Arashiro, L.; Montero, N.; Ferrer, I.; Acién, F.; Gómez, C.; Marianna Garfi' Science of the total environment Vol. 622-623, p. 1118-1130 DOI: 10.1016/j.scitotenv.2017.12.051 Data de publicació: 2018-05 Article en revista
The aim of this study was to assess the potential environmental impacts associated with high rate algal ponds (HRAP) systems for wastewater treatment and resource recovery in small communities. To this aim, a Life Cycle Assessment (LCA) was carried out evaluating two alternatives: i) a HRAP system for wastewater treatment where microalgal biomass is valorized for energy recovery (biogas production); ii) a HRAP system for wastewater treatment where microalgal biomass is reused for nutrients recovery (biofertilizer production). Additionally, both alternatives were compared to a typical small-sized activated sludge system. An economic assessment was also performed. The results showed that HRAP system coupled with biogas production appeared to be more environmentally friendly than HRAP system coupled with biofertilizer production in the climate change, ozone layer depletion, photochemical oxidant formation, and fossil depletion impact categories. Different climatic conditions have strongly influenced the results obtained in the eutrophication and metal depletion impact categories. In fact, the HRAP system located where warm temperatures and high solar radiation are predominant (HRAP system coupled with biofertilizer production) showed lower impact in those categories. Additionally, the characteristics (e.g. nutrients and heavy metals concentration) of microalgal biomass recovered from wastewater appeared to be crucial when assessing the potential environmental impacts in the terrestrial acidification, particulate matter formation and toxicity impact categories. In terms of costs, HRAP systems seemed to be more economically feasible when combined with biofertilizer production instead of biogas. On the whole, implementing HRAPs instead of activated sludge systems might increase sustainability and cost-effectiveness of wastewater treatment in small communities, especially if implemented in warm climate regions and coupled with biofertilizer production.
Petit-Boix, A.; Devkota, J.; Phillips, R.; Vargas Parra, Maria Violeta; Josa, A.; Gabarrell, X.; Rieradevall, J.; Apul, D. Science of the total environment Vol. 621, p. 434-443 DOI: 10.1016/j.scitotenv.2017.11.206 Data de publicació: 2018-04 Article en revista
Water management plays a major role in any city, but applying alternative strategies might be more or less feasible depending on the urban form and water demand. This paper aims to compare the environmental performance of implementing rainwater harvesting (RWH) systems in American and European cities. To do so, two neighborhoods with a water-stressed Mediterranean climate were selected in contrasting cities, i.e., Calafell (Catalonia, Spain) and Ukiah (California, US). Calafell is a high-density, tourist city, whereas Ukiah is a typical sprawled area. We studied the life cycle impacts of RWH in urban contexts by using runoff modeling before (i.e. business as usual) and after the implementation of this system. In general, cisterns were able to supply > 75% of the rainwater demand for laundry and toilet flushing. The exception were multi-story buildings with roofs smaller than 200 m2, where the catchment area was insufficient to meet demand. The implementation of RWH was environmentally beneficial with respect to the business-as-usual scenario, especially because of reduced runoff treatment needs. Along with soil features, roof area and water demand were major parameters that affected this reduction. RWH systems are more attractive in Calafell, which had 60% lower impacts than in Ukiah. Therefore, high-density areas can potentially benefit more from RWH than sprawled cities.
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.
Roca, D.; Lloberas-Valls, O.; Cante, J.C.; Oliver, J. Computer methods in applied mechanics and engineering Vol. 330, p. 415-446 DOI: 10.1016/j.cma.2017.10.025 Data de publicació: 2018-03 Article en revista
A framework, based on an extended Hill–Mandel principle accounting for inertial effects (Multiscale Virtual Work principle), is developed for application to acoustic problems in the context of metamaterials modelling. The classical restrictions in the mean values of the micro-displacement fluctuations and their gradients are then accounted for in a saddle-point formulation of that variational principle in terms of Lagrange functionals. A physical interpretation of the involved Lagrange multipliers can then be readily obtained.
