A New Source Extraction Algorithm for Cyclostationary Sources

Cyclic higher order statistics (CHOS) have powerful signal detection capability and show potential in most mobile communication systems. In this paper, we propose a CMOS-based algorithm to estimate azimuth/elevation using a selected high-resolution planar array to detect nonGaussian coherent cyclostationary sources by designing a fourth-order cyclic cumulant matrix and using eigen vector (EV) approach. For coherent sources caused by multipath propagation, a special forward/backward averaging method is utilized in two-dimension (2-D) case to resolve directions. Simulation results show that, in multipath situation, our algorithm has advantages of suppressing additive stationary noise and Gaussian noise with unknown spatial characteristics, as well as its signal selectivity to remove interferences with different cycle frequencies from the signals of interests (SOI's). Also, array aperture is extended by exploiting a special array geometry.

Most communication signals exhibit cyclostationarity and the overall number of signals impinging on the array is often greater than the number of sensors. In this paper, considering these, we propose a direction-finding algorithm to detect non-Gaussian cyclostationary sources by designing minimum-redundancy linear arrays (MRLAs) based on fourth-order cyclic cumulants using ESPRIT. Simulation results show that our method can effectively suppress additive stationary noise and Gaussian noise in environments where the spatial characteristics of noise are unknown, even when the noise shares the same cycle frequency as the signals of interests (SOIs). Moreover, compared with the designed fourth-order cyclic cumulants method using uniform linear array (ULA), the MRLA method is proved to provide better performance in terms of ability to detect and resolve a greater number of sources. More than 2M-2 sources can be estimated with M sensors.

The application of a refined non-conforming quadrilateral plate bending element in thin plate vibration and stability analysis

The current cargo capacity for aircraft is about 20% of their total weight, increasing this ratio would significantly increase the economics of aircraft logistics. This is why it’s important for material sciences to advance so that the materials used in aircraft construction become lighter while still retaining their structural integrity. In this paper we examined materials used in aircraft construction (steel, aluminum, plastics and composites) at the University of Szeged Faculty of Engineering. Using vibrational analysis we analyzed the test pieces for their natural frequency, we did this to gain insight to the range of frequencies that are least attenuated by the material the aircraft wings are made from. Using the data we gathered we wish to draw conclusions to which materials are more suited for aircraft wing construction.

Discrete singular convolution method for one-dimensional vibration and acoustics problems with impedance boundaries

Blind source separation (BSS) is an emerging field of fundamental research with a wide range of applications such as remote sensing, data communications, speech processing and medical diagnosis. It is motivated by practical scenarios that involve multi-sources and multi-sensors. The key objective of BSS is to retrieve the source signals without resorting to any a priori information about the source signals and the transmission channel. In this paper, a second order statistics based technique and the corresponding algorithm are presented to perform the blind separation of stationary or cyclostationary sources. Finally, a case study with real data having as subject dams displacements monitoring is presented.

Ballistocardiogram (BCG) artifact is considered here as the sum of a number of independent cyclostationary components having the same cycle frequency. Our proposed method, called cyclostationary source extraction (CSE), is able to extract these components without much destructive effect on the background electroencephalogram (EEG). It is shown that the proposed method outperforms other methods particularly in preserving the remaining signals. CSE is utilized to remove the BCG artifact from real EEG data recorded inside the magnetic resonance (MR) scanner, i.e., visual evoked potential (VEP). The results are compared to the results of benchmark BCG removal techniques. Analyzing the power spectral density of the cleaned EEG data, it is shown that CSE effectively removes the frequency components corresponding to the BCG artifact. It is also shown that VEPs recorded inside the scanner and processed using the proposed method are more correlated with the VEPs recorded outside the scanner. Moreover, there is no need for electrocardiogram (ECG) data in this method as the cycle frequency of the BCG is directly computed from the contaminated EEG signals.

Fast Averaged Cyclic Periodogram method to compute spectral correlation and coherence

We propose a new method for blind source separation of cyclostationary sources, whose cyclic frequencies are unknown and may share one or more common cyclic frequencies. The suggested method exploits the cyclic correlation function of observation signals to compose a set of matrices which has a particular algebraic structure. The aforesaid matrices are automatically selected by proposing two new criteria. Then, they are jointly diagonalized so as to estimate the mixing matrix and retrieve the source signals as a consequence. The nonunitary joint diagonalization (NU‐JD) is ensured by Broyden‐Fletcher‐Goldfarb‐Shanno (BFGS) method which is the most commonly used update strategy for implementing a quasi‐Newton technique. The efficiency of the method is illustrated by numerical simulations in digital communications context, which show good performances comparing to other state‐of‐the‐art methods.

