Abstract:Through dynamic time warping analysis to the hot-fire test data and simulated fault data of a certain liquid rocket engine, the warped path sets were obtained. Combined with the decision tree method, fault detection and diagnosis were carried out. Results show that there were no failing report and no misstatement for fault tests, and no misstatement for normal tests. Compared with those results by ANN and SVM methods, the successful application of the dynamic time warping method combined with decision tree was proved.

Abstract:Hypersonic vehicle with scramjet is a new kind of vehicle with bright future. With a study of its standard trajectories in half-velocity coordinate system, the fly velocity and design parameters were found to be the main factors to influence its skipping trajectories. The trajectory simulations in perturbation and standard atmosphere models showed that change of atmosphere parameters could influence the height, maximal load, maximal heat and total heat of trajectories. These factors should be considered while studying the vehicle design parameters, structure parameters, heat shield system and guide navigate and control (GN&C) system.

Abstract:Osculating cone waverider configuration is an important design reference to the powered hypersonic vehicle. This paper parameterized the design process of OC waverider and engineering method was used to evaluate waverider's aerodynamic performances. Based on the orthogonal experiment, L/D ratio, volume and volume efficiency were chosen as optimized objective functions to optimize the configuration. CFD simulation shows that the optimized configuration has better L/D, volume, volume efficiency and uniform flow at the base, thus it is an important design reference in the hypersonic engine-airframe integration design.

Abstract:This article researched the aerodynamic configuration design of the glide/skip trans-atmospheric vehicle(TAV) based on waverider with high lift-to-drag ratio. Firstly, design methods of waverider configuration were put forward, and the waverider shape changed from design parameters was fully investigated. Then, the performances of the optimized waveriders under the varieties of Mach number and differed optimization aims were compared and studied. Finally, a TAV configuration with high L-D ratio and high volumetric efficiency was obtained. The conclusion has important reference value to the research of TAV configuration and waverider.

Abstract:A dynamic analysis of the passive constrained layer damping (PCLD) beam considering randomness of viscoelastic damping layer was studied by using the transfer function method. With an introduction of the state vector, the governing equation of the PCLD beam in state space was established from the six-order differential motion equation，which was derived by using the Hamilton principle. The closed-form solutions of natural frequencies and loss factors of a PCLD beam were obtained by the distributed parameter transfer function method. The parameters in fractional derivative model of viscoelastic material were regarded as the base random variables, which follow normal distribution in this analysis. The influence of parameter randomness on the natural frequency and the mode loss factor of the structure were analyzed by using the Monte Carlo method. Numerical examples show that the randomness has obvious effects on the correlation coefficient of dynamic characteristic, and the maximal value of the loss factor's correlation coefficient is about 4.5 times as much as the one of material parameter. So it is necessary to carry out the random analysis for PCLD structures.

Abstract:Three-dimensional silica fibers reinforced nitride matrix composites （3D SiO₂f/Si₃N₄-BN） were prepared through repeated infiltration and pyrolysis. The ablation performance of the composites was evaluated by arc jet. The ablation surface and microstructures were studied by scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS). The results 　show that the 3D SiO₂f/Si₃N₄-BN composites have a low linear ablation rate of 0.91mm/s under high pressure and heat flux. Silica fibers fused and more heat was absorbed before the fused layer was swept off and the matrix eroding velocity reduced for the protective melt layer. On the other hand, the fused layer was prevented from eroding from the ablation surface as a result of the matrix with high mechanical property and sublimation temperature. The nitride composite is a high-temperature ablation resistance material for its low recession rate under high thermal load.

Abstract:Two-dimensional carbon fiber cloth reinforced silicon oxcarbide (2D C_f/Si-O-C) composites were fabricated with Silicone Resin (SR) as precursors, ethanol as solvent and SiC powder as inert fillers by precursor infiltration and pyrolysis. The effects of the pyrolysis temperature on the microstructure and mechanical properties of 2D C_f/Si-O-C composites were investigated. The results show that the temperature of first cycle has great effect on the mechanical properties of 2D C_f/Si-O-C. The better mechanical properties are attributed to weakening of the fiber/matrix interfacial bonding. When the sixth pyrolysis is carried out at appropriate temperature, the mechanical properties of 2D C_f/Si-O-C composites are enhanced greatly. The flexural strength and fracture toughness of the composites are 263.9MPa and 12.8 MPa?m^1/2, respectively.

Abstract:The analysis of the terminal divert ability of SM-3 is put forward based on the creditability theory. The expression of the maximal zero effort miss which could be corrected by SM-3 during the terminal course was deduced based on relative motion dynamics. Creditability theory was used for modeling the fuzzy parameters in the expression, and fuzzy simulation was adopted to obtain the possibility measured pessimism value and optimism value, creditability measured mean value and normalized variance, and its distribution functions of possibility, necessity and creditability. The research could supply a theoretical support for the motor design of midcourse maneuvering penetration of a ballistic missile, and supply an effective way for get reasonable unknown information from limited known information.

