Abstract:The influence of rarefaction wave on the experimental section in blast shock tube with different isolator lengths was simulated. To simulate the incident wave at the entrance of experimental section exactly and efficiently, a new method which couples 1D and 3D computational programs was adopted, and small scale explosion was utilized to simulate actual overpressure waveforms in 1D computation according to blast similarity rule. The computation results demonstrate the following features: alteration of isolator length L does not affect the peak overpressure; when L is less than or equal to 20m, influence of rarefaction wave will reduce the impact time and impulse of overpressure in experimental section; while L is larger than or equal to 30m, the rarefaction wave doesn't affect these two parameters in experimental section.

Abstract:The point return orbit characteristics for a vehicle from a lunar mission were studied, and how the landing point and reentry point vary was focused upon. Firstly, analysis of some characteristic points was presented, and lunar antipode, reentry point and perigee were included. Then the stabilization property of the latitude and velocity at reentry point was achieved. Furthermore, based on the characteristics of the foregoing three points, approximate method for the theoretical relation of landing point and reentry point was proposed. In addition, relation of lighting condition at landing point and lunar return window was analyzed by using lunar phase law, and the basic conclusions was attained qualitatively. Finally, the orbit simulation was established with double two-body model, which shows the feasibility of this theoretical model in predicting the lunar point return orbit.

Abstract:Based on the detailed DF chemical kinetic models of two different fuel systems, the relevant simplified chemical kinetic mechanisms were presented with the method of sensitivity analysis. It is found that considering the DF “cold reaction” pumping reactions, ignoring DF higher excited vibrational states and omitting the recombination-dissociation reactions have little effect on the total system. The energy transfer reactions in DF and DF deactivations by D, D₂ and HF exhibits strong sensitivity to the chemical kinetics. Compared with the detailed mechanism, the simplified mechanism describes the general DF combustion process effectively, and at the same time reduces the species, element reactions and computational costs to a great extent. Therefore it fits more with coupling with three-dimensional flowfield numerical simulation code or software.

Abstract:Focusing on the shortage of multidisciplinary data management systems of current integrated design environment, a dynamic integration and scheduling strategies of data was built, using a unified multidisciplinary semantic-oriented data management method on the basis of the analysis of characteristics of data in launch vehicle design process. The application in an integrated design environment of a solid rocket vehicle proves that the multidisciplinary semantic-oriented method separates data dealing from processing dealing, and simplifies the data description and access. Consequently, the flexibility, expansibility and versatility of vehicle integration design environment are enhanced.

Abstract:Changeable measurement baseline and diversity of space configuration are advantages of spacecraft formation implementing deep-space exploration mission. They are closely related to the reconfiguration capability of spacecraft formation. Aimed at the issue of optimal control for Halo orbits formation reconfiguration, this study firstly analyzed the configuration characteristics of Halo orbits formation, then the Hamiltonian equation of optimal control for Halo orbits formation reconfiguration were deduced. Iterative method for solving the Hamiltonian equation was built based on the first generating function. Simulation of optimal control for Halo orbits formation reconfiguration in the Earth-Moon system was carried out, and the validity of this iterative method was verified. Simulation results show that sun perturbation has huge influence on the fuel consumption of optimal control during the process of Halo orbits formation reconfiguration, and the fuel consumption can be reduced by selecting the reconfiguration times correctly.

Abstract:The counterflow diffusion combustion of diluted ethanol in various containments was numerically analyzed in the purpose of getting a deep understanding of chemdynamics in a gas generator with low ethanol concentration. A virtual specie with the same thermodynamic and transport property as water but chemically inert was used to distinguish the interference between physical and chemical mechanism. Results reveal that as the concentration of ethanol decrease, the flame front, along with the disappearance of the second exothermic reaction region, tends towards the fuel side as a whole. The H₂O will exert an inhibitory effect when the concentration of ethanol is reduced to the ultimate low value.

