Search Results (938)

We theoretically investigate multiple-Q instabilities in centrosymmetric hexagonal magnets, formulated as superpositions of independent six ordering wave vectors related by sixfold rotational and mirror symmetries. By employing a spin model that incorporates biquadratic interactions and an external magnetic field, we establish a comprehensive low-temperature phase diagram hosting single-Q, double-Q, triple-Q, and sextuple-Q states, as well as skyrmion crystals with topological charges of one and two. The field evolution of the magnetization, scalar spin chirality, and finite wave-vector magnetic amplitudes reveals a hierarchical buildup of multiple-Q order, accompanied by first-order transitions between topologically distinct and trivial phases. At large biquadratic coupling, all six symmetry-related ordering wave vectors coherently participate, giving rise to two sextuple-Q states under magnetic fields and to another spontaneous sextuple-Q state even at zero field. The latter zero-field sextuple-Q state represents a fully developed sixfold interference pattern stabilized solely by the biquadratic interaction, characterized by alternating skyrmion- and antiskyrmion-like cores with vanishing uniform scalar spin chirality. These findings establish a unified framework for understanding hierarchical multiple-Q ordering and demonstrate that the interplay between bilinear and biquadratic interactions under hexagonal symmetry provides a generic route to complex noncoplanar magnetism in centrosymmetric itinerant systems. Full article

This paper presents the design and calculation of wireless power transfer (WPT) integrated with the Hamiltonian Control Law. The proposed controller demonstrates greater effectiveness in terms of system stability and precise energy control, as compared to the commonly used PI controller in industrial applications. The proposed prototype has been built for assessment in both simulation and implementation, with a rated output power of 500 W and 48 V. The load-independent compensating topology, such as the LCC-S resonant tank, is used to transmit power wirelessly through an air core. Finally, in the last stage, the Hamiltonian Control Law with state observer is applied on the dc-to-dc buck mode converter to control the battery current and overall system. Apparently, the charging current can be precisely regulated to a specific value. Full article

This paper evaluates neural-network approaches for lithium-ion battery state-of-charge (SoC) estimation under a unified pipeline, fixed data partitions, and identical preprocessing. We study FNNs trained with Levenberg–Marquardt (LM), Bayesian Regularization (BR), and Scaled Conjugate Gradient (SCG) across three hidden sizes (10, 20, 30) and three topologies: Fitting, Nonlinear Input–Output (Nonlinear I/O), and time-series NAR/NARX. Models are assessed using test MSE and RMSE, correlation (R), generalization gap, convergence indicators (final gradient, damping factor), wall time per epoch, and a relative compute-cost index. On the Fitting task, BR-Fitting-FNN with 20 neurons provides the best accuracy-efficiency balance, while LM-Fitting-FNN with 30 neurons reaches slightly lower error at a higher cost. For Nonlinear I/O, BR-Nonlinear I/O-FNN with 30 neurons achieves the lowest test MSE with clear evidence of effective weight shrinkage; LM-Nonlinear I/O-FNN with 20 neurons is a close alternative. In time-series settings, LM-NAR-FNN with 10 neurons attains the lowest test error and fastest epochs but shows a very negative gap that suggests test-split favorability; BR-NAR-FNN with 30 neurons is more costly yet consistently strong. For NARX, LM-NARX-FNN with 20 neurons yields the best test accuracy and robust convergence. Overall, BR delivers the most reliable accuracy–robustness trade-off as networks widen, LM often achieves the best raw accuracy with careful split validation, and SCG offers the lowest training cost when resources are limited. These results provide practical guidance for selecting SoC estimators to match accuracy targets, computing budgets, and deployment constraints in battery management systems. Full article

This study systematically investigates the propagation characteristics of ring-shaped Airy-Gaussian vortex (RAiGV) beams in a 50 m marine turbulent channel. Utilizing a combined angular spectrum-phase screen model, numerical simulations were conducted to analyze the evolution of light intensity, scintillation index (SI), and detection probability (DP) under varying distribution factors b, topological charge l, and turbulence intensity σ². Results reveal that the SI of RAiGV exhibits a three-stage pattern: initial rise, decline, and subsequent rise. The valley positions of SI correspond one-to-one with self-focusing foci. Smaller b values result in closer foci, with short-range SI reaching its minimum but eventually surpassing long-range SI. At b = 0.15, the beam maintains a flatter SI curve and higher DP over long distances. The l = 1 vortex structure, characterized by its simplicity, demonstrates superior robustness against turbulence compared to higher-order modes. Appropriate selection of b and l enables a trade-off between near-field peak intensity and far-field stability, providing valuable design guidance for underwater OAM multiplexing communications. Full article

