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Renewable energies are increasingly playing an important role in the world's energy supply. Society demands new solutions to solve environmental issues caused by fossil fuels. The importance of photovoltaic technology has been increasing and consequently, the necessity to have more accurate models to characterise the performance of solar cells during their entire lifetime has rose as well. Performance problems may appear during devices' lifetimes associated with factors, such as weather conditions or faulty installation. Cracking might occur, leading to abrupt reductions on the produced power, quite difficult and expensive to fix. The I–V curves of a defected or cracked solar cell might not have the shape imposed by the usual models as 1M5P. In this article, cracked c-Si solar cells are modelled using a novel model: d1MxP. This model is based on the discretisation of the diode's response on models as 1M5P. Instead of imposing a shape and compute some parameters to fit it on experimental data, the proposed model connects every two points. The results suggest a better fit using the proposed model in comparison with the 1M5P, not only in the original curves, but also modelling cracked cells. As consequence of a better fitting, the computation of important figures of merit as maximum power point or fill factor, reveals to be more precise. It is concluded that the proposed model might characterise the performance of a solar cell, even cracked, which is a huge advance aiming the possibility of simulating complex problems during the cells' operation lifetime. [ABSTRACT FROM AUTHOR]

This study used a virtual, simulated 3 vs. 3 rugby task to investigate whether gaps opening in particular running channels promote different actions by the ball carrier player and whether an effect of rugby expertise is verified. We manipulated emergent gaps in three different locations: Gap 1 in the participant's own running channel, Gap 2 in the first receiver's running channel, and Gap 3 in the second receiver's running channel. Recreational, intermediate, professional, and nonrugby players performed the task. They could (i) run with the ball, (ii) make a short pass, or (iii) make a long pass. All actions were digitally recorded. Results revealed that the emergence of gaps in the defensive line with respect to the participant's own position significantly influenced action selection. Namely, "run" was most often the action performed in Gap 1, "short pass" in Gap 2, and "long pass" in Gap 3 trials. Furthermore, a strong positive relationship between expertise and task achievement was found. [ABSTRACT FROM AUTHOR]

[Display omitted] • A flexible thermoelectric device converting heat into electrical energy was performed. • Materials selection improve drastically the composites thermoelectrical properties. • Thermoelectric power factor and figure-of-merit increases up to 9 orders of magnitude. • Printable p-n thermocouples generate nW of power and charge a capacitor with 5 V. Flexible and easy processing lightweight thermoelectric materials for energy harvesting applications have shown an increasing interest. Thermoplastic polyvinylidene fluoride (PVDF) and elastomer styrene-ethylene/butylene-styrene (SEBS) polymers reinforced with thermoelectric ceramics, including bismuth sulfide (Bi 2 S 3), bismuth telluride (Bi 2 Te 3) and antimony telluride (Sb 2 Te 3), and electrically conductive carbon nanotubes (CNT) have been developed, tailoring their thermal and electrical properties for thermoelectric device applications. The Seebeck coefficient of the composites increases with thermoelectric ceramic filler content for semicrystalline PVDF composites, slightly decreasing for amorphous SEBS composite. Thermoelectric power factor and figure-of-merit in the polymer composites increases up to 9 orders of magnitude with respect to the pristine polymer, up to a maximum value of 10−3 µW/(m·K2) and 10−6, respectively, for the PVDF/CNT/Bi 2 Te 3 composite. A device composed by 2 printable p-n thermocouples based on PVDF/50Bi 2 S 3 and PVDF/50Bi 2 Te 3 can generate power in the order of the nW and charge a capacitor with 5 V. Theoretical modeling allows to evaluate different thermoelectric configurations, the effect of the number of thermocouples and the influence of the temperature gradient on device performance. [ABSTRACT FROM AUTHOR]

