Upscaling Method Research Articles

Sharing the safe operating space: Exploring ethical allocation principles to operationalize the planetary boundaries and assess absolute sustainability at individual and industrial sector levels

AbstractIn the light of increasing human pressures on the Earth system, the issue of sharing in the face of scarcity is more pressing than ever. The planetary boundary framework identifies and quantifies nine environmental boundaries and corresponding human pressures. However, when aiming to make the concept operational for decision support it is unclear how this safe operating space (SOS) within each of the planetary boundaries should be shared. This study proposes a two‐step approach, where the operating space is first downscaled to the individual level using ethical allocation principles and next scaled up to a higher organizational level using different upscaling methods. For the downscaling, three allocation principles are demonstrated: egalitarian (equal per capita); grandfathering (proportional to current share of the total impacts); and ability to pay (proportional to economic activity). For upscaling from the individual level final consumption expenditure is used as a proxy for the priority that the individual gives to the product or sector. In an alternative upscaling approach, an additional upscaling factor is based on the eco‐efficiency (ratio between turnover and environmental impact) of the product or sector. A demonstration of the method's application is given by applying the framework to two of the planetary boundaries, climate change and biogeochemical flows, with the Danish, Indian and global dairy sectors as cases. It is demonstrated how the choices of allocation and upscaling approaches influence the results differently in the three cases. The developed framework is shown to support an informed and transparent selection of allocation principles and upscaling methods and it provides a step toward standardization of distributing the SOS in absolute environmental sustainability assessments.

Selective Etching of Graphene Membrane Nanopores: From Molecular Sieving to Extreme Permeance.

Two-dimensional materials are the essential building blocks of breakthrough membrane technologies due to minimal permeation barriers across atomically thin pores. Tunable pore size fabrication combined with independently controlled pore number density is necessary for outstanding performance but remains a challenge. There is a great need for parallel, upscalable methods that can control pore size from sub-nm to >5 nm, a pore size range required for membranes with effective molecular separation. Here we report a dry, facile, and scalable process introducing atomic defects by design, followed by selective etching of graphene edge atoms able to controllably expand the nanopore dimensions from sub-nm to 5 nm. The attainable average pore sizes at 1015 m-2 pore density promise applicability to various separation applications. We investigate the gas permeation and separation mechanisms, finding that these membranes display molecular sieving (H2/CH4 separation factor = 9.3; H2 permeance = 3370 gas permeation units (GPU)) and reveal the presence of interweaved transport phenomena of pore chemistry, surface flow, and gas molecule momentum transfer. We observe the smooth transition from molecular sieving to effusion at unprecedented permeance (H2/CH4 separation factor = 3.7; H2 permeance = 107 GPU). Our scalable graphene membrane fabrication approach in combination with sub-5 nm pores opens a new route employing 2D membranes to study gas transport and effectively paving the way to industrial applications.

Wind Power Prediction for Wind Farm Clusters Based on the Multifeature Similarity Matching Method

Regional wind power prediction (WPP) is conducive to achieving scientific dispatch of the power system as well as improving its reliability. Data mining based on a large number of samples is an effective way to improve the accuracy of WPP. A new regional power forecasting method in the context of data mining is proposed in the article. First, a previously described regional WPP method, single feature similarity matching (SFSM) method, is analyzed and a new multifeature similarity matching (MFSM) method is proposed. Second, the optimization and analysis processes of four key parameters in the MFSM method are proposed and the impact of each key parameter on prediction error and the applicability of the method under different regional scales is analyzed. Finally, the new method and the optimization and analysis processes are verified by wind farm clusters, composed of 52 wind farms in northeast China, and the new method is compared with the conventional method, such as additive method, statistical up-scaling method, and the SFSM method. The results show that the improved MFSM method is superior to the conventional prediction method, whereby the root mean square error (RMSE) of 0 to 2 h is reduced by 3.65% and the RMSE of 0 to 4 h is reduced by 1.56%. The new method has been proved to be an effective WPP method for wind farm clusters and has potential industrial application prospects.

