Wyniki wyszukiwania - BazTech

1

An Assessment of High-Order-Mode Analysis and Shape Optimization of Expansion Chamber Mufflers

Chiu M. C., Chang Y. C.

Archives of Acoustics

|

2014

|

Vol. 39, No. 4

489--499

EN

A substantial quantity of research on muffler design has been restricted to a low frequency range using the plane wave theory. Based on this theory, which is a one-dimensional wave, no higher order wave has been considered. This has resulted in underestimating acoustical performances at higher frequencies when doing muffler analysis via the plane wave model. To overcome the above drawbacks, researchers have assessed a three-dimensional wave propagating for a simple expansion chamber muffler. Therefore, the acoustic effect of a higher order wave (a high frequency wave) is considered here. Unfortunately, there has been scant research on expansion chamber mufflers equipped with baffle plates that enhance noise elimination using a higher-order-mode analysis. Also, space-constrained conditions of industrial muffler designs have never been properly addressed. So, in order to improve the acoustical performance of an expansion chamber muffler within a constrained space, the optimization of an expansion chamber muffler hybridized with multiple baffle plates will be assessed. In this paper, the acoustical model of the expansion chamber muffler will be established by assuming that it is a rigid rectangular tube driven by a piston along the tube wall. Using an eigenfunction (higher- order-mode analysis), a four-pole system matrix for evaluating acoustic performance (STL) is derived. To improve the acoustic performance of the expansion chamber muffler, three kinds of expansion chamber mufflers (KA-KC) with different acoustic mechanisms are introduced and optimized for a targeted tone using a genetic algorithm (GA). Before the optimization process is performed, the higher-order-mode mathematical models of three expansion chamber mufflers (A-C) with various allocations of inlets/outlets and various chambers are also confirmed for accuracy. Results reveal that the STL of the expansion chamber mufflers at the targeted tone has been largely improved and the acoustic performance of a reverse expansion chamber muffler is more efficient than that of a straight expansion chamber muffler. Moreover, the STL of the expansion chamber mufflers will increase as the number of the chambers that separate with baffles increases.

2

An eigenvalue problem for linear Hamiltonian dynamic systems

Bohner M., Hilscher R.

Fasciculi Mathematici

|

2005

|

Nr 35

35-49

EN

In this paper we consider eigenvalue problems on time scales involving linear Hainiltonian dynamic systems. We give conditions that ensure that the eigenvalues of the problem are isolated and bounded below. The presented results are applicable also to Sturm-Liouville dynamic equations of higher order, and further special cases of our systems are linear Hamiltonian differ ential systems as well as linear Hamiltonian difference systems.

3

Green's function for an infinite piezoelectric strip with a general line defect

Nowacki J. P., Alshits V. L., Radowicz A.

Journal of Technical Physics

|

2002

|

Vol. 43, no 2

133-153

EN

The 2D electro-elastic fields are found in the piezoelectric strip with the straight general line defect parallel to the surfaces and consisting of the four coinciding sources: the line of forces, the charged line, the dislocation line and its electrostatic analogue. Electrically, the strip is supposed to be placed between two isotropic dielectric media. Mechanically, three boundary conditions are considered: (i) both the surfaces are free; (ii) both the surfaces are clamped; and (iii) one surface is free and the other is clamped. The solutions obtained for a general case of unrestricted anisotropy are presented in the form of convergent Fourier integrals, in terms of the eigenvectors and eigenvalues of the generalized Stroh problem. Determination of these eigenvalues and eigenvectors requires additional computing. Specific features of the derived solutions at infinity are analyzed.

4

On Application of a Perturbation Method with a Few Perturbation Parameters

Andrianov I., Awrejcewicz J., Matyash M.

Machine Dynamics Problems

|

2000

|

Vol. 24, No. 3

5-10

PL

W wielu układach mechanicznych nieliniowych istnieje potrzeba stosowania niezależnych parametrów perturbacyjnych. Praca przedstawia formalną konstrukcję metody opartej na zastosowaniu dwóch parametrów perturbacyjnych. Ponadto w pracy przedyskutowano przypadki wynikające z relacji pomiędzy wspomnianymi parametrami perturbacyjnymi.

EN

The formal method of application of two perturbation parameters is introduced.

5

A nonstandard difference Sturm-Liouville operator

Javorskij J., Ljance V.

Bulletin of the Polish Academy of Sciences. Mathematics

|

1998

|

Vol. 46, no 3

285-290

EN

After Nelson's Radically Elementary Probability Theory [1] a natural question arises: whether a hyperfinite-dimensional space is sufficiently rich to be used for the same goal as an infinite-dimensional one. Here a hyperfinite 3-diagonal matrix is investigated, which spectral properties are simular to the Naimarks's singular nonselfadjoint Sturm-Liouville differential operator on semi-axis [2, 3].