• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.118-123
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• 1995

Evaluating the moisture content for sand is useful for quality cotnrol of concrete. If water content of evaluate instantly and apply for mix proportion sand of concrete, in mixing propertion of concrete, it can makes to improve of concrete quality. In this study, the evaluating method for moisture content of sand, using the electric velocity and dielectric constant was proposed as a study of quality control of concrete. The obtained results are summarized as follow. The resistance ratio was decreased as the increase of moisture content The dielectric constant was decreased as the sand of the moisture content increase.

• Journal of Environmental Impact Assessment
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• v.8 no.1
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• pp.81-92
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• 1999

This study discussed the appropriateness of organic matter indexes such as biochemical oxygen demand(BOD) and chemical oxygen demand with potassium permanganate($COD_{Mn}$) in water quality environmental standard of streams and lakes and the applicability of the items to water quality environmental standard to add or substitute COD with potassium dichromate ($COD_{Cr}$) and total organic carbon(TOC) being used as index of organic matter. And indexes of organic matter content and organic carbon concentration were distinguished between dissolved and particulate component in water sample to estimate their effect on pollutants loading in lake and stream. The ratio of $COD_{Cr}$/BOD was 5.1 under BOD concentration 3mg/L in river water quality environmental standard II, and 2.67 above it. This ratio was diminished to 2.04 when BOD concentration was more than 8mg/L, in river quality environmental standard IV. Also the ratio of $COD_{Mn}$/BOD showed 2.16 under 3mg/L(BOD), and 1.1 above it. This ratio is also diminished to 0.84 over 8mg/L(BOD). Accordingly, we should apply this ratio depending on the concentration level to add and change organic matter index of water quality environmental standard newly. The ratio $COD_{Cr}/COD_{Mn}$ both in lake and stream shows 2.37(r=0.986, p<0.001). But the ratios showed range of 2.34~2.50, which is no much difference of this ratio according to $COD_{Mn}$ concentration.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.234-238
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• 1998

To select new germplasm for salinity tolerance from new plant type (NPT) breeding lines, the sixty F$_4$ lines selected from the crosses between Korean cultivars and IRRI's NPT lines were evaluated for salinity tolerance at the seedling stage with salinized culture solution (EC=12 dS/m) in the controlled conditions. Two NTP lines derived from a cross between 'Ilmibyeo' and 'IR66152-AC5-1', 'HR15258-7-1' and 'HR15258-27-1', were found to have good tolerance. The salinity tolerance of the lines was compared to their parents and the sensitive ('IR29') and tolerant ('Pokkali') checks in three salinity levels, no salinity (control) and an EC of 12 and 16 dS/m. Visual salinity score, shoot Na+ and Na-K ratio in two NPT lines was significantly low compared with the parents and IR29. Indicating that salinity tolerance of the lines might be derived from a transgressive segregation. The relative water content of the lines was higher than Pokkali, and the dry weight of shoot and root was proportionally decreased to salinity score and salinizing concentration. The visual salinity scores were significantly correlated with shoot Na concentration, Na-K ratio, relative water content, and reduction of dry weight (P<0.01). Their tolerance was attributed to root and shoot characteristics that led to high shoot water content, thus diluting the toxic effect of salts.

• Journal of the Korea Institute of Building Construction
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• v.3 no.2
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• pp.141-148
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• 2003

This study deals with the estimation of material properties according to the construction condition for water-soluble rubberized asphalt waterproofing material of spray type. In this study, the waterproofing material property by the spray construction method is suggested by means of estimation its tensile performance and temperature dependency according to mix proportion ratio(4:1, 8:1), referenced viscosity and solid content (A:360cps, 76%, B:580cps, 79%, C:490cps, 70%), spray angle($30^{\circ}$, $45^{\circ}$, $60^{\circ}$), and spray distance(30cm, 50cm, 70cm). The result of testing are as follows. (1) The mix proportion ratio of principal agent and hardener is 4:1. (2) The viscosity referenced and solid content are 490cps and 70%. (3) The spray angle referenced is $45.^{\circ}$ (4) The distance referenced from concrete surface to spray gun is 40~50cm.

• Korean Journal of Materials Research
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• v.29 no.7
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• pp.399-407
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• 2019

This research is carried out to analyze the effects of Styrene and PVP on the properties of silicone hydrogel lenses. Styrene group and PVP(Polyvinylpyrrolidone) are used as additives for a basic combination containing silicone monomer, TSMA(trimethylsilyl methacrylate) and DMA(n,n-dimethylacrylamide) added to the mix at ratios of 1~10 %. Silicone hydrogel lens is produced by cast-mold method. The polymerized lens sample is hydrated in a 0.9 % saline solution for 24 hours before its optical and physical characteristics are measured. Measurement of the physical characteristics of the produced material shows that the refractive index is 1.3682~1.4321, water content 77.11~45.73 %, visible light transmittance 95.14~88.20 %, and tensile strength 0.0652~0.3113 kgf. The results show a decrease of refractive index as the ratio of additives and water content decreases. The result of the stabilization test of polymerization show an increase of extractables along with increase of the ratio of additives, but the difference is not significant for all samples, so it can be judged that the stabilization of the polymer is maintained. Therefore, the additions of styrene and PVP should be taken into consideration for their effects on the physical properties of silicone hydrogel lens.

