Abstract:Because of emergence of uncertain data stream applications, the traditional multidimensional model based on precise and static data is in the face of some new challenges. This paper proposes a multidimensional uncertain data stream model based on characters of uncertain data stream, such as dynamic, infinite, uncertain and so on. This model introduce uncertain object to depict uncertain facts, and define the time dimension with multi-level time windows to reflect the dynamic and infinite of data stream. Finally, we give the basic algebraic operations and analytic algebraic operations of multi-dimensional uncertain data stream, which gives theoretical support for multidimensional query and analysis of uncertain data stream.

Abstract:Dual-rotor Piston Engine (DRPE) is a new type of differential rotary engine. Compared with traditional engines, DRPE has many advantages. The complex valve systems can be omitted. Its structure is more compact. Its power density is higher, and so forth. In the paper, we analyze the working characteristics of DRPE, and figure out the mechanical structure characteristics of the Differential Velocity Drive Mechanism (DVDM) of the DRPE. Define its kinetic parameters. Then establish the mathematical models for the kineto-static analysis of the DVDM by using vector mechanics methods. The mathematical models were calculated by Matlab. The mechanical characteristics of DRPE’s main components were obtained. In order to verify the rationality of the established mathematical models, multi-body dynamics simulations were done. The virtual prototype model of the DRPE-350 was established in the RecurDyn. The simulation results compared with the calculation results, the value changing rules are almost the same. The changing processes are all four cycles. Impact positions are basically the same. It shows that the established dynamic theory model conforms to the actual situation. It is reasonable and can be trusted. It can be used as the theoretical foundation for the follow-up improvements of the DRPE.

Abstract:Wireless spacecraft data networks can unburden the wire problems of the spacecraft, which makes it a promising technology for spacecraft light miniaturization. To replace the peer-to-peer three-wire Low Voltage Differential Signaling cables in spacecrafts, design of a wireless spacecraft high speed data network based on Impulse Radio Ultra Wideband was proposed. The wireless communication protocol referring to the American military data bus standard MIL-STD-1553B protocol was described in detail. The communication protocol adopted the time division command response mechanism, and its physical layer, data link layer, network layer and application layer were designed to meet the requirements of the wireless spacecraft high speed data communication. The design of a demonstration of the spacecraft high speed data network was tested and verified. It is proved that the system bit error rate is less than 1010^-9. The design of the protocol IP core is flexible, reliable and scalable. 

Abstract:In order to improve the robust performances of Bank-to-turn control system within the morphing phase, a Bank-to-turn autopilot design for the morphing aerial bombs based on the discrete-time sliding mode control principle was proposed. The Bank-to-turn control affine system was modeled. Meanwhile, aiming at the time-varying and coupling characteristics, input-output feedback linearization was utilized to decouple the system into three independent discrete-time subsystems. The aerodynamic coefficient deviation items caused by sampling errors of the sweepback were regarded as the external uncertain disturbances, and a discrete-time sliding mode Bank-to-turn autopilot for the morphing aerial bombs was designed. The simulation results indicate that the discrete-time control system has a good robust performance for the time-varying parametric perturbations engendered by wings morphing and can realize the decoupling control among channels. The tracking delay and errors are related to the sampling period, therefore, the actual hardware performances and command tracking accuracy should be considered in selecting sampling period.

Abstract:Cluster bomb projection is a typical multi-body aerodynamic problem with relative motions, and is also a valuable application area for the overset grid method. The MI-GRID overset software, the fluid dynamic governing equation and the rigid body movement equations were employed to investigate the aerodynamic trajectory and movement characteristics in bomb separation process. The orthogonal experimental design was also employed to discuss even to assess the effect of the initial and aerodynamic interference on bomb separation movement. Results indicate that the bomb in projection flow field is greatly affected gesture motions by the shock interference. When a singular bomb is projected, the shock of the missile makes the pitching movement of the bomb vary abruptly. While the multiple bombs are projected, the reflection shock that is extracted by the bomb makes the bomb rise, which can affect the bomb bay's flowing.

