• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.53-60
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• 2017

Fly ash(FA) which is a byproduct in the coal combustion in thermal power plant contributes to pore structure densification due to pozzolanic reaction, and this leads to long-term strength development and excellent resistance to chloride penetration. In the work, compressive strength and chloride resistance in OPC(Ordinary Portland Cement) and FA-based concrete are evaluated, and the relationships are investigated considering ages. For the work, 3 different W/B (Water to Binder) ratios of 37%, 42%, and 47% are prepared, and 3 substitution ratio of fly ash(0%, 30%, and 50%) are considered as well. At the age of 28 days and 180 days, test results of compressive strength, diffusion coefficients based on Tang's method, and passed charges referred to ASTM C 1202 and KS F 2711 are obtained. With increasing replacement ratio of FA and decreasing W/B, the resistances to chlorides(diffusion coefficient and passed charge) are improved, and the results at the age of 180 days decrease to only 15% level at the age of 28 days due to pozzolanic reaction in FA 50 mixture, which shows that resistance to chloride is much dependent on age effect than strength development. After 180 days, more clear linear relationships are observed between strength and resistance to chloride.

• Journal of Korean Society of Transportation
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• v.27 no.4
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• pp.31-40
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• 2009

Some road charges toll to finance the cost or to manage traffic congestion. With a growth of PPI projects, toll roads would be increase continuously. Tolls have a considerable influence on user's route choice, and sometimes can affect to the departure time and even to mode choice. For modelling toll roads, user's WTP or VOT has an important role and it is general that VOT is equivalent to the wages of workers. The current way of modelling technique yields various toll price elasticity from low to high. When there exist few alternative routes, unrealistic result that all traffic assigned to some shortest path may occur. The toll price elasticity can be influenced by alternative route and congestion level, but some result shows nearly unrealistic patterns. The model to forecast more realistic toll road demand is very essential for estimating toll revenue, choice of optimal toll level & collecting location and establishing toll charge strategy. This paper reviewed some literatures about toll road modelling and tested case study about the assignment technique with different VOT. The case study shows that using different VOT yields more realistic result than the use of single VOT.

• The Journal of the Korean Society for Microbiology
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• v.35 no.2
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• pp.97-108
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• 2000

Two-dimensional gel electrophoresis (2-DE) is an essential tool of proteomics to analyse the entire set of proteins of an organism and its variation between organisms. Helicobacter pylori was tried to identify differences between strains. As the first step, whole H. pylori was lysed using high concentration urea contained lysis buffer [9.5 M Urea, 4% CHAPS, 35 mM Tris, 65 mM DTT, 0.01% SDS and 0.5% Ampholite (Bio-Rad, pH 3-10)]. The extract ($10\;{\mu}g$) was rehydrated to commercially available immobilised pH gradient (IPG) strips, then the proteins were separated according to their charges as the first dimensional separation. The IPG strips were placed on Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) to separate according to molecular mass of the proteins as the second dimension. The separated protein spots were visualised by silver staining in order to compare different expression of proteins between strains. Approximately 120 spots were identified in each mini-protein electrophoresised gel, furthermore about 65 to 75 spots were regarded as identical proteins in terms of pI value and molecular weight between strains used. In addition, distinct differences were found between strains, such as 219-1, Y7 and Y14, CH150. Two representative strains were examined using strips which had pH range from 4 to 7. This strips showed a number of isoforms which were considered large spots on pH range 3-10. Furthermore, the rest of spots on pH 4-7 IPG strips appeared very distinctive compared to broad range IPG strips. 2-DE seems to be an excellent tool for analysing and identifying variations between H. pylori strains.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.467-473
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• 2012

