Academic literature on the topic 'Minimum Energy Pathway'
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Journal articles on the topic "Minimum Energy Pathway"
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Philippe, T., and D. Blavette. "Minimum free-energy pathway of nucleation." Journal of Chemical Physics 135, no. 13 (October 7, 2011): 134508. http://dx.doi.org/10.1063/1.3644935.
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Shim, JaeHwan, Juyong Lee, and Jaejun Yu. "Efficient discovery of multiple minimum action pathways using Gaussian process." Journal of Physics Communications 7, no. 2 (February 1, 2023): 025004. http://dx.doi.org/10.1088/2399-6528/acba83.
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Abstract We present a new efficient transition pathway search method based on the least action principle and the Gaussian process regression method. Most pathway search methods developed so far rely on string representations, which approximate a transition pathway by a series of slowly varying system replicas. Such string methods are computationally expensive in general because they require many replicas to obtain smooth pathways. Here, we present an approach employing the Gaussian process regression method, which infers the shape of a potential energy surface with a few observed data and Gaussian-shaped kernel functions. We demonstrate a drastic elevation of computing efficiency of the method about five orders of magnitude than existing methods. Further, to demonstrate its real-world capabilities, we apply our method to find multiple conformational transition pathways of alanine dipeptide using a quantum mechanical potential. Owing to the improved efficiency of our method, Gaussian process action optimization (GPAO), we obtain the multiple transition pathways of alanine dipeptide and calculate their transition probabilities successfully with density-functional theory (DFT) accuracy. In addition, GPAO successfully finds the isomerization pathways of small molecules and the rearrangement of atoms on a metallic surface.
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Chen, D., W. Hu, F. Gao, H. Deng, and L. Sun. "Tungsten cluster migration on nanoparticles: minimum energy pathway and migration mechanism." European Physical Journal B 80, no. 1 (March 2011): 31–40. http://dx.doi.org/10.1140/epjb/e2011-10629-9.
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Borodin, Dmitriy, Igor Rahinov, Pranav R. Shirhatti, Meng Huang, Alexander Kandratsenka, Daniel J. Auerbach, Tianli Zhong, et al. "Following the microscopic pathway to adsorption through chemisorption and physisorption wells." Science 369, no. 6510 (September 17, 2020): 1461–65. http://dx.doi.org/10.1126/science.abc9581.
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Adsorption involves molecules colliding at the surface of a solid and losing their incidence energy by traversing a dynamical pathway to equilibrium. The interactions responsible for energy loss generally include both chemical bond formation (chemisorption) and nonbonding interactions (physisorption). In this work, we present experiments that revealed a quantitative energy landscape and the microscopic pathways underlying a molecule’s equilibration with a surface in a prototypical system: CO adsorption on Au(111). Although the minimum energy state was physisorbed, initial capture of the gas-phase molecule, dosed with an energetic molecular beam, was into a metastable chemisorption state. Subsequent thermal decay of the chemisorbed state led molecules to the physisorption minimum. We found, through detailed balance, that thermal adsorption into both binding states was important at all temperatures.
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Takizawa, Hiroki, Junichi Iwakiri, Goro Terai, and Kiyoshi Asai. "Finding the direct optimal RNA barrier energy and improving pathways with an arbitrary energy model." Bioinformatics 36, Supplement_1 (July 1, 2020): i227—i235. http://dx.doi.org/10.1093/bioinformatics/btaa469.
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Abstract Motivation RNA folding kinetics plays an important role in the biological functions of RNA molecules. An important goal in the investigation of the kinetic behavior of RNAs is to find the folding pathway with the lowest energy barrier. For this purpose, most of the existing methods use heuristics because the number of possible pathways is huge even if only the shortest (direct) folding pathways are considered. Results In this study, we propose a new method using a best-first search strategy to efficiently compute the exact solution of the minimum barrier energy of direct pathways. Using our method, we can find the exact direct pathways within a Hamming distance of 20, whereas the previous methods even miss the exact short pathways. Moreover, our method can be used to improve the pathways found by existing methods for exploring indirect pathways. Availability and implementation The source code and datasets created and used in this research are available at https://github.com/eukaryo/czno. Supplementary information Supplementary data are available at Bioinformatics online.
