Upscaling Approach Research Articles

Development of Tools and Techniques to Survey, Assess, Stabilise, Monitor and Preserve Underwater Archaeological Sites: SASMAP

Abstract. SASMAP’s purpose is to develop new technologies and best practices in order to locate, assess and manage Europe’s underwater cultural heritage in a more effective way than is possible today. SASMAP has taken an holistic- and process- based approach to investigating underwater environments and the archaeological sites contained therein. End user of the results of SASMAP are severalfold; i) to benefiet the SMEs involved in the project and development of their products for the offshore industry (not just for archaeological purposes) ii) a better understanding of the marine environment and its effect on archaeological materials iii) the collation of the results from the project into guidelines that can be used by cultural resource managers to better administer and optimise developer lead underwater archaeological project within Europe in accordance with European legislation (Treaty of Valetta (1992). Summarily the project has utilised a down scaling approach to localise archaeological sites at a large scale regional level. This has involved using innovative satellite imagery to obtain seamless topography maps over coastal areas and the seabed (accurate to a depth of 6m) as well as the development of a 3D sub bottom profiler to look within the seabed. Results obtained from the downscaling approach at the study areas in the project (Greece and Denmark) have enabled geological models to be developed inorder to work towards predictive modelling of where submerged prehistoric sites may be encountered. Once sites have been located an upscaling approach has been taken to assessing an individual site and the materials on and within it in order to better understand the state of preservation and dynamic conditions of a site and how it can best be preserved through in situ preservation or excavation. This has involved the development of equipment to monitor the seabed environment (open water and in sediments), equipment for sampling sediments and assessing the state of preservation of wood, once of the common materials on archaeological sites. The guidelines and all information and experiences obtained during the course of the project will be utilised to enhance and develop existing legislation and best practice for mapping and preserving Europe’s underwater and coastal heritage. The project started in September 2012 and finished at the end of August 2015 and the aim of the paper is to give a brief introduction to the results of the project. Further information on the project is available at www.sasmap.eu

Satellite observation of tropical forest seasonality: spatial patterns of carbon exchange in Amazonia

Determining the seasonality of terrestrial carbon exchange with the atmosphere remains a challenge in tropical forests because of the heterogeneity of ecosystem and climate. The magnitude and spatial variability of this flux are unknown, particularly in Amazonia where empirical upscaling approaches from spatially sparse in situ measurements and simulations from process-based models have been challenged in recent scientific literature. Here, we use satellite proxy observations of canopy structure, skin temperature, water content, and optical properties over a period of 10 years (2000–2009) to constrain and quantify the spatial pattern and seasonality of carbon exchange of Amazonian forests. We identify nine regions through an optimized cluster approach with distinct leaf phenology synchronized with either water or light availability and corresponding seasonal cycles of gross primary production (GPP), covering more than 600 million ha of remaining old growth forests of Amazonia. We find South and Southwestern regions show strong seasonality of GPP with a peak in the wet season; while from Central Western to Northeastern Amazonia cover three regions with rising GPP in the dry season. The remaining four regions have significant but weak seasonality. These patterns agree with satellite florescence observations, a better proxy for photosynthetic activity. Our results suggest that only one-third of the patterns can be explained by the spatial autocorrelation caused by intra-annual variability of climate over Amazonia. The remaining two-thirds of variations are due to biogeography of the Amazon basin driven by forest composition, structure, and nutrients. These patterns, for the first time, provide a complex picture of seasonal changes of tropical forests related to photosynthesis and influenced by water, light, and stomatal responses of trees that can improve modeling of regional carbon cycle and future prediction of impacts of climate change.

