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Wyświetlanie 1-15 z 48
Tytuł:
Transmission problems for the Helmholtz equation for a rectilinear-circular lune
Autorzy:
Denysenko, V.
Powiązania:
https://bibliotekanauki.pl/articles/255476.pdf
Data publikacji:
2007
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
Helmholtz equation
transmission problem
infinite system of linear algebraic equations
Opis:
The question related to the construction of the solution of plane transmission problem for the Helmholtz equation in a rectilinear-circular lune is considered. An approach is proposed based on the method of partial domains and the principle of reflection for the solutions of the Helmholtz equation through the segment.
Źródło:
Opuscula Mathematica; 2007, 27, 2; 197-203
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the Photoacoustic Helmholtz Resonator with Conical-Ended Duct
Autorzy:
Suchenek, M.
Powiązania:
https://bibliotekanauki.pl/articles/227182.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Helmholtz resonator
influence of duct shape
conical duct model
Opis:
The acoustic properties of the photoacoustic Helmholtz cell can be improved by conical modification of the duct ends. The cone profile of the duct ends was studied, and according to the previous work, not all modifications of the parameters provide an increase of the Q-factor of the resonator. The aim of this work is to investigate the influence of the conical modification of the duct using a step-approximated model.
Źródło:
International Journal of Electronics and Telecommunications; 2017, 63, 2; 123-126
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Moyennes sphériques et opérateur de Helmholtz itéré
Autorzy:
Vieli, Francisco
Powiązania:
https://bibliotekanauki.pl/articles/967089.pdf
Data publikacji:
1995
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Opis:
Il est bien connu qu'une fonction $f$ sur $ℝ^{n}$ est harmonique - Δf = 0 - si et seulement si sa moyenne sur toute sphère est égale à sa valeur au centre de cette sphère. De manière semblable, f vérifie l'équation de Helmholtz Δf + cf = 0 si et seulement si sa moyenne sur la sphère de centre x et de rayon r vaut $Γ(n/2)(r√c/2)^{(2-n)/2} J_{(n-2)/2}(r√c)·f(x)$. Dans ce travail, nous généralisons ces résultats à l'opérateur $(Δ + c)^k$ où k est un entier strictement positif et c une constante non nulle. Bien qu'une méthode pour y parvenir soit esquissée dans [CH] (pp. 286-289), il semble que les calculs explicites nécessaires n'aient jamais été faits en toute généralité pour cet opérateur (voir, pour le cas n=3, [F], p. 87). La formule de la moyenne à laquelle nous aboutissons permet de démontrer - résultat cité par Herz ([H], p. 711) - qu'une fonction bornée f dont le spectre est dans $S^{n-1}$ vérifie $(Δ + 4π^{2})^{k} f =0$ où $k=⌊(n+1)/2⌋$, et ceci sans utiliser Beurling-Pollard.
Źródło:
Colloquium Mathematicum; 1995, 68, 2; 207-218
0010-1354
Pojawia się w:
Colloquium Mathematicum
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mesh-free approach to Helmholtz equation based on radial basis functions
Autorzy:
Kowalczyk, P.
Mrozowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/309385.pdf
Data publikacji:
2005
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
Helmholtz equation
radial basis functions
meshfree method
cylindrical waveguides
Opis:
Recently, a radial basis functions (RBFs) method, which was originally proposed for interpolation problems, has been developed and applied to solve partial differential equations and eigenproblems. Properties of that method (meshfree algorithm) allows one to use it in many areas, including electromagnetics. In this paper the mesh-free RBF method for solving Helmholtz equation was applied and a new adaptive algorithm for defining the set of interpolation centers was proposed. Using the proposed approach the cutoff wavelengths and the field distribution in cylindrical waveguides of arbitrary cross-section were calculated with a high accuracy.
Źródło:
Journal of Telecommunications and Information Technology; 2005, 2; 71-74
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Noise Elimination of a Multi-tone Broadband Noise with Hybrid Helmholtz Mufflers Using a Simulated Annealing Method
Autorzy:
Chiu, M-C.
