Abstract:Aimed at the problems that at present prediction and health management are lack in field evaluate methods and technical measurements after the advanced aero planes come into service, a method to evaluate the PHM system fault diagnosis ability based on prior information is proposed. The method confirms the priori point estimate of diagnostic ability index of the LRU and system by using the diagnostic information of the LRU of a large number of equipment accumulated by the PHM working during the aero plane development and test time. Then the posterior distribution is formed by using the field data to modify the priori distribution. At last, the posterior estimate of the diagnostic ability index of the system and LRU can be obtained by the posterior distribution. With the example of percent detected and percent isolated, lower confidence limit of the percent detected and percent isolated under different confidence level are obtained. The result indicates that the method is scientific and reasonable, practical, and can meet the needs of field evaluation under the condition of small model.

Abstract:Transonic rudder buzz responses and aileron, elevator, flap vibration time responses, are presented by adopting the CFD/CSD loosely coupled method for a tailless flying wing UAV. The RANS NS equations and finite element methods are established based on the detailed aerodynamic and structural model, in which the aerodynamic meshes use the unstructured dynamic meshes based on the combination of the springbased smoothing and local remeshing methods. The LUSGS iteration and HLLEW space discrete methods based on the SST turbulence model are used to calculate the aerodynamic force. The interfaces between the structural and aerodynamic model are built with an exact match surface where load transferring is performed based on 3D interpolation. The constraints of the rudder motions are fixed at the end of the flying wing UAV structural model, and the structural geometric nonlinearities are also considered in the high aspect ratio flying wing UAV. Based on the presented buzz aerodynamic structural coupled method, the flying wing UAV transonic buzz responses and aileron, elevator, flap vibration time responses induced by the rudder motion are studied; the effects of rotating angular frequency on the vibration time responses are also given.

Abstract:Full annulus steady and transient numerical simulations are performed on a lowspeed axialflow compressor isolatedrotor test rig and NASA Rotor 37. Two new boundary methods, i.e. nozzle outlet and throttle outlet, are adopted instead of the traditional outlet boundary condition. The rotor's operation point can be adjusted by changing the computation domain's outlet area and throttle coefficient individually. The simulation results show that compared with the traditional method, the two new methods can calculate the rotor flow field under all mass flow status, including the near stall status and after stall status. By adjusting the throttle coefficient, the "throttle outlet" model can capture the critical stall point accurately, and by so doing this can figure out the way how reversed flow region emerges and develops in the rotor passages. The research finds that the instability flow structure in the blade tip region，i.e. the local reverse flow regions' formation and expansion processes, plays an important role in the two compressor rotors' stall characteristics. The fullannulus transient numerical simulation of the lowspeed axialflow compressor isolatedrotor finds that once the rotor comes to the stall state, two stall regions arise in the blade tip. The two stall regions expand with the increase of rotor revolutions, and the relatively significant stall regions come into being at last.

Abstract:In order to reduce the computational burden of parameters sensitivity analysis in airliner conceptual design and realize the truetime indication of analysis results, a surrogatemodel method for comprehensive analysis of airliner performance is investigated. Firstly, determine design variables and objective parameters as well as select suitable multidimensional design space. Secondly, the sample points in design space are selected with Opt LHD (Optimal Latin hypercube design) method, and are analyzed by an airliner conceptual multidisciplinary analysis code to obtain a series of required objective parameters. A secondorder polynomial response surface is used to construct the surrogatemodel to replace the multidisciplinary analysis code. Finally, various kinds of diagrams are generated using this surrogatemodel to reflect influence of conceptual parameters toward objective parameters. An example of parameters sensitivity analysis for a certain airliner conceptual design is used to verify the method. The results show that the surrogatemodel accuracy is very satisfied when sample points are around 15 times number of design parameters, and the impacts of major design parameters on airliner performance can be depicted simultaneously with tendency chart, surface chart, and Pareto chart.

