Feedbacks between vegetation pattern and resource loss dramatically decrease ecosystem resilience and restoration potential in a simple dryland model

Conceptual frameworks of dryland degradation commonly include ecohydrological feedbacks between landscape spatial organization and resource loss, so that decreasing cover and size of vegetation patches result in higher water and soil losses, which lead to further vegetation loss. However, the impacts of these feedbacks on dryland dynamics in response to external stress have barely been tested. Using a spatially-explicit model, we represented feedbacks between vegetation pattern and landscape resource loss by establishing a negative dependence of plant establishment on the connectivity of runoff-source areas (e.g., bare soils). We assessed the impact of various feedback strengths on the response of dryland ecosystems to changing external conditions. In general, for a given external pressure, these connectivity-mediated feedbacks decrease vegetation cover at equilibrium, which indicates a decrease in ecosystem resistance. Along a gradient of gradual increase of environmental pressure (e.g., aridity), the connectivity-mediated feedbacks decrease the amount of pressure required to cause a critical shift to a degraded state (ecosystem resilience). If environmental conditions improve, these feedbacks increase the pressure release needed to achieve the ecosystem recovery (restoration potential). The impact of these feedbacks on dryland response to external stress is markedly non-linear, which relies on the non-linear negative relationship between bare-soil connectivity and vegetation cover. Modelling studies on dryland vegetation dynamics not accounting for the connectivity-mediated feedbacks studied here may overestimate the resistance, resilience and restoration potential of drylands in response to environmental and human pressures. Our results also suggest that changes in vegetation pattern and associated hydrological connectivity may be more informative early-warning indicators of dryland degradation than changes in vegetation cover.

Fénix: a flexible information exchange data model for natural language processing

In this paper we describe Fénix, a data model for exchanging information between Natural Language Processing applications. The format proposed is intended to be flexible enough to cover both current and future data structures employed in the field of Computational Linguistics. The Fénix architecture is divided into four separate layers: conceptual, logical, persistence and physical. This division provides a simple interface to abstract the users from low-level implementation details, such as programming languages and data storage employed, allowing them to focus in the concepts and processes to be modelled. The Fénix architecture is accompanied by a set of programming libraries to facilitate the access and manipulation of the structures created in this framework. We will also show how this architecture has been already successfully applied in different research projects.

Assessment of University External Internships. Towards a Mixed Model for Measuring the Acquisition of Skills and the Satisfaction of Parties Involved

The continuous improvement of management and assessment processes for curricular external internships has led a group of university teachers specialised in this area to develop a mixed model of measurement that combines the verification of skill acquisition by those students choosing external internships with the satisfaction of the parties involved in that process. They included academics, educational tutors of companies and organisations and administration and services personnel in the latter category. The experience, developed within University of Alicante, has been carried out in the degrees of Business Administration and Management, Business Studies, Economics, Advertising and Public Relations, Sociology and Social Work, all part of the Faculty of Economics and Business. By designing and managing closed standardised interviews and other research tools, validated outside the centre, a system of continuous improvement and quality assurance has been created, clearly contributing to the gradual increase in the number of students with internships in this Faculty, as well as to the improvement in satisfaction, efficiency and efficacy indicators at a global level. As this experience of educational innovation has shown, the acquisition of curricular knowledge, skills, abilities and competences by the students is directly correlated with the satisfaction of those parties involved in a process that takes the student beyond the physical borders of a university campus. Ensuring the latter is a task made easier by the implementation of a mixed assessment method, combining continuous and final assessment, and characterised by its rigorousness and simple management. This report presents that model, subject in turn to a persistent and continuous control, a model all parties involved in the external internships are taking part of. Its short-term results imply an increase, estimated at 15% for the last course, in the number of students choosing curricular internships and, for the medium and long-term, a major interweaving between the academic world and its social and productive environment, both in the business and institutional areas. The potentiality of this assessment model does not lie only in the quality of its measurement tools, but also in the effects from its use in the various groups and in the actions that are carried out as a result of its implementation and which, without any doubt and as it is shown below, are the real guarantee of a continuous improvement.

Chloride Penetration Prediction in Concrete through an Empirical Model Based on Constant Flux Diffusion

An empirical model based on constant flux is presented for chloride transport through concrete in atmospherical exposure conditions. A continuous supply of chlorides is assumed as a constant mass flux at the exposed concrete surface. The model is applied to experimental chloride profiles obtained from a real marine structure, and results are compared with the classical error-function model. The proposed model shows some advantages. It yields a better predictive capacity than the classical error-function model. The previously observed chloride surface concentration increases are compatible with the proposed model. Nevertheless, the predictive capacity of the model can fail if the concrete microstructure changes with time. The model seems to be appropriate for well-maturated concretes exposed to a marine environment in atmospherical conditions.

Logic-Based Outer-Approximation Algorithm for Solving Discrete-Continuous Dynamic Optimization Problems

We present an extension of the logic outer-approximation algorithm for dealing with disjunctive discrete-continuous optimal control problems whose dynamic behavior is modeled in terms of differential-algebraic equations. Although the proposed algorithm can be applied to a wide variety of discrete-continuous optimal control problems, we are mainly interested in problems where disjunctions are also present. Disjunctions are included to take into account only certain parts of the underlying model which become relevant under some processing conditions. By doing so the numerical robustness of the optimization algorithm improves since those parts of the model that are not active are discarded leading to a reduced size problem and avoiding potential model singularities. We test the proposed algorithm using three examples of different complex dynamic behavior. In all the case studies the number of iterations and the computational effort required to obtain the optimal solutions is modest and the solutions are relatively easy to find.