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Avatars, as promising digital representations and service assistants of users in Metaverses, can enable drivers and passengers to immerse themselves in 3D virtual services and spaces of UAV-assisted vehicular Metaverses. However, avatar tasks include a multitude of human-to-avatar and avatar-to-avatar interactive applications, e.g., augmented reality navigation, which consumes intensive computing resources. It is inefficient and impractical for vehicles to process avatar tasks locally. Fortunately, migrating avatar tasks to the nearest roadside units (RSU) or unmanned aerial vehicles (UAV) for execution is a promising solution to decrease computation overhead and reduce task processing latency, while the high mobility of vehicles brings challenges for vehicles to independently perform avatar migration decisions depending on current and future vehicle status. To address these challenges, in this paper, we propose a novel avatar task migration system based on multi-agent deep reinforcement learning (MADRL) to execute immersive vehicular avatar tasks dynamically. Specifically, we first formulate the problem of avatar task migration from vehicles to RSUs/UAVs as a partially observable Markov decision process that can be solved by MADRL algorithms. We then design the multi-agent proximal policy optimization (MAPPO) approach as the MADRL algorithm for the avatar task migration problem. To overcome slow convergence resulting from the curse of dimensionality and non-stationary issues caused by shared parameters in MAPPO, we further propose a transformer-based MAPPO approach via sequential decision-making models for the efficient representation of relationships among agents. Finally, to motivate terrestrial or non-terrestrial edge servers (e.g., RSUs or UAVs) to share computation resources and ensure traceability of the sharing records, we apply smart contracts and blockchain technologies to achieve secure sharing management. Numerical results demonstrate that the proposed approach outperforms the MAPPO approach by around 2% and effectively reduces approximately 20% of the latency of avatar task execution in UAV-assisted vehicular Metaverses.

In the vehicular mixed reality (MR) Metaverse, the discrepancy between physical and virtual entities can be overcome by fusing the physical and virtual environments with multi-dimensional communications in autonomous driving systems. Assisted by digital twin (DT) technologies, connected autonomous vehicles (AVs), roadside units (RSUs), and virtual simulators can maintain the vehicular MR Metaverse via simulations for sharing data and making driving decisions collaboratively. However, it is challenging and costly to enable large-scale traffic and driving simulation via realistic data collection and fusion from the physical world for online prediction and offline training in autonomous driving systems. In this paper, we propose an autonomous driving architecture, where generative AI is leveraged to synthesize unlimited conditioned traffic and driving data via simulations for improving driving safety and traffic control efficiency. First, we propose a multi-task DT offloading model for the reliable execution of heterogeneous DT tasks with different requirements at RSUs. Then, based on the preferences of AV's DTs and real-world data, virtual simulators can synthesize unlimited conditioned driving and traffic datasets for improved robustness. Finally, we propose a multi-task enhanced auction-based mechanism to provide fine-grained incentives for RSUs on providing resources for autonomous driving. The property analysis and experimental results demonstrate that the proposed mechanism and architecture are strategy-proof and effective.

Cardioid microphones/hydrophones have a highly directional gain pattern of $[ \alpha + (1 - \alpha) \cos (\beta) ] \cos ^{k}(\beta)$, where $k$ refers to the sensor's directivity order, $\alpha$ denotes the same sensor's cardioidicity index, and $\beta$ represents an impinging signal's incident direction of arrival relative to the cardioid sensor's axis. Three such cardioids organized in orthogonal orientation in three Cartesian spatial dimensions and in spatial colocation as one sensing unit—such a 3-D triad has already attracted much recent attention in the research literature. However, not all three Cartesian coordinates have equal importance to many acoustical applications, which focus alternatively on the azimuthal direction defined on a flat plane but less on the elevation direction normal to that plane. So, this article will instead analyze a 2-D planar configuration of three colocated/cocentered cardioids differently oriented azimuthally apart by $120^\circ$. This aforesaid coplanar triplet conforms to a flat supporting surface more than a Cartesian tridimensionally perpendicular triad can. For such a coplanar triplet composed of cardioids preset at any specific $(k, \alpha)$, the triplet's polar/azimuthal direction-finding Cramér–Rao lower bounds will be analytically derived in closed forms here in this article. Those bounds will be uncovered to exhibit intricate mathematical structures, which will be dissected in detail to yield refined insights, producing simple “actionable” rules-of-thumb to guide the system engineer to choose the appropriate values for $(k, \alpha)$.

