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6. Dark solitons, modulation instability and breathers in a chain of weakly non-linear oscillators with cyclic symmetry

Author

Fontanela, F., Grolet, A., Salles, L., Chabchoub, A., and Hoffmann, N.

Subjects
Nonlinear Sciences - Pattern Formation and Solitons
Abstract

In the aerospace industry the trend for light-weight structures and the resulting complex dynamic behaviours currently challenge vibration engineers. In many cases, these light-weight structures deviate from linear behaviour, and complex nonlinear phenomena can be expected. We consider a cyclically symmetric system of coupled weakly nonlinear undamped oscillators that could be considered a minimal model for different cyclic and symmetric aerospace structures experiencing large deformations. The focus is on localised vibrations that arise from wave envelope modulation of travelling waves. For the defocussing parameter range of the approximative nonlinear evolution equation, we show the possible existence of dark solitons and discuss their characteristics. For the focussing parameter range, we characterise modulation instability and illustrate corresponding nonlinear breather dynamics. Furthermore, we show that for stronger nonlinearity or randomness in initial conditions, transient breather-type dynamics and decay into bright solitons appear. The findings suggest that significant vibration localisation may arise due to mechanisms of nonlinear modulation dynamics.

Published
2017
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26. Elemental characterization of a Puma concolor fossil by non‐destructive X‐ray techniques.

Author

dos Santos, C. M. S. F. F., Moraes‐Neto, C. R., Araújo, O. M. O., Machado, A. S., dos Santos, R. S., Anjos, M. J., Salles, L. O., Oliveira, D. F., and Lopes, R. T.

Subjects
FOSSILS, FOSSILIZATION, COPPER, ENVIRONMENTAL exposure, X-rays
Abstract

Over the lifetime of an animal, metabolic processes in the body maintain bone tissues in a dynamic state of equilibrium. After the death of the organism, bone tissues undergo diagenesis, an intense transformation that affects its physicochemical constitution. Although many recent works have greatly contributed to the understanding of the processes surrounding diagenesis, there is still much yet to be understood about this multifaceted phenomena. In this work, XRF and microCT were used to characterize the specimen elemental configuration and investigate the fossilization process of a recovered Puma concolor (cranium, mandible and teeth elements), found submerged in a lake in the Impossível‐Ioiô Cave System (Bahia, Brazil). MicroCT enabled the identification of the density distribution throughout the specimens, which were used as reference to XRF analyses. The XRF spectra of the analyzed specimen showed the presence of 11 elements: P, Cl, Ca, Mn, Fe, Cu, Zn, Br, Sr, Y and Hg. Yttrium counts proved to be regular throughout the specimen surface and decreased in the interface between bone surface and interior, evidencing their correspondence to sample environmental exposure. Furthermore, a correlation between fossil surface coloration, element configuration and density is presented. The relatively low presence of Fe and Y in the enamel elicits its elementary and structural preservation. The combined results contribute to the understanding of the physicochemical process of paleomastozoological fossilization, further enriching the comprehension of the process of fossilization in a submerged environment. [ABSTRACT FROM AUTHOR]

Published
2023
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32. Shape Optimisation for Friction Dampers with Stress Constraint

Author

Denimal, E, Chevalier, R, Renson, L, Salles, L, Statistical Inference for Structural Health Monitoring (I4S), Inria Rennes – Bretagne Atlantique, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)-Département Composants et Systèmes (COSYS), Université Gustave Eiffel-Université Gustave Eiffel, Department of Mechanical Engineering [Imperial College London], Imperial College London, and Skolkovo Institute of Science and Technology [Moscow] (Skoltech)

Subjects
resonance mitigation, [SPI.MECA.VIBR]Engineering Sciences [physics]/Mechanics [physics.med-ph]/Vibrations [physics.class-ph], kriging, topological optimisation, nonlinear vibrations, friction damping
Abstract

International audience; Friction dampers are classically used in turbomachinery for bladed disks to control the levels of vibrations at resonance and limit the risk of fatigue failure. It consists of small metal components located under the platforms of the blades, which dissipates the vibratory energy through friction when a relative displacement between the blades and the damper appears. It is well known that the shape of such component has a strong influence on the damping properties and should be designed with a particular attention. With the arrival of additive manufacturing, new dedicated shapes for these dampers can be considered, determined with specific numerical methods as topological optimisation (TO). However, the presence of the contact nonlinearity challenges the use of traditional TO methods to minimise the vibration levels at resonance. In this work, the topology of the damper is parametrized with the Moving Morphable Components (MMC) framework, and optimised based on meta-modelling techniques: here kriging coupled with the Efficient Global Optimisation (EGO) algorithm. The level of vibration at resonance are computed based on the harmonic balanced method augmented with a constraint to aim directly for the resonant solution. It corresponds to the objective function to be minimised. Additionally, a mechanical constraint based on static stress analysis is also considered to propose reliable damper designs. Results demonstrate the efficiency of the method and show that dampers geometries that meet the engineers' requirements can be identified.