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Lee, Brian Hyun-jong, and Gaurav Arya. "Assembly mechanism of surface-functionalized nanocubes." Nanoscale 14, no. 10 (2022): 3917–28. http://dx.doi.org/10.1039/d1nr07995f.
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Schmelzer, Jürn W. P., and Alexander S. Abyzov. "Comment on “Minimum free-energy pathway of nucleation” [J. Chem. Phys. 135, 134508 (2011)]." Journal of Chemical Physics 136, no. 10 (March 14, 2012): 107101. http://dx.doi.org/10.1063/1.3692688.
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Hong, Young J., and Dean J. Tantillo. "The Variediene-Forming Carbocation Cyclization/Rearrangement Cascade." Australian Journal of Chemistry 70, no. 4 (2017): 362. http://dx.doi.org/10.1071/ch16504.
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An energetically viable (on the basis of results from density functional theory computations) pathway to the diterpene variediene is described. Only one of the three secondary carbocations along this pathway is predicted to be a minimum on the potential energy surface.
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Monferrer, Ezequiel, Isaac Vieco-Martí, Amparo López-Carrasco, Fernando Fariñas, Sergio Abanades, Luis de la Cruz-Merino, Rosa Noguera, and Tomás Álvaro Naranjo. "Metabolic Classification and Intervention Opportunities for Tumor Energy Dysfunction." Metabolites 11, no. 5 (April 23, 2021): 264. http://dx.doi.org/10.3390/metabo11050264.
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A comprehensive view of cell metabolism provides a new vision of cancer, conceptualized as tissue with cellular-altered metabolism and energetic dysfunction, which can shed light on pathophysiological mechanisms. Cancer is now considered a heterogeneous ecosystem, formed by tumor cells and the microenvironment, which is molecularly, phenotypically, and metabolically reprogrammable. A wealth of evidence confirms metabolic reprogramming activity as the minimum common denominator of cancer, grouping together a wide variety of aberrations that can affect any of the different metabolic pathways involved in cell physiology. This forms the basis for a new proposed classification of cancer according to the altered metabolic pathway(s) and degree of energy dysfunction. Enhanced understanding of the metabolic reprogramming pathways of fatty acids, amino acids, carbohydrates, hypoxia, and acidosis can bring about new therapeutic intervention possibilities from a metabolic perspective of cancer.
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Singh, Baltej, Mayanak Kumar Gupta, Ranjan Mittal, Mohamed Zbiri, Stephane Rols, Sadequa Jahedkhan Patwe, Srungarpu Nagabhusan Achary, Helmut Schober, Avesh Kumar Tyagi, and Samrath Lal Chaplot. "Superionic conduction in β-eucryptite: inelastic neutron scattering and computational studies." Physical Chemistry Chemical Physics 19, no. 23 (2017): 15512–20. http://dx.doi.org/10.1039/c7cp01490b.
Full textBooks on the topic "Minimum Energy Pathway"
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Blockley, David. 2. Does form follow function? Oxford University Press, 2014. http://dx.doi.org/10.1093/actrade/9780199671939.003.0002.
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In c.15 bc, the Roman Vitruvius stated that a good building should satisfy three requirements: durability, utility, and beauty. ‘Does form follow function?’ examines utility and beauty. It explains that structures are naturally lazy because they contain minimum potential energy. Each piece of structure, however small or large, will move, but not freely as the neighbouring pieces will get in the way. When this happens internal forces are created as the pieces bump up against each other. Force pathways are degrees of freedom and the structure has to be strong enough to resist these internal forces along these pathways. Form-finding structures are exciting and innovative examples of the fusion of engineering and architecture.
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Ross, Andrew. Bird on Fire. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199828265.001.0001.
