Search results for "construct"
showing 10 items of 3723 documents
Study of nucleation and growth processes of ettringite in diluted conditions
2020
Abstract Ettringite is a key compound of cementitious materials, formed during hydration that influences the rheological behavior of the cement paste. Despite its importance, ettringite formation has been poorly studied. In this work, nucleation and growth processes of ettringite were separately investigated. Ettringite nucleation was described using the Classical Nucleation Theory and an interfacial crystal-solution energy was determined. After the initial primary homogeneous nucleation, when the surface of already formed crystals was still low, the precipitation rate was shown to depend almost exclusively on the solution supersaturation. When the surface of crystals in suspension was gett…
Optimization of the Surface Roughness Equation obtained by Al7136 End-Milling
2017
The aim of this paper is to optimize the regression equation of the surface roughness obtained by 7136 aluminium alloy machined by end-milling process. The surface roughness is dependent on certain process parameters, which can vary, causing in this way variations of the surface quality. The research method used in this paper is the experiment and the Taguchi design of experiment. The experiment was performed using an experimental stand, in which every step to get the purpose, is presented. The measurements were made using a portable surface roughness tester. In the first part of the paper the influence percentage of the involved parameters in the machining process, was determined. Then, a …
Atomistic Simulations of the LaMnO3 (110) Polar Surface.
2003
The results of atomic structure calculations, with a focus on the surface relaxation and polarization, are presented for the LaMnO3 (110) O-terminated polar surface. We compare results of the classical shell model calculations for four possible terminations, including (1 × 2) (110) surface reconstruction, and demonstrate that the latter has the lowest surface energy. The surface energy is saturated only when six to eight near-surface atomic planes are relaxed which is accompanied by the considerable dipole moments perpendicular to the surface. Results are compared with those for iso-structural BaTiO3 (110) surfaces.
Geometric Properties of the 3D Spine Curve
2003
Through a 3D reconstruction of the human back surface using structured light techniques, we study the properties of spine curve by means of a set of parameters related to measures commonly applied in medicine. In this way, descriptors for measuring the abnormalities in the projections of the front and sagittal planes can be computed. We build the spine curve in 3D and analyse the behaviour of the Frenet frame when along the curve the deformation processes in idiophatic scoliosis appear.
Algorithms for the calculation of the view factors between human body and rectangular surfaces in parallelepiped environments
1992
Abstract The thermal comfort conditions for people in moderate thermal environments are subjected to spatial changes, depending on the radiative exchanges of the human body with the surrounding surfaces. Radiative thermal exchanges are notably accounted for by means of the “view factors” between a person in a given posture and the surface of the enclosure. These important parameters can be evaluated by means of a large set of graphs by Fanger, for rectangular surfaces. But the handling of graphs could lead to reading errors. In this paper a simple algorithm is presented, which is able to compute the required view factors. A validation, by means of a comparison against experimental data, is …
Experimental research regarding the study of surface quality of aluminum alloys processed through milling
2017
The aim of this paper is to present the necessary steps to conduct a design of experiment with application on the aluminum alloy surface quality obtained by end-milling process. The machined surface quality is influenced by the cutting process parameters, and especially by their variation. The research methods used in this paper are the Taguchi method - to determine the cutting parameters influence, on the surface quality, and the full factorial design of experiment to confirm the results obtained by Taguchi’s method and to determine the percentage of the parameters influence involved in the process.
3D reconstruction of transparent objects exploiting surface fluorescence caused by UV irradiation
2010
In this paper, we present a novel approach exploiting fluorescence imaging to estimate the shape of transparent objects. Classical inspection systems require users to coat transparent objects with some powder before measurement. Methods suggested in literature through non contact measurement do not effectively deal with the refraction problem, thus, providing inaccuracies. The proposed method handles the scanning of transparent objects without using any powder and solving the refraction problem using UV environment. A classical triangulation method based on stereovision scheme using fixed stereoscopic visible range cameras with a fixed UV (Ultra Violet) laser source is implemented. Transpar…
Effective elastic properties of biocomposites using 3D computational homogenization and X-ray microcomputed tomography
2021
A 3D computational homogenization method based on X-ray microcomputed tomography (μCT) was proposed and implemented to investigate how the fiber weight fraction, orthotropy and orientation distribution affect the effective elastic properties of regenerated cellulose fiber-polylactic acid (PLA) biocomposites. Three-dimensional microstructures reconstructed by means of the X-ray μCT were used as the representative volume elements (RVEs) and incorporated into the finite element solver within the computational homogenization framework. The present method used Euclidean bipartite matching technique so as to eliminate the generation of artificial periodic boundaries and use the in-situ solution d…
MUSIC-characterization of small scatterers for normal measurement data
2009
We investigate the reconstruction of the positions of a collection of small metallic objects buried beneath the ground from measurements of the vertical component of scattered fields corresponding to vertically polarized dipole excitations on a horizontal two-dimensional measurement device above the surface of the ground. A MUSIC reconstruction method for this problem has recently been proposed by Iakovleva et al (2007 IEEE Trans. Antennas Propag. 55 2598). In this paper, we give a rigorous theoretical justification of this method. To that end we prove a characterization of the positions of the scatterers in terms of the measurement data, applying an asymptotic analysis of the scattered fie…
Comment on "surface restructuring, kinetic oscillations, and chaos in heterogeneous catalytic reactions".
1999
In a recent article Zhdanov studied the oscillating $\mathrm{NO}+{\mathrm{H}}_{2}$ reaction on the Pt(100) single-crystal surface [V. P. Zhdanov, Phys. Rev. E 59, 6292 (1999)]. We have scrutinized his model and found fundamental errors in the chemical modeling, in the modeling of the surface reconstruction and in the simulation procedure itself.