Abstract This paper focuses on solving the Sasa-Satsuma equation with higher-order terms using the Riemann-Hilbert (RH) method. Firstly, we derive the Lax pairs related to the matrix spectral problem of the equation. Secondly, we perform spectral analysis on the Lax pairs of the equation, thereby constructing a RH problem for the equation. Under the condition of the reflectionless case, we solve for the \(N\)-soliton solutions of the equation and use symbolic computation in Maple to illustrate the graphical forms of the single-soliton and double-soliton solutions.
Abstract Three-dimensional (3D) images have become important information carriers in multimedia, medical treatment, and entertainment. However, existing 3D image hiding and watermarking schemes are mostly limited to single 3D image encryption, resulting in insufficient capacity, low security, and optimizable concealment. To address these issues, this paper proposes a highcapacity multi-3D image watermarking method based on multi-dimensional multiplexing holography and QZ embedding. Multiple 3D images are grouped and encoded into holographic watermarks using a multi-dimensional multiplexing hologram generation algorithm, where chaotic phase masks and spiral phase masks are adopted to expand the key space and enhance security. A contrast-guided embedding strategy is used to locate visually insensitive highcontrast regions in the two-dimensional host image, and the holographic watermarks are embedded into different wavelet sub-bands by combining discrete wavelet transform, singular value decomposition, and QZ embedding to achieve low distortion and strong robustness. Simulation results demonstrate that the proposed method can simultaneously embed sixteen 3D images with high imperceptibility proved by ultrahigh correlation coefficient and negligible entropy variation, good key sensitivity, and reliable robustness against noise and occlusion attacks. Compared with state-of-the-art hologram-based encryption schemes, the proposed method exhibits significant advantages in capacity, security, and concealment, showing potential for secure optical information hiding and copyright protection of 3D visual data.
Abstract This study investigates influence of phosphorus-implanted emitters on Al-BSF p-type crystalline silicon solar cells with 25 cm² active area by varying implantation energy, 30 keV and 40 keV at 5 × 10¹⁵ cm⁻² , annealing parameter of 800 °C and 1050 °C for 15–30 min, and LPCVD Si₃N₄ passivation parameters of 800–850 °C. Comprehensive characterization using four-point probe, simulated dopant profiles, IPCE and J–V measurements demonstrate that moderate 800°C annealing with either implantation energy yields promising photovoltaic performance, achieving peak efficiencies of 9.92%, Jsc up to 28.4 mA/cm², FF of 0.67, and Voc of 0.52 V. These best-performing devices among the eight conditions tested exhibit high EQE (>90%) and IQE (>95%) in the visible spectrum, low front-surface recombination, and balanced emitter profiles with surface concentrations of ~4.5–5.4 × 10¹⁹ cm⁻³ and junction depths of ~1.09 μm. High-temperature 1050°C annealing induces excessive dopant diffusion, phosphorus clustering, and severe recombination losses, particularly in 40 keV samples, resulting in suppressed EQE/IQE, FF as low as 0.271, and efficiencies down to 1.2%. Although the single-layer Si₃N₄ antireflection coating provides moderate optical benefits (5–10% visible reflectance), the findings emphasize the need for precise control across implantation, annealing, and passivation to minimize recombination, highlighting ion implantation's advantages in precision and uniformity over thermal diffusion for scalable industrial silicon PV production. As only one device was fabricated per process condition, these trends should be regarded as preliminary indications rather than statistically validated optima, with replicate devices per condition identified as necessary follow-up work. Repeat measurements taken later on the same devices averaged somewhat lower than the single-scan values reported above, for example, 8.03% versus the 9.92% shown here, most likely reflecting minor changes between the initial and later characterization sessions; both values are reported for completeness, with the repeat-scan average taken as the more conservative estimate.
