Recoilless launch can reduce recoil effectively,but it causes the reduction in low muzzle velocity.To resolve the conflict between muzzle velocity and recoil force,a reverse jet recoilless scheme based on combustible cartridge and electromagnetic induction ignition is proposed.Energy is transmitted to the ignition head through electromagnetic induction,which ignites the fast-burning propellant and combustible cartridge in the chamber to provide the launch energy.After reaching a certain level of pressure,the Laval nozzle is opened,and gas is sprayed backwards to balance the forward impulse of projectile.For high muzzle velocity recoilless launch,the loading density and chamber pressure are high,and the interior ballistics is prone to instability.To increase the stability of interior ballistics,a classic interior ballistic model during the shooting process is established,The performance of interior ballistics is analyzed and the stability of interior trajectory is studied through numerical simulation.The ballistic test research was conducted to verify the proposed scheme.The results show that the proposed scheme.can be used to reduce the recoil impulse to below 1.5N·s without reducing the muzzle velocity of projectile.The scheme can provide new ideas for the future development of light weapons.

According to the high torque density requirement for electric drive system of special vehicle,a multi-physics-based multi-objective optimization design and temperature rise estimation method for in-wheel electric machine is proposed to effectively enhance the peak torque and efficiency,reduce the torque ripple and prevent the in-wheel electric machine from overheating.The electromagnetism finite element model and loss models of in-wheel electric machine are established based on the vehicle mission profile.Non-dominated sorting genetic algorithm-Ⅱ(NSGA-Ⅱ) is applied to optimize the peak torque,torque ripple,efficiency,and heat exchange area of winding.Based on the key geometry parameters and losses characteristics obtained,a temperature rise estimation model for electric wheel lumped parameter thermal network including the electric machine is established to estimate the temperature rise and distribution characteristics under typical working conditions.The accuracy of the temperature rise estimation model is validated through a testbench.The result shows that the peak torque and its efficiency of optimized in-wheel electric machine are increased 5.2% and 1.15%,respectively.The root mean square error of the estimated temperature is less than 4.3℃ compared with experimental result,and the calculation effort is dramatically reduced.

The aircraft swarm represents a significant novel force in modern military confrontations and social activities However,the flight safety of aircraft swarm is challenged by complicated airspace circumstances,dynamic flight conflicts and constrained information acquisition.Safety control is essential to guarantee the effective collaboration of aircraft swarm.The key issues of safety control are summarized from the two perspectives of space-time and information according to the characteristics of aircraft swarm and mission scenarios.A research framework of aircraft swarm safety control is proposed based on the observation-orientation-decision-action (OODA) loop.The related concepts,model description and effectiveness evaluation of swarm safety are discussed from the unstructured flight environment,motion behavior,restricted interaction and uncertain state estimation,and the safety control scheme and crucial technologies of aircraft swarm are elaborated.The future intelligent development of aircraft swarm safety control is discussed to provide the reference and inspiration for building a more perfect safety control technology system.

To solve the problems of slow convergence rate and continuous controller updates in formation control, this paper proposes a prescribed-time formation control method based on event-triggering mechanism for second-order multi-agent systems.Based on a prescribed-time acceleration observer, the followers can estimate the acceleration state of leader within the prescribed time.Moreover, a prescribed-time formation controller based on the event-triggering mechanism is designed to enable the followers to keep up with the leader within the prescribed time.The event-triggering mechanism proposed avoids the continuous updates of controller.Through the rigorous theoretical analysis, it is proved that the proposed method can be used to achieve the prescribed-time formation control for the multi-agent systems without Zeno behavior.Simulated results indicate that the proposed prescribed-time formation control method based on the event-triggering mechanism can make the multi-agent systems form a desired formation configuration within a preset time, and reduce the update frequency of controller to save resources.The feasibility and extensibility of the proposed control method are further verified based on the formation flight test results of quadrotor UAVs.

Autonomous underwater vehicle (AUV),as one of the important underwater detection tools,are widely used in various marine military operations.Most of the existing research on AUV obstacle avoidance and path planning focuses on grid maps,and rarely considers the real maneuverability of AUVs under water.In order to solve this problem,an improved proximal policy optimization based on positive-experience retraining (PR-PPO) algorithm and an AUV obstacle avoidance and path planning method based on artificial potential field are proposed.A dynamic artificial potential field is constructed by using the sensor in AUV model and the underwater environment in the simulation software.Based on the PR-PPO reinforcement learning algorithm,the mapping relationship between the AUV state and the action is established by interacting with the environment.Real-time obstacle avoidance and path planning can be realized without dynamic model and map information.The results show that,compared with the traditional D3QN and PPO algorithms,the proposed algorithm can not only ensure the success rate of the task,but also shorten the model training time and improve the convergence effect.

