Abstract:At present, clicking on the button and waiting for a period of time after completing the sketch fully is the most common recognition method for online sketched symbols. To achieve the continuous feedback, a primitive-based partial sketches recognition algorithm was proposed. In the stage of feature representation, the input strokes were segmented as primitives and then a new feature which presents the spatial relationship between a pair of primitives was come up with. Based on the model of assignment problem, symbols were recognized through the similarity of this feature finally. The proposed method is so easy that one can master it without training and it has nothing with the order of stroke, the number of stroke and the size of graph. Its validity was testified by experiment.

Abstract:The vectorization of algorithm mapping for vector processors is a critical issue. An efficient vectorization method of triangular matrix multiplication which supports the in-place calculation was presented. L1D was configured as SRAM and the ping pong pattern with double buffering was designed to smooth the data transfers of multilevel storage structure, which made the kernel computation overlap the DMA data transfer fully and run with peak speed throughout, so then the optimal computation efficiency was achieved. Irregular triangular matrix multiplication computation was evenly distributed to all vector processing elements to fully exploit multiple levels of parallelism for vector processor. Result matrix was stored in multiplier matrix, thus, the in-place calculation was achieved and the memory space was saved. Experimental results show that the performance of triangular matrix multiplication attained from the presented vectorization method achieves 1053.7 GFLOPS and the efficiency of that reaches to 91.47%.

Abstract:To improve the registration accuracy of point cloud data generated by 3D laser scanning, a new method of iterative interpolation registration based on fast point feature histograms (FPFH) was proposed. Due to the effect of the scanner's resolution in the process of registration, partial or overall density of obtained point cloud data was smaller so that there were no same points even the measuring locations of point cloud data were fixed. Therefore, errors existed between corresponding points. In order to reduce the influence of these errors on the registration accuracy, iterative interpolation method was introduced to increase the overall density of point cloud. The FPFH features of key points were used to find the corresponding relationship; random sample consensus algorithm was used to remove the false correspondence between two point clouds; then the coarse registration rotation and translation matrix was gotten by using singular value decomposition algorithm on the corresponding covariance matrix; at last, the iterative closest point algorithm was employed for the precise registration of point clouds. The experimental results show that the improved registration algorithm is simple, stable and reliable and its computation velocity is faster. This method effectively improves the accuracy of registration results.

Abstract:Taking account of that it is difficult to obtain the error function to make sequential re-sampling optimization when the predicted error of sampling points in radial basis function(RBF) interpolation surrogate model is zero, the constraint of sampling point distribution was applied in the process of sequential re-sampling. Taking advantage of the convergence performance of potential optimal solution, a re-sampling strategy which is suitable for the sequential optimization of RBF interpolation surrogate model was proposed. The strategy matches the input response property of emulation model with the spatial distribution property of sampling points. Simulation results indicate that the optimization efficiency and precision of the proposed strategy is higher than that of the traditional optimization method based on surrogate model. The optimum point can be well predicted and the number of computational times in primitive model can be reduced obviously by the proposed strategy.

Abstract:In view of the matching problem of low texture objects, a line matching algorithm based on local neighboring gradient information and global structural information was proposed. The mean standard deviation line descriptor was redesigned to get the initial matching; the global topological structure between lines was used to get rid of wrong matches; more matches were achieved by utilizing the iterative topological filter. Moreover, global angle constrains were implemented to make the algorithm more efficient and to further remove wrong matches. Experiments show that the proposed algorithm is highly robust under various image changes including heavy illumination change, image rotation, image blur, scale change as well as viewpoint change and is much better than the other two popular methods in terms of matching accuracy and efficiency.

Abstract:As the typical ground objects in near-ground visual navigation application, the three-dimensional geometrical models of trees can improve the visual precision and the reality of virtual scene. However, it may lead to the decrease in rendering efficiency of a wide forest scene and result in the loss of navigation precision. In order to boost the rendering efficiency to ensure the navigation precision and maintain the sense of reality, billboard clouds algorithm was employed to establish the multi-resolution tree models based on view distance and its disadvantages existing in near-ground visual navigation application were improved. To improve the visual navigation precision with high dynamic viewpoint in the near-ground especially the nap-of-the-earth flight further, an accelerating rendering algorithm based on high dynamic viewpoint was proposed in accordance with the characteristics of limited horizon, threatened area and redundant vision. The contrast analysis of experiments testifies that the proposed algorithm improves the rendering efficiency, enhances the vision quality of the scene and raises the navigation precision of virtual scene.

