Abstract:AUSM⁺-up scheme is one of the most important schemes of ASUM-family. By introducing pressure dissipative mechanism into the convective fluxes and velocity diffusion into pressure fluxes, the convergence and robustness are remarkably improved in all Mach number regimes. However, based on an analysis of the scheme, it is found that a nonphysical phenomenon of infinite mass flux emerges when the Mach number is zero. For conquering the imperfection, the analytic solution of pressure discontinuity is obtained by the characteristic method. According to the results, the item of pressure dissipation is modified, and a new AUSM⁺-up scheme is developed. Using the new scheme, the strong discontinuity problems of shock wave, pressure discontinuity and shock wave diffraction are simulated. The Calculation results fit the theory results well.

Abstract:The Central-WENO hybrid schemes (CWENO6 schemes) are developed based on the theory analysis. While the CWENO6 schemes were used in the finite volume method, the 3 order MUSCL deconvolution method was used instead of the origin 5 order WENO deconvolution method to reduce the deconvolution computation cost. According to the numerical test, it is found that the CWENO6 schemes have more powerful ability to represent the details of the flow filed because of its low numerical dissipation comparing to the WENO5 schemes under the same computation mesh. Finally, it is concluded that the CWENO6 schemes are an efficient method for the simulation of multi-dimension complex flow using finite volume method.

Abstract:Based on the diffusion equation of prorous-thermoelastic waves presented by the authors, the problem of reflection of plane p-wave on a free interface was investigated and the expressions of the reflection coefficient were derived. Then, the effect of thermal expansion coefficient of the porothermoelasticity on the propagation speed of p₁ in the medium was discussed firstly. Furthermore, through the analysis of the effect frequency, incidence angle on the amplitude characteristics of reflection wave, the drainage and no drainage conditions were considered, , and the effect of interfacial pervious and impervious conditions was also discussed. It is shown that the thermal physical parameters have a certain effect on the propagation of thermoelastic waves, and such parameters as frequency, incidence angle and surface drainage conditions are factors greatly affecting the reflection amplitude of two types of compression wave, shear wave and thermal wave.

Abstract:In order to study the influence of aerodynamic characteristics on the twist fin vehicle, twist rate and average attack angle was introduced to represent geometric features of tail. By solving the N-S equations in standing state in rotating frame, a numerical simulation of the aerodynamic characteristics of cruciform layout twist fin vehicle was made . The results show that the twist fin can increase the rolling moment and balancing speed of aircraft and the balancing speed is proportional to the twist rate. When the twist rate increases, the twist fin’s initial resistance coefficient increases. When the balancing speed is reached, the resistance coefficient will decrease. In the critical twist rate, increased with the twist rate, the wing surface pressure distribution will be improved effectively at the balancing speed. The research results have reference value for the aerodynamic configuration design stability design of vehicle.

Abstract:A new multiscale method of primary atomization is proposed. The liquid blobs larger than the grid volumes were captured by the volume of fluid algorithm, the droplets comparable with the grid volumes or smaller were simplified to particles and tracked by a Lagrangian particle tracking model on a virtual mesh. Large eddy simulation with one equation sub-grid scale turbulent energy transport model was used to describe the turbulent flow. A new developed code was validated by several cases, and some key parameters were investigated to improve the precision. The primary atomization of a single jet was calculated, and the results of instantaneous and average characteristics are in good agreement with the experimental results.

Abstract:Tone mapping is an efficient image matching algorithm adaptive to brightness and contrast variation. Due to the complex and nonconforming relation between multi-sensor images, tone mapping can hardly be directly used on multi-sensor images to achieve satisfactory results. To improve the matching rate, the local tone mapping algorithm is proposed, which includes the following steps: Firstly, the template map is divided into nonoverlapping blocks., Then, each block is processed through histogram equalization and weak slice transform. Next, the distance maps are calculated for every block by local tone mapping. Finally, the matching result is obtained by fusion all these distance maps. Experimental results show that, the matching rate of local tone mapping significantly outperforms tone mapping and mutual information, while its computation time is slightly longer than that of the tone mapping and less than that of the mutual information.

Abstract:In photorefractive two-wave mixing system with incoherent background beam, many parameters in system will affect the efficiency of mixing. To solve the optimal designing of parameters, a new method based on stochastic resonance (SR) was put forward. Firstly, by analyzing the two-wave mixing process through physical and numerical way, the stochastic resonance essence was discovered in the two-wave mixing. Secondly, a new method for optimal matching parameters designing was suggested from the aspect of SR. In this new method, for the given gain requirement, the length of crystal was decided according to the saturation of signal firstly, and then the ratio of incoherent light was decided by its affection to gain. Numerical results showed that both the SNR and the gain are improved after the optimal designing of parameters.

