La Embajada a Tamorlán. Su recorrido por el Mediterráneo occidental.

Sin resume

On the taxonomic identity of Brachistosternus peruvianus Piza, 1974 (Scorpiones: Bothriuridae)

Se establece la verdadera identidad de Brachistosternus peruvianus Piza, 1974, un controversial escorpión an-dino, previamente confundido con Brachistosternus andinus Chamberlin, 1916. Ambas especies habitan en valles interandinos del sur del Perú, y pertenecen al subgénero Brachistosternus (Ministernus) Francke. Se presenta una detallada redescripción para ambas especies basada en la morfología externa, patrones de pigmentación y caracteres del hemispermatóforo. Se reportan también nuevos registros y una breve discusión sobre la ecología y distribución de estas dos especies.The true identity of Brachistosternus peruvianus Piza, 1974, a controversial Andean scorpion previously confused with Brachistosternus andinus Chamberlin, 1916, is established. Both species inhabit inter Andean valleys of southern Peru and belong to the subgenus Brachistosternus (Ministernus) Francke. A detailed redescription of both species based on external morphology, pigmentation pattern and hemispermatophore features are provided. New records for these species, along with brief discussions of the ecology and distribution are also reported

Improving the functional properties of (K0.5Na0.5)NbO3 piezoceramics by acceptor doping

ZrO2 and TiO2 modified lead-free (K0.5Na0.5)NbO3 (KNN) piezoelectric ceramics are prepared by a conventional solid-state reaction. The effect of acceptor doping on structural and functional properties is investigated. A decrease in the Curie temperature and an increase in the dielectric constant values are observed when doping. More interestingly, an increase in the coercive field E-c and remanent polarization P-r is observed. The piezoelectric properties are greatly increased when doping with small concentrations dopants. ZrO2 doped ceramic exhibits good piezoelectric properties with piezoelectric coefficient d(33) = 134 pC/N and electromechanical coupling factor k(p) = 35%. It is verified that nonlinearity is significantly reduced. Thus, the creation of complex defects capable of pinning the domain wall motion is enhanced with doping, probably due to the formation of oxygen vacancies. These results strongly suggest that compositional engineering using low concentrations of acceptor doping is a good means of improving the functional properties of KNN lead-free piezoceramic system. (C) 2014 Elsevier Ltd. All rights reserved.Postprint (published version

SSP: a simple software process for small- size software development projects

A large number of software development projects in Latin- American countries are small-size, poorly defined and time pressured. These projects usually involve under qualified people. Provided that well-known software development models have shown limited applicability in such scenario, developers usually carry out ad-hoc software processes. Therefore, the obtained results are unpredictable. This article presents a Simple Software Process (SSP) for small-size software projects involving under qualified people. The proposal is motivated by current practice in Chile. SSP proposes a step-by-step process which structures the development activities and it improves the process visibility for clients and team members. Furthermore, SSP formally includes “the user/client” as an active role to be played during the project. This process has been used in 22 software projects and the results are encouraging.1st International Workshop on Advanced Software Engineering: Expanding the Frontiers of Software Technology - Session 3: Software Development ProcessRed de Universidades con Carreras en Informática (RedUNCI

Low temperature dielectric relaxation in ordinary perovskite ferroelectrics: enlightenment from high-energy x-ray diffraction

Ordinary ferroelectrics exhibit a second order phase transition that is characterized by a sharp peak in the dielectric permittivity at a frequency-independent temperature. Furthermore, these materials show a low temperature dielectric relaxation that appears to be a common behavior of perovskite systems. Tetragonal lead zirconate titanate is used here as a model system in order to explore the origin of such an anomaly, since there is no consensus about the physical phenomenon involved in it. Crystallographic and domain structure studies are performed from temperature dependent synchrotron x-ray diffraction measurement. Results indicate that the dielectric relaxation cannot be associated with crystallographic or domain configuration changes. The relaxation process is then parameterized by using the Vogel–Fulcher–Tammann phenomenological equation. Results allow us to hypothesize that the observed phenomenon is due to changes in the dynamic behavior of the ferroelectric domains related to the fluctuation of the local polarization.Postprint (author's final draft

Tuning the microstructure of flash sintered BZT-BCT ceramics to obtain enhanced and singular properties

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Elastic, dielectric and electromechanical properties of (Bi0.5Na0.5)TiO3-BaTiO3 piezoceramics at the morphotropic phase boundary region

A systematic study of the functional properties of the (1-x)(Bi0.5Na0.5)TiO3–xBaTiO3 (BNT-xBT) piezoceramic system for 0.05 = x = 0.07 is performed. The samples are obtained through the conventional solid-state route. The expected microstructure for these compounds, with no significant dependence on the composition, is verified by field-emission scanning electron microscopy. The morphotropic phase boundary (MPB) is detected for x = 0.06–0.07 by means of the Rietveld analysis of X-ray diffraction data. The dielectric spectra show a frequency-independent, completely diffuse phase transition with a composition-dependent diffusivity coefficient. The depolarization temperature is effectively evaluated from pyroelectric measurements, the value being strongly dependent on the composition. A significant contribution of the extrinsic effect to elastic, dielectric and electromechanical properties is revealed for MPB BNT-xBT. The Bi3+ substitution by Ba2+ leads to the formation of A-site vacancies, which give rise to the enhancement of domain wall motion, as occurs in other perovskite-type piezoelectrics. Good functional properties are achieved for x = 0.07 (d33 = 180 pC/N), which are similar or even better than those obtained by complex synthesis routes. This system exhibits a remarkable stability in the permittivity that has hitherto not been reported. This fact may open the way for BNT-BT compositions to be used in specific applications in which lead-free piezoceramics have previously been employed with little success, e.g. in high power devices.Postprint (author's final draft

Preisach modelling of nonlinear response in electrically biased lead zirconate titanate-based piezoceramics

The alteration of the high-field electrical permittivity (nonlinear response) of PZT-based ceramics when an electrical bias field is applied is reported in this work. Large differences are observed between soft and hard PZT behaviours. While in soft PZT a bias field does not modify the nonlinear behaviour, a notable dependence is verified in hard PZT. The Preisach model is satisfactorily used to describe experimental results. A distribution function containing the first terms of the Maclaurin development series of a function composed by two Gaussian-like functions of different amplitudes is proposed. The model gives a satisfactory explanation for the fact that the permittivity depends not only on the amplitude of the applied electric field, but also on the bias field, both for soft and hard ceramics and for poled or unpoled samples.Postprint (published version

Analysis and Design of Mobile Collaborative Applications Using Contextual Elements

Collaborative mobile applications support users on the move in order to perform a collaborative task. One of the challenges when designing such applications is to consider the context where they will execute. Contextualized applications are easy to adopt by the users; unfortunately the design of contextualized tools is not evident. This paper presents a framework of contextual elements to be considered during the conception, analysis and design phases of a mobile collaborative application. This framework supports developers to identify non-functional requirements and part of the architectural design in order to get contextualized applications. The use of this framework is complementary to any structured software process. A framework use example is also presented as an illustration of its applicability