• 한국식품과학회지
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• 제48권1호
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• pp.15-19
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• 2016

Drying process was applied to increase the antioxidant activity of onion powder: freeze-drying or air-drying at 50, 70, and $90^{\circ}C$ and onion extracts were obtained from each powder using water or aqueous ethanol (50%) at $25^{\circ}C$ and $60^{\circ}C$. In the color analysis, the freeze-dried powders showed higher $L^*$ and lower $a^*$ and $b^*$ values than did the air-dried ones. The browning index of powders air-dried at $90^{\circ}C$ was significantly higher than that of freeze-dried powders or those air-dried at temperatures below $90^{\circ}C$. Phenolic content in the extracts was 4.02-23.12 mg gallic acid equivalent/g sample, and was the highest in the extract from the sample air-dried at $90^{\circ}C$, regardless of the extraction condition. The highest antioxidant activity, measured by 2,2-azinobis-3-ethylbenzothiazoline-6-sulfonic acid and 1,1-diphenyl-2-picrylhydrazyl methods, was found in the powder air-dried at $90^{\circ}C$, which induced browning. These findings indicate that antioxidant activity depends more on browning during drying than on extraction conditions.

• Journal of Biosystems Engineering
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• 제23권3호
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• pp.229-244
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• 1998

This study was performed to determine proper fan and heater management schemes for natural air drying of rough rice in round steel bin with stirring device under Korean weather conditions. A computer simulation model was developed to predict moisture content changes, energy requirements, and drymatter losses during drying of rough rice by natural air. Drying test was conducted to validate the simulation model using round steel bin of holding capacity of 300ton at Rice Processing Complex in Jincheon. The bin was filled with rough rice every day and mixing by stirring device. Moisture contents, ambient air temperatures, relative humidities, static pressures in plenum chamber in the bin, airflow rates, and electrical and fuel energy were measured. Relative errors of moisture content changes predicted by the simulation model were below 5ft, and relative errors of final moisture content, final grain weight, required energy ranged from 0.9% to 6%. These not levels indicated that the simulation model can satisfactorily predict the performance factors of natural air drying system such as drying rates and energr consumptions comparing error level of 10% to 15% in other drying simulation models generally used in dryer desists. Twelve different fan and heater management schemes were evaluated using the computer simulation model based on three hourly weather data from Suweon for the period of 1952-1994. The best management schemes were selected comparing the drymatter losses, required drying times, required energy consumptions. Operating fan without heating only when ambient relative humidity was below 85% or 90% appeared to be the most effective method of In operation in favorable drying weather. Under adverse drying climates or to reduce required drying time, operating fan continuously, and heating air with $1.5^{\circ}C$ temperature rise only when ambient relative humidity was over 85% appeared to be the most suitable method.

• 한국토양비료학회지
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• 제50권5호
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• pp.482-488
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• 2017

The measurement based on reliable standard operating procedures (SOPs) is important for consistent information. The objective of this study is to investigate reliable SOPs of soil physical methods, including core method for bulk density, Yamanaka hardness, and air permeameter method for air permeability. The coefficients of variation in bulk density (core method), Yamanaka hardness, and air permeability were ranged of 1~6%, 8~13%, and 10~84%, respectively. The variation in situ measurement such as bulk density, hardness, and air permeability due to spatial variability at measuring site was larger due to the number of replicates, organic matter content, and soil texture. Nevertheless, air permeability had different values as different number of replicates, and thus, it is thought that more replicates can result in higher reliability. It suggested that investigation of soil physical properties for the target sites should required to consider about soil texture, organic matter content, and number of replications before measurement. In conclusion, core sampling for bulk density measurement in upland soil recommended to perform in 3 repetitions with 2 inch core, and 3 inch core sampling for higher organic matter content.

• Journal of Ginseng Research
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• 제39권4호
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• pp.371-375
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• 2015

Background: The current typical drying methods for red ginseng are sun drying and hot-air drying. The purpose of this study was to investigate drying characteristics of red ginseng by using far-infrared drying. Methods: The far-infrared drying tests on red ginseng were conducted at two drying stages: (1) high temperature for 24 h drying and (2) low temperature drying until the final moisture content was $13{\pm}0.5%$ (wet basis). The high temperature drying stage included three drying chamber temperature conditions of $60^{\circ}C$, $65^{\circ}C$, and $70^{\circ}C$. The low temperature drying stage was conducted at temperatures of $45^{\circ}C$ and $50^{\circ}C$. Drying characteristics were analyzed based on factors such as drying rate, color changes, energy consumption, and saponin content. The results were compared with those of the hot-air and sun drying methods. Results: The results revealed that increases in drying temperature caused a decrease in drying time and energy consumption for far-infrared drying. The saponin content decreased under all drying conditions after drying, the highest value (11.34 mg/g) was observed at drying conditions of $60{\sim}50^{\circ}C$. The sun drying condition showed the lowest color difference value when compared with far-infrared and hot-air drying. Conclusion: The far-infrared drying showed a faster drying rate, higher saponin content, lower color difference value, and a decrease in energy consumption than seen in hot-air drying.

• 한국군사과학기술학회지
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• 제20권5호
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• pp.620-632
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• 2017

A chemical vapor curing method(CVC) was developed to cure polycarbosilane(PCS) fibers by using cyclohexene vapour as a non-oxygen active reactant, instead of air in oder to prepare the silicon carbide(SiC) fiber with low oxygen content. A cross-linked PCS fibers by cyclohexene vapor showed a completely different variation in IR spectra in comparison to the air-cured PCS fiber. CVC method resulted in less than 3 wt% in oxygen content. In this experiment conditions, The average tensile strength and modulus of SiC fiber obtained by CVC had 1995 MPa and 183 GPa respectively, which is higher than that of SiC fiber prepared by air-curing process.

