The Particle Collision Algorithm (PCA) is a recently introduced metaheuristic conceptually similar to Simulated Annealing, without, though, the necessity of estimating the free parameters as in the latter algorithm. I...
详细信息
ISBN:
(纸本)0894480596
The Particle Collision Algorithm (PCA) is a recently introduced metaheuristic conceptually similar to Simulated Annealing, without, though, the necessity of estimating the free parameters as in the latter algorithm. It is loosely inspired by the physics of nuclear particle collision reactions, particularly scattering and absorption. A "particle" that reaches a promising area of the search space is "absorbed", while one that hits a low-fitness region is "scattered". PCA is also a Metropolis algorithm, as a solution worse than the currently best may be accepted with a certain probability. In this article, we introduce a populational version of the Particle Collision Algorithm, the Populational PCA (PopPCA), which is a hybridization of the PCA and the genetic algorithm (GA). At the end of a generation, the particles reproduce and the fittest individuals survive. We apply the new algorithm to an optimization problem that consists in adjusting several reactor cell parameters, such as dimensions, enrichment and materials, in order to minimize the average peak-factor in a three-enrichment-zone reactor, considering restrictions on the average thermal flux, criticality and sub-moderation. The populational PCA is compared to other metaheuristics previously applied to the problem and shows to perform better than them, thus demonstrating its potential for other applications and further development.
We have performed physical phantom and simulation study with PET to compare the effects of limiting iterations and post-smoothing. The phantom was designed to mimic small hot lesions typical in FDG PET. The phantom wa...
详细信息
We have performed physical phantom and simulation study with PET to compare the effects of limiting iterations and post-smoothing. The phantom was designed to mimic small hot lesions typical in FDG PET. The phantom was a body-sized 25L phantom. Eight 1cm hot spheres were filled with activity 8x the background. The phantom was scanned in 2D for 15 minutes on a GE Discovery STE. Data were framed into 1, 3, 5, and 15min frames. Images were reconstructed with a variety of subset sizes and up to 60 iterations, with corrections for attenuation, scatter, randoms, and dead-time. All image sets were post-smoothed with 4, 6, 8, 10, and 12mm FWHM Gaussian. ROI's were placed on all hot spheres, and 40 additional background ROI's were placed. Noise was measured as the variation in background ROI's. Additionally, noise was measured on a pixel-by-pixel basis as the variation over the ensemble of realizations of each frame time. Noise vs. contrast (sphere-background) were plotted for each image. The background noise method showed better results for limited iterations (～20% lower noise at a given contrast level) while the ensemble-based noise method favored post-smoothing of high iterations (with a similar ～20% difference). Similar results were obtained for simulations.
The details of two programs: five year dual degree BS mechanical engineering + MS nuclearengineering;and the summer bridge program, are discussed. These programs include use of distance learning in nuclear engineerin...
详细信息
The details of two programs: five year dual degree BS mechanical engineering + MS nuclearengineering;and the summer bridge program, are discussed. These programs include use of distance learning in nuclearengineering and university nuclearengineeringprogram interaction with industry and national laboratories. The students in the first program have five, one quarter Co-op sections - one less than in the standard UC engineering curriculum. The summer bridge program consists of introductory lectures on nuclearengineering and health physics, integrated with laboratory experiences and field trips.
For over 35 years, the UFTR highly-enriched core has been safely operated. As part of the Reduced Enrichment for Research and Test Reactors program, the core is currently being converted to low-enriched uranium fuel. ...
详细信息
ISBN:
(纸本)0894486977
For over 35 years, the UFTR highly-enriched core has been safely operated. As part of the Reduced Enrichment for Research and Test Reactors program, the core is currently being converted to low-enriched uranium fuel. The analyses presented in this paper were performed to verify that, from a neutronic perspective, a proposed low-enriched core can be operated as safely and as effectively as the highly-enriched core. Detailed Monte Carlo criticality calculations are performed to determine: i) Excess reactivity for different core configurations, ii) Individual integral blade worth and shutdown margin, iii) Reactivity coefficients and kinetic parameters, and iv) Flux profiles and core six-factor formula parameters.
暂无评论