Abstract:With the convergence trend of high performance computing, big data processing, cloud computing and artificial intelligence computing, the converged network of high-performance computing network and data center network becomes an important trend. The current research status of converged network was analyzed, and the representative converged networks were described in detail to comprehensively show the latest technologies and trends. The challenges faced by the converged network were put forward, and the trends of converged network were proposed, including the convergence and differentiation coexistence of the converged network protocols, the performance acceleration of the converged network based on in-network computing, and the performance optimization of the converged network for emerging applications.

Abstract:The subgrid species-temperature correlation term significantly affects the accuracy of large eddy simulation of reactive flows. A new filtered pressure model was developed by using the basic characteristics of probability equivalence in the probability density function method, which can well close the subgrid species-temperature correlation term. The probability density function and its coupling solution method were introduced. Then, a new filtered pressure model was derived based on previous models. Numerical tests of different filtered pressure models were carried out in a three-dimensional supersonic hydrogen/air temporally evolving reactive mixing layer. The results show that, compared with the traditional filtered pressure model, the new filtered pressure model can significantly improve the simulation accuracy of the reaction mixing layer. In particular, based on the new filtered pressure model, the large eddy simulation coupled probability density function method can better simulate minor species in the chain reaction such as hydrogen peroxide, which is expected to more effectively reproduce complex combustion phenomena such as self ignition.

Abstract:Health monitoring can effectively improve the reliability of liquid-propellant rocket engines. Aiming at the problem of fault detection in health monitoring for liquid-propellant rocket engines, a method based on Wasserstein distance was proposed and verified using ground hot test data of an LOX/LH2 rocket engine. The core idea was to use Wasserstein generative adversarial network to simulate the sample distribution of normal data, and used its discriminator to calculate the Wasserstein distance between the test sample and the simulated distribution, so as to achieve fault detection. The results show that the proposed method can overcome the difficulty of insufficient fault data, detect the faults in the steady-state process effectively without false alarm, and is sensitive to early anomalies. In the case of a small number of training samples, when the Wasserstein distance threshold is set to 3σ, the method is sensitive to early anomalies during the start-up transient. Starting fault can still be effectively detected with the threshold of 5σ, with a false alarming rate of 12.5%.

Abstract:Most of the existing face forgery detection methods usually achieve acceptable detection performance on known attacks, but still face the risk of overfitting and fail to maintain good detection capability when dealing with unknown scenes. To solve this problem, an effective face forgery detection framework based on multi-view learning and consistent representation was proposed. To capture more comprehensive forgery traces, the input image was transformed into two complementary views and a dual-stream backbone network was used for multi-view feature learning. The consistency metric was introduced to explicitly constrain the similarity of local features output from different viewpoints in a patch-level supervised manner. To improve the detection accuracy of the model, the feature decomposition strategy further optimized the forgery-relevant feature to reduce the interference of irrelevant factors, and the decision made from the forgery-relevant feature space was used as the final prediction. Extensive experiments on benchmark datasets show that the proposed method outperforms the existing mainstream approaches with good cross-domain generalization capability.

Abstract:To achieve better electromagnetic characteristics and more stable radiation properties within an ultra-wide band, a novel dual-polarized ultra-wideband tightly coupled array antenna loaded with wide-angle impedance matching layer on a strip frequency selective surface was proposed. The array elements were studied and analyzed through the truncation by the periodic boundary conditions in high frequency electromagnetic simulation software CST. After investigating its electromagnetic properties of array impedance and radiation, a 6 × 6 array antenna was designed, manufactured for actual measurement. The measurement results show that the standing wave ratio of the antenna in the frequency band of 2~12 GHz is less than 3. The impedance bandwidth is 10 GHz. Moreover, the antenna has stable radiation within frequency band, more electromagnetic energy is concentrated in the mainlobe, and the cross polarization is small. In the operating frequency band, the maximum gain can reach 13 dBi. This kind of array antennas can be applied in the ultra-wideband phased array domain.

