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Different speciation of heavy metal ions has different toxicity level. The different speciation contents can be used as an important basis to evaluate the passivation efficiency of passivator. In this study, Ni2+, Cu2+ and Zn2+ in soil was passivated with thiol-functionalized nano-silica by solidification/stabilization technology, and the behavior of heavy metal ions in soil were explored. The result shows that, passivation time, soil moisture and passivator dosage can influence the toxicity of heavy metal ions via changing the speciation of metal ions. Passivation time and passivator dosage will promote passivation efficiency, while too low or too high soil moisture are not conducive to the passivation. The change of soil moisture will affect the surface charge distribution of soil and passivator, thus influence the migration of metal ions. According to speciation analysis, four kinds of speciation could be transferred reciprocally and the transformation will cause impact on the toxicity of heavy metal ions in soil. We explained the behavior of different metal ions based on the percentage of various speciation of heavy metal ions and inferred the transformation process of such metal ions in the passivation process. At the same time, based on Webber-Morris equation, the kinetic process during passivation process was discussed.

In this study, selective laser melting (SLM) of pure tantalum (Ta) was systematically investigated, with emphasis on densification, microstructure and mechanical properties of Ta specimen. The high laser scanning speed resulted in micropores and discontinuous scan tracks, owing to the elevated instability of the liquid induced by Marangoni convection and the balling effect. However, the interlayer thermal microcracks were produced at a low scanning speed, due to the thermal stress and balling effect. The microhardness and tensile strengths of the optimally SLM-processed Ta parts were improved to 445 HV and 739 MPa, respectively, which were considerably higher than specimens processed by cast (110 HV and 205 MPa) or powder metallurgy (120 HV and 310 MPa) method, due to the fine-grain strengthening. The fracture morphology of the tensile-failed SLM-processed specimens showed that the porosities and incompletely melted particles are responsible for the fracture of porous sample. While for dense sample, cleavage fracture and minor ductile fracture both account for the fracture. And the failure mechanisms were discussed. The reduced coefficient of friction of 0.3 and lowest wear rate of 7.1×10 −3 mm 3 N −1 m −1 in dry sliding wear tests were obtained for the optimally prepared Ta parts due to the formed adhesion of hardened tribolayers.

Registration is a critical step in many biomedical image analysis tasks. In this work, we propose a novel cascaded 3D U-Net with dilated convolution for volumetric image registration. We implement a coarse-to-fine registration strategy that commonly used in traditional registration methods by cascading two 3D U-Net based networks. In the first registration stage, a 3D U-Net network is employed to predict the large and coarse displacements. In order to capture more precise pixel-level displacement field, in the second stage, we propose to substitute the down-sampling operations in the encoding stage of 3D U-Net by dilated convolutions. As result, the resolution of feature map can be maintained as well as its field-of-view and semantic information. In addition, to obtain a more parameter-efficient network that is essential for volumetric image analysis, we replace the 3D convolution kernel by 3D dense separated convolution (3DDSC) module. We evaluated the proposed method on two commonly used datasets, and the results demonstrated that our method could obtain better performance than state-of-the-art image registration algorithms with short execution time.

BACKGROUND Reactive extraction is a promising technique for the recovery of amino acids from aqueous solutions. The reactive extraction of L-valine with di(2-ethylhexyl) phosphate acid (D2EHPA) has been studied in this paper. An expression of equilibrium distribution ratio (D) was proposed to describe the experimental data. RESULTS The diluents, equilibrium pH value (pHeq), the concentrations of L-valine and D2EHPA were found to be the key factors that affected D. The highest D was observed at pHeq around 2.6 with 1-octanol as diluent. D value increased with the increase of the concentration of D2EHPA. In contrast, as the increase of the concentration of L-valine, D value decreased. The extraction mechanism was analyzed by using Fourier infrared spectra. The reactive extraction mechanism of L-valine with D2EHPA was mainly via proton-transfer and ion-exchange process. By fitting the experimental data, (1:1) complex of L-valine with D2EHPA was deduced. The comparison of theoretical D values with the experimental data verified the reliability of the proposed mechanism equations. CONCLUSIONS L-valine was efficiently extracted from aqueous solutions using D2EHPA in 1-octanol, which provide preliminary practical information and theoretical basis for the separation of L-valine, as well as its purification and recovery.

At present, most of the magnetic bearing system adopts the classical proportional–integral–derivative (PID) control strategy. However, the external disturbances, system parameter perturbations, and many other uncertain disturbances result in PID controller difficult to achieve high performance. To solve this problem, a linear active disturbance rejection controller (LADRC) based on active disturbance rejection controller (ADRC) theory was designed for magnetic bearing. According to the actual prototype parameters, the simulation model was built in matlab/simulink. The step and sinusoidal disturbances with PID and LADRC control strategies were simulated and compared. Then, the experiments of step and sinusoidal disturbances were performed. When control parameters are consistent, the experiment showed that the rotor displacement fluctuation decreased by 28.6% using the LADRC than PID control under step disturbances and decreased by around 25.8% under sinusoidal disturbances. When the rotor is running at 24,000 r/min and 27,000 r/min, the displacement of rotor is reduced by around 15% and 13.7%, respectively. Rotate the rotor with step disturbances and sinusoidal disturbances. It can also be seen that LADRC has the advantages of fast response time and good anti-interference. The experiments indicate that the LADRC has better anti-interference performance compared with PID controller.