Abstract In this work, the oscillator strengths and dynamic dipole polarizability of a helium atom, He@Cn, confined within a fullerene cage and simultaneously subjected to an impenetrable spherical confinement and a quantum plasma environment, are investigated. Although the intrinsic optical response of helium is highly limited due to its closed-shell 1s 2 electronic configuration, it is observed that the simultaneous presence of spherical confinement boundary conditions, fullerene cage parameters, and quantum plasma screening profoundly modifies the spatial localization of the wavefunctions and the energy spectrum, leading to a substantial redistribution of oscillator strengths among selected transitions and a pronounced transformation in the resonance structure of the dynamic polarizability. The quantum plasma environment is modeled using the exponential cosine screened Coulomb (ECSC) potential, while the fullerene cage is represented by a Woods-Saxon potential. The electronic structure is obtained using numerical methods within the Hartree-Fock approach under impenetrable spherical confinement boundary conditions. By systematically varying the confinement radius, fullerene parameters, and the plasma screening function, the oscillator strengths for selected dipole transitions are investigated, and the observed spectral redistributions are interpreted in physical terms. In addition, the frequency-dependent contribution of the 1s → np electric dipole transitions to the dynamic dipole polarizability is analyzed in detail, and the systematic evolution of the resonance frequencies under these parameters is discussed.
Abstract The scope of Laue scattering theory was expanded by introducing a novel vector optical source to the Laue scattering research area for the first time. Based on the first-order Born approximation, general analytical expressions for the cross-spectral density matrix of the scattered field were derived. Then, as an example, Laue scattering of an electromagnetic multi-sinc Schell-model beam upon a hexagonal space lattice was investigated, mainly including the scattered spectral density, spectral degree of coherence (DOC) and degree of polarization (DOP). It was found that the scattered light field demonstrated typical Laue spots, which was consistent with the Laue scattering theory. Notably, the scattered spectral density was determined by the source beam width and propagation distance. The spectral degree of coherence is primarily determined by the source coherence length. When increase the coherence length, the width of the primary lobe will increase and will lead to an emergence of higher-order side lobes and secondary peaks. In addition, the degree of polarization exhibits two critical points of complete depolarization, which presents a distinctive double-valley distribution. These interesting findings could have potential applications in medical imaging, materials science, and industrial laser processing.
Abstract Multivariate dynamical systems often generate high-dimensional, heterogeneous, and nonstationary time series, which pose significant challenges for learning expressive and robust representations for downstream tasks such as forecasting and anomaly detection. Existing time series embedding methods typically capture only limited aspects of temporal structure and therefore struggle to simultaneously characterize multiscale temporal dependencies, intervariable causal relationships, and the nonlinear dynamics inherent in complex systems. To address this limitation, this paper proposes a novel Fractal-Causal Temporal Graph Embedding (FCTGE) framework, which unifies multiscale fractal temporal dynamics, time-lagged causal interactions, and variable-level statistical characteristics within a unified graph-based representation learning paradigm. In the proposed framework, multivariate time series are represented as time-evolving graphs, where nodes correspond to system variables and edges represent temporally adaptive causal relationships inferred from the data. Extensive experiments on multiple benchmark multivariate time series datasets demonstrate that FCTGE consistently outperforms a wide range of state-of-the-art methods-including representative Transformer-based and graph-based architectures-in both long-term forecasting and unsupervised anomaly detection tasks. Specifically, FCTGE achieves a substantial reduction in prediction errors (MSE/MAE) and yields superior F1-scores compared to specialized anomaly detection frameworks. These results confirm that by explicitly coupling multifractal dynamics with adaptive causal priors, our framework effectively overcomes the inherent limitations of existing methods in characterizing non-stationary behaviors, providing more robust and physically interpretable representations for complex dynamical systems.