Flexible and stretchable materials are increasingly being investigated for future technological platforms, polymer based materials being the most suitable candidates for those emerging technologies. This work reports on polymer based scintillator composites based on the thermoplastic elastomer Styrene-Ethylene/Butadiene-Styrene (SEBS) and Gd 2 O 3 :Eu 3+ scintillator nanoparticles, to form a polymer-based flexible and stretchable material for X-ray indirect detectors. Further, visible light yield under X-ray irradiation was improved by the inclusion of 2,5 dipheniloxazol (PPO) and (1,4-bis (2-(5-phenioxazolil))-benzol (POPOP) within the polymer matrix. Together with high levels of stretchability, with deformations up to 100%, the films exhibit suitable performance with low mechanical hysteresis (less than 1.5 MJ/m 3 for cycles up to 100% of strain) and reproducibly such as a scintillator material for the conversion of X-ray radiation into visible radiation. The decrease of just ∼13% of the X-ray radiation into visible light upon stretching up to 100% is attributed to a reduction of the effective filler concentration and proves the suitability of the developed materials for large area and stretchable X-ray radiation detectors. [ABSTRACT FROM AUTHOR]

Low-cost and flexible first and second order low-pass filters with adjustable cutoff frequency were designed and printed by inkjet printing technology. The all-inkjet-printed low-pass filters were characterized and an adjustable cutoff frequency feature in form of an inkjet-printed organic thin-film transistors (OTFTs) was added to the filters for application-oriented fine-tuning. The applicability of these small circuits was evaluated by signal filtering for sensor applications. As a result, low-pass filters with an adjustable cutoff frequency ranging from 82 Hz to 740 Hz were obtained, demonstrating their suitability in signal filtering and their promising applicability for tactile sensing characterized by low frequency signals. [ABSTRACT FROM AUTHOR]

Specific tissues, such as cartilage, undergo mechanical solicitation under their normal performance in human body. In this sense, it seems necessary that proper tissue engineering strategies of these tissues should incorporate mechanical solicitations during cell culture, in order to properly evaluate the influence of the mechanical stimulus. This work reports on a user-friendly bioreactor suitable for applying controlled mechanical stimulation-amplitude and frequency-to three-dimensional scaffolds. Its design and main components are described, as well as its operation characteristics. The modular design allows easy cleaning and operating under laminar hood. Different protocols for the sterilization of the hermetic enclosure are tested and ensure lack of observable contaminations, complying with the requirements to be used for cell culture. The cell viability study was performed with KUM5 cells. [ABSTRACT FROM AUTHOR]

A novel approach for tissue engineering applications based on the use of magnetoelectric materials is presented. This work proves that magnetoelectric Terfenol-D/poly(vinylidene fluoride-co-trifluoroethylene) composites are able to provide mechanical and electrical stimuli to MC3T3-E1 pre-osteoblast cells and that those stimuli can be remotely triggered by an applied magnetic field. Cell proliferation is enhanced up to ≈25% when cells are cultured under mechanical (up to 110 ppm) and electrical stimulation (up to 0.115 mV), showing that magnetoelectric cell stimulation is a novel and suitable approach for tissue engineering allowing magnetic, mechanical and electrical stimuli. [ABSTRACT FROM AUTHOR]

Nowadays, optical systems play an important role in communications. Dual depletion PIN photodiodes are common devices that can operate in different optical bands, depending on the chosen semiconductors. However, since semiconductor properties vary with the surrounding conditions, some optical devices/systems can act as sensors. In this research work, a numerical model is implemented to analyze the frequency response of this kind of structure. It considers both transit time and capacitive effects, and can be applied to compute photodiode frequency response under nonuniform illumination. The InP-In 0.53 Ga 0.47 As photodiode is usually used to convert optical into electrical power at wavelengths around 1300 nm (O-band). This model is implemented considering an input frequency variation of up to 100 GHz. The focus of this research work was essentially the determination of the device's bandwidth from the computed spectra. This was performed at three different temperatures: 275 K, 300 K, and 325 K. The aim of this research work was to analyze if a InP-In 0.53 Ga 0.47 As photodiode can act as a temperature sensor, to detect temperature variations. Furthermore, the device dimensions were optimized, to obtain a temperature sensor. The optimized device, for a 6 V applied voltage and an active area of 500 μ m 2 , had a total length of 2.536 μ m , in which 53.95% corresponded to the absorption region. In these conditions, if the temperature increases 25 K from the room temperature, one should expect a bandwidth increase of 8.374 GHz, and if it decreases 25 K from that reference, the bandwidth should reduce by 3.620 GHz. This temperature sensor could be incorporated in common InP photonic integrated circuits, which are commonly used in telecommunications. [ABSTRACT FROM AUTHOR]

