• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4D
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• pp.577-584
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• 2011

A series of field and laboratory permeability tests were performed to investigate the pore-clogging phenomenon of porous concrete used for pavement materials of a road. The field permeability tests were conducted for 37 study points in Jeju city, using the porous concretes with 13mm of maximum coarse aggregate ($G_{max}$). The results show that the service life of porous concrete is about 22 months when the permeability of the porous concrete is designed for 0.01 cm/sec. Some specimens were made with the purpose of recreating pore-clogging phenomenon. Tests were done for injected concentration of pore-clogging materials or size of maximum coarse aggregates ($G_{max}$). The test results demonstrated that relatively long in service life experienced with small amount of injected concentration of pore-clogging materials, whereas relatively short in service life experienced with a reduction in size of maximum coarse aggregates ($G_{max}$). In conclusion, the service life of porous concrete is in proportion to the concentration of pore-clogging material but it is in inverse proportion to the size of maximum coarse aggregate ($G_{max}$). Thus, the persisting period of porous concrete can be determined with respect to concentration of pore-clogging materials or size of maximum coarse aggregates ($G_{max}$).

• Clean Technology
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• v.17 no.4
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• pp.363-369
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• 2011

To evaluate the feasibility of electrodialysis for ammonia nitrogen removal from wastewater, the effects of operating parameters such as diluate concentration, applied voltage and flow rate on the removal of ammonia nitrogen were experimentally estimated. The removal rate was evaluated by measuring the elapsed time for ammonia nitrogen concentration of diluate to reach 20 mg/L. Limiting current density (LCD) linearly increased with ammonia nitrogen concentration and flow rate. The elapsed time was linearly proportional to initial concentration of diluate. Due to relatively large equivalent ion conductivity and ion mobility of ammonia nitrogen, the removal rate increased consistently with flow rate. Increase in the applied voltage gave positive effect to removal rate. From the operation of the electrodialysis module used in this research, the flow rate of 3.2 L/min and 80~90% of applied voltage for LCD are recommended as the optimum operating condition for the removal from high concentrate ammonia nitrogen solution.

• Fire Protection Technology
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• s.5
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• pp.22-32
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• 1989

• Membrane Journal
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• v.12 no.3
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• pp.171-181
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• 2002

The parameter which determines the plateau length of current-voltage curve for ion- exchange membranes was studied at various concentrations of NaCl and different flow rates. Moreover, the feasibility of the electrodialytic removal of 0.1 M NaCl solution at various current densities was tested by assessing the electrodialysis performance parameters such as salt removal efficiency, current efficiency, energy consumption and water dissociation. The diffusion boundary layer (DBL) thickness decreased with the NaCl concentration and flow rate of fled solution and it was observed that the plateau length of current-voltage curves was related with the DBL thickness. The removal efficiency and current efficiency were not affected significantly by the current densities even at the overlimiting current region indicating that most current were passed by electrolyte, and water dissociations are not responsible for the overlimiting current. Energy consumption increased when the current density supplied exceeded the limiting current density (LCD) values, because additional energy was necessary to overcome the plateau potential. Beyond the LCD values the energy consumption required to get a certain removal efficiency was not affected by the current density applied. The result suggests that it is allowed to operate electrodialysis processes at as high as possible current density unless water-splitting does not occur.

• Journal of Bio-Environment Control
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• v.14 no.2
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• pp.128-136
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• 2005

The objective of this study was to determine the effect of calcium concentrations in fertilizer solution on growth and cut flower quality of chrysanthemum 'Biarritz' To achieve this, deficiency symptom and growth characteristics as influenced by controlled Ca concentrations in fertilizer solution were investigated. The analysis of plant tissue and soil solution of root media were also conducted to secure optimum concentration for plant growth. Calcium deficiency developed on the very youngest leaves and the young leaves developed 'cupped' shape as they expand. The cut flower length of 0, 3.0 and 6.0 mM treatments were 105.8, 106.5, and 107.3cm, respectively. Elevated Ca concentration within the range from 0 to 6.0mM in fertilizer solution increased cut flower weight. The cut flower weight of control and 6.0mM treatment were 51.6 and 59.4 g, respectively. The tissue Ca content of 6.0mM treatment in which crops showed the highest growth among treatments was $3.09\%$ based on the dry weight of the youngest fully expanded leaves. From the results, it seems necessary to maintaining tissue Ca content higher than $2.8\%$. Soil Ca concentrations increased as K concentrations in fertilizer solution were elevated. Ca concentration in 0.0, 1.5, 3.0, 4.5 and 6.0mM treatments were 5.0, 7.4, 12.1, 16.5 and $28.2mg{\cdot}L^{-1}$, respectively, at harvesting stage. It is suggested that Ca concentration higher than $25.4mg{\cdot}L^{-1}$ in soil solution of root media is required to maintain normal growth.