Upscaling of CO2 injection into brine with capillary heterogeneity effects

The large-scale simulation of CO2 storage operations can be expensive computationally, particularly when the effects of fine-scale capillary pressure heterogeneity are included. The application of upscaling techniques could lead to substantial reductions in computational cost. This work targets the development of an upscaling procedure that is applicable for the CO2 injection stage, which corresponds to a drainage process. Specifically, we develop and apply a new upscaling technique for two-phase flow in heterogeneous formations with capillary heterogeneity effects. The procedure entails first upscaling capillary pressure in the capillary limit, and then computing coarse-scale relative permeability functions using a global dynamic upscaling procedure. An iterative method is applied to enhance the accuracy of the upscaled capillary pressure functions. The new dynamic upscaling approach is applied to a synthetic heterogeneous two-dimensional aquifer model that involves injection of CO2 into brine. Fine-scale simulation results are compared with coarse-scale results generated using both the dynamic upscaling approach and a simpler method that entails the use of upscaled capillary pressure in conjunction with rock relative permeability curves. It is shown that the dynamic upscaling procedure provides results that are close to those from the fine-scale simulation and are consistently more accurate than results from the simpler method. The upscaling procedure is tested over a range of injection rates spanning three orders of magnitude. We show that, although the upscaled functions are in general rate dependent, accurate coarse-scale results can be obtained using upscaled relative permeability functions computed at only two different flow rates. We also observe that the model constructed using our method retains reasonable accuracy even when the flow problem differs from that used to compute the upscaled functions.

Deriving Regional Crown Closure Using Spectral Mixture Analysis Based on Up-Scaling Endmember Extraction Approach and Validation

This paper investigates the retrieval of forest crown closure (CC) from the Landsat Thematic Mapper (TM) data and aerial images with a linear spectral mixture analysis (SMA) method. Anshan is selected as the study area. Two endmember extraction methods were used in this paper: 1) traditional image-based method and 2) up-scaling method. (When we get the fractions of components from a coregistered 0.6-m spatial resolution image, the linear spectral mixture model is applied to unmix the TM image and obtain the required endmembers.) For both methods, four fraction images (sunlit canopy, shaded canopy, sunlit background, shaded background) were calculated by linear spectral mixture model and used to derive CC. Results showed that CC can be fitted best with sum of fractions of sunlit canopy and shaded canopy at S-shaped curve and the up-scaling endmember extraction method is better than traditional image-based endmember extraction method. Finally, the up-scaling endmember extraction method was used to map forest CC in Anshan forested region. The measured forest CC distribution map was used to validate the estimated map. Results show that the estimated CC and measured CC have little difference and the estimated CC is slightly lower. The majority of Anshan forest CC values were between 0.4 and 0.8.

An up-scalable approach to CH3NH3PbI3 compact films for high-performance perovskite solar cells

In this work, we describe an up-scalable, two step approach to prepare CH3NH3PbI3 perovskite films with high quality and exceptional uniformity at centimeter-scale (5.0cm×5.0cm). The resulting solar cells achieve efficiency up to 16% with an average efficiency of 14.3% for small-area devices. Remarkably, devices with size of 1.0cm×1.0cm made on the 5.0cm×5.0cm perovskite films display a very impressive efficiency up to 12.6% with an average efficiency of 10.9% (for 48 devices), which is significantly superior to previous reports (<9.0% efficiency) with centimeter-sized devices. The present approach combines the advantages of the short reaction time, facile fabrication, exceptional uniformity, good reproducibility, high device performance and up-scalability, enabling it the potential ability in large-scale photovoltaic applications.

Upscaling Kinetics for Field-Scale In-Situ-Combustion Simulation

Summary We demonstrate the effectiveness of a non-Arrhenius kinetic upscaling approach for in-situ-combustion processes, first discussed by Kovscek et al. (2013). Arrhenius reaction terms are replaced with equivalent source terms that are determined by a work flow integrating both laboratory experiments and high-fidelity numerical simulations. The new formulation alleviates both stiffness and grid dependencies of the traditional Arrhenius approach. Consequently, the computational efficiency and robustness of simulations are improved significantly. In this paper, we thoroughly investigate the performance of the non-Arrhenius upscaling method compared with Arrhenius kinetics. We investigate robustness by considering grid effects and sensitivity to heterogeneity. Performance improvements of the new kinetic upscaling approach compared with traditional Arrhenius kinetics are demonstrated through numerical experiments in one and two dimensions for both homogeneous- and heterogeneous-permeability fields.

