• Journal of Information Processing Systems
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• 제15권2호
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• pp.331-343
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• 2019

Dynamic thermal rating of the overhead transmission lines is affected by many uncertain factors. The ambient temperature, wind speed and wind direction are the main sources of uncertainty. Measurement uncertainty is an important parameter to evaluate the reliability of measurement results. This paper presents the uncertainty analysis based on Monte Carlo. On the basis of establishing the mathematical model and setting the probability density function of the input parameter value, the probability density function of the output value is determined by probability distribution random sampling. Through the calculation and analysis of the transient thermal balance equation and the steady- state thermal balance equation, the steady-state current carrying capacity, the transient current carrying capacity, the standard uncertainty and the probability distribution of the minimum and maximum values of the conductor under 95% confidence interval are obtained. The simulation results indicate that Monte Carlo method can decrease the computational complexity, speed up the calculation, and increase the validity and reliability of the uncertainty evaluation.

• 한국유체기계학회 논문집
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• 제18권4호
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• pp.13-21
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• 2015

The system design of the Organic Rankine Cycle(ORC) is greatly influenced by the thermal properties such as the temperature or the thermal capacity of heat source. Typically waste heat, solar energy, geothermal energy, and so on are used as the heat source for the ORC. However, thermal energy supplying from these kinds of heat sources cannot be provided constantly. Hence, an experimental study was conducted to utilize fluctuating thermal energy efficiently. For this experiment, an impulse turbine and supersonic nozzles were applied and the supersonic nozzle was used to increase the velocity at the nozzle exit. In addition, these nozzles were used to adjust the mass flowrate depending on the amount of the supplied thermal energy. The experiment was conducted with maximum three nozzles due to the capacity of thermal energy. The experimented results were compared with the predicted results. The experiment showed that the useful output power could be producted from low-grade thermal energy as well as fluctuating thermal energy.

• Safety and Health at Work
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• 제14권1호
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• pp.107-117
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• 2023

Background: Thermophysiological comfort in a cold environment is mainly ensured by clothing. However, the thermal performance and protective abilities of textile fabrics may be sensitive to extreme environmental conditions. This article evaluated the thermal insulation properties of three technical textile assemblies and determined the influence of environmental parameters (temperature, humidity, and wind speed) on their insulation capacity. Methods: Thermal insulation capacity and air permeability of the assemblies were determined experimentally. A sweating-guarded hotplate apparatus, commonly called the "skin model," based on International Organization for Standardization (ISO) 11092 standard and simulating the heat transfer from the body surface to the environment through clothing material, was adopted for the thermal resistance measurements. Results: It was found that the assemblies lost about 85% of their thermal insulation with increasing wind speed from 0 to 16 km/h. Under certain conditions, values approaching 1 clo have been measured. On the other hand, the results showed that temperature variation in the range (-40℃, 30℃), as well as humidity ratio changes (5 g/kg, 20 g/kg), had a limited influence on the thermal insulation of the studied assemblies. Conclusion: The present study showed that the most important variable impacting the thermal performance and protective abilities of textile fabrics is the wind speed, a parameter not taken into account by ISO 11092.

• 한국재료학회지
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• 제19권12호
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• pp.686-691
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• 2009

The effects of thermal properties on the crystallization behavior of $CaMgSi_2O_6$ glass-ceramics were investigated as a function of sintering temperature from 800$^{\circ}C$ to 900$^{\circ}C$. The crystallization behavior of the specimens depended on the sintering temperature, which could be evaluated from the differential thermal analysis, X-ray diffraction and Fourier transform infrared spectroscopy. With increasing sintering temperature, the thermal conductivity of the sintered specimens increased, while the coefficient of thermal expansion (CTE) of the sintered specimens decreased. These results could be attributed to the increase of crystallization, confirmed from the estimation by density measurements. Also, the thermal diffusivity and specific heat capacity of the sintered specimens were discussed with relation to the sintering temperature. Typically, a thermal conductivity of 3.084 $W/m^{\circ}C$, CTE of 8.049 $ppm/^{\circ}C$, thermal diffusivity of 1.389 $mm^2/s$ and specific heat capacity of 0.752 $J/g^{\circ}C$ were obtained for $CaMgSi_2O_6$ specimens sintered at 900$^{\circ}C$ for 5 h.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2297-2302
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• 2007

