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

Shipping emissions have been considered a significant source of air pollution in the cities along the Yangtze River, with severe impacts on the climate and human health. This study created a complete annual ship emission inventory for the middle reaches of the Yangtze River and assessed its impact on air quality on a regional scale. To estimate the complete emissions, 9 main engine power regression models for different ship types were created to handle those vessels with absent main power data, and a high spatial-temporal resolution annual emission inventory was developed with the activity-based method combined with Automatic Identification System (AIS) data of the full year of 2018. The total emissions of CO2, CO, SO2, NOX, PM2.5, PM10 and HC in middle reaches of the Yangtze River were 5.67 × 105, 1.02 × 103, 5.41 × 102, 1.06 × 104, 2.43 × 102, 2.45 × 102 and 3.52 × 102 tons respectively. Then, the Weather Research and Forecasting with Chemistry (WRF-Chem) model was used to study the dispersion of the ship pollutants in the atmosphere and quantize the impact on the urban area. This research will provide services for the maritime authorities to develop green shipping and emission supervision.@en

The remote monitoring method based on air-quality monitoring sensors is a common way to monitor the FSC (fuel sulfur content) of oils for ships. Considering the influences of geographical environments, atmospheric conditions, regional ship traffic flow, emission characteristics of ships, and height of monitoring sensors on the monitor station chosen, a new method was proposed to optimize the site selection for monitoring the FSC of fuel oils used by ships in waters of the port. SO2 numeric simulation and observation from sensors were integrated to estimate the FSCs. The proposed method was utilized to recommend the sites of the fixed sniffing monitoring stations in Yantian port, Shenzhen, China from June and July 2018. The results showed that the experimental stations could monitor FSCs, and the relative difference between the estimated and actual FSCs of ships was 16.34%. The proposed method for recommending sites of FSC monitoring sensors contributed to intelligently supervising air pollutants emitted from ships and fuel oils of ships in the emission control areas of China.@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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