Abstract:Based on the 2-D Navier-Stokes equations, the shock induced interfacial instabilities of heterogeneous gases was simulated numerically With the finite differential method. After carrying out the comparison between numerical and experimental results, the unsteady and nonlinear characteristics of the flow field was analyzed. From the results, it is observed that the unsteady flow field of numerical simulation is similar to referenced experimentation and CFD results, and the evolvement of sulphur hexafluoride interface and the complicated wave structures are captured from simulation.

Abstract:A piecewise linear JE recursive convolution finite-difference time-domain (PLJERC-FDTD) algorithm is applied to the study of the scattering characteristics of the hypersonic flow field with near wake region of conductive metal sphere. The effects of incidence wave frequency, incidence angle, scattering angle, polarization angle, altitude and Mach number on the radar cross section (RCS) are analyzed. The results illustrate that the forward RCS is the maximal RCS of all scattering orientations' RCS. The forward RCS increases with the rise of incidence wave frequency and Mach number, decreases with the decline of altitude when the Mach number is not less than 14 in this article. The backward RCS and the bistatic RCS of flow fields vary very small with Mach number, altitude and incidence angle for UHF, L and S band, the margin of the backward RCS between flow fields and sphere are small when the Mach number is not more than 10. The backward RCS of flow fields is more than the sphere's because of the formation of wide over-dense plasma wake, the curve of backward RCS varies when the incidence wave frequency can be approached by one line for L, S band if the incidence orientation is perpendicular to the X-axis and the Mach number is not less than 14.

Abstract:A space-based orbit determination method using angle data is discussed in this article, which proposes the method of Vector Projection by unifing several present methods. It is convenient to be extended for other data types, and to build the based condition equations. Meanwhile, the correlative issues are studied, such as evaluation of initial iteration values, elimination of uniform solution and iteration acceleration. The numerical simulations in the end show that the new method is effective and swift in achieving a satisfying result.

Abstract:A schematic manned lunar mission case based on coplanar lunar orbit rendezvous is investigated. Based on the principle of splitting the crew and cargo, the flight case including 3 launches and 2 rendezvous is designed. The launch window meeting the restriction of coplanar rendezvous and the characteristics of trans-lunar trajectory is obtained by precise dynamics model. Finally, the 3 missions of flight are arranged and the scale is estimated. The result from simulation shows that the TOF(time of flight) and energy of this mission case are feasible.

Abstract:With a quasi 1-D unsteady flow model, a numerical simulation is completed to analyze the ignition transient in a small solid rocket motor activated by a rear igniter. Based on the simulation results, a detailed parameter analysis is performed for some key factors which may heavily affect the performance of ignition transient. The results can provide a useful guide for the matching design between the rear igniter and the nozzle seal.

Abstract:The multidisciplinary system analysis models for tactical missile are derived, and the multidisciplinary design optimization (MDO) methods are established accordingly. MDO methods can gain the optimal design consistent with system design constraints and the solid rocket motor thrust time curve, which is a best match for exterior trajectory by looping execution between system design optimization and parallel subsystem solid rocket motor design optimization, thus the design cycle for tactical missile system and solid rocket motor can be greatly reduced. The tactic-technical specifications, including the motion state of 22 typical targets, are taken into account in the design optimization process of tactical missile.

Abstract:Borazine, a precursor for BN, was synthesized by a reaction of LiBH4 with (NH₄)₂SO₄. The composition and structure of the synthesized product was characterized and confirmed by GC-MS, FT-IR and 1H-NMR. Cured polyborazine was obtained by heating borazine at 80℃ for 72hrs and was converted to BN ceramic after pyrolysis. The pyrolysis behavior of polyborazine was investigated based on TG, FT-IR and XRD analysis. The results show that polyborazine still holds some B-H and N-H bonds, which will be continuously dehydrogenated when heated, and the ceramic yield is about 89.5％at 1400℃. Bonds of B-H are broken mainly before 800℃, while disappearance of N-H bonds occurs at much higher temperature. The inorganic extent is high and amorphous BN is obtained when polyborazine is pyrolyzed at 800℃, while h-BN is obtained when it is pyrolyzed at 1600℃.

