4,773 research outputs found
A path planning control for a vessel dynamic positioning system based on robust adaptive fuzzy strategy
The thrusters and propulsion propellers systems, as well as the operating situations, are all well-known nonlinearities which are caused less accuracy of the dynamic positioning system (DPS) of vessels in the path planning control process. In this study, to enhance the robust performance of the DPS, we proposed a robust adaptive fuzzy control model to reduce the effect of uncertainty problems and disturbances on the DPS. Firstly, the adaptive fuzzy controller with adaptive law is designed to adjust the membership function of the fuzzy controller to minimize the error in path planning control of the vessel. Secondly, the H∞ performance of robust tracking is proved by the Lyapunov theory. Moreover, compared to the other controller, a simulation experiment comprising two case studies confirmed the efficiency of the approach. Finally, the results showed that the proposed controller reaches control quality, performance and stability
Heun Functions and the energy spectrum of a charged particle on a sphere under magnetic field and Coulomb force
We study the competitive action of magnetic field, Coulomb repulsion and
space curvature on the motion of a charged particle. The three types of
interaction are characterized by three basic lengths: l_{B} the magnetic
length, l_{0} the Bohr radius and R the radius of the sphere. The energy
spectrum of the particle is found by solving a Schr\"odinger equation of the
Heun type, using the technique of continued fractions. It displays a rich set
of functioning regimes where ratios \frac{R}{l_{B}} and \frac{R}{l_{0}} take
definite values.Comment: 12 pages, 5 figures, accepted to JOPA, november 200
q-deformed harmonic and Clifford analysis and the q-Hermite and Laguerre polynomials
We define a q-deformation of the Dirac operator, inspired by the one
dimensional q-derivative. This implies a q-deformation of the partial
derivatives. By taking the square of this Dirac operator we find a
q-deformation of the Laplace operator. This allows to construct q-deformed
Schroedinger equations in higher dimensions. The equivalence of these
Schroedinger equations with those defined on q-Euclidean space in quantum
variables is shown. We also define the m-dimensional q-Clifford-Hermite
polynomials and show their connection with the q-Laguerre polynomials. These
polynomials are orthogonal with respect to an m-dimensional q-integration,
which is related to integration on q-Euclidean space. The q-Laguerre
polynomials are the eigenvectors of an su_q(1|1)-representation
A case of hepatic cyst-induced internal jugular venous thrombosis
• Echocardiography can demonstrate hepatic cyst–induced right atrial compression. • Hepatic cyst–induced blood flow stasis can cause internal jugular venous thrombus. • Laparoscopic deroofing of hepatic cysts is a safe and effective treatment
Alpha Event-Related Decreases During Encoding in Adults with ADHD - An Investigation of Sustained Attention and Working Memory Processes.
BACKGROUND: Executive functioning deficits are central to established neuropsychological models of ADHD. Oscillatory activity, particularly the alpha rhythm (8-12Hz) has been associated with cognitive impairments in ADHD. However, most studies to date examined such neural mechanisms underlying executive dysfunction in children and adolescents with ADHD, raising the question of whether and to what extent those ADHD-related working memory impairments are still present in adults. To this end, the current study aimed to investigate the role of alpha event-related decreases (ERD) during working memory processes in adults with and without ADHD. METHODS: We collected electroencephalographic (EEG) data from 85 adults with a lifetime diagnosis of ADHD and 105 controls (aged 32-64), while they performed a continuous performance (CPT) and a Sternberg working memory task (SDRT). Time-frequency and independent component analysis (ICA) was used to identify alpha (8-12Hz) clusters to examine group and condition effects during the temporal profile of sustained attention and working memory processes (encoding, maintenance, retrieval), loads (low and high) and trial type (go and nogo). RESULTS: Individuals with ADHD exhibited higher reaction time-variability in SDRT, and slower response times in SDRT and CPT, despite no differences in task accuracy. Although working memory load was associated with stronger alpha ERD in both tasks and both groups (ADHD, controls), we found no evidence for attenuated alpha ERD in adults with ADHD, failing to replicate effects reported in children. In contrast, when looking at the whole sample, the correlations of alpha power during encoding with inattention and hyperactivity-impulsivity symptoms were significant, replicating prior findings in children with ADHD, but suggesting an alternate source for these effects in adults. CONCLUSIONS: Our results corroborate the robustness of alpha as a marker of visual attention and suggest that occipital alpha ERD normalizes in adulthood, but with unique contributions of centro-occipital alpha ERD, suggesting a secondary source. This implies that deviations in processes other than previously reported visuospatial cortex engagement account for the persistent symptoms and cognitive deficits in adults with a history of ADHD
FedDCT: Federated Learning of Large Convolutional Neural Networks on Resource Constrained Devices using Divide and Co-Training
We introduce FedDCT, a novel distributed learning paradigm that enables the
usage of large, high-performance CNNs on resource-limited edge devices. As
opposed to traditional FL approaches, which require each client to train the
full-size neural network independently during each training round, the proposed
FedDCT allows a cluster of several clients to collaboratively train a large
deep learning model by dividing it into an ensemble of several small sub-models
and train them on multiple devices in parallel while maintaining privacy. In
this co-training process, clients from the same cluster can also learn from
each other, further improving their ensemble performance. In the aggregation
stage, the server takes a weighted average of all the ensemble models trained
by all the clusters. FedDCT reduces the memory requirements and allows low-end
devices to participate in FL. We empirically conduct extensive experiments on
standardized datasets, including CIFAR-10, CIFAR-100, and two real-world
medical datasets HAM10000 and VAIPE. Experimental results show that FedDCT
outperforms a set of current SOTA FL methods with interesting convergence
behaviors. Furthermore, compared to other existing approaches, FedDCT achieves
higher accuracy and substantially reduces the number of communication rounds
(with times fewer memory requirements) to achieve the desired accuracy on
the testing dataset without incurring any extra training cost on the server
side.Comment: Under review by the IEEE Transactions on Network and Service
Managemen
Interplay of the Scaling Limit and the Renormalization Group: Implications for Symmetry Restoration
Symmetry restoration is usually understood as a renormalization group induced
phenomenon. In this context, the issue of whether one-loop RG equations can be
trusted in predicting symmetry restoration has recently been the subject of
much debate. Here we advocate a more pragmatic point of view and expand the
definition of symmetry restoration to encompass all situations where the
physical properties have only a weak dependence upon an anisotropy in the bare
couplings. Moreover we concentrate on universal properties, and so take a
scaling limit where the physics is well described by a field theory. In this
context, we find a large variety of models that exhibit, for all practical
purposes, symmetry restoration: even if symmetry is not restored in a strict
sense, physical properties are surprisingly insensitive to the remaining
anisotropy.
Although we have adopted an expanded notion of symmetry restoration, we
nonetheless emphasize that the scaling limit also has implications for symmetry
restoration as a renormalization group induced phenomenon. In all the models we
considered, the scaling limit turns out to only permit bare couplings which are
nearly isotropic and small. Then the one-loop beta-function should contain all
the physics and higher loop orders can be neglected. We suggest that this
feature generalizes to more complex models. We exhibit a large class of
theories with current-current perturbations (of which the SO(8) model of
interest in two-leg Hubbard ladders/armchair carbon nanotubes is one) where the
one-loop beta-functions indicates symmetry restoration and so argue that these
results can be trusted within the scaling limit.Comment: 20 pages, 11 figures, RevTe
- …