Abstract:Structural integrity is an important attribute of aircraft structure. Generally, the description of structural integrity is a qualitative description, which emphasizes the maintenance of structural integrity. However, a lack of quantitative description on structural integrity is disadvantageous to the comprehensive development of structural integrity. For this reason, a concept of structural integrity is proposed in this paper. A quantitative measurement is proposed to measure the structural integrity by the structural integrity degree, and the structural integrity degree is evaluated based on the safety degree, intact degree, survival rate and availability degree of the structure. A structural integrity control concept, taking the maximum structural integrity degree as an optimum structural integrity control scheme, is put forward. And the basic connotation of structural integrity control, including the openloop control, the coordination control and the weighing control, is expounded. Finally, the basic task of the structural integrity control is expounded by the framework of the Establish/AssessmentSustainmentValidationRecovery/Increment–Control. The measure and control method of aircraft structural integrity proposed in this paper is also applicable to the structural integrity of other equipment.

Abstract:Aimed at the problems that military competition and confrontation in the near future is present to the system of the multimedia space, and the most activeservice navigation vehicles are still limited to the single medium space, this paper proposes a brandnew vehicle named airwater transmedia vehicle, conceives a transfiguration vehicle which can travel in multimedia, analyzes the key technologies, and presents the future developing conception.

Abstract:In order to study the effects of the depth of the deflector on the focusing process of the circularshaped cavity in the radial direction of the incident shock wave, experiments are carried out to investigate the radial incident shock focusing with Mach number 1.4 in cavity where the depths of deflectors are 0、5、10、15、17.5、20、25 mm respectively. With the schlieren photos of flow field in cavity captured by highspeed CCD camera, the dynamic pressure sensors is used to measure the pressure variation of the flow field during the focusing process, the behavior of radial incident shock wave reflect and focus in a circularshaped cavity is described. The shock wave focusing processes of different depth of the deflectors are compared. With the increase of the depth of deflectors, the outlet width of the cavity is reduced, and the discharge of the airflow is restricted, resulting in the enhancement of turbulence inside the cavity, due to the strong influence of turbulence, the internal shock wave structure is weakened, which has an impact on the high temperature and high pressure area caused by shock focusing, and is disadvantageous to shock detonation.

Abstract:A method for identification aeroengine rotor-stator rub-impact fault is proposed in view of the concept of the flexible casing design for dualshaft aero-engine. Rub-impact is recognized through seeking the characteristic frequencies from dynamic strain before strain bridges should be installed in the inlet or intermediate casing. A simplified rotorcasing rubimpact dynamics model is established, and the dual-shaft engine rubbing characteristic frequencies are analyzed. Through seeking the characteristic frequencies several rubimpact faults are identified accurately in flight test at a certain aero-engine. Theoretical analysis and flight test show that the casing strain can sensitively pick up rub-impact vibration signals. When rub-impact fault occurs the combined frequencies of the highrotor and lowrotor rotational frequency mΩH±nΩL will appear in vibration spectrum, and the rub-impact fault can be judged from the combined frequencies. The combination frequencies mΩH±ΩL appeared in vibration spectrum are felt to locate a high-pressure rotor rubbing. Similarly, the combination frequencies ΩH±nΩL are felt to a locate low-pressure rotor rubbing.

Abstract:According to the different flight principle and movement characteristics of takeoff at two points and takeoff at three points, two models of mathematical simulation under condition of different takeoff modes are established respectively in this paper. Based on the aerodynamic characteristics of aircraft and the characteristics of landing gear system, the simulation results are carried out according to the whole design parameters, and the performance data of different takeoff modes are given. Taking a certain type of aircraft as an example, the takeoff performance program is programmed to calculate the takeoff performance. Finally, the effects of two different takeoff modes on the distance and velocity of each takeoff phase are analyzed, and the relevant conclusions are given based on the actual flight characteristics of the aircraft，and the accuracy of the simulation model is verified, and a fairly good takeoff mode is given to guide a pilot in flight.

Abstract:In order to reasonably determine the best time for preventive maintenance of cement concrete pavement at military airports, the relationship between the pavement damage index and IRI is established on the basis of the analysis of the existing highway and airport pavement performance model. The decision model of preventive maintenance time for cement concrete pavement of military airport is obtained, combined with the pavement damage index decay model and the damage indexIRI relationship. Based on the current situation that our army still mainly uses the threemeter ruler to test the roughness and a large amount of measured data, the correlation between the IRI and the average clearance of the threemeter ruler is established. Based on the fact that the performance data of cement concrete pavement in military airport accumulate less, the damage status and flatness data several airport cement concrete pavements with similar service environment to our army fitted and analyzed using the method of space generation time. The correctness of the preventive maintenance timing model has been verified, and the specific parameters of the model have been obtained. It can be found that the fasted decay threshold of the damage index, unique to that exists, by the damage indexIRI relationship. Then the damagedecay model is used to find out the useful life of this value, which is the best preventive effect maintenance time.

