Abstract:An optimal trajectory generation strategy based on way-points is presented to solve the fixed-time state transition for spacecraft relative motion in a circular orbit. According to the dynamics of relative motion, the optimal transfer trajectory with continuous thrust is investigated by applying optimal control theory. Furthermore，a set of way-points constrained to be along the optimal transfer trajectory are introduced to parameterize the trajectory with impulsive constraints by multi-impulse control. By changing the positions of way-points and the time between two neighboring impulsive burns, the generated trajectory is optimized with quadratic programming algorithm. The simulations show that the strategy is practical and efficient.

Abstract:Based on the laser signal's emission, propagation and detection during the in-door laser simulation, the effects of the aerosol's Mie scattering is provided for the 1.06μm laser signals. By the construction of the models of the indoor aerosol's scattering, the laser designator's propagation simulation and calculation are carried out. Finally, the discussions related to the arrangement and the methods to reduce the effects of the scattering are delivered in terms of the analysis of and verification by practical measure data.

Abstract:A 3d LU-SGS computational code was developed to solve the hypersonic flows, which was modeled by using the compressible three-dimension Reynold averaged Navier-Stokes equations and a finite volume formulation, the convective parts were discretized with the Harten TVD scheme, and the turbulence effect was modeled utilizing Menter SST two equation turbulence model. The flowfield of 18×18 degree fins generated crossing shock wave/turbulent boundary layer interactions were studied at Mach 4.96, a 3D separated flowfield was analyzed and the numerical results were compared with experimental and numerical results from references.

Abstract:Polysilanes with antimony side groups (PSA) can be synthesized from polymer reaction of polymethylsilane at room temperature. In so doing, the yield of polymer is 75.2% and the average molecular weights of the polymer are around 1600. Its chemical composition and structure can be characterized by elemental analysis, FT-IR, 1H-NMR,²⁹Si CP/MAS NMR, GPC, and UV. It is soluble in the common organic solvent; the UV absorption maximum wavelength is 330nm. The property of pyrolysis shows that its ceramic yield is 80% and it is a potential preceramic polymer. This polymer shows good semiconductive properties, whose intrinsic conductivities are within the range of 10^-8～10^-7S/cm, and can be increased above 10^-5S/cm after being doped with iodine.

Abstract:Because perpendicular impact on the target was required for reentry maneuvering warhead, the integrated guidance law with terminal angular constraint, which comprised diving-plane guidance equation and turning-plane guidance equation, was derived. The robustness was enhanced by adding sliding mode variable structure control to the optimal guidance law. For the sake of reduction of chattering and energy consumption, the RBF(Radius Basis Function) neural network was used to adjust adaptively switching gain, which was demonstrated to be effective through computer simulation. Simulation results still show that, compared with optimal guidance law, the integrated guidance law can still hold the guidance precision when disturbance exists.

Abstract:The theory of generalized thermoelastic diffusion of Sherief is used to investigate the dynamic response of infinite elastic medium with a cylindrical tunnel subjected to a time-dependent thermal shock. Without the customary use of potential functions, the direction method of solution, with the help of Laplace technique, is used to solve the coupling thermal, chemical and mechanical governing equation. The analytical solutions of temperature increment, displacement, stress and chemical potential are obtained in the transform domain, and by using the inverse Laplace transform, the numerical results are obtained and used to analyze the distribution of temperature increment, stress, displacement and chemical potential on the condition of thermo-chemo-mechanical coupling.

Abstract:Analytical study of wave growth on hollow conical liquid sheets was made. By using small wave amplitude model, the linearized perturbation equations of the liquid phase and the gas phase were solved. After some rather tedious algebraic manipulations, the characteristic equations relating the non-dimensional temporal growth rate of a disturbance on conical liquid sheets to the normalized wave numbers were obtained. The numbers are the generalization for the well-known cases of round cylindrical jets and the annular liquid sheets. The characteristic equations are the solid cornerstone of theoretical analysis of conical liquid sheets' atomization.

