Accepted
, , Received Date: 2025-08-10
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The boundary region between the solar radiation zone and the convection zone ($ T\thicksim180$ eV, $ n_e\thicksim $$ 9\times10^{22}\;{\rm{cm}}^{-3}$) is a critical interface where energy transport in the solar interior transitions from radiation-dominated to convection-dominated regimes. This region also serves as a natural laboratory for studying hot dense plasma. The physical properties of this zone are essential for the reliability of stellar evolution models and the stability of energy transport mechanisms. One of major unresolved issue is how electron collision ionization affects the density of free electrons and radiation properties in this plasma, while accurately describing the impact of hot-dense environments on electron impact ionization (EII) (such as electron screening, ion correlation). To fill this gap, we systematically calculate EII cross sections for C, N, and O ions under realistic solar boundary conditions, with a focus on hot-dense environment impacts. We develop a novel computational framework that merges?hot-dense environment effects into atomic structure calculations: the Flexible Atomic Code (FAC) for atomic structure is combined with the Hyper-netted-Chain (HNC) approximation to capture electron-electron, electron-ion and ion-ion correlations, enabling self-consistent treatment of electron screening and ion correlation. Atomic wave functions are derived by solving the Dirac equation within the ion-sphere model, using a modified central potential that incorporates both free-electron screening and ion–ion interactions. EII cross sections are then computed via the Distorted-Wave (DW) approximation in FAC. The results demonstrate that hot-dense environment effects significantly enhance the electron-impact ionization cross sections of C, N, and O compared to those calculated under the free-atom model. Additionally, a notable reduction in the ionization threshold energy is observed. These effects are attributed to the overlap of atomic potentials due to strong ion coupling and the shift in bound-state energy levels caused by free-electron screening. For instance, under solar boundary conditions, the ionization cross section of C+ increased by up to 50%, with the ionization threshold decreasing from about 24 eV (isolated) to 18 eV (with screening). Similar enhancements were observed for nitrogen and oxygen ions across various charge states. By providing updated ionization cross sections for C, N, and O ions under realistic solar interior conditions, this work offers essential parameters for improving radiation transport models, ionization balance calculations, and equation-of-state models in stellar interiors. The results underscore the necessity of including hot-dense environment effects in atomic process calculations for hot dense plasmas, with implications for astrophysics and inertial confinement fusion research.
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In rarefied gas flows, accommodation coefficients (ACs) serve as core parameters for gas-surface interactions and play a crucial role in the accuracy of mesoscopic model simulations. However, there exist significant discrepancies in the ACs obtained by different molecular dynamics simulation methods. To accurately characterize the momentum and energy accommodation properties of rarefied gases with solid surfaces under non-equilibrium conditions, this study systematically investigates the gas-surface interactions between argon molecules and platinum surfaces using molecular dynamics (MD) methods. By employing single scattering (SS) and continual scattering (CS) approaches, the influence of gas-gas collisions on tangential momentum accommodation coefficients (TMAC), normal momentum accommodation coefficients (NMAC), and energy accommodation coefficients (EAC) is comparatively analyzed, along with the operational laws of parameters such as surface morphology, surface temperature, incident velocity, and mean free path (MFP). The results demonstrate that gas density exerts a dual effect on momentum and energy accommodation: at smaller MFP, the high gas density within the interaction region impedes the accommodation of subsequent incident molecules with the surface, resulting in lower ACs; at moderate MFP, gas-gas collisions promote accommodation by increasing the frequency of gas-surface collisions, thereby enhancing ACs. Within the MFP range of 2.0–60.0 nm, the deviation in ACs between the CS and SS methods ranges from –14.88% to 5.21%, validating the dual role of gas density. Furthermore, at larger MFP, the TMAC and NMAC obtained via the CS method exhibit different trends with increasing MFP across surfaces of varying morphologies. In contrast to gas density, increases in both surface temperature and incident velocity shorten the interaction time, leading to reduced ACs. Notably, the effect of temperature varies across surfaces with different morphologies: elevated temperatures on smooth surfaces enhance the thermal fluctuations of surface atoms, thereby increasing NMAC, while elevated temperatures on rough surfaces cause smoothing of rough structures, thus inhibiting accommodation. Under high-speed incident conditions, gas-gas collisions promote NMAC on smooth surfaces, inhibit both TMAC and NMAC on rough surfaces, and suppress EAC across all surfaces. Additionally, the ACs obtained via both the CS and SS methods decrease with increasing incident velocity across surfaces of different morphologies.
