• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.147-148
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• 2007

The compound, Ti3(Al,Si)C2, was synthesized by hot pressing a powder mixture of TiCX, Al and Si. Its oxidation at 900 and 1000 oC in air for up to 50 h resulted in the formation of rutile-TiO2, -Al2O3 and amorphous SiO2. During oxidation, Ti diffused outwards to form the outer TiO2 layer, and oxygen was transported inwards to form the inner mixed layer.

• Journal of Bio-Environment Control
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• v.18 no.3
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• pp.185-191
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• 2009

The construction of experimental greenhouses, operating test, and analysis on variation of different environment factors were conducted to provide fundamental data for design of Korean style air-inflated double-layer plastic greenhouse. The development of technology of attaching plastic to the structure and fasteners to be able to keep airtight was required in order to maintain proper static pressure in air space of double layer coverings. The insulation effect of air inflated greenhouse was better than conventional type. The temperature of arch type roof was greater about $2^{\circ}C$ than peach type roof in air inflated greenhouse. It was recommended that the plastic should be attached at the edges without clearance length in order to ease installation and raise airtightness of double layer coverings. The transmittance of arch type roof was greater than peach type in air inflated one span greenhouse. The transmittance of air inflated greenhouse was greater than conventional type due to frame ratio and distance between double layers in three span greenhouse. The condensation occurred on conventional type greenhouse was more than air inflated type. It was required to examine for a long time in order to analyze it quantitatively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.7
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• pp.778-784
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• 2008

In this paper, a chip antenna using multi-layer configuration for multi-band operation, such as GSM, DCS, pcs, WCDMA, and Mobile WiMAX for 2.3 GHz is proposed. This proposed antenna is a PIFA structure with multi-layer configuration fabricated on R04003 substrate(${\varepsilon}_r=3.4$) and its size is $22{\times}5.5{\times}4.0\;mm^3$. Multi-layer structure can effectively reduce the size of an antenna from a reuse of air-space and can achieve broad bandwidth due to decrement of parallel capacitances from the insertion air-gap to the middle layer. The proposed antenna has a broadband operation by the high order resonance modes and the resonance at the top layer. The measured bandwidths with over 45 % radiation efficiency are 80 MHz($880{\sim}960\;MHz$) at the lower band and 690 MHz($1,710{\sim}2,400\;MHz$) at the higher band.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.587-589
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• 2009

The districts of underground geologic structure in Jeju island where underground air is distributed are lava cave, pyroclastic, open joint, and crushing zone. Such districts are identified to secure an enough airflow when air ventilation layer is to secure 25-35m in depth. In Jeju, Ground air is used for heating greenhouse and fertilizing natural $CO_2$ gas by suppling directly into greenhouse. But the heating method by suppling ground air into greenhouse directly bring about several problem. The occurrence of disease of the crops by high humidity is worried because the underground air which becomes discharge from underground air layer has over 90% relative humidity. The underground air is inadequate in heating for crops which need high temperature heating such as mangos, Hallbong and mandarin orange because the temperature of it is $15{\sim}18^{\circ}C$. Also There is worry where the ventilation loss becomes larger because the air pressure inside greenhouse is high by supplying underground air directly. In this study the heat pump system using underground air as heat source was developed and heating performance of the system was analysed. Heating COP of the system was 2.5~5.0 and rejecting heat into greenhouse and extracting heat from underground air were 40,000~27,000 kcal/h, 30,000~18,000 kcal/h respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.645-648
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• 2005

The grounds of multipurpose practical use degree are built much holding world cup 2002 but material that is used in this building most external membrane ceiling is accomplishing PTEE A master and servant. Therefore, this research analyzed assessment about sound absorption special quality that measure ventilation quantitys of 10 act material and analyze correlation with Air Permeability and the sound absorption rate, and follow in change of layer of air of inside facts material. Result is as following. When Air Permeability good dimension is 5$\sim$15 cc/cm$^2$/sec and acoustic absorptivity is the best as Air Permeability result that measure acoustic absorptivity of inside facts material particularly firstly, could know 8$\sim$9 cc/cm$^2$/sec love. When establish sound absorption inside facts in external membrane as result that measure acoustic absorptivity of inside (acts material secondly, could know that acoustic absorptivity is good though become about minimum back layer of air 900mm.

• Fashion & Textile Research Journal
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• v.23 no.2
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• pp.261-272
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• 2021

The purpose of the present study was to evaluate the thermal insulation of air-filled winter jackets according to the amount of air-filler using a thermal manikin. The insulation of these jackets' was compared to a down padded jacket with an identical design and size. The amounts of air-filler were 100% (26,219 cm³), 70% (18,645 cm³), 50% (13,110 cm³), and 0% (0 cm³). The results showed that a clothing insulation (Icl) of 0%, 50%, 70%, and 100% air, and 100% down jackets was 0.208, 0.243, 0.207, 0.176, and 0.315 clo, respectively. In addition, the down jacket with waisttaped had a clothing insulation of 0.369 clo. However, the highest value of clothing insulation per clothing weight was the 50% air-filled jacket in all conditions. In terms of regional power consumption of the thermal manikin, the down jacket consumed less power for the shoulder and chest than the air-filled jackets. In conclusion, in order to maximize the thermal insulation of air-filled jackets, an optimal amount of air-filler, that is, an amount which does not compromise (break) the layer of inner air between the surface of manikin and the lining of the jacket, should be explored. Further studies on lining materials, end-closed design, and changes in thermal insulation under the conditions of strong wind or heavy snow are recommended.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.33-36
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• 2008

