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1

Research on the influence of airflow resistance of layered porous structures on the sound absorption coefficient

Flach Artur

Vibrations in Physical Systems

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2022

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Vol. 33, nr 3

art. no. 2022311

EN

The paper presents the research on the influence of airflow resistance on the sound absorption coefficient of layered porous structures. For the calculation of the sound absorption coefficient, the models of layered sound-absorbing structures were developed with the use of numerical computational models. Using the developed models, optimization was carried out to maximize the average sound absorption coefficient of the structures for a given frequency range. As a result of the research, the dependence of the change in airflow resistance for the successive layers of the material was determined. The results of the work will be particularly useful in the design of wedges used in anechoic chambers.

2

Experimental verification of similarity criteria for sound absorption of simple metamaterials

Chojak Aleksandra

Vibrations in Physical Systems

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2022

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Vol. 33, nr 2

art. no. 2022211

EN

The paper concerns the dimensional analysis of simple acoustic metamaterials and its experimental verification in a computer model. Due to their decreased thickness possible because of the thermoviscous losses and sound dispersion that occur in acoustic metamaterials, such structures are gaining popularity, both as sound absorbers and diffusers. This implies the need to find their equivalents to be used at scale - both for modeling interiors with metamaterials and developing more complicated structures. The paper discusses the dimensional analysis performed for a generalized unit cell of a metamaterial with a resonator. The dimensional analysis shows the need for scaling both the geometrical dimensions of the structure and the parameters of the medium - air. The dimensional analysis was derived based on the transfer matrix method and was proven correct with the finite element method model. The paper also discusses the consequences of neglecting the air criteria, which are impossible to be fulfilled. This opens the question of finding new criterial numbers allowing the correct reflection of acoustic metamaterials at scale.

3

High sensitive and large dynamic range quasi-distributed sensing system based on slow-light π-phase-shifted fiber Bragg gratings

Dwivedi K. M., Osuch T., Trivedi G.

Opto-Electronics Review

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2019

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Vol. 27, No. 3

233--240

EN

In this paper, we theoretically analyze the slow-light π-phase-shifted fiber Bragg grating (π-FBG) and its applications for single and multipoint/quasi-distributed sensing. Coupled-mode theory (CMT) and transfer matrix method (TMM) are used to establish the numerical modeling of slow-light π-FBG. The impact of slow-light FBG parameters, such as grating length (L), index change (Δn), and loss coefficient (α) on the spectral properties of π-FBG along with strain and thermal sensitivities are presented. Simulation results show that for the optimum grating parameters L = 50 mm, Δn = 1.5×10−4, and α = 0.10 m-1, the proposed slow-light π-FBG is characterized with a peak transmissivity of 0.424, the maximum delay of 31.95 ns, strain sensitivity of 8.380 με-1, and temperature sensitivity of 91.064 °C-1. The strain and temperature sensitivity of proposed slow-light π-FBG is the highest as compared to the slow-light sensitivity of apodized FBGs reported in the literature. The proposed grating have the overall full-width at half maximum (FWHM) of 0.2245 nm, and the FWHM of the Bragg wavelength peak transmissivity is of 0.0798 pm. The optimized slow-light π-FBG is used for quasi-distributed sensing applications. For the five-stage strain quasi-distributed sensing network, a high strain dynamic range of value 1469 με is obtained for sensors wavelength spacing as small as 2 nm. In the case of temperature of quasi-distributed sensing network, the obtained dynamic range is of 133°C. For measurement system with a sufficiently wide spectral range, the π-FBGs wavelength grid can be broadened which results in substantial increase of dynamic range of the system.

4

Some closed-form bending formulas for elastically restrained Euler-Bernoulli beams under point and uniformly distributed loads

Yıldırım V.

Journal of Applied Mathematics and Computational Mechanics

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2018

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Vol. 17, nr 3

97--109

EN

The transfer matrix method based on the Euler-Bernoulli beam theory is employed in order to originally achieve some exact analytical formulas for elastically supported beams under a point force together with uniformly distributed force and uniformly distributed couple moments. Those closed-form formulas can be used in a variety of engineering applications especially at the pre-design stage to get an insight into the response of the structure. Contrary to the classical boundary conditions, it is also observed that the Euler-Bernoulli solutions of a beam with elastic supports are sensitive to the ratio of length to thickness (L/h).

5

O pewnych właściwościach mieszanych ekranów warstwowych

Pawłowski S., Plewko J.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 12

129--132

PL

W artykule zwrócono uwagę na kilka interesujących właściwości mieszanych ekranów warstwowych przewodnik/ferromagnetyk. Szczegółowo zbadano ekran dwuwarstwowy - miedź/stal elektrotechniczna. Stwierdzono występowanie plateau w zależności impedancji powierzchniowej w funkcji częstotliwości w takim układzie oraz obniżenie jej wartości poniżej wartości odpowiadającej jednorodnemu ekranowi miedzianemu. Efekt ten pozwala na obniżenie strat w badanym układzie i poprawę właściwości ekranowania o kilkanaście procent.

EN

The article focuses on some interesting properties of mixed layered conductor/ferromagnetic screens. The two-layer screen: copper/electrical steel was examined in detail. For such a system it was found, that in relation of frequency function on the surface impedance there is a plateau, and surface impedance of analyzed screen reduce its value comparing the value obtained for the homogeneous copper screen. This effect reduces the losses in copper/electrical steel screen system and improves the shielding properties over a dozen percent.

6

Special optical communication filter based on Thue-Morse photonic crystal structure

Alipour-Banaei H., Serajmohammadi S., Mehdizadeh F., Hassangholizadeh-Kashtiban M.

