New understanding of the shape-memory response in thiol-epoxy click systems: towards controlling the recovery process

Our research group has recently found excellent shape-memory response in “thiol-epoxy” thermosets obtained with click-chemistry. In this study, we use their well-designed, homogeneous and tailorable network structures to investigate parameters for better control of the shape-recovery process. We present a new methodology to analyse the shape-recovery process, enabling easy and efficient comparison of shape-memory experiments on the programming conditions. Shape-memory experiments at different programming conditions have been carried out to that end. Additionally, the programming process has been extensively analysed in uniaxial tensile experiments at different shape-memory testing temperatures. The results showed that the shape-memory response for a specific operational design can be optimized by choosing the correct programming conditions and accurately designing the network structure. When programming at a high temperature (T » Tg), under high network mobility conditions, high shape-recovery ratios and homogeneous shape-recovery processes are obtained for the network structure and the programmed strain level (eD). However, considerably lower stress and strain levels can be achieved. Meanwhile, when programming at temperatures lower than Tg, considerably higher stress and strain levels are attained but under low network mobility conditions. The shape-recovery process heavily depends on both the network structure and eD. Network relaxation occurs during the loading stage, resulting in a noticeable decrease in the shape-recovery rate as eD increases. Moreover, at a certain level of strain, permanent and non-recoverable deformations may occur, impeding the completion and modifying the whole path of the shape-recovery process.Postprint (author's final draft

Phenomenological characterization of sequential dual-curing of off-stoichiometric "thiol-epoxy" systems: Towards applicability

An extensive characterization of a sequential dual-curing system based on off-stoichiometric “thiol-epoxy” mixtures was carried out using thiol compounds of different functionality. The intermediate and final materials obtained after each curing stages at different thiol-epoxy ratios were studied by means of thermomechanical and rheological experiments. The storage and loss modulus and the loss factor tan d were monitored during the curing process to analyse gelation and network structure build-up. The critical ratio for gelation was determined making use of the ideal Flory-Stockmayer theory and compared with experimental results. Intermediate materials obtained in the vicinity of the theoretical critical ratio did not have the mechanical consistency expected for partially crosslinked materials, did not retain their shape and even experienced undesired flow upon heating to activate the second curing reaction. The rheological results showed that the critical ratio is higher than the predicted value and that a softening during the second curing stage affects the shape-retention at this ratio. From the thermomechanical results, a wide range of intermediate and final materials with different properties and applicability can be obtained by properly choosing the thiol-epoxy ratio: from liquid-like to highly deformable intermediate materials and from moderately crosslinked (deformable) to highly crosslinked (brittle) final materials.Postprint (author's final draft

A design tool for high-resolution high-frequency cascade continuous- time Σ∆ modulators

Event: Microtechnologies for the New Millennium, 2007, Maspalomas, Gran Canaria, SpainThis paper introduces a CAD methodology to assist the de signer in the implementation of continuous-time (CT) cas- cade Σ∆ modulators. The salient features of this methodology ar e: (a) flexible behavioral modeling for optimum accuracy- efficiency trade-offs at different stages of the top-down synthesis process; (b) direct synthesis in the continuous-time domain for minimum circuit complexity and sensitivity; a nd (c) mixed knowledge-based and optimization-based architec- tural exploration and specification transmission for enhanced circuit performance. The applicability of this methodology will be illustrated via the design of a 12 bit 20 MHz CT Σ∆ modulator in a 1.2V 130nm CMOS technology.Ministerio de Ciencia y Educación TEC2004-01752/MICMinisterio de Industria, Turismo y Comercio FIT-330100-2006-134 SPIRIT Projec

Análisis de las competencias TIC de los alumnos de Educación Secundaria y Bachillerato de Galicia

[Resumen] En el presente trabajo se lleva a cabo una valoración de las competencias en TIC de los alumnos de segundo ciclo de Educación Secundaria Obligatoria y Bachillerato en Galicia. Se ponen de manifiesto, a través de este estudio, las carencias existentes en este ámbito y el fracaso de la formación en TIC a nuestros alumnos. La mirada se centra ahora en las modificaciones realizadas en el currículo entre las que se contempla el “tratamiento de la información y la competencia digital” como una de las 8 competencias básicas para los alumnos.[Abstract] In the present study conducts an assessment of ICT skills of students in second cycle of Compulsory Secondary Education and Bachelor of Galicia. It highlights, through this study, the gaps in this area and the failure of ICT training to our students. The look is now focused on the changes made in the curriculum among which refers to “information processing and digital competence” as one of the 8 basic skills for students

Approach to the potential production of giant reed in surplus saline lands of Spain

Growing energy crops on marginal land has been promoted as a way of ensuring that biomass production involves an acceptable and sustainable use of land. Saline and saline-prone agricultural lands represent an opportunity for growing energy crops avoiding the displacement of food production and contributing to restoration of degraded land. Giant reed (Arundo donax L.) is a perennial grass that has been proposed as a promising energy crop for lignocellulosic biomass production while its tolerance to salinity has been proved. In this work, the identification of surplus saline lands that could be irrigated with saline waters for growing tolerant-energy crops (giant reed) in the mainland of Spain and the assessment of the agronomically attainable yield in these limiting growing conditions were undertaken. To this purpose, a GIS analysis was conducted using geodatabases related to saline areas, agro-climatic conditions, irrigation water requirements, agricultural land availability, restrictions regarding the range of electrical conductivity tolerated by the crop, competition with agro-food crops and irrigation water provisions. According to the approach developed, the irrigated and saline agricultural area available and suitable for biomass production from giant reed amounted up to 34 412 ha. The agronomically attainable yield in these limiting conditions was estimated at 12.7 – 22.2 t dm ha−1 yr−1 and the potential production of lignocellulosic biomass, 597 338 t dm yr−1. The methodology followed in this study can be applied to other target regions; it allows the identification of this type of marginal lands, where salinity-tolerant plant species could be grown for bioenergy purposes, avoiding competition with agro-food crops, and where soil restoration measurements should be undertaken