Abstract:Aiming at the problem of autonomous coordination of networked UAV swarm and the advantages and disadvantages of market auction method, the idea of “computation-for-communication” and its corresponding distributed task scheduling method were proposed. By analyzing explicit and implicit conflicting tasks, a set of task-related agents was established. A local optimization method based on task suppression was proposed to resolve some task conflicts in advance, so as to reduce the number of algorithm iterations. An agent position inference method based on historical bidding information was designed to provide necessary information input for local optimization. Monte Carlo simulation experiments were carried out based on the networking simulation platform and the swarm rescue scenario. The results show that compared with the representative consensus-based bundle algorithm and performance impact algorithm in the market auction method, the proposed method can obtain fewer iterations, shorter convergence time and better scheduling performance.

Abstract:In order to improve the service life of nickel-based single crystal blades and solve the key technology of aeroengine turbine and gas turbine, domestic and overseas researchers carried out a large number of research on the failure and damage mechanism of nickel-based single crystal superalloys under service conditions in recent years. The research achievements and progress of fatigue, creep and thermomechanical fatigue damage mechanism of nickel-based single crystal superalloys under service conditions were concluded. In addition, in view of the time and cost increase caused by a large number of experiments, the research works and achievements in life prediction methods of nickel-based single crystal superalloys in recent years were summarized, and the difficulties and challenges in life evaluation and failure analysis of nickel-based single crystal superalloys were proposed.

Abstract:Based on the technical status and development trend of civil aircraft operation reliability research, the requirements of civil aircraft operation reliability research were expounded according to the current type design, development and actual situation of in-service aircraft. By reviewing the research progress and engineering application status of civil aircraft operational reliability theory, the research status and problems of civil aircraft operational reliability are elaborated from six aspects:operation data acquisition and processing, operational reliability analysis method, operational reliability prediction feedback technology, optimization design based on operational reliability, optimize maintenance tasks, and comprehensive management platform for operational reliability. The future development direction of operation reliability research of civil aircraft is prospected.

Abstract:The application of unified gas kinetic scheme is greatly hindered by the huge requirements of computing resources. Based on Boltzmann-Rykov model equation, a conservative implicit scheme for steady flows in all flow regimes was developed by adopting macroscopic prediction technique, and the macroscopic equation and microscopic equation were solved collaboratively to accelerate the convergence. At the cell interface, a simplified and efficient multi-scale numerical flux was directly constructed from the characteristic difference solution of kinetic model equation. The adoption of non-uniform, unstructured velocity space and velocity space adaptive technology further reduce the requirement of computation and improve computational efficiency. The applications of unstructured discrete velocity space and adaptive discrete velocity space reduced the number of velocity mesh significantly and made the present method be rather efficient. The accuracy and effectiveness of the proposed method were confirmed by the simulations of rarefied supersonic and hypersonic flows over a flat plate, supersonic and hypersonic flows over a sphere. Numerical results indicate that the proposed method can accurately solve two-dimensional and three-dimensional diatomic gas multi-scale flow problems, and it is about one orders of magnitude faster than the explicit discrete unified gas kinetic scheme method.

Abstract:The rubber elastomers, widely used in aeronautical tires, are subject to experience severe dynamic cycling loading during their engineering service. In order to obtain their mechanical characteristics and potential damage mechanisms under those conditions, a dynamic loading methodology was proposed for performing Mullins effect experiments based on stress wave loading. According to the characteristics of stress wave propagation, the dimension parameters of each unit were designed and configured on the basis of Hopkinson pressure bar principle. An experimental system was then built for rubber elastomer materials, and the dynamic cyclic behavior of styrene-butadiene rubber used in tires was obtained. The analyses on the experimental original signals demonstrated that the system can obtain the increasing maximum strain during each cycle, which manifested the system can achieve the dynamic loading of Mullins effect for elastomer. Finally, the loading system specificaitons were discussed for obtaining controllable loading and unloading parameters after finely adjusting system components.

