Proposed Excitation Scheme Research Articles

Design of Two-Phase 4/6 Switched Reluctance Motor for Bidirectional Starting in Washing Machine Application

In this article, design modification of stator poles of conventional two-phase switched reluctance motor is proposed to achieve self-start in both directions of rotation. Stator poles are slanted in a particular direction at the pole tips. This creates a range of rotor positions where torque polarity is the same for both phases, so starting torque is available. A unique excitation scheme is also proposed to run the motor in a particular direction from any initial position. The sequence in which the two phases are excited and the duration of their first excitation decides the direction of continuous rotation. Washing machine is selected as a potential application of the proposed work. Design parameters such as input voltage, rated current, and torque-speed characteristics are investigated to suit top-load washing machines. Simulations are carried out in finite element analysis software. Relation between the slant angle of the stator pole tip and minimum starting torque is analyzed through parametric simulations. Experiments are performed on a prototype two-phase switched reluctance motor. An incremental encoder is used as a position sensor. The initial position is not known, but self-starting in both directions of rotation is achieved with the proposed excitation scheme.

A Laser Excitation Scheme for ^{229m}Th.

Direct laser excitation of the lowest known nuclear excited state in ^{229}Th has been a long-standing objective. It is generally assumed that reaching this goal would require a considerably reduced uncertainty of the isomer's excitation energy compared to the presently adopted value of (7.8±0.5) eV. Here we present a direct laser excitation scheme for ^{229m}Th, which circumvents this requirement. The proposed excitation scheme makes use of already existing laser technology and therefore paves the way for nuclear laser spectroscopy. In this concept, the recently experimentally observed internal-conversion decay channel of the isomeric state is used for probing the isomeric population. A signal-to-background ratio of better than 10^{4} and a total measurement time of less than three days for laser scanning appear to be achievable.

Spatial Filter Based Bessel-Like Beam for Improved Penetration Depth Imaging in Fluorescence Microscopy

Monitoring and visualizing specimens at a large penetration depth is a challenge. At depths of hundreds of microns, several physical effects (such as, scattering, PSF distortion and noise) deteriorate the image quality and prohibit a detailed study of key biological phenomena. In this study, we use a Bessel-like beam in-conjugation with an orthogonal detection system to achieve depth imaging. A Bessel-like penetrating diffractionless beam is generated by engineering the back-aperture of the excitation objective. The proposed excitation scheme allows continuous scanning by simply translating the detection PSF. This type of imaging system is beneficial for obtaining depth information from any desired specimen layer, including nano-particle tracking in thick tissue. As demonstrated by imaging the fluorescent polymer-tagged-CaCO3 particles and yeast cells in a tissue-like gel-matrix, the system offers a penetration depth that extends up to 650 µm. This achievement will advance the field of fluorescence imaging and deep nano-particle tracking.

Phase singularity of surface plasmon polaritons generated by optical vortices

We demonstrate an experimental result that shows the phase singularity of surface plasmon waves generated by the direct transform of optical vortices at normal incidence focused on a structureless metal surface. The near-field two-dimensional intensity distribution near the focal plane is experimentally examined by using near-field scanning optical microscopy and shows a good agreement with the finite-difference time-domain simulation result. The experimental realization demonstrates a potential of the proposed excitation scheme to be reconfigured locally with advantages over structures milled into optically thick metallic films for plasmonics applications involving plasmonic vortices.

Coded excitation for infrared non-destructive testing of carbon fiber reinforced plastics

This paper proposes a Barker coded excitation for defect detection using infrared non-destructive testing. Capability of the proposed excitation scheme is highlighted with recently introduced correlation based post processing approach and compared with the existing phase based analysis by taking the signal to noise ratio into consideration. Applicability of the proposed scheme has been experimentally validated on a carbon fiber reinforced plastic specimen containing flat bottom holes located at different depths.

Structure of excited states inMg21studied in one-neutron knockout

Bound excited states in the neutron-deficient nucleus $^{21}\mathrm{Mg}$ were probed in the one-neutron knockout reaction $^{9}\mathrm{Be}(^{22}\mathrm{Mg},^{21}\mathrm{Mg}+\ensuremath{\gamma})\mathrm{X}$ at 74 MeV/nucleon projectile energy. The low-lying level scheme of $^{21}\mathrm{Mg}$ was investigated for the first time with $\ensuremath{\gamma}$-ray spectroscopy. Contrary to the interpretation of previous particle spectroscopy data, our proposed excitation scheme is in agreement with the mirror nucleus and shell-model calculations in the $p\text{\ensuremath{-}}\mathit{sd}$ shell. Spectroscopic factors for the one-neutron removal from $^{22}\mathrm{Mg}$ to $^{21}\mathrm{Mg}$ are extracted and compared to shell-model calculations using the WBP effective interaction.

Proposed radiofrequency phased‐array excitation scheme for homogenous and localized 7‐Tesla whole‐body imaging based on full‐wave numerical simulations

In this article, a radiofrequency (RF) excitation scheme for 7-Tesla (T) whole-body applications is derived and analyzed using the finite difference time domain (FDTD) method. Important features of the proposed excitation scheme and coil (a potential 7T whole-body transverse electromagnetic [TEM] resonator design), from both operational and electromagnetic perspectives, are discussed. The choice of the coil's operational mode is unconventional; instead of the typical "homogenous mode," we use a mode that provides a null field in the center of the coil at low-field applications. Using a 3D FDTD implementation of Maxwell's equations, we demonstrate that the whole-body 7T TEM coil (tuned to the aforementioned unconventional mode and excited in an optimized near-field, phased-array fashion) can potentially provide 1) homogenous whole-slice (demonstrated in three axial, sagittal, and coronal slices) and 2) 3D localized (demonstrated in the heart) excitations. As RF power was not considered as a part of the optimization in several cases, the significant improvements achieved by whole-slice RF excitation came at the cost of considerable increases in RF power requirements.