DigitalUM :: Browsing by browse.metadata.contributordepartment "Física"

Browsing by browse.metadata.contributordepartment "Física"

Now showing 1 - 20 of 117

Embargo
25th anniversary article: Rise to power - OPV-based solar parks
(Wiley, 2014) Krebs, Frederik C; Espinosa, Nieves; Hösel, Markus; Søndergaard, Roar; Jørgensen, Mikkel; Física
A solar park based on polymer solar cells is described and analyzed with respect to performance, practicality, installation speed, and energy payback time. It is found that a high voltage installation where solar cells are all printed in series enables an installation rate in Watts installed per minute that far exceed any other PV technology in existence. The energy payback time for the practical installation of polymer solar cell foil on a wooden 250 square meter platform in its present form is 277 days when operated in Denmark and 180 days when operated in southern Spain. The installation and de-installation rate is above 100 m min −1 , which, with the present performance and web width, implies installation of >200 W min −1 . In comparison, this also exceeds the overall manufacturing speed of the polymer solar cell foil with a width of 305 mm which is currently 1 m min −1 for complete encapsulated and tested foil. It is also signifi cant that simultaneous installation and de-installation which enables effi cient schemes for decommissioning and recycling is possible. It is highlighted where research efforts should most rationally be invested in order to make grid electricity from OPV a reality (and it is within reach).
Open Access
A global probabilistic dataset for monitoring meteorological droughts
(American Meteorological Society, 2020-10-09) Jerez Rodríguez, Sonia; Turco, Marco; Donat, Markus G.; Toreti, Andrea; Vicente-Serrano, Sergio M.; Doblas-Reyes, Francisco J.; Física
Accurate and timely drought information is essential to move from postcrisis to preimpact drought-risk management. A number of drought datasets are already available. They cover the last three decades and provide data in near–real time (using different sources), but they are all “deterministic” (i.e., single realization), and input and output data partly differ between them. Here we first evaluate the quality of long-term and continuous climate data for timely meteorological drought monitoring considering the standardized precipitation index. Then, by applying an ensemble approach, mimicking weather/climate prediction studies, we develop Drought Probabilistic (DROP), a new global land gridded dataset, in which an ensemble of observation-based datasets is used to obtain the best near-real-time estimate together with its associated uncertainty. This approach makes the most of the available information and brings it to the end users. The highquality and probabilistic information provided by DROP is useful for monitoring applications, and may help to develop global policy decisions on adaptation priorities in alleviating drought impacts, especially in countries where meteorological monitoring is still challenging
Open Access
A global-scale framework for hydropower development incorporating strict environmental constraints
(Nature Research, 2023-01-16) Jerez Rodríguez, Sonia; Xu, Rongrong; Zeng, Zhenzhong; Pan, Ming; Ziegler, Alan D.; Holden, Joseph; Spracklen, Dominick V.; Brown, Lee E.; He, Xinyue; Chen, Deliang; Ye, Bin; Xu, Haiwei; Zheng, Chunmiao; Liu, Junguo; Lin, Peirong; Yang, Yuan; Zou, Junyu; Wang, Dashan; Gu, Mingyi; Yang, Zongliang; Li, Dongfeng; Huang, Junling; Lakshmi, Venkataraman; Wood, Eric F.; Física
The benefits of developing the world’s hydropower potential are intensely debated when considering the need to avoid or minimize environmental impacts. However, estimates of global unused profitable hydropower potential with strict environmental constraints have rarely been reported. In this study we performed a global assessment of the unused profitable hydropower potential by developing a unified framework that identifies a subset of hydropower station locations with reduced environmental impacts on the network of 2.89 million rivers worldwide. We found that the global unused profitable hydropower potential is 5.27 PWh yr−1, two-thirds of which is distributed across the Himalayas. Africa’s unused profitable hydropower is 0.60 PWh yr−1, four times larger than its developed hydropower. By contrast, Europe’s hydropower potential is extremely exploited. The estimates, derived from a consistent and transparent framework, are useful for formulating national hydropower development strategies.