Abstract:In order to study the influence of motion parameters and warhead shape on the oblique entry process of a projectile into water, adopting volume of fraction of gas-liquid two-phase flow and water vapor cavitation model. The three-dimensional kinematics and dynamics of the rigid body were coupled by nested grids, and the motion process of the projectile in the stage of speed 80~100 m/s tilting into water and opening cavitation process was simulated. According to the literature experiments, the prediction errors of the velocity and displacement of the underwater projectile are 0~6% and -8%~0, and the rotation angle error is - 6%~0. Through the simulation study of the water entry velocity and angle of entering water under multiple working conditions, it is found that with the increase of the water entry velocity, the axial impact load of the projectile increases. The maximum load is linearly related to the square of the speed, and the nonlinear attenuation rate of the velocity is large. The larger the angle of entry, the smaller the angular rate of rotation of the projectile body, the stronger the stability of movement. But the velocity decay rate is not affected by the angle of entry.The projectile body adopted a stepped head modification, compared with the conical nose projectile, the average velocity decay rate, rotation angular rate and maximum axial impact load of the body after the head stepped modification are reduced to 66.7%, 40% and 77.2% respectively. The motion stabilitity is improved significantly.

Abstract:Internal waves, occurring in stratified ocean, are ubiquitous in the world oceans. It is of great significance for our country′s marine development to study the generation and evolution of internal waves. Based on the internal wave theory of two-layer and three-layer fluid systems, the KdV(Korteweg-de Vries) internal wave theory, MCC(Miyata-Choi-Camassa) internal wave theory, HLGN(high-level Green-Naghdi) internal wave theory and Dubreil-Jacotin-Long internal wave theory, which were widely used at home and abroad, were selected to review their research progress. The advantages and limitations of different internal wave theories were discussed from mathematical models, theoretical research and numerical simulations. In the view of mathematical derivation, it is proved that MCC internal wave theory is equivalent to the first-level HLGN internal wave theory.

Abstract:Considering the deficiency in the research on transient vibro-acoustic characteristics of cylindrical shell structures, a Jacobi-Ritz semi-analytic method for forced vibration sound radiation of cylindrical shells in time domain was proposed by combining Newmark-β integral method and Kirchhoff boundary element integral equation in time domain. Based on the theory of first-order shear deformation and the idea of element method, a calculation and analysis model of vibration acoustic radiation of cylindrical shell was established. Jacobi polynomial and Fourier series were used to represent the allowable functions of axial and circumferential displacement. The time domain response of forced vibration of cylindrical shell was calculated on the basis of the Rayleigh-Ritz method and Newmark-β integral method. Based on Kirchhoff integral equation, the time domain response of radiated noise was solved, and the acoustic radiation characteristics of forced vibration of cylindrical shell were analyzed. Compared with finite element method/boundary element method numerical results, the proposed method has the characteristics of good convergence and high precision. The peak value of acoustic response of cylindrical structures shifts to the left with the weakening of the boundary condition stiffness, and the vibration acoustic response decreases with the increase of the thickness. When the peak frequency of random load is close to the natural frequency of the structure, strong characteristic line spectrum appears in the acoustic response of the structure.

Abstract:The Blake criterion, which determines the bubble jet direction above a rigid boundary, was obtained through the Kelvin impulse theory. However, the theoretical model has lower prediction accuracy under a specific parameter range. Therefore, a modified judgment criterion for the bubble jet direction was proposed by considering pressure variation inside the bubble and introducing the boundary effect. The boundary element method was used to simulate the results and verify them. Meanwhile, the prediction results of the modified model and the traditional Blake criterion were compared, and the influence of dimensionless strength parameters on the prediction results of the modified model was investigated. Results show that the modified model has higher prediction accuracy than the traditional Blake criterion. The modified theoretical model provides a valuable reference for underwater explosion, seabed geophysical exploration, and related fields.

