46,377 research outputs found
Elementary Excitations in One-Dimensional Electromechanical Systems; Transport with Back-Reaction
Using an exactly solvable model, we study low-energy properties of a
one-dimensional spinless electron fluid contained in a quantum-mechanically
moving wire located in a static magnetic field. The phonon and electric current
are coupled via Lorentz force and the eigenmodes are described by two
independent boson fluids. At low energies, the two boson modes are charged
while one of them has excitation gap due to back-reaction of the Lorentz force.
The theory is illustrated by evaluating optical absorption spectra. Our results
are exact and show a non-perturbative regime of electron transport
Communication and control in an integrated manufacturing system
Typically, components in a manufacturing system are all centrally controlled. Due to possible communication bottlenecking, unreliability, and inflexibility caused by using a centralized controller, a new concept of system integration called an Integrated Multi-Robot System (IMRS) was developed. The IMRS can be viewed as a distributed real time system. Some of the current research issues being examined to extend the framework of the IMRS to meet its performance goals are presented. These issues include the use of communication coprocessors to enhance performance, the distribution of tasks and the methods of providing fault tolerance in the IMRS. An application example of real time collision detection, as it relates to the IMRS concept, is also presented and discussed
Microscopic origin of light emission in Al_yGa_{1-y}N/GaN superlattice: Band profile and active site
We present first-principles calculations of AlGaN/GaN superlattice,
clarifying the microscopic origin of the light emission and revealing the
effect of local polarization within the quantum well. Profile of energy band
and distributions of electrons and holes demonstrate the existence of a main
active site in the well responsible for the main band-edge light emission. This
site appears at the position where the local polarization becomes zero. With
charge injection, the calculated optical spectra show that the broadening of
the band gap at the active site leads to the blueshift of emission wavelength
Box ball system associated with antisymmetric tensor crystals
A new box ball system associated with an antisymmetric tensor crystal of the
quantum affine algebra of type A is considered. This includes the so-called
colored box ball system with capacity 1 as the simplest case. Infinite number
of conserved quantities are constructed and the scattering rule of two olitons
are given explicitly.Comment: 15 page
Scattering Rule in Soliton Cellular Automaton associated with Crystal Base of
In terms of the crystal base of a quantum affine algebra ,
we study a soliton cellular automaton (SCA) associated with the exceptional
affine Lie algebra . The solitons therein are labeled
by the crystals of quantum affine algebra . The scatteing rule
is identified with the combinatorial matrix for -crystals.
Remarkably, the phase shifts in our SCA are given by {\em 3-times} of those in
the well-known box-ball system.Comment: 25 page
Efficiency of Nonlinear Particle Acceleration at Cosmic Structure Shocks
We have calculated the evolution of cosmic ray (CR) modified astrophysical
shocks for a wide range of shock Mach numbers and shock speeds through
numerical simulations of diffusive shock acceleration (DSA) in 1D quasi-
parallel plane shocks. The simulations include thermal leakage injection of
seed CRs, as well as pre-existing, upstream CR populations. Bohm-like diffusion
is assumed. We model shocks similar to those expected around cosmic structure
pancakes as well as other accretion shocks driven by flows with upstream gas
temperatures in the range K and shock Mach numbers spanning
. We show that CR modified shocks evolve to time-asymptotic states
by the time injected particles are accelerated to moderately relativistic
energies (p/mc \gsim 1), and that two shocks with the same Mach number, but
with different shock speeds, evolve qualitatively similarly when the results
are presented in terms of a characteristic diffusion length and diffusion time.
For these models the time asymptotic value for the CR acceleration efficiency
is controlled mainly by shock Mach number. The modeled high Mach number shocks
all evolve towards efficiencies %, regardless of the upstream CR
pressure. On the other hand, the upstream CR pressure increases the overall CR
energy in moderate strength shocks (). (abridged)Comment: 23 pages, 12 ps figures, accepted for Astrophysical Journal (Feb. 10,
2005
Non-Volatile Magnonic Logic Circuits Engineering
We propose a concept of magnetic logic circuits engineering, which takes an
advantage of magnetization as a computational state variable and exploits spin
waves for information transmission. The circuits consist of magneto-electric
cells connected via spin wave buses. We present the result of numerical
modeling showing the magneto-electric cell switching as a function of the
amplitude as well as the phase of the spin wave. The phase-dependent switching
makes it possible to engineer logic gates by exploiting spin wave buses as
passive logic elements providing a certain phase-shift to the propagating spin
waves. We present a library of logic gates consisting of magneto-electric cells
and spin wave buses providing 0 or p phase shifts. The utilization of phases in
addition to amplitudes is a powerful tool which let us construct logic circuits
with a fewer number of elements than required for CMOS technology. As an
example, we present the design of the magnonic Full Adder Circuit comprising
only 5 magneto-electric cells. The proposed concept may provide a route to more
functional wave-based logic circuitry with capabilities far beyond the limits
of the traditional transistor-based approach
Amorphous metallizations for high-temperature semiconductor device applications
The initial results of work on a class of semiconductor metallizations which appear to hold promise as primary metallizations and diffusion barriers for high temperature device applications are presented. These metallizations consist of sputter-deposited films of high T sub g amorphous-metal alloys which (primarily because of the absence of grain boundaries) exhibit exceptionally good corrosion-resistance and low diffusion coefficients. Amorphous films of the alloys Ni-Nb, Ni-Mo, W-Si, and Mo-Si were deposited on Si, GaAs, GaP, and various insulating substrates. The films adhere extremely well to the substrates and remain amorphous during thermal cycling to at least 500 C. Rutherford backscattering and Auger electron spectroscopy measurements indicate atomic diffussivities in the 10 to the -19th power sq cm/S range at 450 C
- …