Embargo
A life cycle analysis of polymer solar cell modules prepared using roll-to-roll methods under ambient conditions
(Elsevier, ) Espinosa, Nieves; García-Valverde, Rafael; Urbina, Antonio; Krebs, Frederik C.; Física
A life cycle analysis was performed on a full roll-to-roll coating procedure used for the manufacture of flexible polymer solar cell modules. The process known as ProcessOne employs a polyester substrate with a sputtered layer of the transparent conductor indium-tin-oxide (ITO). The ITO film was processed into the required pattern using a full roll-to-roll process, employing screen printing of an etch resist and then applying etching, stripping, washing and drying procedures. The three subsequent layers; ZnO, P3HT:PCBM and PEDOT:PSS were slot-die coated and the silver back electrode was screen printed. Finally the polymer solar modules were encapsulated, using a polyester barrier material. All operations except the application of ITO were carried out under ambient conditions. The life cycle analysis delivered a material inventory of the full process for a module production, and an accountability of the energy embedded both in the input materials and in the production processes. Finally, upon assumption of power conversion efficiencies and lifetime for the modules, a calculation of energy pay-back time allowed us to compare this roll-to-roll manufacturing with other organic and hybrid photovoltaic technologies. The results showed that an Energy Pay-Back Time (EPBT) of 2.02 years can be achieved for an organic solar module of 2% efficiency, which could be reduced to 1.35 years, if the efficiency was 3%.
Open Access
A multi-physics ensemble of regional climate change projections over the Iberian Peninsula
(2012) Jerez, Sonia; Montávez, Juan Pedro; Gomez Navarro, Juan José; Lorente Plazas, Raquel; García Valero, Juan Andrés; Jiménez Guerrero, Pedro; Física
This study illustrates the sensitivity of regional climate change projections to the model physics. A single-model (MM5) multi-physics ensemble of regional climate simulations over the Iberian Peninsula for present (1970–1999) and future (2070–2099 under the A2 scenario) periods is assessed. The ensemble comprises eight members resulting from the combination of two options of parameterization schemes for the planetary boundary layer, cumulus and microphysics. All the considered combinations were previously evaluated by comparing hindcasted simulations to observations, none of them providing clearly outlying climates. Thus, the differences among the various ensemble members (spread) in the future projections could be considered as a matter of uncertainty in the change signals (as similarly assumed in multi-model studies). The results highlight the great dependence of the spread on the synoptic conditions driving the regional model. In particular, the spread generally amplifies under the future scenario leading to a large spread accompanying the mean change signals, as large as the magnitude of the mean projected changes and analogous to the spread obtained in multi-model ensembles. Moreover, the sign of the projected change varies depending on the choice of the model physics in many cases. This, together with the fact that the key mechanisms identified for the simulation of the climatology of a given period (either present or future) and those introducing the largest spread in the projected changes differ significantly, make further claims for efforts to better understand and model the parameterized subgrid processes.
Open Access
Aberrometría clínica
(2010-02-23T13:55:29Z) Benito, Antonio; Física; Facultad de Ótica y Optometría
En este capítulo se hace un repaso ed las aberraciones del ojo, y del tratamiento quirúrgico de las mismas, tanto en el ojo normal como operado, mediante aberrometría ocular y topografía corneal.
Open Access
Adaptation to the eye’s chromatic aberration measured with an adaptive optics visual simulator
(Optica Publishing Group, 2020) Fernandez, Enrique J.; Suchkov, Nikolai; Artal, Pablo; Fernandez, Enrique J.; Física
Some aspects of vision after correcting the longitudinal chromatic aberration (LCA) of the eye are not yet completely understood. For instance, correcting the LCA notably alters the through focus visual acuity (VA) curve, but it does not improve the best VA obtained for the natural case. In this work, vision with corrected LCA is further investigated by using an adaptive optics visual simulator (AOVS). VA was measured continuously during 20 minutes in 5 subjects under both natural and corrected LCA conditions to explore possible adaptation effects. Low contrast VA as a function of time exhibited a consistent and significant boost of 0.19 in decimal scale after an average time of 10.9 minutes of continuous testing. For high contrast, only one subject showed a similar increase in VA. These results suggest that some LCA neural adaptation may exist, particularly for low contrast. This adaptation impacts the performance of vision under corrected LCA, and possibly prevents measurement for immediate visual benefit. The results have practical implications for the design and visual testing of optical aids, especially those correcting, or altering, the LCA.
