• Smart Structures and Systems
• /
• 제7권4호
• /
• pp.319-328
• /
• 2011

In this study, the measurements of the dielectric constants of soil at 900 MHz and 1 GHz were made to relate those properties to the moisture content of the soil. This study's intention was to use the relationship between the dielectric constant and the moisture content to develop a landslide prediction system. By monitoring the change of the moisture content within the soil using ground penetrating radar (GPR) systems in the field, the possibility of a landslide is expected to be detected. To establish a database for the dielectric constants and the moisture content, the measurements of soil samples were made using both an open-ended dielectric coaxial probe and the GPR. Based on the measurement results, correlations between the GPR and reflector for each frequency at 900 MHz and 1 GHz were found for the dielectric constants and the moisture content. Finally, the mechanism of the measurement device to be implemented in the field is suggested.

• 한국연초학회지
• /
• 제3권1호
• /
• pp.30-40
• /
• 1981

The moisture sorption and desorption isotherms of various tobaccos were obtained over a relative humidity range from 0 to 90% at $20^{\circ}C$ and $30^{\circ}C$. The hysteresis effect, constant and rate of moisture sorption and desorption, monomolecular-layer moisture content, and specific surface area were analyzed from the obtained data. The moisture sorption and desorption isotherms showed a different characteristics for different tobacco varieties. At a lower humidity range below 50% RH, Burley tobacco had higher moisture sorption and desorption figures than Hicks and Basma, while, at a higher humidity range above 50% RH, Hicks had higher values than the others. The hysteresis effect of tobacco were greater in an intermediate humidity range (40-70% RN), and Basma showed a greater effect than the others. The sorption and desorption constant (K) increased with temperature, but decreased with RH, and Burley tobacco had larger K values, while Hicks had smaller K values than others. The sorption and desorption rate of Burley tobacco were greater than the other tobaccos. The monomolecular-layer moisture was 27.8 and 51.4mg/g, and the specific surface was 101 and $186m^2/g$, for Basma and Burley, respectively.

• 한국식품저장유통학회지
• /
• 제6권1호
• /
• pp.37-42
• /
• 1999

The equilibrium moisture content(EMC) of Shiitake mushroom is and important factor because it has a close relationship to storage and drying problems. The determination of the EMC for Shiitake mushroom was made in atmospheres of various constant humidities at four different constant temperatures and the fitting of the five selected EMC models were performed with the experimental EMC data. The desorption equilibrium moisture contents for Shiitake mushroom were increased as the temperature was decreased and the relative humidity was increased. The significant difference of the equilibrium moisture content was appeared between the cap and the stipe of Shiitake mushroom. The Henderson-Thompson model was fitter than the others with the experimental data.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
• /
• pp.229-232
• /
• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice, brown rife and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The effect of density fluctuation, which is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation and moisture density is proposed for reducing the effects of density fluctuation on the moisture content measurement.

• 한국환경과학회지
• /
• 제4권1호
• /
• pp.1-12
• /
• 1995

The assessment for a degree of drought has been carried out based on the soil moisture index in Korea. The soil moisture index(Im) was calculated assuming of constant evapotranspiration until wilting point as Im = w2/wf $.$100. The soil moisture content(W2) at the final of a period is obtained from W2 : Pe + Wl - E, here the effective precipitation amount is Pe, evapotranspiration E, and the soil moisture content at the beginning of a period is Wl. The filed capacity(Wf), as a mean value of fine sandy loams, was reduced to 92 mm/ft when we accept the wilting point and the available soil moisture content of 42 mm/ft, respectively. The drought begins in Korea when the soil moisture index drops to less than 50%. The value coincides the isoline of 11 or more consecutive days without measureable precipitation. The soil moisture index frequently drops in the northern part of Youngnam area and Honam area so that both areas are well known as the areas of drought. Key word : Droughts, Soil Moisture Index.

• Journal of Electrical Engineering and Technology
• /
• 제13권2호
• /
• pp.892-901
• /
• 2018

Because of excellent electrical properties, epoxy resin is widely used in packaging and casting power equipment. Moisture and temperature in the environment are inclined to seriously affect the insulation tolerance of epoxy resin. This work focuses on the aging characteristics of epoxy resin in hygrothermal environment. Scanning electron microscopy images show that there are micro-crack, micro-slit and holes inside aged samples. The moisture absorption process undergoes three equilibrium stages and it does not follow the Fick's second law. Observing the change of hydrogen bonds in the infrared spectra of the dried samples, it is found that chemically moisture absorption immerges when the physical moisture absorption entered the third equilibrium stage. By Debye equation to fit the imaginary part of the dielectric constant, it is concluded that the uniformity of water molecule has a great influence on the electrical conductivity loss. Furthermore, the polarization loss can be more easily affected by water molecules than small free molecules. After the aged samples being dried, their real and imaginary part of the dielectric constant descend, but their original electrical properties cannot completely restored. After chemical moisture absorption appears inside the material, the residual space charges increase significantly and the charge dissipation rate slow down obviously.