Abstract:Heavy missile launchers mostly use 4-axles linked dual-chamber HPS(hydropneumatic suspension), in order to study their linkage coupling effect for the reference of launcher design. The simulation models of an interconnected HPS of two-axles and four-axles were built based on the mathematic model and AMESim software. Based on this, the influence of the coupling effect of the multi-axles connected twin-accumulator HPS system was analyzed under several different excitation frequencies. The results show that even under low-frequency excitation, the multi-axis interconnected HPS has obvious damping characteristics. Compared with the two-axles interconnected HPS system, the external characteristics of the four-axles interconnected HPS system have advantages. The external characteristics of the connected HPS system are more intense when excited by low frequency and good when excited by high frequency, indicating that the system can attenuate the asynchronous vibration of the system when it is in a high frequency environment.

Abstract:In order to investigate the impact laws of different factors on the muzzle vibration, a multi-body dynamic model of the wheeled assault gun firing on the move was established and verified with experimental results. A road-surface spectrum model was built by using the harmonic superposition method, and the model was calculated under different road conditions and fire line heights. The influence of these two factors on the muzzle vibration was obtained. The model of a vertical stabilizer was set up, and the co-simulation was carried out to compare the muzzle vibration with and without stabilizers. The research results show that:the muzzle vibration amplitude increases with the increase of road roughness; the influence of fire line heights on muzzle vibration is nonlinear; the vertical stabilizer can effectively control muzzle vibration. Compared to the situation without stabilizer, the maximum muzzle altitude angle and altitude angle velocity amplitudes before firing decrease by 94.1% and 97.4% respectively, and the altitude angle amplitude of the muzzle after firing decreases by 16.2%. This research has certain reference significance for the overall design and engineering application of the wheeled assault gun.

Abstract:Aiming at the problems that the wartime equipment maintenance support task is heavy, the repair time is limited, and the type of maintenance support force does not match the damage demand of the equipment to be repaired, which makes it difficult to achieve accurate battlefield support, the multi-objective action control of wartime equipment maintenance support force was studied. Considering complex constraints such as repair time window, equipment damage state, types of maintenance support forces, changes of maintenance support capabilities and non-traversal, a multi-objective emergency repair action control model of maintenance support forces was established, which aims at the sum of equipment importance, the sum of repaired equipment and the sum of time beyond the repair time window. The NSGA-Ⅱ(non-dominated sorting genetic algorithm Ⅱ) with elite strategy is improved, and the VNS(variable neighborhood search) algorithm is combined to strengthen the local search ability of the algorithm. The improved VNSGA-Ⅱ(variable neighborhood search and non-dominated sorting genetic algorithm Ⅱ) hybrid algorithm is designed to solve the model, and the rationality and effectiveness of the model and algorithm are verified by examples.

Abstract:As the risk of “over-storage” or “under-storage” still exists in the emergency equipment reserve, in order to improve the reserve efficiency, it put forward the flexible procurement strategy of emergency equipment, taking the economic benefit of enterprises and the military procurement cost as the optimization target. By establishing the model of optimizing enterprise reserve strategy and military procurement pricing, the optimal flexible pricing of the military and the corresponding enterprise optimal reserve strategy under the external environmental factors such as the probability of the outbreak of war and the price range of equipment spot market were solved. The decision conclusion was verified by an example analysis. The result shows that the implementation of the optimal strategy would be beneficial for the military and enterprises to share the risk of emergency equipment quantity reserve.

Abstract:To clarify the optimal interference parameters of microwave pulses to navigation receivers, by analyzing theoretically the tracking loop correlation processing of navigation receiver under microwave pulse interference, a interference classification method was proposed on the basis of the relationship between microwave pulse spectral lines, spread spectrum code spectral lines and coherent integration time, the correlation output power and carrier-to-noise ratio under microwave pulse interference with different parameters was further derived, finally experimental verification was carried out. Theoretical analysis and experimental results show that when the microwave pulse width is greater than or equal to the spreading code period and less than the coherent integration time, a spreading code spectral line is interfered with multiple microwave pulse spectral lines which enters the bandwidth of the coherent integrator, the microwave pulse has the best interference effect on navigation receivers, and is better than continuous wave interference; with the increase of the number of interference spectral lines, the correlation output power is increased, the carrier-to-noise ratio is decreased, and the interference effect is enhanced.