Published
2022

34. High order direct parametrisation of invariant manifolds for model order reduction of finite element structures: application to large amplitude vibrations and uncovering of a folding point

Author

Vizzaccaro, A, Opreni, A, Salles, L, Frangi, A, Touzé, C, Rolls-Royce Plc, and Engineering & Physical Science Research Council (E

Subjects
cs.CE, math.NA, cs.NA
Abstract

This paper investigates model-order reduction methods for geometrically nonlinear structures. The parametrisation method of invariant manifolds is used and adapted to the case of mechanical systems expressed in the physical basis, so that the technique is directly applicable to problems discretised by the finite element method. Two nonlinear mappings, respectively related to displacement and velocity, are introduced, and the link between the two is made explicit at arbitrary order of expansion. The same development is performed on the reduced-order dynamics which is computed at generic order following the different styles of parametrisation. More specifically, three different styles are introduced and commented: the graph style, the complex normal form style and the real normal form style. These developments allow making better connections with earlier works using these parametrisation methods. The technique is then applied to three different examples. A clamped-clamped arch with increasing curvature is first used to show an example of a system with a softening behaviour turning to hardening at larger amplitudes, which can be replicated with a single mode reduction. Secondly, the case of a cantilever beam is investigated. It is shown that the invariant manifold of the first mode shows a folding point at large amplitudes which is not connected to an internal resonance. This exemplifies the failure of the graph style due to the folding point, whereas the normal form style is able to pass over the folding. Finally, A MEMS micromirror undergoing large rotations is used to show the importance of using high-order expansions on an industrial example.

Published
2021

45. Optimisation of Perioperative Cardiovascular Management to Improve Surgical Outcome II (OPTIMISE II) trial: study protocol for a multicentre international trial of cardiac output-guided fluid therapy with low-dose inotrope infusion compared with usual care in patients undergoing major elective gastrointestinal surgery

