Methodological evolution and frontiers of identifying, modeling and preventing secondary crashes on highways

© 2018 Elsevier Ltd Secondary crashes (SCs) or crashes that occur within the boundaries of the impact area of prior, primary crashes are one of the incident types that frequently affect highway traffic operations and safety. Existing studies have made great efforts to explore the underlying mechanisms of SCs and relevant methodologies have been e volving over the last two decades concerning the identification, modeling, and prevention of these crashes. So far there is a lack of a detailed examination on the progress, lessons, and potential opportunities regarding existing achievements in SC-related studies. This paper provides a comprehensive investigation of the state-of-the-art approaches; examines their strengths and weaknesses; and provides guidance in exploiting new directions in SC-related research. It aims to support researchers and practitioners in understanding well-established approaches so as to further explore the frontiers. Published studies focused on SCs since 1997 have been identified, reviewed, and summarized. Key issues concentrated on the following aspects are discussed: (i) static/dynamic approaches to identify SCs; (ii) parametric/non-parametric models to analyze SC risk, and (iii) deployable countermeasures to prevent SCs. Based on the examined issues, needs, and challenges, this paper further provides insights into potential opportunities such as: (a) fusing data from multiple sources for SC identification, (b) using advanced learning algorithms for real-time SC analysis, and (c) deploying connected vehicles for SC prevention in future research. This paper contributes to the research community by providing a one-stop reference for research on secondary crashes

Bayesian-Based Approaches to Exploring the Long-Term Alteration in Trace Metals of Surface Water and Its Driving Forces

Trace metal pollution poses a serious threat to the aquatic ecosystem. Therefore, characterizing the long-term environmental behavior of trace metals and their driving forces is essential for guiding water quality management. Based on a long-term data set from 1990 to 2019, this study systematically conducted the spatiotemporal trend assessment, influential factor analysis, and source apportionment of trace elements in the rivers of the German Elbe River basin. Results show that the mean concentrations of the given elements in the last 30 years were found in the order of Fe (1179.5 ± 1221 μg·L–1) ≫ Mn (209.6 ± 181.7 μg·L–1) ≫ Zn (52.5 ± 166.2 μg·L–1) ≫ Cu (5.3 ± 5.5 μg·L–1) > Ni (4.4 ± 8.3 μg·L–1) > Pb (3.3 ± 4.4 μg·L–1) > As (2.9 ± 2.3 μg·L–1) > Cr (1.8 ± 2.4 μg·L–1) ≫ Cd (0.3 ± 1.1 μg·L–1) > Hg (0.05 ± 0.12 μg·L–1). Wavelet analyses show that river flow regimes and flooding dominated the periodic variations in metal pollution. Bayesian network suggests that the hydrochemical factors (i.e., TOC, TP, TN, pH, and EC) chemically influenced the metal mobility between water and sediments. Furthermore, the source apportionment computed by the Bayesian multivariate receptor model shows that the given element contamination was typically attributed to the geogenic sources (17.5, 95% confidence interval: 13.1–17.6%), urban and industrial sources (22.1, 18.0–27.2%), arable soil erosion (24.2, 16.4–31.5%), and historical anthropogenic activities (35.2, 32.8–43.3%). The results provided herein reveal that both the hydrochemical influence on metal mobility and the chronic disturbance from anthropogenic activities caused the long-term variation in trace metal pollution

Oikos data-Yi

Oikos data-Y

Real-Time <i>Ab Initio</i> Investigation on Hot Electron Relaxation Dynamics in Silicon

The relaxation of hot electrons in semiconductors is pivotal for both energy harvesting processes and optoelectronics. Utilizing a self-developed non-adiabatic molecular dynamics simulation approach in the momentum space (NAMD_k), we have examined the dynamics of hot electrons in silicon. Whether excited from the Γ or L point, the relaxation dynamics exhibit two distinct stages. Initially, within 100 fs, electrons scatter with phonons throughout the Brillouin zone. Subsequently, over a few picoseconds, they further relax toward the conduction band minimum as a whole. This picture of hot electron relaxation is highly consistent with the quasi-equilibrium hot electron ensemble (HEE) concept. Throughout the hot electron relaxation process, energy transfer to phonons is efficient, leading to time-dependent phonon excitation, which is thoroughly analyzed. This investigation provides a novel perspective on hot electron relaxation in silicon, which holds substantive implications for the realm of photovoltaic and optoelectronic device applications

Lithiation of SiO₂ in Li-Ion Batteries: In Situ Transmission Electron Microscopy Experiments and Theoretical Studies

