A new methodology for ensuring that a three-coil wireless power transfer system is more energy efficient than a two-coil counterpart is presented in this paper. The theoretical proof and the ...conditions for meeting the objective are derived and practically verified in a practical prototype. The key features of the magnetic design are to: 1) shift the current stress from the primary driving circuit to the relay resonator; and 2) generate a large relay current for maximizing magnetic coupling with the receiver coil for efficient power transfer. Consequently, the current rating and cost of the driving circuit can be reduced and the overall quality factor and system energy efficiency are improved. This approach utilizes the combined advantages of the maximum efficiency principle and the use of relay resonator to overcome the energy efficiency problem for applications with extended energy transfer distances.
A method for automatic "maximum energy efficiency tracking" operation for wireless power transfer (WPT) systems is presented in this paper. Using the switched-mode converter in the receiver module to ...emulate the optimal load value, the proposed method follows the maximum energy efficiency operating points of a WPT system by searching for the minimum input power operating point for a given output power. Because the searching process is carried out on the transmitter side, the proposal does not require any wireless communication feedback from the receiver side. The control scheme has been successfully demonstrated in a two-coil system under both weak and strong magnetic coupling conditions. Experimental results are included to confirm its feasibility.
Anyons are exotic quasiparticles obeying fractional statistics, whose behavior can be emulated in artificially designed spin systems. Here we present an experimental emulation of creating anyonic ...excitations in a superconducting circuit that consists of four qubits, achieved by dynamically generating the ground and excited states of the toric code model, i.e., four-qubit Greenberger-Horne-Zeilinger states. The anyonic braiding is implemented via single-qubit rotations: a phase shift of π related to braiding, the hallmark of Abelian 1/2 anyons, has been observed through a Ramsey-type interference measurement.
In this paper, the effects of the magnetic coupling of nonadjacent resonators on the optimal frequency of wireless power transfer are addressed. A power analysis has been carried out to identify the ...adjacent and nonadjacent power flow components. It is found that such cross-coupling effects of nonadjacent resonators would cause the maximum efficiency operation to slightly shift away from the resonance frequency of the resonators. Theoretical reasons for such phenomena are provided and experimentally confirmed with practical measurements in a wireless power transfer system comprising several magnetically coupled resonators arranged in a straight domino form.
Traditional current-mirror methods require one fixed current reference for controlling other current source or sources. In this paper, a new self-configurable current-mirror method that can ...dynamically determine the best current branch as the current reference in order to ensure good balance of all parallel current sources is proposed. The operating principle involves a dynamic and self-configurable transistor-based current-balancing circuit that can be operated in saturation or linear mode. In either operating mode, good current balance or sharing among all parallel-connected current sources can be guaranteed. The novel current-balancing circuit does not require a separate power supply for powering their control circuits. The proposal is a modular one that can be expanded to any number of parallel current sources. Its principle has been successfully applied to current balancing of parallel LED strings.
Abstract
Soft X-ray emissions induced by solar wind ions that collide with neutral material in the solar system have been detected around planets, and were proposed as a remote probe for solar wind ...interaction with the Martian exosphere. A multi-fluid three-dimensional magnetohydrodynamic model is adopted to derive the global distributions of solar wind particles. Spherically symmetric exospheric H, H
2
, He, O, and CO
2
density profiles and a sophisticated hybrid model that includes charge-exchange and proton–neutral excitation processes are used to study the low triplet line ratio
G
=
i
+
f
r
(0.77 ± 0.58) of O
vii
and the total X-ray luminosity around Mars. We further calculate the emission factor
α
-value with different neutrals over wide ion-abundance and velocity ranges. Our results are in good agreement with those of previous reports. The evolution of the charge stage of solar wind ions shows that sequential recombination due to charge-exchange can be negligible in the interaction region. This only appears below an altitude of 400 km. The anonymous low disk
G-
ratio can be easily explained by the collisional quenching effect at neutral densities higher than 10
11
cm
−3
. However, the quenching contribution is small in Mars’ exosphere and only appears below 400 km. Charge-exchange with H
2
and N
2
is still the most likely reason for this low
G
-ratio. X-ray emissivity maps in collisions with different neutrals differ from each other. A clear bow shock arising from the collision with all the neutrals is in accordance with previous reports. The resulting total X-ray luminosity of 6.55 MW shows better agreement with the XMM-Newton observation of 12.8 ± 1.4 MW than that of previous predictions.