Abstract:The eddy current impedance in voice coil affects the behaviors of the high-frequency response of moving-coil loudspeakers under small input voltage. Based on the equivalent electrical circuit method in lumped parametric system and using the power exponent function of angular frequency to fit the magnitude and phase of the eddy current impedance, the power exponent function model of voice-coil eddy-current impedance was presented. The electrical impedance curves of six loudspeaker units in three types were obtained by using the laser impedance measurement system and the model parameters of eddy current impedance were identified by fitting the measured impedance curves with the least square method. Error comparisons between the simulative values and the measured data show that the power exponent function model can accurately reflect the change relationships between the measured eddy-current impedance and frequency. The magnitude and phase have small errors and behave good correspondences with the measured data.

Abstract:Based on the rank C70 high strength concrete, the experiments of the cubic compression, splitting tensile and four-point bending for four kinds of ultra high molecular weight polyethylene (UHMWPE) concrete with different fiber contents were conducted to research the effects of the fiber content on mechanical properties of concrete. The results show that the enhancement effect of the UHMWPE fiber on the compressive strength of concrete is not obvious. However, the added UHMWPE fiber greatly improves the splitting tensile strength and bending strength of concrete and it has excellent effects on toughness and crack resistance of concrete. The splitting tensile strength increases more than 25% when the fiber content is between 0.3% and 0.5%; the bending strength increases more than 23% when the fiber content is 0.5%.

Abstract:A calibration approach based on the invariant of interstar angles was put forward for star trackers. Compared with common approaches, the sine of interstar angle which provides greater sensitivity for the angle changes closed to 0° was adopted to construct the observation equation instead of its cosine. In the calibration procedure, the two-step approach was proposed to estimate the principal point, focal length, and distortion parameters. The iterative optimization was also proposed to get the optimal estimations. In order to improve the accuracy of calibration, the apparent position of star at the observing time was modified. The experimental results indicate that the sine method is more accurate; and the deviation root-mean-square of the measured interstar angle is 2.2×10^-5 rad after calibrated.

Abstract:An automatic tracking measurement system was designed to achieve real-time measurement for motion parameters of long-range air targets, such as aircraft. Hardware, software and key technologies were described in this system. The prototype was made and tested, the software structure design and corresponding functional modules were analyzed. Multiple experiments are presented to testify the working performance of the system. The static verification experiment indicates that the ranging results are stable within 1mm and the azimuth measurement results are stable within 5″. And the dynamic verification experiment indicates that the ranging error of moving target is 2 mm, the ranging frequency is 5Hz, the azimuth measurement error is 0.05°, and the posture measurement error is maintained at a level less than 0.2°, the real time measurement frequency of azimuth and posture are 20Hz. From the above analysis, the system can provide a stable, reliable and high precision automatic real-time measurement when testing motion parameters of aerial target.

Abstract:Designing the trans-lunar orbit is one of the key skills for lunar probe mission, and the differential correction is proved to be one of the effective methods to solve a non-linear iteration equation. According to the requirements of high design precision and rapid calculation speed in designing the trans-lunar orbit, a rapid trans-lunar orbit design method from improved differential correction was proposed. Based on the dynamical model, which contains the sun, the earth, the moon, and the earth's J₂ perturbation force in the DE405/LE405 planet and lunar-ephemeris data, the partial derivative matrix of parameters from the perilune to the perigee was deduced. The differential correction matrix was integrated in company with the orbital state variables and velocity, and the transfer orbit design parameters were converged iteratively and rapidly with the precise differential correction matrix. Simulation result shows that the convergence rate of the integral differential correction method is faster than the frequently-used SQP（Sequential Quadratic Programming）method in dynamical models with the same accuracy.

Abstract:For lunar module with low lift to drag ratio, skip entry trajectory must be flown to extend downrange. According to the key element of skip entry trajectory online planning or predictive guidance is how to predict the downrange of the first entry phase rapidly and precisely, an analytical method was proposed. Firstly, closed-form approximate solution of the longitudinal equation of motion was obtained from using matched asymptotic expansion method. Secondly, the first entry trajectory was divided into three phases. In the first phase, altitude served as the independent variable of integration, downrange was obtained from using a composite trapezoidal-rule. In the second and third phases, quadratic polynomial was used for drag-energy profile fitting, and the polynomial coefficients were solved according to the result of the approximate solution, and downrange was obtained by integrating the reciprocal of drag versus energy function. Finally, the accuracy and computational efficiency of the proposed method were analyzed. Simulation results indicate that the characteristic of the proposed method with high accuracy and computational efficiency is very suitable for online planning and guidance.

