Abstract:According to the drawbacks of traditional surrogate model based airfoil optimization, dynamic mesh based airfoil design optimization was studied. Hicks-Henne parameterization method was improved against the drawbacks of unsmooth tailing edge, which was subsequently utilized for the construction of airfoil dynamic mesh. Commercial software Pointwise and Fluent were integrated by secondary development, which automates the adding boundary condition and CFD calculation. The data flows and work flows between commercial software and programs were realized under iSIGHT platform. An airfoil optimization case study shows that the method can significantly improve aerodynamic performance of airfoils, and save massive repeat operations, which is verified an effective and high efficient method of airfoil design optimization. 

Abstract:The relationship of coefficient of pressure center of body of revolution and angle-of-attack and Mach number was educed, based on the aerodynamic formulas of high-angle-of-attack flow. Adopting a k-ε two-equation turbulence model following the realizable rules, seven kinds of body of revolution with different shapes in high-angle-of-attack flow fields were researched by means of CFD, and the numerical results were derived. The numerical simulation results were consistent with the ones in theoretic analysis. Research results indicate that there is a geometric discriminant, which is correlated with the geometric configuration that has strong influence on the law of variation of the coefficient of pressure center. 

Abstract:The rotating period of the pulsars are highly stable, and the measurement of the pulsars can be adopted to correct the clock error of the satellite-borne atomic clock. In order to solve the problem that the minor system bias can largely worsen the performance of the pulsar timing system, an algorithm for the pulsar timing system with the system bias is proposed. Based on the principle of the pulsar timing system, the system bias was modeled. By using the two-stage Kalman filter, the system state and the system bias were decoupled and estimated. The results of the simulations show that the proposed algorithm can effectively reduce the impact of the system bias and can improve the performance of the pulsar timing system. 

Abstract:Impingement angle and wall curvature are important for liquid film cooling design of liquid rocket engine. The effect of impingement angle and wall curvature on film form and thickness was studied experimentally. The film thickness was calculated by contact needle method. Splash occurred with high Webber number during impingement. The critical Webber number for transformation from adherent to splash is 214.1, and the critical impingement angle is 23.1°, which means the impingement angle can be optimized for different liquid rocket engines.

Abstract:Fault detection and diagnosis is a difficult problem in liquid-propellant rocket engines (LRE) healthy monitoring, but it has important significance for locating an engine fault, preventing tragedy accident from occurring, and maintaining engines. So a fault isolation method in components level based on fuzzy model was proposed to confirm the position of the fault for certain Liquid-propellant rocket engines. Firstly, it divided the engine into several components; secondly the fuzzy model for each component was established and trained; finally the method performed fault diagnosis according to established strategy. The fault isolation algorithm based on fuzzy model was validated by two sets of simulation data. The results indicate that fault isolation algorithm can isolate single fault or multi fault components effectively. 

Abstract:Architecture design and development based on Meta-Model and architecture evaluation method based on executable model are two hot topics in architecture domain study, but there is no study combining these two topics. Based on the conception of Meta-Model Data (DM2) which puts forward DoDAF 2.0, the research combined the idea of DM2 and the evaluation method based on the executable model, analyzed the relationship between the logical data based on DM2 and the executable model, designed the progress of supporting data using DM2 Foundations change directly into executable model, especially focused on the method of changing the architecture data into executing model. The study provides the basis for architecture executable evaluation, and helps to take further study on architecture automatic validation and evaluation. Finally, the case study demonstrates the method proposed in this paper. 

Abstract:Scheduling the contact between the navigation satellites and ground unlink stations and navigation data uplink process is of important significance to keep the accuracy of the navigation data on board. After analyzing the navigation data uplink process of the satellite navigation system, a multi-objective mix-integer model was devised, considering the technological constraints in uplink process. Because of the complexity of the model, a two-phase heuristic algorithm based on rules is devised. A set of test scenarios were devised consulting the COMPASS of China, the GPS Satellite Navigation Systems. The mathematical model and algorithm proved effectively for the uplink task schedule process. Several factors that influence the completion of the uplink tasks were obtained by analyzing the computational results. 