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Phoenix, Arizona is one of America's fastest growing metropolitan regions. It is also its least sustainable one, sprawling over a thousand square miles, with a population of four and a half million, minimal rainfall, scorching heat, and an insatiable appetite for unrestrained growth and unrestricted property rights. In Bird on Fire, eminent social and cultural analyst Andrew Ross focuses on the prospects for sustainability in Phoenix--a city in the bull's eye of global warming--and also the obstacles that stand in the way. Most authors writing on sustainable cities look at places like Portland, Seattle, and New York that have excellent public transit systems and relatively high density. But Ross contends that if we can't change the game in fast-growing, low-density cities like Phoenix, the whole movement has a major problem. Drawing on interviews with 200 influential residents--from state legislators, urban planners, developers, and green business advocates to civil rights champions, energy lobbyists, solar entrepreneurs, and community activists--Ross argues that if Phoenix is ever to become sustainable, it will occur more through political and social change than through technological fixes. Ross explains how Arizona's increasingly xenophobic immigration laws, science-denying legislature, and growth-at-all-costs business ethic have perpetuated social injustice and environmental degradation. But he also highlights the positive changes happening in Phoenix, in particular the Gila River Indian Community's successful struggle to win back its water rights, potentially shifting resources away from new housing developments to producing healthy local food for the people of the Phoenix Basin. Ross argues that this victory may serve as a new model for how green democracy can work, redressing the claims of those who have been aggrieved in a way that creates long-term benefits for all. Bird on Fire offers a compelling take on one of the pressing issues of our time--finding pathways to sustainability at a time when governments are dismally failing their responsibility to address climate change.
Book chapters on the topic "Minimum Energy Pathway"
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Rodrigues, Neshwin, Raghav Pachouri, Shubham Thakare, G. Renjith, and Thomas Spencer. "Integrating Wind and Solar in the Indian Power System." In Energiepolitik und Klimaschutz. Energy Policy and Climate Protection, 139–62. Wiesbaden: Springer Fachmedien Wiesbaden, 2022. http://dx.doi.org/10.1007/978-3-658-38215-5_7.
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AbstractIndia’s coal contribution to the total electricity generation mix stood at 73% in 2018. To meet India’s NDC ambitions, the federal government announced determined targets to integrate 450 GW Renewable Energy in the grid by 2030. This paper explores the pathways to integrate high RE generation by 2030 with effective balancing of supply and demand and associated challenges of flexibility requirements. A Unit commitment and economic dispatch model, which simulates the power system operation was used. The overall share of variable renewables reaches 26% and 32% in the Baseline Capacity Scenario (BCS) and High Renewable Energy Scenario (HRES) respectively. Improved ramp rates and a minimum thermal loading limit induce flexibility in the thermal fleet. In the HRES, more than 16 GW of coal plants are required for two-shift operations in April and more than 50% of days see an aggregate all-India ramp from the coal fleet in excess of 500 MW per minute. Battery Storage provides daily balancing while reducing VRE curtailment to less than 0.2% in the HRES. Nationally Coordinated dispatch shows increased power transfer from high VRE regions to export power during high VRE generation periods. It is thus found that high RE penetration is possible by 2030 at no extra system costs.
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Hurmekoski, Elias, Antti Kilpeläinen, and Jyri Seppälä. "Climate-Change Mitigation in the Forest-Based Sector: A Holistic View." In Forest Bioeconomy and Climate Change, 151–63. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-99206-4_8.
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AbstractForests and wood use can contribute to climate-change mitigation by enhancing carbon sinks through afforestation, reforestation and improved forest management, by maintaining carbon stocks through natural or anthropogenic disturbance prevention, by increasing offsite carbon stocks, and through material and energy substitution by changing the industry production structure and enhancing resource efficiency. As forests grow fairly slowly in Europe, increasing the wood harvesting intensity decreases the carbon stocks in aboveground biomass, at least in the short to medium term (0–50 years) compared to a baseline harvest regime. The key issue is the time frame in which the decreased carbon stock in forests can be compensated for by improved forest growth resulting from improved forest management and the benefits related to wood utilisation. Thus, there is a need to address potential trade-offs between the short- to medium-term and the long-term (50+ years) net emissions. An optimal strategy needs to be tailored based also on regional specificities related to, for example, local climatic and site conditions, the state of the forests, the institutional setting and the industry structures. This chapter presents a way to assess the effectiveness of forest-sector climate-change mitigation strategies across different contexts and time horizons, combining the climate impacts of forests and the wood utilisation of the technosphere. We identify potential ‘no-regret’ mitigation pathways with minimum trade-offs, and conclude with the research and policy implications.
