174,962 research outputs found
Hybrid 6-DoFs magnetic localization for robotic capsule endoscopes compatible with high-grade magnetic field navigation
This paper proposes a hybrid 6-DoFs localization system for endoscopic magnetic capsules, compatible with external high-grade permanent magnetic locomotion. The proposed localization system, which is able to provide an accurate estimation of the endoscopic capsule pose, finds application in the robotic endoscopy field to provide efficient closed-loop navigation of a magnetically-driven tethered capsule. It takes advantage of two optimization steps based on a triangulation approach, i.e. (1) mathematical approximations of the magnetic field, and (2) minimization of the magnetic field mean square deviation. The proposed localization system was tested in two different in-vitro scenarios for mimicking the clinical cases that a magnetic capsule would encounter during tele-operated magnetic navigation. The development phase was preceded by an in-depth work-space analysis to lay the groundwork for the localization design and implementation. Results of the hybrid 6-DoFs localization system show a significant accuracy in accordance with the state-of-the-art, i.e. < 5 mm and < 5° in position and orientation, but introducing benefits in expanding the work-space by increasing the number of electromagnets on the operating table as an independent solution with respect to the external magnetic locomotion source
The multiferroic phase of DyFeO:an ab--initio study
By performing accurate ab-initio density functional theory calculations, we
study the role of electrons in stabilizing the magnetic-field-induced
ferroelectric state of DyFeO. We confirm that the ferroelectric
polarization is driven by an exchange-strictive mechanism, working between
adjacent spin-polarized Fe and Dy layers, as suggested by Y. Tokunaga [Phys.
Rev. Lett, \textbf{101}, 097205 (2008)]. A careful electronic structure
analysis suggests that coupling between Dy and Fe spin sublattices is mediated
by Dy- and O- hybridization. Our results are robust with respect to the
different computational schemes used for and localized states, such as
the DFT+ method, the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional and the
GW approach. Our findings indicate that the interaction between the and
sublattice might be used to tailor ferroelectric and magnetic properties of
multiferroic compounds.Comment: 6 pages, 4 figures-Revised versio
A Magnetically and Electrically Powered Hybrid Micromotor in Conductive Solutions: Synergistic Propulsion Effects and Label-Free Cargo Transport and Sensing
Electrically powered micro- and nanomotors are promising tools for in-vitro
single-cell analysis. In particular, single cells can be trapped, transported
and electroporated by a Janus particle (JP) using an externally applied
electric field. However, while dielectrophoretic (DEP)-based cargo manipulation
can be achieved at high-solution conductivity, electrical propulsion of these
micromotors becomes ineffective at solution conductivities exceeding 0.3mS/cm.
Here, we successfully extended JP cargo manipulation and transport capabilities
to conductive near-physiological (<6mS/cm) solutions by combining magnetic
field-based micromotor propulsion and navigation with DEP-based manipulation of
various synthetic and biological cargos. Combination of a rotating magnetic
field and electric field resulted in enhanced micromotor mobility and steering
control through tuning of the electric field frequency. conditions are
necessary. In addition, we demonstrated the micromotors ability of identifying
apoptotic cell among viable and necrotic cells based their dielectrophoretic
difference, thus, enabling to analyze the apoptotic status in the single cell
samples for drug discovery, cell therapeutics and immunotherapy. We also
demonstrated the ability to trap and transport live cells towards regions
containing doxorubicin-loaded liposomes. This hybrid micromotor approach for
label-free trapping, transporting and sensing of selected cells within
conductive solutions, opens new opportunities in drug delivery and single cell
analysis, where close-to-physiological medi
An Entropy Stable Nodal Discontinuous Galerkin Method for the resistive MHD Equations. Part II: Subcell Finite Volume Shock Capturing
The second paper of this series presents two robust entropy stable shock-capturing methods for discontinuous Galerkin spectral element(DGSEM)discretizations of the compressible magneto-hydrodynamics (MHD) equations. Specifically, we use the resistive GLM-MHD equations, which include a divergence cleaning mechanism that is based on a generalized Lagrange multiplier (GLM). For the continuous entropy analysis to hold, and due to the divergence-free constraint on the magnetic field, the GLM-MHD system requires the use of non-conservative terms, which need special treatment.