, , Received Date: 2025-08-29
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, , Received Date: 2025-08-15
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Nickel-based superalloys are extensively used in aero-engin due to their combined high strength, toughness, corrosion and creep resistance at elevated temperatures. Strain rate, temperature, and strain are important factors influencing the microstructural evolution of nickel-based superalloys. In this work, a typical nickel-based superalloy, GH4738 alloy, is selected to study the dynamic compressive deformation behavior of this material. Split Hopkinson pressure bar (SHPB) compression test was performed on GH4738 superalloy at strain rates of 1000~7500 s-1 with temperature ranges from RT to 500 °C. The yield strength of GH4738 superalloy decreases with increasing temperature and increases with increasing strain rate; however, at the temperature of 500 °C and the strain rate of 7500 s-1, it drops sharply. In order to understand the microscopic deformation behavior of GH4738 superalloy, parallel specimens were prepared with SHPB at frozen strains of -0.02, -0.05, -0.10, -0.20 and -0.25 at a strain rate of 3000 s-1 for the cases of RT, 400 °C and 500 °C, respectively. Neutron diffraction technique was employed to characterize the evolution of lattice constants and elastic lattice strains. We define the horizontal lattice mismatch as the lattice misfit at the γ/γ' interface that is perpendicular to the SHPB compressed direction, and the vertical lattice mismatch as the lattice misfit parallel to the SHPB compression direction. As the frozen strain increases, the horizontal lattice mismatch exhibits positive values and an increasing trend, while the vertical lattice mismatch changes from positive to negative values; the elastic lattice strain of the γ' phase consistently increases, while that of the γ phase remains almost unchanged. The lattice strains of the {111} and {220} planes are negative at 400 °C and 500 °C but positive at RT; the lattice strain of the {200} plane alternates between positive and negative values from RT to 500 °C, while that of the {311} plane remains negative throughout this temperature range. However, at a frozen strain of -0.25, the lattice strain of the {311} plane exhibits a significant rebound at both RT and 500 °C, indicating generation of significant intergranular stresses in the material. Dislocation configurations are characterized using transmission electron microscopy (TEM) to interpret the underlying mechanism. At RT, plastic deformation is dominated by γ-γ' co-deformation, with defects manifesting as parallel slip bands and stacking faults. Lattice misfit is effectively relaxed due to the formation of dislocation networks at γ/γ' interfaces, resulting in minimal residual lattice strain at RT. At 500 °C, dislocation density increases substantially because both γ and γ' phases readily undergo plastic deformation under thermal activation. Under such conditions, dislocation networks fail to compensate for lattice distortions induced by defect multiplication, resulting in high lattice misfit and residual lattice strain. At 400 °C, the alternating dominance of dislocation climb and slip induces fluctuations in both lattice misfit and residual lattice strain. Due to slow dislocation density accumulation, {hkl} lattice strains continuously increase. This contrasts with the RT and 500 °C scenarios, where rising dislocation density partially recovers elastic lattice distortion and even induces {hkl} lattice strain rebound at high strains (ε = -0.20~-0.25).