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Hratchian, Hrant P., and H. Bernhard Schlegel. "Finding minima, transition states, and following reaction pathways on ab initio potential energy surfaces." In Theory and Applications of Computational Chemistry, 195–249. Elsevier, 2005. http://dx.doi.org/10.1016/b978-044451719-7/50053-6.
Full textConference papers on the topic "Minimum Energy Pathway"
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He, Lijuan, and Yan Wang. "A Concurrent Search Algorithm for Multiple Phase Transition Pathways." In ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-12362.
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The challenge of accurately predicting a phase transition in computer-aided nano-design is estimating the true value of transition rate, which is determined by the saddle point with the minimum energy barrier between stable states on the potential energy surface (PES). In this paper, a new algorithm for searching the minimum energy path (MEP) is presented. Unlike existing pathway search methods, the new algorithm is able to locate both the saddle points and local minima simultaneously. Therefore no prior knowledge of the precise positions for the reactant and product on the PES is required. In addition, the algorithm is able to search multiple transition paths on the PES simultaneously. In this method, a Bézier curve is used to represent each transition path. Starting from a single Bézier curve, multiple curves with ends connected can be generated during the search process. For each Bézier curve, the reactant and product states are located by minimizing the two end control points of the curve, while the transition pathway is refined by moving the intermediate control points of the curve in the conjugate directions. A curve subdivision scheme is developed so that multiple transition paths can be located. The algorithm is demonstrated by examples.
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Crnkic, Edin, Lijuan He, and Yan Wang. "Loci Surface Guided Crystal Phase Transition Pathway Search." In ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47750.
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Recently a periodic surface model was developed to assist geometric construction in computer-aided nano-design. This implicit surface model helps create super-porous nano structures parametrically and support crystal packing. In this paper, we propose a new approach for pathway search in phase transition simulation of crystal structures. The approach relies on the interpolation of periodic loci surface models. Respective periodic plane models are reconstructed from the positions of individual atoms at the initial and final states, and surface correspondence are found. With geometric constraints imposed based on physical and chemical properties of crystals, two surface interpolation methods are used to approximate the intermediate atom positions on the transition pathway in the full search of the minimum energy path. This hybrid approach integrates geometry information in configuration space and physics information to allow for efficient transition pathway search. The methods are demonstrated by examples of FeTi and VO2.
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Nie, Zhenguo, Sangjin Jung, Levent Burak Kara, and Kate S. Whitefoot. "Optimization of Parts Consolidation for Minimum Production Costs and Time Using Additive Manufacturing." In ASME 2019 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/detc2019-97649.
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Abstract This research presents a method of evaluating and optimizing the consolidation of parts in an assembly using metal additive manufacturing (MAM). The method generates candidates for consolidation, filters them for feasibility and structural redundancy, finds the optimal build layout of the parts, and optimizes which parts to consolidate using a genetic algorithm. Optimal results are presented for both minimal production time and minimal production costs, respectively. The production time and cost model considers each step of the manufacturing process, including MAM build, post-processing steps such as support-structure removal, and assembly. It accounts for costs affected by parts consolidation, including machine costs, material, scrap, energy consumption, and labor requirements. We find that developing a closed-loop filter that excludes consolidation candidates with structural redundancy dramatically reduces the number of candidates to consider, thereby significantly reducing convergence time. Results show that, when increasing the number of parts that are consolidated, the production cost and time at first decrease due to reduced assembly steps, and then increase due to additional support structures needed to uphold the larger, consolidated parts. We present a rationale and evidence justifying that this is an inherent tradeoff of parts consolidation that generalizes to most types of assemblies. Subsystems that can be oriented with very little support structures, or have low material costs or fast deposition rates can have an optimum at full consolidation; otherwise, the optimum is likely to be less than 100%. The presented method offers a promising pathway to minimize production time and cost by consolidating parts using MAM. In our test-bed results on an aircraft fairing produced with powder-bed electron-beam melting, the solution for minimizing time is to consolidate 48 components into three discrete parts, which leads to a 33% reduction in unit production time. The solution for minimizing production costs is to consolidate the components into five discrete parts, leading to a 28% reduction in unit costs.
