The Brazilian academic genealogy: evidence of advisor–advisee relationships through quantitative analysis

Scientometrics - Science can be examined from several standpoints, such as through a bibliometric analysis of the scientific output of researchers, research groups or institutions. However, there...     

Has hosting on science direct improved the visibility of Latin American scholarly journals? A preliminary analysis of data quality

Scientometrics - Latin American regional journals have adopted measures to increase both their quality and visibility, among which figures the promotion of their inclusion in international...     

How to assess sustainability of countries via inverse data envelopment analysis?

In this paper, two input-oriented and output-oriented inverse semi-oriented radial measures are presented. Such models are applied to determine resource allocation and investment strategies for assessing sustainability of countries. Our proposed models can deal with both positive and negative data. In our proposed inverse input-oriented data envelopment analysis (DEA) model, optimal inputs are suggested while outputs and efficiency score of decision-making unit (DMU) under evaluation are unchanged. Similarly, in our proposed inverse output-oriented DEA model, optimal outputs are proposed while inputs and efficiency score of DMU under evaluation are kept unchanged. For the first time, we propose two new inverse DEA models to handle resource allocation and investment analysis problems given sustainable development aspects in the presence of negative data. A case study is given for assessing sustainability of countries.     

Axial buckling analysis of single-walled carbon nanotubes in thermal environments via the Rayleigh–Ritz technique

Axial buckling characteristics of single-walled carbon nanotubes (SWCNTs) including thermal environment effect are studied in this paper. Eringen’s nonlocal elasticity equations are incorporated into the classical Donnell shell theory to establish a nonlocal elastic shell model which takes small-scale effects into account. The Rayleigh–Ritz technique is implemented in conjunction with the set of beam functions as modal displacement functions to consider the four commonly used boundary conditions namely as simply supported–simply supported, clamped–clamped, clamped–simply supported, and clamped-free in the buckling analysis. Selected numerical results are presented to demonstrate the influences of small scale effect, aspect ratio, thermal environment effects and boundary conditions in detail. It is found that the value of aspect ratio has different effects on the critical axial buckling loads of SWCNTs in low and high temperature environments. Also, it is observed that the difference between the thermal axial buckling responses of SWCNTs relevant to various boundary conditions is more prominent for higher values of nonlocal elasticity constant.     

On the analysis of magnetization and Mössbauer data for ferritin

Experimental data for antiferromagnetic nanoparticles are often analyzed as if the particles were ferromagnetic. However, due to the volume dependence of the magnetization resulting from uncompensated spins, such analysis will yield erroneous results. This is demonstrated as we analyze ac and dc magnetization data as well as M?ssbauer spectra obtained for ferritin. The values of the median energy barrier obtained from the different data are in very close agreement when a distribution of volumes and a volume dependence of the magnetization are taken into account. However, when the volume dependence of the magnetization is neglected, erroneous values of the anisotropy energy barrier and the attempt time τ(0) are obtained.     

How accurate are news mentions of scholarly output? A content analysis

Scientometrics - News mentions are considered as useful source for measuring the societal impact of scholarly output, meanwhile data quality plays a fundamental role in its research and...     

Plate bending analysis using the classical or the Reissner–Mindlin models

Plates can be solved with the classical or the Reissner–Mindlin plate model using the same computer code with an appropriate treatment of the direct boundary element formulation. A field decomposition is employed to establish a connection between these plate models and to obtain a boundary element formulation for the classical model from that used for the Reissner–Mindlin one. The classical model is related to the irrotational component of the field related to the rotations of the plate. The use of this field component in both the fundamental solution and the direct boundary integral equation of the Reissner–Mindlin model carries the classical model approach. Furthermore, the well-known fundamental solution derived from the classical model can be employed as the irrotational field of the fundamental solution of the Reissner–Mindlin model. In this way, the fundamental solution used by Danson to perform classical analysis was used as the irrotational component and the obtained results were compared with those obtained with the well-known Weeën's formulation.     

Understanding the relationship between microstructure and mechanical behavior of plasma-sprayed amorphous Al2O3–YAG ceramic coating based on depth-sensing indentation measurements

Journal of Materials Science - Based on depth-sensing indentation measurements, the relationship between microstructure and mechanical behavior of plasma-sprayed amorphous Al2O3–YAG ceramic...     

Synthesis of an integrated biorefinery via the C–H–O ternary diagram

An integrated biorefinery is designed to handle a wide variety of feedstocks (mainly biomass) and can produce a broad range of products (e.g., biofuel, biochemicals, etc.) via multiple conversion pathways and technologies. Gasification is recognized as one of the most promising technologies for initial processing of biomass. It uses thermal energy to convert the biomass feedstock into a gaseous mixture, which is also known as syngas, consisting mainly of carbon dioxide (CO₂), steam (H₂O), methane (CH₄), carbon monoxide (CO) and hydrogen (H₂). It is noted that the composition of syngas, especially the ratio of H₂ to CO, is crucial when the syngas is further converted to liquid fuels and chemicals. In this work, a graphical targeting approach for the evaluation of gas phase equilibrium composition of biomass gasification is proposed. Based on the targeted composition, a conceptual design of an integrated biorefinery can be systematically developed.     