Abstract:In order to carry out ignition experiment on combustion-driven mixing gasdynamic CO₂ laser based on N₂O/C₇H₈, a liquid N₂O supply system and a N₂O/C₇H₈ mono-injector gas generator were designed. The liquid N₂O supply system, ignition and combustion performances of N₂O/C₇H₈ were studied. Experimental results indicate that N₂O can be supplied in liquid state by the designed liquid N₂O supply system; ignition can be realized under two operating modes(excess oxidizer coefficient is 0.3 or 0.4) in designed time sequence and the combustor pressure is smooth. In addition, with the increase of excess oxidizer coefficient, combustion efficiency improves obviously.

Abstract:The numerical study of hypersonic inlet flow with different inner compression surface was carried out, aimed at exploring the influence of horizontal angle of lower inlet surface on inlet performance specially restarting characteristics. The result shows that the reduction of surface horizontal angle on the tail of separation bubble will improve the performance of unstart flow and decrease the restart Mach number, with the disadvantage of increasing length of inner compression surface and reducing the performance of start flow. To optimize the synthetic performance of inlet, a new design of inner compression lower surface composed of the concave surface in the front and the straight surface with small horizontal angle in the rear was proposed. Compared with the prototype, the performance of start flow drop lightly under the same length for new inlet, but the restart Mach number of latter reduce from 9.4 to 8.

Abstract:A finite element model for supercavitating underwater vehicles was developed and the dynamic stability of supercavitating double shells was investigated to obtain the instability maps for varying vehicle's velocity considering the time-dependent properties of the longitudinal loads. The computational results indicate that with the increment of the thickness of the annular plates linking between inner and outer shells or the number and dimension of the circumferential stiffeners, the frequencies corresponding to dynamic instability decline and the extension of the regions of dynamic instability is reduced lightly, while the frequencies corresponding to dynamic instability ascend and the dynamic stability is enhanced remarkably with the space between inner and outer shells decreased or the number and dimension of the longitudinal stiffeners increased.

Abstract:The free-fight trajectory estimation by a single LEO satellite plays a key role in the space-based early warning system. An actual measurement function was established, and a polynomial approximation algorithm was proposed to reduce the computational amount of the batch algorithm of maximum-likelihood estimation (MLE). The approximate polynomial of the measurement function was evaluated at some deterministic instants to form pseudo measurement data. The raw measurement data were replaced by the pseudo ones to estimate the trajectory. The simulation results show that this new algorithm greatly reduces the computational amount, and can achieve the same accuracy performance as MLE.

Abstract:Effects of edge-sealing on water absorption of glass fiber reinforced epoxy resin composites (GF/E-51) were investigated by weight measurement and volume measurement of composites specimen. The experimental results show that the diffusivity coefficient of edge absorption is far more than that of the surface absorption and the maximum moisture content of the unsealed specimen increases by 73.8%. Meanwhile, the volume dilatation of the unsealed specimen increases by 200.1%, which indicates that the mechanism of water absorption of GF/E-51 can be classified into two types: open-porous absorption and close-porous absorption. Water behaves as a vapor-phase in the porous close composite, but as a liquid-phase in porous open absorption.

Abstract:Tensile, flexural and water resistance properties of four kinds of epoxy resin systems, i.e. CYD-128/THPA/DMP-30 (CTD), TDE-85/THPA/DMP-30 (TTD), CYD-128/IPDA (CI) and TDE-85/IPDA (TI) were investigated. The influences of the epoxy resin types, curing agent types and molecular structures on the properties of the epoxy matrixes were discussed. The results show that, cured with a same curing agent, TDE-85epoxy resin (with ester groups) system exhibits higher flexural strength and Young's modulus than CYD-128 (without ester groups) system. The brittleness order of the four epoxy matrixes is TI>TTD≈CTD>CI. As CTD and CI have less content of polarity groups, such as ester and amine, seawater absorption of CTD and CI is smaller than that of TTD and TI. After seawater immersion, part of the ester groups hydrolyzes and the matrix becomes more brittle. As a result, the tensile and flexural strength of the matrixes are decreased significantly. CTD system recovers about 92% of the original tensile strength after drying processing.

Abstract:A new algorithm for direction of arrival (DOA) of coherent signals using joint diagonalization was proposed. A set of higher-order cumulant matrices were first devised, the generalized array manifold matrix was then estimated using the technology of joint diagonalization. Finally, permutation uncertainty inherent in the estimation of the generalized array manifold matrix was eliminated and DOAs were estimated, based on the matrix structure of the array manifold matrix and properties of minimum polynomial of matrix. The proposed algorithm does not need angle searching, and can be applied to the cases when some DOAs in different coherent group are the same. The effectiveness of the proposed algorithm is verified by computer simulation results.

