2,797 research outputs found

    Synthesis, characterization and performance of robust poison-resistant ultrathin film yttria stabilized zirconia – nickel anodes for application in solid electrolyte fuel cells

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    We report on the synthesis of undoped ∼5 μm YSZ-Ni porous thin films prepared by reactive pulsed DC magnetron sputtering at an oblique angle of incidence. Pre-calcination of the amorphous unmodified precursor layers followed by reduction produces a film consisting of uniformly distributed tilted columnar aggregates having extensive three-phase boundaries and favorable gas diffusion characteristics. Similarly prepared films doped with 1.2 at.% Au are also porous and contain highly dispersed gold present as Ni-Au alloy particles whose surfaces are strongly enriched with Au. With hydrogen as fuel, the performance of the undoped thin film anodes is comparable to that of 10–20 times thicker typical commercial anodes. With a 1:1 steam/carbon feed, the un-doped anode cell current rapidly falls to zero after 60 h. In striking contrast, the initial performance of the Au-doped anode is much higher and remains unaffected after 170 h. Under deliberately harsh conditions the performance of the Au-doped anodes decreases progressively, almost certainly due to carbon deposition. Even so, the cell maintains some activity after 3 days operation in dramatic contrast with the un-doped anode, which stops working after only three hours of use. The implications and possible practical application of these findings are discussed.European Union 298300Ministerio de Economía y Competitividad MAT2013‐40852R, 201560E05

    Using ecological niche models to support tree species selection for forest restoration planning in largely deforested regions

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    Species selection for forest restoration is often supported by expert knowledge on local distribution patterns of native tree species. This approach is not applicable to largely deforested regions unless enough data on pre-human tree species distribution is available. In such regions, ecological niche models may provide essential information to support species selection in the framework of forest restoration planning. In this study we used ecological niche models to predict habitat suitability for native tree species in "Tierra de Campos" region, an almost totally deforested area of the Duero Basin (Spain). Previously available models provide habitat suitability predictions for dominant native tree species, but including non-dominant tree species in the forest restoration planning may be desirable to promote biodiversity, specially in largely deforested areas were near seed sources are not expected. We used the Forest Map of Spain as species occurrence data source to maximize the number of modeled tree species. Penalized logistic regression was used to train models using climate and lithological predictors. Using model predictions a set of tools were developed to support species selection in forest restoration planning. Model predictions were used to build ordered lists of suitable species for each cell of the study area. The suitable species lists were summarized drawing maps that showed the two most suitable species for each cell. Additionally, potential distribution maps of the suitable species for the study area were drawn. For a scenario with two dominant species, the models predicted a mixed forest (Quercus ilex and a coniferous tree species) for almost one half of the study area. According to the models, 22 non-dominant native tree species are suitable for the study area, with up to six suitable species per cell. The model predictions pointed to Crataegus monogyna, Juniperus communis, J.oxycedrus and J.phoenicea as the most suitable non-dominant native tree species in the study area. Our results encourage further use of ecological niche models for forest restoration planning in largely deforested regions

    Predicting temporary wetland plant community responses to changes in the hydroperiod

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    The expected changes on rainfall in the next decades may cause significant changes of the hydroperiod of temporary wetlands and, consequently, shifts on plant community distributions. Predicting plant community responses to changes in the hydroperiod is a key issue for conservation and management of temporary wetlands. We present a predictive distribution model for Arthrocnemum macrostachyum communities in the Doñana wetland (Southern Spain). Logistic regression was used to fit the model using the number of days of inundation and the mean water height as predictors. The internal validation of the model yielded good performance measures. The model was applied to a set of expected scenarios of changes in the hydroperiod to anticipate the most likely shifts in the distribution of Arthrocnemum macrostachyum communities

    A simplified computer vision system for road surface inspection and maintenance

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    This paper presents a computer vision system whose aim is to detect and classify cracks on road surfaces. Most of the previous works consisted of complex and expensive acquisition systems, whereas we have developed a simpler one composed by a single camera mounted on a light truck and no additional illumination. The system also includes tracking devices in order to geolocalize the captured images. The computer vision algorithm has three steps: hard shoulder detection, cell candidate proposal, and crack classification. First the region of interest (ROI) is delimited using the Hough transform (HT) to detect the hard shoulders. The cell candidate step is divided into two substeps: Hough transform features (HTF) and local binary pattern (LBP). Both of them split up the image into nonoverlapping small grid cells and also extract edge orientation and texture features, respectively. At the fusion stage, the detection is completed by mixing those techniques and obtaining the crack seeds. Afterward, their shape is improved using a new developed morphology operator. Finally, one classification based on the orientation of the detected lines has been applied following the Chain code. Massive experiments were performed on several stretches on a Spanish road showing very good performance

    HispaVeg: a new online vegetation plot database for Spain

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    We describe a new online database, named HispaVeg, which currently holds data from 2663 vegetation plots of Spanish woodlands, scrublands and grasslands. Unlike other similar databases, a detailed description of the structure is stored with the floristic data of each plot (i.e., number and physiognomy of the vertical layers, cover values for each layer).Most of the vegetation plots are large rectangles (400 to 2000 square meters) with an average of 34 species per plot. The survey dates range from 1956 to present, with most of the records between 1964 and 1994. The elevation of the plots ranges from 0 to 2880, with most of the plots between 300 and 1500 m. HispaVeg is freely available to the scientific community. Users can query the online database, view printable reports for each plot and download spreadsheet-like raw data for subsets of vegetation plots

