Optimal airport selection utilizing power Muirhead mean based group decision model with 2-tuple linguistic q-rung orthopair fuzzy information

The current generation of ultrahigh temperature ceramic precursors typically encounters obstacles in achieving high ceramic yields (<40 wt.%) due to the challenges in integrating significant amounts of boron, which hampers their conversion into boride-based ultrahigh temperature ceramics. To tackle these challenges, a serious of pioneering liquid multi-component hafnium-containing ceramic SiHfCB precursors (with different Hf/Si ratios) have been developed. These novel precursors are featured with stable molecular structure and high ceramic yield which were successfully created through a novel one-pot polymerization process. They present in liquid form and their structure is characterized by C-C bonds forming its main chain with branched chains of O-Si-O, Si-O-Hf, Si-O-B, and B-O-Hf which have untapped advantages including uniform component dispersion, and excellent fluidity. The ceramic yield of SiHfCB precursor with Hf/Si of 0.2 is remarkably up to 68.6 wt.% at 1500°C, and their Hf content exceeded 50 wt.%. Of particular interest, the pyrolyzed product HfB2-SiC nanopowders derived from the SiHfCB precursor with Hf/Si of 0.2, consist of nanopowders in the 40-60 nm range with a density of 5.23 g·cm−3. Remarkably, this material demonstrates exceptional performance in ultrahigh temperature oxygen-containing environments at 2500°C, showing near-zero ablation with a linear ablation rate of just 2.5 × 10−4 mm·s−1. Post-ablation analysis of the microstructure reveals that the formation of a lava-like HfO2 and HfO2-SiO2 oxide layer effectively blocks oxygen penetration and provides excellent oxidation resistance. The innovative SiHfCB hafnium-containing ceramic precursor offers a groundbreaking solution for the preparation of lightweight ultrahigh-temperature ceramics. This development is poised to provide robust technical support for the use of ultrahigh temperature ceramics in non-ablative thermal protective systems, particularly in the construction of hypersonic vehicles, where ultrahigh temperature resilience is crucial. 

Ultrahigh temperature ablation resistant HfB2-SiC composites: from liquid SiHfCB precursor synthesis to light weight bulk preparation and characterization

HfC-SiC modified C/C composites containing in situ formed Si-HfC-HfSi2 ablation resistant layer and SiC oxidation resistant layer were successfully prepared by reactive melt infiltration (RMI) combined with gaseous silicon infiltration (GSI). A comparative study was conducted on the anti-oxidation and anti-ablation performance of the C/C-HfC-SiC composites with GSI (noted as RG-CHS) and without GSI (noted as R-CHS). After oxidation at 1500 °C for 200 min, the oxide film of RG-CHS remained intact. The mass and linear ablation rates decreased from 1.31 mg/s and 7.36 μm/s to 0.12 mg/s and −0.22 μm/s after GSI process, respectively. The introduction of low melting point phases and reducing surface defects can improve the high temperature oxidation resistance and plasma ablation resistance of the composites. 

C/C-HfC-SiC composites with simultaneous the resistance to ultra-high temperature airflow erosion and high temperature oxidation

To suppress the oxidation loosening of HfB2-SiC coating, the HfB2 was alloyed with HfSi2 in the form of composite powders through self-propagating high-temperature synthesis (SHS) technique, which was then used to prepare HfB2-HfSi2-SiC coatings. Compared to the 60HfB2-SiC coating, the 60(HfB2-HfSi2)SHS-SiC coating exhibited lower oxidation activity and better inert oxygen blocking at 1700 °C. The addition of HfSi2 promoted the homogenization of the Hf-oxides distribution on the glass layer and the formation of the protective phase HfSiO4, further inhibiting oxygen diffusion. The 60(80HfB2-20HfSi2)SHS-SiC coating exhibited optimal oxygen blocking protection after oxidation at 1700 °C, with 87.96% and 92.33% reductions in oxygen permeability and carbon loss rate, respectively. 

