Abstract:Background oriented schlieren (BOS) is a new technique for flow visualization. Compared with schlieren and interferometry, BOS can measure density gradient quantitatively with high spatiotemporal resolution. Based on its principle, a BOS system is set up in this paper. Using this system, the thermal convection flow field over a candle flame is measured, and its transient flow structure is visualized. The whole process verifies the performance of the BOS system. Then, a supersonic mixing layer is studied, its fine flow structures and quantitative density gradient distribution are acquired. The results show obvious advantages of BOS in flow measurement.

Abstract:In the high speed flow field, shock wave will cause obvious aero-optics effect, which can induce the excursion and focusing of the ray and so on. In this paper, the relationships of angle excursion and shock intensity are reviewed theoretically in the condition of different incidence angles. In application to actual problem, the shock field is usually simulated by computational fluid dynamics. In order to trace the ray through the simulated shock field, an idea and the matched method are carried out, which can improve the tracing precision. In this way, the tracing step distance is aimed to be self-adaptive to local refraction index gradient and grid geometry scale. At last, the ray tracing method is validated. The result shows that the method has high precision for ray tracing in the shock field.

Abstract:The fault detection method based on cloud-neural network of LRE (liquid-propellant rocket engine) is studied and realized with fault detection principle. The training results, testing results and fault detection results of the method are given. The method is validated by historical test data. There is no false alarm and missing alarm during testing and validation.

Abstract:The thrust vector control schemes for solid launch vehicle were compared from the view of launching capability. Three multiple-stage solid launch vehicle schemes with different thrust vector control systems were designed, the ascent trajectory of launch vehicle was optimized by combining augmented lagrangian method with Powell method, and the evaluation results of launching capability were provided. Research results show that, with the same take-off mass of 50000 kg and object orbit of 300km SSO, the scheme using jet thrusts and grid vane achieved heavier lauching capability, 115 kg bigger than the scheme using vectored nozzle, and 70 kg bigger than the scheme using jet thrusts and jet vane, respectively. All the above can provide theoretic reference for scheme demonstration of solid launch vehicle.

Abstract:Initial orbit determination of cislunar transfer trajectory with space-based angle measurement is discussed. The measurement platforms include a single satellite and two constellation satellites. First, the smoothness of noise is studied. Second, the effects of arc length and measurement geometry on the orbit determination precise are analyzed. Finally, the disposal of model errors is addressed. According to the research, the constellation synchronized orbit determination is preferred for the initial orbit determination of cislunar Transfer Trajectory.

Abstract:The six degrees of freedom dynamic and motion models of the parachute recovery system were built. In order to solve the problem caused by the lack of measurable experiment data, the genetic algorithm was designed to estimate the aerodynamic parameters of the parachute. Simulation result validates the feasibility of the estimation method and the validity of the estimation model. The aerodynamic parameters of a large ringsail parachute applied to manned spacecraft were estimated through the genetic algorithm and the analysis data from the videos of airdrop test. Furthermore, the stability of the ringsail parachute was analyzed through the estimation results. The conclusion can provide theoretical reference for the design of recovery system.

Abstract:According to the application of GPS differential precise navigation, an ambiguity resolution algorithm is presented. The mathematical model is set up using observations of wide lane double differential carrier phase and double differential pseudorange. In order to make float ambiguity uncorrelated completely, float transformation matrix is constructed by Cholesky decomposition and the integer ambiguity search space is deduced. The criterion of least square residual is used to obtain single-epoch integer ambiguity, OVT (over-the-time) method is applied to verify the consistency of integer ambiguity at different epochs. Experimental results indicate that the mean square deviation of observations has great effect on integer ambiguity's search space and success rate, and the integer ambiguity can be determined correctly and reliably by OVT testing.

Abstract:SiO₂ aerogel insulation composites were prepared by using ceramic fibers as reinforcement via supercritical drying process. Due to the ultra fine skeleton particles and nano-porous structure, silica aerogels have low gas thermal conductivity and solid thermal conductivity, and ceramic fibers greatly decrease radioactive thermal conductivity. Silica aerogel composites show excellent thermal insulation properties. The thermal conductivities at　200℃ and 800℃ are only 0.017W/m?K and 0.042W/m?K, respectively. The strength of the aerogel skeleton is enhanced by high temperature heat treatment, and with the reinforcement of fibers, the aerogel composites exhibit good mechanical 　property. The tensile, bending and compressive strengths at ambient temperature are 1.44MPa, 1.31MPa and 0.98MPa (10%strain), respectively, and the tensile, bending and compressive strengths at 800℃ are 1.95MPa, 1.80MPa and 1.42MPa (10%strain), respectively.

