Top Grid Research Articles

Are Mediterranean Island Mountains Hotspots of Taxonomic and Phylogenetic Biodiversity? The Case of the Endemic Flora of the Balearic Islands.

The Mediterranean islands are exceptionally rich in endemism, most of which is narrowly distributed. Conservation measures, such as protected areas, have been prioritised, mainly on the basis of species richness and endemism, but phylogenetic information should also be taken into account. In this study, we calculated several taxonomic and phylogenetic metrics at a high resolution for the endemic flora of the Balearic Islands (154 taxa), in order to identify (i) the spatial patterns and environmental factors that explain this endemism, (ii) hotspots of species and phylogenetic endemism, and (iii) gaps in the protected areas. The taxonomic and phylogenetic metrics showed different distribution patterns, but the mountainous areas of Mallorca, and some coastal areas of the Balearic Islands, have the highest values. These values were positively related to elevation, precipitation, temperature, and slope, and negatively related to the distance from the coast, aspect, and the temperature of the wettest quarter. We identified top grid hotspots where all the metrics had the highest values, and we also identified nano-hotspots within these hotspots, in some of the highest peaks of Mallorca, where most of these metrics' maximum values coincided. This approach allowed us to identify some gaps in the conservation priority areas, and to highlight the need to review their boundaries and definition.

Cleaning frequency of the solar PV power plant for maximum energy harvesting and financial profit

Cleaning frequency of the solar PV power system plays a major role in energy harvesting. This paper proposed an optimized cleaning frequency for the PV power plants. The objective is to maximize energy harvesting and increase financial profit. The proposed technique is tested in roof top grid connected 20 kW PV power plant in Cairo, Egypt. Experimental results are collected for one year throw the period from January 2021 to December 2021 based on real time monitoring under the regular cleaning of the PV plant every fifteen days. The collected data and results are used for deriving a formula to find the optimal frequency for cleaning the PV cells. This formula can be used for any PV power plant under different operating conditions. Therefore, the formula can detect the financial losses due to the dust accumulated on the surfaces of PV panels. The model proposed in this research is verified by the comparison between the generated power from the photovoltaic power plant and the cost of cleaning (water and cleaning workers) in case of manual cleaning, taking into consideration the various operating conditions though whole the period of the study.

TOP ELECTRODE INVESTIGATION OF OPV MODULES BASED ON P3HT:PC[60]BM FABRICATED VIA ROLL-TO-ROLL PROCESS

Solar photovoltaic (PV) cells allow the direct conversion of sunlight into electricity without CO2 emission. Finding a way to cheaply utilize the vast amount of solar energy is one of the biggest challenges for this technology. The organic photovoltaic cells (OPV) are based on solution-processed photoactive polymers and can be fabricated via roll-to-roll (R2R) processes, which allow high production throughput with low costs. CSEM Brasil is building the foundations of future high-tech industries in Brazil and one of our key technology development areas is OPV modules production using R2R coating. In this work, polymer solar cells based on P3HT: PC[60]BM were prepared by R2R coating (electron transport, active and hole transport layers – ETL, AL and HTL) and by screen printing (top silver electrode). In order to save material and give more transparency of the OPV module were compared and evaluated the performance of two different suppliers of Ag paste (A and B) in three different top contact configurations, solid, grid and honeycomb. Additionally, were compared two different screen suppliers (I and II) for screen printing process and the Ag paste drying time studied. The comparisons were made with modules with an active area of 21.6 cm2 (6 stripes serially connected). Photovoltaic performance was evaluated in terms of Ag paste and screens suppliers, Ag pattern and drying time. Finally, modules were encapsulated in a R2R laminator using a flexible barrier film and evaluated in terms of lifetime.

The development of multi-physics approach with Monte Carlo and computational fluid dynamics coupling for reactor cores

Highly accurate solutions for neutronic and thermal hydraulic phenomena in reactor cores certainly improve the safety conclusions about the reactors. The coupling methodology of governing physics of these two fields by using Monte Carlo and computational fluid dynamics (CFD) methods was described in this study with its application to Istanbul Technical University (ITU) TRIGA Mark II Research Reactor. As a different approach, instead of not modelling top and bottom grid plates of the reactor that is the common practice for geometrical simplification, the effect of grid plates on flow hydrodynamics was included into the conjugate heat transfer calculations as boundary conditions. The investigation on the effect of core element temperature, cross sections, and S(α,β) thermal scattering data showed the need of proper coupling of neutronic and thermal hydraulic fields since 30–45% relative error on excess reactivity value of the ITU research reactor was observed. With the developed loose coupling model, 483 individual cross section and 483 different S(α,β) thermal scattering data were generated by using NJOY nuclear data generation code and MAKSXF and OTF utilization tools of MCNP6.2 code. The reactivity loss against power increase in research reactor value of this study showed 6% relative error with loose coupling comparing to maximum 50% without coupling.