Solar cell equivalent circuit modelling is usually based on continuous I-V models, with a set of data obtained by analytical expressions. This work proposes an almost discrete novel mathematical method and correspondent electrical model, based on the I-V curve adjustment at every two adjacent points. It is based on the discretisation of any diode model behaviour, such as the 1M5P (also known as 1D5P) or the 1M7P (also known as 2D7P). For this reason, the model is named d1MxP, meaning that it is a discrete (d) model (1M) with x parameters (xP). The modelling methodology validation process uses experimental data already published in the literature. According to the presented results, the proposed method shows increased accuracy when compared to the 1M5P or 1M7P equivalent models. The accuracy on the maximum power point and fill factor determination is relevant, resulting in an improvement of up to 3.34% in the maximum power, up to 5.70% in its voltage and up to 8.20% in its current, for the analysed data. Furthermore, Fill Factor values, have variation from up to 35.98%. The temperature influence on the silicon solar cell is also analysed, to validate the results. The proposed method allows highly accurate curve fitting to the (experimental) points and consequently, to obtain a more accurate model to analyse the performance of solar cells under different conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] The possibility of monitoring the mechanical stress over time in prosthesis is presented. [•] High sensitive silicon thin-film piezoresistive sensors were applied. [•] Their performance is appropriate to be implemented in smart prosthesis applications. [Copyright &y& Elsevier]

Abstract: Ultrasound transducers are typically based on piezoelectric materials, due to their good response at high frequencies. Depending on the application, ceramics, polymers and composite materials can be used. In this work, an optimization study of ultrasound transducers for underwater communications is addressed, focusing on a piston type emitter transducer operating in thickness mode (d 33). The piston is constituted by an active element disk with optimized dimensions. It is discussed how the acoustic impedance, thickness, resonance frequency and structure affect the transducer performance. This work allows a better understanding of the emitter transducer characteristics allowing reaching the optimum point of operation for specific applications. Focusing on underwater communication, the acoustic channel is defined and the transducer is optimized by finite element computer simulations. The results were compared with experimental tests, which show that four-layer structures increase up to 16dB in performance versus single-layer. [Copyright &y& Elsevier]

Abstract: N-type hydrogenated nanocrystalline silicon thin film piezoresistors, with gauge factor −28, were deposited on rugged and flexible polyimide foils by Hot-wire chemical vapor deposition using a tantalum filament heated to 1750°C. The piezoresistive response under cyclic quasi-static and dynamical (up to 100Hz) load conditions is reported. Test structures, consisting of microresistors having lateral dimensions in the range from 50 to 100μm and thickness of 120nm were defined in an array by reactive ion etching. Metallic pads, forming ohmic contacts to the sensing elements, were defined by a lift-off process. A readout circuit for the array consisting in a mutiplexer on each row and column of the matrix is proposed. The digital data will be processed, interpreted and stored internally by an ultra low-power micro controller, also responsible for the communication of two-way wireless data, e.g. from inside to outside the human body. [Copyright &y& Elsevier]

Background: In this paper, we explore physical education from a relational worldview. Theoretically guided by an ecological dynamics framework, this perspective calls us to conceptualise 'education' in its etymological roots – ex-ducere – meaning 'to lead' an individual 'out' into the world. In doing so, an educator would employ a 'softer' pedagogy, seeking to guide the attention and encourage exploration of a less experienced individual toward the perception of things that can support, or regulate, their behaviours. This pedagogical approach could help learners to self regulate in the environment, becoming more responsive to emergent opportunities for action available. Theory: This is a pedagogy of exploration, search, discovery, invention and adaptation that is devised from three of the contributing theories to ecological dynamics: ecological psychology, dynamical systems theory and complexity sciences. Throughout this paper we show that this progressive view contrasts with the more traditional perspectives of physical education, grounded in established pedagogical approaches that are often pre-occupied with instilling idealised ways of moving in learners, typically at the expense of appreciating how the environment reciprocally shapes behaviour. Practical Implications: In an effort to support educators with integrating an ecological conceptualisation of PE into their practice we outline three cornerstones. We bring these ideas to life by concluding the paper with the presentation of three practical examples that transcends the physical educational journey from primary/elementary school through to secondary/ high schools. We exemplify how an ecological approach to PE can move us closer to achieving the aim of enabling children to lead a physically active life beyond the school gates. [ABSTRACT FROM AUTHOR]