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Borumand, Mohammad, Taehun Lee, and Gisuk Hwang. "Enhanced Wickability of Thin Non-Uniform Sintered Particle Wicks Using Lattice Boltzmann Method." In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-24311.
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Abstract Thin non-uniform particle size wicks are essential to improve the maximum heat flux of two-phase thermal management systems by improving the wickability. To understand the enhanced wickability, we examine a pore-scale capillary flow within the thin sintered particle wick using a free-energy-based, single-component, two-phase Lattice Boltzmann Method (LBM) with a minimal parasitic current. The developed LBM approach is validated through the rate-of-rise in the two-parallel plates with parallel plates spacing of W = 48 against analytical Bosanquet equation, achieving the RMS error below 10%. The LBM predicts the rate-of-rise through the uniform and non-uniform particle-size wicks between two-parallel plate, including the capillary meniscus front and dynamic capillary filling. At the same plate spacing and porosity, i.e., W = 48 lu and ε = 0.75, the non-uniform particle size wick achieves enhanced wickability by providing the selective flow pathway through pore networks formed in the smaller pores between the small/large particles, which is in qualitative agreement with previous experimental results. The enhancement of the maximum and minimum dimensionless liquid height and the liquid-filled pore ratio of non-uniform particle size wick is found to be up to 11.1, 27.47, and 26.11%, respectively. The simulation results provide insights into the optimal wick structures for high heat flux two-phase thermal management system by enhancing the wickability through the non-uniform particle (or pore) sizes.
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Mohamed Najib, Mohamed Aiman, Yong Ken Phoon, Wan Fatimah Wan Shamshudin, Shazana Sofia Mustapa, Aizuddin Khalid, and Yunus Alwi Yusof. "Limbayong: Decoding Industry Top Decile Reservoir Complexity for Marginal Deepwater Development." In SPE Annual Technical Conference and Exhibition. SPE, 2022. http://dx.doi.org/10.2118/210079-ms.
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Abstract PETRONAS Carigali (PCSB) has developed a solution to monetize industry top decile worth reservoir complexity in the deepwater environment via Limbayong field, Malaysia. The field complexity is acknowledged by Independent Project Analysis (IPA) as industry top decile reservoir complexity due to severe elongated structure (30km length, 2.5km width) with varying faults frequency, vertical intercalation of thin-bed, thick sand reservoir and lateral compartmentalization which impend effectiveness of well drainage and pressure maintenance. The four (4) appraisal wells result since 2002 give diverse subsurface understanding, indicated possible different depositional model and greater degree of complication. This paper describes the key development challenges and strategies that significantly improve the field value proposition for FID. PCSB pivoted to focus assessment on low realization case for development. It generated advanced reservoir mapping to simulate sand distribution and concentration through incorporated faults re-interpretation, refined grid resolution, and change of facies prediction, increasing the stratigraphic compartments. The team performed integrated subsurface-surface flow assurance modeling and validated turndown limit for production and operation. Subsequently, iterated concepts for incremental reservoir recoverable by high-grading producer-injector pairing, wells-facilities design provision for a base, upgrade, or future tie-in. The team formulated industry collaboration (IC) studies in each FEL phase with drivers for deepwater technology enablers implementation in EPCIC primarily via concept selection, engineering standardization, and design competition. Each distinct concept is ratified with project economics group value chain evaluation and stakeholders’ alignment. The breakthrough signifies merit in the key strategies and templates to overcome similar-scale project complexity with viable business cases. The IC affirmed cost proposition of 20 to 30% lower than industry average for deepwater wells and facilities, ensuring it to be positioned in top quartile project performance. It re-defined minimum technical design and demonstrated a prominent value trade-off for scaling-up concepts. It drives momentum to monetize high complexity reservoirs even further in the deepwater environment, which otherwise remains undeveloped. There is potential for replication throughout nearly 800MMboe scattered fields within deepwater offshore Sabah, Malaysia. Deepwater offshore has a niche role in bridging global transition between energy mix offering and net-zero economy target. It produces among the industry's smallest carbon footprints yet with high economic efficiency. Consolidated and efficient development strategies accelerate the decarbonization pathway. It advocates a hybrid capital project management model to manage extreme uncertainties with design thinking, lean startup, and agile approach.
