Abstract:Considering the mutually interacting phenomenon of such aspects as trajectory, solid rocket motor and system, a set of mathematical analytical models for the design and optimization of rocket were developed. An optimizing calculation with 6 design parameters for the rocket was made by using genetic algorithm. It shows that the optimized concept reduced 17.7% of the booster mass of the primary, indicating that the optimized results are satisfactory.

Abstract:The study was conducted to investigate how the hot-spot formation was caused by crack friction in composite solid propellant under mechanic impact. It was concentrated on processes of crack surfaces slip, crack growth and friction heating of closed crack driven by sheer stress, heat conduction, decomposition of solid propellant and its interaction with the gas-phase product. In view of the fracture mechanics, heat conduction and dynamics of thermal decomposition of solid propellant, the meso-scale hot-spot model of crack friction was established. By making numerical calculation of the model, the process and condition for hot-spot formation were discussed, from which it is concluded that friction between crack surfaces slip and crack growth can lead to formation of hot-spot in composite solid propellant.

Abstract:Spaceborne InSAR (Interferometri Synthetic Aperture Radar), whose baselines may undergo complicated variations while the satellite formation flies in the space, is widely used in earth observation. Based on the principle of satellite formation, the even phase configuration for the spaceborne InSAR was defined. Then baselines and their stability were supplied from the principle of InSAR measurement, and the stability of spaceborne InSAR in different even phase configurations was addressed.

Abstract:It is of great necessity for the long term relative motion of formation flying to choose initial conditions and design the nature-periodic-relative rotating obits with the reference orbit eccentricity and the nonlinear relative motions. It is recognized that it yields considerable errors and is insufficient to employ Hill equations in choosing initial conditions and designing formation flying orbits without fuel consumption. With a consideration of the effects resulting from the reference orbit eccentricity and the nonlinearity relative motion, the numerical optimal technology was utilized in the present study. Results of numerical optimization can be used to determine the invariant-periodic-relative rotating conditions, thus gaining a good insight into formation flying. Numerical simulations demonstrate the correctness and effectiveness of the optimaized results.

Abstract:Chemical vapor curing (CVC) method for polycarbosilane (PCS) fiber with unsaturated hydrocarbon vapor, cyclohexene, was studied and compared with air oxidation curing method. The analysis of composition and thermogravimetry of PCS fiber in the process of CVC was also characterized and an elementary reaction mechanism was discussed. The results show that Si-H bond in the molecular structure of PCS reacted during the cyclohexene curing process and the reaction degree increased with the rise of the curing temperature. Simultaneously, gel content of PCS fiber rapidly increased till PCS fiber became infusible. Si-H bond and Si-CH₃ bond broke and formed free radicals through the agency of cyclohexene radical while being heated up, and then formed the structure of Si-CH₂-Si, resulting in cross-linking between PCS molecules.

Abstract:Two C/SiC composits reinforced respectively by T300 and JC2# carbon fibers were fabricated by means of polymer infiltration and pyrolysis (PIP) with polycarbosilane (PCS) as precursor. The composite reinforced by JC2# fiber had perfect mechanical properties, displaying flexural strength of 662MPa and fracture toughness of 19.5MPa. m^1/2, whereas T300 C/SiC composite had low strength and high brittleness, with its flexural strength and fracture toughness were less than one fourth of those of JC2# C/SiC composite. It was found that the fundamental factor to the poor mechanical properties of T300 C/SiC composite was the severe degradation of the fiber during PCS pyrolysis; the other important one was attributed to the strong interfacial bonding between the fiber and agent in the composite.

Abstract:Based on USB interface, the automatic measurement of MMW wide-band RCS was studied by using MMW vector network analyzer. This paper first introduced the design of the hardware system and the program of 82357A interface. Then it elaborated the design of the automatic measurement software, and the RCS measurement error correcting algorithms. Finally, the measurement experiments of background and target were performed and some of the measurement results were presented as illustration.

Abstract:A micro-strip shorted patch antenna with a compact electromagnetic band-gap structure (CEBG) is presented and a performance comparison is made with the conventional short-patched device of identical dimensions. Measured data shows a gain improvement of 3dB and a significant reduction cross polarization for the CEBG antenna. Meanwhile it proves that the design of the same resonant frequency can be attained under such a condition that the CEBG structure cell size is only about 40%～50% of conventional structure. It indicates that the suggested condition is significant in realizing the array of EBG of micro-strip phased antenna.

Abstract:Radiometric calibration is considered as an important and inevitable problem in the development and application of low frequency ultra wide band synthetic aperture radar (UWBSAR) system. Due to the characteristics of the UWSAR, the calibration procedure developed for the regular SAR is no longer feasible. With a careful consideration of the calibrating parameters which vary with the change of the frequency and the aspect angle, this paper proposes that the radiometric calibration method is applicable to the low frequency UWBSAR and a model of radiometric calibration is presented. With the help of such a model, the analysis of the system calibration error was conducted.