Abstract:Facing the varying demand for digital signal processing applications, the existing solution including general-purpose processor, DSP, ASIC and FPGA can not meet the requirements of cost, power consumption, performance and flexibility. To solve these problems, this study combined the technologies of stream processing, and reconfigurable platform, and proposed A Multi-Granularity Reconfigurable DSP based on Stream Architecture Template (MGR-SAT). MGR-SAT uses stream processing techniques to decouple the data on operations and memory access, offering a large-scale data parallel. Meanwhile it uses the reconfigurable technology to accelerate the key algorithms and uses the platform technology to provide fast reconfiguration as well. The experimental results show that MGR-SAT has a great potential to deliver high performance.

Abstract:Neighboring sensors can collaborate with each other to form a virtual sensor based on cooperative sensing and data fusion, which may increase the length of information barrier. A distributed algorithm DVSF for virtual sensor formation based on non-cooperative games was devised. In order to increase the total length of information barrier of the networks, the DVSF chooses appropriate neighboring sensors to form virtual sensors, and it improves the performance of barrier information coverage of the networks. Simulations of the approach demonstrate the effectiveness and the convergence of DVSF.

Abstract:Usually the intermediate results can hardly be obtained in the simulation process from the business architecture (ARC) simulator since its source is non-open. A method based on key data region monitoring was proposed to distill the value in the key region of ARC simulator automatically when it is running. In this way, the results from ARC simulator and RTL simulator can be cross-checked to help the verification engineer debugging the RTL codes quickly and efficiently. Compared with the traditional method, it can speed up the error checking by one order of magnitude according to the experiment and real chip design.

Abstract:Featured characteristic of inertial navigation system (INS) information, as short-term accuracy, ultra stability and self determination, cannot be disturbed by electromagnetic interference. In light of these traits, a novel information processing approach aided by INS position and velocity information for anti-jamming application was proposed,. Based on missile-to-target relative motion model，during the terminal guidance tracking phase of anti-ship missile (ASM), target position and velocity information could be obtained by extended Kalman filtering to suppress seeker random measurement errors. When the jamming was detected, one can combine target position forecast with INS navigation solution to accomplish the homing guidance of ASM, which could help achieve one's purpose of anti-jamming. Simulation was carried out in the presence of a maneuvering ship target, and it shows that this method is effective and feasible because of its preferable anti-jamming performance.

Abstract:When the multiple-access interference (MAI) in DS-CDMA system is very strong, the performance of adaptive blind multiuser detection in the system will degrade significantly. The normal way of solving this problem is increasing the length of spreading code. However, the improvement is limited. This study proposed a novel blind multiuser detection scheme with Kronecker spreading code, which is generated by the kronecker product of normal spreading code. Theoretical analysis and simulation show that the Kronecker spreading code has much more capability of resisting MAI than the normal spreading code, which has the same length of the Kronecker spreading code. Therefore, the Kronecker spreading code performs much better in the adaptive blind multiuser detection.

Abstract:Analytical algorithm for inter-satellite visibility is essential for quantitative analysis of constellation visibility characteristic, which is important for the design of inter-satellite link (ISL) assignment scheme and the design of satellite network topology of autonomous navigation system. Analytical algorithm of inter-satellite visibility is necessary for a satellite to assign ISL autonomously with others. Based on the restriction of scanning range of satellite annular antenna, this study introduced the rules to decide satellites' visibility. According to the Walker constellation's spatial structure and satellite's motion law, it introduced an analytical algorithm of satellite's visibility with satellites in the same obit and different obit. Using the algorithm above to analyze satellites' visibility in Galileo constellation, the simulation results show that in the same and different obit plane each satellite has four visual satellites under the elevation restriction of ［25°, 65°］. The algorithm is also available for the analysis of other circular-like constellation.