Abstract Crack-void interactions are among the major factors governing fracture behaviour in metallic components. Continuum fracture models describe macroscopic fracture behaviour but cannot directly capture atomic bond breaking and local crack - void interactions. Although several atomistic studies have examined individual cracks or voids, the combined effects of crack geometry and void location on the fracture behaviour of single-crystal aluminum remain insufficiently understood. Therefore, this study uses molecular dynamics simulations to investigate the influence of crack-void interactions on Young’s modulus, fracture strength, and atomic-scale fracture behaviour. A face centred cubic Al domain of size 250 × 250 × 40 ų is modelled in LAMMPS and the atomic interactions are dealt using the embedded atom method (EAM) potential. Edge crack (EC) and centre crack (CC) geometries are studied in combination with surface voids (SV) and internal voids (IV), while crack length a/w = 0.01-0.5 (where a is the crack length and w is the domain width) and void diameters (5-30 Å) are varied independently under athermal 0 K, quasi-static incremental Mode-I uniaxial tensile loading, corresponding to a nominal engineering strain rate of approximately 4×109 s-1. Pristine Al showed a Young’s modulus of approximately 71 GPa and a fracture strength of about 9.05 GPa. Defect interactions significantly reduced fracture strength, whereas Young's modulus was mainly affected by crack length and position. Surface voids produced greater strength loss than internal voids, with the most severe reduction observed in surface void-crack interaction cases. Atomistic stress analysis showed that fracture mainly started from strong stress concentration near the crack tip, which was intensified by nearby voids. The comparison between CTR and FAR stresses confirmed that local stress build-up controlled the reduction in overall fracture strength. Among the studied cases, CC-IV exhibited the highest fracture resistance, whereas EC-SV showed the lowest fracture resistance. The findings improve the understanding of interacting defects at the atomic scale and can support the development of multiscale fracture models and the design of damage-tolerant Al structures.
Abstract We investigate the stability of bimeron crystals in a centrosymmetric square-lattice magnet with frustrated interactions, easy-plane anisotropy, and high-harmonic wave-vector interactions under an in-plane magnetic field. Focusing on the effect of uniaxial anisotropy along the [100] direction, we perform simulated-annealing calculations for an effective spin model including primary and higher-harmonic wave-vector components. We find that the bimeron crystal remains stable over a wide range of uniaxial anisotropy, even though the high-field double-$Q$ states are rapidly suppressed by the anisotropy. The bimeron crystal is characterized by an orthorhombically distorted bimeron arrangement, finite uniform scalar spin chirality, and higher-harmonic wave-vector contributions in the spin structure factor. With increasing uniaxial anisotropy, the bimeron crystal changes into an anisotropic double-$Q$ state with a checkerboard-like scalar spin chirality distribution, which can be regarded as a distorted meron--antimeron-like texture. For still stronger anisotropies or higher magnetic fields, the system eventually evolves into single-$Q$ conical spiral and fan states. We also show that weakening the high-harmonic wave-vector interaction substantially reduces the stability region of the bimeron crystal, demonstrating its essential role in maintaining the topological multiple-$Q$ texture against symmetry-lowering perturbations. Our results provide a microscopic guideline for controlling bimeron-based topological spin textures in centrosymmetric magnets with lattice distortions or uniaxial anisotropies.
Abstract In practical image transmission, limited bandwidth and unreliable channels are common challenges. Moreover, multiple images are often transmitted in batches, such as groups of portrait or landscape images. To address these issues in a unified manner, this paper proposes a robust multi-image compression and encryption scheme for channel-impaired environments. First, a Logistic Sine-Cosine Random-Delay (LSCRD) chaotic map is designed. The results of various dynamical system tests demonstrate its strong chaotic characteristics. The proposed chaotic map is used to generate column-dependent measurement matrices for compressed sensing, thereby increasing the diversity and unpredictability of the sensing process. In addition, chaotic sequences are incorporated into the image encryption process to enhance the randomness of the ciphertext. Second, to improve the encryption performance of the overall scheme, a spiral ternary-tree diffusion strategy is designed. This strategy strengthens the interaction among non-adjacent pixels and improves plaintext sensitivity. Finally, to cope with unreliable channels, threshold secret sharing is combined with Reed-Solomon (RS) coding to generate robust share images. As a result, the proposed scheme achieves not only robustness among shares, but also internal robustness within each share. Experimental results show that the proposed scheme maintains high reconstruction quality under different compression ratios, produces near-uniform share images, and supports image recovery from partially corrupted shares when the RS decoding condition is satisfied.
