On the Increase in Signal Depth due to High-Order Effects in Micro- and Nanosized Deformable Conductors

With regard to the transmission of a thermomechanical signal on extremely short temporal and spatial scales, which represents an issue particularly important dealing with micro- and nanosized electromechanical systems, it is well known that the so-called non-Fourier effects become not negligible. In addition, it has to be considered that the interaction among multiple energy carriers has, as a direct consequence, the involvement of high-order terms in the time-differential formulation of the dual-phase lag heat conduction constitutive equation linking the heat flux vector with the temperature variation gradient. Accepting that the deformations caused by the temperature variations are small enough to be modeled under the assumptions typical of the linear thermoelasticity, in the present article we take into account the highest Taylor expansion orders able to guarantee (under appropriate assumptions) stability conditions, thermodynamic consistency, and at the same time the existence of an influence domain of the external data linked to the energy transmission as thermal waves. To this aim, a cylindrical domain filled by an anisotropic and inhomogeneous thermoelastic material is investigated, although the results obtained will be independent from the considered geometry: for such a reason, we will be able to consider as illustrative examples some simulations referred to single-layer graphene and to show how the expansion orders selected strongly influence the domain of influence depth

On microstretch thermoviscoelastic composite materials

In this paper we derive a continuum theory for a thermoviscoelastic composite using an entropy production inequality proposed by Green and Laws, presented in Lagrangian description. The composite is modeled as a mixture of a microstretch viscoelastic material of KelvineVoigt type and a microstretch elastic solid. The strain measures and the basic laws are shown and the thermodynamic restrictions are established. Then the linear theory is considered and the constitutive equations are given in both anisotropic and isotropic cases. Finally, a uniqueness result is established within the framework of the linear theory

Reconstruction of round voids in the elastic half-space: Antiplane problem

We study the reconstruction of geometry (position and size) of round voids located in the elastic half-space, in frames of antiplane two-dimensional problem. We assume that a known point force is applied to the boundary surface of the half-space, and we can measure the shape of the surface over a certain finite-length interval. Then, if the geometry of the defect is unknown, we construct an algorithm to restore its position and size. Some numerical examples demonstrate a good stability of the proposed algorithm

How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons

COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; p < 0.0001) and diagnostic evaluations (16.4% vs. 42.2%; p < 0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; p < 0.0001) or urgent (20.4% vs. 38.5%; p < 0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; p < 0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice

Some continuous dependence results about high-order time differential thermoelastic models

This article aims to contribute to the investigation of the well-posedness question for three different heat conduction thermoelastic models, obtained starting from the dual-phase-lag (DPL) constitutive equation in its most general time differential formulation and considering Taylor expansion orders higher than those most commonly studied in literature so far. It is necessary to emphasize right from now that the investigation of such thermomechanical models, although they originate in terms of constitutive equations from suitable Taylor series expansions, has to be properly interpreted not as an attempt to emulate the delayed behavior characteristic of the original (i.e. not expanded) DPL model, but rather with the awareness of deepening the well-posedness question for three different stand-alone and self-consistent models. In particular, three estimates are obtained (one for each of the considered models) able to show the continuous dependence of the solutions of the related initial boundary value problems with respect to the supply terms and to the initial given data. All the continuous dependence results are obtained without the need to impose particular restrictions involving the delay times, except for the requirement that they are strictly positive

Uniqueness theorems about high-order time differential thermoelastic models

The purpose of the present manuscript is to investigate the well-posedness question for three different stand-alone and self-consistent thermoelastic models derived from the time differential formulation of the dual-phase-lag heat conduction law and characterized by Taylor expansion orders higher than those most commonly considered in literature up to now. The main motivation at the basis of this study is that the interaction among multiple energy carriers progressively gains significance as the observation scales reduce and has, as a direct consequence, the involvement of high-order terms in the time differential dual-phase-lag heat conduction constitutive equation. Considering inhomogeneous and anisotropic linear thermoelastic materials, we are able to prove three uniqueness results through the use of appropriate integral operators and Lagrange identities; the results are proved without any restriction imposed on the delay times other than their positivity

On the Spatial Behaviour for Transversely Isotropic Plates

Taking into account the Mindlin model about the theory concerning a state of bending for a linear transversely isotropic plate, some results about the spatial behaviour of transient solutions are established through appropriate families of line-integral measures. It has to be underlined that results are obtained under relaxed hypotheses on the positive definiteness of elasticity tensor

Some exponential decay estimates for thermoelastic mixtures

This paper concerns the study of time-harmonic vibrations for some classes of homogeneous and isotropic thermoelastic mixtures for which the constitutive coefficients are supposed to satisfy some mild positive definiteness conditions. Introducing some appropriate measures, we evaluate the spatial decay behaviour, when the frequency of harmonic vibrations is lower than a certain critical value