Volume 52, Number 2, March–April 2018
|Page(s)||481 - 508|
|Published online||31 May 2018|
Scalar problems in junctions of rods and a plate
II. Self-adjoint extensions and simulation models
University of Lorraine, IECL, CNRS UMR 7502, 3 rue Augustin Fresnel,
2 Università del Sannio, Department of Engineering, Corso Garibaldi, 107, 82100, Benevento, Italy
3 Mathematics and Mechanics Faculty, St. Petersburg State University, 198504, Universitetsky pr., 28, St. Petersburg, 195251, Russia
4 Institute of Problems of Mechanical Engineering RAS, V.O., Bolshoj pr., 61, St. Petersburg, 199178, Russia
* Corresponding author: firstname.lastname@example.org
Accepted: 11 September 2017
In this work we deal with a scalar spectral mixed boundary value problem in a spacial junction of thin rods and a plate. Constructing asymptotics of the eigenvalues, we employ two equipollent asymptotic models posed on the skeleton of the junction, that is, a hybrid domain. We, first, use the technique of self-adjoint extensions and, second, we impose algebraic conditions at the junction points in order to compile a problem in a function space with detached asymptotics. The latter problem is involved into a symmetric generalized Green formula and, therefore, admits the variational formulation. In comparison with a primordial asymptotic procedure, these two models provide much better proximity of the spectra of the problems in the spacial junction and in its skeleton. However, they exhibit the negative spectrum of finite multiplicity and for these “parasitic” eigenvalues we derive asymptotic formulas to demonstrate that they do not belong to the service area of the developed asymptotic models.
Mathematics Subject Classification: 35B40 / 35C20 / 74K30
Key words: Junction of thin rods and plate / scalar spectral problem / asymptotics / dimension reduction / self-adjoint extensions of differential operators / function space with detached asymptotics
© EDP Sciences, SMAI 2018
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