Abstract:Aimed at the communication blackout problem that a hypersonic aircraft passes through near space atmosphere, a method that an additional magnetic field is used to change electromagnetic environments of plasma sheath is proposed. According to the data provided by radio attenuation measurement C (RAM C) voyage experiment, a model of plasma sheath is established. This paper analyzes the magnetic field intensity and parameters of plasma including plasma thickness, plasma density, plasma collision frequency to get the reflection and attenuation properties of GPS wave propagation in plasma sheath by numerical calculation. Comprehensive analysis shows that additional the magnetic field around aircraft can effectively solve the "communication blackout" problem especially directed against GPS signal in low frequency. When magnetic field intensity is over 2 T，the transmission attenuation values of GPS signal in plasma sheath are all 5 dB below. The communication state is perfect.

Abstract:Aimed at the four typical electrical troubles of power converter in the switched reluctance starting/generation system，and on the basis of analyzing upper and lower following current，and introduction of digitizer ，a new method of fault diagnosis is proposed. Converter's operational principle and the energy convent process are analyzed. The effects of faults on the upper and lower following current are analyzed in exciting state and currentfollowing state, then, according to the faultfeature, the scheme of fault diagnosis is put forward based on the difference between upper and lower following current. Finally, a fault diagnose model of switched reluctance starter/generator is built and validated. The result shows that the fault diagnosis scheme is more accurate than that of the fault diagnosis with only phasecurrent.

Abstract:Aimed at the problems that the signals of traditional remote field eddy current are weak, and the detection sensitivity is low, and how to realize the suppression of the magnetic field in the remote field eddy current is a key problem to improve the detection ability, this paper designs some sensors with different shield structure from the perspective of restraining direct coupling component of magnetic field, analyzes the effect of shield with different materials, and compares the defects, detection sensitivity and the capability of detecting large thick flat geometry. The results show that the sensor with the connected magnetic circuit based on high magnetic shield has a good ability in restraining as for the direct coupling component, and can shorten transient length, can narrow the distances between the excitation and the detection coil, and can improve the sensitivity in detecting defects. And its detection depth can be extended to 25mm as for nonmagnetic plate.

Abstract:Nonfunction attribute such as realtime, security, and reliability, etc. is a key factor in cyberphysical systems applied to many areas. On the basis of analyzing CPS modeling and verification, a CPS behavior modeling and attribute verification is proposed in this paper. In this method, three steps are as follows: (1) to model the behavior of CPS based on hybrid automata; (2) to convert this model to HP model; (3) to verify the HP model in KeYmarera. The structure of behavior model language is introduced. Rules of converting hybrid automata model to hybrid program (HP) model are established. The consistency of the conversion is analyzed. The result shows that this method can depict the behavior of CPS simply and intuitively, and can also verify the properties of CPS strictly. By doing so, this avoids state space explosion in formal verification effectively.

Abstract:To improve the multiple access performance of Transform Domain Communication System, and reduce the bit error rate of system, SPC-TDCS (Spread Phase Coding based TDCS) is proposed based on modified Logistic chaotic sequence. Taking modified Logistic chaotic sequence as a spread sequence in accordance with the principle of the optimized sequence, the random phase vector generated by m sequence is utilized by phase encoding vector to form spread random phase vector (SRPV). The simulation results show that the spread basic function has still more randomness, and the generated SRPV is superior in relative performance to the traditional random phase vector. No matter in the condition of singleuser or multiusers, the spread basic function based on modified Logistic chaotic sequence (SBFML) has an improved gained SNR, and its performance is better than that of the traditional basic function and the spread basic function based Gold sequence. By doing so, this significantly enhances antijamming capability and realizes further TDCS multiple access capability.

Abstract:The technique of extracting isolated target micromotion feature has already been comparative mature in recent years, but the technique of extracting group targets micromotion feature remains to be further studied. Taking space autorotation micromotion as example, a resolution scheme of group targets based on sinusoidal frequency modulation Fourier transform (SFMFT) is proposed in this paper. First, an echo model of group targets with spinning micromotion is established, and SFMFT is applied in extracting microDoppler component on the basis of the above mentioned. Then, a suppression method of crossterm in SFMFT is put forward in view of the problem that the sinusoidal frequency modulation Fourier transform (SFMFT) displays the characteristic crossterm in analyzing multicomponent sinusoidal frequency modulation signals. Finally, combined with the proposed crossterm suppression method, group targets with spinning micromotion are effectively resolved by utilizing the group targets with spinning micromotion signals of the sinusoidal frequency modulation Fourier transform, and the spinning frequency of each subtarget is accurately extracted.

