• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.106-112
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• 1997

This study measured the ignition limits of methane-air, propane-air, ethylene-air, and hydrogen-air mixture gases by discharge spark of D.C. power resistive circuit. The used experimental device is the IEC type spark ignition test apparatus, it consists of explosion chamber and supply -exhaust system of mixture gas. Mixture gases (methane-air, propane-air, ethylene-air, and hydrogen-air) were put into explosion chamber of IEC type spark ignition test apparatus, then it was confirmed whether ignition was made by 3,200 times of discharge spark between tungsten electrode and cadmium electrode. The ignition limits were found by increasing or decreasing the value of current. For the exact experiment, the ignition sensitivity was calibrated before and after the experiment in each condition. The ignition limits were found by changing the value of concentration of each gas-air mixture in D.C. 24 [V] resistive circuit. As the result of experiment, it was found that the minimum ignition limit currents exist at the value of methane-air 8.3 [$Vol\%$], propane-air 5.25[$Vol\%$], ethylene-air 7.8 [$Vol\%$], and hydrogen-air 21[$Vol\%$] mixture gases. For each the minimum ignition concentration of gases, the relationships between voltage and minimum ignition current were found. The results are as follows. - The minimum ignition limits are decreasing in the order of methane, propane, ethylene, and hydrogen. - The value of ignition current is inversely proportional to the value of source voltage. - The minimum ignition limit currents increase sharply at more than 2 [A]. The reason is caused by overheating the electrode.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.5
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• pp.526-538
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• 2007

Since air quality monitoring data sets are important base for developing of air quality management strategies including policy making and policy performance assessment, the environmental protection authorities need to organize and operate monitoring network properly. Air quality monitoring network of Busan, consisting of 18 stations, was allocated under unscientific and irrational principles. Thus the current state of air quality monitoring networks was reassessed the effect and appropriateness of monitoring objectives such as population protection and sources surveillance. In the process of the reassessment, a GIS-based decision support system was constructed and used to simulate air quality over complex terrain and to conduct optimization analysis for air quality monitoring network with multi-objective. The maximization of protection capability for population appears to be the most effective and principal objective among various objectives. The relocation of current monitoring stations through optimization analysis of multi-objective appears to be better than the network building for maximization of population protection capability. The decision support system developed in this study on the basis of GIS-based database appear to be useful for the environmental protection authorities to plan and manage air quality monitoring network over complex terrain.

• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.429-439
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• 2003

Counter-current two-phase flows of air- water in narrow rectangular channels with offset strip fins have been experimentally investigated in a 760 mm long and 100 mm wide test section with 3.0 and 5.0 mm gap widths. The two-phase flow regime, channel-average void fractions and two-phase pressure gradients were studied. Flow regime transition occurred at lower superficial velocities of air than in the channels without fins. In the bubbly and slug flow regimes, elongated bubbles rose along the subchannel formed by fins without lateral movement. The critical void fraction for the bubbly-to-slug transition was about 0.14 for the 3 mm gap channel and 0.2 for the 5 mm gap channel. respectively. Channel-average void fractions in the channels with fins were almost the same as those in the channels without fins. Void fractions increased as the gap width increased, especially at high superficial velocity of air. The presence of fins enhanced the two-phase distribution parameter significantly in the slug flow, where the effect of gap width was almost negligible. Superficial velocity of air dominated the two-phase pressure gradients. Liquid superficial velocity and channel gap width has only a minor effect on the pressure gradients.

• Textile Coloration and Finishing
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• v.11 no.2
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• pp.64-74
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• 1999

The driving characteristics of the 1 tube 2 chamber bent silkworm type dyeing machine are reported. This dyeing machine is a newly developed energy saving machine. In this study, the driving characteristics of the 1 tube 2 chamber bent silkworm type dyeing machine are examined. Specially the relationship between main body pressure and the electric current of the blower motor, the relationship between main body pressure and the air pressure of the blower nozzle, the effect of the air pressure of the blower on the running speed of the fabric, and the effect of main body temperature were discussed experimentally. Through the experimental data, the following results were obtained. 1. Blower motor electric current and blower nozzle air pressure increased as main body pressure increased due to the temperature increase of the main body. 2. The running speed of the fabric increased as blower nozzle air pressure increased. The difference in running speed between winch reel driving and no winch reel driving at a blower frequency of 60Hz was higher than that of 70Hz. 3. The electric current of the blower rioter and blower nozzle air pressure increased rapidly at the initial state. As the experimental time passed, the main body pressure increased slowly. as the main body temperature increased.