Wireless power transfer is gaining attention in medium-to-short-range applications such as 1–3 kW-class UAVs and AGVs due to its safety, reliability, and adaptability to complex environments. The LCC-S topology is widely adopted due to its favorable output characteristics and device voltage-stress distribution. However, under fixed coil parameters and operating frequencies, conventional LCC-S achieves high efficiency only near the optimal equivalent load. When the actual load deviates from this value—especially in heavy-load regions—resonant cavity current increases sharply, voltage gain drops significantly, and overall efficiency deteriorates. To overcome this structural limitation without increasing control complexity or adding active regulation stages, this paper proposes a transformer-assisted LCC-S wireless charging topology based on “equivalent load reconstruction.” First, a unified equivalent circuit is constructed to derive analytical expressions for voltage gain, input impedance, and efficiency under arbitrary coupling coefficients and loads for both the traditional LCC-S and the proposed topology, revealing the mechanism behind efficiency degradation under heavy loads. Building upon this foundation, a high-frequency transformer is introduced, with an efficiency-oriented collaborative design method for its turns ratio and excitation inductance. Furthermore, by integrating simplified copper and iron-loss models, the losses in the resonant cavity and the transformer are decomposed and evaluated. Results demonstrate that when transformer parameters are appropriately selected, the newly introduced transformer losses are significantly smaller than the resonant cavity losses reduced through load reconstruction. The constructed 1 kW, 85 kHz prototype demonstrates that within the 0.5–2.5 Ω load range, the proposed topology achieves efficiency exceeding 88%. Under typical heavy-load conditions, its peak efficiency surpasses that of the conventional LCC-S by approximately 20%. The theoretical analysis, simulation, and experimental results are highly consistent, verifying that the transformer-assisted LCC-S topology and its efficiency-oriented design method can effectively expand the high-efficiency operating range across a wide load spectrum without altering the control strategy. This provides a concise and feasible structural optimization solution for wireless charging systems. Full article

Novel copper(II) coordination compounds with hemiaminal N,O-donor ligands were obtained and synthesized in a one-pot reaction from three appropriate substrates (aldehyde, amine, and copper(II) chloride) in methanol. A dinuclear complex with a [Cu₂Cl₂(hemiaminal)₂(amine)₂] coordination mode was obtained. The complex consists of two five-coordinated central Cu(II) cations with square pyramidal geometry and C_i molecular symmetry. The hemiaminal oxygen atom forms a bridge between the two metallic centers, and that coordination bond is a factor stabilizing these hemiaminal moieties, generally regarded as unstable intermediates. We analyzed the energetic and physicochemical properties of the [Cu₂Cl₂(hemiaminal)₂(amine)₂] complex using density functional theory (DFT). First of all, we predicted the geometrical parameters, molecular electrostatic potential, HOMO and LUMO energies, and reactivity indices to indicate the free radical scavenging capacity. Based on the topological analysis of charge densities, we also characterized the properties of hydrogen bonds. Moreover, the antimicrobial properties of the complex were investigated, and it exhibited the highest activity against Gram-positive bacteria and Candida albicans. Full article

Hexagonal rare-earth manganites, as prototypical improper ferroelectrics in which structural distortions give rise to ferroelectricity, exhibit unique physical phenomena that are absent in conventional proper ferroelectrics. Owing to their Z₂ × Z₃ topologically protected ferroelectric domain structure, characterized by the convergence of six domains at vortex core, hexagonal manganites can host charged domain walls exhibiting multiple distinct conductive states and unconventional physical effects such as the half-wave rectification effect within a single bulk single crystal, opening up promising avenues for the practical applications. Moreover, as an excellent experimental platform for verifying the Kibble–Zurek mechanism, hexagonal manganites not only possess a broad application potential but also embody rich and fundamental physical insights. Given a series of recent advances in this field, it is essential to systematically summarize and discuss the key findings, current progress, and future research perspectives concerning the hexagonal manganite system. In this review, the origin of ferroelectricity in hexagonal manganites are first clarified, followed by a discussion of the formation and transformation mechanisms of unique ferroelectric domain structures, as well as the intrinsic mechanical properties. Subsequently, the manipulation of topological defects are compared, including electric fields, thermal treatment, oxygen vacancies, and stress–strain fields. Building upon these discussions, the distinct physical effects observed in hexagonal manganites are comprehensively summarized, such as domain wall conductance, dielectric and ferroelectric properties, and thermal conductivity. Finally, based on a detailed summary of the major achievements, the unresolved issues that warrant further investigation are highlighted, thereby offering guidance for future research directions and providing valuable insights for the broader study of ferroelectric materials. Full article