• 지질공학
• /
• 제15권3호
• /
• pp.281-288
• /
• 2005

본 연구에서 는 복소유전율상수 반응으로부터 벤토나이트 공시체의 물성치인 체적함수비와 수분분포 특성 을 파악하기 위하여 수행되었다. 벤토나이트 재료는 현재 폐기물처분장에서 차수재료로 널리 이용되고 있다. 차수재료의 경우, 일반적으로 투수계수가 $10^{-7}\;cm/sec$ 이하로 작아야 한다. 난투수성 재료에 대해 온도구배 에 따른 수분분포 특성을 파악하기 위해 FDR-V 측정 장비를 적용해 이들을 측정하였다. 그 결과, 복소유전율상수는 체적 함수비와 온도 증가에 따라 함께 증가함을 알 수 있었다. 온도구배 에 따른 복소유전율상수 변화는 수분이동이 온도가 높은 쪽에서 낮은 쪽으로 증가함을 확인하였으며, 이는 수분분포 특성을 보여 준 것이다.

• Journal of Biosystems Engineering
• /
• 제11권1호
• /
• pp.52-63
• /
• 1986

This study was performed to find out drying characteristics and develop drying model for the design of an efficient dryer or drying system of red peper. The basic model which describes drying phenomenon of red pepper was firstly established, and drying tests were conducted at 14-different drying conditions. In this test, the effects of drying air temperature and relative humidity on the rate of drying were undertaken. Finally, a new drying model based on these experimental results was developed to describe the drying characteristics of red pepper. The results from this study may be summarized as follows. 1. Drying constant of the basic model established from Lewis' experimental model and diffusion equation was theoretically deduced as a function of moisture content and inner-temperature of red pepper. 2. From the results of drying tests, drying air temperature was found to have the greatest effect on the rate of drying. However, the effect of temperature was small for the condition of high relative humidity, and for low temperature, the effect of relative humidity was found to be large even though the range of relative humidity was low. 3. Modified Henderson equation was found to be better than Chung equation as the EMC model for the estimation of the equilibrium moisture content of red Pepper. 4. Constant-rate drying period did not exist in the red pepper drying test. And falling-rate drying period was divided into three distinct phases. Drying rate was dependent on the moisture content, the inner-temperature of red pepper and the change of physical property due to drying. 5. Drying constant increased with decrease of free moisture content, but it decreased at the end of the drying period. Also, drying constant was dependent on the drying air temperature and relative humidity. 6. The new drying model developed in this study was found to be most suitable in describing the drying characteristics of red pepper. Therefore, it may be concluded that drying time could be accurately estimated by the new drying model.

• 한국태양에너지학회 논문집
• /
• 제26권1호
• /
• pp.41-47
• /
• 2006

Moisture in a building is one of the most important variables influencing building performance, human health, and comfort of indoor environment. However, there are still lacks in the knowledge of understanding the moisture problem well and controlling moisture. Accordingly, in order to provide the fundamental data to control moisture contents in the indoor air, this study was to predict moisture contents transferred through building envelopes and indoor moisture generation rate. Moisture transfer model was made by physical relations in each node, and the indoor moisture generation rate was gained by comparing the model with experimental analyses. From the study, we found out that moisture generation rate was critical and day-periodic, so that we predicted the indoor moisture content by substituting the constant value gained from the average in a day for the moisture generation rate.

• 한국연초학회지
• /
• 제15권1호
• /
• pp.90-97
• /
• 1993

1. Average moisture content of tobacco in BIB silo was about 19: 1% until 4hours conditioned time, and then moisture variation of tobacco after 2hr conditioned was very small. 2. Application of mathematical model for ordering system. 1) The constant K in the exponential equation varies inversely with both relative humidity and equilibrium moisture. 2) Time needed to order blending tobacco leaves with standard moisture from bulking and blending silo was 4 hours. 3) Reconstituted tobacco sheet had higher moisture absorption ratio than Oriental and Burley tobacco. 4) For minimize of conditioning time in BIB silo, the values of K and Mo given in this study can be used in equation(1) to calculate moisture absorption ratio and optimum conditioning time. 3. Average moisture content and water activity of conditioned tobacco for 4 hours in BIB silo was about 20% and 0.65. In this condition. microbial life will inhibite 4. Physical properties of conditioned tobacco in bulking and blending silo for 4hours was virtually no change.