• Journal of Applied Reliability
• /
• v.7 no.1
• /
• pp.31-43
• /
• 2007

The function of O-ring seals is to prevent leakage during the service life of the components in which they are installed. The life prediction of O-ring is very important at various industry fields. Generally, to evaluated the long-term performance of O-ring in severe environments has applied a life prediction technique based on accelerated life test (ALT). In this work, Accelerated thermal aging test(l20, 130, 140, $150^{\circ}C$) of O-ring was applied for life prediction of O-ring. The property changes after thermal aging test was measured using TGA, DSC, FT - IR, Video Microscope and SEM. Shape parameter and life prediction were obtained using MINITAB program.

• 한국태양에너지학회:학술대회논문집
• /
• 2011.04a
• /
• pp.25-30
• /
• 2011

In this paper, we analyzed the electrical characteristics with Micro-cracks in Photovoltaic module. Micro cracks are increasing the breakage risk over the whole value chine from the wafer to the finished module, because the wafer or cell is exposed to mechanical stress. And The solar cells have to with stand the stress under out door operation in the finished module. Here the mechanical stress is induced by temperature changes and mechanical loads from wind and snow. So, we experimentally analyze the direct impact of micro-cracks on the module power and the consequences after artificial aging. The first step, we made micro-cracks in PV module by mechanical load test according to IEC 61215. Next, PV modules applied the thermal cycling test, because micro-cracks accelerated aging by thermal cycling test, according to IEC61215. Before every test, we checked output and EL image of PV module. As the result of first step, we detected little power loss(0.9%). But after thermal cycling test increased power loss about 3.2%.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.6
• /
• pp.27-37
• /
• 2014

Heat island is caused by changes of land coverage structure of cities and use of energy in buildings. As a result energy use in buildings get to increase further followed by rising of GHG emission and deteriorating climate change. Eco-friendly housing complex is a kind of plan that applies environmental control elements like water and green spaces to housing complex. With these methods, it can be expected to create thermal environment of indoor and outdoor. In this paper quantitative examination is studied on using CFD to find out the effects of river, water permeable, parks and planting on thermal environment. And by comparing field measurements with CFD results which are aimed to development phase housing complex, feasibility and usability of the CFD analysis results are confirmed. And also, analysis on the ventilation performance followed by natural ventilation system is analyzed by selecting one building in housing complex. Based on the results, the possibilities of energy reduction through making thermal environment and applying natural ventilation are studied. With these outcomes, creating thermal conditions and using natural ventilation would be contributed to GHG reduction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.29 no.2
• /
• pp.89-95
• /
• 2017

This study aimed to compare the primary heating energy consumption of regional apartment houses based on the enhanced thermal insulation performance of building envelope standards. The difference of the heating energy consumption based on the enhanced thermal insulation performance of building envelope standards in the southern region, the largest regional difference in primary heating energy consumption, is $10.3kWh/(m^2{\cdot}year)$. The difference of the heating energy consumption based on the enhanced thermal insulation performance of building envelope standards in the central region is $8.0{\sim}8.5kWh/(m^2{\cdot}year)$ and that of the Jeju region is $0.5kWh/(m^2{\cdot}year)$. These energy consumption differences do not result in building energy efficiency ratings changing. The building energy efficiency ratings have the possibility to be changed.

• Journal of the Korean Geosynthetics Society
• /
• v.6 no.1
• /
• pp.39-43
• /
• 2007

Geocomposites of needle punched and spunbonded nonwovens having the reinforcement and drainage functions were manufactured by use of thermal bonding method. The physical properties (e.g. tensile, tear and bursting strength, permittivity) of these multi-layered nonwovens were dependent on the processing parameters of temperatures, pressures, bonding periods etc. - in manufacturing by use of thermal bonding method. Therefore, it is very meaningful to optimize the processing parameters and physical properties of the geocomposites by thermal bonding method. In this study, an algorithm has been developed to optimize the process of the geocomposites using an artificial neural network (ANN). Geocomposites were employed to examine the effects of manufacturing methods on the analysis results and the neural network simulations have been applied to predict the changes of the nonwovens performances by varying the processing parameters.

