542 research outputs found
Pump-Enhanced Continuous-Wave Magnetometry using Nitrogen-Vacancy Ensembles
Ensembles of nitrogen-vacancy centers in diamond are a highly promising
platform for high-sensitivity magnetometry, whose efficacy is often based on
efficiently generating and monitoring magnetic-field dependent infrared
fluorescence. Here we report on an increased sensing efficiency with the use of
a 532-nm resonant confocal cavity and a microwave resonator antenna for
measuring the local magnetic noise density using the intrinsic nitrogen-vacancy
concentration of a chemical-vapor deposited single-crystal diamond. We measure
a near-shot-noise-limited magnetic noise floor of 200 pT/
spanning a bandwidth up to 159 Hz, and an extracted sensitivity of
approximately 3 nT/, with further enhancement limited by the
noise floor of the lock-in amplifier and the laser damage threshold of the
optical components. Exploration of the microwave and optical pump-rate
parameter space demonstrates a linewidth-narrowing regime reached by virtue of
using the optical cavity, allowing an enhanced sensitivity to be achieved,
despite an unoptimized collection efficiency of <2 %, and a low
nitrogen-vacancy concentration of about 0.2 ppb.Comment: 10 pages and 5 figure
Nitrogen-Vacancy Ensemble Magnetometry Based on Pump Absorption
We demonstrate magnetic field sensing using an ensemble of nitrogen-vacancy
centers by recording the variation in the pump-light absorption due to the
spin-polarization dependence of the total ground state population. Using a 532
nm pump laser, we measure the absorption of native nitrogen-vacancy centers in
a chemical vapor deposited diamond placed in a resonant optical cavity. For a
laser pump power of 0.4 W and a cavity finesse of 45, we obtain a noise floor
of 100 nT/ spanning a bandwidth up to 125 Hz. We
project a photon shot-noise-limited sensitivity of 1
pT/ by optimizing the nitrogen-vacancy concentration and
the detection method.Comment: 7 pages and 5 figure
Optimal Tracking Current Control of Switched Reluctance Motor Drives Using Reinforcement Q-learning Scheduling
In this paper, a novel Q-learning scheduling method for the current
controller of switched reluctance motor (SRM) drive is investigated. Q-learning
algorithm is a class of reinforcement learning approaches that can find the
best forward-in-time solution of a linear control problem. This paper will
introduce a new scheduled-Q-learning algorithm that utilizes a table of Q-cores
that lies on the nonlinear surface of a SRM model without involving any
information about the model parameters to track the reference current
trajectory by scheduling infinite horizon linear quadratic trackers (LQT)
handled by Q-learning algorithms. Additionally, a linear interpolation
algorithm is proposed to guide the transition of the LQT between trained
Q-cores to ensure a smooth response as state variables evolve on the nonlinear
surface of the model. Lastly, simulation and experimental results are provided
to validate the effectiveness of the proposed control scheme.Comment: 8 pages, 10 figure
Constraints for Time-Multiplexed Structured Light with a Hand-held Camera
Multi-frame structured light in projector-camera systems affords high-density and non-contact methods of 3D surface reconstruction. However, they have strict setup constraints which can become expensive and time-consuming. Here, we investigate the conditions under which a projective homography can be used to compensate for small perturbations in pose caused by a hand-held camera. We synthesize data using a pinhole camera model and use it to determine the average 2D reprojection error per point correspondence. This error map is grouped into regions with specified upper-bounds to classify which regions produce sufficiently minimal error to be considered feasible for a structured-light projector-camera system with a hand-held camera. Empirical results demonstrate that a sub-pixel reprojection accuracy is achievable with a feasible geometric constraint
Wall effects on the transportation of a cylindrical particle in power-law fluids
The present work deals with the numerical calculation of the Stokes-type drag undergone by a cylindrical particle perpendicularly to its axis in a power-law fluid. In unbounded medium, as all data are not available yet, we provide a numerical solution for the pseudoplastic fluid. Indeed, the Stokes-type solution exists because the Stokes’ paradox does not take place anymore. We show a high sensitivity of the solution to the confinement, and the appearance of the inertia in the proximity of the Newtonian case, where the Stokes’ paradox takes place. For unbounded medium, avoiding these traps, we show that the drag is zero for Newtonian and dilatant fluids. But in the bounded one, the Stokes-type regime is recovered for Newtonian and dilatant fluids. We give also a physical explanation of this effect which is due to the reduction of the hydrodynamic screen length, for pseudoplastic fluids. Once the solution of the unbounded medium has been obtained, we give a solution for the confined medium numerically and asymptotically. We also highlight the consequence of the confinement and the backflow on the settling velocity of a fiber perpendicularly to its axis in a slit. Using the dynamic mesh technique, we give the actual transportation velocity in a power-law “Poiseuille flow”, versus the confinement parameter and the fluidity index, induced by the hydrodynamic interactions
Deep Injective Prior for Inverse Scattering
In electromagnetic inverse scattering, the goal is to reconstruct object
permittivity using scattered waves. While deep learning has shown promise as an
alternative to iterative solvers, it is primarily used in supervised frameworks
which are sensitive to distribution drift of the scattered fields, common in
practice. Moreover, these methods typically provide a single estimate of the
permittivity pattern, which may be inadequate or misleading due to noise and
the ill-posedness of the problem. In this paper, we propose a data-driven
framework for inverse scattering based on deep generative models. Our approach
learns a low-dimensional manifold as a regularizer for recovering target
permittivities. Unlike supervised methods that necessitate both scattered
fields and target permittivities, our method only requires the target
permittivities for training; it can then be used with any experimental setup.
We also introduce a Bayesian framework for approximating the posterior
distribution of the target permittivity, enabling multiple estimates and
uncertainty quantification. Extensive experiments with synthetic and
experimental data demonstrate that our framework outperforms traditional
iterative solvers, particularly for strong scatterers, while achieving
comparable reconstruction quality to state-of-the-art supervised learning
methods like the U-Net.Comment: 13 pages, 11 figure
Blessing of dimensionality at the edge
In this paper we present theory and algorithms enabling classes of Artificial
Intelligence (AI) systems to continuously and incrementally improve with
a-priori quantifiable guarantees - or more specifically remove classification
errors - over time. This is distinct from state-of-the-art machine learning,
AI, and software approaches. Another feature of this approach is that, in the
supervised setting, the computational complexity of training is linear in the
number of training samples. At the time of classification, the computational
complexity is bounded by few inner product calculations. Moreover, the
implementation is shown to be very scalable. This makes it viable for
deployment in applications where computational power and memory are limited,
such as embedded environments. It enables the possibility for fast on-line
optimisation using improved training samples. The approach is based on the
concentration of measure effects and stochastic separation theorems and is
illustrated with an example on the identification faulty processes in Computer
Numerical Control (CNC) milling and with a case study on adaptive removal of
false positives in an industrial video surveillance and analytics system
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