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Effective detection of low observable moving target at sea is important for remote sensing and radar signal processing. The non-Gaussian property of sea clutter and lack of accurate model make the detection difficult for statistics based detectors. Also the fractal techniques in time domain cannot achieve high detection probability in heavy sea clutter. To help solve the problems, fractal characteristics...
The classical two-scale model based on linear hydrodynamics may account for the “slow signals” which include Bragg scattering from both free and bound capillary waves but it is insufficient to describe the non-Bragg scattering from “fast scatterers” associated with breaking wave crests. Here, a realistic model of the time-varying sea surface with a quadratic phase is proposed and the characteristic...
An underwater terrain navigation method based on Bayesian estimation is proposed for autonomous underwater vehicle (AUV), according to the depths measured by multi-beam echo sounder (MBES). For the shortage of false peak increasing intensely at low characteristic area of this method, the Fisher criterion is introduced. This method effectively reduces the false peaks, enhances the discrimination of...
Firstly, the importance of subjects design in virtual maintenance training system is emphasized, and then the main factors that affect the design for subjects in virtual maintenance training are analyzed. Secondly, the detailed design process of virtual maintenance training subjects is illustrated based on the analysis of training requirements. Finally, this process is applied in the design of a concrete...
In order to effectively detect moving target in strong sea clutter, a detection algorithm for moving target based on clutter map cancellation in fractional Fourier transform (FRFT) domain is proposed. Radar data in FRFT domain are noncoherently accumulated with the single pole feedback clutter map (SPFB-CM) in FRFT domain, which are used to suppress sea clutter and improve signal to clutter ratio...
0.95Pb(Sc0.5Ta0.5)O3-0.05PbTiO3(PSTT5) thin films were prepared on LaNiO3/SiO2/Si substrate by RF sputtering, and the films were annealed by one-step rapid thermal annealing (OSRTA) and two-steps rapid thermal annealing (TSRTA), respectively. Results show that an appropriate repeated heat treatment could improve ferroelectric and dielectric properties of PSTT5 film, Pr and Ec of PSTT5 thin films annealed...
The CoFe2O4/Pb(Mg1/3Nb2/3)O3-PbTiO3 (CFO/PMNT) multilayer thin films have been prepared on LaNiO3/SiO2/Si(100) substrate using radio frequency magnetron sputtering method. The smooth, dense and crack-free surface of CFO/PMNT multilayer thin film shows the excellent crystal quality with root-mean-square (RMS) roughness only 2.9nm. The influence of the interface effect, film thickness, period number...
Mn+Y co-doped Ba0.67Sr0.33TiO3 (BST) powders were fabricated by a citrate precursor method. Mn+Y:BST ceramics were prepared by conventional electronic ceramic process. The microstructure and intrinsic pyroelectric properties of the obtained Mn+Y:BST ceramics were investigated. Adopting fine Mn+Y doped BST powders derived from the citrate method was confirmed to be effective in reducing the sintering...
In order to effectively detect moving target in sea clutter, three methods based on fractal character differences are proposed making use of the different fluctuation of amplitude between sea clutter and moving target in fractional Fourier transform (FRFT) domain. At first, fractal model in FRFT domain is established and simulations of fractal curves of real sea clutter in FRFT domain are conducted,...
A novel adaptive filtering scheme based on Fractional Fourier Transform (FRFT) for time-varying linear frequency modulated (LFM) signal is introduced and characterized using the characteristic of good energy concentration on LFM signal in FRFT domain. Grading iterative calculation method is used to obtain the best rotation angle with low computational complexity. Leakage factor is introduced for adaptation...
To overcome the sensor system problem of fault diagnosis and signal recovery for autonomous underwater vehicle (AUV), a method based on strong tracking filter (STF) theory and singer model of first order time correlation function was proposed. The STF-Singer model by combining the signal processing method and STF method dose not need the accurate mathematical model of the controlled plant, and it...
On the basis of the detection and estimation model of multiple moving targets, a new algorithm based on wavelet packet transform (WPT) and fractional Fourier transform (FRFT) is proposed for weak moving targets detection in sea clutter. The multi-resolution property of WPT and the characteristic of good energy concentration on LFM signals in FRFT domain are combined together. At first, optimal wavelet...
Presents two reaching laws of sliding mode for discrete-time variable structure control systems to solve the problem in designing the system control input. Considering the system control input is restricted, the reaching laws proposed in this paper adopt the approach angle and the distance to the sliding surface to regulate the system control input properly. By applying the proposed reaching laws...
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