Abstract:An inlet has been designed for ramjet assisted range projectile. With the features of ramjet assisted range projectile, such factors as cone parameters, throat parameters, encloser and parameters have been discussed. In particular, an analysis of cone lip parameters and diffuser angle is made. Furthermore, three inlets, single cone with inner contraction, single cone without contraction, and double cone with inner contraction have been designed. With these inlets, numerical simulation and performance also have been conducted. The effect of decisive parameters in inlet design has been analyzed. The result of numerical simulation shows that under the requirement of ramjet assisted range projectile, double cone with inner contraction has better performance.

Abstract:At present, micro satellites and small satellites are under rapid development. The pulsed plasma thruster is a good choice for its propellant system. For space application, the flume is in a great need to be studied. In this paper, DSMC(Direct Simulation Monte Carlo)/PIC (Particle in Cell) fluid hybrid method and one dimension MHD discharge model are used to simulate the NASA Glenn PPT flume from end to end. The distribution of deflection angle at the thruster outlet is achieved by calculation and comparison between experimental results. The results show that the deflection angle at the thruster outlet can improve the diffusion of flume, thus making an important factor influencing the simulation results.

Abstract:Traditionally, the satellite orbit measurement data are reprocessed by least-square polynomial fit method. Because of the non-linear errors in the satellite tracking, the accuracy of data reprocessing is reduced. The current approach, based on the semi-parametric regression model, holds that the observations can be de-noising via wavelet threshold, and the nonlinear errors can be estimated and removed from the observations. The data reprocessing method with semi-parametric regression model based on the wavelet de-nosing approach is proposed to improve the accuracy of data reprocessing. Finally, the simulation of the reprocessing of a united S-band(USB) satellite orbit measurement data showed that the method could separate the white noise and nonlinear errors, and greatly improve the accuracy of data reprocessing.

Abstract:This paper analyzes the principle of GPS precise orbit determination evaluation with satellite laser ranging (SLR) data, and provides a new method to calibrate orbit system error. In order to calibrate the system error and recognize the orbit precision difference in three axes, the new method uses observation data from several stations in one pass arc, and makes orbit error projection at different time. A certain amount of SLR data must be maintained for the method proposed. The simulation results indicate that using orbit error projection for more than 3 stations at different time in one pass arc can calibrate linear system error, and the bigger the angle between station and satellite vectors is, the more accurate the estimation of the system error is.

Abstract:A large misalignment error model of strapdown inertial navigation system(SINS) was deduced for the large relative attitude of rapid transfer alignment existing between the master and slave SINS. The Euler angles were introduced to describe the attitude errors. The Euler's kinematics equations were applied to achieve the accuracy error model. The unscented Kalman filter (UKF) was applied to avoid the derivation calculus of the attitude measurement equations which were complex nonlinear functions. The singular value decomposition (SVD) was used to solve the ill-conditioned problem of covariance matrix. The simulation experiment results show that the alignment accuracy is improved both in small angle uncertainties, and large angle uncertainties.

Abstract:Chopped mullite fiber porous skeleton was sintered at 1260℃ by colloidal silica and B₄C powders. Then Porous skeleton was loaded with silica-sols prepared by tetraethyloxylane(TEOS), deionized water and ethanol. Silica-aerogels loading chopped mullite fiber porous skeleton was achieved by supercritical drying. Via thermogravimetry(TG), differential thermal analysis(DTA) and energy dispersive spectrometry(EDS), it was revealed that at 700℃～900℃, B₄C was oxidized into B₂O₃ which bound chopped fibers. Furthermore, chopped mullite fiber porous skeleton was chemically stable below 1500℃. Insulation tiles possessed nanoporous structure since silica-aerogels filled microporous pores of chopped mullite fiber skeleton. Thus thermal conductivity of insulation tiles was reduced by 44.3%, 33.8%, 34.6%, 29.5% at 300℃, 500℃, 800℃ and 1000℃ respectively. Besides, the loading of silica-aerogels improved flexural strength and compressive strength of porous skeleton at 50% and 40%, respectively.

