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1

Extracting selected tilted fibre Bragg gratings spectrum features

Dziuba-Kozieł Marta, Kozieł Grzegorz

Advances in Science and Technology. Research Journal

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2025

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Vol. 19, no. 12

1--16

EN

Tilted fibre Bragg gratings (TFBG) are used as sensors in the measurement of many physical and chemical quantities. Measurement is performed indirectly by analysing the power of light transmitted at a specific wavelength or in a selected range of light wavelengths. The wavelengths to be used are chosen arbitrarily by the researcher. However, a change of parameters of the TFBG grating requires reselection of the wavelengths to be used in the measurement. Due to the fact that the TFBG spectrum most often shows the most significant sensitivity to changes in the measured parameters in the cladding mode range or a shift of the Bragg resonance, these are most often used in measurements. The need for human selection of the wavelength range to use was the motivation to undertake research into a method for automatic feature extraction of the TFBG spectrum. The method is designed to enable the identification of the cladding mode minima, the range of wavelengths at which they occur, and the wavelength at which the Bragg resonance occurs. In addition, the heights of the cladding mode minima and the Bragg mode were calculated. The developed algorithm detects key features of TFBG transmission spectra for both P and S polarisation. It automatically identifies the cladding mode range, including their minima and maxima. Furthermore, it allows the determination of the position and height of the Bragg mode for TFBGs with tilt angles up to 6 degrees. The present solution is a pioneering work providing a basis for automating the selection of wavelength ranges or spectrum features for use in TFBG-based sensors.

2

Recovering the shape of an equilateral quantum tree with the Dirichlet conditions at the pendant vertices

Dudko Anastasia, Lesechko Oleksandr, Pivovarchik Vyacheslav

Opuscula Mathematica

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2024

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Vol. 44, no. 5

689--705

EN

We consider two spectral problems on an equilateral rooted tree with the standard (continuity and Kirchhoff’s type) conditions at the interior vertices (except of the root if it is interior) and Dirichlet conditions at the pendant vertices (except of the root if it is pendant). For the first (Neumann) problem we impose the standard conditions (if the root is an interior vertex) or Neumann condition (if the root is a pendant vertex) at the root, while for the second (Dirichlet) problem we impose the Dirichlet condition at the root. We show that for caterpillar trees the spectra of the Neumann problem and of the Dirichlet problem uniquely determine the shape of the tree. Also, we present an example of co-spectral snowflake graphs.

3

The spectrum behaviors of light waves on scattering from PT-symmetric semi-soft boundary medium

Xiao Yingying, Liu Chang, Wu Hao, Wang Tao

Optica Applicata

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2024

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Vol. 54, nr 4

511--522

EN

The spectrum behaviors of light waves on scattering from a novel kind of medium, i.e., the PT-symmetric semi-soft boundary medium, were discussed, and the dependence of the presentation of the far-zone scattered spectrum on the characteristics of the scattering medium was investigated. The results show that spectral shifts and spectral switches can be discovered in the scattered field, and the direction of spectral switch is closely related to the non-Hermitian parameter, the boundary characteristic, and the effective width of the scattering medium. These results will further enrich the scattering theory and may have some applications in the reconstruction of the structural information of scattering medium.

4

Radio Altimeter with J-correlation Signal Processing

Sorochan Anatolii, Pawęska Marcin, Kharchenko Volodymyr

Logistics and Transport

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2024

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Vol. 61-62, No. 1-2

115--123

EN

A new approach to the construction of a radio altimeter based on J-correlation processing is proposed. Its operation is based on the transformation of the modulation index of the probing signal into a functionally dependent on the space-time delay. The structural scheme of the device is given, and the signal processing of the device is analyzed. The characteristic of the altitude meter is obtained. For the radio altitude meter of low altitudes (1500 m) the FM signal modulated by a single-tone harmonic oscillation with the following parameters is used: modulating frequency 70 kHz; width of the signal spectrum not more than 1 MHz, measurement accuracy not worse than 0.15 meters.