Abstract:Aimed at the problem of the fast clustering sorting of radar signals under complex conditions of electromagnetic environment, a fast clustering sorting method of radar signals is proposed by adopting a variable precision rough set model based on the similarity of border pulse. In view of some reasons that the similarity of the weighting matrix computed by the original method is determined by experts or experience on no consideration of radar radiated properties, this leads to a low clustering sorting accuracy rate. The improved method is used to obtain the weights of feature parameters in radar emitter by utilizing the variable precision rough set model, further compute similarity by the weighting matrix composed of optimum feature weights, and then perform fast clustering sorting of radar signals by using similarity of border pulse. The simulation results show that the improved method increases the clustering sorting accuracy rate by 5.93% under the same fast clustering sorting capability compared with the original method.

Abstract:The data of Light Detection And Ranging（LiDAR）is a discrete threedimensional point cloud, and the 3D laser foot points belonging to the same building have the characteristics of random distribution. Owing to the varied shapes of building, and the complex environments around building, the extraction of building borderlines becomes more difficult. In extracting borderline, the most important is to extract the edge point. In the paper, a new algorithm of extracting the edge point is presented. Firstly, a specific radius and threshold are set. Secondly, taking the first point as the centre of a circle, a pack circle is built. Thirdly, the distances between the centre and other points are acquired, and the number in the pack circle is counted. And then, the operation throughout all point in the point cloud is done repeatedly. Finally, the point number in every pack circle is compared with threshold to extract the edge point. Compared to the alpha shape algorithm, this algorithm can reduce the running time on the basis of keeping the extraction effect of edge point, and can improve the overall effect obviously.

Abstract:Aimed at the problem that the Grey Wolf Optimization (GWO) algorithm is easily bogged down in local optimization in solving function optimization, this paper proposes a nonlinear adjustment strategy by adopting sinusoid, logarithmic, tangential, cosine and quadratic curves. And at the same time a strategy on mutating position of the agents is presented, whose position is influenced by fitness value. The experimental results for three standard test functions show that the proposed cosine and the quadratic curve strategies are superior to the classical linear strategy, and the others such as the sinusoid strategy, the logarithmic strategy, and the tangential curve strategy are inferior to the linear strategy.

Abstract:The methods of distinguishing radar targets and active decoy are studied based on the radar system taking two receiving stations as a background. Firstly, the doublestation polarization scattering matrix and the doublestation diagonal polarization ratio are defined, and the polarization scattering properties of radar targets and active decoy are studied. Then, a discrimination method is proposed to discriminate the polarizationchanged deceptive jamming by using the discriminate parameter of doublestation diagonal polarization ratio, and the discrimination algorithm is also designed. The simulation result shows that by using the identification algorithm, the correct identification probability of active decoy is always 100%, and the correct identification probability of a radar target can also be over 90%. The effectiveness and the feasibility of the algorithm are validated.

Abstract:A blind 2D DOA estimation algorithm for cylindrical conformal array antenna with respect to polarization is proposed by utilizing the characteristics of the singly curved surface of cylindrical carrier based on typical space DOA estimation theory. The algorithm is used to estimate direction of source exactly without knowing the source polarization and the element pattern. Meanwhile, the method can simplify the estimation without parameters pairing. The new algorithm can be implemented just by using a one-dimensional search and solution of equation. The first simulation estimates the performance of pitch and azimuth angle in the case of different SNR and the same snapshots by using MonteCarlo statistical experiment. The second simulation utilizes the pattern of list to reveal the estimation result of pitch angle, and compares the influence on the estimation of azimuth angle by equation (32) and (33) algorithm in the case of the same SNR and different snapshots. The two simulations demonstrate that the effectiveness of the proposed method is verified.

