Abstract:Based on the computational fluid dynamics module CFX of ANSYS 11.0,RANS 3-D Navier-Stokes equation and SST model are selected. And the numerical method of N-S equation and visual flow-field simulation analysis are used to calculate the aerodynamic characteristics and flow mechanism of the configuration with variable forward swept and orthogonal wing in the stage of low speed taking-off/landing together with high transonic combat utilization. The comparison of the two configurations above is emphasized. The analysis of vortex configuration has shown that the wing leading edge vortex and canard vortex get closer and are enhanced each other in 'V' shape, thus the secondary vortex is induced which greatly raises the control ability of the flow separation upon the wing, so the lift coefficient and stall angle are increased. The numerical results and analysis have proved the rationality of the guiding ideology and can provide theoretical supports to the advanced nature of the aircraft design with the configuration of variable swept wing.

Abstract:The difference between general trapped vortex combustion and CIAC （cavity in a cavity）trapped vortex combustion of ITB (Inter-Turbine Burner) 3-D combustor on two phase combustion flow field and combustion performances are studied by using CFD software. Realizable model is applied to simulating the turbulence. Non-premixed combustion model is used to model the turbulence-chemistry interaction. Then, the analysis and comparison of the temperatures, flow field and species are done in the two different ITB structures. It is found that the ITB of the two structures can yield a substantial increase in the entrance temperature and speed of low-pressure turbine by the results. The temperature of the front half section is higher than that of the rear half section in the circumferential cavity. The fuel participating in the secondary burning in the downstream of the main path way is an incomplete burnt, incomplete oxidized low carbon compound. A fuller combustion and a greater temperature rise are obtained in CIAC (cavity in a cavity) structure. The groove on the top has a well effect on stability of combustion.

Abstract:Finite element software MSC.PATRAN/NASTRAN is applied to analyze the buckling behavior of stiffened composite panel under compress load. In addition, experiment on this kind of structure is conducted in order to obtain the stability performance, failure process and carrying capacity of the structure. It is found that the emulation analysis results are accordant with the test results, which validates the correctness of the modeling and computation. The experiment results indicate that the structure studied has a biggish post-buckling carrying capacity and the finite element method is suitable and can be used for the analysis of the stability of the structure, which offers a reference measure for the optimization design and engineering application of the structure.

Abstract:The effects of organic silicate on the friction performance of HT150/45 steel pair are studied by using an improved friction apparatus. Emphases are mainly put on the mechanisms of surface self-repairing，modification and abrasion-resistant rule . The reagent of ART is added to the pair, and then the friction experiment is carried out under constant load, constant velocity in atmospheric environment. Restoration agent is analyzed by using kevex TEM, S440 SEM etc. The abrasion rate of cast iron is tested, meanwhile, by the test of sample surface microcosmic rigidity and the roughness, observation of the microcosmic appearance and the surface elements analysis and the observation of the metallographic phase organization, the results show that there is an ivory-white film on the surface of HT150. Investigation by microscope indicates that many grey blocks are observed on the specimen surface and some elements of ART are embedded into the surface. The micro-penetration hardness and surface roughness are greatly increased，which are four times as large as the original ones in some parts. At the same time, the surface roughness is obviously decreased, some sample's Ra is 14% of the original one, which demonstrates the pronounced abrasion-resistant effects of organic silicate.

Abstract:Generally, the distance information can't be obtained in maneuver target tracking under the interference environment. In order to get a more accurate tracking result, a new passive tracking algorithm is proposed. Since there is a nonlinear relation between the state variables and the measurements in passive tracking, in the algorithm firstly the least square principle is adopted to pretreatment angle measurements, then the pretreatment result is taken as an input to perform the interacting multiple model filtration. By this, the error brought by the linearization process of the nonlinear measure equation is reduced. However, the accuracy of tracking still cannot be guaranteed because of the localization brought by the fixed structure model muster in interacting multiple model algorithm. In order to enhance the ability to self-adapt to the maneuver target mode, the paper introduces a sequential likelihood ratio test to adjust the model muster, which can reduce the competition among models and ensure the accuracy of tracking. To verify the effectiveness of this algorithm, under the same experiment conditions, using two algorithms to estimate the definite flight track respectively, the simulation shows that the use of the improved algorithm can further improve the accuracy of tracking.

Abstract:Aimed at the tactics application problem of missile early-warning information, a cueing capability evaluation method based on trajectory-missile track parameter error estimate by observation data of missile early-warning satellites during boost phase is put forward. By using statistic and reasoning estimate methods, the calculation models in launch point location, burnout point location and impact point location are established, and then the calculation model of goal-cueing region increase-ratio to missile defense system of missile early-warning satellites is designed. A numerical example is given to further illustrate the validity of the method. The cueing capability evaluation of missile early-warning satellites can provide a reference for the setting in important tactics and technical parameters of missile defense system.

