[en] The pore structure of uranium-bearing sandstone is one of the critical factors that affect the uranium leaching performance. In this article, uranium-bearing sandstone from the Yili Basin, Xinjiang, China, was taken as the research object. The fractal characteristics of the pore structure of the uranium-bearing sandstone were studied using mercury intrusion experiments and fractal theory, and the fractal dimension of the uranium-bearing sandstone was calculated. In addition, the effect of the fractal characteristics of the pore structure of the uranium-bearing sandstone on the uranium leaching kinetics was studied. Then, the kinetics was analyzed using a shrinking nuclear model, and it was determined that the rate of uranium leaching is mainly controlled by the diffusion reaction, and the dissolution rate constant (K) is linearly related to the pore specific surface fractal dimension (D_S) and the pore volume fractal dimension (D_V). Eventually, fractal kinetic models for predicting the in-situ leaching kinetics were established using the unreacted shrinking core model, and the linear relationship between the fractal dimension of the sample's pore structure and the dissolution rate during the leaching was fitted

[en] Investigating the seepage characteristics of the leaching solution in the ore-bearing layer during the in situ leaching process can be useful for designing the process parameters for the uranium mining well. We prepared leaching solutions of four different viscosities and conducted experiments using a self-developed multifunctional uranium ore seepage test device. The effects of different viscosities of leaching solutions on the seepage characteristics of uranium-bearing sandstones were examined using seepage mechanics, physicochemical seepage theory, and dissolution erosion mechanism. Results indicated that while the seepage characteristics of various viscosities of leaching solutions were the same in rock samples with similar internal pore architectures, there were regular differences between the saturated and the unsaturated stages. In addition, the time required for the specimen to reach saturation varied with the viscosity of the leaching solution. The higher the viscosity of the solution, the slower the seepage flow from the unsaturated stage to the saturated stage. Furthermore, during the saturation stage, the seepage pressure of a leaching solution with a high viscosity was greater than that of a leaching solution with a low viscosity. However, the permeability coefficient of the high viscosity leaching solution was less than that of a low viscosity leaching solution

[en] A single-crystalline ZnGa₂O₄ epilayer was successfully grown on a c-plane (0001) sapphire substrate through metalorganic chemical vapor deposition. A metal-semiconductor-metal Schottky deep-ultraviolet (DUV) photodetector based on a ZnGa₂O₄ thin film was fabricated through a simple process of E-gun evaporation and thermal annealing. At a bias of 10 V, the ZnGa₂O₄ photodetectors exhibited excellent performance characteristics such as an extremely low dark current (0.86 pA), a responsivity of 0.46 A/W under 230-nm DUV, a high photo/dark current ratio (up to 4.68 × 10⁴), a sharp cutoff wavelength of approximately 270 nm, and short rise and fall times of 0.96 and 0.34 s. The photogenerated holes trapped in the Schottky barrier and the shrinking of the depletion region under DUV illumination enabled high DUV/visible rejection ratio (3–4 orders with a 20-V bias). Therefore, the Fowler–Nordheim field tunneling emission functioned as the main electron transport mechanism under DUV illumination and improved the photoelectric characteristics of the epilayer.

[en] Based on the theory of dynamics, this paper takes a certain drum-type transmission tower as the research object, performs parametric modelling based on the actual size, and performs modal analysis on the tower structure through the finite element method. The frequency and mode of the first 20 steps of the transmission tower were extracted. The results of modal analysis show the dynamic characteristics and structural characteristics of the drum-type transmission tower, providing a theoretical basis and foundation for studying the earthquake resistance, wind resistance and other environmental incentives of the transmission tower structure. (paper)

[en] To better understand the permeability of uranium sandstone, improve the leaching rate of uranium, and explore the change law of pore structure characteristics and blocking mechanism during leaching, we systematically analyzed the microstructure of acid-leaching uranium sandstone. We investigated the variable rules of pore structure characteristics based on nuclear magnetic resonance (NMR). The results showed the following: (1) The uranium concentration change followed the exponential law during uranium deposits acid leaching. After 24 h, the uranium leaching rate reached 50%. The uranium leaching slowed gradually over the next 4 days. (2) Combined with the regularity of porosity variation, Stages Ⅰ and Ⅱ included chemical plugging controlled by surface reaction. Stage Ⅰ was the major completion phase of uranium displacement with saturation precipitation of calcium sulfate. Stage Ⅱ mainly precipitated iron (Ⅲ) oxide-hydroxide and aluminum hydroxide. Stage Ⅲ involved physical clogging controlled by diffusion. (3) In the three stages of leaching, the permeability of the leaching solution changed with the pore structure, which first decreased, then increased, and then decreased