Dynamic beam scanning metasurface with high reflectivity and independent phase control based on phase change materials

Laser phased array radar has a broad application prospect in extreme weather imaging, real-time meteorological monitoring, intelligent self-driving, and adaptive scanning. Dynamic metamaterials solve the problems of miniaturization and poor robustness of traditional devices and provide the possibility of a tunable phased array. In these metasurfaces, the wavefront control of the incident beam is mainly realized by timing control, with extremely low reflectivity (≤5%) and a small scanning angle. We present an all-solid-state electrically tunable metasurface array based on phase change materials (PCM). Through the simple structure of a tunable vanadium dioxide (VO2) - gold resonator, the top gate is controlled to realize a near-infrared band beam scanning. Close in construction, simple in operation, and portable. It demonstrates the reflection phase and reflectance have high tunability when the operating wavelength is 1.55 um. Driven by the top grid, a phase monotone modulation range of more than 200° is generated, with a minimum reflectivity of more than 15 % and a maximum reflected beam field of view of ±25.6°. In principle, the electrically driven phase control enables a single resonant element to have independent electrical addressing capability, which paves the way for the application of metasurface optical elements in imaging and sensing technologies.

Scalable semitransparent prototype organic photovoltaic module with minimal resistance loss

Semi-transparent organic photovoltaic (ST-OPV) cells are regarded as an attractive solution to building-integrated solar energy harvesting. Both the power conversion efficiency ( PCE ) and average photopic transmission ( APT ) of ST-OPVs have shown substantial increases in recent years. However, less attention has been paid to the area scaling of ST-OPV cells. In this work, we investigate the scalability of ST-OPV cells from 4 mm 2 to 1 cm 2 , as well as 9 cm 2 active area prototype module. By integrating both top and bottom metal grids onto the transparent electrodes, the series resistance loss of 1 cm 2 ST-OPV cell is significantly reduced, and is comparable to that of the grid-free 4 mm 2 cell. Nine 1 cm 2 cells are then connected in a series-parallel circuit to realize a prototype ST-OPV module. A 100% fabrication yield with only 5% PCE deviation among discrete cells is achieved. The semitransparent module shows PCE = 7.2 ± 0.1% under simulated AM 1.5G illumination at 1 sun intensity, which exhibits no connection resistance loss compared to that of the individual cells. The ST-OPV module exhibits an APT = 38.1 ± 1.1%, which enables a light utilization efficiency, LUE = 2.74 ± 0.09%. The method demonstrates a promising way for ST-OPV modules to scale without compromising performance. • Semitransparent organic photovoltaic cells are scaled from 4 mm 2 to 1 cm 2 employing metal grids without loss of performance. • The 9 cm 2 active area prototype modules have 100% cell yield and with performance comparable to that of 4 mm 2 cells. • The module shows PCE = 7.2%, an average photopic transparency of 38.1%, enabling a light utilization efficiency of 2.74%. • The method demonstrates a promising path for scaling to modules without compromising performance.

Fragility Curves for Slope Stability of Geogrid Reinforced River Levees

When constructing flood protection structures such as river levees, oftentimes due to various factors engineers must design composite structures, i.e., reinforced earthen structures which comply with all the stability criteria. The most common way of reinforcing such structures is the usage of geosynthetics, or mostly geogrids when talking about stability. Since geosynthetics are man-made materials produced in a controlled environment and go through quality control measures, their characteristics contain a negligible amount of uncertainty compared to natural soils. However, geosynthetic handling, their installation in the levee, and their long-term degradation can all have significant effects of variable magnitude on geosynthetic characteristics. These effects and their variability can be considered as random variables, which can then be used in probabilistic analyses together with soil properties. To investigate the effects of the geogrid’s resistance variability on slope stability compared to soil properties variability, probabilistic analyses are conducted on a river levee in northern Croatia. It is found that the geogrid’s variability generally has very little effect on the total uncertainty compared to the friction angle’s variability, but out of the three geogrid layers used the top grid has the most influence.