The framework is specifically tailored for modelling the phenomena involved in Locally Resonant Acoustic Metamaterials (LRAM). In this view, several additional hypotheses based on scale separation are used to split the fully coupled micro-macro set of equations into a quasi-static and an inertial system. These are then solved by considering a projection of the microscale equations into their natural modes, which allows for a low-cost computational treatment of the multiscale problem. On this basis, the issue of numerically capturing the local resonance phenomena in a FE
context is addressed. Objectivity of the obtained results in terms of the macroscopic Finite Element (FE) discretization is checked as well as accuracy of the homogenization procedure by comparing with direct numerical simulations (DNS). The appearance of local resonance band-gaps is then modelled for a homogeneous 2D problem and its extension to multi-layered macroscopic material is presented as an initial attempt towards acoustic metamaterial design for tailored band-gap attenuation.
Garrido, F.; Magrinya, F.; Del Moral, C. Journal of urban planning and development Vol. 144, num. 1, p. 04017020-1-04017020-14 DOI: 10.1061/(ASCE)UP.1943-5444.0000407 Data de publicació: 2018-03 Article en revista
The assessment of a future urban area's economic sustainability is more valuable if it is available in the early stages of the planning process, when the characteristics of the urban pattern are being established. With the aim to integrate economic sustainability in the urban planning decision-making process, this study develops a simple methodology to obtain analytical expressions for municipal operating costs and revenues in a future urban development exclusively in terms of its urban basic variables. Said formulas facilitate not only the assessment of the area's economic balance but also the analysis at the local or supralocal level of each variable's economic role. Its application in a sample of Spanish cities with populations between 100,000 and 300,000 inhabitants has shown that, for these cities, municipal revenues depend equally on floor area ratio, property values, and housing density, while expenditures do so first, on relative length of road and second, on housing density. Economic sustainability from the municipal standpoint is usually achieved when housing density ranges from 40 to 80 dwellings per hectare.
Seco, R.; Schellart, Alma Neeltje Antonia; Gomez, M.; Tait, S. Journal of hydraulic engineering Vol. 144, num. 3, p. 04018003-1-04018003-14 DOI: 10.1061/(ASCE)HY.1943-7900.0001422 Data de publicació: 2018-03 Article en revista
Accurate predictions of sediment loads released by sewer overflow discharges are important for being able to provide protection to vulnerable receiving waters. These predictions are sensitive to the estimated sediment characteristics and on the site conditions of in-pipe deposit formation. Their application without a detailed analysis and understanding of the initial conditions under which in-sewer deposits were formed normally results in very poor estimations. In this study, in-sewer sediment samples deposited during dry periods in a combined sewer system were collected, and their properties assessed. Parameters in a sediment transport relationship for in-pipe deposits were estimated by simulating the in-pipe deposit formation conditions in laboratory erosion tests. The measured parameters were then used to simulate sediment transport through a small combined sewer network for a number of rain events for which rainfall, hydraulic, and water quality data were available. Results showed that the model of Skipworth can provide good predictions of the sediment loads released from such in-sewer deposits. The experimentally derived calibration parameters used with Skipworth's model allowed for a realistic simulation of the in-sewer sediment behavior, and so can be used to accurately estimate the sediment load released from combined sewer systems during rainfall events.
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 Data de publicació: 2018-02 Article en 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.
Representing transitions between saturated and unsaturated conditions, during drying, wetting and loading paths, is a necessary step for a consistent unification between saturated and unsaturated soil mechanics. Transitions from saturated to unsaturated conditions during drying will occur at a nonzero air-entry value of suction, whereas transitions from unsaturated to saturated conditions during wetting or loading will occur at a lower nonzero air-exclusion value of suction. Air-entry and air-exclusion values of suction for a given soil will differ (representing hysteresis in the retention behaviour) and both are affected by changes in the dry density of the soil or by the occurrence of plastic volumetric strains. The paper demonstrates, through model simulations and comparison with experimental data from the literature (covering drying, wetting and loading tests), that the Glasgow Coupled Model (GCM), a coupled elasto-plastic constitutive model covering both mechanical and retention behaviour, represents transitions between unsaturated and saturated behaviour in a consistent fashion. Key aspects of the GCM are the use of Bishop’s stress tensor for mechanical behaviour, the additional influence of degree of saturation on mechanical yielding, inclusion of hysteresis in the retention behaviour, and the role of plastic volumetric strains (and not total volumetric strains) in the description of the water retention response. The success of the GCM in representing consistently transitions between saturated and unsaturated conditions, together with subsequent mechanical and retention responses, demonstrates the potential of this coupled constitutive model for numerical modelling of boundary value problems involving saturated and unsaturated conditions.
