Abstract:The unsteady oscillatory characteristics in supersonic cavity are numerically studied in the steady inflow condition. 5 order WENO scheme and 3 order Runge-Kutta algorithm are used. Through numerically calculating and analyzing the pressure changing procedure, sound pressure level, oscillatory frequency in 2D and 3D cavity, it shows that there is typical pressure oscillatory in cavity. The oscillatory has approximate cycle, but the law of cycle is very complex. 3D cavity exerts little effect on the main oscillatory frequency, but the oscillatory intensity is quite different in 2D and 3D.

Abstract:Using N-S equations to describe the ignition transient model of the large aspect ratio solid rocket motor, this model includes the igniter and burning room and nozzle. Comparing the calculation and experiment shows the correction of it. Furthermore, there are vibration and rapping during the ignition transient besides rapid pressure rising.

Abstract:For the purpose of designing a high performance synthetic jet actuator, the performance of actuators has been investigated experimentally for a range of geometric parameters. It is showed that the performance of a synthetic jet actuator is determined by these geometric parameters, the square/rectangle exit-slot is propitious to found a powerful synthetic jet, and the maximal velocity of actuator with dual-membranes is doubled compared with the actuator with a single-membrane. It is also found that varying the pressing states of membrane does not change the main relations between synthetic jets and the exciting frequency but affects the synthetic jet velocity values a lot.

Abstract:Since there are more and more satellites in the constellation, autonomous position determination by using single satellite has been gradually replaced by the whole autonomous navigation by using the inter-satellite relative observation in the constellation. Based on analyzing inter-satellite relative movement for Walker constellation, the resolution expression of the inter-satellite relative distance and the partial derivative with respect to orbit elements are presented firstly. The variation of orbit elements in the inter-satellite measurement is intuitively described in the same orbit plane and different orbit plane. Secondly, based on the relative position of satellites in the constellation, rational restriction and estimation method is put forward. The orbit determination of the whole network of the constellation is realized using the measurement of the inter-satellite distance. Finally, modified results of the orbit elements' system error and random error are compared in different instance using the rational orbit determination method by way of example.

Abstract:A continuous polycarbosilane(PCS) multifilament was melt spun at≈300℃. Spinning was performed with a laboratory scale extrusion apparatus equipped with a multi-hole spinneret. The filament was drawn down to a diameter of 10～25μm, the mechanical stretching being applied to the filament via the take-up reel. The spinning stability was investigated by introducing the ringy spinning channel and mobile take-up reel and changing the melt spinning processing, in order to obtain continuous PCS-derived silicon carbide fiber with fine diameter,lower diameter's dispersion rate and higher tensile strength. The results show that increasing the cooling temperature within the 180～200℃ range, introducing ringy and downward airflow by a special spinning channel, controlling a proper spinning line of about 90cm in length, enhancing fibers' gathering and controlling the stabilities of spinning conditions can improve the spinning stability availably.

Abstract:Information fusion of multiple sources under different population and small sample conditions is a key problem. The reliability testing information fusion methods are summarized under small sample conditions. On some hypotheses, the reliability information fusion methods using the data from the non-identical environment are studied. The simulation shows that by the fusion methods we can take full advantage of the information and give a more reasonable conclusion.

Abstract:The chemical non-equilibrium flows over a teflon ablative wall are calculated numerically by solving NS equations with pure-air and teflon-air chemical reaction system. The overall teflon-air chemical system used consists of 19 species and 28 reactions. The effect of wall injection of teflon ablating material on electron number density are discussed.

Abstract:The basic principle of microaccelerometers is explained and several kinds of them with different structures are investigated, including piezoelectric type, capacitive type, torsional-cantilever type, tunneling type, etc. The characteristics of those types are introduced. Some focused problems are pointed out. Furthermore, several methods and advices are offered to improve the property of microaccelerometers.

Abstract:Based on the avalanche effect, a kind of kilo-volt nanosecond pulsers has been designed, by using microwave PCB (printed circuit board). Its trigger signal with tunable repetition rate is given by a digital circuit. The full width of the pulse is tunable between 400ps and 2ns. Its voltage ranges from 360 to 2600V. And the peak power reaches 135kW. The design of these pulsers is discussed in detail, including the circuit design, the component selection, and the important physical layout. A novel method, called deficit-charge method, and a comb PCB layout are brought forward, aiming at solving the special problems caused by the high-power butultra-narrow pulser. Being used in the impulse radar test system, the circuit performance is excellent and stable.

Abstract:The five-dimension searching algorithm is presented for the alignment automation between a laser diode and a single-mode fiber. The searching path and the parameters are discussed in detail. The novel exponential function approximation algorithm for XY plane searching is also presented first. The experimental results with these algorithms are finally presented. It is confirmed that the searching efficiency of the exponential function approximation algorithm is better than the hill-climbing algorithm. The main reason is that the sample points are reduced. Thus the alignment speed is improved notably.

Abstract:Automatic classification and segmentation of the sound track is an effective approach for video structuring. We use this method to parse soccer video. Firstly, based on the characteristics of soccer video, the paper summarizes three audio classes for soccer video, namely game-audio, advertisement-audio and studio-audio. Then it proposes a framework of audio classification and segmentation using Hidden Markov Model and combining some smoothing rules. We develop a 26-coefficients feature stream for HMM model. And the experimental studies indicate that the proposed framework is effective and robust.

