• Journal of Korean Society of Environmental Engineers
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• v.27 no.3
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• pp.280-285
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• 2005

The method of chemical absorption has been presented to separate and recover acid gases like $CO_2\;and\;H_2S$. But, this method has some problems such as loss of valuable amine and operational problems (forming, corrosion and fouling) by degradation. In this study, we investigated the degradation characteristics of aqueous AMP solution containing additives such as HMDA, MDEA and piperazine. The degradation was affected by temperature and process time. AMP solution absorbing $CO_2\;and\;H_2S$ was degraded 105% and 23% more than pure AMP at $120^{\circ}C$ respectively. In addition, all the additives were degraded significantly as the temperature increased. The order of the degraded amount of additives mixed in the AMP solution containing absorbed $CO_2$ was as followings : HMDA > piperazine > MDEA.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.65-74
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• 2009

Glass fiber reinforced polymer (GFRP) bars are sometimes used when corrosion of conventional reinforcing steel bar is of concern. In this study, a total of 36 beams and one-way slabs reinforced using GFRP bars were tested in flexure. Four different GFRP bars of 13 mm diameter were used in the test program. In most test specimens, the GFRP bars were lap spliced at center. All beams and slabs were tested under 4-point loads so that the spliced region be subject to constant moment. Test variables were splice lengths, cover thicknesses, and bar spacings. No stirrups were used in the spliced region so that the tests result in conservative bond strengths. Average bond stresses that develop between GFRP bars and concrete were determined through nonlinear analysis of the cross-sections. An average bond stress prediction equation was derived utilizing two-variable linear regression. A splice length equation based on 5% fractile concept was then developed. As a result of this study, a rational equation with which design splice lengths of the GFRP bars can be determined, was proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.789-792
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• 2008

Recently, the deteriorations of RC bridge decks on express-way are frequently observed. The major cause of deterioration for the RC concrete bridge decks exposed to de-icing chemiclas would be chloride-induced reinforcement corrosion. Therefore, Waterproofing is necessary for improvement of bridge deck durability and comfortable utility. In this study is to investigate the appearance of deterioration and properties of concrete core from the collect in a bridge deck. The results of this study shows that penetration waterproofing agents shows low infiltration depth and low water-repellent. It appears that the damaging of concrete deck is primarily waterproofing system rather than physical property.

• Journal of Radiation Protection and Research
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• v.2 no.1
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• pp.1-8
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• 1977

A base of photographic posi-film which is commecially available has been found to be a possible alpha-particle track detector. Its neutron dosimetric characteristics, i. e., alpha-particle track registrating efficiency and optimum condition of track formation by chemical etching, have been determined experimentally. The range of neutron fluence and dose capable of being measured by a neutron dosimeter consisting of alpha-particle radiator foils $(^{10}B\;and\;^{27}Al)$ and posi-flim solid state track detector, has been estimated on the basis of experimental results and theoryetical background. This detector seems to be useful for neutron dosimetry because of many favorable properties, i. e., simplicity, cheapness and a wide range of sensitivitiy.

• Journal of Korean Society on Water Environment
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• v.18 no.4
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• pp.379-386
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• 2002

In this study, estimation model for iron compound originated from upflow, anaerobic fixed bed reactor, which treats sewage domestic wastewater, was developed. The estimation model was formulated by a mathematical expression which was based on the mass balance. Below the HRT of 60 minute, sulfide concentration combining with iron $FeS_2$ is the highest because the maximum sulfate consumption rate $V_{maxS}$ and half-saturation constant of sulfate $K_{mS}$ exert an important effect on the estimation model as temperature was increased. But increment of $FeS_2$ concentration is weakened above the HRT of 60 minutes and represent the lowest value at the HRT of 108 minutes. It implies that liquid phase distribution ratio of sulfide ${\alpha}r$ becomes lower as temperature was increased. While phosphorus concentration combining with iron $Fe_3(PO_4)_3$ is increased as HRT and temperature are increased, which is affected by phosphorus removal rate constant $k_p$. As the result of estimating the iron concentrations of corrosion by the model, the concentration of iron corrosion is higher than any other at the HRT of 108 minute and $20^{\circ}C$. The predicted values were compared with measured ones at different HRT(13.5, 27, 54, 108 min) and temperature(20, 25, $30^{\circ}C$). The experimental data could be fitted with the simulated curves. Therefore, the mathematical expression could be applicable to design full-scale wastewater treatment plants.