Lithium-ion batteries (LIBs) dominate energy storage for electric vehicles (EVs) due to their high energy density, long cycle life, and low self-discharge. However, high costs, complex manufacturing, and the requirement for advanced battery management systems (BMSs) constrain their broader deployment. Therefore, extending the utility of LIBs through reuse is essential for economic and environmental sustainability. Retired EV batteries with 70–80% state-of-health (SOH) can be repurposed in battery energy storage systems (BESSs) to support power grids. Effective reuse depends on accurate and rapid assessment of SOH and state-of-safety (SOS), which relies on precise state-of-charge (SOC) detection, particularly for aged LIBs with elevated thermal and electrochemical risks. This review systematically surveys SOC, SOH, and SOS detection methods for second-life LIBs, covering model-based, data-driven, and hybrid approaches, and highlights strategies for a fast and reliable evaluation. It further examines power electronics topologies and control strategies for integrating second-life LIBs into power grids, focusing on safety, efficiency, and operational performance. Finally, it analyzes key factors within the closed-loop supply chain, particularly reverse logistics, and provides guidance on enhancing adoption and supporting the establishment of circular battery ecosystems. This review serves as a comprehensive resource for researchers, industry stakeholders, and policymakers aiming to optimize second-life utilization of traction LIBs. Full article

Over the past thirty years, the focus in singular optics has been on structured beams carrying orbital angular momentum (OAM) for diverse applications in science and technology. However, as practice has shown, the OAM-free structured Gaussian beams with several degrees of freedom are no worse than the OAM beams, especially when propagating through turbulent flows. In this paper, we partially fillthis gap by theoretically and experimentally mapping cyclic changes in vortex-free states (including OAM) as a phase portrait of the beam evolution in an astigmatic optical system. We show that those cyclic variations in the beam parameters are accompanied by the accumulation of the geometric Berry phase, which is an additional degree of freedom. We find also that the geometric phase of cyclic changes in the intensity ellipse shape does not depend on the radial numbers of the Laguerre–Gaussian mode with zero topological charge and is always set by changing the shape of the Gaussian beam. The Stokes parameter formalism was developed to map the beam states’ evolution onto a Poincaré sphere based on physically measurable second-order intensity moments. Theory and experiment are found to be in a good enough agreement. Full article

Quantum mechanics postulates wave–particle duality and assigns amplitudes of the form $e^{iS/\hslash }$, yet no existing formulation explains why physical observables depend only on the phase of the action. Here we show that if the quantum of action ${\hslash }_{\mathrm{geom}}$ is finite, the classical action manifold $\mathbb{R}$ becomes compact under the identification $S\equiv S+2\pi {\hslash }_{\mathrm{geom}}$, yielding a $U\left(1\right)$ action space on which only modular action is observable. Wave interference then follows as a geometric necessity: a finite action quantum forces physical amplitudes to live on a circle, while the classical limit arises when the modular spacing $2\pi {\hslash }_{\mathrm{geom}}$ becomes negligible compared with macroscopic actions. We formulate this as a compact-action theorem. Chronon Field Theory (ChFT) provides the physical origin of ${\hslash }_{\mathrm{geom}}$: its causal field ${\Phi }^{\mu }$ carries a quantized symplectic flux $\oint \omega ={\hslash }_{\mathrm{geom}}$, making Planck’s constant a geometric topological invariant rather than an imposed parameter. Within this medium, the Real–Now–Front (RNF) supplies a local reconstruction rule that reproduces the structure of the Feynman path integral, the Schrödinger evolution, the Born rule, and macroscopic definiteness as consequences of geometric compatibility rather than supplemental postulates. Phenomenologically, identifying the electron as the minimal chronon soliton—carrying the fundamental unit of symplectic flux—links its spin, charge, and stability to topological properties of the chronon field, yielding concrete experimental signatures. Thus the compact-action/RNF framework provides a unified geometric origin for quantum interference, measurement, and matter, together with falsifiable predictions of ChFT. Full article

