National School of Architecture of Montpellier

PurposeThe aim of this article is to understand the definitions, trends and gaps currently existing in the literature regarding the concept of void in the built environment.Design/methodology/approachThe method used for this article is based on a bilingual narrative literature review, the authors being fluent both in French and English. The advantage of any literature review is that it allows researchers to gather and analyse existing academic literature on a specific subject. The chosen technique gives a thorough understanding of the study and helps in identifying research gaps. The literature review was sequential, online and used ScienceDirect, Scopus and Sage Knowledge as databases.FindingsThere are three main findings regarding this literature review. The first shows that the void is lacking consensus regarding its definition and attributes, yet this is unanimously considered as an existing space in the city. The second finding shows that voids are talking to our emotions and perceptions and more studies could investigate a new planning/design approach in taking this into consideration. At last, the third findings shows that there are some gaps that need to be further researched, such as the difference between Western and Eastern cultures to use voids in architecture.Originality/valueIn compiling 35 articles focussing on the void, this article proposes a valuable source of knowledge regarding this topic, as well as delineates new research directions.

La transition numérique dans l’habitat engendre des glissements, résistances et ruptures dans les sphères de la construction et des usages. Par rapport à l’édifice matériel, sont interrogés la relation à la commande et à l’automatisme, le rôle du numérique dans la régulation bioclimatique des bâtiments performants et les différences entre industries du bâtiment et du numérique en termes de série et rapport à la réglementation. L’habitat collectif, formaté par son modèle économique, doit s’adapter aux nouveaux paradigmes comme le télétravail et le numérique dans les usages. Des actualisations typologiques, une re-sociabilisation et une re-matérialisation de l’architecture sont proposées dans un exercice critique et éthique entre continuité et innovation.

This paper presents the first extensive study of the performances of solid polymers used as confinement materials for laser shock applications such as laser shock peening (LSP) as opposed to the exclusively used water-confined regime up to now. The use of this new confinement approach allows the treatment of metal pieces needing fatigue behavior enhancement but located in areas which are sensitive to water. Accurate pressure determination in the polymer confinement regime was performed by coupling finite element simulation and experimental measurements of rear free-surface velocity using the velocity interferometer system for any reflector (VISAR). Pressure could reach 7.6 and 4.6 GPa for acrylate-based polymer and cross-linked polydimethylsiloxane (PDMS), respectively. At 7 and 4.7 GW/cm 2 , respectively, detrimental laser breakdown limited pressure for acrylate and PDMS. These results show that the pressures produced were also as high as in water confinement, attaining values allowing the treatment of all types of metals with LSP and laying the groundwork for future determination of the fatigue behavior exhibited by this type of treated materials.

This article addresses the problem of the Non Unitary Joint Block Diagonalization ( $$\mathsf {NU-JBD}$$ ) of a given set of complex matrices for the blind separation of convolutive mixtures of sources. We propose new different iterative optimization schemes based on Conjugate Gradient, Preconditioned Conjugate Gradient, Levenberg–Marquardt and Quasi-Newton methods. We perform also a study to determine which of these algorithms offer the best compromise between efficiency and convergence speed in the studied context. To be able to derive all these algorithms, a preconditioner has to be computed which requires either the calculation of the complex Hessian matrices or the use of an approximation to these Hessian matrices. Furthermore, the optimal stepsize is also computed algebraically to speed up the convergence of these algorithms. Computer simulations are provided in order to illustrate the behavior of the different algorithms in various contexts: when exactly block-diagonal matrices are considered but also when these matrices are progressively perturbed by an additive Gaussian noise. Finally, it is shown that these algorithms enable solving the blind separation of the convolutive mixtures of sources problem.

This article deals with the problem of joint diagonalization of hermitian and/or complex symmetric matrices. Within the framework of gradient algorithms, we develop various algorithms which are based on different levels of approximation of the classical diagonalization criterion. The algorithms are based on a multiplicative update and on the derivation of an optimal step-size. One of the algorithms is a generalization of DOMUNG to the complex case. Finally, in the blind source separation context, computer simulations illustrate the relative performances of some proposed algorithms in comparison to the true gradient one.

ABSTRACTA methodology is proposed in this paper to compute local probability of fracture of a representative volume element from microstructural and fractographic information. A microscale approach is reported for cleavage fracture modelling of bainitic reactor pressure vessel steel. A fine metallographic and micro‐mechanical characterization has been performed. Morphological information has been used to generate realistic three‐dimensional (3D) aggregates and a suitable calibration process has been set up to identify an accurate crystal plasticity model for A508 bainitic steel. Simulation results have been successfully compared with macroscopic stress–strain curve. Taking benefits of a fine mechanical description of local stress and strain fields in aggregates, a post‐processing has been implemented to compute stress to failure values, for several realizations of an experimental carbides sizes distribution. A cumulative probability of fracture is proposed for this steel.

The paper presents a comparison between two sets of experimental results in a centrifugal flow pump. The tested impeller is the so‐called SHF impeller for which many experimental data have been continuously produced to built databases for CFD code validations with various levels of approximation. Measurements have been performed using optical techniques: 2D particle image velocimetry (PIV) technique on an air test model and 2D laser doppler velocimetry (LDV) technique on a water model, both for different flow rates. For the present study, results obtained by these optical techniques are compared together in terms of phase averaged velocity and velocity fluctuations inside the impeller flow passage for design flow rate.