Volume 182

Polyethylene is the largest and most widely used plastic in the world, playing an irreplaceable role in many fields such as packaging, automotive, medical, and construction. This paper mainly describes the basic characteristics, production methods, and application scope of polyethylene. Firstly, analyze the physical and chemical properties, including mechanical properties, thermal properties, electrical properties, chemical corrosion resistance, etc. The sources of polyethylene raw materials and main production processes were explored, and the effects of different production processes and methods on the molecular structure and properties of polyethylene were analyzed; And the application of polyethylene in packaging, construction, medical and automotive fields has been studied and summarized. On this basis, the following conclusions were drawn through research: The ice template method significantly enhances the composite effect, and room temperature catalytic hydrogenation is the best for modifying the structure of PPS/bP blends. After adding bP, the shear rate increases at the same drop time, which can reduce the reaction temperature. The rheological curve shows a negative correlation between the two, indicating that bP promotes monomer polymerization and thus reduces the temperature. Extending the dripping time and increasing the shear rate synergistically reduce the reaction temperature and accelerate the polymerization of bP. The two-phase model can effectively describe the reaction mechanism of bP/PABS on PMSGF/PPS/BA, and the lattice effect of drilling and welding iron blocks can reduce the reaction position shift. The circumferential embedding of PABS in the needle belt forms an arched ring structure, optimizing the distribution of ferroalloy welding and improving welding accuracy.

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Among all photovoltaic technologies, perovskite solar cells (PSCs) have emerged as a standout, combining record-breaking efficiency with the promise of low-cost, scalable manufacturing. However, the poor stability of perovskite materials remains a major obstacle to their commercialization. To address this challenge, researchers have shifted focus from traditional three-dimensional (3D) PSCs to the development of two-dimensional/three-dimensional (2D/3D) hybrid structures, achieving remarkable progress. This review examines various strategies to improve stability, including constructing 2D/3D heterostructures, surface passivation, interface engineering, optimizing fabrication processes, and material design, with the aim of investigating the mechanisms underlying the enhanced stability of 2D/3D hybrid perovskite solar cells (PSCs) These methods effectively address issues such as ion migration, defect density, and environmental degradation. Key findings show that 2D/3D heterostructures and passivation layers significantly enhance device stability and efficiency, with some achieving power conversion efficiencies (PCEs) over 25%. However, challenges remain in large-scale production and long-term stability under extreme conditions. Future research should focus on developing scalable fabrication techniques, optimizing material systems for durability, and further improving charge transport efficiency to advance the commercial viability of 2D/3D PSCs.

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This paper focuses on the optimization design of thulium-doped fiber lasers in the L+ band (1600-1650nm). Aiming at the problem of low output power and efficiency in this band, it takes silicon-based thulium-doped fiber as the gain medium and studies the influence of parameters such as doping concentration and fiber length on the steady-state characteristics of the laser by establishing a coupled model of three-level rate equations and transmission equations. The simulation results show that there is an optimal combination of parameters: when the doping concentration is about 3×10²⁴/m³ and the fiber length is about 0.4m, the laser has a threshold of about 0.04W, the highest pumping efficiency, and the output power increases linearly with the pumping power. The research also provides theoretical support for the experimental preparation of thulium-doped fiber lasers in the L+ band and looks forward to their application prospects in biomedical, industrial processing and other fields.

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Yellow Dy³⁺-doped ZBLAN fiber lasers emitting in the 560–600 nm window is highly desirable for biomedical imaging, laser display, lidar and atmospheric sensing, yet their performance is still limited by sub-optimal gain design. Here we present an optimization of the Dy³⁺: ZBLAN fiber laser that simultaneously tunes the dopant concentration and the linear-cavity length. A four-level rate-equation model was established and coupled with pump-power and signal-power propagation equations; the system was numerically solved in MATLAB with experimentally reported spectroscopic parameters. Parametric sweeps show that increasing the Dy³⁺ concentration from5×1024m-3to2×1025m-3and adjusting the cavity to 5 m maximizes population inversion while keeping re-absorption loss low. At the identified optimum the laser reaches an external slope efficiency of 38 % and produces 3.77 W of continuous-wave output at 574 nm when pumped with 10 W at 453 nm; the lasing threshold is about equal to 1 W, and no backward pump is required. The model also predicts a nearly linear output–pump characteristic and negligible backward signal, confirming good unidirectional operation. These results provide clear design rules for watt-level, narrow-band yellow fiber lasers and lay the groundwork for compact sources in advanced photonic applications.

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In recent years, fiber lasers have shown significant potential for applications in biomedical imaging and optical fiber communications. However, conventional rare-earth-doped fibers face challenges such as low efficiency and narrow bandwidth. Bismuth (Bi)-doped fibers have emerged as an ideal alternative due to their broadband luminescence characteristics (1100-1800 nm), but issues such as emission cross-section optimization and concentration quenching effects remain unresolved. Bismuth-doped phosphosilicate fibers (BPSFs) have attracted considerable attention for covering the second transmission window. Researchers worldwide have achieved gains exceeding 20 dB in the 1320-1460 nm band by refining fabrication techniques and pump structures. This study focuses on a three-level bismuth-doped fiber laser work in the 1350-1400 nm wavelength range. Through numerical simulations, the following results were obtained: The optical power generated by the laser exhibits a linear relationship with the input power. As the forward pump power propagates through the fiber, it undergoes exponential decay. The backward pump power remains negligible. The forward laser power follows a logarithmic growth distribution. The backward laser power demonstrates an exponential decay distribution. These findings provide theoretical support for the industrial application of fibers doped with bismuth and advance the expansion of the operational bandwidth of fiber amplifiers in communications, medical fields, and beyond.