Abstract:Investigation on mixed structures with hybrid uncertainties was based on the reliability analysis of uncertain structures of the distribution parameters of input variables that acted as the interval model. Considering the available information was quite scanty, the uncertain distribution parameters were treated as the interval model. The reliability analysis model for this hybrid uncertainty was established by separating the distribution parameters from their random variables through using equivalent probability transformation method. Based on the non-probabilistic reliability theory, a high efficient solution method was proposed by successively constructing the limit state function of the proposed hybrid uncertain analytic model in two levels and combing the Kriging surrogate model. The proposed hybrid uncertain analytic model is employed to analyze aircraft structures with hybrid uncertainties, which can demonstrate the rationality of the proposed model and the efficiency and accuracy of the solution model.

Abstract:Based on the example of the quadratic polynomial without cross terms outputs, the structural and correlative contributions of the correlated normal input variables were derived out, which had impact on the variance contributions of output response variables. Numerical results of several examples validate the correctness of analytical solutions. Comparing the presented indices with the existent indices, some general conclusions were drawn from the structural contributions and the correlative contributions, and the differences between them were identified. The proposed analytical solutions can be directly used to identify the structural contributions and the correlative contributions of the quadratic polynomial without cross terms, which offer a reference to other numerical algorithms.

Abstract:The high-precision finite volume method (FVM) and discontinuous Galerkin method (DGM) were compared in different test cases through numerical examples. Results show that:with the same precision, the calculation error of DGM is obviously less than that of FVM; DGM's reconstruction process is comparatively simpler than FVM's, but its computational time is much longer since its freedom-degree of polynomial solution is higher under the condition of high order and it needs to calculate volume points. Decreasing the freedom-degree numbers of polynomial solution in the time evolution process is an essential method for high-precision calculation in the reality applications.

Abstract:On the basis of matrix analytical theory, the identifiability of inertial moment parameters was studied. A linear regression model in term of the unknown parameters was derived from attitude dynamics equations; the condition number of regression matrix was defined as the quantitative index of identifiability degree; taking the maximum of identifiability degree as objective function, an optimal control model was built. The pseudospectral optimal control was employed to solve the command trajectory of control moment gyro and to improve the identification precision and convergence velocity. The method of dual-unscented Kalman filter identified parameters under simulated circumstances. Results demonstrate that the optimal excitation design can improve the performance of parameter's identification and has high robustness to inaccurate priori information.

Abstract:An adaptive backstepping controller based on nonlinear disturbance observer was designed to solve the problem of parameters uncertainty in elastomer model of hypersonic vehicles. The curve-fitted model was expressed as strict feedback form and the method of backstepping was used to design the controller. Dynamic surface method was introduced to obtain the derivatives of virtual control amount, which avoided the explosion of differentiation terms in the traditional backstepping control. In order to enhance the controller’s robustness, a new nonlinear disturbance observer which was based on second order tracking-differentiator was introduced to estimate and compensate the model uncertainties adaptively. Simulation results demonstrate that the controller has high robustness to the model uncertainties and aerodynamics and it can track the reference instructions of velocity and altitude steadily.

Abstract:The volume of fluid method was used to analyze the flow process in pressure swirl injector. SLR camera and phase doppler anemometry were used to measure the spray characteristics of swirl injector and gas-liquid double swirl coaxial injector. Results show that the total pressure loss occurs mainly in inlet section, convergent section, and columned section of swirler trough. The longer the columned section is, the thicker the liquid film and the smaller the spray cone angle is. The range of spay particle distribution increases gradually along the radial direction while the axial velocity distribution decreases firstly and then increases along radial direction. Spray characteristic of gas-liquid double swirl coaxial injector is greatly influenced by gas-liquid ratio (GLR). While GLR is small enough, swirling air increases the spray cone angle and decreases the range of particle distribution; while GLR is large enough, the expansion of air compresses the spray, pushing large droplets to the center of the spray. And at the edge of spray locates small droplets from second atomization.

