Congreso Anual de la Sociedad Española de Ingeniería Biomédica

p. Sesion-14_Order-2_31-pp1-Sesion-14_Order-2_31-pp4

Data de presentació: 2020-11-25

Data: 2020-10-02

European Conference on Innovation and Entrepreneurship

p. 408-416

Data de presentació: 2020-09-15

Jornada R+D+I a l'EPSEB

p. 1-41

Data de presentació: 2020-05-05

Data: 2020-02

Data: 2019-07-27

Resum:

Stable draft of a technical specificatio which specifies the semantics of a protocol for requesting to a remote server (and for receiving the corresponding response) the validation and optionally the augmentation of AdES digital signatures compliant with the following ETSI deliverables: ETSI EN 319 122, ETSI EN 319 132, ETSI EN 319 142, ETSI TS 101 733], ETSI TS 102 778 , ETSI TS 101 903, ETSI TS 103 171, ETSI TS 103 172, and ETSI TS 103 173. It also specifies the syntaxes for two protocols: one using XML syntax, and the other using JSON syntax]]>

Communications in nonlinear science and numerical simulation

Vol. 71, p. 82

DOI: 10.1016/j.cnsns.2018.10.026

Data de publicació: 2019-06-15

Resum:

In this paper, we consider the collinear symmetric four-body problem, where four masses and a¿>¿0, are aligned in this order and move symmetrically about their center of mass. We introduce regularized variables to deal with binary collisions as well as McGehee coordinates to study the quadruple collision manifold for a negative value of the energy. The paper is mainly focused on orbits that eject from (or collide to) quadruple collision. The problem has two hyperbolic equilibrium points, located in the quadruple collision manifold. We use high order parametrizations of their stable/unstable manifolds to devise a numerical procedure to compute ejection-collision orbits, for any value of a. Some results from the explorations done for are presented. Furthermore, we prove the existence of ejection-direct escape orbits, which perform a unique type of binary collisions.]]>

Geomechanics for energy and the environment

Vol. 18, p. 1-12

DOI: 10.1016/j.gete.2018.12.001

Data de publicació: 2019-06

Resum:

The shear modulus (G) of two different bentonites was measured by means of a resonant column apparatus. The samples were compacted at different dry densities and degrees of saturation and tested with different confinement pressures and strains levels for studying the influence of these parameters on the shear modulus. The results show similar tendencies in both bentonites: the shear modulus increases as the dry density increases and exhibits maximum shear modulus when degree of saturation is around 80%. An empirical equation, taking into account the microstructure of the clays, is used to evaluate the shear modulus at small strains as a function of dry density and degree of saturation. Although the values of the shear modulus measured are similar in both bentonites for a given stress and degree of saturation, there is difference in the elastic strain limit of the soil. Bentonite clay is going to be part of the Engineered Barrier System (EBS) in deep geological disposal facilities for the long-term confinement of spent nuclear fuel. In order to fully understand their long-term performance, their behaviour in shearing conditions should be assessed.]]>

Progress in materials science

Vol. 103, p. 319-373

DOI: 10.1016/j.pmatsci.2019.02.003

Data de publicació: 2019-06

Resum:

Carbon-based nanoparticles have recently generated a great attention, as they could create polymer nanocomposites with enhanced transport properties, overcoming some limitations of electrically-conductive polymers for high demanding sectors. Particular importance has been given to the protection of electronic components from electromagnetic radiation emitted by other devices. This review considers the recent advances in carbon-based polymer nanocomposites for electromagnetic interference (EMI) shielding. After a revision of the types of carbon-based nanoparticles and respective polymer nanocomposites and preparation methods, the review considers the theoretical models for predicting the EMI shielding, divided in those based on electrical conductivity, models based on the EMI shielding efficiency, on the so-called parallel resistor-capacitor model and those based on multiscale hybrids. Recent advances in the EMI shielding of carbon-based polymer nanocomposites are presented and related to structure and processing, focusing on the effects of nanoparticle’s aspect ratio and possible functionalization, dispersion and alignment during processing, as well as the use of nanohybrids and 3D reinforcements. Examples of these effects are presented for nanocomposites with carbon nanotubes/nanofibres and graphene-based materials. A final section is dedicated to cellular nanocomposites, focusing on how the resulting morphology and cellular structures may generate lightweight multifunctional nanocomposites with enhanced absorption-based EMI shielding properties]]>

Journal of materials processing technology

Vol. 268, p. 162-170

DOI: 10.1016/j.jmatprotec.2019.01.015

Data de publicació: 2019-06

Resum:

The present work aims to compare two different injection moulding foaming technologies, the already known MuCell® process and the new emerged technology IQ Foam®, as well as the cell structure and mechanical behavior of the obtained components. Glass fiber reinforced-polypropylene (>PP GF<) was employed to produce rectangular plates at solid and foamed conditions by using MuCell® and IQ Foam® processes combined with the complementary Core Back expansion molding technology, and the material structure as well as the tensile, flexural and impact properties were studied. A solid skin-foamed core structure was observed in the samples foamed by both techniques. The mechanical properties decreased gradually with the apparent density of the microcellular plates. By increasing the thickness of the part because of the expansion of the cavity with the Core Back technology, the apparent density decreased but the flexural stiffness was greatly enhanced. Foamed samples obtained by IQ Foam® technology exhibited thicker solid surface layers and lower cell density than that of the MuCell® ones, but consequently higher resistant area, and thus, slightly higher mechanical properties. The new IQ Foam® technology is able to produce foamed parts with properties comparable to that of the MuCell® process, offering additional benefits such as cost-effectiveness, easy to use and machine-independence]]>

