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1

An autonomous vehicle sequencing problem at intersections: A genetic algorithm approach

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Yan F. , Dridi M. , El Moudni A.

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tom Vol. 23, no. 1

183--200

EN

This paper addresses a vehicle sequencing problem for adjacent intersections under the framework of Autonomous Intersection Management (AIM). In the context of AIM, autonomous vehicles are considered to be independent individuals and the traffic control aims at deciding on an efficient vehicle passing sequence. Since there are considerable vehicle passing combinations, how to find an efficient vehicle passing sequence in a short time becomes a big challenge, especially for more than one intersection. In this paper, we present a technique for combining certain vehicles into some basic groups with reference to some properties discussed in our earlier works. A genetic algorithm based on these basic groups is designed to find an optimal or a near-optimal vehicle passing sequence for each intersection. Computational experiments verify that the proposed genetic algorithms can response quickly for several intersections. Simulations with continuous vehicles are carried out with application of the proposed algorithm or existing traffic control methods. The results show that the traffic condition can be significantly improved by our algorithm.

2

Analysis of influencing factors of CO2 emissions in China’s power industry and policy implications

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Wen L. , Yan F. , Li Y.

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nr 1

EN

The Chinese power industry’s CO₂ emissions account for the largest proportion of the country’s total CO₂ emissions. Therefore, studying the influencing factors of CO₂ emissions in the power industry and developing mitigation policies are of great significance for reducing CO₂ emissions. According to the electricity-related data from 2000 to 2014 in China, this paper employed the improved STIRPAT model to examine the impact factors of economic growth, urbanization level, industrialization level, power consumption efficiency, power generation efficiency, and electric power structure of the CO₂ emissions in China’s power industry. Then we adopted the Ridge Regression method to fit the extended STIRPAT model. The results show that power generation efficiency is a decisive factor of CO₂ emissions reduction. Electric power structure and economic growth play important roles in reducing CO₂ emissions. Power consumption efficiency has a large potential to mitigate CO₂ emissions, while urbanization and industrialization levels are less important impact factors. Based on the above conclusions, the Chinese government needs to formulate appropriate policies in terms of power generation, supply, and consumption to reduce the power industry’s CO₂ emissions.

3

Treatment of mixed chemical wastewater by a two-stage A/O process for elimination of COD nitrogen and toxic matters

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Du P. , Li W. , Liang Z. , Chen Y. , Yang S. , Yan F.

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tom 22

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nr 1

EN

In our work a two-stage A/O system consisting of two independent A/O subsystems was used to remove high concentrations of COD, nitrogen, and toxic matter from mixed wastewater discharged by a comprehensive chemical group. The mixed liquid return was not adopted, and the sludge return ratio was kept at a high value of 100-200% to maintain high usable activated sludge concentration. Adequate NaHCO₃ was added to keep the influent alkalinity/KN ratio around 7.14 to 1. The system was running stably during the whole experimental period. Subsystem one obtained high COD and organic nitrogen removal capability without being influenced by the increasing COD loading. 87.6% COD was removed and 75.7% org-N was transformed to NH₄⁺-N. Due to the low COD/KN ratio created by subsystem one, the nitrification efficiency of subsystem two reached a high value of 92.1%. Besides, aerobic biological oxidation of oxic tank one showed excellent ability on toxic matter elimination. The acute toxicity of the whole system dropped from 0.165 to 0.042 mg HgCl₂/L. It has been proven by this study that, using the two-stage A/O system with sludge return only to treat COD nitrogen and toxic matters, laden mixed wastewater from comprehensive chemical groups may be feasible.

4

Influence of organic loading rate on the performance of a two-phase pressurized biofilm (TPPB) system treating food waste

63%

Li Y. , Yan F. , Liu H. , Wang Y. , Nie H. , Jiang H. , Qian M. , Zhou H.

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nr 5

EN

A two-phase pressurized biofilm (TPPB) system, including a continuously stirred tank reactor (CSTR) and a pressurized biofilm anaerobic reactor (PBAR), was used to produce high calorific biogas without additional upgrading equipment. The influence of organic loading rate (OLR) on biogas and methane production performance was investigated. Three different OLR levels (4, 5, and 6 g-COD/L/d) were applied to the PBAR in sequence. The headspace pressure of PBAR was controlled at 1.0 MPa. Biogas production, gas composition, and process stability parameters were measured. Results found that the highest methane yield of 332.8 mL/g-COD was obtained at OLR of 5 g-COD/L/d. As compared to approximately 90% methane concentration at OLR of 3.1 g-COD/L/d, the methane content in produced biogas was only 76% at OLR of 5.0 g-COD/L/d. The pH value in the pressurized reactor has an important impact on the quality of produced biogas. Further study should focus on the solution strategies of maintaining suitable pH under higher pressure and higher OLR.