Aragon Institute of Engineering Research

Zaragoza, Spain

Aragon Institute of Engineering Research

Zaragoza, Spain

Time filter

Source Type

Pena E.,Aragon Institute of Engineering Research | Pena E.,CIBER ISCIII
Journal of the Mechanics and Physics of Solids | Year: 2011

Deformation induced softening is an inelastic phenomenon frequently accompanying mechanical response of soft biological tissues. Inelastic phenomena which occur in mechanical testing of biological tissues are very likely to be associated with alterations in the internal structure of these materials. In this study, a novel structural constitutive model is formulated to describe the inelastic effects in soft biological tissues such as Mullins type behavior, damage and permanent set as a result of residual strains after unloading. Anisotropic softening is considered by evolution of internal variables governing the anisotropic properties of the material. We consider two weight factors wi (softening) and sk (discontinuous damage) as internal variables characterizing the structural state of the material. Numerical simulations of several soft tissues are used to demonstrate the performance of the model in reproducing the inelastic behavior of soft biological tissues. © 2011 Elsevier Ltd.


Pena E.,Aragon Institute of Engineering Research | Pena E.,CIBER ISCIII
Computers and Structures | Year: 2014

A constitutive model is proposed for the description of the inelastic effects of biological tissues. The model can reproduce the Mullins effect, preconditioning, rupture and residual strains by the introduction of three weight factors characterizing the structural state of the material. The collagen fibers are crimped in the slack configuration and are unable to sustain load. As a result, a general theoretical and numerical framework for the constitutive modelling of biological soft tissue including inelastic effects is obtained. Finally, a comparison of numerical and experimental data is provided in order to show the reliability and effectiveness of the assumed formulation. © 2013 Elsevier Ltd. All rights reserved.


Martiez I.,Aragon Institute of Engineering Research
Telemedicine journal and e-health : the official journal of the American Telemedicine Association | Year: 2010

The new paradigm of personal health demands open standards and middleware components that permit transparent integration and end-to-end interoperability from new personal health devices to healthcare information system. The use of standards seems to be the internationally accepted way to face this challenge. In this article, the implementation of an end-to-end standard-based personal health solution is presented. It integrates the ISO/IEEE11073 standard for the interoperability of personal health devices in the patient environment and the ISO/EN13606 standard for the interoperable exchange of electronic healthcare records and proposes a new approach for the end-to-end ISO/IEEE11073-ISO/EN13606 communication. The design strictly fulfills all the technical requirements of the most recent versions of both standards. An entire prototype has been designed, developed, and tested as a proof-of-concept of a personal health solution.


The dependence of the optimal performance of bidirectionally-pumped integrated amplifiers and lasers based on fs-laser written Yb 3+/Er3+-codoped phosphate glass waveguides on the concentration of dopants is numerically analysed. A novel macroscopic rate-equation propagation model is used which considers concentration-dependent rates for the energy-transfer inter-atomic migration-assisted mechanisms. Optimal small-signal gain for an amplifier and output laser power for a ring laser are computed for various working conditions and broad dopants- concentration ranges. Optimal waveguide lengths are also analysed in detail. The large variations obtained in the dopants concentration required for optimal amplifier gain or output laser power and in the waveguide optimal length confirm that a previous rigorous numerical design is essential in order to achieve the optimized performance of these active devices. © 2012 Elsevier B.V. All rights reserved.


Chinesta F.,École Centrale Nantes | Ladeveze P.,Ecole Normale Superieure de Cachan | Cueto E.,Aragon Institute of Engineering Research
Archives of Computational Methods in Engineering | Year: 2011

This paper revisits a new model reduction methodology based on the use of separated representations, the so called Proper Generalized Decomposition-PGD. Space and time separated representations generalize Proper Orthogonal Decompositions-POD-avoiding any a priori knowledge on the solution in contrast to the vast majority of POD based model reduction technologies as well as reduced bases approaches. Moreover, PGD allows to treat efficiently models defined in degenerated domains as well as the multidimensional models arising from multidimensional physics (quantum chemistry, kinetic theory descriptions,...) or from the standard ones when some sources of variability are introduced in the model as extra-coordinates. © 2011 CIMNE, Barcelona, Spain.


The different psychophysical studies carried out on the qualitative properties of simple and complex mixtures are reviewed. Many of the early studies conducted on binary mixtures have been reprocessed and compared by using similar representations and data treatments. Results confirm that the intensity ratio of the mixture constituents is the main driver of quality, so that the most intense compound tends to dominate the overall odour of the mixture. In contrast to what was previously thought, in most binary mixtures one of the components is more powerful than the other, dominating the overall odour of the mixture in a larger range of mixture compositions. In some but not all subsets of odorants, a clear hierarchy in their relative dominance has been observed. Pleasantness, complexity or freshness arise as major but not unique factors determining the order of dominance. Steven's coefficients could also have an influence, while polarity and temporal processing rates seem to have no influence. Competitive interactions at receptor level seem to play a limited role. In some aroma pairs, a small change in odour composition (26%) provokes the shift in odour dominance, while in others a 500% intensity change may be required for the shift. There is sound evidence that one or several odour descriptors of minor non-dominant odour components can be detected in the odour of the mixture. In more complex mixtures, results support the fact that some odorants in specific odour backgrounds are detected more easily than others. The most frequent qualitative outcome of a complex mixture will be an average of the odour qualitative descriptors of the odour chemicals present in the mixture, except when the mixture contains within its constituents a series of odour chemicals at specific intensity ratios able to trigger a configurational recognition process ending with the recognition of a different odour object. Key challenges for the modelling of the aroma properties of complex systems are enunciated. © 2011 John Wiley & Sons, Ltd.