Abstract:In order to implement high accurate and large dynamic test tasks of inertia measurement unit (IMU), 6-degrees of freedom electric dynamic test table of IMU was designed on the basis of Gough-Stewart platform. Error model was established and the effect of electric cylinder length error on the accuracy of the system was analyzed. The passive spiral increment motion of electric cylinder produced in the movement of IMU dynamic test table was analyzed further and the compensation algorithm of the movement was studied. The quantitative analysis of the error brought from the passive spiral increment motion shows that the effect of the motion to the pose accuracy of dynamic test table is significant. In order to clear the effect, the compensation algorithm was accomplished and was applied to the real-time control system of the dynamic test table of IMU. Experimental results show that the position accuracy of dynamic test table of IMU reaches the design specification due to compensation algorithm.

Abstract:In order to investigate the combustion flow field of gas/gas injector in full-flow staged combustion cycle engine, the flowing combustion processes of different velocity ratios between fuels and oxidants were numerically simulated by solving the Navier-Stokes equations. Simulation results which agree well with the experimental results show that: the combustion efficiency increases and the combustion flame surface advances along with the increase of velocity ratio; if the length of the engine is restricted, the effective combustion can be achieved by increasing the velocity ratio appropriately.

Abstract:A spline filtering algorithm based on interacting multiple model algorithm (IMM-SF) was proposed to estimate Line-of-sight (LOS) rate in strap-down seeker system. Based on the mapping relation between body LOS and inertial LOS, the inertial LOS angles were obtained and used as virtual observed data of filters. A set of process noise models were set up, and every model worked independently based on the spline filter. The valuation output of IMM-SF was the weighted composition of the valuation outputs of all parallel spline filters. By using this method, the unknown maneuver models of the target were no longer indispensable, which makes the method more convenient to use. Process noise could be adaptively adjusted under the configuration of IMM. The Monte-Carlo simulation results show that the LOS rate can be estimated effectively based on SF-IMM, which can also improve the accuracy of estimation.

Abstract:According to the data interpolation problems of non-matched meshes in the simulation calculation of thermal-electric solid body field, a interpolation algorithm based on compactly supported radial basis function was proposed. The transfer matrix was derived and the calculation program used for data exchange between two non-matched meshes based on compactly supported radial basis function was developed. An example of several groups of temperature interpolation between two non-matched meshes was verified, and the influence of different parameters on calculation time and precision was analyzed. The result shows that the algorithm is efficient and accurate for data exchange calculation of solid body field coupling non matched meshes, especially for thermal-electric coupling interpolation.

Abstract:To improve the segmentation accuracy of mycobacterium tuberculosis (MTB) objects, a segmentation algorithm for optical microscopic MTB images in region level was proposed. Top-bottom hat transform was used to enhance the contrast of the color images, and the image gradients were computed by comprising local features and global information of the images. Watershed algorithm was employed to implement the initial segmentation. Segmented regions were then merged by using the maximum similarity criterion in adjacent regions in order to obtain integrated object regions. The method of multi-threshold segmentation in terms of the color characteristics of MTB object regions was adopted to filter the impurities and to realize the segmentation of MTB objects. Experimental results indicate that the proposed algorithm can segment MTB objects which have low contrast and saturation and can obtain well-segmented results for images in different dyeing backgrounds.

Abstract:The model-based compressive sensing (CS) dictated that robust signal reconstruction was possible to obtain from fewer measurements, but the computational complexity of this approach was large while using the optimal tree approximation with wavelets. Based on the testified result that the wavelet hierarchical tree was still connected, the model-based wavelet hierarchical connected tree CS algorithm， was proposed. The proposed algorithm which has the equivalent measurements with that of model-based CS can enhance the signal-reconstruction efficiency and guarantee the signal-reconstruction accuracy. Numerical simulations demonstrate the validity of the new algorithm. Furthermore, the proposed algorithm has a distinct advantage when dealing with the mass of data.