Garcia, M.; Gutierrez, R.; Uggetti, E.; Matamoros Mercadal, Víctor; Garcia, J.; Ferrer, I. Biosystems engineering Vol. 166, p. 138-149 DOI: 10.1016/j.biosystemseng.2017.11.016 Data de publicació: 2018-02 Article en revista
Diffuse pollution in rural areas due to agricultural runoff is a widespread and difficult problem to address due to the large areas affected. Drainage channels receive polluted water, but its introduction into conventional treatment network is often unfeasible. Within this context, microalgae-based treatment systems could be used as alternative treatment plants. A new design of semi-closed (hybrid) tubular horizontal photobioreactor (HTH-PBR) with low energy requirements has been evaluated for microalgae cultivation at full-scale (8.5 m3), using agricultural runoff as feedstock. This novel system was tested in batch and continuous mode over 4 and 135 d. Considering a full-scale application in an agricultural context, a batch test was carried out to evaluate the performance of the system. An increase of 22% in the biomass concentration in 4 d was registered, and all nutrients were consumed during the first two days. In the continuous experiment carried out over winter (December–April), productivity was between 2 and 14 g g [TSS] m-3 d, but values up to 76.4 g [TSS] m-3 d were reached at the end of the study in spring, despite the low nutrients concentration in the feedstock. Elimination of emerging contaminants was also evaluated, obtaining the highest removals for the synthetic musk fragrances tonalide and galaxolide (73% and 68%), and the anti-inflammatory drug diclofenac (61%).
Despite its importance in some structures, shear deformation is systematically neglected by most static structural system identification methods. This paper analyzes for the first time in the literature the effect of this deformation in the static inverse analysis of thin web bridges. This study is focused on the observability techniques. The most recent formulation found in the literature is based onthe Euler-Bernoulli beam theory. This formulation is unable to identify correctly the characteristics of a structure (such as flexural stiffness) when shear deformation is not negligible. To solve this problem, the observability method is updated according to Timoshenko's beam theory. This formulation uses an algebraic method which combines a symbolical and a numerical application. Thus, the updated observability formulation is able to obtain not only the flexural stiffness but also the shear one. Besides this, a parametric equation of the estimates is obtained for the first time in the literature. Some examples of growing complexity are used to illustrate the validity of the the proposed formulation formulation.
Nitrate removal through enhanced biological denitrification (EBD), consisting of the inoculation of an external electron donor, is a feasible solution for the recovery of groundwater quality. In this context, liquid waste from wine industries (wine industry by-products, WIB) may be feasible for use as a reactant to enhance heterotrophic denitrification. To address the feasibility of WIB as electron donor to promote denitrification, as well as to evaluate the role of biomass as a secondary organic C source, a flow-through experiment was carried out. Chemical and isotopic characterization was performed and coupled with mathematical modeling. Complete nitrate attenuation with no nitrite accumulation was successfully achieved after 10 days. Four different C/N molar ratios (7.0, 2.0, 1.0 and 0) were tested. Progressive decrease of the C/N ratio reduced the remaining C in the outflow and favored biomass migration, producing significant changes in dispersivity in the reactor, which favored efficient nitrate degradation. The applied mathematical model described the general trends for nitrate, ethanol, dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. This model shows how the biomass present in the system is degraded to dissolved organic C (DOCen) and becomes the main source of DOC for a C/N ratio between 1.0 and 0. The isotopic model developed for organic and inorganic carbon also describes the general trends of d13C of ethanol, DOC and DIC in the outflow water. The study of the evolution of the isotopic fractionation of organic C using a Rayleigh distillation model shows the shift in the organic carbon source from the WIB to the biomass and is in agreement with the isotopic fractionation values used to calibrate the model. Isotopic fractionations (e) of C-ethanol and C-DOCen were -1‰ and -5‰ (model) and -3.3‰ and -4.8‰ (Rayleigh), respectively. In addition, an inverse isotopic fractionation of +10‰ was observed for biomass degradation to DOCen. Overall, WIB can efficiently promote nitrate reduction in EBD treatments. The conceptual model of the organic C cycle and the developed mathematical model accurately described the chemical and isotopic transformations that occur during this induced denitrification.
