Search Results (476)

Accurate State of Charge (SOC) estimation is critical for the safety and efficiency of Battery Management Systems (BMS). While data-driven methods have shown promise, they often exhibit limited generalization capability due to the lack of physical constraints. Incorporating symmetry in the battery, such as through the use of Physics-Informed Neural Networks (PINNs), can mitigate this issue. However, PINNs typically rely on integer-order equivalent circuit model differential equations, which fail to accurately describe the complex electrochemical relaxation processes. To bridge this gap, we propose a novel Fractional Differential Physics-Informed Neural Network (FDE-PINN) framework. Unlike traditional approaches, this method embeds a Fractional-Order Equivalent Circuit Model (FO-ECM) into the Gated Recurrent Unit (GRU) architecture to explicitly capture the anomalous diffusion and long-memory effects inherent in battery polarization. Specifically, the network is trained by minimizing a composite loss function that integrates the data fitting error with residuals from fractional-order governing equations, including Coulomb counting and fractional voltage dynamics. Extensive experiments on the Panasonic 18650PF dataset and CALCE A123 dataset verify the method’s superiority. Results demonstrate that the proposed FDE-GRU model achieves an average MSE of $14.29\times {10}^{-4}$ (with an MAE of 2.43% and RMSE of 3.23%) on the NCA chemistry and $26.24\times {10}^{-4}$ (with an MAE of 3.75% and RMSE of 5.09%) on the LiFePO₄ chemistry, significantly outperforming traditional methods by reducing the estimation error by 35.6% and 26.2% compared to the standard GRU, respectively. Full article

Electron correlation and quantum interference are pivotal in mesoscopic transport. We theoretically study the nonequilibrium transport dynamics of a triangular triple-quantum-dot (TTQD) molecule connected to fermionic reservoirs using the exact hierarchical equations of motion (HEOM) formalism. We demonstrate a counterintuitive transport signature in which the stationary current is significantly enhanced by increasing U, a behavior distinct from the suppression typically observed in linear quantum dot arrays. By analyzing the evolution of spectral functions, we attribute this enhancement to the interplay between Coulomb-interaction-induced energy shifts and quantum interference effects specific to the triangular topology. We also explore how the circulation of chiral currents and electrode coupling strength modulate these interaction effects. Finally, we present a three-dimensional map of the transport current as a function of inter-dot tunneling (t) and Coulomb interaction (U), illustrating their combined effect on the current magnitude and its applications. Full article

With the rapid advancement of exoskeletons and rehabilitation robotics, modern healthcare increasingly demands high dynamic accuracy and reliability from medical devices. However, the dynamic response and durability of mechanical systems are greatly influenced by the inevitable existence of clearances in kinematic joints. Existing studies predominantly focus on simplified planar or spatial mechanisms, offering limited guidance for complex mechanical structures in medical applications. To address this issue, a unified modeling framework is proposed in this study to explore the nonlinear dynamic behavior and wear properties of bionic humanoid rigid mechanisms incorporating revolute joint clearances. A dynamic model that accounts for revolute joint clearances is established, employing the Lankarani–Nikravesh contact model alongside a refined Coulomb friction approach to characterize contact behavior. To characterize the wear progression between the shaft and the bushing, the Archard wear model is employed, while the system’s dynamic equations are formulated using the Lagrange multiplier approach. Systematic simulations are conducted to examine the effects of clearance size, location, and multi-clearance coupling on dynamic response and wear behavior. The results reveal that clearances at the hip joint have the most pronounced impact on system performance, tibiofemoral joint clearances exacerbate precision disturbances, and foot-end clearances considerably undermine system robustness. Increased clearance sizes and the coexistence of multiple clearances aggravate wear and induce more severe nonlinear dynamic phenomena. Phase portraits and Poincaré maps further illustrate that the system may exhibit complex or chaotic behavior under certain conditions. This study offers theoretical insights into performance degradation mechanisms in humanoid robots with joint clearances and introduces a modular “driving–mid–terminal” structure that enhances model generality, enabling its application to exoskeletons and rehabilitation devices for design optimization, service life prediction, and health monitoring. Full article

