• Journal of Korean Elementary Science Education
• /
• v.39 no.3
• /
• pp.433-448
• /
• 2020

In this study, the tasks of thermal equilibrium and heat insulation concept were divided into scientific and everyday contexts to analyzed the level of familiarity, feeling of knowing, state curiosity, and state anxiety that students feel in task contexts and their relationship. The subjects of this study were One hundred nine students in sixth grade of elementary schools located in metropolitan cities. The results of this study were as follows. First, there was no difference in the level of feeling of knowing, state curiosity, and state anxiety in the task of scientific and everyday contexts. In the case of familiarity, there was no consistent tendency in the concept of thermal equilibrium and heat insulation. And the group who recognized the task context familiarly had higher feeling of knowing and lower state anxiety than the group who recognized the task context unfamiliarly. Second, familiarity and feeling of knowing showed high positive correlation, state anxiety and familiarity showed negative correlation, and state anxiety and feeling of knowing had also negative correlation. In addition, familiarity had a negative effect on state anxiety, and FOK had a positive effect on state curiosity and a negative effect on state anxiety. There was no significant moderating effect of the task context. Third, in case of state curiosity, the group perceived the knowledge gap was very small had the highest state curiosity, and the group perceived the knowledge gap was very large had the lowest state curiosity. In case of state anxiety, the less the knowledge gap was perceived, the lower the anxiety was triggered. This study broadens our understanding of the learning process and provides implications for effective instruction strategies for students' cognitive and emotional states.

• Journal of Mechanical Science and Technology
• /
• v.14 no.8
• /
• pp.879-890
• /
• 2000

This study investigates the nonpremixed $H_2/CO$-air turbulent flames numerically. The turbulent combustion process is represented by a reaction progress variable model coupled with the presumed joint probability function. In the present study, the turbulent combustion model is applied to analyze the nonadiabatic flames by introducing additional variable in the transport equation of enthalpy and the radiative heat loss is calculated using a local, geometry independent model. Calculations are compared with experimental data in terms of temperature, and mass fraction of major species, radical, and NO. Numerical results indicate that the lower and higher fuel-jet velocity flames have the distinctly different flame structures and NO formation characteristics in the proximity of the outer core vortex zone. The present model correctly predicts the essential features of flame structure and the characteristics of NO formation in the bluff-body stabilized flames. The effects of nonequilibrium chemistry and radiative heat loss on the thermal NO formation are discussed in detail.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.2
• /
• pp.147-155
• /
• 2001

Experimental investigations were conducted for two hydrogen-nitrogen coaxial jet diffusion flames. A flame was a conventional coaxial jet diffusion flame and the other was a coaxial jet diffusion flame of which ambient air-jet turbulence was intensified. In this study, firstly two kinds of NOx measuring system were campared by using different convertors, secondly the NOx formation characteristics were investigated in order to examine the effect of turbulence intensity. In this study it is known that stainless convertor has some problem in the converting process from NO$_2$to NO in fuel rich region but molybdenum convertor can detect the amount of NOx correctly. The increase of turbulence intensity reduces the thermal NOx less than a half in our experiment and this effect is conspicuous near the nozzle. The conversion rate from NO to NO$_2$and the portion of NO$_2$among NOx are increased with turbulence intensity. These NOx measurements will help to understand the influences of turbulence intensity on NOx formation.

• Transactions on Electrical and Electronic Materials
• /
• v.9 no.4
• /
• pp.143-146
• /
• 2008

In this study the thermal impact characteristics by forest fire are extensively investigated using temperature controlled ovens. The test conditions for thermal impact damage are simulated according to the characteristics of natural forest fire. The test pieces are suspension porcelain insulators made by KRI in 2005 for transmission lines. In the thermal impact cycle tests with $300\;^{\circ}C$ thermal impact gradient (-70 to $230\;^{\circ}C$), cycling in 10 minute periods, no critical failures occurred in the test samples even with long cycle times. But in tests with thermal impact gradient from room temperature to $200-600\;^{\circ}C$, cycling in 10 to 30 minute periods, there were critical failures of the porcelain insulators according to the thermal impact gradient and quenching method. In the case of thermal impact by forest fire, it was found of that duration time is more important than the cycling time, and the initiation temperature of porcelain insulator failures is about $300\;^{\circ}C$, in the case of water quenching, many cracks and fracture of the porcelain occurred. It was found that the thermal impact failure is closely related to the displacement in the cement by thermal stress as confirmed by simulation. It was estimated that the initiation displacement by the thermal impact of $300\;^{\circ}C$ is about 0.1 %. Above 1% displacement, it is expected that the most porcelain insulators would fail.

• Fashion & Textile Research Journal
• /
• v.1 no.3
• /
• pp.264-274
• /
• 1999

The thermal resistance of 60 men's suits for summer and winter was measured to determine their thermal characteristics and physical properties, including air permeability, weight, and thickness of the jackets and trousers consisted of the ensembles were measured to predict the thermal resistance of garments and ensembles. In this study, general physical properties of the men' suit ensembles were determined. In general, thickness and weight of winter ensembles were greater than those of summer ensembles. A factor which could distinguish the difference between summer and winter ensembles was the air permeability. The air permeability of summer ensembles was 3~6 times greater than those of winter ensembles. For the thermal characteristics, the thermal resistance of winter ensembles were higher than those of summer ensembles. When the wind was involved, the thermal resistance of both ensembles decreased up to 30%. In addition, the equations were developed to predict the thermal resistance of the garments and ensembles when there was no air velocity and the thermal resistance of the ensembles with air velocity of 1.2 m/sec. Looking at the equations, thickness, weight, and size of the garments were the definite factors that affect the thermal resistance of the samples.

