Abstract:Characteristics of supersonic cold flows over cavities were investigated experimentally and numerically, and the effects of cavities of different sizes on supersonic flow field were also analyzed. Results indicate that cavity flow structure has little relevance to L/D within the range of 5～9, and the ramp angle of the rear wall will not alter the overall structure of the cavity flow within the range of 300～600, but it can alter the development of the shear layer and the structure of the circumfluence in cavities.

Abstract:LEO satellite formation configurations may get an in-track drift under the perturbation of atmosphere. The area-mass-ratio of the satellite directly influences the decrease of semi-major axis caused by the perturbation atmosphere, so the in-track drift can be controlled by the adjustment of the area-mass-ratio. Taking the drift distance of the formation center and the difference of the semi-major axes as the input, and the change of area-mass-ratio as the control, a fuzzy controller for in-track drift of formation configuration was studied. On the basis of the design of the input fuzzification and the fuzzy rules, the Mamdani inference was used in the fuzzy inference, followed with a centroidal defuzzification. The simulation indicates that the drift distance can be controlled within 20m, with the given condition. The method proves effective, even with the presence of initial errors.

Abstract:In order to launch objects into low-earth circular orbit using an earth-based laser and a lightcraft with 100kg initial mass, the relationships among the concerned parameters such as the laser average power, the characteristics of laser propagation in atmosphere, light receiver size of lightcraft，the specific impulse of engine, and the energy conversion efficiency of engine were investigated. Meanwhile, the optimal trajectory for such a task was also studied. The necessary average laser power was estimated from the initial acceleration of the lightcraft. The minimum size of the lightcraft's light receiver was derived from laser range. Based on the flight dynamic model of lightcraft and the estimated parameters, the optimum trajectory from the ground to low-earth orbit was computed. The results show that the maximum mass-to-orbit is up to 35.5kg, and the optimum specific impulse is 8140m/s.

Abstract:In order to analyze the fatigue behavior of the center-cracked aluminum plates bonded one-sidedly with composite patches, a parametric program based on the ANSYS was developed. The stress intensity factor and its amplitude of the stress intensity factor of the bonded plates were calculated. The Paris equation, which can be expressed as da/dN = C(ΔK)^m, where, da/dN is the propagation rate of the crack and can be measured at specific fatigue cycles experimentally, is an amplitude of the stress intensity factor at the crack tip during a fatigue cycle, and can be obtained by FEM, was used. Results show that the Paris' parameters for the plate bonded one-sidedly with carbon fiber reinforced epoxy composite patches are C =6.76×10^-10and m =2.27, respectively, while for glass fiber reinforced epoxy composite patches, C =7.89×10^-10and m =2.33, respectively.

Abstract:The dynamic scanning calorimetry (DSC) method was used to determine the reaction kinetic parameters of a hybrid resin of E-44/E-21(6∶4) with GA-327 as curing agent. Effects of rate of temperature increasing on the characteristics of DSC curves were investigated. Results suggest that the reaction of the hybrid epoxy resin with GA-327 can be described by the equation of dα/dt =2.27×10⁴exp(- 4764.65/T)(1-α)^0.861, and the curing procedure is then determined as 100℃ for 30min, and then 120℃ for 30min. The degree of curing reaction of the casting bodies of the hybrid epoxy resin reaches 95.7%, and tensile strength and flexure strength of the casting body are 62.71MPa and 97.92MPa, respectively.

Abstract:Properties of anti-oxidation and anti-shock of silicon carbide fiber reinforced siliconoxycarbide(Si-O-C) composites were studied through comparing the changes of mass and flexural strength and those of microstructure. The results indicate that SiC_f/Si-O-C composites have fairly excellent properties. The microstructure and properties of SiC_f/Si-O-C composites were analyzed. It has been found that interface structure changes were mainly attributed to the reduction of mass and flexural strength properties.

Abstract:SHTB tests were conducted and it was found that interfering signals coming from interfaces between specimen and bars influence the experimental results obviously. In order to get the real properties for the tested materials, an improved data processing was performed to revise the interfering signals. The experimental data of an aluminum alloy under the dynamic tension loading were processed by the improved program, and more reasonable results were achieved.

Abstract:The split-tapper Balun was introduced in the high-power ultra-wide-band (UWB) antenna. Finite-difference time-domain (FDTD) was used to analyze the Balun and antenna. The 2×4 elements array was fabricated and the measurement result shows that the antenna can resist high voltage up to 250kV with six multiple frequency (200～12 000MHz) and preserves short pulse waveform well. Outdoor detection experiment system was built by using the antenna array. Target detection experiment was carried outdoors. The experiment result indicates that the array can be used in the practical UWB radar for transmitting antenna arrays, thus making a first step for the application of high-power source in radar detection.