• Journal of Biosystems Engineering
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• 제22권3호
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• pp.279-288
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• 1997

This study was worked out to obtain fundamental data needed for developing a continuous type dryer. The drying process in a cross-flow type continuous dryer was expressed as partial differential equations, and a drying simulation model for predicting rice moisture content, rice temperature, drying air absolute humidity, drying air temperature was developed by using the finite difference method. To validate the performance of the drying simulation model, a prototype continuous dryer was constructed in this study. The size of the test dryer was one-tenth to that of a commercial continuous dryer. The difference in the outlet rice moisture content between the predicted values and the measured values was within 0.5%, that of outlet rice temperature was below $3^{\circ}C$, that of drying air temperature in drying bed was within $8^{\circ}C$ and that of relative humidity of outlet drying air was big because of the different measuring point. In addition, a drying simulation model for a actual size continuous dryer with double flow was developed in this study. This drying simulation model included the rice mixing effect in the middle of drying length. The difference of outlet moisture content between the predicted and the measured values showed below 0.5% in this study.

• 한국농공학회지
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• 제38권5호
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• pp.116-124
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• 1996

The purpose of The work described in this paper is to clear up the initial moisture content, specific surface, air drying and freezing-thawing process on liquid limit of clayey soils distributed widely at estuary of three main rivers in the west coast. To this end, a series of tests were conducted on clayey soils samples with natural state and treated state. From the test results, the liquid limit was decreased with decrement of initial moisture content, air drying process, and freezing-thawing cycles and increased with increment of specific surface. The specific surface which influenced on the liquid limit is over $25 m^2$m$^2$/g, and their relationships are well formulated. Air drying process is expected to improve the engineering properties of the soils such the pro-water properties were changed to anti-water proper-ties through lowering of water holding as resulted to incline from A-7-5 to A-5 on the soil classificaction plastic chart. The freezing-thawing process decreased 20% of liquid limit, especially under the first cycle of the behavious, as a result of above mentioned reasons, phase change of soil-water system brought the decrement of specific surface and affected to the liquid limit.

• Journal of Biosystems Engineering
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• 제6권1호
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• pp.83-92
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• 1981

A simulation model of natural air drying to predict the changes of the grain moisture content and dry matter loss of rough rice was developed by the application of mass diffusion theory. A series of simulated drying tests was conducted using the 10 year weather data (1970-1979) obtained from Cheongju, Chuncheon, Daegu, Daejeon, Jeonju, Jinju and Suweon in Korea. System performance factors treated in this study were initial moisture content, airflow rate, bin diameter and grain depth. The results obtained in this study are summarized as follows: 1) The simulation model used in this study was validated with actual experimental results and was applicable to the natural air drying of rough rice. 2) Minimum airflow rates for safe drying were determined for different initial moisture contents and regional weather conditions as shown in Table 6. 3) Equations for estimating drying time and dry matter loss in terms of airflow rate and initial moisture content were derived in the form of an exponential function. 4) These results show that the natural air drying system of rough rice is feasible in Korea even for the poorest drying condition.

• Journal of Biosystems Engineering
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• 제19권2호
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• pp.112-123
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• 1994

At present, no appropriate drying conditions can be found for the heated-air drying of mushroom in Korea. Usually, mushroom is being dried at the temperature range of 40 to $50^{\circ}C$ until the moisture content reaches 10~13% (wb). However, drying characteristics of the mushroom should be investigated for quality improvement and efficient drying operation of the mushroom. The results of this study may be summarized as follows ; 1. The effect of air temperature on the rate of drying was greater than that of relative humidity for drying of mushroom, and the rate of drying was increased with increase in the air temperature. 2. Drying rate for Shiitake mushroom showed falling-rate period of drying without constant-rate period of drying. Drying rate for Oyster mushroom showed a short constant-rate period at the initial stage of drying process, and followed by falling-rate period of drying. 3. Exponential and App.-Diffusion models were found to describe well the drying process of Shiitake mushroom. Exponential and Thompson models for Oyster mushroom in which Thompson model was the most suitable for Oyster mushroom. 4. The equilibrium moisture content of the mushroom decreased with decrease in the air temperature and increase in the relative humidity. In room condition($20^{\circ}C$, 54% RH), the calculated values of the equilibrium moisture content showed 11.17% for Shiitake mushroom and 13.19% for Oyster mushroom, respectively.

• 산업기술연구
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• 제21권B호
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• pp.249-256
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• 2001

The purpose of this study was to remove the excessive air foaming which was produced in mixing the RSLMC(latex-modified concrete with rapid-setting cement) by choosing the best antifoam agent type. A series of RSLMM(latex-modified mortar with rapid-setting cement) experiments were carried out as a basic experiments for RSLMC with the main experimental variables such as antifiamer types(A, B, C, D), antifoamer contents(0, 1, 2, 3%), and latex contents(10, 15%). Air content test and compressive strength tests were carried out to measure the improved properties of RSLMM. SEM analysis, also, was carried to observe the formation of latex film. The results of RSLMM showed that the decrease of 50% air content was obtained by admixturing an antifoam agent by 1%. This made the strength enhanced and the workability be within the purposed. The best properties of compressive strengths was obtained at latex content of 15% and D antifoam agent of 1%. compressive strength increased about 32.6%. The analysis of SEM results no difference in a formation of later film.