Renewable energy

Vol. 136, p. 1-14

DOI: 10.1016/j.renene.2018.12.096

Data de publicació: 2019-06

Resum:

Floating offshore wind turbines (FOWT) have been extensively proven in model tests and are reaching currently a pre-commercial phase where large scale demonstrators are being built offshore. This transition increases the need for models able to assess the performance at suitable offshore locations. A simplified model is proposed that computes the dynamic response of FOWT to different met-ocean conditions and calculates the energy production considering the behavior of the structure as well as the downtime of the turbine due to exceeding operating limits. The model is validated against FAST and applied to three offshore sites. The motions response and hub acceleration are largest for West of Barra followed by Gulf of Maine and Costa Brava. The energy generation is also the highest at West of Barra, where a capacity factor of 75% is reached. A comparison between the energy generation of a bottom-fixed and FOWT indicates a difference of less than 1% for all sites. Finally, a sensitivity analysis of hub acceleration and platform pitch limits studies the impact on the capacity factor and downtime. The model can be useful for feasibility or pre-engineering studies and can be of interest for both investigators and developers of offshore wind projects.]]>

Future generation computer systems

Vol. 94, p. 148-159

DOI: 10.1016/j.future.2018.11.028

Data de publicació: 2019-05

Resum:

The recent upsurge in the available amount of health data and the advances in next-generation sequencing are setting the ground for the long-awaited precision medicine. To process this deluge of data, bioinformatics workloads are becoming more complex and more computationally demanding. For this reasons they have been extended to support different computing architectures, such as GPUs and FPGAs, to leverage the form of parallelism typical of each of such architectures. The paper describes how a genomic workload such as k-mer frequency counting that takes advantage of a GPU can be offloaded to one or even more FPGAs. Moreover, it performs a comprehensive analysis of the FPGA acceleration comparing its performance to a non-accelerated configuration and when using a GPU. Lastly, the paper focuses on how, when using accelerators with a throughput-oriented workload, one should also take into consideration both kernel execution time and how well each accelerator board overlaps kernels and PCIe transferred. Results show that acceleration with two FPGAs can improve both time- and energy-to-solution for the entire accelerated part by a factor of 1.32x. Per contra, acceleration with one GPU delivers an improvement of 1.77x in time-to-solution but of a lower 1.49x in energy-to-solution due to persistently higher power consumption. The paper also evaluates how future FPGA boards with components (i.e., off-chip memory and PCIe) on par with those of the GPU board could provide an energy-efficient alternative to GPUs.]]>

Information fusion

Vol. 47, p. 45-59

DOI: 10.1016/j.inffus.2018.07.002

Data de publicació: 2019-05-01

Resum:

Hesitant fuzzy linguistic term sets have been an active field of research in recent times. Notwithstanding its usefulness to capture the human way of reasoning using linguistic expressions involving different levels of precision, in some situations they do not depict enough details. In this paper, we present a new kind of linguistic term sets, called free double hierarchy linguistic term sets, and their corresponding free double hierarchy hesitant fuzzy linguistic elements, in order to describe the complexity of linguistic expressions used by the decision makers in a more accurate and precise way. Furthermore, an order and a distance between free double hierarchy hesitant fuzzy linguistic elements are introduced to present an approach based on the TOPSIS method to rank alternatives with free double hierarchy hesitant fuzzy linguistic information by taking into consideration the opinions of a group of decision makers. A case study based on tourism management in Barcelona is also provided to illustrate the usefulness of the presented approach.]]>

Communications in nonlinear science and numerical simulation

Vol. 70, p. 48-73

DOI: 10.1016/j.cnsns.2018.09.006

Data de publicació: 2019-05-01

Resum:

In this work we consider a general class of 2-dimensional hybrid systems. Assuming that the system possesses an attracting equilibrium point, we show that, when periodically driven with a square-wave pulse, the system possesses a periodic orbit which may undergo smooth and nonsmooth grazing bifurcations. We perform a semi-rigorous study of the existence of periodic orbits for a particular model consisting of a leaky integrate-and-fire model with a dynamic threshold. We use the stroboscopic map, which in this context is a 2-dimensional piecewise-smooth discontinuous map. For some parameter values we are able to show that the map is a quasi-contraction possessing a (locally) unique maximin periodic orbit. We complement our analysis using advanced numerical techniques to provide a complete portrait of the dynamics as parameters are varied. We find that for some regions of the parameter space the model undergoes a cascade of gluing bifurcations, while for others the model shows multistability between orbits of different periods]]>

Composites part B: engineering

Vol. 164, p. 235

DOI: 10.1016/j.compositesb.2018.11.065

Data de publicació: 2019-05

Resum:

An experimental program of T-beams strengthened in shear by CFRP sheets has been developed with two longitudinal reinforcement ratios and different externally bonded CFRP shear strengthening amounts in a discontinuous or continuous U-shaped configuration with and without mechanical anchorages. The effectiveness of the external reinforcement without anchorages was low regardless the CFRP reinforcement ratio. There is an evidence of the interaction of the different shear strength components, concrete Vc, transverse steel Vs, CFRP sheets Vf that have been obtained from the registered data of the instrumentation. This interaction might explain that the ultimate shear force of some CFRP-strengthened beams was lower than the one of the control beam. There is a significant difference between the sum of the Vc, Vs, and Vf components and the total shear force. This difference is assumed to be carried out by the flange (including its internal transverse reinforcement), which represents a significant percentage of the total shear strength (with a mean value of 38%). Finally, the contribution of the CFRP has been obtained by different existing guidelines and has been compared to the experimental values.]]>

Journal of materials processing technology

Vol. 267, p. 230-240

DOI: 10.1016/j.jmatprotec.2018.12.022

Data de publicació: 2019-05-01

Journal of cleaner production

Vol. 218, p. 772-781

DOI: 10.1016/j.jclepro.2019.02.054

Data de publicació: 2019-05

Resum:

The integration of sustainable development in higher education is increasingly recognised as a priority for a growing number of universities. Nonetheless, numerous barriers for change remain and particular attention should be given to the success factors fostering an effective integration. The present contribution analyses the extent to which a professional development programme, aimed at engaging and empowering faculty, has positive effects at integrating sustainable human development principles into existing courses of engineering; specifically, in new teaching modules in a subject of basic engineering science, implemented in regular courses of the first year of an engineering degree programme. The methodology includes: i) a focus group conducted with the students of the engineering courses involved in the initiative; and ii) two in-depth interviews conducted with the academic coordinator of the subject analysed. The results of the present case study highlight the relevance of professional development programmes addressed to academics in terms of students’ positive perception of the teaching innovation proposal and the empowerment of the academics involved in the training. The findings also suggest that specific university cultures and values, as well as barriers and resistance of academics to innovative processes, may contribute to frustrating the efforts of motivated professors. The conclusions emphasise the potential of continuous professional development initiatives addressed to small groups of professors, especially if reinforced with appropriate incentives and active institutional support.]]>

Applied mathematical modelling

Vol. 69, p. 201-222

DOI: 10.1016/j.apm.2018.12.004

Data de publicació: 2019-05-01

Resum:

The role of thermal relaxation in nanoparticle melting is studied using a mathematical model based on the Maxwell–Cattaneo equation for heat conduction. The model is formulated in terms of a two-phase Stefan problem. We consider the cases of the temperature profile being continuous or having a jump across the solid–liquid interface. The jump conditions are derived from the sharp-interface limit of a phase-field model that accounts for variations in the thermal properties between the solid and liquid. The Stefan problem is solved using asymptotic and numerical methods. The analysis reveals that the Fourier-based solution can be recovered from the classical limit of zero relaxation time when either boundary condition is used. However, only the jump condition avoids the onset of unphysical “supersonic” melting, where the speed of the melt front exceeds the finite speed of heat propagation. These results conclusively demonstrate that the jump condition, not the continuity condition, is the most suitable for use in models of phase change based on the Maxwell–Cattaneo equation. Numerical investigations show that thermal relaxation can increase the time required to melt a nanoparticle by more than a factor of ten. Thus, thermal relaxation is an important process to include in models of nanoparticle melting and is expected to be relevant in other rapid phase-change processes.]]>

Expert systems with applications

Vol. 121, p. 347-361

DOI: 10.1016/j.eswa.2018.12.039

Data de publicació: 2019-05-01

Resum:

This paper proposes an iterated greedy algorithm for scheduling jobs in F parallel flow shops (lines), each consisting of a series of m machines without storage capacity between machines. This constraint can provoke the blockage of machines if a job has finished its operation and the next machine is not available. The criterion considered is the minimization of the sum of tardiness of all the jobs to schedule, i.e., minimization of the total tardiness of jobs. Notice that the proposed method is also valid for solving the Distributed Permutation Blocking Flow Shop Scheduling Problem (DBFSP), which allows modelling the scheduling process in companies with more than one factory when each factory has an identical flow shop configuration. Firstly, several constructive procedures have been implemented and tested to provide an efficient solution in terms of quality and CPU time. This initial solution is later improved upon with an iterated greedy algorithm that includes a variable neighbourhood search for interchanging or reassigning jobs from the critical line to other lines. Next, two strategies have been tested for selecting the critical line; the one with a higher total tardiness of jobs and the one with a job that has the highest tardiness. The experimental design chooses the best combination of initial solution and critical line selection. Finally, we compare the performance of the proposed algorithm against other benchmark algorithms proposed for the DPFSP, which have been adapted to the problem being considered here since, to the best of our knowledge, this is the first attempt to solve either the Parallel Blocking Flow Shop problem or the Distributed Blocking Flow Shop problem with the goal of minimizing total tardiness. This comparison has allowed us to confirm the good performance of the proposed method.]]>

Science of the total environment

Vol. 662, p. 755-768

DOI: 10.1016/j.scitotenv.2019.01.266

Data de publicació: 2019-04-20

Applied mathematics and computation

Vol. 347, p. 734-740

DOI: 10.1016/j.amc.2018.11.043

Data de publicació: 2019-04-15

Resum:

A k-antimagic labeling of a graph G is an injection from E(G) to {1,2, ..., |E(G)|+k} such that all vertex sums are pairwise distinct, where the vertex sum at vertex u is the sum of the labels assigned to edges incident to u. We call a graph k-antimagic when it has a k-antimagic labeling, and antimagic when it is 0-antimagic. Hartsfield and Ringel conjectured that every simple connected graph other than K2 is antimagic, but the conjecture is still open even for trees. Here we study k-antimagic labelings of caterpillars. We use algorithmic and constructive techniques, instead of the standard Combinatorial NullStellenSatz method, to prove our results: (i) any caterpillar of order n is (¿(n-1)/2¿-2)-antimagic; (ii) any caterpillar with a spine of order s with either at least ¿(3s+1)/2¿ leaves or ¿(s-1)/2¿ consecutive vertices of degree at most 2 at one end of a longest path, is antimagic; and (iii) if p is a prime number, any caterpillar with a spine of order p, p-1 or p-2 is 1-antimagic.

A k-antimagic labeling of a graph G is an injection from E(G) to {1,2, ..., |E(G)|+k} such that all vertex sums are pairwise distinct, where the vertex sum at vertex u is the sum of the labels assigned to edges incident to u. We call a graph k-antimagic when it has a k-antimagic labeling, and antimagic when it is 0-antimagic. Hartsfield and Ringel conjectured that every simple connected graph other than K2 is antimagic, but the conjecture is still open even for trees. Here we study k-antimagic labelings of caterpillars. We use algorithmic and constructive techniques, instead of the standard Combinatorial NullStellenSatz method, to prove our results: (i) any caterpillar of order n is (⌊(n−1)/2⌋−2)-antimagic; (ii) any caterpillar with a spine of order s with either at least ⌊(3s+1)/2⌋ leaves or ⌊(s−1)/2⌋ consecutive vertices of degree at most 2 at one end of a longest path, is antimagic; and (iii) if p is a prime number, any caterpillar with a spine of order p, p−1 or p−2 is 1-antimagic.]]>

IEEE transactions on industrial electronics

Vol. 66, num. 4, p. 2603-2612

DOI: 10.1109/TIE.2018.2844786

Data de publicació: 2019-04-01

Resum:

Permanent magnet machines are not free from the interaction between magnets and the stator and rotor slots, which causes an undesired disturbing torque. Such cogging or detent torque is especially larger with salient pole machines, as it is the case of the Permanent Magnet Hybrid Stepper Machines (PMHSM). Depending on the application requirements, these torque perturbations can be unacceptable and the application of solutions that minimizes the cogging torque effects are mandatory. This paper originally faces the minimization of the cogging torque using resonant controllers. More specifically, the paper details the analysis and design of a speed-adaptive resonant controller, which not only is directly designed in Z domain but also considers the current (or torque) inner loop delay. Pole-zero placement and the disturbance rejection frequency response have been attained in the design of the speed and position speedadaptive controllers. Experimental results with two off-theshelf PMHSMs demonstrate the superior performance of the proposal in both speed and position closed-loop applications for tracking, as well as in disturbance (load impact) rejection tests and against inertia variations. A comparison with a conventional PI has been carried out from the design stage to experimental results and the improvement of the proposal has been numerically quantified.]]>

Separation and purification technology

Vol. 212, p. 180-190

DOI: 10.1016/j.seppur.2018.11.022

Data de publicació: 2019-04-01

Resum:

Acidic mine waters (AMWs) contain, in addition to moderate concentrations of sulphuric acid, relatively high concentrations of transition elements (e.g. Fe, Al, Cu, Zn) and, in some cases, minor amounts of valuable rare earth elements (REEs). The established management routes for AMWs, based on the neutralisation and metal stabilisation as hydroxides, are limited by the associated costs, such as reagent consumption. Nanofiltration (NF)-based treatment processes could improve these management routes by recovering the sulphuric acid and simultaneously increasing the concentration of valuable elements (e.g. Zn, Cu and REEs) for further valorisation after the proper removal of Fe. Three different types of NF membranes with (a) a poly(piperazinamide) active layer (NF270), (b) a double active layer (poly(piperazinamide)/proprietary polyamide) (Desal DL) and (c) a sulphonated poly(ethersulphone) active layer (HydraCoRe 70pHT) were evaluated. The influence of Fe(III) concentration on the sulphuric acid recovery from solutions at pH 1 was characterised. NF270 showed the higher permeate fluxes and the higher heavy and REE metal rejections (i.e. the higher concentration factors). As the Fe(III) concentration increased, higher acid permeation was obtained, which helped to decrease the neutralisation costs during its post-treatment. The membrane chemistry of the active layer (nature and acid-base membrane properties) and structure (single/double layer) were found to be strong parameters in the membrane separation performance. Ion transport data were modelled according to a Solution-Electro-Diffusion model coupled with Ion Reactive Transport and the membrane permeances to ions were determined]]>

Applied mathematics and computation

Vol. 346, p. 127-142

DOI: 10.1016/j.amc.2018.10.066

Data de publicació: 2019-04-01

Resum:

We classify all planar four–body central configurations where two pairs of the bodies are on parallel lines. Using cartesian coordinates, we show that the set of four–body trapezoid central configurations with positive masses forms a two–dimensional surface where two symmetric families, the rhombus and isosceles trapezoid, are on its boundary. We also prove that, for a given position of the bodies, in some cases a specific order of the masses determines the geometry of the configuration, namely acute or obtuse trapezoid central configuration. We also prove the existence of non–symmetric trapezoid central configurations with two pairs of equal masses.]]>

Chemical engineering journal

Vol. 361, p. 839-852

DOI: 10.1016/j.cej.2018.12.148

Data de publicació: 2019-04-01

Resum:

Two low-cost renewable poplar-based materials were manufactured in this work for energy production and as sorbents for lead and terbium removal from aqueous effluents. Torrefaction was used as a pretreatment process for conditioning the raw biomass. Two different operating conditions were used in the multiple-hearth furnace of the torrefaction pilot-plant: i) 250¿°C; ii) 280¿°C, with residence times of 75¿min and 60¿min, respectively. The raw and torrefied biomasses have been characterized using SEM-EDX, FTIR, TGA, XRD and elemental analyses (C, H, N, S, O); an increase of the torrefaction severity, results in an increase of the carbon/oxygen ratio and in a greater mass loss (21% at 250¿°C, and 53% at 280¿°C). The torrefaction had a positive impact on the sorption of metals, it allowed the increase of lignin content of the manufactured materials, and it allowed the storage of the sorbents for longer time with reduced moisture content. The equilibrium studies were performed in batch system and the experimental data were described with the Sips equation. The maximum sorption capacity was found as 30¿mg¿g-1 for lead and 9.4¿mg¿g-1 for terbium (at pH 4). The kinetic profiles were fitted using the pseudo-second order rate equation. The regeneration of the sorbent was demonstrated by three sorption-desorption cycles using dilute HNO3 solution (0.1¿M) as eluent for metal recovery]]>

Industrial crops and products

Vol. 130, p. 301

DOI: 10.1016/j.indcrop.2018.12.090

Data de publicació: 2019-04-01

Resum:

Based on the biodegradable material-polyethylene glycol (PEG)-as the plasticizer, oxidized wood flour (OWF) as the charring agent for polylactide (PLA), a series flame-retardant PLA biocomposites were prepared via melt-compounding and hot-compression. The effect of OWF on the thermal, mechanical and flame retardant properties of biocomposites was investigated systemically. We have found that after the incorporation of PEG and OWF with 10¿wt% into PLA, the biocomposite showed higher tensile elongation than pure PLA. Furthermore, the presence of OWF and ammonium polyphosphate (APP) imparted the biocomposite good flame-retardant performance, shown a remarkable reduction on the peak of heat release rate (PHRR), improved LOI value and passed UL94 V-0 rating. Moreover, Scanning electron microscopy-energy dispersive spectra (SEM/EDS) and thermogravimetric analysis coupled with infrared spectrometer (TG-FTIR) were also performed to understand the flame retardant mechanism. These results proved that OWF could be as new functional filler for polymer composites to further improve their flame retardancy.]]>

International journal of heat and fluid flow

Vol. 76, p. 141-153

DOI: 10.1016/j.ijheatfluidflow.2019.02.004

Data de publicació: 2019-04

Resum:

Direct numerical simulation and large-eddy simulation have been performed for a heated sphere at Reynolds numbers of $Re=1000$ and $Re=10^4$, respectively. The Prandtl number for both simulations has been $Pr=0.7$. Measurements of the local and average Nusselt number are performed and compared with literature available experimental results. Average and front stagnation point Nusselt numbers increase with the Reynolds number, while the minimum value moves towards the sphere apex as the flow enters the sub-critical regime. Differences in both viscous and thermal boundary layers are observed, while the shape factor at Reynolds number $Re=10^4$ behaves similarly to that observed in circular cylinders at comparable Reynolds numbers. It is shown that as the Reynolds number increases, the increase in turbulent kinetic energy promotes the entrainment of irrotational flow thus enhancing the temperature mixing in the zone. The near wake, between $5\leq x/D\leq15$, spreads at a faster rate at $Re=1000$ with a slope close to $x/D^{1/2}$, while at $Re=10^4$ it follows a trend close to $x/D^{1/3}$.]]>

Journal of Vibration and Acoustics, Transactions of the ASME

Vol. 141, num. 2

DOI: 10.1115/1.4041896

Data de publicació: 2019-04-01

Resum:

This article presents a mathematical model used to obtain the vertical vibration of a ballasted railway track when a wheel is passing at a certain speed over a fixed location of the rail. The aim of this simulation is to compare calculated RMS values of the vertical vibration velocity with measured RMS values. This comparison is the basis for a proposed time domain methodology for detecting potential wheel flats or any other singular defect on the wheel rolling bands of metropolitan trains. In order to reach this goal, a wheel-rail contact model is proposed; this model is described by the track vertical impulse response and the vertical impulse response of the wheel with the primary suspension, both linked through a Hertz nonlinear stiffness. To solve the model for obtaining the wheel-rail contact force, a double convolution method is applied. Several kinds of wheel flats are analysed, from theoretical round edged wheel flats to different real wheel profile irregularities. Afterwards, the vertical vibration velocity at a fixed point on the rail is obtained using a variable kernel convolution method. Running different simulations for different wheel flats, a study of the vertical vibration attenuation along the rail is carried out. Finally, it is proceeded to obtain the temporary evolution of the RMS value for the rail vertical vibration velocity in order to be used as a reference for detecting wheel flats or any other defect. This last aspect will be presented in more detail in a second article.]]>

