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Modeling gas flow through fractures of subsurface rock is a particularly challenging problem because of the heterogeneous nature of the material. High-fidelity simulations using discrete fracture network (DFN) models are one methodology for predicting gas particle breakthrough times at the surface, but are computationally demanding. We propose a Bayesian machine learning method that serves as an efficient surrogate model, or emulator, for these three-dimensional DFN simulations. Our model trains on a small quantity of simulation data and, using a graph/path-based decomposition of the fracture network, rapidly predicts quantiles of the breakthrough time distribution. The approach, based on Gaussian Process Regression (GPR), outputs predictions that are within 20-30% of high-fidelity DFN simulation results. Unlike previously proposed methods, it also provides uncertainty quantification, outputting confidence intervals that are essential given the uncertainty inherent in subsurface modeling. Our trained model runs within a fraction of a second, which is considerably faster than other methods with comparable accuracy and multiple orders of magnitude faster than high-fidelity simulations.

We model flow and transport in three-dimensional fracture networks with varying degrees of fracture-to-fracture aperture/permeability heterogeneity and network density to show how changes in these properties can cause the emergence of anomalous flow and transport behavior. If fracture-to-fracture aperture heterogeneity is increased in sparse networks, velocity fluctuations can inhibit high flow rates and solute transport can be delayed, even in cases where hydraulic aperture is monotonically increased. As the density of the networks is increased, more connected pathways allow for particles to bypass these effects. We discover transition behavior where with relatively few connected pathways in a network from inflow to outflow boundaries, the first arrival times of particles are not heavily affected by fracture-to-fracture aperture heterogeneity, but the scaling behavior of the tails is strongly influenced due to the particles being forced to sample some of the heterogeneity in the velocity field caused by aperture differences. These results reinforce the importance of considering multi-scale effects in fractured systems and can inform flow and transport processes in both natural and engineered fracture systems, especially the latter where high aperture fractures are often stimulated and connect to existing fracture networks with smaller apertures.

We performed a set of numerical simulations to characterize the interplay of fracture network topology, upscaling, and mesh refinement on flow and transport properties in fractured porous media. We generated a set of generic three-dimensional discrete fracture networks at various densities, where the radii of the fractures were sampled from a truncated power-law distribution, and whose parameters were loosely based on field site characterizations. We also considered five network densities, which were defined using a dimensionless version of density based on percolation theory. Once the networks were generated, we upscaled them into a single continuum model using the upscaled discrete fracture matrix model presented by Sweeney et al. We considered steady, isothermal pressure-driven flow through each domain and then simulated conservative, decaying, and adsorbing tracers using a pulse injection into the domain. For each simulation, we calculated the effective permeability and solute breakthrough curves as quantities of interest to compare between network realizations. We found that selecting a mesh resolution such that the global topology of the upscaled mesh matches the fracture network is essential. If the upscaled mesh has a connected pathway of fracture (higher permeability) cells but the fracture network does not, then the estimates for effective permeability and solute breakthrough will be incorrect. False connections cannot be eliminated entirely, but they can be managed by choosing appropriate mesh resolution and refinement for a given network. Adopting octree meshing to obtain sufficient levels of refinement leads to fewer computational cells (up to a 90% reduction in overall cell count) when compared to using a uniform resolution grid and can result in a more accurate continuum representation of the true fracture network., Comment: 31 pages, 11 figures, 3 tables

Modelling fluid flow and water-rock interaction in fractured crust using a Discrete Fracture Network approach Groundwater accounts for around 25% of the world’s fresh water supply. Due to the increasing anthropogenic pressure on shallow aquifers as well as climate change that is impacting global groundwater recharge, there is an increasing need to access deeper groundwater resources, which are frequently hosted in fractured-rock formations. The migration of groundwater (and other types of fluids, in general) in fractured rocks allows the contact between fluids in geochemical disequilibrium with the host rocks (i.e., large geochemical gradients) promoting water-rock reactions inside the fractures. These reactions may influence the permeability and porosity, as well as they may lead to fracture sealing. So, a thorough understanding of the coupled hydro-chemical processing that occur in fractured media is important for applications such as the sustainable exploitation of the afore-mentioned reserves, the protection and remediations of aquifers used for drinking water production or the safety analyses of deep geological repositories for spent nuclear fuel. In fractured rocks, groundwater flows in specific pathways and interacts with the host rock which may lead to the change in the hydro-geochemical conditions. The prediction of these interactions become critical for a proper management of the different applications. Therefore, the understanding and modelling of fluid-fracture interaction is of high scientific and commercial interest. Using the software dfnWorks, it is possible to model the fluid transport using a non-reactive Lagrangian method (particle tracking). In this contribution, we intend to implement geochemical reactions in dfnWorks to quantify the impact of these reactions in the fracture network. In fact, flow of water through Discrete Fracture Networks leads to interaction between water and the minerals occurring in the fracture plane and thus alters the underlying groundwater flow patterns. Thus, using these DFN-based reactive transport simulations, we aim at predicting the effect that chemical reactions have on flow and channeling. Besides presenting a proof-of-concept set of calculations, we will also present preliminary results of a real-case application, where fracture filling is produced as a result of a chemical imbalance.

