• Journal of the Korean Society of Visualization
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• v.9 no.3
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• pp.59-64
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• 2011

In this study the change of free surface vortex is expressed through the time volume fraction using multiphase unsteady condition in sump, because in previous studies of the pump sump did not represent the behavior of the free surface vortex exactly due to the reason it was calculated using single phase and steady condition. The reliability of the computational analysis is verified through comparing experimental results with that of present numerical analysis. Homogeneous free surface model is used to apply interactions of air and water. The results show that the free surface vortex can be identified on the isotropic surface at air volume fraction 1%~5%. The vortices make an air column from the free surface to the sump intake and are created and destroyed repeatedly. The behavior of free surface vortex at numerical analysis is quite similar to experimental test. The result of vortex motion according to time, works on a cycle.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.35-42
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• 1998

Laser Raman scattering method has been applied to measure equivalence ratio of methane/air and propane/air mixture in constant volume combustion chamber. We used high power KrF excimer laser$(\lambda=248nm)$ and a high gain ICCD camera to capture low intensity Raman signal. Raman shifts and Ram cross-sections of $H_2,\;O_2,\;N_2,\;CO_2,\;CH_4\;and\;C_3H_8$ were measured precisely. Our results showed an excellent agreement with other groups. Mole fraction measurement of $O_2\;and\;N_2$ from air showed that $O_2\;:\;N_2$ = 0.206 : 0.794. We used constant volume combustion chamber and gas injector which is operated at $5\sim10barg$. Methane and propane are used as a fuel. 50 Raman signal are obtained and ensemble averaged for measurement of equivalence ratio. Our measured results showed that the equivalence ratio of fuel/air mixture is reasonable at ${\pm}5%$ error range.

• Journal of the Korean Institute of Landscape Architecture
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• v.34 no.5 s.118
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• pp.70-75
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• 2006

The purpose of this study is to explore the effects of difference in urban tree plantings on microclimate amelioration, and to suggest essential information for quantifying urban energy budgets and energy savings. This study was focused on measuring and analyzing air temperature and relative humidity in summer. Daytime air temperatures at places with 8%, 24%, 44%, 79%, and 100% cover of woody plants were, respectively, $0.6^{\circ}C,\;1.3^{\circ}C,\;2.4^{\circ}C,\;3.5^{\circ}C,\;and\;4.8^{\circ}C$ cooler, compared to a place with 0% cover. A 10% increase of woody plant cover was estimated to reduce the temperature by approximately $0.55^{\circ}C$. The temperature reduction effects were relatively greater between places with lower cover of woody plants than between those with higher cover. Woody plant cover and crown volume were the appropriate indicators which quantified the effects of tree plantings on air temperatures, based on the correlation analysis. Regression equations to estimate temperature change ($Y:^{\circ}C$) using woody plant cover ($X_1:%$) or crown volume ($X_2:m^3$) as independent variables are as follows: $$1nY=3.3233-0.0018X_1\;(r^2=0.99,\;p<0.0001)\;Y=27.5297-0.0019X_2\;(r^2=0.96,\;p=0.0007)$$

• Journal of Electrical Engineering and Technology
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• v.11 no.5
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• pp.1348-1356
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• 2016

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.42 no.3
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• pp.28-36
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• 2010

Today We have three full series of the annals of Joseon Dynasty. Taebaeksan volume which is one of them shows comparatively good maintenance but Taebaeksan volume also decomposed in patches. The size of cover and inner paper were increased in late Joseon Dynasty, but the weight, thickness and basis weight bears no relation to each other. The oxidation index of paper in annals of pre-periods of King Sunjo shows very high value. After the annals of King Sunjo, the oxidation index of paper is very similar to today's Hanji. L.a.b values of inner paper in the Taebaeksan volume are similar generally. The average length of fiber using image analysis soft ware is 8.08~9.92 mm, that like immediate value of measurement. The air fraction of fiber's range is 1.20~2.12%. It lower than today's Hanji. After considering the factors of the length of fiber, air fraction and FE-SEM, we reached that no difference between raw material of inner paper in the Taebaeksan volume.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.169-173
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• 2010

Many salts have the ability to attract and remove water vapor from the surrounding environment. The ability of each salt to remove water vapor is based on the flow rate and temperature of air in surrounding. The objective of this study was toinvestigate the humid control characteristics in air-water system by using a desiccants. The aim is to asses the influence of three parameters on the humid control process which are air volume rate, air temperature and desiccant amount. Humidity control materials which consist of K (potassium) or Na (sodium) have been synthesized by the aqueous process. The humidity control properties of materials have been also investigated. Experiment results are as following. Thermal characteristics of desiccants showed similar properties regardless of processing condition. The experiments were examined by using artificial air-water system (humidity : 70~93%, air volume rate : $0.22{\sim}0.69m^3/s$). The results showed that the Na-type desiccant was an effective material. It was found that dew point increased with air volume rate, and the humidity change in humid control process was depended on desiccants amount.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.323-332
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• 2005

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of a homogeneous charged methane-air mixture under various overall charge pressures, excess air ratios and ignition times. The flow characteristics, including the mean velocity and turbulence intensity, were analyzed with a hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer, a flame propagation image acquired by ICCD camera and exhaust emissions measured by 2-valve gas chromatography were used to investigate effects of initial pressures, excess air ratios and ignition times on the combustion characteristics. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to a near-zero value after 3000 ms and that the combustion duration was shorten and the flame speed and laminar burning velocity had the highest value under the condition of an excess air ratio of 1.1, an overall charge pressure of 0.15 MPa and an ignition time of 300 ms in the present study. The $CO_2$ concentration was proportional to the ignition time and overall charge pressure, the $CO_2$ concentration was proportional to the excess air ratio, and the UHC concentration was inversely proportional to the ignition time and overall charge pressure.

• Journal of Hydrogen and New Energy
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• v.24 no.6
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• pp.518-523
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• 2013

This paper describes the reduction of a hydrogen sulfide ($H_2S$) generated from a biogas plant. Micro bubble system is adopted to supply air into the water in the reaction chamber, which can increase the contact area of the supplied air to the reserving water. Two stage reaction chambers having two reaction rooms are designed and manufactured to enhance the reduction rate of a hydrogen sulfide. Sodium hydroxide (NaOH) is also considered to get rid of a hydrogen sulfide. Air volume rate to the water in a reaction chamber is maintained between 0.5 and $1.0m^3/min$. Throughout experimental measurement of the concentration of a hydrogen sulfide by changing the volume of supplied air into the water, reduction rate of a hydrogen sulfide increases as air volume increases. Adding sodium hydroxide to the water with the air supply can reduce effectively a hydrogen sulfide up to 99.5% from biogas. It is noted that a hydrogen sulfide generated by a biogas plant can reduce by supplying micro bubble air and sodium hydroxide effectively.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.04a
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• pp.37-38
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• 2002

부유먼지가 인체에 미치는 유해성을 평가하기 위해서는 무엇보다도 공인되어 있고 신뢰성 있는 측정방법이 마련되어 있어야 한다. 대기중 부유먼지의 측정방법에는 여러 가지가 있으나 측정원리의 측면에서는 중량법과 광학적방법으로, 포집유량의 측면에서는 high-volume 과 low-volume으로 구분되어지며 임자의 크기별 포집장치의 부착유무에 따라 입도 분리형과 비분리형으로 구분되어지기도 한다. (중략)

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.100-102
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• 1998

This paper presents technique to control blower at constant air volume rate using V/F Control. Especially, this control method have not pressure sensors to measure because of using torque-speed relation based on the fan laws. Therefore, this technique is very simple and practical.