[en] We study the adsorption of zigzag graphene nanoribbons (GNRs) on Si(001) substrates using the first-principles density functional theory, exploring the effects of the interface interaction on the structural and electronic properties of both GNRs and the substrate. By comparing the adsorption structures predicted by the local density approximation, the generalized gradient approximation, and the DFT-D2 approach, we confirm that both edge and inner C atoms of GNRs can form covalent bonds with the substrate. The GNR/substrate interaction destroys the antiferromagnetic coupling of the edge states in GNRs. The charge transfer from the substrate to GNRs exhibits a complicated pattern and is mainly localized near the C–Si bonds. We also observe a strong perturbation of the surface states and a surface reconstruction transition induced by the GNR adsorption. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] The structural and electronic properties of N-doped zigzag graphene nanoribbons (N-ZGNRs) adsorbed on Si(001) substrates are investigated with first-principles density functional calculations. Compared with the free-standing N-ZGNRs, the energy difference between the substitutional doping at the edge and the inner sites is significantly decreased on the Si substrate. The distribution of the extra charge induced by the N substitutional dopant keeps the Friedel oscillation feature, and is a main effect that influences the C–Si bonding strength. When N is doped in regions with high C–Si bond densities, the strain induced by the dopant also plays an important role in determining the C–Si bonding interactions. Similar to the undoped case, the strong N-ZGNR/Si interaction destroys the antiferromagnetic coupling of the edge states in N-ZGNR, leading to a non-magnetic ground state for the N-ZGNR/Si heterostructures. (paper)

[en] Fluid mechanics has been linked to a wide range of disciplines, such as atmospheric science, oceanography and astrophysics. In this paper, we focus our attention on a (3 + 1)-dimensional variable-coefficient Kadomtsev-Petviashvili-like equation in a fluid. Through the Hirota method, we derive a bilinear form. We obtain an auto-Bäcklund transformation based on the truncated Painlev´e expansion and a bilinear Bäcklund transformation based on the bilinear form. With the variable coefficients α(t), β(t), γ (y, t), δ(t) and μ(t) taken as certain constraints, one- and two-kink solutions are shown. Based on the one-kink solutions, we take γ (y, t) as the linear and trigonometric functions of y, and then give the ring-type and periodic-type one-kink waves, where t and y are the independent variables. According to the two-kink solutions, we obtain the parabolic-type, linear-type and periodic-type kink waves. (author)

[en] The porous corrosion deposits (known as CRUD) adhered to the cladding have an important effect on the heat transfer from fuel rods to coolant in PWRs. The vapor film is the main constituent in the two-phase film boiling model. This paper presents a vapor film thickness correlation, associated with CRUD porosity, CRUD chimney density, CRUD particle size, CRUD thickness and heat flux. The dependences of the vapor film thickness on the various influential factors can be intuitively reflected from this vapor film thickness correlation. The temperature, pressure, and boric acid concentration distributions in CRUD can be well predicted using the two-phase film boiling model coupled with the vapor film thickness correlation. It suggests that the vapor thickness correlation can estimate the vapor film thickness more conveniently than the previously reported vapor thickness calculation methods

[en] Highlights: • A $(3+1)$-dimensional generalized nonlinear evolution equation arising in the shallow water waves. • Fusion and fission phenomena of the X-type, Y-type and periodic lump-stripe solitons are observed. • Influences of the coefficients of the equation on the periodic lump-stripe soliton solutions are analysed. Water waves are observed in, e.g., the rivers, lakes or oceans. In this Letter, the investigation is conducted on a $(3+1)$-dimensional generalized nonlinear evolution equation arising in the shallow water waves. Based on the Hirota method and symbolic computation, we obtain some X-type, Y-type and periodic lump-stripe soliton solutions. For the X-type soliton solutions, we observe the fusion and fission phenomena. For the Y-type soliton solutions, combined with the asymptotic analysis, we observe the fission phenomenon. For the periodic lump-stripe soliton solutions, we observe the fusion phenomenon between the periodic lump and stripe soliton. Periodic lump disappears and is finally swallowed by the stripe soliton during the propagation, which implies that the interaction is inelastic. Furthermore, we analyse the influences of the coefficients of the equation on the periodic lump-stripe soliton solutions.