International audience; evaluate the use of graphs as a fast and relevant substitute to DFNs. Graphs reduce the DFNs’ complexity to their connectivity structure by forming an assembly of nodes connected by edges, to which physical properties, like a conductance, can be assigned. Both the graph architecture (either fracture- or intersection- based) and the edge conductance definition, have an impact on the estimation of flow and transport parameters. The intersection graph brings a reliable description of the flow connectivity but with edge redundancy in fractures with a large number of intersections. As a consequence, the expression of the edge conductances should depend on the number of intersections in the fracture plane. We first introduce some of our previous work which propose a reliable expression of the edge conductance in the case of a pair of intersections. For the intersection graph, a correction on the conductance expression is proposed for fractures with a large number of intersections. Both graphs provide very good estimate of the bulk permeability although they tend to slightly overestimate it when the DFN connectivity increases (~×2) certainly due to fractures with large intersection numbers. We address this issue by analyzing flow simulations on a fracture with multiple intersections. We also propose another way to correct the intersection graph, which consists in removing redundant edges. The method drastically simplifies the intersection graph, which is promising in term of computational time. The bulk permeability is overestimated by a factor of 2.3 but independently of the DFN density and connectivity.

We present the near-Maximal Algorithm for Poisson-disk Sampling (nMAPS) to generate point distributions for variable resolution Delaunay triangular and tetrahedral meshes in two and three-dimensions, respectively. nMAPS consists of two principal stages. In the first stage, an initial point distribution is produced using a cell-based rejection algorithm. In the second stage, holes in the sample are detected using an efficient background grid and filled in to obtain a near-maximal covering. Extensive testing shows that nMAPS generates a variable resolution mesh in linear run time with the number of accepted points. We demonstrate nMAPS capabilities by meshing three-dimensional discrete fracture networks (DFN) and the surrounding volume. The discretized boundaries of the fractures, which are represented as planar polygons, are used as the seed of 2D-nMAPS to produce a conforming Delaunay triangulation. The combined mesh of the DFN is used as the seed for 3D-nMAPS, which produces conforming Delaunay tetrahedra surrounding the network. Under a set of conditions that naturally arise in maximal Poisson-disk samples and are satisfied by nMAPS, the two-dimensional Delaunay triangulations are guaranteed to only have well-behaved triangular faces. While nMAPS does not provide triangulation quality bounds in more than two dimensions, we found that low-quality tetrahedra in 3D are infrequent, can be readily detected and removed, and a high quality balanced mesh is produced., Comment: arXiv admin note: substantial text overlap with arXiv:2105.10079

We propose a two-stage algorithm for generating Delaunay triangulations in 2D and Delaunay tetrahedra in 3D that employs near maximal Poisson-disk sampling. The method generates a variable resolution mesh in 2- and 3-dimensions in linear run time. The effectiveness of the algorithm is demonstrated by generating an unstructured 3D mesh on a discrete fracture network (DFN). Even though Poisson-disk sampling methods do not provide triangulation quality bounds in more than two-dimensions, we found that low quality tetrahedra are infrequent enough and could be successfully removed to obtain high quality balanced three-dimensional meshes with topologically acceptable tetrahedra.

When it comes to eating fruits and vegetables, the average U.S. diet falls short of Federal recommendations. According to the 2020–2025 Dietary Guidelines for Americans, about 90 percent of the U.S. population does not meet the recommendation for vegetables and 80 percent consumes too little fruit. There are many factors that could influence food choices, including taste, convenience, and the link between diet and health. For lower income households, affordability can also be a factor.