The high-power diesel generator set for vehicles is the power supply unit of heavy-duty series hybrid electric vehicles.Due to the coupling effect of the torque impact of multi-cylinder diesel engine crankshaft and the electromagnetic torque pulsation of generator,the system torsional vibration phenomenon is prominent,and the dynamic quality is poor.A dynamic model of engine-generator set considering the electromechanical coupling effect is established,and the influence of electromechanical coupling effect on the inherent characteristics of the system is analyzed.The law of variation of torsional vibration characteristics with the parameters,such as electromagnetic stiffness,rotor eccentricity and torsional damper stiffness,is revealed.The dynamic response characteristics of the system under the combined excitation of engine and motor are analyzed,and the order of the main response is clarified.A torsional vibration control overall framework based on dual loop decoupling is proposed to solve the problem of excessive low-frequency torsional vibration response.An independent modal space optimal controller for the start stop process and an adaptive filtering compensating controller for steady-state operating conditions are designed for the suppression of engine main harmonic disturbances,and are verified through simulation.The results show that the proposed torsional vibration active control algorithm can achieve the suppression of main harmonic torsional vibration in the full speed domain of the engine.

At present,the traffic management relying on manpower is characterized by inaccurate statistics and delayed feedback.A vehicle detection algorithm based on the improved YOLOv7-tiny algorithm suitable for deploying on edge terminal devices is proposed to better protect people’s lives and property.A deep powerful residual (DP_Res)convolutional block isconstructed to perform the lightweight improvements on the efficient layer aggregation network-tiny (ELAN-T) module of backbone network.By reducing branches,the lightweight improvement on the ELAN-T module of the feature fusion network is made to reduce the number of parameters and computational load of the network,and the structure of the feature fusion network is reconstructed;The efficient channel attention mechanism and the EIOU bounding box loss function are introduced to improve the accuracy of the algorithm.The experiment is conducted on the preprocessed UA-DETRAC dataset,and the parameters of the improved algorithm are reduced by 15.1% compared to those of the original YOLOv7-tiny,with a reduction in computation of 5.3% and an increase in mAP@0.5 of 5.3 percentage points.The experimental results show that the improved algorithm not only achieves lightweight,but also improves the detection accuracy,making it suitable for deployment on edge terminal devices to complete the task of detecting vehicles on the road.

Due to the characteristics of hypersonic glide vehicles (HGVs) being unpowered and uncontrollable in axial overload,a significant positional error of HGV often exists at the transition between the gliding phase and the terminal phase,thereby substantially impacting the precision of coordinated strikes during the terminal phase.To address this issue,a formation control method for HGVs is proposed,which considers the capability of adjusting the position in launch direction.Fixed-time consensus controllers are devised for the second-order multi-agent system,serving as the foundation for an underactuated formation control framework.The underactuated control characteristics of HGV formation is analyzed.An adjustment strategy for HGV position in launch direction is formulated,and an analytical relationship between launch-direction position adjustments and additional lateral velocity is established.After enabling the capability for launch-direction adjustment,a three-dimensional artificial potential field is established,and a collision avoidance control strategy for HGV formation is proposed.Theoretical analysis and numerical simulations demonstrate that the proposed method can support the formation and maintenance of a group of HGVs in scenarios such as dispersion,contraction,collective steering,and high and low flying of formation.

Ceramics will undergo when operating under long-term high temperature and high stress conditions,which promotes the generation and propagation of cracks and eventually leads to failure.The evolution of creep damage is closely related to the microstructure of ceramics.Establishing a microscopic finite element model of ceramic materials is conducive to a more in-depth understanding of this relationship.For this purpose,a dynamics-based 3D crystal deposition model is proposed by taking Si₃N₄ ceramics as the research object.The sintering process of Si₃N₄ ceramics is simulated by the Monte Carlo Potts crystal growth model,striving to reproduce the dynamic growth process of Si₃N₄ ceramics as well as the microstructure characteristics,such as the size,shape and orientation distribution of crystals after crystallization,and the size,shape and distribution of pores.Based on the geometric boundary description generated by this simulation,a Python script is automatically generated to complete the finite element modeling in a FEA software.The statistical elastic constants of Si₃N₄ ceramics are verified using this finite element model.By comparing the calculated results with the experimental data,it is shown rhat the relative error is approximately 4.5%,which shows a good agreement.