Abstract:According to the formation principle of the Kelvin Transverse Wave(KTW), the KTW crest model was elaborated and analyzed. An automatic method for KTW detection and vessel velocity estimation was put forward on the basis of generalized Hough transform. The KTW detection results in remote sensing images were satisfactory and the vessel velocities were thus estimated. The method presented here will be helpful in marine transportation and harbor management.

Abstract:By using the cyclostationarity property of communication signals, a higher-order cyclic cumulants based carrier phase estimation algorithm for QAM signals is proposed. Normalized higher-order cyclic cumulants were utilized for the estimation, and the effect of the signal energy, time delay and pulse function with different roll-off parameters on the estimator was eliminated by the normalization. The correctness and effectiveness of the proposed estimation algorithm were verified via theoretical analysis and simulations.

Abstract:Analysis of short sequence motifs is an important component of gene sequence analysis. Information of motifs is usually used for identifying biological signals. However, the number of short sequence motifs is very large. If all of them are used for signal identification, there will be too many parameters, thus covering the main characteristics of the signal. To find out the key short sequence motifs for signal identification, in this paper, a stepwise strategy was adopted to rank motifs by their information gain. As a result, the motifs were selected orderly for signal identification. In so doing, good results were achieved with fewer motifs. Consisted with the selected motifs, maximum entropy model was used as the approximation of the true distribution of the signal sequences, thus realizing the identification of a given sequence. Finally, the model was used to identify 5'splice sites, and approving experiment results were achieved.

Abstract:Regarding the fact that space target recognition is a challenging research problem, this paper proposes a space target recognition algorithm based on the two-dimensional wavelet transform. Firstly, the two-dimension wavelet transform of ISAR image of space target was proceeded. Then singular value feature was extracted from approximate and detail parts. Finally, the radial base function(RBF) neural network was used to classify space targets. Computer simulation shows that such an algorithm achieves good recognition effect.

Abstract:According to the concept and the features of complex system of systems, its structure was synthetically analyzed with its mission and elements composing. Both the three-phase mission decomposing process, which consists of goal decomposing, function decomposing and action decomposing, and the three-element structure framework, which includes system unit, system compound and its environment, were described for complex system of systems. On this basis, a new design method which utilizes the “two-level, four-grade” framework to effectively model the structure for complex system of systems was presented. At the same time, aimed at the location level and function interrelation existing in complex system of systems, such terms as measuring entity, level mapping, relationship between systems and soft structure level were defined. This clarifies the essence of level mapping in the structure analyzing and modeling of system of systems. Therefore, some theoretic guidance for the effectiveness evaluation and the upgrading and optimization of complex system of systems is revealed through this kind of analyzing and modeling methodology.

Abstract:This paper proposes a Wallace-tree based new DCT/IDCT architecture, which does not depend on ROM and multipliers any more, but utilizes low cost adders, shifts and 4-2 compressors to implement the multiplication-dense DCT/IDCT algorithm. Designed and synthesized by SMIC 0.18 μm technology, the architecture could achieve 100Mpixels/sec throughout with cost of only36 141transistors and 1024 bits transform memory. As a result, a far better performance of time series and space is obtained than that of the existing architecture.

Abstract:Video content is the basis for effective video management. As video is characterized by multi-modality and multi-level structure, this paper presents a 3-D model of video content. Furthermore, it proposes an open framework for video management, in which video data and the contents of video are stored and managed separately. The connection between video data and contents was maintained by an associating mechanism, through which multiple logical descriptions between video data and contents could be created. This framework is applicable to the management of different videos while users can search them with “multi-modal query” as well.

Abstract:Clustering is one of the focused problems in multimedia data mining, and similarity measurement among data is fundamental to clustering. In multimedia data clustering, the corresponding vector features are always of high dimensionality. Most traditional measurement methods, however, are only efficient for low dimensional data. This paper, based on an analysis of general characteristics of data presented in high dimensional spaces, proposes a new similarity measurement for multimedia data mining. It used a special strategy to split the original data space before computing the similarity among data points, thus efficiently avoiding the influence of noisy data in high dimensional dimensional spaces. Experiments show that the new method presented is effective.

Abstract:Such problems as the difficulty to set up models and the inaccurateness occur when the classical effectiveness analysis method is used to analyze the measurement of force effectiveness (MOFE) of the reconnaissance and surveillance (S&R) system. Considering the intelligence-supported aim of S&R system, a new method to assess its effectiveness based on information needs is put forward.

Abstract:Based on an analysis of the wavelet multi-scale transform in target image, this paper puts forward a new method to extract the main features of the transform. It, in terms of the energy concentricity of the image's wavelet coefficients, selected the parts with concentrated energy to construct the feature vectors, which include most of the edge, texture, luminance and structure features. As there is no limit to the distribution of the image feature information, the method can be used in many kinds of image feature extraction, thus solving the problem of feature illegibility with which the single-feature extraction is confronted. In the experiment, normal white noises with different ranges were added to the images and the result approves that the feature vectors are robust to noise.

