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The comprehensive utilization of waste cooking oil (WCO) and waste engine oil (WEO) is of great significance to build a sustainable society because recycling WCO and WEO to develop a rejuvenator for asphalt pavement not only aids the reduction of environmental pollution, but also brings about significant benefits to the Earth's sustainable development. With a clear aim to contribute to a more efficient reuse of the waste oils and recycled asphalt mixtures, this paper develops a high-efficiency compound rejuvenator and determines the optimal combination of its main constituents (WCO and WEO) through orthogonal tests. Furthermore, the performance of the rejuvenator is verified by means of the four-fraction test and the traditional asphalt performance tests (penetration, ductility, softening point). These tests confirm the regeneration efficiency of the compound rejuvenator, and the optimum dosage of the compound rejuvenator is found of 7%. Subsequently, the mechanism of the compound rejuvenator in aged asphalt is examined, and following the application of the compound rejuvenator, it was concluded that the reclaimed asphalt pavement (RAP) could be maximized by 45%. Consequentially, the results of this research promote the recycling of WEO, WCO, and waste asphalt pavement materials, ultimately advocating the sustainability of pavement construction.

Single-atom catalysts provide efficiently utilized active sites to improve catalytic activities while improving the stability and enhancing the activities to the level of their bulk metallic counterparts are grand challenges. Herein, we demonstrate a family of single-atom catalysts with different interaction types by confining metal single atoms into the van der Waals gap of two-dimensional SnS2. The relatively weak bonding between the noble metal single atoms and the host endows the single atoms with more intrinsic catalytic activity compared to the ones with strong chemical bonding, while the protection offered by the layered material leads to ultrahigh stability compared to the physically adsorbed single-atom catalysts on the surface. Specifically, the trace Pt-intercalated SnS2 catalyst has superior long-term durability and comparable performance to that of commercial 10 wt% Pt/C catalyst in hydrogen evolution reaction. This work opens an avenue to explore high-performance intercalated single-atom electrocatalysts within various two-dimensional materials.

At present, the single-point observation method is not able to effectively monitor the overall settlement of the target surface of an embankment. The 3D laser scanning technology was, therefore, introduced to help solve this problem. In this study, the overall settlement of the Shi'an highway extended embankments were dynamically monitored and a series of point cloud data were obtained by 3D laser scanning. Due to the characteristics of point cloud data, the grid analysis and interpolation method in MATLAB were proposed for the analysis, so as to obtain the overall settlement displacements of the extension embankment. Furthermore, the reliability and accuracy of the 3D laser scanning were verified through comparison with the single-point observation, and the results are as follows: during the embankment extension construction process, the monitoring accuracy was improved by 25.8% at least when compared to the single-point observation method; during the asphalt pavement construction, the maximum settlement of single-point monitoring and the 3D laser scanning method recorded similar values of 1.6 mm and less than 2 mm, respectively; throughout the course of the 3-year post-construction settlement observation, the monthly settlement rate was maintained at an insignificant 0.01–0.09 mm/month for the single-point monitoring, and a similar rate of less than 0.05 mm for the 3D laser scanning method. These results show that the 3D laser scanning could reflect the overall settlement dynamics much better, and that combined with its advantages of fast and accurate observation, could be used to evaluate the settlements of new and old embankments in extension projects.

The novel crumb rubber (CR)/styrene–butadiene-styrene (SBS) composite modified asphalt has shown through various researches to have a better engineering performance than many commonly used modified asphalts. On the basis of the optimal preparation scheme of composite asphalt rubber, dynamic shear rheology (DSR) test was conducted to evaluate the rheological property of the modified asphalt, and performance tests were conducted on the composite asphalt rubber mixture. The influence of gradation type and anti-rutting agent on its mixture’s performance improvement was then summarized. Three different micro analysis test methods were used to observe the distribution and morphological changes of the modifier in the asphalt. Furthermore, the subsequent physical and chemical reactions that occurred between asphalt and modifier during the modification process were also studied. The results showed that the viscosity of composite asphalt rubber decreased as shear time increased. The rutting factor and the creep rate of the composite asphalt rubber were about 77.9% and 4.4%, respectively, both higher than that of the asphalt rubber. Meanwhile, when compared with the anti-rutting agent used in practical engineering, the high-temperature performance of HXR-I (anti-rutting agent) was improved by 45.3%, the low-temperature performance was improved by 6.3%, and the water stability was improved by 17.8%. The microscopic test results showed that the rubber particles in the composite asphalt rubber swelled and were wrapped by asphalt and distributed around the aggregate. At the same time, it also illustrated that adding anti-rutting agent can improve the performance of the composite asphalt rubber in an effective way, which could adequately meet the required low-temperature performance, thus expanding its application in road engineering.

Despite extensive research on recently discovered layered ferromagnetic (FM) materials, their further development is hampered by the limited number of candidate materials with desired properties. As a much bigger family, layered antiferromagnetic (AFM) materials represent excellent platforms to not only deepen our understanding of fundamental physics but also push forward high-performance spintronics applications. Here, by systematic first-principles calculations, we demonstrate pressure and carrier doping control of magnetic properties in layered AFM CoPS3, a representative of transition metal phosphorus trichalcogenides. In particular, pressure can drive isostructural Mott transition, in sharp contrast to other transition metal thiophosphates. Intriguingly, both pressure and carrier doping can realize the long-sought FM half-metallic states with 100% spin polarization percentage, which is good for improving the injection and detection efficiency of spin currents among others. Moreover, the Mott transition is accompanied by instantaneous spin-crossover (SCO) in CoPS3, and such cooperative SCO facilitates the implementation of fast-response reversible devices, such as data storage devices, optical displays and sensors. We further provide an in-depth analysis for the mechanisms of FM half-metallicity and SCO. Tunable magnetism in layered AFM materials opens vast opportunities for purposeful device design with various functionalities.