Abstract:In generally large-scale and strong distributed P2P systems, updates issued by replicas may be delayed, and then resource location performance on the Internet may be depressed. According to the characteristics of updates about key-attributes in P2P systems, an optimistic data consistency maintenance algorithm is proposed. The update about key-attributes was separated from user update request, and based on classifying key-update conflicts, a double-level mechanism including preprocessing buffer and key-update table were applied to detect and reconcile conflicts, and then conflicts were solved by policies as last-writer-win and divide-and-rule. Delaying key-attributes updates cannot occur by the optimistic disposal method, and then it cannot depress efficiency of resource location based on key-attributes, which adapts well to P2P systems for Internet. The simulation results show that it is an effective optimistic data consistency algorithm, achieving good consistency overhead, resource location and resource access overhead, and having strong robustness.

Abstract:By exploiting query predicate similarities in the data streams, queries optimization is a mainly strategy to share computation. In this paper, based on the sliding windows, an approach is presented for the multiple range aggregation queries over spatio-temporal streams. Time fragments were employed to describe the overlaps between sliding windows and spatial fragments for the overlaps between spatial range predications. Then a technique was proposed to partition the streams into different spatio-temporal fragments without any overlaps. The final query results could be captured from the temporary query results over the spatio-temporal fragments. Experimental result shows that our approach can substantially increase performance of the multiple range aggregation queries over spatio-temporal streams.

Abstract:LS-DSP, of which the inner coprocessor is composed of process unit PE, is a Digital Signal Processor used for aerospace image processing. Router is a special unit which interlinks PE net array, and it is also the part most frequently used for operation. How to depress power of processor and elevate calculate efficiency is an important topic for research. Aimed at a low power improvement in the circuit of LS-DSP router, a design base on clock-gating was carried out, and the algorithm was taken as an example to make the power consumption analysis and comparison of the control and operation process. The experimental results show that the improved architecture can reduce the router power consumption by 76%.

Abstract:In the dither ring laser gyro (RLG) strapdown inertial navigation system (SINS), gyro outputs are often pre-filtered to eliminate the dither bias, so the distortion of magnitude and phase of filtered data induce the additional attitude algorithm errors. In this paper, the dither demodulation filter was analyzed and its influence on attitude algorithms was researched. The formulas of optimized attitude algorithm were derived to match the response of the filter. The optimization technology did not complex the algorithms because only the algorithms coefficients were amended. The simulations and experiments illustrate that the optimized algorithms can reduce effectively the additional algorithm errors and increase obviously the algorithms precision. The algorithms have great value to real application.

Abstract:Solving coupling-wave differential equations with boundary-value conditions is a basic method for investigating waveguide mode converters with varying radius or bent axis. A matrix method according to microwave net theory is presented to make the solution simple and explicit with clearer physical meanings. For a group of coupling-wave differential equations in which N coupling waveguide modes are considered, the transmitting matrix and scattering matrix of the converter described by the equations can be obtained by solving the differential equations 2N times with different initial value conditions, respectively. Then with use of the scattering matrix, the solution of the coupling-wave differential equations with boundary-value conditions can be educed.

Abstract:EOS (Earth Observing Satellite) imaging scheduling process should generate the sequence of imaging requests. It is a complex combinatorial optimization problem. Considering the imaging constraints of EOS, to make replete use of the resource, the label vertex digraph without circuit as the model of imaging scheduling problem was adopted. On the basis of this model, a multi-objective scheduling method, based on the Strength Pareto Evolutionary Algorithm 2, was presented and also genetic operators to handle the imaging constraints were proposed. This method was tested on three real problems with two objective functions. From the results, it can be said that the proposed method can resolve the EOS scheduling problem efficiently.

Abstract:A method is presented for the localization of manmade objects in remote sensing images with complex scenes. The methodology was based on mean shift clustering in high dimension by extracting multiple features of manmade objects and forming them into a feature vector. By clustering the feature vectors, the manmade objects were segmented from the complex scenes. Results obtained on the detection of architectures in the image show that this methodology has good robustness and autonomy.

Abstract:Time Domain Electric Field Integral Equation (TDEFIE) based on Marching-On in Time (MOT) algorithm suffers from late time oscillations for analysis of scattering from conducting targets, which will induce late-time instability in MOT algorithm. An implicit iterative solver is presented by the analysis of explicit and implicit solutions of Time Domain Magnetic Field Integral Equation (TDMFIE), and then it can be implemented more easily. Numerical results demonstrate that it has more excellent stability compared with TDEFIE and that the proposed solver postpones the late-time oscillation for TDMFIE MOT iterative solution.

Abstract:A new tracking filter is proposed for the highly non-linear single observer passive location and tracking (SOPLAT) system based on the observation of bearing, bearing rate and difference time of arrival of emitter. The new method used the Jerk model for the maneuvering target, and then used the IMM algorithm basing UKF to keep the tracking of the emitter. By using this method, the precision of the tracking filter can be improved, and it is also good to the filter's stability. The simulations proved the feasibility and availability of the new method. At last, further research directions of the IMM-Jerk were discussed.

