Mapping the development of Open Access in Latin America and Caribbean countries. An analysis of Web of Science Core Collection and SciELO Citation Index (2005–2017)

Scientometrics - Open Access (OA) initiatives and knowledge infrastructure represent vital elements for both producing significant changes in scholarly communication and reducing limitations of...     

Algorithmic Aspects of Proportional Symbol Maps

Proportional symbol maps visualize numerical data associated with point locations by placing a scaled symbol—typically an opaque disk or square—at the corresponding point on a map. The area of each symbol is proportional to the numerical value associated with its location. Every visually meaningful proportional symbol map will contain at least some overlapping symbols. These need to be drawn in such a way that the user can still judge their relative sizes accurately.     

High-Frequency Induction Hardening with Controlled Capacitors-Discharge Pulse-Operation Processes

Induction hardening processes with power pulses obtained by means of capacitors-discharge high-frequency generators are discussed. The process is characterized by high-power densities and heating times on the order of some tens or hundreds of milliseconds together with cooling rates obtained by self-quenching without the use of auxiliary means. The possibility of obtaining the most favorable transient temperature distribution in the workpieces by controlling the shape of the pulses and therefore the variable time rate energy supply is examined. The influence of shape of pulses and discharge circuit's electrical parameters on the heating and cooling transients has been analyzed by a thermal model which allows prediction of the depths of hardening. Measurements from hardening tests carried out on steel samples varying the pulse shapes are given in support of the calculation results.     

A simplified broadband coupling approach applied to chemically robust sol-gel, planar integrated optical waveguides

A new generation waveguide spectrometer with broadband coupling capabilities has been developed. As opposed to previous devices, this attenuated total reflection (ATR) spectrometer is much simpler in design, is more chemically robust, and transmits light down to at least 400 nm. The attenuated total reflection element consists of a single-mode, planar integrated optical waveguide fabricated by dip-coating a approximately 300 nm thick, sol-gel composite layer on a glass substrate. A commercially available prism is used as the incoupler with an integral holographic diffraction grating acting as the dispersive outcoupling element. The transmission of narrow band-pass filters was used to compare the response of the waveguide spectrometer to that of a conventional transmission instrument. Spectral resolution was assessed by measuring the fwhm of various laser lines, which were found to range from 0.5 to 1.3 nm. The measured limits of detection for the waveguide spectrometer from 400 to 600 nm are 8.0 and 10.1 milliabsorbance units for TE and TM polarizations, respectively. Finally, to demonstrate the application of this technology to a molecular film confined to a solid-liquid interface, visible ATR spectra of an adsorbed submonolayer of horse heart cytochrome c were acquired. A procedure to correct the waveguide spectra for the wavelength dependence in ATR path length is described.     

Silicone microlenses and interference gratings

Interference gratings, plano-convex microlenses, and spherical microlenses have been made in silicone. Lenses were fabricated by the melting method. Two substrates have been tried: glass and Teflon. The latter substrate lets us fabricate low-f-number lenses. We made spherical microlenses by placing pieces of silicone near a thermal source and studied resolution of the lenses by investigating the images they gave of a test chart. We made low-spatial-frequency gratings by recording interference patterns and studied parameters involved in the recording. A study of the profile of the gratings and lenses was done with a mechanical surface analyzer.     

Reflective grating interferometer: a folded reversal and shearing wave-front interferometer

The reflecting grating interferometer (RGI) is a folded and reversal wave-front interferometer sensitive only to asymmetrical aberrations such as third-order coma. The RGI can isolate and evaluate coma both in nearly collimated and in noncollimated beams. We propose a RGI with a different optical configuration that includes a lateral shearing in addition to folding and reversal operations. With lateral shear, the RGI also becomes sensitive to other terms of third-order aberrations such as defocusing, astigmatism, and spherical aberration. Optical path difference equations for interpreting interferograms and numerical simulations are presented to show how the interferometer works in the shearing configuration. Its potential applications are described and discussed.     

