• Journal of Biosystems Engineering
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• 제5권1호
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• pp.15-23
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• 1980

Natural-air drying systems have been extensively used for cereal grains, and many researches on the systems have been conducted in foreign countries. However, little research on drying rough rice with natural air has been done. Especially . little research on natural air drying of rough rice based on weather data has been done in Korean. The objective of this study was to present fundamental data for estimating optimum requirements and basic information available for natural air drying of rough rice based on the weather data . The weather data analyzed in this study were the 10-year (1969 to 1978) record of air temperatures, wet-bulb temperatures and relative humidities, which were three-hourly observations in Taegu area. The results of this study are summarized as follows ; 1 From the results of weather data analysis the average air temperature was about $14.8^\circ$and the average relative humidty 67.5% . Average equilibrium moisture content appeared to be 13.8 percent on wet basis, which showed great potential for natural air drying in Taegue area in October. 2. Possible fan operation time based on the equilibrium moisture content of 15% on wet basis was about 14 hours a day during October in Taegu area. Probabilities of possible drying days based on minimum time available for drying in a day were analyzed. 3. Minimum air flow requirements based on the worst year were determined for different fan operation methods and initial moisture contents.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.896-905
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• 1993

Thin-layers of wheat and barley are dried at near-ambient temperatures(3.5$^{\circ}C$ -5$0^{\circ}C$) in order to obtain the intrinsic drying data. The well established apparatus was modified to enable it to record all the sample weight data in still air by using a purpose -built automatically controlled sliding valve. The air could be diverted in less than 0.5seconds and a 7 second period was required to attain a steady weight reading. With this apparatus, very smooth drying curves were obtained. The data of sample weight , drying temperature and dew point temperature wee recorded continuously . The drying process was terminated when the moisture content change in 24 hours was less than 0.004 d.b. This was achieved by drying a sample for about a week . The final points were recorded as the dynamic equilibrium moisture content(EMC). The drying data were than fitted to the exponential Newton model and the dynamic EMC data were fitted to the Modified-Chung-Pfost Model . All the fitted parameters are given and comparison is made with previous published data. The comparisons who that the current drying constants are lower than the previous data, the dynamic EMC data obtained for wheat and barely agree with the previous data. The results show that to obtain the drying constant in the exponential Newton model, adequate drying time is necessary.

• 펄프종이기술
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• 제43권3호
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• pp.11-20
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• 2011

The conditions to which pulp fibers are exposed during paper production, converting, storage, use, and recycling can induce various changes in fiber morphology, surface characteristics, and suitability for paper production by recycled fibers. Most of those changes can be described by hornification. Paper has highly hygroscopic properties which affect dimensional change by relative humidity variation of surrounding condition. The purpose of this study was to investigate the dimensional stability, moisture contents and dip elongation of handsheets at different relative humidity conditions of recycled kraft pulp and BCTMP. By using recycled fibers, dimensional stability was increased because hygroscopic properties of fibers decreased with repeated recycling treatment. Dip elongation of recycled pulp was higher than that of virgin pulp because of its weak fiber-to-fiber bonding. By recycling pulp, the relative bonded area was decreased because fiber could not swell more than virgin pulp. Dimensional stability largely depended on the equilibrium moisture contents of paper, the fiber-to-fiber bonding strength, and the relative bonded area.

• 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.

• 한국가구학회지
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• 제17권1호
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• pp.1-10
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• 2006

Movement behavior, shrinkage and equilibrium moisture content (EMC), in this experiment reflected a change of hygroscopicity mainly affected by continuously compressive load during radio-frequency/vacuum (RF/V) drying and humidity changes during equilibrating. As a result of interaction of the compressive load and moisture content changing under the RF/V condition, the shrinkages in loading direction were significantly increased while those perpendicular to loading direction were decreased. The shrinkages were affected most in tangential, and least in longitudinal direction. The shrinkages showed higher values in continuous drying than in intermittent drying. In the direction of increased shrinkage, all the movements were also increased, for example, the tangential movement for the loaded-RS and the radial movement for loaded-TS; in the direction of decreased shrinkage, all the movements except the tangential movement for the loaded-TS were decreased such as the tangential and radial movements for the loaded-ES, and the radial movement for the loaded-RS, comparing with those of the load-free. EMCs of the loaded specimens were all higher than that of the load-free specimen, and the highest for the loaded-TS, the lowest for the loaded-ES. The transverse hygroscopicity of specimen was reduced for the loaded-ES, but increased for the loaded-TS.