AbstractThis study constructs an oligopoly model in public utilities sector to explore the optimal privatisation policy and the factors affecting equilibrium outcomes and explores the optimal proportion of state-owned shares. We also offer empirical evidence of China’s public utilities from 1985 to 2019 to prove the applicability of model results. The results show that, depending on product differentiation, cost variance, technical level, nationalisation, partial or full privatisation can be optimal. Improving capital efficiency increases social welfare in Model PP, but not in Model PS. Product differentiation improves social welfare at the expense of profits in SS model. In Model PM, technical improvements boost private enterprise profits but induce a decrement in social welfare. A high proportion of state-owned shares fail to improve social welfare in Model SM. In a word, the value range of parameters and competition modes in public utilities sector affect market players’ welfare distribution, which identifies with the empirical analysis of China’s public utilities development.

AbstractThis paper constructs a multi-oligopoly model of emergency supplies and analyses the market equilibrium results under normal conditions and epidemic conditions. The impacts of the degree of change in market demand, externalities, the material cost of emergency supplies and government regulation on the equilibrium results, especially on the prices of emergency supplies, are discussed. The results show that an increase in material cost will lead to low output and social welfare and a high price, under either normal conditions or epidemic conditions. Moreover, under epidemic conditions, the degree of change in market demand, externalities, material cost and the presence and mode of government regulation all have multiple and complex influences on the equilibrium results. Under epidemic conditions, both government output and price regulation can increase the supply of emergency supplies. In addition, when market demand changes drastically, consumer surplus and social welfare can be enhanced by the implementation of regulations. Particularly, price regulation is more effective when there is a high material cost.

AbstractThis article constructs a duopoly market with product differentiation and analyses profits, consumer surplus and social welfare under three conditions: (a) two enterprises have sufficient capacity; (b) one enterprise has insufficient capacity, and another enterprise has excess capacity that is not shared; and (c) one enterprise has insufficient capacity, and another enterprise has excess capacity and engages in capacity sharing. Through comparison, the implementation conditions for and effects of capacity sharing and the role of product differentiation are revealed. The results show that capacity sharing helps increase producer surplus and social welfare. Capacity constraints reduce social welfare but can be solved by capacity sharing. Capacity sharing can only be realised when both enterprises are profitable, and the charge for capacity sharing should not be too high or too low. Product differentiation has impacts on output, profit, consumer surplus and social welfare, and these impacts are restricted by the existence of capacity constraints and capacity sharing.

Chitosan (CS)/SiO2composites film were synthesized by the sol-gel method in the moderate environment. The polymer composites were characterized by FTIR, UV-Visible, SEM, TEM and DSC techniques. SiO2nanoparticles were dispersed homogeneously within the sphericity. Significantly, the resultant CS/SiO2composites film showed the specific fluorescence response to Al3+over than other metal ions. CS/SiO2gel sensor exhibits a detection range from 0 mg/L to 8.82 × 10−4mg/L (LOD=1.4 ×10−5mg/L). The gel sensor was successfully used for the detection of Al3+in water samples. Therefore, the gel sensor had a broad application prospect in other promising applications such as environmental quality and food safety monitoring.

AbstractThis study constructs an oligopoly model composed of mixed-ownership and private enterprises, examining the equilibrium results of three cases: when two enterprises compete with sufficient capacity (Model AA), insufficient capacity and overcapacity coexist without sharing (Model IA), and sharing (Model IS). This study also explores the effects of the proportion of state-owned shares, capacity constraints, and capacity prices. The realisation conditions and impacts of capacity sharing are further analysed. The results show that the efficiency of state-owned capital affects the effects of state-owned shares on the equilibrium results. An optimal capacity price exists for the capacity provider (private enterprise). Capacity sharing can effectively allocate resources and increase profits; however, consumers and society do not necessarily benefit from it. Full privatisation and the highest proportion of state-owned shares may be the best choice for the government under certain conditions. The government can intervene in enterprises’ capacity decision-making through subsidies to promote social welfare and realise capacity sharing simultaneously. Moreover, the government subsidises different enterprises when the proportions of state-owned shares and capacity prices are within different ranges.

