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[en] Highlights: • FEM is used to simulate the LTW process and is validated by the experiments. • The molten pool geometry (both width and depth) are studied in detail by FEM. • RSM models are developed between process parameters and responses of interest. • The interaction effects of process parameters on the WW and DTA are investigated. • The influence of molten pool D/W ration on the shear strength is firstly studied. - Abstract: This study concerns the laser transmission welding (LTW) of polyethylene terephthalate (PET) and polypropylene (PP) which are widely used in the automotive, aerospace and medical industries. The relationships of process parameters, molten pool geometry (both width and depth) and shear strength (SS) in LTW process are systematically investigated through finite element method (FEM), response surface methodology (RSM) and experiments. Thereinto, the relationships between the molten pool depths to width (D/W) ratio and SS are firstly investigated. Firstly, a three-dimensional thermal model is developed to simulate the temperature field and molten pool geometry of the LTW process. The simulation results are confirmed by experiments. Then RSM is utilized to design the experiments and establish the mathematical relationships between the process parameters and molten pool geometry based on the simulation results. The interaction effects of the process parameters on the molten pool geometry are analyzed. Finally, the simulation results are further used for searching the relationships between the molten pool D/W ratio and the SS (from tensile experiments). The maximum value of the SS and the corresponding molten pool D/W ratio is found. The result reveals that the molten pool D/W ratio has a significant influence on the SS. Moreover, this finite element model can also play a commendable guiding role in the LTW experiments with acceptable accuracy

[en] As a novel concept of vircator geometry proposed, the outward-emitting coaxial vircator (OECV) is at the cutting edge in the field of high-power microwave (HPM) source researches. Theoretical analyses are carried out to study the space-charge-limiting current in coaxial configuration and the terms of virtual cathode formation. According to the simulation results, OECV has the advantages in energy conversion efficiency and bears the potentialities in increasing the high-power microwave pulse width, as well as in generating HPM in relatively low bands. Two kinds of geometries for HPM emission are also given

[en] LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 (NCA) microspheres covered by a nanoscale Li_2TiO_3-based shell were synthesized by a facile strategy based on a solvothermal pre-coating treatment combined with a post-sintering lithiation process. The morphology, structure and composition of the Li_2TiO_3-coated NCA samples were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning scanning electron microscope (SEM) with an energy-dispersive X-ray spectroscope (EDS), and transmission electron microscopy (TEM). Owing to the complete, uniform and nanoscale Li_2TiO_3 coating shell, the resultant surface-modified NCA microspheres used as Li-ion battery cathode materials manifest remarkably enhanced cycling performances, attaining 94% and 84% capacity retention after 200 and 400 cycles at 0.5 C, respectively, which is much better than the pristine NCA counterpart (60% retention, 200 cycles). More impressively, the surface-modified NCA also shows an intriguing storage stability. After being stored at 30 °C for 50 days, the coated NCA-based cells are subjected to be cycled both at room and elevated temperatures, in which the aged cells can still remain 84% capacity retention after 200 cycles at 25 °C and 77% capacity retention after 200 cycles at 55 °C, respectively. All these results demonstrate that the Li_2TiO_3-coated LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 microsphere is a promising cathode material for Li-ion batteries with long lifespan. - Graphical abstract: Nanoscale Li_2TiO_3-based shell encapsulated LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 (NCA) microspheres are fabricated through a solvothermal pre-coating treatment combined with post-lithiation process. The surface-coated NCA as cathode materials shows a remarkably enhanced cycling performance and storage stability for long lifespan Li-ion batteries. - Highlights: • Li_2TiO_3 is used as coating materials for layer structured LiNi_0_._8Co_0_._1_5Al_0_._0_5O_2 cathode. • Solvothermal coating strategy is employed to strengthen surface coating. • Coating layer improves the velocity of Li"+ migration on electrode surface. • Erosion from the HF and CO_2 on electrode is greatly suppressed.

[en] The paper discussed the main problems of the release limit of radioactive liquid effluents in operating nuclear power plants, described the principles of the review, and introduced the review practice of the release limit of liquid effluents in Qinshan phase three, Daya Bay and Tianwan nuclear power plants. (authors)