Powiązania:
https://bibliotekanauki.pl/articles/176674.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
multiple tones
hybrid
Helmholtz
four-pole transfer matrix method
SA method
Opis:
Noise control is essential in an enclosed machine room where the noise level has to comply with the occupational safety and health act. In order to overcome a pure tone noise with a high peak value that is harmful to human hearing, a traditional reactive muffler has been used. However, the traditional method for designing a reactive muffler has proven to be time-consuming and insufficient. In order to efficiently reduce the peak noise level, interest in shape optimization of a Helmholtz muffler is coming to the forefront. Helmholtz mufflers that deal with a pure tone have been adequately researched. However, the shape optimization of multi-chamber Helmholtz mufflers that deal with a broadband noise hybridized with multiple tones within a constrained space has been mostly ignored. Therefore, this study analyzes the sound transmission loss (STL) and the best optimized design for a hybrid Helmholtz muffler under a space- constrained situation. On the basis of the plane wave theory, the four-pole system matrix used to evaluate the acoustic performance of a multi-tone hybrid Helmholtz muffler is presented. Two numerical cases for eliminating one/two tone noises emitted from a machine room using six kinds of mufflers (muffler AF) is also introduced. To find the best acoustical performance of a space-constrained muffler, a numerical assessment using a simulated annealing (SA) method is adopted. Before the SA operation can be carried out, the accuracy of the mathematical model has been checked using the experimental data. Eliminating a broadband noise hybridized with a pure tone (130 Hz) in Case I reveals that muffler C composed of a one- chamber Helmholtz Resonator and a one-chamber dissipative element has a noise reduction of 54.9 (dB). Moreover, as indicated in Case II, muffler F, a two-chamber Helmholtz Resonator and a one-chamber dissipative element, has a noise reduction of 69.7 (dB). Obviously, the peak values of the pure tones in Case I and Case II are efficiently reduced after the muffler is added. Consequently, a successful approach in eliminating a broadband noise hybridized with multiple tones using optimally shaped hybrid Helmholtz mufflers and a simulated annealing method within a constrained space is demonstrated.
Źródło:
Archives of Acoustics; 2012, 37, 4; 489-498
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of the CRLC models describing the Helmholtz type cells for the nondestructive photoacoustic spectroscopy
Autorzy:
Chrobak, Ł. B.
Maliński, M. A.
Powiązania:
https://bibliotekanauki.pl/articles/221397.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nondestructive testing
photoacoustic spectroscopy
photoacoustic cells
Helmholtz cells
Opis:
The photoacoustic cell is the heart of the nondestructive photoacoustic method. This article presents a new simple lumped-components CRLC model of the Helmholtz type photoacoustic cell. This model has been compared with the well known literature models describing the Helmholtz type cells for photoacoustic spectroscopy. Experimental amplitude and phase frequency data obtained for the two photoacoustic cells have been presented and interpreted in a series of models. Results of the fitting of theoretical curves, obtained in these models, to the experimental data have been shown and discussed.
Źródło:
Metrology and Measurement Systems; 2014, 21, 3; 545-552
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the robustness of the topological derivative for Helmholtz problems and applications
Autorzy:
Leugering, Günter
Novotny, Antonio André
Sokolowski, Jan
Powiązania:
https://bibliotekanauki.pl/articles/2183490.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
topological derivative
shape optimization
inverse problems
Helmholtz problem
numerical methods
complex variables
Opis:
We consider Helmholtz problems in two and three dimensions. The topological sensitivity of a given cost function J(uɛ) with respect to a small hole Bɛ around a given point x0ɛ ∈ Bɛ ⊂ Ω depends on various parameters, like the frequency k chosen or certain material parameters or even the shape parameters of the hole Bɛ. These parameters are either deliberately chosen in a certain range, as, e.g., the frequencies, or are known only up to some bounds. The problem arises as to whether one can obtain a uniform design using the topological gradient. We show that for 2-d and 3-d Helmholtz problems such a robust design is achievable.
Źródło:
Control and Cybernetics; 2022, 51, 2; 227--248
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Windowless Open Photoacoustic Helmholtz Cell
Autorzy:
Starecki, T.
Powiązania:
https://bibliotekanauki.pl/articles/1811562.pdf
Data publikacji:
2008-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.38.Zp
43.58.Kr
Opis:
A phenomenon which is usually considered as the main disadvantage of photoacoustic Helmholtz cells is photoacoustic background signal resulting from the light absorption by the cell windows. Although there are methods which reduce this background signal, e.g. light wavelength modulation or time domain filtering of the photoacoustic response from the sample, the methods are limited to particular applications, and none of them would completely remove the mentioned background signal. The paper presents design of a windowless open photoacoustic Helmholtz cell, and preliminary results of frequency response measurements of such a cell. Removal of the windows eliminated the main source of the photoacoustic background signal. Additionally, the proposed design allows for unrestricted or forced flow of the fluid filling the cell. As a result, the cell can be easily adapted for continuous, real-time photoacoustic measurements. Under proper selection of the cell dimensions, Q-factors of such open photoacoustic Helmholtz resonators are comparable to the Q-factors of corresponding closed Helmholtz cells.
