Abstract:To obtain the aerodynamic forces accurately and provide theoretic guide for the design of missile's configurations, a numerical simulation of the flow fields around an actual configuration of air-to-air missiles (AAM) is performed by solving the Reynolds averaged Navier-Stokes equations (RANS). The Spalart-Allmaras（S-A） one equation turbulence model is coupled to close the governing equations. The Jameson's finite volume multistage Rung-Kutta time-stepping scheme and spatial central difference coupled with artificial viscous terms are used in the computation. A patched multi-block structured grid is generated around the complex configuration using the multi-zone technique and elliptic partial differential equations. The simulations are conducted in supersonic flow at different angles of attack. Aerodynamic forces and moments acting on the body, rudders and ailerons of the AAM with or without angle of roll are calculated. These results agree well with the experiment and those using other codes, and they show that the scheme can be adopted in the computations of the complex flow fields around actual configuration of multi-wing missiles.

Abstract:Current flight data processing research about data's inner attributes and interrelations between different data are lacking in depth. In this paper, theory and method of Takens are used to reconstruct the phase space of primal FDR flight data. The qualitative analytic methods, such as power spectrum figure and etc., are used to study the flight data. All the data curves are continuous and have wide peak characteristics. In the quantitative analysis, Wolf method on the basis of phase trajectory evolution is applied to estimating the largest Lyapunov exponents in different dimensions, and the results show that all the exponents are positive. So the chaotic characteristic of the flight data is verified. This conclusion is of novel reference value for the following-on research of this kind.

Abstract:The problem of forecasting the service performance of airport pavement is studied. Various parameters influencing the service performance of airport pavement are analyzed, the genetic algorithm and BP neural network are combined to forecast the service performance of airport pavement. The genetic algorithm overall optimization is used to optimize the weight and threshold of neural network, then, LM optimization algorithm is used to increase the training speed and make the training avoid getting into local minimum. The neural network is trained with the data of the past years, and the model of neural network is used to forecast the service performance of airport pavement. The result shows that this method is precise enough to be applied to the engineering practice.

Abstract:To study the long-term storage distortion of turbo pump end-face seal, the interference fit and long term storage creep character of the stationary seal ring of end-face seal is analyzed using finite element software. The creep behavior is formulated using strain ratio harden material model. The stress-strain of the module and the deflection of the graphite annulus are present in different storage life. And turbo pump end-face seal's reliability is obtained using hierarchical Bayesian zero-failure estimation and stress-strength interference method. In the latter method, simulation result is employed. The long-lime storage reliability estimation using field test information and simulation information can effectively increase the accuracy of estimator under small sample situation, and is more credible.

Abstract:Isolator is a key component of Scramjet in achieving dual-mode and mode transition, and it separates the inlet from the combustion chamber, thus preventing the effect of combustion back pressure on the inlet and guaranteeing the security and stabilization of aircraft. Combined with the problem of combustion chamber work stability, a numerical simulation of axial symmetry isolators with same cross section is performed with FLUENT6.2. When the Mach number of the inflow is 2, isolator with different ratios of length to height is investigated and the influence of back pressure on the location and structure of the shock train and on the performance of the isolator is analyzed. The results show that the back pressure has ahead transmission on the shock train of the isolator, which results in the complexity of the shock train structure and the decrease of the outlet distortion degree. The ratio of length to height has a great influence on the correlation between the location of the shock train and the back pressure. If the ratio of length to height is not too high, the location of the first shock wave will have a linear relation with the back pressure, and the changing speed is in direct proportion to the ratio of length to height. Otherwise, the linear correlation will not hold true.

Abstract:It is an important way to reveal the law of war by humankind behavior under modern complicated information-based situation. A nonlinear autonomy alternant model of potential strategic warfare is presented through the analysis of essence of modern war by the view of potential war theory of the author. And then, the analytic solution process on phase plane is carried out, the Four cases of the eventual situation are described by parameters, the mechanisms of war trend and pursuing peace situation (peace equilibration) are stressed. Finally, some results, notes and problems for further research are pointed out.

Abstract:The performance analysis of CMCAM detector in clutter edges is carried out. Under Swerling Ⅱ assumption, the analytic expression of the peak of false alarm rate at clutter edges is derived, and compared with that of OS CFAR detector. The analytic results show that the ability of CMCAM to control the rise of false alarm is more effective than that of OS. The peak of false alarm rate of CMCAM 1-2 order of magnitude lower than that of OS with ,and the peak of false alarm rate of CMCAM is also less than that of OS with .With the results proposed by \[7\], the analytic results show that the detection performance of CMCAM is superior to that of OS in both homogeneous background and in non-homogeneous backgrounds. Because the automatic censoring technique is adopted in CMCAM detector, the anti-jamming capability is increased, and the parameter can be selected freely. In CMCAM detector the mean value of CM and CA local estimations is taken as the noise power estimation, so the sample sorting time of CMCAM is only half of that of OS. In a word, it is a easily realized CFAR scheme.

