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Search results for: time-frequency domain
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High resolution optical time-domain reflectometry using sub-picosecond laser sources
PublicationPrzedstawiono działanie sensorów światłowodowych wykorzystujących reflektometrię optyczną w dziedzinie czasu. Omówiono ograniczenia możliwości pomiarowych tej klasy sensorów wynikające z zastosowania w nich reflektometrów światłowodowych zaprojektowanych do zastosowań w telekomunikacji. Zaprezentowano sensory wykorzystujące specjalizowane reflektometry o dużej rozdzielczości. Przedstawiono koncepcję sensora wykorzystującego dwa...
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A time-frequency method for detection of electromagnetic field interference on metal constructions.
PublicationPrzedstawiono metodę detekcji oddziaływania pola elektromagnetycznego na metalowe konstrukcje podziemne. Polega ona na czasowo-częstotliwościowej analizie rejestrów zmian potencjału źródła pola (np. prądów błądzących) oraz potencjału konstrukcji podziemnej, z wykorzystaniem krótkoczasowej transformaty Fouriera STFT. Wnioski o oddziaływaniu pola na konstrukcję metalową wyciąga się na podstawie analizy uzyskanych widm.
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Metrological characteristics of the flat voltammetric electrode in time domain with a reversible electrochemical reaction running on the surface
PublicationW artykule przedstawiono właściwości metrologiczne płaskich elektrod woltamperometrycznych. Omówiono wpływ napięcia polaryzującego na wartości parametrów charakteryzujących te elektrody.
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A fast time-frequency multi-window analysis using a tuning directional kernel
PublicationIn this paper, a novel approach for time-frequency analysis and detection, based on the chirplet transform and dedicated to non-stationary as well as multi-component signals, is presented. Its main purpose is the estimation of spectral energy, instantaneous frequency (IF), spectral delay (SD), and chirp rate (CR) with a high time-frequency resolution (separation ability) achieved by adaptive fitting of the transform kernel. We...
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THE PROBLEM OF THE CALCULATION OF THE FREQUENCY OF DIAGNOSTIC EXAMINATIONS BASED ON DEVICE’S PROPER OPERATION TIME
PublicationThe paper presents the proposal to apply the normal distribution to solve the problem of the frequency of diagnostic tests. Particular emphasis is placed on simplicity of the method. This method may be useful for the average user technical system. The method reduces the number of assumptions to a minimum. The results do not raise of serious doubts but they require verification of course.
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APPLICATION OF COHEN'S CLASS TIME-FREQUENCY DISTRIBUTIONS IN THE BELOUSOV–ZHABOTINSKY REACTION ANALYSIS
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Application of Cohen's class time-frequency distributions in the Belousov-Zhabotinsky reaction analysis.
PublicationW publikacji przedstawiono analizę rejestrów potencjałowych chemicznej reakcji oscylacyjnej Biełousowa-Żabotyńskiego z wykorzystaniem czasowo-częstotliwościowych rozkładów z klasy Cohen'a. Do analizy zastosowano rozkład Wignera-Ville'a, Choi-Williams'a i stożkowy. Opisano zalety oraz wady powyższych metod oraz wnioski o częstotliwościowej kompozycji oscylacji jakie można wyciągnąć na podstawie uzyskanych spektrogramów.
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Decoding of the FSK signal with noise and distortion with the use of coefficients of the time-frequency transform.
PublicationStreszczenie: Przeanalizowano sygnał z modulacją FSK wykorzystując metodę transformacji czasowo-częstotliwościowej różniące się sposobem podziału płaszczyzny TF na atomy: krótko-okresowej transformacji Fouriera, transformacji falkowej i transformacji pakietami falkowymi. Transformacja falkowa zapewnia dobrą lokalizację czasową zakłóceń o wielkiej częstotliwości, podczas gdy transformacja pakietami falkowymi zapewnia dobrą lokalizację...
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Photoplethysmographic Time-Domain Heart Rate Measurement Algorithm for Resource-Constrained Wearable Devices and its Implementation
PublicationThis paper presents an algorithm for the measurement of the human heart rate, using photoplethysmography (PPG), i.e., the detection of the light at the skin surface. The signal from the PPG sensor is processed in time-domain; the peaks in the preprocessed and conditioned PPG waveform are detected by using a peak detection algorithm to find the heart rate in real time. Apart from the PPG sensor, the accelerometer is also used to...
