752 research outputs found
The linear constraints in Poincar\'{e} and Korn type inequalities
We investigate the character of the linear constraints which are needed for
Poincar\'e and Korn type inequalities to hold. We especially analyze
constraints which depend on restriction on subsets of positive measure and on
the trace on a portion of the boundary.Comment: Revised versio
On doubling inequalities for elliptic systems
We prove doubling inequalities for solutions of elliptic systems with an
iterated Laplacian as diagonal principal part and for solutions of the Lame'
system of isotropic linearized elasticity. These inequalities depend on global
properties of the solutions.Comment: 13 pages, submitted for publicatio
Stable determination of an inclusion in an elastic body by boundary measurements (unabridged)
We consider the inverse problem of identifying an unknown inclusion contained
in an elastic body by the Dirichlet-to-Neumann map. The body is made by
linearly elastic, homogeneous and isotropic material. The Lam\'e moduli of the
inclusion are constant and different from those of the surrounding material.
Under mild a-priori regularity assumptions on the unknown defect, we establish
a logarithmic stability estimate. For the proof, we extend the approach used
for electrical and thermal conductors in a novel way. Main tools are
propagation of smallness arguments based on three-spheres inequality for
solutions to the Lam\'e system and refined local approximation of the
fundamental solution of the Lam\'e system in presence of an inclusion.Comment: 58 pages, 4 figures. This is the extended, and revised, version of a
paper submitted for publication in abridged for
Two new Horaiclavus (Horaiclavidae, Conoidea) species from the Indo-Pacific region
The genus Horaiclavus includes eight Holocene Indo-Pacific species (Appeltans et al. 2012). Herein, we describe two
new species that resemble members of this genus in some aspects of shell morphology, but otherwise show features that
suggest that they differ from “typical” Horaiclavus species
Uniqueness in the determination of loads in multi-span beams and plates
Most of the results available on the inverse problem of determining loads acting on elastic beams or plates under transverse vibration refer to single beam or single plate. In this paper, we consider the determination of sources in multi-span systems obtained by connecting either two Euler-Bernoulli elastic beams or two rectangular Kirchhoff-Love elastic plates. The material of the structure is assumed to be homogeneous and isotropic. The transverse load is of the form g(t)f(x), where g(t) is a known function of time and f(x) is the unknown term depending on the position variable x. Under slight a priori assumptions, we prove a uniqueness result for f(x) in terms of observations of the dynamic response taken at interior points of the structure in an arbitrary small interval of time. A numerical implementation of the method is included to show the possible application of the results in the practical identification of the source term
Experimental verification of the interpolation method on a real damaged bridge
The identification of damage in a bridge from changes in its vibrational behavior is an
inverse problem of important practical value. Significant advances have been obtained on this
topic in the last two-three decades, both from the theoretical and applied point of view. One of
the main problems when dealing with the assessment of vibration based damage identification
methods is the lack of experimental data recorded on real damaged structures. Due to this, a large
number of damage identification algorithms are tested using data simulated by numerical
models. The availability of data recorded on a damaged bridge before its demolition gave the
authors the uncommon chance to verify the sensitivity and reliability of the IDDM basing on
data recorded on a real structure. Specifically data recorded on a reinforced concrete single-span
supported bridge in the Municipality of Dogna (Friuli, Italy) were used to apply the damage
localization algorithm. Harmonically forced tests were conducted after imposing artificial,
increasing levels of localized damage. In this paper the sensitivity of the method is discussed
with respect to the number of instrumented locations and to the severity of the damage scenarios
considere
Reconstructing Loads in Nanoplates from Dynamic Data
It was recently proved that the knowledge of the transverse displacement of a nanoplate in an open subset of its mid-plane, measured for any interval of time, allows for the unique determination of the spatial components (Formula presented.) of the transverse load (Formula presented.), where (Formula presented.) and (Formula presented.) is a known set of linearly independent functions of the time variable. The nanoplate mechanical model is built within the strain gradient linear elasticity theory, according to the Kirchhoff–Love kinematic assumptions. In this paper, we derive a reconstruction algorithm for the above inverse source problem, and we implement a numerical procedure based on a finite element spatial discretization to approximate the loads (Formula presented.). The computations are developed for a uniform rectangular nanoplate clamped at the boundary. The sensitivity of the results with respect to the main parameters that influence the identification is analyzed in detail. The adoption of a regularization scheme based on the singular value decomposition turns out to be decisive for the accuracy and stability of the reconstruction
On Isospectral Composite Beams
We consider a composite system consisting of two identical straight elastic beams under longitudinal vibration connected by an elastic interface capable of counteracting the relative vibration of the two beams with its shearing stiffness. We construct examples of isospectral composite beams, i.e., countable one-parameter families of beams having different shearing stiffness but exactly the same eigenvalues under a given set of boundary conditions. The construction is explicit and is based on the reduction to a one-dimensional Sturm–Liouville eigenvalue problem and the application of a Darboux’s lemma
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