Attenuation due to liquid water is one of the largest uncertainties in radar observations. The effects of attenuation are generally inversely proportional to the wavelength, i.e. observations from X-band radars are more affected by attenuation than those from C- or S-band systems. On the other hand, X-band radars can measure precipitation fields in higher temporal and spatial resolution and are more mobile and easier to install due to smaller antennas. A first algorithm for attenuation correction in single-polarized systems was proposed by Hitschfeld and Bordan (1954) (HB), but it gets unstable in case of small errors (e.g. in the radar calibration) and strong attenuation. Therefore, methods have been developed that restrict attenuation correction to keep the algorithm stable, using e.g. surface echoes (for space-borne radars) and mountain returns (for ground radars) as a final value (FV), or adjustment of the radar constant (C) or the coefficient a. In the absence of mountain returns, measurements from C- or S-band radars can be used to constrain the correction. All these methods are based on the statistical relation between reflectivity and specific attenuation. Another way to correct for attenuation in X-band radar observations is to use additional information from less attenuated radar systems, e.g. the ratio between X-band and C- or S-band radar measurements. Lengfeld et al. (2016) proposed such a method based isotonic regression of the ratio between X- and C-band radar observations along the radar beam. This study presents a comparison of the original HB algorithm and three algorithms based on the statistical relation between reflectivity and specific attenuation as well as two methods implementing additional information of C-band radar measurements. Their performance in two precipitation events (one mainly convective and the other one stratiform) shows that a restriction of the HB is necessary to avoid instabilities. A comparison with vertically pointing micro rain radars (MRR) reveals good performance of two of the methods based in the statistical k-Z-relation: FV and a. The C algorithm seems to be more sensitive to differences in calibration of the two systems and requires additional information from C- or S-band radars. Furthermore, a study of five months of radar observations examines the long-term performance of each algorithm. From this study conclusions can be drawn that using additional information from less attenuated radar systems lead to best results. The two algorithms that use this additional information eliminate the bias caused by attenuation and preserve the agreement with MRR observations.
The interaction of dislocation pile-ups with several tilt grain boundaries (GB) is studied in copper by using a hybrid continuum-atomistic approach. The effects of temperature, pile-up intensity and GB structure on absorption and transmission of slip as a function of local stress state are explored. By considering several high-angle GBs with different misorientation angles, we demonstrate that GB atomic structure primarily defines its ability to accommodate incoming pile-up dislocations, thus limiting the direct transmission of pile-ups through the interface.
Cavaco, E.; Neves, L.; Casas, J. Structure and infrastructure engineering: maintenance, management, life-cycle design and performance Vol. 14, num. 2, p. 1-55 DOI: 10.1080/15732479.2017.1333128 Fecha de publicación: 2018-02 Artículo de revista
Management of existing structures has traditionally been based on condition assessment, based on visual inspections, disregarding the susceptibility of different structural types to aging and deterioration. Robustness, as a measure of the effects of unpredictable damage to structural safety can be a complementary information to the results of inspection. Although robustness has mostly been used to evaluate the consequences of extreme events, a similar framework can be used to investigate the result of aging, allowing a better understanding of the potential effects of deterioration and allowing a better allocation of available maintenance funding. In this work, a probabilistic structural robustness indicator is used to quantify the susceptibility of structures to corrosion. The methodology is exemplified through a case study comprising an existing reinforced concrete bridge deck, heavily damaged due to reinforcement corrosion, and finally demolished due to safety concerns. Robustness measures the bridge deck safety tolerance to reinforcement corrosion. The principal effects of corrosion, including loss of area and bond between concrete and steel are modelled using a non-linear finite-element model, coupled with a Response Surface Method to compute the bridge reliability as a function of the corrosion level, and finally used to assess robustness. Results show that the redundancy of the bridge allows significant redistribution of loads between elements with different corrosion levels. As a result, the bridge presents significant robustness and tolerance to reinforcement corrosion.
In this paper we analyse the ejection-collision (EC) orbits of the planar restricted three body problem. Being µ¿¿¿(0, 0.5] the mass parameter, and taking the big (small) primary with mass (µ), an EC orbit will be an orbit that ejects from the big primary, does an excursion and collides with it. As it is well known, for any value of the mass parameter µ¿¿¿(0, 0.5] and sufficiently restricted Hill regions (that is, for big enough values of the Jacobi constant C), there are exactly four EC orbits. We check their existence and extend numerically these four orbits for µ¿¿¿(0, 0.5] and for smaller values of the Jacobi constant. We introduce the concept of n-ejection-collision orbits (n-EC orbits) and we explore them numerically for µ¿¿¿(0, 0.5] and values of the Jacobi constant such that the Hill bounded possible region of motion contains the big primary and does not contain the small one. We study the cases 1¿=¿n¿=¿10 and we analyse the continuation of families of such n-EC orbits, varying the energy, as well as the bifurcations that appear.
For complex geometries, the definition of the subsystems is not a straightforward task. We present here a subsystem identification method based on the direct transfer matrix, which represents the first-order paths. The key ingredient is a cluster analysis of the rows of the powers of the transfer matrix. These powers represent high-order paths in the system and are more affected than low-order paths by damping.
Once subsystems are identified, the proposed approach also provides a quantification of the degree of coupling between subsystems. This information is relevant to decide whether a subsystem may be analysed in a computer model or measured in the laboratory independently of the rest or subsystems or not. The two features (subsystem identification and quantification of the degree of coupling) are illustrated by means of numerical examples: plates coupled by means of springs and rooms connected by means of a cavity.
Chicardi, E.; Bermejo, R.; Gotor, F.; Llanes, L.; Torres, Y. International journal of refractory metals and hard materials Vol. 71, p. 82-91 DOI: 10.1016/j.ijrmhm.2017.11.003 Fecha de publicación: 2018-02 Artículo de revista
The effect of the temperature on the mechanical strength of WC-Co cemented carbides with different microstructures (grain size and binder content) was evaluated. Biaxial flexural tests were performed on three cemented carbide grades at 600 °C using the ball-on-three-balls (B3B) method. Results were interpreted by Weibull statistics and compared to biaxial strength results at room temperature. A detailed fractographic analysis, supported by Linear Elastic Fracture Mechanics, was performed to differentiate the nature and size of critical defects and the mechanism responsible for the fracture. A significant decrease in the mechanical strength (around 30%) was observed at 600 °C for all grades of cemented carbides. This fact was ascribed to the change in the critical flaw population from sub-surface (at room temperature) to surface defects, associated with the selective oxidation of Co. Additionally, an estimation of the fracture toughness at 600 °C was attempted for the three cemented carbides, based upon the B3B strength results, the corresponding number of the tested specimens fragments and the macroscopic area of the B3B fracture surfaces. The fracture toughness was not affected by the temperature, at least up to 600 °C. In addition, the good agreement with the Single Edge Notch Beam toughness data suggests the possibility of employing this approach for fracture toughness evaluation of brittle materials under different testing conditions.
