Search

Dissipation of imidacloprid (IMI) and its metabolites (urea, olefin, 5-hydroxy, guanidine, 6-chloronicotinic acid) in Chinese prickly ash (CPA) was investigated using QuEChERS combined with UPLC-MS/MS. Good linearity (r2 ≥0.9963), accuracy (recoveries of 71.8–104.3%), precision (relative standard deviations of 0.9–9.4%), and sensitivity (limit of quantification ≤0.05 mg kg−1) were obtained. After application of IMI at dosage of 467 mg a.i. L−1 for three times with interval of 7 d, the dissipation dynamics of IMI in CPA followed first-order kinetics, with half-life of 6.48–7.29 d. IMI was the main compound in CPA, followed by urea and guanidine with small amounts of olefin, 5-hydroxy, and 6-chloronicotinic acid. The terminal residues of total IMI and its metabolites at PHI of 14–21 d were 0.16–7.80 mg kg−1 in fresh CPA and 0.41–10.44 mg kg−1 in dried CPA, with the median processing factor of 3.62. Risk assessment showed the acute (RQa) and chronic dietary risk quotients (RQc) of IMI in CPA were 0.020–0.083% and 0.052–0.334%, respectively. Based on the dietary structures of different genders and ages of Chinese people, the whole dietary risk assessment indicated that RQc was less than 100% for the general population except for 2- to 7-year-old children (RQc of 109.9%), implying the long-term risks of IMI were acceptable to common consumers except for children.

The present study was carried out to profile the dissipation patterns and residues of five pesticides (triazophos, profenofos, chlorpyrifos, etoxazole and bifenthrin) on kumquat using QuEChERS method coupled with HPLC-MS/MS. The corresponding dietary health risks were also estimated. In the method validation, satisfactory results of good linearity (r2 ≥ 0.9956), sensitivity (limits of quantification ≤0.01 mg/kg), recoveries (71.0–95.7%) with relative standard deviations (0.70–9.4%) were obtained. The half-lives of the five pesticides in kumquat were 13.6–38.5 d under field conditions according to first-order kinetics. Based on the final residue experiment, dietary exposure risks of profenofos, chlorpyrifos, etoxazole and bifenthrin were all acceptably low, with RQc and RQa values of 0.00199–0.122 and 0.00145–0.200, respectively. However, exposure intake of triazophos posed unacceptable acute and chronic health risks for Chinese residents, especially for children with RQa and RQc up to 4.25 and 2.19. Forbidden use suggestion of triazophos and recommended MRLs of profenofos and bifenthrin were put forward in kumquat for safe production and consumption. This work was significant in providing guidance on appropriate application and MRL establishment of pesticides in kumquat.

Rule-based and optimization-based autonomous intersection management (AIM) policies have been evaluated against traditional signal controls in terms of intersection safety, efficiency and emission. As one of AIM policies, reservation-based control has further taken advantage of the benefits of AIM, especially via optimization approaches. This paper presents a time-independent trajectory optimization approach for connected and autonomous vehicles under reservation-based intersection control. The existing approaches assign an arrival time and speed to vehicles ahead of entering the intersection. However, the vehicles may not follow the planned trajectory once the traffic condition varies sharply and thus the trajectory solution becomes infeasible with respect to the assigned arrival time and speed. The proposed approach aims to solve the fail-follow problem by separating the optimization between arrival time, speed, and trajectory planning by optimizing the trajectory without arrival time and speed predetermined. The approach finds the optimal solution in terms of the intersection efficiency meanwhile keeps the feasibility of trajectory planning by formulating the variation of acceleration rate and breaking a whole trajectory into an enlarged set of segments. Two different control strategies, BATCH and ZONE, are also proposed to test the performance of the optimization approach in comparison with another Dynamic Batch strategy. The results validate that the proposed approach can adapt to extremely high traffic demand scenario. Sensitivity analyses also evaluate the performance of the proposed approach under different problem settings in terms of intersection efficiency.

Typical traffic control and operations at work zones are not effective in mitigating the work zone bottleneck, as the common early merge behavior limits utilizing the available capacity in the closed lane. Recently, using late merge strategy is encouraged to fully utilize the closed lane, therefore increasing efficiency of the work zone. In practice, the late merge strategy does not work effectively due to the lack of compliance by drivers. This paper is aimed at exploring two work zone late merge strategies with and without enabling connected vehicles (CV) technology. This first strategy is the late merge without CV enabled. The second strategy incorporates CV-enabled cooperative merge to enhance the work zone efficiency through communications between vehicles in the open and closed lanes. The CV-enabled strategy employs a rule based decentralized control algorithm. The paper has implemented both late merge strategies in microsimulation and evaluated the operational performances. Three major performance measures, which are throughput, delay and queue length, are used in the evaluation. The results indicate that the operational performance of the CV-enabled cooperative late merge is superior to the late merge strategy without CV in most cases, especially when traffic demand is moderate, while both late merge strategies outperform the traditional early merge strategy. Moreover, effects of the control variables including the traffic demand, heavy vehicle percentage, lane distribution percentage, late merge length, reduction of gap acceptance factor, and compliance rate, have been analyzed. Ultimately, sensitivity analysis has been performed to investigate the trend of effects from the significant variables control.

Waste cooking oil (WCO) and stearic acid (SA) were considered to be renewable and readily available bio-oil resources to produce bio-fuel via catalytic hydrodeoxygenation. The most often used catalysts for hydrodeoxygenation were the vulcanized NiMo catalysts, however, the vulcanized catalysts tend to deactivate due to the loss and oxidation of sulfur upon treating bio-oil with high oxygen content. Therefore, it is necessary to develop sulfur-free catalysts. In present study, the reduced NiMo catalysts were prepared by loading Ni and Mo on different supports (γ-Al2O3, HZSM-5, β-zeolite, activated carbon and bentonite) using incipient-wetness impregnation method, and followed by H2 reduction. The effects of the properties of supports (acidity, porosity) and H2 reduction on the dispersity and valence state of metal components were investigated. The hydrodeoxygenation activities of the reduced catalysts were evaluated by catalytic WCO and SA. It was found that when Ni2+ was loaded on a slightly acidic supports such as γ-Al2O3 and activated carbon, Ni2+ was easier to be reduced, and aggregate to form larger particles. When Ni2+ was loaded on a strongly acid supports e.g. HZSM-5, β-zeolite or bentonite, Ni2+ was more difficult to be reduced but could uniformly disperse on the supports. The aggregated Ni atoms could promote the formation of C17, while the dispersed Ni atoms could promote the formation of C18. γ-Al2O3 supported catalyst achieved the highest SA (97.9%) and WCO (80%) conversion under the mild reaction conditions of 300 °C and 2 MPa H2 for 3 h, exhibiting the superior catalytic activity.