• Computers and Concrete
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• v.12 no.5
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• pp.669-680
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• 2013

This paper unveils a new computer based stabilization methodology for automated modeling analysis and its experimental verification for corrosion in reinforced concrete structures under the effect of varying oxygen concentration. Various corrosion cells with different concrete compositions under four different environmental conditions (air dry, submerged, 95% R.H and alternate wetting-drying) have been investigated under controlled laboratory conditions. The results of these laboratory tests were utilized with an automated computer-aided simulation model. This model based on mass and energy stabilization through the porous media for the corrosion process was coupled with modified stabilization methodology. By this coupling, it was possible to predict, maintain and transfer the influence of oxygen concentration on the corrosion rate of the reinforcement in concrete under various defined conditions satisfactorily. The variation in oxygen concentration available for corrosion reaction has been taken into account simulating the actual field conditions such as by varying concrete cover depth, relative humidity, water-cement ratio etc. The modeling task has been incorporated by the use of a computer based durability model as a finite element computational approach for stabilizing the effect of oxygen on corrosion of reinforced concrete structures.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.84.1-84.1
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• 2010

Currently, new and renewable energy come into the spotlight, such as solar energy, wind power, fuel cell, hybrid car etc., due to the energy resource is being depleted. Especially, in order to solve like this problem, the study of solar cell manufacturing systems are being extensively researched such as vacuum process. But the major fault of the vacuum process are its expensive production price. On the order hand, Roll-to-roll printing system, the new technology of solar cell manufacturing, has low production price compare with the vacuum process. Also roll-to-roll printing system can decrease the 95% of waste water and 99.9% of harmful gasses than the vacuum process. So we addressed the roll to roll printing system for the flexible solar cell by using printing technology. This roll-to-roll printing system is comprised of various modules, such as web handling module, fine pattern printing module, dry/curing module, uniform coating module and laminating module etc.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.164-165
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• 2015

Modular construction technique is an adaptation of factory-based mass production concept in ordinary manufacturing industries to construction industry and it assumes that panels, units, etc. are fabricated in factories and assembled in construction sites. Given its structural limitations, modular construction technique is primarily used in low-story buildings whose maximum height is usually five stories, but researchers are actively studying possible adaptation of modular construction technique to high-rise building designs these days as in the case of infill-type modular construction design. Infill-type modular construction technique, most frequently used in high-rise building construction projects, completes frame construction first in reinforced concrete structures and fills unit modules in such structures. However, infill-type modular construction technique leads to longer construction schedule accompanying increase in construction cost, cost overrun due to additional of temporary work, and possible damage to units in the wake of facility construction. Accordingly, this study is performed as a basic study for the development of bottom-up infill-type modular construction technique intended to construct structural frames and fill in units sequentially in a bid to address such drawbacks of current infill-type modular construction technique.

• Computers and Concrete
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• v.20 no.2
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• pp.119-127
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• 2017

Time-dependent buckling of embedded straight concrete columns armed with Silicon dioxide($SiO_2$) nano-particles exposed to fire is investigated in the present study for the fire time. The column is simulated mathematically with Timoshenko beam model. The governing mass conservation equations to describe heat and moisture transport in concrete containing free water, water vapor, and dry air in conjunction with the conversion of energy are considered. The characteristics of the equivalent composite are determined using Mori-Tanaka approach. The foundation around the column is simulated with spring and shear layer. Employing nonlinear strains-displacements, energy methods and Hamilton's principal, the governing equations are derived. Differential quadrature method (DQM) is used in order to obtain the critical buckling load and critical buckling time of structure. The influences of volume percent of $SiO_2nano-particles$, geometrical parameters, elastic foundation and concrete porosity are investigated on the time-dependent buckling behaviours of structure. Numerical results indicate that reinforcing the concrete column with $SiO_2nano-particles$, the structure becomes stiffer and the critical buckling load and time increase.

• Geomechanics and Engineering
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• v.13 no.4
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• pp.671-683
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• 2017

Groundwater control is a significant issue in most underground construction. An estimate of the inflow rate is required to size the pumping system, and treatment plant facilities for construction planning and cost assessment. An estimate of the excavation-induced drawdown of the initial groundwater level is required to evaluate potential environmental impacts. Analytical and empirical methods used in current engineering practice do not adequately account for the effect of the jointed-rock-mass anisotropy and heterogeneity. The impact of geostructural anisotropy of fractured rocks on tunnel inflows is addressed and the limitations of analytical solutions assuming isotropic hydraulic conductivity are discussed. In this paper the unexcavated Zagros tunnel route has been classified from groundwater flow point of view based on the combination of observed water inflow and numerical modeling results. Results show that, in this hard rock tunnel, flow usually concentrates in some areas, and much of the tunnel is dry. So the remaining unexcavated Zagros tunnel route has been categorized into three categories including high Risk, moderately risk and low risk. Results show that around 60 m of tunnel (3%) length can conduit the large amount of water into tunnel and categorized into high risk zone and about 45% of tunnel route has moderately risk. The reason is that, in this tunnel, most of the water flows in rock fractures and fractures typically occur in a clustered pattern rather than in a regular or random pattern.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.11
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• pp.683-689
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• 2015

