A robust component mode synthesis method for stochastic damped vibroacoustics

International audienceIn order to reduce vibrations or sound levels in industrial vibroacoustic problems, the low-cost and efficient way consists in introducing visco- and poro-elastic materials either on the structure or on cavity walls. Depending on the frequency range of interest, several numerical approaches can be used to estimate the behavior of the coupled problem. In the context of low frequency applications related to acoustic cavities with surrounding vibrating structures, the finite elements method (FEM) is one of the most efficient techniques. Nevertheless, industrial problems lead to large FE models which are time-consuming in updating or optimization processes. A classical way to reduce calculation time is the Component Mode Synthesis method (CMS), whose classical formulation is not always efficient to predict dynamical behavior of structures including visco-elastic and/or poro-elastic patches. Then, to ensure an efficient prediction, the fluid and structural bases used for the model reduction need to be updated as a result of changes in a parametric optimization procedure. For complex models, this leads to prohibitivenumerical costs in the optimization phase or for management and propagation of uncertainties in the stochastic vibroacoustic problem. In this paper, the formulation of an alternative CMS method is proposed and compared to classical (u,p) CMS method: the Ritz basis is completed with static residuals associated to visco-elastic and poro-elastic behaviors. This basis is also enriched by the static response of residual forces due to structural modifications, resulting in a so-called robust basis, also adapted to Monte Carlo simulations for uncertainties propagation using reduced models

Méthodologie de conception robuste en vibroacoustique

International audienc

Component mode synthesis methods for damped vibro-acoustic problems

September 15-17International audienc

A robust component mode synthesis method for stochastic vibroacoustic problems

September 2-5International audienc

As-projective-as-possible image stitching with moving DLT

The success of commercial image stitching tools often leads to the impression that image stitching is a "solved problem". The reality, however, is that many tools give unconvincing results when the input photos violate fairly restrictive imaging assumptions; the main two being that the photos correspond to views that differ purely by rotation, or that the imaged scene is effectively planar. Such assumptions underpin the usage of 2D projective transforms or homographies to align photos. In the hands of the casual user, such conditions are often violated, yielding misalignment artifacts or "ghosting" in the results. Accordingly, many existing image stitching tools depend critically on post-processing routines to conceal ghosting. In this paper, we propose a novel estimation technique called Moving Direct Linear Transformation (Moving DLT) that is able to tweak or fine-tune the projective warp to accommodate the deviations of the input data from the idealised conditions. This produces as-projective-as-possible image alignment that significantly reduces ghosting without compromising the geometric realism of perspective image stitching. Our technique thus lessens the dependency on potentially expensive postprocessing algorithms. In addition, we describe how multiple as-projective-as-possible warps can be simultaneously refined via bundle adjustment to accurately align multiple images for large panorama creation.Julio Zaragoza, Tat-Jun Chin, Quoc-Huy Tran, Michael S. Brown, and David Sute

Rational design for the microplasma synthesis from vitamin B9 to N-doped carbon quantum dots towards selected applications

Available online 8 July 2022N-doped carbon quantum dots (NCQD) are rationally designed and synthesised, for the first time, from folic acid (Vitamin B9) by a non-thermal microplasma jet. A new conceptual design was developed to synthesise the desirable NCQD for three main applications (nanopesticides, water purification, and theranostic treatment). The structural and analytical characterisation confirmed an average size of 3.1 nm for the synthesised NCQD with the multi-functional groups (-OH, –COOH, –NH2) on their surface. The TEM results indicated that the core of NCQD was a multilayered structure, including single defected graphene sheets of graphitic-nitrogen and pyrrolicnitrogen. In addition, fluorescence performance and stability of the as-prepared NCQD were determined. The quantum yield of NCQD was 35%, which is relatively high, with a strong blue fluorescence. A basis for predicting colloidal behaviours based on balancing molecular attractive and repulsive forces was elucidated by applying the Derjaguin, Landau, Vervey, and Overbeek (DLVO) theory. Finally, compared with other similar microplasmaassisted synthesis processes, this developed method has proven the ability to provide a tailored and scalable synthesis process of high-quantum-yield NCQD at gram-scale production.Quoc Hue Pho, LiangLiang Lin, Nam Nghiep Tran, Tung T. Tran, An Hoa Nguyen, Dusan Losic, Evgeny V. Rebrov, Volker Hesse

The association between birth order and childhood brain tumors: a systematic review and meta-analysis

The incidence of childhood brain tumors (CBT) has increased worldwide, likely resulting from the improvements of early diagnostics. We conducted a systematic review and meta-analysis to clarify the association between birth order and CBT. We followed established guidelines to systematically search Ovid Medline, PubMed, and the Cochrane Library for English language studies, published before March 2018. Quality assessment was performed using the Newcastle-Ottawa Scale. Meta-analysis provided pooled risk estimates and their 95% confidence intervals (CIs) for birth order and CBT. We identified 16 case-control studies with a total sample of 32 439 cases and 166 144 controls and three prospective cohort studies (i.e. 4515 incident cases of CBTs among 5 281 558 participants). Compared with first birth order, the meta-odds ratio for second birth order in case-control studies was 1.04 (95% CI: 1.01-1.07), that for third birth order was 0.98 (95% CI: 0.90-1.06), and that for fourth order was 0.85 (95% CI: 0.78-0.92). The meta-hazard ratio for second or higher birth order compared with first birth order in cohort studies was 1.00 (95% CI: 0.96-1.05). We found no association between birth order and CBT in both case-control and cohort study designs; the small association observed for fourth birth order deserves further consideration

Diaphragm-sparing nerve blocks for shoulder surgery

Copyright © 2016 by American Society of Regional Anesthesia and Pain Medicine. Shoulder surgery can result in significant postoperative pain. Interscalene brachial plexus blocks (ISBs) constitute the current criterion standard for analgesia but may be contraindicated in patients with pulmonary pathology due to the inherent risk of phrenic nerve block and symptomatic hemidiaphragmatic paralysis. Although ultrasound-guided ISB with small volumes (5 mL), dilute local anesthetic (LA) concentrations, and LA injection 4 mm lateral to the brachial plexus have been shown to reduce the risk of phrenic nerve block, no single intervention can decrease its incidence below 20%. Ultrasound-guided supraclavicular blocks with LA injection posterolateral to the brachial plexus may anesthetize the shoulder without incidental diaphragmatic dysfunction, but further confirmatory trials are required. Ultrasound-guided C7 root blocks also seem to offer an attractive, diaphragm-sparing alternative to ISB. Ho