In order to improve the stride length and impact resistance of quadruped robots during movement,a cheetah is used as a bionic object to analyze the motion mechanism,and a discrete bionic spine joint with series elastic actuator (SEA) is designed.The SEA is used as the driving unit,which is arranged between the spinal box and leg joints to simulate the characteristics of biological muscles and provide passive compliance.The overall design of the spine adopts 2-DoFs discrete configuration to achieve two running postures of extension and curling,thus improving the stride length.Based on the D-H parameter method,a kinematic model of quadruped robot with 2-DoF discrete spine is established,and the stride length of quadruped robot is analyzed.An experimental platform of quadruped robots with SEA spine is constructed for performance testing experiment.The experimental results under the bound gait show that the stride length of quadruped robot with SEA spine is increased by 73.72%.Compared with the rigid trunk,the SEA spine joint can reduce the peak torques of front leg thigh motor,front leg calf motor,hind leg thigh motor and hind leg calf motor by 35.2%,12.0%,45.7% and 10.3%,respectively,during jumping.And the mean and standard deviation of the output torque of each joint motor are significantly reduced.

The multi-missile aiming points optimization algorithm has the low computation efficiency,weak stability and insufficient optimization capability for the area targets with complex shapes.An efficient aiming point optimization algorithm (EAPOA) based on the damage probability matrix library (DPML) of circular error probable(CEP)and the improved simulated annealing mechanism is proposed.An optimization model of multi-missile aiming points is developed,which takes into account the impacts of the direct damage,the indirect damage,and the combined damage of multi-missiles on the Target damage effect except for target shape irregularity and missile damage capacity.The proposed DPML method can improve the optimization efficiency and robustness of damage probability estimation algorithm.In addition,a candidate aiming point set-based optimization framework is designed,and a heuristic optimization method based on a global searching and improved simulated annealing that is helpful for escaping from local minima is developed.The performance of the proposed algorithm is verified by using six complex area target test cases.The results show that the proposed EAPOA has stronger optimization ability compared with the genetic algorithm with enhanced elite retention strategy,and the average optimization time is only 1/5-1/3,which has obvious advantages in optimization income and computational efficiency.

In order to improve the confidentiality of physical layer of wireless communications,a dynamic double-layer generalized multi-parameter weighted fractional Fourier transform (DDL-GMPWFRFT) secure communication method based on two-dimensional Hénon-cosine-exponent (2D-HCE) chaotic encryption is proposed.A 2D-HCE hyper-chaotic map is constructed by introducing the cosine and power-exponent nonlinear terms to Hénon map,which is verified by using Lyapunov exponential and system bifurcation diagram.64 kinds of double-layer GMPWFRFTs (DL-GMPWFRFTs) are designed and constructed based on GMPWFRFT and double-layer WFRFT structure.2D-HCE chaotic sequence is used to implement the amplitude-phase encryption of constellation,and DL-GMPWFRFT transformation type is randomly selected for the dynamic transformation encryption of constellation to further conceal the modulated signal style and improve the system’s defense ability against parameter detection.Simulated results show that the constellation map encrypted by the proposed method presents a Gaussian distribution,and the keyspace is up to 2²¹⁸.The key sensitivity is much higher,and the bit error rate of eavesdropper is still in the range from 0.4 to 0.5 even if there is an error of 10^-15 between the key from an eavesdropper and the correct key.

A modeling method is proposed for a pneumatic drum braking system in military double-trailer truck,which takes the response delay of pneumatic braking,the brake fade due to temperature increase during braking processes,and the dynamic involvement of anti-lock braking system (ABS) into considerstion A model of pneumatic braking system is established by analyzing its structure and operating principle.A co-simulation of the pneumatic braking system model and the vehicle’s multi-body dynamics model is conducted to validate theaccuracy of proposed model.The effects of different road adhesion conditions on the braking performance of actual vehicle are analyzed through simulation.The results show that the simulated chamber pressure,vehicle speed,braking distance,and braking time are highly consistent with the experimental data,with the prediction errors for braking distance and time being less than 3.9% and 2.4%,respectively.Furthermore,the braking performance under various road surface adhesion conditions is simulated and analyzed.The results confirms the model’s effectiveness,further substantiating the feasibility of the proposed modeling method.