3D-nano-hetero-structured n/n junction, CuO/Ru–ZnO thin films, for hydrogen generation with enhanced photoelectrochemical performances

Hydrogen, derived from solar-water splitting, is a clean and renewable fuel for which per gram energy storage capacity is even higher than fossil fuels. Towards the development of a viable technology for above conversion, this report describes enhanced performance in photoelectrochemical water splitting using uniquely evolved nano-hetero-structured bilayered thin films, CuO/Ru–ZnO as photoanode. Grown over ITO (In:SnO2) glass substrates by using low-cost and easily up-scalable wet chemical methods, films were characterized for microstructure, optical behaviour and surface characteristics, using XRD and other spectral measurements viz. FESEM, AFM, TEM, UV–Visible Spectroscopy, EDX and XPS. Against monolayered pristine films of CuO and ZnO, bilayered films yielded a major gain in PEC water splitting photocurrent, on being used as working electrode in PEC cell, in conjunction with platinum counter electrode and saturated calomel reference electrode (electrolyte solution 0.1 M NaOH solution, pH 13, temperature 30 ± 3.6 °C). Films with 1% Ru-incorporation yielded highest photocurrent (2.04 mA/cm2). Enhanced photoactivity of bilayered films was found correlated with increments in light absorption, charge carrier density and film surface area, coupled with reduced electrical resistivity. The study highlights an important role played by Ru added in ZnO overlayer, apparently existing as RuO2 nanoparticles dispersed in ZnO lattice, in hole-transfer from valence band of CuO underlayer to electrolyte, thereby imparting a significant boost on photocurrent generation.

Surface Modified Copper Alloy Powder for Reliable Laser-based Additive Manufacturing

Owing to the high optical reflectivity of copper, silver, and gold in the infrared region, high laser power is required for laser-based additive manufacturing (L-AM). This increases the risk of damaging the laser optics due to sustained back-reflections and renders L-AM of reflective metals an unsustainable technology. To tackle this issue, a novel, industrially upscalable powder surface modification method is proposed and validated using a CuCr1 alloy. The surface of CuCr1 powder is modified by the outward diffusion of chromium in a nitrogen atmosphere, forming a rim around the powder particles. This doubled the optical absorption of the powder. Consequently, a mere 20% of the laser energy is required to process the surface-modified powder by laser powder bed fusion compared to the virgin CuCr1 powder. The fabricated parts demonstrate a very high thermal conductivity of 370 ± 15 W/(m·K) and tensile strength of 439 ± 19 MPa, after applying a suitable post-heat treatment.

Perfil de velocidad promedio entre una capa de fluido y un medio poroso: La capa límite de Brinkman

It has been mentioned that, the existence of some terms in Darcy's law are the result of the up-scaling method applied to the Stokes flow problem at the pore scale. To address this debate, in this work we perform, at the pore-scale, flow simulations in a free fluid/porous medium system using different models of granular porous media. The local velocity obtained from the Stokes equation allows to obtain the Darcy-scale velocity profiles by a direct averaging instead of using the up-scaled model. The results show the existence of a smooth transition zone in the average velocity profiles near the free fluid/porous medium inter-region. The size and shape of such transition zone depend on the size of the averaging domain and they are a result of averaging local quantities and not a result of solving average equations. In this way, we confirm the existence of an average velocity boundary layer (i.e. Brinkman boundary layer); thus the pertinence of considering other terms in Darcy's law can be certainly justified. We have also determined the extension of the influence of the flow in the free fluid inside the porous medium and the perturbation of the flow in porous medium on the flow in the free fluid.

Upscaling capillary pressure curves for numerical modeling of gravity-capillary driven flow

This work investigates upscaling of capillary pressure curves for modeling gravity segregation under the influence of capillary heterogeneity. We consider two flowing phases driven by gravity and capillary forces and seek the saturation spatial and temporal variation until equilibrium is reached. Existing upscaling methods, found in the literature, are applied to a number of cases. Resulting saturation solutions are compared to fine-scale simulations and the different methods are evaluated, showing in general that the popular capillary limit method produces the best results. However, a large number of cases are found to have significant errors. This leads to the conclusion that all existing methods are often inadequate and developing new methods should be considered. We therefore propose a new optimization-based upscaling method. Using this approach it is shown that capillary pressure can be upscaled to Brooks-Corey type functions and produce accurate upscaled simulations matching the fine-scale solutions. Optimization upscaling is computationally demanding and requires the fine-scale simulations for minimizing an objective function. However, it is shown that the upscaled curves can be applied to different permeability realizations to calculate ensemble average saturation solutions.

