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

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

Unique determination of a single crack in a uniform simply supported beam in bending vibration

In this paper we consider one of the basic inverse problems in damage detection based on natural frequency data, namely the identification of a single open crack in a uniform simply supported beam from measurement of the first and the second natural frequency. It is commonly accepted in the literature that the knowledge of this set of spectral data allows for the unique determination of the severity and the position (up to symmetry) of the damage. However, in spite of the fact that many numerical evidences are in support of this property, the result is rigorously proved only when the severity of the crack is small. In this paper we definitely show, by means of an original constructive method, that the above result holds true for any level of crack severity. (C) 2016 Elsevier Ltd. All rights reserved

A Case of Concurrent Riedel's, Hashimoto's and Acute Suppurative Thyroiditis

Riedel's thyroiditis (RT) is a rare form of infiltrative and inflammatory disease of the thyroid, first described by Bernard Riedel in 1896. The concurrent presence of RT and other thyroid diseases has been reported, but, the association of RT with Hashimoto's thyroiditis and acute thyroiditis has not yet been reported. We present a case of concurrent Riedel's, Hashimoto's and acute thyroiditis that occurred in a 45-year-old patient

Identification of general added mass distribution in nanorods from two-spectra finite data

Nanomechanical resonators consisting in one-dimensional vibrating structures have remarkable performance in detecting small adherent masses. The mass sensing principle is based on the use of the resonant frequency shifts caused by unknown attached masses. In spite of its importance in applications, few studies are available on this inverse problem. Dilena et al. (2019) presented a method for reconstructing a small mass distribution by using the first N resonant frequencies of the free axial vibration of a nanorod under clamped end conditions. In order to avoid trivial non-uniqueness when spectral data belonging to a single spectrum are used, the mass variation was supposed to be supported in half of the axis interval. In this paper, we remove this a priori assumption on the mass support, and we show how to extend the method to reconstruct a general mass distribution by adding to the input data the first N lower eigenvalues of the nanorod under clamped-free end conditions. The nanobeam is modelled using the modified strain gradient theory to account for the microstructure and size effects. The reconstruction is based on an iterative procedure which takes advantage of the closed-form solution available when the mass change is small, and turns out to be convergent under this assumption. The results of an extended series of numerical simulations support the theoretical results.The authors from Universidad Carlos III de Madrid wish to acknowledge Ministerio de Economía y Competitividad de España for the financial support, under Grants No. DPI2014-57989-P and PGC2018-098218-B-I00. The authors from University of Udine gratefully acknowledge the financial support of the National Research ProjectPRIN 2015TT JN95 Identification and monitoring of complex structural systems

Recovering added mass in nanoresonator sensors from finite axial eigenfrequency data

In this paper we present a method for solving a finite inverse eigenvalue problem arising in the determination of added distributed mass in nanoresonator sensors by measurements of the first N natural frequencies of the free axial vibration under clamped end conditions. The method is based on an iterative procedure that produces an approximation of the unknown mass density as a generalized Fourier partial sum of order N, whose coefficients are calculated from the first N eigenvalues. To avoid trivial non-uniqueness due to the symmetry of the initial configuration of the nanorod, it is assumed that the mass variation has support contained in half of the axis interval. Moreover, the mass variation is supposed to be small with respect to the total mass of the initial nanorod. An extended series of numerical examples shows that the method is efficient and gives excellent results in case of continuous mass variations. The determination of discontinuous coefficients exhibits no negligible oscillations near the discontinuity points, and requires more spectral data to obtain good reconstruction. A proof of local convergence of the iteration algorithm is provided for a family of finite dimensional mass coefficients. Surprisingly enough, in spite of its local character, the identification method performs well even for not necessarily small mass changes. To the authors' knowledge, this is the first quantitative study on the identification of distributed mass attached on nanostructures modelled within generalized continuum mechanics theories by using finite eigenvalue data

Hearing distributed mass in nanobeam resonators

One-dimensional vibrating nanostructures show remarkable performance in detecting small adherent masses added to a referential configuration. The mass sensing principle is based on measuring the resonant frequency shifts caused by the unknown attached masses. In spite of its important application in several fields, few studies have been devoted to this inverse eigenvalue problem. In this paper we have developed a distributed mass reconstruction method for initially uniform nanobeams based on measurements of the first lower resonant frequencies of the free bending vibration. Two main inverse problems are addressed. In the first problem, the mass variation is determined by using the first lower eigenfrequencies of a supported nanobeam, under the a priori assumption that the mass variation has support contained in half of the axis interval. In the second problem, we show that the a priori assumption can be removed, provided that the spectral input data include an additional set of first lower eigenfrequencies belonging to a second spectrum associated to different end conditions. The nanobeam is modelled using the modified strain gradient elasticity accounting for size effects. The reconstruction is based on an iterative procedure which takes advantage of a closed-form solution when the mass change is small, and shows to be convergent under this assumption and for smooth mass variation. The accuracy of the reconstruction deteriorates in presence of discontinuous mass variation. For these cases, a constrained least-squares optimization filtering shows to be very effective to reduce the spurious oscillations around the target coefficientThe authors from Universidad Carlos III de Madrid wish to acknowledge the Ministerio de Economía y Competitividad de España for the financial support under Grants numbers DPI2014-57989-P and PGC2018-098218-B-I00. The authors from University of Udine gratefully acknowledge the financial support of the National Research Project PRIN 2015TT JN95 "Identification and monitoring of complex structural systems". The authors wish to thank the two reviewers and the editor for constructive criticism and, in particular, for suggesting the experimental application reported at the end of Section 2