Abstract:The integral manufacturing for composites adapter skirt used for solid rocket motor is very beneficial to lighter weight and higher properties of the skirt. The integral composites adapter skirt was designed and made by RTM process, and the axial compression test of the skirt was conducted. The experimental results show that under the effect of the design loading, the strain of the skirt is less than 0.5%, and the structural stiffness of the skirt reaches 40.9GPa.

Abstract:A novel multifunctional UV-curable waterborne polyurethane acrylate (WPUA) was synthesized from polycaprolactone diols(PCL), isophorone diisocyanate(IPDI), dimethylol propionic acid (DMPA) and pentaerythritol triacrylate(PETA). Waterborne UV-curable hybrid materials were prepared from WPUA as organic phase and γ-trimethoxysilyl-propyl methacrylate (TMSPM) modified nanosilica as inorganic phase. The structure of products was characterized by FT-IR spectrum, and the surface morphology, thermal stability, UV curing kinetics and mechanical properties of hybrid films were investigated. The results showed that the structure was identified and the modified nanosilica was dispersed into hybrids homogeneously and stably. Furthermore, it has been found that the thermal stability and mechanical properties of hybrid films were improved with the addition and increase of nanosilica, while the curing rate and final gel content were still in good levels.

Abstract:Large data volume and computation burden are the main characteristics of real-time ultra-wide band synthetic aperture Radar (UWB SAR) processing. The nonlinear chirp scaling (NCS) algorithm adopted in the real-time processing needs large data volume. In order to reduce the data volume demand, an improved NCS algorithm is proposed. Meanwhile, the flow of Real-time UWB SAR processing is given, and the effect of forward velocity error is also analyzed, and it can be removed by real-time pulse repeat frequency (PRF) adjusting. The performance of loss of sight (LOS) compensation in improved NCS algorithm based on the data measured is analyzed. Finally, the performances of the algorithm are verified by the simulation and real UWB SAR data

Abstract:The high computational complexity and large memory requirements will be encountered when the transient responses from electrically large complex objects are considered using time domain integral equation (TDIE) numerical technique. Time domain adaptive integral method (TDAIM) is employed for reducing the computational scale of TDIE. The parallel technology was researched and the distributed electromagnetic computation based on .NET Remoting was implemented. Results show that the parallel scheme is effective for improving computational efficiency and solving the large scale electromagnetic problem.

Abstract:Memory consistency research, as one of the core issues of computer architecture, mainly focused on the CPU access memory，while the consistency issues of DMA operations is seldom studied. According to the idea of integrating the architecture design of I/O and memory, the paper defines the concept of general program included I/O operations, aimed at the consistency issues of DSM (distributed shared memory) systems with global DMA operations. The paper studies the general memory consistency model, and builds the general scope consistency model. Based on the general scope memory consistency model, the Cache-Memory-I/O consistency protocol and its implement technology are studied. All this may help the global shared parallel I/O system design for DSM system.

Abstract:Baseline estimation is important to generate accurate DEM with SAR interferometry. A novel method for baseline estimation was introduced after an initial review of classical methods. The SRTM DEM and coarse orbital parameter were first used to produce a topographic-free residual interferogram. Accurate orbital parameter was then achieved by spatial-frequency analysis of the residual interferogram. This method has the advantage of spatial and precise orbital free ability. Validation was carried out with ERS-1/2tandem data over the Mani mountain area of Tibet. Some representative methods of baseline estimation were then compared with the method introduced and the results showed more accurate estimation.

Abstract:Towards single-event transients (SETs) in charge pumps (CPs) for phase-locked loops (PLLs), the effects brought about by different frequency SETs induced currents are analyzed. Based on frequency domain analyses, the relation between loop parameters and SET response is investigated with respect to gain and bandwidth. The results reveal that decreasing the loop filter resistance to decrease the gain can significantly mitigate the SET induced voltage perturbation of the voltage-controlled oscillator's (VCO) control voltage, and that increasing the damping ratio or the nature frequency to increase the bandwidth can filter out more SET currents in a wider frequency range and effectively reduce the PLL recovery time. Therefore, decreasing the loop filter resistance, increasing the damping ratio or the nature frequency are effective radiation-hardened-by-design techniques. Eventually, the conclusions are validated by transistor-level simulations for a 1GHz PLL.

