60 research outputs found
Role of Correlation and Exchange for Quasi-particle Spectra of Magnetic and Diluted Magnetic Semiconductors
Theoretical foundation and application of the generalized spin-fermion (sp-d)
exchange lattice model to magnetic and diluted magnetic semiconductors are
discussed. The capabilities of the model to describe spin quasi-particle
spectra are investigated. The main emphasis is made on the dynamic behavior of
two interacting subsystems, the localized spins and spin density of itinerant
carriers. A nonperturbative many-body approach, the Irreducible Green Functions
(IGF) method, is used to describe the quasi-particle dynamics. Scattering
states are investigated and three branches of magnetic excitations are
calculated in the regime, characteristic of a magnetic semiconductor. For a
simplified version of the model (Kondo lattice model) we study the spectra of
quasi-particle excitations with special attention given to diluted magnetic
semiconductors. For this, to include the effects of disorder, modified mean
fields are determined self-consistently. The role of the Coulomb correlation
and exchange is clarified by comparing of both the cases.Comment: 34 page
An associative memory of Hodgkin-Huxley neuron networks with Willshaw-type synaptic couplings
An associative memory has been discussed of neural networks consisting of
spiking N (=100) Hodgkin-Huxley (HH) neurons with time-delayed couplings, which
memorize P patterns in their synaptic weights. In addition to excitatory
synapses whose strengths are modified after the Willshaw-type learning rule
with the 0/1 code for quiescent/active states, the network includes uniform
inhibitory synapses which are introduced to reduce cross-talk noises. Our
simulations of the HH neuron network for the noise-free state have shown to
yield a fairly good performance with the storage capacity of for the low neuron activity of . This
storage capacity of our temporal-code network is comparable to that of the
rate-code model with the Willshaw-type synapses. Our HH neuron network is
realized not to be vulnerable to the distribution of time delays in couplings.
The variability of interspace interval (ISI) of output spike trains in the
process of retrieving stored patterns is also discussed.Comment: 15 pages, 3 figures, changed Titl
An approach for measuring the degree of comparability of financial accounting information
This contribution sets out to provide an index to measure comparability of financial accounting information concerning specific kinds of transactions or events. It suggests definitions for the terms of comparability of financial accounting information and of accounting method. Requirements are derived from these definitions which must be met by an index of comparability, and entropy is shown to be an appropriate measure fulfilling these requirements. The problem of multiple reporting is dealt with separately. Finally, the measurement concept developed is applied to an example from the FEE report for 1989.
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