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Adaptive cruise control (ACC) vehicles have the potential to impact traffic flow dynamics. To better understand the impacts of ACC vehicles on traffic flow, an accurate microscopic car-following model for ACC vehicles is essential. Most of the ACC car-following models utilize a continuous function to describe vehicle acceleration and braking, e.g., the optimal velocity relative velocity (OVRV) model. However, these models do not necessarily describe car-following behavior with sufficient accuracy. Recent studies have proposed switching models to better describe realistic ACC dynamics. However, they often fail to accurately capture the driving behavior around the switching points, where a vehicle switches between acceleration and deceleration. In this study, we develop a two-condition, continuous asymmetric car-following (TCACF) model to capture ACC driving behavior in a physically interpretable manner, while preserving numerical soundness. The proposed TCACF model and multiple other car-following models are calibrated based on a real-world ACC trajectory dataset. The results show that the TCACF model better describes the asymmetric driving behavior of ACC vehicles than any of the commonly used car-following models, especially at switching points. The results indicate that the TCACF model considerably increases model accuracy by up to 32.46% when compared with other switching models and by up to 36.98% when compared to commonly used car-following models. The TCACF model is expected to offer new insights into modeling and simulating emerging ACC car-following dynamics with a higher degree of accuracy and can be used in applications where correctly simulating acceleration behavior is important.

Cobalt oxides, including spinel Co3O4and rock-salt CoO, have been widely reported as promising catalysts for oxygen reduction reaction (ORR). However, three types of cobalt ions, i.e., Co2+in the tetrahedral site (Co2+Td), Co3+in the octahedral site (Co3+Oh), and Co2+in the octahedral site (Co2+Oh), are included in these oxides, and the roles of cobalt geometric occupancy and valance states have remained elusive. Here, for the first time, we investigated the effects of cobalt geometric occupancy on the ORR activity by substituting Co2+Tdand Co3+Ohof Co3O4with inactive Zn2+and Al3+, respectively. The ORR activity decreases in the order of Co3O4(Co3+Oh, Co2+Td) < ZnCo2O4(Co3+Oh) ≪ CoAl2O4(Co2+Td) in accordance with the ORR overpotentials at the current density of 0.1 mA cmOx–2. Furthermore, by comparatively investigating the activity and stability of Co3O4(Co3+Oh) and CoO (Co2+Oh) nanoparticles, by virtue of the electrochemical technique, the high-resolution transmission electron microscopy, and the in operando fuel cell–X-ray absorption spectroscopy techniques, it was revealed that Co2+Ohin CoO is the main active site, which under electrochemical conditions tends to transform into Co3+Ohand form Co3O4with a hollow structure due to the Kirkendall effect; nevertheless, it retains decent ORR activity due to the formation of the unique hollow structure.

Carbon supported Pt–Ni nanoparticles (NPs) electrocatalysts with nominal Pt/Ni atomic ratios of 3:1, 2:1, and 1:1, denoted as Pt3Ni/C, Pt2Ni/C, and Pt1Ni/C, respectively, were obtained by a modified polyol process. The structure of PtnNi/C (n= 3, 2, 1) electrocatalysts was studied by using an X-ray absorption spectroscopy technique combined with X-ray diffraction and transmission electron microscopy. Significantly, the NPs of Pt3Ni/C in air are demonstrated to have a quasi core–shell structure consisting of a core of metallic Pt surrounded by many small NiOxclusters. In contrast, both Pt2Ni/C and Pt1Ni/C are demonstrated to have an alloy structure with partial oxidation on the surface. Under the atmosphere of H2at 393 K, the PtnNi/C became the expected bimetallic alloy. At last, we discuss the effect of Ni amount on the structure of PtnNi/C and estimate their possible catalytic activity for methanol oxidation reaction. Our results further confirmed that the structure of Pt–Ni NPs can be influenced by Ni amount and this effect may be enlarged by environment effects.