Abstract:The spatial polarization characteristic of electromagnetic field radiated by linear dipole array and planar-array antenna scanning in different direction was derived and modeled theoretically and mathematical in this paper. The calculation results and simulation analysis show that the polarization properties of phased arrays in various beam positions are diverse, and the polarization state of EM wave will change with the azimuth and elevation of the electrical boresight when the target direction deviates from the antenna boresight direction. The conclusion is of significance to high-precision modeling and simulation for phased array antennas, and is also important for anti-interference by making use of polarization information.

Abstract:Knowledge reduction is an important issue in data mining. This paper focuses on the problem of attribute reduction in incomplete decision tables. Three types of incomplete conditional entropy are introduced based on tolerance relation, such as H′conditional entropy, E′conditional entropy, and I′conditional entropy, which are proved to be an extension of the concept of conditional entropy in incomplete decision tables. Compared with H′and I′conditional entropy, E′ conditional entropy decreases monotonously with the　amount of attributes. Based onE′conditional entropy, a new reduced definition is presented, which integrates the complete and incomplete information systems into the corresponding reduced algorithm. Finally, the experimental result shows that this algorithm can find the reduct of decision tables.

Abstract:To address the state explosion problem in model checking parameterized systems, this paper proposes a generic framework of two-dimension abstraction (TDA), in which the size of the state transition graph for individual process is reduced independently at first, and the whole system composed of reduced processes is then abstracted based on the design method of parameterized systems, thus avoiding the construction of the unreduced model that might be too big to fit into memory. Formal model with true concurrency semantics for parameterized systems, more suitable for describing general concurrency systems, is introduced, which effectively solves the problem of verifying both homogeneous and heterogeneous systems. Results from the theoretical reasoning and the example given demonstrate that TDA is correct and feasible.

Abstract:Cohen proved that there was no algorithm that can perfectly detect all possible viruses. Malicious Code Detection and Prevention Model (MCDPM) is a behavior-based malicious code detection mechanism, and its purpose is to get rid of the limitation of Cohen's findings. MCDPM disassembles program behaviors into virtual behavior parts and actual behavior parts, and monitors the virtual behaviors as well as the results of these behaviors. MCDPM determines whether an executable is malicious by analyzing the virtual behaviors of a program. Since the determination is made upon unchangeable program behaviors, it has a low false positive rate and a low false negative rate as well. To those non-malicious programs, MCDPM will perform their behavior results really taken place in the platform by the actual behavior function, so that the consistency of system is assured. MCDPM is effective in detecting unknown malicious codes, and it also supplies an accurate approach to clean the viruses in the system. MCDPM can also be used to provide the assurance to the transitive trust mechanism in trusted computing platform technology.

Abstract:In the field of bioinformatics, recently more and more researches are launched on the studies of the structure and topology of metabolic networks. We first review the progress for metabolic network reconstruction and representation. Then we look into the macro-structural and topological properties of metabolic networks which are meaningful for uncovering how metabolic networks evolve and why they are robust. Finally we expound our viewpoints on the current issues and the prospective studies in this field.

Abstract:Dither control is an important factor for the performance of dither ring laser gyro (DRLG). The decoupling method of DRLG dither control system is studied based on gyro oscillation characteristics. It is studied that the phase feedback is a good selection to trace resonant dither frequency. On tracing resonant frequency, as well as changing amplitude of dither drive signal on the zero-position-point, the dither amplitude responses can be simplified as a 1-order system, and the dither-amplitude-control is independent to frequency-tracing to realize the decoupling control，which improves the control performance of DRLG dither control system.

Abstract:In order to incarnate “multithreading” of news event reporting, the paper studies the validity of graph theory for managing news video database. Firstly, news stories similarity and graph theory are studied for digesting complicated relations of all stories reporting the same event. Then, a method based on minimal spanning tree is presented for predigesting the similarity graph into a simple tree with “multithreads”. Experiments show that the method is a research issue with great theoretical and pratical significance for browsing, searching and abstracting in news video database.