Surface passivation has become a routine strategy of design to mitigate the chemomechanical degradation of high-capacity electrodes by regulating the electrochemical process of lithiation and managing the associated deformation dynamics. Oxides are the prevalent materials used for surface coating. Lithiation of SiO₂ leads to drastic changes in its electro-chemo-mechanical properties from an electronic insulator and a brittle material in its pure form to a conductor and a material sustainable of large deformation in the lithiated form. We synthesized SiO₂-coated SiC nanowires that allow us to focus on the lithiation behavior of the sub-10 nm SiO₂ thin coating. We systematically investigate the structural evolution, the electronic conduction and ionic transport properties, and the deformation pattern of lithiated SiO₂ through coordinated in situ transmission electron microcopy experiments, first-principles computation, and continuum theories. We observe the stress-mediated reaction that induces inhomogeneous growth of SiO₂. The results provide fundamental perspectives on the chemomechanical behaviors of oxides used in the surface coating of Li-ion technologies

Adsorption and Deposition of Li₂O₂ on the Pristine and Oxidized TiC Surface by First-principles Calculation

We investigate Li₂O₂ adsorption and deposition on the low index surfaces of pristine and oxidized TiC, which has been demonstrated recently to be an excellent cathode for Li–air batteries. We found that the pristine TiC surface is not stable toward interaction with Li₂O₂ and that surface stability can be enhanced greatly by surface oxidation as shown by surface energy reduction from 102 to 23 meV/Ų for the TiC{100} surface and from 208 to 39 meV/Ų for the TiC{111} surface after oxidation. Adsorption of two Li₂O₂ clusters on the 2 × 2 Ti-terminated TiC{111} surface (TiC{111}_Ti) resulted in spontaneous destruction of Li₂O₂ clusters and formation of a saturated periodic two atomic layer coating in which each O atom is bonded to three Ti atoms to form an O layer equivalent to the layer formed by O₂ surface oxidation, and Li atoms sit on the top. The atomic arrangement of O and Li layers resembles that of Li1O2 layers normal to the [0001] direction in the Li₂O₂ crystal structure. Interface models constructed based on this lead showed that the growth of Li₂O₂ can be continued on oxidized TiC{111}_Ti through a surface conduction mechanism to form Li₂O₂ coating with lattice parameters almost identical to those of the standard Li₂O₂ unit cell. On the oxidized TiC{100} surface (TiC{100}_TiO), two Li₂O₂ clusters adsorbed on two adjacent Ti sites by Ti–O bonding with the O–O axis in Li₂O₂ perpendicular to the surface resulted in a Li and O atom configuration which is similar to O2Li3O4 layers in the Li₂O₂ crystal structure, indicating a potential path for Li₂O₂ nucleation on the TiC{100}_TiO surface. Interface models by following this path suggested that Li₂O₂ coating may be grown on the TiC{100}_TiO surface with a dihedral angle between 11.4° and 22.4°, and strains inside the Li₂O₂ could induce conductivity. These atomistic insights are in good agreement with the experimental findings

Morphological changes in acellular conjunctiva matrix and denuded amniotic membrane after 0.25% collagenase digestion.

<p>Morphological changes in acellular conjunctiva matrix and denuded amniotic membrane after 0.25% collagenase digestion.</p

Adsorption of Phenanthrene on Multilayer Graphene as Affected by Surfactant and Exfoliation

Surfactant mediated exfoliation of multilayer graphene and its effects on phenanthrene adsorption were investigated using a passive dosing technique. In the absence of surfactant (sodium cholate, NaC), multilayer graphene had higher adsorption capacity for phenanthrene than carbon nanotube and graphite due to the higher surface area and micropore volume. The observed desorption hysteresis is likely caused by the formation of closed interstitial spaces through folding and rearrangement of graphene sheets. In the presence of NaC (both 100 and 8000 mg/L), phenanthrene adsorption on graphene was decreased due to the direct competition of NaC molecules on the graphene surface. With the aid of sonication, multilayer graphene sheets were exfoliated by NaC, leading to better dispersion. The degree of dispersion depended on the graphene-NaC ratio in aqueous solution rather than critical micelle concentration of NaC, and the good dispersion occurred after reaching adsorption saturation of NaC molecules on graphene sheets. In addition, exfoliation weakened the competition between phenanthrene and NaC and enhanced the adsorption capacity of graphene for phenanthrene due to exposed new sites. The findings on exfoliation of graphene sheets and related adsorption properties highlight not only the potential applications of multilayer graphene as efficient adsorbent but also its possible environmental risk

Postoperative tracking of donor cells on the recipient cornea.

<p>More donor cells were detected on peripheral region of the rabbit cornea transplanted with aCM (A) compared with that transplanted with dAM (B) at days 7 and 30. At day 30, more donor cells had migrated into the central cornea region transplanted with aCM-based corneal epithelium (A), whereas few cells were detected in the central cornea transplanted with dAM-based corneal epithelium (B). Scale bar: 100 µm.</p

Biocompatibility of acellular conjunctiva matrix in vivo.

<p>Representative slit-lamp photographs just after intracorneal transplantation (A) and one month later (B). H.E. staining showed that transplanted aCM (arrow) adapted well to the host corneal stroma, with no evidence of inflammatory cells or stromal edema. Scale bar: 100 µm (C) and 50 µm (D).</p