5

Suitability of acoustic power amplifiers as power amplifiers in underwater communication systems

Schmidt Aleksander M., Schmidt Jan H., Kochańska Iwona

International Journal of Electronics and Telecommunications

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2024

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Vol. 70, No. 4

831-838

EN

The paper presents selected acoustic power amplifiers from among those currently available. The results of a series of measurements characteris ing the amplifiers are presented. The measured amplitude and phase characteristics as a function of frequency for four selected amplifiers are analysed. The spectra of the output signal in the band from 4 kHz to 30 kHz are presented. The usefulness of the selected amplifiers in an underwater communication system is assessed.

6

A modified method of spectral analysis of radio signals using the operator approach for the fourier transform

Sobchuk Valentyn, Laptiev Serhii, Laptievа Tetiana, Barabash Oleg, Drobyk Oleksandr, Sobchuk Andrii

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2024

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T. 14, nr 2

56--61

EN

The article proposes the improved method of spectral analysis of radio signals. The improvement is achieved due to the use of special operators in the signal conversion process. This allows you to distinguish the signal accurately and to determine its characteristics at the background of many airspace obstacles. The obtained graphical results fully confirm the advantages of the proposed method. The simulation results proved the advantage of the improved method of spectral analysis of radio signals; the advantage is achieved through the usage summing matrix functions in the process of signals conversion. The proposed improved method increases the accuracy of signals detection of secretly obtaining information means by 12%.

PL

W artykule zaproponowano udoskonaloną metodę analizy widmowej sygnałów radiowych. Poprawę osiąga się dzięki zastosowaniu specjalnych operatorów w procesie konwersji sygnału. Pozwala to na dokładne rozróżnienie sygnału i określenie jego charakterystyki na tle wielu przeszkód w przestrzeni powietrznej. Uzyskane wyniki graficzne w pełni potwierdzają zalety proponowanej metody. Wyniki symulacji wykazały przewagę udoskonalonej metody analizy widmowej sygnałów radiowych; zaletę uzyskuje się poprzez wykorzystanie funkcji macierzy sumującej w procesie konwersji sygnałów. Zaproponowana udoskonalona metoda zwiększa o 12% dokładność wykrywania sygnałów tajnego pozyskiwania informacji.

7

The cello sound generation mechanism in vibroacoustic studies of the impact of the endpin material on the cello sound

Gorazd Łukasz, Pochel Maja

Vibrations in Physical Systems

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2023

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Vol. 34, nr 2

art. no. 2023201

EN

The aim of the paper is to present the structure of the mechanism that excites the cello strings to vibrate, used in vibroacoustic research of the impact of the endpin material on the cello sound. The construction of the device is inspired by the hurdy-gurdy mechanism. In the acoustic study of string instruments, it is hard to take into account the human factor during the generation of sound. When playing an instrument, there is difficulty in obtaining repeatability of the generated sound, especially with a large number of repetitions. The presented device is particularly useful during vibroacoustic tests of bowed string instruments. It enables the generation of continuous sound and ensures the repeatability of excitation. In addition to the description of the construction of the mechanism, vibroacoustic tests related to the determination of the influence of the cello endpin material on its timbre were also presented. The impact of the endpin material on the cello sound was determined based on measurements as well as subjective impressions of the musicians.

8

Wykorzystanie rekonfigurowalnych matryc antenowych wraz z informacją kontekstową

Kułacz Łukasz, Kliks Adrian

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2023

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nr 4

281--284

PL

Rekonfigurowale matryce antenowe mogą zostać użyte z powodzeniem do sterowania środowiskiem radiowym. Proste sterowanie kątem odbicia sygnału od powierzchni pozwala na maksymalizację lub minimalizację odbieranej mocy w określonych miejscach. W artykule przedstawiono symulacje, gdzie możliwy jest odbiór sygnału w miejscu, w którym nie było to możliwe, wykrycie zajętości widma w miejscu, w którym detektor nie był w stanie dokonać prawidłowej detekcji, czy zminimalizowanie zakłóceń w konkretnym odbiorniku.