Abstract:The vertical take-off event of launch vehicle was divided into static phase, hold-down phase and release phase, and the computational result fields of the previous phase provided the initial condition fields of the next phase. A new analysis method to compute the launch vehicle's structure transient response during the hold-down and release phase was proposed in this paper, using the field transferring function and group analysis function of the MSC.Patran/Nastran software. This analysis method solved the difficulty brought about by the changed boundary condition (the separate face between the launch vehicle and the launch pad) during the structure transient response computation course. Several examples of launch vehicle's structure transient response during the hold-down and release phase were analyzed by the proposed method. The variety characteristics of hold-down force during hold-down phase and the vehicle's structure transient response during the release phase were obtained. The computational results indicated that the analysis method is both simple and convenient, and the computational result was quite accurate. The method can be used to make efficient analysis of the influence of the different release time, the disappearing characteristics of the hold-down force, the dispersion of the release time, the restrain force of soft release mechanism to the vehicle's structure transient response. It can provide reference for the design of the hold-down and release mechanism.

Abstract:For the need of modern intense acoustics technology research, the performance parameters of a hydrodynamic intense sound generator are investigated experimentally. The rules of the influences of the operating pressure, the distance between the reed and nozzle, and the angle of the reed on the SPL(sound pressure level) in the acoustic radiation field are explored and obtained. The results show that, under the optimal circumstance, the SPL in the outlet of the generator can be larger than 140dB.

Abstract:As the large-scale data on molecular interaction available increases, the study on biological networks has ignited more and more attention. As the execution level of cellular functions, the structural composition of metabolic networks not only reflects the execution of cellular functions step by step, but also influences the pathway analysis of metabolic engineering. Hence, as a key step, a sound decomposition of global metabolic networks is not only significant for further exploring the structure and function of genome-scale biological networks, but also necessary for favorably developing the pathway analysis of metabolic engineering. Having reviewed the fruitful study of the macro-structure and topological characteristics, and analyzed some available decomposition approaches, this paper concludes that the lack of reasonable and purposeful evaluation criterions is one urgent problem in the present study of metabolic network decomposition. Besides, the future trend is to develop more effective decomposition models with more information and by more advanced approaches, as well as expanding the application range of network decomposition.

Abstract:Continuing growth in link speeds and the number of advertised IP prefixes places increasing demands on the performance of Internet routers. In view of this fact, a parallel router architecture based on partial forwarding and pipelining switching is proposed. The architecture consists of multi-stage, lower speed nodes performing IP-lookups and switching independently, thus IP-lookups and switching for multiple packets have been pipelined. We investigate the key technologies of this architecture including the logical mapping from subtries to function components as well as the pipelining IP-lookup mechanism based on subtrie. Finally, future directions and possible open problems are discussed.

Abstract:Based on the compact support property of popular multi-channel filter banks, a low-memory implementation of generic tree-structured filter banks (TSFBs), called the stripe-based tree-structured filter bank (SBFB), is presented by utilizing the first-in first-out (FIFO) buffer technique. The SBFB has two advantages: (1) It produces exactly the same sub-band coefficients as the conventional global implementation of TSFB does, while the memory budget is unrelated to the image height and only dependent on the image width and the TSFB adopted. As a result, the memory budget of SBFB is only a fraction of that of the global implementation; (2) It generates integral parent-children trees (PCTs), which are completely contained in its buffers. The SBFB lends itself to PCT-based coders in that no intermediate buffering is needed between the SBFB and the coder. By analyzing the dataflow of different levels of TSFB, the relation between the samples and the sub-band coefficients is also attained, by which the correctness of the SBFB is strictly proved.

Abstract:A network active defense technology based on multi-layers deception in the distributed deception space is proposed to meet the needs of network countermeasure and network security. This technology simulates usual network service programs and forges vulnerabilities to lure the intruder. With operation control at kernel level, file system mirror and information deception, it creates the deceiving operating environment on the platform of Windows and Linux. Thus the process of intrusion is fully deceived, monitored and controlled. This technology breaks the limitation of a single layer deception used by other general honeypots, and obviously promotes the level of deception, interaction and ensures security.

