704 research outputs found
A physical interpretation for broken reciprocity in spatiotemporal modulated periodic rods
No full textPeriodic systems have long been known for their peculiar characteristics in wave propagation and have been studied in many fields over the last century, going from electro-magnetics and optics to elastic structures, which drew an increasing interest in structural and mechanical engineering for vibration suppression and control spanning over broadband frequency ranges. Recently, on the stream of other studies conducted in different fields, spatiotemporal modulated elastic structures have been studied, showing promising results for wave control in that one-way propagation in the so called directional-bands can be achieved, constituting what may be called a mechanical diode. Despite of the fact that mathematical methods for the analysis of such structures have already been developed, often physics behind them is difficult to grasp. In this work, a simplified interpretation of the undergoing phenomena is thus given relating wave propagation in the mean to its physical characteristics as well as to modulation parameters. Exploiting Doppler effect and passive equivalent structures, it is shown that the broken reciprocity is due to the fact that opposite travelling waves effectively see two different periodic structures. To this aim the rod case is analysed for low modulation speeds and low modulation amplitudes; finally, in the light of the previous analysis, an explanation for First Brillouin Zone's asymmetry is given
YetAnotherFEcode
No full textA simple MATLAB-based code for implementing the Finite Element method in an object oriented fashion.
The main idea behind this package is to enable rapid prototyping and reproducible research related to finite element applications and/or reduced-order modeling in a user-friendly MATLAB environment.
On one hand, commercial packages lack the flexibility needed for testing new ideas essential for research, especially in the context of reduced-order modeling, where FE problems are indeed just applications but still require mild intrusion/access to the functionality. Open source packages, on the other hand, allow endless access to the implementation but tend to be very cumbersome to hack, and require significant time and training to be able to test even the simplest of ideas. This code is particularly aimed towards users/researchers who are interested in intrusive finite-element modeling without getting lost in gory details of open source FE packages.
A distinguishing aspect of this package is that apart from using existing elements in our library, one can program new elements with relative ease and flexibility. These elements may also arise from multi-physics problems, e.g., thermo-mechanical problems which involve the numerical solution of different partial differential equations governing heat and momentum balance on the same physical domain.
Without worrying about the cumbersome details of finite-element assembly, a researcher can simply focus on the element-level implementation to quickly obtain results. At the same time, developers are also encouraged to contribute new and alternative ideas to improve this environment and potentially publish them, allowing future users to access and build upon their work. This allows for rapid development and testing of ideas, especially valuable in research efforts.
To use the code, simply add the main folder and its contents to the MATLAB path. Feel free to play with examples in the examples directory. Further usage and development instructions to follow.
To showcase the relevance, please cite the following reference if you use this package in your work
Shobhit Jain, Jacopo Marconi & Paolo Tiso (2020). YetAnotherFEcode. Zenodo. http://doi.org/10.5281/zenodo.4011281
Please report any issues/bugs to Shobhit Jain [email protected] or Jacopo Marconi [email protected]
Release Notes:
Introduced the procedure to add code associated to scientific publications (see "how to contribute" in the papers folder)
Added code associated to the following publications:
A nonlinear reduced order model with parametrized shape defects https://doi.org/10.1016/j.cma.2019.112785
A higher-order parametric nonlinear reduced-order model for imperfect structures using Neumann expansion https://doi.org/10.1007/s11071-021-06496-y
Sensitivity Analysis of Nonlinear Frequency Response of Defected Structures https://doi.org/10.21203/rs.3.rs-1707949/v1
Bug fixes and plot function update for multi-element meshes
Subwavelength negative refraction and flexural wave lens design via resonant double-negative piezoelectric metamaterial
No full textWe report the concept and demonstration of a double-negative, resonant metamaterial characterized by both dynamic negative mass and stiffness for negative refraction of flexural wave modes by means of a lens designed using this concept. The negative equivalent material properties are obtained in the subwavelength regime by concurrently exploiting both the effect of mechanical resonators (negative mass) and of piezoelectric patches with inductive resonant shunts (negative stiffness), leading to double-negative behavior. Following the theoretical foundations based on a modal framework, we analytically derive the frequency-dependent mass and stiffness properties as a function of the electromechanical parameters. The findings are corroborated by numerical computation of dispersion properties and simulations showing the focusing of a point source. As a case study, energy harvesting performance enhancement by exploiting the piezoelectric effect at the focal spot is also discussed