Understanding the solidification and microstructure evolution during CSC-MIG welding of Fe–Cr–B-based alloy

The present is a study of the solidification and microstructure of Fe–28.2%Cr–3.8%B–1.5%Si–1.5%Mn (wt.%) alloy deposited onto a 1020 plain carbon steel substrate using the controlled short-circuit metal inert gas welding process. The as-solidified alloy was a metal matrix composite with a hypereutectic microstructure. Thermodynamic calculation based on the Scheil–Gulliver model showed that a primary (Cr,Fe)₂B phase formed first during solidification, followed by an eutectic formation of the (Cr,Fe)₂B phase and a body-centered cubic Fe-based solid solution matrix, which contained Cr, Mn and Si. Microstructure analysis confirmed the formation of these phases and showed that the shape of the (Cr,Fe)₂B phase was irregular plate. As the welding heat input increased, the weld dilution increased and thus the volume fraction of the (Cr,Fe)₂B plates decreased while other microstructural characteristics were similar.     

Computational engineering analysis with the new-generation space–time methods

This is an overview of the new directions we have taken the space–time (ST) methods in bringing solution and analysis to different classes of computationally challenging engineering problems. The classes of problems we have focused on include bio-inspired flapping-wing aerodynamics, wind-turbine aerodynamics, and cardiovascular fluid mechanics. The new directions for the ST methods include the variational multiscale version of the Deforming-Spatial-Domain/Stabilized ST method, using NURBS basis functions in temporal representation of the unknown variables and motion of the solid surfaces and fluid meshes, ST techniques with continuous representation in time, and ST interface-tracking with topology change. We describe the new directions and present examples of the challenging problems solved.     

Natural element analysis of the Cahn–Hilliard phase-field model

We present a natural element method to treat higher-order spatial derivatives in the Cahn–Hilliard equation. The Cahn–Hilliard equation is a fourth-order nonlinear partial differential equation that allows to model phase separation in binary mixtures. Standard classical C⁰{{mathcal{C}}^0}-continuous finite element solutions are not suitable because primal variational formulations of fourth-order operators are well-defined and integrable only if the finite element basis functions are piecewise smooth and globally C¹{{mathcal{C}}^1}-continuous. To ensure C¹{{mathcal{C}}^1}-continuity, we develop a natural-element-based spatial discretization scheme. The C¹{{mathcal{C}}^1}-continuous natural element shape functions are achieved by a transformation of the classical Farin interpolant, which is basically obtained by embedding Sibsons natural element coordinates in a Bernstein–Bézier surface representation of a cubic simplex. For the temporal discretization, we apply the (second-order accurate) trapezoidal time integration scheme supplemented with an adaptively adjustable time step size. Numerical examples are presented to demonstrate the efficiency of the computational algorithm in two dimensions. Both periodic Dirichlet and homogeneous Neumann boundary conditions are applied. Also constant and degenerate mobilities are considered. We demonstrate that the use of C¹{{mathcal{C}}^1}-continuous natural element shape functions enables the computation of topologically correct solutions on arbitrarily shaped domains.     

Statistical tolerance analysis using the unified Jacobian–Torsor model

This paper presents the results of ongoing research aimed at developing an integrated computer-aided tolerancing tool. A unified Jacobian–Torsor approach has been developed for deterministic (worst case) computer-aided tolerancing. The paper describes how one can use the same set of interval-based deterministic equations in a statistical context. The nature of the resulting equations lends itself to very fast computations to determine the percentage of rejected assemblies produced given some statistical distribution of the tolerances of their constituent parts. An example application is also presented to illustrate the use of the developed tool.     

