268
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• 2001

In this study, CT specimens were prepared from spring steel(SUP9) processed shot peening which was room temperature, low temperature and high temperature experiment. And we got the following characteristics from fatigue crack growth test carried out in the environment of room, and high temperature at $25^{\circ}C,\; 50^{\circ}C, \;100^{\circ}C,\; 150^{\circ}C,\; and\; 180^{\circ}C$ in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range $\DeltaK_{th}$ in the early stage of fatigue crack growth (Region I ) and stress intensity factor range $\Delta$K in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• Journal of Ocean Engineering and Technology
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• v.16 no.5
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• pp.80-87
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• 2002

In this study, CT specimens were prepared from spring steel(SUP9) which was used in suspension of automobile for room temperature and low temperature service. We got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{\circ}C$, ­3$0^{\circ}C$, ­5$0^{\circ}C$, ­7$0^{\circ}C$ and ­10$0^{\circ}C$ in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range ΔKth in the early stage of fatigue crack growth (Region I) and stress intensity factor range ΔK in the stable of fatigue crack growth (Region II) was decreased in proportion to descend temperature. It is assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• Transactions of Materials Processing
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• v.13 no.8
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• pp.704-709
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• 2004

The effect of annealing temperature on microstructures and mechanical properties of the 5052 Al sheets rolled 88% reduction at cryogenic temperature was investigated for the annealing temperature of 150 ~ $300^{\circ}C$, in comparison with those rolled at room temperature. The presence of equiaxed grains, whose size is about 200nm in a diameter, was observed in the alloy deformed 88% and annealed $200^{\circ}C$ for an hour. When compared with the deformation at room temperature, the deformation at cryogenic temperature showed the higher strengths and equivalent elongation after annealing at the annealing temperature below $200^{\circ}C$. However, for annealing above $250^{\circ}C$ materials deformed at cryogenic temperature showed the lower strength than those deformed at room temperature. This behavior might be attributed to the higher rate of recrystallization and growth in materials deformed at cryogenic temperature during annealing, due to the lager density of dislocations accumulated during the deformation.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.83-90
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• 2004

In this study, CT specimens were prepared from spring steel(SUP9) processed shot peening which was room temperature and low temperature experiment. And we got the following characteristics from fatigue crack growth test carried out in the environment of room temperature and low temperature at $25^{\circ}C$, $-30^{\circ}C$, $-50^{\circ}C$, $-70^{\circ}C$,$-100^{\circ}C$, and $-150^{\circ}C$, in the range of stress ratio of 0.05 by means of opening mode displacement. The threshold stress intensity factor range ΔKth in the early stage of fatigue crack growth (Region I)was increased but stress intensity factor range ΔK in the stable of fatigue crack growth (Region II) was decreased in proportion to decrease temperature. It is assumed that the fatigue resistance characteristics and fracture strength at low temperature and high temperature is considerably higher than that of room temperature in the early stage and stable of fatigue crack growth region.

• Journal of environmental and Sanitary engineering
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• v.17 no.3
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• pp.67-74
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• 2002

Nowadays, a new word called SBS(sick building syndrome) has been come into existence. Since most people spend a large majority of their time indoors, indoor air may affect human health more than outdoor air. This outline survey was carried out to investigate the extent of indoor air pollution in singing room and PC room. The concentrations of major indoor air pollutants(carbon dioxide, total suspended particulate, airborne microbes) and Thermocircumstance(temperature, relative humidity, intensity of illumination) were observed from October 1 to 31, 2001. As results of the survey, the mom values of thermocircumstance in singing room and PC room were $22.1^{\circ}C$ of temperature, 37.1% of humidity, 75 Lux of intensity of illumination and $22.0^{\circ}C$ of temperature, 52.6% of humidity, 135 Lux of intensity of illumination, respectively. The mean concentrations of carbon dioxide were 1589 ppm in singing room and 615 ppm in PC room, respectively The concentrations of carbon dioxide in singing room were higher than the indoor environmental standard of the first clause of Article 45 of public utilization service which is showed at public hygiene of the Ministry of Health and Social Affairs. The mean concentrations of total suspended particulate were $0.33{\;}mg/\textrm{m}^3$ in singing room and $0.57{\;}mg/\textrm{m}^3$ in PC room respectively. The mean concentrations of airborne microbe were $16{\;}CFU/\textrm{m}^3$ in singing room and $12{\;}CFU/\textrm{m}^3$ in PC room, respectively.