Abstract:The imaging principle of spaceborne ISAIL for space debris is analyzed. An imaging algorithm combining compressed sensing with complex inverse Radon transform is proposed to solve the limitation of low Pulse Repetition Frequency (PRF). By using this algorithm, the compact of laser signal modulation on imaging is reduced through reducing the bandwidth at the same time. The imaging experiment with numerical data verifies the feasibility and effectiveness of the proposed method.

Abstract:The paper studies the firepower allocation of multi-layered BMD system. Firstly, the firepower allocation of multi-layered BMD system is described. Then the total expected value of surviving assets of each stage is taken as the objective of firepower allocation model of multi-layered BMD system. Because of the difficulty in solving firepower allocation model of multi-layered BMD system, a linear approximation to the objective in firepower allocation of multi-layered BMD system is proposed. The results of simulation and of application of the method to a problem show that the linear programming model is of validity and real-time.

Abstract:In order to solve the degeneracy of the jamming ability of chaff cloud, a compound jamming method is proposed. The jamming process is as follows: The signal of enemy airborne fire control radar or air missile's seeker is received by airborne electronic jamming equipment, and then the signal is irradiated on chaff cloud by airborne complexity launching antenna. The jammed signal is reflected by chaff cloud, which will be received by enemy radar, forming a false target, and this false target is different from the false target formed by the irradiation on chaff cloud of radar signal. The simulation results show that using this compound scheme the scatter area of chaff cloud received by enemy is enlarged by even hundreds of times compared with the original one, enhances blanketed ratio. So the spread time of chaff cloud is shortened and the feasibility of this method is validated. The comprehensive jamming ability of aircraft is boosted by using the compound jamming method. Therefore, the method, to some extent, is of a stronger practical value.

Abstract:This article studies a method of eliminating the false localization of multiple targets on the basis of air based double flat roof, and gives a passive localization method based on min-angle threshold judgment. In this method first the "least distance method" cross-localization algorithm is used to work out the estimation value of the target position, and work out the pitch angle of the value compared with the value of main scout. Then, the D-value between the foregoing value and measured pitch value of main scout is worked out. Finally, by comparing the certain threshold with the D-value, the false dot which exceeds the threshold is eliminated. The result of simulation shows that using the method can enhance the correct probabilities of data association and reduce the calculation times which can meet the need of project.

Abstract:This paper presents a new type of microstrip composite right/left handed transmission line (CRLH TL) constructed by Minkowski loop shaped complementary split ring resonators (M-CSRRs) and interdigital capacitor in the upper metal level. Transmission behavior of novel CRLH TL is researched by EM simulation as well as electrical simulation and validated by experimental measurement. By using the CRLH TL effect, a broadband quadrature power splitter (QPS) is designed and fabricated. The simulation and tested results show that within the frequency band range of 2.7-6.6 GHz, all return losses are greater than 10dB while the isolation is better than 15dB, phase non-equilibrium and transmission magnitude difference between two outputs are less than 90°±7° and 0.8 dB respectively，thus the relative bandwidth reaches 83.9%.

Abstract:The application of cognitive theory in Unmanned Combat Aerial Vehicles (UCAV) Intelligent navigation is studied profoundly. The latest trend of cognitive theory application research at home and abroad is summarized. Then, the present researches of UCAV Intelligent navigation are introduced in three aspects of navigation method, path planning and autonomous landing. Based on analyzing these recent researches, a new technology of cognitive navigation developed from integrated navigation is proposed, and furthermore, the basic connotation and main functions of the cognitive navigation are illustrated respectively. Finally, the characteristics of the cognitive navigation are shown in detail, which clearly show the way to the further research.

Abstract:For reducing the complexity of non-circular signal, the paper proposes a computationally efficient direction-of-arrival (DOA) estimation algorithm for noncircular signals. Firstly, the array extension matrix is constructed and the covariance matrix is formed by the characteristics of non-circular signal. Secondly, the noise subspace is achieved by using the extended propagator method without the eigendecomposition of the covariance matrix. Thirdly, the estimating value of DOA is obtained by the polynomial rooting method based on uniform linear arrays. The simulation results indicate that the performances of the algorithm are close to those of NC-root-MUSIC, NC-ESPRIT and NC-MSWF- MUSIC. The analysis of the complexity show that the proposed algorithm is computationally efficient in comparison to the above mentioned algorithms without complex computation and also demonstrate the rapid and effective performances of the proposed algorithm.