Open Access
Agreement Between Refractive and Corneal Astigmatism in Pseudophakic Eyes
(Lippincott, Williams & Wilkins, 2013-06) Tejedor, Jaime; Guirao, Antonio; Física
Purpose: To examine the agreement and relationship between refractive and corneal astigmatism in a population of pseudophakic eyes. Methods: Patients of age at least 40 years, visual acuity 20/40 or better, and no ocular disease were included (n = 111). Refractive astigmatism was obtained by subjective refraction. Corneal astigmatism was measured by automated keratometry and Scheimpflug scanning analysis. All refractive values were converted to power vector components J0 and J45 for comparison and regression analysis of refractive versus corneal astigmatism. Main outcome measures were refractive and corneal astigmatism components. Results: Median single Jackson cylinder (J) was similar in refractive [0.37 diopter (D)], keratometric (0.46 D), and Pentacam astigmatism (0.49 D) (P = 0.157). Median J0 astigmatic component was slightly negative, indicating against-the-rule (ATR) astigmatism, in refractive and Scheimpflug, but not in keratometric astigmatism (refractive J0: −0.10 D; keratometric J0: 0.05 D; Pentacam J0: −0.08 D) (P = 0.049). J45 astigmatic component was nearly zero and similar with the 3 methods (P = 0.416). Refractive and keratometric J0 were significantly correlated (r = 0.7, P < 0.01), as well as the corresponding J45 values (r = 0.65, P < 0.01). Refractive and Pentacam astigmatic components were worse correlated (J0: r = 0.36, P = 0.01; J45: r = 0.45, P < 0.01). Keratometric and Pentacam astigmatic components were also significantly correlated (J0: r = 0.58, P < 0.01; J45: r = 0.51, P < 0.01). Conclusions: Mean internal ATR astigmatism, which comes mainly from the posterior corneal surface, adds to anterior corneal astigmatism, resulting in ATR refractive astigmatism. Correlation between refractive and corneal astigmatism components is better when keratometric data are used.
Open Access
An action-oriented approach to make the most of the wind and solar power complementarity
(Wiley, American Geophysical Union, 2023-06-08) Jerez Rodríguez, Sonia; Barriopedro, David; López García, Alejandro; Lorente-Plazas, Raquel; Somoza Gimeno, Andrés Manuel; Turco, Marco; Carrillo, Judit; Trigo, Ricardo M.; Física
Solar and wind power are called to play a main role in the transition toward decarbonized electricity systems. However, their integration in the energy mix is highly compromised due to the intermittency of their production caused by weather and climate variability. To face the challenge, here we present research about actionable strategies for wind and solar photovoltaic facilities deployment that exploit their complementarity in order to minimize the volatility of their combined production while guaranteeing a certain supply. The developed methodology has been implemented in an open-access step-wise model called CLIMAX. It first identifies regions with homogeneous temporal variability of the resources, and then determines the optimal shares of each technology over such regions. In the simplistic application performed here, we customize the model to narrow the monthly deviations of the total wind-plus-solar electricity production from a given curve (here, the mean annual cycle of the total production) across five European domains. For the current shares of both technologies, the results show that an optimal siting of the power units would reduce the standard deviation of the monthly anomalies of the total wind-plus-solar power generation by up to 20% without loss in the mean capacity factor as compared to a baseline scenario with an evenly spatial distribution of the installations. This result further improves (up to 60% in specific regions) if the total shares of each technology are also optimized, thus encouraging the use of CLIMAX for practical guidance of next-generation renewable energy scenarios.
Open Access
Arrangement of the photoreceptor mosaic in a diabetic rat model imaged with multiphoton microscopy
(Frontiers Media, 2020-08-07) Bueno García, Juan Manuel; Cruz-Castillo, Ricardo; Avilés-Trigueros, Marcelino; Bautista-Elivar, Nazario; Física
Diabetic retinopathy (DR) is defined as a microvascular pathology. However, some data have suggested that the retinal photoreceptors (PRs) might be important in the pathogenesis of this ocular disease. In this study the organization of the PRs in control and diabetic-induced rats was compared using multiphoton microscopy. The PR mosaic was imaged at different locations in non-stained retinas. The density of PRs was directly quantified from cell counting. The spatially resolved density presents a double-slope pattern (from the central retina towards the periphery) in both healthy and pathological samples, although the values for the latter were significantly lower all across the retinas. Moreover, Voronoi analysis was performed to explore changes in PR topography. In control specimens a hexagonally packed structure was dominant. However, despite the non-controlled effects of the disease in retinal structures, this PR regularity was fairly maintained in diabetic retinas.