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In the field of solar cell technology, the conversion efficiency of silicon heterojunction (SHJ) solar cells has reached 27.08%. Meanwhile, perovskite/SHJ tandem solar cells based on this structure have achieved an efficiency of 34.85%, surpassing the 33.7% theoretical limit for single-junction devices. As the industry shifts from single-junction to tandem configurations, SHJ cells—benefiting from their distinctive structure and low-temperature fabrication process—offer superior compatibility with perovskite layers. This positions SHJ technology to play a critical role in the development of perovskite/tandem solar cells.
The application of high-performance silver-coated copper (Ag@Cu) paste for electrode metallization provides a viable approach to reduce the cost and improve the performance of SHJ cells. However, the micron-scale particle size of Ag@Cu powder (typically several micrometers) limits the packing density of the electrode layer. To address this, nano-silver powder (~100 nm) is commonly introduced as an additive, enhancing both the packed density of the powder and the electrical conductivity through nano-effects. Although many studies focus on isolated aspects such as paste conductivity, a systematic evaluation covering contact resistivity, printed and cured electrode morphology, overall cell performance, and long-term stability remains scarce. Potential adverse effects of nano-silver addition have also been overlooked. Therefore, a thorough investigation into the role of nano-silver in low-temperature Ag@Cu pastes is necessary.
Highly conductive low-temperature curing pastes typically employ binary or ternary composite powders with well-separated particle sizes to achieve high packing density according to the dense packing theory. In this work, we systematically adjusted the proportions of three conductive powders: micro-sized Ag@Cu (3-5 μm), sub-micron silver (500 nm), and nano-silver (100 nm), to study the effect of nano-silver on key properties of Ag@Cu paste. These include: curing temperature and sintering behavior, microstructure of cured electrodes, interface structure between electrodes and the silicon wafer, electrical resistivity, and the overall conversion efficiency of SHJ solar cells. The aim is to clarify the underlying mechanisms and optimize the nano-silver content.
This research reveals several significant impacts of nano-silver addition on Ag@Cu paste properties: (1) It markedly reduces the resistivity of the cured electrode. Compared to sub-micron silver, nano-silver facilitates improved lateral conductivity at lower sintering temperatures. (2) It introduces additional pores at the contact interface with the silicon wafer, increasing contact resistivity. A thickened organic layer at the interface also forms, which reduces the open-circuit voltage of the cell. (3) It enhances paste thixotropy, leading to narrower printed electrode lines that reduce shading loss and increase short-circuit current density. Concurrently, it raises electrode height and cross-sectional area, which helps improve the fill factor. (4) With nano-silver content controlled at 15%, the efficiency of SHJ cells matches or approaches that of reference cells with pure silver electrodes, mainly due to enhanced fill factor and short-circuit current density.
In summary, an optimized amount of nano-silver powder (e.g., 15%) enables simultaneous improvement in electrode conductivity, printability, and opto-electrical performance, yielding SHJ cells with efficiency comparable to those using pure silver electrodes. This demonstrates the potential of Ag@Cu pastes as a cost-effective alternative without compromising performance. Future studies should focus on the long-term reliability of such paste systems and their scalability, supporting the mass adoption of this technology in perovskite/SHJ tandem solar cells.
The application of high-performance silver-coated copper (Ag@Cu) paste for electrode metallization provides a viable approach to reduce the cost and improve the performance of SHJ cells. However, the micron-scale particle size of Ag@Cu powder (typically several micrometers) limits the packing density of the electrode layer. To address this, nano-silver powder (~100 nm) is commonly introduced as an additive, enhancing both the packed density of the powder and the electrical conductivity through nano-effects. Although many studies focus on isolated aspects such as paste conductivity, a systematic evaluation covering contact resistivity, printed and cured electrode morphology, overall cell performance, and long-term stability remains scarce. Potential adverse effects of nano-silver addition have also been overlooked. Therefore, a thorough investigation into the role of nano-silver in low-temperature Ag@Cu pastes is necessary.