Numerical simulations are conducted to analyze conjugate heat transfer characteristics in a ribbed channel. In this simulation, the effects of Reynolds number and heat capacity of the solid channel wall on convective heat transfer are observed in the turbulent flow regime. In the case of the conducting wall against isothermal wall, the relative ratio of the thermal resistance between the solid wall and the flow field varies with Reynolds number. Thus the characteristics of the conjugate heat transfer are changed with the Reynolds number. Heat capacity ratio affects the temperature fluctuation inside solid wall. The temperature fluctuation inside the solid wall decreases with increasing the heat capacity of the solid wall so that the convective heat transfer increases. When the thermal conductivity ratio is smaller than 10, the effects of flow characteristics on heat transfer are changed.

• 한국기계가공학회지
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• 제10권1호
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• pp.62-66
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• 2011

In this study, the thermal performance of disk can be compared with disk and disk with holes through numerical analysis. The capacity of thermal emission on general disk becomes more than on disk with holes at the distribution of temperature at first and the magnitude of equivalent stress on general disk becomes less than on disk with holes at the distribution of stress. The capacity of thermal emission or the magnitude of thermal deformation on disk with holes becomes less than that on general disk 30 minutes later. The disk with holes is worn less and more durable than general disk. The performance of cooling and braking force at disk and pad can be improved by installing the disk with holes.

• 한국작물학회지
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• 제51권2호
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• pp.148-153
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• 2006

Effects of ${\alpha}$-chymotrypsin modification on degree of hydrolysis (DH), solubility, emulsifying capacity and thermal aggregation of laboratory-purified soy protein isolate (SPI) using a lipoxygenase-defected soybean (Jinpum-kong) and commercial soy protein isolate (Supro 500E) were compared. SPIs were hydrolyzed by ${\alpha}$-chymotrypsin at pH 7.8 and $37^{\circ}C$ for 30 min. DHs of Supro 500E and Jinpum-kong SPI were increased by ${\alpha}$-chymotrypsin modification, and DH of Supro 500E was higher than that of Jinpum-kong SPI. DH of ${\alpha}$-chymotrypsin treated Jinpum-kong SPI was similar with untreated Supro 500E and DH of treated Supro 500E was the highest. Solubility, emulsifying capacity and thermal aggregation of SPIs were increased by ${\alpha}$-chymotrypsin modification, and these changes were highly related to changes in DH. Functional properties of Supro 500E were higher than Jinpum-kong SPI in both of untreated and ${\alpha}$-chymotrypsin treated SPIs.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.130-135
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• 2000

To enhance heat transfer characteristics of water, fine ice was added to it. The convective heat transfer characteristics of the ice slurry were investigated in a flow loop with a constant heat flux test section. The Nusselt number and Fanning friction coefficient of water flow were found to be similar to the expected curve by Petukhov. The Nusselt number of the ice sin flow was higher than the Nusselt number of water. Effective thermal capacity of the 10.84% ice slurry was found to have 2.39 times of the thermal capacity of water.

• 한국안전학회지
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• 제29권3호
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• pp.8-13
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• 2014

Accidents involving portable ranges occurred total 133 cases for the last five years(2008~2012). It accounted for 18.0% of all gas accidents(739 cases). Major causes of accidents are using of excessive hot grill, leaving a butane can near fire and overheating of a butane can during cooking. In this study, it is a desire to investigate the relationship between thermal behavior mechanism depending on characteristics of cooking equipment materials of portable gas ranges. It shows that slope of temperature change curve correlates with difference of heat capacity on thermal behavior characteristics experiment depending on materials of cooking equipment. In conclusion, temperature characteristics appear differently depending on variables such as materials of cooking equipment. Especially, it is necessary to restrict using cooking equipment made of stones, because it is very dangerous that temperature of can is rapidly increasing caused by high heat capacity of stone.

• 설비공학논문집
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• 제13권12호
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• pp.1275-1281
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• 2001

Aqueous polymer solutions are known to have small pressure reduction. Paraffin slurries are known to have high thermal capacity. Paraffin particles are mixed into an aqueous polymer solution to make a new heat transfer fluid having high thermal capacity but low pressure reduction. The heat transfer characteristics of the new slurry was tested in a circular tube having a constant heat transfer boundary condition. The new slurry was found to have high Nusselt numbers as well as high thermal capacity and low pressure reduction in the laminar flow. The trends of the Nusselt numbers along the heating test section were studied for various heating conditions.