Abstract:A high performance measurement of initial phase via a Dual Interpolated DFT method based on error information is presented. Theory analysis and numerical simulation results all indicate that the performance of the method is close to the Cramer-Rao Bound.

Abstract:MUSIC algorithm is a classic subspace method for spatial spectrum estimation. In this paper, a pretreatment model is presented to construct the reference signal. The configuration of the multi-stage Wiener filter that is fit for MUSIC algorithm is proposed. Due to avoiding eigenvalue decomposition of the sampling data autocorrelation, the new method has less computational complexity. Simulation results demonstrate the effectiveness of the new method.

Abstract:A new Doppler Estimation Method based on frequency and frequency rate estimation and pulse period estimation is proposed. The new method is intended for solving the unmatched sampling problems and obviating the judgments of pulse edge, which permits the pulse period estimation based on intermediate frequency sampling signals. The frequency and frequency rate estimation technique was introduced, and based on that, the theoretic precision and error origins are discussed. The feasibility and availability of the new method were proved by the simulations.

Abstract:False alarm of Built-in Test(BIT) has important influence on system readiness and usage cost. Aimed at solving the problem of false alarm caused by environmental factors, a Time Stress Measurement Device(TSMD) was designed to sample the temperature and vibration of the system. The relationship between false alarm and environmental factors was built based on Support Vector Machine(SVM) which has the advantage of small sample learning. The occurring rule of false alarm was described by using Hidden Markov Model (HMM) which can process dynamic sequential signal well. Then, an intelligent method of reducing false alarm was proposed in terms of TSMD-SVM-HMM. Finally, the method was applied and validated on a helicopter heading attitude system. The experimental results show that the method can effectively recognize and reduce false alarms caused by environmental factors.

Abstract:Aimed at rapidly building simulation systems, service oriented simulation development is put forward, based on ontology and web service mechanism to custom and compose simulation services. First, some basic definitions, simulation services customization model were proposed and its supporting system framework were presented, among which domain ontology, requirement ontology and service ontology were particularly described. Logical relationship between requirement goals and simulation services were analyzed, upon which the general process of service composition were studied. In the end, with the support of Grid Toolkit a prototype system was realized to testify the feasibility of our methods.

Abstract:Magnetorheological (MR) jet polishing (MJP), a new type of precision polishing technology in the material removal mechanism, was studied by the method of computational fluid dynamics (CFD). In MJP, the MR jet containing abrasives was magnetized by a local longitudinal magnetic field near the exit of the nozzle so that it could maintain the coherent and stable structure for a long distance. Firstly the mechanism and experiment set-up of MJP were introduced. Secondly the formation of collimated MR jet in a uniform axial magnetic field was analyzed. And then a series of static experiments were conducted to show the characteristics of the distribution of the material removal during the process of MJP. Finally the characteristics of the power density under conditions of both normal and oblique impingements were simulated by CFD method. Simulation and experiment results demonstrate that the material is removed by shearing actions caused by the radial spread flow of the MR jet over the workpiece surface. The method of CFD can accurately predict the 3-D removal rate distribution (polishing spot), thereby facilitating the accurate prediction of spot shapes on surface geometries.

Abstract:A method for quartz rate sensor (QRS) using digital correlation detection is proposed to improve the performance of QRS. It requires a pair of orthogonal signals as input of two correlates, which can extract the in-phase and quadrature-phase component from QRS' readout signal. Then the input angular rate will be obtained from these two components. A reference channel is used to generate a pair of orthogonal signals. Phase-locked loop (PLL) and Hilbert transform can be used as the reference channel. By comparison it is concluded that the PLL has better performance than Hilbert transform.

Abstract:Based on the vehicle virtual prototype simulation, a new method for auto parts fatigue analysis is presented to avoid the real vehicle tests. In consideration of the modal stress recovery (MSR), the method can accurately solve the flexible multi-body system dynamics under the modal coordinate. By using MSR, the loading spectra of auto parts can be acquired after the virtual prototype's road tests. Then the fatigue test of the parts can be conducted with the loading spectra. This test method was applied to a lower control arm (LCA) of a car's front independent suspension. The result indicates that this virtual fatigue test method is an effective means for auto design and test.

Abstract:Based on the component analysis of missile system, the survivability block model of series, parallel, backup were built, and the analytical solution for structuralized model were illustrated. Finally, an example was presented to show the analysis process.

Abstract:The computation consumption of Bayesian network increases exponentially with the nodes number and that limits the application of large－scale Bayesian network. In order to relieve this situation, this paper makes use of the independence condition to decompose the whole Bayesian network according to the characteristics of safety analysis, compresses the items number in reasoning process, proposes the algorithms for top event probability and cut sets, simultaneously analyses the computational complexity. Compared with BDD－based FTA algorithm, the proposed algorithms showed a lower memory demand and a higher speed performance when meeting the need of safety engineering.