• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.5-8
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• 2006

In this study, various fundamental experiments including durability and time-dependent deformation are performed to compile a database for a utilization of high-strength concrete for PSC bridges. In the mix design, concrete strength at early age when prestressing forces are introduced to the PSC member and slumpflow suitable for pumping of concrete are considered to make a concrete fit for PSC bridges. The main parameters investigated are the kinds and replacement ratios of mineral admixtures and low-heat cement. Experimental tests on durability include penetration of chloride ions, freezing-thawing, combined deterioration, and simple adiabatic temperature rise test. In addition, time-dependent deformation such as creep, drying and autogenous shrinkage, which is particularly important factor in the design and construction of PSC bridges, is tested and analyzed.

• Journal of Venture Innovation
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• v.5 no.2
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• pp.85-99
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• 2022

Dryers becoming commercially available for experimental and industrial use are classified to general drying oven, hot-air dryer, vacuum dryer, freezing dryer, etc. and kinds of them are various from the function, size and volume, etc. But the moisture measurement is not applied although it is important factor for the quality control and the performance improvement of products, and then now is very passive because the weight is weighed arbitrarily after dry-end. Generally the method for measuring moisture is divided by a direct measurement method and a indirect measurement method, and the former such as the change of weight or volume on the front and rear of separation of moisture, etc. is mainly used. Relatively a indirect measurement is very limited to apply due to utilize measurement apparatuses using temperature conductivity and micro-wave etc. In this research, we easily designed the moisture measurement system using the open-source based Arduino, and monitored moisture fluctuations and weight profiles in the real-time without the effect of external environment. Concretely the temperature-humidity and load cell sensors were packaged into a drying oven and the various change values were measured, and their sensors capable to operate 60℃ and 80℃ were selected to suitable for the moisture sensitive materials and the food dry. And also the performance safety using the organic samples of banana, pear, sawdust could be secured because the changes of evaporation rate as the dry time and temperature, and the measurement values of load cell appeared stable response characteristics through repeated experiments. Hereafter we judge that the reliability can be improved increasingly through the expansion of temperature-humidity range and the comparative analysis with CFD(Computational Fluid Dynamics) program.

• Journal of Biosystems Engineering
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• v.24 no.4
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• pp.317-324
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• 1999

This study was conducted to decide several design criterion for clean-washed rice processing system development. A Computer simulation was used to predict and analyze the mass balances and moisture changes of the process of clean-washed rice processing system. The following results were obtained from this study. 1. In order to attain the processing capacity of 1,000kg/h of the clean-washed rice processing system, that of the system was designed as 1,400kg/h which was based on the safety factor of 40% and handling capability of mass variations occurred during processing. 2. It was analyzed that the proper time required for aqueous cleaning process should be within one minute. 2. It was analyzed that the proper time required for aqueous cleaning process should be within one minute. 3. The final moisture content of clean-washed rice was controlled being 15%(w.b.) for the sake of safe storage. 4. It was proven that the optimum drying time was three minutes for the clean-washed rice dried by a rotary dryer.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.71-78
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• 2010

The stability analysis of unsaturated infinite slope under rainfall-induced infiltration condition was performed using the generalized effective stress that unifies both saturated and unsaturated condition recently proposed by Lu and Likos(2004, 2006). The Soil-Water Characteristic Curve (SWCC) of the sand with the relative density of 75% was first measured for both drying and wetting processes. The Hydraulic Conductivity Function (HCF) and Suction Stress Characteristic Curve (SSCC) were subsequently estimated. Also, under the rainfall-induced infiltration condition transient seepage analysis of unsaturated infinite slope was performed using the finite element program, SEEP/W. Based on these results, the stability of unsaturated infinite slope under rainfall-induced infiltration condition was examined considering the suction stress. According to the results, the negative pore water pressure and water content within the soil changed with time due to the infiltration. Also, the variation of those caused the variation of suction stress and then the factor of safety of slope changed consequently during the rainfall period.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.1-8
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• 2014

Numerical stability analysis of an unsaturated infinite slope under rainfall-induced infiltration conditions was performed using generalized effective stress to unify both saturated and unsaturated conditions The soil-water characteristic curve (SWCC) of sand with a relative density of 75% was initially measured for both drying and wetting processes. The hydraulic conductivity function (HCF) and suction stress characteristic curve (SSCC) were subsequently estimated. Under the rainfall-induced infiltration conditions, transient seepage analysis of an unsaturated infinite slope was performed using the finite element analysis program, SEEP/W. Based on these results, the stability of an unsaturated infinite slope under rainfall-induced infiltration conditions was examined in relation to suction stress. According to the results, the negative pore-water pressure and water content within the slope soil changed over time due to the infiltration. In addition, the variation of the negative pore-water pressure and water content led to a variation in suction stress and a subsequent change in the slope's factor of safety during the rainfall period.