Abstract:Based on the research of parallel simulation technology for equipment remaining life prediction, the state equations under different degradation states was unified, the construction method of prediction model library and the selection algorithm of predictive model morphological were proposed, and the online model evolution workflow of “model morphology library construction—model selection—data assimilation—model evolution” was designed. Using extended Kalman filter and maximum likelihood estimation algorithm, the online dynamic evolution of parallel simulation model for equipment remaining life prediction was realized. The effectiveness of the model morphology selection algorithm and the model online evolution workflow is verified by simulation experiments, and good simulation results are obtained.

Abstract:In order to explore the protective effect of pump-jet propulsion submarine under the two typical working modes of electric field protection and impressed current cathodic protection, the boundary element method was used to establish the corrosion-related electrostatic field model of the submarine. The influence of fairing and guide vane on the electric field protection and cathodic protection performance was simulated and analyzed. The results show that compared with the traditional propulsion mode, the peak-to-peak value of electric field of pump-jet propulsion submarine in seawater is reduced by about 38%, and it can achieve better electric field protection effect with only about 50% current value. In addition, no matter whether the whole boat coating is intact or not in the cathodic protection process, the peak electric field at the pump-jet propulsion device is reduced to a certain extent, indicating that the pump-jet propulsion device has better electric field stealth performance. However, in the process of impressed current cathodic protection for pump-jet propulsion submarines, good protection effect can only be achieved at the hull and the major axis. The impeller and guide vane inside the fairing are difficult to reach the protection potential, which is in an under-protection state, so local corrosion protection still needs to be strengthened.

Abstract:In order to study the fatigue characteristics of FRC/steel embedded T-joint, the vacuum forming process (VARTM) and stitching technology were used to make T-joint, and the tension-tension fatigue test was carried out on the joint using the Letry fatigue testing machine. According to the fatigue test results, the initial damage characteristics and damage evolution of T-joints under tension-tension fatigue load were studied; based on the two-parameter Weibull distribution model, fatigue reliability analysis of T-joint connection joints was carried out, and the distribution law of fatigue life of joints under different stress levels was fitted. The fatigue reliability function of joints under different stress levels was given, as well as the stress/life double logarithmic curve relationship (R-lnS-lnN curve) of joints under specified reliability levels.The results show that ln ln[1/R(N)] has a good linear relationship with lnN, and the fatigue life of T-joints follows Weibull distribution; the double logarithmic equation of fatigue life reliability establishes the relationship between reliability, fatigue life and fatigue stress, which can guide the fatigue reliability design and engineering application of joints.

Abstract:An improved CBBA(consensus-based bundle algorithm) was proposed to solve the heterogeneity of task resources carried by multi-UAVs during reconnaissance and strike missions, and the requirements of tasks for heterogeneous resources. Considering the mission value, mission execution time window and range cost, a task allocation model of multi-UAV reconnaissance and attack on ground targets was established.K-medoids clustering analysis method was used to cluster multi-UAVs based on distance and the balance of carrying resources to solve the requirements of multi-UAVs for heterogeneous resource types. The attack task was generated into subtasks, and the improved CBBA was used to solve the established task allocation model. The feasibility and effectiveness of the algorithm are verified by comparison simulation experiments.

Abstract:To transfer the life prediction model, an LSTM-fine-tune(long short-term memory fine tune) model was proposed. The model was trained by using experimental data under ideal conditions. During the transfer process, part of the LSTM network layer was frozen, and other parts of the network were modified by using data in actual service environment. In order to verify the generalization ability of the model, sinusoidal functions with different phases and amplitudes to generate data were used, obtained the knowledge of the sinusoidal function, and applied it to the regression of other sinusoidal functions. The results show that the LSTM-fine-tune model can be fitted quickly, and the average mean square error is only 1.033 5. It is significantly lower than the direct prediction error 1.536 8. In order to test the generalization ability of this method through actual monitoring data, the data of oxygen concentrators under test conditions and actual service environment respectively is obtained, verifies the generalization ability of the model. The results show that the prediction accuracy of the training set is improved by 43.0% and that of the test set is improved by 20.2%.