Abstract:A picosecond fiber laser was applied for high power supercontinuum generation (SCG) in photonic crystal fiber (PCF), the key technical issues of fabricating high power all fiber supercontinuum sources were considered and the advantages and disadvantages of picosecond fiber lasers in several configurations for SCG in PCF were analyzed. By using a repetition rate increasing system, a high power picosecond fiber laser suitable for SCG was constructed. By enlarging the core of the PCF at the input end through post-processing method, low splicing loss was realized between the double cladding fiber and the PCF. 35.6 W supercontinuum output is realized with spectrum covering the wavelength range from 650 nm to 1700 nm.

Abstract:The physical model of multiple beams interference fringes was established for unstable resonator alignment, and the characteristics of interference fringes with different misalignment angles were calculated by a homemade software, in which augmented matrices of misaligned optical systems was applied to compute the decentration and tilt of Gaussian beams. The ABCD law was applied to calculate the multi-pass propagation of Gaussian beam q parameter. Furthermore, the interference fringe for unstable resonator alignment was calculated by adding the complex electrical field of multiple Gaussian beams. The calculated interference fringe was found to fit well with the experimental results, which shows that the physical model is correct. Therefore, this model can quantitatively explain the relation between the characteristics of interference fringes and the misalignment of the resonator, and then can be a theoretical guidance for compute-aided automatic alignment of the resonators. 

Abstract:With Gaussian intensity distribution or normal random intensity distribution, the correction of Zernike aberrations by a 37-element curvature adaptive optics system was simulated, and compared to the correction with uniform intensity distribution. In the case of Gaussian intensity distribution, the nonuniform of intensity brings about some influence into the correction of Zernike aberrations. The influence on Zernike aberrations with non-zero curvature is more serious than that to Zernike aberrations with zero curvature. In the case of normal random intensity distribution, the influence on Zernike aberrations is small. The correction of Zernike aberrations with zero curvature is more accurate than that for the non-zero curvature aberrations. The results indicate that the 37-element curvature adaptive optics system can correct low order Zernike aberrations when the nonuniform intensity is not very serious.

Abstract:The analytic expressions for the scattered distributions at the focal plane of the Ritchey-Chretien reflective system (R-C system) from the primary mirror and the second mirror were derived. Aiming at the scattered distribution in a typical R-C system, the excellent agreement of the computing results according to the formula introduced in this study with the simulating results provided by the commercial optical analysis software shows that the formula derived is believable and reasonable. Compared with the diffracted distribution at the focal plane, it is more convenient to analyze the saturated effects at the focal plane of the system irradiated by intense light. The results indicate that in the typical R-C system, diffraction is the dominant factor of the saturating effect inside 2.5mm, while surface scattering saturates the detector outside this range. This result provides a theoretical basis for the further study of intense light induced saturating effects in optical system. 

Abstract:Based on the spectrum analysis of the experimental intensive acoustic pulse waveform using FFT, the current research found that the dominating energy of the spectrum is below 100 kHz. It is well known that one of the chemical compositions in sea water, MgSO₄, will cause excessive absorption of acoustic energy due to its chemical relaxation. Starting from a modified equation of state, with special consideration of the relaxation absorption of MgSO₄ in seawater, a new wave propagation equation of intensive acoustic pulse was deduced. Combined with the numerical algorithm, the propagation process of the pulse was simulated and the effects of MgSO₄ relaxation on waveform and spectrum were analyzed. The results indicate that relaxation process will flatten and smooth the steep pulse waveform, and reduce the acoustic energy to low frequency end. The chemical relaxation effects will cause extra loss of the pulse energy, in addition to the geometric spreading effects of pulse wavefront. 

Abstract:Coherent beam combining (CBC), used in scaling power by phase-locking multi-lasers, is an efficient approach to achieve high brightness laser. Based on this approach, the current study analyzed the mechanism of mutual injection-locking and its influence to the laser coherence. Furthermore, two independent Nd:YAG lasers were associated with each other by polarized elements, achieving the mutual-injection-locking of two lasers. Coherent laser power reached 4.4W and the peak intensity rosed up to 1.4 factor. Thus , this research made an tentative exploration of the high power coherent beam combining laser.

