Scaling properties of work fluctuations after quenches at quantum transitions

We study the scaling properties of the statistics of the work done on a generic many-body system at a quantum phase transition of any order and type, arising from quenches of a driving control parameter. For this purpose we exploit a dynamic finite-size scaling framework. Namely, we put forward the existence of a nontrivial finite-size scaling limit for the work distribution, defined as the large-size limit when appropriate scaling variables are kept fixed. The corresponding scaling behaviors are thoroughly verified by means of analytical and numerical calculations in two paradigmatic many-body systems as the quantum Ising model and the Bose-Hubbard model.Comment: 30 pages, 6 figures. Revised versio

Granular Jamming as Controllable Stiffness Mechanism for Endoscopic and Catheter Applications

peer reviewe

Granular Jamming as Controllable Stiffness Mechanism for Endoscopic and Catheter Applications

Context During minimally invasive procedures, most of the devices (endoscopes, catheters, guidewires, etc.) need to be sufficiently flexible to avoid damaging patient tissues or causing pain, but have to be stiff enough to transmit force for support or for puncture. In the case of vascular stenosis, the guidewire has to be flexible to reach the stenosis (through the blood vessels), but it requires a rigid support to pass through the occlusion for treatment, to avoid buckling or deformation due to the force application. In order to solve this duality on the rigidity, controllable stiffness mechanisms can be used. Various mechanisms to control the stiffness can be found in the literature [1]. One of the promising solutions to achieve this objective is based on granular material jamming [2]. This research aims at studying the scaling laws of such solutions for miniaturized applications (with diameters below 3mm), the mechanical rules of design and the optimization based on the stiffness performances. Granular jamming The granular jamming is based on the locking of granular material. In this study, a flexible membrane is filled with a granular material (glass beads). When the pressure difference between outside and inside the membrane is low, the grains are free to move with respect to each other. In this configuration, the system is very flexible. Once the difference of pressure is increased, the grains are locked to each other due to the inter-grain friction. In this configuration, the system is more rigid. It is possible to adjust the stiffness of the device by controlling the pressure difference across the membrane. Materials and methods In this work, the performances of the stiffness change thanks to the granular jamming are quantified by mechanical testing. On the one hand, three point bending and cantilever beam tests are performed to quantify the flexural stiffness EI (product of the Young Modulus, E, and the second moment of area, I) of the solutions. Various granular materials and diameters of the samples are studied. On the other hand, triaxial compression tests are performed to observe the influence of the pressure difference on the rigidity obtained via granular jamming, using different granular materials. Results and discussion The tests described previously provide information on the performances of the granular jamming solution as well as an indication of the most important parameters to optimize. An optimal size of grains is highlighted by the results of these mechanical tests. The results of the triaxial compression tests show that the pressure difference is the most important parameter influencing the Young Modulus. The bending tests show that the second moment of area greatly impacts this stiffness. Removing the influence of the geometry, the equivalent Young Modulus is positively influenced for smaller diameters which is promising for the applications targeted in this work. Some of these results, as well as pictures and conclusions are illustrated in the poster file available in the following link : https://dipot.ulb.ac.be/dspace/bitstream/2013/239703/3/20161125PosterNCBMElblanc.pdf. One of the perspectives of this work is to develop a model for linking the results obtained from the different mechanical tests and to observe the optimization of the grains (shape and size) and cross-section of the samples with respect to the change of stiffness obtained. Further studies on stimulation method and on materials should be performed. References - [1] Kuder, I. K. et Al., ?Variable stiffness material and structural concepts for morphing applications?, Progress in Aerospace Sciences, pp.33-55, 2013. - [2] Loeve, A. J. et Al., ?Vacuum packed particles as flexible endoscope guides with controllable rigidity?, Granular Matter, pp. 543-554, 2010

Characterization and Modeling of Granular Jamming: Models for Mechanical Design

peer reviewedThe use of granular jamming is proposed for designing structures with tunable rigidity of their tools (with the ability of being flexible devices for shaping and deformation but rigid for shape-locking and force transmission). The granular jamming consists in modifying the apparent rigidity of a structure by controlling the vacuum in a membrane filled with granular material. When the difference of pressure is low, the grains are free to move with respect to each other and the structure is flexible. When the vacuum in the membrane is increased, the grains are blocked and the structure is more rigid. Different mechanical characterizations of the granular jamming have been performed (triaxial compression and tension and cantilever beam bending tests) for different glass bead sizes ranging between 100 μm and 1 mm (used as granular material) at different vacuum levels (between 0 kPa and 90 kPa ). The grain size slightly influences the stiffness while the pressure difference is the main parameter to tune the stiffness of the structure. Based on these experiments, analytical models have been developed and validated. The tension characteristics can be directly deduced from the compression behavior and the bending modulus can be obtained by a combination of the tension and compression moduli. The proposed analytical models present the advantage of a simple formulation and are suitable for estimating the performance of other structures based on the granular jamming. The models can estimate and predict satisfactorily the results of granular jamming and can be used for designing mechanical structures based on this mechanism

Granular jamming as controllable stiffness mechanism for endoscopic and catheter applications

peer reviewe

Conception assistée par ordinateur de gammes opératoires d'assemblage

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Mécanique rationnelle II

IR2, IR MATH107info:eu-repo/semantics/published

A pragmatic approach to computer-aided assembly planning

info:eu-repo/semantics/publishe

Cours de mécanique rationnelle II

2e candi. Sc. appl. - MATH 107info:eu-repo/semantics/published

Algèbre et géométrie

SYL-7903 = Fascicule 1 ;SYL-7906 = Fascicule 3Fascicule 1 et 3 :Edition 1993-1994SCA-1er CANDIinfo:eu-repo/semantics/publishe