scholarly journals Effect of Suction Cycles and Suction Gradients on the Water Retention Properties of a Hard Clay

2015 ◽  
Vol 2015 ◽  
pp. 1-6
Author(s):  
Liufeng Chen ◽  
Hua Peng
Keyword(s):  
Diffusion Coefficient ◽  
Relative Humidity ◽  
Water Retention ◽  
Moisture Diffusion ◽  
Two Dimensional ◽  
Moisture Diffusion Coefficient ◽  
Dimensional Diffusion ◽  
Water Retention Properties ◽  
Cylindrical Samples ◽  
Hydration And Dehydration

The effect of suction cycles and suction gradients on a hard clay is investigated. The cylindrical samples of the hard clay are prepared to carry out the hydration and dehydration tests with different suction gradient and suction cycles. The results show that the suction gradient has little effect on the suction-water content relation, while the suction cycle has great effect on it, particularly the first cycle of hydration and dehydration. The apparent moisture diffusion coefficient of the hard clay has been identified by the use of a two-dimensional diffusion model. The moisture diffusion coefficient varies between 4.10−11 m2/s and 2.10−10 m2/s and it decreases during dehydration while the relative humidity is less than 85%. The results also show that the suction cycles play little effect on the moisture diffusion coefficient.

scholarly journals Evaluation of the Mass Diffusion Coefficient and Mass Biot Number Using a Nondominated Sorting Genetic Algorithm

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 260 ◽  
Author(s):  
Radosław Winiczenko ◽  
Krzysztof Górnicki ◽  
Agnieszka Kaleta
Keyword(s):  
Genetic Algorithm ◽  
Diffusion Coefficient ◽  
Biot Number ◽  
Moisture Diffusion ◽  
Absolute Error ◽  
Mass Diffusion ◽  
Precise Determination ◽  
Nsga Ii ◽  
Moisture Diffusion Coefficient ◽  
Nondominated Sorting

A precise determination of the mass diffusion coefficient and the mass Biot number is indispensable for deeper mass transfer analysis that can enable finding optimum conditions for conducting a considered process. The aim of the article is to estimate the mass diffusion coefficient and the mass Biot number by applying nondominated sorting genetic algorithm (NSGA) II genetic algorithms. The method is used in drying. The maximization of coefficient of correlation (R) and simultaneous minimization of mean absolute error (MAE) and root mean square error (RMSE) between the model and experimental data were taken into account. The Biot number and moisture diffusion coefficient can be determined using the following equations: Bi = 0.7647141 + 10.1689977s − 0.003400086T + 948.715758s2 + 0.000024316T2 − 0.12478256sT, D = 1.27547936∙10−7 − 2.3808∙10−5s − 5.08365633∙10−9T + 0.0030005179s2 + 4.266495∙10−11T2 + 8.33633∙10−7sT or Bi = 0.764714 + 10.1689091s − 0.003400089T + 948.715738s2 + 0.000024316T2 − 0.12478252sT, D = 1.27547948∙10−7 − 2.3806∙10−5s − 5.08365753∙10−9T + 0.0030005175s2 + 4.266493∙10−11T2 + 8.336334∙10−7sT. The results of statistical analysis for the Biot number and moisture diffusion coefficient equations were as follows: R = 0.9905672, MAE = 0.0406375, RMSE = 0.050252 and R = 0.9905611, MAE = 0.0406403 and RMSE = 0.050273, respectively.

scholarly journals Humidity interaction of lichens under astrobiological aspects: the impact of UVC exposure on their water retention properties

2015 ◽  
Vol 14 (3) ◽  
pp. 445-456 ◽  
Author(s):  
J. Jänchen ◽  
J. Meeßen ◽  
T.H. Herzog ◽  
M. Feist ◽  
R. de la Torre ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Thermal Analysis ◽  
Low Temperature ◽  
Water Retention ◽  
The Other ◽  
Dry Conditions ◽  
Buellia Frigida ◽  
Water Retention Properties ◽  
The Impact ◽  
Hydration And Dehydration

AbstractWe quantitatively studied the hydration and dehydration behaviour of the three astrobiological model lichens Xanthoria elegans, Buellia frigida and Circinaria gyrosa by thermoanalysis and gravimetric isotherm measurements under close-to-Martian environmental conditions in terms of low temperature and low pressure. Additionally, the impact of UVC exposure on the isolated symbionts of B. frigida and X. elegans was studied by thermoanalysis and mass spectrometry as well as by gravimetric isotherm measurements. The thermal analysis revealed whewellite as a component of C. gyrosa which was not found in B. frigida and X. elegans. Neither the water retention nor the thermal behaviour of symbionts changed when irradiated with UVC under dry conditions. On the other hand, UVC irradiation of the wet mycobiont of B. frigida had a distinct impact on the hydration/dehydration ability which was not observed for the mycobiont of X. elegans. Possibly the melanin of B. frigida's mycobiont, that is not present in X. elegans, or a specifically damaged acetamido group of the chitin of B. frigida may be the sources of additional UVC-induced sorption sites for water associated with the UVC exposure.

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