• Journal of Environmental Impact Assessment
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• v.7 no.2
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• pp.5-14
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• 1998

This study was performed to estimate interrelation between characteristics of sediment and nutrient releare from sediment in Dae-cheong lake. For the investigations, sediments were sampled in June and October 1997 at fish farms, embayment, and the main stream of Dae-cheong lake. Items for investigation are as follows; water content, weight loss on ignition(IG), porosity of sediment, Total Kjeldahl Nitrogen(TKN), content of element(H, N, C), nutrient release rate. Water content and porosity were measured to conjecture the physical trait and grain size. And weight loss on ignition was measured to determine the contents of organic substance. For the determination of nutrient release rate, $PO_4-P$ and $NH_4-N$ concentration of interstitial water and overlying water were measured. Release rate of nutrients which has direct influenced upon the water quality were 0.05-8.63mg-$P/m^2{\cdot}day$ and 4.99-36.56mg-$N/m^2{\cdot}day$. And it was found that release rate was measured higher in the 1st sampling than in the 2nd sampling. And for determination of the humus level of sediment, carbon and nitrogen content were measured by using elemental analyzer. Generally, C/N ratio is used to determine humus level of lake sediment. As a result of elemental analysis, C/N ratio was determined in the range of 7.64~11.55, so humus level of Dae-cheong lake sediment was estimated from mesohumic state to oligohumic state.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.57-63
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• 2017

In this study, we identified how the water content change in various NCO index affects the static comfort of polyurethane seat foam pad for automobiles. In order to identify factors that affect the static comfort, a static load test was performed using UTM to plot a hysteresis curve. The hardness of the foam when it was modified by 25, 65%, hysteresis loop area, hysteresis loss (%), and Sag factor were also obtained. By measuring the swelling ratio, it was confirmed that, as the water content increased in a fixed NCO index, the hardness and crosslinking density increased while the restoring force decreased due to the increase of urea bond. Also the Sag factor decreased due to the increase of surface hardness. As the NCO index increased in a fixed water content, the urethane and urea bond reacted more with isocyanate, leading to an increase in hardness and decrease in restoring force.

• The Korean Journal of Food And Nutrition
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• v.7 no.2
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• pp.137-143
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• 1994

To optimize extrusion cooking condition of single screw extuder for production of puffed rice extrudate using response surface methodology (RSM), moisture content, barrel temperature and screw speed were determined from contour maps, showing relationship between dependent (hardness, expansion ratio, water absorption index, water solubility Index, degree of gelatinization) and independent variables. Optimum operational conditions for production of puffed rice extrudate with suitable quality properties were moisture content 17%, barrel temperature 1$25^{\circ}C$ and screw speed 210 rpm, respectively.

• Journal of environmental and Sanitary engineering
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• v.15 no.3
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• pp.24-30
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• 2000

In this study, to determine the optimum fermentation process for the feed production of food wastes and estimate the practical value of fermented feed using kudzu creeper and sawdust as bulking agent. This study considered initial C/N ratio control as the fermentation process variables. The result are summarized as follows. Minimum water contents of byproducts in the fermentation feed production showed 39%(kudzu), 37%(sawdust) at the C/N ratio 25 and 45%(kudzu, sawdust) at the C/N ratio 35. Temperature variations in the fermentation feed production at the C/N ratio 25 indicated $68^{\circ}C$(kudzu), $70^{\circ}C$(sawdust). Optimum condition of fermentation process of water content, C/N ratio and permeability (porous structure of the mixture). For optimum fermentation gravitationally dewatered garbage, the proper mixing ratios of kudzu(moisture contents : 17.3%) and sawdust(moisture contents : 13.2%) were 41% and 39%, respectively. Major biological reaction in the aerobic fermentation feed production occurred during 12~24hrs.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.3
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• pp.57-63
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• 2004

This study was performed to evaluate the engineering properties of cement mortar brick with loess and fly ash. The unit weight was in the range of $2,068{\sim}2,137\;kgf/m^{3}$ and $1,899{\sim}2,045\;kgf/m^{3}$ in water and dry curing, respectively It was decreased with increasing the loess content. The absorption ratio was in the range of $5.2{\sim}13.1%$ and $8.5{\sim}13.2%$ in water and dry curing, respectively. The compressive strength was decreased with increasing the loess content. The compressive strength of the 193 $kgf/m^{2}$ in water and 188 $kgf/m^{2}$ in dry curing at the curing age 28 days of the binder volume ratio 35% was exceeded in 163 $kgf/m^{2}$ of standard compressive strength about cement bricks. The carbonation depth was in the range of $0.9{\sim}1.4$ mm, $1.2{\sim}3.6$ mm, $1.4{\sim}6.7$ mm and $2.4{\sim}12.5$ mm in dry curing of curing age 14days, 28days, 90days and 360days, respectively.