Abstract:A saliency based heavy fixed pattern noise suppression algorithm for IR image which is captured by infrared focal-plane-array sensors in remote observation is proposed. The properties of the typical IR images characterized with small targets and heavy fixed pattern noise were analyzed, and it was found that the target regions are more salient than the background for observer in IR image. Using the saliency detection algorithm to detect target regions, the proposed algorithm processes different regions separately and suppresses the heavy fixed pattern noise effectively. Experiments indicate that our algorithm can detect the target regions accurately and suppress the heavy fixed pattern noise effectively.

Abstract:The temperature variation characteristic of the input axis misalignment angle of fiber optic gyro has become one of the key problems of orthogonal calibration of the fiber optic gyro inertia system. Firstly, a kind of measurement method, which can eliminate the measurement errors effectively, was presented. Then, the input axis misalignment angles of three fiber optic gyros with elliptical-structure optical fiber rings were measured. It is found that the three samples have similar input axis misalignment angles; the input axis misalignment angles vary non-monotonously with the changing of temperature; and the varying velocity is fast relatively in high temperature region. The results may be useful for improving the manufacturing technology of the fiber ring of the fiber optic gyro and will be helpful to prompt the temperature compensation technology of the orthogonal calibration in fiber optic gyro inertia system.

Abstract:Aiming at solving the low detection probability problem of space-based AIS, the received signal collision phenomenon and ship detection probability model were studied. The difference between Space-based AIS and traditional terrestrial AIS was compared and analyzed. And the new technical challenge of space-based AIS was pointed out. The problem of AIS signals collision from multi SOTDMA cells was studied in detail. The detection probability model based on ship density function was established theoretically. The effects of slot collision, orbit height, antenna swath and Class B ships on detection probability were estimated quantitatively by simulations, which can provide theoretical reference for designing and evaluating the space based AIS in the future.

Abstract:Aiming at the effects of space objects visibility constraints including the Earth masking, the Earth shadow, the sunlight, the Moon light and the relative angle velocity between space object and platform, the sun-synchronous twilight circularity orbit was selected and the improved multi-mutation adaptive genetic algorithm was adopt to solve the single platform orbit inclination angle optimization based on Two-line Elements (TLE) of catalog objects. Simulation results show that the improved multi-mutation adaptive genetic algorithm can effectively solve the optimum individual while the multi-mutation adaptive genetic algorithm may not. In addition, it is found that the calculation capacity can be improved with a magnitude in equivalent performance using about 10% random selected objects.

Abstract:Satellite orbit measurement based on ground station, such as USB and VLBI, is restricted in its observation arcs. In addition, the long distance of deep space explorer mission forms a new challenge to current satellite TT&C system. If the satellite can estimate its position by its own CCD camera, the time and distance constraints will be eliminated. With a view of this, a vision-based position estimation method for satellite was proposed. It registered satellite image with a reference image and then estimated the satellite’s position according to photogrammetry. An experiment using the image, orbit data of space mission was conducted. By mutually verifying the vision method and the traditional method, it illustrates the effectiveness and accuracy. Our vision-based position estimation method is a good complement to the traditional method; it can save work of ground observation stations and have a promising application prospect in deep space exploration.

Abstract:Quality factor is a key parameter determining the performance of the micro-machined gyroscope. The conventional measurement, the half-power bandwidth method, is low in efficiency, since it requires the user to store and deal with a multitude of amplitude-frequency response data. Based on the analyses on the dynamics model, the quality factor can be calculated according to the resonance frequency and first derivation of the phase-frequency function at the resonance frequency point, and the phase-frequency graph is approximately linear near the resonance point. Upon these characteristics, an online and quick quality factor measurement method was put forward. First, the gyroscope was excited near the resonance point to obtain the phase-frequency data. Then, the slope of the phase frequency was estimated by using the recursive least squares method. Finally, the quality factor was obtained according to the slope and the resonant frequency. The simulation and experimental results verify the correctness and feasibility of the proposed method.

