Multiple-frequency synchronization of the four exciters in a far super-resonant vibrating system with an isolation frame

Generally, the synchronization studies on two or multiple exciters are preconditioned by being a single frequency, while the multiple-frequency synchronization problems in a vibrating system, including double-frequency and triple-frequency, are less considered, which are also very significant in engineering. This paper attempts to solve this issue by considering a dynamical model with an isolation frame, driven by the four exciters. The synchronization for the four exciters and its stability under the double-frequency and triple-frequency conditions are studied in detail. Firstly, the mathematical modeling of the system is established, and the corresponding motion differential equations are derived. Using the asymptotic method and the average method, yields the theoretical condition of implementing multiple-frequency synchronization, and the theoretical condition for stability of the system complies with the Routh–Hurwitz criterion. The dynamic characteristics of the system, including stable phase differences, stability abilities, responses of the system, and relative motion relationship, are qualitatively discussed by numeric. Finally, simulations are performed by applying a Runge–Kutta program to validate the theoretical and numerical qualitative results. It is shown that, by reasonably matching the key parameters of the system, the stronger, stable, and valuable motion states of vibrating machines, including vibration amplitudes, frequencies, and motion trajectory, can be realized, which are exactly the desires in engineering.

Harmoni: a Method for Eliminating Spurious Interactions due to the Harmonic Components in Neuronal Data

Cross-frequency synchronization (CFS) has been proposed as a mechanism for integrating spatially and spectrally distributed information in the brain. However, investigating CFS in Magneto- and Electroencephalography (MEG/EEG) is hampered by the presence of spurious neuronal interactions due to the non-sinusoidal waveshape of brain oscillations. Such waveshape gives rise to the presence of oscillatory harmonics mimicking genuine neuronal oscillations. Until recently, however, there has been no methodology for removing these harmonics from neuronal data. In order to address this long-standing challenge, we introduce a novel method (called HARMOnic miNImization - Harmoni) that removes the signal components which can be harmonics of a non-sinusoidal signal. Harmoni's working principle is based on the presence of CFS between harmonic components and the fundamental component of a non-sinusoidal signal. We extensively tested Harmoni in realistic EEG simulations. The simulated couplings between the source signals represented genuine and spurious CFS and within-frequency phase synchronization. Using diverse evaluation criteria, including ROC analyses, we showed that the within- and cross-frequency spurious interactions are suppressed significantly, while the genuine activities are not affected. Additionally, we applied Harmoni to real resting-state EEG data revealing intricate remote connectivity patterns which are usually masked by the spurious connections. Given the ubiquity of non-sinusoidal neuronal oscillations in electrophysiological recordings, Harmoni is expected to facilitate novel insights into genuine neuronal interactions in various research fields, and can also serve as a steppingstone towards the development of further signal processing methods aiming at refining within- and cross-frequency synchronization in electrophysiological recordings.

HF MODEM CLOCK AND FREQUENCY SYNCHRONIZATION ALGO-RITHM

The article proposes an algorithm for time-frequency synchronization of a high-speed modem operating under conditions of a highly dispersing channel, supplemented by an autocorrelation algorithm. It is shown that under the conditions of ray energy redistribu-tion, the proposed algorithm makes it possible to achieve satisfactory synchronization.

Ultra-high Accuracy Microwave Positioning System based on Free Space Frequency Synchronization

The ultra-high accuracy indoor and outdoor positioning is fundamental for a variety of applications such as industrial automation, Internet of Things and structure monitoring. Approaches based on optical methods, ultrasound and computer vision areoften suffer from limited coverage areas, obstruction by objects and high computing load. While the GNSS and conventionalradar-like radio frequency (RF) methods can suffer from insufficient accuracy and are not feasible for many scenarios. Now weachieve an inverse GPS microwave positioning system based on ultra-stable frequency synchronization in free space andcarrier phase difference principle to surpass the limitation of current methods. The stability of frequency synchronization link isbetter than 10−13/s . The distance resolution retrieved from phase information is 25 micrometres and the Mean Squred Error(MSE) of three-dimensional positioning is 16 micrometres. An ultra-high accuracy positioning system with large coverage area,compatibility and versatility can potentially be achieved gearing to extensive needs.