EN

Reconfigurable intelligent surfaces can be successfully used to control the radio environment. Simple control of the reflection angle of the signal from the surface allows maximization or minimization of the received power in specific places. The paper presents simulations where it is possible to receive a signal in a place where it was not possible, to detect the occupancy of the spectrum in a place where the sensor was unable to make correct detection or to minimize interference in a specific receiver.

9

A note on Hausdorff convergence of pseudospectra

Lindner Marko, Schmeckpeper Dennis

Opuscula Mathematica

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2023

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Vol. 43, no. 1

101--108

EN

For a bounded linear operator on a Banach space, we study approximation of the spectrum and pseudospectra in the Hausdorff distance. We give sufficient and necessary conditions in terms of pointwise convergence of appropriate spectral quantities.

10

Porównanie metod detekcji zajętości widma radiowego z wykorzystaniem uczenia federacyjnego z oraz bez węzła centralnego

Kułacz Łukasz

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2022

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nr 4

421--424

PL

Systemy dynamicznego dostępu do widma w celu podjęcia decyzji o przydziale widma dla nowego urządzenia przeważnie wymagają informacji o zajętości widma, a tym samym o obecności innych użytkowników. Proste metody detekcji zajętości widma są często dalekie od niezawodnych, stąd często i z powodzeniem stosowane są algorytmy detekcji zajętości widma wspierane uczeniem maszynowym czy też sztuczną inteligencją. W celu ochrony prywatności danych użytkowników i redukcji ilości danych kontrolnych przekazywanych w systemie interesującym podejściem okazuje się użycie federacyjnego uczenia maszynowego. W tej pracy porównane zostały dwa podejścia do projektowania systemu wykorzystujące federacyjne uczenie maszynowe: z wykorzystaniem węzła centralnego oraz bez wykorzystania węzła centralnego.

EN

Dynamic spectrum access systems typically require information about the spectrum occupancy and thus the presence of other users in order to make a spectrum allocation decision for a new device. Simple methods of spectrum occupancy detection are often far from reliable, hence spectrum occupancy detection algorithms supported by machine learning or artificial intelligence are often and successfully used. To protect the privacy of user data and to reduce the amount of control data, an interesting approach is to use federated machine learning. This paper compares two approaches to system design using federated machine learning: with and without a central node.

11

On spectrum of Metzler matrices

Domka Michał, Mitkowski Wojciech

Przegląd Elektrotechniczny

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2022

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R. 98, nr 12

121--123

EN

In the paper it was proven that spectrum of Metzler matrix must belong to a certain cone in the complex plane. The result is derived from the analytical characterization of spectra of positive matrices obtained by Karpelevich. Furthermore, it was shown that in case of 3x3 matrices this property yields also a sufficient condition that a set of numbers must satisfy in order to be spectrum of some Metzler matrix.

PL

W pracy wykazano, że widmo macierzy każdej Metzlera należy do pewnego stożka na płaszczyźnie zespolonej. Wykorzystano w tym celu analityczną charakteryzację widma macierzy dodatniej wyznaczoną przez Karpielewicza. Ponadto wykazano, że w przypadku macierzy 3x3 własność ta pozwala wyznaczyć również warunek wystarczający, który spełniać musi zbiór liczb zespolonych, aby był widmem pewnej macierzy Metzlera.

12

Zastosowanie szeregów trygonometrycznych Fouriera w pomiarach parametrów struktury geometrycznej powierzchni walcowych

Filipowski Ryszard, Zawora Józef

Obróbka Metalu

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2022

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nr 2

38--42

PL

Strukturę geometryczną powierzchni opisuje się za pomocą parametrów chropowatości oraz odchyłek kształtu. W artykule, do analizy stanu powierzchni, (rodzaju i wartości ich nierówności) wykorzystano szeregi trygonometryczne Fouriera przeprowadzając analizę ich widm: amplitudowego i fazowego. Zastosowano kroczący szereg Fouriera o trzech lub pięciu harmonicznych. W każdym przykładowym cyklu obliczeń, do obliczania stałych w szeregach Fouriera pobierano siedem lub jedenaście wartości odchyłek. Program umożliwia obliczanie wartości parametrów chropowatości: Ra, Rq oraz Rt.