Satellite Remote Sensing Contributions to Wildland Fire Science and Management

This paper reviews the most recent literature related to the use of remote sensing (RS) data in wildland fire management. Studies dealing with pre-fire assessment, active fire detection, and fire effect monitoring are reviewed in this paper. The analysis follows the different fire management categories: fire prevention, detection, and post-fire assessment. Extracting the main trends from each of these temporal sections, recent RS literature shows growing support of the combined use of different sensors, particularly optical and radar data and lidar and optical passive images. Dedicated fire sensors have been developed in the last years, but still, most fire products are derived from sensors that were designed for other purposes. Therefore, the needs of fire managers are not always met, both in terms of spatial and temporal scales, favouring global over local scales because of the spatial resolution of existing sensors. Lidar use on fuel types and post-fire regeneration is more local, and mostly not operational, but future satellite lidar systems may help to obtain operational products. Regional and global scales are also combined in the last years, emphasizing the needs of using upscaling and merging methods to reduce uncertainties of global products. Validation is indicated as a critical phase of any new RS-based product. It should be based on the independent reference information acquired from statistically derived samples. The main challenges of using RS for fire management rely on the need to improve the integration of sensors and methods to meet user requirements, uncertainty characterization of products, and greater efforts on statistical validation approaches.

Identifying determinants of straw open field burning in northeast China: Toward greening agriculture base in newly industrializing countries

Abstract Soil depletion caused by SB and its negative repercussions on food safety and the sustainable development of agriculture are essential concerns in newly industrializing countries. Understanding and curtailing SB in specific regions is related to the analysis of its structural characteristics and justice transition. Due to the banning policy in China, the large-scale interview of farmers' motivations and behavior regarding SB is impracticable. As such, we attempted to improve the understanding of the influencing factors of SB in northeast China (a commodity grain base) by applying the up-scaling method, by using MODIS fire data on cropland, statistical socioeconomic data, and resource and environment data as well as factor analysis and multiple linear regression analysis. We found that bio-physical factors, agricultural input-output, economic development, and crop types are significant determinants of the intensity of SB. In the end, we asserted policy implications for addressing SB in northeast China.

An efficient method to prepare supported bismuth nanoparticles as highly selective electrocatalyst for the conversion of CO2 into formate.

We report a cost-effective, straightforward synthesis of a novel electrocatalyst for the reduction of CO2 to formate, which achieves nearly complete Faradaic efficiency (FE) at an overpotential (η) of 0.88 V under ambient conditions. The electrocatalyst was prepared using bismuth subsalicylate as precursor and consists of bismuth nanoparticles (Bi NPs) with an average diameter of 5.5 nm supported on activated carbon.

Sensitivity of methods for calculating environmental flows based on hydrological characteristics of watercourses regarding the hydropower potential of rivers

The paper analyses selected problems with the estimation of environmental flows (EF) in the aspect of hydroelectric potential of rivers. The study was conducted for mountain catchments located in the upper Vistula catchment in Poland: Mszanka, Poroniec, Grajcarek, Ochotnica, and Kamienica Nawojowska. The data for calculations, in the form of observational series of daily flows in the years 1985-2014, were obtained from the Institute of Meteorology and Water Management of the National Research Institute in Warsaw. Based on the data, environmental flows were calculated as 25% Mean Annual Flow (MAF), 70% Median Flow, Q90, 7Q10, 7Q2, and additionally with the Eflows Management Framework and Upscaling method (EMFU). The calculations made it possible to indicate the main problems related to the calculation of environmental flows using hydrological methods: selection of the appropriate characteristic flow, the method of determining guaranteed flows, selection of appropriate statistical distributions or sensitivity of environmental flows to the length of the observation series for which they are esteemed. In addition, the paper showed that the choice of method for calculating the environmental flow influences the volume of electricity production in hydroelectric plants. For watercourses not covered by specific forms of protection, the compromise between environmental protection and investment economics seems to be calculating the EF value by 25% MAF or Q90. It was also found that it is optimal to maintain the value of EF (from the point of view of caring caring for the aquatic environment) along with choosing the economically justified options.

