1,125 research outputs found
Outflows driven by Giant Protoplanets
We investigate outflows driven by a giant protoplanet using three-dimensional
MHD nested grid simulations. We consider a local region around the protoplanet
in the protoplanetary disk, and calculate three models: (a) unmagnetized disk
model, (b) magnetized disk model having magnetic field azimuthally parallel to
the disk, and (c) magnetic field perpendicular to the disk. Outflows with
velocities, at least, 10 km/s are driven by the protoplanets in both magnetized
disk models, while outflow does not appear in unmagnetized disk model.
Tube-like outflows along the azimuthal direction of the protoplanetary disk
appear in model with magnetic field being parallel to the disk. In this model,
the magnetically dominated regions (i.e., density gap) are clearly contrasted
from other regions and spiral waves appear near the protoplanet. On the other
hand, in model with magnetic field being perpendicular to the disk, outflows
are driven by a protoplanet with cone-like structure just as seen in the
outflow driven by a protostar. Magnetic field lines are strongly twisted near
the protoplanet and the outflows have well-collimated structures in this
model.These outflows can be landmarks for searching exo-protoplanets in their
formation stages. Our results indicate that the accretion rate onto the
protoplanet tend to have a larger value than that expected from previous
hydrodynamical calculations, since a fraction of the angular momentum of
circum-planetary disk is removed by outflows, enhanced non-axisymmetric
patterns caused by magnetic field, and magnetic braking. Possible implications
for observation are also briefly discussed.Comment: 11 pages, 3 figures, Submitted to ApJL, For high resolution figures
see http://www2.scphys.kyoto-u.ac.jp/~machidam/jupiter/doc/resubmit_0703.pd
Chiral spin-wave edge modes in dipolar magnetic thin films
Based on a linearized Landau-Lifshitz equation, we show that two-dimensional
periodic allay of ferromagnetic particles coupled with magnetic dipole-dipole
interactions supports chiral spin-wave edge modes, when subjected under the
magnetic field applied perpendicular to the plane. The mode propagates along a
one-dimensional boundary of the system in a unidirectional way and it always
has a chiral dispersion within a band gap for spin-wave volume modes. Contrary
to the well-known Damon-Eshbach surface mode, the sense of the rotation depends
not only on the direction of the field but also on the strength of the field;
its chiral direction is generally determined by the sum of the so-called Chern
integers defined for spin-wave volume modes below the band gap. Using simple
tight-binding descriptions, we explain how the magnetic dipolar interaction
endows spin-wave volume modes with non-zero Chern integers and how their values
will be changed by the field.Comment: 18 pages, 16 figures, some trivial typo in equations are fixe
Ultra Low Loss Trench Gate PCI-PiN Diode with VF<350mV
PiN diode forward voltage drop was reduced to as low as 325mV by the pulsed carrier injection (PCI) mechanism with trench MOS gate as the integrated injection control switch. The conventional PiN diodes have voltage drop of about 0.8V which is equivalent to 1%-2% energy loss in home appliances. The proposed PCI-PiN diode reduces the loss by more than 50% and the diode structure has process compatibility to conventional IGBTs and trench MOSFETs for easy implementation into mass production. The authors also confirmed PCI concept with the experiment with BSIT.2011 23rd International Symposium on Power Semiconductor Devices & Ics (ISPSD. 2011), May 23?26, 2011, San Diego, California, US
Topological chiral magnonic edge mode in a magnonic crystal
Topological phases have been explored in various fields in physics such as
spintronics, photonics, liquid helium, correlated electron system and
cold-atomic system. This leads to the recent foundation of emerging materials
such as topological band insulators, topological photonic crystals and
topological superconductors/superfluid. In this paper, we propose a topological
magnonic crystal which provides protected chiral edge modes for magnetostatic
spin waves. Based on a linearized Landau-Lifshitz equation, we show that a
magnonic crystal with the dipolar interaction acquires spin-wave volume-mode
band with non-zero Chern integer. We argue that such magnonic systems are
accompanied by the same integer numbers of chiral spin-wave edge modes within a
band gap for the volume-mode bands. In these edge modes, the spin wave
propagates in a unidirectional manner without being scattered backward, which
implements novel fault-tolerant spintronic devices.Comment: 12 pages, 7 figure
On Galloping Oscillation of Square Prism in Two Dimensional Uniform Flow
In the connection of frequently used structural members of longspanned bridges, the aeroelastic characteristics of a square prism are investigated, based on the quasi-steady theory. The experimental results of the wind tunnel tests are compared with the theoretical characteristics, using the theory given by G. V. Parkinson. In this paper, some considerations on the critical wind velocity for galloping phenomenon of square prism are presented. Also, the qualitataive method to determine the induced amplitude is discussed
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