Over the last decades, engineering faculties and universities have become increasingly engaged in integrating sustainable development into their different functions. Notwithstanding, more effort is required to effectively integrate sustainability principles as a whole-university approach, and specifically, in technical universities. Scientific literature highlights the main barriers to the success of initiatives that address this shortcoming. A better understanding of the scientific profile of the academics who engage in sustainable development activities can help to develop and promote initiatives for increasing faculty engagement in all academic functions. For this purpose, this study presents a bibliometric analysis of the scientific production of an academic community involved in a European initiative aimed at capacitating engineering academics for sustainable development. Specifically, two groups of academics with different degrees of expertise and involvement in sustainable development were characterized and compared, revealing common trends and similarities of their research production. The results have different implications for future strategies aimed at engaging specific academic profiles in the field of engineering, highlighting especially health science–related fields linked with engineering as a potential opportunity of promoting the integration of sustainable development in engineering education. Further analysis is required to determine the university rankings and their potential implications for the integration of sustainable development, as well as appropriate policies and mechanisms of faculty rewarding and promotion.
Se ha diseñado un sistema que a partir de una foto a color de una superficie de hormigón realiza las siguientes tareas: Detectar fisuras, medir su ángulo y ancho, clasificar los patrones de fisuración asociados a tres patologías del hormigón; el cual ha sido implementado en el lenguaje de programación MATLAB. El sistema se divide en tres partes: Detección y medición de fisuras; algoritmo de análisis de grupos de fisuras y clasificación de patrones de fisuración.El algoritmo de detección de fisuras detecta los pixeles en donde hay fisuras dentro de una región de interés y mide el ancho y ángulos de dichas fisuras. La región de interés es segmentada varias veces: Primero con una red neuronal artificial que clasifica teselas de la imagen en dos categorías "Fisura" y "No fisura"; después se hace otra segmentación con un filtro Canny de detección de bordes y finalmente se segmenta con la media y desviaciones intensidades en teselas de la imagen. Entonces todas las localidades de la máscara de imagen obtenida con las segmentaciones anteriores se las pasa por varios filtros de detección de líneas diseñados para detectar y medir las fisuras. Este algoritmo resulta en dos máscaras de imagen con los anchos y ángulos de todas las fisuras encontradas en la región de interés. El algoritmo de análisis de grupos de teselas reconocidas como fisuras se hace para intentar reconocer y contar cuantas fisuras aparecen en la región de interés. Para lograr esto se diseñó una función de distancia para que teselas de fisura alineadas se junten; después con un algoritmo basado en la conectividad entre estas teselas o vectores fisura se obtienen los grupos de fisura. La clasificación de patrones de fisuración toma las máscaras de imagen del paso de detección de fisuras y lo toma como dato de entrada para una red neuronal diseñada para clasificar patrones de fisuración en tres categorías seleccionadas: Flexión, Cortante y Corrosión-Adherencia. Las máscaras de imagen de ancho y ángulo se transforman en una matriz de características para reducir los grados de libertad del problema, estandarizar un tamaño para la entrada al modelo de red neuronal. Para lograr clasificaciones correctas cuando más de 1 patología está presente en las vigas, cada máscara de imagen de ángulos y anchos de fisura se divide en cuantos cuantos grupos de teselas de fisuras haya en la imagen, y para cada uno se obtienen una matriz de características. Entonces se clasifican separadamente dichas matrices con la red neuronal artificial diseñada.Varias fotos con superficies de hormigón se presentan como ejemplos para evaluar la precisión de las mediciones de ancho y ángulo del paso de detección de fisuras. Otras fotos mostrando patrones de fisuración en vigas de hormigón se muestran para revisar las capacidades de diagnóstico del paso de clasificación de patrones de fisuración. La conclusión más importante de este trabajo es la transferencia del conocimiento empírico de la rehabilitación de estructuras hacia un modelo de inteligencia artificial para diagnosticar el daño en un elemento de la estructura. Esto abre un campo grande de líneas de investigación hacia el diseño e implementación de sistemas automatizados con más utilidades, más patologías y elementos para clasificar.
