Abstract:The adaptive multi-null monopulse principle of phased array radar， derived from the maximum likelihood estimation, was introduced. It was found that the failure of double-null monopulse technique in multiple group targets was caused by a large iteration step. In order to optimize the iteration in angular estimation, a method of weighted step was proposed. By the proposed method, an accurate angular estimation of multiple group targets was achieved with a few computations. Several simulation results demonstrate that the angular estimation error of three targets is about 0.15 beamwidth in medium signal to noise ratio. However, the performance will get worse when there are a large number of group targets or the phase offset of echoes is closed to 0.

Abstract:The differences between the two kinds of almanac in the new BDS civil navigation message and the navigation message of BeiDou-2 were analyzed, and the influence of various almanacs on the initial positioning time of the receiver was analyzed. Based on the actual data of almanac, the user algorithms of different almanac types were compared, and the influence of different age data on the initial positioning performance of receivers was analyzed. The results show that the performance of the precise ephemeris with a week of data is more stable, and the accuracy of medium accuracy almanac is lower than the accuracy of the precise ephemeris, but the performance can close to that of the precise ephemeris as a result of simplifying the message space. The contracted almanac further simplifies the parameter number and message space, although the location error achieved hundreds of kilometers, but can keep the corresponding precision after a few months, and shorten the initial positioning time of the receiver.

Abstract:In order to increase the message volume in limited bandwidth for new generation BDS（BeiDou navigation satellite system） RDSS(radio determination satellite service), the signal was modulated on multi-subcarriers inferring to orthogonal frequency division multiplexing. Modulation on multi-subcarriers was rarely used in navigation systems. Corresponding analysis mainly focuses on multiple access affection, and loss caused by carrier frequency offset and code phase offset were analyzed separately. It is not considered that when using the same synchronization head, the signals on other subcarriers can cause high correlation peak for the observed subcarrier. This may affect the receiving of signals. The mechanism is analyzed and two correlation mitigation methods are supplied, which offers certain guidance for the design of the follow-up system.

Abstract:In order to solve the shortcomings of signal separation methods based on the dictionary learning in phase information loss and cross representation, a signal separation algorithm based on the discriminative amplitude-phase dictionary learning was proposed. In discriminative amplitude-phase dictionary learning method, a model of amplitude-phase dictionary was proposed to solve the problem of phase information loss. Meanwhile, based on the idea of discriminative dictionary learning, a penalty term of cross representation was added into the object function of dictionary learning to solve the problem of cross representation, which happens to the mixed signal projected in joint dictionary. Experiment results show that the amplitude and phase information of low probability of intercept signals can be fully represented by amplitude-phase dictionaries. Meanwhile, the proposed penalty term within discriminative amplitudephase dictionary learning algorithm can profitably restrain the cross representation between signals and the proposed algorithm has a significant performance in signal separation.

Abstract:In order to solve the problem of the interference management in D2D(device-to-device) underlaid cellular networks, a new design of stochastic geometry based access control for D2D communications was proposed. Based on the stochastic process theory and the stochastic geometry tool, the cellular services′ access failure probability expression was derived to determine the impact from other-cell base stations and D2D communications on the cellular communication. Given the constraint of access failure probability, the maximum D2D transmitters density was calculated according to the expression. As a result, the base stations realized the access control for D2D users and guaranteed the access failure probability of cellular services. The calculated access failure probability of cellular services was validated by extensive simulations. The simulation results verify that the estimation result from the proposed numerical calculation is consistent with the Monte Carlo simulation result, and the cellular services′ access failure probability requirement can be satisfied by limiting the density and the transmission power of D2D transmitters.

Abstract:To achieve the blind jamming cancellation and signal recovery under MIMO(multiple-input multiple-output) system with intended jamming attacks, a structure of dual-array-antenna receiver was proposed to achieve the blind jamming cancellation without the consideration of the correlation between jamming and the transmitted signal. Data free of jamming have an obvious characteristic of tensor slice. They were stacked into a 3-order tensor and then the CP decomposition was performed to recover the original signal directly without channel estimation. Compared with the traditional method based on channel estimation, the tensor-based algorithm can avoid the error caused by channel estimation, which can largely improve the recovery precision. Simulation results show that the tensorbased method achieves better recovery performance with less training overhead than the traditional training sequence based channel estimation method.