Abstract Reduced graphene oxide (rGO) has been recognized as a high-performance electrode material for supercapacitors. There is an urgent need to develop a green, efficient, low-temperature method for the reduction of graphene oxide (GO) with control capabilities. In this study, an atmospheric-pressure argon plasma, which requires no chemical reducing agents or organic solvents, and operates under a peak-to-peak voltage of 9 kV with a gas flow rate of 4 slm, is employed to produce rGO. The interaction between the GO surface and high-energy plasma species, including electrons, metastable Ar* and Ar+ ions, is suggested as the dominant reduction mechanism. The results demonstrate that energetic bombardment and the subsequent energy transfer process are responsible for the cleavage of C=O and C–O bonds, which enables the reconstruction of the graphitic structure. Accordingly, the plasma-reduced rGO obtained in this work delivers a high specific capacitance of 368 F/g at a current density of 1 A/g. The assembled symmetric supercapacitors exhibit excellent cycling stability, with a capacitance retention of 98.87% after 5,000 cycles, and possess superior interfacial properties verified by electrochemical impedance spectroscopy. This work provides new insights into the physical mechanisms underlying plasma-induced GO reduction, and presents a scalable, solvent-free preparation methodology for the development of graphene-based energy storage technologies.
Abstract The study explores the resistive switching (RS) application of Ti3C2Tx MXene thin films prepared by ultrasonic spray coating technique using stable colloids of delaminated Ti3C2Tx MXene in deionized (DI) water. Adherent Ti3C2Tx thin films were fabricated on ITOcoated glass substrate without the use of binders. An RS device with the structure ITO/Ti3C2Tx/Cu, stable up to 1500 seconds, was fabricated. The Ti3C2Tx MXene thin film supports the data retention of the device, as the mobility of Cu ions was confined to the locations of MXene. To the best of our knowledge, this is the first report on the use of an ultrasonic spray coating technique to fabricate MXene thin film for resistive switching applications.
Abstract Defect-induced non-radiative recombination and insufficient long-term stability hinder the commercial viability of organic-inorganic lead halide perovskites. Here we compare ethylammonium iodide (EAI) with its fluorinated analog 2,2,2-trifluoroethylammonium iodide (TFEAI) as additives in methylammonium lead triiodide (MAPbI 3 ) perovskite solar cells. Combining density functional theory calculations with experiments, we show that the trifluoroethyl group strengthens electrostatic interactions with the perovskite lattice, forming stronger coordination bonds with undercoordinated Pb 2+ ions at lead vacancies ( V Pb ) and thereby reducing the trap-state density, as quantified by space-charge-limited current measurements, from 4.61 × 10 16 cm −3 in the control to 3.47 × 10 16 cm −3 in TFEAI-treated films. TFEAI-treated films consequently exhibit prolonged carrier lifetime and suppressed non-radiative recombination, along with improved grain morphology, optimized energy level alignment, and enhanced hydrophobicity. These advantages enable TFEAI-modified devices to achieve a champion power conversion efficiency of 18.0%, outperforming control devices (16.8%). After 300 h of ambient aging, the fluorinated device retains 79.7% of its initial efficiency versus only 47.8% for the control. This work establishes that cationic fluorination of ammonium salt passivators provides a rational molecular design route to simultaneously boost efficiency and stability in perovskite photovoltaics.
Abstract This study presents a numerical investigation of a lead-free, all-inorganic halide perovskite solar cell featuring a double absorber layer architecture. The proposed device uses a hole transport layer-free configuration with the structure FTO/ZnS/RbGeI 3 /RbGeBr 3 /Au, employing RbGeI 3 and RbGeBr 3 as the top and bottom absorber layers, respectively. The physical parameters of the proposed structure, including thickness, doping density, and defect density in the absorber layers, have been optimized and evaluated using SCAPS-1D software. In addition, an analysis of the internal electric field variation, energy band diagrams, and recombination rate has been carried out. The simulation results show that using the RbGeI 3 /RbGeBr 3 perovskite heterojunction as a double absorber layer increases the external quantum efficiency of the proposed model, particularly in the wavelength range of 750–950 nm. Due to the increase in photogenerated carriers and the formation of an internal electric field at the RbGeI 3 /RbGeBr 3 interface, the transport of charge carriers is facilitated, thereby improving the overall device performance. Ultimately, for the proposed optimized structure, an efficiency of 29.22% is achieved, with an FF of 84.51%, a J sc of 34.26 mA cm −2 , and a V oc of 1.01 V. These values are significantly higher compared to the efficiencies of 21.54% for the single layer RbGeI 3 and 18.80% for the single layer RbGeBr 3 . The findings of this study indicate that the use of RbGeI 3 /RbGeBr 3 perovskite heterojunctions represents a promising approach for advancing practical applications in photovoltaics.