Abstract:Chemo-rheological of AFG-90 epoxy resin modified with new organic-inorganic hybrid nano-materials POSS was studied in this paper. A rheological model based on dual-Arrhenius equation was established and used to simulate chemo-rheological behavior of this resin system. The estimated viscosity of the model was in good agreement with that of the experiment in the initialization reaction stage. The processing window of the resin system can be well determined based on the rheological model.

Abstract:A side window is usually adopted by the kinetic kill vehicle (KKV) operating in higher atmosphere as a basic layout. The engagement result is gravely influenced by the side window orientation which involves many factors. On the basis of some ideal hypothesis, the regularity of the line-of-sight variation rate is investigated, and the effect of the attack angle induced by the orientation is analyzed theoretically. Consequently, the optimal direction of the side window orientation is educed as the aerodynamic force taken into account only. Subsequently, the law to determine the orientation directions at all fighting altitudes are put forward, when the aerodynamic force, the divert and attitude control system are concerned. The numerical simulation result shows that this method can meet the side window detection command and the KKV only needs one orienting action to finish the interception in most circumstances.

Abstract:The fluoropolymer-based reactive material is a kind of sub-stable energetic composites which contain metal powders, fluoropolymer and fillings. It is also a new kind of energetic material widely reported in recent years. In this paper, the PTFE/Al reactive material was prepared by using the cold press and hot sinter method. The physicochemical performance and mechanical property of PTFE/Al were studied, and the pressing and sintering technical parameters were optimized.

Abstract:As one of the most important components participating in the pumping reaction of CW DF/HF chemical laser, the distribution of fluorine-atom has direct influence on pumping and lasing especially for the cold-reaction operation. Because of free-stream recombination and wall-catalytic recombination, some of the fluorine atoms will be recombined with molecules before entering into the reaction region. It's very important to investigate fluorine-atom' distribution for the analysis and optimization of lasers. Some experimental methods have been developed and theoretical model has been established. The model and general computational fluid dynamics (CFD) tool were combined to compute the fluorine atom distribution. Its validity was tested, and cases under different converge contour were numerically studied.

Abstract:Regarding the state space explosion problem in model checking Cache coherence protocol, the concept of pseudo-cutoff, a limit of the nodes which share the same memory block, is put forward in this paper. Based on the analysis of the inherent characteristics of parallel programs, the pseudo-cutoff value in relaxed consistency Cache coherent non-uniform memory access system under certain conditions is deduced. The state space of the directory-based Cache protocol is optimized effectively using pseudo-cutoff, and a new scheme to small probability matter of wide sharing is presented. Experimental results show that, the method of protocol model optimization based on pseudo-cutoff can effectively reduce the state space of Cache protocol, accelerate verification speed and improve the capability of verifying large scale Cache protocol.

Abstract:For the reliability growth tests with delayed-fix mode, the life in a stage can be assumed to follow the exponential distribution with a constant failure rate. However the reliability between stages has a growth. Usually, growth factor was used for the information transfer between stages. Thus the determination of growth factor becomes very important. The limitation of ML-Ⅱmethod commonly used is analyzed and a modified ML-Ⅱmethod is given. Then Bayesian evaluation method of reliability is deduced. At last, the example shows the feasibility of the modified ML-Ⅱmethod.

Abstract:In view of the characteristics of P2P storage, a novel Erasure Code based segmented file P2P storage strategy is designed, and the Chord protocol based P2P storage structure is constructed. The effective file storage, access and update function of the novel strategy overcome the deficiencies of the traditional Erasure Code P2P storage strategy, enabling the stored file to have a certain data revision capability and structure expansion-contraction capability. Theoretical analysis and experimental simulation verify that the novel strategy has reasonable feasibility and effectiveness.