Abstract:Model of a relay mirror system was established, and the relationships between system damage effect and the uplink telescope aperture in a 30km-altitude relay mirror system were calculated. Results show that, with the increase of the uplink telescope aperture, the system damage effect increases significantly when the uplink telescope aperture is less than 0.42m; the system damage effect decreases sharply when the uplink telescope aperture is in 0.42-0.54m; the system damage effect increases when the uplink telescope aperture is greater than 0.54m，while gradient of the increasing reduces; the system damage effect tends to be a stable value when the telescope aperture is greater than a certain size. Reasons for the steep fall in 0.42-0.54m are analyzed, and it is demonstrated that the intensity non-uniformity of the received beam causes the reduction of the new source beam quality and the steep fall of the system damage effect. The results of the study can provide reference for the relay mirror system.

Abstract:A scalable architecture for coherent combining of pulsed lasers with active phase control using stochastic parallel gradient descent (SPGD) algorithm is proposed and demonstrated. A low-pass filter is introduced to eliminate the fluctuation of the metric function caused by pulsed lasers and extract the exact phase noise signal, and an active control is thereby built with SPGD algorithm and stable coherent beam combining can be obtained at the receiving plane. Theoretical analysis and numerical simulation were made and an experiment of coherent beam combining two-channel pulsed fiber lasers was also conducted. Experiment results shows that the power encircled in the main-lobe is 1.6 times increased and the fringe visibility of the long exposure pattern is increased from 0 to 0.43 when the system evolves from open-loop to closed-loop. This architecture can be easily scaled up to high power by increasing the number of channel for coherent combining and adding power amplifiers in each channel. 

Abstract:Coherent beam combination of fiber laser/amplifiers is believed to be a promising way to acquire the high power and beam quality laser. Some key technologies are studied in this paper, including dithering phase-locking technology, laser beams combining technology and PZT phase modulator, which can provide reference for development of coherent beam combination of fiber lasers.

Abstract:In order to meet the requirements of multi-agents (MAS) emergency response simulation, the complexity of building a MAS emergency response simulation framework was firstly analyzed. Based on this, the Component Simulation Framework (CSF) was proposed and designed. Through using theories and methods of Ontology, Semantic Net and Production Rules Reasoning, the architecture of scene-modeling and evacuee agents-modeling which work as critical components of CSF were constructed. Finally, the test to the prototype system which is implemented as the framework was carried out, and the result shows that it can efficiently meet the requirements of multi-agents emergency simulation. 

Abstract:Reliability assessment is an important way to evaluate the reliability of system, and it has been an essential way to control the reliability of system quantitatively. But there are some difficulties in achieving an objective result on reliability of complex system using the traditional way of statistics based on large samples due to time and cost. Thus, the reliability assessment of this kind of system has been a problem in reality. Considering the problem met in the reliability assessment and the life prediction for complex system, the reliability information fusion method based on mean interactive entropy is proposed. Based on mean interactive entropy, the weight of fusion was achieved, and the reliability of system was assessed by fusion of multiple prior distributions. By reducing uncertainty in the process, the new method increased the dependence of assessment and was less subjective. Finally, a simulation example was presented to illustrate the efficiency of the fusion method.

Abstract:Synthetic Engineering is an important topic in the study of complex scientific research procedures. In light of this, the current study proposed a system building method for synthetic engineering and concept demonstration, in which the specific details and consistency problems were discussed. The method was applied to the research of radar target signatures, in which an extendable system of electromagnetic scattering characteristics verification and demonstration was established.

Abstract:Based on the controlled mobility of UAV, an augmentation edge heuristic node movement control algorithm is proposed for the realization of the fault tolerant UAVs Ad Hoc networks. Memetic algorithm was developed to get a cheapest possible set of additional edges which make the given communication topology graph vertex-biconnected. With the augmentation edges as heuristics, the vertexes which the edges connected move towards each other to establish edges, the related nodes also move as the follower with the leader-follower movement control algorithm based on the consensus algorithm. After nodes moved, the changed network becomes vertex-biconnected so that the fault tolerant configuration is achieved. The simulation experiment results show that the proposed algorithm is effective, and the total distance metric is improved by comparison with the block movement algorithm and the contraction algorithm.

