Traffic congestion plagues cities around the world. Recent years have witnessed an unprecedented trend in applying reinforcement learning for traffic signal control. However, the primary challenge is to control and coordinate traffic lights in large-scale urban networks. No one has ever tested RL models on a network of more than a thousand traffic lights. In this paper, we tackle the problem of multi-intersection traffic signal control, especially for large-scale networks, based on RL techniques and transportation theories. This problem is quite difficult because there are challenges such as scalability, signal coordination, data feasibility, etc. To address these challenges, we (1) design our RL agents utilizing ‘pressure’ concept to achieve signal coordination in region-level; (2) show that implicit coordination could be achieved by individual control agents with well-crafted reward design thus reducing the dimensionality; and (3) conduct extensive experiments on multiple scenarios, including a real-world scenario with 2510 traffic lights in Manhattan, New York City 1 2.
This paper describes full-field, three-dimensional, non-contact measurements of displacement and strain under high temperature condition based on digital image correlation (DIC). To conduct DIC measurements at high temperatures, two important factors need to be considered:(1) the ability of the coating to resist heat and withstand deformation without cracking or peeling off; (2) the radiation from the specimen's surface at high temperature. This paper proposes a solution to both of the most important issues in high temperature DIC measurement. First, different coating materials were investigated, and a procedure to generate a necessary speckle pattern required by DIC to resist heat and withstand deformation at high temperature has been developed. Second, a monochromatic illumination system in combination with a filter set has been studied to eliminate the radiation effect. A DIC system which enables a high temperature displacement and strain measurement up to 1100 • C is presented and demonstrated by experimental measurements.
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