Abstract:In order to provide a scientific basis for the rational allocation of development and construction funds required in further system optimization to improve system design, an airborne C I system performance assessment index system is proposed according to the function, characteristics and the applied research of airborne CI system, in which all factors and additional indicators expertise on airborne CI system performance are taken into consideration comprehensively, and the airborne CI system efficiency is quantified by combining the subjective and the objective to enhance the comprehensive ability in evaluation. The use of fuzzy comprehensive evaluation method in evaluating the static system performance will combine the static and dynamic assessments to obtain a total evaluation of the system performance. An example analysis is done, which shows that this method is feasible and effective.

Abstract:In order to optimize design and establish a study foundation for outside flow-field, computational models for solving pressure, velocity of water column and friction force in the launch pipe of pulsed anti-riots water cannon are H55established. Commercial software FLUENT is used to simulate the process of high-pressure gas impinging into water column,k-εmodel is used to describe the turbulence distribution, and VOF model is used to trace the gas-liquid interface in pipe. Through the simulation, the gas-liquid interface evolvement image, vector distribution of exit velocity and pressure distribution at symmetrical axis in launch pipe are gained. The theoretical calculation values of the established models are compared with the simulation results, and the situation of their conforming with each other is analyzed. The move of water column is influenced by the inertia force primarily, not by the gravitation. The greater pressure grad presents in the water column area, the theoretical calculation value and the simulation result match well, and the latter one can be used to amend the computational model. The conclusion obtained has some guide sense in the study of outside flow-field, the design of water cannon or same non-lethal weapons.

Abstract:Through the analysis of the aerial defense equipment maintenance support system in war, the causality and flow figures of system are established, and the confrontation simulation is analyzed by using the software of system dynamics. Considering the targets such as the success percent of enemy airplane repair, the percentage of discarding the damaged aerial defense equipment, the intercept ability of the aerial defense equipment and the percentage of successful maintenance, the system action is simulated and the results shows that the model has some practicability, and can provide a basis for improving the system support efficiency.

Abstract:In order to mitigate narrow-band interference in DS system, a phase spectrum reservation processing is proposed in DS signal receiving and an iterative algorithm is employed in the method to reduce computational complexity. The suppressing narrow-band interference principle is discussed and the performance loss in AWGN channel is analyzed. A method of calculating the performance loss is presented. The numeric simulation results of receiving DS signal by phase reservation processing are presented for variety of interference conditions. These results demonstrate that the narrow band interference can be effectively suppressed and no obvious performance loss is caused after the phase spectrum reservation processing

Abstract:This paper discusses the limitation of multi-ply feedback neural network algorithm, presents a fast intrusion detection algorithm, i.e. IBP algorithm, based on the modified BP algorithm: adding a momentum in decreasing gradient formula to calculate the cascade weight value of neuron j to neuron i ,adopting alterable learning rate strategy, choosing batch processing sample input while training the neural network. Bigger learning rates η=0.5 and η=0.65 are selected in the improved algorithm and the structure of three-ply neural network is adopted. The simples of input and output are of fifteen dimension and sixteen dimension. The simulation with computer shows that the modified algorithm is superior to the traditional algorithm in constringency speed, susceptiveness to the initial weight value, stabilization in network.

Abstract:According to the present High Frequency (HF) Air-Ground Communications, this paper derives the function relation between aircraft flying position and time, simultaneously proposes a new frequency changing strategy based on SNR sorting. This new strategy based on ITS area SNR data ascertains the distribution curve of each channel's SNR along time on the route through interpolation method. At the same time, real time frequency application plan on the whole route of plane is given by this strategy, thus ensuring that the channel communication quality should be maintained at a high level, and the REL be regarded as the evaluation standard of channel quality. Simulation results demonstrate the great improvement on average SNR and communication reliability on the route, which insures communications during flying always being at the optimal channel and overcomes the disadvantage that one frequency only fits one area's communications.

Abstract:Along with the rapid expansion of Internet, the infrastructure of Internet is becoming increasingly complicated. Network topology discovering has becomes an effective way to research the Internet. The key point of network topology discovery is to discover the connectivity between Routers. Because Router usually has several network addresses, Router alias resolution is important to network topology discovering. In this paper, the alias merge of the router is specified and the key technology has been researched. Then a router alias discovery and merging algorithm is proposed. The algorithm gets the address aggregate through data analyses. The test shows that the actual connection of network can be obtained by the algorithm.