The molecular electrostatic surface potential (MESP) has become a key theoretical tool for probing reactivity in chemical systems. It reveals electrophilic and nucleophilic regions on molecular surfaces, underpinning the understanding of noncovalent interactions such as hydrogen, triel, tetrel, pnictogen, chalcogen, halogen, matere, and aerogen bonding, among many others. These interactions, driven by Coulombic attraction, govern aggregation in molecular and supramolecular systems across solid, liquid, and gas phases. MESP applications span crystal engineering, polymers, biology, catalysis, photovoltaics, and drug discovery. While limitations exist—such as the arbitrariness in defining isodensity surfaces—its impact on advancing both theoretical and applied chemical research is substantial. This review outlines the conceptual foundations of MESP and highlights its broad relevance across the chemical sciences. Full article

The prediction of dynamic responses of offshore wind turbine foundations under wind-wave-current multi-field coupled loads is the cornerstone of safety in offshore wind power engineering. The currently widely adopted equivalent load application method, while computationally efficient, simplifies loads into concentrated forces applied at the pile top and tower top, neglecting fluid-structure dynamic interaction mechanisms, which leads to deviations in response predictions. To overcome this limitation, this paper proposes a high-precision bidirectional fluid-structure interaction numerical framework. The fluid domain employs computational fluid dynamics (CFD) to construct an air-seawater two-phase flow model, utilizing the standard k-ε turbulence model and nonlinear wave theory to accurately simulate complex marine environments. The solid domain establishes a wind turbine-stratified seabed system via the finite element method (FEM), describing soil-rock mechanical properties based on the Mohr-Coulomb constitutive model. Comparative studies indicate that the equivalent static method significantly underestimates the displacement response of pile foundations, particularly under the extreme shutdown conditions examined in this study. This value should be interpreted as a case-specific observation rather than a universal deviation, and the discrepancy may vary with sea state, wind speed, current velocity, and wind–wave misalignment, thereby leading to non-conservative estimates of stress distribution. In contrast, the fluid-structure interaction method can reveal key physical processes such as local flow acceleration and wake–interference effects around the tower and the parked rotor under shutdown conditions, and the nonlinear interaction and resistance-increasing mechanisms between waves and currents. This model provides a reliable tool for safety assessment and damage evolution analysis of wind turbine foundations under extreme marine conditions, promoting the transformation of offshore wind power structure design from empirical formulas to mechanism-driven approaches. Full article

Lithium metal batteries (LMBs) have been widely studied due to their high energy density; however, the practical implementation of LMBs is limited by issues of uncontrolled dendrite growth, continuous electrolyte decomposition, and poor Coulombic efficiency (CE). Highly concentrated electrolytes (HCEs) have emerged as a promising approach to addressing the above issues. In this work, we propose a new HCE system based on a single carbonate solvent of 2,2,2-trifluoroethyl methyl carbonate (FEMC) with a high concentration of lithium bis(fluorosulfonyl)imide (LiFSI). The resulting electrolytes exhibit enhanced anodic stability and improved compatibility with lithium metal anodes and high-voltage cathodes. The optimized 4 M LiFSI–FEMC HCE achieved the highest CE for Li plating/stripping in Li/Cu cell and lowest overpotential in Li/Li symmetric cells, outperforming both low-concentration FEMC and ethyl methyl carbonate (EMC)-based electrolytes. In full-cell configurations with LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes, the HCE demonstrates stable cycling with minimal capacity fade over 250 cycles. Importantly, the HCE enables stable operation of 4.6 V high-voltage NCM811/Li cells for more than 120 cycles with a high-capacity retention of 88.61%. Post-mortem analysis revealed a more uniform and compact solid electrolyte interphase and a thinner cathode electrolyte interphase, contributing to the enhanced cycling performance. Full article

