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Weiming Mai

Publications and source records attributed to Weiming Mai.

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PedNStream: Scalable Network Flow Simulation for Pedestrian Traffic Management

Evaluating operational crowd management at network scale requires simulations that can be run repeatedly while adapting interventions to changing conditions. Microscopic models can represent detailed individual movement, but their computational cost may limit their use in such repeated, network-scale evaluations. This paper presents PedNStream (Pedestrian Network Flow Simulation), an open-source, Python-native simulator for macroscopic pedestrian network simulation based on the Link Transmission Model (LTM). PedNStream extends LTM-based pedestrian models with stochastic link dynamics that represent local variation in pedestrian flow. It uses a utility-based route-choice model to capture how pedestrians adjust their route choices in response to congestion and control interventions as conditions change over time. The modular framework provides controller interfaces for gating, flow separation, and route guidance. We evaluate PedNStream in a staged manner. Synthetic scenarios verify key crowd-dynamics mechanisms, including queue formation, spillback, congestion dissipation, and adaptive rerouting. Real-network experiments assess large-scale behavior against observed pedestrian counts. A closed-loop case study demonstrates controller integration, and a runtime analysis quantifies scalability. These results position PedNStream as an efficient and practical testbed for large-scale pedestrian network simulation and crowd management research.

cs.AI

Learning Personalized Utility Functions for Drivers in Ride-hailing Systems Using Ensemble Hypernetworks

In ride-hailing systems, drivers decide whether to accept or reject ride requests based on factors such as order characteristics, traffic conditions, and personal preferences. Accurately predicting these decisions is essential for improving the efficiency and reliability of these systems. Traditional models, such as the Random Utility Maximization (RUM) approach, typically predict drivers' decisions by assuming linear correlations among attributes. However, these models often fall short because they fail to account for non-linear interactions between attributes and do not cater to the unique, personalized preferences of individual drivers. In this paper, we develop a method for learning personalized utility functions using hypernetwork and ensemble learning. Hypernetworks dynamically generate weights for a linear utility function based on trip request data and driver profiles, capturing the non-linear relationships. An ensemble of hypernetworks trained on different data segments further improve model adaptability and generalization by introducing controlled randomness, thereby reducing over-fitting. We validate the performance of our ensemble hypernetworks model in terms of prediction accuracy and uncertainty estimation in a real-world dataset. The results demonstrate that our approach not only accurately predicts each driver's utility but also effectively balances the needs for explainability and uncertainty quantification. Additionally, our model serves as a powerful tool for revealing the personalized preferences of different drivers, clearly illustrating which attributes largely impact their rider acceptance decisions.

cs.LG