Optica Applicata

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2016

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Vol. 46, nr 1

145--152

EN

In this paper we proposed a novel narrowband optical filter for wavelength division multiplexing applications. Due to their high transmission efficiency and very narrowband properties, we used the 5th generation Thue-Morse structure for designing our proposed filter. But novelty of our work is introducing another ID photonic crystal structure as a defect structure into the Thue-Morse structure in order to create pass band inside the photonic band gap of the Thue-Morse structure. All of the simulations and calculations have been done using the transfer matrix method. The most interesting property of this filter is that by increasing the number of the periods of the ordinary 1D photonic crystal, the number of the pass bands increases.

7

Odtwarzanie rozkładu odkształcenia przy pomocy światłowodowej siatki Bragga

Detka M., Kaczmarek Z.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 4

84-88

PL

W artykule przedstawiono rekonstrukcję rozłożonego odkształcenia działającego na światłowodową siatkę Bragga na podstawie jej widma odbitego. Wykorzystano do tego celu metodę macierzy przejścia oraz nieliniową metodę optymalizacji Neldera-Meada. Wyniki przeprowadzonych symulacji i odtwarzania profili odkształcenia wskazują na dobrą ich zgodność z oryginalnymi profilami odkształcenie; błędy rekonstrukcji tych profili nie przekraczają pojedynczych procentów.

EN

In this paper, we present a reconstruction of the distributed strain affecting the fiber Bragg grating performed by means of its reflection spectrum. For this purpose, we applied the transfer matrix method and the Nelder-Mead nonlinear optimization method. Reconstruction results of the strain profile carried out on the basis of a simulated reflection spectrum as well as measured reflection spectrum of the FBG indicate good agreement with the original strain profile; the profile reconstruction errors are within the single digit percentage range.

8

Odtwarzanie rozkładu odkształcenia na podstawie widma światłowodowej siatki Bragga

Detka M., Kaczmarek Z.

Pomiary Automatyka Kontrola

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2013

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R. 59, nr 4

295--299

PL

W artykule przedstawiono syntezę parametrów światłowodowej siatki Bragga (FBG) oraz rekonstrukcję rozłożonego odkształcenia działającego na siatkę na podstawie jej widma odbitego. Wykorzystano do tego celu metodę macierzy przejścia oraz nieliniową metodę optymalizacji Neldera- Meada. Wyniki przeprowadzonych symulacji i odtwarzania profili odkształcenia wskazują na dobrą ich zgodność z oryginalnymi profilami odkształcenie; błędy rekonstrukcji tych profili nie przekraczają pojedynczych procentów. Na tej podstawie stwierdza się, że metodę optymalizacji Neldera-Meada w połączeniu z metodą macierzy przejścia można z powodzeniem stosować w zadaniach miernictwa wielkości rozłożonych.

EN

A synthesis of the fiber Bragg grating (FBG) parameters and reconstruction of the distributed strain affecting the grating performed by means of its reflection spectrum is presented. For this purpose, there are applied the transition matrix method and the Nelder-Mead nonlinear optimization method. The essence of both methods is described. First, simulations of reconstruction of the grating parameters and the linear distributions of compressive strains were performed. The results of these simulations are presented in Section 3. Then the reconstruction of the compressive strain profiles was carried out on the basis of the measured spectrum of the grating. The results of those calculations are given in Section 4. The reconstruction results of the strain profile carried out on the basis of the simulated reflection spectrum and the measured reflection spectrum of the FBG show good agreement with the original strain profile; the profile reconstruction errors are within the single digit percentage range. One can conclude that the Nelder-Mead optimization method combined with the transition matrix method can be used for distributed sensing problems.

9

Distributed strain reconstruction based on a fiber Bragg grating reflection spectrum

Detka M., Kaczmarek Z.

Metrology and Measurement Systems

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2013

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Vol. 20, nr 1

53-64

EN

In this paper, we present a synthesis of the parameters of the fiber Bragg grating (FBG) and the reconstruction of the distributed strain affecting the grating, performed by means of its reflection spectrum. For this purpose, we applied the transition matrix method and the Nelder-Mead nonlinear optimization method. Reconstruction results of the strain profile carried out on the basis of a simulated reflection spectrum as well as measured reflection spectrum of the FBG indicate good agreement with the original strain profile; the profile reconstruction errors are within the single digit percentage range. We can conclude that the Nelder-Mead optimization method combined with the transition matrix method can be used for distributed sensing problems.

10

Pulsation induced by rotor-stator interaction: CFD vs. transfer matrix method

Rudolf P., Haban V., Kubalek J.

Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne

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2008

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Z. 10, Vol. 2

157-164

EN

Rotor-stator interaction is a source of high-frequency pulsations. Presented paper focuses on simulation of these pulsations in low specific speed pump with guide vanes. Two approaches are compared: 3D simulation in time domain and 1D simulation in frequency domain. Three-dimensional unsteady computations of turbulent flow were carried out using commercial CFD software. Resulting pressure pulsations spectra were compared to simulations obtained by one-dimensional transfer matrix method.

11

GA optimization on single-chamber muffler hybridized with extended tube under space constraints

Chang Y. C., Yeh L. J., Chiu M. C.

Archives of Acoustics

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2004

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Vol. 29, no. 4

577-596

EN

Mufflers are habitually adopted in gas venting systems under space constraint for maintenance and operation. The shape optimization in the muffler to maximize the sound performance is then highly focused, accordingly. In this paper, the shape design of a muffler with extended tubes optimized by the genetic algorithm (GA) is presented. A numerical case in eliminating the pure tone noise is introduced. Before optimization, the mathematical model is compared by the experimental data for an accuracy check. The results indicate that the sound transmission loss (STL) is maximized exactly at the designed frequency. Consequently, we demonstrate a successful GA application on the muffler design.