This study aimed to investigate the incidence, topographical distribution, morphology, and interrelationship of the metopism and Wormian bones (WBs) in dry adult-Chinese skulls.
In this study, 285 ...dried adult-Chinese skull specimens from the Department of Anatomy at the Southern Medical University were examined. The incidence of different types of metopism and WBs were recorded. The length of the metopic suture was measured using a flexible ruler. Additionally, the lengths and widths of the WBs were measured using a vernier calliper.
The incidence of metopism and WBs in Chinese adults were estimated at 10.18% (29/285) and 63.86% (182/285), respectively. The metopism always accompanied WBs (26/29, 89.66%), but the WBs did not necessarily accompany metopism (26/182, 14.29%). The locations of the WBs in the order of decreasing incidence were the lambdoid suture (78.57%, 143/182), pterion (34.62%, 63/182), asterion (12.09%, 22/182), lambda (8.24%, 15/182), sagittal suture (4.95%, 9/182), and Inca bone (3.85%, 7/182). These locations differed in topographical distribution and morphological patterns.
Chinese adults differ in incidence of metopism and WBs from adults of other races, indicating racial differences. The characteristics of WBs vary depending on the cranial site of occurrence. The metopism always accompanies WBs, but the WBs do not necessarily accompany metopism.
The stochastic hyperbolic heat conduction problem is addressed. The random field is approximated by using the Karhunen–Loeve expansion truncated after a finite numbers of terms, and a modified ...stochastic perturbation method (MSPM) is proposed for the stochastic hyperbolic heat conduction problems. The MSPM is based on the stochastic perturbation theory, and can provide the mean and covariance of the random temperature including some third- and forth-order terms. Compared with the original stochastic perturbation method, the MSPM is more accurate and is more convenient for the numerical implementation, and hence is more applicable for the stochastic hyperbolic heat conduction problem. Two numerical examples demonstrate that the proposed method can provide very accurate results and can be used for the stochastic hyperbolic heat conduction problems.
The Magnetic Field Structure of Mercury's Magnetotail Rong, Z. J.; Ding, Y.; Slavin, J. A. ...
Journal of geophysical research. Space physics,
January 2018, 2018-01-00, 20180101, Letnik:
123, Številka:
1
Journal Article
Recenzirano
In this study, we use the magnetic field data measured by MErcury Surface, Space ENvironment, GEochemistry, and Ranging from 2011 to 2015 to investigate the average magnetic field morphology of ...Mercury's magnetotail in the down tail 0–3 RM (RM = 2,440 km, Mercury's radius). It is found that Mercury has a terrestrial‐like magnetotail; the magnetic field structure beyond 1.5 RM down tail is stretched significantly with typical lobe field 50 nT. A cross‐tail current sheet separating the antiparallel field lines of lobes is present in the equatorial plane. The magnetotail width in north‐south direction is about 5 RM, while the transverse width is about 4 RM. Thus, the magnetotail shows elongation along the north‐south direction. At the cross‐tail current sheet center, the normal component of magnetic field (10–20 nT) is much larger than the cross‐tail component. The lobe‐field‐aligned component of magnetic field over current sheet can be well fitted by Harris sheet model. The curvature radius of field lines at sheet center usually reaches a minimum around midnight (100–200 km) with stronger current density (40–50 nA/m2), while the curvature radius increases toward both flanks (400–600 km) with the decreased current density (about 20 nA/m2). The half‐thickness of current sheet around midnight is about 0.25 RM or 600 km, and the inner edge of current sheet is located at the down tail about 1.5 RM. Our results about the field structure in the near Mercury's tail show an evident dawn‐dusk asymmetry as that found in the Earth's magnetotail, but reasons should be different. Possible reasons are discussed.
Key Points
The magnetic field distribution, configuration, and current density in Mercury's magnetotail are quantitatively addressed
Mercury's magnetotail is elongated along the south‐north direction, which is probably due to the effect of the dipole offset or the induction effect of core
The magnetic structure of tail current sheet shows a clear dawn‐dusk asymmetry with smaller Bz and less flaring field on the duskside
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