Sunyaev-Zel'dovich clusters reconstruction in multiband bolometer camera surveys

We present a new method for the reconstruction of Sunyaev-Zel'dovich (SZ) galaxy clusters in future SZ-survey experiments using multiband bolometer cameras such as Olimpo, APEX, or Planck. Our goal is to optimise SZ-Cluster extraction from our observed noisy maps. We wish to emphasize that none of the algorithms used in the detection chain is tuned on prior knowledge on the SZ -Cluster signal, or other astrophysical sources (Optical Spectrum, Noise Covariance Matrix, or covariance of SZ Cluster wavelet coefficients). First, a blind separation of the different astrophysical components which contribute to the observations is conducted using an Independent Component Analysis (ICA) method. Then, a recent non linear filtering technique in the wavelet domain, based on multiscale entropy and the False Discovery Rate (FDR) method, is used to detect and reconstruct the galaxy clusters. Finally, we use the Source Extractor software to identify the detected clusters. The proposed method was applied on realistic simulations of observations. As for global detection efficiency, this new method is impressive as it provides comparable results to Pierpaoli et al. method being however a blind algorithm. Preprint with full resolution figures is available at the URL: w10-dapnia.saclay.cea.fr/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=728Comment: Submitted to A&A. 32 Pages, text onl

Two approaches for the simultaneous separation and deblurring ; application to astrophysical data

Two approaches are presented to solve the problem of simultaneously deconvolving and separating mixtures of components. The first one uses a statistical description of the wavelet coefficients of the signals. The second one consists in minimizing a variational functional. Both methods are applied to the reconstruction of Sunyaev-Zel’dovich galaxy clusters from Cosmic Microwave Background experiments such as ACT. We find that both methods, when tuned, yield similar results and that the reconstruction of intense clusters is substantially improved when their non-gaussianity is taken into account.Nous présentons deux approches pour résoudre le problème de séparation et de déconvolution simultanées de mélanges de composantes. La première est basée sur une description statistique des coefficients d’ondelettes des signaux. La seconde consiste à minimiser une fonctionnelle variationnelle. Nous appliquons ces deux méthodes à la reconstruction des amas de galaxies par l’effet Sunyaev-Zel’dovich dans le cadre de la mission d’observation du fond diffus cosmique par ACT. Nous trouvons que pour des paramètres appropriés, les deux méthodes donnent des résultats comparables et que prendre en compte le caractère nongaussien des amas très intenses améliore nettement leur reconstruction

Deux méthodes de déconvolution de mélanges de composantes; application à la reconstruction des amas de galaxies

Nous présentons deux approches pour résoudre le problème de séparation et de déconvolution simultané de mélanges de composantes. La première est basée sur une description statistique des coefficients d'ondelettes des signaux. La seconde est nouvelle et consiste à minimiser une fonctionnelle variationnelle. Nous appliquons ces deux méthodes à la reconstruction des amas de galaxies par l'effet Sunyaev-Zeldovich dans le cadre de la mission d'observation du fond diffus cosmique ACT. Nous trouvons que pour des paramètres appropriés, les deux méthodes donnent des résultats comparables et que prendre en compte le caractère non-gaussien des amas très intenses améliore nettement leur reconstruction

Indirect structural health monitoring (iSHM) of transport infrastructure in the digital age

Workshop reportCopyright © Joint Research Centre (European Commission). The existing European motorway infrastructure network is prone to ageing and subject to natural events (e.g. climate change) and hazards (e.g. earthquakes), necessitating immediate actions for its maintenance and safety. Within this context, the structural health monitoring (SHM) framework allows a quantitative assessment of the structural integrity, serviceability and performance, facilitating better-informed decisions for the management of the existing infrastructure. The European Commission Joint Research Centre (JRC) established the exploratory research project MITICA (Monitoring Transport Infrastructures with Connected and Automated vehicles) to investigate the opportunity to use novel methods for infrastructure motoring, aiming at the efficient maintenance of the European aging road infrastructure. This report summarizes the discussion and the outcomes of a workshop held at the JRC in Ispra (Italy) on June 6-7 2022, as part of the MITICA project. Considering the EU priority “A Europe fit for the digital age”, the workshop was dedicated to SHM and its application to civil infrastructure, focusing on innovative indirect structural health monitoring (iSHM) approaches that rely on the vehicle-bridge interaction and the deployment of sensor-equipped vehicles for the monitoring of the existing bridge infrastructure. The report aims to become a reference document in the area of iSHM using passing vehicles, for both scholars and policy makers

An embedded cohesive crack model for finite element analysis of brickwork masonry fracture

This paper presents a numerical procedure for fracture of brickwork masonry based on the strong discontinuity approach. The model is an extension of the cohesive model prepared by the authors for concrete, and takes into account the anisotropy of the material. A simple central-force model is used for the stress versus crack opening curve. The additional degrees of freedom defining the crack opening are determined at the crack level, thus avoiding the need of performing a static condensation at the element level. The need for a tracking algorithm is avoided by using a consistent procedure for the selection of the separated nodes. Such a model is then implemented into a commercial code by means of a user subroutine, consequently being contrasted with experimental results. Fracture properties of masonry are independently measured for two directions on the composed masonry, and then input in the numerical model. This numerical procedure accurately predicts the experimental mixed-mode fracture records for different orientations of the brick layers on masonry panels

Homogenization and seismic assessment : review and recent trends

The mechanics of masonry structures has been for long underdeveloped in comparison with other fields of knowledge. Presently, non-linear analysis is a popular field in masonry research and advanced computer codes are available for researchers and practitioners. The chapter presents a discussion of masonry behaviour and clarifies how to obtain the non-linear data required by the computations. The chapter also addresses different homogenisation techniques available in the literature in the linear and rigid-plastic case, aiming at defining a catalogue and at discussing the advantages and disadvantages of the different approaches. Special attention is given to stress assumed models based either on a polynomial expansion of the micro-stress field or in the discretization of the unit cell by means of a few constant stress finite elements CST with joints reduced to interfaces. Finally, the aspects of seismic assessment are presented and case studies involving the use of macro-block analysis, static (pushover) analysis and time integration analysis are discussed.(undefined