To address the challenge of surrounding rock instability in deep-buried tunnels crossing fractured fault zones, this study focuses on the Xigu Tunnel of the Lanzhou–Hezuo Railway. A combination of laboratory triaxial tests, an optimized multi-source advanced geological prediction workflow, and a site-specific parameter-weakened Mohr–Coulomb numerical simulation is employed to systematically reveal the physical–mechanical properties, spatial distribution, and deformation response of fractured rock masses under excavation-induced disturbance. The triaxial test results show that the average peak strength of the surrounding rock reaches 149.04 MPa; however, significant variability is observed among samples, and the failure mode exhibits a typical brittle–shear composite feature. The measured cohesion and internal friction angle are 20.57 MPa and 49.91°, respectively, indicating high intrinsic strength of individual rock blocks. Nevertheless, due to the presence of densely developed joints and crushed structures, the overall mass is loose and highly sensitive to dynamic disturbances such as blasting and excavation, revealing a unique mechanical paradox of high-strength rock blocks with low overall rock mass stability in deep-buried fractured zones. Joint TSP (Tunnel Seismic Prediction Ahead) and ground-penetrating radar (GPR) prediction reveals decreased P-wave velocity, increased Poisson’s ratio, and intensive seismic reflection interfaces; a quantitative index system for identifying the boundaries of narrow deep-buried fractured zones is proposed based on these geophysical characteristics. Combined with geological face mapping, these results confirm the existence of a highly fractured zone approximately 130 m in width, characterized by well-developed joints, heterogeneous mechanical properties, and localized risks of blockfall and groundwater ingress. The developed numerical model, with parameters weakened based on triaxial test and geological prediction data, effectively reproduces the deformation law of the fractured zone, and the simulation results agree well with field monitoring data, with peak displacement concentrated at section DK4 + 595, thus accurately identifying the center of the fractured belt as a key engineering validation result of the integrated technical framework. During construction, based on the identified spatial characteristics of the fractured zone and the proposed targeted support insight, enhanced dynamic monitoring and targeted support measures at the fractured zone center are required to ensure structural safety and long-term stability of the tunnel. This study develops an integrated engineering-oriented technical framework for deep-buried tunnels crossing narrow fractured zones, and provides novel mechanical insights and quantitative identification indices for such complex geological engineering scenarios. Full article

Addition theorems have been indispensable tools for the reduction of quantum transition amplitudes. They are normally utilized at the start of the process to move the angular dependence within plane waves, Coulomb potentials, and the like, into a sum over spherical harmonics that allows the angular integration to be carried out. These have historically been “two-range” addition theorems, characterized by the two-fold notation $r_{>}=Max[r_1,r_2]$ and $r_{<}=Min[r_1,r_2]$ and comprising a single infinite series. More recently, “one-range” addition theorems have been created that have no such piecewise notation, but at the cost of the introduction of another infinite series. We use a very different approach to derive an infinite set of addition theorems for Slater orbitals, hydrogenic and Hylleraas wave functions, and so on, that retain the one-range variable dependence but have, at worst, a finite second series rather than an infinite one. In addition, unlike previous addition theorems, they are applicable to more than one coordinate system. One of these addition theorems may also be used for Yukawa-like functions that may appear late in the reduction of amplitude integrals, and we show its utility for an integral that has stubbornly defied reduction to analytic form for nearly sixty years. Finally, we craft indefinite integrals of 15 half-integer Macdonald functions multiplied by (inverse) powers and negative exponentials containing squares of the integration variable. Full article

Calcium-ion batteries (CIBs) offer several advantages. CIBs are viable alternatives to lithium-based battery systems owing to the natural abundance, low cost, and high volumetric capacity of calcium. However, their development has been severely constrained by electrolyte instability and water sensitivity. We conducted a systematic examination of Ca(ClO₄)₂ and Ca(PF₆)₂ electrolytes, focusing on low-cost salt production, solvent selection, and stringent dehydration procedures. Acetonitrile (ACN) was the ideal solvent for high salt solubility and reversible Ca²⁺ electrochemistry, while carbonate solvents failed rapidly. We found that even a small amount of moisture in the electrolyte significantly affected the electrochemical performance. This study improved the dehydration process by using 3 Å molecular sieve (MS3A) and vacuum drying to reduce moisture to ppm levels, stabilizing the electrolyte. Prussian blue (PB) half cells exhibited reversible capacities of up to ≈95 mAh g⁻¹, whereas PB-hard carbon full cells utilizing dried Ca(ClO₄)₂ showed stable cycling over 240 cycles with a Coulombic efficiency of ≈99% and capacity loss of only ≈17%. This study establishes a moisture-controlled electrolyte as a critical enabler for practical CIBs. Full article