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TIME-DOMAIN NUMERICAL EVALUATION OF SHIP RESISTANCE AND MOTION IN REGULAR WAVES BY USING THE CFD URANS METHOD
PublicationTaking into account the International Maritime Organisation’s (IMO) strategy to radically reduce the GHG emitted by the shipping industry towards zero emission operation, today's assessment of ship behaviour in waves, its seakeeping characteristics and resistance and their interrelation with fuel consumption and emissions are one of the most attended research subject. There are three methods to conduct this analysis, which are...
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TIME-DOMAIN NUMERICAL EVALUATION OF SHIP RESISTANCE AND MOTION IN REGULAR WAVES BY USING THE CFD URANS METHOD
PublicationTaking into account the International Maritime Organization's (IMO) strategy to radically reduce the...
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A new time-frequency detection method of stray current field interferenceon metal structures.
PublicationA new detection method has been presented of stray current field interference on underground metal structures. The method employs short time Fourier transformation (STFT). This method of analysis allows determination of signal spectral power density changes (e.g., structure potential) in the function of time. In the paper results have been presented of total time–frequency analysis of a pipeline potential in a stray current field...
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Application of the short time Fourier transformation to the continuous frequency method of measurement of electrode impedance
PublicationPrzedstawiona została nowa metoda pomiaru impedancji elektrodowej. Wykorzystuje ona jako pobudzenie niestacjonarny sygnał napięciowy, którego częstotliwość jest liniową funkcją czasu. Zastosowanie transformacji STFT do analizy napięciowego sygnału pobudzenia i odpowiedzi prądowej umożliwia wyznaczenie widma impedancyjnego. Dokładność otrzymywanych wartości impedancji uwarunkowana jest wielkością okna i zastosowanej funkcji analizującej.
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Application of Cohen´s class time-frequency distributions in the Belousov-Zhabotinsky reaction analysis
PublicationPrzedstawiono rezultaty spektralnej analizy rejestrów Biełousowa-Żabotyńskiego za pomocą czasowo-częstotliwościowych metod analizy sygnałów należących do klasy Cohen´a. Przykładowy rejestr zmian potencjału elektrody bromo-selektywnej został poddany analizie z wykorzystaniem rozkładu Wignera-Ville´a oraz rozkładu stożkowego. Zastosowanie powyższych algorytmów pozwoliło na uzyskanie spektrogramów przedstawiających zależność pomiędzy...
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Analytical Expression for the Time-Domain Discrete Green's Function of a Plane Wave Propagating in the 2-D FDTD Grid
PublicationIn this letter, a new closed-form expression for the time-domain discrete Green's function (DGF) of a plane wave propagating in the 2-D finite-difference time-domain (FDTD) grid is derived. For the sake of its verification, the time-domain implementation of the analytic field propagator (AFP) technique was developed for the plane wave injection in 2-D total-field/scattered-field (TFSF) FDTD simulations. Such an implementation of...
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Analytical Expression for the Time-Domain Green's Function of a Discrete Plane Wave Propagating in the 3-D FDTD Grid
PublicationIn this paper, a closed-form expression for the time-domain dyadic Green’s function of a discrete plane wave (DPW) propagating in a 3-D finite-difference time-domain (FDTD) grid is derived. In order to verify our findings, the time-domain implementation of the DPW-injection technique is developed with the use of the derived expression for 3-D total-field/scattered-field (TFSF) FDTD simulations. This implementation requires computations...
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Influence of the Square Wave Voltage on Dynamical Properties of a Flat Voltammetric Electrode in the Time Domain by the Electrochemical Reversible Reaction
PublicationIn this article there is a presentation of the analysis of the polarizing voltage shape influencing dynamic properties of voltammetric electrodes when on their surface reversible reaction takes place in the time domain. The electrode polarization with linearly increasing voltage and with a square component, was analyzed. The analysis that were conducted showed that the voltammetric electrode behaves like a first order transducer....
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Volterra series usefulness in modelling of the time-domain cross-talk phenomena in coupled microstrip lines with nonlinear termination
PublicationW pracy przedyskutowano możliwość wykorzystania szeregów Volterry do analizy zjawiska przesłuchu w sprzężonych liniach mikropaskowych z nieliniowym obciążeniem. Apracowano algorytm metody, zaś uzyskane wyniki numeryczne zweryfikowano poprzez porównania z wynikami badań eksperymentalnych linii obciążonych w torze transmisyjnym diodą Schottky'ego.