3D analysis of paper microstructures at the scale of fibres and bonds

The evolution of paper microstructure parameters, such as porosity and fibre orientation, as a function of papermaking conditions is most often studied at a macroscopic scale. However, modelling the physical and mechanical properties of papers using upscaling approaches requires understanding the deformation micro-mechanisms that are induced by papermaking operations within the structure of paper fibrous networks for individual fibres and fibre-to-fibre bonds. We addressed this issue by analysing three-dimensional images of model papers. These images were obtained using X-ray microtomography. The model papers were fabricated by varying forming, pressing, and drying conditions. For each image, this analysis enabled an unprecedented large set of geometrical parameters to be measured for individual fibres (centreline, shape and inclination of the fibre cross sections) and fibre-to-fibre bonds (inter-bond distance, number of bonds per unit length of fibre, bond surface area) within the fibrous networks. The evolution of the as-obtained microstructure parameters was analysed as a function of papermaking conditions. All results were in accordance with the data available in the literature. A key result was obtained for the evolution of the number of fibre-to-fibre contacts per fibre as a function of the network density. A representative number of contacts was obtained using relatively small imaged volumes. These volumes must only contain enough fibre segments the cumulated length of which is of the same order as the mean fibre length. These results were also used to validate microstructure models for the prediction of the number of fibre-to-fibre contacts within fibrous networks.

On the upscaling of mass transfer rate expressions for interpretation of source zone partitioning tracer tests

AbstractAnalysis of partitioning tracer tests conducted in dense nonaqueous phase liquid (DNAPL) source zones relies on conceptual models that describe mass exchange between the DNAPL and aqueous phases. Such analysis, however, is complicated by the complex distribution of entrapped DNAPL mass and formation heterogeneity. Due to parameter uncertainty in heterogeneous regions and the desire to reduce model complexity, the effect of mass transfer limitations is often neglected, and an equilibrium‐based model is typically used to interpret test results. This work explores the consequences of that simplifying assumption on test data interpretation and develops an alternative upscaled modeling approach to quantify effective mass transfer rates. To this end, a series of partitioning tracer tests is numerically simulated in heterogeneous two‐dimensional PCE‐DNAPL source zones, representative of a range of hydraulic conductivity and DNAPL mass distribution characteristics. The effective mass transfer coefficient corresponding to each test is determined by fitting an upscaled model to the simulated data, and regression analysis is performed to explore the correlation between various source zone metrics and the effective mass transfer coefficient. Results suggest that vertical DNAPL spreading, Reynolds number, pool fraction, and the effective organic phase saturation are the most significant parameters controlling tracer partitioning rates. Finally, a correlation for prediction of the effective (upscaled) mass transfer coefficient is proposed and verified using existing experimental data. The developed upscaled model incorporates the influence of physical heterogeneity on the rate of tracer partitioning and, thus, can be used for the estimation of source zone mass distribution characteristics from tracer test results.

Numerical study of solute transport in shallow beach aquifers subjected to waves and tides

AbstractA numerical study was conducted to investigate the fate of solute in a laboratory beach in response to waves and tides. A new temporal upscaling approach labeled “net inflow” was introduced to address impacts of waves on solute transport within beaches. Numerical simulations using a computational fluid dynamic model were used as boundary conditions for the two‐dimensional variably saturated flow and solute transport model MARUN. The modeling approach was validated against experimental data of solute transport due to waves and tides. Exchange fluxes across the beach face and subsurface solute transport (e.g., trajectory, movement speed, and residence time) were quantified. Simulation results revealed that waves increased the exchange fluxes, and engendered a wider exchange flux zone along the beach surface. Compared to tide‐only forcing, waves superimposed on tide caused the plume to be deeper into the beach, and to migrate more seaward. The infiltration into the beach was found to be directly proportional to the general hydraulic gradient in the beach and inversely proportional to the matrix retention (or capillary) capacity. The simulations showed that a higher inland water table would attenuate wave‐caused seawater infiltration, which might impact beach geochemical processes (e.g., nutrient recycle and redox condition), especially at low tide zone. The concept of biochemical residence time maps (BRTM) was introduced to account for the net effect of limiting concentration of chemicals on biochemical reactions. It was found that waves shifted the BRTMs downward and seaward in the beach, and subsequently they engendered different biochemical conditions within the beach.