Multiresolution simultaneous upscaling of two features of the reservoir using the bandwidth of the kernel function and wavelet transformation

In this paper, we employ a new multiresolution upscaling method for the data in porous media. The method employs an adaptive bandwidth of the kernel function as the multiresolution upscaling operator. We have implemented a hierarchical multiresolution upscaling strategy, which is based on maintaining the important fine scale model structures of the reservoir. In this method, bandwidth is a function of the variability of cell, which controls the upscaling process. In areas with a high variability of the considered feature, small bandwidth leads to maintaining the fine scale structures; and in homogeneous reservoir areas, large bandwidths will lead to coarse-sized cells. In this paper, we have used this proposed method for simultaneous upscaling of two features: density and neutron logs. Determination of optimal bandwidth or threshold for each feature is an important challenge in the bandwidth method. Due to different variabilities of two properties or features, simultaneous upscaling should be performed to capture the variability of both features in the model. The concept of simultaneous upscaling provides a common coarse model for two properties. To prepare the SUTF model, two minimum and maximum bandwidth approaches are used. The upscaling algorithm has been applied for density and neutron logs. Although the fine scale model contains 2290 cells, the number of coarsened cells in SUTF model based on the minimum bandwidth and maximum bandwidth approaches are 402 and 110, respectively. In addition to this new proposed method, the method of wavelet transform has also been used as a well-known method for upscaling, and finally, the results of the two methods are compared. By comparing the results of the two methods, we observe that the upscaling error in the kernel bandwidth method is less than that in the wavelet transform method. The advantage of the kernel bandwidth method over the wavelet transform is the reduction of the loss of the main information as well as the reduction of the numerical dispersion in the new proposed method compared to the wavelet transform method. These benefits have appeared at the upscaling error that is less in the proposed method.

Evaporative fraction and its application in estimating daily evapotranspiration of water-saving irrigated rice field

Evaporative fraction (EF), which is known to exhibit variation in response to changes in crop species, soil and meteorologic conditions, plays an important role in interpreting the components of energy budget and estimating evapotranspiration (ET), while such information is scarce for humid rice fields. The present study discussed the variation of energy balance components and then examined the pattern of hourly, daytime and daily EF after monitoring energy components by eddy covariance for water-saving irrigated (WSI) rice paddies of 2015 and 2016. Then the daily ET was estimated by an improved EF up-scaling method in the subtropical monsoon climate region of East China. Diurnally, hourly EF is deemed as an approximately concave-up shape in different growth stages of rice season. The seasonal average EF varies gently, with a minimum around 10:00–11:00 AM. Seasonally, the mean daytime EF for the whole growth stage is 0.86, 7% lower than the daily value. Daily EF exhibits mostly higher than 0.8 except later yellow ripening period, approaching 1.0 in the milk stage. EF over WSI rice exhibits obviously greater than the reports that from upland crops. In addition, differences are noted in the results with respect to the daily ET estimation by EF up-scaling method. The estimated daily ET (ETEF,d) from hourly EF during 10:00–11:00 h is highly correlated to the measured ET (ETtrue) by the weighed micro-lysimeters though the ETEF,d value is underestimated. Such a considerable gap serves in forming a relationship between ETEF,d and ETtrue,d, that is, by simply multiplying the representativeness ET value based on the EF up-scaling method by a correction procedure calibrated for this region. In conclusion, an improved EF up-scaling method is proposed for extrapolating remote sensing based ET estimates to daily values.