Oxygen blocking enhancement of HfB2-SiC coating using HfB2-HfSi2 alloyed composite powders by self-propagating high-temperature synthesis

To improve the infrared emissivity and the ablation resistance of HfB2/SiC/TaSi2 coatings for serving in heat flux of 4400 kW/m2, HfB2/SiC/TaSi2 coatings with different contents of high-emissivity Gd2O3 were prepared using atmospheric plasma spraying. The highest emissivity in 3–5 μm can reach up to 0.92 at 1273 K when the Gd2O3 content is at 10 vol.%. The increase in the emissivity is attributed to the additional electronic transitions induced by oxygen vacancies, which are generated by substituting Hf4+ with Gd3+. Due to the high emissivity, the surface temperature of the coating modified with 10 vol.% Gd2O3 was decreased by ~100 K. Meanwhile, the mass and the liner ablation rate are confirmed to be 4.28 × 10−7 kg/s and 2.15 × 10−7 m/s, respectively, which are decreased by 80% and 31% compared to the undoped HfB2/SiC/TaSi2 coating. During ablation, HfB2/SiC/TaSi2/Gd2O3 coating was oxidized to HfO2, Gd2Ta2O7, HfSiO4, and GdTaO4. A stable Hf–Ta–Gd–Si–O multiphase glass was formed on the surface of the coating, which could restrain oxygen penetration. However, the excessive amount of Gd2O3 is detrimental to the ablation performance due to its consumption of the SiO2 glass layer. These findings indicate that the addition of an appropriate amount of Gd2O3 could improve the anti-ablation performance of the modified coating. 

Effects of Gd2O3 Content on the Infrared Emissivity and Ablation Resistance of HfB2/SiC/TaSi2 Coating at 4400 kW/m2

To inhibit the destructive evolution of the HfB2-SiC coating during oxidation, La2O3 was added to modify the oxygen-blocking capability of the HfB2-SiC coating. The effect of La2O3 content on the oxygen barrier capacity of HfB2-SiC was investigated. The addition of 5 vol.% La2O3 lowered the oxidation activity and strengthened the inert oxygen barrier capacity of the HfB2-SiC coating, which made the oxygen permeability and maximum weight change rate of the coating decrease by 30.32% and 73.97%, respectively. Due to the solid solution reaction of the dispersed La2O3, HfO2, and SiO2 nanoparticles, a stable Hf-B-La-Si-O multiphase glass was formed on the surface of the coating. Besides, the high-melting-point particles, such as HfO2, La2Hf2O7, and HfSiO4, dispersed in the glass layer as hard particles and formed a mosaic structure based on the Hf-B-La-Si-O compound, which increased the cumulative protection efficiency of the HfB2-SiC coating to 98.5% and reduced the inert factor value by 84.57%. However, the excessive consumption of SiO2 glass by La2O3 results in dendritization of the generated glass when the La2O3 content is above 10 vol.%, which reduced the self-healing capability of the generated glass and instead weakened the oxygen barrier properties of the HfB2-SiC-La2O3 coatings. 

Effect of La
 2
 O
 3
 content on the oxygen barrier ability of the HfB
 2
 ‐SiC coating at 1973 K

How to efficiently guide passengers and ensure the order of airport operation is an urgent transport problem for airport management. Based on the analysis of the factors that affect the driver’s decision-making, this paper deeply explores the collaborative association of the core factors, such as the number of flight arrivals in different periods and the average seeking distance of taxis. Firstly, according to the GPS data of taxis, the paper uses clustering algorithm to get the average passenger-seeking time from the airport and makes matching interaction between the number of flights based on time distribution and the average passenger-carrying capacity of vehicles in the parking garage, so as to build a decision-making model based on the number of taxis N; secondly, it takes passenger safety and traffic order as the priority and uses M/M/S queuing model to integrate the two factors. Taking the maintenance cost and passenger evacuation time as constraints, the judgment condition of minimum cost Zmin and the optimal number of boarding points Sm are solved. Finally, taking the flight and taxi data of Shanghai Hongqiao Airport as an example, the driver’s decision-making standard is simulated, and the accuracy of the model is verified by the deviation rate. It can provide decision-making support for taxi management of urban transportation hub and rapid evacuation of airport passengers, so as to realize the collaborative optimization of airport flight arrival and taxi carrying order.

/pdf/the-optimization-of-airport-management-based-on-3ak2uxvj.pdf

The Optimization of Airport Management Based on Collaborative Optimization of Flights and Taxis

Oxygen barrier resistance of HfB2-MoSi2-TaB2 coatings in a wide temperature region

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Effect of La 2 O 3 content on the oxygen barrier ability of the HfB 2 ‐SiC coating at 1973 K

The Optimization of Airport Management Based on Collaborative Optimization of Flights and Taxis

Oxygen barrier resistance of HfB2-MoSi2-TaB2 coatings in a wide temperature region

Oxygen blocking enhancement of HfB2-SiC coating using HfB2-HfSi2 alloyed composite powders by self-propagating high-temperature synthesis