Multiscale Analysis of Trabecular Bone

2000 ◽  
Author(s):  
Frederic Bouyge ◽  
Iwona Jasiuk
Keyword(s):  
Trabecular Bone ◽  
Elastic Properties ◽  
Hierarchical Structure ◽  
Hierarchical Model ◽  
Multiscale Analysis ◽  
Random Network ◽  
Theoretical Models ◽  
Collagen Fibrils ◽  
Laminated Structure ◽  
Multi Scale

Abstract Bone has a complex hierarchical structure. We study trabecular bone as a multi-scale material. In particular, we distinguish the following scales: nanostructural (collagen fibrils and apatite crystals), microscale (single laminae and laminated structure), mesoscale (random network of struts), and macroscale. We first present experimental observations and an overview of existing theoretical models of bone. Then, we construct a hierarchical model to predict elastic properties of trabecular bone.

Mechanical Principles of a Self-Similar Hierarchical Structure

2009 ◽  
Vol 1188 ◽  
Author(s):  
Huajian Gao
Keyword(s):  
Aspect Ratio ◽  
Hierarchical Structure ◽  
Hierarchical Model ◽  
Characteristic Length ◽  
Hierarchical Structures ◽  
Hierarchical Level ◽  
Multi Scale ◽  
Flaw Tolerance ◽  
Email Address ◽  
Self Similar

AbstractNatural materials such as bone, shell, tendon and the attachment system of gecko exhibit multi-scale hierarchical structures. Here we summarize some recent studies on an idealized self-similar hierarchical model of bone and bone-like materials, and discuss mechanical principles of self-similar hierarchy, in particular to show how the characteristic length, aspect ratio and density at each hierarchical level can be selected to achieve flaw tolerance and superior stiffness and toughness across scale. Tel.: (401) 863-2626; Email address:

scholarly journals A parametric prediction of the Young’s modulus of polymers enhanced with ΜWCNTs

2018 ◽  
Vol 233 ◽  
pp. 00025
Author(s):  
P.V. Polydoropoulou ◽  
K.I. Tserpes ◽  
Sp.G. Pantelakis ◽  
Ch.V. Katsiropoulos
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
Young's Modulus ◽  
Experimental Results ◽  
Scale Model ◽  
Fe Model ◽  
Multi Scale ◽  
Unit Cells ◽  
Random Dispersion

In this work a multi-scale model simulating the effect of the dispersion, the waviness as well as the agglomerations of MWCNTs on the Young’s modulus of a polymer enhanced with 0.4% MWCNTs (v/v) has been developed. Representative Unit Cells (RUCs) have been employed for the determination of the homogenized elastic properties of the MWCNT/polymer. The elastic properties computed by the RUCs were assigned to the Finite Element (FE) model of a tension specimen which was used to predict the Young’s modulus of the enhanced material. Furthermore, a comparison with experimental results obtained by tensile testing according to ASTM 638 has been made. The results show a remarkable decrease of the Young’s modulus for the polymer enhanced with aligned MWCNTs due to the increase of the CNT agglomerations. On the other hand, slight differences on the Young’s modulus have been observed for the material enhanced with randomly-oriented MWCNTs by the increase of the MWCNTs agglomerations, which might be attributed to the low concentration of the MWCNTs into the polymer. Moreover, the increase of the MWCNTs waviness led to a significant decrease of the Young’s modulus of the polymer enhanced with aligned MWCNTs. The experimental results in terms of the Young’s modulus are predicted well by assuming a random dispersion of MWCNTs into the polymer.

Background Synaptic Activity as a Switch Between Dynamical States in a Network

2003 ◽  
Vol 15 (7) ◽  
pp. 1439-1475 ◽  
Author(s):  
Emilio Salinas
Keyword(s):  
Random Network ◽  
Red Light ◽  
Theoretical Models ◽  
Reciprocal Inhibition ◽  
Synaptic Activity ◽  
Dynamic State ◽  
Motor Action ◽  
Sustained Activity ◽  
Uniform Background ◽  
Background Input

A bright red light may trigger a sudden motor action in a driver crossing an intersection: stepping at once on the brakes. The same red light, however, may be entirely inconsequential if it appears, say, inside a movie theater. Clearly, context determines whether a particular stimulus will trigger a motor response, but what is the neural correlate of this? How does the nervous system enable or disable whole networks so that they are responsive or not to a given sensory signal? Using theoretical models and computer simulations, I show that networks of neurons have a built-in capacity to switch between two types of dynamic state: one in which activity is low and approximately equal for all units, and another in which different activity distributions are possible and may even change dynamically. This property allows whole circuits to be turned on or off by weak, unstructured inputs. These results are illustrated using networks of integrate-and-fire neurons with diverse architectures. In agreement with the analytic calculations, a uniform background input may determine whether a random network has one or two stable firing levels; it may give rise to randomly alternating firing episodes in a circuit with reciprocal inhibition; and it may regulate the capacity of a center-surround circuit to produce either self-sustained activity or traveling waves. Thus, the functional properties of a network may be drastically modified by a simple, weak signal. This mechanism works as long as the network is able to exhibit stable firing states, or attractors.

scholarly journals Multi-scale identification of the elastic properties variability for composite materials through a hybrid optimisation strategy

2019 ◽  
Vol 176 ◽  
pp. 107193 ◽  
Author(s):  
Lorenzo Cappelli ◽  
Georgios Balokas ◽  
Marco Montemurro ◽  
Frédéric Dau ◽  
Laurent Guillaumat
Keyword(s):  
Composite Materials ◽  
Elastic Properties ◽  
Multi Scale

A Multi-scale, Hierarchical Model to Map Riparian Zones

2016 ◽  
Vol 32 (8) ◽  
pp. 1709-1720 ◽  
Author(s):  
J. A. Salo ◽  
D. M. Theobald
Keyword(s):  
Hierarchical Model ◽  
Riparian Zones ◽  
Multi Scale

Dehydration and Rehydration Alter Elastic and Viscoelastic Nanomechanical Properties of Cortical and Trabecular Bone

2010 ◽  
Author(s):  
Suzanne Ferreri ◽  
Bing Hu ◽  
Yi-Xian Qin
Keyword(s):  
Trabecular Bone ◽  
Elastic Properties ◽  
Mechanical Loading ◽  
Bone Mineral ◽  
Viscoelastic Properties ◽  
Therapeutic Interventions ◽  
Critical Importance ◽  
Nanomechanical Properties

Evaluation of bone’s response to mechanical loading is of critical importance in studies addressing the overall efficacy of therapeutic interventions. Moreover, thorough characterization of bone’s response to applied loads should reflect the contributions of both bone mineral (elastic properties) and collagen (viscoelastic properties).

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