Modular multilevel converters (MMC) inherent features are gaining more attention for dc voltage transmission systems. One of the main research paths regarding the converter performance deals with its voltage modulation. Specifically, for medium voltage applications with relatively small number of submodules, the voltage modulation techniques impact on the MMC performance needs to be studied. This work provides an extensive review of the carrier-based pulse with modulation (CB-PWM) techniques proposed to be applied on previous multilevel inverter versions. The CB-PWM methods were adapted to be compatible with an additional cell ranking and selection algorithm to ensure equal energy distribution on the arm cells. The state-of-the-art of zero sequence signals (ZSS) applied on three-phase inverters is also reviewed. The alliance between the ZSS with the CB-PWM, as well as the nearest level modulation (NLM), has an important impact on the MMC harmonic content, efficiency and voltage ripple of its cells capacitors. A 15 MW 28-cell-based MMC is used to investigate each particular combination between the modulation method and the common mode ZSS.
Dielectric properties are important for predicting dielectric heating of foodstuffs. The dielectric properties of three types of milk (raw, skimmed and concentrated non-fat) were analyzed at high frequencies between 10 MHz and 2450 MHz for producing temperatures between 20 °C and 150 °C. The study of cow milk dielectric constants (e' and e¿) at conditions above 100 °C is needed to evaluate dielectric sterilization of milk. The dielectric constant (e') was found to decrease with frequency at all temperatures but increase with temperature at low frequencies and decrease with temperature at high frequencies. The dielectric loss factor (e¿) decreased with frequency and increased with temperature in almost the entire range of frequencies. Ionic conduction was the dominant mechanism across most of the frequency range. For milk samples with higher ash content (related to salt content), e' was higher at low frequencies and lower at high frequencies, whereas e¿ was higher for all frequencies. Penetration depth was lower for milk samples with higher ash content.
In the present paper, acoustic emission was studied in honing experiments obtained with different abrasive densities, 15, 30, 45 and 60. In addition, 2D and 3D roughness, material removal rate and tool wear were determined. In order to treat the sound signal emitted during the machining process, two methods of analysis were compared: Fast Fourier Transform (FFT) and Hilbert Huang Transform (HHT). When density 15 is used, the number of cutting grains is insufficient to provide correct cutting, while clogging appears with densities 45 and 60. The results were confirmed by means of treatment of the sound signal. In addition, a new parameter S was defined as the relationship between energy in low and high frequencies contained within the emitted sound. The selected density of 30 corresponds to S values between 0.1 and 1. Correct cutting operations in honing processes are dependent on the density of the abrasive employed. The density value to be used can be selected by means of measurement and analysis of acoustic emissions during the honing operation. Thus, honing processes can be monitored without needing to stop the process.
Phosphorus (P) is a vital macronutrient required to improve the agricultural yields but its excessive use as a fertilizer has resulted in pollution of water bodies leading to eutrophication. With no reserves of phosphorus source in Spain, increased dependence on phosphorus in agriculture have not only increased dependence on imports but also has raised concerns on its future availability as a resource. A Phosphorous Flow Analysis (PFA) was conducted for Spain for the year 2012 focusing on the food production and consumption systems. The results obtained were finally compared with PFA at both country level and continent level (EU-27). To quantify food and non-food flows systems, country specific data were considered. The sectors covered were crop production (CP), animal production (AP), food processing (FP), non-food production (NF) and consumption (HC). The findings reveal that a total of 325 kt P was imported by Spain in 2012; 66% of which was accumulated in markets stock of food and feed, fertilizers and non-food (91 kt P) while 33% was lost to the environment through land-fill, losses to water bodies, land accumulation and incineration. The largest proportion of losses is associated with water bodies (44.7 kt P) followed by agriculture and land accumulation (42.1 kt P). Wastewater treatment plants (WWTPs) received around 79.5 kt P within wastewater, with 60% being removed in sewage sludge. The 31.7 kt P discharged within final effluent represented the 71% of the total losses to water bodies. Around 69% of the sewage sludge was recycled to agriculture and 27% was sent directly to landfill including the ashes from incineration. Net accumulation was 1.84 kg P/cap which was similar to values reported for the EU-27 average (2.5 kg P/cap).
Guaya, D.; Valderrama, C.; Farran, A.; Sauras, T.; Cortina, J. Science of the total environment Vol. 612, p. 728-738 DOI: 10.1016/j.scitotenv.2017.08.248 Fecha de publicación: 2018-01-15 Artículo de revista
The removal of nutrients (nitrogen (N), phosphorous (P)) from waste water has become a resource recovery option in recent regulations worldwide, as observed in the European Union. Although both of these nutrients could be recovered from the sludge line, > 70–75% of the N and P is discharged into the water line. Efforts to improve the nutrient recovery ratios have focused on developing low-cost technologies that use sorption processes. In this study, a natural zeolite (clinoptilolite type) in its potassium (K) form was impregnated with hydrated metal oxides and used to prepare natural hybrid reactive sorbents (HRS) for the simultaneous recovery of ammonium (NH4 +) and phosphate (PO4 3 -) from treated urban waste water. Three unfertile soils (e.g., one acidic and two basic) amended with N-P-K charged HRS were leached with deionized water (e.g. to simulate infiltration in the field) at two- and three-day time intervals over 15 different leaching cycles (equivalent to 15 bed volumes). The N-P-K leaching profiles for the three charged hybrid sorbents exhibited continuous nutrient release, with their values dependent on the composition of minerals in the soils. In the basic soil that is rich in illite and calcite, the release of potassium (K+) and ammonium (NH4 +) is favoured by-ion exchange with calcium (Ca2 +) and accordingly diminishes the release of phosphate (PO4 3 -) due to its limited solubility in saturated calcite solutions (pH 8 to 9). The opposite is true for sandy soils that are rich in albite (both acidic and basic), whereas the release of NH4 + and K+ was limited and the values of both ions measured in the leaching solutions were below 1 mg/L. Their leaching solutions were poor in Ca2 +, and the release of PO4 3 - was higher (up to 12 mg P-PO4 3 -/L). The nutrient releases necessary for plant growth were provided continuously and were controlled primarily by the soil mineral dissolution rates fixing the soil aqueous solution composition (e.g. pH and ionic composition; in particular, the presence of calcite is a determinant for nutrient release, especially in alkaline soils). The N-P-K charged HRS sorbents that were used for soil amendment may be an alternative for avoiding nutrient leaching and reaching the goals of soil sustainability in agriculture and reducing the nutrient overloading of surface waters.
In this paper a short introduction of human-computer interaction is presented taking into
account the relationship between interaction design and universal design. From the conference
Interaccion 2015, some selected papers in the field of interaction design for healthcare are presented,
Methods, tools, interface design, user evaluation are considered with the aim to improve the quality of
life of citizens using technology.