Abstract:The elementary bifurcation theory is utilized to study the bifurcation of singularities of general parallel mechanisms. Based on constraint equations, some typical motion bifurcation of simple parallel mechanisms are researched and they can be classified into different styles by codimensions of constraint equations at actuator singular points or end-effector singular points. Finally, this paper discusses how the disturbance of mechanism parameters affects the bifurcation diagram of singularities and results show that those nonpersistent bifurcations of parallel mechanisms can be transformed into those persistent bifurcations so that the motion uncertainty at singularities can be overcome.

Abstract:Regular radiometric calibration techniques developed for high frequency narrow band radar system are not applicable for low frequency ultra-wideband radar (UWBR). The low frequency scattering model is calculated using method of moment (MOM) and asymptotic waveform evaluation (AWE) technique, and the calibration method is proposed. Computer simulation is used to verify the validity of this calibration method.

Abstract:The FPGA realization of a floating-point FFT processor is proposed to get over the poor precision of the fixed-point FFT processor.The definition of the floating-point format,the selection of arithmetic and the key techniques of the FPGA realization are discussed. Such a processor has been put into service and has stable performance. Its operating frequency is 80MHz and it can finish 1024 point FFT/IFFT in 64μs with an error less than -80dB.

Abstract:The normal receivers of DSSS system despread and demodulate the IF signal separately, their process-gains are the period of the pseudo-noise sequence. But these process-gains usually cannot satisfy a low bit-error-rate if the signal-noise-ratio of input signal is very low. In a DSSS system based on the software radio, the receiver can despread and demodulate the IF signal simultaneously. It can be proved that this method can get a higher process-gain when the sample rate meets a certain condition, so it can be used in a low signal-noise ratio system.

Abstract:A useful method for calculating RCS of complex objects is given. First, it models the armored car with triangular element by using 3D Studio Max. Radar scattering character is calculated with Ludwig's integration and the physics theory of diffraction. The method is effective validated by calculating RCS of the cuboids. The radar cross section of armored cars and tanks is presented, which is important in studying scattering characters of the targets.

Abstract:A CGF behavioral scheduling technique is presented. The method addresses the scheduling of behaviors generated by CGF of the local simulation node and the remote model in other nodes. All the behaviors are scheduled in a centralized way. The behavior priority and executive deadline of the remote model are decided by the interest domain of CGF in the local node, through the combination of all the CGF interest domain to reduce the number of remote models, and the cost of the simulation node computing. The method can effectively ensure the requirement of real-time and quality of the distributed virtual battlefield environment.

Abstract:A calculating method of bookbinding parameters of the liquid propellant utilizing system is designed, and the integrating method is studied of the distributed computation based on CORBA. It is proved practical in the software project and can meet the need of the distributed computation.

Abstract:Distance join is widely used in spatial database. Selectivity estimation for distance join is the basis of optimizing the query of the distance. Incorporating the existing selectivity estimation techniques, a new selectivity estimation method for the distance join based on Minkowski sum and histogram is proposed. The experimental results show that the method is efficient for selectivity estimation for the distance joins.

Abstract:The network-centric operation is a new concept of information warfare. According to the concept of network-centric operation, the network-centric operation C⁴ISR architecture of the antiaircraft missile system is studied. The function units of combat zone are basic nodes of the architecture, the network-centric operation C⁴ISR architecture is composed of three logical networks, namely track-guide network, command-control(C²) network and weapon networks. The function and composition of the logic networks are defined. The architecture is valuable in network centric warfare of the antiaircraft missile system.

Abstract:Since the locally linear embedding method is sensitive to noise, a new method is presented to solve this problem. This new method, namely robust locally linear embedding method, is constructed by analyzing noise influence on the character of the data set's local neighborhood. Compared with LLE, the RLLE is insensitive to noise and adaptive to the selection of neighborhood, which is verified by theoretical analysis and practical experiments. Therefore, the RLLE can discover the intrinsic structure of the data set and visualize the data better.

Abstract:Generally speaking,a strategy Ψ is said to be an arbitrage if it makes something out of nothing without risk,i.e V_T(Ψ) is strictly positive with positive probability and with its initial wealth 0.If the net capital gains are strictly positive with positive probability,we can't tell whether it is an arbitrage.How do you tell whether a strategy is an arbitrage with its initial wealth unequal to 0? We give another definition of arbitrage and have shown that judging whether a strategy is an arbitrage is to judge whether its discounted gains are strictly positive with positive probability. We give the equivalent expression forms in mathematics of the original market and different discounted markets with respect to no arbitrage ,and correspondingly we get equivalent expression forms in mathematics with respect to no arbitrage with different strategy requirements.

Abstract:In order to solve the security problem of digital video, a hierarchical authorization scheme on digital video is presented，which utilizes modern strong cipher to protect digital video's transport and realize hierarchical authorization. Owing to the use of fully mature digital video broadcast technology, the scheme has high security, simple framework, and low cost.

Abstract:We introduce a new algorithm for subset sum problem. For any given problem with A(1)，A(2)，…，A(n-1)，A(n),and M, the time complexity of the algorithm is O(n^log₂^(M+1)+1)and the space complexity is O(n), where A(1)，A(2)，…，A(n-1)，A(n),and M are all positive integers. This result is better than that of the two-list algorithm when M is relatively small.