Multiscale Mass-Spring Models of Carbon Nanotube Arrays Accounting for Mullins-like Behavior and Permanent Deformation

Based on a one-dimensional discrete system of bistable springs, a mechanical model is introduced to describe plasticity and damage in carbon nanotube (CNT) arrays. The energetics of the mechanical system are investigated analytically, the stress-strain law is derived, and the mechanical dissipation is computed, both for the discrete case as well as for the continuum limit. An information-passing approach is developed that permits the investigation of macroscopic portions of the material. As an application, the simulation of a cyclic compression experiment on real CNT foam is performed, considering both the material response during the primary loading path from the virgin state and the damaged response after preconditioning

Consolidation of Geologic Studies of Geopressured-Geothermal Resources in Texas: Colocation of Heavy-Oil and Geothermal Resources in South Texas

In a five-county area of South Texas, geopressured-geothermal reservoirs in the Eocene Wilcox Group occur below heavy-oil reservoirs in the Eocene Jackson Group. This colocation warrants consideration of the use of geothermal fluids for a thermally enhanced waterflood. Geothermal fairways comprise thick deltaic sandstones within growth-fault-bounded compartments containing geopressured water in excess of 250°F. Geothermal reservoirs occur at depths of 11,000 to 15,000 ft in continuous sandstones 100 to 200 ft thick. Permeability ranges from 1 to 150 md, and porosity from 12 to 24 percent. Updip pinch-out of shallowly buried (200 to 2,000 ft) barrier-bar/strandplain sandstones largely controls the distribution of heavy-oil reservoirs. Subtle structure, small faults, and sandbody pinch-outs form lateral barriers of the reservoirs. Structural, depositional, and diagenetic variations affect reservoir compartmentalization. The heavy-oil reservoirs are typically porous (25 to 35 percent), permeable (100 to 1,000 md), slightly clayey fine to medium sand. Calcite-cemented zones of low porosity (>5 percent) and permeability (0.01 md) compartmentalize reservoirs. Injection of hot (300°F), moderately fresh to saline brines will improve oil recovery by lowering viscosity and decreasing residual oil saturation. Matrix clays are smectites, which could swell and clog pore throats if injected waters were fresh. The high temperature of injected fluids will collapse some of the interlayer clays, thus increasing porosity and permeability. Reservoir heterogeneity resulting from facies variation and diagenesis must be considered when siting production and injection wells within the heavy-oil reservoir. The suitability of abandoned gas wells as geothermal production wells and their long-term well productivity also affect the economics of geothermally enhanced hot-water flooding.Bureau of Economic Geolog

Continuum limits of bistable spring models of carbon nanotube arrays accounting for material damage

Using chains of bistable springs, a model is derived to investigate the plastic behavior of carbon nanotube arrays with damage. We study the preconditioning effect due to the loading history by computing analytically the stress-strain pattern corresponding to a fatigue-type damage of the structure. We identify the convergence of the discrete response to the limiting case of infinitely many springs, both analytically in the framework of Gamma-convergence, as well as numerically.Comment: 11 pages, 1 figur

Consolidation of Geologic Studies of Geopressured-Geothermal Resources in Texas

In a five-county area of South Texas, geopressured-geothermal reservoirs in the upper Wilcox Group are colocated with heavy-oil reservoirs in the overlying Jackson Group. In 1990, research at the Bureau of Economic Geology concentrated on evaluating the potential of using geopressured-geothermal water for hot-water flooding of heavy-oil reservoirs. Favorable geothermal reservoirs are defined by thick deltaic sandstones and growth-fault-bounded compartments. Potential geothermal reservoirs are present at a depth of 11,000 ft (3,350 m) to 15,000 ft (4,570 m) and contain water at temperatures of 350°F (177°C) to 383°F (195°C) in Fandango field, Zapata County. One potential geothermal reservoir sandstone in the upper Wilcox (R sandstone) is composed of a continuous sand body 100 ft (30 m) to greater than 200 ft (>61 m) thick. Fault blocks average 2 to 4 mi^2 (5.2 to 10.4 km^2) in area. Both heavy-oil (average API=19) and light-oil (average API=26) reservoirs in South Texas are present in sandstones of the Jackson Group Mirando trend. The updip pinch-out of strike-oriented sheet sandstones in the Jackson Group largely controls the distribution of Mirando-trend heavy-oil reservoirs. The lateral continuity of heavy-oil reservoirs minimizes reservoir compartmentalization, which could disrupt injected-fluid flow paths. Geologic and engineering research that still needs to be conducted includes (1) studies of the chemical compatibility between injected geothermal fluids and clay matrix of heavy-oil reservoirs, (2) detailed field studies of geometry and size of geothermal reservoirs, (3) detailed field studies of geometry and size of heavy-oil reservoirs, and (4) studies of changes in the temperature and chemistry of geothermal fluids when injected into heavy-oil reservoirs.Bureau of Economic Geolog

Interactions of ingested food, beverage, and tobacco components involving human cytochrome P4501A2, 2A6, 2E1, and 3A4 enzymes.

Human cytochrome P450 (P450) enzymes are involved in the oxidation of natural products found in foods, beverages, and tobacco products and their catalytic activities can also be modulated by components of the materials. The microsomal activation of aflatoxin B1 to the exo-8,9-epoxide is stimulated by flavone and 7,8-benzoflavone, and attenuated by the flavonoid naringenin, a major component of grapefruit. P4502E1 has been demonstrated to play a potentially major role in the activation of a number of very low-molecular weight cancer suspects, including ethyl carbamate (urethan), which is present in alcoholic beverages and particularly stone brandies. The enzyme (P4502E1) is also known to be inducible by ethanol. Tobacco contains a large number of potential carcinogens. In human liver microsomes a significant role for P4501A2 can be demonstrated in the activation of cigarette smoke condensate. Some of the genotoxicity may be due to arylamines. P4501A2 is also inhibited by components of crude cigarette smoke condensate. The tobacco-specific nitrosamines are activated by a number of P450 enzymes. Of those known to be present in human liver, P4501A2, 2A6, and 2E1 can activate these nitrosamines to genotoxic products

Taking a PEEK into YOLOv5 for Satellite Component Recognition via Entropy-based Visual Explanations

The escalating risk of collisions and the accumulation of space debris in Low Earth Orbit (LEO) has reached critical concern due to the ever increasing number of spacecraft. Addressing this crisis, especially in dealing with non-cooperative and unidentified space debris, is of paramount importance. This paper contributes to efforts in enabling autonomous swarms of small chaser satellites for target geometry determination and safe flight trajectory planning for proximity operations in LEO. Our research explores on-orbit use of the You Only Look Once v5 (YOLOv5) object detection model trained to detect satellite components. While this model has shown promise, its inherent lack of interpretability hinders human understanding, a critical aspect of validating algorithms for use in safety-critical missions. To analyze the decision processes, we introduce Probabilistic Explanations for Entropic Knowledge extraction (PEEK), a method that utilizes information theoretic analysis of the latent representations within the hidden layers of the model. Through both synthetic in hardware-in-the-loop experiments, PEEK illuminates the decision-making processes of the model, helping identify its strengths, limitations and biases