2,702 research outputs found
High efficiency multifrequency feed
Antenna systems and particularly compact and simple antenna feeds which can transmit and receive simultaneously in at least three frequency bands, each with high efficiency and polarization diversity are described. The feed system is applicable for frequency bands having nominal frequency bands with the ratio 1:4:6. By way of example, satellite communications telemetry bands operate in frequency bands 0.8 - 1.0 GHz, 3.7 - 4.2 GHz and 5.9 - 6.4 GHz. In addition, the antenna system of the invention has monopulse capability for reception with circular or diverse polarization at frequency band 1
Chaotic itinerancy and power-law residence time distribution in stochastic dynamical system
To study a chaotic itinerant motion among varieties of ordered states, we
propose a stochastic model based on the mechanism of chaotic itinerancy. The
model consists of a random walk on a half-line, and a Markov chain with a
transition probability matrix. To investigate the stability of attractor ruins
in the model, we analyze the residence time distribution of orbits at attractor
ruins. We show that the residence time distribution averaged by all attractor
ruins is given by the superposition of (truncated) power-law distributions, if
a basin of attraction for each attractor ruin has zero measure. To make sure of
this result, we carry out a computer simulation for models showing chaotic
itinerancy. We also discuss the fact that chaotic itinerancy does not occur in
coupled Milnor attractor systems if the transition probability among attractor
ruins can be represented as a Markov chain.Comment: 6 pages, 10 figure
Making sense of internal logic Theory and a case study
Motivated by the interf aciology proposed by Otto Rossler, we have attempted to construct a framework of internal logic of the mind and brain. We propose a functional equation as an abstract form representing mental processes. We consider a method by which such internal logic can be interpreted and understood by an (external) observer. For this purpose, we propose a theory for cognitive experiments. Applying this theory to simple deductive inference processes exhibited by animal subjects in an experimental setting, with the assumption that syllogism is expressed as a composite mapping corresponding to the product operation of two implications A-t Band B -t C, an interpretation of the neural activity associated with the behavior in these experiments is obtained. This theory is consistent with the internal description hypothesized by Rob Rosen
A transceiver module of the Mu radar
The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna
Many-Polaron Effects in the Holstein Model
We derive an effective polaronic interaction Hamiltonian, {\it exact to
second order in perturbation}, for the spinless one-dimensional Holstein model.
The small parameter is given by the ratio of the hopping term () to the
polaronic energy () in all the region of validity for our
perturbation; however, the exception being the regime of extreme
anti-adiabaticity () and small electron-phonon coupling () where the small parameter is . We map our polaronic
Hamiltonian onto a next-to-nearest-neighbor interaction anisotropic Heisenberg
spin model. By studying the mass gap and the power-law exponent of the
spin-spin correlation function for our Heisenberg spin model, we analyze the
Luttinger liquid to charge-density-wave transition at half-filling in the
effective polaronic Hamiltonian. We calculate the structure factor at all
fillings and find that the spin-spin correlation length decreases as one
deviates from half-filling. We also extend our derivation of polaronic
Hamiltonian to -dimensions.Comment: Content changed. Accepted in Phys. Rev.
Heterogeneity Induced Order in Globally Coupled Chaotic Systems
Collective behavior is studied in globally coupled maps with distributed
nonlinearity. It is shown that the heterogeneity enhances regularity in the
collective dynamics. Low-dimensional quasiperiodic motion is often found for
the mean-field, even if each element shows chaotic dynamics. The mechanism of
this order is due to the formation of an internal bifurcation structure, and
the self-consistent dynamics between the structures and the mean-field.
Keywords: Globally Coupled Map with heterogeneity, Collective behaviorComment: 11 pages (Revtex) + 4 figures (PostScript,tar+gzip
Can stochastic renewal of maps be a model for cerebral cortex?
We introduce a new type of stochastic dynamics as stochastic renewal of maps, relating to the neurodynamics of cortical memory process. This stochastic dynamics can be reformulated by a skew product transformation of two kinds of variables, one of which describes an underlying dynamical system and the other describes chaotic dynamics, say, Bernoulli shift. The feature of orbits in phase space is investigated in the particular case of neurodynamics model for cortical chaotic memories. A new computational result on the functional role of cortical chaos is obtained. We also present a neurobiological interpretation of psychological perception and memories by means of the notion of chaotic itinerancy
Towards an interpretation of dynamic neural activity in terms of chaotic dynamical systems
Using the concepts of chaotic itinerancy and Cantor coding, we present an interpretation of dynamic neural activity found in cortical and subcortical areas. The discovery of chaotic itinerancy and Cantor coding in high- dimensional dynamical systems has motivated a new interpretation of this dynamic neural activity, cast in terms of the high-dimensional transitory dynamics among quasi-attractors
Phase transition and phase diagram at a general filling in the spinless one-dimensional Holstein Model
Among the mechanisms for lattice structural deformation, the electron-phonon
interaction mediated Peierls charge-density-wave (CDW) instability in single
band low-dimensional systems is perhaps the most ubiquitous. The standard
mean-field picture predicts that the CDW transition occurs at all fillings and
all values of the electron-phonon coupling and the adiabaticity parameter
. Here, we correct the mean-field expression for the Peierls
instability condition by showing that the non-interacting static
susceptibility, at twice the Fermi momentum, should be replaced by the dynamic
one. We derive the Luttinger liquid (LL) to CDW transition condition, {\it
exact to second order in a novel blocked perturbative approach}, for the
spinless one-dimensional Holstein model in the adiabatic regime. The small
parameter is the ratio . We present the phase diagram at
non-half-filling by obtaining the surprising result that the CDW occurs in a
more restrictive region of a two parameter ( and )
space than at half-filling.Comment: Made changes in the appendices and also in notatio
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