• Journal of the Korea Institute of Building Construction
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• v.6 no.2 s.20
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• pp.73-79
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• 2006

The purpose of this study is to enhance the development of construction waste-recycling technologies and its economical efficiency by developing environment-friendly tetrapod, precast concrete, where recycled aggregate is used in order to promote recycling of waste concrete. The results of concrete mechanic characteristics experiments by the circulation coarse aggregate-replacement ratio are as the following. The circulation aggregate is lower and higher than natural aggregate in specific gravity and absorption ratio, respectively so that in case of mix proportioning, unit volume increases, while unit aggregate amount decreases. From the result, sufficient experiments of physical characteristics of circulation aggregate are required to get proper mix proportioning. When circulation aggregate-replacement ratio increases, compressive strength tends to decrease comprehensively, but 50% of replacement ratio is good enough to use. When circulation coarse aggregate's replacement ratio is 0%, drying shrinkage, which causes cracks in concrete and deteriorates durability, shows the minimum length change and the higher the ratio, the larger the length change. Thus. when using circulation coarse aggregate, drying shrinkage should be fairly examined. In freezing-and-thawing resistance, weight loss tends to comprehensively increase its loss at the circulation aggregate-mixed site. And the examination of surface aggregate-omission ratio is further needed and dynamic elastic modulus and durability factor(DF) require more study as well. In order to use circulation aggregate to tetrapod, a clear standard for strength should be first prepared and at the same time, more study about durability is needed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.2
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• pp.235-244
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• 2011

The physicochemical properties and quality changes in salted and dried brown croaker products using deep seawater salt were investigated for preparation with different pretreatment, salting and drying conditions. Optimum salt concentration, salting time and drying time for product were 20% of body weight, 12 hrs at room temperature ($25{\pm}2^{\circ}C$), and 24 hrs at $30{\pm}2^{\circ}C$, respectively. The volatile basic nitrogen (VBN), peroxide value (POV), viable cell count and acid value (AV) of viscera and blade removed products were 18.9~22.4 mg%, 21.0~32.5 meq/L, and 2.3~4.4 mg/mL, $2.0\sim3.5{\times}10^3$ CFU/g, respectively and only viscera removed products were 31.2~38.1 mg%, 40~55.2 meq/L, 7.0~11.5 mg/mL, $4.1\sim5.5{\times}10^3$ CFU/g, respectively. Changes in quality of salted and dried brown croaker products were investigated during storage at room temperature and $5{\pm}2^{\circ}C$. The POV, AV and viable cell counts of salted and dried brown croaker products increased in commercial salt used and only viscera removed products compared with deep seawater salt used and viscera and blade removed products during storage time. Results in this study showed that the deep seawater salt was very effective for quality control of salted and dried brown croaker products and pretreatment method was a very important factor for preparation products. The optimum conditions for preparation of salted and dried brown croaker product were 20% of body weight for salt concentration, 12 hrs at $25{\pm}2^{\circ}C$ for salting time, and 24 hrs at $30{\pm}2^{\circ}C$ for drying time. Optimum storage time for quality maintenance was 14 days at $5{\pm}2^{\circ}C$.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.73-76
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• 2009

In ultra-high-strength concrete, chemical shrinkage is larger than drying shrinkage due to using a large amount of cement and admixtures, and this is a factor deteriorating the quality of structures. Thus, we need a new technology for minimizing the shrinkage strain of ultra-high-strength concrete. So, this study have prepared super-high-strength concrete with specified mixing design strength of over 100MPa and have evaluated a method of reducing chemical shrinkage by using expander and shrinkage-reducing agent. According to the results of this study, with regard to the change in length by chemical shrinkage, an expansion effect was observed until the age of seven days. The expansion effect was higher than previous research that used only expander or shrinkage reducing agent. In addition, ultra-high-strength concrete showed a shrinkage rate that slowed down with time, and the effect of the addition of expander material on compressive strength was insignificant. That is shown that required more database to be accumulated through experimental research for the shrinkage strain of members.

• Korean Journal of Remote Sensing
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• v.20 no.1
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• pp.1-11
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• 2004

Based on surface energy balance climatology, surface temperatures should respond to drying conditions well before plant response. To test this hypothesis, land surface temperatures (LST) derived from MODIS data were analyzed to determine how the data were correlated with climatic water balance variables and NDVI anomalies during a growing season in Western and Central Kansas. Daily MODIS data were integrated into weekly composites so that each composite data set included the maximum temperature recorded at each pixel during each composite period. Time-integrated, or cumulative values of the LST deviation standardized with mean air temperatures had significantly high correlation coefficients with SM, AE/PE, and MD/PE, ranging from 0.65 to 0.89. The Standardized Thermal Index (STI) is proposed in this study to accomplish the objective. The STI, based on surface temperatures standardized with observed mean air temperatures, had significant temporal relationships with the hydroclimatological factors. STI classes in all the composite periods also had a strong correlation with NDVI declines during a drought episode. Results showed that, based on LST, air temperature observations, and water budget analysis, NDVI declines below normal could be predicted as early as 8 weeks in advance in this study area.

• Journal of the Korean Ceramic Society
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• v.54 no.2
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• pp.108-113
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• 2017

The use of aluminum-based coagulants in water pretreatment is being carefully considered because aluminum exposure is a risk factor for the onset of Alzheimer's disease. Lightly burned-dolomite kiln dust (LB-DKD) was evaluated as an alternative coagulant because it contains high levels of the healthful minerals calcium and magnesium. An organic pore forming agent (OPFA) was incorporated to prepare porous granules after OPFA removal through a thermal decomposition process. A spray drying method was used to produce uniform and reproducible spherical granules with low density, since fine dolomite particles have irregular agglomeration behavior in the hydration reaction. The use of fine dolomite powder and different porosity granules led to a visible color change in raw algae (RA) containing water, from dark green to transparent colorlessness. Also, dolomite powders and granules exhibited a mean removal efficiency of 48.3% in total nitrogen (T-N), a gradual increase in the removal efficiency of total phosphorus (T-P) as granule porosity increased. We demonstrate that porous dolomite granules can improve the settling time and water quality in summer seasons for the emergent treatment of excessive algal blooms in eutrophic water.