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Wyniki wyszukiwania dla: high-frequency data
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Dew and hoarfrost frequency, formation efficiency and chemistry in Wroclaw, Poland
PublikacjaThis article presents the results of a research study concerning a comparison of frequency, formation efficiency and basic physico-chemical properties of dew and hoarfrost in urban conditions. Longer than two-year series of measurements was carried out from 1 February 2008 to 10 March 2010 in Wroclaw, Poland. Sampling of atmospheric deposits was made by means of insulated plain passive radiative condensers, which allowed to collect...
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Detection of People Swimming in Water Reservoirs with the Use of Multimodal Imaging and Machine Learning
PublikacjaEvery year in many countries, there are fatal unintentional drownings in different water reservoirs like swimming pools, lakes, seas, or oceans. The existing threats of this type require creating a method that could automatically supervise such places to increase the safety of bathers. This work aimed to create methods and prototype solutions for detecting people bathing in water reservoirs using a multimodal imaging system and...
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THE APPLICATION OF THE MECHANOCHEMICAL SYNTHESIS FOR THE PREPARATION OF ADVANCED CERAMICS BASED ON BARIUM TITANATE
PublikacjaIn the present study, the lead-free BaTi1-xZrxO3 (for x = 0, 0.05 and 0.15) ceramics were prepared by High-Energy Ball Milling and heat treatments. The performed X-ray, SEM and EDS measurements confirmed high purity, good quality and the expected quantitative composition of the obtained samples. The study of dielectric properties was performed by means of broadband dielectric spectroscopy at the frequency ranging from 0.1 Hz to...
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A Model-Order Reduction Approach for Electromagnetic Problems With Nonaffine Frequency Dependence
PublikacjaThe 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 Guided Generalized Adaptive Notch Filtering - Tracking Analysis and Optimization
PublikacjaGeneralized adaptive notch filters (GANFs) are estimators of coefficients of quasi-periodically time-varying systems, encountered e.g., in RF applications when Doppler effect takes place. Current state of the art GANFs can deliver highly accurate estimates of system variations’ frequency, but underperform in terms of accuracy of system coefficient estimates. The paper proposes a novel multistage GANF with improved coefficient...
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Chirp Rate and Instantaneous Frequency Estimation: Application to Recursive Vertical Synchrosqueezing
PublikacjaThis letter introduces new chirp rate and instantaneous frequency estimators designed for frequency-modulated signals. These estimators are first investigated from a deterministic point of view, then compared together in terms of statistical efficiency. They are also used to design new recursive versions of the vertically synchrosqueezed short-time Fourier transform, using a previously published method (D. Fourer, F. Auger, and...
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Generalized Chebyshev Bandpass Filters With Frequency-Dependent Couplings Based on Stubs
PublikacjaThis paper presents an accurate synthesis method for inline and cross-coupled generalized Chebyshev bandpass filters with frequency-dependent couplings implemented via open and short stubs. The technique involves the synthesis of a lumped-element prototy pe in the form of a coupling matrix with a frequency-dependent term and the conversion of this prototype to a distributed-element mode l composed of sections of TEM lines. This...
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Assessment of Fuel Cells’ State of Health by Low-Frequency Noise Measurements
PublikacjaWe proposed applying low-frequency (flicker) noise in proton-exchange membrane fuel cells under selected loads to assess their state of health. The measurement set-up comprised a precise data acquisition board and was able to record the DC voltage and its random component at the output. The set-up estimated the voltage noise power spectral density at frequencies up to a few hundred mHz. We observed the evolution of the electrical...
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A fast time-frequency multi-window analysis using a tuning directional kernel
PublikacjaIn 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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Accurate design of pseudoelliptic inline SIW filters with frequency-dependent couplings
PublikacjaThis paper presents an accurate synthesis method for inline SIW (Substrate Integrated Waveguide) generalized Chebyshev bandpass filters with frequency-dependent couplings. The technique is based on the synthesis of a coupling matrix that takes into account the impedance of the frequency-dependent stub. Thus, a loading effect compensation in adjacent resonators (via resonant frequency adjustment) and coupling elements (via coupling-value...
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Throughput-Coverage Characteristics for Soft and Partial Frequency Reuse in the LTE Downlink
PublikacjaThe paper presents results of simulation and evaluation of throughput-coverage characteristics for the OFDMA-based LTE network with Soft Frequency Reuse or Partial Frequency Reuse. Firstly, simulation results of throughput characteristics for a single user connection are presented, which allow the evaluation of the stability and availability of bit rate achieved in different areas of a cell. Secondly, the capacity characteristics...