Abstract:Based on the presentation of the security vulnerability of the event-driven system, this paper points out the deep reasons for the vulnerability of system: (1) The system ignores the inherent correlation among events; (2) The system trusts events from any sources without condition. In view of these two reasons, this paper presents an analytical model for security of event sequence, and an evaluation model of trustworthiness based on event source. Furthermore, this paper constructs an improved event-driven system infrastructure based on the two models.

Abstract:Architecture is a blueprint of system design and implementation, and whether it can guide practice correctly largely depends on the architecture verification and evaluation. Executable architecture provides a new way to validate and evaluate the architecture. In order to make all architecture products into a whole executive entity, this paper puts forward a new concept—execution rules description. Execution rules describe the execution, call and data flow relationship between architecture products, and thus provide special background information for the architecture execution. Through standard dynamic executive model interfaces, execution rules can call the models' executable engines, and then attain the aim to run the architecture on the whole. That architecture can run successfully, providing justification for architecture verification, and its executive result also provides justification for architecture evaluation.

Abstract:Universities play an important role in the national innovation system, and the research on the university S&T innovation capability evaluation is of great significance. Kernel principal component analysis(KPCA) method is proposed for the evaluation of university S&T innovation capability. This method, in comparison with Principal Component Analysis (PCA) method, can solve nonlinear correlation problem of evaluation index in the analysis of the S&T data released in 2002 from 15 universities directly subordinate to Chinese Ministry of Education. In particular, the result shows that contribution of the first and second principle components are more concentrated by KPCA than by PCA, and KPCA has better evaluation performance than PCA.

Abstract:The absolute value distribution of the Walsh spectrums of Boolean functions is presented and studied. The absolute value distribution of the Walsh spectrum is invariant under affine transformations. Then Walsh spectrums' absolute value distributions of all n-variable Boolean functions are obtained for. The relationships of the absolute value distributions of the Walsh spectrums and the support of the Walsh spectrums and the number of nonzero values of the Walsh spectrums and other problems are studied. Finally, the size of the absolute value distribution of the Walsh spectrum of Boolean functions is studied.

Abstract:In the test evaluation for small sample size, the prior information is generally fused to obtain the evaluation result with weight calculated by the data consistency check for test information and prior information. However, in small sample case, the consistency between two kinds of samples may be unstable. To improve this situation, the physical equivalency credibility is defined by analyzing different test surroundings. Moreover, the composite equivalency weight of prior sample is decided by fusing physical equivalency credibility and data consistency. A weighted method for considering the credibility of the prior information is proposed for Bayesian estimation algorithm and the weighted estimation of normal inverse-Gamma distribution parameters is provided. The efficiency of the prior sample is analyzed by comparing the posterior variances for different cases, and is further applied to determine whether the prior samples should be fused in the conception that only those prior samples which can reduce the posterior variance should be used. Theoretical analysis and simulation demonstrate that this method is credible.

Abstract:With the multiplicative map theory on matrix and its applications, a lot of attempts have been made for judging whether a multiplicative map can preserve certain desired numerical characters and obtain the explicit form of a multiplicative map under the restriction of perserving some numerical characters. In this respect, multiplicative maps without assuming linearity on matrix algebra, which have certain rank preserving or norm preserving properties, are considered mainly in this paper. By virtue of a way of construction, the complete descriptions of those maps are presented, and it is shown that a maximum column sum norm preserving multiplicative map is one of Frobenius norm and a Frobenius norm preserving multiplicative map must preserve spectral radius, numerical radius, normality, unitarity etc.. In particular, a new approach is also provided for judging whether a multiplicative map preserves rank.