• Journal of Technologic Dentistry
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• v.34 no.4
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• pp.337-344
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• 2012

Purpose: This study examined the corrosion level by alloy type and pH, and used the corrosion levels as the dental health data. The study utilized one Ni-Cr alloy for the full and removable partial denture metal frameworks and two Ni-Cr alloys for porcelain-fused-to-metal crown, among the non-beryllium dental casting non-precious Ni-Cr alloys. Methods: The alloy specimens were manufactured in $10cm^2$ and stored in the corrosive solution(pH 2.2-4.4) in the electrical water bath($37^{\circ}C$) for seven days. Afterwards, the metal ions were quantitatively analyzed using the ICP. Results: Of the three metal alloys, Bellabond-Plus$^{(R)}$alloy and SOLIBOND N$^{(R)}$alloy, with 22% or higher chrome chemical contents, had higher corrosion resistance than Jdium-100$^{(R)}$alloy with 20% chrome chemical content. In all three alloys, the corrosion of Ni was highest, and metal ion corrosion was higher in the pH 2.2 corrosive solution. Conclusion: Although Ni-Cr alloy was not very corrosive, a Ni-allergic patient should not have Ni-Cr alloy prosthesis. The Ni-Cr alloy for porcelain-fused-to-metal crown should be designed for the dental porcelain to cover the whole crown.

• Atmosphere
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• v.20 no.3
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• pp.379-386
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• 2010

Impact of global warming on the ocean environment is reviewed based on most recently published publications. The most significant impact of global warming on marine environment is due to the melting of mountain and continental glaciers. Ice melting causes slow down and/or shut down of thermohaline circulation, and makes hypoxic environment for the first time, then makes anoxic with time. This can cause decreasing biodiversity, and finally makes global extinction of animals and plants. Furthermore, global warming causes sea-level rise, soil erosion and changes in calcium carbonate compensation depth (CCD). These changes also can make marine ecosystem unstable. If we emit carbon dioxide at a current rate, the global mean temperature will rise at least $6^{\circ}C$ at the end of this century, as predicted by IPCC (Intergovernmental Panel on Climate Change). In this case, the ocean waters become acidic and anoxic, and the thermohaline circulation will be halted, and marine ecosystems collapsed.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.78-83
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• 2012

Steel fiber reinforced shotcrete in tunneling construction has some problems in terms of constructability, durability and lots of rebound wastage. In order to resolve these problems, this pater proposes polyamide fiber reinforced shotcrete technology. And this paper presents the results of experimental construction of the polyamide fiber reinforced shotcrete technology. The results of the study are as follows. 1. The polyamide fiber reinforced shotcrete suggested in this paper shows outstanding mechanical performance that meets various Korean tunnel construction design criteria. 2. In addition, the results of experimental constructions show that the polyamide fiber reinforced shotcrete creates less rebound and wasted product than the steel fiber reinforced shotcrete. Based on the above results, it is concluded that the polyamide fiber reinforced shotcrete technology can be used as economical and environmentally friendly construction of tunnel.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.535-541
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• 1997

It is proper that the load distribution and the actual stress of members is analyzed by field measurement in estimating to the behavior of truss railway bridges, but those procedures are very difficult. So, the studies for the deduction of the stress, using the indirect data which are able to get from the research and investigation without field measurement, are needed. In this study, to investigate quantitically the variation of the stress of members, the stresses are obtained from the simulation which is considered the the reduction of the section area and the stiffness due to the corrosion and the degree of the stress ratio and the distribution is calculated. As the results, the stress of truss members is almost lineary increased to the decreasing of the area and the lower chord is greatly affected. And the increasing of the stress is predicted by the superposition to the results of the amount of that in each members.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.71-83
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• 2008

In this paper, the basic principle, the application and the limitation of Infrared thermography technique to detect defects in different kinds of concrete structures are reviewed. Considered are voids beneath the concrete surface with experiments, delamination between concrete surface and fiber reinforced polymer sheet, the deterioration of steel bars in reinforced concrete, surface defects in historical buildings, pavements, bridges, and railway track graves. As a result, we conclude that infrared thermography methods are useful for fast detecting defects; however, they are influenced by environmental factors, specially temperature. Therefore it is recommended to use the infrared thermography technique with other NDT equipments to expect better result.