Abstract:In view of the designing method for C2 structure and action plan in manned/unmanned aerial vehicle (MAV/UAV) cooperative engagement system based on the granular computation theory, a hierarchical adaptive design method is proposed. The plan is classified into four smaller subproblems, i.e., platform marshalling scheme generation, task schedule scheme generation, platform marshalling scheme adjustment, and task schedule scheme adjustment, reducing the problem solving scale by so doing. Firstly, an adaptive design framework is established, and a formalized description to key element attributes is given. Secondly, the coupling relationship of subproblems is analyzed in detail, and lastly, the corresponding adaptive design methods for four subproblems are presented.

Abstract:According to the secondorder coherence of thermal light applied in optics, such as associated imaging, clock synchronization, and correlated ranging, etc. under condition of extending the knowledge mentioned above into the microwave frequency band, thermal microwave signal can be utilized for carrying out the second-order coherence navigation ranging and angle measurement. The process of the thermal microwave signals based ranging and angle measurement by using secondorder coherence reads as follows. First of all, a power splitter is utilized for splitting the prepared thermal microwave signal into two equal power paths, and two thermal microwave signals are transmitted through two antennas. At the receiving end, the realtime power of two signals is measured by signal receiver, then the correlation operations on the measured power waveforms are made. Through the extraction of correlation peaks, the distance difference between the two channels of signal propagation is calculated, then the target azimuth information is derived from the principle of interferometric angle measurement. The result shows that due to the truly random nature of the thermal microwave signals, the problem of integer ambiguity caused by periodicity of signals in traditional radio navigation positioning is solved. And the antinoise performance, and the antimultipath capability ate better, and the positioning accuracy is improved.

Abstract:In view of airtoground quantum communication of the AEW platform, in this paper, the main factors influencing transmission channel are analyzed. On the basis, a process of airtoground quantum is constructed to facilitate twoway pointing and tracking, and then to fulfill the transmission of quantum bits. A quantum widearea network can be established based on this communication process, which is composed of multiple airplatforms, ground stations and etc. Three kinds of routing strategies are proposed, and then analyzed based on the different communication nodes, and its feasibility is verified. Finally, the quantum bit error rate of the transmission is analyzed. The simulation results show that the improvement of channel coefficient, the reduction in the deviation angle of measurement based, error caused by entanglement swapping and classical information can result in a decrease of the transmission error rate.

Abstract:Aimed at the problems that in the existing high frequency communication, the frequency parameter prediction methods are tedious formalities in operation and shortage in precision, this paper presents a prediction model of frequency parameters of shortwave communication based on long shortterm memory recurrent neural networks. This neural network can break through the limitations of traditional neural networks and establish longterm correlations on data sequences. The experimental results show that the mean square error (MSE) can be control below 2% and the model reduced the error by 7%. And this method is effective and superior to the traditional prediction method.

Abstract:In the light of the asymmetric channel of intersatellite optical communication subject to pointing errors, an optimal signal input probability distribution can be found to maximize the mutual information of the link. Considering the aperture size of receiving antenna, beam width and the parameters of pointing errors distribution, the channel matrix of intersatellite optical communication is given, and the optimization model of mutual information is established, when the pointing errors obey Beckmann distribution. The Lagrange multiplier method is used to solve the model, and the closed expression of the signal input probability distribution is obtained when the mutual information is maximized. Through numerical simulation, the optimal signal input probability distribution, channel capacity and the difference of mutual information vary with the normalized decision threshold, beam width and the parameters of pointing errors distribution are analyzed numerically. The simulation results show that the mutual information between input signal and output signal under the optimal signal input probability distribution is obviously higher than that under the equal probability distribution. Using the results of numerical simulation, the optimal source input can be selected on the basis of known distribution of pointing errors, so that the intersatellite optical communication channel can achieve the maximum information transmission capacity.

Abstract:A new network security risk assessment method based on hidden Markov model is proposed in order to accurately assess the network security risk in real time. The method is based on Hidden Markov model to model the target network. The security risk of node is quantified by direct risk and indirect risk caused by correlation of the node. Considering the importance of nodes in the network, the overall security risk of the target network is quantified on the basis of node security risk. The experimental results show that the method can quantify the network security risk caused by the correlation and importance of the node, which makes the network security risk assessment results more accurate and credible. Compared with traditional network security risk assessment methods, this method can detect abnormal risk changes in the work more timely ,which can provide the basis for the timely adjustment of the network security defense strategy.