Abstract:Considering the performance of Global Positioning System (GPS)/Dead Reckoning (DR) integrated system degrading dramatically when GPS signal is outage or blocked, a Compressed Extend Kalman Filter (CEKF) based Simultaneous Localization and Mapping (SLAM) aided GPS/ DR integrated navigation method was addressed. The error of DR system was restrained with SLAM correction when the GPS solutions were unavailable. Accordingly, the GPS location corrected the error and improves the uncertainty of SLAM mapping when GPS positioning was accessible. A filter of CEKF based SLAM/GPS integrated was designed to realize the real time implement of SLAM/GPS in a large scale environment. Compared with the SLAM locating using the real experiment dataset, the SLAM aided GPS/DR integrated method enhanced the system performance of positioning as well as the accuracy of SLAM mapping raised approximate 10m.

Abstract:Aiming at solving the problem of target information break in the process of handing over the guidance of Mid-Long range air-to-air missile between the same kinds of aircrafts in cooperative air combat, a method of “virtual target” was proposed: the virtual target approached the real target gradually, when the aspect angle of missile-virtual target and the missile-real target matched, and the process of handing over the guidance was over. Three different modes of approaching movement was proposed, and the affection on the over loading of air-to-air missile was analyzed through simulation of the situation of the target in the process of maneuvering and not maneuvering. The simulation results showed that handing over the guidance appropriately and moderately can transform the break information which is unmanageable into the break information which is manageable, and can avoid the information breaking into improper value if the guidance is handed over roughly.

Abstract:The maneuver strategy solving method for fighter avoiding the attack from missile in the endgame is developed by using the theory of nonlinear model predictive control. According to the situation of the engagement of missile and fighter, the motion differential equation was established. The guidance law was introduced into the missile kinematic model, and the system predictive model was set up together with the fighter’s model. Then, the kinematic constraint of the fighter and missile was analyzed. The performance indices of the fighter avoiding missile attack were proposed based on the analysis of the structure limitation and tactical characteristics of missile and the optimal control model was built. The Gauss Pseudospectral Method was used to solve the model, and the close-loop solution is realistic by using the RHC strategy. The Maximum Likelihood Estimation method was used to estimate the aerodynamic parameter and navigation ratio aiming at the problem of the uncertain and measurement noise, and the feedback correction of the system predictive model is realistic. The numerical simulation result shows that the maneuvering strategy can help the fighter avoid the missile attack.

Abstract:A novel interplanetary DTN routing protocol (IDRP) is designed to provide a general networking solution over interplanetary network scenarios. IDRP enables DTN nodes to estimate the recovery time to its neighbor nodes using the historical connection information. When two DTN nodes in the same region contact each other, they exchange their estimations to decide whether to use each other as a relay. For storage resource is constraint in deep space nodes, IDRP also takes storage consumption into consideration. Simulations based on NS2 were conducted in a Mars-to- Earth scenario. A modified epidemic routing strategy and an only-gateway-selected routing strategy are used as contrast. The simulation results show that IDRP achieves 14% higher delivery ratio and 50% less average transmission delay than the other two strategies, as well as better storage utilization.

Abstract:The non-localizable WSN in the initial deployment is focused upon, and a fine-grained distributed localization-oriented adjustment approach, named as LODA, is proposed. LODA decides the strategy of the node based on the path information to achieve the network localizability in an initially non-localizable network. Compared with the current network adjustment approaches, the approach proposed merely adjusts less than 11% nodes in a sparse network to achieve localizability, which is about 40% better than the current best approach. Besides, the algorithm in a distributed manner is designed to balance the communication load caused by the adjustment. Therefore, the scalability limitation in the previous centralized approaches is overcome. Extensive simulation results show that our approach outperforms the previous method in adjustment efficiency.

Abstract:Software systems situated in open environment like the Internet are increasingly characterized as socio technical systems that evolve dynamically various variations and changing requirements. To construct such complex software system has become an open issue in the literature of software engineering. This research takes socio technical systems as multiple agent organizations and presents an organization-based program model ORAP that introduces organization metaphors like organization, agent, role and position to construct complex socio technical systems. A series of programming mechanisms like role binding and composition, role-based interaction and self-management of organization were designed to tackle the dynamics issues of socio technical systems by categorizing the organization dynamics at different organization levels. Furthermore, an organization-based programming language called OragentL for implementing social technical systems were proposed, which involves its syntax formal definition at organization, role and composition levels respectively. The OragentL’s compiler and running environment called OragentBurg were introduced and a sample was studied to illustrate our approach and show its effectiveness. 