Abstract:In order to realize the application of patch antenna in missileborne terminal guidance, a new directivity patch antenna based on the phase gradient is designed. This paper utilizes phase gradient metasurface for changing the characteristics of electromagnetic wave propagation in direction, and designs a new patch antenna whose main lobes are deviated from normal of patch antenna at large angle. The antenna consists of seven Hshaped patches, and a desired phase gradient is obtained by optimizing the structure parameters. The results show that with the introduction of phase gradient, the main lobes of the antenna deviated from normal are about 45° in maximum gain direction while operating frequency is 9.6 GHz.

Abstract:In order to enable equipments to be noninterference in each other's normal work among equipments, consideration must be given to both the heat dissipation of equipments and the electromagnetic compatibility of equipments with the increase of HF electronic equipments and their dense distribution. This paper analyzes and calculates the radiation fields of the louver of HF electronic equipments, the common rectangular and circular louver's radiation field by analytical method, and then compares the both field results. Under condition that louvers are made in HF electronic equipments, and the outcome electromagnetic wave's frequency is known, i.e. the wavelength is constant, the width of rectangular louver should be less than or equal to 0.1λ, and the smaller the size of rectangular louver, the better the its performance, and the bigger the length-width ratio, the better the its performance. In the condition of same area of louver, the radiation fields of circular louver are smaller than that of rectangular one. The best way is to make a circular louver, and the diameter of a louver should be less than or equal to 0.1λ as far as possible. In this case the radiation field of louver is the smallest, and its influence on external equipments and internal circuits is comparatively weak.

Abstract:An overview of the studies on the FISSTbased multiple extended targets tracking techniques is analyzed here. The contents of the overview include the shape modeling methods, the optimal multitarget Bayes filter and its principled approximations, RFSbased trackvalued estimation and so on in the overview. Finally, on the basis of the existing research in these areas，some key issues of the RFSbased multiple extended targets tracking techniques are paying a great deal of attention to the researchers for solution. These contents consist of combination of shape modeling and group target profile modeling, multiple maneuvering extended target tracking, performance evaluation method of extended target tracking, extended target tracking based on nonlinear and nonGaussian, extended target tracking with nonstandard measurement.

Abstract:Aimed at the present situation that the characteristics of force and deformation of the culvert under high embankment slope has not been systematically studied, the distribution characteristics of surrounding soils and deformation laws of the culvert are studied by PLAXIS finite element software combined with the culvert project under super-high embankment loess slope at Yan'an airport. Compared the studied results with the positive buried culvert of the same working condition, some laws of force and deformation are obtained and some problems needed to be solved in the practical project are put forward. The results show that the culvert under high embankment slope is obvious in bias pressure, and incline and deflection appear in vertical and in lateral direction. The boundary effect of slope appears when the slope ratio is 1:2 and the horizontal distance between the highest point of slope and culvert's center line is more about 10 times than the culvert's diameter under the action of culvert subjected to the bias pressure. The vertical earth pressure of culvert top under high embankment slope can be referred to earth pressure of positive buried culvert, which is designed by the filling depth of the culvert under slope, and the specific relationships between them remain to be further studied.

Abstract:Aimed at the deficiencies of Zheng sign cryptic scheme and SK sign cryptic scheme, this paper proposes improved schemes respectively by utilizing the principle, i.e. sign cryptic information and open information for restoring the information needed by sign decryptic scheme to the needs of safety and efficiency. The difficulty of solving oneway function is utilized to improve Zheng sign cryptic scheme. The security has been greatly improved compared with the original scheme without affecting the efficiency of the case, and has forward security and public verifiability. The bilinear pairing of elliptic curve and identitybased cryptosystem are used to improve SK sign cryptic scheme, and the safety and the efficiency of the improved scheme both have been greatly improved with the public verifiability, and the communication cost and the computation cost are reduced. The results show that the safety and the efficiency of the improved schemes have been improved and meet the basic requirements of sign cryptic scheme.