• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1639-1645
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• 1991

Because of the important role LD converters play in the production of high quality steel, various dynamic models have been attempted in the past by many researchers not only to understand the complex chemical reactions that take place in the converter process but also to assist the converter operation itself using computers. And yet no single dynamic model was found to be completely satisfactory because of the complexity involved with the process. The process indeed involves dynamic energy and mass balances at high temperatures accompanied by complex chemical reactions and transport phenomena in the molten state. In the present study, a mathematical model describing the dynamic behavior of LD converter process has been developed. The dynamic model describes the time behavior of the temperature and the concentrations of chemical species in the hot metal bath and slag. The analysis was greatly facilitated by dividing the entire process into three zones according to the physical boundaries and reaction mechanisms. These three zones were hot metal (zone 1), slag (zone 2) and emulsion (zone 3) zones. The removal rate of Si, C, Mn and P and the rate of Fe oxidation in the hot metal bath, and the change of composition in the slag were obtained as functions of time, operating conditions and kinetic parameters. The temperature behavior in the metal bath and the slag was also obtained by considering the heat transfer between the mixing and the slag zones and the heat generated from chemical reactions involving oxygen blowing. To identify the unknown parameters in the equations and simulate the dynamic model, Hooke and Jeeves parttern search and Runge-Kutta integration algorithm were used. By testing and fitting the model with the data obtained from the operation of POSCO #2 steelmaking plant, the dynamic model was able to predict the characteristics of the main components in the LD converter. It was possible to predict the optimum CO gas recovery by computer simulation

• Nuclear Engineering and Technology
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• v.24 no.2
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• pp.154-162
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• 1992

Two major goals for chemical cleaning on the secondary side of nuclear steam generators are to remove sludge effectively and to minimize corrosion of base metals. In this work, electrochemical and sludge dissolution behaviors have been investigated in order to find out which parameters are critical and important during a copper removal process for chemical cleaning and to evaluate safety aspects and effectiveness of two major copper removal processes developed commercially in foreign countries. Hydrogen peroxide is vert effective for the process to use EDTA, NH$_4$OH and EDA at 38$^{\circ}C$ to control the potential of copper in a potential range sood for copper sludge removal. Corrosion rates for carbon steel SA 285 Gr.C and Alloy 600 are very small during this process if it is controlled properly. However, the corrosion rate of SA 285 Gr.C will be increased greatly if its corrosion potential is maintained below -450mV. The process to use EDA and ammonium carbonate is effective at 6$0^{\circ}C$ to dissolve copper sludge if the corrosion potential of copper can be controlled above -200mV. However, it is very difficult to raise the corrosion potential of copper to this range by air blowing and stirring.

• Journal of Bio-Environment Control
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• v.29 no.1
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• pp.73-79
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• 2020

The objective of this study is to analyze the heat transfer loss of covering materials in a single-span plastic greenhouse under the steady-state wind environment. To achieve this objective, the following were conducted: (1) design of a small-scaled wind tunnel (SCWT) to analyze heat losses of the greenhouse and its performance; (2) determination of the overall heat transfer coefficient (OHTC) for the covering materials using a small-scaled greenhouse model. The SCWT consists of the blowing, dispersion, steady flow, reduction and testing areas. Each part of the SCWT was customized and designed to maintain air flow at steady state and to minimize the variances in the SCWT test. In this study, the OHTCs of the covering materials were calculated by separating each with the roof, side wall, front and back of the small-scaled greenhouse model. The results of this study show that the OHTC of the roof increases as wind speed increases but the zones in which the increase rate of the OHTC decreased, were distinguished by wind tunnel wing speed of 2 ms^-1. For the side wall, the increase rate of the OHTC was particularly higher in the 0-1 ms^-1 zone.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.1
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• pp.65-78
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• 2007

The pollutants (Rn, CH, CO, HS, radioactive gas from radiolysis) were generated from the process of construction and operation of underground repository, and after disposal of low-intermediate radioactive waste inside there must be controlled by a ventilation system to distribute them in area where enough air is supported. Therefore, a suitable technical approach is needed especially at an underground repository that is equipped with many entry tunnels, storage tunnels, exhaust-blowing tunnels, and vertical shafts in complicated network form. For the technical approach of such a ventilation system, WIPP (Waste Isolation Pilot Plant) in U. S and SFR (Slutforvar for Reaktorafall) low-intermediate radioactive waste repository in Sweden were selected as the models, for calculating the required air quantity, organizing a ventilation network considering cross section, length, surface roughness of the air passage, and describing a calculation of resistance of each circuit. Based on these procedures, a best suited ventilation system was completed with designing proper capacity of fans and operating plan of vertical shafts. As a result of comparing the two repositories based on the geometry dimensions and ventilation facility equipment operation, more parallel circuit as in WIPP, brought decrease in resistance for entire system leading to reduce of operating costs, and the larger cross-sectional area of the SFR, the greater the percentage of disposal capacity. Accordingly, the mixture of parallel circuit of WIPP repository for reducing resistance and SFR repository formation for enlargement of disposal capacity would be the most rational and efficient ventilation system.