The discovery of intrinsic 2D ferromagnets provides exciting possibilities for spintronics applications. A particularly attractive example is CrI3, whose monolayer is ferromagnetic while bilayer shows antiferromagnetic coupling. Because of weak interlayer coupling, the magnetism of bilayer CrI3 can be easily modulated by external perturbations, such as gating or pressure. Here, we constructed a magnetic phase diagram of bilayer CrI3 under arbitrary biaxial strain (within ±4%) from compression to stretch, and found that compressive strain can effectively convert the antiferromagnetic coupling of bilayer CrI3 to ferromagnetic. Detailed analyses on electronic structure were then performed to unravel the underlying mechanism of the magnetic phase transition. It was shown that both band gap and orbital composition at conduction band minimum play important roles in determining magnetic ground states of strained bilayer CrI3. These results strengthen our understanding of the interlayer magnetism of 2D magnets and provide a feasible way to modulate the magnetism in 2D layered materials.

Developing alternative oxygen reduction reaction (ORR) catalysts to replace precious Pt-based metals with abundant materials is the key challenge of commercial application of fuel cells. Owing to their various compositions and tunable electronic properties, transition metal dichalcogenides (TMDs) have the great potential to realize high-efficiency catalysts for ORR. Here, various 3R-phase dichalcogenides of group VB and VIB transition metals (MX2, M = Nb, Ta, Mo, W; X = S, Se, Te) are investigated for ORR catalysts by using density functional theory calculations. The computed over-potentials of group VB TMDs are much less than those of group VIB TMDs. For group VB TMDs, a volcano-type plot of ORR catalytic activity is established on the adsorption energies of *OH, and NbS2 and TaTe2 exhibit best ORR activity with an over-potential of 0.54 V. To achieve even better activity, strain engineering is performed to tune ORR catalytic activity, and the minimum over-potential of 0.43 V can be realized. We further demonstrate that the shift of p orbital center of surface chalcogen elements under strain is responsible for tuning the catalytic activity of TMDs.

Vertical heterostructures based on two-dimensional (2D) materials have attracted widespread interest for their numerous applications in electronic and optoelectronic devices. Herein, we report the direct construction of an abnormal graphene/ReSe2 stack on Au foils by a two-step chemical vapor deposition (CVD) strategy. During the second growth stage, monolayer ReSe2 is found to preferentially evolve at the interface between the first-grown graphene layer and the Au substrate. The unusual stacking behavior is unraveled by in-situ “cutting open” the upper graphene from the defects to expose the lower ReSe2 using scanning tunneling microscopy (STM). From combination of these results with density functional theory calculations, the domain boundaries and edge sites of graphene are proposed to be adsorption sites for Re and Se precursors, further facilitating the growth of ReSe2 at the van der Waals gap of graphene/Au. This work hereby offers an intriguing strategy for obtaining vertical 2D heterostructures featured with an ultra-clean interface and a designed stacking geometry.

In this paper, we consider the risk probability minimization problem for infinite discounted continuous-time Markov decision processes (CTMDPs) with unbounded transition rates. First, we introduce a class of policies depending on histories with the additional reward levels. Then, we construct the corresponding probability spaces, and also establish the non-explosion of the state process. Secondly, under suitable conditions we prove that the value function is a solution to the optimality equation for the probability criterion by an iteration technique, and obtain a value iteration algorithm to compute (at least approximate) the value function. Furthermore, under an additional condition we establish the uniqueness of the solution to the optimality equation and the existence of an optimal policy. Finally, we illustrate our results with two examples. The first one is used to verify our conditions for CTMDPs with unbounded transition rates, the second one for the numerical calculation of the value function and an optimal policy.

Monolayer transition metal dichalcogenides (TMDs) have become essential two-dimensional materials for their perspectives in engineering next-generation electronics. For related applications, the controlled growth of large-area uniform monolayer TMDs is crucial, while it remains challenging. Herein, we report the direct synthesis of 6-inch uniform monolayer molybdenum disulfide on the solid soda-lime glass, through a designed face-to-face metal-precursor supply route in a facile chemical vapor deposition process. We find that the highly uniform monolayer film, with the composite domains possessing an edge length larger than 400 µm, can be achieved within a quite short time of 8 min. This highly efficient growth is proven to be facilitated by sodium catalysts that are homogenously distributed in glass, according to our experimental facts and density functional theory calculations. This work provides insights into the batch production of highly uniform TMD films on the functional glass substrate with the advantages of low cost, easily transferrable, and compatible with direct applications., Growth of large-area monolayer transition metal dichalcogenides is critical for their application but remains challenging. Here Yang et al. report rapid chemical vapor deposition of 6-inch monolayer molybdenum disulfide by sufficiently uniformly supplying the precursors and catalysts.

This paper is the first attempt to investigate the risk probability criterion in semi-Markov decision processes with loss rates. The goal is to find an optimal policy with the minimum risk probability that the total loss incurred during a first passage time to some target set exceeds a loss level. First, we establish the optimality equation via a successive approximation technique, and show that the value function is the unique solution to the optimality equation. Second, we give suitable conditions, under which we prove the existence of optimal policies and develop an algorithm for computing e-optimal policies. Finally, we apply our main results to a business system.