Aiming at the issue of optimal energy consumption of UAV time-varying formation under multiple constraints,an optimal control method based on an dynamic parameter extended high-order control barrier function is proposed.The method is used to improve the existing high-order control barrier function.In consideration of the motion states of UAV and obstacles,an the extended state dynamics model is established.The safety constraints of dynamic target obstacle avoidance are expanded on the extended state dynamics model,and the extended high-order control barrier function used to establish dynamic target obstacle avoidanceis obtained.For the feasibility and conservatism of the extended high-order control barrier function constraints,the adaptive rules of the class K function parameter are designed to obtain the dynamic parameter extended high-order control barrier function,which improves the feasibility and reduces the conservatism for the solution of constraint optimization problem.The control barrier function and the extended high-order control barrier function are used to establish the multi-constraints,and an objective function is established by the consistency condition and Hamiltonian analysis.The energy consumption optimization problem of time-varying formation is transformed into a multi-constraint optimization problem,and the quadratic programming is used to solve the problem to obtain the optimal control input.Simulated results demonstrate that the proposed method has superior obstacle avoidance and lower energy consumption compared to the fixed parameter high-order control obstacle functions and the artificial potential field.

The traditional loop closure detection algorithm relies on the accuracy of odometer and the external global positioning information,which consumes too much computing resources,and the existing lightweight loop closure detection algorithm has poor translation invariance and difficulty in adapting to the sparse environmental characteristics in off-road road environment.In order to improve the positioning capability of unmanned platform in the condition of satellite rejection for a long time and a large range of tasks,a lightweight loop closure detection algorithm using light detection and ranging (LiDAR) point clouds to describe the ground feature is proposed.It is different from extracting the point cloud features from single or multi-frame point clouds by deep learning.And a global descriptor is constructed.The fast LiDAR point clouds ground feature description approach is used to achieve the fast feature extraction of single frame point cloud and the globally consistent position feature description,and the multi-frame LiDAR point clouds ground features are aggregated into the sub-map loop closure detection descriptors.A lightweight global descriptor is constructed by odometer pose between adjacent frames,and the global descriptors are matched and the loop closure detection is realized without prior position information.The proposed algorithm is verified by using the mechanical and solid-state LiDAR in off-road environment.Compared with the existing lightweight loop closure detection algorithms,the proposed algorithm has the advantages of high recall rate,good real-time performance and less resource consumption in the off-road environment.

In order to investigate the influence of different nose shapes on the oblique penetration of jacketed rods into the metal targets,the experiments are conducted for three types of jacketed rods with varying shapes obliquely penetrating 4340 steel targets at 45°.The jacketed rods and tungsten alloy projectiles are compared through numerical simulation,and the penetration processes and characteristics of the three kinds of jacketed rods are analyzed.The results indicate that,compared to homogeneous tungsten alloy projectiles,the jacketed rods exhibite superior penetration performance under the same kinetic energy oblique penetration conditions.However,the significant resistance difference between the jacket and the core of the jacketed rod results in more severe trajectory deviation.When the jacketed rods obliquely penetrate into 4340 steel targets at 45° at about 1450m/s,the jacketed rod with hemispherical nose demonstrates superior trajectory stability,while the jacketed rod with truncated cone nose exhibites the most significant trajectory deviation.The oblique penetration process can be delineated into three phases:head coarsening deviation,stable oblique penetration,and penetration termination.The trajectory deviations of the jacketed rods mainly occur after the head coarsening deviation stage.The fundamental factors influencing the trajectory deviations of the jacketed rods are the lateral force acting on the rod nose at the penetration hole-opening stage and the morphology of the penetration hole.The angle between the direction of the combined resistance force experienced by the jacketed rod truncated cone nose with at the head coarsening deviation stage and the axial direction of jacketed rod is maximized,resulting in the largest deflection torque and maximum bending deformation of the nose.Additionally,the lower side of the initial penetration hole is nearly parallel to the inclined cone surface of the nose,leading to the maximum trajectory deviation.On the other hand,the jacketed rod with hemispherical nose experiences the smallest deflection torque at the penetration hole-opening stage,thus it possesses better stability in the penetration.At different impact angles,the trajectory deviation of jacketed rods with truncated cone nose is most affected by the changes in the impact angle,while the jacketed rods with hemispherical nose are least affected,exhibiting the best trajectory stability during oblique penetration.