Highly conductive low-temperature curing pastes typically employ binary or ternary composite powders with well-separated particle sizes to achieve high packing density according to the dense packing theory. In this work, we systematically adjusted the proportions of three conductive powders: micro-sized Ag@Cu (3-5 μm), sub-micron silver (500 nm), and nano-silver (100 nm), to study the effect of nano-silver on key properties of Ag@Cu paste. These include: curing temperature and sintering behavior, microstructure of cured electrodes, interface structure between electrodes and the silicon wafer, electrical resistivity, and the overall conversion efficiency of SHJ solar cells. The aim is to clarify the underlying mechanisms and optimize the nano-silver content.
This research reveals several significant impacts of nano-silver addition on Ag@Cu paste properties: (1) It markedly reduces the resistivity of the cured electrode. Compared to sub-micron silver, nano-silver facilitates improved lateral conductivity at lower sintering temperatures. (2) It introduces additional pores at the contact interface with the silicon wafer, increasing contact resistivity. A thickened organic layer at the interface also forms, which reduces the open-circuit voltage of the cell. (3) It enhances paste thixotropy, leading to narrower printed electrode lines that reduce shading loss and increase short-circuit current density. Concurrently, it raises electrode height and cross-sectional area, which helps improve the fill factor. (4) With nano-silver content controlled at 15%, the efficiency of SHJ cells matches or approaches that of reference cells with pure silver electrodes, mainly due to enhanced fill factor and short-circuit current density.
In summary, an optimized amount of nano-silver powder (e.g., 15%) enables simultaneous improvement in electrode conductivity, printability, and opto-electrical performance, yielding SHJ cells with efficiency comparable to those using pure silver electrodes. This demonstrates the potential of Ag@Cu pastes as a cost-effective alternative without compromising performance. Future studies should focus on the long-term reliability of such paste systems and their scalability, supporting the mass adoption of this technology in perovskite/SHJ tandem solar cells.
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Optical Stokes vector skyrmions, as novel fully Poincaré spherical vector beams, hold broad application prospects in optical communication, optical computing, multiplexing, and super-resolution imaging. However, existing research primarily focuses on the controllable generation of single optical skyrmions, with limited exploration of continuous modulation of different skyrmion configurations and insufficient investigation into generation in the terahertz frequency band. This paper proposes a multilayer metasurface that generates higher-order topological configurations of Stokes vector skyrmions through rotation. For instance, a two-layer structure enables rotational control of two skyrmion types, while a three-layer design achieves control over four skyrmion types. A twist-tunable double-layer Moiré metasurface design is simultaneously developed, where the two metasurface layers are designed with complementary Moiré phases to achieve continuous modulation of the radial skyrmion order. By synergistically modulating the geometric and dynamic phases of the metasurface, the topological invariance of free-space propagating skyrmions is preserved while maintaining beam intensity. The paper presents detailed theoretical analysis and numerical results, validated through full-wave simulation studies. This multilayer metasurface design enables dynamic control of Stokes vector and skyrmion configurations solely by adjusting the relative rotation angles between layers, eliminating the need to alter incident light or external conditions. This approach breaks through the limitations of traditional phase modulation methods reliant on phase-change materials. Furthermore, the dual-layer Moiré metasurface design significantly enhances device integration, offering a highly integrated and flexible technical pathway for realizing multidimensional light field manipulation and long-distance terahertz optical communication systems.