• Investigative Magnetic Resonance Imaging
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• v.23 no.3
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• pp.202-209
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• 2019

Purpose: To investigate the temperature-based differences of cortical bone ultrashort echo time MRI (UTE-MRI) biomarkers between body and room temperatures. Investigations of ex vivo UTE-MRI techniques were performed mostly at room temperature however, it is noted that the MRI properties of cortical bone may differ in vivo due to the higher temperature which exists as a condition in the live body. Materials and Methods: Cortical bone specimens from fourteen donors ($63{\pm}21$ years old, 6 females and 8 males) were scanned on a 3T clinical scanner at body and room temperatures to perform T1, $T2^*$, inversion recovery UTE (IR-UTE) $T2^*$ measurements, and two-pool magnetization transfer (MT) modeling. Results: Single-component $T2^*$, $IR-T2^*$, short and long component $T2^*s$ from bi-component analysis, and T1 showed significantly higher values while the noted macromolecular fraction (MMF) from MT modeling showed significantly lower values at body temperature, as compared with room temperature. However, it is noted that the short component fraction (Frac1) showed higher values at body temperature. Conclusion: This study highlights the need for careful consideration of the temperature effects on MRI measurements, before extending a conclusion from ex vivo studies on cortical bone specimens to clinical in vivo studies. It is noted that the increased relaxation times at higher temperature was most likely due to an increased molecular motion. The T1 increase for the studied human bone specimens was noted as being significantly higher than the previously reported values for bovine cortical bone. The prevailing discipline notes that the increased relaxation times of the bound water likely resulted in a lower signal loss during data acquisition, which led to the incidence of a higher Frac1 at body temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.175-179
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• 2004

Since the formability of AZ31 magnesium alloy is not good in room temperature, it is known that high temperature forming is advantageous. However, many studies are necessary to find the proper forming temperature for Mg alloy. In this study, experimental and FEM analysis are performed to investigate the forming temperature for AZ31 sheet. The deep drawing process of square cup is used in forming experiment and FEA. The investigations are performed in three forming temperature, room temperature, $250^{\circ}C\;and\;400^{\circ}C$. The square cup is well formed in $250^{\circ}C$ forming temperature, on the other hand, the crack and failure is presented in corner section in room and $250^{\circ}C$ forming temperature. The main cause is investigated as the effect of hardening range by the experimental and FEM results.

• Journal of the Semiconductor & Display Technology
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• v.17 no.2
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• pp.6-11
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• 2018

In this study, we have studied the effect of substrate temperature and hydrogen flow rate on the characteristics of MZO thin films for the TCO(Transparent conducting oxide). MZO thin films were deposited by RF magnetron sputtering at room temperature and $100^{\circ}C$ with various $H_2$ flow rate(1sccm~4sccm). In order to investigate the effect of hydrogen gas flow rate on the MZo thin film, we experimented with changing the hydrogen in argon mixing gas flow rate from 1.0sccm to 4.0sccm. MZO thin films deposited at room temperature and $100^{\circ}C$ show crystalline structure having (002), (103) preferential orientation. The electrical resistivity of the MZO films deposited at $100^{\circ}C$ was lower than that of the MZO film deposited at room temperature. The decrease of electrical resistivity with increasing substrate temperature was interpreted in terms of the increase of the charge carrier mobility and carrier concentration which seems to be due to the oxygen vacancy generated by the reducing atmosphere in the gas. The average transmittance of the MZO films deposited at room temperature and $100^{\circ}C$ with various hydrogen gas flow was more than 80%.

• Journal of the Korean Society of Combustion
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• v.8 no.2
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• pp.7-16
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• 2003

The transfer of air pollutants between passenger room and service room in train are investigated by the computational analysis. The effects of service room temperature, inlet velocity, initial concentration and heating are studied. The flow induced by the difference of density between two rooms is found to take the major role in transfer of polluted air. Low temperature of service room enhances the polluted air flow into passenger room along the floor. Exhaust fan above the door between two rooms is not effective for this case. Strong inlet flow is found to suppress polluted air flow from service room. The heating of passenger room can promote air pollution.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.170-175
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• 2013

For this study, the domestically developed bootstrap reservoir of the aircraft is set up in accordance with the temperature and humidity conditions depicted on the qualification test, and the variation in the internal pressure of the bootstrap reservoir of the aircraft is examined. The study shows that the bootstrap reservoir has less variation in the internal pressure at room temperature than at low temperature($-40^{\circ}C$). As a result, the internal pressure can be maintained stably when the temperature of working fluid in the bootstrap reservoir and the atmosphere environment is over room temperature($25^{\circ}C$). Therefore the keeping of temperature above room temperature is very important to operate the bootstrap reservoir of the aircraft properly.