56 research outputs found
Prediction of Vibrations of Footings for Highly Sensitive Devices
When planning foundations for devices sensitive to vibrations the planned location should be investigated for vibrations. These investigations have to include the existing sources in the vicinity as for instance street or rail traffic as well as exciting devices to be installed at the same building site like compressor stations or other machines. The present paper shows a procedure to estimate the vibrations at the planned locations for sensitive devices. The procedure includes investigations of the dynamic soil properties, the decrease of the vibrations with distance, and the transfer functions of rigid footings. It takes into consideration stochastic excitation as well as harmonic ones. As the result of this procedure it will be possible to state minimum admissible distances and to specify probabilities of exceeding the given boundary values for admissible vibrations
Time-dependent bond-current functional theory for lattice Hamiltonians: fundamental theorem and application to electron transport
The cornerstone of time-dependent (TD) density functional theory (DFT), the
Runge-Gross theorem, proves a one-to-one correspondence between TD potentials
and TD densities of continuum Hamiltonians. In all practical implementations,
however, the basis set is discrete and the system is effectively described by a
lattice Hamiltonian. We point out the difficulties of generalizing the
Runge-Groos proof to the discrete case and thereby endorse the recently
proposed TD bond-current functional theory (BCFT) as a viable alternative.
TDBCFT is based on a one-to-one correspondence between TD Peierl's phases and
TD bond-currents of lattice systems. We apply the TDBCFT formalism to
electronic transport through a simple interacting device weakly coupled to two
biased non-interacting leads. We employ Kohn-Sham Peierl's phases which are
discontinuous functions of the density, a crucial property to describe Coulomb
blockade. As shown by explicit time propagations, the discontinuity may prevent
the biased system from ever reaching a steady state.Comment: 11 pages, 7 figure
Nonlinear Transport through Quantum Dots Studied by the Time-Dependent DMRG
Recent developments on studies of transport through quantum dots obtained by
applying the time-dependent density matrix renormalization group method are
summarized. Some new aspects of Kondo physics which appear in nonequilibrium
steady states are discussed both for the single dot case and for the serially
coupled double-quantum-dot case.Comment: 8 pages, 15 figure
Charge transport through single molecules, quantum dots, and quantum wires
We review recent progresses in the theoretical description of correlation and
quantum fluctuation phenomena in charge transport through single molecules,
quantum dots, and quantum wires. A variety of physical phenomena is addressed,
relating to co-tunneling, pair-tunneling, adiabatic quantum pumping, charge and
spin fluctuations, and inhomogeneous Luttinger liquids. We review theoretical
many-body methods to treat correlation effects, quantum fluctuations,
nonequilibrium physics, and the time evolution into the stationary state of
complex nanoelectronic systems.Comment: 48 pages, 14 figures, Topical Review for Nanotechnolog
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