    AATR an ionospheric activity indicator specifically based on GNSS measurements

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    This work reviews an ionospheric activity indicator useful for identifying disturbed periods affecting the performance of Global Navigation Satellite System (GNSS). This index is based in the Along Arc TEC Rate (AATR) and can be easily computed from dual-frequency GNSS measurements. The AATR indicator has been assessed over more than one Solar Cycle (2002–2017) involving about 140 receivers distributed world-wide. Results show that it is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity (i.e. DST or Ap), it is sensitive to the regional behaviour of the ionosphere and identifies specific effects on GNSS users. Moreover, from a devoted analysis of different Satellite Based Augmentation System (SBAS) performances in different ionospheric conditions, it follows that the AATR indicator is a very suitable mean to reveal whether SBAS service availability anomalies are linked to the ionosphere. On this account, the AATR indicator has been selected as the metric to characterise the ionosphere operational conditions in the frame of the European Space Agency activities on the European Geostationary Navigation Overlay System (EGNOS). The AATR index has been adopted as a standard tool by the International Civil Aviation Organization (ICAO) for joint ionospheric studies in SBAS. In this work we explain how the AATR is computed, paying special attention to the cycle-slip detection, which is one of the key issues in the AATR computation, not fully addressed in other indicators such as the Rate Of change of the TEC Index (ROTI). After this explanation we present some of the main conclusions about the ionospheric activity that can extracted from the AATR values during the above mentioned long-term study. These conclusions are: (a) the different spatial correlation related with the MOdified DIP (MODIP) which allows to clearly separate high, mid and low latitude regions, (b) the large spatial correlation in mid latitude regions which allows to define a planetary index, similar to the geomagnetic ones, (c) the seasonal dependency which is related with the longitude and (d) the variation of the AATR value at different time scales (hourly, daily, seasonal, among others) which confirms most of the well-known time dependences of the ionospheric events, and finally, (e) the relationship with the space weather events.Postprint (published version

    Modelado e implementación de un sistema de enseñanza de Lenguaje de Señas Mexicano

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    En este artículo se muestra un sistema que permite el estudio y práctica del Lenguaje de Señas Mexicano (LMS), el cual es el método de comunicación de las personas que padecen un trastorno de procesamiento auditivo. El sistema propuesto en este artículo consta de un guante de tela instrumentado con sensores de flexión, una etapa de acondicionamiento de señales y una tarjeta de adquisición de datos; que en su conjunto constituyen el Hardware. El software esta formado por un programa de adquisición de datos y una interfaz de usuario, ambos codificados en Visual Basic Net. El sistema propuesto se modela por medio del lenguaje de modelado unificado (UML), ya que Visual Basic es un lenguaje orientado a eventos.En este artículo se muestra un sistema que permite el estudio y práctica del Lenguaje de Señas Mexicano (LMS), el cual es el método de comunicación de las personas que padecen un trastorno de procesamiento auditivo. El sistema propuesto en este artículo consta de un guante de tela instrumentado con sensores de flexión, una etapa de acondicionamiento de señales y una tarjeta de adquisición de datos; que en su conjunto constituyen el Hardware. El software esta formado por un programa de adquisición de datos y una interfaz de usuario, ambos codificados en Visual Basic Net. El sistema propuesto se modela por medio del lenguaje de modelado unificado (UML), ya que Visual Basic es un lenguaje orientado a eventos

    Critical thickness estimation in ISO-MC cards injection using CAE toolsls

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    Injection moulding is a widely used polymer processing operation because of its ability to produce net-shaped components of good dimensional accuracy with a relatively short cycle time. Nevertheless, only few industries use CAE tools to optimise the injection process or to design the mould. Today, many industries have more confidence in their know-how than in the prediction on a commercial simulation software package. In this work we use C-MOLD to estimate the critical thickness for injection by studying the flow parameters in the thinnest section point of the ISO-MC card. We simulated the process with the geometry of a microchip credit card, which has a minimum thickness of 250 μm (memory microchip area thickness), and studied the variation of different process parameters as this thickness increased. The maximum thickness was fixed at 800 μm (global thickness) and the minimum thickness was modified from 250 to 500 μm. Different injection points and filling times were used to optimise the process. The pressure and temperature variations during the filling process are the most sensitive parameter. The plot of these parameters versus the minimum thickness allowed us to estimate the critical thickness of 360–390 μm for this geometry using different ABS plastics formulations. The plots show how the magnitudes are stabilised in a plateau when the thickness is higher than 390 μm but they increase as the thickness decreases below 360 μm

    Methodological proposal to implement enterprise resource planning systems

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    Enterprise resource planning system is one of the most important projects on business optimization than anenterprise could attempt. Their use can be seen at small, medium and big enterprises. Project management andimplementation methodology is a critical success factor mentioned in literature. At this paper is presented aproposal of implementation methodology based on researched literature and the activities that should be donein each phase. It also presented the selection process as other critical success factor and suggestions for futureresearch regarding Petri Nets as a computation intelligence that could be used to simulate selection process

    Semantic Characterization of Context of Use and Contents for User-Centric Media Retrieval

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    When users access online media, they need and desire to get an experience tailored to their specific, personal context and situation. This is becoming more and more relevant with the ever-increasing amount of available contents users may choose from. In order to provide user-centric functionalities (such as relevant searches, content adaptation, customization and recommendation), both the annotation of contents with semantically rich metadata and an accurate model of the individual users and their respective contexts of use are needed. In this context, we propose a solution to automatically characterize both the context of use and the contents. It provides dynamic, adaptive user models, with explicit and implicit information; as well as content descriptors that may be later used to match the most suitable contents for each user. Users always keep a pivotal role throughout the whole process: providing new contents, contributing to moderated folks onomies, overseeing their own user model, etc
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