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Bearing estimation using double frequency reassignment for a linear passive array
PublikacjaThe 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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TIME- AND FREQUENCY-DOMAIN QUASI-2D SMALL-SIGNAL MOSFET MODELS
PublikacjaA novel approach to small-signal MOSFET modeling is presented in this book. As a result, time- and frequency-domain physics-based quasi-2D NQS four-terminal small-signal MOSFET models are proposed. The time-domain model provides the background to a novel DIBL-included quasi‑2D NQS four-terminal frequency-domain small-signal MOSFET model. Parameters and electrical quantities of the frequency-domain model are described by explicit...
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Fast surrogate-assisted frequency scaling of planar antennas with circular polarisation
PublikacjaIn this work, the problem of computationally efficient frequency scaling (re-design) of circular polarisation antennas is addressed using surrogate-assisted techniques. The task is challenging and requires the identification of the optimum geometry parameters to enable the operation of the re-designed structure at a selected (required) centre frequency. This involves handling several performance figures such as the antenna gain,...
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Identification of quasi-periodically varying systems with quasi-linear frequency changes
PublikacjaThe problem of identification of linear quasi-periodically varying systems is considered. This problem can be solved using generalized adaptive notch filtering (GANF) algorithms. It is shown that accuracy of system parameter estimation can be increased if the results obtained from GANF are further processed using a cascade of appropriately designed filters. The resulting generalized adaptive notch smoothing (GANS) algorithms can...
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Using Fast Frequency Hopping Technique to Improve Reliability of Underwater Communication System
PublikacjaAcoustic underwater communication systems designed to work reliably in shallow coastal waters must overcome major limitations such as multipath propagation and the Doppler effect. These restrictions are the reason for the complexity of receivers being built, whose task is to decode a symbol on the basis of the received signal. Additional complications are caused by the low propagation speed of the acoustic wave in the water and...
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Parametry uziemień przy przebiegach udarowych i wysokoczęstotliwościowych
PublikacjaW artykule skupiono się na porównaniu dwóch metod badania impedancji uziemienia odgromowego: udarowej z wysoką częstotliwościową. Zestawiono wyniki pomiarów istniejących uziemień z wynikami komputerowych obliczeń symulacyjnych przeprowadzonych w środowisku programu PSIM. Uzyskane wyniki wskazują na poprawność przyjętego toku modelowania, a uzyskane w ten sposób dane mogą być przydatne w fazie projektowania do szacowania...
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Low-frequency noise in ZrS3 van der Waals semiconductor nanoribbons
PublikacjaWe report the results of the investigation of low-frequency electronic noise in ZrS3 van der Waals semiconductor nanoribbons. The test structures were of the back-gated field-effect-transistor type with a normally off n-channel and an on-to-off ratio of up to four orders of magnitude. The current–voltage transfer characteristics revealed significant hysteresis owing to the presence of deep levels. The noise in ZrS3 nanoribbons...
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Rapid Microwave Design Optimization in Frequency Domain Using Adaptive Response Scaling
PublikacjaIn this paper, a novel methodology for cost-efficient microwave design optimization in the frequency domain is proposed. Our technique, referred to as adaptive response scaling (ARS), has been developed for constructing a fast replacement model (surrogate) of the high-fidelity electromagnetic-simulated model of the microwave structure under design using its equivalent circuit (low-fidelity model). The basic principle of ARS is...
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Multiple-channel frequency-adaptive active vibration control using SONIC
PublikacjaSONIC (self-optimizing narrowband interference canceller) is an acronym of a new approach to rejection of sinusoidal disturbances acting at the output of a discretetime stable linear plant with unknown and possibly timevarying dynamics. The paper presents two frequency-adaptive extensions of the multivariate SONIC algorithm. The efficacy of the proposed solutions is tested using our laboratory-scale active vibration control plant.
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Substrate Integrated Waveguide-Based Frequency-Tunable Self-Octaplexing Antenna
PublikacjaThis communication presents the first-ever substrate integrated waveguide (SIW)-based frequency-tunable self-octaplexing antenna (SOA) for wireless communication. The structure is arranged by implementing eight distinct patches with planar 50-ohm feedlines at the top of the SIW cavity, which realize eight distinct resonant frequencies. Independent tuning of each resonant frequency is achieved by incorporating appropriately allocated...
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Resonance Frequency Calculation of Spherical Microstrip Structure Using Hybrid Technique
PublikacjaIn this paper the spherical microstrip structure is considered. The structure is composed of a metallic patch with an arbitrary shape placed on a dielectric coated metallic sphere. In the analysis the hybrid technique is utilized. In this approach the finite-difference technique is applied in a cavity model to determine the current basis functions on the patch. Next, using method of moments, the resonance frequency of the structure...