The parachute landing injuries of paratroopers have been a focal point in aviation medicine and special medical studies.It is very important to investigate the biomechanical mechanisms of landing injuries for the protection and prevention of parachute landing injuries.The factors influencing the lower limb injuries of paratroopers subjected to landing impact are numerically simulated by using the global human body models consortium (GHBMC) full-body finite element model.The findings indicate that the long bones of the lower limbs such as femur and tibia are less likely to be injured during normal landing impact.However,the calcaneus,talus and meniscus are susceptible to injury due to compression from the long bones,and the vulnerable area includes the medial tubercle of calcaneus,the trochlea of talus,and the anterior horn of lateral meniscus.The study also reveals the variations in injury mechanisms in different landing scenarios.The descent speed significantly affects ground impact forces,thereby greatly increasing the probability of stress fractures in the long bones of lower limbs.The horizontal wind speed can alter the center of gravity to increase the likelihood of ankle injuries.The ground conditions influence the duration of impact contact,increasing the probability of injuries to the ankle,particularly the calcaneus.

In order to accurately reveal and describe the overload environment and dynamic response of the core components inside the fuze of projectile-fuze system in the process of penetrating into typical targets,the interaction between projectile and target during penetrating are obtained based on the cavity expansion theory,and the propagation effects of stress waves inside the warhead are analyzed.The load transfer characteristics of threaded connection between warhead and fuze and the nonlinear response mode of a cushioning material are introduced.A nonlinear dynamic response model of projectile-fuze system under high-speed penetration is constructed,and the model parameters are determined by using the theoretical and experimental methods.The dynamic response characteristics of projectile-fuze system and the influence mechanisms and regularity of projectile and target parameters on overload signals are researched through finite element numerical simulation.The results indicate that the time-frequency domain characteristics of the proposed nonlinear dynamic response model consistent with the numerically simulated results well,which can more accurately describe the overload transfer characteristics of projectile-fuze system and the real dynamic responses of internal components under high speed penetration.The response mode is mainly the coupling superposition of rigid overload and high frequency structural vibration,the threaded connection amplifies the overload signal,and the polyurethane material exhibits a certain energy absorption and filtering effect in the penetration and impact environment.The overload signals of the projectile-fuze system penetrating a multi-layered target are more complex and intense those when penetrating a single semi-infinite target.The frequency characteristics of interaction between projectile and target are determined by projectile and target parameters.When the frequency of interaction between warhead and target in penetrating multiple layers of spaced targets is closer to the integer multiples of inherent frequency of projectile-fuze system,the acceleration overload exhibit the phenomenon of significantly increased peak,intensified oscillation,and severe signal adhesion.The research results provide the technical references for rapidly and effectively predicting the real response and overload characteristics of critical modules inside the fuze under the conditions of different projectile and target characteristics and evaluating its safety and reliability,and the integrated design and optimization of projectile and fuze.

To meet the increasingly complex operational demands and improve the guidance performance of micro-guided munitions at close range,a impact angle constraint guidance law based on deep reinforcement learning (DRL) is proposed by considering the field-of-view (FOV) limitations.The estimation formula for the impact angle error of missile relative to a moving target is derived,the impact angle error and view angle are used as state variables,and a piecewise reward function is constructed.The guidance problem is modeled as a time-discrete Markov decision process (MDP).The required guidance commands are obtained through biased proportional navigation,and a bias term is output by the DRL policy network.The network is trained using the proximal policy optimization (PPO) algorithm,resulting in an optimal guidance strategy that ensures the constraints on both view and impact angles without information about missile-target distance.Numerical and Monte Carlo simulations under different initial conditions and the comparative analyses of capture regions of missiles at various speeds are conducted.The results show that the proposed guidance law maintains excellent guidance performance under various initial conditions,provides a larger capture region in close-range engagements compared to existing guidance laws,and demonstrates a smaller impact angle error distribution under interference,thus validating its effectiveness and superiority.