Abstract:For the drawbacks existent in single-thread fetch pipeline to improve the efficiency, a high-performance fetch pipeline structure is proposed in this paper based on the platform of the VLIW digital signal processor (DSP). It can support the detection and void for the invalid fetch, bypass for the missing fetch, which reduces the unnecessary cache access and fetch pipeline stall. The structure also inducts dedicated hardware which supports the software pipeline of scheduled compilation to improve the parallelism of instruction. It reduces the code memory space, and the idle cycles of released single-threaded pipeline is reached up to about 46.34%. Compared with the fetch pipeline before optimized, experiment results show that the code storage space is reduced about 11.93%, the average execution cycle is shortened about 8.67%, the cache access times is decreased about 12.84%, the suspension period of instruction cache is shortened about 7.86%, and the single-threaded instruction throughput of processor is increased by 11.7%.

Abstract:In the navigation war, the prevention of timing service to adversaries in local area can be realized by turning off all the navigation signals of visible satellites artificially. This study takes turning off the navigation signal for preventing the timing service in local area as an example, describing the simulation process of prevention of timing service by turning off the navigation signal in local area, and puts forward the evaluation method of positioning and timing performance as well. The effect of preventing timing service on the performance of global positioning and timing service is analyzed subsequently. The results imply that, with the prevention of timing service in local area by partially turning off the navigation signal, both positioning and timing service are limited to the civilian users around the site, and the accuracy of positioning will become worse in the global area. Moreover, the availabilities of positioning and timing will be decreased in global area under the circumstance of partially turning off the navigation signal for preventing the timing service in local area.

Abstract:It is confirmed by theoretical analysis and simulation results that, whether the Rayleigh fading channel is perfectly estimated or not, the Max-Log-MAP algorithm is independent of the channel signal-to-noise ratio (SNR).In addition, the Max-Log-MAP algorithm does not depend on any other channel parameter. By scaling the soft output, the Max-Log-MAP decoder performs nearly as well as the Log-MAP decoder, while this gain is achieved without any complexity increase. As no channel parameter estimator is needed, from a practical point of view, decoding turbo codes on the Rayleigh fading channels with the Scaled Max-Log-MAP algorithm is a good compromise among the performance, the complexity and the system robustness.

Abstract:In CPOF, two-handed interaction which can increase the communication bandwidth applies commanders' common skills to the interaction with computers for releasing their cognitive burden and improving command efficiency. The research proposed studied key technology of infrared multi-touch recognition and position, analyzed the method of two-handed-touch-based interaction and its state model, and discussed the model of two-hand interaction process. Finally, a touch-based two-handed command and discussion system was designed, and the result proved the validity of the interaction methods.

Abstract:In order to get the error-correcting coding information of the unknown lines in digital communication, a fast blind recognition method of Reed-Solomon(RS) coding is presented. RS coding length, the order of the primitive polynomial and the possible primitive polynomials were detected by seeking the roots of binary form of RS codes. The true primitive polynomial and generator polynomial of the unknown line were gained by the position and number of the connective zeros in the Galois Fields Fourier Transform (GFFT) of RS codes using the possible primitive polynomials. The results of experiments and performance analysis show that this method can blind recognize the RS coding of the great mass of unknown lines, and can obviously reduce the number of primitive polynomials searched in the recognition compared with the existing algorithms.

Abstract:For the application to the ground target matching system of the aircraft, an INS-aided (Inertial Navigation System) template correction method is proposed. Firstly, the perspective projection model of the ground target was established according to the position of target and the pose (position and attitude) of camera. Then, the correction equations between the templates were deduced according to their pose parameters. By analyzing the relationship of the depth of field between each point and the centric of the target, the correction equations were transformed to an easier solved form and a complete correction algorithm was proposed. In the experiment, a virtual target simulation platform was employed to get the real scenes corresponding to the INS information. In comparing the corrected template with the real-time scene, it is found that they are apparently consistent in scale, rotation, perspective, etc. Tracking with the corrected template can avoid the template drift, and improve the performances significantly.

Abstract:The design of fault tolerant motor was studied in order to minimize the volume and weight of direct drive electromechanical actuator, and to improve the fault tolerant and reliability. The design requirements of fault tolerant motor were analyzed, and a three-phase twenty-four-slot twenty-pole surface permanent magnet synchronous motor was designed to meet the requirements. The parameters of the motor were optimized. The finite element model of the motor was established to simulate a single phase short circuit or open circuit fault. The simulation results show that the motor has a perfect property in the magnetic isolation and fault tolerant, and can meet the fault tolerant requirements of direct drive electromechanical actuator.