EN

The geometric structure of the surface determine the roughness, wave and shape deviations. Trigonometric series Fourier was used to analyze the type of inequality on the surface by analyzing its amplitude and phase spectrum. A stepping series of Fourier with three or five harmonics was used. Seven or eleven measuring points are charged to calculate solid in Fourier's ranks in each calculation cycle. In the final phase, the program calculates the roughness parameters.. Programs with EQTRG3T or EQTRG5T names, were written in Fortran. Programs compiled by Digital Visual Fortran 6 is exploited on desktop and laptops.

13

On the basis property of root vectors related to a non-self-adjoint analytic operator and applications

Ellouz Hanen, Feki Ines, Jeribi Aref

Journal of Mathematics and Applications

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2022

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Vol. 45

59--86

EN

In the present paper, based on a separation condition on the spectrum of a self-adjoint operator T0 on a separable Hilbert space H, we prove that the system of root vectors of the perturbed operator T (ε) given by T (ε) := T0 + εT1 + ε2T2 + . . . + εkTk + . . . is complete and forms a basis with parentheses in H, for small enough |ε|. Here ε ∈ C and T1, T2, . . . are linear operators on H having the same domain D ⊃ D(T0) and satisfying a specific growing inequality. The obtained results are of importance for applications to a non-self-adjoint Gribov operator in Bargmann space and to a non-self-adjoint problem deduced from a perturbation method for sound radiation.

14

On linear chaos in function spaces

Jimenez John M., Markin Marat V.

Demonstratio Mathematica

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2022

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Vol. 55, nr 1

119--135

EN

We show that, in Lp(0,∞) ( 1≤p<∞ ), bounded weighted translations as well as their unbounded counterparts are chaotic linear operators. We also extend the unbounded case to C0[0,∞) and describe the spectra of the weighted translations provided the underlying spaces are complex.

15

Comparison of two concepts for modeling of lightning strike into overhead line

Aniserowicz Karol

Przegląd Elektrotechniczny

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2021

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R. 97, nr 12

97--100

EN

The paper presents a comparison of results of determining the lightning current flow in the shield wires of a high voltage line, using the model of lightning in the form of a lumped current generator and the antenna model, which takes the electromagnetic coupling into account. The usability of these two models is discussed.

PL

Przedstawiono porównanie wyników wyznaczenia rozpływu prądu piorunowego w linkach odgromowych linii wysokiego napięcia, z użyciem modelu pioruna w postaci skupionego generatora prądowego oraz modelu antenowego, uwzględniającego sprzężenie elektromagnetyczne. Przedyskutowano użyteczność tych dwóch modeli.

16

Spectrum localization of a perturbed operator in a strip and applications

Gil Michael

Opuscula Mathematica

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2021

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Vol. 41, no. 3

395–-412

EN

Let A and A be bounded operators in a Hilbert space. We consider the following problem: let the spectrum of A lie in some strip. In what strip the spectrum of A lies if A and Ä are “close”? Applications of the obtained results to integral operators and matrices are also discussed. In addition, we apply our perturbation results to approximate the spectral strip of a Hilbert-Schmidt operator by the spectral strips of finite matrices.

17

Overview of skin diagnostic techniques based on multilayer skin models and spectrophotometrics

Michalska Magdalena

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2021

|

T. 11, nr 3

30--33

EN

Today, spectrophotometrics is a promising tool for non-invasive examination of the optical properties of human skin. The spectrum obtained during the study is carefully analysed by models developed by many scientists. Developed multilayer models are designed to reflect the most faithful processes occurring in the skin, its layers and essential elements. Many skin diseases are diagnosed: vitiligo, hemangios, skin birthmarks, melanoma. The article provides an overview of interesting solutions using spectrophotometrics in the process of diagnosing skin diseases.