Abstract:Joint Space-time Anti-jamming technique has better performance than both space domain processing and time domain processing, but its implementation is difficult due to its computational complexity. With the toeplitz feature of the observation covariance matrix, the covariance matrix to a big toeplitz matrix can be expanded. Based on the new toeplitz matrix and the FFT technique, a fast implementation approach of MSNWF was proposed for joint space-time processing. The comparison result of computation consumption shows that the new approach is efficient, making it easier for the application of joint space-time anti-jamming technique.

Abstract:The chaotic encryption system which makes use of chaos mapping system to carry on the secret correspondence is introduced. The method which makes use of the chaos dynamics equation to carry on encrypting to pictures is put forward and realized with the program. For the one-dimension chaotic encryption method, it is successfully deciphered by the phase-space reconstruction theory and exhaustive method with the encryption function, parameter and the original value completely unknown. In the end, the advantages and the disadvantages of the encrypting and deciphering methods are discussed and a kind of encrypting project which is more difficult to be deciphered is put forward.

Abstract:In order to make weapons much more effective in hostile environments, new developments in embedded GNSS/INS integration architectures which offer the possibility of substantial improvements in jamming immunity have aroused great attention from the researchers. This paper introduced the principle and construct of embedded GNSS/MIMU integrated navigation receiver, and presented the method of using MIMU to aid GNSS receiver tracking loop. This technique improved the accuracy of the estimated Doppler frequency, which resulted in higher dynamic and anti-jamming performance. Finally, the paper analyzed anti-jamming performance of embedded GNSS/MIMU integrated navigation receiver. According to the sample of GPS/MIMU, the simulation was done. The simulation results show that anti-jamming performance of embedded GNSS/MIMU integrated navigation receiver has 11dB improvement in comparison with the traditional GNSS receiver.

Abstract:Motion compensation, which usually includes range alignment and phase compensation, plays a key role in ISAR imaging. As the basis of phase compensation, range alignment has been investigated comprehensively and multifarious range alignment methods have been proposed. When the impact of range alignment cannot be judged directly, it is necessary to choose the optimal range alignment method. An evaluation method based on variance of range bins is proposed. It makes use of weighted sum of range bins' variance from range alignment to evaluate impact of range alignment method directly. The results of simulation verify the effectiveness of the method.

Abstract:A comparative analysis of replication algorithms in P2P systems and a novel replication algorithm Dyre based on LDPC codes were presented. Dynamic replica placement was proposed. With this method, blocks are stored in predecessor and success nodes to improve the availability, and blocks are restored when the number of available blocks is small in this algorithm. Simulation results show that the algorithm can significantly enhance the data availability, even when the node reliability is low.

Abstract:The training of support vector machine is a difficult issue in classifying large-scale data set. Incremental learning is one of the solutions to the difficulty. After new samples were added to training set, the possible changes of support vector set, were analyzed and a removing algorithm based on density for incremental support vector machine learning was presented. It discarded useless samples, kept the testing accuracy and reduced the training time. Experiments show the validity of this algorithm.

Abstract:An effective task allocating is important for MAS to complete its mission through efficient cooperation among agents. A new approach is introduced on the basis of the theory of information granulation, which includes two phases: the phase of granulating agents and tasks and the phase of allocating tasks in granular. The mathematical formulation of the first phase is presented, and its solution is proposed based on genetic algorithm. A numerical example shows a better performance of the proposed method.

Abstract:Concerning the problem that the existence of secret information of the stego-image on wavelet domain is subject to detection by histogram analysis for wavelet coefficient, and the visual property that human eyes are less sensitive to textured areas of an image, a novel steganography on wavelet domain against statistical analysis based on HVS (human visual system) was proposed. First, an image was divided into blocks of prescribed size, and every block was decomposed into wavelet using IWT (integer wavelet transform) based on lifting scheme. Then, all nonzero wavelet coefficients were classified into two categories according to their sign and parity, and marked by steganographic 0 and 1 respectively. If the identifier of wavelet coefficients was different from secret bit, it would be modified to the opposite one, otherwise unchanged. And more secret information was in turn embedded into 2 or more level wavelet coefficients in textured blocks so that good visual imperceptibility was obtained. Finally, the stego-image was obtained by the inverse wavelet transform. From the experimental results, the proposed method effectively keeps the identity of histogram for wavelet coefficients and maintains a good visual quality of stego-image.

Abstract:Target discrimination is a key step of SAR-ATR, which can remove many false ROI chips obtained by prescreening adopting anomaly detection. A new method of automatic target discrimination was proposed in this paper. Firstly, the results of CFAR detection were discriminated using the area of target, and ROI chips are exported. The features were extracted from the ROI chips, and then the ordered discrimination was realized by comparing the features with the thresholds based on the features. The real X band SAR image data was used to test the discrimination algorithm above mentioned, and finally the discriminated ROIs were presented.

Abstract:A novel chaos based pulse amplitude modulated ultra-wide band (CPAMUWB) imaging radar was presented. The proposed radar has good range resolution and excellent range side lobe suppression characteristics that enhance its imaging performance, better than that of the conventional time modulated UWB (TMUWB) radars in reducing false alarms. Numerical electromagnetic (EM) simulations using finite difference time domain (FDTD) method illustrate the definite advantages of the proposed radar under different scenarios.

