Abstract:In order to clarify the technical characteristics of precast concrete pavements and facilitate the selection of repair technologies in airfield concrete pavement repairs, a literature review is conducted. Typical pavement structure combination with connection joints are summarized. Construction quality control and digital management techniques are introduced, and comparisons among pavement repair technologies are made in terms of load adaptability, lifespan, and construction efficiency. The results show that welded clamps exhibit ease of use in construction process.With the use of pre-stressing joints and demountable devices,the bending resilience and reusability of pavements can be respectively enhanced. Construction work can be elevated efficiency by adopting cutting machines, lifting steel beams, and lifting devices. Regarding application scenarios, precast concrete pavements are suitable for long-time heavy loads and large repair operations. When such an advantage is combined with rapid repair concrete materials, the resilience recovery capability of airfield concrete pavements can be improved.

Abstract:Aimed at the problems that the hydration of Portland cement commonly used in pavement repair is tending towards stagnation, and the strength is difficult to generate under severe cold environment (-20 °C),a magnesium phosphate cement is selected which can still hydrate normally under negative temperature environment. The effects of water-cement ratio(W/C), borax content, polycarboxylate superplasticizer content and naphthalene superplasticizer content on the early performance of magnesium phosphate cement in severe cold environment are studied, and the optimal ratio is given. The results show that the increase of W/C in cold environment enables to reduce the flexural strength and prolong the condensation time, but has little effect on the compressive strength. The borax dosage and strength basically show a trend of increasing first and then decreasing, and the strength performance is better at 5%. With the increaseof polycarboxylate superplasticizer, the compressive strength shows a trend of increasing first and then decreasing. And the flexural strength shows the same law at 1 h, and then shows a negative correlation at the later stage. The content of naphthalene superplasticizer is negatively correlated with strength. Therefore, this paper recommendes to choose the mix ratio of 0.16 W/C, 5% borax dosing and 0.4% polycarboxylate superplasticizer dosing in the cold environment. The results of this paper can provide a theoretical support for the rapid repair of airport pavement in the severe cold environment.

Abstract:The technical maintenance quality of micro-surface for airport pavement is for the performance of its agglutination material to decide. In order to clarify the effect of water-based resin polymer content on the rheological properties of modified emulsified asphalt for micro-surfacing, WER/WPU modified emulsified asphalt and WER/WPU/EVA modified emulsified asphalt for micro-surfacing are prepared. With the help of dynamic shear rheological test, linear amplitude scanning test and bending beam rheological test, the high temperature deformation resistance, medium temperature fatigue performance and low temperature creep characteristics of modified emulsified asphalt under different water-based resin polymer content are proved. The rheological properties of WER/WPU modified emulsified asphalt and WER/WPU/EVA modified emulsified asphalt are compared and analyzed. The anti-deformation and anti-cracking ability of the modified emulsified asphalt in the existing research are compared and evaluated. The results show that the high temperature deformation resistance, medium temperature fatigue life and low temperature flexibility of emulsified asphalt material are effectively improved after resin polymer is being added, and the improvement range increases with the increase of water-based resin polymer content. The high temperature deformation resistance of WER/WPU/EVA-15 modified emulsified asphalt is slightly better than that of WER/WPU-15 modified emulsified asphalt, but its fatigue characteristics and low temperature crack resistance are slightly lower than that of WER/WPU-15 modified emulsified asphalt. The resin-based modified emulsified asphalt developed in this paper is significant advanced.

Abstract:The process of airport pavement destroyed by loads such as wheel crushed down during pavement operation can be regarded as a process of unfavorable disturbance, and the ability of the pavement system characterized by adopting the pavement resilience index unfavorable for defending against adverse disturbances and recovering from disturbances is a hot research issue. In this paper, first, an index node for pavement resilience evaluation is established by introducing an economic index in combination with pavement condition index, pavement structural condition index, pavement flatness index and pavement friction coefficient. And then, the topological network is constructed based on the node relationships according to the topology theory, and the strength of nodes is calculated based on the theory of toughness triangle. Finally, the resilience in the airport pavement system is determined by calculating the overall strength of the topological network. The Tianshui Airport’s pavement resilience index is measured by this measure, and the results show that the evaluation method is “good”, and can provide an important reference for the evaluation of the safe operation of the airport pavement system.

