Efficient realization of infrared coherent radiation by the method of parametric light amplification in nonlinear photonic crystals

The process of parametric amplification of light from short laser pulses in nonlinear photonic crystals is analyzed numerically. The calculations were carried out taking into account the effects of the dispersion of the medium up to the third order and cubic nonlinearity of the Kerr type. It is shown that a change in the size of domains can significantly affect the formation of a signal wave pulse. On the basis of the results obtained, we analyzed the optimal values of the domain size at which the efficient energetic generation of the signal wave is observed.

On the Impact of the Data Acquisition Protocol on ECG Biometric Identification

Electrocardiographic (ECG) signals have been used for clinical purposes for a long time. Notwithstanding, they may also be used as the input for a biometric identification system. Several studies, as well as some prototypes, are already based on this principle. One of the methods already used for biometric identification relies on a measure of similarity based on the Kolmogorov Complexity, called the Normalized Relative Compression (NRC)—this approach evaluates the similarity between two ECG segments without the need to delineate the signal wave. This methodology is the basis of the present work. We have collected a dataset of ECG signals from twenty participants on two different sessions, making use of three different kits simultaneously—one of them using dry electrodes, placed on their fingers; the other two using wet sensors placed on their wrists and chests. The aim of this work was to study the influence of the ECG protocol collection, regarding the biometric identification system’s performance. Several variables in the data acquisition are not controllable, so some of them will be inspected to understand their influence in the system. Movement, data collection point, time interval between train and test datasets and ECG segment duration are examples of variables that may affect the system, and they are studied in this paper. Through this study, it was concluded that this biometric identification system needs at least 10 s of data to guarantee that the system learns the essential information. It was also observed that “off-the-person” data acquisition led to a better performance over time, when compared to “on-the-person” places.

Color Digital Holography Based on Generalized Phase-Shifting Algorithm with Monitoring Phase-Shift

Color digital holography (DH) has been researched in various fields such as the holographic camera and holographic microscope because it acquires a realistic color object wave by measuring both amplitude and phase. Among the methods for color DH, the phase-shifting DH has an advantage of obtaining a signal wave of objects without the autocorrelation and conjugate noises. However, this method usually requires many interferograms to obtain signals for all wavelengths. In addition, the phase-shift algorithm is sensitive to the phase-shift error caused by the instability or hysteresis of the phase shifter. In this paper, we propose a new method of color phase-shifting digital holography with monitoring the phase-shift. The color interferograms are recorded by using a focal plane array (FPA) with a Bayer color filter. In order to obtain the color signal wave from the interferograms with unexpected phase-shift values, we devise a generalized phase-shifting DH algorithm. The proposed method enables the robust measurement in the interferograms. Experimentally, we demonstrate the proposed algorithm to reconstruct the object image with negligibly small conjugate noises.

How Does the Input Signal Shape Affect the Pass Efficiency After Stochastic Resonance?

Stochastic Resonance is a phenomenon first discovered in 1981. The phenomenon describes that under certain conditions, in a non-linear system, a noise added to an input can make the input signal pass the non-linear barrier. This study will investigate how the shape of the input signal wave can affect the output efficiency. A circuit with a noise source, an AC source, a Schmitt trigger (act as the non-linear system) is simulated. Various shapes of the wave were tested in the simulator, which resulted in different spectrums and voltage-time graphs of the output and output efficiencies. After comparing the results for different wave shapes, the pulse wave and the square wave are observed to have the highest output efficiency and signal-to-noise ratio, followed by sinusoidal wave, triangular wave, and sawtooth wave in that order.

