• Journal of the Korean Solar Energy Society
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• v.21 no.2
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• pp.27-34
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• 2001

The greenhouse heating system using solar energy has been realized in the protective agriculture in this study in order to analyse the thermal energy characteristics of the system the effects of ambient air temperature, solar radiation, relative humidities and water content of ambient air on the greenhouse air temperature were investigated through computer simulation experimental analysis for validation of the simulation. The results from this study are summarized as follows: 1) The expected values of inside air temperature for the system solar energy were very much close to the experimental values. 2) In the system using solar energy, the expected values of daytime surface temperature of soil by computer simulation were very much similar to the measured values, but those of nighttime were higher than the measured value by almost $2.5^{\circ}C$. 3) Heat loss of daytime was found to be larger than that of night time as much as 2.0 to 4.2 times for the system using solar energy. 4) In the system using solar energy. while the ambient air temperature varied between $-7^{\circ}C$ and $-3.8^{\circ}C$, the temperature of the inside air was maintained between $0^{\circ}C$ and $22^{\circ}C$. 5) At the minimum ambient temperature of $-7^{\circ}C$, the temperature of the inside air was $0^{\circ}C$.

• 한국태양에너지학회:학술대회논문집
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• 2008.04a
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• pp.263-268
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• 2008

Building Integrated PV(BIPV) is one of the best fascinating PV application technologies. To apply PV module in building, various factors should be reflected such as installation position, shading, temperature, and so on. Especially a temperature should be considered, for it affects both electrical efficiency of a PV module and heating/cooling load in a building. This study investigates a semitransparent PV module that is designed as finished material for windows. Therefore it needs to considerate about the optical characteristics of the transparent module. It reports the effect of thermal and optical characteristics of the PV module on generation performance. The study was performed by measuring sun spectrum and luminance through the PV modules and by monitoring the temperature and experiment. The results showed that 1 degree temperature rise reduced about 0.48% of output power.

• Journal of IKEEE
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• v.12 no.2
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• pp.102-109
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• 2008

In this paper, the thermal characteristics of a tunable all-optical fiber Bragg grating(FBG) filter was investigated by numerical analysis. From the results, it is possible to tune a Bragg center wavelength along temperature variation because a Bragg center wavelength is varied linearly according to its operating temperature, however, the reflectivity of a Bragg center wavelength was reduced over a limited high temperature. Accordingly, it is possible to obtain the stability of a tunable all-optical FBG filter within $600^{\circ}C$, but it is difficult to tune a Bragg center wavelength over this temperature.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.234-240
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• 2016

Energetically-modified material using reject fly ash (RFA), generated from thermal power plants, was manufactured to investigate the effect of the material on the physical and chemical characteristics of cement mortar. In order to modify reject fly ash, a vibration mill was used. Particle size, grain shape, and crystal structure of the ash were analyzed. Then, the compressive strength of the mortar using energetically-modified reject fly ash (ERFA) was measured. Microstructure and X-ray diffraction (XRD) patterns were also used in the analysis. As the replacement rate of ERFA increased, the value of the compressive strength tended to decrease. However, it was found that the compressive strength values of 7 and 28 days-cured specimens were higher than those of conventional ordinary Portland cement (OPC) mortar with 10 % replacement rate condition.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.11
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• pp.97-104
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• 1996

Because of the novel characteristics such as chemical stability, hardness, electrical resistivity and thermal conductance, diamond-like carbon (DLC) film is a suitable materials for the passivation layers. For this purpose, DLC films are synthesized under various conditions and are characterized. Adhesive stregth is excellent and increased with the increase of the hydrogen gas flow rate. The resistivity of approximately 5.3X10$^{8}{\Omega}{\cdot}cm$ is measured by automatic spreading resistance probe analysis method. The thermal conductivity of DLC films is superior to that of PSG oxide and improved by increasing the hydrogen gas flow rate. The patterning techniques of the DLC films is developed using the lift-off and RIE methods to form 5${\mu}$m line. Finally, power transistor with the DLC film as passivation layer is fabricated and analyzed. The test result shows the improsved long-term stability and higher breakdown voltage.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.479-482
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• 2008

In order to more closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, the thermal-fluid characteristics of high current vacuum arcs were calculated by a commercial multiphysics package, ANSYS, in order to obtain Joule heat, Lorentz force and the interactions with flow variables. We assumed the diffused-mode arc within an AMF vacuum interrupter. It was found with four different currents that the temperature distributions on the anode surface are diffused uniformly without concentration in 7kA for both types (cup and coil-type). But the arc plasma transition and an increase of thermal flux density for increasing the applied current have caused the change of temperature distributions on the anode surface. We should need further studies on the two-way coupling method and radiation model for arc plasmas in order to accomplish the advanced analysis method for multiphysics.