Bueno, I.; España, E.; Gene, A.; Ondategui-Parra, JC; Zapata, C. Journal of Innovative Optical Health Sciences Vol. 11, num. 2, p. 1-15 DOI: 10.1142/S1793545818500013 Fecha de publicación: 2018-01-02 Artículo de revista
The aim of this paper was to examine the distribution of macular, retinal nerve fiber layer (RNFL) thickness and optic disc parameters of myopic and hyperopic eyes in comparison with emmetropic control eyes and to investigate their variation according to axial length (AL) and spherical equivalent (SE) in healthy children. Methods: This study included 293 pairs of eyes of 293 children (145 boys and 148 girls), ranging in age from 6 to 17 years. Subjects were divided according to SE in control (emmetropia, 99 children), myopia (100 children) and hyperopia (94 children) groups and according to axial AL in 68 short ((Formula presented.)22.00(Formula presented.)mm, 68), medium (from (Formula presented.)22.00(Formula presented.)mm to 25.00(Formula presented.)mm, 189) and long eyes ((Formula presented.)25.00(Formula presented.)mm, 36). Macular parameters, RNFL thickness and optic disc morphology were assessed by the CirrusTM HD-OCT. AL was measured using the IOL-Master system. Littmann’s formula was used for calculating the corrected AL-related ocular magnification. Results: Mean age ((Formula presented.)(Formula presented.)SD) was 10.84(Formula presented.)(Formula presented.)(Formula presented.)3.05 years; mean ((Formula presented.)(Formula presented.)SD) SE was (Formula presented.)0.14(Formula presented.)(Formula presented.)(Formula presented.)0.51 D (range from (Formula presented.)8.75 to (Formula presented.)8.25 D) and mean AL ((Formula presented.)(Formula presented.)SD) was 23.12(Formula presented.)(Formula presented.)(Formula presented.)1.49. Average RNFL thickness, average macular thickness and macular volume decreased as AL and myopia increased. No correlations between AL/SE and optic disc parameters were found after correcting for magnification effect. Conclusions: AL and refractive error affect measurements of macular and RNFL thickness in healthy children. To make a correct interpretation of OCT measurements, ocular magnification effect should be taken into account by clinicians or OCT manufacturers.
We study the problem of the hydrogen atom interacting with a circularly polarized microwave field, and more specifically, we focus on the so called to and fro motion, that is, the erratic trajectories described by the electron making several large distance excursions and close passages to the nucleus. The skeleton of such trajectories is based on the so called ejection-collision orbits (ECO), that is, orbits ejected from the nucleus, describing several far/close passages to the origin and finally colliding with it. The computation and continuation of families of ECO, as well as their bifurcations is analysed, and finally the consequences of such orbits to explain to and from motion as well as ionization of an electron by the external field are also described.
This paper proposes an analytical solution of the Inverse Kinematics (IK) problem at dead point configurations for any planar one degree of freedom linkage mechanism, with regard to the continuity C n of the motion law. The systems analyzed are those whose elements are linked with lower pairs and do not present redundancies. The study aims to provide the user with some rules to facilitate the design of feasible motion profiles to be reproduced by conventional electrical actuators at these configurations. During the last decades, sev- eral methods and techniques have been developed to study this specific configuration. However, these techniques are mainly focused on solving numerically the IK indetermi- nacy, rather than analyzing the motion laws that the mechanisms are able to perform at these particular configurations. The analysis presented in this paper has been carried out differentiating and applying l’Hôpital’s rule to the system of constraint equations / ð q Þ of the mechanism. The study also considers the feasibility of the time-domain profiles to be reproduced with conventional electrical actuators (i.e. AC/DC motors, linear actuators, etc.). To show the usefulness and effectiveness of the method, the development includes the analytical application and numerical simulations for two common one degree of free- dom systems: a slider-crank and a four linkage mechanisms. Finally, experimental results are presented on a four linkage mechanism test bed.
Fuzzy subgroups and T-vague groups are interesting fuzzy algebraic structures that have been widely studied. While fuzzy subgroups fuzzify the concept of crisp subgroup, T-vague groups can be identified with quotient groups of a group by a normal fuzzy subgroup and there is a close relation between both structures and T-indistinguishability operators (fuzzy equivalence relations).
In this paper the functions that aggregate fuzzy subgroups and T-vague groups will be studied. The functions aggregating T-indistinguishability operators have been characterized  and the main result of this paper is that the functions aggregating T-indistinguishability operators coincide with the ones that aggregate fuzzy subgroups and T-vague groups. In particular, quasi-arithmetic means and some OWA operators aggregate them if the t-norm is continuous Archimedean.
We present a conceptual and numerical approach to model processes in the Earth's interior that involve multiple phases that simultaneously interact thermally, mechanically and chemically. The approach is truly multiphase in the sense that each dynamic phase is explicitly modelled with an individual set of mass, momentum, energy and chemical mass balance equations coupled via interfacial interaction terms. It is also truly multi-component in the sense that the compositions of the system and its constituent thermodynamic phases are expressed by a full set of fundamental chemical components (e.g. SiO$_2$, Al$_2$O$_3$, MgO, etc) rather than proxies. In contrast to previous approaches these chemical components evolve, react with, and partition into, different phases with different physical properties according to an internally-consistent thermodynamic model. This enables a thermodynamically-consistent coupling of the governing set of balance equations. Interfacial processes such as surface tensions and/or surface energy contributions to the dynamics and energetics of the system are also taken into account. The model presented here describes the evolution of systems governed by Multi-Phase Multi-Component Reactive Transport (MPMCRT) based on Ensemble Averaging and Classical Irreversible Thermodynamics principles. This novel approach provides a flexible platform to study the dynamics and non-linear feedbacks occurring within various natural systems at different scales. This notably includes major-and trace-element transport, diffusion-controlled trace-element re-equilibration or rheological changes associated with melt generation and migration in the Earth's mantle.
Raboshchuk, G.; Nadeu, C.; Vidiella, S.; Ros, O.; Muñoz, B.; Riverola , A. Biomedical signal processing and control Vol. 39, p. 390-395 DOI: 10.1016/j.bspc.2017.07.024 Fecha de publicación: 2018-01-01 Artículo de revista
The sounds occurring in the noisy acoustical environment of a Neonatal Intensive Care Unit (NICU) are thought to affect the growth and neurodevelopment of preterm infants. Automatic sound detection in a NICU is a novel and challenging problem, and it is an essential step in the investigation of how preterm infants react to auditory stimuli of the NICU environment. In this paper, we present our work on an automatic system for detection of vocalization sounds, which are extensively present in NICUs. The proposed system reduces the presence of irrelevant sounds prior to detection. Several pre-processing techniques are compared, which are based on either spectral subtraction or non-negative matrix factorization, or a combination of both. The vocalization sounds are detected from the enhanced audio signal using either generative or discriminative classification models. An audio database acquired in a real-world NICU environment is used to assess the performance of the detection system in terms of frame-level missing and false alarm rates. The inclusion of the enhancement pre-processing step leads to up to 17.54% relative improvement over the baseline.