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Siegel, Nathan P., and Ben Conser. "A Techno-Economic Analysis of Solar-Driven Atmospheric Water Harvesting." In ASME 2020 14th International Conference on Energy Sustainability. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/es2020-1619.
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Abstract Water may be produced from atmospheric humidity anywhere on Earth; however, current approaches are energy intensive and costly, thus limiting the deployment of atmospheric water harvesting (AWH) technologies. A system level thermodynamic model of several AWH pathways is presented to elucidate the important energy flows in these processes as a means to reducing the energy required to produce a unit of water. Model results show that fresh water may be produced from humid air via processes driven solely with solar electricity in an arid climate with an energy input between 158 kWhe/m3 and 1021 kWhe/m3, depending on atmospheric conditions and processing configuration. We describe a novel, desiccant-based AWH approach in which the latent heat of vaporization is internally recovered resulting in a significant reduction in energy requirements relative to the state of the art. Finally, a parametric model of a desiccant-based AWH system is used to estimate the minimum levelized cost of water (LCOW) via solar-driven AWH at 6.5 $/m3 when both latent and sensible energy are recovered internally.
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Fyffe, John R., Aaron K. Townsend, and Michael E. Webber. "Methodology for Comparing End-of-Life Pathways for Non-Recycled Materials." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64131.
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Recycling plastics is widely accepted as the most beneficial end use of plastic products. Consequently, many cities are turning towards single-stream recycling to make it easier for consumers to recycle and to increase the total amount of municipal solid waste (in particular, energy-dense plastic waste) that is diverted to recycling facilities. However, single-stream recycling Materials Recovery Facilities (MRFs) are now faced with sorting more diverse material flows with increased contamination from the mixing of recyclable and non-recyclable materials, leading to roughly 5–10% of the incoming material being sent to landfills. Converting the energy dense MRF waste material into solid recovery fuel (SRF) pellets creates an additional use for the products, diverts the material from the landfill, and displaces some fossil fuel use. However, there are some non-obvious energetic and environmental tradeoffs that require analysis to quantify. That is the intent of the research presented here. To analyze the potential of SRFs as viable alternative fuel sources, a first-order thermodynamic materials and energy balance was constructed using cement kilns as a test-bed. The proposed methodology allows for a range of traditional fuels to be compared with and without supplemental SRF. The SRF case can be benchmarked against the reference case, or conventional plastic end-of-life pathway, landfilling of the non-recycled plastic. The comparison includes transportation and processing steps required for each pathway, including any additional sorting needed for creating the SRF as well as the pelletization process itself. A robust methodology was created that allows for the MRF residue to be adjusted on a compositional basis because residue composition varies by season and location, which affects the analysis. Additionally, proximity to SRF conversion facilities and cement kilns will vary for each MRF and can impact the analysis so the methodology allows these factors to be adjusted. A test case was studied to compare the landfilling or combustion of MRF residue in a cement kiln at a rate of 0.9 metric tons per hour (7884 metric tons for a one year period). The analysis details the total energy consumed, landfill avoidance, amount of fuel displaced, and the total equivalent CO2 emissions of each scenario. The methodology successfully models the reference and SRF case and is robust enough to be used with a wide variety of potential SRF scenarios. A few parametric studies were performed on the transportation and landfill variables to determine their relative effect on results. It was found that additional transportation would have minimal effect of total energy consumption. When using SRF as a supplementary cement kiln fuel, the equivalent CO2 reductions are higher in scenarios with low methane capture efficiency at the landfill. Overall, it was found that using SRF as a supplementary fuel at cement kilns reduces the total fossil energy consumption and total equivalent CO2 reductions by 6% and 76%, respectively.