• The Journal of Korean Academy of Prosthodontics
• /
• v.37 no.6
• /
• pp.730-740
• /
• 1999

The purpose of this study was to investigate setting and thermal expansion of dental soldering investments. In order to compare expansion rates and to investigate the effect of water/powder ratio on expansion, setting and thermal expansion of low dental soldering investments were measured under three different water/powder ratio conditions. standard, 20% decreased and 20% increased. Setting expansion of investments was measured by use of dialgauge method. Each measurement was started two minutes later from the beginning of spatulation and recorded every one minute for one hour. Thermal expansion of cylindrical test specimens, 10mm diameter, 50mm length, was recorded in a thermodilatometer at heating rate of $10^{\circ}C$ per minute from $25^{\circ}C\;to\;700^{\circ}C$. The results of this study were obtained as follows: 1. Setting expansion rates under the standard water/powder ratio condition were 0.198% in Speed-E, 0.090% in Deguvest, 0.080% in CM and Hi-temp. Setting expansion of Speed-E was significantly different from those of CM, Deguvest and Hi-temp, and setting expansion of Deguvest was significantly different from those of CM and Hi-temp(p<.05). 2. Under the decreased water/powder ratio condition, there was significant increase in setting expansion of 4 dental soldering investments (p<.05). 3. There were no significant differences in setting expansions of investments except Hi-temp between standard and increased water/powder ratio condition(p<.05). 4. Thermal expansion rates under the standard water/powder ratio condition were 1.923% in Deguvest, 1.629% in Speed-E, 1.619% in Hi-temp and 1.580% in CM. No significant differences in thermal expansions under the standard water/powder ratio condition existed only between Speed-I and Hi-temp(p<.05) 5. Under the decreased water/powder ratio condition, there was significant increase in thermal expansion of CM and Deguvest but decrease in thermal expansion of Speed-E (p<.05). 6. Under the increased water/powder ratio condition, there was significant decrease in thermal expansion of CM, Deguvest and Speed-I but decrease in thermal expansion of Hi-temp(p<.05).

• Journal of The Korean Society of Agricultural Engineers
• /
• v.46 no.4
• /
• pp.39-46
• /
• 2004

This experiment was carried out to study on the effect of surface coating on thermal insulation of farm structures to improve thermal resistance and reflective effect of solar radiation. Nine different types of experimental specimen were compared in the temperature variations of inside and outside; A, B, C, D. E and F types are box container and G, H and I types are drum container. The size of these containers is $1,500{\times}2,000{\times}2,500$ mm and ${\varphi}$ $280{\times}330$ mm, respectively. Specimen of 3-type box(A, B, C) is galvanized steel sheet of thickness 0.45 mm. D, E and F types are sandwich panel of the thickness 50 mm inserted with urethane, glass wool and polystyrene form, respectively. G, H and I types are paint pot using in general. The surface of A. D, E, F and I types didn't any treatment, B, C and G types were treated with thermal insulation coating on the outside surface(B, G) or the inside and outside surface(C). And H type was treated with water paint coating on the only outside surface. In general, the experimental results showed the following tendencies; In case of A, B and C types. it was found that the thermal insulation effect of types coated with thermal insulation coating was improved remarkably than that of no treatment. And the thermal insulation effect between steel sheet and sandwich panel type was nearly similar There was not a significant difference of thermal insulation effect between thermal insulation coating and water paint coating. In time of drum container filled with rough rice, The difference of heat transfer tendency and temperature variation among surface treatments was nearly similar that of box types of galvanized steel sheet. And there was time lag about 6 hours between the temperature of middle part of rice and that of inside or outside surface.

• Journal of Soil and Groundwater Environment
• /
• v.22 no.4
• /
• pp.9-26
• /
• 2017

When a warm well located downgradient is captured by cold thermal plume originated from an upgradient cold well, the warm thermal plume is pushed further downgradient in the direction of groundwater flow. If groundwater flow direction is parallel to an aquifer thermal energy storage (ATES), the warm well can no longer be utilized as a heat source during the winter season because of the reduced heat capacity of the warm groundwater. It has been found that when the specific discharge is increased by $1{\times}10^{-7}m/s$ in this situation, the performance of ATES is decreased by approximately 2.9% in the warm thermal plume, and approximately 6.5% in the cold thermal plume. An increase of the specific discharge in a permeable hydrogeothermal system with a relatively large hydraulic gradient creates serious thermal interferences between warm and cold thermal plumes. Therefore, an area comprising a permeable aquifer system with large hydraulic gradient should not be used for ATES site. In case of ATES located perpendicular to groundwater flow, when the specific discharge is increased by $1{\times}10^{-7}m/s$ in the warm thermal plume, the performance of ATES is decreased by about 2.5%. This is 13.8% less reduced performance than the parallel case, indicating that an increase of groundwater flow tends to decrease the thermal interference between cold and warm wells. The system performance of ATES that is perpendicular to groundwater flow is much better than that of parallel ATES.

• Proceedings of the KWS Conference
• /
• 1992.10a
• /
• pp.213-214
• /
• 1992

No Abstract, See Full Text

• Proceedings of the KSME Conference
• /
• 2005.11a
• /
• pp.3.1-3.1
• /
• 2005