Rambo, D.; Blanco, A.; de Figueiredo, A.D.; dos Santos , E.; Toledo Filho, R.; Martins Gomes , O. Construction & building materials Vol. 158, p. 443-453 DOI: 10.1016/j.conbuildmat.2017.10.046 Fecha de publicación: 2018-01 Artículo de revista
This paper presents an experimental investigation on the applicability of the Barcelona (BCN) test to evaluate the mechanical properties of a macro-synthetic fiber reinforced concrete (MSFRC) submitted to high temperature environments (up to 600 °C). BCN tests demonstrated that the MSFRC gradually loses tensile strength an energy consumption density with increasing temperature. Temperatures of 400 °C and 570 °C shown to be critical to the MSFRC mechanical performance. The residual mechanical behavior of the macro-synthetic fibers was not affected by the temperature up to 100 °C. For higher temperatures, the reinforcement showed that may lose part of its crystallinity compromising the MSFRC post-cracking performance. The constitutive model used to determine the stress-strain curves of the MSFRC was capable to reproduce the composite behavior after the event of a fire.
Urqueta, H.; Jódar, J.; Herrera Lameli, Ch.; Wilke, H.; Medina, A.; Urrutia, J.; Custodio, E.; Rodríguez, J. Science of the total environment Vol. 612, p. 1234-1248 DOI: 10.1016/j.scitotenv.2017.08.305 Fecha de publicación: 2018-01 Artículo de revista
Land surface temperature (LST) seems to be related to the temperature of shallow aquifers and the unsaturated zone thickness (¿ Zuz). That relationship is valid when the study area fulfils certain characteristics: a) there should be no downward moisture fluxes in an unsaturated zone, b) the soil composition in terms of both, the different horizon materials and their corresponding thermal and hydraulic properties, must be as homogeneous and isotropic as possible, c) flat and regular topography, and d) steady state groundwater temperature with a spatially homogeneous temperature distribution. A night time Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image and temperature field measurements are used to test the validity of the relationship between LST and ¿ Zuz at the Pampa del Tamarugal, which is located in the Atacama Desert (Chile) and meets the above required conditions. The results indicate that there is a relation between the land surface temperature and the unsaturated zone thickness in the study area. Moreover, the field measurements of soil temperature indicate that shallow aquifers dampen both the daily and the seasonal amplitude of the temperature oscillation generated by the local climate conditions. Despite empirically observing the relationship between the LST and ¿ Zuz in the study zone, such a relationship cannot be applied to directly estimate ¿ Zuz using temperatures from nighttime thermal satellite images. To this end, it is necessary to consider the soil thermal properties, the soil surface roughness and the unseen water and moisture fluxes (e.g., capillarity and evaporation) that typically occur in the subsurface.
With the rapid development of very large, diverse, complex, and distributed datasets generated from internet transactions, emails, videos, business information systems, manufacturing industry, sensors and internet of things etc., cloud and big data computation have emerged as a cornerstone of modern applications. Indeed, on the one hand, cloud and big data applications are becoming a main driver for economic growth. On the other hand, cloud and big data techniques may threaten people and enterprises’ privacy and security due to ever increasing exposure of their data to massive access. In this paper, aiming at providing secure cloud data sharing services in cloud storage, we propose a scalable and controllable cloud data sharing framework for cloud users (called: Scanf). To this end, we introduce a new cryptographic primitive, namely, PRE+, which can be seen as the dual of traditional proxy re-encryption (PRE) primitive. All the traditional PRE schemes until now require the delegator (or the delegator and the delegatee cooperatively) to generate the re-encryption keys. We observe that this is not the only way to generate the re-encryption keys, the encrypter also has the ability to generate re-encryption keys. Based on this observation, we construct a new PRE+ scheme, which is almost the same as the traditional PRE scheme except the re-encryption keys generated by the encrypter. Compared with PRE, our PRE+ scheme can easily achieve the non-transferable property and message-level based fine-grained delegation. Thus our Scanf framework based on PRE+ can also achieve these two properties, which is very important for users of cloud storage sharing service. We also roughly evaluate our PRE+ scheme’s performance and the results show that our scheme is efficient and practica for cloud data storage applications.
Boano, F.; Rizzo, A.; Samsó, R.; Garcia, J.; Revelli, R.; Ridolfi, L. Science of the total environment Vol. 612, p. 1480-1487 DOI: 10.1016/j.scitotenv.2017.08.265 Fecha de publicación: 2018-01 Artículo de revista
The average organic and hydraulic loads that Constructed Wetlands (CWs) receive are key parameters for their adequate long-term functioning. However, over their lifespan they will inevitably be subject to either episodic or sustained overloadings. Despite that the consequences of sustained overloading are well known (e.g., clogging), the threshold of overloads that these systems can tolerate is difficult to determine. Moreover, the mechanisms that might sustain the buffering capacity (i.e., the reduction of peaks in nutrient load) during overloads are not well understood. The aim of this work is to evaluate the effect of sudden but sustained organic and hydraulic overloads on the general functioning of CWs. To that end, the mathematical model BIO_PORE was used to simulate five different scenarios, based on the features and operation conditions of a pilot CW system: a control simulation representing the average loads; 2 simulations representing +10% and +30% sustained organic overloads; one simulation representing a sustained +30% hydraulic overload; and one simulation with sustained organic and hydraulic overloads of +15% each. Different model outputs (e.g., total bacterial biomass and its spatial distribution, effluent concentrations) were compared among different simulations to evaluate the effects of such operation changes. Results reveal that overloads determine a temporary decrease in removal efficiency before microbial biomass adapts to the new conditions and COD removal efficiency is recovered. Increasing organic overloads cause stronger temporary decreases in COD removal efficiency compared to increasing hydraulic loads. The pace at which clogging develops increases by 10% for each 10% increase on the organic load.
The discovery of a formal process model from event logs describing real process executions is a challenging problem that has been studied from several angles. Most of the contributions consider the extraction of a model as a one-class supervised learning problem where only a set of process instances is available. Moreover, the majority of techniques cannot generate complex models, a crucial feature in some areas like manufacturing. In this paper we present a fresh look at process discovery where undesired process behaviors can also be taken into account. This feature may be crucial for deriving process models which are less complex, fitting and precise, but also good on generalizing the right behavior underlying an event log. The technique is based on the theory of convex polyhedra and satisfiability modulo theory (SMT) and can be combined with other process discovery approach as a post processing step to further simplify complex models. We show in detail how to apply the proposed technique in combination with a recent method that uses numerical abstract domains. Experiments performed in a new prototype implementation show the effectiveness of the technique and the ability to be combined with other discovery techniques.