Abstract:The charge-coupled device (CCD) is the key component of the beacon subsystem in optical satellite communication system, whose efficiency determines the integral performance of the optical communication system. According to the theory of Shockley-Read-Hall, the theoretical analysis of CCD equipment under particle radiation is made, and the numerical calculations are developed based on the theoretical analysis. The calculation results show that the mean dark current of P-CCD increases with the increase of operation temperature, the stronger particle radiation leads to the higher mean dark current and the hot spikes are strongly random; the temperature more effectively induces CCD mean dark current density and its hot spikes than particle radiation fluency. Therefore, the temperature-controlling chips and technique will play a key role in determining the CCD position accuracy.

Abstract:An adopted auto control of bias voltage of Electro-optical modulator (EOM) is adopted to innovate the traditional manner that gives a constant voltage to the Electro-optical modulator. The use of auto-control of bias voltage makes EOM could have a good effect at different temperatures to acclimate all kinds of environment, in this way the bias voltage of EOM can always be at the midpoint of the zone of linearity, which can guarantee an adequate modulation without any distortion. The photoelectric detection and error analysis are adopted to judge and identify the shifting of the half voltage of EOM. Then PID control algorithm is used to realize a high precision auto-control. Finally, the EOM with the auto-control is applied to the EO modulation crystal to perform a high-speed modulation experiment.

Abstract:Based on that the high order band-pass frequency selective surface (FSS) has the advantages of bandwidth controllable flexibility, stable performance, flat pass band and low insertion loss, a second-order FSS with good band-pass performances is designed in this paper. The designed FSS is composed of two layers of dielectric boards loaded with three layers of metallic patterns sheets. The two outer layers are of circular metallic patches while the middle layer is of circular aperture. The straight-line method is used to analyze and calculate the structure of the FSS, and a test sample is fabricated and measured to verify the results. The experiment results show that such a three-layer FSS has the desired second-order band-pass properties,the 3 dB bandwidth is of 4.21 GHz, the relative bandwidth is 21%, and the pass-band is quite flat and smooth in which the insertion loss is low. Moreover, the FSS can keep stable performances under different incident angles and polarization states.

Abstract:A high-order Perfectly Matched Layer (PML) applied to time domain finite element method (TDFEM) is obtained by proper selection of the parameter of PML. Furthermore, a composite PML composed of UPML and SCPML is derived, and the application of it to explicit TDFEM is investigated. The reflection coefficient of waveguide is calculated using the high-order PML and composite PML, the result shows that the finite element calculation result is accurate and stable. Compared with the ordinary PML, the numerical results show that the high-order PML and composite PML are highly effective in absorbing both evanescent and low-frequency waves, which will lay the good foundation for the widespread use of TDFEM.

Abstract:The spread of some communicable diseases often has a certain periodicity. By incorporating the periodic parameters of disease transmission into the classical SIS epidemic model, an SIS epidemic model with periodic parameters is established. By means of the comparison theorem and the stability theory of ordinary differential equations, the threshold determining whether the disease dies out or not and determining the dynamical behaviors of the model is obtained via qualitative analysis. When the threshold is negative, the disease-free periodic solution of the model is globally asymptotic stable, which implies that the disease dies out eventually. When the threshold is positive, the disease-free periodic solution of the model is unstable, and the model still has a unique endemic periodic solution that is globally stable. This implies that the disease persists in the population, and that the number of the infected individuals will change with a certain periodicity.

Abstract:The wide area differential GNSS can be used to improve the accuracy, credibility and integrity of the navigation by broadcasting augmentation messages for receivers of the covering areas through geostationary earth orbit (GEO) satellites. But in cities with more building obstacles or in rooms, it is unable to realize the high accurate navigation. The way that the navigation augmentation messages are broadcast through internet has its unique advantages. The configuration and the network structure of internet-based wide area DGNSS (IBWD) are designed in this paper. According to node heterogeneity, the nodes that would join IBWD are classified into differential node types including proxy nodes and general nodes. The hierarchy mix multicast system based on node heterogeneity is constructed by the combination of application layer multicast where IP route information table is applied and i3 multicast. The results of simulation show that IBWD allows nodes to leave and join dynamically, and it is highly robust against failures. IBWD allows real time communication and the throughput of server is lower than other systems, so it can well meet the need of applications of large scale and real time broadcasting for the augmentation messages of GNSS through internet.

Abstract:Three parameters of Zwicker's loudness model, the excitation at threshold in quiet, the excitation that corresponds to the test signal and the reference intensity are researched in order to extract the loudness feature of signals. The sound intensity level at threshold in quiet state is introduced, corresponding to the centre frequency of the 24 critical-bands in equal-loudness contours. Then, an improved algorithm based on Zwicker's loudness model is put forward, with which the specific loudness values can be calculated quantitatively by using the energy of signals. Then a 24-D loudness characteristic vector is composed of the specific loudness values of the critical-bands, which can be used for signal analysis, mode classification and so on. The mode classification experiment of underwater targets is performed. The result shows that the improved algorithm based on Zwicker's loudness model is effective and practicable.