Abstract:A new entry guidance method combined predictor-corrector guidance and reference trajectory guidance was proposed for reducing calculated amount in predictor corrector entry guidance. Predictor-corrector guidance was applied in initial entry phase to improve robustness, and reference trajectory guidance was applied in second entry phase to reduce calculated amount. Through the information of reference trajectory, it was less time consumed in predicting. The method with a new command fast iterative algorithm was designed to reduce the iterative times. The reference command profile was revised according to actual condition of lunar capsule in transfer position so as to compensate error and to improve the quality of the second entry guidance performance. Numerical simulation results demonstrate that the combined entry guidance method is able to lessen time in predicting and fasten correction, and it has the characteristics of high precision and robustness.

Abstract:Landing conditions of space capsule have a great effect on impact characteristics. Firstly, the analysis and simulation model of space capsule was established and validated according to an available experimental data. Methods for explicit nonlinear kinetics analysis were used to simulate the landing impact process of space capsule. And the significance effect and the influence disciplines of parameters related to landing conditions on impact characteristics were analyzed by the orthogonal test design. Results demonstrate that the vertical velocity, the pitch angle, the heeling angle and their interactions significantly influence the maximum impact acceleration, while the horizontal velocity and the rolling angle rarely influence it. These conclusions can provide important reference to both the ground tests of landing impact as well as the structural analysis and design.

Abstract:Under the early warning of two passive satellite-borne sensors, the exponential weighted recursive least square method was applied to the burnout states estimation of ballistic targets. Due to the weighting factor can characterize the local quasi-linearity of the boost phase trajectory of the target, so to some extent the dilemma that generic polynomial cannot handle the whole boost phase of the target can be overcome. Through a dynamic analysis, the kinematic characteristics of boost phase target along the orientation of vertical surface were explored. On that basis, a novel boost phase motion model is proposed, which is more accurate than traditional planar motion model. Simulation results show that the proposed approach is superior to the traditional ones.

Abstract:To assess the risk of the rocket trail cover separation movement, the multi-body dynamic model in separation process was established according to the Kane's equation, and the collision checking model based on the relative location estimation of the key point-collision boundary was built. The Monte Carlo method and the Morris screening method were used to analysis the uncertainty of the separation process when the input parameters had random deviations. The dispersion characteristics of the separation motion state were got from the Monte Carlo method and the sensitivity of each parameter was ranked by using the Morris screening method. Results show that the trail cover separation solutions possess high reliability, which can satisfy the security requirements in the case of the input parameters with deviations. Among all the input parameters, wind interference and the thrust deviation of the thruster from ejection pistons has greatly influenced the distance of drop points, and the horizontal distance between the rocket and the trail cover has been greatly affected by the wind and the out canister velocity under the circumstances of ignition.

Abstract:The ignition process of boron particles in relatively static atmosphere was studied systemically. In view of the gas flow around the boron particle, the heat and mass transfer process between the boron particle and the surroundings, a one dimensional ignition model of boron particles was proposed. The changing regularities of important parameters of the gas and the particle in the two typical cases, namely, the successful ignition case and the degenerate ignition case were studied. And the mechanisms for them were analyzed in detail. The result shows that Stefan flow in both typical cases will undergo changing flow direction. Stefan flow undergoes flowing to the particle surface from the gas, and then it flows to the gas from the particle surface. Study of ignition process of boron particles in the paper shows that ignition time decrease with consideration of Stefan flow at the particle surface. And the effect increases with the ambient pressure.

Abstract:In order to improve the gliding ability in mid-course trajectory of the aerial time-sensitive guided bombs, a combinatorial optimization design method which can be applied to the extended-range project of aerial time-sensitive guided bombs was proposed by combining the minimum principle with the adaptive evolutionary particle swarm algorithm. In the base of the model of mass-centre motion in longitudinal plane, performance index function and inequality constraint functions were derived. Hamilton equation was established by introducing Lagrange multiplier vectors to convert the unconstrained functional extremum problem and deduce the satisfactory optimization model which gave consideration to all optimization object functions. By means of the adaptive evolutionary particle swarm algorithm, double design variables, attack angle and wing gears, of extended trajectory were optimized combinatorially. The simulation results indicate that the range of the guided bombs controlled by double variables is obviously more than that of bombs controlled by single variable as long as the constraint condition of state equation is satisfied. The optimization results have reference value for trajectory design of guided bombs.

