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This article presents a hierarchical control framework for autonomous vehicle trajectory planning and tracking, addressing the challenge of accurately following high-speed, at-limit maneuvers. The proposed time-optimal trajectory planning and tracking (TOTPT) framework utilizes a hierarchical control structure, with an offline trajectory optimization (TRO) module and an online nonlinear model predictive control (NMPC) module. The TRO layer generates minimum-lap-time trajectories using a direct collocation method, which optimizes the vehicle's path, velocity, and control inputs to achieve the fastest possible lap time, while respecting the vehicle dynamics and track constraints. The NMPC layer is responsible for precisely tracking the reference trajectories generated by the TRO in real time. The NMPC also incorporates a preview algorithm that utilizes the predicted future travel distance to estimate the optimal reference speed and curvature for the next time step, thereby improving the overall tracking performance. Simulation results on the Catalunya circuit demonstrated the framework's capability to accurately follow the time-optimal raceline at an average speed of 116 km/h, with a maximum lateral error of 0.32 m. The NMPC module uses an acados solver with a real-time iteration (RTI) scheme, to achieve a millisecond-level computation time, making it possible to implement it in real time in autonomous vehicles.
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Purpose: To explore the effects of the clinical pathway on the outcomes of patients with non-variceal upper gastrointestinal bleeding. Materials and Methods: Randomized controlled trial. The study was conducted in two medical centers in China from 1 June 2022 to 31 December 2022. Patients with a diagnosis of non-variceal upper gastrointestinal bleeding who provided written informed consent were consecutively assigned to the intervention group. The patients in the intervention group were treated using the clinical pathway, while the control group received routine care and follow-up. Time, cost, complications, and prognostic indicators were analyzed. Intentional-to-treat analysis and per-protocol analysis were used for data analysis. Results: A total of 114 eligible patients with non-variceal upper gastrointestinal bleeding were randomly divided into two groups and included in the intention-to-treat analysis. In addition, 106 patients were included in the per-protocol analysis. The median age of the 106 patients was 57 years (range, 18-92 years) and 83.0% were male. There were no significant differences between groups regarding the baseline characteristics. The intervention group demonstrated a statistically significantly shorter length of stay, lower hospital cost (ie, cost during hospitalization, cost in the emergency room, and cost in the ward), significantly fewer cases of complications, and a higher level of patient satisfaction when compared with the control group. There was no significant difference between the two groups in the rates of transfusion, repeat endoscopy, rebleeding readmission, and mortality. Conclusion: The implementation of the clinical pathway for patients with non-variceal upper gastrointestinal bleeding may help improve patient outcomes and satisfaction. Trial Registration Number: ChiCTR2200060316. Registration Link: https://www.chictr.org.cn/.
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Revegetation facilitated by legume species introduction has been used for soil erosion control on the Loess Plateau, China. However, it is still unclear how vegetation and soil resources develop during this restoration process, especially over the longer term. In this study, we investigated the changes of plant aboveground biomass, vegetation cover, species richness and density of all individuals, and soil total nitrogen, mineral nitrogen, total phosphorus and available phosphorus over 11 years from 2003 to 2013 in three treatments (natural revegetation, Medicago sativa L. introduction and Melilotus suaveolens L. introduction) on the semi-arid Loess Plateau. Medicago significantly increased aboveground biomass and vegetation cover, and soil total nitrogen and mineral nitrogen contents. The Medicago treatment had lower species richness and density of all individuals, lower soil moisture in the deep soil (i.e., 1.4-5m), and lower soil available phosphorus. Melilotus introduction significantly increased aboveground biomass in only the first two years, and it was not an effective approach to improve vegetation biomass and cover, and soil nutrients, especially in later stages of revegetation. Overall, our study suggests that M. sativa can be the preferred plant species for revegetation of degraded ecosystems on the Loess Plateau, although phosphorus fertilizer should be applied for the sustainability of the revegetation.
