Search results for "theoretical model"
showing 10 items of 107 documents
Unraveling the LiNbO3 X-cut surface by atomic force microscopy and density functional theory
2014
The ${\text{LiNbO}}_{3}$(2$\overline{1}\overline{1}0$) surface, commonly referred to as X-cut, is investigated by means of atomic force microscopy and first-principles calculations. Atomically resolved atomic force microscopy images show geometrical patterns not compatible with truncated bulk terminations. Fast Fourier transformation of the real-space images shows an oblique surface unit cell with lattice parameters of $a=0.75\ifmmode\pm\else\textpm\fi{}0.02$ nm, $b=0.54\ifmmode\pm\else\textpm\fi{}0.02$ nm, and $\ensuremath{\alpha}=94.{8}^{\ensuremath{\circ}}$. Comparing these experimental results with the theoretical models of stable surface terminations provides clear evidence for the for…
Positive Psychological Assessment in Latin America
2014
This chapter describes the development and adaptation of instruments to assess Positive Psychology’s constructs in Latin America. Results from the conducted literature review are presented according to PP pillars, as proposed by Seligman: positive emotions, positive traits, positive institutions and positive relationships. The criteria used to analyze the assessment instruments found included country’s contribution, number of tests locally developed vs adapted tests, psychometric properties of assessment instruments and theoretical models in which tests are grounded.
THE COST AS THE MAIN DETERMINANT OF THE LOCATION OF LOGSTICS CENTERS
2018
Apropriate location of the logistics center allows entrepreneurs to significantly reduce the costs of transport. On the other hand, it has a positive impact on the development of the transport infrastructure of the region.This paper presents the practical aspects of the localization problem of logistics center with the use of a geographic information system. It shows differences between theoretical models, the needs of decision-makers, and the data available to make the necessary calculations. The results of computational experiments were introduced to illustrate the effects of this approach.
Kinetics of doublet formation in bicomponent magnetic suspensions: The role of the magnetic permeability anisotropy
2017
Micron-sized particles (microbeads) dispersed in a suspension of magnetic nanoparticles, i.e., ferrofluids, can be assembled into different types of structures upon application of an externalmagnetic field. This paper is devoted to theoretical modeling of a relative motion of a pair of microbeads (either soft ferromagnetic or diamagnetic) in the ferrofluid under the action of applied uniform magnetic field which induces magnetic moments in the microbeads making them attracting to each other. The model is based on a point-dipole approximation for the magnetic interactions between microbeads mediated by the ferrofluid; however, the ferrofluid is considered to possess an anisotropic magnetic p…
Determination of the Stress Intensity Factor by Means of the Espi Technique
2007
The experimental determination of stress intensity factors by means of non-destructive techniques is a research topic of actual interest, In fact there are many applications, where a reliable and accurate experimental procedure is needed to evaluate numerical or theoretical models about the behaviour of cracked or notched structures.
Experimental analysis and micromechanical models of high performance renewable agave reinforced biocomposites
2017
Abstract The present work deals with the experimental study of high performance biocomposites reinforced with optimized agave fibers, as well as the successive implementation of reliable micromechanical models that can be used at the design stage. In detail, systematical experimental analyses performed on biocomposites with epoxy or PLA matrix, have permitted to highlight that for short fibers biocomposites the reinforcing leads to a significant improvement of the matrix stiffness, whereas the particular damage mechanism based essentially on the matrix failure with consequent tensile failure of the fibers aligned with the applied load, does not allow to obtain an actual reinforcing of the m…
Switching direction of laterally ordered monolayers induced by transfer instability
2007
Langmuir-Blodgett monolayers may show nanoscopic periodic patterns parallel and/or perpendicular to the transfer direction. The experimental findings are interpreted by a nonequilibrium model based on the stability of surfactant concentration and film thickness coupled fluctuations near the meniscus of a surfactant-covered receding thin film. In the high and low transfer speed limits, periodic fluctuations of the fluid subphase thickness, respectively perpendicular and parallel to the transfer, are selected. A qualitative phase diagram shows how transfer speed and film density manage the pattern shape.
Analytical prediction of the shear connection capacity in composite steel–concrete trussed beams
2016
Steel–concrete trussed composite beams are a particular types of composite girders constituted by a steel truss embedded in a concrete core. The truss is typically composed by a steel plate or a precast concrete slab working as bottom chord while coupled rebars are generally used to form the upper chord. Moreover, a system of ribbed or smooth steel rebars welded to the plate and forming the diagonals of the truss, works as web reinforcement. In the present study, the attention is focused on the evaluation of the shear resistance of the connection between bottom steel plate (the bottom chord) and concrete core through the diagonal bars of the truss developing a mechanical model able to accou…
Random short sisal fiber biocomposites: Optimal manufacturing process and reliable theoretical models
2018
Although several works have been published in literature on agave fibers and their biocomposites, accurate information about the choice of both the fibers and the manufacturing processes that allow the user to optimize the biocomposites properties in terms of strength and stiffness are not yet available; also, no theoretical models that can be used for an accurate evaluation of the mechanical properties of these biocomposites, are reported.To this aim, the present work intends to give a contribution by considering green epoxy biocomposites reinforced by both short and discontinuous sisal agave fibers arranged in proper MAT-type fabrics. In particular, an optimized manufacturing process that…
Electrochemical Conversion of CO2 to HCOOH at Tin Cathode: Development of a Theoretical Model and Comparison with Experimental Results
2018
The electrochemical reduction of pressurized carbon dioxide at tin cathode is considered a very promising process for the production of formic acid. Here, the process was studied in an undivided cell with the aim of developing a simple theoretical model. First, a large series of polarization and electrolyses was performed in order to evaluate the kinetic of the process. According to the literature, experimental results can be described by a simple reaction mechanism, which involves the following key stages: (i) mass transfer of CO2 to the cathode; (i) its adsorption described by a Langmuir equation; (iii) the reduction of adsorbed CO2. A simple model was developed based on the cathodic conv…