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Czy teoria mechanizmu akomodacji głoszona przez Helmholtza jest nadal aktualna?

Kałużny Bartłomiej J., Ostrowicka Sylwia

Optyka

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2019

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Nr 3

60--62

PL

Teoria mechanizmu akomodacji zaproponowana przez Helmholtza w XIX wieku, mimo upływu lat i pojawienia się nowych poglądów w kolejnym wieku, wciąż stanowi najbardziej powszechny model akomodacji przedstawiany w literaturze. Ponadto, oko schematyczne Gullstranda stworzone zostało na podstawie tej idei. Czy dziś – w XXI wieku – nadszedł czas na zaakceptowanie innych poglądów?

2

Noise Elimination of a Multi-tone Broadband Noise with Hybrid Helmholtz Mufflers Using a Simulated Annealing Method

Chiu M-C.

Archives of Acoustics

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2012

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Vol. 37, No. 4

489-498

EN

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.

3

Genetic Algorithms in Electromagnetism : The Helmholtz Coils

Borowska B., Nadolski S.

Journal of Applied Computer Science

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2006

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Vol. 14, nr 2

109-118

EN

In this work, the modified genetic algorithm has been applied to solve the Helmholtz coil problem. The task of the algorithm was to determine the radius of the coils and the distance between them, which would assure that a priori assumed level of non-homogeneity of magnetic field is maintained. In the implemented genetic algorithm, the ternary system of representation has been used. Based on the results of performed experiments, the accuracy, efficiency and usefulness of the proposed algorithm has been assessed.

4

Antilogarithms of second order in algebras with logarithms and their applications to special functions

Przeworska-Rolewicz D.

Annales Societatis Mathematicae Polonae. Seria 1: Commentationes Mathematicae

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2004

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Vol. 44, nr spec.

167-191

EN

In the paper [PR5] it was shown that the so-called special functions of Mathematical Physics can be obtained by means of antilogarithms of the second order for the usual differential operator ^j. The same method applied to a right invertible operator D in a commutative Leibniz algebra with logarithms permits to determine eigenvectors of linear equations of order two in D with coefficients in the algebra X under consideration by a reduction to the generalized Sturm-Liouville operator. It seems that, in a sense, the proposed method is an answer for the question of Gian-Carlo Rota concerning a unified approach to special functions (cf. [Rl], problem 4). Section 6 of the present paper is devoted to some summations formulae expressing special functions by means of exponentials. Note that, in general, we do not need any assumption about the Hilbert structure of the algebra X.