Estimation of Suspended Sediment Concentration by M5 Model Tree Based on Hydrological and Moderate Resolution Imaging Spectroradiometer (MODIS) Data

The Estimation of suspended sediment concentration (SSC) is an important factor in river engineering, which is used as an indicator of land-use change, water quality studies, and all projects related to constructions in rivers. In this research, the M5 model tree and the Moderate Resolution Imaging Spectroradiometer (MODIS) data were utilized to estimate the SSC at Ahvaz station on the Karun River. In this study, 135 cloud-free images of the MODIS sensor on the Terra satellite were taken for days corresponding to field SSC data, during the years 2000 to 2015. Input parameters of the model tree in this study were flow discharge, derived from hydrological data, and red (R), near-infrared (NIR) bands, and NIR/R ratio extracted from MODIS imagery. The results of statistical analysis illustrate that the M5 model outperforms the sediment rating curve (SRC) method, which is the most common method of estimating suspended sediment load. The Nash-Sutcliffe efficiency index for the M5 model tree of 0.58 was achieved, which was much better than that of the SRC method (0.26). At high fluxes, the efficiency of the SRC method significantly reduced, while the model tree provides acceptable results. The global sensitivity analysis on the M5 model pointed out that 93% of output variance was established by the main effects of input parameters, and less than 7% belong to the interaction effects. 73% and 12% of output variance specified by the main effects of flow discharge and NIR/R ratio, respectively.

     

Monoclinic RbD2PO4: Room temperature synthesis,chemical and structural stability upon heating

Monoclinic RbD₂PO₄ polycrystals (DRDP) were synthesized via the room temperature crystallization of RbH₂PO₄ (RDP) dissolved in D₂O. Powder X-ray diffraction (XRD) data collected at T = 25 °C indicate that this deuterated compound crystallizes in spacegroup P2₁/m with unit cell parameters a = 7.688 Å, b = 6.192 Å, c = 4.781 Å and β = 109.02°, and is isomorphic with the intermediate-temperature phase of its hydrogenated counterpart RDP. We found no evidence of a previously reported [Phase Transitions80, 17 (2007)] polymorphic phase transition in DRDP upon heating from room temperature to 210 °C. All lattice parameters vary smoothly within this temperature range, demonstrating that the P2₁/m phase persists upon heating. In addition, the unit cell volume of monoclinic DRDP is ∼1% greater than that of its RDP polymorph at all temperatures between 150 °C and 210 °C, which indicates the absence of significant deuterium-hydrogen isotope exchange. Further heating to 240 °C leads to the thermal decomposition of the title compound via dehydration.