Uniaxial flicker analysis of the psychophysical Stiles–Crawford effects

Purpose: We report on a semi-automated system for frequency analysis of the Stiles–Crawford effect of the first kind (SCE-I) using flicker methodology designed to gain insight into the temporal dynamics of the perceived visibility for alternating pupil entrance points. We describe the system and its calibration in detail and discuss psychophysical measurement data obtained for the two authors. Methods: A uniaxial system is used for SCE-I characterization of two emmetropic subjects as a function of flicker frequency for narrow wavelength bands chosen in the range of 450–700 nm using a fibre-guided tungsten–halogen lamp as light source. The flicker is realized using two orthogonally mounted galvanometric scanning mirrors that allow linear trajectories at any angle across the pupil. A fast tuneable liquid-crystal neutral density filter is used for brightness adjustment and another liquid-crystal filter is used for wavelength adjustment at each pupil point allowing simultaneous hue-shift determination for the Stiles–Crawford effect of the second kind (SCE-II). Results: Validation of the system is realized with a CCD camera, a spectrometer and a powermeter, and the data obtained are used in the software to calibrate all subsequent human subject measurements. The psychophysical data obtained show a strong frequency dependence of the Gaussian SCE-I with a characteristic directionality parameter, ρ, that is found to increase from 0.03 to 0.06/mm² with flicker in the range of 1–10 Hz. The simultaneously determined hue shift could not be determined beyond 1 Hz due to the longer time required for a subjective determination. Conclusion: We have reported on a fast uniaxial system for temporal characterization of the SCE-I. The psychophysical results obtained show that accurate specification of frequency in flicker analysis is mandatory when comparing SCE-I visibility and directionality curves obtained with those obtained using quasi-static bipartite fields. A uniaxial design offers unique advantages over that of common two-channel systems by completely eliminating spectral errors or brightness differences in the two branches that otherwise will impose on those of the visual system and degrade the psychophysical data. Future work with more subjects will be used to narrow the uncertainty and the causes of the effects observed.     

Controlling a re-entrant manufacturing line via the push–pull point

A reduced model of a re-entrant semiconductor factory exhibiting all the important features is simulated, applying a push dispatch policy at the beginning of the line and a pull dispatch policy at the end of the line. A commonly used dispatching policy that deals with short-term fluctuations in demand involves moving the transition point between both policies, the push–pull point (PPP), around. It is shown that, with a mean demand starts policy, moving the PPP by itself does not improve the performance of the production line significantly over policies that use a pure push or a pure pull dispatch policy, or a CONWIP starts policy with pure pull dispatch policy. However, when the PPP control is coupled with a CONWIP starts policy, then for high demand with high variance, the improvement becomes approximately a factor of 4. The unexpected success of a PPP policy with CONWIP is explained using concepts from fluid dynamics that predict that this policy will not work for perishable demand. The prediction is verified through additional simulations.     

On the fatigue crack growth–microstructure relationship in ultrafine-grained interstitial-free steel

The crack growth behavior in an ultrafine-grained (UFG) interstitial-free (IF) steel processed by equal channel angular pressing (ECAP) was investigated utilizing miniaturized compact-tension specimens with different microstructural characteristics. The current results demonstrate that both the ECAP processing route and the direction of crack growth with respect to the extrusion direction dictate the crack growth behavior in UFG IF steel. Specifically, the highest crack growth rates and the lowest threshold values were observed for the lowest grain size. Moreover, an unusual deviation from the expected direction of crack expansion was observed, where the deviation depended on the processing route and direction of crack growth. This deviation is attributed to the presence of elongated structures in the microstructure, which were mainly detectable in the UFG IF steel following a small number of pressings, and to a smaller extent in the optimized microstructures. Specifically, these elongated structures formed parallel to the material’s plastic flow during ECAP processing and moved the crack away from the expected direction of growth due to the high stress concentration zones they created along with the process-induced damages.     

On the particle–particle contact effects on the hole cleaning process via a CFD–DEM model

ABSTRACT

The accurate and precise computational models in order to predict the hole cleaning process is one of the helpful assets in drilling industries. Besides the bulk properties such as the flow velocity, particles average size, cleaning fluid properties, etc., that will affect the cleaning process, there is an unanswered question about the microscopic properties of the particles, particularly those which determines the contact characteristics: Do those play a major role or not? The rudimentary answer is not. The first purpose of the present work is to answer this question via a developed computational fluid dynamics coupled with discrete element method (CFD–DEM) in which the six unknown rolling and sliding friction coefficients of particle–particle contact, particle–wall contact, and particle–drill contact are considered as the main microscopic properties of the contacts. The second purpose is to search for optimum values of these coefficients in order to calibrate the CFD–DEM model with the experimental data for a near horizontal well cleaning available in the literature. The verification of the calibrated CFD–DEM model is checked by simulation of the hole cleaning process for different inclination angles of the deviated well. The results indicate the pivotal role of the microscopic properties of the particles on the characteristics of the particle transport mechanism.     

Solution to the Bagaryatskii and Isaichev ferrite–cementite orientation relationship problem

The Bagaryatskii and Isaichev orientation relationships between cementite and ferrite are closely related but not identical. They cannot easily be distinguished using ordinary electron diffraction methods and precise methods indicate that the Bargaryatski orientation does not exist. The issue is important when considering the mechanism by which cementite forms during the tempering of martensite or the formation of lower bainite, where the iron and substitutional solutes are unable to diffuse during the course of precipitation. It is demonstrated here that just one of the orientation relationships is consistent with the mechanism of precipitation at low temperatures, and is associated with much smaller deformations than the other.