Abstract:In light of the time-continuity of warships’air defense process and the uncertainty effect of intercepting operation a novel generating method of intelligent planning and scheduling for the air defense of warships is proposed. When a new anti-ship target is detected, the air defense system of the warship will search the constraint satisfaction plan with the highest intercepting probability immediately. Then, when one intercepting operation fails, the secondary intercepting strategy will be generated timely. The current conventional methods all handle it as the Weapon-Target Assignment (WTA) problem, which cannot model the time-continuous and uncertain process, while the method proposed integrates the planning and Scheduling strategies. For each new detected or failed intercepted target, the action-reasoning algorithm of the AI (Artificial Intelligence) planning system is used to search the possible candidate intercepting plans. Then, the optimal scheduling algorithm checks the temporal and resource conflicts among the actions of each candidate plans, and returns the constraint satisfaction strategy with the highest intercepting probability. Planning and scheduling process takes the weapons coordination, the time-continuity and uncertainty of the intercepting operation, and the optimal intercepting time selection into account. Compared with the discrete-time based algorithm used for WTA, the Planning-Scheduling model is more appropriate to describe the air defense process. The property of the algorithm is verified by the Monte Carlo simulation experiment, which shows the method proposed provides a new approach to handle the automatic air defense problem of the warship. 

Abstract:In spacecraft launch engineering, it is very difficult to quantify reliability of implementation process. In terms of the peculiarities which the reliability of implementation process presents, such as many sub-processes having concurrency and every sub-process having the Markovian property and homogeneity. this research presents a model of implementation processes reliability with multi-absorbing state by utilizing the model of continuous-time Markov chain (CTMC), which simplifies the state space of the implementation processes reliability through the use of bisimulation equivalence relation. Moreover, the calculation method for various state transition rates and implementation process reliability is also presented. Finally，the simulation case by engineering data verifies the role and significance of the model in the assessment schedule of spacecraft launch engineering.

Abstract:The opinion evolution results of both dynamic models of group experts round discussion and free discussion in collective discussion are analyzed and compared by computer simulation. Statistical results show that under the same initial conditions, the model of free discussion using the speech sequence rule of authoritative experts first and then experts with the maximum of opinion cumulative change first has less average opinion clusters. It also finds that discussions after 15 rounds have less improved impact on indicators. As the free discussion is followed by serial speeches that are less efficient, in the actual selection of the mode of discussion, when there are fewer experts and plenty of time, it should use free discussion, and vice versa it should adopt discussion by round.

Abstract:This study addresses the robust distributed relay network (DRN) beamforming design problems for a distributed Amplify-and-Forward (AF) relay aided multiuser peer-to-peer communication system in the presence of imperfect channel state information (CSI). By adopting a stochastic CSI error model, two robust optimal design problems are considered. One is aimed at balancing the signal-to-interference plus noise ratio (SINR) at destinations under the DRN total transmit power constraint concerning the fairness, the other is to minimize the DRN total transmit power with the guarantee of QoS requirements (SINRs exceed preassign thresholds) at destinations concerning the efficiency. The analysis and modeling indicates that the problems above are the intractable problems. By introducing the semidefinite relaxation (SDR) technique, the intractable problems hereinbefore can be converted into the semidefinite program (SDP) problems which can be solved efficiently through the interior-point method. The robust performance of the proposed designs is demonstrated through simulations. 

Abstract:Under the condition of platform maneuvers, the accuracy of the motion compensation in frequency-domain cannot meet the focusing need of airborne Ultra-wideband Synthetic Aperture Radar (UWB SAR) because of strong motion errors. The time-domain Back Projection (BP) algorithm can be used in this instance, whereas the large amount of computation limits its application. In light of this, a strategy of processing the airborne UWB SAR data with platform maneuvers is proposed by using the Sub-image Fast Factorized Back Projection (SIFFBP) algorithm. The constrain relationship between the sub-aperture and sub-image factorization was derived, and then the implementation approach was listed with the computation volume being analyzed. The processing results of the simulated and real data show that SIFFBP algorithm is applicable for the focusing of airborne UWB SAR under the condition of platform maneuvers with high precision and efficiency. 

Abstract:Aiming at the problem of blind identification of underdetermined mixtures, an underdetermined blind identification algorithm is proposed, based on the detection of time-frequency single source point and cluster validation technique. Firstly, single source point of each source signal was detected. Then the mixing vector in the corresponding single source point set was estimated by Singular Value Decomposition (SVD). Finally the number of the source signals and the mixing matrix simultaneously were estimated by the cluster validation technique based on k-means clustering algorithm. Compared with the conventional algorithms with single source hypothesis, the proposed algorithm relaxes the sparsity requirement of the source signals and can estimate the mixing matrix under the assumption that there exist disjointed single source points for each source signal. Meanwhile, the proposed algorithm can estimate the number of the source signals while the conventional algorithms require it to be known as a priori. Simulation results display the efficiency of the proposed algorithm. 