Resolution enhancement of textual images via multiple coupled dictionaries and adaptive sparse representation selection

Resolution enhancement has become a valuable research topic due to the rapidly growing need for high-quality images in various applications. Various resolution enhancement approaches have been successfully applied on natural images. Nevertheless, their direct application to textual images is not efficient enough due to the specificities that distinguish these particular images from natural images. The use of insufficient resolution introduces substantial loss of details which can make a text unreadable by humans and unrecognizable by OCR systems. To address these issues, a sparse coding-based approach is proposed to enhance the resolution of a textual image. Three major contributions are presented in this paper: (1) Multiple coupled dictionaries are learned from a clustered database and selected adaptively for a better reconstruction. (2) An automatic process is developed to collect the training database, which contains writing patterns extracted from high-quality character images. (3) A new local feature descriptor well suited for writing specificities is proposed for the clustering of the training database. The performance of these propositions is evaluated qualitatively and quantitatively on various types of low-resolution textual images. Significant improvements in visual quality and character recognition rates are achieved using the proposed approach, confirmed by a detailed comparative study with state-of-the-art upscaling approaches.

Anchoring ultra-fine TiO2–SnO2solid solution particles onto graphene by one-pot ball-milling for long-life lithium-ion batteries

A low cost, up-scalable and one-pot wet-mechanochemical approach is designed for fabricating TiO2–SnO2@graphene nanocomposites where TiO2and SnO2solid solution nanoparticles are evenly anchored on graphene sheets.

An up-scaling approach for vapour extraction process in heavy oil reservoirs

Although some studies are performed and a series of analytical models are developed, it has been found that current analytical models are not accurately predicting the production rate by VAPEX. This is largely because the diffusion used in the current model is based on a single fluid property (oil viscosity only) while other properties such as permeability, porosity and cementation factor carry large amount of uncertainties. The main objective of this study was to use the experimental data obtained from two-dimensional (2D) and three-dimensional (3D) physical models and develop a new and more accurate correlation for diffusivity that takes into account fluid and reservoir properties based on Butler's equation. In order to develop such an accurate correlation, various parameters such as porosity, cementation factor, permeability, and viscosity were included to history match the experimental data and tune the diffusivity correlation. Next the validity of the correlation was proved using 3D experimental data and data obtained from a field pilot test. It has been observed that diffusion rate is not only a function of viscosity but also it is a function of permeability, porosity, and cementation factor. [Received: October 16, 2013; Accepted: April 24, 2014]

Fano-resonant aluminum and gold nanostructures created with a tunable, up-scalable process

An up-scalable approach for creating Fano-resonant nanostructures on large surfaces at visible wavelengths is demonstrated. The use of processes suitable for high throughput fabrication and the choice of aluminum as a cost-efficient plasmonic material ensure that the presented insights are valuable even in consideration of typical industrial constraints. In particular, wafer-scale fabrication and the process compatibility with roll-to-roll embossing are demonstrated. It is shown that through adjustment of readily accessible evaporation parameters, the shape and position of the optical resonance can be tuned within a spectral band of more than 70 nm. The experimental data are complemented with rigorous coupled wave analysis and surface integral equation simulations. Calculated electric fields as well as surface charges shed light onto the physics behind the present resonances. In particular, a surface plasmon polariton is found to couple to a localized plasmonic mode with a hexapolar charge distribution, leading to a Fano-like resonance. Further understanding of the interactions at hand is gained by considering both aluminum and gold nanostructures.