Abstract:The conventional methods for finger-vein structure description could not fully describe the distinct and steady line-structures of finger-vein. Therefore, a finger-vein structure description method based on B-spline was proposed. The new method obtained the coordinate set of all target points on every finger-vein branch by using line scanning operation on thinned finger-vein images. A B-spline function was used to fit the curves of finger-vein branches. The control-point coordinates of every B-spline curve were gained, and they were used to describe the line-structures of finger-vein. Experiments show that the new method can availably describe line-structures of finger-vein with little description error and small storage space requirements. Furthermore, this method can improve the recognition rates of finger-vein.

Abstract:Many of the real-world graphs are edge-labeled or node-labeled. A foundational operation on these labeled graphs is how to answer reachability queries fast. For the label-constraint reachability computation problem, a computation method called RP-Hop based on recursive partition was proposed. RP-Hop first utilized the hierarchical structure and independent set property to partition the origin large graph recursively, while keeping reachability and labels on paths between node pairs simultaneously. Combined with greedy and recursive labeling strategies, RP-Hop produced a compressed index for label-constraint reachability queries. Experiments on synthetic and real-world graph data sets demonstrate that RP-Hop can reduce index size and construction time, and guarantee the query efficiency.

Abstract:The G⁰ distribution is capable of fitting radar clutter with different degrees of heterogeneity, so the accurate simulation of bi-dimensional correlated G⁰ distributed radar clutter is a vital step in the radar system design and evaluation. In the base of the nonlinear transformation which was expressed approximately by the method of piecewise polynomial fitting, the simulation method of bi-dimensional correlated G⁰ distributed radar clutter based on memoryless nonlinear transformation was proposed by taking the bi-dimensional correlated Gaussian process as input. Furthermore, in order to control the amplitude and correlation of radar clutter independently and simulate coherent radar clutter with in-phase and quadrature component, the characteristic function of the haplopia G⁰ distribution was derived and the simulation methods based on spherically invariant random process were proposed. Simulation results show that both two methods can generate bi-dimensional correlated G⁰ distribution radar clutter which meets the requirements of amplitude and correlation.

Abstract:Ranging accuracy is an important indicator to assess the performance of satellite autonomous integrity monitoring receivers in the threat environment. Analytical expressions of the relationship between the accuracy of code tracking loop and the parameters of International Civil Aviation Organization 2nd-order step threat model when employing coherent early-late processing in the satellite autonomous integrity monitoring receiver were presented. Theoretic analysis and simulation results show that the code phase estimator output curve will be biased under the digital failure model and the failure parameters will rarely impact the ranging variance. While the analog failure will distort the cross-correlation function and the code phase estimator output the curve, the curve is almost unbiased, and the ranging variance is affected by the analog failure parameters and receiver parameters such as front-end filter bandwidth and early late code space.

Abstract:Ethernet for space utilization added time-triggered protocol to a star topology network that was used for Ethernet service; moreover it was fully compatible with the standard IEEE802.3. This Ethernet can effectively solve the problems of real-time, uncertainty and reliability on communications for payload communicating through standard Ethernet. Time-triggered Ethernet was based on global reference time, and the real-time data transmission kept strict timing, supported time and event-triggered communication simultaneously. Time-triggered channel in this Ethernet was suitable for real-time synchronous or periodic message transmission, while event-triggered channel was suitable for sporadic or aperiodic message transmission. To prove the result that Ethernet can ensure the network reliability and security, enhance flexibility, and can greatly improve network availability, many work have to be done. For example, it designed an Ethernet topology and protocol stack for space utilization, described system communication process, studied time-triggered protocol, and simulated synchronization and network performance.

Abstract:The streamline method is an important method in the visualization of 3D vector fields. A view-dependent streamline simplification method for 3D vector fields based on feature-preservation was proposed to solve the problems of streamline occlusion and visual confusion caused by excessive streamlines, and to ensure the streamlines could present the variation law and important features of vector fields exactly. A streamline set of 3D vector fields was generated by particle tracking and was mapped between view-dependents. A feature-preservation computation of the streamline set was implemented. The streamline set is effectively simplified by computing visual effect metric based on iteration. Experimental results show that the visual effects of the streamlines are enhanced on the basis of valid feature-preservation of vector fields.

