Abstract:The soil freeze-thaw controls the hydrological and carbon cycling and thus affects water and energy exchanges at land surface. This article reported a newly developed algorithm for distinguishing the freeze/thaw status of surface soil. The algorithm was based on information from Advanced Microwave Scanning Radiometer Enhanced (AMSR-E) which records brightness temperature (Tb) in the afternoon and after midnight. The criteria and discriminant functions were obtained from both radiometer observations and model simulations. First of all, the microwave radiation from freeze-thaw soil was examined by carrying out experimental measurements at 18Ð7 and 36Ð5 GHz using a Truck-mounted Multi-frequency Microwave Radiometer (TMMR) in the Heihe River of China. The experimental results showed that the soil moisture is a key component that differentiates the microwave radiation behaviours during the freeze-thaw process, and the differences in soil temperature and emissivity between frozen and thawed soils were found to be the most important criteria. Secondly, a combined model was developed to consider the impacts of complex ground surface conditions on the discrimination. The model simulations quite followed the trend of in situ observations with an overall relation coefficient (R) of approximately 0Ð88. Finally, the ratio of Tb18Ð7H (horizontally polarized Tb at 18Ð7 GHz) to Tb36Ð5V was considered primarily as the quasi-emissivity, which is more reasonable and explicit in measuring the microwave radiation changes in soil freezing and thawing than the spectral gradient. By combining Tb36Ð5V to indicate the soil temperature variety, a Fisher linear discrimination analysis was used to establish the discriminant functions. After being corrected by TMMR measurements, the new discriminant algorithm had an overall accuracy of 86% when validated by 4-cm soil temperature. The multi-year discriminant results also provided a good agreement with the classification map of frozen ground in China.
Taking advantage of the formation and assembly of cellulose nanocrystal surfactants (CNCSs) at the water-oil interface, where polar cellulose nanocrystals (CNCs) and end-functionalized polymer chains interact, the preparation and stability of emulsions prepared with CNCSs were investigated. The packing density of CNCSs at the interface can be adjusted by tuning parameters such as pH, ionic strength, and concentration/molecular weight of the end-functionalized polymer ligands. Stable non-spherical emulsions are obtained during homogenization, as a result of the interfacial jamming of CNCSs, with pH-triggered reconfigurability. Porous materials are prepared by freeze-drying creamed, CNCS-stabilized emulsions. The cells of the porous materials have a controlled pore size and shape that are commensurate with the droplets in the emulsion and are responsive to pH. The behavior of the adaptive, reconfigurable supracolloidal system is coupled to its internal and surrounding environment.
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