Abstract:Observability of a part of states (partial observability) of unobservable system is very important for fault detection of large systems. Measurement points optimization of unobservable linear discrete systems based on partial observability was studied. It was proved that a sufficient and necessary condition of the partial observability can be obtained by a matrix which is formed by limited observations of the system. Then the rank characteristic of a matrix was proved to be able to be applied to express how observable those partial states are. Finally, an index of this partial observability was presented for the measurement optimization. 

Abstract:The reentry trajectory of glide missile can be divided into three phases: descent and pull-up phase, glide phase and terminal phase. According the characteristics descent and pull-up phase, an optimization model of reentry trajectory was introduced, and the Gauss Pseudospectral Method was used to solve the optimization problem. Based on onboard trajectory optimization, the control command was obtained and updated onboard, and the closed-loop control trajectories were generated. The results show that the Gauss Pseudospectral Method works well with high precision and fast speed, and the presented closed-loop control can provide a missile capability of satisfying the desired objectives under various disturbances and uncertainties. 

Abstract:Testability indexes are the basis of testability design, validation and evaluation. To address the problems that the traditional testability indexes are mainly used to evaluate fault detectability level and fault isolability level, and are unable to describe testability level for equipment health management (EHM) comprehensively, based on the qualitative intrinsic requirements analysis of EHM on testability, five testability indexes were defined from the universe and instantaneous angles to describe the testability level for EHM quantitatively, and the detailed analysis and calculation process of the proposed indexes were presented based on failure mode state vector. A certain diesel engine body subsystem was introduced as a case example to illustrate the testability indexes calculation process, and application results show that the proposed indexes are feasible and rational, and they can guide the testability optimization design for EHM effectively.

Abstract:For the characteristics of capacitor’s stochastic deterioration, the research studied the scheme design and strategy optimization problem of its preventive maintenance based on semi-Markov process. Taking the inspecting time as optimization variable and considering the threshold of preventive maintenance times, the research built the long-run expense rate optimizing model of the capacitor based on the Gaussian-Poisson process model of its stochastic deterioration. The analysis shows that for the capacitors preventive maintenance is superior to posterior replacement in the saving of long-run expense rate.

Abstract:In order to enhance the understanding, comparison and integration of architecture developed under different architecture frameworks and tools, and to promote the sharing and reuse of architecture data, a new method, named meta-model based methodology of architecture modeling, was proposed. Based on the idea of model driven architecture (MDA), this method presented a transformation approach from architecture meta-model to modeling languages with the extensible markup language (XML) format. On the other hand, the modeling method under the meta-model specification was proposed and three mapping specifications mentioned in the method were designed. To verify its feasibility, the IDEF3-based modeling methods of operation rule model was designed, and the main rule-named modeling primitives and patterns based transformation was analyzed.

Abstract:Multi-satellites’ cooperated observation is an effective way to maximize satellite system performance. How to deploy these satellites is an optimization problem, which involves a huge design space and many design parameters. For this problem, an improved generalized pattern search algorithm, which is based on Kriging model, was put forward. For the search step, two point selection mechanisms were constructed. One is to choose the point with maximal predict value about the surrogate and the other is to choose point with maximal expect improvement. For the poll step, the surrogate was used to predict the expected improvement of the points in the poll set and rank them accordingly. It can reduce the unnecessary simulation analysis. Finally, the proposed algorithm was applied to deploy multi satellites for a given scenario. Compared with the results obtained by STK-Analyzer, the proposed algorithm operated better in performance. The results prove the feasibility and effectiveness of the algorithm.

