Abstract:Liquefaction scheme based on the supersonic lifting-pressure principle of steam injector has good performance on outlet pressure and liquefaction speed. However, the physical proceed of equipment is very complex; many parameters haven't been contained in the theory equations. The paper established the theory equations which consider the heat and mass transfer between the steam and water. The effects made by the coolant water temperature, injection coefficient, convergent ratio, water undercooling and speed difference are analyzed. The results show that the water should be atomized as smaller as possible, the coolant temperature should be lower, and injection coefficient should be 6～8. If design is correct, the lifting-pressure ratio of the convergent-divergent type steam injector can reach three times than the original.

Abstract:Based on the DSMC method, a two-way coupled mechanical and thermal model for high-altitude two-phase rarefied flow is presented with considering of particles' micro flow properties. An approach of DSMC is developed for multiphase flow in the transitional regime of rarefied gas. Simulations are performed for the verified case and the results show that the model agrees closely with the momentum and energy transfer mechanism.

Abstract:Influent factors' sensitivity in the huge parachute's deployment load is discussed in this paper. The dynamic model during parachute inflation is based on the inflation time method, the numerical experimentation is designed by orthogonal experiment approach for analyzing the influence and sensitivity of 21 parameters such as initial conditions, recovery object parameters, pilot parameters, main parachute parameters and environment conditions etc. about 5 indexes such as two parachutes' deployment force peak and the dynamic pressure when the main parachute deployed. Four numerical experiment results obtained from four different initial conditions are compared in this paper, the main factors which influence pilot and main parachute's deployment load are presented, and the influent mode of every factor is concretely analyzed.

Abstract:Orbital net capture is an innovative mission concept, and has special potential on space debris disposal and OOS (on-orbit service). Dynamics of orbital net casting is a key technique of the orbital net capture system design and application, for which two major feasible investigation means have been suggested: dynamic modeling, simulation and ground test. Based on dumped-mass model, a model of the system dynamics was derived, and a ground test device was designed to verify the simulation result. The comparison of several ground tests and simulations shows that the model can be used to design orbital net capture systems. Relevant pictures of ground test and simulation were presented.

Abstract:The thermal aging properties, including the mechanical property, the gel property and interfacial property, were measured to analyze the aging characteristics of nitrate ester plasticized polyether (NEPE) propellant during aging process under 20% constant strain. The results show that the maximum tensile strength is decreased while the elongation at maximal has no obvious change. The performances deterioration of NEPE propellant is the invalidation of the strength. The gel fraction and the work of adhesion are decreased along with the aging time. The main aging mechanism is the degradation of the binder matrix and interfacial dewetting. There is a correlation between the maximum tensile strength and the gel fraction, the adhesion work. The equation is calculated to determine the relationship. The method is established to evaluate the macroscopical mechanical property by microcosmic property. Storage life of propellant under 20% constant strain is 8.3 years, while the value of deterioration of maximum tensile strength changes to 30%, it will reach the invalidation point.

Abstract:Explosive logic network is a key technology to the aimable warhead, and gap null gate is a basic logic element of explosive logic network. It is necessary to realize the function of the gap null gate. A transmitting-explosive based on RDX was developed, and a gap null gate with the transmitting-explosive was validated experimentally. Formulations of the transmitting-explosive and the gap distance suitable for the gate were concluded. The detonation velocity of the selected transmitting-explosive was measured, and a gap null gate in small scale was designed. The gap null gate will proved reference for designing the explosive logic network.

Abstract:The solutions to Lambert problem are mostly based on two-body supposition, which may bring inconvenience to accurately control of orbital transfer. Therefore, an approach to amend the impulses of Lambert transfer is presented. In terms of the perturbation, the precise dynamical model of spacecraft is established. Based on the result of Lambert algorithm, Quasi-Newton iterative method is employed to correct the impulses and reduce the errors of final state in orbital transfer. The approach is then used in the problem of time-fixed accurate impulse transfer. Finally, a two hierarchical programming model is established to solve the problem, which was proved to be right by an example.

Abstract:To analyze the flexibility effect of shearing deformation on cantilever box girder of sandwich composite materials，the equivalent bending stiffness and shear stiffness of the box girder are deduced，the cantilever box girder is equivalent to an isotropy box girder which has the same long-span and stiffness. The flexibility which takes shear deformation into account of sandwich composite materials of cantilever box girder is analyzed by primary beam theory. The effect of shear deformation to the whole flexibility of the box girder is analyzed. The methods and conclusions are available for the designers on box girder of sandwich composite materials.

Abstract:The aid-sliding technology is the one of key technologies for guided weapons to augment the range and enhance maneuver penetration ability. This technology has a high demand on vehicle's attitude control and the compound control system. Aiming at vehicles controlled by the linkage mode with aerodynamic rudders and gas rudders, the integrated dynamic model is set up and the complete linearization small deviation equations on pitching, yawing and roll loops are elaborated in the derivation. Combined with typical trajectory data, figures of dynamic coefficients are presented, and according to these figures, the vehicle's stability in each phase of the boost gliding trajectory is analyzed. On the basis of the above work, the low altitude point 260s in reentry phase is picked as characteristic point and the attitude control system of this point is designed. Simulation results indicate the correctness of linearization small deviation equations and the validity of the control system. This research can provide helpful reference to stability analysis and designing attitude control system for this kind of vehicles.