Abstract:Fourier telescopy is a kind of active imaging technique which has won great attention for these years. In that technique, fringe patterns is used to extract Fourier components of target object, and random phase shift can be eliminated by phase closure, so that high resolution image of the target at geosynchronous ranges can be reconstructed. This paper deduced the basic theory of Fourier telescopy and gave a simulative study on this imaging technique. It showed the validity and feasibility of Fourier telescopy by reconstructing the image of two simulative targets.

Abstract:This paper presents a high power low inductance dummy load made of metal film resistors, of which the resistance is 90Ω,and the inductance is ～55nH, nearly without stray capacitance. Cooperated with a capacitive divider, the dummy load has been utilized to measure high voltage pulse with a rise time of several ns for testing a 10-stage wave erection Marx generator. Experimental results verify the high performance of this load, compared with a water resistor load of the same resistance. This high performance is determined by two virtues in the design: one is for using non-capacitance of the metal film resistors and the other is for adopting a structure of impedance tapering line. Power tolerance of the load is evaluated theoretically. In addition, the response ability fed by a square voltage wave is simulated by PSpice software. The dummy load has been tested on the wave erection Marx generator, producing a high voltage pulse with an amplitude of ～210kV, a pulse width of ～40ns and a rise time of ～5ns, and long term operations show its high reliability and stability.

Abstract:The statistical model of clutter is a key factor which determines the performance of a CFAR algorithm for target detection in SAR image. The distribution is able to accurately model the homogeneous, heterogeneous and extremely heterogeneous regions in a single look or multi-look SAR image. But its applicability is greatly limited by its disadvantages that the parameter estimation is complex and the threshold cannot be acquired easily. In view of these problems, this paper uses the moment estimation and dichotomy method to complete the parameter estimation and the threshold acquirement. In addition, pre-filtering the target candidate regions and iterative calculation are used to increase the efficiency. A new algorithm is proposed, aiming at the effectiveness and efficiency at the same time. The experimental results prove its practicability.

Abstract:Based on the MIMO idea and the circular array radar, the meter-wave circular radar for MIMO systems is proposed. For the meter-wave circular array radar using MIMO systems, the correlation between the target and the image is reduced, the effective aperture of virtual array is also increased, and the two-dimension angles of the target and the image can be estimated. Theory analyses and simulation experiment results show that the meter-wave circular array radar for MIMO systems not only can obtain the azimuth angle of the target, but also can make the differentiation between the target and the image from the elevation.

Abstract:Our work focuses on permutation scheduling and permutation searching methods for the scheduling problem of satellites' randomized data transmission. A time window preempted permutation scheduling algorithm is put forward, which can ensure searching for optimal scheduling. A genetic stochastic search method is designed to carry out the search procedure for optimal permutations, using a stochastic neighborhood search algorithm with memory. Computational results show that our method can enhance the local search ability for genetic search, and makes an average improvement of about 2.72%.

Abstract:Striking a better balance between the push and pull of the event data is the key factor to the energy saving for the data dissemination algorithms in wireless sensor networks(WSNs). Two typical structured and unstructured data dissemination algorithms (DCS and CN) are analyzed first. By incorporating the push-pull strategies of the two algorithms, two new algorithms(SDC1 and SDC2) are proposed for the ANY-type queries in the different application situation in WSNs. They have resolved the problems of the high load of the hotspot, the large number of the event data replicas and the low energy efficiency of queries on the premise that it may ensure the balance between the push and pull. Results from the analysis indicate that they are much more appropriate for the WSNs which are large-scale and have large volume of data to be dealt with, and they are two energy-efficient data dissemination algorithms.