Abstract:Researches on constructing English sentiment lexicon is relatively mature, and there are abundant and reliable lexical resources. Whereas for Chinese studies, the research history is short, and there are only a few Chinese sentiment lexicon resources. With reliable English sentiment lexicon as reference, an automatic constructing approach was proposed, based on semantic relationships. Firstly the Chinese sememe and words were extracted from the defination of concepts in HowNet and the semantic analysis was carried out upon them; secondly the sentimental value of each sememe and word was retrieved from the English sentiment lexicon SentiWordNet according to the DEF attributes of concepts in HowNet, and the final sentimental value of each word was calculated on the semantic relations of the sememe and words. The ready English lexicon was used without manual labeling in the method, and diverse information of words was recorded in the final lexicon, including semantic relations and sentimental values, which remedy the lack of other lexicons. The experimental results show that the resulted sentiment lexicon can achieve better performance in the recall and F value measurements under the condition of approaching other lexicons on the precision measurements.

Abstract:The evaluation of the fitness is computationally very expensive for some optimization problems; therefore a genetic algorithm named FAGA with fitness approximate mechanisms is introduced. In order to effectively control the accuracy and frequency of the fitness approximation, a fitness approximate model based on the concept of fidelity was established. The fitness of a particular individual in the population was obtained as weighted averages of other individuals within a certain area, the size of the area was limited by the fitness sharing radius, the weights of different individuals were determined by the non-dimensional Euclidean distances between individuals and the particular one, and whether to use the real fitness functions or not was decided by the fidelity thresholds. Besides, mechanisms of the loss of fidelity was adopted to reduce the approximate errors from spread and accumulation, and mechanisms of removing redundancy individuals in order to reduce the computing consumption was used at the same time. Three benchmark functions were used to test the convergence and effectiveness of FAGA. The test results show that FAGA achieves satisfactory the optimal solution among the three test functions, and more than 60% of the computation can be reduced at the same time.

Abstract:In order to solve the problems of unified identity management in large organizations’ information systems, a new identity management alliance for large organizations is proposed. Through consulting the Liberty Framework raised by the Liberty Alliance Organization, as well as reforming its structure and its pattern of building trust relationships among IDPs, the new identity management alliance is more suitable than the Liberty Framework for large organizations, which are distributed, autonomous, globally unified, and coordinated. In terms of physical structure, the new identity management alliance can be regarded as a tree consisting of multiple IDP nodes while each node must and can only develop trust relationships with its father node and child nodes. This is totally in line with the tree-like hierarchy of every large organization in the real world. In the system realization, based on the tree-like structure of the new identity management alliance, a hierarchical storage of the authentication data is achieved by adopting LDAP. In addition, the user access control was conducted by a security authentication gateway at the network layer, which consequently makes it possible to support B/S and C/S application systems at the same time.

Abstract:The model of urban cabs moving is one of the key issues for model building. The model needs reflecting moving state information of cabs. More importantly, users can quickly query the moving cabs. Under the condition of real time information of cabs which is hard to obtain, we should model the moving points and forecast the state information according to the moving history. A method which applies Hidden Markov theory to model of the moving trajectory is proposed. Through an analysis of real trajectory data of San Francisco, the caps moving model which is used to query the caps by users was constructed. Experiment with real datasets shows that the method proposed can simulate the moving state of caps. Users can also quickly obtain the useful location information from the model. 

Abstract:The phase signature of active decoy and its application in angular deception Jamming using Interrupted-Sampling Repeater Jamming(ISRJ) were investigated in detail. After the principles of ISRJ were expounded, the phase signature of different-order active decoy and the influential factors were analyzed. According to the principle of monopulse radar angle tracking, several conditions that should be met for jamming source were deduced, including the repeater power, the delay time and frequency of repeater. Then, the effects of correlative and non-correlative interference on angular deception were discussed, respectively. Simulation results show that the decoy can bait monopulse radar system by flexible parameter design. This research is beneficial to the jamming design and use of ISRJ．

Abstract:A cascade channel estimation of Amplify-and-Forward (AF) two-way relay networks (TWRN) was investigated, and a new estimator was proposed based on Kalman filter. Firstly, a cascade channel of AF TWRN was divided into self-interference part and transmission part functionally. Then, auto-correlation functions of these two parts (ACF) were approximated by auto-regressive (AR) model to obtain the Gauss-Markov process of the channel, and the resultant Kalman estimator was deduced according on the received training signals. After the property of convergence was proved, the bound of mean square error (MSE) was also derived in the form of Riccati equation. The final numeral simulation demonstrates that the new estimator outperforms its maximum likelihood (ML) counterpart in the merit of MSE.