Abstract:The combined modulation methods as well as various encoding methods adopted in Joint Tactical Information Distribution System (JTIDS) guaranteed the message transmission reliability. The anti-jamming performance of JTIDS on rice fading channel is analyzed; the symbol error rate and the message discarded rate of the system in partial band noise interference are derived by simulation. The simulation result shows that various anti-jamming technology such as RS encoding, and Interleaving and DS/FFH MSK modulation combined in JTIDS can improve the performance of data link communication so much that a lower symbol error rate and message discarded rate can be obtained in complex channel environment and the requirement of message transmission reliability is satisfied.

Abstract:A set of interaction handed-gestures were defined for Human-Machine Interaction (HMI) in command post according to the requirement of command tasks. Based on the statistical analysis of coordination relationship between touch points in the course of accomplishing the touch gestures, the current research designed a recognition method which is independent of hardware for these interaction handed-gestures. Finally, aimed at the definition and identification of interaction handed-gestures, some experiments had been tested on infrared multi-point touch table to verify the stability, validity and expansibility of this method.

Abstract:There are small sample and zero failure characteristics in space bearing reliability modeling and analysis. Although performance reliability method may be available, insufficient performance data are still impediments. In the paper, a hierarchy Bayes modeling and analysis method is presented to solve the difficulties under small sample circumstance. Based on failure mechanism analysis, a performance degradation model is built at first. Then multiple methods and information including bootstrap method, experiment data, physics model and expert experience are utilized to determine the Bayes prior distribution. The Bayes calculation problem is settled using MCMC method. Example analysis shows that the method provided in the paper is well applicable, and is an effective method solving reliability modeling and analysis problem of long life products under small sample condition.

Abstract:Science and technology innovation capability is a key index of universities. This paper studies the theories and methods of science and technology innovation capability evaluating in view of research teams. It also analyzes the constituents and its structure of science and technology innovation capability. Furthermore, it defines an extensible evaluation index system from five aspects. This paper also proposes the evaluation method for science and technology innovation capability, based on Multiple Attribute Decision Making (MADM).

Abstract:Calibration error analysis of inertial measurement units (IMU) is significant for evaluating navigation system performance, allotting errors, and choosing devices in projects. However, few researches on IMU calibration give the quantificational forms of calibration errors. Based on quaternion, this paper constructs an error model about axes perpendicularity errors and angle control errors of a turntable. Considering measurement errors of gyroscopes and accelerometers in an IMU, we derive the calibration parameters' errors using a typical multi-position calibration method. Finally simulations and calibration tests of a laser gyro strapdown inertial navigation system are performed to verify the calibration error analysis.

Abstract:It is important to understand the functional activity of the human brain during the resting state by analyzing the functional connectivity between the regions. The resting-state brain functional network was constructed based on the complex network theory. The result of analyzing the structure and topology of network showed that the resting-state brain functional network was a sparse and scale-free small-world network. Furthermore, a probabilistic mixture models was introduced to detect the community structure, which revealed 10 sub-networks underlying the network, including the visual system, auditory system, motor system, and default-mode network, as well as the brain regions associated with the executive and working memory function. Our findings suggested that the resting-state functional network of human brain was composed of these relatively independent and overlapping sub-networks, and the precuneus and cingulate gyrus played important roles in dispatching and transferring information of network.

Abstract:A novel micro in-pipe robot, which possesses the advantages of big driving force, fast and long-distance moving ability, is developed. The robot creeps bidirectionally and is driven by motors. It consists of self regulating mechanism, flexible holding mechanism, flexible shaft driving mechanism and unloading mechanism, which can adapt itself to micro pipelines with diameters ranging from 15 to 20mm. Based on the robot's operating principle and mechanism structure, dynamic characteristics of each mechanism are analyzed. The virtual simulation and prototype experiment results demonstrate that the robot can pass the elbows whose radius of curvature is not less than 80mm, move bidirectionally with a speed of 8-10mm/s, climb the oblique pipes angled 0-90°, and carry a load of at least 10N while the ratio of load to deadload is up to 6.67∶1.

Abstract:The characteristics for semi-martingale predictable representation are obtained (theorem2.2), which is derived from the functional representation theorem in martingale space, the Hahn-Banach theorem in functional analysis, and the Girsanov theorem for the semi-martingale vector stochastic integral. In light of the semi-martingale vector stochastic integral used, this method is a generalization of the classical result．