Single-phase Near-well Permeability Upscaling and Productivity Index Calculation Methods

Reservoir models with many grid blocks suffer from long run time; it is hence important to deliberate a method to remedy this drawback. Usual upscaling methods are proved to fail to reproduce fine grid model behaviors in coarse grid models in well proximity. This is attributed to rapid pressure changes in the near-well region. Standard permeability upscaling methods are limited to systems with linear pressure changes; therefore, special near-well upscaling approaches based on the well index concept are proposed for these regions with non-linear pressure profile. No general rule is available to calculate the proper well index in different heterogeneity patterns and coarsening levels. In this paper, the available near-well upscaling methods are investigated for homogeneous and heterogeneous permeability models at different coarsening levels. It is observed that the existing well index methods have limited success in reproducing the well flow and pressure behavior of the reference fine grid models as the heterogeneity or coarsening level increases. Coarse-scale well indexes are determined such that fine and coarse scale results for pressure are in agreement. Both vertical and horizontal wells are investigated and, for the case of vertical homogeneous wells, a linear relationship between the default (Peaceman) well index and the true (matched) well index is obtained, which considerably reduces the error of the Peaceman well index. For the case of heterogeneous vertical wells, a multiplier remedies the error. Similar results are obtained for horizontal wells (both heterogeneous and homogeneous models).

Instantaneous-to-daily GPP upscaling schemes based on a coupled photosynthesis-stomatal conductance model: correcting the overestimation of GPP by directly using daily average meteorological inputs.

Daily canopy photosynthesis is usually temporally upscaled from instantaneous (i.e., seconds) photosynthesis rate. The nonlinear response of photosynthesis to meteorological variables makes the temporal scaling a significant challenge. In this study, two temporal upscaling schemes of daily photosynthesis, the integrated daily model (IDM) and the segmented daily model (SDM), are presented by considering the diurnal variations of meteorological variables based on a coupled photosynthesis-stomatal conductance model. The two models, as well as a simple average daily model (SADM) with daily average meteorological inputs, were validated using the tower-derived gross primary production (GPP) to assess their abilities in simulating daily photosynthesis. The results showed IDM closely followed the seasonal trend of the tower-derived GPP with an average RMSE of 1.63 g C m(-2) day(-1), and an average Nash-Sutcliffe model efficiency coefficient (E) of 0.87. SDM performed similarly to IDM in GPP simulation but decreased the computation time by >66%. SADM overestimated daily GPP by about 15% during the growing season compared to IDM. Both IDM and SDM greatly decreased the overestimation by SADM, and improved the simulation of daily GPP by reducing the RMSE by 34 and 30%, respectively. The results indicated that IDM and SDM are useful temporal upscaling approaches, and both are superior to SADM in daily GPP simulation because they take into account the diurnally varying responses of photosynthesis to meteorological variables. SDM is computationally more efficient, and therefore more suitable for long-term and large-scale GPP simulations.

Carbon dioxide emissions from dry watercourses

Temporary watercourses that naturally cease to flow and run dry comprise a notable fraction of the world’s river networks, yet estimates of global carbon dioxide (CO2) emissions from watercourses do not consider emissions from these systems when they are dry. Using data from a sampling campaign in a Mediterranean river during the summer drought period, we demonstrate that the CO2 efflux from dry watercourses can be substantial, comparable to that from adjacent terrestrial soils and higher than from running or stagnant waters. With an up-scaling approach, we show that including emissions from dry watercourses could increase the estimate of CO2 emissions from watercourses in our study region by 0.6–15%. Moreover, our results tentatively illustrate that emissions from dry watercourses could be especially important in arid regions, increasing the estimate of global CO2 emissions from watercourses by 0.4–9%. Albeit relatively small, the contribution of dry watercourses could help to constrain the highly uncertain magnitude of the land carbon sink. We foresee that in many areas of the world, the expected increase in the extent of temporary watercourses associated with future global change will increase the relevance of CO2 emissions from dry watercourses.