Fast Super-Resolution of 20 m Sentinel-2 Bands Using Convolutional Neural Networks

Images provided by the ESA Sentinel-2 mission are rapidly becoming the main source of information for the entire remote sensing community, thanks to their unprecedented combination of spatial, spectral and temporal resolution, as well as their associated open access policy. Due to a sensor design trade-off, images are acquired (and delivered) at different spatial resolutions (10, 20 and 60 m) according to specific sets of wavelengths, with only the four visible and near infrared bands provided at the highest resolution (10 m). Although this is not a limiting factor in general, many applications seem to emerge in which the resolution enhancement of 20 m bands may be beneficial, motivating the development of specific super-resolution methods. In this work, we propose to leverage Convolutional Neural Networks (CNNs) to provide a fast, upscalable method for the single-sensor fusion of Sentinel-2 (S2) data, whose aim is to provide a 10 m super-resolution of the original 20 m bands. Experimental results demonstrate that the proposed solution can achieve better performance with respect to most of the state-of-the-art methods, including other deep learning based ones with a considerable saving of computational burden.

Dominance-caused differences in transpiration of trees in a Karst broadleaved mixed forest

Estimating stand transpiration of natural forests using traditional methods through up-scaling of sap flux density from sample trees based on stand sapwood area only is difficult because of the complexity of species, ages, and hierarchical structure of natural forests. To improve stand transpiration estimation, we developed an up-scaling method by considering the tree dominance effect based on the assumption that individual tree transpiration is affected by crown dominance and species, in addition to factors previously considered such as meteorological conditions, sapwood area, and soil moisture. In this study, the meteorological factors, soil moisture, and sap flux density of 15 sample trees of different species and dominance in a natural evergreen and deciduous broadleaved mixed forest were simultaneously monitored from March 2012 to February 2014 in the Karst mountain region in southwestern China. After establishing a single tree transpiration model which considers the effects of dominance and species, an up-scaling method was explored to estimate stand transpiration. The results show that the transpiration intensity increased exponentially with increasing tree dominance. The contribution to annual stand transpiration from a few dominant trees (5.4% of trees, 28.2% of basal area) was up to 65.0%. The corresponding contribution was 16.2% from sub-dominant trees (7.6% of trees, 16.2% of basal area) and 22.8% from middle- and lower-layer trees (87.0% of trees, 55.6% of basal area). The variation of individual tree transpiration was mainly (97.9%) explained by tree dominance, but very weakly by tree species. The estimated annual stand transpiration was 300.2 mm when using the newly developed method which considers tree dominance, 52.5 mm (14.9%) lower than the estimation (352.7 mm) of traditional method which considers only the sapwood area effect, and 8.5 mm (2.7%) lower than the estimation (308.6 mm) which considers the effects of both species composition and sapwood area. The main tree characteristics affecting stand transpiration are tree size (sapwood area) and dominance. Consideration of tree dominance will significantly improve stand transpiration estimation and provide a more solid basis for guiding integrated forest–water management at stand scale.

Evaluation and improvement of macroscopic yield criteria of porous media having a Drucker-Prager matrix

A large number of analytical strength criteria have been developed for porous materials having a Drucker-Prager solid matrix by using different up-scaling methods. A number of representative exisitng criteria are selected and summarized. These criteria are first evaluated and compared both analytically and numerically with new FEM solutions obtained in this work. A wide variety of new numerical results are then provided from finite element simulations to enlarge the comparisons. In particular, the strength under the pure shear condition is discussed and studied in depth, either numerically and theoretically. Based on these comparisons, a new improvement of the prediction of pure shear strength is established. With this improvement, we derive a new macroscopic strength criterion for the porous materials with a Drucker-Prager type solid matrix. The new criterion is validated against those numerical solutions for a wide range of porosity and frictional coefficient. The special case of a porous material with a von Mises type solid matrix is also studied with a good validation.

Direct Observation of Plasmon Band Formation and Delocalization in Quasi-Infinite Nanoparticle Chains.

Chains of metallic nanoparticles sustain strongly confined surface plasmons with relatively low dielectric losses. To exploit these properties in applications, such as waveguides, the fabrication of long chains of low disorder and a thorough understanding of the plasmon-mode properties, such as dispersion relations, are indispensable. Here, we use a wrinkled template for directed self-assembly to assemble chains of gold nanoparticles. With this up-scalable method, chain lengths from two particles (140 nm) to 20 particles (1500 nm) and beyond can be fabricated. Electron energy-loss spectroscopy supported by boundary element simulations, finite-difference time-domain, and a simplified dipole coupling model reveal the evolution of a band of plasmonic waveguide modes from degenerated single-particle modes in detail. In striking difference from plasmonic rod-like structures, the plasmon band is confined in excitation energy, which allows light manipulations below the diffraction limit. The non-degenerated surface plasmon modes show suppressed radiative losses for efficient energy propagation over a distance of 1500 nm.

