Loop Theory Research Articles

W-band Communication System with Direct Frequency Shift Keying Modulation to Phase-locked Oscillator

Based on the theory of phase-locked loop, the analysis and simulation of direct frequency shift keying to phase-locked oscillator is presented. Then, a W-band digital communication system is developed, in which the millimeter wave phase-locked oscillator of the transmitter is modulated directly by 15grades 2048 kbit/s signal. The results of the experiment in the field show that the phase-locked loop has little influence on the modulating signal. It is a good way to simplify the transmitter configuration and suitable for high bit rate communication.

Phase Noise Model of Single Loop Frequency Synthesizer

The phase noise spectrum of a single loop frequency synthesizer for S-band, which can be utilized in broadcasting terminals, was predicted based on the analyses for phase noise contributions of noise sources. The proposed phase noise model in this paper more accurately predicts the phase noise spectrum of a frequency synthesizer. To accurately model the phase noise contributions of noise sources in the frequency synthesizer, the phase noise sources were analyzed via modeling of the frequency divider and phase noise components using Leeson model for the reference signal source and VCO. The phase noise transfer functions to VCO from noise sources were analyzed by superposition theory and linear operation of the phase-locked loop. The frequency synthesizers were fabricated and the phase noise prediction model was evaluated by measured data and prediction data.

Content-Specific Delusions From Right Caudate Lacunar Stroke: Association with Prefrontal Hypometabolism

Content-Specific Delusions From Right Caudate Lacunar Stroke: Association with Prefrontal Hypometabolism

SRAR loops with more than two commutators

Possession of a unique nonidentity commutator/associator is a property that dominates the theory of loops whose loop rings, while not associative, nevertheless satisfy an “interesting” identity. For instance, until now, all loops with loop rings satisfying the right Bol identity (such loops are called SRAR) have been known to have this property. In this paper, we present various constructions of other kinds of SRAR loops.

Automatic Construction and Verification of Isotopy Invariants

We extend our previous study of the automatic construction of isomorphic classification theorems for algebraic domains by considering the isotopy equivalence relation. Isotopism is an important generalisation of isomorphism, and is studied by mathematicians in domains such as loop theory. This extension was not straightforward, and we had to solve two major technical problems, namely, generating and verifying isotopy invariants. Concentrating on the domain of loop theory, we have developed three novel techniques for generating isotopic invariants, by using the notion of universal identities and by using constructions based on subblocks. In addition, given the complexity of the theorems that verify that a conjunction of the invariants form an isotopy class, we have developed ways of simplifying the problem of proving these theorems. Our techniques employ an interplay of computer algebra, model generation, theorem proving, and satisfiability-solving methods. To demonstrate the power of the approach, we generate isotopic classification theorems for loops of size 6 and 7, which extend the previously known enumeration results. This work was previously beyond the capabilities of automated reasoning techniques.

Cyclic Stress in 316L Austenitic Stainless Steel at Low Temperatures

Austenitic stainless steel was cycled at a series of temperatures in the interval from 296 K to 113 K. Constant plastic strain amplitude loading at different levels of plastic strain amplitude and testing similar to multiple step test method were applied at different temperatures. The stress amplitude was continually recorded and selected hysteresis loops were stored and later analyzed using statistical theory of the hysteresis loop. Effective stress component and probability density function as a function of temperature were evaluated. The results were discussed in terms of the temperature dependence of the cyclic yield stress and its sources.

Control properties of bottom fired marine boilers

Abstract This paper focuses on model analysis of a dynamic model of a bottom fired one-pass smoke tube boiler. Linearized versions of the model are analyzed and show large variations in system gains at steady state as function of load whereas gain variations near the desired bandwidth are small. An analysis of the potential benefit from using a multivariable control strategy in favor of the current strategy based on single loop theory is carried out and proves that the interactions in the system are not negligible and a subsequent controller design should take this into account. A design using dynamical decoupling showed substantial improvement compared to a decentralized scheme based on sequential loop closing. Similar or better result is expected to be obtainable using a full Multiple input Multiple output scheme. Furthermore closed loop simulations, applying a linear controller to the nonlinear plant model, prove that the model does not call for nonlinear control. However, the results indicate that input constraints will become active when the controller responds to transient behavior from the steam flow disturbance. For this reason an MPC (model predictive control) strategy capable of handling constraints on states and control signals should be considered.

Polyakov loop in chiral quark models at finite temperature

We describe how the inclusion of the gluonic Polyakov loop incorporates large gauge invariance and drastically modifies finite temperature calculations in chiral quark models after color neutral states are singled out. This generates an effective theory of quarks and Polyakov loops as basic degrees of freedom. We find a strong suppression of finite temperature effects in hadronic observables triggered by approximate triality conservation (Polyakov cooling), so that while the center symmetry breaking is exponentially small with the constituent quark mass, chiral symmetry restoration is exponentially small with the pion mass. To illustrate the point we compute some low energy observables at finite temperature and show that the finite temperature corrections to the low energy coefficients are $N_c$ suppressed due to color average of the Polyakov loop. Our analysis also shows how the phenomenology of chiral quark models at finite temperature can be made compatible with the expectations of chiral perturbation theory. The implications for the simultaneous center symmetry breaking-chiral symmetry restoration phase transition are also discussed.