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The determination and identification of stray current source influences on buried pipelines using time/frequency analysis
PublicationZaprezentowano metodę detekcji źródła interferencji prądów błądzących na rurociągach podziemnych w aglomeracjach miejskich z wykorzystaniem łącznej analizy czasowo-częstotliwościowej mierzonych sygnałów. Badania przeprowadzono na rurociągu podziemnym zlokalizowanym w sąsiedztwie dwóch trakcji elektrycznych: tramwajowej i kolejowej. Wyniki analiz zaprezentowano w formie spektrogramów, które ilustrują zmiany spektralnej gęstości...
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Estimation of time-frequency complex phase-based speech attributes using narrow band filter banks
PublicationIn this paper, we present nonlinear estimators of nonstationary and multicomponent signal attributes (parameters, properties) which are instantaneous frequency, spectral (or group) delay, and chirp-rate (also known as instantaneous frequency slope). We estimate all of these distributions in the time-frequency domain using both finite and infinite impulse response (FIR and IIR) narrow band filers for speech analysis. Then, we present...
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Cost-Efficient Surrogate Modeling of High-Frequency Structures Using Nested Kriging with Automated Adjustment of Model Domain Lateral Dimensions
PublicationSurrogate models are becoming popular tools of choice in mitigating issues related to the excessive cost of electromagnetic (EM)-driven design of high-frequency structures. Among available techniques, approximation modeling is by far the most popular due to its versatility. In particular, the surrogates are exclusively based on the sampled simulation data with no need to involve engineering insight or problem-specific knowledge....
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Time-domain measurement methods for R, L and C sensors based on aversatile direct sensor-to-microcontroller interface circuit
PublicationtIn the paper new time-domain measurement methods for determining values of resistive (R), inductive(L) and capacitive (C) sensors based on a versatile direct sensor-to-microcontroller interface for microcon-trollers with internal analog-to-digital converters (ADCs) and analog comparators (ACs) are presented.The interface circuit consists of a reference resistor Rrworking as a voltage divider, a given R, L or C sensorand a microcontroller...
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Application of Time-Frequency Analysis of Acoustic Signal to Detecting Flat Places on the Rolling Surface of a Tram Wheel
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3-D finite-difference time-domain modelling of ground penetrating radar for identification of rebars in complex reinforced concrete structures
PublicationThis paper presents numerical and experimental investigations to identify reinforcing bars using the ground penetrating radar (GPR) method. A novel element of the paper is the inspection of different arrangements of reinforcement bars. Two particular problems, i.e. detection of few adjacent transverse bars and detection of a longitudinal bar located over or under transverse reinforcement, have been raised. An attention was also...
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Laboratory Load Model Based on 150 kVA Power Frequency Converter and Simulink Real-Time – Concept, mplementation, Experiments
PublicationFirst section of the paper provides technical specification of laboratory load model basing on 150 kVA power frequency converter and Simulink Real-Time platform. Assumptions, as well as control algorithm structure is presented. Theoretical considerations based on criteria which load types may be simulated using discussed laboratory setup, are described. As described model contains transformer with thyristor-controlled tap changer,...
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Analysis of electrochemical parameters in time domain during the passive layer cracking occurring on the 304L stainless steel in chlorides solution under tensile stresses
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Analysis of electrochemical parameters in time domain during the passive layer cracking occurring on the 304L stainless steel in chlorides solution under tensile stresses.
PublicationDynamiczna Elektrochemiczna Spektroskopia Impedancyjna została wykorzystana do szczegółowej analizy zakresu przejścia stan pasywny - stan aktywny podczas procesu pękania warstwy pasywnej. Wpływ potencjału oraz naprężeń mechanicznych na niszczenie warstwy ochronnej występującej na stali 304L w środowisku 0.5M NaCl w pokojowej temperaturze został przestudiowany. Praca prezentuje chwilowe widma impedancyjne uzyskane przy różnych warunkach...
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Age, frequency of volunteering, and Present-Hedonistic time perspective predict donating items to people in need, but not money to combat COVID-19 during lock-down
PublicationRestrictions due to COVID-19 necessitated staying at home, but in some cases, encouraged charitable behavior, e.g., donating items to people in need (e.g., clothes, food), or money to support combatting COVID-19. Drawing on the previous findings regarding helping during disastrous situations and roles of time perspective in helping behaviors, the study tested the predictive value of age, gender, previous volunteering, altruistic...
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Comments on “Closed Form Variable Fractional Time Delay Using FFT”
PublicationIn this letter drawbacks of the aforementioned paper are pointed out. The proposed approach is improved with minor modifications of the discrete frequency response. This allows for design of fractional delay filters which are close to optimal and can be efficiently implemented in the frequency domain using the sliding DFT based structure. Alternatively, the derived equivalent closed form formulae for offset windows can be used...