• Korean Chemical Engineering Research
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• v.55 no.5
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• pp.618-622
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• 2017

Gasoline is a widely used product as a source for energy in homes, the automotive industry, and for industrial power generation, and it is also a product with a high risk of fire and explosion. In this study, to examine the risk for explosion for gasoline, PG, MG and RG, which are categorized according to octane number, were used as test specimens to measure their explosion limit according changes in oxygen concentration. The explosion limit for 21% oxygen concentration in air were confirmed to be 1.5~10.9%, 1.4~8.1%, and 1.3~7.6%, respectively, and the MOC for each of the test sample were confirmed to be 10.9%. The explosion limit measured in the test performed in this study confirmed between a 1.2%~7.6% wider explosion limit for the currently accepted MSDS for gasoline, and therefore it is considered that the results of this study can provide significant reference for preventing fires and explosions for process used gasoline.

• KSBB Journal
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• v.5 no.1
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• pp.75-80
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• 1990

The investigations of specific growth rate, specific alcohol production rate, cell yield, alcohol yield of K. marxianus LG were performed according to the sugar concentrations, 50, 80, 110, 190, and 250g/l of extracted solution of Jerusalem Artichoke. The functipnal relationship between specific growth rate, specific alcohol production rate, and alcohol concentrations were devoted study to. In case of low concentration of alcohol, the fuctions were linear relationships. But in the region of high concentration of alcohol, they expressed the exponential relationships. The growth rate of K. marxianus was prohibited at higher than 50g/l of alcohol concentrations regardless of concentration of residual sugar. Cell and alcohol yield showed the maximum values around 25g/l of alcohol concentraton without being related to initial sugar concentrations.

• Korean Journal Plant Pathology
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• v.11 no.2
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• pp.107-115
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• 1995

들깨 '수원25호', 담배 'L8', 'KF109'와 'NC82', 시금치 '입추'와 나팔꽃을 생장혼경조절이 가능한 대기오염원 노출상에서 SO? 140ppb/시간 또는 O? 150ppb/시간의 농도로 하루 24시간 10일 동안 노출시킨 결과 '수원25호' 들깨와 담배 'L8'은 SO?에 민감한 반면, 담배 'L8'과 나팔꽃은 오존에 아주 민감한 것으로 판명되었다. 위의 농도에서 가시적 피해가 조사식물의 50%에서 발생하는 병반발생빈도 50%(SF?)를 기준으로 설정한 한계노출시간 조사에서 오존에 대한 한계 노출시간은 담배 'L8'의 경우 24시간, 나팔꽃의 경우 72시간, 담배 'NC82'와 'KF109'의 경우 144시간 내외, 시금치의 경우 216시간으로 추정되었으며, SO?에 대한 한계노출시간은 담배 'L8'의 240시간을 제외하고는 모든 식물에서 240시간 이상으로 추정되었다.

• Journal of Radiation Protection and Research
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• v.24 no.3
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• pp.171-184
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• 1999

In this paper, using statistical theory the basic concepts and the formulars of lower limit of detection were deasribed. Assuming that risks of 5% are acceptable (95% confidence level), lower limits of detection were calculated on the measuring apparatus for alpha, beta and gamma nuclides. Also, on the basis concepts of lower limit of detection, the MDA values were calculated for the radionuclides detected easily in the environment. These results make it possible to evaluate confidence limits on the radioanalytical results in the environmental sample.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.257-263
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• 2008

We have examined explosion characteristics of bituminous coal dusts in cement manufacturing process. In order to find the thermal properties, we investigated weight loss and ignition temperature of coal materials using TGA and DSC. Also specific surface area of dust was investigated. Dust explosion experiments with Hartman's dust explosion apparatus have been conducted by varying concentration and size of coal dust for explosion probability and lower limit explosion concentration. According to the results for thermal properties, there is a little change by dust size. However, the specific surface area of dust is increased by decreasing dust size. The explosion test results show that small size and increasing concentration of dusts make dust explosion easier. And we find that the lower limit explosion concentration of bituminous coal is $0.3mg/cm^3$ and the probability is 100% on $0.9mg/cm^3$ in 170/200 mesh used in cement manufacturing process.