Abstract:The estimation of resource level’s envelope is a basic problem in constructing a feasible schedule for resource utilization. A new resource reasoning description method that combining resource temporal network, constraint network and temporal network was proposed by analyzing the resource constraint characteristics, such as coexistence of sharing and detaching resource, coexistence of cumulative and instantaneous consumption, coexistence of over-subscription and interval scheduling resource. Considering the specific characteristic of resource temporal network, a resource model was constructed, and two algorithms of the EBA (Envelop Based Algorithm) based on maximal flow and the ESTA^c (Early Start Time Algorithm with Chaining) based on early start time solution to solve with a resource feasible solution were given. The incremental EBA algorithm and ESTA^c algorithm were presented to get a feasible solution quickly. Finally, some experiments were presented to prove the validity of the methods. Results show that the efficiency and validity of the proposed methods are better than EBA algorithm and ESTA^c algorithm in solving the problems of resource constraint reasoning.

Abstract:Goodness-of-fit test plays an important role in the statistics and reliability fields. Goodness-of-fit test for the common life distribution of unknown parameters was based on the resembling idea of parametric bootstrap. Simulation results show that goodness-of-fit test based on parametric bootstrap is superior to the traditional EDF tests, such as Liefors test, CvM test and AD test, especially in small samples.

Abstract:As various issues and impacting factors involved in the safety risk of complex systems, systematic and operational approach was desirable to instruct the evaluation process of safety risk for complex systems. Among the safety risks of a system, failure safety risk, the risk of accidents caused by various failures, is the most common system safety problem, so the evaluation of failure safety risk for complex systems was studied. The evaluation requires the support of explicit parameters and proper approach. Therefore, the paper presented the evaluation process of failure safety risk for complex systems, hierarchical evaluation parameters and approach, and examples were applied to demonstrate the evaluation process in detail. Results show that the proposed evaluation approach provides a feasible solution to evaluate the failure safety risk of complex system.

Abstract:The approach of network modeling and structure optimization for technology system of systems was researched to solve the problems of reusability and redundancy which are key properties of the development and management of weapon technologies. Abstracting weapon technologies as nodes and abstracting technology relationships as sides, the network modeling approaches based on the description property framework of weapon technologies and the analysis of technology relationships were proposed; three typical approaches of the network community detection were applied to cluster the weapon technologies and the optimization method of technology clustering was generated by comparing the evaluation index of this three approaches; at last, the weapon technologies which are the most influential factors to the redundancy of system were identified at the basis of the centrality measure of weighted networks. A case which includes 235 laser weapon technologies was studied to validate the efficiency of the proposed approach and to summarize the structure optimization method of the system.

Abstract:The micro motion target image of SAR can be used in radar target recognition since it can reflect the attribute of target information. Based on the fact that the SAR echo of the micro motion target is sparse, the sparse signal representation was established under an over-complete dictionary. A new sparse Bayesian learning named expansion-compression variance-component based method was employed, which only assigns the distinct variance components to the significant signal elements. In addition, the expansion-compression variance-component based method has much less parameters. The imaging results of SAR micro motion target can estimate the micro motion parameter better, and achieve the fine SAR micro motion image under the low signal to noise ratio.

Abstract:It is a difficult task for an unmanned ground vehicle (UGV) to sense obstacles in out fields or unstructured environments. Because the height information is a vital feature to boost the performance of obstacle discrimination, the three-dimensional imaging technique for sensing obstacles ahead UGV of interferometric synthetic aperture radar (InSAR) was presented. The basic signal process flow of InSAR was reviewed. Special factors of the UGV platform that impact the digital elevation model (DEM) measurement precision were analyzed, such as the baseline length, platform motion errors. The DEM of a partial sight-blocked obstacle scene was obtained by processing the three-dimensional InSAR image, which proved the feasibility of applying InSAR to obstacle sensing of UGV.

Abstract:Quantum technology have been exploited to increase the performance of classical devices in science and engineering fields, such as electronic information and computer technology. Radar, as a typical electronic information system, suffers more and more challenge in target detection, for the widespread applications of stealth and electronic countermeasure technology. The system models of target detection, and the related research advance of the combination of quantum technology and radar technique were overviewed. The basic concept, classification and typical instances of quantum radar system were introduced. The significant research progress of how quantum phenomena enhance the radar target detection performance was analyzed. Directions of future work including key technologies and main problems in the realization of quantum radar were presented.