Abstract:The packet segment offloading and sending mechanism was proposed and the prototype system was implemented. This mechanism, based on the multi-core packet processing system with lightweight input/output, was aimed to reduce the cost of large packet segmentation, copy overhead, hardware and software complexity. It offloaded the complex parts of hardware implementation to the drive including packet segmentation, packet head encapsulation. It reduced the whole data copy cost to the copy cost of the new packets header, combined the chain direct memory access technology to provide an effective solution of packet forwarding on the multicore system. The packet sending performance based on domestic general multi-core and field-programmable gate array platform was tested. The experimental data shows that the packet segment offloading and sending mechanism can significantly enhance the performance, and effectively solve the problem of the large packet sending on the multicore network processing system.

Abstract:Clock synchronization protocol, as an important component of the time-triggered networks, is the key to the instantaneity and certainty of the time-triggered networks. The modeling and verification of clock synchronization protocol were studied. The protocol′s behaviors were modeled by the extended labeled transition systems, and its correctness was verified by model checking technique. The verification results certified the correctness of this protocol even under different startup scenarios. Experimental results also show the effectiveness of extended labeled transition systems in protocol verification.

Abstract:In order to improve the accuracy and adaptability of image registration algorithm, the hypergraph constraint and the improved NCC(normalized cross correlation) were applied to image registration. The proposed algorithm used the HessianAffine detection affine invariant region instead of the fixed window to improve the NCC method and obtained the initial matching point pairs. The similarity degrees between the hyperedges of hypergraph were calculated by Martensitic distance, and the matching scores of the matching pairs calculated by hypergraph constraint were used to sort the matching pairs. The transformation matrix was initialized with some matching points of higher matching scores, and was circularly updated by filtering matching pairs to get the optimal transformation matrix, which was used to implement registration. Experimental results show that the proposed method has better performance in matching and rejecting mismatch, and it also has better registration performance in different types of image registration.

Abstract:The simulation model of dynamic response characteristics of solenoid valve was established based on Ansoft Maxwell software, and the accuracy of it was verified by experiment. The sensitivity analysis of parameters affecting the dynamic response characteristics of solenoid valve was conducted by the method of integrating ISIGHT with the model, the Pareto of parameters on the dynamic response characteristics was obtained. The multi-parameter optimization design of solenoid valve was carried out based on genetic algorithm, the optimum parameter combination was achieved, and the comparison experimental research of dynamic response characteristics of solenoid valve before and after parameter optimization was conducted by the experimental bench. The result shows that compared with the original parameter scheme, the dynamic response characteristics of solenoid valve after parameter optimization are improved greatly, and the opening and closing response time is reduced by 59.1% and 47.2% respectively.

Abstract:In order to study the three-dimensional effect on the oscillated vertical axis tidal turbine, the CFX software was employed to simulate the oscillated (surge and sway) turbine with different span-chord ratios. The simulation results were then compared with those in 2D situation. And then, the time series curves of thrust and lateral force coefficients of the hydraulic turbine with different aspect ratios were fitted by least square method, and the damping and additional mass coefficients were obtained. The results show that the current power output efficiency of the turbine increases with the span-chord ratio increased. The hydrodynamic load of three-dimensional oscillating tidal turbine is positively correlated with the elongation of the turbine. When the spanchord ratio reaches 10, the hydrodynamic loads and power conversion efficiency of the 3D oscillating turbine are basically the same as those of the 2D one. The constant and damping terms of the hydrodynamic coefficients of the 3D turbine increase with the increase of spanchord ratio.

Abstract:In order to study the hydrodynamic ram generated by high velocity fragment impacting fluid-filled container, a set of experiment device and testing method was designed to record the evolution of the cavity inside the container, the pressure changes at different positions in the liquid and the deformation of the front and rear panels. Experimental results show that a circle of cavitation bubbles will appear when the fragments impact the rear panel of the container, and the bubbles rapidly expand radially from the point of impact on the inner surface of the rear panel. In the shock phase of the hydrodynamic ram, large negative pressure appears in the area close to the impact point after the initial shock wave pressure pulse, and the area away from the impact point is not affected by the negative pressure. The fragment impact velocity has little effect on the maximum deformation of the front panel and the deformation range expands along the impact point as the impact velocity increases.

Abstract:In order to establish the finite element grid model of the tube structure accurately and quickly, a parametric modeling method based on the Python script language operating unit and the node coordinates was proposed to establish the finite element grid model of the body tube. Through this method, the finite element mesh model of the tube bore (including the medicine chamber, the slope and the guide part) and the external contour were accurately established and parameterized. In addition, with the 76 mm artillery as the object, the finite element model of the coupling of the barrel and the projectile was established, and the full ballistic motion of the projectile was calculated and verified with the corresponding experiment. The results show that the method can accurately and quickly establish the finite element mesh model of the tube structure.

