Modular autonomous vehicle (MAV), as a novel mode of public transportation, is anticipated to reshape the next generation of transportation systems, with the potential to adapt to diverse travel demand patterns in urban areas. In this study, we consider a MAV hub-and-spoke public transportation system (MAV-HSPTS). Each MAV can operate independently for first-mile/last-mile transport of passengers. Multiple MAVs can assemble into a modular bus, operating synchronously on mainline corridors with predetermined routes, stations, and timetables. We formulate a MAV routing, scheduling and repositioning model in a rolling horizon framework to capture the operation of the system. A heuristic algorithm that assigns passenger requests to MAVs is developed to reduce the computation time. The model and solution algorithm are evaluated on a bus transit corridor in Shanghai, China. Results demonstrate that the MAV service can reduce passenger travel time by over 20 % compared to conventional bus service, and over 90 % of the passengers could benefit from the convenience of in-bus transfers. MAV reposition proves to be an effective method to reduce the operational costs, especially in scenarios with imbalanced demand distribution.

Surface degradation is a common challenge for many electrode materials. The active surface usually reacts with the molecules in the surrounding environment to form byproducts that hinder the diffusion channels for Li ions and electrons, increase the energy barrier for (de)lithiation reactions, and ultimately shorten the cycle life. Herein, the growth of surface Li ₂ CO ₃ on LiNi _x Co _y Mn _y O ₂ (x = 0.33, 0.6, 0.7, 0.8, x + 2y = 1) cathodes upon storage has been systematically investigated. Ni-rich surfaces are found to result in more Li ₂ CO ₃ growth, based on which three discrete degradation models for layered oxides are proposed. The increase and discretization of the energy barrier for individual particles also explain the State-of-Charge heterogeneity phenomena observed by in situ XRD and the change of cyclic voltammetry curves. By providing a comprehensive picture of surface deterioration of the NCM cathode family, this study enhances the understanding of the degradation mechanism that determines the cycle life of electrode materials.

Through a facile sodium sulfide (Na₂S)-assisted hydrothermal treatment, clean and nondefective surfaces are constructed on micrometer-sized Li₄Ti₅O₁₂ particles. The remarkable improvement of surface quality shows a higher first cycle Coulombic efficiency (≈95%), a significantly enhanced cycling performance, and a better rate capability in electrochemical measurements. A combined study of Raman spectroscopy and inductive coupled plasma emission spectroscopy reveals that the evolution of Li₄Ti₅O₁₂ surface in a water-based hydrothermal environment is a hydrolysis–recrystallization process, which can introduce a new phase of anatase-TiO₂. While, with a small amount of Na₂S (0.004 mol L⁻¹ at least), the spinel-Li₄Ti₅O₁₂ phase is maintained without a second phase. During this process, the alkaline environment created by Na₂S and the surface adsorption of the sulfur-containing group (HS⁻ or S²⁻) can suppress the recrystallization of anatase-TiO₂ and renew the particle surfaces. This finding gives a better understanding of the surface–property relationship on Li₄Ti₅O₁₂ and guidance on preparation and modification of electrode material other than coating or doping.