Reproduction wavefield reverse time migration

The reverse time migration (RTM) aims to image subsurface reflectors by incorporating with the two-way wave equation. RTM has advantages that it does not have dip limitations and can generate subsurface images clearly even in the case of complex geological structures in the near surface. We have proposed a reproduction wavefield reverse time migration (RWRTM) algorithm implemented with backward reproduced wavefield instead of the back-propagation of the observed data. Reproduced wavefield can be achieved by using the same modelling algorithm used in the source propagation. In general acquisition systems, e.g. streamer in marine or surface geophone in land, conventional RTM back-propagates data acquired on the top grid points in the numerical domain while RWRTM back-propagates reproduced data located on all grid points in the numerical domain, which lead to the generation of migration images with less migration noises and well-balanced migrated events. To validate RWRTM, numerical tests are conducted. For our examples, RWRTM images have better resolution, improved continuity of structure, reduced migration noises, and balanced amplitude compared to the conventional RTM.

The Stokes drift in ocean surface drift prediction

ABSTRACT The importance of explicitly resolving the Stokes drift in ocean surface drift modelling is demonstrated by comparing four models with 58,612 observational data points obtained from undrogued drifting buoys in the Estuary and Gulf of St. Lawrence, Canada. Drift model inputs are obtained from regional atmosphere and ocean circulation, and spectral wave models. The control drift model considers near-surface currents provided by the top grid cell of the ocean circulation model, which is 5-m thick, and a correction term proportional to the near-surface wind. The three other drift models account for the unresolved near-surface current shear by extrapolating the near-surface currents to the surface assuming Ekman dynamics. Two of these models consider explicitly the Stokes drift, with and without a wind correction term. Proposed models reduce the mean separation distance between observed and predicted trajectories by 34–40% relative to the control model, on average, for forecast times ranging from 3 to 72 h. The best improvement with respect to all metrics used is, however, obtained for the model that takes into account the near-surface shear correction and the Stokes drift, without any wind correction term (skill score of 0.93 after 3 h and 0.81 after 72 h).

Pre-existing lithospheric weak zone and its impact on continental rifting – The Mid-Polish Trough, Central European Basin System

The large portion of Central and NW Europe was subjected to widespread continental rifting since the Carboniferous-Permian transition. This process led to nucleation of several large depocentres, coalescing from the late Permian onwards into the extensive Central European Basin System (CEBS), that grew and evolved until the regional-scale Late Cretaceous inversion. Development of deep grabens from Germany to the Netherlands and the North Sea was connected with volcanism and crustal thinning. The exception makes the Mid-Polish Trough (MPT), trending NW-SE across Poland along the Teisseyre-Tornquist Zone (TTZ) at the margin of the East European Craton (EEC). The MPT is underlain by relatively thick lithosphere and its formation was not associated with volcanic activity in the direct neighbourhood. To investigate this anomaly, we compiled grids for key horizons defining the crustal architecture, separately for NW European and Polish sectors of the CEBS. Seismic reflection and well data were used to build the base Permian grid, whereas deep seismic refraction and reflection data along with constrained gravity inversion were employed to construct the top basement and Moho grids. Based on a dense net of seismic refraction profiles, the additional top Ediacaran grid was created solely for the Polish part of the CEBS. Our data show distinct crystalline crust thinning SW of the TTZ (β factor = 3.68) expressed in both shallowing of Moho and deepening of the crystalline basement. We interpret this feature as a fossilised crustal neck inherited after an Ediacaran rifting preceding the break-up of Rodinia. The early Permian rifting moderately contributed to the crustal thinning (β factor = 1.4), overprinting the primary rifted margin geometry. The 8 km deep MPT developed in front of a pre-existing crustal neck that obstructed further propagation of extensional deformation. Lithospheric mantle beneath a rift axis was probably too strong to accommodate extension but the thinner lithosphere farther west was weak enough to be stretched. Therefore, the location of the pre-existing weakness zone relative to a change in lithosphere thickness may localise a rift graben and shift the magmatism away from the surface expression of the rift. Thus, our study demonstrates that fossil crustal architecture was a key factor controlling the amount, distribution, and style of continental rifting.

Compact Slot Antenna Integrated with a Photovoltaic Cell

This paper presents a compact low-profile slot antenna integrated with a photovoltaic cell. The photovoltaic cell consists of a top metal grid, gallium arsenide substrate, and metallic bottom contact. The metallic bottom contact was used as a ground plane where the slot was etched for resonance. A second substrate was placed under the ground plane, and a 50 Ω microstrip line was printed on its bottom side to excite the slot. A chip inductor was used as a radio frequency (RF) choke in the alternating current blocking circuit to suppress RF current leakage towards the photovoltaic cell. Hence, the proposed antenna has a unique feature of functioning simultaneously as a photovoltaic cell and an antenna. The overall dimensions––25 mm × 31.75 mm × 0.893 mm (0.48λo × 0.61λo × 0.017λo at 5.77 GHz)––of the photovoltaic cell-integrated slot antenna structure can be used effectively with Internet of Things devices.