• Journal of Environmental Science International
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• v.14 no.8
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• pp.785-792
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• 2005

In order to reduce roadside and indoor air pollution for volatile organic compounds VOC), it may be necessary to apply photocatalyst-coated construction materials. This study evaluated the technical feasibility of the application of $TiO_2$ photocatalysis for the removal of VOC present in roadside or indoor air. The photocatalytic removal of five target VOC was investigated: benzene, toluene, ethyl benzene and o,m,p-xylenes. Variables tested for the current study included ultraviolet(UV) light intensity coating materials, relative humidity (RH), and input concentrations. Prior to performing the parameter tests, adsorption of VOC onto the current experiment was surveyed, and no adsorption was observed. Stronger UV intensity provided higher photocatalytic destruction(PCD) efficiency of the target compounds. For higher humidity, higher PCD efficiency was observed. The PCD efficiency depended on coating material. Contrary to certain previous findings, lower PCD efficiencies were observed for the experimental condition of higher input concentrations. The current findings suggested that the four parameters tested in the present study should be considered for the application of photocatalyst-coated construction materials in cleaning VOC of roadside or indoor air.

• Journal of Biosystems Engineering
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• v.22 no.3
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• pp.311-316
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• 1997

Two methods were used to detrermine the net photosynthetic rate(NPR) in the plug stand using a wind tunnel for plug seedlings Production. One is called as the integration method in which NPR calculated by the use of air current speed and $CO^2$ concentration measured at any heights above the medium surface in a wind tunnel were summed. It was assumed that the air flow at any layer did not mix with the lower or upper air layer. The other is called as the diffusion method in which eddy diffusivities above the plug stand were used to determine the NPR in the plug stand. In this method, $CO^2$ above or inside the plug stand was assumed to be absorbed vertically. NPR determined by the diffusion method was 28~45% of the NPR calculated by the integration method. Considering the magnitude of NPR and the effects of the air current speed on NPR, the integration method would be adequate for the calculation of NPR in the plug stand. Maximum NPR determined using the integration method appeared at the air current speed of 0.7m $s^{-1}$. It was ascribed to the decreased diffusion resistances of $CO^2$ with the increasing air current speed. NPR at the rear region in plug stand was 20~34% lower than that at the front region. NPR sharply decreased with the increase of an elapsed time after the beginning of photoperiod. Therefore $CO^2$ enrichment would be effective to force the growth of plug seedlings in a semi-closed ecological system under artificial lighting.

• 전기의세계
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• v.23 no.3
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• pp.60-66
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• 1974

This paper is to study on the phenomena that the compound dielectric strength through double layers of air-insulating oil dielectrics is much lower than that of air dielectrics only. the change of the dielectric strength by the variance of air gap depends on the characteristics of air gap discharge and, in case of commercial voltage, the degree of dependance is greeter than in case of direct current voltage.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.5
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• pp.574-580
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• 2013

Green technology encompasses a growing group of methods and materials, from techniques for generating energy and alternative resources to non-toxic cleaning products. Green technology is expected to solve current problems in atmospheric environment such as climate changes due to green house gases and hazardous air pollutants. This paper provides a review on the status of green technology and policy guidelines in Korea as well as the green technology for air pollutants. It presents the R&D projects and future direction in atmospheric environment, and the green technology in mobile source air pollution. Emerging green technology contributes to sustainable growth and development of atmospheric environmental industry for better air quality.

• The Korean Journal of Air & Space Law and Policy
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• v.14
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• pp.331-379
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• 2001

The purpose of this study is provide better suggestions to utilize the small aircraft by examining current situations of those airports. Then, the results of this study should help explain about the Availability of the airports for small aircraft in view of airplane exhibition, air-sports activity fields for aviation sports population, aviation theme park, and aviation-related education facility. This study examines current situations of the small airports for small aircraft which have been limited in their utility and compares the airports at the same level abroad. By examining these airports, this paper can make suggestions for the Availability of the small airports. Significance of the study lies in providing businessmen planning to invest the small airports and owners of airports with profitable consequences. At the macro level, it is expected to have a more effective development of land and an increase of aviation market value.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1150-1154
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• 2003

The voltage profile during discharge of the zinc air battery has very flat pattern until reach to end of discharge voltage. But, when zinc air battery is discharged by high current, the discharge voltage and energy becomes low. Therefore, we focused on effects of catalyst size to solve this problems by increasing active sites of oxygen reduction reaction. The size of catalyst was reduced from 27 to l${\mu}{\textrm}{m}$ and we examined average discharge voltage, capacity, energy, resistance and characteristics during GSM pulse discharge of zinc air battery with change of current density. And we also measured porosity of the cathode according to the ASTM. So we have got improvement of average discharge voltage and energy when catalyst was minimized and we have got optimum size of catalyst at 5${\mu}{\textrm}{m}$.