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Time-frequency analysis in optical coherence tomography for technical objects examination
PublikacjaOptical coherence tomography (OCT) is one of the most advanced optical measurement techniques for complex structure visualization. The advantages of OCT have been used for surface and subsurface defect detection in composite materials, polymers, ceramics, non-metallic protective coatings, and many more. Our research activity has been focused on timefrequency spectroscopic analysis in OCT. It is based on time resolved spectral analysis...
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A spice equivalent circuit for modeling the performance of dual frequency echo-sounder
PublikacjaThe paper presents novel network equivalent circuit of piezoceramic circular disc transducers that takes into account thickness and radial mode of vibrations. The starting point of the analysis is 4-port description of circular disc element representing the solution of wave equation set in radial and thickness directions. The approximate solution for harmonic case is represented in the form of 4x4 matrix, which is synthesised and...
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A Novel Synthesis Technique for Microwave Bandpass Filters with Frequency-Dependent Couplings
PublikacjaThis paper presents a novel synthesis technique for microwave bandpass filters with frequency-dependent couplings. The proposed method is based on the systematic extraction of a dispersive coupling coefficient using an optimization technique based on the zeros and poles of scattering parameters representing two coupled resonators.The application of this method of synthesis is illustrated using two examples involving four and five-pole...
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Fracture surface topography measurements analysis of low-alloyed corrosion resistant steel after bending-torsion fatigue tests
PublikacjaIn this paper, an assessment of a topography measurement method for fracture surfaces of 10HNAP steel after bending-torsion fatigue tests was performed. Surface roughness was measured by using a non-contact Focus Variation Microscopy (FVM) technique in which the non-measured points (NMPs) and outliers (spikes) were removed by the application of general methods. The results revealed, that the optical measurement method introduced...
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Electromagnetic Field Measurements of Bow Thruster Drive with Frequency Converter
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First natural transverse frequency of truncated cone and wedge beams
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Natural Frequency of Rc Walls with Various Sizes And Locations of Opening
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Errors analysis of differential single-frequency geo-positioning algorithm
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Influence of the operating frequency on DC-DC converters for HVDC grids
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Dual-Frequency Induction Heating Generator With Adjustable Impedance Matching
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Assessing Grounding Frequency using Ship Traffic and Waterway Complexity
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Frequency response based identification of fractional order dynamical systems
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Stereometry of turned surfaces in a frequency-domain formulation of profile irregularities
PublikacjaPrzedstawiono częstotliwościowe składowe nierówności powierzchni toczonych. Ponieważ nierówności mają charakter szerokopasmowy, trudny do wartościowania parametrami normatywnymi, zastosowano ich analizę amplitudowo-częstotliwościową, opartą na szybkiej transformacie Fouriera. Przedstawiono kształtowanie nierówności wzdłużnych dla toczenia. Zaproponowano oryginalny układ pomiaru sygnału przemieszczeń narzędzia względem przedmiotu...
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On the use of instantaneous complex frequency for analysis and modification of simple sounds
PublikacjaW pracy przedstawiono możliwości wykorzystania zespolonej pulsacji chwilowej do analizy i modyfikacji prostych dźwięków. Opisywany algorytm składa się z dwóch kroków: bifaktoryzacji sygnału na obwiednię minimalnofazową i fazor dodatnipskrętny, a następnie estymacja i modyfikacja zespolonej pulsacji chwilowej obu czynników faktoryzacji.
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Design and evaluation of a flow-to-frequency converter circuit with thermal feedback
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Frequency distribution of chemical oscillations in the closed Belousov Zhabotinsky reaction.
PublikacjaW publikacji przedstawiono wykorzystanie metody STFT (krótkoczasowej transformaty Fouriera) do analizy oscylacji chemicznych. Badano rejestry potencjałowe reakcji Biełousowa Żabotyńskiego. Wykazano niestacjonarność analizowanych przebiegów. Wykazano liniową zależność pomiędzy częstotliwością oscylacji a stężeniem jednego z komponentów reakcji (bromian potasu). Udowodniono przydatność analizy czasowo-częstotliwościowej do analizy...
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Time-frequency characteristics of chemical oscillations. Experimental and model studies.
PublikacjaW publikacji zaprezentowano wykorzystanie czasowo-częstotliwościowych metod analizy sygnałów niestacjonarnych do badania reakcji Biełousowa-Żabotyńskiego. Zastosowanie krótkoczasowej transformaty Fouriera (STFT) pozwoliło na uzyskanie spektrogramów przedstawiających zmiany energii i częstotliwości oscylacji w trakcie trwania reakcji chemicznej. Przedyskutowano podobieństwa i różnice pomiędzy spektrogramami wygenerowanych dla eksperymentalnych...