The dynamic three-point bending test of zirconia ceramics is carried out by using the split Hopkinson pressure bar (SHPB) device combined with a newly designed fixture.The fracture initiation time of the specimen is determined by the strain gauge and finite element simulation,and the bending strength of the specimen is calculated from a transmission bar signal.It is found that the fracture initiation time of the specimen matches well with the peak moment of the transmitted wave,so that the peak value of the transmitted wave can be used to determine the bending strength.The force equilibrium of the specimen during loading is verified by analyzing the experimental data.In addition,the accuracy of determined fracture initiation time is verified by high-speed photography.The results show that the bending strength of the specimen shows a positive correlation with the loading rate and the fracture initiation time of the specimen shows a negative correlation with the loading rate in the loading rate range of 85.4-239.7TPa/s.With the increase in loading rate,the failure mode of zirconia ceramic specimens changes from a mixture mode of transgranular fracture and intergranular fracture to a failure mode dominated by transgranular fracture.

For the interception issue of multiple intruders in area defense missions,a multi-UAV sequential capture algorithm is proposed by taking into account the temporal relationship between pursuit tasks and the overall interception effectiveness.The temporal and spatial rewards are constructed based on the long-term planning benefits and short-term execution effects of the tasks,which serve as the optimization objectives for task allocation and execution,respectively,and the dynamic and real-time solutions are achieved for complex game-theoretical problems.A reachability-set-based approach is used to describe the advantage levels of both attackers and defenders,and a deep Q-network is introduced to estimate the temporal rewards for tasks and then guide task allocation.The single attacker pursuit-evasion game problem is solved based on the spatial reward of task,and an optimal control strategy is presented for task execution in a continuous action space.Simulated results show that the peoposed algorithm optimizes the temporal and spatial rewards to facilitate the effective cooperation among multiple UAVs,enhances the capture success rate of the defenders,and has an increased scalability.

Global navigation satellite system(GNSS)users are often located far away from satellites,making them vulnerable to intentional interference and deception.Ensuring the provision of high-precision navigation positioning,speed measurement,and timing information to GNSS users becomes a primary task in navigation warfare.To enhance the anti-jamming capability of user-ends and promote the development and maturity of their anti-jamming technologies,there is an urgent need for doing research on user-end anti-jamming performance evaluation.The existing studies have mostly focused on single-type indices or specific application scenario when researching user-end anti-jamming algorithms and analyzing their performance,resulting in insufficient research on related evaluation.Therefore,this study sets up typical application scenarios,such as single-antenna anti-jamming,array antenna anti-jamming,inertial navigation-assisted anti-jamming,and unmanned aerial vehicles(UAV)anti-jamming,and establishes a user-end anti-jamming performance evaluation index system based on multi-application scenario.Furthermore,the method including availability(A),dependability(D)and capability(C)is introduced to improve the limitations of existing models,and a sub-item performance evaluation method for user-end anti-jamming is proposed.Finally,based on fuzzy comprehensive assessment approach and improved combination weighting method that enhances the existing weighted product models,a comprehensive capability assessment method for user-end anti-jamming is proposed.The experimental results show that compared with the existing models,the proposed method is used to realize the serial connection of multiple models in the application scenario,reduce the tracking threshold of receiver to less than 45° and the dynamic measurement error rate to less than 1,and increase the array gain to no more than 36 dB,thereby improving the accuracy of the performance evaluation of the measured equipment and its ability to resist jamming threats.It can effectively assist the upgrade and performance optimization of the equipment in multiple application scenarios.

The recovery device carried outside the vehicle is susceptible to the interference from flow noise and has an effect on the acoustic stealthiness of underwater vehicle during the acoustic guidance.Regarding the aforementioned problems,this paper numerically simulates the flow noise of underwater vehicle based on Lighthill acoustic analogy theory and large eddy simulation (LES),compares the sound pressure level spectra and directivities of different shaped docking stations,and analyzes the sound pressure levels at different locations in the basin.The results show that the outboard recovery device is the main source of the radiated noise,which is about 50 dB higher than the maximum sound pressure level of the non-attached underwater vehicle,and the high sound pressure level is mainly concentrated between the middle and low frequencoes.For the recovery dock with the same profile areas,the maximum sound pressure level of horn-shaped guide housing is 1.62dB lower than that of the rectangular guide housing.The results can provide theoretical reference for reducing the flow noise during the process of underwater vehicle recovery and improving the recovery efficiency and acoustic stealth of underwater vehicle.