Editorial: Inflammatory disorders of the oral mucosa: current challenges and future perspectives
No full textBackbone curve tailoring via Lyapunov subcenter manifold optimization
No full textWe present a technique for the direct optimization of conservative backbone curves in nonlinear mechanical systems. The periodic orbits on the conservative backbone are computed analytically using the reduced dynamics of the corresponding Lyapunov subcenter manifold (LSM). In this manner, we avoid expensive full-system simulations and numerical continuation to approximate the nonlinear response. Our method aims at tailoring the shape of the backbone curve using a gradient-based optimization with respect to the system’s parameters. To this end, we formulate the optimization problem by imposing constraints on the frequency-amplitude relation. Sensitivities are computed analytically by differentiating the backbone expression and the corresponding LSM. At each iteration, only the reduced-order model construction and sensitivity computation are performed, making our approach robust and efficient
Topology optimization of nonlinear structural dynamics with invariant manifold-based reduced order models
No full textWe present a structural topology optimization method to tailor the hardening/softening dynamic response of nonlinear mechanical systems. The coefficient that controls this behavior is computed analytically using the third-order normal-form parametrization of the Lyapunov subcenter manifold, which eliminates the need for expensive full-order simulations and numerical continuation to approximate the so-called backbone curve of the system. The method further leverages the adjoint method for efficiently computing sensitivities of the objective function and constraints, while the explicit formulation of nonlinear internal elastic forces through tensor notation simplifies these evaluations. Notably, this tensorial approach is computationally efficient, especially when applied to a regular grid of elements. Consequently, the proposed approach offers a robust and efficient framework for optimizing the dynamic performance of nonlinear mechanical structures modeled with high-dimensional finite element models. The findings are corroborated through examples of two geometrically nonlinear systems, a Messerschmitt-Bölkow-Blohm (MBB) beam and a microelectro-mechanical system (MEMS) inertial resonator
Jacopo Sadoleto: De Laocoontis statua (1506) (FONTES 5)
No full textWhen the statue of Laocoon and his two sons in the clutch of the serpents was discovered near the Colosseum at the beginning of 1506 the excitement was great, and young Jacopo Sadoleto, later a cardinal, then a devoted humanist, composed a poem on this masterpiece based on classical verse. Sadoleto’s text is not without echoes of Vergil’s famous lines about Laocoon and his fate, and with an astonishingly independent judgment on the quality of the subject. This text has been printed in various modern publications on Sadoleto, respect to the Laocoon, but only the edition by the present author, produced in 1992, offered a critical text based on a comparison of all extant printed versions from the 16th and 17th centuries, along with a brief linguistic commentary. Since no other attempt to recover the original text and no more recent commentary have hitherto appeared, the text and commentary of the 1992 publication are here reprinted in a partly abridged, partly enlarged form in order to provide the interested scholar with a reliable text and some linguistic basics as materials for further interpretation
Plausibility or truth. Archival notes and reflections on the canvas of the ‘Militant and triumphant Church’ ascribed to Jacopo Zucchi
No full textWhile retracing the traditional history of the painting, which was fi rst ascribed to Federico Zuccari and later to
Jacopo Zucchi, the author hereby presents the long and painstaking research that has gradually confi rmed this
second hypothesis. The reader will, therefore, fi nd a synthesis of the history of this painting, which was surely
enough fi rst hosted in St Peter's Basilica, then moved to the Church of St Catherine of Alexandria and fi nally to
the Vatican Sacristy. Based on a number of inconsistencies which emerged during archival research, doubts still persist with regard to
the historicity of this historical-artistic tradition. Despite the fact that scholars are fi rmly inclined to ascribe the
painting to Zucchi, some unpublished documents tend to undermine this assumption, while still implying that the
painting might be by an artist of the Zuccari famil
Three-Dimensional Culture System: A New Frontier in Cancer Research, Drug Discovery, and Stem Cell-Based Therapy
No full textTwo-dimensional culture systems have been used for a long time in the research field but their disadvantages make it difficult to reproduce the in vivo environment. Three-dimensional culture systems overcome these limitations, simulating the physiological context of an organism, from the molecular level to the cellular, tissue, and organ complexity levels. This review focuses on 3D cellular models, such as spheroids and tumoroids, which reproduce tumor heterogeneity and microenvironments. It also includes 3D cultures of mesenchymal stem cells (MSCs), particularly those derived from teeth. In conclusion, 3D models are profoundly impacting the biomedical field by offering more accurate in vitro platforms for drug development and disease modeling, thereby significantly reducing the reliance on animal testing and leading to the advancement of personalized and regenerative medicine
- …
