15 research outputs found
Generating Interpretable Fuzzy Controllers using Particle Swarm Optimization and Genetic Programming
Autonomously training interpretable control strategies, called policies,
using pre-existing plant trajectory data is of great interest in industrial
applications. Fuzzy controllers have been used in industry for decades as
interpretable and efficient system controllers. In this study, we introduce a
fuzzy genetic programming (GP) approach called fuzzy GP reinforcement learning
(FGPRL) that can select the relevant state features, determine the size of the
required fuzzy rule set, and automatically adjust all the controller parameters
simultaneously. Each GP individual's fitness is computed using model-based
batch reinforcement learning (RL), which first trains a model using available
system samples and subsequently performs Monte Carlo rollouts to predict each
policy candidate's performance. We compare FGPRL to an extended version of a
related method called fuzzy particle swarm reinforcement learning (FPSRL),
which uses swarm intelligence to tune the fuzzy policy parameters. Experiments
using an industrial benchmark show that FGPRL is able to autonomously learn
interpretable fuzzy policies with high control performance.Comment: Accepted at Genetic and Evolutionary Computation Conference 2018
(GECCO '18
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Unlubricated sliding properties of ion beam and excimer laser mixed Fe-Ti-C multilayered films
Multilayered Fe-Ti-C films consisting of eleven sublayers were vacuum deposited onto an AISI 304 stainless steel substrate and subsequently mixed using either 400 keV Xe ions or an excimer laser, operating at a wavelength of 308 nm. Ion mixing was accomplished in a two step process: the multilayers were first irradiated with 1 /times/ 10/sup 17/ Xe/cm/sup 2/ at 520 C, after which half of the sample was irradiated with 5 /times/10/sup 15/ Xe/cm/sup 2/ at O C. Laser mixing was carried out at both 1.1 and 1.7 J/cm/sup 2/ with the number of pulses varied between 1 and 10. Pin-on-disc studies revealed only slight differences between the two kinds of ion beam mixed samples, whereas the dry sliding properties of laser mixed samples were strongly dependent on the total fluence used. In the optimum conditions similar friction coefficients were obtained on both kinds of samples. 13 refs., 4 figs
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Nitrogen and boron ion implantation into electrodeposited hard chrome
Electrodeposited hard chrome was ion implanted with N alone, B alone, and a combination. Separate N and B implantation was done at 75 keV and incident doses of 2, 4, and 8x10{sup 17} at/cm{sup 2}. Samples with both N/B implants used 75 keV and incident dose levels of 4x10{sup 17} N- and B-at/cm{sup 2}. Beam-line system was used. Retained dose was measured using ion beam analysis, which indicated most of the incident dose was retained. Surface hardness, wear coefficient, and friction coefficient were determined by nanohardness indentation and pin-on-disk wear. At a depth of 50 nm, surface hardness increased from 18{+-}1 GPa (unimplanted) to a max of 23{+-}4 GPa for B implant and 26{+-}1 GPa for N implant. the wear coefficient was reduced by 1.3x to 7.4x, depending on implantation. N implant results in lower wear coefficients than B implant
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Tribological properties of nitrogen implanted and boron implanted steels
Samples of a steel with high chrome content was implanted separately with 75 keV nitrogen ions and with 75 keV boron ions. Implanted doses of each ion species were 2-, 4-, and 8 {times} 10{sup 17}/cm{sup 2}. Retained doses were measured using resonant non-Rutherford Backscattering Spectrometry. Tribological properties were determined using a pin-on-disk test with a 6-mm diameter ruby pin with a velocity of 0.94 m/min. Testing was done at 10% humidity with a load of 377 g. Wear rate and coefficient of friction were determined from these tests. While reduction in the wear rate for nitrogen implanted materials was observed, greater reduction (more than an order of magnitude) was observed for boron implanted materials. In addition, reduction in the coefficient of friction for high-dose boron implanted materials was observed. Nano-indentation revealed a hardened layer near the surface of the material. Results from grazing incidence x-ray diffraction suggest the formation of Fe{sub 2}N and Fe{sub 3}N in the nitrogen implanted materials and Fe{sub 3}B in the boron implanted materials. Results from transmission electron microscopy will be presented
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Development of ion beam techniques for the study of special nuclear materials related problems
This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The scientific objective of this project was to develop the ion beam techniques for the characterization of actinides and their effects on other materials. It was designed to enhance their ability to quantitatively understand the oxidation, corrosion, diffusion, stability, and radiation damage of actinides and the materials with which they are in contact. The authors developed and applied several low-energy nuclear techniques (resonant and nonresonant backscattering, nuclear reaction analysis, and particle-induced x-ray emission) to the quantitative study of the near surfaces of actinide and tritide materials, and determined the absolute accuracy and precision of ion beam measurements on these materials. They also demonstrated the use of variable-energy alpha beams for the study of accelerated aging of polymeric materials in contact with actinide materials
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Development and application of the Los Alamos nuclear microprobe: hardware, software, and calibration
There is a great demand for spatially resolved quantitative trace element analyses of geologic samples. This class of samples is characteristically heterogeneous, fine grained, and compositionally complex. The Los Alamos nuclear microprobe has been developed for, and applied to, non-destructive in-situ geochemical analysis, primarily using the proton induced x-ray emission technique (PIXE). Characteristic x-ray spectra are acquired by bombardment with 1 to 200 nA beams of protons from the Los Alamos vertical Van de Graaff accelerator. Beam spot diameters of 10 ..mu..m are routine. After spectrum deconvolution, detection limits of approximately 5 ppM are obtained for an integrated charge on the order of 10 ..mu..C. Applications, concomitant with development have included analyses of meteorites, including one potential sample of Mars, terrestrial oil shales, archaeological artifacts, and ore mineral samples
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Indirect measurements of hydrogen: The deficit method for a many-component system
We have developed a simple technique for determining hydrogen atomic fraction from the ion backscattering spectrometry (IBS) signals of the remaining species. This technique uses the surface heights of various IBS signals in the form of a linear matrix equation. We apply this technique to in situ analysis of ion-beam-induced densification of sol-gel zirconia thin films, where hydrogen is the most volatile species during irradiation. Attendant errors are discussed with an emphasis on stopping powers and Bragg`s rule