Applied Mechanics and Materials Vols. 568-570

Abstract: Smart jamming based on convolution modulation brings a great threat to active radar seeker. In order to counter the jamming, a method of orthogonal projection is designed. Firstly, both the mathematic models of linear frequency modulation (LFM) signal and convolution modulation smart jamming are made. Secondly, the anti-interference principle of orthogonal projection is analyzed, on the basis of which a reasonable filter is designed. Thirdly, simulations of signals respectively convolved with noise, triangle pulse sequence and rectangular pulse sequence are made, which verifies its good interference effects. The conclusion is that the method can effectively suppress the convolution modulation smart jamming.

Abstract: Nyquist Folding Receiver is a novel reconnaissance receiver structure which is able to use single ADC to sample Ultra-wideband signals. And the Synchronous Nyquist Folding Receiver (SNYFR) is an improved structure of NYFR. When input is multicomponent single-frequency signal, with the consideration of the characteristics of the output we propose an algorithm of Nyquist Zone(NZ) judgment and parameters estimation based on scaling search in Fractional Fourier Transform (FRFT) domain to avoid detection error occurring when the input signal components locate in the NZ fuzzy area. Computer simulation show that when SNR beyond, the Probability of Correct Decision(PCD) of signal detection can be achieved 100% and the mean square error of parameters estimation can be approached Cramer-Rao Bound(CRB) simultaneously.

Abstract: In this paper, the hyperbolic S-transform (HS-transform) has been generalized with the introduction of the whole time frequency regulation factor and making the HS window function proportional to the square root of the frequency. Meanwhile, combined with the idea of incomplete S-transform, a rapid power quality detection based on generalized HS-transform (GHST) is proposed. Firstly, the fast Fourier transform (FFT) was performed and dynamic measurement was utilized to describe the envelope of power spectrum so as to detect the valid frequency samples of FFT. Then the GHST was specifically performed for these samples and a complex matrix was generated. Finally, these feature vectors extracted from the complex matrix were used to detect the power quality disturbances. Simulation results demonstrate that the proposed method can accurately detect the power quality disturbances with high computation speed and low sensitivity to noise, and it is suitable for practical applications.

Abstract: To deal with the AB data with zero-point drift, Swanson and Schlamminger have proposed a filter method to remove the drift of any desired polynomial order, and then give the best linear unbiased estimator of the observable, on the condition that the order of drift is known. Since this method directly removes the drift, one can not know the tendency of the systematic error. This paper proposes to construct a semiparametric regression model for the data, and then take the penalized least squares method to estimate the observable and the drift tendency simultaneously. Simulation analysis shows that the semiparametric method can reach the same accuracy of the filter method, and the estimation of the drift fits well with its actual value.

Abstract: By combining likelihood estimation method and Kalman filtering tracking approach, feature extraction algorithm was developed in this paper to extract the harmonic feature from the underwater noise radiated by different kinds of ships. The ability of harmonic features extrication algorithm is demonstrated by simulation and real shallow water data set comprised of a number of ships. The processing results of real data set also show that he harmonics of different kinds of ships can be used to separate from each other.

Abstract: The speech aerodynamics signal is one of the most important physiological signal in language research, plays an important role in human phonation process. Recently, there are a lot of equipment for speech aerodynamics signal research, mainly used in the field of medical research. But the supporting software can't satisfy the need of phonetics research. In this paper, according to the need of phonetics research, through the analysis of signal to KAYPENTAX speech aerodynamic devices, and used the MATLAB programming to establish the analysis platform to extracting parameters. The platform can read the NSP format file and output relevant parameters.

Abstract: Strong motion stations have been constructed as a part of earthquake early warning system for high-speed train in China. They are deployed near railways and influenced by train-induced vibration. Then, picking seismic phase, estimating azimuth and extracting predominant frequency become difficult in this scenario. These procedures play a crucial role in locating earthquake, estimating its magnitude and then providing reliable warning to trains. In this paper, instantaneous mixing model was used to describe this problem and show that this influence could be removed by independent component analysis utilizing double sensors.

Abstract: The functional study of artificial heart valve has the positive significance on the postoperative care of the patients with valvular heart disease and the precaution of postoperative complications. The analysis of the heart sounds is the most direct way to estimate the function normally of heart. Because of the heart sound is nonlinear and nonstationary. Compared with the normal method of time-frequency analysis, Hilbert-Huang transform can analyze the nonstationary and nonlinear signals more accurate and more effective. Hilbert-Huang transform is introduced to the functional study of artificial heart valve. It used for extracting the inherent characteristics. Using the empirical mode decomposition (EMD), the heart sound was decomposed into a series of intrinsic mode functions (IMF). The Hilbert spectrum was established by the calculating results of these IMFs. The Hilbert spectrum has the characters of time-frequency-energy, and then the marginal spectrum was structured. Comparison with the characters of pre-operation and post-operation was used for reveal the function of artificial heart valve. At last, we use the short-time average energy and the short-time average range to verify the credibility of Hilbert-Huang transforms method. The result of simulation show that this method was well analyzed the function of artificial heart valve.

Abstract: A variety of coupled hidden Markov models (CHMMs) have recently been proposed as extensions of HMM to better characterize multiple interdependent sequences. The resulting models have multiple state variables that are temporally coupled via matrices of conditional probabilities. A generalised fuzzy approach to statistical modelling techniques is proposed in this paper. Fuzzy C-means (FCM) and fuzzy entropy (FE) techniques are combined into a generalised fuzzy technique and applied to coupled hidden Markov models. The CHMM based on the fuzzy c-means (FCM) and fuzzy entropy (FE) is referred to as FCM-FE-CHMM in this paper. By building up a generalised fuzzy objective function, several new formulae solving Training algorithms are theoretically derived for FCM-FE-CHMM. The fuzzy modelling techniques are very flexible since the degree of fuzziness, the degree of fuzzy entropy.

Abstract: When we use the laser auto collimation theodolite to measure the azimuth error angle of air target, the strong noise background reduces the spot imaging quality and seriously influences the measuring angle ability of the theodolite. In order to solve the problem, a photoelectric detection system used to detect the weak signal is designed based the correlation detection principle and the principle of correlation detection technology is introduced. We use Simulink software presenting a simulation to the detection system and do a feasibility analysis. Finally, it’s proved that the photoelectric detection system could suppress the strong noise background, improve the SNR greatly and detect the weak signal effectively.