Abstract:The earth rotation has two main effects on the distributed spaceborne SAR-GMTI. Firstly, the baseline must orient the same direction of radar's footprint on the rotating earth to mitigate the fluctuant terrain clutter and satisfy ATI, DPCA or STAP condition, which means that proper relationships must be maintained between satellites' orbit parameters. Secondly, Doppler is dependent on range, so yaw steering technique is required to mitigate the warping or extended clutter notch. Based on the two effects, a distributed spaceborne SAR system composed of 3 small satellites was designed to perform GMTI function. Performance simulation was made to scale the system capability through SCNR loss metric for both X and L bands.

Abstract:The current-loop is a key subsystem of the magnetic levitation controller on maglev vehicle. Based on the analysis of controlling features of PI and time-optimal current-loop, the paper presents a design of hypo-time-optimal current-loop control system, which has the advantages of fast adjustment, strong anti-disturbance and insensitiveness to system's parameter. Simulation results show that the hypo-time-optimal current loop was as fast as the time-optimal current-loop and had less vibration when noise interfuses into the system. The experiment results indicate that the hypo-time-optimal current-loop can be regulated conveniently, and can also be successfully applied in magnetic levitation control system.

Abstract:This paper introduces the experimental principle and method on undulatory dorsal fin propulsion of gymnarchus niloticus, a large aggressive fish whose swimming mode is referred to as amiiform mode. The fish is propelled by undulations of a long-based dorsal fin while the body axis is in many cases held straight in swimming. In order to investigate the undulatory dorsal fin propulsion and its potential for providing alternative approaches for future underwater vehicle design, the kinematics of steady forward swimming of gymnarchus niloticus was described and the geometric features of the body and locomotive characteristic and parameters of the flexible dorsal fin were discussed. Furthermore, a simplified kinematic model on locomotion of the undulatory long dorsal fin propulsion was established according to the observation and experimental data. By applying the large-amplitude elongated-body theory, the estimation shows that the hydromechanical efficiency of the undulatory long dorsal fin system is more than 83.12%. It is suggested that the undulatory long dorsal fin propulsion is an adaptation to swimming with high hydromechanical efficiency.

Abstract:Most of the blind source separation methods were dependent on the fact that the observing sensors are more than or equal to the number of signal source. The algorithm in this paper is aimed to research into the blind source separation of noisy harmonic signals from rotating machine when the underlying system is underdetermined, that is, the cases in which the separation of n sources is made from m mixtures while m is smaller than n. Based on the assumption that the input distribution is sparse and the mixture procedure is instantaneous, a potential-function clustering method for estimating the number of information sources was proposed and a calculation on the attenuation matrix and the delay matrix were made. Signal simulation in experiment shows the applicability and reliability of the method under discussion.

Abstract:Currently, horizontal direction drilling (HDD) has been considered as the mainstream in the trenchless technology used for municipal construction, in which the geo-radar and electromagnetic-based underground pipe detectors are widely used to find the distribution of pipes near the construction route so as to avoid destroying the latent buried pipes. Limited by detection principles, many objects cannot be detected effectively. In this paper, a novel solution for detecting underground pipes is proposed. By introducing tiny ultrasonic detecting system installed on the head of HDD, an online surveillance system for underground pipes was implemented with drilling and detecting implemented simultaneously. As a result, the system gave warning to the operators of the drilling when it detected pipes under the construction route. The experimental results show that construction risks of HDD were reduced considerately and the system proved to be effective.

Abstract:Considering the fact that the camera calibration method based on perspective projection model yield intricate and unstable result, a new calibration algorithm based on affine approximation was presented. The affine projection matrix was led out and then some parameters were decomposed. Under the presumption of taking image center as principal point, other parameters were solved. At last, all the parameters' precision was improved on the basis of the cost function of re-projection error. Simulation and real image experiments show that the new method can produce more stable result than the usual one.

Abstract:An efficient simulation procedure for stochastic analysis of nonlinear dynamical systems with multi-degree freedom based on Monte Carlo simulation (MCS) is presented. A simple criterion was established for indicating the importance of each dynamical response sample. According to this criterion, Russian Roulette and Split (RRS) method was applied to deal with the selected samples. The efficiency of this algorithm was much higher than that of direct MCS while the number of response samples in the low probability regions was increased. The result of evaluated examples demonstrates that the methodology presented in this paper has the advantage of being simple in operation, thus applicable to realistic engineering calculation.

Abstract:According to the theory of target-directed deformable warhead, a structural model was designed and an experiment of explosion was carried out. Based on the experiment results, the finite element analytic model was established. By utilizing the code LS-DYNA, the deforming process of the deformable warhead and the projectile process of its fragments were numerically simulated. The results of simulation and experiment show that the density and velocity of the fragments are greatly enhanced in the target direction and the simulation is consistent with experiment.