170,190 research outputs found
Small signal characteristics of diode stabilized linear integrated devices
Small signal characteristics of diode stabilized linear integrated device
A systems approach to device-circuit interaction in electrical power processing Annual status report, 1 Jun. 1967 - 31 May 1968
Initial research on switched and modulated networks, tunable and bandwith-adjustable filter and FET current density for device circuit interaction in power processin
Zeeman and Orbital Effects of an in-Plane Magnetic Field in Cuprate Superconductors
We discuss the effects of a magnetic field applied parallel to the Cu-O
() plane of the high cuprate superconductors. After briefly reviewing
the Zeeman effect of the field, we study the orbital effects, using the
Lawrence-Doniach model for layered superconductors as a guide to the physics.
We argue that the orbital effect is qualitatively different for in-plane and
inter-layer mechanisms for superconductivity. In the case of in-plane
mechanisms, interlayer couplings may be modeled as a weak interlayer Josephson
coupling, whose effects disappear as ; in this case Zeeman
dominates the effect of the field. In contrast, in the inter-layer mechanism
the Josephson coupling {\em is} the driving force of superconductivity, and we
argue that the in-plane field suppresses superconductivity and provides an
upper bound for which we estimate very crudely.Comment: 4 pages with 1 embedded ps figure. Manuscript submitted to the MMM'99
conferenc
Emergent Geometry and Quantum Gravity
We explain how quantum gravity can be defined by quantizing spacetime itself.
A pinpoint is that the gravitational constant G = L_P^2 whose physical
dimension is of (length)^2 in natural unit introduces a symplectic structure of
spacetime which causes a noncommutative spacetime at the Planck scale L_P. The
symplectic structure of spacetime M leads to an isomorphism between symplectic
geometry (M, \omega) and Riemannian geometry (M, g) where the deformations of
symplectic structure \omega in terms of electromagnetic fields F=dA are
transformed into those of Riemannian metric g. This approach for quantum
gravity allows a background independent formulation where spacetime as well as
matter fields is equally emergent from a universal vacuum of quantum gravity
which is thus dubbed as the quantum equivalence principle.Comment: Invited Review for Mod. Phys. Lett. A, 17 page
Ant colony optimization with immigrants schemes in dynamic environments
This is the post-print version of this article. The official published version can be accessed from the link below - Copyright @ 2010 Springer-VerlagIn recent years, there has been a growing interest in addressing dynamic optimization problems (DOPs) using evolutionary algorithms (EAs). Several approaches have been developed for EAs to increase the diversity of the population and enhance the performance of the algorithm for DOPs. Among these approaches, immigrants schemes have been found beneficial for EAs for DOPs. In this paper, random, elitismbased, and hybrid immigrants schemes are applied to ant colony optimization (ACO) for the dynamic travelling salesman problem (DTSP). The experimental results show that random immigrants are beneficial for ACO in fast changing environments, whereas elitism-based immigrants are beneficial for ACO in slowly changing environments. The ACO algorithm with hybrid immigrants scheme combines the merits of the random and elitism-based immigrants schemes. Moreover, the results show that the proposed algorithms outperform compared approaches in almost all dynamic test cases and that immigrant schemes efficiently improve the performance of ACO algorithms in DTSP.This work was supported by the Engineering and Physical Sciences Research Council (EPSRC) of UK under Grant EP/E060722/1
Spin mapping, phase diagram, and collective modes in double layer quantum Hall systems at
An exact spin mapping is identified to simplify the recently proposed
hard-core boson description (Demler and Das Sarma, Phys. Rev. Lett., to be
published) of the bilayer quantum Hall system at filling factor 2. The
effective spin model describes an easy-plane ferromagnet subject to an external
Zeeman field. The phase diagram of this effective model is determined exactly
and found to agree with the approximate calculation of Demler and Das Sarma,
while the Goldstone-mode spectrum, order parameter stiffness and
Kosterlitz-Thouless temperature in the canted antiferromagnetic phase are
computed approximately.Comment: 4 pages with 2 figures include
A system identification technique based on the random decrement signatures. Part 1: Theory and simulation
Identification of the system parameters of a randomly excited structure may be treated using a variety of statistical techniques. Of all these techniques, the Random Decrement is unique in that it provides the homogeneous component of the system response. Using this quality, a system identification technique was developed based on a least-squares fit of the signatures to estimate the mass, damping, and stiffness matrices of a linear randomly excited system. The mathematics of the technique is presented in addition to the results of computer simulations conducted to demonstrate the prediction of the response of the system and the random forcing function initially introduced to excite the system
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