Abstract:In the condition of navigation war, civil or indoor environment, when the visible satellite number is less than 3 and users’ position is unknown, one-way timing solution is no longer unavailable. Based on the characteristics of Chinese navigation satellite system such as COMPASS and CAPS, a doppler positioning timing method based on IGSO satellite is proposed. By measuring the doppler frequency shift and counting the integral Doppler, the user position and time are computed. Analysis result shows that the positing and timing usability can reach nearly 100% in Chinese domain when using 3 IGSO satellites with transponders. The position precision can achieve 3m and the timing error is less than 100ns for static users with long time measurement. Because only one IGSO satellite is needed and there is no requirement for demodulating navigation message, this method provides a novel timing method for the navigation war background and weak signal environment. 

Abstract:Because of the limited bandwidth of filter and the high-power amplifier nonlinear effect, there will be phase noise for the constant envelope signals, which will affect navigation signals in the PLL tracking error of carrier tracking. To address this issue, the generic model for analyzing navigation signals non-linear distortion was established, and the relation between high-power amplifier nonlinear effect and performance of PLL tracking error were simulated and analyzed.

Abstract:The ability of navigation receiver to track signals is affected by phase locked loop tracking accuracy. Phase discriminator plays an important role in the design of phase locked loop. Base on the influence on the finite word length effect to the dot product and the arctangent discriminator’s performance, a word length error model was proposed. The theoretical analysis of the finite word-length affected to the discriminator’s converge range and gain was presented by deducing the input signal’s statistical characteristic. Analysis and simulation show that the deviation of input signals of the phase discriminator with up to 3 bits has no influence on the carrier tracking accuracy.

Abstract:At long baseline, for multipath and ionospheric residual bias, classical CIR can get wrong ambiguity resolution at some epoch, and requires a large search area on basic carrier. In this research, ambiguity errors of CIR were analyzed, and an approach to improved CIR based on carrier phase smoothing pseudorange and eliminating ionosphere delay is presented and errors variance was analyzed. Finally, CIR and improved CIR were compared at both short and long baseline by compass measured datum. The result shows that improved CIR can obtain correct double difference extra wide lane ambiguity and wide lane ambiguity on one epoch, and reduce the search area on basic carrier ambiguity. 

Abstract:At present, frequency estimation algorithm based on DFT interpolation is widely used because of it’s high operation efficiency, but the estimating accuracy is dependent on the signal frequency, and for specific frequency, the estimation performance is bad. To solve this problem, a high accuracy frequency estimation algorithm with lower calculating complexity is proposed. In this algorithm, the signal frequency was estimated by Secant Method based on the DFT samples, and decimal fraction frequency of peak magnitude DFT sample was estimated to generate new DFT samples, thus reducing the DFT sample interval with little calculating burden, then improving the estimating accuracy. In addition, through removing the frequency reliant characteristics of estimation which exist in traditional frequency estimator based on the DFT interpolation, this algorithm increased the iterative estimation. To analyze the performance of the algorithm, a simulation was fulfilled. The simulation results show that the single frequency estimator without iterative estimation has asymptotic estimating variance less than 1.2 times the CRLB, which is better than the traditional frequency estimator based on the DFT interpolation, with calculation labor of N log₂N+2N complex multiplications, and the iterative frequency estimator has estimating variance about CRLB for all signal frequency calculation labor of N log₂N+2N complex multiplications, and N is the number of the DFT samples. 

Abstract:In global navigation satellite system (GNSS) receivers, matched filters should be applied in time delay estimation to maximize signal-to-noise ratio of tracking loops. Integrate and dump filters are often used as a simplification to reduce hardware cost; however, there is no quantitative conclusion about its performance degradation yet. To deal with this issue, analytical expression of performance degradation is derived, and Monte Carlo simulations are given to support the analysis. Theoretical and simulated results show that the performance degradation is about 0.44dB if sampling frequency is twice of signal bandwidth, and it can be neglected if sampling frequency is increased to four times of signal bandwidth.