Open Access
Assessing the carbon footprint of photovoltaic modules through the EU Ecodesign Directive
(2023-04-19) Polverini, D.; Espinosa Martinez, M. D. L. N.; Eynard, U.; Leccisi, E.; Ardente, F.; Mathieux, F.; Física
As announced in the European Green Deal, it is critical to decarbonise the European Union energy system in order to reach climate objectives by 2030 and 2050. According to the REPowerEU plan, photovoltaics (PV) is expected to play a major role in this. Therefore, it is crucial to ensure that newly installed PV modules in the EU are affordable and competitive on the one hand and environmentally friendly on the other. Bearing in mind that the environmental hotspots for PV modules mainly occur during the manufacturing phase, the aim of the paper is to develop a fully-fledged and adapted methodology for calculating the carbon footprint of PV modules, with particular regard to the manufacturing and shipping phases, following a cradle-to-gate approach based on the Product Environmental Footprint Category Rules for PV modules. The implications of requirements for the carbon footprint of PV modules, under the existing legal framework of the Ecodesign Directive, are also discussed.
Open Access
Assessing the effects of compound events of temperature and air pollution on weekly mortality in Spain using random forests
(Elsevier, 2025-10-18) Garnés-Morales, Ginés; Tortosa, Javier; Jiménez Guerrero, Pedro; Gil Guirado, Salvador; García Fernández, Esther; Montávez, Juan Pedro; Física
Open Access
Assessment of the corneal collagen organization after chemical burn using second harmonic generation microscopy
(Optica Publishing Group, 2021-01-11) Bueno García, Juan Manuel; Ávila, Francisco J.; Lorenzo-Martín, Elvira; Gallego-Muñoz, Patricia; Martínez-García, M. Carmen; Física
The organization of the corneal stoma is modified due to different factors, including pathology, surgery or external damage. Here the changes in the organization of the corneal collagen fibers during natural healing after chemical burn are investigated using second harmonic generation (SHG) imaging. Moreover, the structure tensor (ST) was used as an objective tool for morphological analyses at different time points after burn (up to 6 months). Unlike control corneas that showed a regular distribution, the collagen pattern at 1 month of burn presented a non-organized arrangement. SHG signal levels noticeably decreased and individual fibers were hardly visible. Over time, the healing process led to a progressive re-organization of the fibers that could be quantified through the ST. At 6 months, the stroma distribution reached values similar to those of control eyes and a dominant direction of the fibers re-appeared. The present results show that SHG microscopy imaging combined with the ST method is able to objectively monitor the temporal regeneration of the corneal organization after chemical burn. Future implementations of this approach into clinically adapted devices would help to diagnose and quantify corneal changes, not only due to chemical damages, but also as a result of disease or surgical procedures.
Embargo
Automated Detection of Corneal Edema With Deep Learning-Assisted Second Harmonic Generation Microscopy
(Institute of Electrical and Electronics Engineers, 2023-11-06) Anton, Stefan; Martínez Ojeda, Rosa M.; Hristu, Radu; Stanciu, George A.; Toma, Antonela; Banica, Cosmin K.; Fernández, Enrique J.; Huttunen, Mikko J.; Bueno, Juan M.; Stanciu, Stefan G.; Stanciu, Stefan G.; Bueno, Juan M.; Física
Second Harmonic Generation Microscopy (SHG) is widely acknowledged as a valuable non-linear optical imaging tool, its contrast mechanism providing the premises to non-invasively identify, characterize, and monitor changes in the collagen architecture of tissues.However, the interpretation ofSHGdata can pose difficulties even for experts histopathologists, which represents a bottleneck for the translation of SHG-based diagnostic frameworks to clinical settings. The use of artificial intelligence methods for automated SHG analysis is still in an early stage, with only few studies having been reported to date, none addressing ocular tissues yet. In this work we explore the use of three Deep Learning models, the highly popular InceptionV3 and ResNet50, alongside FLIMBA, a custom developed architecture, requiring no pre-training, to automatically detect corneal edema in SHG images of porcine cornea. We observe that Deep Learning models building on different architectures provide complementary results for the classification ofcornea SHG images and demonstrate an AU-ROC=0.98 for their joint use. These results have potential to be extrapolated to other diagnostics scenarios, such as automated extraction of hydration level of cornea, or identification of corneal edema causes, and thus pave the way for novel methods for precision diagnostics of the cornea with Deep-Learning assisted SHG imaging.
