1,014 research outputs found
Asymptotic expansion for reversible A + B <-> C reaction-diffusion process
We study long-time properties of reversible reaction-diffusion systems of
type A + B C by means of perturbation expansion in powers of 1/t (inverse
of time). For the case of equal diffusion coefficients we present exact
formulas for the asymptotic forms of reactant concentrations and a complete,
recursive expression for an arbitrary term of the expansions. Taking an
appropriate limit we show that by studying reversible reactions one can obtain
"singular" solutions typical of irreversible reactions.Comment: 6 pages, no figures, to appear in PR
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
1.57 μm InGaAsP/InP surface emitting lasers by angled focus ion beam etching
The characteristics of 1.57 μm InGaAsP/InP surface emitting lasers based on an in-plan ridged structure and 45° beam deflectors defined by angled focused ion beam (FIB) etching are reported. With an externally integrated beam deflector, threshold currents and emission spectra identical to conventional edge emitting lasers are achieved. These results show that FIB etching is a very promising technique for the definition of high quality mirrors and beam deflectors on semiconductor heterostructures for a variety of integrated optoelectronic devices
Ultrafast Molecular Transport on Carbon Surfaces: The Diffusion of Ammonia on Graphite
We present a combined experimental and theoretical study of the
self-diffusion of ammonia on exfoliated graphite. Using neutron time-of-flight
spectroscopy we are able to resolve the ultrafast diffusion process of adsorbed
ammonia, NH, on graphite. Together with van der Waals corrected density
functional theory calculations we show that the diffusion of NH follows a
hopping motion on a weakly corrugated potential energy surface with an
activation energy of about 4 meV which is particularly low for this type of
diffusive motion. The hopping motion includes further a significant number of
long jumps and the diffusion constant of ammonia adsorbed on graphite is
determined with D=3.9 \cdot 10^{-8}~\mbox{m}^2 /\mbox{s} at 94 K
Modelling customer satisfaction for product development using genetic programming
Product development involves several processes in which product planning is the first one. Several tasksnormally are required to be conducted in the product-planning process and one of them is to determinesettings of design attributes for products. Facing with fierce competition in marketplaces, companies try to determine the settings such that the best customer satisfaction of products could be obtained.To achieve this, models that relate customer satisfaction to design attributes need to be developed first. Previous research has adopted various modelling techniques to develop the models, but those models are not able to address interaction terms or higher-order terms in relating customer satisfaction to design attributes, or they are the black-box type models. In this paper, a method based on genetic programming (GP) is presented to generate models for relating customer satisfaction to design attributes. The GP is first used to construct branches of a tree representing structures of a model where interaction terms and higher-order terms can be addressed. Then an orthogonal least-squares algorithm is used to determine the coefficients of the model. The models thus developed are explicit and consist of interaction terms and higher-order terms in relating customer satisfaction to design attributes. A case study of a digital camera design is used to illustrate the proposed method
Investment Opportunities Forecasting: Extending the Grammar of a GP-based Tool
In this paper we present a new version of a GP financial forecasting tool, called EDDIE 8. The novelty of this version is that it allows the GP to search in the space of indicators, instead of using pre-specified ones. We compare EDDIE 8 with its predecessor, EDDIE 7, and find that new and improved solutions can be found. Analysis also shows that, on average, EDDIE 8's best tree performs better than the one of EDDIE 7. The above allows us to characterize EDDIE 8 as a valuable forecasting tool
Onboard Evolution of Understandable Swarm Behaviors
Designing the individual robot rules that give rise to desired emergent swarm behaviors is difficult. The common method of running evolutionary algorithms off‐line to automatically discover controllers in simulation suffers from two disadvantages: the generation of controllers is not situated in the swarm and so cannot be performed in the wild, and the evolved controllers are often opaque and hard to understand. A swarm of robots with considerable on‐board processing power is used to move the evolutionary process into the swarm, providing a potential route to continuously generating swarm behaviors adapted to the environments and tasks at hand. By making the evolved controllers human‐understandable using behavior trees, the controllers can be queried, explained, and even improved by a human user. A swarm system capable of evolving and executing fit controllers entirely onboard physical robots in less than 15 min is demonstrated. One of the evolved controllers is then analyzed to explain its functionality. With the insights gained, a significant performance improvement in the evolved controller is engineered
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