• Plant Journal
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• v.12 no.1
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• pp.29-36
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• 2016

It is becoming increasingly important to make use of alternative energy source. because It is not able to rely on only fossil fuel for the recent increasing demand of energy consumption. With this situation, lots of studies for utilizing low grade energy such as industrial waste heat, solar energy, and geothermal energy have been conducted. The aim of this study is to predict the operation characteristics of working fluid by using performance analysis program (ThermoFlex) through the system analysis which is not mixing district return water but using ORC(Organic Rankine Cycle, hereinafter ORC) as a downstream cycle when accumulating district heating (hereinafter DH). In this study, We conducted the performance analysis for the case which has the district heating water temperature($120^{\circ}C$) and Flow rate of $163m^3/h$ (including District Heating return water flow), and examined several working fluid which is proper to this temperature. The case using R245fa (which is the best-case) showed 269.2kW power output, 6.37% efficiency. Additionally, Cut down on fuel was expected because of the boiler inlet temperature increase by being Formed $57.3{\sim}85^{\circ}C$ in a temperature of district heating return water, depending on a pressure change of a condenser in ORC system.

• Conservation Science in Museum
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• v.6
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• pp.55-66
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• 2005

Three types of epoxy resins (Epo-Tek 301, Araldite 103, and Araldite 106) and three types of pigments (bunche, pastel, and conté), which are materials for porcelain restoration, were selected as examination materials. The tone change, porosity, and sedimental resulting from the mixtures of varying ratios of these three materials were observed. Samples were also made from the mixture of Epo-teck 301, four kinds of white pigments, and six types of fillers and subjected to ultraviolet ray penetration for 200 hours to observe the oxidation of the epoxy resins. The result showed that the chemical composition of pastel drastically changed when mixed with Epo-tek 301. Although bunche and conté displayed clear colors, those of conté were less clear when it was mixed with other substances. Adding a small amount of Epo-tek 301 tended to be driven into the corner, whereas mixing a large amount caused saturation and boiling. On the other hand, AW 106 did not display clear colors owing to its high viscosity; when mixed in large amounts, however, the clarity of colors improved. For AY 103, a similar standard of color clarity was maintained regardless of the mixture ratio. The following was ranked according to the level of porosity: [Pastel>bunche≒conté]. In terms of sedimentary, however, [bunche>conté>Pastel], [Epo-tek 301> AY 103> AW 106]. The result of measuring the degree of yellowing revealed that titanium, pastel, silicon dioxide, and kaolin tended to turn yellow, whereas bunche, conté, diatomaceous earth, and calcium hydroxide tended to resist yellowing.

• Nuclear Engineering and Technology
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• v.14 no.4
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• pp.186-195
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• 1982

The steam line break accident for Kori Unit 1 is analyzed by a code SYSRAN which calculates nuclear power and heat flux using the point kinetics equation and the lumped-parameter model and calculates system transient using the mass and energy balance equation with the assumption of uniform reactor coolant system pressure. The 1.4 f $t^2$ steam line break accident is analyzed at EOL (End of Life), hot shutdown condition in which case the accident would be most severe. The steam discharge rate is assumed to follow the Moody critical flow model. The results reveal the peak heat flux of 38% of nominal full power value at 60 second after the accident initiates, which is higher than the FSAR result of 26%. Trends for the transient are in good agreement with FSAR results. A sensitivity study shows that this accident is most sensitive to the moderator density coefficient and the lower plenum mixing factor. The DNBR calculation under the assumption of $F_{{\Delta}H}$=3.66, which is used in the FSAR with all the control and the shutdown assemblies inserted except one B bank assembly and of Fz=1.55 shows that minimum DNBR reaches 1.62 at 60 second, indicating that the fuel failure is not anticipated to occur. The point kinetics equation, the lumped-parameter model and the system transient model which uses the mass and energy balance equation are verified to be effective to follow the system transient phenomena of the nuclear power plants.lear power plants.

• Journal of the Korean Wood Science and Technology
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• v.11 no.1
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• pp.12-17
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• 1983

The shear strength of plywoods using Douglus-fir bark powder and particlebard sander dust(PSD), abandoned materials in plywood and particleboard industries, as extender to UF resin, was compared with that of plywoods using wheat flour. Extenders were mixed at the rate of 0%, 5%, 10%, 20%, and 30% of UF resin weight. In obtained results, the dry shear strength of all extended plywoods was highest at extending ratio 5% and the wet shear strength was highest at no extending and 5%. Douglas-fir bark powder-and PSD-extended plywoods had as high dry and wet shear strength as wheat flour-extended plywoods up to extending ratio 10% and 20% respectively. But at 300%, wheat flour-extended plywoods had higher shear strength. Douglas-fir bark powder and PSD size should have been reduced (enough to pass through 325 mesh screen) in order to develop the satisfactory mixing, spreading and plywood bond quality. But in this study the powders to pass through 100 mesh screen were used.