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Ni, Siliang, and Dan Zhao. "Numerical Study of Thermal Performance and NOx Emission for An Ammonia-Fuelled Micro-Combustor With Ring-Shaped Ribs in Lean Combustion." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59226.
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Abstract As a renewable energy source, ammonia is regarded as one of the ideal gases that can replace fossil fuels and has been extensively studied in large-scale combustion. However, studies on energy conversion efficiency and NOx emission in microscale are still inadequate. In this work, ammonia/oxygen premixed cylindrical micro-combustors with inner ribs under condition of lean combustion is numerically investigated. The key geometrical parameters of the ribs and the ammonia/oxygen equivalence ratio are evaluated based on thermal performance and NOx emission performance. Finally, the sensitivity analysis of NO and related reaction pathways are analyzed under different equivalence ratios. The results show that increasing the height of the rib and decreasing the distance between the first rib and the inlet can effectively inhibit the generation of NO. Among all cases, the combustor with U-shaped ribs is observed the minimum mole fraction of NO at the outlet under the same working condition, which is 16% less comparing to the rectangular-shaped one. Besides, the mean wall temperature shows a weak correlation with NO emission. Increasing the equivalence ratio can help gain higher mean wall temperature, but at the same time promotes NOx production. This study is helpful to the design and improvement of micro-combustors fuelled by ammonia.
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Moghadam, A., and A. N. Corina. "Modelling Stress Evolution in Cement Plugs During Hydration." In 56th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2022. http://dx.doi.org/10.56952/arma-2022-0966.
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ABSTRACT: In this work, we have developed a methodology to model the stress evolution in cement plugs during hydration. The model begins with the slurry state of cement and calculates the water consumption and void creation over time as the hydration reactions progress. The void volume change due to chemical shrinkage is imported into a coupled mechanical model that calculates the pore pressure drop and the resulting change in stresses. The results of the proposed modelling methodology are verified using lab experiments from the literature. The results provide new insights in understanding cement behavior under lab and field conditions. Under most scenarios, cement’s pore pressure drops to saturation pressure of water which leads to partial evaporation of the remaining pore water. This pore pressure drop controls the radial stress change, according to the theory of poroelasticity. For a plug set under an initial pressure of 5 MPa, the radial stress drops to 1.6 MPa after 20 hours of curing. This stress drop can cause the cement to debond from the casing, if the fluid pressure above the plug exceeds the final radial stress. This methodology can be extended to annular cements and initial cement stress after placement can be readily calculated. 1. INTRODUCTION Zonal isolation in active and abandoned wells is paramount to ensure minimal fugitive methane emissions and to protect shallow freshwater aquifers. Wells penetrate different strata and can create a leakage pathway in case of a damaged cement sheath. This has been linked to methane emissions to the atmosphere (Schout et al., 2019), and aquifers (Osborn et al., 2011). Historically, oil and gas wells have been the main culprit in providing the leakage pathway for unwanted fluids. As more geothermal, energy, and carbon storage wells are drilled as part of the energy transition, zonal isolation challenges require more attention due to the long expected lifetime for these wells and unique operating conditions.
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Sun, Liyong, and Adam S. Hollinger. "Modeling of Heat Removal in a Single-Channel Microscale Fuel Cell." In ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology collocated with the ASME 2017 Power Conference Joint With ICOPE-17, the ASME 2017 11th International Conference on Energy Sustainability, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fuelcell2017-3405.