• Journal of the Korean Graphic Arts Communication Society
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• v.31 no.1
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• pp.39-49
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• 2013

Nowadays the printing market has shift from 2D(two dimension) industry to 3D(three dimension) industry, along with IT. With rapidly changing market, it's true that the effort to develop the printing materials and upgrade the printing qualities is produced actively in the country. Particularly, the differences in printing materials can often determine the quality of printings in the printability. In the case of the printability of offset, 9 items(paper, ink, order of printing, ink supply, blowing-up halftone, grey balance, key color(base color), overlap efficiency, quality at the halftone dot reproduction etc.) are usually considered as the important factors and used to estimate the printability at abroad. However, in domestic, ink-jet paper is not used for the printing/publishing by ink-jet printing for digital, but done mainly for offset printing. Because the paper of gloss coated type, which is the ink-jet paper, has high price, it's too hard to manufacture massively printing/publishing. Also, in the case of the paper of uncoated type, in spite of its reasonable price rather than the former, the type of uncoated one also has demerit that the ink-jet paper has a clear difference between the front and the back. Therefore, it's tough reality that Ink Jet paper is hardly taken advantage of as the printing/publishing. Thus, what is done in the first to print and/or publish on ink-jet paper is that the front and the back must be printed evenly, and appropriate to the printability of ink-jet. Although there're some kinds of ink-jet paper in the country, it has not been produced in true domestic production yet. In addition, thanks to the brightness of fluorescence brightening agent, the foreign product can offer the good-qualified one-time printing. But when it comes to the printing/publishing, there're difficulties that it may cause the Ocular Fatigue because of long-term exposure of the eyes to text. This research tries to find out the optimum ink-jet paper in domestic for the printing/publishing by studying on the printability of ink-jet on digital web-printing. And it also tries to look for the paper's brightness which can be reduce the possibility to cause the consumers' Ocular Fatigue.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.10
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• pp.1129-1135
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• 2005

In this study. the applicability of a rotating reactor for the oxidative removal of aqueous humic substances extracted from the Han River in Seoul, Korea was investigated. As air blowing for proper mixing of $TiO_2$ photocatalyst could inhibit UV-irradiation between a UV lamp and photocatalyst by air bubbles, a rotating reactor with some baffles was used for better UV-irradiation effect in this study. Han River humic substances are different from the other commercial humic substances(e.g., from Aldrich and International Humic Substance Society). Their characteristics were investigated with structural and spectroscopic analyses using FT-IR(Fourier transform-infrared), and $^{13}C$-NMR (nuclear magnetic resonance). The humic substances were extracted by XAD-7HP and treated with $TiO_2$-coated hollow beads under UV-A and UV-C irradiation in order to solve problems of separation and recovery of photocatalyst after reaction. At approximately 5 mg/L of initial TOC concentration, pH 3 and $2.0\;g-TiO_2/L$ dose, photocatalytic oxidation of Han River humic substances showed the optimum removal efficiency. Also, UV-C and UV-A lamps showed similar TOC removal efficiency. However, under UV-C irradiation, Han River humic substances were degraded to smaller compounds and increased the proportion of low molecular weight fractions compared to UV-A.

• Elastomers and Composites
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• v.46 no.4
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• pp.343-351
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• 2011

We prepared polyurethane foam/cloisite30B/phosphates composites and characterized their rise time, density, cell morphology, and thermal properties. The composites were synthesized with polyadipatediol-cloisite30B composite (f=2.0), polyether-polyol (f=4.6), polymeric 4,4-diphenyl methane diisocyanate (f=2.5), and D-580 (phenyl polyoxyalkenyl phosphate). As a blowing agent, cyclopentane and distilled water were used at various concentrations of D-580 from 0 to 2.81 wt%. The rise times of PUF/Closite30B/Phosphate composites blown with distilled water were faster than those blown with cyclopentane by 30%. The composites blown with cyclopentane had spherical-shape cells and the cell diameter was decreased with increasing D-580 wt%. While $T_g$ of the composites blown with cyclopentane linearly decreased with increasing the D-580 content, the $T_g$ of the composites blown with distilled water increased with the D-580 content. All PUF/Closite30B/Phosphate composites began to decompose from $250^{\circ}C$. The composites blown with cyclopentane showed the second thermal decomposition at temperatures higher than $500^{\circ}C$. The thermal stability of all composites increased with the D-580 content. The effect of D-580 on the thermal stability of the composites was measured higher at the composites blown with distilled water.