Abstract:By analyzing the strength and the stability after the topological optimization design of the open-hole topology of the solid floor in the inner pressure-resistant tank, it is found that the solid floor opened near the inner keel is better for the inner pressure-resistant tank with a circumferential range of 162°. It has little effect on its own stability for the opening of the solid floor, but the stress of the MIMES will change. The stability of the liquid tank structure will be slightly reduced when the hole is opened. So, the structure requires strengthening when designing the liquid tank structure in the later stage.

Abstract:Based on the error analysis of the BDS(BeiDou navigation satellite system) triple-frequency carrier phase observations, the screening criteria for the optimal carrier phase linear combination coefficients was determined. For high-dimensional multifrequency mixed data sets, a weighted fuzzy C-means clustering algorithm was used to assign partial BDS triple-frequency carrier phase observations obtained by traditional ergodic search methods through assigning different weight values to different clusters on the same dimension. The combined observations were optimized for classification and selection, which effectively solved the problem of low efficiency of the traditional GNSS(global navigation satellite system) carrier phase observations selection method, and provided an idea for the optimal selection of the combined observation value coefficients of multi-system multi-frequency data. Finally, the classification results were analyzed, and the applicable range of all kinds of combined observations was determined. The integer ambiguity of the optimal combination is calculated by using the geometric-freed CIR(cascading integer resolution) algorithm and the measured data, and the feasibility and reliability of the method are proved.

Abstract:In ground operation and control subnet and payload information network using IPsec, GRE or RFC2003 three IP tunnel protocol, through the platform information network and the telemetry, tracking, and command network, the user data encapsulated into IP tunnel protocol can be routed in communication link between the spacecraft and the ground so as to support the payload and the ground transport flexible end-to-end communication between two control terminals. The information management architecture of world integration was designed to support IP communication, the setting of router and IP address allocation were given，and the communication efficiency and timeliness of three IP tunnel protocols were calculated and analyzed. The analysis result shows that the IP tunnel protocol is of revolutionary significance to change the traditional ground operation and control mode and improve the efficiency of operation and control.

Abstract:In order to simulate forward looking infrared seeker′s matching guidance process, an acceleration strategy aiming at the contrast-limit adaptive histogram equalization and the normalization cross correlation algorithms was researched to realize realtime target tracking judgment. The real-time processing acceleration strategy of foggy images based on CUDA(compute unified device architecture) was proposed. The final real-time graph preprocessing acceleration schema implements two main design parameters′ optimization, including blocksize and blockgrid. Experimations show that using CUDA acceleration schema, the work efficiency is 5~20 times faster than the original algorithm. The proposed acceleration schema can satisfy the realtime target tracking judgment and can provide references to researchers devoted to the related work.

Abstract:The aviation aluminum alloy accelerated corrosion test spectrum was established according to the environment spectrum conducting process after collecting the airports environment data. Based on the accelerated corrosion test spectrum, aluminum alloy LD2CS pre-corroded fatigue test was carried out. Test data were analyzed statistically and the three main corrosion damage characterization factors, namely maximum pit depth, maximum pit width and pit surface rate, were sifted out by using MIV (mean impact value) method. Then the corrosion damage composite indictor α was computed by applying the normalization non-dimension and the weighted average methods. By comparing the characteristics of fatigue precrack propagation behaviors at different corrosion damage levels, the corrosion acceleration coefficient Ω(α) was defined to correct the classical fatigue crack growth formula. The validity of Ω(α)expression was verified by employing test data corroding the 18th to 20th equivelent years and the relative errors were all below 10%. It demonstrates that the corrected fatigue crack growth function in flight transfer environment is appropriate for reflecting the corrosion damage acceleration effect on crack propagation, which proposing new ideas for aviation aluminum alloy damage tolerance design.

Abstract:Aimed at the distributed chilling demand of next generation marine electric propulsion plants, the self-reconfiguration and self-healing problem of marine central cooling system, a multi-agent autonomous control framework for a certain type of central cooling system was proposed. The specific structure of individual agent and systematic configuration of agent group was designed. The agent alliance and acquaintance mechanism was adopted to improve contract net cooperation model. The cooperation process of multi-agent system during task allocation and fault recovery was optimized. On this basis, a prototypical apparatus of the central cooling system was designed, the experimental research platform for multi-agent autonomous control system was built, and the performance analysis and verify of control system was carried out. The results show that the designed multi-agent autonomous control architecture implements dynamic reconfiguration and fault recovery process autonomously, and enable marine central cooling system to have the ability of selfreconfiguration and selfhealing.