Impact of Synthetic Porous Medium Geometric Properties on Solute Transport Using Direct 3D Pore-Scale Simulations

Transport processes in porous media have been traditionally studied through the parameterization of macroscale properties, by means of volume-averaging or upscaling methods over a representative elementary volume. The possibility of upscaling results from pore-scale simulations, to obtain volume-averaging properties useful for practical purpose, can enhance the understanding of transport effects that manifest at larger scales. Several studies have been carried out to investigate the impact of the geometric properties of porous media on transport processes for solute species. However, the range of pore-scale geometric properties, which can be investigated, is usually limited to the number of samples acquired from microcomputed tomography images of real porous media. The present study takes advantage of synthetic porous medium generation to propose a systematic analysis of the relationships between geometric features of the porous media and transport processes through direct simulations of fluid flow and advection-diffusion of a non-reactive solute. Numerical simulations are performed with the lattice Boltzmann method on synthetic media generated with a geostatistically based approach. Our findings suggest that the advective transport is primarily affected by the specific surface area and the mean curvature of the porous medium, while the effective diffusion coefficient scales as the inverse of the tortuosity squared. Finally, the possibility of estimating the hydrodynamic dispersion coefficient knowing only the geometric properties of porous media and the applied pressure gradient has been tested, within the range of tested porous media, against advection-diffusion simulations at low Reynolds (<10-1) and Peclet numbers ranging from 101 to 10-2.

A novel flow-based geometrical upscaling method to represent three-dimensional complex sub-seismic fault zone structures into a dynamic reservoir model

Most hydrocarbon reservoirs contain faults, which are highly complex heterogeneous and anisotropic three-dimensional (3D) volumes of deformed rock. A major technical challenge in full-field flow simulation is to represent the effects of 3D fault zone structure within the two-dimensional (2D) fault planar surfaces using the industry standard commercial reservoir flow simulator due to its limited functionality. Therefore, a new flow-based geometrical upscaling (FBGU) method has been developed for capturing the effects of 3D fault zone structures in conventional low-resolution upscaled flow simulation models. Geometrical upscaling (GU) is the process of calculating across-fault and up-fault transmissibility arising from 3D flow paths through fault zones, and expressing these transmissibilities as implicit connections in a low-resolution upscaled flow simulation model. The high accuracy of the method is demonstrated by comparing the flow responses of high-resolution (referred as truth model in this paper) simulation models in which the 3D fault zone structure is represented explicitly in the grid geometry, with that of conventional resolution models in which it is upscaled using FBGU method. The flow results show that the newly developed FBGU method is extremely accurate and geometrically flexible.

Hybridized Guided-Mode Resonances via Colloidal Plasmonic Self-Assembled Grating.

For many photonic applications, it is important to confine light of a specific wavelength at a certain volume of interest at low losses. So far, it is only possible to use the polarized light perpendicular to the solid grid lines to excite waveguide–plasmon polaritons in a waveguide-supported hybrid structure. In our work, we use a plasmonic grating fabricated by colloidal self-assembly and an ultrathin injection layer to guide the resonant modes selectively. We use gold nanoparticles self-assembled in a linear template on a titanium dioxide (TiO2) layer to study the dispersion relation with conventional ultraviolet–visible–near-infrared spectroscopic methods. Supported with finite-difference in time-domain simulations, we identify the optical band gaps as hybridized modes: plasmonic and photonic resonances. Compared to metallic grids, the observation range of hybridized guided modes can now be extended to modes along the nanoparticle chain lines. With future applications in energy conversion and optical filters employing these cost-efficient and upscalable directed self-assembly methods, we discuss also the application in refractive index sensing of the particle-based hybridized guided modes.