Abstract:In deep space exploration, normal points FFT cannot exactly fulfill the frequency guide for very weak signals while very large size FFT cannot be computed by COTS. A parallel FFT method based on digital channelization is proposed to fulfill the frequency guide. The input signal is first divided into several narrow bands and FFT is computed in every sub-band. Then frequency estimation is performed by jointly detecting the valid sub-band spectrum lines. In FPGA implementation of the module equivalent to 29 points FFT，the FFT module is reused for resource saving. The test results show that the resolution is less than 10Hz when the sampling rate is 8MHz.

Abstract:Anomaly detection has been one of the most important applications for hyperspectral imagery. A new lossy compression method for hyperspectral imagery oriented anomaly detection is proposed. In order to keep the performance of anomaly detection, the anomalous vectors detected by the improved RX algorithm are preprocessed. Furthermore, virtual dimensionality algorithm is introduced to estimate the Intrinsic Dimensionality (ID) of original data while Karhunen-Loeve transform is used to provide spectral decorrelation. In addition, based on the virtual dimensionality, a new method for the number of principle component determination is presented. The bit rate of each principle component is distributed by optimal rate allocation strategy for spatial compression by SPIHT algorithm. Experimental results show that the proposed algorithm provides better compression performance, as well as efficient preservation for anomalous pixels.

Abstract:Two methods are used to compute the STAP weights in application, named as data domain algorithm and mean square domain algorithm, which are represented by QR decomposition algorithm and sample matrix inversion (SMI) algorithm respectively. In comparison, SMI algorithm can be realized simply with sample covariance matrix inversion, QR decomposition algorithm can be mapped onto systolic array with a high design cost. The inner parallelism of different algorithms of matrix inversion is reviewed firstly, the implementation of SMI method based on single DSP is proposed based on the on-chip parallel technique, the numerical stability of the proposed method is also given, and experiments with the data measured verify the validity of the proposed method.

Abstract:This paper presents a real-time system structure for high precision GPS measurement simulation. Firstly, the principle, function composing and appropriate mathematical models used in measurement simulation were studied. Secondly, according to different time constrains of different models' realization, a distributed simulation system was proposed to simulate GPS measurement. The system was divided into negative real time part, week real time part and strong real time part accordingly. Finally, an investigation experiment was made. The results showed that simulation system could satisfy the strong real time demand, and the simulated measurement reached a good degree of accuracy.

Abstract:Due to the frequency sharing, Electro Magnetic Compatibility between GPR and Mobile Telephone System is crucial. In the current study, the properties of the random RFI signal received by GPR are analyzed in detail, and the differences between the random RFI and target signal are presented in wavelet field. Furthermore, the method of random RFI suppression based on wavelet transform is proposed. Additionally, the two types of data are collected to validate the performance of the method. Finally, the experimental results prove the effectiveness of the method.

Abstract:There are several sub-transmission processes before matching-position parameters are transferred into combination-filter in INS/SAR integrated navigation system. In this paper these processes were studied, and the relations between them were analyzed, including the transmission of position information from ground matching centre to SAR phase centre, the transmission of position information from SAR phase centre to assistant INS centre, and the transmission of position information from assistant INS centre to master INS centre. Based on the analysis, a mathematical model of parameter-transfer was established. Modified inertial navigation parameters based on the model are reasonable, and results of transfer errors are rational, which prove the efficiency and flexibility of the model proposed.

Abstract:Most sensor deployments so far scarcely consider the non-uniform energy consumption in wireless sensor networks. As a result, considerable energy is wasted and energy utilization is low when networks fail. Therefore minimum nodes deployment problem is raised, which is subject to coverage and networking lifetime threshold. Motivated by delivery characteristics in wireless sensor networks, two solutions, nodes decreasing placement and density decreasing deployment, are presented, aiming at high energy utilization and minimum residual energy. Compared with the existing deployments, the two novel schemes deploy less sensor nodes, maintain less energy when nodes fail. Simulations reveal that energy efficiency of two schemes nearly reaches 3～4 times of the existing solutions.

Abstract:Because of the requirement of software reuses determined by adaptability, the component model has become an ideal choice of software architecture in research of pervasive computing. To abstract the characteristics of components precisely in the pervasive computing-oriented environments, as a part of research in a self-adaptive pervasive computing-oriented software platform UbiStar, a component definition language UCDL is presented. The design of UCDL refers to the manner of using IDL3 and CIDL to abstract the characteristics of components in CORBA Component Model. In the end, an example of the application of UCDL is also presented.