Abstract:Aimed at the problem that the UAV′s(unmanned aerial vehicle′s) single station angle and distance measurement are greatly affected by the UAV′s attitude angle error, a method was proposed to solve the UAV′s attitude by detecting the auxiliary beacon and combining with the inertial sensor. The attitude solving model of inertial sensor based on cubature Kalman filter was established. By using the gradient descent method, the attitude parameters of UAV based on auxiliary beacons were solved, and the results were comprehensively used to estimate and correct the attitude error of UAV. Finally the targets′ location and simulation calculation under different fields of view were completed. The results show that the proposed method can improve the precision of UAV target location.

Abstract:Due to the complicated interference pattern of the infrared decoy and the variable shape of the target maneuver, the traditional proportional guidance law is easily interfered. In order to improve the performance of missiles using the proportional guidance method, an intelligent guidance law that uses the RBF(radial basis function) network to control the proportional coefficient and the timing of missile launch is proposed. Taking the flight time and miss distance as reference, the weighted index function is used to transform the optimal proportional coefficient and launch timing problem into a single objective optimization problem. The quantum particle swarm optimization algorithm is introduced to solve the optimal decision parameters which are used as the network output, and the interference pattern is used as the network input to train the RBF network offline. To improve the training efficiency, the RBF network is initialized by combining the Kmeans and KNN(K nearest neighbors) algorithms. Simulation results show that the intelligent guidance law is better than the extended proportional guidance law and the adaptive sliding mode guidance law when there is infrared decoy interference.

Abstract:In order to analyze the static electric field distribution of non-steady-state process under concentration polarization conditions,the Laplace transform was used to solve the change of oxygen concentration on the surface of the electrode based on the Fick second law. The current density of galvanic corrosion controlled by oxygen concentration was analyzed through Faraday law, in the basis of which the instant potential and static electric field in any position of electrolyte can be obtained through current element, and then to verify the correctness by experimental results. The results show that the static electric field and potential decrease with time and reach a steady state finally, while the current density decreases with the decrease of oxygen concentration.

Abstract:A circuit analog absorber with double hexagonal loops units was proposed. An equivalent circuit model was established according to the dual-frequency characteristics of the units. The equivalent period concept was proposed by analyzing the periodic distribution of the units, and the extraction of distribution electrical parameters was given. The structural parameters were simulated and analyzed with the proposed method, the simulated results were in agreement with the results given by HFSS software, and the accuracy was verified. Finally, a sample was fabricated and measured. The measured results show good broadband absorption in 1.9~8.9 GHz for normal incidence, and the accuracy of the proposed method is verified further.

Abstract:Surrogate methods (metamodels) are convenient to determine the mathematical relationship underlying the high dimensional complex systems, which are usually computationally expensive. Various stand-alone metamodels have been proposed in literature, and the ensemble of metamodels was being intensively studied recently to utilize the information reveals in construction of different metamodels. Compared with the stand-alone metamodels, the ensembled models were more robust and adaptable. The strategy of the ensemble by comparing the difference of the probability distribution of predictions was considered, where the Kullback-Leibler divergence was introduced to calculate the differences. Experiments show that the strategy has comparable accuracy in predictions with the most accurate standalone metamodel, and it can also perform better in recovering the distribution of the true response.

Abstract:In order to study the influence maximization problem in complex networks, a heuristic framework was developed. Based on the in-depth analysis of information transmit process between node pairs, the probability of a node being in the informed state was obtained, and then an approximation of spreading influence of seed nodes was conducted through expectation calculation. A fast evaluation algorithm was proposed based on sequential seeding strategy. Specifically, simulation results on six real networks from various fields all show that the proposed algorithm is able to distinguish a small set of influential seed nodes. Moreover, the influence scope of the seed nodes selected by the method is significantly better than three benchmark influence maximization algorithms under three common measurements.

Abstract:The designs for computer experiments attract more and more attention, and the nested Latin hypercube designs play significant roles in computer experiments, for they mainly deal with the experiments which have high-accuracy and lowaccuracy parts. However, most nested Latin hypercube designs have the restriction that the run sizes of lowaccuracy experiments should be the multiple of highaccuracy experiments. A general multi-layer nested Latin hypercube design which has flexible run sizes for different accuracy experiments was proposed by improving the traditional construction method. This design method can achieve the desirable one-dimensional uniformity. Numerical simulations show that this method perform well on the sampling variance.

Abstract:Based on the traditional linear regression model of guidance instrumental systematic error, the advantages and disadvantages of three parameter estimation methods were compared, namely Bayes estimate, principal component analysis and regularization method, and the practical limitations were presented. Combined with the specific initial error of sea-based missile, three estimation strategies named overall were designed, namely piecewise and iteration estimate strategy and giving detail estimate procedures, and the following separation steps were provided. Results show that the principal component analysis and regularization method are better than Bayes estimation, and the new proposed estimation strategies are better than the traditional one.