Coenzyme Q10 (CoQ10) is a natural lipid cofactor with antioxidant and anti-aging properties as cosmetic and food ingredients, involved in cellular energy metabolism. Here, nano-emulsions with CoQ10 were fabricated with lecithin, ethanol, oil, and sorbitan monostearate (Arlacel 60), as major components. Phase inversion emulsion method with ultrasonicator was utilized in producing CoQ10 solution, and stabilization effects from lecithin and ethanol and other diverse perturbation factors were evaluated over time. Physical properties of the emulsion were characterized such as its size, surface charges by zeta-potential, and the overall structures. Optimal concentrations of CoQ10 and Arlacel 60 were 0.8% and 3%, respectively, for producing the smallest sizes of nanoemersions in a 100 nm diameter with best morphology. No notable changes in the size were observed over 7 days from Ostwald ripening, when the concentration of Arlacel 60 was higher than 2%. Even after 270 days at room temperature, the size of nanoemulsions maintained as 115 nm in diameter, revealing only a 10% increase with high degrees of long termed stability and substantiality. In addition, changes in the surface potential occurred possible due to the flocculation effect on the nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.120-120
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• 2011

Graphene is a carbon based material and it has great potential of being utilized in various fields such as electronics, optics, and mechanics. In order to develop graphene-based logic systems, graphene field-effect transistor (GFET) has been extensively explored. GFET requires supporting devices, such as volatile memory, to function in an embedded logic system. As far as we understand, graphene has not been studied for volatile memory application, although several graphene non-volatile memories (GNVMs) have been reported. However, we think that these GNVM are unable to serve the logic system properly due to the very slow program/read speed. In this study, a GVM based on the GFET structure and using an engineered graphene channel is proposed. By manipulating the deposition condition, charge traps are introduced to graphene channel, which store charges temporarily, so as to enable volatile data storage for GFET. The proposed GVM shows satisfying performance in fast program/erase (P/E) and read speed. Moreover, this GVM has good compatibility with GFET in device fabrication process. This GVM can be designed to be dynamic random access memory (DRAM) in serving the logic systems application. We demonstrated GVM with the structure of FET. By manipulating the graphene synthesis process, we could engineer the charge trap density of graphene layer. In the range that our measurement system can support, we achieved a high performance of GVM in refresh (>10 ${\mu}s$) and retention time (~100 s). Because of high speed, when compared with other graphene based memory devices, GVM proposed in this study can be a strong contender for future electrical system applications.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.1
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• pp.73-81
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• 2020

Strontium (⁹⁰Sr) and nickel (⁵⁹Ni) have been considered as key radionuclides in the safety assessment of radioactive waste disposal. Through various efforts to impede the migration of radioactive nuclides underground, it has been established that some minerals generated from the corrosion of the waste containers have a positive chemical interaction with these radionuclides. Among these minerals we selected mackinawite (FeS), an iron and sulfur compound, and performed a sorption experiment for the Sr and Ni in FeS under anoxic and alkaline conditions by reflecting deep underground environments. The effects of pH on sorption were likewise investigated in the pH range of 8 ~ 12. As a result, it was found that strontium failed to exhibit a good sorption capacity in a weak alkaline range, while nickel showed a noticeably higher sorption affinity over the entire experimental pH range. Moreover, we determined that as the pH increased in the solution, the distribution coefficients (K_d) were increased for both nuclides, which reflects when an alkalinity increses, the surface of the mineral charges much negatively by detaching the hydrogen or cations on the mineral surface. Thus, it can be concluded that the cationic nuclides of Sr and Ni can attach easily to the mineral under strong alkalinity.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.914-919
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• 1997

On the basis of theory of Bratsch's electronegativity equalization, the electronegativity equalization, the group electronegativities and the group partial charges for anionic and nonionic surfactants could be calculated by using Pauling's electronegativity parameters. From calculated results, we have investigated how CMC, hydrophilic and hydrophobic groups, group partial charge, electronegativity of hydrophilic and hydrophobic groups, structural stability of micelle for anionic and nonionic surfactants are related. It was fround that CMC depends upon group partial charge and group electronegativity of hydrophilic and hydrophobic groups of surfactants. For the anionic surfactants, negative partial charge in hydrophobic group is delocalized as the carbon number in hydrophobic group increase. So negative partial charge of hydrophilic group has very large electronegativity that is decreased. And CMC decreases as hydration ability of hydrophilic groups which decreases relatively. For the nonionic surfactant, partial charge and electronegativity in hydrophobic group increases with the increment of carbon number in hydrophobic group. And CMC decreases because electronegativity of hydrophilic group is decreased with the increment of electronegativity of hydrophilic group. However, with the increase of repeating units in hydrophilic group, the negative partial charge of hydrophilic group increases. So CMC increases because surfactants hydrate rather than form micelles in aqueous solution by the increase of hydration ability.

