Search Results (12,236)

With the rapid development of laser processing and infrared imaging, the demand for flat-top beams with high uniformity has become increasingly urgent. Conventional beam-shaping techniques based on bonded aspheric lenses are inherently bulky and inflexible, which limits their compatibility with modern optical systems. In this work, we propose a dielectric metasurface for laser beam shaping operating at 1064 nm, where the target phase distribution is derived by the given initial phase and is represented by a hyperbolic phase. An inverse optimization algorithm is proposed to optimize the unit cell consisting of silicon carbide (SiC) nanopillars and the silicon dioxide (SiO₂) substrate. Numerical results show that, after transmission through the designed metasurface, the beam forms a circular flat-top spot with a radius of 2 μm at the target plane, exhibiting an intensity uniformity of 0.1021 and an energy efficiency of 76.3%. This study offers a compact and highly efficient solution for the flat-top beam shaping, demonstrating significant potential for applications in precision-laser processing, optical trapping, and bioimaging. Full article

This study systematically evaluated the response mechanisms of water and sediment processes in the Kuye River Basin to climate change and human activities from 2023 to 2053 by integrating multi-source climate scenarios (CMIP5 models), land-use change projections (based on the Markov chain model), and a distributed hydrological model (SWAT model). The results indicate that under the RCP8.5 high-emission scenario, annual precipitation in the basin shows a non-significant increasing trend but with intensified interannual variability. Spatially, precipitation exhibits a pattern of increasing from northwest to southeast, with a marked decadal transition occurring around 2043. Land-use structure undergoes significant transformation, with construction land projected to account for 30.54% of the total basin area by 2050, while grassland and cropland continue to decline. Water and sediment processes display distinct phased characteristics: a fluctuating adjustment phase (2023–2033), a relatively stable phase (2034–2043), and a sharp growth phase (2044–2053). Parameter sensitivity analysis identifies the curve number (CN2) and soil bulk density (SOL_BD) as key regulatory parameters, revealing the synergistic mechanism by which land-use changes amplify climatic effects through alterations in surface properties. Based on the findings, an adaptive watershed management framework is proposed, encompassing dynamic water resource regulation, spatial zoning, targeted erosion control, and iterative scientific management. Particular emphasis is placed on addressing hydrological transition risks around 2043 and promoting low-impact development practices in high-erosion areas. This study provides a scientific basis for the integrated management of water and soil resources in the context of ecological conservation and high-quality development in the Yellow River Basin. The methodology developed herein offers a valuable reference for predicting water and sediment processes and implementing adaptive management in similar semi-arid basins. Full article

This study investigates the influence of vanadium–nitrogen (V-N) microalloying design on the microstructure and mechanical properties of 700 MPa grade ultra-high-strength steel bars. Through the control of the V/N ratio and cooling rate, a yield strength exceeding 700 MPa was achieved in a steel with a pearlite–ferrite matrix. Microstructural characterization via optical microscopy (OM) and scanning electron microscopy (SEM) revealed that a V/N ratio of approximately 1:10 combined with a rolling cooling rate of 1–3 °C/s resulted in the steel bar exhibiting a yield strength of 774.21 MPa and a tensile strength of 971.13 MPa. The primary microstructure of the steel consisted of ferrite and pearlite. The steel featured fine grains and favorable crystallographic orientations, which contributed to its high yield strength and good ductility. Transmission electron microscopy (TEM) analysis indicated that under hot-rolling conditions, vanadium precipitated predominantly as nano-scale V(C,N) particles. These precipitates were distributed in both the pearlite and ferrite phases, thereby enhancing the tensile and yield strength. Furthermore, the steel with an optimal nitrogen content (0.0166 wt.%) and the finest grain structure (average grain size ≈ 2.618 μm) showed the lowest stress corrosion cracking (SCC) susceptibility, characterized by an elongation loss rate (I_δ) of 12.51%, demonstrating excellent SCC resistance. Full article