A cold metal transfer (CMT)-wire-arc additive manufacturing technology is used to fabricate high nitrogen steel walls at the interlayer temperatures of 50℃,150℃ and 250℃,and the relationships among the interlayer temperatures,the resulting microstructures and the material properties are studied.The results show that the interlayer temperature has significant effect on the forming quality,and the optimal results can be obtained at 50℃.The additive manufactured parts are primarily comprised of austenite and ferrite,where the ferrite is distributed within the austenite matrix in a skeletal and worm-like manner.The interlayer temperature can be reduced to enhance the cooling rate of the molten pool,reduce the spacing between secondary dendrite arms,and inhibit the growth of nitrogen bubbles,thus diminishing the size and number of micrometer-sized nitrogen pores and minimizing nitrogen loss.However,the hardness and tensile strength decrease as the interlayer temperature increases.Lower interlayer temperature promotes the formation of fine grains,enhancing hardness.Higher interlayer temperature lead to grain coarsening,reducing hardness.Regarding the tensile properties,the lower interlayer temperature strengthens the tensile strength,whereas the high temperature improves the ductility through the precipitation of a second phase.The material exhibits anisotropy,and the transverse specimens have superior tensile strength.The fracture morphology reveals a micro-void coalescence fracture mode,where the presence of manganese oxides and nitrogen pores adversely affects the tensile performance of additive manufactured workpiece.Moreover,the defects such as gas pores can act as initiation sites for corrosion,while the chloride ions facilitate the formation of primary cells on the surface of high-nitrogen steel,leading to chloride ion erosion.Nitrogen in solid solution can prevent a decrease in the pH value of solution in high-nitrogen steel,facilitate the rapid repassivation of sample surface,and prolong the maintenance of passivation state.However,an increase in interlayer temperature results in a decrease in the nitrogen content,which leads to reduced corrosion resistance of the additive manufactured parts.

In a complex communication environment,it is difficult for the global navigation satellite system (GNSS) to provide users with stable and accurate location information.An enhanced adaptive genetic location (EAGL) algorithm is proposed to solve the problem of positioning bias caused by the uncertainty of measured data.In the proposed algorithm,a localization model based on time difference of arrival is established to reflect the relationship between the location of target source and the signal environment.The possible solutions satisfying the objective function are encoded in real number,and the fitness function is established,which is used to calculate the fitness value of each individual.The selection operation is performed on the population,and the improved adaptive crossover and mutation operation are used to improve the genotype quality of the population and avoid falling into the dilemma of local optimal solution.The genotype of the individual with the highest fitness value is obtained by iteration to get the exact coordinates of a target source.The simulated results show that the positioning accuracy of the proposed algorithm is higher than those of the simple genetic algorithm (SGA) and Chan-Taylor algorithm.With the gradual increase in the error of the measured value,the error fluctuation of EAGL algorithm under different error conditions is the smallest.As a result,EAGL algorithm is stable and capable of achieving the high-precision positioning.

With the progress of information technology,the human-computer interaction modes of armored vehicles have been constantly updated.In order to explore the mission performance of occupant in new multimodal interaction and guide the design of multimodal operation and warning modes of future armored vehicles,a human-computer interaction experimental system which integrates multimodal interaction and adjusts the environmental load is established.Based on this system,20 adult males were recruited to conduct an ergonomics experiment involving operation (input) mode,warning (output) mode and environmental load level. The simulated target hitting experiments under different experimental conditions are performed in a virtual experimental platform,and the mission performances of occupants are analyzed.The experimental results show that the reaction time of occupant under mechanical input is the shortest and the operation error rate is the highest compared with those under touch input or voice input.The mission completion time of occupant under mechanical input and touch input is much shorter than that under voice input.Compared to the single modal visual (V) warning,the visual+tactile (V+T) dual-modal warning superimposed with tactile warning is used to significantly shorten the reaction time of occupant,while the visual+auditory (V+A) dual-modal warning superimposed with auditory warning has no significant difference.V+T or V+A dual-modal warning can significantly shorten the mission completion time of occupant.For the influence of environmental load,the mission performance of crew under low environmental load is significantly higher than that under high environmental load.As the environmental load increases,superimposing A warning in V+T warning will cause warning redundancy.The research can provide a practical basis for the design of multi-modal human-computer interaction in the armored vehicle cabin.