This volume addresses challenges and solutions in transport and mobility of people and goods with respect to environment, safety, security and socio–economics issues, exploring advanced computational research work and the latest innovations in transport. This book brings together lectures presented at the ECCOMAS Thematic CM3 Conference on Transport held in Jyväskylä, Finland, 25-27 May 2015. It is divided into three parts, I: Reviews and Perspective, II: Computational Methods and Models and III: Translational Research. Each of these parts consists of contributions that present solutions to many transport challenges in this complex, rapidly changing subject. The work contains the latest achievements of European research and technological developments needed for the next decade through computational results of scientific and technical experts who have made essential contributions in transport efficiency in Europe. The material presented here is the state of the art in Transport Modeling, Simulation and Optimization in the fields of Aeronautics, Automotive, Logistics, Maritime and Rails. Furthermore, this volume also answers the question how to apply Computational Research in Transport in order to provide innovative solutions to Green Transportation challenges of identified in the ambitious Horizon 2020 program. This book is intended for students, researchers, engineers and practitioners that are computationally involved in the deployment of Intelligent Transport Systems (ITS) in the areas of optimal use of road, traffic and travel data, traffic and freight management ITS services, road safety and security, sea traffic management, etc.
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.
This is a pre-copyedited, author-produced PDF of an article accepted for publication in
Geophysical journal international following peer review. The version of record Oliveira, B.,
Afonso, J., Zlotnik, S., Diez, P. Numerical modelling of multi-phase multi-component reactive transport in the Earth's interior. "Geophysical journal international", 1 Gener 2018, vol. 212, núm. 1, p. 345-388 is available online at: https://doi.org/10.1093/gji/ggx399.
Torres, A.; Oliete, S.; Magrinya, F.; Gauthier, J. Transportation research. Part A, Policy and practice Vol. 107, p. 216-228 DOI: 10.1016/j.tra.2017.11.016 Data de publicació: 2018-01 Article en revista
Road conditions in Sub-Saharan Africa are typically poor, and only a subset of the newly constructed or rehabilitated roads reach their design life. Truck overloading generally causes this rapid deterioration. In Africa, there are few success stories on the imposition of axle-load limits. This study examines the existing regulations on the Douala-N'Djamena international road, which is the main transport corridor in Central Africa and the backbone for internal transport in Cameroon. It benefits from the detailed existing weighing data recorded since 1998 in the corridor's 10 weighing stations. This vast amount of traffic data, together with available information on road structure and deterioration over time, has been used to conduct an accurate calculation of load equivalency factors. The HDM 4 model has been applied to three scenarios between 2000 and 2015: (1) no axle-load control, (2) the real situation and (3) no overloading tolerance. Results show that axle-load regulations have been reasonably well applied in Cameroon and have contributed to maintaining the corridor in fair condition. In spite of the fact that significant traffic increases are presently counterbalancing the damage avoided by axle-load limits, benefits provided by axle-load control have been substantial: in the period of 2000–2015, every € invested or spent on axle-load control has generated more than €20 of savings in road user costs and in road maintenance and rehabilitation expenditure, which represents, in absolute terms, more than €500 million.
Arias , D.M.; Sole, M.; Marianna Garfi'; Ferrer, I.; Garcia, J.; Uggetti, E. Bioresource technology Vol. 247, p. 513-519 DOI: 10.1016/j.biortech.2017.09.123 Data de publicació: 2018-01-01 Article en revista
In this study, microalgae digestate and secondary effluent were used to grow microalgae in a tertiary wastewater treatment, and then, the biomass was co-digested for biogas generation. A 30 L closed-photobioreactor was used for microalgae cultivation. The biomass, mainly composed by Scenedesmus sp., reached and maintained a concentration of 1.1 gTSS/L during 30 days. A complete removal of N-NH4 + and P-PO4 3- and high nitrates and organic matter removals were achieved (58% N-NO3 - and 70% COD) with 8 d of HRT. The potential biogas production of the cultivated microalgae was determined in batch tests. To improve their biodegradability, a novel method combining their co-digestion with activated sludge after a simultaneous autohydrolysis co-pretreatment was evaluated. After the co-pretreatment, the methane yield increased by 130%. Thus, integrating microalgae tertiary treatment into activated sludge systems is a promising and feasible solution to recover energy and nutrients from waste, improving wastewater treatment plants sustainability.
