Parallel Scheme for Multi-Layer Refinement Non-Uniform Grid Lattice Boltzmann Method Based on Load Balancing

The large-scale numerical simulation of complex flows has been an important research area in scientific and engineering computing. The lattice Boltzmann method (LBM) as a mesoscopic method for solving flow field problems has become a relatively new research direction in computational fluid dynamics. The multi-layer grid-refinement strategy deals with different-level of computing complexity through multi-scale grids, which can be used to solve the complex flow field of the non-uniform grid LBM without destroying the parallelism of the standard LBM. It also avoids the inefficiencies and waste of computational resources associated with standard LBMs using uniform and homogeneous Cartesian grids. This paper proposed a multi-layer grid-refinement strategy for LBM and implemented the corresponding parallel algorithm with load balancing. Taking a parallel scheme for two-dimensional non-uniform meshes as an example, this method presented the implementation details of the proposed parallel algorithm, including a partitioning scheme for evaluating the load in a one-dimensional direction and an interpolation scheme based on buffer optimization. Simply by expanding the necessary data transfer of distribution functions and macroscopic quantities for non-uniform grids in different parallel domains, our method could be used to conduct numerical simulations of the flow field problems with complex geometry and achieved good load-balancing results. Among them, the weak scalability performance could be as high as 88.90% in a 16-threaded environment, while the numerical simulation with a specific grid structure still had a parallel efficiency of 77.4% when the parallel domain was expanded to 16 threads

Runoff Simulation in the Upper Reaches of Heihe River Basin Based on the RIEMS–SWAT Model

In the distributed hydrological simulations for complex mountain areas, large amounts of meteorological input parameters with high spatial and temporal resolutions are necessary. However, the extreme scarcity and uneven distribution of the traditional meteorological observation stations in cold and arid regions of Northwest China makes it very difficult in meeting the requirements of hydrological simulations. Alternatively, regional climate models (RCMs), which can provide a variety of distributed meteorological data with high temporal and spatial resolution, have become an effective solution to improve hydrological simulation accuracy and to further study water resource responses to human activities and global climate change. In this study, abundant and evenly distributed virtual weather stations in the upper reaches of the Heihe River Basin (HRB) of Northwest China were built for the optimization of the input data, and thus a regional integrated environmental model system (RIEMS) based on RCM and a distributed hydrological model of soil and water assessment tool (SWAT) were integrated as a coupled climate–hydrological RIEMS-SWAT model, which was applied to simulate monthly runoff from 1995 to 2010 in the region. Results show that the simulated and observed values are close; Nash–Sutcliffe efficiency is higher than 0.65; determination coefficient (R2) values are higher than 0.70; percent bias is controlled within ±20%; and root-mean-square-error-observation standard deviation ratio is less than 0.65. These results indicate that the coupled model can present basin hydrological processes properly, and provide scientific support for prediction and management of basin water resources

Runoff Simulation by SWAT Model Using High-Resolution Gridded Precipitation in the Upper Heihe River Basin, Northeastern Tibetan Plateau

The scarcity and uneven distribution of precipitation stations in the inland river basins of the Northeastern Tibetan Plateau restrict the application of the distributed hydrological model and spatial analysis of water balance component characteristics. This study used the upper Heihe River Basin as a case study, and daily gridded precipitation data with 3 km resolution based on the spatial interpolation of gauged stations and a regional climate model were used to construct a soil and water assessment tool (SWAT) model. The aim was to validate the precision of high-resolution gridded precipitation for hydrological simulation in data-scarce regions; a scale transformation method was proposed by building virtual stations and calculating the lapse rate to overcome the defects of the SWAT model using traditional precipitation station data. The gridded precipitation was upscaled from the grid to the sub-basin scale to accurately represent sub-basin precipitation input data. A satisfactory runoff simulation was achieved, and the spatial variability of water balance components was analysed. Results show that the precipitation lapse rate ranges from 40 mm/km to 235 mm/km and decreases from the southeastern to the northwestern areas. The SWAT model achieves monthly runoff simulation compared with gauged runoff from 2000 to 2014; the determination coefficients are higher than 0.71, the Nash–Sutcliffe efficiencies are higher than 0.76, and the percentage bias is controlled within ±15%. Meadow and sparse vegetation are the major water yield landscapes, and the elevation band from 3500 m to 4500 m is the major water yield area. Precipitation and evapotranspiration present a slightly increasing trend, whereas water yield and soil water content present a slightly decreasing trend. This finding indicates that the high-resolution gridded precipitation data fully depict its spatial heterogeneity, and scale transformation significantly promotes the application of the distributed hydrological model in inland river basins. The spatial variability of water balance components can be quantified to provide references for the integrated assessment and management of basin water resources in data-scarce regions

Quantified effect of quench rate on the microstructures and mechanical properties of an Al–Mg–Si alloy

It is well known that lower quench rate leads to the formation of precipitate free zones (PFZs) adjacent to grain boundaries in aging hardening materials such as Al–Mg–Si alloys. However, the combined effect of PFZs and intragranular precipitates on the yield strength of Al–Mg–Si alloys is not systematically understood. To clarify this, an Al–Mg–Si alloy was water/oil/air quenched after solid solution treatment, then aged at 180 °C for 6 h. It was found that a lower quench rate led to coarser precipitates and wider PFZs. The effects of PFZs and precipitates on the yield strength of the Al–Mg–Si alloy were separated by quantitative characterization of multi-scale microstructures and mechanical simulations. Wide PFZs were found to have a notable effect on yield strength, amounting over half the strengthening effect of intragranular precipitates. This effect increases as the width of PFZ increases, due to more serious strain localization caused by PFZs. A corresponding equation has thus been proposed to describe the deleterious effects of PFZs on yield strength of Al–Mg–Si alloys

Gelatin and catechol-modified quaternary chitosan cotton dressings with rapid hemostasis and high-efficiency antimicrobial capacity to manage severe bleeding wounds

The development of functional wound dressings capable of both rapid hemostasis and high-efficiency antimicrobial is essential for the management of severe bleeding wounds. Cotton dressings are widely used in clinical practice; however, few dressings can simultaneously achieve rapid hemostasis and high-efficacy antimicrobial. Herein, a versatile cotton dressing (GCQCNF-5) was masterly developed by sequentially deposition catechol modified quaternary chitosan (CQCS) and gelatin onto a cotton nonwoven fabric (NF) surface. Because of the presence of a gelatin sponge layer with suitable thickness and porosity on its surface, GCQCNF-5 exhibits a notably enhanced hemostatic effect compared to NF both in vitro and in vivo, which is even slightly superior to that of MHS (a commercial gelatin hemostatic sponge). Moreover, after exerting a rapid hemostasis effect, GCQCNF-5 can further exploit CQCS to exert excellent immediate antimicrobial and long-lasting bacteriostatic effects. In vivo wound healing experiments further indicated that GCQCNF-5 could significantly promote rapid healing of infected wounds by effectively sterilizing, absorbing exudates, and providing moist healing environments. This study clearly demonstrated that GCQCNF-5 is a versatile wound dressing that can achieve simultaneously rapid hemostasis, high-efficiency antimicrobial, and promote rapid healing of infected wounds, with great application potential for the treatment of severe bleeding wounds