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Against the backdrop of China's 2025 carbon neutrality goals and the State Administration of Affairs' (2024) full-cycle cost control mandate. By deploying LSTM-based residual value prediction (MAE 8.2%), carbon-sensitive genetic algorithms (20.3% fuel savings), and 5G-enabled digital twins, this study framework achieves an 18.7% reduction in equipment-related costs for the Shanghai-Nanjing High-Speed Railway Expansion. Empirical results show that the equipment utilization is 29.5% higher, the carbon intensity is 20.6% lower, and the resilience to fuel - price volatility is 68% greater. This research develops a novel cost-carbon-schedule optimization paradigm—a three-dimensional framework integrating lifecycle economics, real-time carbon accounting, and dynamic scheduling—to advance intelligent infrastructure governance in China’s smart construction era. Significant potential for broader industialapplications is possessed by the framework looking ahead.With digital technologies advancing continuously,AI and blockchain integration into the framework might be considered—data security,transparency,and pblueictive accuracy thus it can be seen would see improvements. Exploration of emerging energy sources as well as storage technologies by future research should also be undertaken—the framework’s adaptability to shifting energy demands examples could be further expanded.

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Rare-earth-doped fiber lasers, as core components in next-generation optical communication and laser technologies, demonstrate advantages such as high gain and low noise. They overcome the gain saturation issues of traditional semiconductor optical amplifiers, meeting the demands for high-power long-distance communication while expanding the application scope of laser technology. Through MATLAB numerical simulations, we obtained power transmission characteristics under various operating conditions. Simulation results indicate that at 1W pump power, the laser achieves a maximum output power of 850mW with a power conversion efficiency of 85%, reaching optimal performance at 15m fiber length. When the doping concentration is 1×10²⁵ m⁻³ and the pump power is 1W, the system exhibits excellent gain characteristics, showing a typical signal power growth pattern that first increases then saturates with fiber length. Under different pump power conditions, 0.5W pump yields 380mW output power, while 1.5W pump delivers 1180mW output power, with further improved conversion efficiency achievable through optimized doping concentration. This research provides crucial theoretical foundations and parameter guidance for engineering design of high-performance rare-earth-doped fiber lasers. Compared to traditional amplifiers, this technology significantly enhances transmission distance and signal quality in optical communication networks, potentially enabling long-distance relay-free communication exceeding 100km per span.

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To address the demand for efficient and compact light sources in the 1200-1250 nm spectral range for applications in biomedical imaging and nonlinear frequency conversion, this paper proposes a theoretical design and performance simulation scheme of a bismuth-doped fiber laser. A steady-state rate-equation model based on a quasi-four-level system is established, which comprehensively describes the power evolution of forward and backward pump and signal light within a linear cavity structure. The resulting two-point boundary value problem is solved numerically using MATLAB's bvp4c solver. The simulation results indicate that the designed laser possesses excellent performance potential, clearly revealing the processes of pump attenuation and signal amplification within the cavity. The findings validate the effectiveness of the established model and quantitatively predict the feasibility of achieving high-efficiency operation from a 1200 nm bismuth-doped fiber laser. This work provides significant theoretical guidance and a design basis for the experimental fabrication, parameter optimization, and performance enhancement of fiber lasers in this spectral range.

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With the gradual development of laser technology, early gas lasers and solid-state lasers were marked by substantial size, low efficiency, inadequate heat dissipation, and the necessity for intricate optical path adjustments. These constraints-imposed limitations on their applications in domains such as industry and medicine. The wavelength range of traditional rare-earth ions is limited. Due to the multi-valence states of bismuth ions and their multiple splitting characteristics in different matrix fields, bismuth-doped optical fibers exhibit an extremely wide coverage band. Therefore, bismuth (Bi) ions have become a current research hotspot. Given that ytterbium ions have a low luminous efficiency in the 1150 - 1200 nm wavelength band, this paper conducts a numerical simulation study on the dynamic characteristics of bismuth-doped fiber lasers in the 1150 - 1200 nm wavelength band. This experiment is based on the three-level rate equation model and the boundary value problem solution method to establish a theoretical model of aluminosilicate bismuth-doped fiber lasers. By analyzing the mutual relationships among the pump power, fiber length, and output power, the threshold characteristics and gain saturation phenomenon of bismuth-doped lasers in this band are verified.

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Double clad erbium-doped fiber lasers have important application value in 5G/6G communication, industrial precision machining, medical minimally invasive surgery and other fields. This study focuses on the optimization of its power transmission characteristics and doping concentration. Through a benchmark experiment with a fixed doping concentration (1.0×10²⁴ ions/m³), the low threshold of 1.80 mW and the slope efficiency of 15.4% of the laser were revealed, and the transmission evolution laws of pump light and signal light were analyzed. Further experiments showed that the threshold was the lowest (1.76 mW) when the doping concentration was 1.6×10²⁴ ions/m³, while the slope efficiency was the highest (32.73%) when the doping concentration was 4.0×10²⁴ ions/m³, providing accurate basis for concentration selection in different application scenarios. The research results have laid an important foundation for the performance optimization and practical application of fiber lasers. In the future, further exploration of diverse doping systems and environmental adaptability can be conducted to expand their application scope.

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