Survey on digital twins for Internet of Vehicles:Fundamentals,challenges,and opportunities

As autonomous vehicles and the other supporting infrastructures(e.g.,smart cities and intelligent transportation systems)become more commonplace,the Internet of Vehicles(IoV)is getting increasingly prevalent.There have been attempts to utilize Digital Twins(DTs)to facilitate the design,evaluation,and deployment of IoV-based systems,for example by supporting high-fidelity modeling,real-time monitoring,and advanced predictive capabilities.However,the literature review undertaken in this paper suggests that integrating DTs into IoV-based system design and deployment remains an understudied topic.In addition,this paper explains how DTs can benefit IoV system designers and implementers,as well as describes several challenges and opportunities for future researchers.

Safety Evaluation of Concrete Structures Based on a Novel Energy Criterion

In this article,the post-peak softening stage of the constitutive relation and the elastic stiffness degradation of concrete are investigated,and a highly reasonable constitutive relation curve is proposed.At the material level,the energy change in the concrete failure process is studied based on the different stress-strain curves of concrete under uniaxial tension and compression.The concrete failure criterion based on elastic strain energy density is deemed suitable and consistent with the experimental phenomena.The hysteresis phenomenon(lags behind the peak strength)is also discussed.At the structure level,the strength reduction method is employed for the stability analysis,the energy change in the failure process of the Long Xi-Kou Dam is examined,and the results show that the dam failure criterion based on elastic strain energy shows a greater significance in practical applications compared with other conventional structural failure criteria in engineering.This criterion is objective and can avoid subjective arbitrariness.

Evaluating a river's ecological health: A multidimensional approach

Evaluating the health of river surface water is essential,as rivers support significant biological resources and serve as vital drinking water sources.While the Water Quality Index(WQI)is commonly employed to evaluate surface water quality,it fails to consider biodiversity and does not fully capture the ecological health of rivers.Here we show a comprehensive assessment of the ecological health of surface water in the lower Yangtze River(LYR),integrating chemical and biological metrics.According to traditional WQI metrics,the LYR's surface water generally meets China's Class II standards.However,it also contains 43 high-risk emerging contaminants;nitrobenzenes are found at the highest concentrations,representing 25e90%of total detections,while polycyclic aromatic hydrocarbons present the most substantial environmental risks,accounting for 81e93%of the total risk quotient.Notably,the plankton-based index of biological integrity(P-IBI)rates the ecological health of the majority of LYR water samples(59.7%)as‘fair’,with significantly better health observed in autumn compared to other seasons(p<0.01).Our findings suggest that including emerging contaminants and P-IBI as additional metrics can enhance the traditional WQI analysis in evaluating surface water's ecological health.These results highlight the need for a multidimensional assessment approach and call for improvements to LYR's ecological health,focusing on emerging contaminants and biodiversity rather than solely on reducing conventional indicators.

Occurrence and risk assessment of azole fungicides during the urban water cycle:A year-long study along the Yangtze River,China

Azole fungicides(AFs)play an important role in the prevention and treatment of fungal diseases in agricultural crops.However,limited studies are addressing the fate and ecological risk of AFs in the urban water cycle at a large watershed scale.To address this gap,we investigated the spatiotemporal distribution and ecological risk of twenty AFs in the lower reaches of the Yangtze River across four seasons.Carbendazim(CBA),tebuconazole(TBA),tricyclazole(TCA),and propiconazole(PPA)were found to be the dominant compounds.Their highest concentrations were measured in January(188.3 ng/L),and November(2197.1 ng/L),July(162.0 ng/L),and November(1801.9 ng/L),respectively.The comparison between wastewater treatment plants(WWTPs)effluents and surface water suggested that industrial WWTPs are major sources of AFs in the Yangtze River.In particular,TBA and PPA were found to be the most recalcitrant AFs in industrial WWTPs,while difenoconazole(DFA)was found to be the most potent pollutant in municipal WWTPs,with an average removal rate of less than60%.The average risk quotient(RQ)for the entire AFs was 6.45 in the fall,which was higher than in January(0.98),April(0.61),and July(0.40).This indicates that AFs in surface water posed higher environmental risks during the dry season.Additionally,the exposure risk of AFs via drinking water for sensitive populations deserves more attention.This study provides benchmark data on the occurrence of AFs in the lower reaches of the Yangtze River,and offers suggestions for better reduction of AFs.

Coupling mechanism of mathematical models for sediment transport based on characteristic theory

This paper aims to explore the coupling mechanism between flow movement, sediment transport and riverbed evolution in currently widely used mathematical models for sediment transport. Based on characteristic theory, analytic forms of eigenvalues,eigenvectors and characteristic relationships of total-sediment transport model, bed-load transport model and suspenedload transport model were derived, respectively. The singular perturbation technology was implemented to obtain the asymptotic solutions to different families of eigenvalues. The results indicate that, interactions between motion variables were explicitly coupled in the characteristics of total-sediment transport model and bed-load transport model. Further qualitative and quantitative analysis demonstrates that high sediment transport intensity and significant riverbed change will inevitably affect the property of flow movement. In the process of deposition, sediment-laden flow will move faster when sediment transport intensity becomes stronger. In contrast, the wave of flow will propagate at slower speed as erosion intensity becomes stronger.For most existing suspended-load transport models, however, the characteristics are decoupled as the interactions between motion variables cannot be integrally illustrated in eigenvalues, eigenvectors and characteristic relationship.