• Journal of Korea Foundry Society
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• v.2 no.1
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• pp.2-11
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• 1982

In order to investigate the relationship between the thermal characteristics of the various molds as green sand mold, dry sand mold, $CO_2$ mold and shell mold, and the solidification characteristics of molten metal, the thermal analysis of rarious molds and melt were performed. The structure of Al-Castings was a/so observed. Results obtained in this experiment were as follows : 1) The heating rate of the molds was increased in the order of green sand mold, $CO_2$ mold, dry sand mold and shell mold, On the other hand the solidification time of the melts was shortened in the order of dry sand mold castings, $CO_2$ mold castings, green sand mold castings and shell mold castings. 2) The arrest temperature period in the heating curve of the green sand mold was resulted from the eraporation of moisture contained in mold, which was transfered to the outer side of the mold. 3) The temperature fluctuation of the melt in the shell mold was considered to be resulted from the combution heat of resin contained in the mold. 4) The amounts of heat absorption of the molds were increased in the order of dry sand mold, $CO_2$ mold, green sand mold and shell mold. 5) The higher the solidification rate was, the longer was its shrinkage pipe and the finer its grain size.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.614-618
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• 2006

Recycling of asphalt including shingle is much important for economic aspects such as a decrease of treatment cost. This research was carried out in order to process the recycled shingle to asphalt concrete which is a pavement material. Pure asphalt and the mixture of recycled asphalt were tested in terms of the thermal characteristics, viscosity, and penetration. DSC analysis indicates that the thermal characteristics of separate shingle showed similar properties regardless of processing conditions. Melting of asphalt separated from shingle occurred at $170^{\circ}C$. The viscosity and penetration of the 1~5 wt% of mixed recycling asphalt and raw material asphalt are suitable for the pavement material standard.

• Journal of the Korean Solar Energy Society
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• v.27 no.4
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• pp.59-65
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• 2007

This study is to propose the basic data for deciding remodeling of wornout educational facilities. In order of it, the indoor environmental standard, the actual conditions of thermal environment and sound insulation of walls were examined through field measurement in the subjected open elementary school(J school) and modernization model of elementary school(Y school) which they are located in Seoul. As the result, standard for indoor environmental factors of educational facilities which is established by Ministry of Education is not subdivided into indoor environmental performances considering usages and characteristics of classrooms for comfortable indoor environment. The vertical temperature difference in general classroom and in open classroom showed to be $11.2^{\circ}C$ and $12.1^{\circ}C$ respectively, while indoor temperature of special classroon was, on the whole, higher than that of any other classroom due to its specific heat flux of wall materials. The sound insulation performance of the masonry brick wall of classroom satisfied the minimum standard of AIJ, Architectural Institute of Japan, in the open elementary school and the modernization model of elementary school. That is to say, the movable partition wall between the classroom and the corridor disturbed students in their class in the open school.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.477-483
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• 2000

Fly ash is the unburned residue resulting from the combustion of coal in utility and industrial boilers such as thermal power plants. Annually about 5 million tons of fly ash is being produced in korea. Less than 25 percent of total volume of fly ash is currently being used effectively for some ways. In the future, the volume of fly ash discharge from thermal power stations will be increasing more and more, and the development of the utilization of high volume fly ash is required. Fly ash has a lower compacted density and specific gravity than coarse grained natural aggregates but equivalent strength properties indicating that the fly ash could be used as a structural fill materials. So, clay-fly ash mixtures can be used as a fill material in the construction of embankments. Laboratory tests have been carried out to determine the physical, chemical, and geotechnical characteristics of the clay and fly ash. The fly ash is mixed with the clay in different proportions and the geotechnical characteristics of the mixtures have been studied also. In this study describes the results of the experimental study. The implications of the use of clay and clay-fly ash mixtures on the stability of embankments are discussed.