• Journal of the Korea Organic Resources Recycling Association
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• v.9 no.3
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• pp.104-110
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• 2001

In this study, the effect of physico-chemical variables on sludge conditioning was determined to enhance dewaterability of effluent produced from the thermophilic anaerobic digestion of food waste. The gas production rate and methane content during the anaerobic digestion of food waste were $1.1m^3/kg$ VS and 63%, respectively, and the biodegradability of volatile solids was 87.5%. The concentrations of CODcr, TKN and TP of effluent from digestor were 18,500mg/L, 2,800mg/L, and 582mg/L, respectively. At the jar test to screen the flocculant for the dewatering of effluent from digestor, $FeCl_3$ and strong cationic polymer were effective on making flocs in the effluent. The condition of flocculation of effluent were 500mg/L of $FeCl_3$ and 50-100 mg/L of strong cationic polymer, respectively. As the result of measuring of dewaterability potential of effluent to determine the mixing ratio between $FeCl_3$ and polymer by capillary suction time(SCT), optimum condition was 500mg/L of $FeCl_3$ and 80mg/L of strong cationic polymer.

• Korean Journal of Health Education and Promotion
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• v.20 no.2
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• pp.95-112
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• 2003

Objectives： Oral health care program for the elementary school children (ESOHCP) should be met the first priority because dental caries are highly sensitive and prevalent among them. This study was performed to enhance the efficiency of ESOHCP, and their oral health promotion. Methods： The Subjects were 346 students (3rd grade 163, 6th grade 185) of one elementary school in Busan. Dental IQ and actual oral health status； the decayed, mixing and filling teeth were checked through questionnaire and oral health examination from April to June 2002. Dental IQ was presented out of one hundred, and data analysis was done using SAS (ver 8.1) program. Results： The students' cognitive level about the causative and preventive factor of dental caries was relatively high. However, the practical aspects of preventive behavior - tooth brushing； three times per day (20％), three minutes per time (22％), oral health examination； one time per three months (10％) left much to be desired. And, only 27％ of the subjects had experienced in school oral health education. The mean level of dental IQ was 79 out of 100, and 51 ％ and 42％ of them had the decayed and teeth with filling, respectively, with the rate of DMFT 82％, DT 43％, FT 57％. The level of dental IQ was higher in case of having his (her) own tooth brush (p＝0.072), standard tooth brushing (p<0.001) three times per day, post meal, three minutes per time, present experience of oral health examination (p<0.001) and dental clinic visit (p<0.001). The grade of caries was more serious in case of 6th grade (p＝0.059), an absence of his (her) own tooth brush (p＝ 0.090), present experience of oral health examination (p＝0.021), and an absence of regular dental clinic visit (p＝0.003). The frequency of oral health examination (γ＝ 0.620), tooth brushing； times per day (γ＝0.445), post meal (γ＝0.355), expending times per brushing (γ＝0.352), right cognition to the treatment of caries (γ＝0.401), positive attitude to dental treatment (γ＝0.387), the frequency of dental clinic visit for the past one year (γ＝0.152) showed significant correlation with dental IQ. In the multivariate analysis, dental IQ was influenced by the frequency of oral health examination, right cognition to the cause of caries, times of teeth brushing per day, right cognition to the treatment of caries, etc., with adjusted R2＝0.857. Conclusion： Though the students' cognitive level about the causative and preventive factor of dental caries was high, the practical aspects of preventive behavior left much to be desired. Ant the current ESOHCP considered to be still inefficient. However, frequent dental visits had apparent correlation with hish level of dental IQ. The specialized and practical program should be needed for the efficient ESOHCP. Harmonized effort from educational, health and dental society is essential.

• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.285-293
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• 2001

To improve the vulnerable point and the mechanical property of the existing lightweight foamed concrete, this study was intend to manufacture the lightweight foamed concrete with wasted expanded poly-styrene, examinate and analyze the mechanical property of its. The experiment was being processed with mixing the wasted expanded poly-styrene maximum 40 % by stages and which was mainly basis on the practical mixture. The results of the experiment are following. The flow value is most affected by the mixtured rate of the wasted expanded poly-styrene. The more the mixtured ratio, the less the flow value and the more the more the unit quantity of cement and the W/C, the more the flow value. The apparent specific gravity indicated 0.31∼0.54 and which is seemed to be mainly included in the 0.4 degree and 0.5 degree that are regulated in the KS F 4039. The more the mixtured wasted poly-styrene ratio, the less the apparent specific gravity. The absorbing ratio which was depend on the mixture condition indicated 11 ∼46% and the more the mixtured ratio of the wasted expanded poly-styrene, the less the absorbing ratio remarkably. The compressive strength of the lightweight foamed concrete had a tendency to increase as the mixtured ratio of the wasted poly-styrene, the ratio quantity of cement and the apparent specific gravity increasing but as the ratio of bubble decreasing. The W/C affected little.

• Journal of Environmental Science International
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• v.16 no.10
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• pp.1179-1187
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• 2007

This paper represents the statistical characteristics of sources and receptors for road traffic noise in apartment complex. Also we suggested that the site-specific characteristics of vertical and horizontal distributions in the complex apartment have been derived using a different analysis for evaluating levels of Leq1h by the apartment floor at a given distance from a road in terms of the flow rate, the mean speed of the traffic, and the percentage of the type vehicles in the day and night periods. As a result, the contribution orders of traffic quantity by the type of vehicles showed as followed: light vehicle>medium vehicle>heavy vehicle>motorcycle. Especially, the mixing ratio of entering the road on the heavy vehicle in the daytime was two times higher than that of in the night. The speed in all types of vehicle is in the range of 41 and 81 km/hr and noise level was not significantly different in day and night-time. The sources of road traffic noise had different variations and uncertainties using a random variable and probability distribution. The sound distribution to receptors by the apartment floor showed S curve between 1st floor and $15^{th}$ floor With the normality test, the normal distributions using Anderson-Darling Test followed $1^{st},\;3^{th},\;13^{th}$ and $15^{th}$, floor in the daytime and all floors except $7^{th}$ floor in the night (p>0.05). And also, the value of the pearson correlation coefficient (r) obtained in this study have significantly different at the range of floor. In conclusion, the results suggested that the distribution characteristics of levels of $Leq_{1h}$ on the sources and receptors of road traffic noise in apartment complex must be improved and developed on the guideline of regulation of road traffic noise.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.355-365
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• 2015

This study examined the fluidity and strength properties, water resistance, durability, and freeze-thaw of cementless loess mortar using an eco-friendly hardening agent. The experimental result indicates that 28 days compressive and flexural strength of the loess mortar was increased regardless of the weathered granite soil and loess mixture ratio as the replacement ratio of the hardening agent increases. The strengths were significantly increased until 14 days regardless of the hardening agent, while the effect on the strengths increasement was relatively low after 14 days. Thus, the strength development of loess mortar concrete was found to be faster than that of the normal concrete. In addition, when the hardening agent of 10% was used, the average flexural strength was 1.7MPa which is insufficient compared to the 28-day flexural strength of 4.5MPa for the paving concrete. However, the flexural strengths of the loess mortar concrete using the hardening agents of 20% and 30% were 4.0MPa and 5.3MPa, respectively. Thus, the hardening agent need to be at least 20% so that the loess mortar can be used for paving concrete. The experiment for water resistance shows that the repeated absorption and dry reduced mass regardless of the mixing ratio of the loess. The maximum length change also decreased with increasing the substitution rate loess mixture ratio and the hardening agent. The result of the freeze-thaw resistance test indicates that the relative dynamic modulus of elasticity at 300 cycle freeze-thaw with the hardening agents of 20% and 30% were 75% and 79%, relatively. Thus, the hardening agent of at least 20% is required to obtain the relative dynamic modulus of elasticity of 60% for the loess mortar.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.418-424
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• 2016

This study is an experimental study on the recycling of bottom ash in coal ash discharged from a thermal power plant. Bottom ash has limited research on recycling because it has more porous and higher water absorption ratio than fly ash. In this paper, the bottom ash was pulverized to a specific surface area of $4,000cm^2/g$ in order to use as a binder, and the flow, compressive strength test and microstructure analysis of the bottom ash based geopolymer mortar were performed. The flow measurement results of the geopolymer mortar showed that the flow rate was improved by increasing mixing water as the molar concentration of activator was increased. Compressive strength increased with increasing curing temperature and molar concentration. Through the microstructure analysis, we could confirm the geopolymer gel produced by the reaction of the condensation polymerization. It is considered that it is possible to make the bottom ash based geopolymer concrete through proper molar concentration of activator and high temperature curing.