Author

Edwards M, Forbes G, Berdunov V, Mihaylova B, Dias P, Thomson A, Grocott M, Mythen M, Gillies M, Phan T, Evered L, Wijeysundera D, McCluskey S, Hofer C, Abukhudair H, Szczeklik W, Hajjar L, Kahan B, Pearse R, MacDonald N, Abbott T, Martin T, Januszewska M, Niebrzegowska E, Bekele S, Pates K, Haines R, Walker S, Fowler A, Oliveira M, Whalley J, Stephens T, Amaral V, May S, Manou V, Jones T, Dunkley S, Pakats M, Griffiths B, Fernandez M, Jonas M, Bolger C, Collings N, Burnish R, Kelleher M, Dawson H, Lang A, Campbell R, Rea N, Clark S, Blunt M, Rosbergen M, Hodgson R, Wittenberg M, Filipe H, Gleeson Y, Pakou G, Szakmany T, Gunter U, Hodkinson G, Reay M, Gidda R, Allcock C, Cole A, Watts A, Gardner W, Tindall M, Anumakonda V, Agarwal N, Price T, Clark P, Thompson R, Fowler S, Gray K, McGregor A, Smith T, Wilson T, Guha A, Hodgson A, McSkeane A, Barberis L, Mohamed M, Prentice S, Saunders Z, Ratnam V, Pawa N, Sayan A, Thankachen M, Svensson M, Raj A, Ahmad N, Ivermee C, Cashman J, Smee E, Kanapeckaite L, Corcoran P, Fitzgerald E, Peyton P, Buckley A, Baulch S, Claxton G, Harris S, Sidiropolous S, de Almeida J, Simoes C, Galas F, Camara L, Malbouisson L, Soares S, Fernandes C, Joaquim E, Stefani L, Falcao L, Salgado M, Guimaraes G, Gomes M, Lineburger E, Navarro L, Salles L, Azi L, Prado R, Benedetti R, de Godoy E, Bastos F, da Silva R, dos Santos W, Pazmino-Canizares J, Parotto M, Wasowicz M, Beattie S, Meineri M, Clarke H, Ladha K, Jerath A, Ayach N, Poonawala H, Sellers D, Duncan D, Carroll J, Hudson C, van Vlymen J, Jaeger M, Shelley J, Shore D, McQuaide S, Richebe P, Godin N, Gobert Q, Fortier L, Verdonck O, Sato H, Schricker T, Codere-Maruyama T, Lattermann R, Hatzakorzian R, Moore A, Sato T, Funk D, Kowalski S, Girling L, Monterola M, Fidler K, Sander M, Markmann M, Schulte D, Singer R, Koch C, Ruhrmann S, Habig L, Edinger F, Schneck E, Treskatsch S, Ertmer M, Trauzeddel R, Weyland A, Diers A, Grote T, Pabel S, Lipka A, Nannen L, Fleischer A, Wittmann M, Winkler A, Neumann C, Fingerhut M, Ehrentraut H, Guttenthaler V, Heringlake M, Brandt S, Olsson S, Schmidt C, Schemke S, Murat L, Abu Khudair H, Farhoud E, Ghidan A, Al Masri M, Abu Kwiak S, Abdel-Nabi H, Grigoras I, Ristescu I, Jitaru I, Manole M, Rusu D, Gata A, Aldecoa C, Gonzalez A, Alfonso S, Perz L, Feijoo J, Guerra Y, Herrero A, Ripolles-Melchor J, Abad-Motos A, de Pablo E, Martinez-Hurtado E, Abad-Gurumeta A, Salvachua-Fernandez R, Nozal-Mateo B, de Nadal M, Galan P, Visauta E, Peral E, Da Prat I, Suarez S, Peral C, Una-Orejon R, Caldera-Alvarez M, Fernandez-Francos S, Davila A, Ortola C, Gutierrez A, Mugarra A, Romero E, Soro M, Gracia E, Pozo N, Villafane A, Diez A, Sanchez C, Buron F, Blanco R, Duran M, Parada P, Torres M, Rivas M, Brage S, Castro A, Conde M, Pardal C, Ben M, Perez A, Sancho J, Alarcon M, Mariotti S, Marcolino I, Winter A, McGrane T, Craven D, Turnbo T, Mayo G, Campbell D, Klintworth S, Tilley A, Weinstein M, Horan A, Chowdary R, Carlon V, Balasinorwala T, Yang G, and OPTIMISE II Investigators

Published
2019

46. Integrating Computational Methods to Investigate the Macroecology of Microbiomes

Author

Mascarenhas, R., Ruziska, F.M., Moreira, E.F., Campos, A.B., Loiola, M., Reis, K., Trindade-Silva, A.E., Barbosa, F.A.S., Salles, L., Menezes, R., Veiga, R., Coutinho, F.H., Dutilh, B.E., Guimaraes, P.R., Jr., Assis, A.P.A., Ara, A., Miranda, J.G.V., Andrade, R.F.S., Vilela, B., Meirelles, P.M., Mascarenhas, R., Ruziska, F.M., Moreira, E.F., Campos, A.B., Loiola, M., Reis, K., Trindade-Silva, A.E., Barbosa, F.A.S., Salles, L., Menezes, R., Veiga, R., Coutinho, F.H., Dutilh, B.E., Guimaraes, P.R., Jr., Assis, A.P.A., Ara, A., Miranda, J.G.V., Andrade, R.F.S., Vilela, B., and Meirelles, P.M.

Abstract

Contains fulltext : 218139.pdf (publisher's version ) (Open Access), Studies in microbiology have long been mostly restricted to small spatial scales. However, recent technological advances, such as new sequencing methodologies, have ushered an era of large-scale sequencing of environmental DNA data from multiple biomes worldwide. These global datasets can now be used to explore long standing questions of microbial ecology. New methodological approaches and concepts are being developed to study such large-scale patterns in microbial communities, resulting in new perspectives that represent a significant advances for both microbiology and macroecology. Here, we identify and review important conceptual, computational, and methodological challenges and opportunities in microbial macroecology. Specifically, we discuss the challenges of handling and analyzing large amounts of microbiome data to understand taxa distribution and co-occurrence patterns. We also discuss approaches for modeling microbial communities based on environmental data, including information on biological interactions to make full use of available Big Data. Finally, we summarize the methods presented in a general approach aimed to aid microbiologists in addressing fundamental questions in microbial macroecology, including classical propositions (such as "everything is everywhere, but the environment selects") as well as applied ecological problems, such as those posed by human induced global environmental changes.

Published
2019

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