Abstract:In order to speed up the face recognition algorithm under the condition of keeping high accuracy, a discriminative feature selection algorithm is proposed to handle multi-class face recognition problems. It is supported by vector machine to select features and employ total probability rule to integrate feature selection and multi-class classification into an integral frame. The experiment on the face databases of UMIST and FERET displays that the proposed algorithm can effectively select the features which have obvious physical meanings, thus speeding up the response of classifier without degrading the generalization performance.

Abstract:MIMO radar obtains spatial diversity by distributed sensors, which are difficult for the estimation by DOA. In this paper, the transmit elements are widely separated with the receiving elements closely spaced. By transmitting orthogonal signals, virtual subarrays are designed through filters, and the Subarrays Selection(SAS) algorithm is proposed. The algorithm obtains spatial diversity as well as robust super-resolution direction-of-arrival estimation. The proposed algorithm is extended in 2-D location of MIMO, then it obtains spatial diversity as well as increased freedoms. Finally the simulated results show that the SAS algorithm is effective.

Abstract:The maintenance of OWL-S ontology syntactic consistency is very important in the evolution of semantic web services. In this paper, the differences between OWL-S and domain ontology are analyzed, and a maintenance framework is proposed to guide engineers to maintain the syntactic consistency of OWL-S. After the elementary changes of OWL-S are defined and abstracted, the change relation matrix is given to define the dependency between them, then, an algorithm to generate potential changes based on relation matrix is shown, and the time complexity of this algorithm is also analyzed. The syntactic consistency rules of OWL-S are divided into two types: mandate rules and optional rules while the descriptions and formal definitions of these rules are also given. In so doing, the agent can check these rules automatically, and help engineers to maintain the syntactic consistency of OWL-S ontology.

Abstract:Data sets of point and interval dimensions are important in spatial database system and GIS. This paper proposes an index structure PI-tree for the data sets of point and interval dimensions, based on an analysis of R^*-tree and SS-tree, of which the former is used to demarcade multidimensional space of data set using hyper-sphere with the aim of improving accessing and reducing the I/O times of inserting data. Furthermore, the algorithm of insertion, deletion and retrieval of PI-tree is also presented. Finally, the analysis and results of experiment show that PI-tree outperforms R^*-tree.

Abstract:In order to extropolate what are involved in materiel requirements, problem frame for materiel requirements is provided and substantive properties which belong to materiel requirements are rigorously analyzed based on key artifacts, which are distilled from the wide variations in the use of terms. Problem frame for materiel requirements focuses on the key artifacts, their attributes, and relationships at a general level. By using higher-order logical notational conventions, formal analyses are made, describing the relations that material requirements and their reflection must satisfy. Adequacy, precondition, feasibility, necessity, and hierarchy of materiel requirements are included. Adequacy, necessity, and guidablity of materiel requirements reflection are also included. Finally, an example about the presumed urban antimissile defense system shows that the approach is highly feasible, effective and promising.

Abstract:In order to achieve high excitation efficiency, a resonance loop for microgyroscope is designed based on phase control technology to generate drive mode resonance. In order to improve the stability of microgyroscope, a PID controller with best ITAE criterion is designed to keep the drive oscillation amplitude invariable. A closed-loop drive circuit is fabricated and tested. The results show that the oscillation frequency of the fabricated drive loop is very close to the drive mode frequency. With the adoption of PID controller, the variance rate of the drive oscillation amplitude is merely 0.1% in the temperature range of -40℃～80℃.

Abstract:To insure the credibility of large-scale complex system simulation, it is very significant to study verification, validation and accreditation in modeling and simulation of the whole life cycle. The VV&A methodology and principle for LCSS are represented by theoretic research. Taking the case of HLS dimulatopm for example, the VV&A process is studied at three levels, the simulation component, federate and federation levels. The research is applied in the anti-ship missile's penetration federation. The practice shows that this research will give good guidance to the VV&A job for LCSS, which will ensure the credibility of simulation.

Abstract:Space force command scheme in joint operation determines the efficiency of the relevant command system, so it is necessary to quantitatively evaluate the command schemes and to optimize them. This paper introduces how to evaluate command scheme by the efficiency of the space force command system in joint operation. Based on command activities the command efficiency index architecture is built, and a blueprint of the simulation system for command scheme evaluation is suggested.

Abstract:Perfect nonlinear functions are widely used in the design and analyses of cryptosystem. Based on the method of algebraic number theory, the properties of preimage distributions of perfect nonlinear functions over finite abelian group are studied. Necessary conditions for the existence of perfect nonlinear functions over finite abelian group are presented, which proves that there are no perfect nonlinear functions for some abelian groups. Finally, the preimage distributions of perfect nonlinear functions over some prime fields are presented.

Abstract:The eigenvalue and the singular value of a quatemion matrix play important roles in the applications of quaternion matrix theory. By virtue of the blocked matrix and the corresponding identities, several inequalities on the eigenvalue and the singular value of quaternion matrices are established, which generalize the corresponding results existing in the real or the complex matrix theory. The results of this paper may help to improve the applications of quaternion algebra in such related fields as quantum mechanics, robot technology and the like.