Active-control coils on Keda Torus eXperiment (KTX) are used to suppress error fields and mitigate MHD instabilities, thereby extending discharge duration and improving plasma confinement quality. Achieving effective active MHD control imposes stringent requirements on the coil power supplies: wide-bandwidth and high-precision current regulation, deterministic low-latency response, and tightly synchronized operation across 136 independently driven coils. Specifically, the supplies must deliver up to ±200 A with fast slew rates and bandwidths up to several kilohertz, while ensuring sub-100 μs control latency, programmable waveforms, and inter-channel synchronization for real-time feedback. These demands make the power supply architecture a key enabling technology and motivate this work. This paper presents the design and simulation of the KTX active-control coil power supply. The system adopts a modular AC–DC–AC topology with energy storage: grid-fed rectifiers charge DC-link capacitor banks, each H-bridge IGBT converter (20 kHz) independently drives one coil, and an EMC filter shapes the output current. Matlab/Simulink R2025b simulations under DC, sinusoidal, and arbitrary current references demonstrate rapid tracking up to the target bandwidth with ±0.5 A ripple at 200 A and limited DC-link voltage droop (≤10%) from an 800 V, 50 mF storage bank. The results verify the feasibility of the proposed scheme and provide a solid basis for real-time multi-coil active MHD control on KTX while reducing instantaneous grid loading through energy storage. Full article

Based on the extended Huygens–Fresnel principle and mode expansion theory, we derive the expression for the Coherence-Orbital Angular Momentum (COAM) matrix of twisted Gaussian Schell-model (TGSM) beams propagating through non-Kolmogorov turbulence. Using numerical simulations, we compare the evolution characteristics of the COAM matrix in free space and under non-Kolmogorov turbulence conditions. The study analyzes the variation patterns in the absolute values, real parts, and imaginary parts of the COAM matrix elements under different topological charges, and provides a detailed investigation of the influence of various beam parameters and turbulence parameters on these elements. The results show that by selecting appropriate parameters, the negative impact of turbulence on the correlation between orbital angular momentum (OAM) modes can be effectively mitigated. This work provides theoretical support for parameter selection and optimization in atmospheric optical communication systems. Full article

Battery energy storage systems can mitigate power fluctuations and enhance system reliability; however, cell-to-cell inconsistencies and aging in large-capacity battery packs can lead to imbalance. To address the limitations of passive balancing, which suffers from high energy loss and low efficiency, this work proposes a high-current active balancing system based on a single-input multiple-output (SIMO) topology. The system enables energy transfer through a full-bridge converter and transformer, supporting series discharge and selective charging of lithium iron phosphate (LFP) cells. To optimize system performance, a small-signal model was established, and corresponding control strategies were designed: the primary-side inverter employs quasi-open-loop control, while the secondary-side charging modules use a voltage–current dual-loop control. The effectiveness of the model and control strategies was validated via QSPICE simulations. Furthermore, a hybrid active–passive balancing strategy based on a voltage-difference threshold was proposed, allowing for real-time dynamic adjustment of the operating mode according to individual cell voltages. Experimental results on a large-capacity LFP battery demonstrate that the system achieves fast balancing with high accuracy, maintaining cell voltage differences within 30 mV. This provides a practical and effective solution for maintaining cell consistency in electric vehicles and grid-scale energy storage systems. Full article

Efficient control a system of multiple Automated Guided Vehicles (AGVs) is crucial for modern intralogistics given the growing importance of energy consumption and operating costs. This study investigates the impact of two deadlock handling methods: Chain Of Reservations (COR) and Structural On-line Control Policy (SOCP), on the energy efficiency and performance of AGV systems operating in a production environment described as square topology. A simulation model developed in FlexSim implemented both methods using real AGV data on electricity consumption during various tasks. The analysis also discusses the adopted battery charging strategy. Simulation experiments combined each deadlock handling method with two path-planning strategies: shortest path and fastest path. Pseudocode algorithms for determining these paths in an environment described as square topology are provided. System performance was evaluated across a wide range of AGV fleet sizes, focusing on key indicators such as total energy consumption, time to complete transportation tasks, and AGV utilization rate. Multi-criteria optimization reduced the problem to two conflicting objectives: energy consumption and completion time, with Pareto fronts generated for each configuration studied. The results demonstrate that both the deadlock handling strategy and the selected pathfinding algorithm significantly influence the evaluation criteria. This original research integrates solving the deadlock problem with controlling energy efficiency and task completion time in structured transportation environments that are not deadlock-free by design. Full article

Optical skyrmions, as topologically protected quasiparticles, hold great promise for on-chip photonic technologies. However, achieving programmable control over their properties through subtle structural changes remains challenging. This study introduces a minimal perturbation engineering strategy on a plasmonic metasurface. By applying controlled geometric perturbations (either continuous shortening or discrete segmentation) to a single edge of a hexagonal groove structure, combined with incident phase perturbations, we systematically manipulate the evolution of the skyrmion texture. These minimal perturbations induce reproducible shifts in the skyrmions’ center intensity and peak position, yielding up to ~32% center suppression, while the global topological charge remains conserved. This “geometry × phase” dual-perturbation approach provides a straightforward and efficient approach for engineering programmable topological light fields on a chip, with promising applications in integrated photonic devices. Full article