Search results for "construct"

Reconstruction of an effective magnon mean free path distribution from spin Seebeck measurements in thin films

2017

A thorough understanding of the mean-free-path (MFP) distribution of the energy carriers is crucial to engineer and tune the transport properties of materials. In this context, a significant body of work has investigated the phonon and electron MFP distribution, however, similar studies of the magnon MFP distribution have not been carried out so far. In this work, we used thickness-dependence measurements of the longitudinal spin Seebeck (LSSE) effect of yttrium iron garnet films to reconstruct the cumulative distribution of a SSE related effective magnon MFP. By using the experimental data reported by Guo et al. [Phys. Rev. X 6, 031012 (2016)], we adapted the phonon MFP reconstruction algo…

Statistical Reconstruction of Microstructures Using Entropic Descriptors

2018

We report a multiscale approach of broad applicability to stochastic reconstruction of multiphase materials, including porous ones. The approach devised uses an optimization method, such as the simulated annealing (SA) and the so-called entropic descriptors (EDs). For a binary pattern, they quantify spatial inhomogeneity or statistical complexity at discrete length-scales. The EDs extract dissimilar structural information to that given by two-point correlation functions (CFs). Within the SA, we use an appropriate cost function consisting of EDs or comprised of EDs and CFs. It was found that the stochastic reconstruction is computationally efficient when we begin with a preliminary synthetic…

Box 5: Surface Crystallography Terminology

2009

The crystalline nature of the surface differs from the bulk because atoms on the surface experience a different force field due to unterminated bonds, oxidation by adatoms etc. [1]. Free energy minimisation leads to reconstruction of the surface layer from the bulk by formation of dimers and displacement of atoms from their normal sites.

Metal artifact reduction in x-ray computed tomography: Inpainting versus missing value

2011

A comparison of algorithms for reduction of metal artifacts in x-ray cone beam computed tomography (CBCT) is presented. In the context of algebraic reconstruction techniques (ART) several inpainting algorithms in the image domain are evaluated against missing data strategies. A GPU-based iterative framework is employed for a meaningful comparison of both. Simulation results from an extended Shepp-Logan phantom and real world dental data are given.

On cone-beam computed tomography artifacts induced by titanium implants

2010

Objectives: To briefly review the mathematical background of beam-hardening artifacts in cone-beam computed tomography (CBCT)-reconstruction and to investigate geometrical properties relevant for these reconstruction errors. By means of simulated and experimental results, beam-hardening effects caused by titanium implants are evaluated. Materials and methods: The geometrical and physical properties of the acquisition process of the projections used for 3D reconstruction are investigated and their effects on the CBCT images in the presence of titanium implants are derived. Beam-hardening effects are computed for a simplified polychromatic situation (three energy subsets of 80 and 110 kV) and…

Auto calibration of a cone-beam-CT

2012

Purpose: This paper introduces a novel autocalibration method for cone-beam-CTs (CBCT) or flat-panel CTs, assuming a perfect rotation. The method is based on ellipse-fitting. Autocalibration refers to accurate recovery of the geometric alignment of a CBCT device from projection images alone, without any manual measurements. Methods: The authors use test objects containing small arbitrarily positioned radio-opaque markers. No information regarding the relative positions of the markers is used. In practice, the authors use three to eight metal ball bearings (diameter of 1 mm), e.g., positioned roughly in a vertical line such that their projection image curves on the detector preferably form l…

Compressive response of substandard steel-jacketed RC columns strengthened under sustained service loads: From the local to the global behavior

2018

Abstract This paper presents an experimental investigation on substandard partially steel jacketed RC columns strengthened under sustained loads and loaded until failure. The aim of the study is to compare the compressive response of preloaded columns with respect to the tests without preload to obtain a more realistic prediction of load-carrying capacity of structural columns after retrofitting under serviceability loads. The influence of the preload level, the delayed contribution of the confining device during the loading process and the time dependent effects are highlighted for the tested specimens. Based on the experimental observations, an analysis-oriented model is proposed for the …

Conjectural reconstruction from archive drawings: methodological aspects

2018

The digital reconstruction of architectural projects starting from archive sources is a well established disciplinary application useful for the study and analysis of architecture and its relations with the historical context as well as for the representation of volumes and spaces not visible in the original documents. Given the importance recognized to these operations which inevitably involve processes of hermeneusi we propose methodological guidelines for the drafting a protocol limiting arbitrariness as much as possible. The analysis was carried out on three projects by Giuseppe Damiani Almeyda (Capua 1834 - Palermo 1911), Ernesto Basile (Palermo 1857-1932) and Salvatore Benfratello (Pa…

2014

This paper investigates the finite-time distributedL2–L∞consensus control problem of multiagent systems with parameter uncertainties. The relative states of neighboring agents are used to construct the control law and some agents know their own states. By substituting the control input into multiagent systems, an augmented closed-loop system is obtained. Then, we analyze its finite-time boundedness (FTB) and finite-timeL2–L∞performance. A sufficient condition for the existence of the designed controller is given with the form of linear matrix inequalities (LMIs). Finally, simulation results are described.

Elementary Newtonian Mechanics

2010

This chapter deals with the kinematics and the dynamics of a finite number of mass points that are subject to internal, and possibly external, forces, but whose motions are not further constrained by additional conditions on the coordinates. Constraints such as requiring some mass points to follow given curves in space, to keep their relative distance fixed, or the like, are introduced in Chap. 2. Unconstrained mechanical systems can be studied directly by means of Newton’s equations and do not require the introduction of new, generalized coordinates that incorporate the constraints and are dynamically independent. This is what is meant by “elementary” in the heading of this chapter — thoug…