11,113 research outputs found
A critical examination of discrete lattice and dispersed barrier hardening
Critical assessment of discrete lattice and dispersed barrier hardening theories of thermally activated deformation of metal
Antisymmetrized molecular dynamics of wave packets with stochastic incorporation of Vlasov equation
On the basis of the antisymmetrized molecular dynamics (AMD) of wave packets
for the quantum system, a novel model (called AMD-V) is constructed by the
stochastic incorporation of the diffusion and the deformation of wave packets
which is calculated by Vlasov equation without any restriction on the one-body
distribution. In other words, the stochastic branching process in molecular
dynamics is formulated so that the instantaneous time evolution of the averaged
one-body distribution is essentially equivalent to the solution of Vlasov
equation. Furthermore, as usual molecular dynamics, AMD-V keeps the many-body
correlation and can naturally describe the fluctuation among many channels of
the reaction. It is demonstrated that the newly introduced process of AMD-V has
drastic effects in heavy ion collisions of 40Ca + 40Ca at 35 MeV/nucleon,
especially on the fragmentation mechanism, and AMD-V reproduces the
fragmentation data very well. Discussions are given on the interrelation among
the frameworks of AMD, AMD-V and other microscopic models developed for the
nuclear dynamics.Comment: 26 pages, LaTeX with revtex and epsf, embedded postscript figure
Using single quantum states as spin filters to study spin polarization in ferromagnets
By measuring electron tunneling between a ferromagnet and individual energy
levels in an aluminum quantum dot, we show how spin-resolved quantum states can
be used as filters to determine spin-dependent tunneling rates. We also observe
magnetic-field-dependent shifts in the magnet's electrochemical potential
relative to the dot's energy levels. The shifts vary between samples and are
generally smaller than expected from the magnet's spin-polarized density of
states. We suggest that they are affected by field-dependent charge
redistribution at the magnetic interface.Comment: 4 pages, 1 color figur
Real-space observation of current-driven domain wall motion in submicron magnetic wires
Spintronic devices, whose operation is based on the motion of a magnetic
domain wall (DW), have been proposed recently. If a DW could be driven directly
by flowing an electric current instead of a magnetic field, the performance and
functions of such device would be drastically improved. Here we report
real-space observation of the current-driven DW motion by using a well-defined
single DW in a micro-fabricated magnetic wire with submicron width. Magnetic
force microscopy (MFM) visualizes that a single DW introduced in the wire is
displaced back and forth by positive and negative pulsed-current, respectively.
We can control the DW position in the wire by tuning the intensity, the
duration and the polarity of the pulsed-current. It is, thus, demonstrated that
spintronic device operation by the current-driven DW motion is possible.Comment: Accepted and published in PR
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The Lunar Surface Gravimeter as a Lunar Seismograph
Introduction: The primary objective for the Lunar Surface Gravimeter (LSG) on Apollo 17 was to search for gravitational waves, but it failed in detecting them [1]. When the instrument was deployed on the Moon, the sensor beam could not be balanced in the proper equilibrium position. Consequently, the LSG was not able to function as originally designed. Lauderdale and Eichelman (1974) [1] concluded that “no provision has been made to supply data from the experiment to the National Space Science Data Center.” However, it was reported in Giganti et al. (1977) [2] that though they had not detected gravitational waves, after a series of reconfigurations the beam was recentered and the LSG gathered useful data. Besides the observation of gravitational waves, the LSG was also designed to observe seismic signals and tidal deformations [3]. According to Giganti et al. (1977) [2] LSG’s sensitivity covered the frequency range from 1~16Hz (Fig.1). There are several types of moonquakes reported, deep moonquakes, meteorite impacts, and high frequency teleseismic (HFT). Each of the moonquakes is known to have a resonant frequency around 1Hz and in addition, HFT has a predominant frequency around 10 Hz [4]. Therefore it is likely that the LSG was detecting the seismic events on the Moon. However, the LSG data have not been analyzed from a seismological point of view
First-Principles Study on Leakage Current through Si/SiO Interface
The relationship between the presence of defects at the stacking structure of
the Si/SiO interface and leakage current is theoretically studied by
first-principles calculation. I found that the leakage current through the
interface with dangling bonds is 530 times larger than that without any
defects, which is expected to lead to dielectric breakdown. The direction of
the dangling bonds is closely related to the performance of the oxide as an
insulator. In addition, it is proved that the termination of the dangling bonds
by hydrogen atoms is effective for reducing the leakage current.Comment: 11 pages. to be published in Phys. Rev.
Nonequilibrium spin distribution in single-electron transistor
Single-electron transistor with ferromagnetic outer electrodes and
nonmagnetic island is studied theoretically. Nonequilibrium electron spin
distribution in the island is caused by tunneling current. The dependencies of
the magnetoresistance ratio on the bias and gate voltages show the
dips which are directly related to the induced separation of Fermi levels for
electrons with different spins. Inside a dip can become negative.Comment: 11 pages, 2 eps figure
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