Cavity limitations and interspecific competition render large macaws valuable models for elucidating the integration of parental care, pair-bond maintenance, and nest defense across reproductive stages. Through continuous video monitoring of a single artificial polyvinyl chloride nest box in the Tambopata National Reserve, Peru, we quantified the complete breeding cycle of a resident green-winged macaw (Ara chloropterus) pair and the visitation behavior of a sympatric scarlet macaw (Ara macao) pair within the same cavity. We constructed daily time budgets for 17 behaviors, categorized into seven functional groups, from motion-triggered video clips; employed multivariate tests; and generalized additive models with beta error distribution to describe the temporal changes across the five reproductive stages. The resident A. chloropterus exhibited a significant reorganization of parental investment, with early courtship behaviors transitioning to peak nest attendance and sentinel vigilance during incubation and early brooding. In later stages, locomotion increased significantly, associated with chick provisioning, whereas the frequency of allopreening remained relatively constant throughout the cycle. The visiting A. macao displayed a brief, behaviorally rich prospecting phase, characterized by nest inspection and locomotion, followed by a sharp decline in minimal activity. These divergent strategies align with owner–intruder asymmetries and floater dynamics, indicating that artificial cavities can support A. chloropterus breeding, while suggesting that additional cavities may redistribute breeding opportunities among competing macaws, a hypothesis necessitating multi-nest and multi-year evaluation. Full article

The western Kuqa Foreland Basin exhibits complex hydrocarbon distribution with unclear accumulation processes. This study integrated seismic data, microscopic observations, crude oil properties, and basin modelling to establish a dynamic hydrocarbon migration model for the study area. The results indicated two distinct accumulation phases. During the early phase (16–5 Ma), hydrocarbons migrated eastward along a single unconformity and accumulated in the buried-hill reservoir of well E937 in the southern part of the Baicheng hydrocarbon-generating depression. In contrast, the southwestern region failed to accumulate hydrocarbons because of its distance from the Triassic source rock hydrocarbon generation centre and complex migration pathways. During the late phase (5–0 Ma), the Jurassic hydrocarbon generation centre shifted westward, and hydrocarbons migrated through a composite conduit system comprising faults, weathered crust, and sandstone structural ridges. This process promoted the expansion of the eastern E937 well trap, whereas well WEN54 and other southwestern wells exhibited hydrocarbon accumulation potential. The simulation results predicted that hydrocarbon reservoirs in the eastern region were mainly concentrated in the Qiulitage structural belt east of well E938. This study provides a theoretical basis and predictive guidance for hydrocarbon exploration in this area. Full article

To address the stringent insulation safety requirements of modern high-voltage transformers, accurately characterizing the transient electric field is critical. However, a significant problem remains: current engineering models typically rely on static capacitive distributions, failing to capture the dynamic electric field distortion induced by rapid space charge injection under lightning impulses. Therefore, a non-contact spatial electric field measurement method based on the optical Kerr effect was employed to analyze the influence of electrode material, voltage amplitude, and wavefront time. Unlike traditional simulation models that often assume constant mobility and focus solely on the shielding effect, this study reveals a non-monotonic electric field evolution driven by a ‘Static-Dynamic’ mode transition. The proposed model highlights two critical breakthroughs: (1) Mechanism Innovation: It experimentally verifies that charge injection is governed by the ion charge-to-mass ratio rather than just the work function, leading to a newly identified field enhancement phase during the wavefront that overcomes the limitations of capacitive models that underestimate transient stress. (2) Parameter Quantification: Precise spatiotemporal thresholds are established—negative charges traverse the gap within ~200 ns, while positive charges require ~10 μs to reach equilibrium. These findings provide experimentally calibrated time constants for simulation correction and offer new criteria for optimizing electrode materials in UHV transformers to mitigate transient field distortion. Full article

