Trois dimensions | EPFL Graph Search

Trois dimensions, tridimensionnel ou 3D sont des expressions qui caractérisent l'espace qui nous entoure, tel que perçu par notre vision, en ce qui concerne la largeur, la hauteur et la profondeur. Le terme « 3D » est également (et improprement) utilisé (surtout en anglais) pour désigner la représentation en (numérique), le relief des images stéréoscopiques ou autres , et même parfois le simple effet stéréophonique, qui ne peut par construction rendre que de la 2D (il ne s'agit donc que du calcul des projections perspectives, des ombrages, des rendus de matières). Mathématiques En mathématiques, cette notion correspond à la géométrie euclidienne dans l’espace ; l’espace est repéré par trois axes orthogonaux, contrairement au plan composé de deux dimensions. Les trois dimensions géométriques sont :

la largeur (gauche/droite) d'axe x, ou abscisse ;
la profondeur (avant/arrière) d'axe y, ou ordonnée ;
la hauteur (haut/bas) d'axe z, ou cote.

En mathématiques, la no

A simplified modeling method for multi-particle damper: Validation and application in energy dissipation analysis

Qianqing Wang

Particle dampers have received considerable attention in recent years as a novel damping technique. However, due to its high degree of nonlinearity, no mature damping model has been constructed. This article proposes an equivalent raft model that takes into account both the three-dimensional geometry and the material property. The model is validated by comparing the benchmark results with experimental observations and to simulations using the discrete element method. The equivalent raft model predicts the behavior of the structure-damper system in the presence of ground motion. Additionally, it can compute the time evolution of particles' displacement and force in three different function modes. Moreover, the energy dissipation mechanism of particle damper is investigated using the suggested model to analyze the impact of load amplitude, load frequency, container size, particle mass, and particle material.

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD2022

Amplitude and phase reconstruction for Low-Energy Electron Holography of individual proteins

Hannah Julia Ochner

Single-molecule imaging methods are of importance in structural biology, and specifically in the imaging of proteins, since they can elucidate conformational variability and structural changes that might be lost in imaging methods relying on averaging processes. Low-energy electron holography (LEEH) is a promising technique for imaging individual proteins with negligible radiation damage, which can be combined with a sample preparation process by native electrospray ion beam deposition (native ES-IBD) ensuring the creation of chemically pure samples suitable for holographic imaging.The central step in the analysis of data measured by LEEH is the numerical reconstruction of the object from the experimentally acquired holograms.Full information about the imaged object consists of both amplitude and phase information imprinted on the scattered wave during the interaction of the electron beam with the molecule and encoded in the hologram created by the interference of the scattered wave and the transmitted incident wave. A propagation-based algorithm with the goal of reconstructing the wave field in the plane of the object is presented and applied to holograms of individual proteins prepared by ES-IBD and measured with a low-energy electron holography microscope. The information retrieved from the reconstruction of the amplitude distribution in the object plane is discussed by analysing holograms of antibodies, demonstrating that the inherent conformational variability of these molecules can be mapped by LEEH. The influence of the sample preparation process on the surface conformations is tracked by tuning the landing energy of the proteins during deposition.To complement the amplitude data, an iterative phase retrieval algorithm is implemented to reconstruct the phase distribution in the object plane along with the amplitude distribution. The algorithm's performance and robustness is thoroughly evaluated and simulations regarding multiple scattering effects and element-dependent variations in scattering strength are carried out to provide a reference for the interpretation of phase data retrieved from experimentally acquired holograms. The iterative phase retrieval algorithm is then applied to protein data, indicating that both molecular density and charges can be related to features in the phase reconstructions, while the presence of metals does not correlate with specific phase signals at the current resolution obtainable from the experimental data.Since proteins are inherently three-dimensional, approaches towards three-dimensional reconstruction schemes are discussed, which will be the focus of future work.

EPFL2022

Amplitude and phase reconstruction for Low-Energy Electron Holography of individual proteins

Hannah Julia Ochner

EPFL2022