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Results for “optimization methods”
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Double sweep preconditioner for optimized Schwarz methods applied to the Helmholtz problem
This paper presents a preconditioner for non-overlapping Schwarz methods applied to the Helmholtz problem. Starting from a simple analytic example, we show how such a preconditioner can be designed by approximating the inverse of the iteration operator for a layered partitioning of the domain. The preconditioner works by propagating information globally by concurrently sweeping in both directions over the subdomains, and can be interpreted as a coarse grid for the domain decomposition method. The resulting algorithm is shown to converge very fast, independently of the number of subdomains and frequency. The preconditioner has the advantage that, like the original Schwarz algorithm, it can be implemented as a matrix-free routine, with no additional preprocessing.
Managing connected and automated vehicles at isolated intersections: From reservation- to optimization-based methods
Not provided.
Machine learning-based optimization of air-cooled heat sinks
Machine learning-based models using Artificial Neural Network (ANN) and greedy search algorithm are used to optimize air-cooled parallel plate-finned heat sinks (PPFHSs) subjected to laminar flow over an extensive range of design parameters. Here, the thermal and hydraulic performances of PPFHSs are represented by heat transfer coefficient (h) and pressure drop (ΔP), respectively. Optimization objectives for PPFHS designs can vary from industry to industry depending on their design priorities. The present study proposes a novel and generalized optimization method that defines practical optimization objectives and provides an accurate optimization process to design effective PPFHSs for a wide range of industrial applications with different design requirements. Three optimization objectives are presented in this study: (i) the largest h PΔ, (ii) the largest h within a specified maximum allowed flow rate, and (iii) the lowest weight that maximizes h for operation within the maximum allowed flow rate. While the shortcoming of the first objective is demonstrated, the other two objectives are found to be suitable for designing effective heat sinks (HSs) across different applications. Results suggest a promising trend from the third objective to develop HSs with ~ 37-68% lower weight, 80-85% reduced ΔP, and negligible penalty in h compared with optimized HSs obtained from the second objective. However, since the third objective leads to HSs with thinner fins, structural analysis should be performed to ensure reliable operation of the HSs.
Properties of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters
The structures of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters with up to 44 atoms have been determined theoretically using an unbiased structure-optimization method in combination with a parametrized, density-functional description of the total energy for a given structure. By analyzing the total energy in detail, particularly stable clusters are identified. Moreover, general trends in the structures are identified with the help of specifically constructed descriptors.
Experimental and modeling study of chemical-based strategies for mitigating dust formation in fusion reactors [Plasma Flow Reactor Chemical Kinetics: A Method Toward Optimizing Nano-Manufacturing and Laser Inertial Fusion Energy Strategies]
We studied carbon/hydrogen/oxygen chemical kinetics at time scales and thermal conditions relevant to fusion energy applications using a custom-built plasma flow reactor to investigate chemical-based strategies for eliminating carbon dust formation in fusion reactors. Acetylene and oxygen gases under varying conditions of initial concentrations are injected into an inductively coupled argon plasma where complete molecular dissociation occurs. The evolution of chemical species is investigated along the plasma flow reactor as a function of temperature and residence time. Atomized species of C, H, and O cool from 5000 K to 1000 K within 30 ms at atmospheric pressures. We employed optical emission and infrared absorption spectroscopy to measure the reaction intermediates (e.g. C 2 ) and products (e.g. C 2 H 2 ). Chemical equilibrium models are inadequate to describe the evolution of carbon molecular products, and thus a chemical kinetics model is developed. In both experiments and kinetic modelling, we find that the addition of oxygen in 1:1 proportion to carbon strongly favors the formation of CO, preventing the formation of acetylene (an important soot precursor) in less than 10 milliseconds. The kinetics model is also used to perform a reaction sensitivity and a rate of production analyses to identify the rate determining steps and the major chemical pathways that control the acetylene production/consumption. The results demonstrate the feasibility of chemical-based strategies for eliminating the formation of carbonaceous particles in fusion energy reactors.
XFEL diffraction: Developing processing methods to optimize data quality
Serial crystallography, using either femtosecond X-ray pulses from free-electron laser sources or short synchrotron-radiation exposures, has the potential to reveal metalloprotein structural details while minimizing damage processes. However, deriving a self-consistent set of Bragg intensities from numerous still-crystal exposures remains a difficult problem, with optimal protocols likely to be quite different from those well established for rotation photography. Here several data processing issues unique to serial crystallography are examined. It is found that the limiting resolution differs for each shot, an effect that is likely to be due to both the sample heterogeneity and pulse-to-pulse variation in experimental conditions. Shots with lower resolution limits produce lower-quality models for predicting Bragg spot positions during the integration step. Also, still shots by their nature record only partial measurements of the Bragg intensity. An approximate model that corrects to the full-spot equivalent (with the simplifying assumption that the X-rays are monochromatic) brings the distribution of intensities closer to that expected from an ideal crystal, and improves the sharpness of anomalous difference Fourier peaks indicating metal positions.
Dynamic Programming Method to Optimally Select Power Distribution System Reliability Upgrades
Not Available
Structured Quasi-Newton Methods for Optimization with Orthogonality Constraints
Not provided.
A Method of Optimizing Field Roll-Off and the Peak Field of Hybrid Planar Undulators
Two new advancements have recently been made concerning hybrid planar undulator design. The first finding is how precisely the field roll-off in the x-direction can be controlled by altering the pole’s xy chamfer dimension. The second finding is how effectively the peak field can be increased by use of a large pole xx chamfer. The detailed field calculations regarding these pole chamfers are reported in this technical note.
Additive Manufacturing as a Hybrid Synthesis-Joining Method to Optimize Magnetic and Mechanical Properties of Dissimilar Alloys.
Abstract not provided.
Presentation: Bench Scale Development of a Novel Direct Air Capture Technology Using High-Capacity Structured Sorbents
The presentation provides a status report of bench-scale development of a DAC technology, specifically sorbent washcoat optimization, sorbent stability, desorption method optimization, heating layer performance, and bench-scale design & testing.
A gradient-based method for optimization with Shock Response Spectra
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Method for optimization of experiment design in aerosol size distribution measurement using multi-angle light scattering
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Linear unfolding methods and optimization for X-ray and similar spectra.
X ray and similar spectra optimization for unfolding reexamined stressing accuracy limitations
A method for optimizing control-free costs in systems with linear controllers.
Optimization of control independent cost functions in multidimensional system with linear controllers