• Proceedings of the KSME Conference
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• 2004.04a
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• pp.2035-2040
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• 2004

A cone cylinder is used to obtain variable operation conditions for the sonic ejector-diffuser system. The cone cylinder is designed to move upstream and downstream to change the ejector throat area ratio, thus obtaining variable mass flow rates. The present study investigates the effects of ejector throat area ratio and operating pressure ratio on the entrainment of secondary stream for the variable sonic ejector system. In experiment, the ejector throat area is varied in the range from ${\psi}=11.88$ to 66.69, and the operating pressure ratio from $p_{0p}/p_a=1.25$ to 9.0. The results show that the variable sonic ejector system is suitable for a required entrainment ratio of secondary stream by altering the ejector throat area ratio and operating pressure ratio.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.414-417
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• 2004

A cone cylinder is used to obtain variable operation conditions for the sonic ejector-diffuser system. The cone cylinder is designed to be shifted upstream and downstream to change the ejector throat area ratio, thus obtaining variable mass flow rates. The present study investigates the effects of ejector throat area ratio and operating pressure ratio on the entrainment of secondary stream for the variable sonic ejector system. The study is carried out experimentally. The ejector throat area is varied at the range from Ψ= 11.88 to 66.69, and the operating pressure ratio is changed from $P_{op}$ / $P_{a}$=1.25 to 9.0. The results show that the variable sonic ejector system can be operated to obtain specific entrainment ratio of secondary stream by altering the ejector throat area ratio and operating pressure ratio.o.

• KIEAE Journal
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• v.10 no.5
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• pp.95-100
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• 2010

Buildings receive solar radiation through windows and the solar radiation helps to save heating energy in winter. Therefore the bigger the glazing ratio is, the larger the amount of solar radiation we can receive. In this study we analysed the glazing ratio of Certified Green Building Apartments. And we verified whether the glazing ratio reflects energy saving through accepting solar radiation with correlation analysis. For glazing ratio analysis, we selected 116 apartment buildings of 19 apartment complexes that certified in 2008-2009 and took pictures of outside windows of the buildings. After that, we analysed the building's glazing ratio with 4 azimuth and checked distinction of the glazing ratio between 6 coupled azimuths. And we analysed the correlation between importance order of azimuth for energy saving and the glazing ratio change with the azimuth. The analysis showed that the glazing ratio does not reflect energy saving through accepting solar radiation.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.127-130
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• 2015

The objective of this study is to investigate the real flame shape and characteristic of annular combustor. To identify the effects of combustor length ratio and equivalence ratio on the flame shape in annular combustion configuration, the employed parameters are combustor length ratio 0.6-1.0, equivalence ratio 0.7-1.1. The flame shape is visualized using DSLR camera and precision optic mirror. The flame intensity is analyzed by $OH^{*}$ chemiluminescence images with ICCD camera. CO and NOx emission performance is also examined using an exhaust gas analyzer. From the visualized images, it is confirmed that the different tendency appeared in combustor length ratio 0.6-0.7 and 0.8-1.0. The results of $OH^{*}$ chemiluminescence show that the flame intensity is the most uniform for equivalence ratio 0.9. The smaller equivalence ratio is, the less emission of CO and NOx will be in this investigation range.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.553-558
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• 2001

To find the effective combinations of blowing ratio and injection angle for a straight slot film cooling, film cooling characteristics was investigated using both flow visualization experiment and numerical simulation. Injection angles from $15^{\circ}\;to\;50^{\circ}$ and blowing ratios from 0.2 to 3.0 were selected for the simulation. Comparison between experimental and numerical results shows a good agreement, for the case of the injection angle of $30^{\circ}$ and blowing ratio ranging from 0.55 to 2.0. Film cooling effectiveness was found to be an increasing function of blowing ratio. The effects of injection angle became prominent as the blowing ratio increases. An interesting phenomenon was found for the injection angle of $15^{\circ}$ : the lowest film cooling effectiveness for the blowing ratio smaller than 1.0, but the highest film cooling effectiveness for the blowing ratio greater than 2.0 within wide range of downstream region. There exist optimum injection angles corresponding to maximum film cooling effectiveness : injection angle of $25^{\circ}$ for the blowing ratio from 0.2 to 2.0, and injection angle of $15^{\circ}$ for the blowing ratio of 3.0. Present study provides a design combination among film cooling effectiveness, blowing ratio, and injection angle.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.311-316
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• 2001

This study analyzed the influence of paste fluidity and vibration time for fundamental properties of porous concrete. Results of this study were shown as follows; 1) Even if target void ratio is same, void ratio and compressive strength of porous concrete is different according to w/c, paste flow and vibration time. So, In case of target void ratio, we must consider the influence of w/c, paste flow, and vibration time. 2) Though w/c and vibration time are same, as paste flow increase, all void ratio, continuous void ratio, and compressive strength decrease and difference between upper and lower void ratio increase. 3) Though w/c and paste flow are same, as vibration time increase, all void ratio and continuous void ratio decrease and difference between upper and lower void ratio increase. Also, compressive strength increase by 10 seconds and decease after 10 seconds. 4) As types of superplasticizer is different, all void ratio, continuous void ratio, and compressive strength are different. So, we must give consideration to paste fluidity and vibration time in order that increase of strength of porous concrete and distribution of uniform void.

