Search results for "Shells"
showing 10 items of 66 documents
New Alternative in the Methodology of Extraction and Dyeing with Active Molecules Derived from Vegetal Sources
2016
Abstract The general objective of this study refers to the identification of a sustainable and physical methodology of extraction of active compounds, envisaging the preservation of the high purity active natural dye molecule from nut shell (juglone), even under the conditions of an extraction performed in a mixt solvent medium (water-ethanol). The second major objective of the study consists of the application of these above mentioned dyes onto natural and synthetic substrates, thus making a correlation between their colour attributes and the fibrous composition of the substrates they are applied on. The motivation of this research was given by the identification of an improved extraction …
Discontinuous Galerkin models for composite multilayered shells with higher order kinematics
2021
Composite multilayered shells are widely employed in aerospace, automotive and civil engineering as weight-saving structural components. In multilayered shells, despite its versatility, the interplay between the curved geometry and the properties of the composite layers induces a complex distribution of the mechanical fields, which must be accurately resolved to safely employ generally curved composite shells as load-bearing structures. The problem can be addressed through the two-dimensional shell theories, which are based on suitable assumptions on the behavior of the mechanical fields throughout the thickness of the considered structures and are a viable strategy for reducing the computa…
Thermally Induced Structural Modification of Silica Nanoparticles Investigated by Raman and Infrared Absorption Spectroscopies
2010
We report an experimental investigation by Raman and infrared (IR) absorption spectroscopies on the structural modifications induced by isochronal thermal treatments on amorphous SiO2 nanoparticles (fumed silica). In particular, three different commercial types of this material, characterized by particle mean diameters of 7, 14, and 40 nm, were subjected to thermal treatments from 100 up to 1000 °C. We found that some properties of fumed silica, such as the SiOSi mean bond angle, ring size distribution, and surface adsorbed water content, are drastically different from those of common bulk silica materials and intimately related to the particles' dimension. The SiOSi mean bond angle, probed…
TRANSIENT AND FREE-VIBRATION ANALYSIS OF LAMINATED SHELLS THROUGH THE DISCONTINUOUS GALERKIN METHOD
2022
This paper presents a novel formulation for linear transient and free-vibration analysis of laminated shell structures based on Interior Penalty discontinuous Galerkin (DG) methods and variable-order through-the-thickness kinematics, whose combined use allows solving the shell problem with high-order accuracy throughout both the shell thickness and the shell modelling domain. The shell geometry is described via a generic system of curvilinear coordinates using either an analytical or a NURBS-based parametrization of the shell mid surface; the formulation also allows for the presence of cut-outs, which are implicitly represented by means of a level set function. After deriving the governing …
Buckling analysis of multilayered structures using high-order theories and the implicit-mesh discontinuous Galerkin method
2022
This work presents a novel formulation for the linear buckling analysis of multilayered shells. The formulation employs high-order Equivalent-Single-Layer (ESL) shell theories based on the through-the-thickness expansion of the covariant components of the displacement field, whilst the corresponding buckling problem is derived using the Euler’s method. The novelty of the formulation regards the solution of the governing equations, which is obtained via implicit-mesh discontinuous Galerkin (DG) schemes. The DG method is a high-order accurate numerical technique based on a discontinuous representation of the solution among the mesh elements and on the use of suitably defined boundary integral…
High-fidelity analysis of multilayered shells with cut-outs via the discontinuous Galerkin method
2021
Abstract A novel numerical method for the analysis of multilayered shells with cut-outs is presented. In the proposed approach, the shell geometry is represented via either analytical functions or NURBS parametrizations , while generally-shaped cut-outs are defined implicitly within the shell modelling domain via a level set function . The multilayered shell problem is addressed via the Equivalent-Single-Layer approach whereby high-order polynomial functions are employed to approximate the covariant components of the displacement field throughout the shell thickness. The shell governing equations are then derived from the Principle of Virtual Displacements of three-dimensional elasticity an…
A study of noise transmission through cylindrical shell using modal truncation approach
2011
International audience; The study of the vibroacoustic behaviour of cylindrical structure like aircraft fuselage requires the establishment of very large models, and the numerical results which can be obtained are often difficult to interpret. On the other hand, the study of simple structures such as cylindrical shells is useful to validate the criteria and tools that can be used to simplify the models of complex structures. The presented study concerns the sound transmission through a cylindrical shell coupled to a cavity and subjected to an incident acoustic wave. Noise reduction is obtained and validated by a numerical method which uses structural and acoustical modes. A criterion for se…
The formation and mineralization of mollusk shell.
2011
27 pages; International audience; In the last years, the field of mollusk biomineralization has known a tremendous mutation. The most recent advances deal with the nanostructure of shell biominerals, and with the identification of several shell matrix proteins: on one hand, the complex hierarchical organization of shell biominerals has been deciphered in few models, like nacre. On the other hand, although proteins represent a minor shell component, they are the major macromolecules that control biocrystal synthesis. Until recently, the paradigm was to consider that this control occurs by two antagonist mechanisms: crystal nucleation and growth inhibition. Emerging models try to translate a …
The shell-forming proteome of Lottia gigantea reveals both deep conservations and lineage-specific novelties
2013
19 pages; International audience; Proteins that are occluded within the molluscan shell, the so-called shell matrix proteins (SMPs), are an assemblage of biomolecules attractive to study for several reasons. They increase the fracture resistance of the shell by several orders of magnitude, determine the polymorph of CaCO(3) deposited, and regulate crystal nucleation, growth initiation and termination. In addition, they are thought to control the shell microstructures. Understanding how these proteins have evolved is also likely to provide deep insight into events that supported the diversification and expansion of metazoan life during the Cambrian radiation 543 million years ago. Here, we p…
Revalorization of Almond By-Products for the Design of Novel Functional Foods: An Updated Review
2021
The search for waste minimization and the valorization of by-products are key to good management and improved sustainability in the food industry. The great production of almonds, based on their high nutritional value as food, especially almond kernels, generates tons of waste yearly. The remaining parts (skin, shell, hulls, etc.) are still little explored, even though they have been used as fuel by burning or as livestock feed. The interest in these by-products has been increasing, as they possess beneficial properties, caused by the presence of different bioactive compounds, and can be used as promising sources of new ingredients for the food, cosmetic and pharmaceutical industry. Additio…