Abstract:Based on the GPS broadcast ephemeris parameters, the nonlinear least square fit algorithm of broadcast ephemeris parameters was developed, and the relevant calculation formulas were derived. Since geostationary satellite's orbit inclination is equal to zero approximately, it will result in the ambiguity of satellite's orbit ascending node and the singularity of the normal matrix in the process of fitting. By transforming the geostationary satellite's orbit inclination, the accuracy of broadcast ephemeris was achieved. Finally, the rationality of formulas and algorithm were validated by simulation.

Abstract:The more bandwidth efficient modulation schemes are used for high speed data transmission systems in the satellite communication. But these schemes are sensitive to the nonlinearity of high power amplifiers (HPA). The nonlinearity of HPA causes inter symbol interference (ISI) and adjacent channel interference (ACI). A scheme for adaptive digital predistortion based on RBF neural network for HPA onboard the satellites was proposed to linearization HPA . And the adaptive arithmetic of stochastic gradient method was derived. Simulation results show that the scheme can not only correct the constellation distortion obviously, but also improve the system BER performance greatly.

Abstract:Focusing on the problem of moving object detecting before tracking in image sequences with complex background, a new salient feature extraction algorithm that fuses the motion characteristics of objects is proposed. The algorithm fuses the gray-level and the detail and motion of the objects to form a robust salient image. The regions with salient multi-features are enhanced and the others are restrained, so moving objects will easily be detected in the salient image. The salience of the objects in the algorithm is derived from the local difference of multi-bottom features of the image, so the algorithm is robust. The experimental results show that the new algorithm is practical and stable, and has the strong anti-jamming capacity. The visual effect of the experiments demonstrates that this method can improve the signal-clutter ratio.

Abstract:A Cross-correlation Integral based Unintentional Modulation Identification (CCI-UMI) method is proposed for Power Amplifier (PA) fingerprinting, assuming that the PA is excited by continuous signals of the same frequency. The model of the PA and the theory probability density along trajectory is presented. Then an algorithm is given, using multi-scale comparison to distinguish the two signals with tiny difference. The actual measurement experiment of the signal generator shows that the developed CCI-UMI method is better than the Power Spectral Density based method and the Phase Space Difference method in lower SNR.

Abstract:Based on the principle of parametric curve paths CNC interpolating, it is pointed out that the Taylor series methods and “Parameter-Arc-length” curve fitting methods for CNC curved path interpolation are not perfect in theory. Thus a novel curved path interpolation method is proposed with Newton iteration functions. The detailed realization of the proposed algorithm has also been given. It has many advanced features, such as good stability, fast convergence, low computational effort and high precision. Simulations and experimentations show that the proposed algorithm can reduce the feedrate fluctuation by 10²-10⁷times with equal or little more computational effort comparing with Taylor series methods.

Abstract:In this paper ,the structure properties and computational methods for Polynomial Reproducing Kernels are discussed. It is proved that polynomial reproducing kernels with arbitrary functional constraints can be obtained via the projective remainders of reproducing kernels with initial value constraints. Specific algorithms for computing polynomial reproducing kernels are given.

Abstract:Being the main source of vehicles' movement state parameters, wheel speed is central for control systems and its accuracy affects their performance. In order to attenuate the wheel speed sensor errors and reduce the research and manufacture cost, an error estimation method based on resilient back propagation (BP) is presented. The improved resilient BP neural network is applied to estimate the sensor errors. Matching algorithm is illustrated to realize the corresponding errors. Theoretical analysis and simulation results show that the proposed method can make the error less than 2×10^-4 rad, so it can effectively attenuate the sensor errors and improve the accuracy of the wheel speed signal.

Abstract:The extensively focused target recognition is one of the important problems for SAR imagery interpretation. With the aim to real-time processing, a fast SAR target recognition system is built, which utilizes the principal component analysis (PCA) for feature extraction and a multi-layer neural network (MLP NN) as the classifier. The experimental results show that it consumes little memory and runs very fast, thus can be used in the real-time situation.