The Collatz map is investigated from a nonlinear-dynamics perspective with emphasis on the structure of its iterative orbits. By embedding integers within Sharkovsky’s ordering, odd initial values are shown to be sufficient for a complete characterization of dynamics. A “direction-phase” decomposition is introduced to separate iterative orbits into upward and downward phases, yielding a family of recursive functions parameterized by the number of upward phases. This formulation reveals a logarithmic scaling relation between the total iteration count and the initial value, confirming finite-time convergence to the period-three orbit. The Collatz dynamics is further shown to be dynamically equivalent to a binary shift map, whose ergodicity implies inevitable evolution toward attractors, thereby reinforcing convergence. Numerical analysis indicates that attraction basins follow a power-law distribution and display pronounced self-similarity. Moreover, odd integers grouped by upward-phase counts are found to follow Gamma statistics. Beyond its research implications, the framework provides a concise pedagogical case study illustrating how nonlinear dynamics, symbolic dynamics, and statistical characterization can be integrated to analyze a classical discrete problem. Full article

Single-phase grounding is the dominant fault type in urban power distribution networks. Because the total magnetic flux would not change around the cable under a single-phase grounding fault, ferromagnetic zero-sequence current sensors cannot distinguish the faulted phase of belted cables, which are the main type in 10 kV distribution networks. To fill this gap, a two-step methodology is proposed using an annular TMR magnetic sensor to measure the magnetic field intensity at six points on the cable surface and to distinguish the faulted phase using the magnetic field intensity differences between the TMRs. The first step is calculating the rotation angles between the six magnetic sensors and the three cable cores after installation. A differential evolution algorithm is used to calculate the rotation angles in the sensing model. The second step is to detect the fault phase under a single-phase grounding fault transient, with the magnetic field intensity difference taken as the criterion. The methodology is verified through simulation and experiment. The results show that the relative errors of the rotation angles are all less than 1%. Under a single-phase grounding fault, the faulted phase can be accurately identified. The proposed method can effectively identify the faulted phase of 10 kV three-core cables under single-phase grounding and has significant engineering application value. Full article

The widespread adoption of nonlinear loads in industry has introduced significant power quality issues in electric power distribution grids. The integration of these nonlinear loads has led to the proliferation of serious power quality problems such as the generation of harmonics and reactive power that negatively impact the quality and stability of the electrical grid. In addition to eliminating current harmonics, a shunt active power filter (APF) can also provide reactive power compensation. By dynamically adjusting the reactive power injection, these APFs can improve the power factor of the system and maintain the desired voltage regulation. The proposed control leverages the differential flatness property of the SAPF system, allowing for exact linearization and simplified tracking control without requiring complex modulation techniques. In this paper, a flatness-based control scheme is proposed for a three-phase three-level Neutral Point Clamped (NPC) APF. The main objectives of this work are twofold. The first objective is to mitigate current harmonics and compensate the reactive power drawn by nonlinear loads. The second objective focuses on maintaining a stable DC-link capacitor voltage of the active power filter (APF). To meet these requirements, a cascaded control structure is used, where the external loop regulates the DC-link voltage, while the inner loop is responsible for harmonic current compensation. The effectiveness of the proposed control strategy is validated through simulation results obtained using the MATLAB/Simulink R2024a environment. Full article