International audience; In fractured media, fluid flow depends on and induces coupled processes (hydrogeological-mechanical-chemical-biological-thermal) across a wide range of time and length scales. Understanding fluid flow and its coupling with different processes is critical for numerous subsurface applications including petroleum and geothermal reservoir management, environmental remediation, carbon sequestration, and long-term radioactive waste isolation. This session focuses on recent research that provides mechanistic understanding and predictive capability of physical processes in fractured media including coupled flow and geomechanics, non-Fickian transport, colloid and bacterial transport, mixing and reaction, fluid/mineral interactions, and biofilm formation. In particular, we encourage submissions related to (1) experiments and field observations, (2) new theoretical and numerical modeling approaches (direct simulation in single fractures, discrete fracture network modeling, upscaling methodologies, and multi-scale methods), and (3) the integration of data and models for observational interpretation and model validation..

International audience; In fractured media, fluid flow depends on and induces coupled processes (hydrogeological-mechanical-chemical-biological-thermal) across a wide range of time and length scales. Understanding fluid flow and its coupling with different processes is critical for numerous subsurface applications including petroleum and geothermal reservoir management, environmental remediation, carbon sequestration, and long-term radioactive waste isolation. This session focuses on recent research that provides mechanistic understanding and predictive capability of physical processes in fractured media including coupled flow and geomechanics, non-Fickian transport, colloid and bacterial transport, mixing and reaction, fluid/mineral interactions, and biofilm formation. In particular, we encourage submissions related to (1) experiments and field observations, (2) new theoretical and numerical modeling approaches (direct simulation in single fractures, discrete fracture network modeling, upscaling methodologies, and multi-scale methods), and (3) the integration of data and models for observational interpretation and model validation.

ERS researchers calculated the average cost to consume 157 fresh and processed fruits and vegetables by adjusting for inedible parts and losses that may occur in cooking. A greater share of vegetables (77 percent) than fruits (47 percent) cost less than 80 cents per cup equivalent.

Given that most Americans do not consume enough whole grains to satisfy Federal dietary recommendations, in 2009, the U.S. Dept. of Agriculture (USDA) altered its Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) by adding 100-percent whole-wheat bread (and other whole-grain options like brown rice) to food packages for children and pregnant or breastfeeding women. Published research suggests that participant diet quality has likely improved, but study results are mixed. Other research has explored the availability and cost of whole-grain products in the WIC-allowed, 1-pound (16-ounce) package size at retail stores. In 2014, USDA asked the National Academies of Sciences, Engineering, and Medicine (NASEM) to convene a committee of experts to conduct an independent, comprehensive scientific review of WIC food packages and recommend cost-neutral changes in line with the nutritional status and food and nutrition needs of the WIC-eligible population. In 2017, that committee recommended a number of changes to participants’ food assistance benefits. These include offering bread and other whole-grain products in more standard package sizes. Concurrent to NASEM’s review of the WIC food package, the Agricultural Act of 2014 required the Dietary Guidelines for Americans to expand to include infants and toddlers from birth to 2 years, as well as women who are pregnant, beginning with the 2020 edition. USDA will consider changes to the WIC food packages once this work is complete. In this study, we use a combination of store- and household-level purchase data to revisit some key questions about WIC participants’ whole-grain benefits. We focus on bread in a case study of the products that may be purchased with these benefits., Store-level purchase data from Information Resources, Inc. (IRI) were used to examine the price and sales volume of 100 percent whole-wheat bread, and household-level data from the National Household Food Acquisition and Purchase Survey (FoodAPS) were used to examine the propensity of WIC households to purchase whole-grain breads. In this report, the term “100 percent whole wheat” is used when referring specifically to bread of this type, and the term “whole grain” is used elsewhere in the report. A variety of statistical techniques were used in the analysis, including summary statistics and T-tests for differences between group means. To capture the full association between WIC participation and whole-grain purchases among households, ERS would need to include separate analyses for all relevant whole-grain product types, which is beyond the scope of our study and data.

Food away from home (FAFH) has become increasingly integral to the American diet. In 2010, the share of Americans’ food budget for FAFH—reaching 50 percent (up from 41 percent in 1984)—surpassed the share for food at home (FAH) for the first time. Likewise, Americans’ share of energy intake from FAFH rose from 17 percent in 1977-78 to 34 percent in 2011-12, with differences in growth across types of FAFH (e.g., full- and quick-service restaurant foods, school meals, etc.). Along with the demand for FAFH, availability of FAFH has also increased, with much of the growth in recent years attributable to quick-service restaurants. The growing presence of FAFH in Americans’ diets reflects changes in consumer demand and producer behavior and affects the health and nutrition of individuals over time. This report takes a comprehensive look at the role of FAFH in American diets, exploring nutritional composition of FAFH and key Federal programs that may influence FAFH. The report also discusses how FAFH choices and availability relate to diet quality, income, age, and other socioeconomic factors.