Abstract:In order to further improve the assessment system for civil airport runway pavements, a new rigid pavement vulnerability evaluation system is developed on the basis of existing technical specifications for pavement evaluation and management.This system comprehensively evaluates the vulnerability of pavements in consideration of both structural and functional aspects.Five representative structural indicators and four functional indicators are selected, and their weights within the sub-systems are determined by using entropy weight method.With the aid of an advantage of the prominent ability of the fuzzy cloud evaluation model in transforming between qualitative concepts and quantitative descriptions, a Strong-Fuzzy Cloud Mode(SFCM) is proposed based on the Extended Cloud Model(ECM).Then, the comprehensive vulnerability assessment model for runway pavements is established.By analyzing the actual pavement inspection data from a southern airport, the comprehensive vulnerability assessment value for this pavement is determined as 2.277, indicating a high level of vulnerability.The confidence level of the assessment results is close to 1, demonstrating the validity of the calculated results.Furthermore, the assessment result is consistent with the evaluation result (2.123) obtained by using ECM, confirming the reliability of the assessment outcome.The SFCM takes into account the non-conformity of evaluation indicators to the standard normal distribution, constructs skewed distributions, and enhances the fuzziness of interval transitions, whereas the results of assessment conform even more to reality.

Abstract:The reinforced grassy pavement structure is a new type of simple pavement structure, and has significant technical advantages in the construction of runways for general aviation, emergency rescue and other scenarios. In this paper, a typical geo-cell reinforcement material is selected to study its mechanical properties (tensile and compressive properties) and durability properties (aging resistance and erosion resistance) through laboratory tests. And the application effects are analyzed based on the field bearing capacity test.The results show that the tensile strength and tensile modulus of single and two assembled geocells are 6.62 MPa and 1.09 MPa, respectively. The tensile modulus is 100.52 MPa and 21.27 MPa respectively. The compressive strength and compressive modulus of geo-cell materials are 101.09 MPa and 93.60 MPa respectively. The tensile properties of geo-cell materials affected by high temperature, low temperature and ultraviolet rays decrease to a great extent, but they still have a certain anti-aging ability. The geo-cell material is not affected by water erosion, and its tensile performance decreases after the erosion of deicing agent and gasoline, but there is no mass loss. Under the compaction degree of 85%, the resilience modulus of the geo-cell strengthened grassland pavement increase by 28%, and this indicates that the geo-cell material has a certain strengthening effect on the bearing capacity of the grassy pavement.

Abstract:In order to investigate the law of spontaneous combustion in the integrated afterburner, taking the fuel injection system in the integrated strut as a research object and adopting the spontaneous combustion flame of the fuel under the condition of high temperature inflow recorded by high-speed photography, the effects of input temperature, inlet velocity, residual gas coefficient and fuel nozzle type on the spontaneous combustion properties of the integrated afterburner are investigated.The results show that the increment of afterburner inlet temperature makes spontaneous combustion easy, and spontaneous combustion can occur under all conditions when the inlet temperature exceeds 1200 K. The increment of afterburner flow velocity is advantageous to the suppression of spontaneous combustion, making the spontaneous combustion delay distance of fuel increase. In the case of lean oil, fuel particles can absorb more heat from the environment, and the delay distance of spontaneous combustion is reduced. Conical atomizing nozzles with good atomization effect are prone to spontaneous combustion, while direct atomizing nozzles with poor atomization effect are relatively stab. The research results provide a preliminary reference value for the design of oil supply system and ignition system of integrated afterburner.