Sgroi, M.; Pelissari, C.; Roccaro, P.; Sezerino, P.; Garcia, J.; Vagliasindi, F.; Avila, C. Chemical engineering journal Vol. 332, p. 619-627 DOI: 10.1016/j.cej.2017.09.122 Data de publicació: 2018-01 Article en revista
The elimination of organic carbon, nitrogen, five emerging organic contaminants (EOCs) and fluorescence signature was evaluated in two treatment lines comprising different constructed wetland (CW) configurations: (i) partially saturated vertical subsurface flow (SVF) wetland (treatment line 1) and (ii) unsaturated vertical subsurface flow (UVF), horizontal subsurface flow (HF) and free water surface (FWS) wetlands in series (treatment line 2). Results showed important differences between the different CW configurations. The highest removal of BOD5 (81%), COD (67%), TOC (72%) and fluorescing organic matter were observed in the UVF wetland, whereas the HF and FWS wetlands were the most efficient units for total nitrogen removal (60 and 69%, respectively). The SVF wetland showed a greater performance in the reduction of total nitrogen than the UVF bed (52 vs. 35%). In addition, the SVF wetland exhibited a higher removal of the EOCs caffeine (95 vs. 90%), trimethoprim (99 vs. 87%) and sulfamethoxazole (64 vs. 4%), as opposed to DEET (34 vs. 63%), whose removal was superior in the UVF unit. Sucralose was negligibly removed in all the CWs. PARAFAC analysis of fluorescence measurements revealed that the proteinaceous tryptophan-like fluorescent component was the most highly removed one in all the investigated CWs (>28%) and, particularly, in the UVF wetland (66%), whereas humic and fulvic-like components resulted recalcitrant to decomposition. Increases of fluorescence intensities were often observed for fulvic-like substances in CWs operating with saturation of the bed, and these were particularly relevant in the SVF unit. Finally, important correlations (r > 0.7) between the tryptophan-like fluorescent component and the wastewater quality parameters COD and BOD5 suggest fluorescence spectroscopy as an useful monitoring tool for water treatment efficiency in CW systems.
Mamo, J.; Garcia, M.; Stefani, M.; Rodriguez, S.; Barceló, D.; Monclus, H.; Rodríguez-Roda, I.; Comas, J. Chemical engineering journal Vol. 331, p. 450-461 DOI: 10.1016/j.cej.2017.08.050 Data de publicació: 2018-01 Article en revista
The removal of pharmaceuticals (PhACs) present in urban wastewater by membrane bioreactors (MBRs) followed by reverse osmosis (RO) or nanofiltration (NF) membranes has been frequently addressed in the literature. However, data regarding the removal of their main human metabolites and transformation products (TPs) is still scarce. In this study, the presence of 13 PhACs and 20 of their metabolites and TPs was monitored during 2 consecutive years in the different treatment steps of urban raw wastewater (sewer, primary treatment, MBR and RO/NF). Rejection of the selected contaminants when using low pressure NF membranes (NF-90) or RO membranes (ESPA 2) after the MBR step was also investigated. The analgesic acetaminophen, which was found at the highest concentrations in the sewer and influent samples (18–74 µg L-1) over the two experimental periods, was fully eliminated during MBR treatment. Those PhACs that were only partially removed after the MBR, were almost completely removed (>99%) by the RO membrane working under different process conditions. At a similar average permeate fluxes (18 L m-2 h-1), the NF membrane showed high removal efficiencies (>90%) for all of the PhACs and their metabolites, though lower than those achieved by the RO membrane. When the flux of the NF90 membrane was increased to 30 L m-2 h-1 (while still operating at a feed pressure lower than the RO membrane at 18 L m-2 h-1) the performance of the membrane increased, achieving 98% rejection of PhACs.
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 Data de publicació: 2018-01 Article en 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 Data de publicació: 2018-01 Article en 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.
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 Data de publicació: 2018-01 Article en 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 concentration of atmospheric tracers in groundwater samples collected from springs and deep wells is, in most cases, the result of a mixture of waters with a wide range of residence times in the ground. Such is the case of an unconfined aquifer recharged over all its surface area. Concentrations greatly differ from the homogeneous residence time case. Data interpretation relies on knowledge of the groundwater flow pattern. To study relatively large systems, the conservative ion chloride and the decaying radiocarbon (14C) are considered. Radiocarbon (14C) activity in groundwater, after correction to discount the non-biogenic contribution, is often taken as an indication of water age, while chloride can be used to quantify recharge. In both cases, the observed tracer content in groundwater is an average value over a wide range which is related to water renewal time in the ground. This is shown considering an unconfined aquifer recharged all over its area under arid conditions, in which a period of greater recharge happened some millennia ago. The mathematical solution is given. As the solution cannot be made general, to show and discuss the changes in water reserve and in chloride and radiocarbon concentration (apparent ages), two scenarios are worked out, which are loosely related to current conditions in Northern Chile. It is shown that tracer concentration and the estimated water age are not directly related to the time since recharge took place. The existence of a previous wetter-than-present period has an important and lasting effect on current aquifer water reserves and chloride concentration, although the effect on radiocarbon activity is less pronounced. Chloride concentrations are smaller than in current recharge and apparent 14C ages do not coincide with the timing, duration and characteristics of the wet period, except in the case in which recharge before and after the wet period is negligible and dead aquifer reserves are non-significant. The use of chloride concentration in springs as a proxy of chloride concentration in recharge to estimate recharge from atmospheric deposition leads to recharge value larger than the real one and it approaches the wet period recharge. Drawing inferences about radiocarbon data and recharge by the chloride balance method has rarely been taken into account before. It is important to consider the variable aquifer groundwater reserve. Current recharge estimation can be improved by careful selection of groundwater samples, supported by tritium and radiocarbon measurements.
