Search

• Impacts of wall porosity on fracture flow were systematically investigated at pore scale. • Mechanisms governing direction and magnitude of fluid exchange at the fracture-matrix interface were elucidated. • Flux contributions of porous walls to fracture outlet and fracture-matrix interface were functionalized by wall porosity. • Influence of porous walls cannot be equivalently represented by applying slip boundary conditions. This study investigates the influence of porous walls on fluid flow behavior in single rough-walled fractures. A series of direct numerical simulations (DNS) were conducted to examine fluid flow through rough-walled fractures surrounded by porous walls under various hydraulic gradients. The simulation results clearly demonstrate the progressively significant impact of porous walls on flow characteristics as porosity increases. Regression analyses indicate that the Forchheimer's law, which characterizes the nonlinear flow of rock fractures, remains valid in the presence of porous walls. Moreover, increased porosity enhances fluid exchange and leads to an increased ability for single fractures to transmit fluid. Two double-parameter equations were established to quantitatively characterize the effects of porous walls on hydraulic conductivity of the fracture and fluid exchange between porous walls and the fracture. Further analysis revealed that the angle between the fracture profile and main flow direction profoundly influences the inflow/outflow exchange between the fracture and its adjacent porous walls. Moreover, the pore-scale results indicate that it is unreasonable to equate the effect of porous walls with slip boundaries as suggested in previous studies. The results and findings of this study deepen our understanding of flow behavior at the interface between the rough-walled fracture and adjacent porous walls, and they serve as a basis for accurately simulating large-scale fracture networks that consider the hydraulic contribution of fracture walls. [ABSTRACT FROM AUTHOR]

Black-phase formamidinium lead iodide (FAPbI3), with a narrow bandgap and high thermal stability, has emerged as an in-demand material for highly efficient perovskite solar cells (PSCs). In a two-step sequential deposition, the PbI2 film plays an important role in the formation of a perovskite film with desirable qualities. This paper explores using N-methyl-2-pyrrolidone (NMP), a strong Lewis base, and N,N-dimethylformamide (DMF) as a mixed precursor solvent (DMF/NMP) of PbI2 and reports on preparing PbI2 films with a porous morphology by thermal treatment. Porous PbI2 films ensure the diffusion and sufficient reaction of the formamidinium iodide solution to form a smooth perovskite film. In addition, a dynamic spin coating method is also introduced to improve the uniformity of the perovskite film. Both methods yield a pure α-phase FAPbI3 film immediately in the unannealed state, which is necessary for the perovskite film to maintain phase stability. Finally, PSCs with a power conversion efficiency of 21.20% (0.13 cm2) are fabricated and optimized. The unencapsulated PSCs retain 90% of the initial efficiency for 1000 hours in dry air and exhibit a good thermal stability when heated to 85 °C. [ABSTRACT FROM AUTHOR]

A large-scale obliquely inclined bedding rockslide, activated by a heavy rainstorm, occurred on July 8, 2020, at 7:05 (UTC + 8) in Shiban Village, Songtao Miao Autonomous County, Guizhou Province, China. The loss of life in this event was greatly reduced owing to the local warning system for rainstorm-induced geohazards. To understand the failure characteristics, triggering factors, the genetic mechanism of the landslide, the geomorphological features, geological characteristics, hydrological conditions, and rainfall characteristics were systematically studied by a synthetic approach including field investigations, satellite imagery, unmanned aerial vehicle (UAV) photography, laboratory tests, and rainfall data statistics. The results indicated that the interface between the soft and hard rock, the well-developed joints, and the free face in front of the slope constituted the boundaries of this landslide. The concave topography at the back and southern edge of the landslide, the bare ground, and the cataclastic structure of the rock mass provided favorable conditions for the collection or infiltration of rainwater. The concentrated rainstorm was the direct trigger for the landslide, which led to a rapid inflow and retention of rainfall in the landslide through favorable landform and geological conditions. The groundwater recharge that cannot be drained in time caused the mechanical deterioration of rock mass and induced a rapid increase in pore water pressure in the landslide. Moreover, the water level of the Ganlong River at the toe of the slope also rose rapidly, and the uplift pressure in front of the slope increased accordingly. Under the combined action of these adverse factors, the overall anti-sliding force of the slope was less than the sliding force, finally resulting in the landslide. Remarkably, the local warning system for rainstorm-induced geohazards successfully forecasted the landslide, but the shortcoming is that the forecast time in advance is short. Nevertheless, the prediction has significantly reduced human casualties and provided valuable experience for the prediction of this type of landslide. [ABSTRACT FROM AUTHOR]