The transient behavior of a passive air breathing direct methanol fuel cell (DMFC) operated on vapor-feeding mode is studied in this paper. It generally takes 30 minutes after starting for the cell response to come to its steady-state and the response is sometimes unstable. A mathematical dynamic one-dimensional model for simulating transient response of the DMFC is presented. In this model a DMFC is decomposed into its subsystems using lumped model and divided into five layers, namely the anodic diffusion layer, the anodic catalyst layer, the proton exchange membrane (PEM), the cathodic catalyst layer and the cathodic diffusion layer. All layers are considered to have finite thickness, and within every one of them a set of differential-algebraic governing equations are given to represent multi-components mass balance, such as methanol, water, oxygen and carbon dioxide, charge balance, the electrochemical reaction and mass transport phenomena. A one-dimensional, isothermal and mass transport model is developed that captures the coupling between water generation and transport, oxygen consumption and natural convection. The single cell is supplied by pure methanol vapor from a methanol reservoir at the anode, and the oxygen is supplied via natural air-breathing at the cathode. The water is not supplied from external source because the cell uses the water created at the cathode using water back diffusion through nafion membrane. As a result of simulation strong effects of water transport were found out. The model analysis provides several conclusions. The performance drop after peak point is caused by insufficiency of water at the anode. The excess water at the cathode makes performance recovery impossible. The undesired crossover of the reactant methanol through the PEM causes overpotential at the cathode and limits the feeding methanol concentration.

• Clean Technology
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• v.28 no.1
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• pp.18-23
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• 2022

Using air as an insulator due to its low heat transfer coefficient has been studied and has been widely commercialized to save energy in the field of thermal insulation technology. In this study, we analyzed the heat insulating effect of hollow silica nanoparticles mixed in non-uniform size, and the maximum heat insulating efficiency of these particles given the limited number of particles that can be mixed with a medium such as paint. The hollow silica nanoparticles were synthesized via a sol-gel process using a polystyrene template in order to produce an air layer inside of the particles. After synthesis, the particles were analyzed for their insulation effect according to the size of the air layer by adding 5 wt % of the particles to paint and investigating the thermal insulation performance by a heat transfer experiment. When mixing the particles with white paint, the insulation efficiency was 15% or higher. Furthermore, the large particles, which had a large internal air layer, showed a 5% higher insulation performance than the small particles. By observing the difference in the insulation effect according to the internal air layer size of hollow silica nanoparticles, this research suggests that when using hollow particles as a paint additive, the particle size needs to be considered in order to maximize the air layer in the paint.

• KIEAE Journal
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• v.15 no.1
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• pp.77-82
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• 2015

The purpose of this study is to compare the thermal insulation performance of windows according to the formation of air layer and to evaluate its energy efficiency on a selected standard house. A thermal insulation test, KS F 2278 was used to measure U-values (Heat transmission coefficients) for the following three cases: the first case (Case 1) is a Low-E pair glass (Argon injected), the second case (Case 2) is a Low-E pair glass with the air cap attached on the glass surface, and the third case (Case 3) is a Low-E pair glass, on the frame of which the air cap is attached. The evaluation of the energy efficiency was conducted according to a building energy calculation method from ISO 13790, calculation of energy use for space heating and cooling, using the U-values obtained from the thermal insulation tests. As results of the tests, the U-values of Case 1, Case 2, and Case 3 were $1.668W/m^2{\cdot}K$, $1.568W/m^2{\cdot}K$, and $1.319W/m^2{\cdot}K$ respectively. The Case 2 had about 5.9% lower value than the Case 1, and the Case 3 had about 20.9% lower value than the Case 1. It seems that the thermal performance of the windows is attributed to an increase of the heat resistance and the thickness of air layer. An evaluation of the energy efficiency of the three cases on the selected standard house showed that the amount of heating energy demand per unit area was $7.776kWh/m^2{\cdot}yr$ for the Case $1,6.856kWh/m^2{\cdot}yr$ for the Case 2, and $4.856kWh/m^2{\cdot}yr$ for the Case 3. This study suggests that the formation of air layer (by using air cap) and its thickness should reduce the heat energy demand and thus improve the energy saving efficiency

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.3
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• pp.117-128
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• 2002

This paper describes the smoke filling process of a fire field model based on a self-deve-loped SMEP (Smoke Movement Estimating Program) code to the simulation of fire induced flows in the two types of atrium space containing a ceiling heat flux. The SMEP using PISO algorithm solves conservation equations for mass, momentum, energy and species, together with those for the modified k-$\varepsilon$ turbulence model with buoyancy production term. Also it solves the radiation equation using the discrete ordinates method. Compressibility is assumed and the perfect gas law is used. Comparison of the calculated upper-layer average tempera-ture and smoke layer clear height with the zone models has shown reasonable agreement. The zone models used are the CFAST and the NBTC one-room. For atrium fires with ceiling glass the ceiling heat flux by solar heat causes a high smoke temperature near the ceiling. However, it has no effect on the smoke movement such as the smoke layer clear heights that are important in fire safety. In conclusion, the smoke layer clear heights that are important in evacuation activity except the early of a fire were not as sensitive as the smoke layer tem-perature to the nature of ceiling heat flux condition. Thus, a fire sensor in atrium with ceiling glass has to consider these phenomena.