Ionic rare earth ore is a type of featured rare earth ore in China. Its mining process suffers from a long leaching cycle and considerable consumption of leaching agents. Improving mining efficiency requires a sound physical understanding of the leaching process. In this study, the CFD-based numerical model is used to analyze the physical process of leaching through porous media formed by particles. The simulation results indicate that a lower packing porosity and smaller particles packed granular porous medium result in much larger energy dissipation during seepage, and the energy dissipation increases with seepage velocity. It is found that when the seepage velocity increases to a certain high value, the energy dissipation exceeds the value predicted by Darcy’s law, which is mainly caused by liquid turbulence. Additionally, the effect of particle shape is examined. The results show that the granular medium composed of prolate particles causes larger energy dissipation than oblate particles, and spherical particles play the least role. This phenomenon may result from the particle shape affecting the area of the frontal contact surface between particles and liquid. The results provide new insights into the fundamental understanding of percolation and seepage behaviors in the ion-adsorption-type rare earth ore leaching process.@en

Three upcoming Martian missions will deploy a ground-penetrating radar (GPR) to reveal the fine-resolution subsurface structure and dielectric properties of materials beneath the surface. Numerical forward simulations of radar echo using a model of the near-surface structure at the landing site can provide a valuable reference for processing and interpretation of future radar data collected on Mars. In this study, based on the geological information of the Jezero crater, a detailed stratigraphic model of the near-surface structure is derived, which includes several key features, for example, the randomness of the medium, terrain, and cracks. To identify correctly the reflections of subsurface interfaces and fractures from the radar image, a v(z) f-k migration is carried out, the performance of which is evaluated using the GPR data obtained near Antarctic Zhongshan Station since the electrical properties of Antarctic glaciers and Martian materials are to some extent comparable. The results in this work show that compared with common migration algorithm, the v(z) f-k method not only improves the clarity of radar image but also provides the permittivity profiles to infer the composition of the substrate, leading to a better understanding of Martian near-surface geology.

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This paper presents an ultrasound receiver ASIC in 180nm CMOS that enables element-level digitization of echo signals in miniature 3D ultrasound probes. It is the first to integrate an analog front-end and a 10-b Nyquist ADC within the 150 μ m element pitch of a 5-MHz 2D transducer array. To achieve this, a hybrid SAR/shared-single-slope architecture is proposed in which the ramp generator is shared within each 2 × 2 subarray. The ASIC consumes 1.54mW/element and has been successfully demonstrated in an acoustic imaging experiment.

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Abstract: At 1023 K, the electrochemical behavior of Si(IV) on the tungsten electrode in CaCl₂–CaF₂–CaO–SiO₂ molten salt was studied by cyclic voltammetry, square-wave voltammetry and open-circuit chronopotentiometry. The reduction potential of Si(IV) started at –0.68 V, and the intermediate product CaC₂ was observed at –1.78 V. The reduction of Si(IV) on the tungsten electrode was a one-step four-electron transition, which was a diffusion-controlled mass transfer process. The diffusion coefficient for the reduction process of Si(IV) ions was estimated to be 3.22 × 10^–5 cm² s^–1 at 1023 K. With the temperature interval from 993 to 1183 K, the diffusion activation energy was calculated to be 4.425 kJ mol^–1. Moreover, the deposition of Si(IV) occurs when the applied potential is less than –0.6 V (vs. Pt wire). The present electrochemical study on Si(IV) in the molten salt will be a theoretical reference for future silicon electrorefining.

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