• KSBB Journal
• /
• v.9 no.5
• /
• pp.492-498
• /
• 1994

A hollow fiber device was utilized to perform a dialysis culture for E. coli. Acetic acid inhibition on the growth of E. coli was relieved by dialyzing the acid from broth into a dialysate reservoir. The rate of acetic acid formation was very sensitive to the concentration of glucose and dissolved oxygen. Therefore it was found that the glucose permeation rate should be balanced with the oxygen supply rate. Specific growth rate of E. coli was determined by the glucose permeation rate through membrane. Under a low permeation rate, acetic acid formation was depressed in accordance with high dissolved oxygen concentration as well as low glucose concentration.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.265-269
• /
• 2017

Because of abrupt changes for velocity in water, transient flow is occurred in practical life. To reduce and avoid the high or low pressure of pipe network system, various surge protection facilities are used to prevent the risk in pipe network system. Especially, we focused on study not only preventing positive and negative pressure but also selecting adequate equipment for high pressurized pipelines. Several critical cases were considered by undertaking a steady state hydraulic study and transient dynamic simulation and we suggested that the surge vessel of various surge protection system was recommended to control high and low pressures on pipeline system in perspective.

• Cement Symposium
• /
• s.49
• /
• pp.27-28
• /
• 2022

The cement industry emits a large amount of CO₂, and 60~65% of the CO₂ is generated from calcination of raw materials. So, the CO₂ from cement industry can be reduced by substituting decarbonated materials for limestone. In this study, the chemical composition and grindability of three types of steel slag were evaluated and the application of those materials will be examined for the production of low heat portland cement.

• Kyungpook Mathematical Journal
• /
• v.45 no.2
• /
• pp.167-169
• /
• 2005

Here we introduce and study vector bundles, E, on a smooth projective curve X having many "spread" sections and for which $E^{*}\;{\otimes}{\omega}X$ has many "spread" sections. We show that no such bundle exists on X if the gonality of X is too low.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1996.06a
• /
• pp.151-151
• /
• 1996

• International Journal of Highway Engineering
• /
• v.19 no.1
• /
• pp.45-52
• /
• 2017

PURPOSES : The main purpose of this study is to develop a high elastic modulus and low-shrinkage roller-compacted concrete base (RCCB) in order to prevent fatigue cracking and reflective cracking in the asphalt surface layer of composite pavement. Using a rigid base material with low shrinkage can be a solution to this problem. Moreover, a strong rigid base with high elastic modulus is able to shift the location of critical tensile strain from the bottom of the asphalt layer to the bottom of the rigid base layer, which can prevent fatigue cracking in the asphalt layer. METHODS : Sensitivity analysis of composite pavement via numerical methods is implemented to determine an appropriate range of elastic modulus of the rigid base that would eliminate fatigue cracking. Various asphalt thicknesses and elastic moduli of the rigid base are used in the analysis to study their respective influences on fatigue cracking. Low-shrinkage RCC mixture, as determined via laboratory testing with various amounts of a CSA expansion agent (0%, 7%, and 10%), is found to achieve an appropriate low-shrinkage level. Shrinkage of RCC is measured according to KS F 2424. RESULTS : This study shows that composite pavements comprising asphalt thicknesses of (h1) 2 in. with E2 > 19 GPa, 4 in. with E2 > 15 GPa, and 6 in. with E2 > 11 GPa are able to eliminate tensile strain in the asphalt layer, which is the cause of fatigue cracking in this layer. Shrinkage test results demonstrate that a 10% CSA RCC mixture can reduce shrinkage by 84% and 93% as compared to conventional RCC and PCC, respectively. CONCLUSIONS : According to the results of numerical analyses using various design inputs, composite pavements are shown to be able to eliminate fatigue cracking in composite pavement. Additionally, an RCC mixture with 10% CSA admixture is able to reduce or eliminate reflective cracking in asphalt surfaces as a result of the significant shrinkage reduction in the RCC base. Thus, this low-shrinkage base material can be used as an alternative solution to distresses in composite pavement.

• Korean Chemical Engineering Research
• /
• v.47 no.1
• /
• pp.46-53
• /
• 2009

Phase equilibrium and dynamic behavior studies were performed in systems containing $C_{12}E_5$ nonionic surfactant solution and nonpolar hydrocarbon oil. The phase behavior result showed an oil-in-water(O/W) microemulsion(${\mu}E$) in equilibrium with excess oil phase at low temperatures and a water-in-oil(W/O) ${\mu}E$ in equilibrium with excess water phase at high temperatures. For intermediate temperatures a 3 phase region containing excess water, excess oil, and a middle-phase microemulsion was observed and the transition temperature was found to increase with an increase in the chain length of a hydrocarbon oil. Dynamic behavior at low temperatures showed that an oil drop size decreased linearly with time due to solubilization into micelles and the solubilization rate decreased with an increase in the chain length of a hydrocarbon oil. On the other hand, both spontaneous emulsification of water into oil phase and expansion of oil drop with time were observed because of diffusion of surfactant and water into oil phase. Under conditions of a 3 phase region including a middle-phase ${\mu}E$, both rapid solubilization and emulsification of oil into aqueous surfactant solution were found mainly due to the existence of ultra-low interfacial tension. Interfacial tensions were measured as a function of time for n-decane oil drops brought into contact with 1 wt% surfactant solution at $25^{\circ}C$. Both equilibrium interfacial tension and equilibration time were found to increase with an increase in the chain length of a hydrocarbon oil.

• Applied Chemistry for Engineering
• /
• v.20 no.5
• /
• pp.473-478
• /
• 2009

Phase equilibrium and dynamic behavior studies were performed on systems containing $C_{10}E_5$ nonionic surfactant solutions and nonpolar hydrocarbon oils. The phase behavior showed an oil in water (O/W) microemulsion (${\mu}E$) in equilibrium with excess oil phase at low temperatures and a water in oil (W/O) ${\mu}E$ in equilibrium with excess water phase at high temperatures. For intermediate temperatures a three-phase region containing excess water, excess oil, and a middle-phase microemulsion was observed and the transition temperature was found to increase with an increase in the chain length of a hydrocarbon oil. Dynamic behavior at low temperatures showed that an oil drop size decreased linearly with time due to solubilization into micelles and the solubilization rate decreased with an increase in the chain length of a hydrocarbon oil. On the other hand, both spontaneous emulsification of water into oil phase and expansion of oil drop were observed because of diffusion of surfactant and water into oil phase. Under conditions of a 3 phase region including a middle-phase ${\mu}E$, both rapid solubilization and emulsification of oil into aqueous solutions were found mainly due to the existence of ultra-low interfacial tension. Interfacial tensions were measured as a function of time for n-decane oil drops brought into contact with 1 wt% surfactant solution at $25^{\circ}C$. Both equilibrium interfacial tension and equilibration time increased with an increase in the chain length of a hydrocarbon oil.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.09b
• /
• pp.1174-1175
• /
• 2005

• Journal of the korean Society of Automotive Engineers
• /
• v.23 no.3
• /
• pp.69-71
• /
• 2001