Abstract:Since the slowly growing psendo-range errors existing in the pseudo-range measurements of satellite navigation system may further lead to the decreasing of position accuracy, a robust extended Kalman filter (EKF) method based on sliding and accumulated residuals was proposed. The method based on the robust EKF algorithm cumulated the residual vectors for multi epochs in the sliding window and increased the pseudo-range error of standardized residual vector, which improved the robustness of slowly growing pseudo-range error. Results show that the method can effectively eliminate or weaken the position error caused by slight pseudo-range error and slowly growing pseudo-range error. Compared with the traditional robust EKF algorithm, the positioning accuracy of this method is improved obviously.

Abstract:For the requirement of high-power transmit signals in long-distance submarine detection, a high-power siticon controlled rectifier switching power amplifier (SPA) was used. The operating principle of this SPA was analyzed and the equivalent circuit models were established under different working states including critical commutating state, natural commutating state and compulsive commutating state. The equivalent circuit models were emulated in OrCAD when the SPA worked in critical commutating state. For the acquisition of power amplifier and load current value about SPA in natural and compulsive commutating state, the nonlinear mathematical models were established in the base of equivalent circuit models, then they were solved by fourth-order Runge-Kutta method under the platform of Matlab and VC++. The methods mentioned can calculate the voltage and current at any time any point of the SPA; it can reflect the working state of circuit objectively and factually; the research may be of certain reference for engineering application.

Abstract:For the demand of hypersonic aircraft for generic shingle ceramic thermal protection system (TPS), the transient heat transfer model of TPS structure was established and the influences of some factors, such as material properties, thickness, phase change materials and its location, on heat transfer properties were investigated. Results show that: material properties and thickness of heat insulation layer play a key role in heat transfer properties, while these of the heat protection layer almost exist no effect; the introduction of phase change materials obviously improves the heat transfer properties of TPS structure; the location optimization of phase change layer is an effective method to improve the heat transfer properties and reduce the thickness; the thickness optimization of heat insulation layer can provide reference for the TPS design. 

Abstract:Taking polycarbosilane and antimony-modified polysilane for precursors and drawing lessons from the transformation process of high temperature graphitization of spare free carbon in SiC materials, the polymer-derived SiC nanocomposites were prepared by employing hot-press sintering, precursor infiltrating-cracking methods and annealing. The phases and microstructures were characterized and analyzed by using SEM, TEM, XRD and Raman test methods. The thermoelectric parameters of samples, such as thermal conductivity, electrical conductivity and Seebeck coefficient, were studied. Results show that the dense SiC nanocomposites acquired are n-type thermoelectric materials. The thermal conductivity is suppressed at the range of 4～8W/(m?K) due to the function of nano-graphite. At the annealing temperature of 1600°C, the thermal conductivity reduces while both the electrical conductivity and the Seebeck coefficient increase, and ZT value of SiC nanocomposites derived from precursor reaches to 0.0028（650°C）, which is higher than that of SiC/C composites or nanocomposites ever reported.

Abstract:Focusing on the problem that the traditional finite element analysis results of the cylindrical shell with prefabricated defects couldn't be applied on the engineering practice effectively due to the low computing precision of stress and strain, an equivalent crack analysis method with high redundancy was proposed. Treat the prefabricated defects as typical crack, and analyze the crack stability with the singular crack element method, then assess the structural integrity of the cylindrical shell with prefabricated defects according to the analytical results of the crack stability. The analysis result obtained through this new method is more reliable than the traditional finite element method, and it is practical in promoting the safety margin of the engineering design, especially for the prefabricated defects of cylindrical shell structure working in severe environment with high risk coefficient like linear explosive separation device of the missile.

Abstract:The invulnerability characteristic of communication system is an important element in the study of military combat system. According to the organization structure and countermeasure of anti-air communication system, performance evaluation process algebra(PEPA) was introduced to describe the evolution process of anti-aircraft communication system by the state. PEPA-based invulnerability analysis method of communication system was proposed. A case study was given to testify the organization structure and the capacity against soft destruction or hard destruction of communication system by modeling and simulating. Experimental results show that PEPA is available for anti-aircraft communication systems' modeling and analyzing, which can realize the structural modeling in antagonistic process of anti-air communication system. The different elements of communication system have different influence on the invulnerability. Effective strategies can be taken to enhance the invulnerability of anti-aircraft communication system.