"When a vehicle is cruising, unpleasant noise in the high-frequency band between 4 kHz and 5 kHz can occasionally be heard at the centers of front seats in the vehicle cabin. To search for the generation source of this noise, a study of the correlation between the cabin noise and airborne noise at the outer surface of the transmission, and an analysis of vibration transfer paths in the interior of the transmission were conducted. The results indicated that the source was the 0th-order breathing mode unique to electric-drive motors. For making it possible to predict this at the desk, vibrational analysis method for an electric-drive motor comprising laminated electrical steel sheets and segmented coils was proposed. Material property data for the electrical steel sheets and the coils was employed unmodified in the electric-drive motor vibrational analysis model. In addition, Laminate electrical steel sheets and the coils were modeled accurately. The analysis model defined the small sliding contact between the layers and also the contact between the electrical steel sheets and the coils taking into consideration. The contact stiffness between the electrical steel sheets and the coils was defined. First, the results of an eigenvalue analysis of the electrical steel sheets in isolation and of an experimental modal analysis were compared. The natural frequencies and eigenmodes in both sets of results corresponded well, with a difference of within 2%, up to 6 kHz. Next, vibrational analysis was conducted using an electric-drive motor model in which the coils were inserted into the laminated electrical steel sheets. the coil model used a rectangular cross-section, and defined equivalent material properties using a finite element analysis model in order to make it possible to accurately reproduce twist stiffness and bending stiffness. A comparison of the results of the analysis conducted using the electric-drive motor model and the experimental modal analysis using an electromagnetic shaker demonstrated the phenomenon of the peaks of natural frequencies exceeding 2 kHz becoming unclear. In addition, eigenmodes up to 5 kHz, in particular the 0th-order mode at 4.2 kHz, were accurately reproduced. Finally, this electric-drive motor was mounted into a transmission case and the modal analysis of structural vibration was conducted. Consequently, the tendency of the vibration level between the simulation and the measurement agreed well."

By exploiting cyclostationarity of received signals at certain cycle frequency, i.e., evaluating the cyclic correlation or cyclic spectrum of the received signals at certain cycle frequency, the signal-selective time-difference-of-arrival (TDOA) estimation algorithms which based on cyclic statistics are highly tolerant to the interference and Gaussian noise. However, conventional cyclostationary TDOA methods based on the second-order cyclic correlation function or cyclic spectrum will degenerate severely in impulsive noise. In this paper, a new time delay estimation algorithm based on the fractional lower-order statistics (FLOS) and cyclostationarity is proposed for communications signals under non-Gaussian alpha stable distribution impulsive noise. Simulation results show that the proposed method is efficient and stable, and it outperforms the cyclostationarity based multi-cycle and FLOS based methods under impulsive noise and interference.

Cyclostationary signal-processing techniques implemented by means of acousto-optics are considered. Cyclic-processing methods are reviewed and motivated, such as the cyclic correlation and the cyclic spectrum. It is shown that the cyclic correlation can be computed at cycle frequencies of interest by use of one-dimensional time-integrating correlators in additive or multiplicative configurations. Detection of cycle frequencies is briefly considered, and a one-dimensional acousto-optic spectrum-analysis approach is described that is effective for amplitude-modulated signals. The problem of computing the two-dimensional cyclic correlation for all cycle frequencies and lags is then considered. This is accomplished by means of an acousto-optic triple-product processor configured in a manner similar to that used for ambiguity-function generation. The cyclic spectrum can be obtained in a postprocessing step by Fourier transformation of the cyclic correlation in one dimension. Higher-order extensions of the cyclic correlation are also discussed, and it is shown how a two-dimensional slice of the three-dimensional cyclic triple correlation can be computed by use of an acousto-optic four-product processor.

Investigation of stiffness of small wind turbine blade based on vibration analysis technique

With increases in ship size and speed, shipboard vibration becomes a significant concern in the design and construction of vessels. Excessive ship vibration is to be avoided for passenger comfort and crew habitability. In addition to the undesired effects on humans, excessive ship vibration may result in the fatigue failure of local structural members or malfunctioning of machinery and equipment. The propeller induces fluctuating pressure on the surface of the hull, which induces vibration in the hull structure. These pressure pulses acting on the ship hull surface above the propeller are the predominant factor for vibrations of ship structures are taken as excitation forces for forced vibration analysis. Ship structures are complex and may be analyzed after idealization of the structure. Several simplifying assumptions are made in the finite element idealization of the hull structure. In this study, a three-dimensional finite element model representing the entire ship hull, including the deckhouse and machinery propulsion system, has been developed using solid modeling software for local and global vibration analyses. Vibration analyses have been conducted under two conditions: free–free (dry) and in-water (wet). The wet analysis has been implemented using acoustic elements. The total damping associated with overall ship hull structure vibration has been considered as a combination of the several damping components. As a result of the global ship free vibration analysis, global natural frequencies and mode shapes have been determined. Moreover, the responses of local ship structures have been determined as a result of the propeller-induced forced vibration analysis.

Coarse mesh finite element model for cruise ship global and local vibration analysis