549 research outputs found
Decentralized formation control with connectivity maintenance and collision avoidance under limited and intermittent sensing
A decentralized switched controller is developed for dynamic agents to
perform global formation configuration convergence while maintaining network
connectivity and avoiding collision within agents and between stationary
obstacles, using only local feedback under limited and intermittent sensing.
Due to the intermittent sensing, constant position feedback may not be
available for agents all the time. Intermittent sensing can also lead to a
disconnected network or collisions between agents. Using a navigation function
framework, a decentralized switched controller is developed to navigate the
agents to the desired positions while ensuring network maintenance and
collision avoidance.Comment: 8 pages, 2 figures, submitted to ACC 201
Composite Adaptive Lyapunov-Based Deep Neural Network (Lb-DNN) Controller
Recent advancements in adaptive control have equipped deep neural network
(DNN)-based controllers with Lyapunov-based adaptation laws that work across a
range of DNN architectures to uniquely enable online learning. However, the
adaptation laws are based on tracking error, and offer convergence guarantees
on only the tracking error without providing conclusions on the parameter
estimation performance. Motivated to provide guarantees on the DNN parameter
estimation performance, this paper provides the first result on composite
adaptation for adaptive Lyapunov-based DNN controllers, which uses the Jacobian
of the DNN and a prediction error of the dynamics that is computed using a
novel method involving an observer of the dynamics. A Lyapunov-based stability
analysis is performed which guarantees the tracking, observer, and parameter
estimation errors are uniformly ultimately bounded (UUB), with stronger
performance guarantees when the DNN's Jacobian satisfies the persistence of
excitation (PE) condition. Comparative simulation results demonstrate a
significant performance improvement with the developed composite adaptive
Lb-DNN controller in comparison to the tracking error-based Lb-DNN
Metabolomics demonstrates divergent responses of two Eucalyptus species to water stress
Past studies of water stress in Eucalyptus spp. generally highlighted the role of fewer than five âimportantâ metabolites, whereas recent metabolomic studies on other genera have shown tens of compounds are affected. There are currently no metabolite profiling data for responses of stress-tolerant species to water stress. We used GCâMS metabolite profiling to examine the response of leaf metabolites to a long (2 month) and severe (Ψpredawn < â2 MPa) water stress in two species of the perennial tree genus Eucalyptus (the mesic Eucalyptus pauciflora and the semi-arid Eucalyptus dumosa). Polar metabolites in leaves were analysed by GCâMS and inorganic ions by capillary electrophoresis. Pressureâvolume curves and metabolite measurements showed that water stress led to more negative osmotic potential and increased total osmotically active solutes in leaves of both species. Water stress affected around 30â40% of measured metabolites in E. dumosa and 10â15% in E. pauciflora. There were many metabolites that were affected in E. dumosa but not E. pauciflora, and some that had opposite responses in the two species. For example, in E. dumosa there were increases in five acyclic sugar alcohols and four low-abundance carbohydrates that were unaffected by water stress in E. pauciflora. Re-watering increased osmotic potential and decreased total osmotically active solutes in E. pauciflora, whereas in E. dumosa re-watering led to further decreases in osmotic potential and increases in total osmotically active solutes. This experiment has added several extra dimensions to previous targeted analyses of water stress responses in Eucalyptus, and highlights that even species that are closely related (e.g. congeners) may respond differently to water stress and re-waterin
Potential Energy Surface for H_2 Dissociation over Pd(100)
The potential energy surface (PES) of dissociative adsorption of H_2 on
Pd(100) is investigated using density functional theory and the full-potential
linear augmented plane wave (FP-LAPW) method. Several dissociation pathways are
identified which have a vanishing energy barrier. A pronounced dependence of
the potential energy on ``cartwheel'' rotations of the molecular axis is found.
The calculated PES shows no indication of the presence of a precursor state in
front of the surface. Both results indicate that steering effects determine the
observed decrease of the sticking coefficient at low energies of the H_2
molecules. We show that the topology of the PES is related to the dependence of
the covalent H(s)-Pd(d) interactions on the orientation of the H_2 molecule.Comment: RevTeX, 8 pages, 5 figures in uufiles forma
Intertwinings for general β Laguerre and Jacobi processes
We show that, for βâĽ1, the semigroups of β-Laguerre and β-Jacobi processes of different dimensions are intertwined in analogy to a similar result for β-Dyson Brownian motion recently obtained in Ramanan and Shkolnikov (Intertwinings of β-Dyson Brownian motions of different dimensions, 2016. arXiv:1608.01597). These intertwining relations generalize to arbitrary βâĽ1 the ones obtained for β=2 in Assiotis et al. (Interlacing diffusions, 2016. arXiv:1607.07182) between h-transformed KarlinâMcGregor semigroups. Moreover, they form the key step toward constructing a multilevel process in a GelfandâTsetlin pattern leaving certain Gibbs measures invariant. Finally, as a by-product, we obtain a relation between general β-Jacobi ensembles of different dimensions
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