Abstract:A novel approach of warship radio noise feature extraction using Dopplerlet transform was proposed in this paper, and decompose flow of Dopplerlet transform was typed. An experimentation of warship radio noise classification was tried out using different feature extraction methods, such as Dopplerlet transform method, wavelet transform method, wave structure method and natural measure method. Experimentation result shows that the warship radio noise feature extraction method using Dopplerlet transform is more effective than other methods.

Abstract:With the rapid development of digital applications, it is crucial to guarantee the reliability, high-power, operatability and manageability of IP broadband network. According to the requirements of carrier-grade IP broadband network, based on the detailed study of IP protocol, the challenges of carrier-grade IP broadband network on the aspects of service quality, which guarantee the network operation, were analyzed. To satisfy the requirements of network design, operation management and increment businesses, a metrics system is proposed. Then, combined with existing measurement methods, a solution to building carrier-grade IP broadband networks based on network measurement and monitor was proposed.

Abstract:Time stress measurement device (TSMD) technology is a measurement and recording technology that can be used for stress history recording and data analyzing. The principle and development history of the TSMD were introduced in brief. Then, some relation analysis technologies between time stress and electromechanical system faults based on FMESA and logistic regression were studied. In order to improve the validity of our technologies, a case about the gyro was studied. The results of the case show that the relation analysis technologies between time stress and electromechanical system faults in this paper can effectively find out the electromechanical system faults induced by critical stresses, and can be applied in the fault diagnosis and prediction of electromechanical system.

Abstract:To better actualize product's modular design, the clustering algorithm based on graph partitioning for product's conceptual elements was introduced into the process of product's conceptual design on basis of FBCS (function，behavior，conceptual structure), and a FBCS-based method for product's conceptual module identifying was presented. Stacker's push-puller is taken as a type example while the method of product's conceptual design was analyzed. The method achieved the iterative transforming form function to behavior，form behavior to conceptual structure，form conceptual structure to sub function according to the product's general technology characteristic. To describe the conceptual product，the conceptual product's modeling method which combined black box with function description of IDEF0 was presented to construct the product's function-conceptual structure model. Then，the correlation analysis approach of product's conceptual elements (function，behavior，conceptual structure，interface) was established. To realize the identifying of product's conceptual module，the clustering algorithm based on graph partitioning was adopted to converge product's conceptual elements. This method was proved to be feasible and effective by identifying of the push-puller's conceptual module.

Abstract:Based on the theory of SR for detecting weak signals, a novel approach of detecting the weak periodic signal using additional-signal-enhanced SR was presented. This method was analyzed with simulated signals. Through a kind of normalized scale transform, the frequency restriction condition of the signal to be detected was eliminated. The result shows that this method is simple and feasible. The weak sinusoid signal of low signal-to-noise ratio can be extracted from loud noise. The detecting approach indicates a promising prospect for mechanical fault diagnosis.

Abstract:According to the functional requirement and material characteristic of microwave ferrite substrates, the simulation process of relative motion trace was studied in the parallel lapping and polishing area by using coordinate transformation method, and it provided the theoretic foundation for the reasonable selection of processing parameters. The influence rules of various parameters on lapping efficiency were studied with the orthogonalizing experimental method. On the basis of the above, the parallel lapping and polishing experiments of microwave ferrite substrates were completed by using the optimum combination of processing parameters, and the quality of these substrates satisfied or preponderated the requirements.

Abstract:A new active heave compensation system (AHCS) was proposed, based on a differential planet transmission mechanism. The velocity adjusting feature of differential gear train was analyzed and the working and compensation principles of the AHCS were presented. Furthermore, in terms of the two main purposes of heave compensation and in accordance with the whole process of hoisting from despot ship to aim ship, a mathematical model was established for the computer control of the system.

Abstract:Several key technologies were introduced in the development of the air-gap magnetic field measurement system of high-speed magnetic levitation vehicle. The design method of the three-dimensional magnetic sensors and the voltage proportional magnetic field measurement method based on Hall-effect devices were put forward in this paper. It also presented a motion control system with high precision designed for the sensor. The research shows that the developed system has high measurement and orientation precision, and it can perform automatic measurement of the air gap magnetic fields of high speed magnetic levitation vehicle.

Abstract:In order to study the terminal precision guidance of the hypersonic air-to-surface missile with constraints, the guidance law was designed respectively in the pitching plane and swerve plane. After the constraints of miss-distance, impact angular and orientation angular were considered synthetically, and the three-dimensional optimal variable structure guidance law was derived from the optimal control. Moreover, the traditional algorithm of max-velocity control was also mended by the adaptive gradient method and Takagi-Sugeno fuzzy system. Through the simulation test of the characteristic trajectory, the optimal variable structure guidance law with constraints is not only satisfied with the precision guidance in the multi-constraint conditions, but also has excellent trajectory in terminal guidance.