Abstract:Collaborative Design has currently become one of key technologies to solve complex product design problems. Based on new problems of existing collaborative design, the study puts forward a method of building VPDM, and uses an exchanging method of feature-adding data to resolve problems of heterogeneous PDM and CAD systems among enterprises. Firstly, a definition of VPDM was presented, and the basic principle of VPDM-based collaborative design was introduced. Secondly, the framework of VPDM-based collaborative design was proposed and each components of VPDM were analyzed. Then, the operation model and the unified feature model represented by Express-G were built and mapped into database. Finally, the feature-adding collaborative design sequence diagram was described in VPDM environment. By using the above method, the prototype system developed in the study enables the collaborative design in two kinds of CAD and PDM software in principle.

Abstract:The metallized film capacitor is one of the most important components of the inertial confinement fusion (ICF) facility. The effective residual life forecasting of capacitors affects the reliability of the whole facility. In order to forecast the residual life of a single capacitor effectively, a method which fuses prior degradation information and its own degradation data was presented. Firstly, the capacitor's degradation process was modeled with Wiener process, whose parameter's prior distribution was established on the basis of prior degradation information. Then the real-time residual life forecasting of the capacitor was proposed by Bayes method. Finally, the significance and practical value of this research was verified by an example.

Abstract:To improve the accuracy of inertial navigation system (INS) during long time operation, the rotation modulation technology (RMT) was employed to modulate the errors of the inertial sensors into periodically varied signals in navigation frame, and, as a result, to suppress the divergence of INS errors. Firstly, the principle of single-axis RMT was expounded based on the measurement error model of inertial measurement unit (IMU). Then, the effects of vehicle angle motion upon RMT were analyzed theoretically. Error equation of equivalent gyroscopic bias in navigation frame was derived. Finally, the simulation and wobble tests were performed. The results show that the average effect of the RMT is negated by vehicle level angle motion; the more the angle amplitude and speed, the more inefficient of RMT, thus, the performance of INS is in low. It can serve as the reference for INS performance analysis and inertial sensors selection of single-rotating INS.

Abstract:Traditional service description model cannot completely and normally describe military information services' non-functional restrictions, such as service using right, service using scope and so on. Aimed at this problem, a behavior restriction based description method that extends the common web service description model was proposed to support the description of the functionality, behavior restrictions and QoS attributes of military information services. By adopting level based matching idea, a behavior restriction based filter method was provided. The method imported similar degree and matching arithmetic to compute the similarity of restrictions quantificationally to improve the precision and efficiency of service discovery. Case analysis and simulation results testify the feasibility and effectiveness of the method.

Abstract:Responding to the serious challenge of unconventional emergencies under the new situation is the urgent problem of governments. Integrating Artificial Societies-Computational Experiments-Parallel Execution, ACP is an effective method to solve the unconventional emergency management. Firstly, the ACP method was introduced, which was used as the dynamic simulation engine for constructing high performance society computing experiments. Then, the architecture of the dynamic simulation engine D-PARSE was designed following the concept of hierarchy and modularity. The specific function of each component was described in detail. D-PARSE was implemented based on the (sik parellel simulation engine. Finally, the influence of different event-send-strategy on simulation system performance was tested.

Abstract:In order to cope with the interdependence and interrelationship between evaluation criteria in conventional power index model, and to eliminate the subjectivity of expert's preference in the evaluation process, this study proposes a framework to create a novel Analytic Network Process (ANP) power index model for operational capability evaluation of submarine equipments based on simulation experiment. Then, by taking an anti-ship operations scenario of submarine as example, the method to design and optimize of networked evaluation index system, the approach to construct ANP Supermatrix based on expert's knowledge and simulation, and the approach to construct power index model based on criteria weights, were presented in detail. Through comparing and analyzing the results of ANP power index model and the results of AHP power index model for operational capability of submarine anti-ship, the feasibility and effectiveness of proposed framework was verified.