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In the realm of nanopore sensing, one of the most fundamental questions that needs to be answered is how ions are transported through nanochannels. The changes in current caused by the molecule moving through the nanopores provide us with useful information about the size, conformation, and charge of the test substance. In this context, we have fabricated a nanometer-sized pore in a suspended nanocrystalline graphite membrane and found that when negatively charged deoxyribonucleic acid (DNA) molecules pass through the pore, the current increases. Using the Navier–Stokes and Poisson–Nernst–Planck coupling models, we calculated the current reduction due to the steric hindrance effect of DNA molecules, as well as the current increase due to the enhanced ion concentration in nanopores, which is attracted by DNA surface charges. The results from these studies provide a new nanopore material for basic and applied nanofluidic research and reveal that the electroosmotic flow plays a role in driving DNA transport and generating conductive events due to polarization effects. This finding not only expands our understanding of the physical principles governing DNA–nanopore interactions but also holds promise for advancing the sensitivity and specificity of nanopore-based molecular detection. [ABSTRACT FROM AUTHOR]

The bottom platform is an important underwater sensor that can be used in communications, early warning, monitoring, and other fields. It may be affected by earthquakes, winds, waves, and other loads in the working environment, causing changes in posture and affecting its sensing function. Therefore, it is of practical engineering significance to analyze the force conditions and posture changes in the bottom platform. In order to solve the problem of postural stability of the underwater bottom platform, this paper establishes a fluid and structural simulation model of the underwater bottom platform. First, computational fluid dynamics (CFD) technology is used to solve the velocity distribution and forces in the watershed around the bottom platform under a 3 kn ocean current, where the finite element method (FEM) numerical calculation method is used to solve the initial equilibrium state of the bottom platform after it is buried. On this basis, this paper calculates the forces on the bottom platform and the posture of the bottom platform at different burial depths under the action of ocean currents. Additionally, the effects of different burial depths on the maximum displacement, deflection angle, and postural stability of the bottom platform are studied. The calculation results show that when the burial depth is greater than 0.6 m, and the deflection angle of the bottom platform under the action of the 3 kn sea current is less than 5°, the bottom platform can maintain a stable posture. This paper could be used to characterize the postural stability of underwater bottom platforms at different burial depths for the application of underwater sensors in ocean engineering. [ABSTRACT FROM AUTHOR]

The electron tunneling rates between a two-dimensional electron gas (2DEG) and self-assembled InAs quantum dots are studied by applying a magnetic field perpendicular to the tunneling direction. For both the ground and the first excited states, the tunneling rate can be modified by a magnetic field. The field dependence of both the s and p state tunneling rates can be explained with a model, based on momentum matching between the Fermi surface of the 2DEG and the wave function of the quantum dots in momentum space. The results, together with the comparison between charging and discharging rates, provide insight into the filling sequence of the p-state electrons. [ABSTRACT FROM AUTHOR]

Due to limitations in operational scope and efficiency, a single Autonomous Underwater Vehicle (AUV) falls short of meeting the demands of the contemporary marine working environment. Consequently, there is a growing interest in the coordination of multiple AUVs. To address the requirements of coordinated missions, this paper proposes a comprehensive solution for the coordinated development of multi-AUV formations, encompassing long-range ferrying, coordinated detection, and surrounding attack. In the initial phase, detection devices are deactivated, employing a path planning method based on the Rapidly Exploring Random Tree (RRT) algorithm to ensure collision-free AUV movement. During the coordinated detection phase, an artificial potential field method is applied to maintain AUV formation integrity and avoid obstacles, dynamically updating environmental probability based on formation movement. In the coordinated surroundings attack stage, predictive capabilities are enhanced using Long Short-Term Memory (LSTM) networks and reinforcement learning. Specifically, LSTM forecasts the target's position, while the Deep Deterministic Policy Gradient (DDPG) method controls AUV formation. The effectiveness of this coordinated solution is validated through an integrated simulation trajectory. [ABSTRACT FROM AUTHOR]