Assessing the sensitivity of site index models developed using bi-temporal airborne laser scanning data to different top height estimates and grid cell sizes

Site productivity and forest growth are critical inputs into projecting wood volume and biomass accumulation over time. Site productivity, which is determined most commonly using site index models is also the primary criterion to consider many forest management decisions. Most of the previous research utilizing the remote sensing data for assessment of site index with forest height are based on the existing site index models developed with traditional dendrometric methods. However, these traditional methods are both time-consuming and expensive. This study demonstrates how bi-temporal airborne laser scanning (ALS) data collected within the 8-year period can be used for the development of site index models for Scots pine. The accuracy of ALS-derived models was assessed by comparison to the reference site index model developed based on data from stem analysis of 174 felled Scots pine trees. We evaluated the effect of different height metrics and grid cell size on the trajectory of site index models developed from ALS-derived measurements. Four methods of estimating top height from ALS point clouds were evaluated: 95th, 99th and 100th percentiles of point clouds and an individual tree detection approach (ITD). The models were created for a range of grid cell sizes: 10 × 10 m, 30 × 30 m, and 50 × 50 m. The results indicate that bitemporal ALS data could substitute traditional methods that have been applied to date for stand growth modelling. It was found that top height increment can be estimated by using both ITD approach and the 100th percentile of point cloud giving an appropriate top height (TH) increment estimation. Observed growth curves of reference trees agreed best with the trajectories that were obtained based on TH calculated using ITD method (R2 = 0.892) and 100th percentile (R2 = 0.797). In case of TH obtained from 99th and 95th percentiles only weak correlation was found: R2 = 0.358 and R2 = 0.213, accordingly. The height growth models developed with 95th and 99th percentiles of point cloud were not compatible with the reference model. We also found that grid cell size did not affect the model height growth trajectories. Irrespective of the grid cell size, the obtained model trajectories for the given method of TH estimation are nearly identical for cells 10 × 10, 30 × 30 and 50 × 50 m.

Extrapolating Eulerian ocean currents for improving surface drift forecasts

ABSTRACT Predictions of drift trajectories based on four drift models were compared with observations from drifting buoys deployed in 2014 and 2015 in the Estuary and Gulf of St. Lawrence to show the impact of the current vertical shear on the surface drift predictions. Input of ocean currents and winds are obtained from ISMER's 5 km resolution ocean circulation model and from the Canadian Regional Deterministic Prediction System, respectively. The control drift model A considers depth-averaged near-surface currents (0–5 m) provided by the top grid cell of the ocean circulation model. Model B performs a linear extrapolation assuming a constant vertical shear equal to that between the first two cells of the ocean model. Models C and D perform a dynamic extrapolation assuming an Ekman layer with a constant or linearly increasing vertical viscosity, respectively. Model performance is evaluated based on several error metrics. Drift models based on extrapolated surface currents reduce separation distances relative to the control model by 25% (model B), 31% (model C) and 35% (model D) on average, for lead times from 3 h to 72 h. We thus recommend the use of extrapolation methods of near-surface ocean currents for improving surface drift forecasting skills in support of emergency response.

Various Metal Sandwich Layer Oriented Efficiency Enhancement Superiority on CuInGaSe2 Thin Film Solar Cells

The good quality CuInGaSe2 (CIGS) thin film solar cells were fabricated on molybdenum metal coated soda lime glass substrate. Three-stage co-evaporation method was utilized for the fabrication of high quality p-type CIGS thin film absorber layer. Further, n-type CdS layer, high resistive intrinsic ZnO layer and transparent conducting AlZnO layers were fabricated by CBD method and vacuum sputtering methods. We made three various top metal sandwich grid patterns, i.e. Al, Al/Cu and Cu/Al which were utilized to investigate the metal sandwich layer oriented efficiency enhancement superiority on CuInGaSe2 thin film solar cells. The investigated specific CIGS solar cell device efficiency with respect to various top metal grid sandwich patterns is presented and discussed.

21.8% Efficient Monolithic Perovskite/Homo-Junction-Silicon Tandem Solar Cell on 16 cm2

A monolithic (FAPbI3)0.83(MAPbBr3)0.17 perovskite/rear-textured-homo-junction-silicon tandem solar cell with a steady-state 21.8% efficiency has been achieved on 16 cm2 using a new front top metal grid design producing an impressive fill factor (76% under forward scan or 78% under reverse scan). The efficiency and fill factor are the highest for monolithic perovskite/Si tandems larger than 10 cm2.