• The perovskite film was prepared by ultrasonic spraying method. • Isopropyl alcohol (IPA), a green solvent with low boiling point, was introduced into perovskite precursor solution. • IPA-based PSCs exhibit the champion device efficiency of 22.43 %. The ultrasonic spray coating has been shown to be an effective technique for scaling up production. The nucleation and crystallization process of the perovskite film prepared by the ultrasonic spraying approach is more complicated than that by the spin coating, but they are essential to gaining efficient perovskite solar cells (PSCs). At the same time, the green solvent is the primary problem that must be solved in the process of PSCs commercialization. In this paper, the low boiling point and green solvent isopropyl alcohol (IPA) is introduced into the perovskite precursor solution to prepare FAPbI 3 perovskite by ultrasonic spraying. The addition of IPA enhanced the saturated vapor pressure of the precursor solution, which can create the local chemical microenvironment on the film surface and subsequently retard the nucleation rate from 8.31 s to 8.54 s at nucleation stage. The local chemical improves the initial homogeneity of the sol–gel phase and then leads to improved structural and optoelectronic properties within the FAPbI 3 film via sufficient crystallization from the sol–gel phase to α-FAPbI 3. Ultimately, IPA-based PSCs exhibit the champion device efficiency of 22.43 %. The good long-term stability of PSCs (maintain more than 90 % of the initial efficiency after 1000 h, and keep 80 % after 400 h) in ambient conditions. [ABSTRACT FROM AUTHOR]

• Influencing factors of infiltration modes were systematically investigated. • A semi-analytical model for three infiltration scenarios was established. • Evolution features of water head and stratified wetting zone were revealed. The classic GA model assumes a constant-head ponded water and with a saturated water content above the wetting zone, which limits its application. This study investigated a semi-analytical method for predicting rainwater infiltration into an inclined soil interlayer considering time-varying head and stratified water content. An evolving wetting profile and a half-parabolic wetting profile of transient zone were observed during infiltration process based on numerical simulations. The water head in the fissure showed a linearly-increasing characteristic before the soil interlayer was fully saturated, while showed an exponentially-increasing feature after the soil interlayer was fully saturated. A semi-analytical model was subsequently established for predicting the variables (time-dependent water head and the length of the stratified wetting zone) based on the classical GA equation, Darcy's law, and mass conversation law, as well as the numerical simulation calibration. This semi-analytical model describes three specific infiltration scenarios (scenarios I, II, and III) involving two infiltration modes (i.e., rainfall infiltration and constant-head infiltration), which were comprehensively shaped by fissure height, rain intensity, and duration. This model has a concise expression satisfying dimensional consistency and can be successfully reduced to the classic GA model. The validity of this semi-empirical model was further confirmed by numerical simulations, which showed good performance by capturing the evolving trends of the water head, saturated, transitional, and wetting zones in the inclined soil interlayer. The results and findings deepen the understanding of transient infiltration in rock slopes with inclined soil interlayer, and are helpfully for assessing the evolving slope stability during rainfall. [ABSTRACT FROM AUTHOR]

• Influencing factors of infiltration modes were systematically investigated. • A semi-analytical model for three infiltration scenarios was established. • Evolution features of water head and stratified wetting zone were revealed. The classic GA model assumes a constant-head ponded water and with a saturated water content above the wetting zone, which limits its application. This study investigated a semi-analytical method for predicting rainwater infiltration into an inclined soil interlayer considering time-varying head and stratified water content. An evolving wetting profile and a half-parabolic wetting profile of transient zone were observed during infiltration process based on numerical simulations. The water head in the fissure showed a linearly-increasing characteristic before the soil interlayer was fully saturated, while showed an exponentially-increasing feature after the soil interlayer was fully saturated. A semi-analytical model was subsequently established for predicting the variables (time-dependent water head and the length of the stratified wetting zone) based on the classical GA equation, Darcy's law, and mass conversation law, as well as the numerical simulation calibration. This semi-analytical model describes three specific infiltration scenarios (scenarios I, II, and III) involving two infiltration modes (i.e., rainfall infiltration and constant-head infiltration), which were comprehensively shaped by fissure height, rain intensity, and duration. This model has a concise expression satisfying dimensional consistency and can be successfully reduced to the classic GA model. The validity of this semi-empirical model was further confirmed by numerical simulations, which showed good performance by capturing the evolving trends of the water head, saturated, transitional, and wetting zones in the inclined soil interlayer. The results and findings deepen the understanding of transient infiltration in rock slopes with inclined soil interlayer, and are helpfully for assessing the evolving slope stability during rainfall. [ABSTRACT FROM AUTHOR]

Highlights: [•] Self-assembly of recombinant rotavirus virus-like particles. [•] Post-purification assembly yields homogeneous particle. [•] Virion-like epitopes on virus-like particles by on antibody binding analysis. [•] Improved stability, antigenicity and protective efficacy of double-layered VP2/6 VLPs. [•] Resemblance of Escherichia coli-derived VLPs to virus-derived double-layered particles. [Copyright &y& Elsevier]