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Bearing estimation using double frequency reassignment for a linear passive array
PublicationThe paper demonstrates the use of frequency reassignment for bearing estimation. For this task, signals derived from a linear equispaced passive array are used. The presented method makes use of Fourier transformation based spatial spectrum estimation. It is further developed through the application of two-dimensional reassignment, which leads to obtaining highly concentrated energy distributions in the joint frequency-angle domain...
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A Model-Order Reduction Approach for Electromagnetic Problems With Nonaffine Frequency Dependence
PublicationThe aim of this paper is to present a novel model-order reduction (MOR) technique for the efcient frequency-domain nite-element method (FEM) simulation of microwave components. It is based on the standard reduced-basis method, but the subsequent expansion frequency points are selected following the so-called sparsied greedy strategy. This feature makes it especially useful to perform a fast-frequency sweep of problems that lead...
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Frequency Diagnostics of Transformer Insulating Parameters
PublicationIn the article is presented experimental analysis and diagnostics of insulating system oil-paper for power transformers, mainly by progressive frequency method – dielectric spectroscopy. In the 1-st part of the article is described base theory about measurement and diagnostics insulating part (oil and paper) of power transformers. In the 2-nd part of article is described measuring method of insulating frequency diagnostics - frequency...
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Analysis and interpretation of radiometric signals in a liquid-gas bubble flow
PublicationThe article presents the analysis of signals from a radiometric system consisting of two scintillation probes and two gamma radiation sealed sources. Calculations and interpretation were carried out for the bubble flow of the water-air mixture in the horizontal pipeline. The analysis of the obtained signals was done in time and frequency domain. In the frequency domain, a range of usable frequencies was identified, which were associated...
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FDTD Method for Electromagnetic Simulations in Media Described by Time-Fractional Constitutive Relations
PublicationIn this paper, the finite-difference time-domain (FDTD) method is derived for electromagnetic simulations in media described by the time-fractional (TF) constitutive relations. TF Maxwell’s equations are derived based on these constitutive relations and the Grünwald–Letnikov definition of a fractional derivative. Then the FDTD algorithm, which includes memory effects and energy dissipation of the considered media, is introduced....
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Multiple sound sources localization in real time using acoustic vector sensor
PublicationMethod and preliminary results of multiple sound sources localization in real time using the acoustic vector sensor were presented in this study. Direction of arrival (DOA) for considered source was determined based on sound intensity method supported by Fourier analysis. Obtained spectrum components for considered signal allowed to determine the DOA value for the particular frequency independently. The accuracy of the developed...
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Dynamic mass measurement in checkweighers using a discrete time-variant low-pass filter
PublicationConveyor belt type checkweighers are complex mechanical systems consisting of a weighing sensor (strain gauge load cell, electrodynamically compensated load cell), packages (of different shapes, made of different materials) and a transport system (motors, gears, rollers). Disturbances generated by the vibrating parts of such a system are reflected in the signal power spectra in a form of strong spectral peaks, located usually in...
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Usage of concentrated spectrogram for analysis of acoustical signals
PublicationA novel precise method of signal analysis in the time-frequency domain is presented. A signal energy distribution is estimated by discard and displacement of energy parts of the classical spectrogram. A channelized instantaneous frequency and a local group delay are used in order to energy replacement. Additionally, newly introduced representations such as: a channelized instantaneous bandwidth and a local group duration are used...
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Tolerance-Aware Optimization of Microwave Circuits by Means of Principal Directions and Domain-Restricted Metamodels
PublicationPractical microwave design is most often carried out in the nominal sense. Yet, in some cases, performance degradation due to uncertainties may lead to the system failing to meet the prescribed specifications. Reliable uncertainty quantification (UQ) is therefore important yet intricate from numerical standpoint, especially when the circuit at hand is to be evaluated using electromagnetic (EM) simulation tools. Tolerance-aware...
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Dissecting gamma frequency activities during human memory processing
PublicationGamma frequency activity (30-150 Hz) is induced in cognitive tasks and is thought to reflect underlying neural processes. Gamma frequency activity can be recorded directly from the human brain using intracranial electrodes implanted in patients undergoing treatment for drug-resistant epilepsy. Previous studies have independently explored narrowband oscillations in the local field potential and broadband power increases. It is not...