Future generation computer systems

Vol. 93, p. 515-528

DOI: 10.1016/j.future.2018.10.058

Data de publicació: 2019-04

Resum:

The fast development of IoT in general and wearable smart sensors in particular in the context of wellness and healthcare are demanding for definition of specific infrastructure supporting real time data analysis for anomaly detection, event identification, situation awareness just to mention few. The explosion in the development and adoption of these smart wearable sensors has contributed to the definition of the Internet of Medical Things (IoMT), which is revolutionizing the way healthcare is tackled worldwide. Data produced by wearable sensors continuously grow and could be spread among clinical centers, hospitals, research labs, yielding to a Big Data management problem. In this paper we propose a technological and architectural solution, based on Open Source big data technologies to perform real-time analysis of wearable sensor data streams. The proposed architecture is composed of four distinct layers: a sensing layer, a pre-processing layer (Raspberry Pi), a cluster processing layer (Kafka’s broker and Flink’s mini-cluster) and a persistence layer (Cassandra database). A performance evaluation of each layer has been carried out by considering CPU and memory usage for accomplishing a simple anomaly detection task using the REALDISP dataset]]>

Science of the total environment

Vol. 659, p. 1567-1576

DOI: 10.1016/j.scitotenv.2018.12.348

Data de publicació: 2019-04

Resum:

A Life Cycle Assessment was carried out in order to assess the environmental performance of constructed wetland systems for winery wastewater treatment. In particular, six scenarios which included the most common winery wastewater treatment and management options in South-Western Europe, namely third-party management and activated sludge systems, were compared. Results showed that the constructed wetland scenarios were the most environmentally friendly alternatives, while the third-party management was the worst scenario followed by the activated sludge systems. Specifically, the potential environmental impacts of the constructed wetlands scenarios were 1.5–180 and 1–10 times lower compared to those generated by the third-party and activated sludge scenarios, respectively. Thus, under the considered circumstances, constructed wetlands showed to be an environmentally friendly technology which helps reducing environmental impacts associated with winery wastewater treatment by treating winery waste on-site with low energy and chemicals consumption.]]>

Science of the total environment

Vol. 661, p. 187-195

DOI: 10.1016/j.scitotenv.2019.01.136

Data de publicació: 2019-04

Resum:

This article presents the feasibility evaluation and preliminary design of a wastewater treatment plant upgrade supported by simulation. The existing facility was based on trickling filters, and the objective of the upgrade was to achieve nutrients removal. The proposed solution modifies the existing primary clarifier to host an anaerobic-anoxic suspended growth reactor, which is an alternative that, to our knowledge, has not been proposed or explored so far. The trickling filters would remain as aerobic reactors. In this study, the novel treatment scheme has been assessed for the first time, through model simulations. The modified treatment train was simulated, showing that the anoxic zone is able to denitrify satisfactorily achieving the required effluent nitrogen concentration. However, to promote biological phosphorus removal, an additional aerobic zone combined with a bypass of activated sludge from the anoxic zone to the first trickling filter is needed, in order to provide aerobic conditions to the phosphate accumulating organisms. Several combinations of additional aerobic volume and sludge bypass flowrate were found to successfully achieve both nitrogen and phosphorus removal, using the existing facilities without the need for new reactors neither implementing modifications that could put the trickling filters' physical integrity at risk. The novel treatment scheme could be applied in other cases with similar flowsheet in the same context.]]>

Computational materials science

Vol. 160, p. 42-52

DOI: 10.1016/j.commatsci.2018.12.048

Data de publicació: 2019-04

Resum:

A spring element model that takes into account the dynamic effects associated with fibre failure in composite materials is presented. The model is implemented in a parallel environment to allow a better performance in the prediction of the complex mechanisms associated with longitudinal tensile failure. The model is used to identify the changes in the stress fields around a broken fibre representing fibre failure as a dynamic phenomenon. In light of these changes in the stress fields, the cluster formation and failure development is analysed and the results are compared with the static spring element model. It is observed that the stress redistribution around a broken fibre is strongly dependent on the dynamic effects and it varies with the material in study, specially if the matrix is considered linear elastic. The changes in local stress redistribution are seen to affect the materials tensile behaviour and cluster formation, being this changes higher for a material with an elastic matrix.]]>

Journal of alloys and compounds

Vol. 779, p. 314-325

DOI: 10.1016/j.jallcom.2018.11.083

Data de publicació: 2019-03-30

Resum:

The photodegradation of diclofenac from aqueous medium under UV-A light condition has been essayed using co-doped with manganese and silver TiO2 photocatalysts. X-ray diffraction, Raman spectroscopy, Scanning electron microscopy, Transmission electron microscopy, High resolution transmission electron microscopy, Energy dispersive X-ray, N2 adsorption-desorption measurements at 77¿K, UV–Visible diffuse reflectance, X-ray photoelectron spectroscopy and photoluminescence analyses were used to characterize the materials. A high surface specific area of 165¿m2/g, low band gap energy (2.7¿eV) and effective charge separation were obtained for the 0.5%Ag-0.6%Mn/TiO2 photocatalyst. The results of the photocatalytic experiments showed that co-doping improved the photocatalytic activity of TiO2. In particular, TiO2 co-doped with 0.6¿mol% Mn and 0.5¿mol% Ag exhibited the maximum diclofenac removal (86%) after 4¿h under UV-A light irradiation. The photodegradation rates followed a first order kinetics according to the Langmuir-Hinshelwood model, being the highest apparent rate of 0.0064 min-1. The photocatalytic performance appears as related to the specific surface area, the low optical band gap energy, the creation of surface oxygen vacancies and the efficient separation of photogenerated electron-hole pairs.]]>

Journal of fluid mechanics

Vol. 863, p. 341-363

DOI: 10.1017/jfm.2018.1000

Data de publicació: 2019-03-25

Resum:

Backward-facing step (BFS) constitutes a canonical configuration to study wall-bounded flows subject to massive expansions produced by abrupt changes in geometry. Recirculation flow regions are common in this type of flow, driving the separated flow to its downstream reattachment. Consequently, strong adverse pressure gradients arise through this process, feeding flow instabilities. Therefore, both phenomena are strongly correlated as the recirculation bubble shape defines how the flow is expanded, and how the pressure rises. In an incompressible flow, this shape depends on the Reynolds value and the expansion ratio. The influence of these two variables on the bubble length is widely studied, presenting an asymptotic behaviour when both parameters are beyond a certain threshold. This is the usual operating point of many practical applications, such as in aeronautical and environmental engineering. Several numerical and experimental studies have been carried out regarding this topic. The existing simulations considering cases beyond the above-mentioned threshold have only been achieved through turbulence modelling, whereas direct numerical simulations (DNS) have been performed only at low Reynolds numbers. Hence, despite the great importance of achieving this threshold, there is a lack of reliable numerical data to assess the accuracy of turbulence models. In this context, a DNS of an incompressible flow over a BFS is presented in this paper, considering a friction Reynolds number ( ¿ ) of 395 at the inflow and an expansion ratio 2. Finally, the elongation of the Kelvin–Helmholtz instabilities along the shear layer is also studied.]]>

Neuroscience letters

Vol. 696, p. 20-27

DOI: 10.1016/j.neulet.2018.12.014

Data de publicació: 2019-03-23

Resum:

Neuronal activity can be modulated by endogenous control mechanisms that either facilitate or suppress it. With this idea in mind, we attempted to evaluate and correlate spinal neuronal activity with the amplitude of corticogram (ECoG) event related potentials (ERP) in the presence of nociceptive stimulation in rats. We evaluated the ERP in response to noxious stimuli, endogenous analgesic actions, different frequencies, and heterotopic nociceptive stimulation, as well as in conjunction with recordings from neurons in the spinal cord that are activated by noxious stimuli. Computational tasks enabled us to establish correlations between the amplitude of ERP and neuronal firing of cells in the spinal dorsal horn. Our results show that the ERP amplitude could be modified by previous activity in the cerebral cortex, but the activity in the spinal cord did not change. Previous activity could originate spontaneously or could be driven by sensory stimulation. A recurrent inhibitory cortical action is proposed that could explain the suppression of pain perception during electrical or magnetic transcranial stimulation, as well as during heterotopic stimulation. This study aims to uncover a local recurrent inhibitory cortical action that could modify the sensory information.]]>

Science of the total environment

Vol. 656, p. 902-909

DOI: 10.1016/j.scitotenv.2018.11.420

Data de publicació: 2019-03-15

Resum:

This study presents the financial assessment for implementing an ammonium and phosphate simultaneous recovery process based on the use of calcium activated synthetic zeolites in a large urban Waste Water Treatment Plant (WWTP) located in the Metropolitan Area of Barcelona. A calcium activated synthetic zeolites was selected, after a benchmarking analysis, as it reported capability for simultaneously recover ammonium and phosphate by a combined mechanism of ion exchange for ammonium and formation of insoluble mineral phase for phosphate. The loaded sorbent, rich in ammonium and phosphate, can be used as slow-release fertilizer. Financial indexes such as the net present value, the internal return rate, the return of investment and the payback period were calculated concluding that the integration of a zeolite-based sorption treatment stage in the main stream is economically feasible, with a reasonable payback period. The need, to achieve low-levels of P and N on the discharged waters and the need to develop more sustainable WWTP facilities indicate that the deployment of nutrient recovery solutions will be encouraged. The sensitivity analysis carried out to define the critical parameters of the economic performance of the technology allows concluding that the main variable in the viability of the nutrient recovery unit is related to the nutrients sorbent, both in the cost of purchase and in the market for the sorbent loaded with nutrients.]]>

Mechanical systems and signal processing

Vol. 119, p. 432-456

DOI: 10.1016/j.ymssp.2018.09.042

Data de publicació: 2019-03-15

Resum:

The objective of this work is to demonstrate the feasibility of utilising vibration data to generate a set of spectral domain-based indicators purposed to assess the degradation and reinforcement on structures. These indicators are derived from the complex frequency domain assurance criterion (CFDAC) matrices, corresponding to the altered and pristine state of a monitored structure. The CFDAC operator is similar to the MAC (modal assurance criterion) but formulated in the complex spectral domain. The indicators, referred to as spectral correlation indices (SCI), are aimed to quantify the strength of correlation between an altered state and a reference state so structural alteration can be assessed. In this paper, a numerical and experimental investigation on the feasibility of the proposed approach for structural assessment is presented, by examining the spectral correlation indices in front of multiple alteration scenarios on a square aluminium plate under one-edge-clamped boundary conditions. A comprehensive parametric, sensitivity and stability analysis in front of the FRF synthesis and acquisition parameters is undertaken, both experimentally and numerically, to deepen the knowledge concerning stability properties of the indicators. Once stability thresholds are identified, experimental results are compared to numeric outcomes, allowing conclusions to be drawn regarding the capability and suitability of proposed SCI indicators for structural assessment and damage identification. This research is aimed to serve as a first step towards the development of a fully functional SHM system based on spectral domain indices.]]>

Chemical engineering journal

Vol. 360, p. 890-899

DOI: 10.1016/j.cej.2018.12.004

Data de publicació: 2019-03-15

Resum:

Ammonium salts Hollow fibre Hydrophobic membrane Nutrient recovery Urban wastewater Water transport]]>

Science of the total environment

Vol. 656, p. 209-230

DOI: 10.1016/j.scitotenv.2018.11.188

Data de publicació: 2019-03-15

Resum:

Water resources in high mountain karst aquifers are usually characterized by high rainfall, recharge and discharge that lead to the sustainability of the downstream ecosystems. Nevertheless, these hydrological systems are vulnerable to the global change impact. The mean transit time (MTT) is a key parameter to describe the behavior of these hydrologic systems and also to assess their vulnerability. This work is focused on estimating MTT by using environmental tracers in the framework of high-mountain karst systems with a very thick unsaturated zone (USZ). To this end, it is adapted to alpine zones a methodology that combines a semi-distributed rainfall-runoff model to estimate recharge time series, and a lumped-parameter model to obtain ¿¿¿. The methodology has been applied to the Port del Comte Massif (PCM) hydrological system (Southeastern Pyrenees, NE Spain), a karst aquifer system with an overlying 1000¿m thick USZ. Six catchment areas corresponding to most important springs of the system are considered. The obtained results show that hydrologically the behavior of the system can be described by an exponential flow model (EM), with MTT ranging between 1.9 and 2.9¿years. These ¿¿¿ values are shorter than those obtained by considering a constant recharge rate along time, which is the easiest and most applied aquifer recharge hypothesis when estimating ¿¿¿ through lumped-parameter models.]]>

Computer networks

Vol. 151, num. march, p. 1-11

DOI: 10.1016/j.comnet.2019.01.002

Data de publicació: 2019-03-14

Journal of alloys and compounds

Vol. 777, p. 593-601

DOI: 10.1016/j.jallcom.2018.11.001

Data de publicació: 2019-03-10

Resum:

A deep knowledge of micromechanical properties of each constitutive phase of cemented carbides is crucial to improve their performance on the basis of microstructural design optimization. In the present work, a systematic experimental procedure has been followed to determine the intrinsic hardness of individual WC and (W,Ti,Ta,Nb)C particles, as well as that of the metallic binder, within a WC-Co composite containing a solid solution of mixed carbide as a third phase. In doing so, massive nanoindentation and statistical analysis of the gathered data are combined. Results showed that (W,Ti,Ta,Nb)C particles are significantly harder than WC ones, independent of the hardness anisotropy exhibited by the latter. Hardness assessment for the metallic binder required further analysis, including data deconvolution using thin film models and consideration of substrate effects. The attained hardness values are then used for estimation of effective flow stress of the metallic phase by means of Tabor's equation, yielding values ranging between 1.3 and 2.0¿GPa. These high constraining-related values are finally validated by experimental assessment of stress levels at which strain bursts are identified in stress-strain curves obtained by uniaxial compression of micropillars.]]>

Journal of parallel and distributed computing

Vol. 125, p. 31-44

DOI: 10.1016/j.jpdc.2018.10.010

Data de publicació: 2019-03

Resum:

Voltage scaling to values near the threshold voltage is a promising technique to hold off the many-core power wall. However, as voltage decreases, some SRAM cells are unable to operate reliably and show a behavior consistent with a hard fault. Block disabling is a micro-architectural technique that allows low-voltage operation by deactivating faulty cache entries, at the expense of reducing the effective cache capacity. In the case of the last-level cache, this capacity reduction leads to an increase in off-chip memory accesses, diminishing the overall energy benefit of reducing the voltage supply. In this work, we exploit the reuse locality and the intrinsic redundancy of multi-level inclusive hierarchies to enhance the performance of block disabling with negligible cost. The proposed fault-aware last-level cache management policy maps critical blocks, those not present in private caches and with a higher probability of being reused, to active cache entries. Our evaluation shows that this fault-aware management results in up to 37.3% and 54.2% fewer misses per kilo instruction (MPKI) than block disabling for multiprogrammed and parallel workloads, respectively. This translates to performance enhancements of up to 13% and 34.6% for multiprogrammed and parallel workloads, respectively.]]>