Hennemann et al. ["A provably entropy stable subcell shock capturing approach for high order split form DG for the compressible Euler equations". JCP, 2020] recently presented an entropy stable shock-capturing strategy for DGSEM discretizations of the Euler equations that blends the DGSEM scheme with a subcell first-order finite volume (FV) method. Our first contribution is the extension of the method of Hennemann et al. to systems with non-conservative terms, such as the GLM-MHD equations. In our approach, the advective and non-conservative terms of the equations are discretized with a hybrid FV/DGSEM scheme, whereas the visco-resistive terms are discretized only with the high-order DGSEM method. We prove that the extended method is entropy stable on three-dimensional unstructured curvilinear meshes. Our second contribution is the derivation and analysis of a second entropy stable shock-capturing method that provides enhanced resolution by using a subcell reconstruction procedure that is carefully built to ensure entropy stability.
We provide a numerical verification of the properties of the hybrid FV/DGSEM schemes on curvilinear meshes and show their robustness and accuracy with common benchmark cases, such as the Orszag-Tang vortex and the GEM (Geospace Environmental Modeling) reconnection challenge. Finally, we simulate a space physics application: the interaction of Jupiter's magnetic field with the plasma torus generated by the moon Io
Novel permanent magnet motor drives for electric vehicles
Novel permanent magnet (PM) motor drives have been successfully developed to fulfil the special requirements for electric vehicles such as high power density, high efficiency, high starting torque, and high cruising speed. These PM motors are all brushless and consist of various types, namely rectangular-fed, sinusoidal-fed, surface-magnet, buried-magnet, and hybrid. The advent of novel motor configurations lies on the unique electro-magnetic topology, including the concept of multipole magnetic circuit and full slot-pitch coil span arrangements, leading to a reduction in both magnetic yoke and copper, decoupling of each phase flux path, and hence an increase in both power density and efficiency. Moreover, with the use of fractional number of slots per pole per phase, the cogging torque can be eliminated. On the other hand, by employing the claw-type rotor structure and fixing an additional field winding as the inner stator, these PM hybrid motors can further provide excellent controllability and improve efficiency map. In the PM motors, by purposely making use of the transformer EMF to prevent the current regulator from saturation, a novel control approach is developed to allow for attaining high-speed constant-power operation which is particularly essential for electric vehicles during cruising. Their design philosophy, control strategy, theoretical analysis, computer simulation, experimental tests and application to electric vehicles are described. © 1996 IEEE.published_or_final_versio
Pegasus: A New Hybrid-Kinetic Particle-in-Cell Code for Astrophysical Plasma Dynamics
We describe Pegasus, a new hybrid-kinetic particle-in-cell code tailored for
the study of astrophysical plasma dynamics. The code incorporates an
energy-conserving particle integrator into a stable, second-order--accurate,
three-stage predictor-predictor-corrector integration algorithm. The
constrained transport method is used to enforce the divergence-free constraint
on the magnetic field. A delta-f scheme is included to facilitate a
reduced-noise study of systems in which only small departures from an initial
distribution function are anticipated. The effects of rotation and shear are
implemented through the shearing-sheet formalism with orbital advection. These
algorithms are embedded within an architecture similar to that used in the
popular astrophysical magnetohydrodynamics code Athena, one that is modular,
well-documented, easy to use, and efficiently parallelized for use on thousands
of processors. We present a series of tests in one, two, and three spatial
dimensions that demonstrate the fidelity and versatility of the code.Comment: 27 pages, 12 figures, accepted for publication in Journal of
Computational Physic
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