Grouping of particles in a wideband ultrasonic field

In this paper, we propose to expand the capabilities of wideband levitation and show the possibility of forming a structure of a complex shape based on focusing a wideband field in a given area. Focusing the field of planar radiating arrays makes it possible to form a region of stable levitation in a plane parallel to the arrays. The counter radiation of the two arrays creates a standing wave, at the nodes of which the particles are grouped. The use of a wideband signal makes it possible to create many stable nodes of standing waves in specified areas, and to realize the required shape of the levitating object. Simultaneous monitoring of multiple particles in a wideband ultrasonic field may become a new direction in the development of methods of acoustic trapping and control of particles, as well as technologies of acoustic tweezers.

Photovoltaic Power Quality Analysis Based on the Modulation Broadband Mode Decomposition Algorithm

The Broadband Mode Decomposition (BMD) method was previously proposed to solve the Gibbs phenomenon that occurs during photovoltaic signal decomposition; its main idea is to build a dictionary which contains signal features, and to search in the dictionary to solve the problem. However, BMD has some shortcomings; especially if the relative bandwidth of the decomposed signal is not small enough, it may treat a square wave signal as several narrowband signals, resulting in a deviation in the decomposition effect. In order to solve the problem of relative bandwidth, the original signal is multiplied by a high-frequency, single-frequency signal, and the wideband signal is processed as an approximate wideband signal. This is the modulation broadband mode decomposition algorithm (MBMD) proposed in this article. In order to further identify and classify the disturbances in the photovoltaic direct current (DC) signal, the experiment uses composite multi-scale fuzzy entropy (CMFE) to calculate the components after MBMD decomposition, and then uses the calculated value in combination with the back propagation (BP) neural network algorithm. Simulation and experimental signals verify that the method can effectively extract the characteristics of the square wave component in the DC signal, and can successfully identify various disturbance signals in the photovoltaic DC signal.

ОСОБЛИВОСТІ ОБРОБКИ ТА ОЦІНЮВАННЯ ВЗАЄМНОЇ ЗАТРИМКИ ВИПАДКОВИХ ШИРОКОСМУГОВИХ СИГНАЛІВ НА ТЛІ НЕГАУСОВИХ ЗАВАД

Peculiarities of operation conditions of methods and tools for assessing delay and angular position of the source of a random wideband signal when it is received by two spatially displaced sensors are analyzed. Special attention is paid to modeling of possible non-Gaussian noise and analyzing its effect on estimation results. It is assumed that digital processing of received signals is carried out in intervals of certain duration (parts of a second). The first feature is that, unlike many other applications of cross-correlation processing of received broadband signals or their analogs, the information component is characterized by possible nonstationarity both in terms of power and, accordingly, the signal-to-noise ratio, and spectral composition of oscillations. The second feature is that both due to possible low signal-to-noise ratios in some areas, and as a result of non-Gaussian noise, that usually has a distribution with heavy tails, abnormal estimates of the delay, and angular position of a source are possible. In such situations, it is desirable to apply a method for estimating the delay of random broadband signals, which will be robust to non-Gaussian noise and exclude abnormal estimates or at least to the maximum extent reduce the probability of their occurrence. The purpose of this work is to study the possibilities of using other measures of similarity and analysis of processing efficiency. It is shown that this can be achieved due to the use of methods based on the calculation of robust distances. The efficiency of various modifications of the proposed method is shown depending on the intensity and impulsivity of the noise. Following various criteria, the efficiency of processing is assessed and the need for automatic obtaining of information about the noise characteristics is shown. The studies are carried out using a test wideband signal. The tasks that must be solved first of all to ensure a high efficiency of processing are formulated. The results obtained in the simulation process can be used in many technical fields, where the processing of the received signal in hard noise conditions is kept.