Rare type-II spin-gapless semiconductors (SGSs), in which electrons and holes are 100% spin polarized in different directions to the Fermi level, have attracted increasing attention. Motivated by the recent findings of type-II SGS VSi2P4 with ferromagnetic characteristics and a high Curie temperature (350 K), we investigated the interface contacts and spin transport properties of different devices composed of VSi2P4 ferromagnetic layers. It was found from the first-principles calculations combined with nonequilibrium Green's function that different potential barriers appear on the interface pinning and ultimately determine the conductive characteristics. The T-MoTe2/VSi2P4/H-MoTe2/VSi2P4/T-MoTe2 device (1H device) shows a large tunnel magnetoresistance (TMR) of 3.35 × 103% resulting from the interfacial spin filtering, and the T-MoTe2/H-MoTe2/VSi2P4/H-MoTe2/VSi2P4/H-MoTe2/T-MoTe2 device (3H device) accompanied with many resonant states presents increased TMR (1.83 × 104%). The transport properties of two devices are explained from the spin-dependent band structures, local density of states, transmission coefficients and eigenstates. These results indicate that VSi2P4 is a promising material for designing vertical van der Waals (vdW) heterostructures with a giant TMR in spintronic applications. [ABSTRACT FROM AUTHOR]

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Gas diffusion layers (GDLs) in high-temperature, high-humidity, and high-electric-potential environments can be affected by the carbon corrosion and degradation of Polytetrafluoroethylene (PTFE) network structures, resulting in reduced reliability and hydrophobicity. By using cyclic voltammetry and offline characterization, a high-potential scanning of 1–1.5 V is applied to the GDL in the three-electrode system, considering the role of gradient graphitization degree and pore size structure in corrosion. Accelerating the electrochemical corrosion process of carbon and PTFE allows the identification of corrosion location, extent, and determinants. The results indicate that after 800 cycles of high-potential triangulation scanning, the graphitization of gas diffusion base has the most significant impact on the GDL's durability. On the other hand, the durability of the GDL's microporous layer is influenced by its small pore size structure rather than its graphitization degree. Furthermore, the corrosion process of GDLs with a small pore size structure tends to be relatively slow, providing a basis for GDL selection and durability prediction. [ABSTRACT FROM AUTHOR]

Due to the non-renewable nature and pollution associated with fossil fuels, there is widespread research into alternative energy sources. As a novel energy device, a proton exchange membrane fuel cell (PEMFC) is considered a promising candidate for transportation due to its advantages, including zero carbon emissions, low noise, and high energy density. However, the commercialization of fuel cells faces a significant challenge related to aging and performance degradation during operation. In order to comprehensively address the issue of fuel cell aging and performance decline, this paper provides a detailed review of aging mechanisms and influencing factors from the perspectives of both the PEMFC system and the stack. On this basis, this paper offers targeted solutions to degradation issues stemming from various aging factors and presents research on aging prediction methods to proactively mitigate aging-related problems. Furthermore, to enhance prediction accuracy, this paper categorizes and analyzes the degradation index and accuracy evaluation criteria commonly employed in the existing fuel cell aging research. The results indicate that specific factors leading to aging-related failures are often addressed via targeted solving methods, corresponding to specific degradation indexes. The significance of this study lies in the following aspects: (1) investigating the aging factors in fuel cells and elucidating the multiple aging mechanisms occurring within fuel cells; (2) proposing preventive measures, solutions, and aging prediction methods tailored to address fuel cell aging issues comprehensively, thereby mitigating potential harm; and (3) summarizing the degradation index and accuracy evaluation standards for aging prediction, offering new perspectives for resolving fuel cell aging problems. [ABSTRACT FROM AUTHOR]

Due to its advantages of high acceleration, reusability, environmental protection, safety, energy conservation, and efficiency, electromagnetic energy has been considered as an inevitable choice for future space launch technology. This paper proposes a novel three-level orbital launch approach based on a combination of a traditional two-level orbital launch method and an electromagnetic boost (EMB), in which the traditional two-level orbital launch consists of a turbine-based combined cycle (TBCC) and a reusable rocket (RR). Firstly, a mathematical model of a multi-stage coil electromagnetic boost system is established to develop the proposed three-level EMB-TBCC-RR orbital launch approach, achieving a horizontal take-off–horizontal landing (HTHL) reusable launch. In order to optimize the fuel quality of the energy system, an artificial intelligence algorithm parameters-sensitivity-based adaptive quantum-inspired glowworm swarm optimization (AQGSO)is proposed to improve the performance of the electromagnetic boosting system. Simulation results show that the proposed AQGSO improves the global optimization precision and convergence speed. By using the proposed EMB-TBCC-RR orbital launch system and the optimization approach, the required fuel weight was reduced by about 13 tons for the same launch mission, and the energy efficiency and reusability of the spacecraft was greatly improved. The spacecraft can be launched with more cargo capacity and increased payload. The proposed novel three-level orbital launch approach can help engineers to design and optimize the orbital launch system in the field of electromagnetic energy conversion and management. [ABSTRACT FROM AUTHOR]