Matta, F.; Martelli, S.; Caon, T.; Velasco J.I.; Cardoso, R.; Bilck, A.; Innocentini, L. LWT-food science and technology Vol. 87, p. 293-300 DOI: 10.1016/j.lwt.2017.08.056 Fecha de publicación: 2018-01-01 Artículo de revista
In this study, edible films were prepared with different wheat gluten (GLU) and gelatin (GEL) ratios by the solvent casting technique using glycerol (GLY) or sorbitol (SOR) as plasticizers. Fatty acids (caproic, caprylic, capric, lauric, myristic or palmitic) were also added to a previously selected GLU/GEL/sorbitol film, and the effect of GLU:GEL proportion and type of fatty acid on the film properties were tested. Films plasticized with GLY presented a more significant reduction in the elongation at break (EB). In contrast, films plasticized with SOR did not show a significant difference in the EB. The film's water vapor permeability (WVP) and acid solubility increased with increasing proportions of GEL while the water solubility was decreased. On the other hand, the elongation at break of the films decreased with increasing GEL content, which may be associated with its more rigid structure. The addition of fatty acids resulted in lower WVP and the plasticizing effect was dependent on the degree of interaction with the proteins of the film (identified by thermal analysis). The GLU:GEL proportion and the type of fatty acid affect the film properties (mechanical, solubility, opacity, water vapor barrier), allowing the development of new materials with different and useful functional properties according to the desired application
Space Division Multiplexing (SDM) is a key technology to cope with the bandwidth limitations of single mode fibers. Multi-Core Fibers (MCFs) are considered as a promising candidate technology to implement SDM, due to their low inter-core crosstalk (ICXT), experimentally proven in laboratory prototypes. Among the different channel allocation options making use of the newly enabled space dimension, the so-called spatial super-channel (Spa-SCh) is the most likely solution to be implemented, given the inherent cost reduction of the joint-switching operation (i.e., jointly switching a spectrum portion in all MCF cores at once). This work targets the cost-effective Spa-SCh allocation over MCF-enabled Flex-Grid optical core networks. To this goal, state-of-the-art 22-core MCFs are assumed, although the proposed solutions are applicable to any MCF type. In particular, we propose and evaluate a partial-core assignment as a cost-effective strategy to improve spectrum utilization and save Capital Expenditure (CapEx) costs by minimizing the number of optical transceivers used per Spa-SCh. Numerical results reveal that reductions up to 44% and 33% in the number of active transceivers in the network can be obtained in national- and continental-wide backbone networks, respectively, without affecting the network Grade-of-Service (GoS), measured in terms of Bandwidth Blocking Probability (BBP). To evaluate the impact of the ICXT, we also compare the performance of the MCF scenarios under study against equivalent Multi-Fiber (MF) ones. From the obtained results, ICXT in MCF scenarios requires the utilization of less efficient modulation formats, which reduces the admissible offered network load by up to 17% for a 1% BBP target. Furthermore, this lower spectral efficiency also demands an increase of the symbol rate per sub-channel up to a 26%, a key indicator of the modulator electronic complexity.
This note is devoted to the study of the time decay of the onedimensional dual-phase-lag thermoelasticity. In this theory two delay parameters tq and t¿ are proposed. It is known that the system is exponentially stable if tq < 2t¿ . We here make two new contributions to this problem. First, we prove the polynomial stability in the case that tq = 2t¿ as well the optimality of this decay rate. Second, we prove that the exponential stability remains true even if the inequality only holds in a proper sub-interval of the spatial domain, when t¿ is spatially dependent.
For each two-dimensional vector space V of commuting n×n matrices over a field F with at least 3 elements, we denote by V˜ the vector space of all (n+1)×(n+1) matrices of the form [A¿00] with A¿V. We prove the wildness of the problem of classifying Lie algebras V˜ with the bracket operation [u,v]:=uv-vu. We also prove the wildness of the problem of classifying two-dimensional vector spaces consisting of commuting linear operators on a vector space over a field.
Asef, P.; Bargallo, R.; Barzegaran, M.; lapthorn, A.; Mewes, D. Electric power systems research Vol. 154, p. 484-492 DOI: 10.1016/j.epsr.2017.08.041 Fecha de publicación: 2018-01-01 Artículo de revista
In this paper, the influence of gap consideration on load identification under various Halbach-array-based topologies (HABOs) is investigated while the system is on-duty. The load characteristics of a radial flux generator with closed-slots and the exterior rotor topology is discussed, where the effect of eddy-currents are observed. This comparative study deals with the consideration of the combined moment of inertia calculation that demonstrates how electromagnetic-based post processing calculations are estimated without the aid of nominal machine parameter values. The analysis was performed using a 2-D finite-element simulation of different HABOs with the gap consideration between the segments. Additionally, a comprehensive comparison with no gap is considered. Also, the dynamic analysis using an uncontrolled conventional rectifier model is used to derive effected key output parameters such as torque, output power, power factor, and line-to-line voltage. The major objective of the study is to determine corresponding load results in order to employ the most suitable and capable magnetization topology from the load perspective in the PM synchronous generator (PMSGs). Accordingly, the maximum power (MP) point was carried out to maximize the output DC power. With respect to the combined moment of inertia estimation, the load parameter estimation is verified experimentally on a surface-mounted PMSG using different magnetization topologies. Furthermore, commercial and environmental issues of the project are considered to reduce CO2 emissions as part of green power generation development.
This paper investigates how the characteristics of operational processes—systematic and project-based—affect the impact of adopting the safety management systems on different performance metrics. The proposed approach allows the development of a framework which matches safety problems and risks encompassed by organizational tasks with solutions generated by new safety knowledge linked to the adoption of the OHSAS 18001 standard. Our analysis of the effect over work accidents, as well as operational and economic performance of implementing the OHSAS 18001 in Spanish manufacturing, construction and professional services organizations during 2006–2009 shows that organizations modify existing safety practices to mitigate work accidents, and that safety learning effects widely vary across industry sectors. Organizations whose current knowledge is mostly codified and processes are highly systematic benefit more from safety knowledge and experience, whereas the effects of the OHSAS 18001 dilute in organizations whose knowledge is high in tacitness, and whose processes difficult the visibility of the consequences of work accidents. This study has important implications for managing knowledge acquisition processes. The findings offer valuable insights on how managers can develop communication and coordination actions to cope with the potential incompatibilities between safety management systems, the properties of knowledge and work environmental conditions.
Bayés, À.; Sama, A.; Prats, A.; Perez, C.; Moreno, J.; Rodriguez-Martin, D.; Cabestany, J. Gait and posture Vol. 59, p. 1-6 DOI: 10.1016/j.gaitpost.2017.09.031 Fecha de publicación: 2018-01-01 Artículo de revista
The treatment of Parkinson's disease (PD) with levodopa is very effective. However, over time, motor complications (MCs) appear, restricting the patient from leading a normal life. One of the most disabling MCs is ON-OFF fluctuations. Gathering accurate information about the clinical status of the patient is essential for planning treatment and assessing its effect. Systems such as the REMPARK system, capable of accurately and reliably monitoring ON-OFF fluctuations, are of great interest. Objective To analyze the ability of the REMPARK System to detect ON-OFF fluctuations. Methods Forty-one patients with moderate to severe idiopathic PD were recruited according to the UK Parkinson's Disease Society Brain Bank criteria. Patients with motor fluctuations, freezing of gait and/or dyskinesia and who were able to walk unassisted in the OFF phase, were included in the study. Patients wore the REMPARK System for 3 days and completed a diary of their motor state once every hour. Results The record obtained by the REMPARK System, compared with patient-completed diaries, demonstrated 97% sensitivity in detecting OFF states and 88% specificity (i.e., accuracy in detecting ON states). Conclusion The REMPARK System detects an accurate evaluation of ON-OFF fluctuations in PD; this technology paves the way for an optimisation of the symptomatic control of PD motor symptoms as well as an accurate assessment of medication efficacy.
