• Magazine of the Korea Concrete Institute
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• v.10 no.1
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• pp.179-188
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• 1998

캔틸레버 공법으로 시공되는 프리스트레스트 콘크리트 박스거더 교량의 구조적 거동은 단계적 시공에 따른 구조물의 순차적 변화 및 콘크리트의 재료적 특성에 의해 시간 의존적 거동을 나타낸다. 콘크리트의 시간의존적 특성, 즉 콘크리트의 크리프 및 건조수축 특성은 현장타설 세그멘탈 캔딜레버공법으로 가설되는 콘크리트 교량의 설계 및 시공에서 매우 중요한 역할을 한다. 본 연구에서는 콘크리트의 크리프 및 건조수축 특성이 교량의 시간의존적 거동, 특히 처짐 및 텐던응력예측에 미치는 영향을 연구하였다. 교량해석은 본 연구진에 의해 개발된 프리스트레스트 콘크리트 교량해석기법 및 프로그램을 이용하여 크리프의 ACI 모델, CEB-FIB모델, 그리고 국내 도로교 시방서 모델을 고려하여 해석하였다. 해석결과 최종크리프 값의 크기에 따라 장기처짐의 발생량이 차이가 큰 것으로 나타나고 있으며, 최종건조수축량과 상대습도도 영향을 주는 것으로 나타났다. 또한 ACI 모델과 CEB-FIB모델간에도 차이가 큰 것으로 나타나 실제교량의 크리프 특성 및 건조수축 특성의 정확한 예측이 교량의 정밀시공 및 거동예측에 매우 중요한 것으로 나타나고 있다.

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.313-317
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• 2017

With the continuous increase of energy demand, low-grade coal is regarded as one of new energy sources. However, due to the high water content, the utilization efficiency of low-grade coal is not good to be used in recent conversion plants. Therefore, it requires a drying process to lower the water content in low-grade coals. Although a variety of drying experiments were conducted, drying characteristics in accordance with the pressure change has not been progressed. In this study, the flash drying characteristics of low grade coal with high moisture content (21.5 wt%) were determined in a pressurized micro-riser. The effect of operation conditions such as pressure (1-40 bar), dryer temperature ($200-600^{\circ}C$), and tube length (2-6 m) on drying ratios were investigated.

• Food Science and Preservation
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• v.23 no.6
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• pp.819-824
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• 2016

The changes in physicochemical characteristics and sensory evaluation of bracken (Pteridium aquilinum) and Aster scaber dried by different methods sun-dried, hot-air-dried and freeze-dried were investigated. The freeze-dried Aster scaber showed the lowest moisture content than those of sun-dried and hot-air-dried. Freeze-dried bracken and Aster scaber showed higher rehydration rate than sun-dried and hot-air-dried. In the color values, the freeze-dried bracken and Aster scaber had the highest $L^*$ value of 29.48 and 32.73, respectively, while freeze-dried Aster scaber showed the lowest $a^*$ value of -6.78. Rehydrated bracken and Aster scaber after freeze-dried were the highest value in $L^*$ and $b^*$, while the lowest in $a^*$ value. In sensory evaluation, freeze-dried bracken and Aster scaber showed the highest in color, appearance, flavor, texture and overall acceptability. There were no significant differences in texture between hot-air-dried bracken and freeze-dried bracken after rehydrating. However, freeze-dried bracken and Aster scaber were the highest in color, appearance, flavor and overall acceptability. In conclusion, freeze-dried bracken and Aster scaber showed the best rehydrated rate, color and sensory properties.

• Food Engineering Progress
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• v.22 no.4
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• pp.344-352
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• 2018

The effects of chemical compositions (protein, lipid, and dietary fiber) on the physical properties of dried biji powders were investigated. The raw biji was freeze-dried (control) and hot-air dried (untreated). The untreated biji was further defatted and deproteinated. The prepared biji powders were analyzed for the proximate composition, total dietary fiber (TDF), water absorption index (WAI), water solubility index (WSI), swelling power, solubility (including the quantification of soluble carbohydrate and protein fractions), and final viscosity (using a rapid visco analyzer). Control and untreated biji powders exhibited the similar chemical compositions. The defatted biji possessed higher TDF, although its protein content did not significantly differ for control and untreated ones. The deproteinated biji consisted mainly of TDF. WAI and swelling power increased in the order: deproteinated > defatted > control > untreated biji powders. WSI and solubility increased in the order: control > untreated > defatted > deproteinated biji powders. The similar patterns were observed for soluble carbohydrate and protein fractions. The deproteinated biji revealed the highest viscosity over applied temperatures, while the untreated one was lowest. Overall results suggested that the physical properties of the dried biji powder were reduced by protein and fat, but enhanced by dietary fiber.