PL

Obecnie spektrofotometria jest obiecującym narzędziem do nieinwazyjnego badania właściwości optycznych ludzkiej skóry. Otrzymane podczas badania widma poddawane są wnikliwej analizie dzięki opracowanym przez wielu naukowców modeli. Opracowane modele wielowarstwowe mają na celu oddać najwierniej procesy zachodzące w skórze, jej warstwy i istotne elementy. Diagnozowanych jest wiele chorób skóry: bielactwo, naczyniaki, znamiona skórne, czerniak. Artykuł przedstawia przegląd ciekawych rozwiązań z użyciem spektrofotometrii w procesie diagnostyki chorób skóry.

18

Simulation of the MW =7.9 Gulf of Alaska earthquake on January 23, 2018, by the stochastic fnite fault model

Qicheng Li, Shupeng Yuan, Xinjuan Zheng

Acta Geophysica

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2021

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Vol. 69, no. 2

415--425

EN

On the premise of constraining the seismogenic fault structure of a future large earthquake, we proposed using empirical equations to determine the length, width, seismic moment and slip distribution of a large seismogenic fault plane and using the stochastic fnite fault model to predict future large earthquakes. The ground motion time histories and response spectra recorded by 12 seismic stations on bedrock during the MW =7.9 Gulf of Alaska earthquake on January 23, 2018, were simulated. The simulation error determined by the average ratio of the simulated spectrum amplitude to the recorded spectrum amplitude varied between 1.08 and 0.92 in the period range of 0–10 s, and the standard deviation of the simulation error at diferent frequencies did not exceed 1; the 95% confdence interval also did not change signifcantly with the period. The above analyses show that our simulation results refect the mean ground motion. To further discuss the reliability of predicting future large earthquakes by the stochastic fnite fault model, we redistributed the initial rupture point and slip distribution on the seismogenic fault plane by the quasi-random method, and the simulation errors and simulation results of the redistribution model were similar to those of the previous model. Further research confrmed that our method for obtaining the seismic source parameters is viable and that the stochastic fnite fault model for the prediction of future large earthquakes is reliable, especially for large far-feld earthquakes. The seismic stations that we used are all situated on bedrock on one side of the fault and do not involve rupture directivity, i.e., the seismic wave pathways may be similar, so the simulation results are ideal. However, if the rupture directivity, diferent site conditions, surface topography and basin efects are considered, it will be necessary to amend the proposed method.

19

Modele matematyczne piorunowych udarów prądowych

Aniserowicz Karol

Przegląd Elektrotechniczny

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2020

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R. 96, nr 12

134--139

PL

Opisano wyrażenia matematyczne często stosowane podczas modelowania przebiegów prądu wyładowania atmosferycznego. Przedstawione wzory są użyteczne zarówno podczas obliczeń analitycznych, jak i numerycznych dotyczących analizy zagrożenia piorunowego obiektów i przewodzących instalacji.

EN

Mathematical expressions frequently used for the modeling of the atmospheric discharge current waveforms are described. The presented formulas are useful for both analytical and numerical calculations related to the analysis of lightning hazard of objects and conductive installations.

20

Comparison of electric and radiometric methods for liquid dielectric diagnostic

Krbal Michal, Štěpánek Jaroslav, Pelikán Luděk, Orságová Jaroslava, Kolcunová Iraida

Przegląd Elektrotechniczny

|

2019

|

R. 95, nr 6

15--22

EN

This paper is focused on the description and comparison the alternative photometric and radiometric methods for liquid dielectric quality diagnostic and parameters measurement, long-term practical verification and comparison of obtained data with conventional methods. The proper function and accuracy of the measured methods are verified in the Light Laboratory and in the CVVOZEPowerLab in Brno University of Technology.

PL

W artykule porównanie metody fotometrycznej i radiometrycznej stosowanej do diagnostyki właściwości dielektrycznych płynów. Przedstawiono weryfikację długoterminową oraz porównanie otrzymanych danych w wynikami metody konwencjonalnej.