Computer-Aided Intracranial EEG Signal Identification Method Based on a Multi-Branch Deep Learning Fusion Model and Clinical Validation

Surgical intervention or the control of drug-refractory epilepsy requires accurate analysis of invasive inspection intracranial EEG (iEEG) data. A multi-branch deep learning fusion model is proposed to identify epileptogenic signals from the epileptogenic area of the brain. The classical approach extracts multi-domain signal wave features to construct a time-series feature sequence and then abstracts it through the bi-directional long short-term memory attention machine (Bi-LSTM-AM) classifier. The deep learning approach uses raw time-series signals to build a one-dimensional convolutional neural network (1D-CNN) to achieve end-to-end deep feature extraction and signal detection. These two branches are integrated to obtain deep fusion features and results. Resampling is employed to split the imbalanced epileptogenic and non-epileptogenic samples into balanced subsets for clinical validation. The model is validated over two publicly available benchmark iEEG databases to verify its effectiveness on a private, large-scale, clinical stereo EEG database. The model achieves high sensitivity (97.78%), accuracy (97.60%), and specificity (97.42%) on the Bern–Barcelona database, surpassing the performance of existing state-of-the-art techniques. It is then demonstrated on a clinical dataset with an average intra-subject accuracy of 92.53% and cross-subject accuracy of 88.03%. The results suggest that the proposed method is a valuable and extremely robust approach to help researchers and clinicians develop an automated method to identify the source of iEEG signals.

The glacier seismo-acoustic monitoring system in the Ukrainian Antarctic Station region

<p>Continuous long-term monitoring of the glacier is not an easy task. For the Woozle Hill ice cap near the Vernadsky Research Station, which is located on Galindez Island (Argentine Islands Archipelago), the task was solved by periodic ice sampling, GNSS measurements, photometry, and the use of GPR in the summer season. Some meteorological parameters were also periodically measured inside the ice cave in the glacier when conditions were favorable. In the past few years, GPR measurements have become more constant, and now they are carried out monthly. For continuous monitoring of the internal stresses of the glacier, we proposed using a network of seismoacoustic mini-arrays located along the perimeter of the glacier. Each array consists of four seismoacoustic sensors arranged in a cross. The length of the line between the extreme sensors reaches 100 meters. Proprietary sensors use an optical system for recording the seismic and infrasonic vibrations. The built-in microcontroller of each sensor transmits the digitized data (16 bit, 100(300) Hz) to the main unit based on the LattePanda, where preprocessing is performed. GPS receiver is also connected here for data synchronization. There is a Wi-Fi module for transmitting data to the collection station. Also, data can be transmitted to the collection station by wires installed on the cable-growth. Power is supplied 220 V through an adapter and a 12V battery. The sensors are waterproof, the rest of the equipment is assembled in a sealed waterproof box. There are three such arrays, in their turn, they form a regular triangle with a side of 700 meters, inside which there is a glacier. The processing consists of detecting signals in each array by the STA / LTA method, followed by correlation processing of the selected data fragment and calculating the azimuth to the signal, wave velocity, period, and amplitude. Also, the isolation of the coherent part of the low-intensity signal at the noise level can be carried out without preliminary STA / LTA detection, using algorithm F-statistics. Correlated interference is clipped in azimuth. The intersection of two or three azimuths allows you to locate the signal source. All parameters of detections with time stamps are recorded in the database and can be further processed using station meteorological data. The system began to be deployed around the glacier in January 2021. The presentation will present the first results of the deployed monitoring system.</p>

Relativistic Equation Failure for LIGO Signals

Signal waves of the monotone increasing frequency detected by LIGO are universally considered to be gravitational waves of spiral binary stars, and the general theory of relativity is thus universally considered to have been confirmed by the experiments. Here we present a universal method for signal wave spectrum analysis, introducing the true conclusions of numerical calculation and image analysis of GW150914 signal wave. Firstly, numerical calculation results of GW150914 signal wave frequency change rate obey the com quantization law which needs to be accurately described by integers, and there is an irreconcilable difference between the results and the generalized relativistic frequency equation of the gravitational wave. Secondly, the assignment of the frequency and frequency change rate of GW10914 signal wave to the generalized relativistic frequency equation of gravitational wave constructs a non-linear equation group about the mass of wave source, and the computer image solution shows that the equation group has no GW10914 signal wave solution. Thirdly, it is not unique to calculate the chirp mass of the wave source from the different frequencies and change rates of the numerical relativistic waveform of the GW150914 signal wave, and the numerical relativistic waveform of the GW150914 signal wave deviates too far from the original waveform actually. Other LIGO signal waveforms do not have obvious characteristics of gravitational frequency variation of spiral binary stars and lack precise data, so they cannot be used for numerical analysis and image solution. Therefore, LIGO signals represented by gw50914 signal do not support the relativistic gravitational wave frequency equation. However, whether gravitational wave signals from spiral binaries that may be detected in the future follow the same co quantization law? The answer is not clear at present.