Southern pine beetle infestations impact ecosystems throughout the southeastern US. Our understanding of hydrologic and biogeochemical impacts on ecosystem structure and function is largely guided by severe outbreaks occurring in the western US. A simulated mortality experiment was conducted on loblolly pine trees via girdling with and without blue-stain fungi inoculation to mimic a small-scale infestation. We measured whole-tree water use, canopy-derived hydrologic and biogeochemical fluxes, soil moisture, and soil respiration for two years following treatments to quantify the impacts of tree mortality on water, carbon, and nitrogen cycles. In the second year of our study, a significant drought occurred, subjecting study trees to a secondary stressor. We found that compared to control trees, girdled trees exhibited reduced water uptake within 6 months and succumbed to mortality within 18 months. We found that by the time trees reached the gray phase of attack, stemflow was 1.7-times lower in girdled trees compared to control trees. Stemflow from girdled trees had up to 7.2-times higher concentrations of ammonium and 2.8-times higher concentrations of total nitrogen. Although stemflow carbon concentrations were indistinguishable between treatments, total carbon flux in stemflow was 2.0-times greater in non-girdled trees (p = 0.030). Finally, even though soil moisture and respiration were not different between treatments, it was not possible to isolate the response of these to mortality versus drought. Our results present the connection between bark beetle outbreaks and the initial impacts on forest biogeochemistry. Changes in the distribution of canopy-derived water inputs, coupled with altered carbon and nitrogen fluxes, serve as hot spots around bark beetle-killed trees. Further research is necessary to understand whether these isolated hot spots may prime the system, alter microbial and invertebrate communities, and lead to changes in decomposition processes at larger scales. Full article

Glioblastoma multiforme (GBM) is an aggressive brain tumor with limited treatment options and poor survival outcomes. This study evaluated the anticancer potential of seco-duocarmycin SA (seco-DSA), a potent DNA-alkylating agent, alone and in combination with proton radiation in human GBM cell lines. Human glioblastoma cell lines T98G and LN18 were treated with varying concentrations of seco-DSA, proton radiation doses (2, 4, or 8 Gy), or both. Proton irradiation was delivered with a 250-MeV beam. Clonogenic survival, cell proliferation, and cell cycle distribution were analyzed using colony formation and flow cytometry assays. Proteomic analysis of LN18 cells was performed by LC-MS/MS followed by bioinformatic pathway analysis. Statistical significance was determined using a two-tailed unpaired t-test (p ≤ 0.05), and Bliss synergy scores were calculated to assess treatment interactions. Combination therapy produced additive and synergistic inhibition of colony formation and enhanced G2/M phase arrest compared with either treatment alone. Apoptosis and necrosis increased modestly but did not fully account for observed cytotoxicity. Proteomic profiling revealed differential expression of proteins involved in DNA repair, apoptosis, and senescence, indicating that seco-DSA broadened radiation-induced stress responses. Seco-DSA potentiates the cytotoxic effects of proton radiation in GBM cells through enhanced clonogenic inhibition and modulation of cell cycle and DNA repair pathways. These findings support seco-DSA as a promising radiosensitizer for further preclinical evaluation. Full article

This study investigates the thermodynamic and experimental aspects of producing a chromium–manganese ligature under high-temperature smelting conditions using low-grade iron–manganese ore and ferrosilicochrome (FeSiCr) dust as both a reducing agent and a chromium source. Thermodynamic modeling of the multicomponent Fe–Cr–Mn–Si–Al–Ca–Mg–O system was carried out using the HSC Chemistry 10 and FactSage 8.4 software packages to substantiate the temperature regime, reducing agent consumption, and conditions for the formation of a stable metal–slag system. The calculations indicated that efficient reduction of manganese oxides and formation of the metallic phase are achieved at a smelting temperature of 1600 °C with a reducing agent consumption of approximately 50 kg. Experimental smelting trials conducted in a laboratory Tammann furnace under the calculated parameters confirmed the validity of the thermodynamic predictions and demonstrated the feasibility of obtaining a concentrated chromium–manganese ligature. The resulting metallic product exhibited a high total content of alloying elements and had the following chemical composition (wt.%): Fe 35.41, Cr 41.10, Mn 8.15, and Si 4.31. SEM–EDS microstructural analysis revealed a uniform distribution of chromium and manganese within the metallic matrix, indicating stable reduction behavior and favorable melt crystallization conditions. The obtained results demonstrate the effectiveness of an integrated thermodynamic–experimental approach for producing chromium–manganese ligatures from low-grade mineral raw materials and industrial by-products and confirm the potential applicability of the proposed process for complex steel alloying. Full article