Farm-to-school programs began in the 1990s and have been encouraged by the U.S. Department of Agriculture (USDA) through grant funding, technical assistance, and changes to school meal procurement regulations. In 2012, USDA’s Farm to School Program was formally established to improve access to local foods in eligible schools. Today, more than 4 in 10 school districts report serving local foods or implementing other farm-to-school activities. To examine progress toward USDA’s goal of daily availability of locally produced foods for all students and to identify potential targets for technical assistance, this report uses data from the 2013 Farm to School Census to measure the prevalence of school districts that serve local food daily and the characteristics of those districts.

Many consumers may perceive fruit and vegetable recommendations in USDA's Dietary Guidelines for Americans as too expensive. ERS illustrates how a family of four can meet these recommendations on a limited budget.

USDA’s Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) is the Nation’s third-largest food and nutrition assistance program. WIC partici - pants receive Food Instruments they can exchange for foods like infant formula, milk, fruit juice, whole-grain bread, and cold cereal at authorized retail stores. Since partici - pants incur no out-of-pocket costs when purchasing WIC foods, they may be less sensitive to prices when choosing among allowed food items. In this study, we analyze household purchases of cold cereals. Findings show that WIC households buy less costly cereals than non-WIC households, all else constant, when paying out of pocket. Not surprisingly, they purchase with relatively less regard to price when using their WIC benefits, which may increase the program’s food costs. Findings also suggest that some restrictions imposed by WIC State agencies on brands and package sizes may help contain program costs. However, it may also be possible to develop incentives that encourage participants to purchase lower cost products without the negative impact that restrictions may have on participant satisfaction and program participation.

This report provides the latest estimates by USDA’s Economic Research Service (ERS) on the amount and value of food loss in the United States. These estimates are for more than 200 individual foods using ERS’s Loss-Adjusted Food Availability data. In 2010, an estimated 31 percent or 133 billion pounds of the 430 billion pounds of food produced was not available for human consumption at the retail and consumer levels. This amount of loss totaled an estimated $161.6 billion, as purchased at retail prices. For the first time, ERS estimates of the calories associated with food loss are presented in this report. An estimated 141 trillion calories per year, or 1,249 calories per capita per day, in the food supply in 2010 went uneaten. The top three food groups in terms of share of total value of food loss are meat, poultry, and fish (30 percent); vegetables (19 percent); and dairy products (17 percent). The report also provides a brief discussion of the economic issues behind postharvest food loss.

Restaurant foods are typically higher in calories than meals consumed at home. Menu labeling regulations by the U.S. Food and Drug and Administration aim to inform consumers about the calorie content of menu items. However, some consumers may already be making at least partially informed decisions. For example, as a rule of thumb, a consumer may be aware that deep-fried foods are higher in calories. He or she may also know to avoid side dishes like French fries and onion rings. Indeed, it has been argued that some consumers can already identify which foods best satisfy their needs and wants and gain little new information from menu labeling. In this study, following research in marketing science and behavioral economics, we assume that a representative consumer employs rules-of-thumb nutrition knowledge to judge the calorie content of restaurant foods when explicit information is unavailable. We then investigate whether rules of thumb accurately predict the calorie content of 361 meals sold by 2 major fast-food restaurants and 5,752 meals sold by 5 major full-service restaurants. Results show that some simple rules of thumb are fairly reliable predictors of actual calorie content. They and other information available at the point of sale also explain about half of the total variation in calories in restaurant foods. Nonetheless, we find that menu labeling still imparts substantial new information. In particular, it is likely that many Americans are already able to make crude choices between high- and low-calorie foods, based on their pre-existing understandings of nutrition. Menu labeling allows them to make finer adjustments in their food choices and behavior, if they wish to.