Manya J.J.,Aragon Institute of Engineering Research
Environmental Science and Technology | Year: 2012

According to the International Biochar Initiative (IBI), biochar is a charcoal which can be applied to soil for both agricultural and environmental gains. Biochar technology seems to have a very promising future. Nevertheless, the further development of this technology requires continuing research. The present paper provides an updated review on two subjects: the available alternatives to produce biochar from a biomass feedstock and the effect of biochar addition to agricultural soils on soil properties and fertility. A high number of previous studies have highlighted the benefit of using biochar in terms of mitigating global warning (through carbon sequestration) and as a strategy to manage soil processes and functions. Nevertheless, the relationship between biochar properties (mainly physical properties and chemical functionalities on surface) and its applicability as a soil amendment is still unclear and does not allow the establishment of the appropriate process conditions to produce a biochar with desired characteristics. For this reason, the need of enhancing the collaboration among researchers working in different fields of study is highlighted: production and characterization of biochar on one hand, and on the other measurement of both environmental and agronomical benefits linked to the addition of biochar to agricultural soils. In this sense, when experimental results concerning the effect of the addition of biochar to a given soil on crop yields and/or soil properties are published, details regarding the properties of the used biochar should be well reported. The inclusion of this valuable information seems to be essential in order to establish the appropriate process conditions to produce a biochar with more suitable characteristics. © 2012 American Chemical Society.


The different psychophysical studies carried out on the quantitative properties of binary mixtures are reviewed. Results from 520 mixtures have been reprocessed and plotted together. The most likely outcome of a binary mixture of two different odorants at supra-threshold levels is a significant reduction of its odour intensity not only with respect to the total addition of intensities, but also to what could be expected from an auto-addition following Stevens's law. Half of the mixtures behave asymmetrically, so that one of the odorants can reduce the overall odour intensity of the mixture more efficiently than the other. This is most frequent when there is a marked difference in the hedonic character of the odorants, and the least pleasant odorant plays the role of suppressor. Such suppression can be quantitatively relevant. The addition of the third, fourth or fifth isointense constituent do not cause any further intensity increase, which indicates the existence of strong signal compression mechanisms at supra-receptor level. Synergism is highly infrequent and may be linked to the appearance of new odour concepts. In the case of mixtures of sub-threshold odorants, the oldest reports are based on the odour activity value concept, and, in general, show the existence of a certain degree of cooperation between the components of the mixture. The most recent research makes use of detectability functions and probabilistic considerations and has demonstrated that cooperation can be categorized as hypoaddition, perfect addition (independence of response) or even synergy. Hypoaddition is most frequent at higher concentrations. Some reports suggest that hypoaddition is related to the structural similarity but results are not conclusive. Other reports demonstrate that under or peri-threshold odorants are able to introduce significant qualitative and quantitative changes on supra-threshold odour solutions. So far it is not feasible to assess when and why this enhancing effect takes place. It can be hypothesized that the answer will require an integral treatment of quality and intensity. © 2011 John Wiley & Sons, Ltd.


Mediano A.,Aragon Institute of Engineering Research | Sokal N.O.,Design Automation , Inc
IEEE Transactions on Power Electronics | Year: 2013

This paper shows a new class-E amplifier topology with the objective to increase the nominal class-E output power for a given voltage and current stress on the power transistor. To obtain that result, a parallel LC resonator is added to the load network, tuned to the second harmonic of the switching frequency. A class-E power amplifier is obtained whose transistor-voltage waveform peak value is 81% of the peak value of the voltage of a nominal class- E amplifier using the same dc supply voltage. In this amplifier, the peak voltage across the transistor is 3.0 times the dc supply voltage, instead of the 3.6 times associated with nominal class-E amplifiers. A normalized design is presented, and the behavior of the circuit is analyzed with simulation showing that the ratio of output power versus transistor peak voltage times peak current is 20.4% better than the nominal class E. The proposed converter and normalized design approach are verified by simulations and measurements done on an experimental prototype. © 1986-2012 IEEE.


Carvalho M.,Aragon Institute of Engineering Research | Lozano M.A.,Aragon Institute of Engineering Research | Serra L.M.,Aragon Institute of Engineering Research
Applied Energy | Year: 2012

The necessity of considering the environment as an additional design factor arises due to increasing environmental conscience worldwide and stricter requirements to reduce the environmental impact of energy systems. Designing such systems very often involves conflicting objectives as eco-friendly technologies are usually more expensive. This paper considers simultaneously economic and environmental criteria in the synthesis of a trigeneration system to be installed in a hospital. Synthesis includes optimal configuration (commercially available equipment) and optimal operation throughout the year. The multiobjective optimization accounts for minimization of total annual cost and CO2 emissions released in the atmosphere, as well as the Eco-indicator 99 (EI-99) in order to broaden environmental considerations in the impact assessment. A Pareto frontier, set of solutions representing optimal trade-offs between the economic and environmental objectives, is obtained from the solution of a Mixed Integer Linear Programming (MILP) model. Two bicriteria problems were solved using the MILP model: (1) annual cost (€/yr) versus CO2 emissions (kg CO2/yr) and (2) annual cost (€/yr) versus EI-99 Single Score (points/yr). The Pareto solutions consist of optimal configurations that adapt their operational strategy during a specific range in the Pareto frontier. Solutions are compared and it is observed that some configurations are more stable along the Pareto frontier, and that significant reductions in economic cost can be attained if the environmental impact is partially compromised. After the judgment of the solutions obtained and the trade-offs involved, one ultimate configuration is selected, which presents a flexible range of adaptability in the economic/CO2 and economic/EI-99 optimizations. © 2011 Elsevier Ltd.

Loading Aragon Institute of Engineering Research collaborators
Loading Aragon Institute of Engineering Research collaborators