• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.417-420
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• 2012

This study is about reduction reaction making 2, 4-dinitrotoluene (2, 4-DNT) to 2, 4-toluene diisocyanate (2,4-TDI) with Pd/$SiO_2$. Catalytic systems based on Pd/$SiO_2$ at about $200^{\circ}C$ and under 100 bars of carbon monoxide. We studied the effect of pyridine on the yield of the TDI. TDI was not created without pyridine, but created with pyridine, at the reaction result. According to research, homogeneous synthesis of TDI with direct carbonylation, palladium and pyridine complexion is known to catalyze. When adding pyridine the reason of TDI synthesis is palladium leaching, ICP-AES was performed to confirm it. As a result, the proportion of Pd loaded in $SiO_2$ was decreased 52% than before, after the reaction by adding 20 vol% pyridine. Generating TDI by adding pyridine might be the effect of the complex ion, which is composed of leached palladium and pyridine.

• Journal of the Korean Chemical Society
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• v.36 no.6
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• pp.791-795
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• 1992

The limiting equivalent conductances of LiCl, NaCl, KCl and KBr have been obtained in water using conductometric method from 1 to 2000 bars at $25^{\circ}C$. From the limiting equivalent ionic conductances (obtained using TATB[Tetraphenyl Arsonium Tetraphenyl Borate]method) of $Li^+$, $Na^+$, $K^+$, $Cl^-$, and $Br^-$ ions and viscosity of water at given pressure, their Stokes radii have been calculated. From the corrected radii caliberated by Nightingale method and the crystallographic radii at a given pressure, the volume of hydration-shell surrounding ion was calculated and hydration numbers of $Li^+$, $Na^+$, $K^+$, $Cl^-$, and $Br^-$ ions were obtained. From the experimental results, it was found that the hydration number of $Li^+$, $Na^+$, $K^+$, $Cl^-$, and $Br^-$ ions slightly decreased with increasing pressure. This trend may be explained by Horne's suggestion[Advances in High Pressure Research]. Comparing results of this study with those of Nakahara's, the hydration numbers of $K^+$ and $Cl^-$ ions were almost twice as large as those of Nakahara's[Rev. Phys. Chem. Japan, 42, 12 (1972)]. By comparing the present results with those of Kollman's [J. Am. Chem. Soc., 113, 2481 (1991)], the hydration number obtained by applying TATB method and Nightingale method may be inferred to be reasonable.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.6
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• pp.829-843
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• 2017

Subsea tunnel needs to be built over 50 km long to connect between nations and continents. However there are only 19 tunnels longer than 5 km until recently. And there is no history of constructing and operating tunnel longer than 50 km. In Korea, subsea tunnels with a length of more than 50 km are being planned, such as Korea~Japan, Korea~China, Honam~Jeju subsea tunnels. Because of the geographical conditions of Korea, most of these tunnels are inter-contry tunnels. So technology preemption for the subsea tunnel construction is getting more and more important. Most of these subsea tunnels are ultra-long tunnels under high water pressure conditions. So new technologies are required such as ventilation and disaster prevention of high-speed tunnels, securing of structural stability under high pressure conditions, and pressure reduction in high-speed conditions. These technologies are different from those of ground tunnels. Therefore, this paper describes the ultra-long subsea tunnel design under high water pressure of maximum 16 bars through the Honam (land) - Jeju (island) virtual subsea project. We proposed a reasonable solution to various problems such as securing structural stability in high pressure condition and ventilation disaster prevention system of ultra long-tunnel.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.129-138
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• 2007

The cases of drunk driving accidents have been steadily increasing every year. The number of accidents was quadrupled from 7,303 cases in 1990 to 25,150 cases in 2004. In addition, the proportion of drunk driving accidents to total traffic accidents was 2.9% in 1990 but it increased to 13.0% in 2003. Studies of drunk driving accidents have been focusing on analyzing psychological decisive factors, classifying drivers' individual characters and types of drunk driving accidents by considering the location of drunk driving accidents. This study assumed that drunk driving accidents would have regular characteristics in respect to spatiality and analyzed its relation with spatial factors such as, accident black spot, the location of bars, the distance of drivers' houses, and spatio-temporal distributional characteristics through drawing density distribution and connecting the time of accidents. In order to achieve the goal of this study, the individual location information was organized and drawn as types of GIS data. From the result of density distribution using Kernel Density Mapping and analysis through the coefficient of areal correspondence, it was understood that drunk driving accidents correlates with some spatial factors.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.23-31
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• 2007