Abstract:Based on the common index system of performance evaluation of supply chain and the characteristics of modern warfare ordnance maintenance equipment supply chain, the current study established the index system of performance evaluation of ordnance maintenance equipment supply chain during wartime from source, output and flexibility. Considering the information is fuzzy and uncertain under the environment of war, the evidence theory model was established to evaluate the performance of ordnance maintenance equipment supply chain. Finally, a wartime ordnance maintenance equipment supply chain was explored as a case study, using the index system and the evaluation model which was established earlier to study its performance. The result shows that the performance evaluation model of ordnance maintenance equipment supply chain during wartime is feasible and effective.

Abstract:It is important in military field to detect landmine using vehicle-mounted ultra band ground penetrating radar, which has the capability to detect landmines over large area. The extraction of steady features has been the crucial factor in the practical use of ultra-band ground penetrating radar. In light of this, a new feature extraction and classification method was proposed based on the time-frequency atom decomposition. The method extracted the two-dimension time-frequency image based on four-dimension scatter function. After analyzing the character of time-frequency image, the time- frequency atoms were used to decompose the one-dimension range profile of landmine. Several time- frequency atoms which could describe the time-frequency character of landmine were sent to hierarchy classifier as features. It was proved by real data that the method was applicable to vehicle-mounted ultra band ground penetrating radar. Compared with the conventional feature extraction algorithms based on time or frequency field, the proposed method can extract steadier feature and improve the performance of landmine detection effectively.

Abstract:QoS routes searching in tactical MANETs is a NP-complete problem, to which the ant-colony optimization algorithm is an effective solution. To improve the efficiency of ACO based QoS routing algorithms, an ant-colony optimized QoS routing algorithm (MTS-AQRA) based on multiple transferring strategies was proposed. MTS-AQRA integrates link’s stability and route’s congestion into conventional QoS requirements in the process of routing. By utilizing the diversity of route-search ants and the concurrent route-searching result from the multiple transferring processes, MTS-AQRA can work rapidly and effectively to establish stable routes which satisfy the QoS requirements of certain services. Simulation results show that MTS-AQRA outperforms AODV, QoS-Aware ACO and AntHocNet in terms of packet delivery ratio, end-to-end delay, end-to-end throughput and route stability.

Abstract:In order to select SAR matching areas with high matching accuracy and matching probability, the current study analyzed the error influence of INS and imaging parameters on the matching area, designed several kinds of rules for suitability analysis, and proposed a coarse-to-fine selecting method. The method fully considers the macroscopic and microcosmic requirements, and keeps it away from the difficulty of constructing predicting functions. Experiment results indicate that the method can select good matching areas in the SAR image matching system, and achieve an over 97% matching probability of the selected matching area.

Abstract:To solve the isolation problem of transmitting-receiving antenna in very-near anti-missile system, this research analyzed the equivalent model of AMC, which is made of high-impedance electromagnetic surface, and shows the relationship between its reflectance and phase offset. Then a novel method wa put forward to improve the isolation by the AMC and the experiments show that the method is able to make the isolation reach -80dB in a 200MHz band. So it has a good application value because of its simple structure and low cost.

Abstract:Present analytical conclusion of GNSS carrier tracking digital phase-locked loop (DPLL) phase jitter due to oscillator phase noise is derived based on the linear model of analog PLL. It is, however, not able to reveal the relationship between phase jitter and the coherent integration time (CIT), and it cannot guide the high sensitivity and high precision carrier tracking DPLL parameter design effectively. Firstly, this research derived the power spectral density of white frequency and random walk frequency phase noise sequences output from the phase detector. Secondly, the formulae of phase jitter were obtained based on the DPLL linear model and verified by simulation. Finally, analytical and numerical analysis on the obtained phase jitter formulae was carried out. The analysis results show that, both of DPLL phase jitter due to white and random walk frequency noise increase as the CIT grows, and decrease firstly and then increase as the loop bandwidth grows. The phase jitter formulae and the conclusions, which describe the relationship between DPLL phase jitter and the loop bandwidth and the CIT, can be used as guideline for GNSS carrier tracking DPLL parameter design.