Identifiability of parameters in structural system identification (SSI) is of primary importance in any SSI method. It depends on the number and the location of the measurements, which is linked with sensor configuration. In this paper, under the framework of SSI by observability method (OM), the number of necessary measurements to identify all parameters of structural system was clarified first. Then, an example was solved step by step to show the lacking constraints among unknowns in SSI by OM. In a frame example, it was found that no measurement set having as many measurements as the number of unknowns was able to identify all parameters. To further understand this phenomenon, the observability of a simply supported beam was analyzed in an exhaustive way using 252 possible measurement sets. Three quarters of these sets were not able to identify all the parameters. In order to solve this issue, for the very first time, SSI by constrained observability method (COM), which appends the nonlinear constraints to SSI by OM, was proposed. With SSI by COM applied, the observability of the structural parameters with respect to the 252 sets was greatly improved. Finally, the efficacy of SSI by COM was verified by a 13-story frame building.
This is the peer reviewed version of the following article: [Lei J, Nogal M, Lozano-Galant JA, Xu D, Turmo J. Constrained observability method in static structural system identification. Struct Control Health Monit. 2018;25:e2040. https://doi.org/10.1002/stc.2040], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/stc.2040/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
In this work, a new strategy for solving multiscale topology optimization problems is presented. An alternate direction algorithm and a precomputed offline microstructure database (Computational Vademecum) are used to efficiently solve the problem. In addition, the influence of considering manufacturable constraints is examined. Then, the strategy is extended to solve the coupled problem of designing both the macroscopic and microscopic topologies. Full details of the algorithms and numerical examples to validate the methodology are provided.
In this work, a new strategy for solving multiscale topology optimization problems is presented. An alternate direction algorithm and a precomputed offline microstructure database (Computational Vademecum) are used to efficiently solve the problem. In addition, the influence of considering manufacturable constraints is examined. Then, the strategy is extended to solve the coupled problem of designing both the macroscopic and microscopic topologies. Full details of the
algorithms and numerical examples to validate the methodology are provided.
In this work we put the method proposed by van Hinsberg et al.  to the test, highlighting its accuracy and efficiency in a sequence of benchmarks of increasing complexity. Furthermore, we explore the possibility of systematizing the way in which the method's free parameters are determined by generalizing the optimization problem that was considered originally. Finally, we provide a list of worked-out values, ready for implementation in large-scale particle-laden flow simulations.
Due to the inevitable noise existing in the measured responses, structural system identification is often a challenging task in terms of the accuracy of the estimations. Structural system identification by the observability method, which is characterized by the analysis of null spaces, is a powerful tool to determine the observability of structural parameters. However, it did not cope well with measurement errors so far. In this paper, for the first time, functional relations among displacements, denoted by the term compatibility conditions, in beam-like structures are derived by the observability method. Then, compatibility conditions are imposed in an optimization procedure to minimize the discrepancy between the measured response and the compatible one. The compatible response obtained by the optimization is used to obtain the final estimations of the parameters. In a simply supported bridge example, the proposed method is thoroughly evaluated regarding the number of measurements, error levels, and load cases. In an example of a continuous bridge, different load cases are used to estimate the bending stiffnesses of different zones. The accuracy and the efficacy of the proposed method are verified by the numerical results.