Phosphine-catalyzed divergent [4+3] domino annulations of fluorinated imidoyl chlorides with MBH carbonates were developed. Two classes of perfluoroalkylated benzazepines were obtained in moderate to good yields via an interesting dearomatization/rearomatization sequence. Remarkably, the fluorinated imidoyl chlorides could be utilized for the first time as a new four-atom building block in phosphine catalysis. Moreover, the proposed mechanism is supported by capturing the intermediate.

ABSTRACTChinese energy industries are facing serious problems such as excess capacity, homogeneous product, and soft budget constraint. This paper provides a duopoly model to investigate the influence of heterogeneity and soft budget constraint on production capacity decision and internal action mechanism, respectively, under Cournot and Bertrand competitions, which reveals the formation mechanism of excess capacity. We conclude that excess capacity would exist when the products are not wholly heterogeneous under Cournot competition, and the higher level of the soft budget constraint or the more homogeneous the products are, the worse the excess capacity will be. The insufficient capacity would exist provided that products are not wholly heterogeneous under Bertrand competition, and the higher level of soft budget constraint or the more homogeneous the products are, the more insufficient capacity will be. Both soft budget constraint and product heterogeneity mutually affect to decision-making of capacity and output.

A finite element model of ASTM 114.3 mechanical tee backsheet is established by using the finite element software ANSYS. The stress distribution of backsheet under pretension force load is obtained through the strength analysis, and based on it, a topology optimisation calculations of backsheet is analysed. According to the topology optimisation results, the backsheet structure is redesigned and the finite element analysis to it shows that reducing the volume of the model of the backsheet while improving its stress distribution, the maximum equivalent stress is reduced and the enhanced chip reliability.

Divergent domino annulation reactions of sulfur ylides and azadienes were developed. A wide range of functionalized benzofuran-fused six- and seven-membered nitrogen–heterocyclic compounds were prepared in moderate to excellent yields under mild conditions. It is worth noting that the crotonate-derived sulfur ylides could be used as a novel C2 synthon or C3 synthon selectively by simply transforming the base.

Li-air battery has high theoretical energy density, which is considered a powerful candidate for flexible electrical products power supply. However, there are many challenges to commercialize Li-air battery in wearable devices. For example, how to solve the problem of H2O and CO2gas pollution and electrolyte volatilization caused by open structure. In addition, the construction of high efficiency flexible cathode, effective protection of anode materials and suppression of Li dendrites, and reasonable temperature control methods are all problems to be solved. At present, great progress has been made in the research of Li-air batteries, but there is still a lack of decisive breakthrough, which is due to the insufficient basic research. This review summarizes the research progress and challenges of flexible Li-air batteries in recent years for wearable devices, and prospects its future development direction.

To analyze the ultimate bearing capacity of concrete-filled stainless steel tube (CFSST) stub columns confined by carbon fiber reinforced polymer (CFRP) under axial compression, this study conducted theoretical analysis, experimental research, and finite element simulation on CFRP-confined CFSST stub columns under axial compression. Through the theoretical analysis, using the continuous strength method and limit equilibrium method, a theoretical calculation model of the ultimate bearing capacity of the columns was established considering the evident strain hardening effect of stainless steel. In addition, through experimental research, it was found that the failure mode of CFRP-confined CFSST specimens is the typical CFRP fracture and that CFRP can effectively improve the axial compression performance of specimens and restrain the local buckling deformation of the stainless steel tube. Based on experimental research, a finite element model of the CFRP-confined CFSST stub column was established, and a parameter database for the finite element numerical analysis was established. By comparing the experimental results with the aforementioned parameter database, the theoretical model was verified to have a high accuracy in predicting the ultimate bearing capacity of CFRP-confined CFSST stub columns.