Źródło:
Acta Physica Polonica A; 2008, 114, 6A; A-211-A-216
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An alternating current calibration method for Helmholtz coil constant based on orthogonal calculation principle
Autorzy:
Zhang, Kuankuan
Cao, Mingxing
He, Jian
Gong, Wenjie
Huang, Yunhua
Powiązania:
https://bibliotekanauki.pl/articles/27311758.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
Helmholtz coils constant
alternating current method
induction voltage
orthogonal calculations
Opis:
The Helmholtz coil constant (ℎ) is a crucial standard in magnetic moment measurement devices for permanent magnet materials. To overcome the problem of low accuracy of the direct-current (DC) calibration method, this study used a constant sinusoidal current in the Helmholtz coil and measured the induced voltage of the detection coil with known coil turns and coil area. Subsequently, the ℎ was calculated. The noise signal deduction rate in the induction voltage of the detection coil was greater than 99%, its influence on the induction voltage is less than 0.005%, and the repeatability of the calibration results is 0.003% (1). The results reveal that the alternating current (AC) method and orthogonal calculation (OC) can accurately measure the valid values of the voltage signal under the influence of the spatial stray field during the calibration of ℎ.
Źródło:
Metrology and Measurement Systems; 2023, 30, 3; 549--561
0860-8229
Pojawia się w:
Metrology and Measurement Systems
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Method comparison of statistical averaging on the Helmholtz coils calibration example
Porównanie metod uśredniania statystycznego na przykładzie wzorcowania cewek Helmholtza
Autorzy:
Janeczko, M.
Powiązania:
https://bibliotekanauki.pl/articles/407984.pdf
Data publikacji:
2016
Wydawca:
Politechnika Lubelska. Wydawnictwo Politechniki Lubelskiej
Tematy:
calibration of Helmholtz coils
statistical averaging
Monte Carlo method
wzorcowanie cewek Helmholtza
uśrednianie statystyczne
metoda Monte Carlo
Opis:
During a calibration of Helmholtz coils, in which more than one parameter is measured directly, there are various approaches to statistical averaging. In this paper will be discussed two of them: the averaging at the beginning of directly measured magnitude and the averaging of the final value. In order to compare the methods they will be referenced to the Monte Carlo method, having regard to the uncertainty of type A.
Podczas wzorcowania cewek Helmholtza podczas których mierzy się bezpośrednio więcej niż jeden parametr możliwe są różne podejścia do uśredniania statystycznego. W pracy omówione będą dwa z nich: uśrednianie na początku bezpośrednio zmierzonych wielkości oraz uśrednianie wielkości końcowej. W celu porównania metod zostaną one odniesione do Metody Monte Carlo z uwzględnieniem niepewności typu A.
Źródło:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska; 2016, 3; 24-27
2083-0157
2391-6761
Pojawia się w:
Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kelvin-Helmholtz instabilities in the Colorado River Delta, Gulf of California
Autorzy:
Carbajal, N.
Vargas, J.T.
Rodriguez, J.H.G.
Montano Ley, Y.
Salas de Leon, D.A.
Powiązania:
https://bibliotekanauki.pl/articles/2078904.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:
Kelvin-Helmholtz instability
Colorado River Delta
tidal current
bottom sediment
bathymetry
suspended sediment
satellite image
Opis:
In the Colorado River Delta, the interaction of tidal currents and sea-bottom sediment formed, in geological times, large-scale seabed patterns known as sandbanks. These patterns are oriented along the delta, almost parallel to the dominant tidal flow, with the bathymetry having an undulating character across the delta. Calculations and analysis showed that the interaction of tidal currents with the bathymetry causes velocity shears, faster flowing over the ridges than in the troughs. Kelvin-Helmholtz instabilities emerge from the velocity shear, and a large amount of suspended sediment makes the instabilities visible in satellite images. The physical and dynamic conditions allowed us to find an explanation for the existence of these Kelvin-Helmholtz instabilities. Since sandbanks have been observed in different seas such as the North Sea, The Gulf of Korea, the Gulf of Khambhat in India, the Jiangsu coast in China, the Persian Gulf, and Moreton Bay in Australia, the results suggest the existence of instabilities in these areas. Satellite images, intense tidal currents, undulating topography, and suspended sediment made it possible to explain the generation and identification of KelvinHelmholtz instabilities.
Źródło:
Oceanologia; 2021, 63, 3; 321-328
0078-3234
Pojawia się w:
Oceanologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Boundary value problems for the Helmholtz equation in a rectangular polyhedral angle of the Euclidean n-space
Autorzy:
Filar, M.
Powiązania:
https://bibliotekanauki.pl/articles/963395.pdf
Data publikacji:
1984
Wydawca:
Polskie Towarzystwo Matematyczne
Opis:
The article contains no abstract
Źródło:
Commentationes Mathematicae; 1984, 24, 1; 277-284
0373-8299
Pojawia się w:
Commentationes Mathematicae
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 48

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