In this work, a hybrid polymer electrolyte integrating single- and dual-ion conducting systems was developed for lithium-ion batteries using bio-based materials, namely oleic-acid derivatives and epoxidized soybean oil, through an in situ polymerization process. The fixed FSI anions in LiEFSOA enhance the selectivity of Li⁺ transport, while the cross-linked network formed by ESO provides mechanical stability, and the LiFSI incorporated into the polymer matrix helps maintain sufficient overall ionic conductivity. In addition, the long C18 oleic chains increase the internal free volume of the matrix, thereby improving segmental mobility within the amorphous phase. The in situ polymerization inside the cell causes intimate interfacial contact between the electrode and electrolyte, achieving an ionic conductivity of 1.05 × 10⁻⁴ S cm⁻¹ at 30 °C. Electrochemical evaluation using LiFePO₄/FSOA-2/Li cells shows an initial discharge capacity of 149.09 mAh g⁻¹ and a capacity retention of 81.09% after 100 cycles, and the average coulombic efficiency was 99.62%, demonstrating that the designed FSOA electrolyte exhibits stable cycling performance and competitive capacity. Overall, the combination of eco-friendly materials and a hybrid ion transport strategy provides a promising platform for developing sustainable and high-performance polymer electrolytes for lithium-ion batteries. Full article

Aqueous zinc-ion batteries (AZIBs) are promising for large-scale grid storage due to inherent safety, low cost, environmental compatibility, high theoretical capacity (820 mAhg⁻¹), and suitable redox potential (−0.763 V vs. SHE). However, practical deployment is hindered by coupled challenges at the zinc anode–hydrogen evolution, dendrite growth, and corrosion/passivation, which severely limit cycle life and coulombic efficiency. This review systematically summarizes key advances in AZIB research. It first elucidates working principles and four cathode energy storage mechanisms: Zn²⁺ insertion/extraction, H⁺/Zn²⁺ co-insertion, chemical conversion, and dissolution/deposition. Second, it examines four mainstream cathodes (manganese-based, vanadium-based, Prussian blue analogs, and organic compounds), analyzing performance bottlenecks and corresponding optimization via structural modification. Third, it explores functional mechanisms of advanced separators (polymer, inorganic/ceramic composite, MOF-based, and cellulose-based) in regulating uniform Zn²⁺ deposition and suppressing dendrites. Fourth, it summarizes anode optimization strategies: artificial protective layers for interface stabilization, electrolyte additives to modulate Zn²⁺ solvation/deposition, and 3D porous structures to reduce local current density and provide nucleation sites. Finally, key scientific challenges and future directions are discussed—multi-strategy synergy, in situ characterization, practical battery construction, and sustainable technological development, offering theoretical guidance for advancing AZIBs toward large-scale applications. This review aims to provide a comprehensive perspective spanning from materials to systems, and from mechanisms to applications. Its core objective is not merely to list the types of cathode materials, but to establish a logical bridge directly connecting “key challenges” to “optimization strategies,” with a particular emphasis on the issues and solutions related to the cathode side. Full article