Abstract:Cooperative positioning refers to a new positioning technique that receivers share critical positioning information with each other by communication system so as to achieve relative localization. The receivers estimated their position with available secondary nodes which included the localized neighbor receivers and the visible satellites. The cooperation of receivers resulted in the increasing of the available secondary nodes for position estimation, so the calculated amount and the computing time were increased. With the increasing of available secondary nodes, the receivers may fail to estimate their position in real-time. A new node selection algorithm called improved quasi-optimal node selection algorithm was proposed. The nodes to be selected obtained an importance value by calculating the unit vector differences between nodes, and the ones with the maximum importance value were selected as the secondary nodes in each iterate. The new algorithm was compared with four typical node selection algorithms. Simulation result shows that the nodes selected by the proposed algorithm are very close to the ones selected by the optimal algorithm, but the former algorithm costs less time. And the comprehensive performance of the new algorithm is better than the typical node selection algorithm.

Abstract:Because of the emergence of uncertain data stream applications, the traditional multi-dimensional model based on precise and static data is confronted with some new challenges. A multi-dimensional uncertain data stream model based on characters of uncertain data stream was presented, such as dynamic, infinite, uncertainty and so on. This model introduced uncertain object to depict uncertain facts, and defined the time dimension with multi-level time windows to reflect the dynamic and infinity of data stream.The basic algebraic operations and analytic algebraic operations of the multi-dimensional uncertain data stream was defined formally, which gives theoretical support to multidimensional query and analysis of uncertain data stream were provided.

Abstract:To solve the problem of redundant tasks in space reconnaissance demand, a method for space reconnaissance task relevant degree analysis was proposed, considering the sources of demand, requirements of quality, time preference and spatial range. The relevant elements of space reconnaissance were analyzed, and calculation method of task relevant degree was given based on these four elements. A specific algorithm to reduce probability of redundancy tasks was proposed with task relevant degree. An algorithm of redundancy analysis was considered in the case of accurate priority, justice and hybrid. An example was given to illustrate the effectiveness of this method. The results show that the method has good versatility, which can effectively support space reconnaissance missions preprocessing.

Abstract:Networked air & missile defense (NAMD) which is evolving in the context of networked centric warfare is the coming trend of the air & missile defense domain. Given its initial exploring phase of theories, modeling and simulation, and based on the ideology of composable modeling framework, a conceptual diagram composed of command and control, sensors and weapons networks about the structure of NAMD systems was designed, and CMFs about top level, decision, and data link were developed. Eventually, the composibility and rationality of CMFs were validated by a simulation case of NAMD systems warfare. Significant implication is revealed for modeling and effectiveness simulation of NAMD systems.

Abstract:Dual-rotor Piston Engine (DRPE) is a new type of differential rotary engine. Compared with traditional engines, DRPE has many advantages. The complex valve systems can be omitted. Its structure is more compact. Its power density is higher, and so forth. By analyzing the working characteristics of DRPE, the mechanical structure characteristics of the Differential Velocity Drive Mechanism (DVDM) of the DRPE were figured out. Its kinetic parameters were defined. Then the mathematical models for the kineto-static analysis of the DVDM were established by using vector mechanics methods. The mathematical models were calculated by Matlab. The mechanical characteristics of DRPE’s main components were obtained. In order to verify the rationality of the established mathematical models, the virtual prototype model of the DRPE-350 was established in the RecurDyn based on multi body dynamics simulations. Comparing the simulation results with the calculation results, the value changing rules are almost the same. The changing processes are all four cycles. Impact positions are basically the same. It shows that the established dynamic theory model conforms to the actual situation. It is reasonable and can be trusted. It can be used as the theoretical foundation for the follow-up improvements of the DRPE.