• The Journal of Engineering Research
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• v.6 no.1
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• pp.97-109
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• 2004

The synthesis and crystal structure of amorphous calcium carbonate obtained from gas-liquid reaction of CaO-$C_2 H_5 OH$-$CO_2$ system according to change of added amount of calcium oxide by blowing $CO_2$ gas and reaction time using ethanol and ethylene glycol were investigated by electric conductivity, X-ray diffraction, and scanning electron microscope. The powdery or gelatinous phases were prepared by passing $CO_2$ gas at a flow rate of 1$\ell$/min into the suspensions containing 10~40g of CaO in mixing solutions 900ml of $C_2 H_5 OH$- and 100ml of ethylene glycol. By rapid filtration and drying the both phases at $60^{\circ}C$ under reduced pressure, the phases converted to the spherical vaterite and amorphous phase. The stable phase of amorphous calcium carbonate(ACC) was formed in the region pH 7-9 but the formation regions of amorphous phase were remarkably affected by pH in the mother liquor. It seems that a part of ACC changed into chain calcite as an intermediate products. The initial reactants prior to the formation of precipitated calcium carbonate is ACC. And ACC is unstable in the aqueous solution and crystallizes finally to calcite by the through-solution reaction. Especially ACC was produced or gelatinous phase which precipitated from the reaction of CaO-$C_2 H_5 OH$-$CO_2$ system.

• Journal of Preventive Medicine and Public Health
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• v.18 no.1
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• pp.83-89
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• 1985

The result of the close analysis of the health status of 549 working students (the experimental group) of a high school attached to an industry and that of 1,259 non-working students (control group) based on the question provided by CMI from 1st, June to 31st, July 1984 has been revealed as follows: 1. In contrast with the control group, the experimental one is statistically noticeably higher (p<0.01) in their average complaints both in terms of the whole items(A-R) and the physical items (A-L) 2. In the experimental group, particularly the item(L) for habits has the highest rate of average complaints, followed by the item(B) for the respiratory system and the item(E) for the musculoskeletal system. 3. The average complaints of the individual class in both the experimental group and the control group have the tendency to be on the increase accordingly as the school year goes up, and the increasing rate of the experimental group has turned out to be higher than that of the control group. 4. The average complaints of the experimental group based on residential types are the highest(34.7%) in the case of cooking food for oneself, followed by a dormitory(30.3%), and one's own house (28.5%). 5. The average complaints based on the individual working place has been found out to be higher than the rest in the item of the miscellaneous disease of the blowing and roving parts, the respiratory system of the carding part, the fatigability of the spinning part, the tension of inspecting part.

• Korean Journal of Food Science and Technology
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• v.25 no.4
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• pp.379-385
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• 1993

Antioxidative effectiveness and oxidized products in mixture of methyl linoleate(ML) and phenolic compounds were investigated under oxygen blowing at $37^{\circ}C$ for 9 days. Caffeic acid (3,4-dihydroxy cinnamate ; CML) and phloroglucinol(1,3,5-trihydroxy benzene ; PML) showed higher antioxidative effectiveness for methyl linoleate than 0.05% ${\alpha}-tocopherol$ (TML). Oxidized products in ML group were methyl 8-(2-furyl)-octanoate, 9,13-trans, cis hydroperoxide isomer, 9,13-trans, trans hydroperoxide isomer, and 9-TMSO-12,13-epoxy-10-octadecenoate. In CML group the oxidized products were methyl-8-(2-furyl)-octanoate, 9-trans, cis hydroperoxide isomer and 9-trans, trans hydroperoxide isomer, but 13-hydroxy isomer was not identified. It was shown that CML were oxidized more slowly than ML group and at 6th day of oxidation, caffeic quinone was found to be major oxidized product of caffeic acid. Oxidixed Products in PML group were methyl-8-(2-furyl)-octanoate, 9-trans, cis hydroperoxide isomer, and 9-trans, trans hydroperoxide isomer but phloroglucinol was not oxidized even at the 9th day of reaction.