Relativistic Equation Failure for LIGO Signals

Signal waves of the monotone increasing frequency detected by LIGO are universally considered to be gravitational waves of spiral binary stars, and the general theory of relativity is thus universally considered to have been confirmed by the experiments. Here we present a universal method for signal wave spectrum analysis, introducing the true conclusions of numerical calculation and image analysis of GW150914 signal wave. Firstly, numerical calculation results of GW150914 signal wave frequency change rate obey the com quantization law which needs to be accurately described by integers, and there is an irreconcilable difference between the results and the generalized relativistic frequency equation of the gravitational wave. Secondly, the assignment of the frequency and frequency change rate of GW10914 signal wave to the generalized relativistic frequency equation of gravitational wave constructs a non-linear equation group about the mass of wave source, and the computer image solution shows that the equation group has no GW10914 signal wave solution. Thirdly, it is not unique to calculate the chirp mass of the wave source from the different frequencies and change rates of the numerical relativistic waveform of the GW150914 signal wave, and the numerical relativistic waveform of the GW150914 signal wave deviates too far from the original waveform actually. Other LIGO signal waveforms do not have obvious characteristics of gravitational frequency variation of spiral binary stars and lack precise data, so they cannot be used for numerical analysis and image solution. Therefore, LIGO signals represented by gw50914 signal do not support the relativistic gravitational wave frequency equation. However, whether gravitational wave signals from spiral binaries that may be detected in the future follow the same co quantization law? The answer is not clear at present.

Relativistic Equation Failure for LIGO Signals

Signal waves of the monotone increasing frequency detected by LIGO are universally considered to be gravitational waves of spiral binary stars, and the general theory of relativity is thus universally considered to have been confirmed by the experiments. Here we present a universal method for signal wave spectrum analysis, introducing the true conclusions of numerical calculation and image analysis of GW150914 signal wave. Firstly, numerical calculation results of GW150914 signal wave frequency change rate obey the com quantization law which needs to be accurately described by integers, and there is an irreconcilable difference between the results and the generalized relativistic frequency equation of the gravitational wave. Secondly, the assignment of the frequency and frequency change rate of GW10914 signal wave to the generalized relativistic frequency equation of gravitational wave constructs a non-linear equation group about the mass of wave source, and the computer image solution shows that the equation group has no GW10914 signal wave solution. Thirdly, it is not unique to calculate the chirp mass of the wave source from the different frequencies and change rates of the numerical relativistic waveform of the GW150914 signal wave, and the numerical relativistic waveform of the GW150914 signal wave deviates too far from the original waveform actually. Other LIGO signal waveforms do not have obvious characteristics of gravitational frequency variation of spiral binary stars and lack precise data, so they cannot be used for numerical analysis and image solution. Therefore, LIGO signals represented by gw50914 signal do not support the relativistic gravitational wave frequency equation. However, whether gravitational wave signals from spiral binaries that may be detected in the future follow the same co quantization law? The answer is not clear at present.

Электромагнитные волны в волноводе с периодически модулированным магнитодиэлектрическим заполнением

The propagation of electromagnetic waves in an ideal regular waveguide, filling of which is periodically modulated in space and time, is considered. It is assumed that the modulation depths are small and the modulation of the waveguide filling does not lead to the interaction between different waveguide modes. Wave equations are obtained for transverse-electric (TE) and transverse-magnetic (TM) fields in the waveguide with respect to the longitudinal components of the magnetic and electric vectors, respectively, are obtained. They represent second order partial differential equations with periodic coefficients. By changing the variables these equations are reduced to ordinary differential equations with periodic coefficients of the Mathieu-Hill type. Solutions of these equations are found in the first approximation with respect to small modulation depths in the region of “weak” interaction between the signal wave and the modulation wave (the Wulff-Bragg condition is not satisfied). The obtained results show that TE and TM fields in the waveguide in the above approximation are represented as the sum of three space-time harmonics (zero and plus and minus first) with complicated amplitudes and frequencies.