Abstract:The frequency difference of arrival (FDOA) estimation is the key point in a passive location system, and the estimation accuracy of FDOA determines the location performance. The FDOA estimation methods have been widely studied, but theoretical maximal accuracy of FDOA estimation is barely referred. To explore the ultimate performance of the FDOA estimation, the CRLB of frequency FDOA estimation accuracy was studied. On the basis of building a mathematical model, the quantitative relationship between the FDOA estimation accuracy and the parameters of received signal was investigated. By the means of mathematical deduction and numerical simulation, the algebraic expression of the CRLB was conducted in different application modes. Finally the characteristic of the CRLB was evaluated, and the conclusion can be used to direct the design of passive location system based on FDOA.

Abstract:GNSS receiver synchronizes local clock by calibrating clock error obtained from GNSS satellite signal. A novel local clock error calibration algorithm is developed. The time synchronization procedure was considered as a PLL model. In this model, phase detector was achieved by PVT solution, VCO was achieved by local clock adjusting interface, and the PLL lock the phase of local clock and GNSS clock. The total PLL time synchronization loop errors were analyzed, the relationship of each error item and parameters of PLL was analyzed, and the best PLL design criteria were developed. Finally, the time synchronization algorithm was tested on a COMPASS navigation receiver.

Abstract:The storage and access of massive small files are one of the challenges in the design of DFS(Distributed file system). Most of the DFSs, such as GFS and HDFS, are designed for handling massive big files. The performance of DFSs decreases greatly when accessing massive small files without special optimization for small files. This research focuses on the optimizing of the performance of data server in handling massive small files, and presents a Flat Lightweight File System called FlatLFS in which the user data are managed flat in disks. FlatLFS is supposed to substitute the traditional file system when accessing user data for upper DFSs. With the improvement of the performance of small data block processing on data servers by FlatLFS, the performance of the whole DFSs is greatly improved. The effectiveness of FlatLFS is proved with intensive experiments: when the size of data block is 1M, the performance of random read of FlatLFS is 135%, 112% and 122% higher than ext 3 ,ext4 and reiserfs respectively. 

Abstract:Expert finding is an important part of entity retrieval. Classical expert finding models rest upon the conditional independence assumption between the candidate and term-given document. However, this assumption is usually invalid in real world applications, which makes the performances of classical expert finding models not ideal. In this research, an expert finding method is proposed based on the topic model (EFTM). This method discards the conditional independence assumption in classical models and is more maneuverable. In addition, a ranking truncation approach which largely decreases the computational complexity of the model was used. Finally, the performances of the new model were evaluated using the CSIRO Enterprise Research Collection. The results shows that the EFTM model outperformed the classical model significantly on all the metrics and can effectively improve the performances of the expert finding system. 

Abstract:Many information retrieval applications have to present their results in the form of ranked lists, in which documents must be sorted in a descending order according to their relevance to a given query. This has led the interest of the information retrieval community in methods that automatically learn effective ranking models, and recently machine learning techniques have also been applied to model construction. Most of the existing methods do not take into consideration the fact that significant homogeneity exists between query-document pairs related to user’s feedback. In this research, a novel method which clusters patterns in the training data with their relevance from the user, and then uses the discovered rules to rank documents at query-time. A systematic evaluation of the proposed method using the LETOR benchmark dataset is posposed. The experimental results show that the proposed method outperforms the state-of-the-art methods with no need of time-consuming and laborious pre-processing.

Abstract:The advantage of reconfigurable computing system is in conflict with its complex design, and the Reconfigurable Computing Application Framework (RCAF) supplies a rewarding approach. But by the limitation of applicability and general purpose, some RCAF(especially some commercial version) only supports the static reconfiguration. This research proposes a kind of Reconfigurable Computing Application Framework BSRRCS-RCAF for the specific application of Broadband Signal Reconnaissance, which extracts and collects the computing and function modules as the form of library of configurable files. When the system of Broadband Signal Reconnaissance needs to be modified or reconstructed, the user, who is also the designer of the system, only needs to schedule the components from the library dynamically, or complement the special functions of the system, then the framework of the system will be reused conveniently. Based on BSRRCS RCAF, it is easily and quickly to realize the system with multi-functions.

Abstract:Aiming at the face recognition problem, a new supervised dimensionality reduction algorithm is presented. On the basis of sparse representation theory, the proposed algorithm uses the within-class sparse construction to construct graph. This scheme can avoid the difficulty of parameter selection in traditional graph construction methods, and characterize the within-class information well. Furthermore, the multi-class nonparametric discriminant scatter is applied to characterize the between-class information, which will be more discriminative than parametric discriminant scatter in dealing with complex-distributed data. By maximizing the nonparametric between-class scatter and preserving the within-class sparse reconstructive relationship, the proposed algorithm can seek for the optimal projection matrix. Experimental results on ORL and Extended Yale B dataset show that the proposed method can achieve good recognition effect. 