Schillaci, E.; Favre, F.; Antepara, O.; Balcazar, N.; Oliva, A. International journal of computational methods and experimental measurements Vol. 6, num. 1, p. 98-109 DOI: 10.2495/CMEM-V6-N1-98-109 Fecha de publicación: 2018 Artículo de revista
In this work, a numerical framework for the direct numerical simulation of tsunami waves generated by landslide events is proposed. The method, implemented on the TermoFluids numerical platform, adopts a free surface model for the simulation of momentum equations; thus, considering the effect of air on the flow physics negligible. The effect of the solid motion on the flow is taken into account by means of a direct forcing immersed boundary method (IBM).
The method is available for 3-D unstructured meshes; however, it can be integrated with an adaptive mesh refinement (AMR) tool to dynamically increase the local definition of the mesh in the vicinity of the interfaces, which separate the phases or in the presence of vortical structures.
The method is firstly validated by simulating the entrance of objects into still water surfaces for 2-D and 3-D configurations. Next, the case of tsunami generation from a subaerial landslide is studied and the results are validated by comparison to experimental and numerical measurements. Overall, the model demonstrates its efficiency in the simulation of this type of physics, and a wide versatility in the choice of the domain discretization.
The role of edge dislocations as sinks for small radiation induced defects in bcc-Fe is investigated by means of atomistic computer simulation. In this work we investigate by Molecular Statics (T = 0K) the interaction between an immobile dislocation line and defect clusters of small sizes invisible experimentally. The study highlights in particular the anisotropy of the interaction and distinguishes between absorbed and trapped defects. When the considered defect intersects the dislocation glide plane and the distance from the dislocation line to the defect is on the range between 2 nm and 4 nm, either total or partial absorption of the cluster takes place leading to the formation of jogs. Residual defects produced during partial absorption pin the dislocation. By the calculation of stress-strain curves we have assessed the strength of those residues as obstacles for the motion of the dislocation, which is reflected on the unpinning stresses and the binding energies obtained. When the defect is outside this range, but on planes close to the dislocation glide plane, instead of absorption we have observed a capture process. Finally, with a view to introducing explicitly in kinetic Monte Carlo models a sink with the shape of a dislocation line, we have summarized our findings on a table presenting the most relevant parameters, which define the interaction of the dislocation with the defects considered.
Borroto-Ramírez, A.; Bruyère, S.; Thurieau, N.; Gendarme, C.; Jimenez-Pique, E.; Roa, J.J.; Pierson, J.F.; Mücklich, F.; Horwat, D. Journal of alloys and compounds Vol. 729, p. 137-143 DOI: 10.1016/j.jallcom.2017.09.153 Fecha de publicación: 2017-12-30 Artículo de revista
Zr1-xMox thin films were synthesized on glass substrates by co-sputtering molybdenum and zirconium targets in the presence of argon with x in the 0.32–0.95 range. From X-ray diffraction analyses and transmission electron microscopy images it was possible to observe an evolution of the samples structure from a nano-crystalline solid solution of Zr in the bcc lattice of Mo to clusters of Zr(Mo) nano-crystalline in an amorphous matrix. The coherence length deduced from X-ray diffractograms was around 1 nm–8 nm depending on the composition. Mechanical measurements show that the films exhibited high hardness H, low Young's modulus E and therefore high H/E ratio compared with the bulk of Zr and Mo. We also found a low friction coefficient values for all the samples. Finally, an inverse Hall-Petch effect was observed for coherence length lower than 6 nm.
The feasibility of using ultrasound transmission method to assess raw earthen materials is investigated. Results indicate that this technique is effective at controlling the drying process of raw earthen materials. Near the hygrometric equilibrium, there is a linear relationship between the moisture content of the earthen material and the ultrasound transmission speed, which increases during the drying process. For the tested compressed earth, the hygrometric equilibrium is reached when the ultrasound transmission speed is over 1100 m/s. In addition, ultrasound transmission method is useful to reliably calculate the dynamic Young's modulus of raw earthen materials.
An optimization framework is presented to support the model builder in elucidating compartmental models that plausibly describe data obtained during experimentation. Here, one specifies a priori the maximum number of compartments and type of flows to contemplate during the optimization. The mathematical model follows a ‘superstructure’ approach, which inherently considers the different feasible flows between any pair of compartments. The model activates those flows/compartments that provide the optimal fit for a given set of experimental data. A regularized log-likelihood function is formulated as the performance metric. To deal with the resulting set of differential equations orthogonal collocation on finite elements is employed. A case study related to pharmacokinetics of an oncological agent demonstrates the advantages and limitations of the proposed approach. Numerical results show that the proposed approach can provide 33% smaller mean square prediction error in comparison with a compartmental model previously suggested in the literature.
In this work, we study a one-parameter family of differential equations and the different scenarios that arise with the change of parameter. We remark that these are not bifurcations in the usual sense but a wider phenomenon related with changes of continuity or differentiability. We offer an alternative point of view for the study for the motion of a system of two particles which will always move in some fixed line, we take R for the position space. If we fix the center of mass at the origin, the system reduces to that of a single particle of unit mass in a central force field. We take the potential energy function U(x)=|x|ß, where x is the position of the single particle and ß is some positive real number.
Roitero, E.; Lasserre, F.; Roa, J.J.; Anglada, M.; Mücklich, F.; Jimenez-Pique, E. Journal of the european ceramic society Vol. 37, num. 15, p. 4876-4887 DOI: 10.1016/j.jeurceramsoc.2017.05.052 Fecha de publicación: 2017-12 Artículo de revista
The aim of this study is to characterize in detail the microstructural changes and collateral damage induced by direct laser patterning on the surface of dental-grade zirconia (3Y-TZP) employing an interference setup with the 532 and 355. nm harmonics of a Nd:YAG laser (pulse duration of 10. ns).Laser-material interaction mainly results in thermal effects for both wavelengths studied. Upon laser irradiation the material locally melts producing pattern and establishing a steep thermal gradient on the surface. This generates a. ~. 1. µm thick heat affected zone where microcracking, directional recrystallization, phase transformation (from tetragonal to monoclinic, t ¿. m) and texturization (ferroelastic domain switching) take place. In addition, surface coloration results from the activation of F-centers as a consequence of high energy radiation exposure. No chemical segregation or diffusion was detected. All these microstructural changes should be taken into account to ensure integrity and long-term reliability of the zirconia components.
The most singular characteristic of pervious concrete is its interconnected porosity that allows water to flow through at high rates. The objective of this paper is to develop and validate an advanced DEM-CFD model to assess the permeability of pervious concrete numerically, taking into account the influence of the composition and of the compaction process. An extensive experimental program with 1 aggregate grading size, 4 paste contents and 3 degrees of compaction was conducted to validate the numerical approach. Results show that the DEM-CFD model is capable of predicting the permeability depending on the variables considered here. Moreover, flow parameters derived from the numerical simulations help understand the experimental results. The study confirms that, instead of relying on trial and error experiments, it is possible to use advanced numerical models to accelerate the definition of mixes and the production process, reducing the time, efforts and costs required.
