| 1. |
- Lu, Wenqi, et al.
(author)
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TD3LVSL : A lane-level variable speed limit approach based on twin delayed deep deterministic policy gradient in a connected automated vehicle environment
- 2023
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 153
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Journal article (peer-reviewed)abstract
- Variable speed limit (VSL) control plays a vital role in the emerging connected automated vehicle highway (CAVH) system, which can alleviate recurrent traffic congestion caused by capacity drop and accidents. However, the effect of the VSL on improving traffic efficiency is still controversial. It is necessary to study how to explore the potential benefits of the VSL by balancing its influence on reducing crash risk and enhancing traffic efficiency. To fill the technological gap above, this paper proposes a reinforcement learning-based lane-level VSL (LVSL) control approach to conduct refined traffic control on the mainlines. Firstly, an actor-critic framework is developed to generate and evaluate the discrete speed limits of each lane in continuous action space. To optimize traffic control performance, a hybrid reward function is developed by synchronously considering traffic safety and traffic efficiency of the bottleneck area. Then, to solve the overestimation bias problem of the actor-critic methods caused by function approximation error, a twin delayed deep deterministic policy gradient (TD3) method is introduced to train the framework of the LVSL method. Finally, a real-world recurrent bottleneck of the State Route 91 highway in California is simulated with consideration of the connected automated vehicles to examine the performance of the TD3-based LVSL (TD3LVSL) controller. The simulation results reveal that the proposed method is capable of reducing crash risk and improving traffic efficiency synchronously. Compared with the LVSL controller based on the deep deterministic policy gradient approach, the TD3LVSL controller shows better performance in terms of traffic safety and efficiency. These findings indicate that the proposed controller could contribute to future traffic control in a CAVH environment.
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| 2. |
- Quax, Tessa E. F., et al.
(author)
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Differential Translation Tunes Uneven Production of Operon-Encoded Proteins
- 2013
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In: Cell Reports. - : Elsevier BV. - 2211-1247. ; 4:5, s. 938-944
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Journal article (peer-reviewed)abstract
- Clustering of functionally related genes in operons allows for coregulated gene expression in prokaryotes. This is advantageous when equal amounts of gene products are required. Production of protein complexes with an uneven stoichiometry, however, requires tuning mechanisms to generate subunits in appropriate relative quantities. Using comparative genomic analysis, we show that differential translation is a key determinant of modulated expression of genes clustered in operons and that codon bias generally is the best in silico indicator of unequal protein production. Variable ribosome density profiles of polycistronic transcripts correlate strongly with differential translation patterns. In addition, we provide experimental evidence that de novo initiation of translation can occur at intercistronic sites, allowing for differential translation of any gene irrespective of its position on a polycistronic messenger. Thus, modulation of translation efficiency appears to be a universal mode of control in bacteria and archaea that allows for differential production of operon-encoded proteins.
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