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The Mongolian Plateau (MP), with its unique geographical landscape and cultural features, plays an important role in the safety of the regional ecological environment and sustainable development in North Asia. Land-cover data form the basis of MP studies; however, global-scale data products often fail to reflect regional characteristics. Despite improvements in data resolution, the level of detail remains insufficient for MP studies. This study aimed to improve the land cover classification system for MP. Based on multi-source data and extensive sample annotations, we constructed a high-quality land cover dataset for the MP and analyzed regional land cover changes. In this study, we used Landsat 5 and 8 images as primary data, which were supplemented by NASADEM, nighttime light data, ESA WorldCover, and other multi-source data for auxiliary analysis. The MP was divided into 13 major land cover categories: forest, shrub, meadow steppe, real steppe, desert steppe, wetland, water, cropland, built areas, bare area, desert, sand, and ice. For these categories, we manually labeled the samples for seven periods: 1990, 1995, 2000, 2005, 2010, 2015, and 2020. We constructed a set of image features and used a random forest model to train and predict land-cover data from 1990 to 2020. The overall accuracy of the land-cover products was 83.9 %, with a kappa coefficient of 0.817. Analysis of land cover changes over the past 30 years revealed that 65.04 % of land cover types in the MP remained unchanged from 1990 to 2020. The sandy area decreased annually, with a significant trend of bare areas transitioning to vegetation. The land-cover dataset produced in this study includes land-cover data and labeled samples for seven periods, exhibiting high application potential. It can be used for research on land-cover changes and related resource and environmental issues in the MP, providing data to support ecological protection and natural resource management in the region. [ABSTRACT FROM AUTHOR]

The differences of SARS-CoV-2 variants brought the changes of transmission characteristics and clinical manifestations during the prevalence of COVID-19. In order to explore the evolution mechanisms of SARS-CoV-2 variants and the impacts of variant evolution, the classic SIR (Susceptible-Infected-Recovered) compartment model was modified to a generalized SVEIR (Susceptible-Vaccinated-Exposed-Infected-Recovered) compartment model with age-group and varying variants in this study. By using of the SVEIR model and least squares method, the optimal fittings against the surveillance data from Fujian Provincial Center for Disease Control and Prevention were performed for the five epidemics of Fujian Province. The main epidemiological characteristics such as basic reproduction number, effective reproduction number, sensitivity analysis, and cross-variant scenario investigations were extensively investigated during dynamic zero-COVID policy. The study results showed that the infectivities of the variants became fast from wild strain to the Delta variant, further to the Omicron variant. Meanwhile, the cross-variant investigations showed that the average incubation periods were shortened, and that the infection scales quickly enhanced. Further, the risk estimations with the new variants were performed without implements of the non-pharmaceutical interventions, based on the dominant variants XBB.1.9.1 and EG.5. The results of the risk estimations suggested that non-pharmaceutical interventions were necessary on the Chinese mainland for controlling severe infections and deaths, and also that the regular variant monitors were still workable against the aggressive variant evolution and the emergency of new transmission risks in the future. [ABSTRACT FROM AUTHOR]

Bond-type anchorages with plain carbon fiber–reinforced polymer (CFRP) tendon, ribbed CFRP tendon, and CFRP tendon with metallic ribs were fabricated and tested. The contributions of chemical adhesion force, friction force, and bearing force of the surface ribs to the maximum pullout load of a bond-type anchorage with ribbed CFRP tendon were discussed. The influences of the metallic rib type, metallic rib number, and preloading force on the anchoring performance of a bond-type anchorage with CFRP tendon were also investigated. Finite-element simulation was also conducted to help study the working mechanism of wedge plug type ribs. Results show that bilinear and trilinear bond-slip models can characterize the bond performance of a bond-type anchorage with plain and ribbed CFRP tendon, respectively. In addition, bearing forces of surface ribs are limited due to the low shear strength of the CFRP material. However, metallic ribs can address this problem and promote the anchoring performance if the connection between the CFRP tendon and the metallic rib is reliable. A wedge plug type rib exerts a larger contact pressure on the surface of the CFRP tendon during the plugging and loading procedure compared with chip-type rib, making it more reliable than the chip-type rib. Moreover, preloading the wedge plug type rib after plugging eliminates the initial slip between the CFRP tendon and the metallic rib. This allows the wedge plug type rib to function sensitively under pullout load. Consequently, the bond between the CFRP tendon and the grout can work together with the friction between the CFRP tendon and the wedge plug type rib, and thus can avoid the "snap back" phenomenon in the pullout test. [ABSTRACT FROM AUTHOR]