Abstract:TACAN phased-array antenna is a large antenna of TACAN beacon. Because the antenna should be formed into a rotating nine-lobed cordate pattern, real-time control must be performed for the phase of the phased-shifter controlling the phase of radiated signal. The veracity of the antenna pattern is determined by the initial phase of the phased-shifter, so, only when phase calibration is done, can TACAN phased-array antenna work normally. In this paper, based on the analysis of the direction pattern forming principle and phase calibration method for TACAN phased-array antenna, and by adopting Fourier theory and vector accumulation principle, a realizable phase calibration algorithm on the basis of vector accumulation is put forward. By using this algorithm, the times of calculation can be reduced, the calibration speed is enhanced and the requirements for hardware are moderated. The experiment result shows that this algorithm is reasonable and effectual in precise phase calculation, fast in phase calibration. And this algorithm has been successfully applied in the TACAN phased-array antenna.

Abstract:To cope with the circumstance without considering wideband for the DOA estimation method under SαSnoise, on the basis of analyzing the character of wideband array output matrix in SαS noise, the temporal method and the frequency domain method are combined by constructing every frequency band of fraction cumulant of the L-shape array, which could extend 1-dimension wideband signal to 2-dimension. Meanwhile, using the CSM focusing method, the direction matrixes at different frequencies are transformed to matrixes at the same reference frequency of matrix by k focusing matrixes, and the improved MFLOM is adopted as the estimator of co-variation matrix. Thus the 2-dimension DOA estimation of wideband signal under SαS noise is realized. The algorithm is effective through simulation and analysis.

Abstract:In order to enhance the robustness of digital watermarking, to make the system possess the zoom resistance capability and to estimate the zoom resistance degree of the system, a difference feature point grid is constructed, and a zoom resistance embedding and extracting scheme of digital watermarking is designed. At the same time, the zoom capability of difference feature point grid is analyzed emphatically. The anti-zoom capability is judged by analyzing the successful detecting instance of basic points. If the image is magnified, the basic points can be detected all the time. If the image is dwindled, the basic points can be detected when the dwindling scale of one orientation is within the scope of 0.5 to 1, but the basic points can not always be detected when the dwindling scale of one orientation is below 0.5. So, a conclusion is obtained that the difference feature point grid can ensure that the basic points still exist in the difference feature points after the image suffered attacks. The difference feature point grid has a good capability in zoom resistance, and it serves a key function in zoom resistance of digital watermarking.

Abstract:Scientific and exact evaluation for equipment maintenance support system is important for improving the shortage of system and enhancing support effectiveness. In fact, because of the uncertain information in evaluation, it is difficult to obtain exact conclusion. To counter the shortage about the uncertainty in current evaluation methods, an evaluation model based on degree of grey incidence and evidence theory is proposed. Through establishing the evaluation index system and calculating degree of grey incidence between the system condition gained with different methods and the evaluation grade of system, the basic probability assignments for evaluation grade are derived, and then the combination rule of evidence theory is used to fuse the evaluation grade in different methods for evaluation conclusion. The practical calculation result shows that the model is effective.

Abstract:With the analysis of the multiaxial fatigue behavior of the thin wall specimens and notched specimens of GH4169 alloy as well as the state of the stress-strain by using the Finite Element Method (FEM), a new damage parameter for multi-axial fatigue is proposed by means of von-Mises criterion based on the critical plane approach. In the new damage parameter, the triaxial factor is introduced. For the new damage parameter, the maximum shear strain and normal strain on the critical plane are taken into account, and the effect of stress state under the multiaxial cyclic loading condition on the fatigue life is taken into account as well. This parameter without containing empirical constants is easy and convenient for engineering application. By combining the proposed damage parameter with the Manson-Coffin equation, the fatigue life prediction model is established. And the experimental verifications show that the new fatigue life prediction model is more accurate in predicting the high temperature multiaxial fatigue life of the thin wall specimens and the notched specimens.

Abstract:After analyzing the disadvantages of the original penalty function algorithm, a smoothing parameter is introduced into constructing the continuous and differential penalty function with parameter for the constraint optimal control problem, and a smoothing penalty function algorithm is proposed, then the constrained optimal control problem is converted into the unconstrained optimal control problem. According to continuous dependence on parameter for the solution of differential equation, an approximate minimum principle is obtained under non-constrained condition. With this approach, the fault of the conventional penalty function, i.e. the non-differentiable, is overcome and this approach is simple, feasible and easy to come true. Finally, the numerical simulation example shows the effectiveness of the algorithm.