Abstract:The existing passive synthetic array algorithms all make too ideal assumptions on the way of sensor moving and cannot endure the influence of phase noise very well. So the current research firstly presents a general processing algorithm of passive synthetic array. By carefully analyzing the phase noise model, a new estimation means of maximum coherence time and valid synthetic sensor number is proposed and then the steering vector of passive synthetic array is reconstructed. Furthermore, an improved passive synthetic array algorithm based on the phase noise model is presented. Considering the effect of phase noise, the theoretical lower bound on the variance of DOA estimate of passive synthetic array is given by deducing the Cramér–Rao Bound. Simulation results show that the proposed algorithm can enhance the precision of DOA estimate effectively comparing with the existing algorithm.

Abstract:Huge code cubage and poor code density have always been a serious problem in VLIW processors. Through analyzing the code characteristics of a series of typical applications on stream processor, a novel domain-divided VLIW code compression scheme to eliminate the nop operations in each domain, and a distributed instruction memory to decompress and execute of the codes are proposed. The experiments show that this scheme can reduce nearly 39% of the off-chip instruction memory accessing and about 65% of the on-chip instruction memory space demand. Meanwhile, it can also depress the area of on-chip instruction memory and MASA stream processor by 37% and 8.9% respectively.

Abstract:A novel method using digital streak photography technique based on line-scan camera is proposed in order to circle out the problem in the digital improvement of the traditional streak facility in test range. The projectile’s stereo images were firstly collected by using a calibrated line-scan camera and a mirror, and then some special points were picked to compute the initial guess of the projectile’s velocity and attitude. The initial guess was further refined by using an optimization model established on the matching measure of the simulated and the real images contours. The speed and the attack angle were ultimately obtained. The accuracy of the estimation was experimentally tested.

Abstract:The topic evolution was investigated for network public opinion analysis. The properties of network public opinion information were analyzed firstly. Based on the properties, the latent semantics of textual data for network public opinion was described by using the topic model, and the text streams are modeled with a consideration of time for online analysis. Furthermore, a topic evolution method based on OLDA was proposed by incorporating the correlation of topics among time slices. The proposed method was experimentally verified to be efficient for detecting topic evolution of network public opinion. 

Abstract:A new uniform threshold function of wave-shrink for image denoising is proposed. The new function has the advantage of satisfying the shrinkage condition. By changing the parameter u,we can change the trend of this new function, which makes it possible to find an adaptive method whenever using the wavelet shrinkage method for image denoising. Finally, efficient formulas for computing mean , variance and risk of the new uniform threshold function are derived. Numerical experiments and comparative studies are performed, demonstrating the effectiveness of our threshold function. Additionally, the proposed new function can also give better performance in terms of both PSNR and in visual quality.

Abstract:The percutaneous coronary intervention virtual simulation system about coronary heart disease is one of the important tools for medical intervention training. To satisfy the clinical training needs, the key techniques about geometry modeling, heartbeat simulation, liquid simulation and flexible instrument movement processing in systerm development were discussed. A blood vessel model based on NURBS surface and a heartbeat model based on a combined mass-spring were proposed. Contrast media injection and flexible instrument movement were realized by the particle systerm and the multi-branch tree method. A simulation platform and technology support was supplied for percutaneous coronary intervention training. 

Abstract:According to the appearance of fractal feature degeneration during fractal morphing, a new feature corresponding method based on local attractor’s approximate convex hull (LAA) and revolving matching method (RMM) is introduced. The local attractor, part of the whole IFS attractor, is indicated by an independent IFS code, whose internal contractive affine transformations have unique fixed points, and the LAA is constructed by contouring the convex hull of all the fixed points of the IFS. It is proved that the similarity between different IFS’s LAAs is equivalent to the similarity of its local attractors, so the feature corresponding can be built upon the LAAs. The matching between two LAAs is based on RMM and the matching order is restricted clockwise or anticlockwise. Then, the feature corresponding between two IFS’s local attractors is determined by searching for the most similar matching of the LAAs. Finally, the parameters of the iterated function are linearly interpolated to finish the morphing procedure of two IFS’s fractal attractors and to perform the fractal morphing with fractal feature preserved.