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Considerable waste heat is generated via the oxygen reduction reaction in polymer electrolyte membrane fuel cells. Consequently, heat generation and removal in conventional fuel cell architectures has been carefully investigated in order to achieve effective thermal management. Here we present a novel microscale fuel cell design that utilizes a half-membrane electrode assembly. In this design, a single fuel/electrolyte stream provides an additional pathway for heat removal that is not present in traditional fuel cell architectures. The model presented here investigates heat removal over a range of inlet fuel temperatures. Heat generation densities are determined experimentally for all inlet fuel temperatures. The simulations presented here predict thermal profiles throughout this microscale fuel cell design. Simulation results show that the fuel stream dominates heat removal at room temperature. As inlet fuel temperature increases, the majority of heat removal occurs via convection with the ambient air. The model also shows that heat transfer through the oxidant channel is minimal over the range of inlet fuel temperatures.
Reports on the topic "Minimum Energy Pathway"
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Brosh, Arieh, Gordon Carstens, Kristen Johnson, Ariel Shabtay, Joshuah Miron, Yoav Aharoni, Luis Tedeschi, and Ilan Halachmi. Enhancing Sustainability of Cattle Production Systems through Discovery of Biomarkers for Feed Efficiency. United States Department of Agriculture, July 2011. http://dx.doi.org/10.32747/2011.7592644.bard.
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Feed inputs represent the largest variable cost of producing meat and milk from ruminant animals. Thus, strategies that improve the efficiency of feed utilization are needed to improve the global competitiveness of Israeli and U.S. cattle industries, and mitigate their environmental impact through reductions in nutrient excretions and greenhouse gas emissions. Implementation of innovative technologies that will enhance genetic merit for feed efficiency is arguably one of the most cost-effective strategies to meet future demands for animal-protein foods in an environmentally sustainable manner. While considerable genetic variation in feed efficiency exist within cattle populations, the expense of measuring individual-animal feed intake has precluded implementation of selection programs that target this trait. Residual feed intake (RFI) is a trait that quantifies between-animal variation in feed intake beyond that expected to meet energy requirements for maintenance and production, with efficient animals being those that eat less than expected for a given size and level of production. There remains a critical need to understand the biological drivers for genetic variation in RFI to facilitate development of effective selection programs in the future. Therefore, the aim of this project was to determine the biological basis for phenotypic variation in RFI of growing and lactating cattle, and discover metabolic biomarkers of RFI for early and more cost-effective selection of cattle for feed efficiency. Objectives were to: (1) Characterize the phenotypic relationships between RFI and production traits (growth or lactation), (2) Quantify inter-animal variation in residual HP, (3) Determine if divergent RFIphenotypes differ in HP, residual HP, recovered energy and digestibility, and (4) Determine if divergent RFI phenotypes differ in physical activity, feeding behavior traits, serum hormones and metabolites and hepatic mitochondrial traits. The major research findings from this project to date include: In lactating dairy cattle, substantial phenotypic variation in RFI was demonstrated as cows classified as having low RMEI consumed 17% less MEI than high-RMEI cows despite having similar body size and lactation productivity. Further, between-animal variation in RMEI was found to moderately associated with differences in RHP demonstrating that maintenance energy requirements contribute to observed differences in RFI. Quantifying energetic efficiency of dairy cows using RHP revealed that substantial changes occur as week of lactation advances—thus it will be critical to measure RMEI at a standardized stage of lactation. Finally, to determine RMEI in lactating dairy cows, individual DMI and production data should be collected for a minimum of 6 wk. We demonstrated that a favorably association exists between RFI in growing heifers and efficiency of forage utilization in pregnant cows. Therefore, results indicate that female progeny from parents selected for low RFI during postweaning development will also be efficient as mature females, which has positive implications for both dairy and beef cattle industries. Results from the beef cattle studies further extend our knowledge regarding the biological drivers of phenotypic variation in RFI of growing animals, and demonstrate that significant differences in feeding behavioral patterns, digestibility and heart rate exist between animals with divergent RFI. Feeding behavior traits may be an effective biomarker trait for RFI in beef and dairy cattle. There are differences in mitochondrial acceptor control and respiratory control ratios between calves with divergent RFI suggesting that variation in mitochondrial metabolism may be visible at the genome level. Multiple genes associated with mitochondrial energy processes are altered by RFI phenotype and some of these genes are associated with mitochondrial energy expenditure and major cellular pathways involved in regulation of immune responses and energy metabolism.