Abstract:Ionosphere is a typical dispersive medium, which may cause frequency depended delay to navigation signal. In the practical applications, the ionosphere delay between signals at different frequencies is considered only, while the effect of ionosphere dispersion on the receiving for a single navigation signal is usually ignored. A module was established to analyze the effect of ionosphere dispersion. Base on this module, the effect of ionosphere dispersion on some typical wide-band navigation signals was analyzed, such as BPSK(10), BOC(14,2), AltBOC(15,10) signals. The analysis results indicate that the effect on BPSK(10) signal can be ignored, but some correlation loss and carrier phase tracking error will be introduced into the track of high order BOC signals, such as BOC(14,2) signal and AltBOC(15,10) signal, and the correlation loss and carrier phase tacking error of AltBOC(15,10) can be 1.4dB and 0.185 cycles separately.

Abstract:A novel spatial-time-frequency data association (STFDA) algorithm is proposed by taking advantage of the time-frequency separation between different frequency-hopping signals, which uses the time-frequency center as the basis of association. The time-frequency characteristics extracted from time-frequency analysis were used to design appropriate core function and construct a simplified TF-MUSIC algorithm. The Hungarian algorithm was incorporated in STFDA to search the best association scheme according to the cost functions from the time-frequency distance of different signals. Appropriate window function designed on time-frequency distance can prevent the side robe leakage from decreasing the precision of direction estimation, and improve the association correction probability. The simulation results confirm the feasibility and superiority of the proposed algorithm.

Abstract:In order to recognize radar antenna scan type (AST) automatically, an improved antenna scan pattern simulator was developed, and features extraction and automatic recognition methods for electronic scan type (EST) and mechanical scan type (MST) were studied respectively. EST was firstly distinguished from MST based on the characteristic parameters extracted from the maximum main beam pulse sequence; then 8 MSTs were automatically recognized based on the parameters extracted from the pulse sequence in a scan period. The simulation results show that it is able to distinguish between one-dimensional EST, two-dimensional EST and MSTs by this method. Moreover, the correct recognition ratio of MSTs by support vector machine decision tree (SVMDT) is higher than that by decision tree (DT).

Abstract:Aimed at the problem that maneuver detection delay causes the uncertainty of tracking maneuvering target, a combined detection method (χ² -β) was proposed for tracking maneuvering spacecraft with impulse power. By using Observation Innovation and α-βmaneuver dynamics model, the method detected the impulse maneuver to track maneuvering satellite. Through simulation and analysis, a comparison between the χ² detection method with β detection method was made. It proves that the sensitivity of χ² detection to maneuvering frontier correlate with the sampling points and motor threshold. The combined detection method does not incur much computation and,is superior to the traditional method, thus it has practicality in satellite engineering.

Abstract:To reduce the pressure of data processing, the dechirp operation is adopted. However, dechirp will result in range-dependent phase errors in the beat signal. an algorithm to compensate the range-dependent phase error is proposed, using the phase error extracted from the transmitted signal with the supposition that the phase error varies slowly. The compensation approach is executed in two steps: first, compensating the phase error involved by the transmitted signal after dechirp; second, compensating the residual phase error after RVP correction. Both the simulation and the real data experiments suggest that the proposed algorithm is effective.

Abstract:By analyzing the limitation of the traditional sparse representation based classification, a novel classification framework called two dimensional Local-constrained Coding and Sparse Representation (2D-LSRC) is proposed for Synthetic Aperture Radar (SAR) images recognition. Different from other recent popular vector-based representation, 2D-LSRC preserves the global linear coding coefficients between the input matrix and these elementary matrices, as well as the local data structure. Extensive experimental results of MSTAR datasets show the effectiveness of the proposed algorithms and its robustness for the number of the training dataset.

Abstract:Air defense is a basic operational pattern of large surface warship formation. The PEPA (Performance Evaluation Process Algebra) method was applied to model the whole-process air defense operation of surface warship formation. The main air defense process, such as early warning, information transmission, giving orders and interception, was described formally. The established model which has the hierarchical structure takes into account the cooperation among elements and represents the concurrency and distributed character of the air defense operation. By doing performance index choosing and steady state analysis, it obtains the influences of different factors on the performance of air defense of warship formation. The appropriate composition of the basic formation elements in air defense operation is also obtained. Therefore, it provides a new method to deal with the air defense problem of warship formation.