Fast bridge construction has been increasingly needed according to the changed construction environment. This paper deals with quasi-static tests on precast piers for bridge substructures. One of the most crucial aspect of the design of precast prestressed concrete bridge piers is the seismic performance. Seven precast pier elements were fabricated. The amount of prestressing bars, the prestressing force, and the location and number of the joint between segments were the main test parameters. Test results showed that the introduced axial prestress made the restoration of the deformation under small lateral displacement and minor damage. However, there was no effect of the prestress when the plastic hinge region was damaged severely due to large lateral displacement. Judging from the observed damage, the design of the joints in precast piers should be done for the first joint between the foundation and the pier segment. The amount of the necessary prestressing steel may be designed to satisfy the P-M diagram according to the service loads, not by having the same steel ratio as normal RC bridge piers. In order to satisfy the current required displacement ductility, it is necessary to have the same amount of the transverse reinforcements as RC piers. As the steel ratio increases, the energy absorption capacity increases. The number of joints showed a little influence on the energy absorption capacity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.1-8
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• 2010

The Fourier series uses a vibrating wave that possesses an amplitude that is like the one of the sine curve. Therefore, the functions used in the Fourier series do not change due to the value of the frequency and that set a limit to express irregular signals with rapid oscillations or with discontinuities in localized regions. However, the wavelet series analysis(WSA) method supplements these limits of the Fourier series by a linear combination of a suitable number of wavelets. By using the wavelet that is focused on time, it is able to give changes to the range in the cycle. Also, this enables to express a signal more efficiently that has singular configuration and that is flowing. The main objective of this study is to propose a scheme called wavelet series analysis for the application of wavelet theory to one-dimensional problems represented by the second-order elliptic equation and to evaluate theperformance of proposed scheme comparing with the finite element analysis. After a through evaluation of different types of wavelets, the HAT wavelet system is chosen as a wavelet function as well as a scaling function. It can be stated that the WSA method is as efficient as the FEA method in the case of axial bars with distributed loads, but the WSA method is more accurate than the FEA method at the singular points and its computation time is less.

• Corrosion Science and Technology
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• v.13 no.1
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• pp.20-27
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• 2014

The structures of reinforced concrete has been extensively increased with rapid development of industrial society. Futhermore, these reinforced concretes are easy to expose to severe corrosive environments such as sea water, contaminated water, acid rain and seashore etc.. Thus, corrosion problem of inner steel bar embedded in concrete is very important in terms of safety and economical point of view. In this study, multiple mortar test specimen(W/C:0.4) with six types having different cover thickness each other was prepared and was immerged in seawater solution for five years to evaluate the effect of cover thickness and immersion years to corrosion property of embedded steel bar. And the polarization characteristics of these embedded steel bars was investigated using electrochemical methods such as measuring corrosion potential, cathodic polarization curve, and cyclic voltammogram. At the beginning of immersion, the corrosion potentials exhibited increasingly nobler values with increasing cover thickness. However, after immersed for 5 years, the thicker cover of thickness, the corrosion potentials shifted in the negative direction, and the relationship between corrosion potential and cover thickness was not in good agreement with each other. Therefore, it is considered that the thinner cover of thickness, corrosive products deposited on the surface of the embedded steel bar plays the role as a resistance polarization which is resulted in decreasing the corrosion rate as well as shifting the corrosion potential in the positive direction. As a result, it seemed that the evaluation which corrosion possibility of the reinforced steel would be estimated by only measuring the corrosion potential may not be a completely desirable method. Therefore, it is suggested that we should take into account various parameters, including cover thickness, passed aged years as well as corrosion potential for more accurate assessment of corrosion possibility of reinforced steel which is exposed to partially or fully in marine environment for long years.