The contribution of hydrogen bonding interactions to the formation of local density inhomogeneities in supercritical water at near-critical conditions has been extensively studied by means of molecular dynamics simulations. The results obtained have revealed the strong effect of water molecules forming one and two hydrogen bonds on the determination of the local density augmentation in the fluid. The local structural order has also been studied in terms of the trigonal and tetrahedral order parameters, revealing the correlation between local orientational order and hydrogen bonding. The dynamics of the structural order parameters exhibit similarities with local density ones. The local structural analysis performed in terms of nearest neighbors around the individual molecules provides additional significant evidence about the existence of a liquid-like to gas-like structural transition in supercritical water at the density range close to 0.2 ¿c, further supporting previous suggestions based on the interpretation of experimental thermodynamic data.
Guha, A.; Williams, E.R.; Boldi, R.; Satori, G.; Nagy, T.; Bór, J.; Montaña, J.; Ortega, P. Journal of atmospheric and solar-terrestrial physics Vol. 165-166, p. 25-37 DOI: 10.1016/j.jastp.2017.11.003 Fecha de publicación: 2017-12 Artículo de revista
The Earth's naturally occurring Schumann resonances (SR) are composed of a quasi-continuous background component and a larger-amplitude, short-duration transient component, otherwise called ‘Q-burst’ (Ogawa et al., 1967). Sprites in the mesosphere are also known to accompany the energetic positive ground flashes that launch the Q-bursts (Boccippio et al., 1995). Spectra of the background Schumann Resonances (SR) require a natural stabilization period of ~10–12 min for the three conspicuous modal parameters to be derived from Lorentzian fitting. Before the spectra are computed and the fitting process is initiated, the raw time series data need to be properly filtered for local cultural noise, narrow band interference as well as for large transients in the form of global Q-bursts. Mushtak and Williams (2009) describe an effective technique called Isolated Lorentzian (I-LOR), in which, the contributions from local cultural and various other noises are minimized to a great extent. An automated technique based on median filtering of time series data has been developed. These special lightning flashes are known to have greater contribution in the ELF range (below 1 kHz) compared to general negative CG strikes (Huang et al., 1999; Cummer et al., 2006). The global distributions of these Q-bursts have been studied by Huang et al. (1999) Rhode Island, USA by wave impedance methods from single station ELF measurements at Rhode Island, USA and from Japan Hobara et al. (2006). The present work aims to demonstrate the effect of Q- bursts on SR background spectra using GPS time-stamped observation of TLEs. It is observed that the Q-bursts selected for the present work do alias the background spectra over a 5-s period, though the amplitudes of these Q- bursts are far below the background threshold of 16 Core Standard Deviation (CSD) so that they do not strongly alias the background spectra of 10–12 min duration. The examination of one exceptional Q-burst shows that appreciable spectral aliasing can occur even when 12-min spectral integrations are considered. The statistical result shows that for a 12-min spectrum, events above 16 CSD are capable of producing significant frequency aliasing of the modal frequencies, although the intensity aliasing might have a negligible effect unless the events are exceptionally large (~200 CSD). The spectral CSD methodology may be used to extract the time of arrival of the Q-burst transients. This methodology may be combined with a hyperbolic ranging, thus becoming an effective tool to detect TLEs globally with a modest number of networked observational stations.
The search for environmentally neutral alternative fuels had revived the interest for microalgae-bacteria wastewater treatment systems. The potential achieving of bioproducts from microalgae biomass has also greatly contributed. The reactions that occur in these systems are complex, and the degree of scientific knowledge is still scarce compared to that of conventional bacteria wastewater treatments. Mathematical models offer a great opportunity to study the simultaneous effect of the multiple factors affecting microalgae and bacteria, thus allowing for the prediction of final biomass production, and contributing to the system design optimization in terms of operation and control. During the last decades, numerous models describing microalgae growth have been proposed. However, a lower number of integral models considering microalgae as well as bacteria is available. In this paper, the evolution of microalgae models from simple steady-state models (usually dependent on one factor) to more complex dynamic models (with two or more factors) has been revised. A summary of integrated microalgae-bacteria models has been reviewed, outlining their main features and presenting their processes and value parameters. Eventually, a critical discussion on integrated models has been put forward.
An integral mechanistic model describing the complex interactions in mixed algal-bacterial systems was developed. The model includes crucial physical, chemical and biokinetic processes of microalgae as well as bacteria in wastewater. Carbon-limited microalgae and autotrophic bacteria growth, light attenuation, photorespiration, temperature and pH dependency are some of the new features included. The model named BIO_ALGAE was built using the general formulation and structure of activated sludge models (ASM), and it was implemented in COMSOL Multiphysics™ platform. Calibration and validation were conducted with experimental data from two identical pilot HRAPs receiving real wastewater. The model was able to simulate the dynamics of different components in the ponds, and to predict the relative proportion of microalgae (58–68% in average of total suspended solids (TSS) and bacteria (30–20% in average of TSS). Microalgae growth resulted strongly influenced by the light factor fL(I), decreasing microalgae concentrations from 40 to 60%. Furthermore, reducing the influent organic matter concentration of 50% and 70%, model predictions indicated that microalgae production increased from (8.7 g TSS m- 2d- 1 to 13.5 g TSS m- 2d- 1) due to the new distribution of particulate components. The proposed model could be an efficient tool for industry to predict the production of microalgae, as well as to design and optimize HRAPs.
Nadal, A.; Alamús, R.; Pipia, L.; Ruiz , A.; Corbera, J.; Cuerva, E.; Rieradevall, J.; Josa, A. Science of the total environment Vol. 601-602, p. 1-15 DOI: 10.1016/j.scitotenv.2017.03.214 Fecha de publicación: 2017-12-01 Artículo de revista
The integration of rooftop greenhouses (RTGs) in urban buildings is a practice that is becoming increasingly important in the world for their contribution to food security and sustainable development. However, the supply of tools and procedures to facilitate their implementation at the city scale is limited and laborious. This work aims to develop a specific and automated methodology for identifying the feasibility of implementation of rooftop greenhouses in non-residential urban areas, using airborne sensors. The use of Light Detection and Ranging (LIDAR) and Long Wave Infrared (LWIR) data and the Leica ALS50-II and TASI-600 sensors allow for the identification of some building roof parameters (area, slope, materials, and solar radiation) to determine the potential for constructing a RTG. This development represents an improvement in time and accuracy with respect to previous methodology, where all the relevant information must be acquired manually.
The methodology has been applied and validated in a case study corresponding to a non-residential urban area in the industrial municipality of Rubí, Barcelona (Spain). Based on this practical application, an area of 36,312 m2 out of a total area of 1,243,540 m2 of roofs with ideal characteristics for the construction of RTGs was identified. This area can produce approximately 600 tons of tomatoes per year, which represents the average yearly consumption for about 50% of Rubí total population.
The use of this methodology also facilitates the decision making process in urban agriculture, allowing a quick identification of optimal surfaces for the future implementation of urban agriculture in housing. It also opens new avenues for the use of airborne technology in environmental topics in cities.