• Structural Engineering and Mechanics
• /
• v.36 no.4
• /
• pp.401-419
• /
• 2010

This paper focuses on the development, verification and application of a three-dimensional nite element code for coupled thermal and structural analysis of roller compacted concrete arch dams. The Ostour Arch dam located on Ghezel-Ozan River, Iran, which was originally designed as conventional concrete arch dam, has been taken for the purpose of verication of the nite element code. In this project, RCC technology has been ascertained as an alternative method to reduce the cost of the project and make it competitive. The thermal analysis has been carried out taking into account the simulation of the sequence of construction, environmental temperature changes, and the wind speed. In addition, the variation of elastic modulus with time has been considered in this investigation using Concard's model. An attempt was made to compare the stresses developed in the dam body five years after the completion of the dam with those of end of the construction. It was seen that there is an increase in the tensile stresses after five years over stresses obtained immediately at the end of construction by 61.3%.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.8 no.1
• /
• pp.73-83
• /
• 2000

The purpose of this study is to analyze and characterize the correlation of the thermal comfort sensation with physiological responses for men in winter indoor environment. A number of experiments were conducted under twenty different environmental conditions with college male students. Clinical information on each participant was reported in terms of electrocardiogram (ECG), electroencephalogram (EEG) and self-centered evaluation. The comfort zone in winter is found, throughout the study, at Standard New Effective Temperature (SET$T^+$) of 25.2$^{\circ}C$, Predicted Mean Vote (PMV) between 0.27 and 0.62, and Thermal Sensation Vote (TSV) in the range of -0.76 and 0.36. The largest difference in skin temperature is measured at the calf area with respect to air temperature changes. Skin sensitivity to environment temperature is explained as calf, head, chest and abdomen in descending order. Change in heat rate is analyzed to be in parallel with that of SET$T^+$.

• Korean Journal of Materials Research
• /
• v.14 no.2
• /
• pp.94-100
• /
• 2004

We have investigated the magnetic domain structure and the thermal stability of magnetotransport properties of IrMn biased spin-valves containing Co, CoFe and NiFe. The magnetic domain structures were imaged using a magneto-optical indicator film(MOIF) technique. To investigate the thermal stability, magnetoresistance(MR) was measured at annealing temperature(TANN) and room temperature($T_{RT}$) followed by the annealing. Domain imaging reveal that the increase of annealing temperature led to changes in the exchange coupling between the two ferromagnet(FM) layers through nonmagnetic layer rather than between FM and antiferromagnet. unlike the NiFe biased IrMn spin valve with large domains, MOIF pictures of Co and CoFe biased IrMn spin valve structures show the formation of many small microdomains. The magnetic structure, as revealed by the domain images, appeared unchanged while the MR dropped dramatically. From the combined giant magnetoresistance(GMR) and MOIF results, it was apparent that the decrease of MR ratio was not related to the spin valve magnetic structure up to about $350^{\circ}C$($T_{RT}$ ).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.248-251
• /
• 2003

In this paper, it was experimented about thermal and mechanical insulation properties of a elastic epoxy specimen. We made elastic epoxy specimen adding a ratio of 0[phr], 20[phr], 35[phr] and 53[phr] with modifier to existing epoxy. Each specimen was absorbed by 25h, 196h, 361h 484h with water. In water-absorption state, it was experimented a change of heat flows by temperature of elastic epoxy and changes of thermal expansion coefficient. Also, a hardness-change of each specimen was experimented by change of water-absorption time. In this experiment DSC (Differential Scanning Calorimetry) and TMA (Thermomechanical Analysis) were used. A temperature range of DSC was changed from -0[$^{\circ}C$] to 200[$^{\circ}C$], TMA was changed from -0[$^{\circ}C$] to 350[$^{\circ}C$]. In addition, we investigated structural analysis of water absorbed specimen using SEM (Scanning electron microscope).

• Nuclear Engineering and Technology
• /
• v.50 no.5
• /
• pp.683-689
• /
• 2018

To evaluate equipment survivability of the polymer Viton, used in sealing materials, the effects of its thermal degradation were investigated in severe accident (SA) environment in a nuclear power plant. Viton specimens were prepared and thermally degraded at different SA temperature profiles. Changes in mechanical properties at different temperature profiles in different SA states were investigated. The thermal lag analysis was performed at calculated convective heat transfer conditions to predict the exposure temperature of the polymer inside the safety-related equipment. The polymer that was thermally degraded at postaccident states exhibited the highest change in its mechanical properties, such as tensile strength and elongation.