Environmentally-friendly materials are being pursued world-wide for applications across a wide range of technologies. For application in spray-printed radiation detectors, water-based scintillator inks have been produced by combining a thermoplastic elastomer poly (vinyl) alcohol (PVA) and Gd 2 O 3 :Eu 3+ scintillator nanoparticles. Formulations of these green inks with different concentrations of scintillator nanoparticles have been assessed in terms of their rheological properties: the optimal concentration of scintillator nanoparticles in the water-based ink for spray-printing was 0.75 wt%. This optimized ink formulation exhibits Newtonian behavior with a viscosity around 100 cps and performance characteristics suitable for spray-printing scintillators for indirect X-ray detectors. [ABSTRACT FROM AUTHOR]

In recent years, printed electronics reached enormous popularity as a result of their huge potential to offer unique features that are not attainable through traditional fabrication, namely low‐cost production, multifunctionality, stretchability, sustainability, and flexibility. Being expected a galloping increase in the use of printed technologies in the near future, due to the digitalization efforts associated with the Internet of Things and the 4.0 revolution, it is timely and desirable to discuss the joint features, the interrelations, the complementarities, the interdependency, and the most demanding challenges linked to the relation between printed technologies and electronic materials. In this context, this study offers a broad review of the numerous printing technologies used in the processing of electronics, commonly used substrates, the most effective printed electronic materials, and the key post‐printing treatments such as sintering. Disruptive challenges in various printing techniques, (un)expected future research directions of printed electronics, and imminent application trends are also highlighted, following a critical and subjective perspective. [ABSTRACT FROM AUTHOR]

Polymer-based scintillator composites have been produced by combining polystyrene (PS) and GdO:Eu scintillator nanoparticles. Polystyrene has been used since it is a flexible and stable binder matrix, resistant to thermal and light deterioration and with suitable optical properties. GdO:Eu has been selected as scintillator material due to its wide band gap, high density and visible light yield. The optical, thermal and electrical characteristics of the composites were studied as a function of filler content, together with their performance as scintillator material. Additionally 1 wt.% of 2,5-diphenyloxazole (PPO) and 0.01 wt.% of 1,4 di[2-(5phenyloxazolyl)]benzene (POPOP) were introduced in the polymer matrix in order to strongly improve light yield, i.e., the measured intensity of the output visible radiation, under X-ray irradiation. Increasing scintillator filler concentration (from 0.25 to 7.5 wt.%) increases scintillator light yield and decreases the optical transparency of the composite. The addition of PPO and POPOP strongly increased the overall transduction performance of the composite due to specific absorption and re-emission processes. It is thus shown that GdO:Eu/PPO/POPOP/PS composites with 0.25 wt.% of scintillator content with fluorescence molecules are suitable for the development of innovative large-area X-ray radiation detectors with huge demand from the industries. [ABSTRACT FROM AUTHOR]

The energy harvesting efficiency of poly(vinylidene fluoride–trifluoroethylene) spin coated films and its nanocomposites with piezoelectric BaTiO 3 have been investigated as a function of ceramic filler size and content. It is found that the best energy harvesting performance of ∼0.28 μW is obtained for the nanocomposite samples with 20% filler content of 10 nm size particles and for 5% filler content for the 100 and 500 nm size fillers. For the larger filler average sizes, the power decreases for filler contents above 5% due to increase of the mechanical stiffness of the samples. Due to the similar dielectric characteristics of the samples, the performance is mainly governed by the mechanical response. The obtained power values, easy processing and the low cost and robustness of the polymer, allow the implementation of the material for micro and nanogenerator applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electrospun fibers of PVDF (PVDF-TrFE) and composites with BaTiO3 have been prepared. [•] The influence of the processing parameters on fiber size and distribution is determined. [•] The energy harvesting of the fibers has been evaluated. [•] Power outputs up to 25μW have been obtained. [•] The obtained values are among the largest found in the literature. [Copyright &y& Elsevier]