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This study employs a phase-field–lattice Boltzmann coupled model to investigate the effect of forced convection on the lamellar eutectic growth of Al-Cu alloys. Results indicate that forced convection tilts lamellar structures toward the flow direction, enhances solute diffusion, and causes solute concentration to deviate asymmetrically from the solid phase centerline. Greater convection intensity leads to more pronounced interface asymmetry. Increased undercooling weakens convective effects and reduces tilt angles, while larger lamellar widths diminish convective influence and yield smaller tilt angles. The study reveals a synergistic regulatory mechanism between these factors. Simulations indicate that without convection, layers grow vertically with solute symmetrically distributed along the solid centerline. Interlayer lateral diffusion promotes synergistic α-β phase growth. Forced convection (along the x+ direction) enhances solute transport in the flow direction while weakening counter-current transport. This shifts the triple point and creates asymmetric solute distribution—e.g., higher α phase concentration to the left of the centerline—causing layer tilting. Increasing convection intensity (expressed as A/A0, where A0 corresponds to the coefficient for a 0.5° tilted layer) exacerbates asymmetry at the solid-liquid interface and reduces the distance between the interface peak and the triple point. Higher undercooling (0.8-1.4 K) enhances growth driving force and reduces solute trapping capacity, weakening convective effects and decreasing the tilt angle. When undercooling is minimal and convection is strong, the tilt angle significantly increases. As the interlayer spacing (6.4-19.2 μm) increases, solute exchange at the interface becomes more frequent, convective interference weakens, and the tilt angle decreases; under conditions of small spacing and strong convection, solutes are easily washed away, inhibiting lamellar growth. In summary, forced convection directly alters the morphology of the solute transport control layer. Supercooling and interlayer width indirectly modulate convective effects by influencing growth driving forces and interfacial solute exchange. These three factors synergistically regulate eutectic growth, providing a theoretical basis for controlling eutectic microstructure.
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Frequency modulation continuous wave ranging technology is widely used in industrial manufacturing. Because the on site working environment are complex, the measured target may have slight vibration. The Doppler frequency shift generated by the vibration leads to the beat frequency signal broaden of the frequency continuous wave ranging system generated by the reference light wave and the measuring light wave superposition, which decreases the measurement accuracy of the ranging system. This paper first analyzes the measurement principle of frequency modulation continuous wave ranging technology and the influence of target vibration to the range measurement accuracy. The analysis results show that the target vibration displacement can magnify the measurement error by dozens of times to hundreds of times. To address the above measurement error by the tiny vibration displacement, this paper proposed the vibration suppresses method on the frequency modulation continuous wave ranging based on the four-wave mixing effect. Firstly, the generation principle of four-wave mixing is introduced. The single-frequency laser is used as the pump light, and the tunable laser is used as the signal light. These two lights are simultaneously incident into the highly nonlinear fiber. The converted light is generated by the third-order parametric process of the nonlinear medium of the fiber. The converted light and the signal light from the tunable laser form a symmetrical light source with a completely opposite scanning direction. When the superimposed upper and lower scanning light are filtered by high-pass filtering, the vibration influence on the measurement signal is suppressed. Secondly the four-wave mixing frequency modulation continuous wave experimental system is built and the single-point measurement stability is verified. Based on the Mach-Zehnder interferometric measurement principle, a four-wave mixing effect frequency modulation continuous wave range measurement system is constructed. The statical target at 6.9m away was measured by this constructed ranging system. The distance of peak to bottom range is reduced from 199.8 μm before vibration suppression to 16μm, which improves more than 12 times. The ranging accuracy comparison experiment in the range of 6m ~ 7.2m was also carried out, and the ranging accuracy is lower than 9.4 μm. Experimental results show that the vibration suppression method based on four-wave mixing effect can effectively improve the measurement accuracy of the frequency modulation continuous wave ranging, which of great significance in the industrial scenes.