Restaurant foods are typically higher in calories than meals consumed at home. Menu labeling regulations by the U.S. Food and Drug and Administration aim to inform consumers about the calorie content of menu items. However, some consumers may already be making at least partially informed decisions. For example, as a rule of thumb, a consumer may be aware that deep-fried foods are higher in calories. He or she may also know to avoid side dishes like French fries and onion rings. Indeed, it has been argued that some consumers can already identify which foods best satisfy their needs and wants and gain little new information from menu labeling. In this study, following research in marketing science and behavioral economics, we assume that a representative consumer employs rules-of-thumb nutrition knowledge to judge the calorie content of restaurant foods when explicit information is unavailable. We then investigate whether rules of thumb accurately predict the calorie content of 361 meals sold by 2 major fast-food restaurants and 5,752 meals sold by 5 major full-service restaurants. Results show that some simple rules of thumb are fairly reliable predictors of actual calorie content. They and other information available at the point of sale also explain about half of the total variation in calories in restaurant foods. Nonetheless, we find that menu labeling still imparts substantial new information. In particular, it is likely that many Americans are already able to make crude choices between high- and low-calorie foods, based on their pre-existing understandings of nutrition. Menu labeling allows them to make finer adjustments in their food choices and behavior, if they wish to.

This report provides the latest estimates by USDA’s Economic Research Service (ERS) on the amount and value of food loss in the United States. These estimates are for more than 200 individual foods using ERS’s Loss-Adjusted Food Availability data. In 2010, an estimated 31 percent or 133 billion pounds of the 430 billion pounds of food produced was not available for human consumption at the retail and consumer levels. This amount of loss totaled an estimated $161.6 billion, as purchased at retail prices. For the first time, ERS estimates of the calories associated with food loss are presented in this report. An estimated 141 trillion calories per year, or 1,249 calories per capita per day, in the food supply in 2010 went uneaten. The top three food groups in terms of share of total value of food loss are meat, poultry, and fish (30 percent); vegetables (19 percent); and dairy products (17 percent). The report also provides a brief discussion of the economic issues behind postharvest food loss.

Children today are consuming close to 200 more calories a day from snacks than they did in the 1970s. Replacing a calorie-dense snack food with a fruit or vegetable could reduce calorie intake and improve diet quality. Swapping common snack foods with a ½-cup serving of fruits or vegetables can be done without compromising a household’s food budget.

Federal dietary guidance advises Americans to consume more vegetables and fruits because most Americans do not consume the recommended quantities or variety. Food prices, along with taste, convenience, income, and awareness of the link between diet and health, shape food choices. We used 2008 Nielsen Homescan data to estimate the average price at retail stores of a pound and an edible cup equivalent (or, for juices, a pint and an edible cup equivalent) of 153 commonly consumed fresh and processed fruits and vegetables. We found that average prices ranged from less than 20 cents per edible cup equivalent to more than $2 per edible cup equivalent. We also found that, in 2008, an adult on a 2,000- calorie diet could satisfy recommendations for vegetable and fruit consumption in the 2010 Dietary Guidelines for Americans (amounts and variety) at an average price of $2 to $2.50 per day, or approximately 50 cents per edible cup equivalent.

Federal dietary guidance advises Americans to consume more vegetables and fruits because most Americans do not consume the recommended quantities or variety. Food prices, along with taste, convenience, income, and awareness of the link between diet and health, shape food choices. We used 2008 Nielsen Homescan data to estimate the average price at retail stores of a pound and an edible cup equivalent (or, for juices, a pint and an edible cup equivalent) of 153 commonly consumed fresh and processed fruits and vegetables. We found that average prices ranged from less than 20 cents per edible cup equivalent to more than $2 per edible cup equivalent. We also found that, in 2008, an adult on a 2,000- calorie diet could satisfy recommendations for vegetable and fruit consumption in the 2010 Dietary Guidelines for Americans (amounts and variety) at an average price of $2 to $2.50 per day, or approximately 50 cents per edible cup equivalent.

Traumatic injuries to teeth and supporting structures are a common occurrence which often require immediate treatment for optimal recovery. An interactive microcomputer program was developed to assist emergency facility personnel in the initial treatment of oral injuries. The program determines the combination of the patient's injuries and prints an optimal treatment sequence.

Pressure on employers to train their employees has seldom been higher as evidence accumulates that the skills of British workers and managers relevant for modern industry lag behind those of competitor countries, contributing to economic decline and long-term unemployment. This paper discusses these issues.

Children today are consuming close to 200 more calories a day from snacks than they did in the 1970s. Replacing a calorie-dense snack food with a fruit or vegetable could reduce calorie intake and improve diet quality. Swapping common snack foods with a ½-cup serving of fruits or vegetables can be done without compromising a household’s food budget.