Abstract:In order to improve lift and drag characteristics of ground effect aircraft, experiments are made by measuring lift, drag characteristics, and wake velocity fields with a downward-forward swept wing and a biomimetic wing. On the basis of analyzing the wing tip vortex flow field structure, the mechanism of wing lift and drag changes is discussed from the perspective of spanwise flow. The results show that within the ground effect zone, the downward-forward structure can effectively improve the flow characteristics of the wing, suppress the formation and development of wing tip vortex flow, increase the vortex center distance, the effect is made with the lift being increasing and drag force being decreasing, and the closer the wing is to the ground, the more obvious the effect is. On this basis, the concave convex leading edge can further optimize the flow characteristics of the wing, reduce the intensity of the wing tip vortex, and reduce the induced drag. In small clearance ratio and small angle of attack conditions, the biomimetic wing with a downward-forward sweep structure with a concave convex leading edge has the optimal navigation economy. This provides a reference for improving the flight performance of ground effect wings and promoting the development of ground effect wing design theory

Abstract:Aiming at the problems of slow search speed and many redundant nodes of traditional A* algorithms in UAV trajectory planning when facing complex environments and high-dynamic tasks, a 3D UAV trajectory planning method based on the combination of optimized bi-directional A* algorithm and artificial potential field is proposed. By adopting a bidirectional search mechanism and setting weight coefficients to optimize the heuristic function, introducing an adaptive step-size strategy, and dynamically adjusting the bidirectional A* search step-size by using an adjustment factor, the Bi-A*PF algorithm is proposed by comprehensively considering the global planning and real-time obstacle avoidance requirements. Simulation experiments show that compared with traditional trajectory planning methods, the Bi-A*PF algorithm not only enables the UAV to efficiently plan a desired trajectory in a 3D environment, but also effectively avoids unexpected threats.

Abstract:Being low at expansion coefficient, low at heat-conductivity coefficient, low at permittivity and at dielectric loss, good in corrosion resistance, and high at thermal-stability, fused silica is sometimes thought of as being the promising candidate for radome in aero-craft.In the present study, researchers reveal the influence of thermal-shock experiment on the material properties of fused silica radome via mechanical/thermal tests, scanning electron microscopy, and X-Ray diffraction. It is found that mechanical strength of fused silica is incremental after thermal-shock experiment. And the reason is that the occurrence of diffusion migration happens during the experiment to make the fused silica particles fused and recombined flakily. In addition, the effects of thermal-shock experiment on expansion coefficient, heat-conductivity, permittivity and dielectric loss are comparatively minor.

Abstract:In view of the complex operation mechanism of anti-missile equipment system, the unclear structure which makes it difficult to select a suitable efficiency evaluation model, so the effectiveness evaluation of anti-missile equipment system is studied by the method of "data-driven + deep learning". ased on the operational process of the anti-missile equipment system, the evaluation index of the effectiveness of the anti-missile system is constructed from four aspects: detection and tracking, command and control, firepower interception and integrated support. To solve the problems of PSO algorithm, such as local extremum and premature convergence, an improved particle swarm optimization algorithm is proposed to optimize the parameters of SVR, and an IPSO-SVR efficiency evaluation model is established. On the basis of extracting, processing and analyzing a large number of experimental data, the IPSO-SVR model is trained and studied to obtain nonlinear fitting of the effectiveness of the anti-missile equipment system. The experimental results show that the proposed method has a very small error between the expected output and the actual output and it has high fitting accuracy, which means this method has high reliability and feasibility

Abstract:In view of site selection problems for support and logistics notes of ground-based air defense equipment under complex constrains caused by modern ground-based air defense operations increasingly turning towards distributed structures, modular design, and enhanced mobility, this paper tackles a complex problem of selecting optimal sites for support and logistics nodes, and proposes an innovative genetic-K-means-genetic algorithm (GAKGA). And the algorithm is utilized for stratifying different combat modules into different hierarchical tiers by hierarchical clustering idea, reflecting the intricacies of real-world operational constraints. Within each tier, the K-means algorithm is utilized to identify solutions satisfied with the problem’s constraints. By integrating genetic algorithms, the initialization of the K-means algorithm is optimized, leveraging the genetic algorithm’s strength in global search optimization. The final step involves using genetic algorithms to refine the selection of support nodes based on the results from each tier. The experimental results show that the enhanced GAKGA significantly improves solution efficiency, yielding shorter paths in complex site selection problems, thus facilitating a more agile response to the support needs of distributed ground-based air defense equipment.