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Optical pressure measurement technology, which is based on non-contact monitoring of pressure by observing the luminescent characteristics of luminescent materials under pressure influence, has always been widely popular. Therefore, the development of luminescent materials with high pressure-sensitivity, high accuracy, and a wide pressure application range has become a key focus. In this paper, the optical pressure sensing performance of a Mn2+-based pyroxene-type luminescent material (CaZnGe2O6:0.02Mn2+) is reported. Within the pressure range of 0.33~9.49 GPa, it demonstrates high sensitivity and excellent cyclic repeatability based on the pressure measurement strategies of both the spectral shift and luminescent intensity ratio. As the pressure increases, the maximum absolute sensitivity (Sa) values (dλ/dP) of the green and red emission positions of Mn2+ at different sites in the matrix reach 10.47 nm/GPa and 4.83 nm/GPa, respectively, which are 28.7 and 13.2 times those of the ruby pressure gauge (Al2O3:Cr3+). Compared to the traditional method that uses a single luminescent peak, this pressure measurement method employing the position shift os dual-luminescent emission can enhance the accuracy and reliability of pressure measurement more effectively. In addition, it is the first time to calculate the pressure sensitivity of Mn2+-based luminescent materials using the ratio of spectral integral intensities in selected areas, and the obtained maximum relative pressure sensitivity (Sr) value is 64.28 %/GPa, with Sr remaining above 16.06 %/GPa throughout a rather wide pressure range. Undoubtedly, CaZnGe2O6:0.02Mn2+ exhibits extremely outstanding optical pressure measurement performance, demonstrating its great application potential in the field of optical pressure sensing.
, , Received Date: 2025-08-01
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Porous anodic aluminum oxide (AAO) films, due to their excellent dielectric, mechanical, and optical properties, have been widely used in electronic devices, catalytic supports, and optical materials. Anodization is the primary method for fabricating high-quality porous AAO films. The conductive behavior and mechanism of commonly used carbon rod counter electrodes are significant factors influencing the microstructure and properties of the films. In this study, a phosphoric acid solution with a mass fraction of 6% is used as the electrolyte, circular aluminum foil serves as the anode, and carbon rods are used as the counter electrodes spaced 15 cm apart. The oxidation time is fixed at 40 s. The conductive behaviors of the carbon rod under oxidation voltages ranging from 100 to 140 V are experimentally investigated. The results show that the pore depth and diameter of the AAO film symmetrically decrease from the film center toward the edges. When the oxidation voltage is below 110 V, the gradients of pore depth and diameter from the center outward are relatively small, resulting in a macroscopically uniform structural color. At an oxidation voltage of 110 V, the gradients of pore depth and diameter increase significantly, resulting in iridescent concentric ring structural colors. As the voltage increases further, the gradients become more pronounced, the number of structural color rings increases, and the visible color gamut significantly broadens. Electromagnetic and electrochemical theories are utilized to calculate the conductive behaviors of the carbon rod under different oxidation voltages and to analyze its conduction mechanism. The carbon rod is found to exhibit “quasi-point electrode” conductive characteristics, with the selection of point electrode positions on the carbon rod following the principle of minimizing the resistance between the two electrodes. This finding not only enriches the electrochemical theory of anodization but also provides theoretical and experimental support for fabricating multifunctional AAO films.
, , Received Date: 2025-08-01
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This research adopts an innovative method, i.e. proton irradiation technology, for realizing defect control in practical engineering yttrium barium copper oxide (YBCO) tapes, in order to improve the critical current density of YBCO high-temperature superconducting tapes in high magnetic fields. Based on the material irradiation terminal of the 4.5 MV electrostatic accelerator at Peking University, systematic irradiation experiments are conducted using 3 MeV proton beams on YBCO superconducting tapes at different fluence rates, successfully constructing high-density, low-dimensional controllable artificial pinning centers in the high superconducting tapes. This defect engineering significantly suppresses the flux creep phenomenon and enhances the pinning effect by creating low-energy pinning sites for flux lines, thereby significantly weakening the inhibitory effect of external magnetic fields on critical current (Ic). Comparative analysis of superconducting tapes before and after irradiation is conducted, including superconducting transition temperature, superconducting critical performance, and dependence of critical current density on magnetic field. As the irradiation dose increases, high-density point defects (vacancies, interstitial atoms, etc.) and a small number