Romanini, M.; Del Barrio, M.; Macovez, R.; Ruiz, M.; Capaccioli, S.; Tamarit, J. Ll. Scientific reports Vol. 7, num. 1346, p. 1-11 DOI: 10.1038/s41598-017-01464-2 Fecha de publicación: 2017-12-01 Artículo de revista
We probe the temperature- and pressure-dependent specific volume (v) and dipolar dynamics of the amorphous phase (in both the supercooled liquid and glass states) of the ternidazole drug (TDZ). Three molecular dynamic processes are identified by means of dielectric spectroscopy, namely the a relaxation, which vitrifies at the glass transition, a Johari-Goldstein ßJG relaxation, and an intramolecular process associated with the relaxation motion of the propanol chain of the TDZ molecule. The lineshapes of dielectric spectra characterized by the same relaxation time (isochronal spectra) are virtually identical, within the studied temperature and pressure ranges, so that the time-temperature-pressure superposition principle holds for TDZ. The a and ßJG relaxation times fulfil the density-dependent thermodynamic scaling: master curves result when they are plotted against the thermodynamic quantity Tv¿, with thermodynamic exponent ¿ approximately equal to 2. These results show that the dynamics of TDZ, a system characterized by strong hydrogen bonding, is characterized by an isomorphism similar to that of van-der-Waals systems. The low value of ¿ can be rationalized in terms of the relatively weak density-dependence of the dynamics of hydrogen-bonded systems.
The Discrete Element Method (DEM) has been used for modelling continua, like concrete or rocks. However, it requires a big calibration effort, even to capture just the linear elastic behavior of a continuum modelled via the classical force-displacement relationships at the contact interfaces between particles. In this work we propose a new way for computing the contact forces between discrete particles. The newly proposed forces take into account the surroundings of the contact, not just the contact itself. This brings in the missing terms that provide an accurate approximation to an elastic continuum, and avoids calibration of the DEM parameters for the purely linear elastic range.
This paper deals with the problem of inferring the signals and parameters that cause neural activity to occur. The ultimate challenge being to unveil brain’s connectivity, here we focus on a microscopic vision of the problem, where single neurons (potentially connected to a network of peers) are at the core of our study. The sole observation available are noisy, sampled voltage traces obtained from intracellular recordings. We design algorithms and inference methods using the tools provided by stochastic filtering that allow a probabilistic interpretation and treatment of the problem. Using particle filtering, we are able to reconstruct traces of voltages and estimate the time course of auxiliary variables. By extending the algorithm, through PMCMC methodology, we are able to estimate hidden physiological parameters as well, like intrinsic conductances or reversal potentials. Last, but not least, the method is applied to estimate synaptic conductances arriving at a target cell, thus reconstructing the synaptic excitatory/inhibitory input traces. Notably, the performance of these estimations achieve the theoretical lower bounds even in spiking regimes.
Context. Requirements engineering is a discipline with numerous challenges to overcome. One of these challenges is the implementation of requirements reuse approaches. Although several theoretical proposals exist, little is known about the practices that are currently adopted in industry.
Objective. Our goal is to contribute to the investigation of the state of the practice in the reuse of requirements, eliciting current practices from practitioners, and their opinions whenever appropriate. Besides reuse in general, we focus on requirement patterns as a particular strategy to reuse.
Method. We conducted an exploratory survey based on an online questionnaire. We received 71 responses from requirements engineers with industrial experience in the field, which were analyzed in order to derive observations.
Results. Although we found that a high majority of respondents declared some level of reuse in their projects (in particular, non-functional requirements were identified as the most similar and recurrent among projects), it is true that only a minority of them declared such reuse as a regular practice. Larger IT organizations and IT organizations with well-established software processes and methods present higher levels of reuse. Ignorance of reuse techniques and processes is the main reason preventing wider adoption. From the different existing reuse techniques, the simplest ones based on textual copy and subsequent tailoring of former requirements are the most adopted techniques. However, participants who apply reuse more often tend to use more elaborate techniques. Opinions of respondents about the use of requirement patterns show that they can be expected to mitigate problems related to the quality of the resulting requirements, such as lack of uniformity, inconsistency, or ambiguity. The main reasons behind the lack of adoption of requirement patterns by practitioners (in spite of the increasing research approaches proposed in the community) are related to the lack of a well-defined reuse method and involvement of requirement engineers.
Corada, M.; Candela, L.; Torres-Fuentes, N.; Pintado-Herrera, M.; Paniw, M.; González-Mazo, E. Science of the total environment Vol. 605-606, p. 770-783 DOI: 10.1016/j.scitotenv.2017.06.049 Fecha de publicación: 2017-12 Artículo de revista
This study is focused on the Guadalete River basin (SW, Spain), where extreme weather conditions have become common, with and alternation between periods of drought and extreme rainfall events. Combined sewer overflows (CSOs) occur when heavy rainfall events exceed the capacity of the wastewater treatment plants (WWTP), as well as pollution episodes in parts of the basin due to uncontrolled sewage spills and the use of reclaimed water and sludge from the local WWTP. The sampling was carried out along two seasons and three campaigns during dry (March 2007) and extreme rainfall (April and December 2010) in the Guadalete River, alluvial aquifer and Jerez de la Frontera aquifer. Results showed minimum concentrations for synthetic surfactants in groundwater (< 37.4 µg·L- 1) during the first campaign (dry weather conditions), whereas groundwater contaminants increased in December 2010 as the heavy rainfall caused the river to overflow. In surface water, surfactant concentrations showed similar trends to groundwater observations. In addition to surfactants, pharmaceuticals and personal care products (PPCPs) were analyzed in the third campaign, 22 of which were detected in surface waters. Two fragrances (OTNE and galaxolide) and one analgesic/anti-inflammatory (ibuprofen) were the most abundant PPCPs (up to 6540, 2748 and 1747 ng·L- 1, respectively). Regarding groundwater, most PPCPs were detected in Jerez de la Frontera aquifer, where a synthetic fragrance (OTNE) was predominant (up to 1285 ng·L- 1).
Mendez, C.; Podestá, J.; Lloberas-Valls, O.; Toro, S.; Huespe, A.; Oliver, J. International journal for numerical methods in engineering Vol. 112, num. 10, p. 1353-1380 DOI: 10.1002/nme.5560 Fecha de publicación: 2017-12 Artículo de revista
A topology optimization technique based on the topological derivative and the level set function is utilized to design/synthesize the micro-structure of a pentamode material for an acoustic cloaking device. The technique provides a micro-structure consisting of a honeycomb lattice composed of needle-like and joint members. The resulting metamaterial shows a highly anisotropic elastic response with effective properties displaying a ratio between bulk and shear moduli of almost 3 orders of magnitude. Furthermore, in accordance with previous works in the literature, it can be asserted that this kind of micro-structure can be realistically fabricated. The adoption of a topology optimization technique as a tool for the inverse design of metamaterials with applications to acoustic cloaking problems is one contribution of this paper. However, the most important achievement refers to the analysis and discussion revealing the key role of the external shape of the prescribed domain where the optimization problem is posed. The efficiency of the designed micro-structure is measured by comparing the scattering wave fields generated by acoustic plane waves impinging on bare and cloaked bodies.