Abstract:This paper proposes a quadric fitting polynomial texture mapping model based on moving least squares. The proposed model is mainly applied in image deformation techniques using control meshes. The shape in the image is firstly embedded into a control mesh which is deformed. Then the deformed shape is rendered by using texture mapping on the control mesh. Displaces of the vertices in the control mesh are treated as known function values. The MLS method is used to compute the quadric function for texture mapping. Compared with texture mapping using linear function, the method proposed can greatly improve the smoothness of the texture mapping function, and the deformation result is more natural and physically plausible.

Abstract:The vehicle-mounted forward-looking ground penetrating SAR(VMFL-GPSAR) is a kind of bistatic SAR. Fast factorized backprojection(FFBP) originally developed for unistatic SAR fails to efficiently form well-focused VMFL-GPSAR image. A bistatic FFBP algorithm is derived after the analysis of the round trip range error of FFBP in VMFL-GPSAR. In the bistatic FFBP, the range error can be reduced by rational subaperture center configuration and by polar angle interval constraint. Besides, by combining range phase compensation and 2D linear interpolation, the bistatic FFBP can perform faster with the same focus precision. Simulation and VMFL-GPSAR raw data processing validate the bistatic FFBP algorithm, achieving a 2.31 times speedup.

Abstract:Quality of service(QoS) is a critical research issue in optimizing service composition execution path. Unfortunately, the currently existing methods ignore the hidden competition pressure between service providers which can push them to dynamically change their initial QoS values in that the initial optimal execution path can be changed. To address this isssue, an iteratively bargaining-based constraint correction strategy is proposed. With this method, an initial execution path for a service composition is firstly built by using the local optimization policy. Based on this path, the global QoS aggregating and checking models are used to determine all occurred QoS constraint violations. For all violations, the proposed bargaining strategy can be recursively used to correct such violations. Finally, an optimized path can be rebuilt to meet the overall end-to-end QoS requirements expressed by a user.

Abstract:Visual cryptography is a cryptographic technique to achieve visual secret sharing. Shares are distributed to several participants and overlapping a number of shares can recover the original secret without any cryptographic computation. A verifiable visual cryptography scheme is proposed to verify whether the share is authorized by introducing the Third Trusted Party (TTP) whose action is guaranteed and the public key cryptographic infrastructure based on message identification model. The scheme solves the problem of dishonest distribution center to improve the security of visual cryptography schemes.

Abstract:This paper presents a kind of fractional delay filter algorithm on the basis of Lagrange interpolation in order to improve delay-time precision and to simplify the structure of LMS array signals. A sort of fractional delay filter is designed according to approximative algorithm in frequency-domain, the digital signal can be delayed with a fraction of the sample interval by it, and it is widely applied to the subjects which need accurate delay-time. Simulation results show that the fractional filter can fulfill the different delay-time desire for synthesizing array signal with high precision.

Abstract:A more efficient adaptive GPS anti-jamming algorithm is designed by utilizing single dual-polarized antenna and its performance is discussed. While keeping intact the quality of the expected navigation signal, the new algorithm is able to do with either narrow or wide jamming while only occupying a single antenna position. Therefore, the new algorithm presents a better solution for improving anti-jamming ability of the small volume equipment. Simulation result shows that the new algorithm is feasible and efficient.

Abstract:The context-based adaptive binary arithmetic coder (CABAC) is the preferred entropy encoding method in the main profile of H.264/AVC, for it can offer more bit rate saving than other entropy coding methods. However, high computational complexity and poor parallelism make it unsuitable for chip multicore processors application. A new CABAC parallel encoding method is proposed for the troubleshooting. Results from experiments show that the proposed method can indeed strike a near balanced workload partition while achieving a peak speedup of 1.78 when solely applied.