On the interface boundary conditions for the Stokes-Darcy coupling problem

Recently, the Stokes-Darcy coupling flow problem has been taken much attention because of its importance in the fractured vuggy carbonate reservoirs. However, the descriptive equations for a free-flow region and a porous medium are different from each other due to the scale difference. Therefore, a suitable interface boundary conditions should be found to couple such two flows. To this end, a theoretical development is conducted based on the volume averaging up-scaling approach, which starts from the mathematical models on the micro pore-scale. After that, a novel set of interface conditions at the fluid-porous interface is developed. Such novel interface conditions are similar to the Beavers-Joseph conditions. However, a new coefficient has been introduced to modify the Darcy velocity. This coefficient is not only the function of the porosity and permeability of the porous medium, but also related to the structure characteristic of the interface transition zone. We have compared the theory with the experimental studies of Beavers-Joseph and our LDA experiment data. The results have shown that our new interface boundary conditions provide better agreement with the experimental data than the previous study.

A simple and scalable approach towards the preparation of superhydrophobic surfaces – importance of the surface roughness skewness

A simple and easily up-scalable approach towards the preparation of fluorine-free superhydrophobic surfaces is proposed. Surfaces with water contact angle (WCA) as high as 170° and contact angle hysteresis (CAH) down to 5° are obtained on industrial metallic foils (cold-rolled aluminium foils and electrodeposited copper foils) coated thanks to an atmospheric pressure plasma-enhanced chemical vapour deposition method. Nano- and micro-scale roughness characterisation of the surface, performed by atomic force microscopy (AFM) and confocal microscopy, provided evidence for the substrate surface skewness as the major parameter influencing the WCA for identical nano-rough plasma-polymerised PDMS coatings. A symmetric height distribution, Rskm = 0, is shown to be more desirable to achieve superhydrophobic surfaces.

Mini-Workshop: Numerical Upscaling for Media with Deterministic and Stochastic Heterogeneity

This minisymposium was third in series of similar events, after two very successful meetings in 2005 and 2009. The aim was to provide a forum for an extensive discussion on the theoretical aspects and on the areas of application and validity of numerical upscaling approaches for heterogeneous problems with deterministic and stochastic coefficients. The intensive discussions during the meeting contributed to a better understanding of upscaling approaches for multiscale problems with stochastic coefficients, and for synergy between scientists coming to this topic from the area of deterministic multiscale problems on one hand, and those coming from the area of SPDE on the other hand. Recent advanced results on upscaling approaches for deterministic multiscale problems were presented, well mixed with strong presentations on SDE and SPDE. The open problems in these areas were discussed, with emphasis on the case of stochastic coefficients brainstorming numerous numerical upscaling approaches. A number of young researchers, very actively working in these areas, were involved in the workshop discussing the links between scales., thus ensuring the continuity between the generations of researchers.

Large-scale mapping of aboveground biomass of tropical rainforest in Sulawesi, Indonesia, using Landsat ETM+ and MODIS data

This study combined 30-m spatial resolution Landsat Enhanced Thematic Mapper Plus (ETM+) data and 500-m spatial resolution Moderate Resolution Imaging Spectroradiometer (MODIS) data, together with field data, to up-scale aboveground biomass (AGB) of tropical rainforests in Sulawesi, Indonesia. Contrasting to usual up-scaling approaches, this study uses in the intermediate step an estimation method based on application of geostatistics in the Landsat ETM+ spectral feature space. To connect ground-based measurements with spectral reflectance in Landsat ETM+ bands, this method employs ordinary Kriging in the three-dimesional (3-D) space where spectral features of satellite data are used instead of geographic coordinates. The most appropriate combination of the 3-D space spectral bands (bands 4 and 5) was then assigned with corresponding MODIS bands. In the final step, AGB could be mapped over the large area covered by the MODIS data. The results of the study indicate the effectiveness of the developed up-scaling method with respect to dealing with the problem of resolution mismatch between the ground sampling plots and the MODIS data.