A UML profile for multidimensional modeling in data warehouses

The multidimensional (MD) modeling, which is the foundation of data warehouses (DWs), MD databases, and On-Line Analytical Processing (OLAP) applications, is based on several properties different from those in traditional database modeling. In the past few years, there have been some proposals, providing their own formal and graphical notations, for representing the main MD properties at the conceptual level. However, unfortunately none of them has been accepted as a standard for conceptual MD modeling.

In this paper, we present an extension of the Unified Modeling Language (UML) using a UML profile. This profile is defined by a set of stereotypes, constraints and tagged values to elegantly represent main MD properties at the conceptual level. We make use of the Object Constraint Language (OCL) to specify the constraints attached to the defined stereotypes, thereby avoiding an arbitrary use of these stereotypes. We have based our proposal in UML for two main reasons: (i) UML is a well known standard modeling language known by most database designers, thereby designers can avoid learning a new notation, and (ii) UML can be easily extended so that it can be tailored for a specific domain with concrete peculiarities such as the multidimensional modeling for data warehouses. Moreover, our proposal is Model Driven Architecture (MDA) compliant and we use the Query View Transformation (QVT) approach for an automatic generation of the implementation in a target platform. Throughout the paper, we will describe how to easily accomplish the MD modeling of DWs at the conceptual level. Finally, we show how to use our extension in Rational Rose for MD modeling.     

Identification of semi-physical and black-box non-linear models: the case of MR-dampers for vehicles control

The topic of this paper is the identification of an accurate model for magneto-rheological (MR) dampers. A semi-active MR-damper is a dynamic system, where the inputs are the elongation velocity and the command current; the current is the control input which modulates at high-bandwidth the damping characteristic through the variation of a magnetic field. The output is the force delivered by the damper. Among the broad set of applications where MR-dampers can be used, the results proposed in this work refer to MR-dampers for the control of vehicle dynamics.MR-damper are highly non-linear systems, and their accurate modeling is a non-trivial task. MR-dampers can be modeled using two different model classes: semi-physical models and black-box models. Both approaches are considered in this work.The purpose of this brief paper is to make a concise but complete presentation and discussion of a non-trivial system identification problem. The problem considered herein is particularly interesting from the system identification point of view: from one side, the MR-damper is a very attractive actuator, which is likely to become the key device for many dynamics and vibration control systems in the near future; on the other side, it is an example of an application problem where the accurate modeling of the actuation device is one of the most crucial part of the whole control design problem.     

Independent Component Analysis for Solid-State Chemical Sensor Arrays

Electronic noses and tongues are two recent examples in chemical sensing that employ statistical array techniques in order to overcome the intrinsic limitations of current solid-state chemical sensors like ion-selective field transistors (ISFET). In particular, ISFETs are sensitive to the concentration of a particular ion in a solution to be measured, but they can be also strongly affected by several interfering ions found in the solution. Hence, they must be employed in regions in which the effect of interferences is negligible thus limiting their range of operation. However, as we show, ISFETs behave as non-linear mixers of main ion activities and interfering ones and thus an attempt to separate the original main ion activity and interferences from the mixed response is suitable with independent component analysis (ICA) methods. In this direction, a novel learning algorithm is proposed which synergistically combines ICA and linear regression for dealing with the separation in ISFET responses and further reconstruction of ion activities in those operating regions in which interferences notably affect their response. Several experiments with real ISFET measurements demonstrate the interest of proposed methods.     

Characterization of γ-alumina doped with Li and K by infrared studies of CO adsorption and27Al-NMR

The influence of alkali metals on the Lewis acid sites of gamma-alumina has been studied with NMR and IR of adsorbed CO. The physical properties of the alumina are slightly changed by the addition of low alkali metal concentrations. Li and K are adsorbed selectively on tetrahedral Lewis Al³⁺ sites of the alumina surface. These effects on the tetrahedral cations are more marked with increasing molar concentration and ionic radius of the alkali metal added to alumina. Results demonstrate that the influence of the alkali metals is not only due to steric factors but also to possible electronic modifications.This work was supported by a grant from CONICET, Argentina.