Abstract:Due to the difficulty of dynamics modeling in fish surrounding by the fluid, little progress has been made in the design of the current pectoral locomotion. With the rapid development of the high performance computers and numerical methods, finite element modeling applied to explore the hydrodynamics of the fish has become a hot topic recently. The kinematics modeling is usually the first step in sovling the problem. Therefore, the kinematics modeling of pectoral locomotion in fish is proposed. The pectoral locomotion is simulated with the physical character and kinematic parameter, and the kinematic formula of the pectoral locomotion in batoid fish is simplified. Along with the boundary condition of the above kinematic formula, the finite element modeling in Cownose Ray is finally simulated in order to study the kinematics. The simulation modeling, compared with the observation results, is proved to be valid.

Abstract:Under the background of creative research of six wheeled lunar exploration robot, and based on the analyses of the locomotion mechanisms of foreign space exploring robots, one hundred and twenty five kinds of creative schemes are proposed by mechanism creation and composition. ADAMS12.0 and Matlab6.5 are used to evaluate and optimize the mechanical and control system of lunar exploration rover at the levels of scheme creation, scheme composition and scheme optimum. Several optimized schemes and their parameters are obtained. Finally, an optimized scheme is chosen to produce a physical lunar rover with good performance.

Abstract:Numerical simulation of an amphibious vehicle's ambient flow field which accounts free surface effort is made by using RNG-turbulence model, volume of fluid (VOF) model and Pressure Implicit with Splitting of Operators (PISO) method based on multi-block hybrid meshes. The computed total resistance less than 9% difference from corresponding experimental data, the agreement is good. Then primary research has been done on optimizing the geometrical characteristics of the amphibious vehicle which influence the hydrodynamic characteristics, including the cavity of the wheel, cut angle in the bodywork, the state of the wheel and the leading board in foreside. The computational results show that the hydrodynamic characteristics of the vehicle which has been improved is better than that of the original, which diminishes the total resistance 69.2% at the speed of 10km/h.

Abstract:It is important to research the flight control system of tailless aircraft, which has been considered the future aircraft development direction. The gain scheduling method based LPV system was studied, and the polytope model was used to gain-scheduling. A simple but applicable method to convex decomposition was proposed. This decomposition has optimal performance with guaranteed stability. The uncertainties were considered fully, and the robust controller was designed using LMI, which can reduce the constraints and computation. The controller was designed based on LMI. From nonlinear simulation, it can be seen that the controller can control the tailless aircraft to convergence within 0.5s and with small overshoot when the scheduling variable has big variation, and the method was proved feasible in the tailless flight control system.

Abstract:In order to exclude the effect of dissimilar genes, a new missing value estimation method based on KNN-SVR is proposed. This method selects a group of complete genes most similar to target genes by K-nearest neighbor (KNN) and uses them to estimate missing values by Support Vector Regression (SVR). This paper also suggests using the variance of Normalized Root Mean Squared Error (NRMSE) to measure the stability of estimation methods and the reliability of estimated values. This method improves the validity of missing value estimation by filtering genes. The experiment results show that KNN-SVR method has better accuracy and stability.

Abstract:Integrated with matter-element theory, a new theory of matter-element bayes network is put forward, in terms of an analysis of the limitation in the process of modeling bayes network. This new theory can syncretize each advantage of both theories, which can be used to handle the uncertainty of complex systems and make full use of all the useful information in these systems at the same time. Therefore, a better evaluation of complex systems can be obtained with this new theory.

Abstract:The weapon equipment system of sytems capability is an important part of the weapon equipment system of sytems. In this paper, the weapon equipment system of sytems capability is described formally, and the character is given. The weapon equipment system of sytems capability spaces is analyzed and the relation between the capabilities is defined from different viewpoints. The weapon equipment system of sytems capability subsystem is built. Based on the singer capability, capability relation and capability system, the weapon equipment system of sytems capability is discussed, which establishes the basis for the study of the weapon equipment system of sytems and the weapon equipment system of sytems capability.