[en] Highlights: • B, E and v increase as pressure increases, except for a sudden decrease at 40 GPa. • WSe₂ under pressure has larger shear modulus and higher hardness than WSe₂ at 0 GPa. • WSe₂ has an isostructural semiconductor-semimetal phase transition at 40 GPa. • The covalent bonding between Se and W atoms in the slabs is enhanced under pressure. • The distance of the stacked Se–W–Se slabs is decreased with the increasing pressure. - Abstract: Effect of pressure on elastic, mechanical and electronic properties of WSe₂ has been investigated using the first-principles calculations. The calculated lattice parameters, band structure and elastic constants of WSe₂ at 0 GPa are in good agreement with the available experimental and calculational values. With the increasing pressure, the lattice parameters and volume of WSe₂ decrease whereas the total enthalpy increases. The bulk modulus, Young's modulus and Poisson's ratio of WSe₂ increase with the increasing pressure, except for a sharp decrease at the pressure of 40 GPa. WSe₂ under pressure has larger shear modulus and higher hardness than WSe₂ at 0 GPa. With the increase of pressure, the covalent bonding between Se and W atoms in the slabs is enhanced whereas the distance of the stacked slabs is decreased. Additionally, an isostructural semiconductor-semimetal phase transition of WSe₂ is found to take place at 40 GPa, which is consistent with the experimental observations

[en] Isolation technology can effectively reduce the acceleration of the superstructure of the nuclear power plant (NPP), however, under the strong earthquake, the large displacement of the isolation layer may lead to pipeline breakage. In this paper, a negative stiffness damping (NSD) system was proposed based on the principle of surface motion and the prestressing spring expansion and contraction. The negative stiffness was achieved by the spherical hinge movement on the curved surface of the arch, and its viscous damping worked in the spring compression direction. The theoretical restoring force model of negative stiffness system was also put forward and its mechanical properties were analyzed. The negative stiffness device was designed and the static test was competed. The test results are highly consistent with the theoretical restoring force model. The comparative analysis of seismic responses between isolated structure with NSD nuclear power plant and that with isolated nuclear power plant was carried out. By comparing the seismic responses under different seismic wave inputs, the results show that the proposed NSD system can effectively reduce the upper acceleration response and isolation displacement response. (authors)

[en] Highlights: • Li_4Ti_5O_1_2 (LTO) spheres are prepared by molten-salt and TiO_2 spheres as template. • The LTO spheres are potential for using as anode for AC//LTO hybrid capacitor. • The AC//LTO hybrid supercapacitor presents good electrochemical performance. - Abstract: There is a growing demand for hybrid supercapacitor systems to combine the advantages of both lithium-ion battery and supercapacitors for the application of electric vehicles. We describe in this paper one kind of hybrid supercapacitor comprising spherical Li_4Ti_5O_1_2 as negative electrode and activated carbon (AC) as positive electrode in the non-aqueous electrolyte. The Li_4Ti_5O_1_2 spheres were synthesized using a LiCl-KCl molten-salt method and TiO_2 spheres as the template. The Li_4Ti_5O_1_2 spheres revealed high discharge capacity (168 mAh g"−"1 at 0.2 C), and a good capacity retention with high coulombic efficiency after cycling, which can be potential anode material for lithium ion batteries and negative material for hybrid supercapacitor. The AC//LTO hybrid supercapacitor exhibits excellent capacity retention of 93% after 500 cycles and offers higher energy density and power density than the AC//AC symmetric supercapacitor. The presented AC//LTO hybrid supercapacitor could be a competitive candidate for the promising energy storage devices

[en] The studies of petrography, mineral paragenesis, and fluid inclusion of 302 uranium deposit show there are three types of fluid inclusion that include H₂O-type, H₂O-CO₂-type, and CO₂-type, occur in pitchblendequartz veins and alteration quartz grains. The melting of ice of H₂O inclusions is from -0.8 ℃ to -3.4 ℃, corresponding to the salinities between 2.39% wt_NaCl equiv and 5.55% wt_NaCl equiv, the homogenization temperatures range from 106 ℃ to 254 ℃. About the H₂O-CO₂ inclusions, their filling degree are commonly from 20% to 90%, with total homogenization temperatures are from 198 ℃ to 354 ℃, and salinities span from 3.76% wt_NaCl equiv to 9.24% wt_NaCl equiv. The homogenization temperatures of CO₂ inclusions are from 17.8 to 22.1 ℃. The petrography observation and microthermometry of fluid inclusion suggest the ore-forming fluid has experienced CO₂ effervescence which is probably the important mineralization mechanism. The mineralization temperature is about 250 ℃, with pressure is about (1.0∼1.1) × 10⁸ Pa. (authors)

[en] An irreversible cycle model of magnetic Brayton refrigerators is established, in which the thermal resistance and irreversibility in the two adiabatic processes are taken into account. Expressions for several important performance parameters, such as the coefficient of performance, cooling rate and power input are derived. Moreover, the optimal performance parameters are obtained at the maximum coefficient of performance. The optimization region (or criteria) for an irreversible magnetic Brayton refrigerator is obtained. The results obtained here have general significance and will be helpful to understand deeply the performance of a magnetic Brayton refrigeration cycle