Bench marking of grid tied solar roof top photovoltaic system: a case comparison

Indian power sector having the target of 175GW of power from renewable energy, out of that 40 GW from Rooftop solar Photovoltaic system by 2022. The installed capacity of solar photovoltaic until 2017 is about 14.77 GW only. Even though in depth study has been carried out on the performance analysis, there is no bench marking has been arrived for the Indian Roof Top Solar PV system. Hence this paper has made an attempt by calculating the various parameters like performance ratio, plant capacity utilization ratio for the two 20KWp grid connected rooftop power plant in Telangana state. In addition to the above, it needs to do in depth analysis of power quality issues on roof top grid tied system.

HWCVD of B-doped silicon carbide thin films for SHJ solar cell technology

ABSTRACTBoron-doped SiC thin films were deposited on N-type Si(100) substrates at various deposition conditions by means of HWCVD technology using silane (SiH4), methane (CH4), hydrogen(H2), diborane (B2H6, 5vol.% in H2) and argon (Ar) gas as precursors. Elements concentration was determined by RBS and ERD method. Chemical compositions were analyzed by FTIR and Raman spectroscopy. Solar cell structure with top grid Al electrode was prepared to investigate the photovoltaic response and to gain insight about the quality of films and their suitability for photovoltaic applications. Comparison of open-circuit voltage (VOC), short-circuit current (Isc), fill factor (FF) and efficiency (Ef) was discussed.

A method to fabricate high-aspect-ratio microstructures using PMMA photoresist

Fabrications of high-aspect-ratio microstructures (HARMS) using negative photoresist have been studied a lot by researchers recently, but the removal of the resist is still a problem. We report a method to fabricate HARMS using PMMA, a positive photoresist. A classical microstructure, densely packed micro square columns, was tried in our study. A top grid made of negative photoresists was employed to join all the separate parts together to prevent them from tilting or clumping. The development and electroplating processes were not influenced by the top grid. Excellent nickel micro-pores-structures were obtained finally, demonstrating that the method is a promising way to fabricate HARMS especially when the resist needs to be removed.

Packing of cylindrical particles: DEM simulations and experimental measurements

In order to achieve efficient particle packing, minimizing the space of occupation and maximizing the strength of packing, it is important to understand the best methods of fill and the effects of various particle properties, including particle shape. In this study, the packing behavior of cylindrical particles is studied via both Discrete Element Method (DEM) simulations and complementary experiments. The effects of coefficient of friction, coefficient of restitution, drop height, fill height, packing method, deposition intensity (number of particles deposited per second), container size, surface roughness, and Young's modulus are investigated. In addition, two methods of packing density analysis from DEM simulations - a center of particle method and a top grid analysis method - are introduced. It is found that the packing density increases with fill height, container diameter, coefficient of restitution and drop height and decreases with coefficient of friction, surface roughness and Young's modulus. Different packing methods are explored, and it is found that the most efficient packing scheme is to pouring particles over the whole cross-section with low deposition intensity and at a variable drop height. Finally, DEM simulation predictions for particle packing of cylinders show good agreement with experimental measurements.

Nafion-Modified PEDOT:PSS as a Transparent Hole-Transporting Layer for High-Performance Crystalline-Si/Organic Heterojunction Solar Cells with Improved Light Soaking Stability.

We demonstrate the chemistry of amphiphilic perfluorosulfonic copolymer Nafion-coated conductive poly(3,4-ethyelenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and its effect on the photovoltaic performance of PEDOT:PSS/crystalline Si (c-Si) heterojunction solar cells. The highly hydrophilic sulfonate group of insulating, chemically stable Nafion interacts with PSS in PEDOT:PSS, which reduce the Coulombic interaction between PEDOT and PSS. The highly hydrophobic fluorocarbon backbone of Nafion favorably interacts with hydrophobic PEDOT of PEDOT:PSS. These factors give rise to the extension of π-conjugation of PEDOT chains. Silver paste used as a top grid electrode diffused into the Nafion layer and contacted with underneath Nafion-modified PEDOT:PSS layer. As a consequent, solution-processed Nafion-coated PEDOT:PSS/c-Si heterojunction solar cells exhibited a higher power conversion efficiency of 14.0% with better stability for light soaking rather than that of the pristine PEDOT:PSS/c-Si device by adjusting the layer thickness of Nafion. These findings originate from the chemical stability of hydrophobic fluorocarbon backbone of Nafion, diffusivity of silver paste into Nafion and contact with PEDOT:PSS, and Nafion as an antireflection layer.