Abstract Advanced nonlinear optical (NLO) nanomaterials play a pivotal role in the development of compact and high-performance ultrafast laser systems. In this study, a van der Waals MoAlB/Co 3 O 4 heterojunction is designed, fabricated, and employed as an efficient saturable absorber (SA) for femtosecond pulse generation. The constructed heterostructure enables optimized interfacial charge migration and energy band rearrangement, leading to a remarkable improvement in NLO modulation. By utilizing interface energy band engineering and interlayer charge redistribution, the as-fabricated SA achieves enhanced nonlinear modulation capability and robust operation stability. When the prepared SA is used in the laser cavity, it achieves stable conventional soliton, bound-state soliton, and a wide range of tunable high-order harmonic mode-locking operations. Experimental results verify that the MoAlB/Co 3 O 4 heterojunction exhibits large modulation depth, low saturation intensity, and high laser damage threshold. These findings demonstrate that the MoAlB/Co 3 O 4 heterojunction serve as a highly promising NLO material with significant potential for application as an SA in ultrafast photonic generation.
Abstract Spin Hall magnetoresistance (SMR) serves as a sensitive technique for discerning the magnetic states within non-equilibrium spin systems. In the heavy metal/collinear antiferromagnet (AFM) heterostructure, the AFM Néel vector n typically aligns perpendicular to the external magnetic field H ext , producing a negative SMR with a phase change of 90 ∘ . However, in scenarios where AFM and weak ferromagnetism (FM) components coexist, such as canted AFM, defect-induced dilute FM, or uncompensated spin-induced net surface magnetization, net weak FM theoretically contributes to a positive SMR. In this study, we report interfacial-enhanced FM in Pt /orthoferrite SmFeO 3 (SFO) heterostructures, evidenced by a increase in the SMR amplitude at 10 K compared to room temperature. The temperature-dependent SMR exhibits a direct correction with the weak FM moment derived from superconducting quantum interference device magnetometry, confirming the interfacial origin of the effect. Our findings highlight that the SMR response is intrinsically linked to the spin mixing conductance ( G ↑↓ ), which characterizes the spin transparency at the Pt/SFO interface. These results establish a general approach for electrically probing interfacial magnetism in orthoferrite-based multiferroic.
Abstract Motivated by observations of double layers (DLs) in the Martian magnetosheath plasma, we theoretically investigate the existence of DLs and their coexistence in a dusty plasma system. The considered negatively charged dusty plasma system consists of warm positive ions, warm negatively charged dust grains, and superthermal electrons. To study large amplitude nonlinear structures, the Sagdeev pseudopotential method is used, and the corresponding energy integral equation is derived. Numerical analysis reveals that the plasma system supports both compressive and rarefactive solitary waves as well as DLs. Interestingly, the plasma system exhibits not only the coexistence of positive and negative polarity solitons but also the coexistence of DLs under appropriate parametric conditions. The monopolar positive and negative electric field structures associated with the predicted DLs are qualitatively similar to the electric field signatures of DLs reported in observations of the Martian magnetosheath. In addition, the model predicts positive and negative bipolar electric field pulses associated with solitary waves, and the corresponding phase-space trajectories have also been examined. The results show that the formation and characteristics of DLs are highly sensitive to key plasma parameters, including the dust charge number, Mach number, superthermal parameter ( k ) , and dust density. The potential structures corresponding to the coexistence of DLs are illustrated through the associated Sagdeev pseudopotential profiles. These findings are directly relevant to dusty plasma environments in the Earth’s ionosphere and provide deeper insight into the dynamics of large-amplitude nonlinear structures and their role in energy transport and dissipation in dusty plasmas.