The presence of positive feedback mechanism affecting the stability of combustion process as the plasma jet expands in a liquid media limits its further practical application.In order to explore the expansion characteristics of plasma jet in an integrated liquid working medium,a two-dimensional axisymmetric unsteady mathematical physical model of the interaction between plasma jet and liquid working medium is established and verified.A four-stage gradually expanding liquid-filled chamber structure is designed,and the expansion characteristics of plasma jet in liquid propellant LP1846 are numerically analyzed.The spatial and temporal distributions of the characteristic parameters,such as pressure,velocity and temperature,in the plasma jet field were obtained.The results show that the four-stage gradually expanding liquid- filled chamber structure can be used to enhance the radial expansion ability of plasma jet in the chamber and the radial influence range in the high pressure and temperature region of plasma jet head,so as to control the axial expansion speed and pulsation of plasma jet.The liquid propellant LP1846 with high viscosity and density is used to simulate the working medium,The gradually expanding liquid-filled chamber structure can slow down the axial expansion speed of plasma jet,effectively inhibits the Kelvin-Helmholtz instability and Taylor instability,and helps to enhance the expansion stability of plasma jet.The near-field pressure and temperature fluctuate due to the alternating generation of expansion and compression waves near the nozzle.

Individual equipment is closely related to the user’ height and weight as well as the task division,and has the characteristics of high customization and mass production,which bring great challenges to the production and delivery of individual equipment.Packing is the last step of individual equipment production,and is also the most difficult step to achieve customization and mass production.To solve this problem,an optimization method of individual equipment packing production process based on digital twin is proposed.First,a digital twin model of individual equipment packing production process is established.Secondly,the whole production process of individual equipment,such as distribution and replenishment,transportation,workers’ picking and boxing,is described by simulation,and the production process is optimized by an improved genetic algorithm.Finally,the proposed method is actually applied in equipment production.The optimal design and optimization of the cargo location,the number of workers and the number of handling equipment are realized by iterative simulation,thus effectively solving the problems of highly dynamic,congestion and transportation conflicts,long production cycle,unbalanced busy and idle stations,and delayed detection of misloading in large-scale customized production of individual equipment.The production efficiency of soldier equipment packing is improved by 11.18%.

Wingless payload is a common type of payload in the rocket sled test system,which is susceptible to head-up and head-down phenomena during separation due to the multi-field coupling of unsteady aerodynamics,vibration and aeroacoustic noise during the horizontal running in a wide speed domain.The,acoustic-vibration force coupling of horizontal boost glide in a wide speed domain ( Mach number of 0.4-2.0) is numerically simulated by taking a wingless payload test system of double-track rocket sled as the research object.The results show that a low-pressure region is generated between the payload and the booster during running,and the range of action is continuously expanded with the running speed.The aerodynamic load of high-speed flow field gradually makes the rocket sled produce large deformation at the head and tail positions of the payload,which is mainly manifested as a “head-up” phenomenon.The aerodynamic noise of the horizontal booster running in the wide speed domain increases with the running speed,and the high sound pressure level region gradually expands from the center to the periphery.The relevant research can provide technical support for the design of new generation of hypersonic rocket sled test system and the high-precision ground dynamic test.

In order to improve the obstacles avoidance ability of intelligent vehicles,an trajectory planning and control method of intelligent vehicles is proposed based on velocity obstacle model.The proposed method is used to establish a velocity obstacle model for intelligent vehicles by combining the velocity obstacle method and obstacle expansion method,The motion uncertainty of dynamic obstacles in the velocity space is transformed into the positional uncertainty,and the safety margin is adaptively adjusted by obstacle size and relative velocity.To balance trajectory tracking accuracy and driving stability,a fuzzy model predictive controller (FMPC) is designed based on the equation of state for vehicle,the fuzzy control principle and the model predictive control principle.A simulation model is established to verify the effectiveness of the proposed method.The simulated results show that the proposed method can be used to avoid the multiple random static and dynamic obstacles,and the reference trajectory can be quickly and smoothly tracked after obstacles avoidance.Based on the analysis of obstacles avoidance stability,it is concluded that the target speed is 100km/h,the maximum lateral speed is 4.01km/h,the maximum yaw rate is 20.8°/s,and the maximum centroid side slip angle is 2.32°,which meet the requirements of driving stability.The proposed method effectively improves the obstacle avoidance ability and driving stability of intelligent vehicles.