Spatial resolution is a critical parameter for optical frequency domain reflectometry (OFDR). Phase-sensitive OFDR (Φ-OFDR) measures strain by detecting phase variations between adjacent sampling points, having the potential to achieve the theoretical limitation of spatial resolution. However, the results of Φ-OFDR suffer from large fluctuations due to multiple types of noise, including coherent fading and system noise. This work presents an OFDR-based strain sensing method that combines phase demodulation with cross-correlation analysis to achieve high spatial resolution. In the phase demodulation, the frequency-shift averaging (FSAV) and rotating vector summation (RVS) algorithms are first employed to suppress coherent fading noise and achieve accurate strain localization. Then the cross-correlation approach with an adaptive window is proposed. Guided by the accurate strain boundary obtained from phase demodulation, the length and position of the cross-correlation window are automatically adjusted to fit for continuous and uniform strain regions. As a result, an accurate and complete strain distribution along the entire fiber is finally obtained. The experimental results show that, within a strain range of 100–700 με, the method achieves a spatial resolution of 0.27 mm for the strain boundary, with a root-mean-square error approaching 0.94%. The processing time reaches approximately 0.035 s, with a demodulation length of 1.6 m. The proposed approach offers precise spatial localization of the strain boundary and stable strain measurement, demonstrating its potential for high-resolution OFDR-based sensing applications. Full article

Fe-rich phases are unavoidable intermetallic compounds in aluminum alloys, particularly in recycled aluminum. Their needle-like morphology not only impairs the mechanical performance of the alloy by disrupting the continuity of the matrix but also significantly reduces the allowable addition of recycled aluminum materials. Based on this, this study focuses on the Al-7Si-0.35Mg-0.35Fe alloy with a high Fe content. The Cr was introduced to modify the characteristics of the Fe-rich phase, and the microstructural evolution and mechanical properties of the aluminum alloy with different Cr content (0–0.25 wt.%) were investigated. Experimental results show that the secondary dendrite arm spacing of the alloy is significantly refined after Cr addition. Meanwhile, the Fe-rich phase gradually transitions from β-Al₅FeSi with needle-like morphology to α-Al₁₅(Fe,Cr)₃Si₂ with short rod-like or blocky morphology as the Cr content increases. Notably, the Fe-rich phase in the 0.20Cr alloy exhibits an approximately 65% increase in sphericity and an 84% reduction in equivalent diameter compared to those in the 0Cr alloy. The morphological blunting and dispersed distribution of Fe-rich phases lead to a broad effective Cr addition range of 0.05–0.20 wt% in the alloy. Among them, the 0.20Cr alloy exhibited the best comprehensive mechanical properties, with its ultimate tensile strength and elongation approximately 19% and 107% higher than those of the 0Cr alloy, respectively. Furthermore, the fracture morphology and the relationship between the Fe-rich phase and microcracks in Al-7Si-0.35Mg-0.35Fe alloys with different Cr contents were also analyzed. Full article

The transition toward sustainable and resilient new-type power systems requires robust diagnostic frameworks for terminal power supply units to ensure continuous grid stability. To ensure the resilience of modern power systems, this paper proposes a multi-source domain deep Transfer Learning method for the abnormal condition diagnosis of low-voltage distribution nodes within a cloud-edge collaborative framework. This approach integrates feature selection based on the Categorical Boosting (CatBoost) algorithm with a hybrid architecture combining a Convolutional Neural Network (CNN) and a Residual Network (ResNet). Additionally, it utilizes a multi-loss adaptation strategy consisting of Multi-Kernel Maximum Mean Difference (MK-MMD), Local Maximum Mean Difference (LMMD), and Mean Squared Error (MSE) to effectively bridge domain gaps and ensure diagnostic consistency. By balancing global commonality with local adaptation, the framework optimizes resource efficiency, reducing collaborative training time by 19.3%. Experimental results confirm that the method effectively prevents equipment failure, achieving diagnostic accuracies of 98.29% for low-voltage anomalies and 88.96% for three-phase imbalance conditions. Full article