This is the peer reviewed version of the following article: [Lei J, Xu D, Turmo J. Static structural system identification for beam-like structures using compatibility conditions. Struct Control Health Monit. 2018;25:e2062. https://doi.org/10.1002/stc.2062], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/stc.2062/full. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Olea, R.; Raju, N.; Egozcue, J. J.; Pawlowsky, V.; Singh, S. Stochastic environmental research and risk assessment Vol. 32, num. 1, p. 241-259 DOI: 10.1007/s00477-017-1390-3 Data de publicació: 2018-01 Article en revista
The area east of Varanasi is one of numerous places along the watershed of the Ganges River with groundwater concentrations of arsenic surpassing the maximum value of 10 parts per billion (ppb) recommended by the World Health Organization in drinking water. Here we apply geostatistics and compositional data analysis for the mapping of arsenic and iron to help in understanding the conditions leading to the occurrence of elevated level of arsenic in groundwater. The methodology allows for displaying concentrations of arsenic and iron as maps consistent with the limited information from 95 water wells across an area of approximately 210 km2; visualization of the uncertainty associated with the sampling; and summary of the findings in the form of probability maps. For thousands of years, Varanasi has been on the erosional side in a meander of the river that is free of arsenic values above 10 ppb. Maps reveal two anomalies of high arsenic concentrations on the depositional side of the valley, which has started seeing urban development. The methodology using geostatistics combined with compositional data analysis is completely general, so this study could be used as a prototype for hydrochemistry mapping in other areas.
Ruiz Gironès , E.; Oliver , A.; Socorro, G.; Cascón, J.; Escobar, J.M.; Montenegro, R.; Sarrate, J. International journal for numerical methods in engineering DOI: 10.1002/nme.5706 Data de publicació: 2018 Article en revista
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high-quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.
This is the peer reviewed version of the following article: Ruiz Gironès , E., Oliver , A., Socorro, G., Cascón, J., Escobar, J.M., Montenegro, R., Sarrate, J. Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures. "International journal for numerical methods in engineering", 2018, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/nme.5706/pdf. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
A methodology to integrate geographical information system (GIS) data with large-scale pedestrian simulations has been developed. Advances in automatic data acquisition and archiving from GIS databases, automatic input for pedestrian simulations, as well as scalable pedestrian simulation tools have made it possible to simulate pedestrians at the individual level for complete cities in real time. An example that simulates the evacuation of the city of Barcelona demonstrates that this is now possible. This is the first step towards a fully integrated crowd prediction and management tool that takes into account not only data gathered in real time from cameras, cell phones or other sensors, but also merges these with advanced simulation tools to predict the future state of the crowd.
The final publication is available at Springer via http://dx.doi.org/10.1007/s40571-016-0154-z
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.
A diffusion-reaction model for the carbonation process of oilwell cement exposed to carbonated brine under CO2 geological storage conditions is presented. The formulation consists of two main diffusion/reaction field equations for the concentrations of aqueous calcium and carbon species in the pore solution of the hardened cement paste, complemented by two diffusion-only field equations for chloride and alkalis concentrations, and by a number of chemical kinetics and chemical equilibrium equations. The volume fraction distribution of the solid constituents of the hardened cement paste and the reaction products evolve with the progress of the reaction, determining the diffusivity properties of the material. The model is used to simulate experimental tests performed by Duguid and Scherer (2010), leading to promising results indicating that the fundamental aspects of the phenomenon are captured.
Sierra, J.P.; Garcia, M.; Gracia, V.; Sanchez-Arcilla, A. Proceedings of the Institution of Civil Engineers. Maritime engineering Vol. 170, num. 2, p. 55-66 DOI: 10.1680/jmaen.2016.23 Data de publicació: 2017-12-22 Article en revista
Harbour operability may be hampered by climate change. Green solutions can be used to provide extra flexibility with respect to present grey infrastructure to adapt to, and mitigate, such functional disruptions with affordable costs. This paper assesses the performance of a green solution (a seagrass meadow) by assessing its effectiveness through numerical modelling. The analysis is carried out at two harbours that, under the present climate, are prone to wave agitation and overtopping problems. The efficiencies of different seagrass layouts are tested at both sites, by comparing the relevant hydrodynamic parameters. It is concluded that, for moderate sea level rise (SLR) rates, illustrated by the central trend of a medium scenario from the Intergovernmental Panel on Climate Change, the use of seagrass meadows would be effective enough to attenuate the impact of SLR on breakwater overtopping. In addition, the use of such measures could attenuate the increases in port agitation due to changes in wave direction caused by climate change. Nevertheless, the complexity of the interactions between hydrodynamics and seagrass would require periodic monitoring and re-evaluation to maintain acceptable risk levels, especially in case of extreme scenarios.