of vacancy clusters are implanted inside the superconducting tape, resulting in a corresponding decrease in the superconducting phase. Therefore, as the dose increases, the orderliness of the superconducting phase in the superconducting tape decreases sharply, leading to a gradual widening of the superconducting transition temperature zone. By measuring the hysteresis loops of samples irradiated with different doses of protons and calculating the critical current density Jc based on the Bean model, the experimental data show that under irradiation conditions with a fluence rate of 8×1016 P/cm2, the critical current of the sample under extreme operating conditions of 4.2 K and 6.5 T achieves an 8-fold breakthrough improvement. Meanwhile, the maximum improvement factors in critical current density at 20 K and 5 T and 30 K and 4 T are also 5.5 times and 4.8 times, respectively. The logarithmic curve is fitted using the Jc ∝ B-α power exponent model, with the power parameter α values of 0.276, 0.361, and 0.397 for the variation of critical current density with magnetic field in three temperature ranges of 4.2 K, 20 K, and 30 K, respectively. This indicates that the superconducting tape irradiated with protons will form more effective strong pinning centers at lower temperatures, reducing the dependence of the critical current density of the superconducting tape on the magnetic field. This performance breakthrough significantly enhances the application potential of high superconducting tapes in low-temperature and high magnetic fields environments, especially in frontier fields such as particle accelerators and fusion reactors, where there is an urgent demand for high-performance superconducting magnets. This work confirms that the proton irradiation technology can efficiently optimize critical performance through defect engineering without changing the existing preparation process of YBCO tapes, thereby providing a highly feasible and process-compatible technical path for realizing the practical performance control of superconducting materials.
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In response to the technical issue in Raman distributed optical fiber technology where the traditional meter-level spatial resolution performance is insufficient, leading to a decline in system measurement accuracy within sub-spatial resolution fiber segments along the sensing fiber, a threshold coefficient fitting technique based on a one-dimensional peak-seeking method is proposed in this study. Significant temperature measurement errors of up to tens of degrees Celsius are caused by the overlap of Raman scattering signals from non-detection regions when the detection fiber length is shorter than the system's spatial resolution. This severely limits the technology application in scenarios requiring precise temperature monitoring. To overcome the above bottleneck, a purely algorithmic approach is introduced, which reconstructs the temperature field without requiring hardware modifications. The sensing fiber was globally scanned using the one-dimensional peak-finding algorithm to precisely locate sub-spatial resolution detection fiber regions. Simultaneously, the peak intensity, full width at half maximum (FWHM), and location were extracted from the temperature rise curve within the fiber under test (FUT). Through pre-calibration experiments, a quantitative fitting model was established between peak temperature rise curves and threshold coefficients, revealing a quantitative mapping relationship between FWHM and sensing distance, as well as length of FUT. The results indicated that FWHM exhibited a significant positive linear correlation with sensing distance, independent of temperature variations. This characteristic enabled FWHM to serve as a reliable feature parameter for identifying the actual length of detection fibres. During real-time measurements, the detection fiber length was determined via the mapping model based on extracted FWHM and location. Then the corresponding threshold coefficient fitting model is selected to compensate for distorted temperature rise peaks, thereby reconstructing distributed temperature field. Experimental results demonstrated that over a 10-kilometre sensing distance, the results indicate that the application of this technique significantly enhanced the temperature measurement accuracy within the 30 cm detection fiber, achieving 1.5 °C compared to the baseline accuracy of 34.7 °C before compensation. Conclusions indicate that the proposed threshold coefficient fitting technique, through algorithmic innovation, effectively overcomes the technical limitation of deteriorating temperature measurement accuracy in sub-spatial resolution regions within Raman distributed fibre optics sensing. The constructed FWHM quantitative mapping model provides critical basis for threshold compensation, ultimately achieving precise temperature monitoring of sub-metre regions within long-distance sensing contexts. This solution features a streamlined structure, low cost, and ease of engineering integration. It offers a novel approach for long-term, high-precision temperature monitoring in fields such as power cable fault orienation, oil and gas pipeline micro-leakage early warning, and civil structural health monitoring.
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