Polymer based smart materials and, in particular, piezoresistive ones, are increasingly being used in a wide variety of applications ranging from automotive components to medical devices. This work reports on water-based piezoresistive polymer composites developed from thermoplastic poly (vinyl alcohol) (PVA) filled with carbon nanotubes (MWCNT) for the fabrication of high performance piezoresistive materials and sensors. PVA is a water-soluble synthetic polymer with suitable mechanical properties for the development of large strain sensors. MWCNT/PVA nanocomposites with good linearity between deformation and electrical resistance variation and with gauge factors up to 3 were achieved. Further, the materials were formulated in the form of inks for spray and screen printing of the sensors, which demonstrated a good performance for strain sensing both under laboratory tests conditions and when connected to a readout and communication system. Therefore, polymer based piezoresistive sensors were developed by a green approach and capable to be implemented by scalable printing technologies. [ABSTRACT FROM AUTHOR]

Polymer based scintillator composites have been produced by combining poly(vinylidene fluoride), PVDF, and Gd 2 O 3 :Eu 3+ scintillator nanoparticles. Additionally, 2,5 dipheniloxazol (PPO) and (1,4-bis (2-(5-phenioxazolil))-benzol (POPOP) were introduced in the polymer matrix in order to improve visible light yield under x-ray irradiation. It is shown that addition of PPO and POPOP has no influence on the polymer structure, increases dielectric constant from ∼7 to ∼14, which is suitable for improving energy resolution, and increases in 40% the overall transduction performance of the composite without sacrificing its homogeneity and transparency. Thus, the developed Gd 2 O 3 :Eu 3+ /PPO/POPOP/PVDF composites are appropriate for large area X-ray radiation detectors. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), electrospun membranes were obtained from a mixture of dimethylformamide (DMF) and methylethylketone (MEK) solvents. The inclusion of MEK to the solvent system promotes a faster solvent evaporation allowing complete polymer crystallization in the jet traveling between the tip and the grounded collector. The main electrospinning processing parameters were systematically changed to study their influence on fiber dimensions and distribution. Applied voltage and inner needle diameter do not have a large influence on the electrospun fiber average diameter but do on the fiber diameter distribution. On the other hand, increasing the distance between the needle tip and the collector gives origin to fibers with larger average diameter. Independently of the processing conditions, all membranes are produced in the electroactive phase of the polymer. Further, MC-3T3-E1 cell adhesion is not inhibited by the fiber membrane preparation, showing their potential use for biomedical applications. [ABSTRACT FROM AUTHOR]

Abstract: Four profiles of estuarine sediments obtained from boreholes drilled in the Algarve, Southern Portugal were studied in order to reconstruct the process of sediment accumulation driven by the postglacial sea level rise. In addition to the sedimentological analysis, the Foraminifera Index of Marine Influence (FIMI) permitted assessment of the nature and organization of sedimentary facies in the Beliche–Guadiana and Gilão–Almargem estuaries. The Beliche–Guadiana CM5 and Almargem G2 profiles accumulated in a sheltered environment, with the former presenting an almost continuous record of the sea level rise since ca 13 000calyrBP. The G1 and G3 profiles from the Gilão–Almargem area represent a more discontinuous record of the last 8000 years, which accumulated in the more dynamic environment of an outer estuary. The integration of all radiocarbon ages of dated levels, led to an estimate of sediment accumulation rates. Assuming a constant position of the sediment surface with respect to the tidal range and a negligible compaction of sediment, the sea level rose at the rate of 7mmyr−1 in the period from 13 000 to 7500calyrBP. This process slowed down to ca 0.9mmyr−1 from 7500calyrBP until the present. The marked historical change in the rate of sediment accumulation in these estuaries also occurred with the accumulation of organic matter and is, therefore, important data for global biogeochemical models of carbon. The main obstacle to obtain higher temporal resolution of the sedimentary processes was the intense anaerobic respiration of organic matter via sulphate reduction, which did not allow any accumulation of peat and, furthermore, led to erasure of the palaeontological record by acid formed from the subsequent oxidation of sulphides. [Copyright &y& Elsevier]