• Health Policy and Management
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• v.22 no.1
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• pp.29-48
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• 2012

The purpose of this study is to analyze medical expenses by decedents in their last year of life and compare them with those by survivors during the year 2008. This study is conducted firstly in Korea, except some studies focusing on medical cost of decedents from specific diseases. To study this, national health insurance(NHI) claims data was used with medicaid claims data. The study group(decedents) was selected from the insurance entitlement file who were dropped out from January to December of 2008. The control group(survivors) was selected from the entitlement file by stratified sampling with keeping age-sex composition of the study group. The medical expenses of decedents during one year before death were measured and compared with those of survivors by sex and age. And the medical expenses were analyzed by causes of death, and also the expenses were examined by each item of medical services. On average, the medical expense amounted to 11 million Korean Won per decedent during their last year of life in 2008. The medical expense per decedent was 9.3 higher than that of survivor. The death-related expense of under the age 35 was about 16 million Won, compared with 4 million Won in the case of over the age 95, in average. The death-related expense is higher in younger ages. This means that more medical resources are put in to save life in younger ages. Total death-related expenditure took 8.3 percent in total NHI expenditures. Of the death-related medical expenses, the largest one was injection-related cost which shares twenty five percent, and the second largest one was hospitalization charges, and then the third one was surgery cost. The results of this study suggested that we should pay attention to the medical expenses in the last of year of life when we study health care expenditure in Korea. In addition, we have to deliberate health care policy to cope with medical expenditures before death in more efficient way.

• Journal of Science Education
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• v.41 no.1
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• pp.152-165
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• 2017

The magnetic field due to a current is one of the core concepts in electromagnetism which has been taught in secondary science education. In addition, it is a representative example of using visual representations to explain the relation between invisible physical quantities; current and magnetic field. In this study we investigated middle school students' representational competence into three components; interpretation, construction, and application of visual representations. According to the analysis, more than 75 % of the respondents interpreted the meaning of the arrows for current and magnetic field correctly. However, half of them confused the movement of electric charges with the direction of magnetic field. Over 60 % of the students constructed the magnetic field representation as circular closed curves, but many of them could not express the density of field lines properly. In application of visual representations, more than half failed to draw the direction of compass needle correctly. The scores were in order of interpretation, construction and application. There were also significant correlations among three components of representational competence. More attention and research on students' representational competence and effective use of visual representations is needed to better support science learning and teaching.

• Korean Journal of Environmental Agriculture
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• v.3 no.1
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• pp.52-56
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• 1984

In order to evaluate the applicability of two kinds of antibiotic fermentation residues on rice and tomato growth, yield, yield components, and some indicators for plant growing status were checked including analysis of physico-chemical properties of these two antibiotic fermentation residues. The results obtained are as follows: 1) These two antibiotic fermentation residues contain high organic matter ($21.6{\sim}24.2%$), phosphorus ($2900{\sim}4600 ppm$) and exchangeable cations ($55.4{\sim}138.3 meq/100 g$,), showing their pH values of $7.0{\sim}8.0$ range. 2) Both have developed net positive charge rather high and stiffly that exhibits high negative ion adsorption capacities, accordingly showing higher zero point of charges($pH 7.0{\sim}8.0$) than those of common soils. 3) The effect of the two kinds of antibiotic fermentation residues on rice growth was more or less the same comparable to the effect of the other fertilizers applied, showing the maximum yield at the application rate of 40 ㎏/10a. 4) The effect of these antibiotic fermentation residues on tomato growth was also similar to effects on rice plant showing the yield increment upon fertilizer application including two antibiotic fermentation residues but no significant differences among fertilizers. 5) According to the plant growing status, plant height, dry matter, number of effective tillers and grain number per panicle of rice and plant height and fresh weight of plant of tomato showed similar trend with yield of both plants.