• Food Science and Preservation
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• v.12 no.5
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• pp.449-454
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• 2005

The objective of this study was to investigate the effect of drying methods on the physicochemical characteristics of Ponciri fructus. Immature fruits of Poncirus trifoliata were harvested, dried by shade, infrared, or freeze drying, and powdered to size of 20 mesh. Then, extracted for 3 hrs with hot-water or 40% ethanol(80$\circC$℃). Freeze dried powder showed significantly higher L and -a value. The content of hesperidin was not affected by drying methods. The yield was the highest from freeze drying. Water extracts showed significantly more browning color, and higher acidity and total sugar content than those of ethanol extracts. Acidity and total sugar of water extracts were the highest in infrared drying and freeze drying, respectively. Browning color, pH, acidity and total sugar of ethanol extracts were not affected by the drying methods. The results suggest that freeze drying has a beneficial effects to enhance the quality of Ponciri fructus.

• Applied Biological Chemistry
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• v.17 no.1
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• pp.42-48
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• 1974

Hot air thin layer drying method was studied for red pepper, Capsicum annum var. longum as the whole and cut pod states, at various temperature and air velocities. Drying curve of whole pod showed a settling down period followed by the first and second falling rate periods. By lowering the drying temperature, the first falling rate period approached to a constant rate one. Cut drying curve had simple falling rate period and also cut drying method could effectively shorten the drying time. Drying rate constant, k, was varied with time for both the drying methods and the plots of k vs. time in two methods sugested the different drying mechanisms. When an average k was taken as a constant value, the following equations; $M-M_e/M_o-M_e=e^{-0.118t}$ and $M-M_e/M_o-M_e=e(-0.342t^{0.128})$ were applicable for whole and cut drying, respectively.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.2
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• pp.250-254
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• 2007

In an attempt to find ways of improving the quality of dried Shiitake mushroom, this study compared a conveyer-type far-infrared drying method with a traditional heated air drying method. The conveyer-type far-infrared dryer was performed at air velocity of 0.6 and 0.8 m/s under drying air temperature of 60, 70 and $80^{\circ}C$, respectively. Drying characteristics, antioxidant activities and the antioxidant compounds of Shiitake mushroom dried by far-infrared dryer were investigated. Generally, drying rate with the conveyer-type far-infrared drying method was faster than that with the traditional heated air drying method. In the conveyer type far infrared drying method, drying rates were increased with increasing temperature and air velocity. The loss of antioxidant activities during the conveyer-type far-infrared drying method at 60-0.6, 60-0.8, and $70^{\circ}C-0.6m/s$ was less than the traditional drying method. However, the loss of antioxidant activities at 70-0.8, 80-0.6, and $80^{\circ}C-0.8m/s$ was higher than that of the traditional drying method. Therefore, the conveyer type far infrared drying conditions with below $70^{\circ}C$ and 0.6 m/s air velocity may produce dried Shiitake mushroom with relatively higher antioxidant activities and antioxidant compounds.

• Food Science and Preservation
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• v.13 no.1
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• pp.37-42
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• 2006

In recent, Kimchi is produced in the scale of industry, Consumers show increased demand of safety and high quality and hygienic process control. So, sun drying, hot air drying and cold air drying methods were investigated to compare the demand Sun drying took 96 hrs, hot air drying took 4 hrs at $70^{\circ}$ and cold air drying took 102 hrs at $10^{\circ}C$ in removing water to $90\%$ from radish. Brownness of radish was expressed as absorbance. Absorbance were 0.20, 2.04 and 1.87 and also Vit-C contents were 0.14 mg/g, 0.12 mg/g and 0.096 mg/g in dried radish according to cold air drying, hot air drying and sun drying, respectively. From overall experimental results, cold air drying method was found as superior drying method to other drying methods.

• Food Science and Preservation
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• v.19 no.4
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• pp.485-491
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• 2012

This study was conducted to investigate the pH, soluble solid contents, color difference, mineral contents, free sugar contents, and sensory quality of infrared- and cold-air-dried peaches. The pH, soluble solid contents, and free sugar contents of the infrared-dried peaches were higher than those of the cold-air-dried peaches. In the Hunter's color value, the L and ${\Delta}E$ values of the infrared-dried peaches were higher than those of the cold-air-dried peaches; but the a and b values of the cold-air-dried peaches were higher than those of the infrared-dried peaches. The major organic acids of the dried peaches were citric acid, malic acid, and oxalic acid. The minerals with the highest to lowest contents, in that order, were K, Mg, Ca, Na, Fe, Zn, Cu, and Al. The mineral contents of the cold-air-dried peaches were higher than those of the infrared-dried peaches. The appearance and taste of the infrared-dried peaches were better than those of the cold-air-dried peaches. These results indicate that infrared drying is the effective drying method for the production of high-quality dried peaches.

• Magazine of the Korea Concrete Institute
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• v.8 no.1
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• pp.111-120
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• 1996

Drying shrinkage is a very important properties of concrete, which is affected by environmental conditions. The environmental conditions are temperature, relative humidity, and wind speed, which is quite variable and its effct on drying shrinkage is quite complex, too. In this study, environmental effects on drying shrinkage wrer integrated into one variable-evaporation rate. In several different environmental conditions, evaporation rate was measured with Evaporometer and compared with PCA chart, and also compared with measured drying shirnkage to verify the possibility of being a single parameter. The results are summarized in a prediction chart and prediction equation for drying shrinkage.