An approach to quantify value provided by an engineered asset according to the ISO 5500x series of standards

Asset Intelligence through Integration and Interoperability and Contemporary Vibration Engineering Technologies : Proceedings of the 12th World Congress on Engineering Asset Management and the 13th International Conference on Vibration Engineering and Technology of Machinery. 2-4 August 2017, Brisbane, AustraliaThe purpose of any asset is to provide value to the organization and its stakeholders. In Asset Management, the concept of value encompasses quantitative and qualitative, as well as tangible and intangible benefits that assets may provide to an organization. The definitions of asset and value are not only closely linked but also complementary. An “asset” provides the means for the realisation of “value” thus the management of an asset is strategic and has to be linked to an organization’s value norms. This paper extrapolates from the definitions in ISO 5500x series of standards to describe a generic approach for quantifying the value provided by engineered assets deployed by a business organisation.Unión Europea. 64573

Advanced Techniques for Assets Maintenance Management

16th IFAC Symposium on Information Control Problems in Manufacturing INCOM 2018 Bergamo, Italy, 11–13 June 2018. Edited by Marco Macchi, László Monostori, Roberto PintoThe aim of this paper is to remark the importance of new and advanced techniques supporting decision making in different business processes for maintenance and assets management, as well as the basic need of adopting a certain management framework with a clear processes map and the corresponding IT supporting systems. Framework processes and systems will be the key fundamental enablers for success and for continuous improvement. The suggested framework will help to define and improve business policies and work procedures for the assets operation and maintenance along their life cycle. The following sections present some achievements on this focus, proposing finally possible future lines for a research agenda within this field of assets management

Skills for Learning Network of High School Students in Galicia

El objetivo del presente trabajo radica en identificar las necesidades formativas para el trabajo en red de los alumnos de secundaria de Galicia. Se presenta un análisis exploratorio de sus niveles de competencia en esta materia valorados autopercibidos por los propios alumnos y percibidos por sus profesores. Los resultados muestran niveles de preparación superiores en competencias instrumentales, e insuficientes en otras mas directamente relacionadas con el aprendizaje autónomo y orientado a la creación de conocimiento, sugiriendo la necesidad de propuestas de formación que mejoren la explotación y el uso de las TIC para la optimización de los procesos de aprendizaje.The aim of the present study is to identify the training needs for educational network of secondary education students in Galicia. An exploratory analysis of the competence levels in educational network assessed by the own students and by their teachers. The results show higher levels in instrumental competences, and insufficient in those competences related to autonomous learning and knowledge development. Therefore, these data suggest the need of curricular and systematic training to improve the exploitation and management of the ICT in order to optimize the learning process

Rheological and mechanical characterization of dual-curing thiol-acrylate-epoxy thermosets for advanced applications

Mechanical and rheological properties of novel dual-curing system based on sequential thiol-acrylate and thiol-epoxy reactions are studied with the aim of addressing the obtained materials to suitable advanced applications. The crosslinking process is studied by rheological analysis in order to determine conversion at gelation and the critical ratio. These parameters are used to discuss the intermediate material structure for each acrylate proportion and their possible application in the context of dual-curing and multi-step processing scenarios. Results from dynamo-mechanical analysis and mechanical testing demonstrate the high versatility materials under investigation and revealed a wide range of achievable final properties by simply varying the proportion between acrylate and thiol group. The intermediate stability between curing stages has been analysed in terms of their thermal and mechanical properties, showing that these materials can be stored at different temperatures for a relevant amount of time without experiencing significant effects on the processability. Experimental tests were made to visually demonstrate the versatility of these materials. Qualitative tests on the obtained materials confirm the possibility of obtaining complex shaped samples and highlight interesting shape-memory and adhesive properties.Postprint (published version

Aplicaciones basadas en las propiedades eléctricas y térmicas de recubrimientos de sílice-cb obtenidos por el método sol-gel

En los últimos años el interés en los recubrimientos obtenidos por sol-gel ha aumentado mucho en aplicaciones de protección y refuerzo de superficies contra la corrosión. Asimismo, el uso de polimorfos de carbono (nanofibras de carbono, grafeno, grafito...) para mejorar las propiedades mecánicas y conferirle propiedades conductoras a algunos materiales, también se ha desarrollado mucho en los últimos años. En trabajos previos se prepararon y estudiaron recubrimientos híbridos de sílice-CB obtenidos por el método sol-gel. Mediante el estudio de la microestructura y composición de estos recubrimientos (SEM, Raman, ATD-TG, y FT-IR) y de las propiedades eléctricas se obtuvo que en función la temperatura de sinterización de los recubrimientos, se podía controlar la respuesta eléctrica de los composites. Esto permite abrir enormemente el campo de aplicaciones, ya que para temperaturas de sinterización por debajo de 400ºC se consiguen resistividades del orden de 10-4Ωm, apropiadas para aplicaciones en dispositivos electrónicos, electrodos, apantallamiento de interferencias electromagnéticas y radiofreciencia, etc; mientras que para temperaturas de sinterización por encima de 400ºC, obtenemos recubrimientos más resistivos que pueden aplicarse como dispositivos calefactores, anticongelantes. Por tanto, el objetivo de este trabajo es desarrollar más profundamente estas aplicaciones, así como diseñar experimentos que demuestren las múltiples posibilidades que estos recubrimientos conductores obtenidos por sol-gel pueden aportar