• Korean Journal of Food Science and Technology
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• v.8 no.2
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• pp.113-118
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• 1976

For this study, from July to December in 1975, the total of 160 samples of packaged ice creams(75 samples of carton, 50 samples of cone, and 35 samples of bar), manufactued by five different plants, were collected at markets in Seoul city area. And the chemical composition and microbial quality of those were analyzed and compared with each other samples. The results obtained are as follows: 1. The average milk fat contents of ice cream samples were 6.28% in carton, 6.42% in cone and 4.94% in bar. 2. The average total solid contents of ice cream samples were 33.45% in carton, 34.22% in cone and 29.46% in bar. 3. The average total protein contents of ice cream samples were 3.45% in carton, 3.16% in cone and 2.42% in bar. 4. The average milk solids-not-fat contents of ice cream samples were 10.46% in carton, 8.52% in cone and 7.72% in bar. 5. The average milk lactose contents of ice cream samples were 6.42% in carton, 5.57% in cone and 4.94% in bar. 6. The average crude ash contents of ice cream samples were 0.86% in carton, 0.78% in cone and 0.67% in bar. 7. The average Reichert-Meissl values of ice cream samples were 28.82 in carton, 27.85 in cone and 25.97 in bar. 8. In the both experiments of standard plate count and coliform count, the samples of ice cream in cone and carton showed lesser numbers than those in the form of bars. Of a total 160 samples examined, 6 samples gave standard plate counts of over 40,000/ml and 14 samples gave coliform counts of over 10/ml.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.502-507
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• 2001

The effect of solidification rate on the microstructure of directionally solidified IN792+ Hf superalloy has been studied. Solidification sequence and precipitation behavior of the alloy have been analysed by microstructural observation. The script carbide transformed to faceted carbide with decreasing solidification rates. The incorporation of ${\gamma}$ phase into the faceted carbide was due to dendritic growth of carbides. Some elongated carbide bars formed along the grain boundaries at a solidification rate of 0.5$\mu\textrm{m}$/s. Two zones, ${\gamma}$' forming elements enriched zone and depleted zone, were found in the residual liquid area. Eutectic ${\gamma}$/${\gamma}$' nucleated in the f forming elements enriched zone. Formation of eutectic ${\gamma}$/${\gamma}$' increased the ratio of (Ti+Hf+Ta+W)/Al and induced η phase precipitation. The ratio of (Ti+Hf+Ta+W)/Al decreased at lower solidification rates due to sufficient back diffusion in the residual liquid area. Hence, the Precipitation of the η Phase efficiently suppressed at the lower solidification rate.

• Korean Journal of Health Education and Promotion
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• v.19 no.2
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• pp.57-72
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• 2002

Students spend most of their time in school. Schools have the possibility of unanticipated accidents, however, and the rate of accidents in schools is increasing. The purpose of this study were to understand the accidents that arise in schools as well as the school safety management system and by analyzing affects that school safety management system has on accidents in schools, to come lip with a preventive plan. 906 high school sophomore students attending in Seoul were surveyed 1Tom November 12th to 23rd 2001. The results were following: 1. Students surveyed comprised of the following: Male 48.9%, Female 51.1% Public Schools 32.6%, Private Schools 67.4% Boys Schools 48.9%, Girls Schools 51.1% 2. In the past year, male students had more accidents(p〈.05) in school. 3. In examining students safety management control, 94.0% said that, there is an infirmary, there is a clear distinction between the playing fields and pathways(74.8%), and the chemicals in the labs are kept in a safe manner(77.2%). The above items were generally well maintained. However, the following recorded low scores. There are warning signs in hazardous places and facilities(30.5%), There is guiding principle to examine the safeness on a regular basis(24.9%), and There are slogans and posters preventing accidents(40.3%). 4. In examining the facilities of the schools that were surveyed, the majority answered, yes to the following. There are hazardous facilities or materials at school(62.9%), There are sharp edges in educational supplies and equipment(59.8%), There are nails or other components that are sticking out of desks and chairs(75.9%), There are slippery spots in the corridors and classrooms(69.3%), There are stones, scrap metal, broken glass, and trash on the playing fields(66.6%). Furthermore, the students surveyed said, yes to the following although in low percentages. The amount of sand on the playing fields is sufficient(49.1%), The soccer and basket goal posts are fastened (53.7%), There are safety bars on the windows of classrooms and corridors (27.4%), There are safety mats on the entrance to restrooms preventing slips (14.2%), The stairs have slip protection measures(49.1%). 5. In analyzing the affect that the school safety management system has on accidents in school, schools that had slogans and posters preventing accidents had a 50% less chance of accidents(p〈.05), schools with chemicals and equipment in the labs that were safely maintained had an 80% less probability of accidents(p〈.0l), and the schools that had sharp edges in the educational supplies and equipment had an 80% greater chance of accidents(p〈.01).