• Plant Journal
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• v.7 no.2
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• pp.44-51
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• 2011

Given the fact that the entire bituminous coal used for a boiler is imported, the supply of coal is often affected by the rise of international coal price. Moreover, coal suppliers have been diversified due to the competition among power generation companies for reducing costs and inexpensive sub-bituminous coal is used. As a result, boilers combustion conditions have been deviated from the initial boiler design. This requires the selection of adequate excessive air ratio for different combustion conditions to enhance the efficiency of boiler operation. The boiler efficiency has been identified through an examination on the change of excessive air ratio by mixed fuel in unit 8 of Dangjin power plant complex. In addition, an excessive air ratio was calculated based on the examination result. According to the study result, the adequate excessive air ratio was 13% when Macquarie and Powder river were mixed at a ratio of 5:5 and when Sonoma and Megaprima persada were mixed at a ratio of 5:5. When BHP Billiton and Powder river were mixed at a ratio of 4:6 and Centennial and Batubara were mixed at a ratio of 3:7, the adequate excessive air ratio was 11%.

• Journal of Environmental Health Sciences
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• v.32 no.6
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• pp.578-584
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• 2006

This research was conducted to estimate the effect of C/N ratio control on composting of TNT (2,4,6 trinitrotoluene)-contaminated soil. Glucose or acetone was selected to control C/N ratio of the contaminated soil. The C/N ratios of the controlled experiment and no controlled one were 26.0 and 6.6, respectively. During 45days, the degradation efficiency (96.0 or 91.8%) of acetone or glucose C/N ratio controlled soil was higher than that (78.4%) of no C/N ratio controlled case. The first order degradation rate constant of glucose or acetone C/N ratio control was 0.0641 or 0.0820/day. This constant was over twice 0.0356/day of no C/N ratio control. The C/N ratio control with glucose or acetone also showed a rather high $CO_2$ evolution than that without C/N ratio control. It was proven that C/N ratio control for composting of TNT-contaminated soil improved the treatment efficiency.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.239-244
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• 1999

Radial immersion ratio is an important factor to determine the threshold in face milling and should be estimated in process for automatic force regulation. In this paper, presented is a method of on-line estimation of radial immersion ratio using cutting force. When a tooth finishes sweeping, sudden drop of cutting forces occurs. These force drops are equal to the cutting forces that act on a single tooth at the swept angle of cut and can be acquired from cutting force signals in feed and cross-feed directions. The ratio of cutting forces in feed and cross-feed directions acting on the single tooth at the swept angle of cut is a function of the swept angle of cut and the ratio of radial to tangential cutting force. In the research, it is found that the ratio of radial to tangential cutting force is not affected by cutting conditions and axial rake angle. Therefore, the ratio of radial to tangential cutting force determined by just one preliminary experiment can be used regardless of the cutting conditions. Using the measured cutting forces and predetermined ratio, the redial immersion ratio is estimated. various experiments show that the radial immersion ratio can be estimated by the proposed method very well.

• The Journal of the Korean life insurance medical association
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• v.7 no.1
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• pp.180-188
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• 1988

A study on the standard cardiothoracic ratio calculated from the photofluorography film of chest in a total of 8,030 insured persons(3,449 men and 4,581 women) was undertaken. The results were as follows: 1) The linear regression equations were formed from the 99% confidence ilmits of actually measured average cardiothoracic ratio by weight index. The cardiothoracic ratios by weight index estimated by above mentioned equations, namely theoretic values of cardiothoracic ratio, should be regarded as the standard cardiothoracic ratios. 2) It seems that the standard cardiothoracic ratio${\pm}10%$ deviation should be regarded as the normal limits of cardiothoracic ratio. 3) The tables of standard cardiothoracic ratio by weight index and the normal limits of cardiothoracic ratio by weight index were presented. 4) The average weight index and cardiothoracic ratio in all males and females were 0.993 and 43.3%, and 0.997 and 46.3% respectively. 5) In order to evaluate the cardiothoracic ratio more accurately, the establishment of the standard cardiothoracic ratio by build is considered to be reasonable.