Abstract:To meet the practical needs of large thrust, high energy and special electromagnetic environment in the process of the missile launching and reducing the magnitude of the driving current, a mode of the missile’s entire augmented electromagnetic rail launcher by quadrupole magnetic field and a mode of the missile’s segmented augmented electromagnetic rail launcher by quadrupole magnetic field are proposed. The energy conversion efficiencies of two models are analyzed theoretically and recounted by the specific example. Current distributions in rails, thrust performances of models and loading characteristics of the launcher’ modules are studied by the finite element analysis. The results show that the segmented augmented model’s energy conversion efficiency is higher than entire augmented model’s, and increases with the number of segments. Under the action of the protector plate, the proximity effects of currents in rails of two models are alleviated. Propulsive force of augmented models is higher than that of the basic model, the driving current magnitude can be reduced to guarantee the same propulsive force. The rail and the protector plate of segmented augmented model take less force, and they are periodic changes in the launching process, while the rail and protector plate of the entire augmented model take more. These augmented models both optimize the launcher’s performances in varying degrees. This can apply the missile electromagnetic launch engineering practice with theoretical guidance The comprehensive performances of the segmented augmented model are better than that of the entire augmented model.

Abstract:Hostile and complex environment causes the subsurface corrosion for inservice aviation structures, posing a severe threat to the structural integrity. As for the integration of pulsed eddy current testing with uniform excitation yields Gradientfield Pulsed Eddy Current testing(GPEC), the gradientfield pulsed eddy current testing has reflected its advantages in detection and evaluation of corrosion in conductive structures. This paper focuses on experimental investigation of GPEC further. Aimed at the problems that the imaging information of subsurface corrosion obtained in aviation structures is not abundant, the paper further proposes the relevant imaging processing along with a new image feature proposed. The proposed imaging processing method is further discussed regarding superiority in subsurface corrosion visualization. The results show that the image feature extracted from the postprocessing images has the linear correlation with the corrosion depth, which, in conjunction with acquired corrosion images, and benefits the quantitative evaluation of subsurface corrosion in aviation structures.

Abstract:The feature analysis and extraction of lowaltitude targets based on LTE signal is of great significance for lowaltitude target surveillance and key site protection. One of the core techniques of LTE communication signals is multi carrier orthogonal frequency division multiplexing (OFDM), i.e. Time Division Duplex (TDD) and Frequency Division Duplex (FDD). In this paper, a radar echo model of lowaltitude targets with rotors is established based on FDDOFDM signal, the parameterized expressions of Doppler and microDoppler of target scattering points are derived, and the factors of microDoppler frequency of rotating parts are analyzed. On this basis, the micromotion parameters of the target are extracted by a method consisting of time frequency analysis and Hough transform. The feasibility and the validity of feature extraction of lowaltitude micromotion targets are verified under passive FDDOFDM bistatic radar.

Abstract:To deal with the problem of multipoint source interference including main lobe interference, the two methods of suppressing the mainlobe interference based on blocking matrix preprocessing and based on eigenprojection matrix preprocessing are quite good in antiinterference effect, and their main ideas are mainlobe interference eliminated by pretreatment of first, then the conventional adaptive beam formation, the implementation of the mainlobe interference suppression, but the two methods need to expect a prior information matrix to construct the pretreatment and interference .Aimed at the problem that the prior information fails to be obtained directly in the practical application, a new type of principal antimultipoint source interference algorithm without prior information is proposed in combination with the method of the preprocessing of the characteristic projection with the estimation of the arrival direction of the strong and weak signal. The simulation results show that the proposed method is fairly good in the effectiveness of antimultipoint source interference effect without knowing the prior information of angle.

Abstract:In view of the new generation HF 3GALE signal applied in US Army to multiple data encoding on communication link layer to improve the transmission reliability of its protocol information, a modified pulse jamming method is proposed against such multiple data encoding. Firstly, a jamming model affected on the periodic pulse signal which can be in advance scrambled by public pseudo random scrambling sequence is built up. Then, on the basis of formula derivation for signal receiving and processing, the impacts on jamming performance are analyzed from some jamming parameters such as pulse duty ratio and pulse period, along with other parameters such as scrambling sequence's missynchronization and jamming frequency offset. Finally, this jamming method is carried on simulation experiment, resulting in some relevant conclusions. The experiment results prove the effectiveness of the modified pulse jamming against the reliable transmission of 3GALE signal protocol information. The jamming effect is the best when the pulse duty ratio is set 75% and the pulse period is set to make pulse duration equal to integer multiple symbol time length TB. The decline of jamming effect resulting from scrambling sequence's missynchronization within 2TB or jamming frequency offset within 80 Hz, can be improved fairly by increasing the jamming-to-signal power ratio.