Mapping the terraces on the Loess Plateau based on a deep learning-based model at 1.89 m resolution.

Terraces on the Loess Plateau play essential roles in soil conservation, as well as agricultural productivity in this region. However, due to the unavailability of high-resolution (<10 m) maps of terrace distribution for this area, current research on these terraces is limited to specific regions. We developed a deep learning-based terrace extraction model (DLTEM) using texture features of the terraces, which have not previously been applied regionally. The model utilizes the UNet++ deep learning network as its framework, with high-resolution satellite images, a digital elevation model, and GlobeLand30 as the interpreted data and topography and vegetation correction data sources, respectively, and incorporates manual correction to produce a 1.89 m spatial resolution terrace distribution map for the Loess Plateau (TDMLP). The accuracy of the TDMLP was evaluated using 11,420 test samples and 815 field validation points, yielding classification results of 98.39% and 96.93%, respectively. The TDMLP provides an important basis for further research on the economic and ecological value of terraces, facilitating the sustainable development of the Loess Plateau.

A Distributionally Robust Optimization Method for Passenger Flow Control Strategy and Train Scheduling on an Urban Rail Transit Line.

Regular coronavirus disease 2019 (COVID-19) epidemic prevention and control have raised new requirements that necessitate operation-strategy innovation in urban rail transit. To alleviate increasingly serious congestion and further reduce the risk of cross-infection, a novel two-stage distributionally robust optimization (DRO) model is explicitly constructed, in which the probability distribution of stochastic scenarios is only partially known in advance. In the proposed model, the mean-conditional value-at-risk (CVaR) criterion is employed to obtain a tradeoff between the expected number of waiting passengers and the risk of congestion on an urban rail transit line. The relationship between the proposed DRO model and the traditional two-stage stochastic programming (SP) model is also depicted. Furthermore, to overcome the obstacle of model solvability resulting from imprecise probability distributions, a discrepancy-based ambiguity set is used to transform the robust counterpart into its computationally tractable form. A hybrid algorithm that combines a local search algorithm with a mixed-integer linear programming (MILP) solver is developed to improve the computational efficiency of large-scale instances. Finally, a series of numerical examples with real-world operation data are executed to validate the proposed approaches.