The increasing integration of renewable energy sources, such as solar photovoltaics, requires low-cost, scalable energy storage solutions suitable for decentralized systems. This work experimentally evaluates an iron chloride concentration redox flow battery (FeCl-CFB) coupled to a photovoltaic system. The battery, which employs the Fe²⁺/Fe³⁺ redox couple to store energy through a chemical concentration gradient, was electrochemically characterized using different carbon-based electrode materials and operated under solar charging for 25 charge–discharge cycles. A maximum power density of 6.3 W·m⁻² was achieved at the cell level, with stable cycling behavior under variable solar irradiance. Coulombic and energy efficiencies remained within ranges of 63–72% and 20–28%, respectively, throughout the cycles. Despite these moderate efficiencies, the system demonstrated a consistent and functional usable capacity. The main limitation identified was a decrease in maximum power after prolonged cycling, attributable to resistance and polarization losses rather than electrolyte instability. These preliminary results characterize the initial performance of the FeCl-CFB under solar-driven conditions, highlighting significant efficiency and stability challenges that must be addressed through further optimization to determine the future potential for decentralized energy storage. Full article

Microbial fuel cells (MFCs) are an emerging technology that converts the chemical energy stored in organic substrates into electrical energy using microorganisms as catalysts. However, their performance is often limited by the anode design and architecture. To address this, conductive anodes with well-defined pore sizes were manufactured via 3D printing and evaluated for electrical energy generation and wastewater treatment in microbial fuel cells. The maximum power density, coulombic efficiency, and accumulated biomass observed were 14.94 mW/m², 4.87 ± 0.56%, and 0.186 ± 0.025 g, respectively, for the anode with a 2.3 mm pore size. The maximum chemical oxygen demand (COD) removal efficiency was 86.98 ± 1.89% for the anode with a pore size of 1.6 mm. However, this difference was minimal and not significant compared to the anode with a 2.3 mm pore size, which achieved 85.77 ± 2.31%. Additionally, the lowest internal resistance observed was 1246.44 Ω, corresponding to the MFC equipped with the anode with a pore size of 2.3 mm. Taken together, these results indicate that, when using 3D-printed anodes with controlled architectures, an intermediate pore size, neither too large nor too small, provides an adequate balance between electrochemical performance and efficient wastewater treatment in microbial fuel cells. Full article

Present and future rare isotope accelerator facilities provide new opportunities to explore the structure of unstable nuclei. We report the measurements of the elastic scattering angular distributions of ²¹Na and ²²Na on the doubly magic ⁴⁰Ca above the Coulomb barrier energies, using high-purity post-accelerated ISOL beams from Beijing Radioactive Ion Beam Facility (BRIF). Angular distributions were measured with a silicon detector telescope array, and relative cross sections were determined with a CaF₂ target on Au backing. The data were well reproduced by optical model calculations with Woods–Saxon and USNP potentials, the latter giving better agreement. These results confirm the stable operation and performance of the BRIF ISOL production and post-acceleration system, demonstrate its capability to provide radioactive beams of useful intensity and purity for future investigations of reaction dynamics and astrophysically relevant processes involving proton-rich nuclei, and simultaneously extend proton-rich elastic scattering studies to heavier systems. Full article

Metal-free two-dimensional (2D) polymers built from open-shell π-conjugated units offer a promising platform for realizing correlation-driven magnetism without transition metal elements. Here, we present a systematic first-principles study of phenalenyl-based 2D polymers that elucidates how atomic-level chemical substitution controls magnetic order through the interplay of electronic correlation and sublattice symmetry. Combining density functional theory with an effective tight-binding and Hubbard model analysis, we show that atomic substitution with boron or nitrogen on phenalenyl building blocks acts as a sublattice-resolved tuning knob for both the ratio of on-site Coulomb interaction to inter-site hopping (U/t) and the relative on-site energies of the two sublattices. Sublattice-asymmetric substitution with boron or nitrogen breaks sublattice equivalence and drives the system from an antiferromagnetic Mott-insulating state into spin-polarized semiconducting phases with pronounced spin-dependent gaps. In contrast, uniform substitution on both sublattices preserves symmetry and yields nonmagnetic metallic states characterized by rigid band shifts rather than correlation-driven spin polarization. These results establish a unified microscopic framework in which electronic correlations and sublattice symmetry emerge as cooperative yet independently tunable parameters, providing general design principles for metal-free 2D π-conjugated materials with tailored magnetic and spintronic functionalities. Full article