For the formation of $N^+$ doping, the antimony ions are mainly used for the fabrication of a BJT (bipolar junction transistor), CMOS (complementary metal oxide semiconductor), FET (field effect transistor) and BiCMOS (bipolar and complementary metal oxide semiconductor) process integration. Antimony is a heavy element and has relatively a low diffusion coefficient in silicon. Therefore, antimony is preferred as a candidate of ultra shallow junction for n type doping instead of arsenic implantation. Three-dimensional (3D) profiles of antimony are also compared one another from different tilt angles and incident energies under same dimensional conditions. The diffusion effect of antimony showed ORD (oxygen retarded diffusion) after thermal oxidation process. The interfacial effect of a $SiO_2/Si$ is influenced antimony diffusion and showed segregation effects during the oxidation process. The surface sputtering effect of antimony must be considered due to its heavy mass in the case of low energy and high dose conditions. The range of antimony implanted in amorphous and crystalline silicon are compared each other and its data and profiles also showed and explained after thermal annealing under inert $N_2$ gas and dry oxidation.

• Journal of environmental and Sanitary engineering
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• v.20 no.2 s.56
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• pp.47-55
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• 2005

The World Health Organization(WHO, 1998) and the United States Environmental Protection Agency (USEPA, 1992) recommended $2{\mu}\;guranium/{\ell}$ in drinking water as a guideline. The Korea Institute for Environmental Research recently reported that the radioactive pollution in ground water was almost negligible In Korea$(1999\~2002)$. Cs were cast into beads(2mm in wet form) and treated with hexamethylene diisocyanate for stability in acidic aqueous solution through cross-linking of the beads surfaces. The removal study was carried out in a static batch system and a flow system. In the static system, a certain amount of sample water was confined in a vessel and beads(dry weight 0.5g) were packed into it in order to adsorb uranium for a certain period of time. Afterwards the remaining uranium in water vessel was determined by inductively coupled plasma mass spectrometry. The effective pH range was 4 to 8. The smaller the size of beads, the better the removal efficiency. Furthemore, the lower the flow rates, the higher the removal efficiency. The results showed that chitosan beads can be effectively used for the removal of uranium contained in water.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.12
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• pp.1049-1059
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• 2003

R410A is considered as an alternative refrigerant to R22 for air conditioners. An experimental investigation was made to study the characteristics of the heat transfer and pressure drop for R410A flowing in a fin-and-tube heat exchanger used for commercial air-conditioning units. Experiments were carried out under the conditions of inlet refrigerant temperature of 6$0^{\circ}C$ and refrigerant mass flux varying from 150 to 250 kg/$m^2$s for refrigerant side. The inlet air has dry bulb temperature of 35$^{\circ}C$, relative humidity of 40% and air velocity varying from 0.68 to 1.6 m/s. Experiments show that air velocity decreased by 16% is needed for R410A than that of R22 for subcooling temperature of 5$^{\circ}C$, which resulted in air-side pressure drop decrease of 15% for R410A as compared to R22. As a consequence, in order to provide the same design condition of a condenser, the fan requires lower electric-power consumption with R410A than that with R22.

• KSBB Journal
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• v.19 no.4
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• pp.291-294
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• 2004

The aim of this study was to figure out the antibacterial pattern of leucocin A transformed yeast with culture. Dry cell weight, total secreted protein, and antibacterial activity were increased to 12 hour, after then they showed decrease while protease activity represented the opposite pattern. This implied the production of leucocin A was growth-related. Compared to the result of one hour culture broth, antibacterial activity was about 3.24 fold at 12 hour culture. Maximum growth inhibition rate was 70.57% compared to nontransformed yeast. As the increase of protease in the supernatant, the antibacterial activity was diminished. This study could permit the mass production of bacteriocin to use as antibiotics or food preservatives.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.4
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• pp.431-441
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• 2011

Microbial colorants produced from Zooshikella sp. were developed as a reddish dye for fabrics. The reddish colorants were extracted from cell mass of Zooshikella sp. using 100% ethanol and were identified as prodiginine by 1H-NMR and FT-IR analysis. Microbial prodiginine had a maximum spectrophotomatric absorbance at 530nm and were chemically stable and 30 to $60^{\circ}C$. The microbial prodiginine could dye natural fibers such as cotton, silk, and wool as well as synthetic fibers such as nylon. The maximum K/S values of the dyed fiber were shown at 540 run with a color appearance of RP (reddish purple). Silk and nylon had an excellent dyeability among the experimental fibers. The optimum pH for the dyeing of experimental fibers was at pH 3.0 and dyeability was improved as the temperature increased. The cover change of dyed multifiber fabrics with the microbial prodiginine were measured after washing with detergents and a dry cleaning solvent for the selection of a proper fabric against microbial prodiginine. Among the experimental fibers, silk and nylon did not show significant color change after washing. Therefore, under the criteria of dyeability, silk and nylon were excellent fabrics for being dyed by microbial prodiginine.