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Digital rock twins are widely used to obtain hydraulic properties of porous media by simulating pore-scale fluid flow. Multifractal characteristics of pore geometry and flow velocity distribution have been discovered with two-dimensional (2D) images and three-dimensional (3D) models, whereas the dependency of results on the resolution is not well known. We investigated resolution-dependent multifractal properties of 3D twin models for a sandstone sample with originally 3 μm resolution images. 3D pore-scale water flow was simulated with the lattice Boltzmann method (LBM). As indicated by multifractal analyses, the generalized dimension spectra, the Hölder exponent spectra, and singularity spectra of the flow velocity are similar to that of the pore geometry but different in ranges and sensitivities to the change in the model resolution. Nonlinear dependencies of 2D/3D porosity, holistic/slice permeability, equivalent pore radius squared, and multifractal parameters on the resolution were discussed.

Additional file 1: Figure S1. Sampling sites on the Tibetan Plateau. Figure S2. Physicochemical parameters in saline and nonsaline soil on the Tibetan Plateau. Figure S3. The difference of bacterial community functions in saline and nonsaline soil on the Tibetan Plateau. Figure S4. Normalized abundance of functional pathways of carbon fixation (a) and methane metabolism (b) of bacterial community in saline and nonsaline soil on the Tibetan Plateau. Figure S5. The ratio of sulfur cycling genes in saline and nonsaline soil on the Tibetan Plateau. Figure S6. The normalized abundance of heavy metal(loid)s resistance genes in saline and nonsaline soil on the Tibetan Plateau. Figure S7. The normalized abundance of environmental stress response genes in saline and nonsaline soil on the Tibetan Plateau. Figure S8. The correlation analysis of bacterial community composition and function with environmental factors in saline and nonsaline soil on the Tibetan Plateau. Table S1. The alpha diversity of bacterial community in saline and nonsaline soils of Tibetan Plateau. Table S2. The topology structure characteristics of network of bacteria and environmental factors. Table S3. Genera in different modules in network of genus and environmental factors.

Groundwater flow system has long been recognized as the local, intermediate and regional flow systems since Toth (1963). For groundwater flow in an unconfined aquifer between two parallel rivers (or ditches), as indicated by Hubbert (1940), there are two local flow systems contributing groundwater discharge to the two rivers from infiltration recharge. Surprisingly, this model has never been examined until Han et al. (2019) pointed out that something may be wrong: not only two flow systems exist. The problem was further investigated with a two-dimensional numerical model on MODFLOW for saturated groundwater flow below the arch-shape water table receiving a uniform infiltration recharge. Streamlines were obtained with MODPATH to identify the flow systems. We discovered that an abnormal groundwater flow system could emerge beneath the two local flow systems under some conditions, which forms a pass through flow from the high river to the low river. This pass-through flow system exists when the water level difference between the two rivers is sufficiently large and the infiltration recharge is sufficiently low. As a result, the base flow of the low river may be not only attributed to the captured infiltration recharge from the nearby local flow system but also partly originated from the high river. The ratio of the contribution from the pass-through flow system to the total groundwater discharge toward the low river could be higher than 20% and almost linearly increases with the water level difference between two rivers. More details of such an abnormal groundwater flow system were investigated as well.

A bifunctional imidazolium functionalized Zr-based metal–organic framework, (I–)Meim-UiO-66, was successfully prepared, which can serve as an efficient heterogeneous catalyst towards the capture and coupling of CO2 with epoxides., A bifunctional imidazolium functionalized zirconium metal–organic framework (Zr-MOF), (I–)Meim-UiO-66 (2), was successfully prepared from the imidazole-containing Zr-MOF Im-UiO-66 (1) by a post-synthetic modification (PSM) method. It was found that the crystal size and pore features of the imidazole-containing 1 could be tuned at the nanoscale. The bifunctional MOF 2, containing Brønsted acid sites and iodide ions, was shown to be an efficient and recyclable heterogeneous catalyst for the cycloaddition of carbon dioxide (CO2) with epoxides, without the use of any co-catalyst, at ambient pressure. The solvent-free synthesis of the cyclic carbonate from CO2 and an epoxide was monitored by in situ Fourier transform infrared spectroscopy (FT-IR) and an acid/base synergistic catalysis mechanism was proposed. We hope that our strategy provides an effective approach for the introduction of functional N-heterocyclic groups into MOFs for potential applications.

Based on the state equation and thermal shear stress. the tertiary pyroelectric effect of thick ferroelectric crystal plates with partially uniform heating is discussed. The polarizations of 2, 3m and 4mm point group crystals produced by the tertiary pyroelectric effect are derived. The results show that at the upper and lower surface separation of heated and nonheated region, electric charges will be induced with density proportional to the temperature gradient at the separation and to the thickness of the plate. Calculations concerning LiNbO3 crystal are in accord with experiments.

Optical transmissions of z-cut and x-cut ferroelectric LiTaO3 single crystals are measured from 200 nm to 25 μm. The optical properties of poled and annealed samples are compared and discussed respectively.

Based on the state equation and theory of stresses in plates and shells, the tertiary pyroelectric effect due to nonuniform temperature distribution is discussed for single axial ferroelectric crystal wafers with simply supported edges boundary conditions. The tertiary pyroelectric coefficients are derived for temperature gradients parallel to and vertical to the polar axis.

A confined aquifer may become unconfined near the pumping wells when the water level falls below the confining unit in the case where the pumping rate is great and the excess hydraulic head over the top of the aquifer is small. Girinskii's potential function is applied to analyze the steady ground water flow induced by pumping wells with a constant-head boundary in a mixed confined-unconfined aquifer. The solution of the single-well problem is derived, and the critical radial distance at which the flow changes from confined to unconfined condition is obtained. Using image wells and the superposition method, an analytic solution is presented to study steady ground water flow induced by a group of pumping wells in an aquifer bounded by a river with constant head. A dimensionless function is introduced to determine whether a water table condition exists or not near the pumping wells. An example with three pumping wells is used to demonstrate the patterns of potentiometric surface and development of water table around the wells.

Investigation of electronegative plasmas has now been atrractive due to the advantages of negative-ion assisted etching and charge-free ion implantation in semiconductor manufacture. Langmuir electrostatic probe, as a simple, inexpensive and good spatial resolution diagnosic tool, is popularly used in investigating electronegative plasmas. In this paper, the Langmuir electrostatic probe is proposed to measure the capacitively coupled Ar plasmas with added electronegative gases, such as O2, Cl2 and SF6. The experimental results from the measurements of Ar plasmas with added electronegative gases driven by a 40.68 MHz field indicate that, with increasing flow rate of electronegative gas, high energy peak will occur in electron energy possibility function and shift towards higher energyside. The addition of electronegative gases reduces the electron density significantly as the electron temperature increases. We also calculate the electronegativity of Ar plasmas for the three kinds of electronegative gases. The preliminary interpretations of the above experimental phenomena are presented.