Open Access
Blind deconvolution of second harmonic microscopy images of the living human eye
(Optica Publishing Group, 2023-04-19) Mugnier, Laurent M.; Martínez Ojeda, Rosa María; Artal Soriano, Pablo; Bueno García, Juan Manuel; Física
Second harmonic generation (SHG) imaging microscopy of thick biological tissues is affected by the presence of aberrations and scattering within the sample. Moreover, additional problems, such as uncontrolled movements, appear when imaging in-vivo. Deconvolution methods can be used to overcome these limitations under some conditions. In particular, we present here a technique based on a marginal blind deconvolution approach for improving SHG images obtained in vivo in the human eye (cornea and sclera). Different image quality metrics are used to quantify the attained improvement. Collagen fibers in both cornea and sclera are better visualized and their spatial distributions accurately assessed. This might be a useful tool to better discriminate between healthy and pathological tissues, especially those where changes in collagen distribution occur.
Open Access
Cirugía corneal
(2009-10-06T14:08:27Z) Benito, Antonio; Física; Facultad de Ótica y Optometría
Material utilizado en clase para hacer un recorrido de la cirugía refractiva aplicada a la córnea, incluyendo una descripción de las técnicas, principios teóricos, avances y resultados.
Open Access
Climate change impacts on wildfires in a Mediterranean environment
(2014) Turco, Marco; Llasat, Maria-Carmen; Hardenberg, Jost von; Provenzale, Antonello; Física
We analyse the observed climate-driven changes in summer wildfires and their future evolution in a typical Mediterranean environment (NE Spain). By analysing observed climate and fire data from 1970 to 2007, we estimate the response of fire number (NF) and burned area (BA) to climate trends, disentangling the drivers responsible for long-term and interannual changes by means of a parsimonious Multi Linear Regression model (MLR). In the last forty years, the observed NF trend was negative. Here we show that, if improvements in fire management were not taken into account, the warming climate forcing alone would have led to a positive trend in NF. On the other hand, for BA, higher fuel flammability is counterbalanced by the indirect climate e↵ects on fuel structure (i.e. less favourable conditions for fine-fuel availability and fuel connectivity), leading to a slightly negative trend. Driving the fire model with A1B climate change scenarios based on a set of Regional Climate Models from the ENSEMBLES project indicates that increasing temperatures promote a positive trend in NF if no further improvements in fire management are introduced.
Open Access
Comparison of binocular through-focus visual acuity with monovision and a small aperture inlay
(2014) Schwarz, C.; Manzanera Román, Silvestre; Prieto Corrales, Pedro María; Fernández Martínez, Enrique Josua; Artal Soriano, Pablo; Física
Open Access
Contribution of fine particulate matter to present and future premature mortality over Europe: A non-linear response
(Elsevier, 2021-03-08) Tarín Carrasco, Patricia; Im, Ulas; Geels, Camilla; Palacios Peña, Laura; Jiménez Guerrero, Pedro; Física
Open Access
Decreasing Fires in Mediterranean Europe
(Public Library of Science, 2016) Turco, Marco; Bedia, Joaquín; Di Liberto, Fabrizio; Fiorucci, Paolo; Hardenberg, Jost von; Koutsias, Nikos; Llasat, Maria-Carmen; Xystrakis, Fotios; Provenzale, Antonello; Física
Forest fires are a serious environmental hazard in southern Europe. Quantitative assessment of recent trends in fire statistics is important for assessing the possible shifts induced by climate and other environmental/socioeconomic changes in this area. Here we analyse recent fire trends in Portugal, Spain, southern France, Italy and Greece, building on a homogenized fire database integrating official fire statistics provided by several national/EU agencies. During the period 1985-2011, the total annual burned area (BA) displayed a general decreasing trend, with the exception of Portugal, where a heterogeneous signal was found. Considering all countries globally, we found that BA decreased by about 3020 km2 over the 27-year-long study period (i.e. about -66% of the mean historical value). These results are consistent with those obtained on longer time scales when data were available, also yielding predominantly negative trends in Spain and France (1974-2011) and a mixed trend in Portugal (1980-2011). Similar overall results were found for the annual number of fires (NF), which globally decreased by about 12600 in the study period (about -59%), except for Spain where, excluding the provinces along the Mediterranean coast, an upward trend was found for the longer period. We argue that the negative trends can be explained, at least in part, by an increased effort in fire management and prevention after the big fires of the 1980’s, while positive trends may be related to recent socioeconomic transformations leading to more hazardous landscape configurations, as well as to the observed warming of recent decades. We stress the importance of fire data homogenization prior to analysis, in order to alleviate spurious effects associated with non-stationarities in the data due to temporal variations in fire detection efforts.