Abstract:In order to determinate the orbit of space objects, an orbit-determination method with particle swarm optimization (PSO) using space-based optical short-arc observation in admissible region was proposed. The concepts of the attributes, the admissible region and the construction of optimization-function were introduced. A method with PSO for searching best key to optimization-function was proposed to avoid the problem of various keys, local optimizations and mass calculations. An orbit-determination course was simulated with 3rd part software to validate the correctness of the proposed orbit-determination method. Simulation results indicate the proposed method with PSO reaches more precise orbit without various keys and mass calculations, the performance of proposed method is close to Crame-rao low bound.

Abstract:Automatic image annotation is a challenge task due to the well-known semantic gap. Considering the difference between low-level visual features and high-level semantic concepts, the framework of automatic image annotation from the two aspects, image representation and semantic modeling, was constructed. For image representation, a new method of regularized nonnegative tensor representation (RNTP) was presented to abstract the detailed high-order tensor structures according to human’s intuitive recognition. A three-level hierarchical Bayesian model, extended latent Dirichlet allocation (ELDA), was developed for semantic modeling. In ELDA, each item of multiple image factors was modeled as a finite mixture over latent variables. Meanwhile, an efficient expectation-maximization algorithm based on variational inference was proposed for parameter estimation. Extensive experimental results are reported on the NUS-WIDE dataset to validate the effectiveness of our proposed solution to the automatic image annotation problem by comparing with other state-of-the-art methods.

Abstract:The modeling and simulation of intelligence，surveillance，reconnaissance(ISR) is difficult and important for joint campaign-level simulation. In the simulation, ISR model is required that it not only can accurately reflect the perception interaction between battle space entities, but also has a high running speed. To solve this problem, the modeling method of joint campaign-level ISR based on randomness theory was proposed. It took the modeling procedure of regional reconnaissance of aircraft image intelligence for example and described the main links of the modeling method. The modeling method was verified by the simulation experiment, and it showed the validity and applicability of the modeling method. Compared with traditional certain ISR modeling methods, it improves the efficiency of simulation on the condition of insuring simulation precision，and it also provides a reference method of C⁴ISR modeling and simulation in joint campaign-level warfare simulation.

Abstract:The dynamic equations of system centroid orbit and tether oscillation were established. And the dynamic characteristics of tether oscillation without tether control and the effects of tether control on tether oscillation were analyzed. An expect rate of tether which suppress tether oscillation was constructed and tether tension control law was designed. Simulation results indicate that when there is no tether control, tether oscillation is in periodic reciprocating motion around the equilibrium position. The tether tension control is continuous and smooth, which makes tether actual length keep well track of the expected length, and the tether oscillation is suppressed effectively at the same time.

Abstract:A robust control method for new type wave compensation systems that based on cable-driven parallel mechanisms were presented. The environmental forces and immeasurable parameters were separated from the dynamic equations and treated as disturbances. Then a sliding mode control law was derived using Lyapunov stability theory. For redundant mechanisms, a tension distribution algorithm based on alternating projection was proposed. When feasible solutions exist, this algorithm leads to a "safe" optimum solution that is kept away from all the boundaries of the tension constraints. Even if no feasible solution exists, a best approximate solution will be got which satisfies the tension constraints. An identification method was also proposed to enhance the practicability of the robust control method. Simulation results show that the proposed theories and methods are effective for such wave compensation systems.

Abstract:In order to analyze the effects of geometric parameters on the stiffness of bolted flange joint, a parameterized model of bolted flange joint was constructed by using PCL (Patran Command Language) on the platform of software MSC.Patran. The law of the stiffness of bolted flange joint with the change of geometric parameters was studied, and the sensitivity of geometric parameters was analyzed based on the parameterized model. The results show that the ratio of the location of hole is the most sensitive factor to the stiffness of bolted flange joint, and the next one is thickness of upper flange. When the length of upper body is up to a const, the stiffness of bolted flange joint is insensitive to the length of upper body, and this conclusion can provide a reference to simplify the dynamic model of joint.

Abstract:The effects of joint clearance on robot manipulators positional error were investigated. The kinematic model was built by using the D-H method to research the six degrees of freedom mechanical arm. The central error propagation model was established. The simulations of error distribution were conducted in MATLAB with Monee Carlo method. The distribution characteristic and probability distribution of positional error of mechanical arm's end, which is caused by the joint clearance, were obtained from the simulations at different levels of joint clearance. This research provides basis for error compensation and positional error evaluation.