Abstract:The efficient high-speed VLSI implementations of sphere detector providing soft information for a subsequent error correcting decoder are not trivial due to their high computational complexity. Therefore, a VLSI solution for soft-output sphere detector based on depth-first tree search and ONPC architecture is presented. In a 0.13-μm CMOS process, the proposed detector solution can achieve 14 Mbps at a signal-to-noise ration of 17.7dB for 4×4 MIMO system with 64-QAM using only approximately 4.1mm², and realize a better BER performance than K-best algorithm with 256 survivor paths based on depth-first search.

Abstract:Aiming at the problem of implementing optical buffers in the present high performance computer optical interconnection, a bufferless optical interconnection, named BOIN, is put forward. Based on modeling and analyzing the network topology, the relationship between the network throughput and the offered loads as well as network sizes is studied. Then the condition of maximum throughput of the network in a fixed offered loads and total number of nodes is presented. Finally, the simulation results show that the correctness is confirmed.

Abstract:The paper proposes a new classification feature: DI(Diversity Index), considering the characteristics of satellite cloud image. The DI feature presents the structure of cloud effectively and it has a good robustness. The DI feature avoids the influence exerted by the variety of cloud positions. This paper proposes the semi-supervised FCM (SSFCM) method in the domain of satellite cloud images classification. The SSFCM method overcomes the blindness brought by the FCM method without considering the domain knowledge. The SSFCM method uses a small number of samples labeled by experts to direct the clustering process through comparing with the labeled samples in terms of similarity. These labeled samples represent the domain knowledge. The experiments demonstrate that the SSFCM method improves the accuracy of cloud classification based on the DI feature.

Abstract:Z39.50 is widely used for searching and retrieving information spread over a number of heterogeneous sources, but it is hard to construct the mapping relationships between Z39.50 and the data sources, since the semantics of the dynamic and autonomy data sources cannot be exactly derived so as to achieve an exact information retrieval operation. This paper proposes the extend hyper graph data model based on HDM, which can be abstracted into levels, taking two kinds of nodes and edges of EHDM as access points ofZ39.50. It can solve the problems of badly supporting of querying on structured data sources and query failures by constructing the DL layer between EHDM and Z39.50, in which the concepts and derived concepts are mapped onto Z39.50 wrappers. Thus, defining three layers structure as in dataspace systems can realize the data integration strategy named “integrate when needed”.

Abstract:With regard to the attribute values in decision table, which are described with hybrid data, a new algorithm of attribute reduction based on rough set theory is proposed. First, the similarity relations among objects with hybrid data are defined. In order to obtain reasonable soft partitions among objects, the optimization model for threshold accounting is presented. Then, based on the upper and lower approximation concept from rough set theory, the covering upper and lower similar partitions among objects are obtained. In succession, through descriptions of the upper and lower similar distribution matrixes found on condition attributes and decision attribute, the two attribute reduction results of different viewpoints can be retrieved intuitively, based on the max-distribution matrixes. Finally, the experiment results prove that this algorithm is effective and feasible.

Abstract:A subsection calculating numerical simulating method is presented, based on the different dynamic responses of rock under blasting and the different limitations of dynamic finite element algorithms and traditional numerical simulating algorithms of seismic wave. The subsection calculating method divides the simulating region into an elastic region in which dynamic finite element algorithms are applied and an inelastic region in which traditional numerical simulating algorithms are applied while displacement is applied to the boundary conditions between different regions. The numerical simulating results indicate that the subsection calculating method is correct and effective in numerical simulations of seismic wave in rock under blasting.

Abstract:In view of the factors such as the element pattern and the element direction for an arbitrary airborne radar conformal array, the spatial snapshot and the subarraying are studied, and a general clutter model at the element level is introduced on the basis of the fact that the conformal array spatial matched filter, which is different from that of routine planar array, is provided. Finally, clutters and their distribution of several conformal arrays for airborne radar are simulated and analyzed respectively. The Results validates the feasibility of the clutter model.