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Detection of dialogue in movie soundtrack for speech intelligibility enhancement
PublicationA method for detecting dialogue in 5.1 movie soundtrack based on interchannel spectral disparity is presented. The front channel signals (left, right, center) are analyzed in the frequency domain. The selected partials in the center channel signal, which yield high disparity with left and right channels, are detected as dialogue. Subsequently, the dialogue frequency components are boosted to achieve increased dialogue intelligibility....
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The accuracy of pulse rate estimation from the sequence of face images
PublicationThe goal of this paper is to analyze the accuracy of pulse rate estimation from the sequence of face images. Simulated and real signals were used to evaluate two pulse rate estimators; one for frequency domain and the second one for time domain using the autocorrelation function. The results show that the mean difference between the reference measurements and estimated pulse rate values are about 2bpm. In the analysis of short...
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Simulation of Signal Propagation Along Fractional-Order Transmission Lines
PublicationIn this paper, the simulation method of signal propagation along fractional-order (FO) transmission lines is presented. Initially, fractional calculus and the model of FO transmission line are introduced. Then, the algorithm allowing for simulation of the nonmonochromatic wave propagation along FO transmission lines is presented. It employs computations in the frequency domain, i.e., an analytical excitation is transformed to the...
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Improving listeners' experience for movie playback through enhancing dialogue clarity in soundtracks
PublicationThis paper presents a method for improving users' quality of experience through processing of movie soundtracks. The dialogue clarity enhancement algorithms were introduced for detecting dialogue in movie soundtrack mixes and then for amplifying the dialogue components. The front channel signals (left, right, center) are analyzed in the frequency domain. The selected partials in the center channel signal, which yield high disparity...
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Efficient signal processing in spectroscopic optical coherence tomography
PublicationSpectroscopic optical coherence tomography (SOCT) is an extension of a standard OCT technique, which allows to obtain depth-resolved, spectroscopic information on the examined sample. It can be used as a source of additional contrast in OCT images e.g. by encoding certain features of the light spectrum into the hue of the image pixels. However, SOCT require computation of time-frequency distributions of each OCT A-scan, what is...
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Fast bubble dynamics and sizing
PublicationSingle bubble sizing is usually performed by measuring the resonant bubble response using the Dual Frequency Ultrasound Method. However, in practice, the use of millisecond-duration chirp-like waves yields nonlinear distortions of the bubble oscillations. In comparison with the resonant curve obtained under harmonic excitation, it was observed that the bubble dynamic response shifted by up to 20 percent of the resonant frequency...
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GPR simulations for diagnostics of a reinforced concrete beam
PublicationThe most popular technique for modelling of an electromagnetic field, the finite difference time domain (FDTD) method, has recently become a popular technique as an interpretation tool for ground penetrating radar (GPR) measurements. The aim of this study is to detect the size and the position of damage in a reinforced concrete beam using GPR maps. Numerical simulations were carried out using the finite differ-ence time domain...
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THIRD-ORDER EXPONENTIAL INTEGRATOR FOR LINEAR KLEIN–GORDON EQUATIONS WITH TIME AND SPACE-DEPENDANT MASS
PublicationAllowing for space- and time-dependance of mass in Klein–Gordon equations re- solves the problem of negative probability density and of violation of Lorenz covariance of interaction in quantum mechanics. Moreover it extends their applicability to the domain of quantum cosmology, where the variation in mass may be accompanied by high oscillations....
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THIRD-ORDER EXPONENTIAL INTEGRATOR FOR LINEAR KLEIN–GORDON EQUATIONS WITH TIME AND SPACE-DEPENDANT MASS
PublicationAllowing for space- and time-dependance of mass in Klein–Gordon equations re- solves the problem of negative probability density and of violation of Lorenz covariance of interaction in quantum mechanics. Moreover it extends their applicability to the domain of quantum cosmology, where the variation in mass may be accompanied by high oscillations....
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Investigating Feature Spaces for Isolated Word Recognition
PublicationMuch attention is given by researchers to the speech processing task in automatic speech recognition (ASR) over the past decades. The study addresses the issue related to the investigation of the appropriateness of a two-dimensional representation of speech feature spaces for speech recognition tasks based on deep learning techniques. The approach combines Convolutional Neural Networks (CNNs) and timefrequency signal representation...
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On time-dependent nonlinear dynamic response of micro-elastic solids
PublicationA new approach to the mechanical response of micro-mechanic problems is presented using the modified couple stress theory. This model captured micro-turns due to micro-particles' rotations which could be essential for microstructural materials and/or at small scales. In a micro media based on the small rotations, sub-particles can also turn except the whole domain rotation. However, this framework is competent for a static medium....