• Journal of the Korean Wood Science and Technology
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• 제26권4호
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• pp.1-5
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• 1998

In this study, it was examined the method to estimate equilibrium moisture content(EMC) at high vapor pressures and high temperatures above $100^{\circ}C$. The material used for the experiment was Sugi(Cryptomeria japonica). EMC was investigated at temperatures ranging from $100^{\circ}C$ to $160^{\circ}C$ and under saturated vapor pressures above 1 atm. The correlation between temperatures and vapor pressures have a good agreement with those observed by thermocouple and pressure gauge in the air state of autoclave, respectively. A sensitivity of quartz spring was 65mm/g. Moisture content(MC)s calculated from the quartz spring elongation by vapor sorption showed a good agreement with MCs by oven-dried method. Using this system, it was found that EMC at high vapor pressures and high temperatures above $100^{\circ}C$ were higher than EMC of wood in 1 atm pressure conditions. With this system, therefore, it was concluded that the EMCs of wood and wood-based materials at high temperatures were able to be evaluated.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1999년도 동계 학술대회 논문집
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• pp.456-461
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• 1999

• 한국연초학회지
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• 제9권2호
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• pp.95-104
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• 1987

1. Under the current workroom conditions It is very difficult to control the moisture contents of raw materials in season of summer or winter. 2. The moisture absorption of the materials under the contributive conditions showed the efficiency of 65% in relative humidity and temperature of the currant workroom. 3, The results from this study, however , appeared the deviation of moisture content of the products by the order of 0.1% compared to the current deviation of 2.6~2.7%. 4. Equilibrium moisture contents of the tobacco was Inversely proportional to the temperature and directly related to the relative humidity of the workroom. 5. On the basis of the above results , the standard conditions of the workroom obtained from this study considering with the external temperature in winter could reduce energy by 17.4% through 38.4% .

• Journal of Biosystems Engineering
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• 제27권3호
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• pp.219-226
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• 2002

Desorption equilibrium moisture contents of oak mushroom were measured by the static method using salt solutions at flour temperature levels of 35$\^{C}$, 45$\^{C}$, 55$\^{C}$ and 6$\^{C}$ and five relative humidity levels in the range from 11.0% to 90.8%. EMC data were fitted to the modified Henderson, Chung-Pfost, modified Halsey and modified Oswin models using nonlinear regression analysis. Drying tests far oak mushroom were conducted in an experimental dryer equipped with air conditioning unit. The drying test were performed in triplicate at flour air temperatures of 35$\^{C}$, 45$\^{C}$, 55$\^{C}$ and 65$\^{C}$ and three relative humidities of 30%, 50% and 70% respectively. Measured moisture ratio data were fitted to the selected four drying models(Lewis, Page, simplified diffusion and Thompson models) using stepwise multiple regression analysis. The results of comparing root mean square errors for EMC models showed that modified Halsey was the best model, and modified Oswin models could be available far oak mushroom. The results of comparing coefficients of determination and root mean square errors of moisture ratio for four drying models showed that Page model were found to fit adequately to all drying test data with a coefficient of determination of 0.9990 and root mean square error of moisture ratio of 0.00739.

• 한국식품과학회지
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• 제22권6호
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• pp.690-695
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• 1990

커피의 저장 중 흡착에 가장 많은 영향을 미치는 인자로는 수분활성 및 온도이다. 따라서 커피의 제조공정 중 추출시 건조방법의 차이에 따른 세 종류의 제품에 대한 흡착 특성을 조사하고 수분활성, 온도 및 시간의 변화에 따른 흡착량을 측정하여 조건변수의 변화에 따른 흡착량의 변화를 예측할 수 있는 예측모델식을 수립하였다. 흡착거동은 전형적인 Sigmoid 형태를 나타냈으며 평형수분함량과 단분자층 수분함량은 동결 건조제품이 가장 높게 나타났으며 이는 건조방법에 의해 생성된 다공성구조에 기인된 것으로 사료된다. 기 발표된 여러 형태의 등온흡착곡선 모델식에 적용시켜 본 결과 Halsey 모델식의 상관계수 r값이 $0.98{\sim}0.99$로 가장 적합하였다. 또한 예측모델식은 SPSS COMPUTER PROGRAM을 이용하여 가장 오차가 적은 범위에서 수분활성, 온도 및 시간의 변화에 따른 흡착량의 변화를 예측할 수 있는 최종적인 모델식을 수립하였다.