Abstract:PN code ranging technique based on DSSS is widely used in satellite navigation, radar, and aerospace TT&C. The phase distortion introduced by RF link and cable multi-path will greatly affect the signal time delay of spread spectrum. The traditional definition of group delay is incapable of describing the holistic phase character of signal bandwidth, thus having difficulty in establishing relationship with the spread spectrum signal delay. To resolve these problems, a new group delay definition has been put forward, based on Taylor series expansion, which uses zero order group delay, linear group delay and parabolic group delay to describe phase distortion. The influence of the different order group delay on PN code ranging was analyzed and simulated. The results show that the parabolic group delay has greatest effect on PN code ranging.

Abstract:The vehicle-mounted forward-looking ground penetrating imaging radar (VFGPIR) is a feasible facility to detect shallow buried objects, but it faces a high false alarm rate. The combined detection, by using the sequence features, is proposed as the key to solve this problem. Firstly, we use the Fisher's discriminating ratio (FDR) to quantificationally evaluate the discriminating power of the individual feature component extracted from the single or serial images. Since the optimal individual sequence feature cannot satisfy the needs, a multi-features joint detection method based on the decision-level weighting fusion is presented in this paper. Finally, the receiver operating characteristic (ROC) curve is exploited to demonstrate the validity of the proposed method. Experimental results of the data show that the features extracted from the sequence images have better discriminating power, and the suggested method has a better detection performance than that of the optimal individual sequence feature, feature vector, and majority voting fusion rule. The approach is expected to satisfy the requirements of landmine detection in the practical application.

Abstract:A common issue in pulsed radar is the eclipsing effect for near range target. Firstly, theoretical analysis is presented to show that the radar's minimum operating range is not subject to pulse width, and then by using Chirp pulse as an example, a fast search algorithm suitable for both near and far range target is proposed. Compared with conventional search algorithms, which need multiple search wave form to cover the entire range domain, the presented algorithm needs only one single search mode, and thus reducing search time. Finally, simulation results validate the correctness of the theoretical analysis and effectiveness of the processing algorithm.

Abstract:In tracking maneuvering target, target state and target motion mode must be estimated at the same time, and parameters or structure of filtering function should be modified according to estimation results, so that it can reduce the difference between filtering function and target motion mode, and increase tracking accuracy of maneuvering target. For overcoming the shortcomings of the present suboptimal multiple model algorithms, a new suboptimal multiple model (MTMM) algorithm is introduced, based on multiple target motion mode distribution. Simulation results show the validity of MTMM algorithm.

Abstract:The spherical gear is a new gear-driven mechanism with a double degree of freedom. Based on the mathematical models of spherical gears, the meshing model is obtained and tooth contact analysis is performed, so the location of contact points on teeth surfaces is received by using nonlinear solver. The structural shape of the tooth surface is studied. To the point contact form of meshing spherical gears between a convexity and a saddle surface, contact ellipses of meshing tooth surfaces are studied, and then the movement rule of contact ellipses when spherical gear pairs mesh in any swaying plane that passes through polar axes of spherical gear pairs is gained: Contact ellipses are little on teeth base and teeth tip, so contact stress is large; Contact ellipses are relatively large on teeth mid-position, so contact stress is little. Finite element analysis is applied to perform bending stress analysis and tooth contact stress analysis, and the result validates the correctness of the movement rule of contact ellipses. The study is useful for further investigations in transmission theory and practical applications of spherical gear pairs.

Abstract:It is not easy to find a set of control parameters to stabilize the magnetic suspension system when the suspension clearance, velocity of electromagnet and current are taken as the feedback state variables, and control parameters affect each other. To tackle those problems, the suspension clearance, velocity of electromagnet and magnetic flux are taken as the state variables. It is easy to find the stable control parameters in experiment when this method is taken. Simulation proves the validity of the second control method.

Abstract:The simultaneous complex diagonalization (SCD) of two rectangular quaternionic matrices is introduced, moreover, SCD of a set of rectangular quaternionic matrices is also introduced, and some necessary and sufficient conditions for the existence of the SCD are derived.