Abstract:Theory and method research of equipment measurability is very important for improving the metrology support ability of equipment. Aiming at the lack of equipment measurability model inland, the multi-signal model method is presented for the measurability analysis and design. The basic theory of the measurability multi-signal model was summarized systematically, the optimum seeking method of the out-of-tolerance detection and position，and the design method of measure strategy were introduced in detail on the single out-of-tolerance assumption, without considering component reliability, measurement time and cost implications. The multi-signal model of self developed signal produce system was established, the correlation matrix was given and the verification tree was analyzed. The conclusions agree with the actual verification method of signal produce system, which proves that the measure strategy is reasonable and effective. 

Abstract:How to improve the performance of piezoelectric vibration energy harvesting (PVEH) with nonlinearities is a key problem in engineering applications. A mathematic model of nonlinear PVEHs was built in this research. A fast numerical method based on the principle of the definite integral was proposed to solve the nonlinear model. Then the effects of these nonlinear parameters on the performance of nonlinear PVEHs were simulated. The results demonstrate that both reducing nonlinear damping and increasing nonlinear piezoelectric coupling coefficients will improve the performance, and reducing nonlinear stiffness will increase the output of low frequency vibration energy harvesting, and decrease its resonant bandwidth. 

Abstract:Time-tag error is an important error source of K-band ranging (KBR) system, and the present methods for time-tag error correction are dependent upon accurate measurement of inter-satellite time-tag offset. Aiming at the problem that currently the national measurement accuracy of inter-satellite time-tag offset cannot satisfy the demand for time-tag error correction, a novel correction method based on the combination of two optimal frequencies is proposed, and the quantity relation of the optimal frequencies is deduced. Research on the realization for combination of two optimal frequencies, which shows that it is unrealizable utilizing the existing KBR system, was performed. Consequently, a new KBR system adopting an advanced frequency flow was designed and realized. The experimental results demonstrate that the proposed method and the advanced KBR system effectively reduce the requirement for measurement accuracy of inter-satellite time-tag offset. 

Abstract:Solving the spatial optimization problems can be a complex and difficult task, since it has to handle some high-dimension, non-linear, complicated relationships. Many efforts have been made with regard to this specific issue, and the strong ability of artificial immune system algorithms has been proven in previous studies. In this study, a novel framework used for spatial optimization based on clonal selection algorithms, which are the most popular immune algorithms in geoscience, is proposed. Then, the spatial optimization platform was designed based on the architecture of “plugins – platform”, and some key technologies about the developing of immune operator plugins and spatial optimization application plugins were described. Based on the standard APIs provided by this platform, researchers can develop their own problem-specific application plugins to solve the practical problems or to implement some advanced immune operators into the platform to improve the performance of the algorithm. Finally, the functionality, reusability and extensibility of platform were tested by using the Traveling Salesman Problem as a benchmark testing. Experiments show that, the platform is capable of solving various optimization problems, and it is expected to bridging the gap between the immune algorithm researchers, geographers and decision makers.

Abstract:Based on partial differential equation of heat conduction, a temperature field model of fiber optic gyroscope (FOG) was established. The steady-state temperature field and the transient temperature field were given. A circuit to measure temperature using a platinum resistor was designed. The experiment results are compared with the simulated ones and the error is less than 3%, which validates the legitimacy of the simulation. The structure of FOG was redesigned to improve the thermal symmetry of the fiber ring. The steady-state temperature field indicates that the temperature difference of the fiber ring is reduced 73.7 percent to 0.05 degree after structure redesign. The transient temperature field in 10 min shows that the temperature difference of the fiber ring is reduced 42.1 percent to 0.11 degree after structure redesign. 

Abstract:Infrared target segmentation is very valuable to infrared target detection and tracking. The research proposes an effective infrared target segmentation based on background and target gray character. The method avoids gray instability in the interior of the targets caused by temperature instability. Firstly, two-dimensional MCC based on gray-salience was proposed to segment targets. Then, improved region-growing algorithm based on random reed points was presented to extract background. Finally, morphological operation improved the segmentation performance. Compared with the traditional algorithms of target segmentation, this algorithm has better anti-jamming and robust. The method can be used not only for target segmentation but also for other similar segmentation.