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Study on the time-frequency analysis of nonstationary, electrochemical and corrosion processes
PublikacjaW pracy przedstawiono możliwości zastosowania czasowo-częstotliwościowych metod analizy sygnałów do badania niestacjonarnych procesów elektrochemicznych, chemicznych i korozyjnych. Wnikliwej analizie z wykorzystaniem metod STFT, rozkładu Wignera-Ville'a oraz przekształceń z klasy Cohena poddano rejestry oscylacji chemicznych, elektrochemicznych i rejestry korozji wżerowej.
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Application of residual current devices in electrical installations with frequency converters
PublikacjaW instalacjach elektrycznych, w których znajdują się przemienniki częstotliwości mogą pojawić się prądy zwarcia doziemnego o różnej częstotliwości lub stałe. Większość wyłączników różnicowoprądowych nie reaguje na tego typu prądy, co powoduje, że ochrona przeciwporażeniowa jest nieskuteczna. W obwodach z przemiennikami częstotliwości mogą pojawiać się przejściowe i ustalone prądy upływowe o znacznych wartościach. Prądy te znacząco...
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Application of time-frequency methods for analysis of dynamic silo flow
PublikacjaW artykule przedstawiono możliwość stosowania metod czasowo-częstotliwościowych w analizie dynamicznego przepływu materiału sypkiego w silosie. W pracy omówiono wyniki FT (Fourier Transform), STFT (Short Time Fourier Transform) oraz WT (Wavelet Transform)
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A Compact Basis for Reliable Fast Frequency Sweep via the Reduced-Basis Method
PublikacjaA reliable reduced-order model (ROM) for fast frequency sweep in time-harmonic Maxwell’s equations by means of the reduced-basis method is detailed. Taking frequency as a parameter, the electromagnetic field in microwave circuits does not arbitrarily vary as frequency changes, but evolves on a very low-dimensional manifold. Approximating this low-dimensional manifold by a low dimension subspace, namely, reduced-basis space, gives...
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Generalized adaptive notch filters with frequency debiasing for tracking of polynomial phase systems
PublikacjaGeneralized adaptive notch filters are used for identification/tracking of quasi-periodically varying dynamic systems and can be considered an extension, to the system case, of classical adaptive notch filters. For general patterns of frequency variation the generalized adaptive notch filtering algorithms yield biased frequency estimates. We show that when system frequencies change slowly in a smooth way, the estimation bias can...
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A review of design approaches for the implementation of low-frequency noise measurement systems
PublikacjaElectronic noise has its roots in the fundamental physical interactions between matter and charged particles, carrying information about the phenomena that occur at the microscopic level. Therefore, Low-Frequency Noise Measurements (LFNM) are a well-established technique for the characterization of electron devices and materials and, compared to other techniques, they offer the advantage of being non-destructive and of providing...
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Design of Frequency-Reconfigurable Branch-Line Crossover Using Rectangular Dielectric Channels
PublikacjaThis paper presents an efficient yet straightforward passive reconfiguration technique to tune the operating frequency of a branch-line crossover (BLCO). The underlying principle is to fill rectangular dielectric channels (RDCs) prepared beforehand with either air or materials of different relative permittivity. Two configurations (one RDC and three RDCs in each arm) of the branch-line crossover are employed to estimate the tunability...
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Influence of a Radio Frequency on RF Fingerprinting Accuracy Based on Ray Tracing Simulation
PublikacjaIn this paper the influence of a radio signal frequency on performance of Indoor Positioning System based on fingerprinting has been examined using ray-tracing simulations. It has been simulated how spatial distribution of an RF signal strength change with the signal’s frequency. The results were used to show its’ impact on the behavior of localization algorithms that are employing RSS measurements to determine node’s position...
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SONIC - Self-optimizing narrowband interference canceler: comparison of two frequency tracking strategies
PublikacjaThis paper presents a new approach to rejection of complex-valued sinusoidal disturbances acting at the output of a discrete-time linear stable plant with unknown and possibly time-varying dynamics. It is assumed that both the instantaneous frequency of the sinusoidal disturbance and its amplitude may be slowly varying with time and that the output signal is contaminated with wideband measurement noise. The proposed disturbance...
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Continuous wave sonar with hyperbolic frequency modulation keyed by pseudo-random sequence
PublikacjaA CW FM type sounding signal is used in the classical solution of silent sonar. While the signal provides a relatively simple implementation of digital signal processing, and ensures good detection conditions, unfortunately, in the presence of the Doppler effect, distance measurement results tend to be wrong. This is due to the fact that the received signal’s instantaneous frequency value is dependent both on the distance to the...
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THE PROBLEM OF THE CALCULATION OF THE FREQUENCY OF DIAGNOSTIC EXAMINATIONS BASED ON DEVICE’S PROPER OPERATION TIME
PublikacjaThe 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.