Abstract:This paper designs a deep learning model MLSTM-FCN in combination with the advantages of fully convoluted neural network, recurrent neural network and compression and excitation module aimed at the problems that the existing air target recognition methods are not high enough in agility and reliability. The complex local features can be extracted from the air combat data by the fully convoluted network, and the long and short memory neural network can capture the temporal features of air combat intention data. The results of ablation experiments and comparative experiments show that the MLSTM-FCN model is superior to the existing air target intention recognition model in terms of intention recognition accuracy, reaction speed and anti-interference ability, and the results of sota are obtained, providing a more effective basis for commanders in making air combat decisions.

Abstract:In view of the time-frequency representation (TFR) reconstruction of the micro-motion signals under conditions of incomplete data, a reconstruction method of micro-motion is proposed based on the adaptive parameter estimation. Firstly, the missing micro-motion TFR reconstruction problem is modeled on the LP norm minimization sparse reconstruction problem, and by introducing Hadamard product parameter (HPP), the LP norm minimization sparse reconstruction problem is transferred to a joint minimization problem with multiple L2 norm, and solved by using iterative Tikhonov regularization. Simultaneously, the regularization parameter is estimated adaptively in each iteration based on reconstruction results. Finally, the amplitude decay of the reconstructed TFR is reduced by the de-biasing process. Compared with the traditional micro-motion echo time-frequency representation reconstruction method, the proposed method avoids the disadvantage of setting the regularization parameter manually, and the reconstructed TFR is more complete. The effectiveness and robustness of the proposed method is verified by simulation and measured data processing

Abstract:Aimed at the problems that mine wireless communications are low-accuracy in channel estimation caused by complicated and random characteristics, a multi-user mine communication system assisted by intelligent reflecting surface (IRS) technique is proposed in this paper to improve the accuracy of channel estimation by optimizing the transmission path and reassigning the wireless transmission environment. First, in combination with IRS technique, a model of the IRS-assisted multi-user information transmission in the mine is established. And then, the parallel factor (PARAFAC) decomposition channel estimation algorithm is derived, and the performances of PARAFAC algorithm in the IRS-assisted mine wireless communications is simulated based on the model. The simulation results show that compared with the traditional least-square (LS) algorithm and orthogonal matching pursuit algorithm, the proposed PARAFAC algorithm can obtain about 8 dB signal-to-noise ratio (SNR) gain at the same normalized mean-square error 10-2 while the execution time is slightly less than that of LS algorithm.

Abstract:Federated learning is a successful solution for shared knowledge in the context of data islands. However, with the advent of new attacks such as gradient reverse reasoning, the security of federated learning is faced with a new challenges again. In the federated learning, an inter-generational model leakage problem under the asynchronous federated learning framework is proposed aimed at the problem that participants maliciously steal gradient information from other clients by any possibility. By utilizing the characteristics of central server receiving then aggregating, multiple malicious clients can reversely compute other clients’ model update data through inter-generational versions of the global model in a specific update order. In view of this problem, a random aggregation algorithm based on α moving average is proposed. Firstly, the model update being received each time, the central server is to aggregate it with the global model randomly selected from the latest α aggregations, and shuffle the clients’ update order through the randomness of the aggregation. Secondly, as the number of global iterations increases, the central server performs a moving average on the global model of the latest aggregation to calculate the final global model. The experiment simulations show that the FedAlpha method can effectively reduce the possibility of inter-generational model leakage in comparison with the asynchronous federated learning method.