Abstract For the coverage of the intended region, narrow beam radiation patterns are required in wireless communication. multiple-input multiple-output (MIMO) and 5G solve the problem of large spectrum, coverage, capacity, and data rates required for the intended user/direction. The presented 4-input 4-output Butler matrix fed antenna array design covers 26.86–29.05 GHz (2.18 GHz bandwidth) and frequency band of 2:1 voltage standing wave ratio (return loss − 10 dB). Butler matrix fed antenna array is designed on Rogers RO5880 substrate having a dimension of 48.82 mm × 38.76 mm × 0.254 mm. The research presents design and implementation of a narrow-beam 4 × 4 Butler matrix fed antenna array to cover − 22 degree, 11 degree, − 11 degree, and 22 degree directions for the 5G millimeter wave beamforming applications. The proposed design utilizes hybrid couplers, delay lines, crossovers and phase shifters to achieve multiple narrow-beam states. The presented design can be integrated with millimeter wave microwave circuits, arrays, and MIMO-arrays. The presented Butler matrix fed antenna array gain is 14.65 dBi at the radiating ports and at each port simulated radiation efficiency is better than 89.85 % .
Abstract We investigate impurity-induced spectral transitions in a non-Hermitian Hatano–Nelson chain with a non-local rank-one separable potential, providing a minimal yet analytically tractable framework for exploring the interplay between asymmetric hopping and directional impurities. By employing the Green’s function formalism in conjunction with the Sherman–Morrison identity, we derive a closed-form spectral equation for the impurity-induced eigenvalues and analyze their evolution in the complex energy plane. Under periodic boundary conditions, we demonstrate that the system undergoes a real-to-complex spectral transition, which is consistently associated with the contact between the impurity state and the bulk spectral boundary of the Hatano–Nelson model. In the weakly non-Hermitian regime, a real isolated bound state remains stable. However, as the asymmetric hopping strength increases, the impurity state hybridizes with the bulk spectrum, leading to the emergence of complex eigenvalues. In the strongly non-Hermitian regime, the imaginary parts of the impurity spectrum decrease again, revealing a tendency toward suppression of the imaginary component within the present directional separable impurity model. Furthermore, spectral phase diagrams in parameter space reveal the competition among the non-Hermiticity strength, impurity coupling, and impurity localization range. These results provide a simple and analytically transparent framework for understanding impurity-driven spectral transitions and directional effects in non-Hermitian systems.
Abstract Recent advancements in combined pulse laser ablation have demonstrated its high efficiency in material processing. However, within this promising framework, the temporal coordination remains insufficiently investigated, specifically regarding the impact of nanosecond (ns) pulse intervention timing during the millisecond (ms) heating window. In this study, a high-energy ns-laser-induced air-breakdown was integrated with a 90% duty cycle ms fiber laser to systematically investigate the delay-dependent ablation dynamics of 304 stainless steel. Experiments reveal that while maintaining identical laser energy parameters, the synergistic effectiveness exhibits significant sensitivity to the delay time. Quantitative results show that the ablation depth and material removal rate reach a maximum of 1.015 mm and 1.713 × 10 −4 mm 3 J −1 , respectively, at a delay time (Δ t ) of 140 ms. This represents a five-fold increase compared to the 0 ms delay condition. High-speed imaging and real-time thermography confirm that this optimal synchronization triggers a fundamental transition from inefficient surface melting to high-efficiency liquid-phase expulsion. These findings provide critical mechanistic insights for optimizing spatiotemporal energy coupling in advanced hybrid laser processing applications.
Abstract A new 3D-sine-cosine-Hénon (3D-SCH) discrete hyperchaotic system is proposed in the present investigation and the hyperchaotic characteristics are verified through Lyapunov exponents and bifurcation properties. The complexity and initial value sensitivity of the system are analyzed, and high complexity and extreme sensitivity to initial values are confirmed. In the encryption process of color images, initial conditions are perturbed by plaintext eigenvalues, two rounds of global cross-plane permutation and two rounds of forward and backward diffusion dependent on sequence indices are adopted, channel limitations are broken, and excellent permutation and diffusion effects are acquired. It is demonstrated that outstanding security and robustness are provided by the proposed 3D-SCH system for encrypting color images of different sizes, various key attacks and noise attacks can be resisted, and high practical significance is owned by the designed encryption scheme.