Bol loops as sections in semi-simple Lie groups of small dimension

Using the relations between the theory of differentiable Bol loops and the theory of affine symmetric spaces we classify all connected differentiable Bol loops having an at most nine-dimensional semi-simple Lie group as the group topologically generated by their left translations. We show that all these Bol loops are isotopic to direct products of Bruck loops of hyperbolic type or to Scheerer extensions of Lie groups by Bruck loops of hyperbolic type.

Accounting for sequential trial effects in the flanker task: Conflict adaptation or associative priming?

The conflict-control loop theory proposes that the detection of conflict in information processing triggers an increase in cognitive control, resulting in improved performance on the subsequent trial. This theory seems consistent with the robust finding that conflict susceptibility is reduced following correct trials associated with high conflict: the conflict adaptation effect. However, despite providing favorable conditions for eliciting and detecting conflict-triggered performance adjustments, none of the five experiments reported here provide unequivocal evidence of such adjustments. Instead, the results corroborate and extend earlier findings by demonstrating that the conflict adaptation effect, at least in the flanker task, is only present for a specific subset of trial sequences that is characterized by a response repetition. This pattern of results provides strong evidence that the conflict adaptation effect reflects associative stimulus-response priming instead of conflict-driven adaptations in cognitive control.

The Lure of the Unknown

Using event-related fMRI, Bunzeck and Düzel show that midbrain regions putatively housing dopamine cell bodies activate more for novel pictures than for negative pictures, pictures requiring a motor response, or repeated pictures. These findings indicate that midbrain regions preferentially respond to novelty and suggest that novelty can serve as its own reward.

Different canonical formulations of Einstein’s theory of gravity

We describe the four most famous versions of the classical canonical formalism in the Einstein theory of gravity: the Arnovitt-Deser-Misner formalism, the Faddeev-Popov formalism, the tetrad formalism in the usual form, and the tetrad formalism in the form best suited for constructing the loop theory of gravity, which is now being developed. We present the canonical transformations relating these formalisms. The paper is written mainly for pedagogical purposes.

Halting in single word production: A test of the perceptual loop theory of speech monitoring

The perceptual loop theory of speech monitoring ( Levelt, 1983) claims that inner and overt speech are monitored by the comprehension system, which detects errors by comparing the comprehension of formulated utterances to originally intended utterances. To test the perceptual loop monitor, speakers named pictures and sometimes attempted to halt speech in response to auditory (Experiments 1 and 3) or visual (Experiments 2, 4, and 5) words that differed from the picture name. These stop-signal words were varied in terms of their semantic or phonological similarity to the intended word. The ability to halt word production was sensitive to phonological similarity and, in Experiment 5, to emotional valence, but not to semantic similarity. These results suggest that the perceptual loop detects errors by making comparisons at a level where phonological knowledge is represented. These data also imply that dialogue, back channeling, and other areas where speech production is affected by simultaneous comprehension may operate based on phonological comparisons.

Building a Collaborative Culture with Managed Feedback Loops and Cybernetics Theory: The PLDT Transition

Building a Collaborative Culture with Managed Feedback Loops and Cybernetics Theory: The PLDT Transition

Origin of artificial electrodynamics in three-dimensional bosonic models

Several simple models of strongly correlated bosons on three-dimensional lattices have been shown to possess exotic fractionalized Mott insulating phases with a gapless ``photon'' excitation. In this paper we show how to view the physics of this ``Coulomb'' state in terms of the excitations of proximate superfluid. We argue for the presence of ordered vortex cores with a broken discrete symmetry in the nearby superfluid phase and that proliferating these degenerate but distinct vortices with equal amplitudes produces the Coulomb phase. This provides a simple physical description of the origin of the exotic excitations of the Coulomb state. The physical picture is formalized by means of a dual description of three-dimensional bosonic systems in terms of fluctuating quantum mechanical vortex loops. Such a dual formulation is extensively developed. It is shown how the Coulomb phase (as well as various other familiar phases) of three-dimensional bosonic systems may be described in this vortex loop theory. For bosons at half-filling and the closely related system of spin-$1∕2$ quantum magnets on a cubic lattice, fractionalized phases as well as bond- or ``box''-ordered states are possible. The latter are analyzed by an extension of techniques previously developed in two spatial dimensions. The relation between these ``confining'' phases with broken translational symmetry and the fractionalized Coulomb phase is exposed.

Theory and phenomenology of the Polyakov loop in QCD thermodynamics

A synthesis of Polyakov loop models of the deconfinement transition and quasiparticle models of gluon plasma thermodynamics leads to a class of models in which gluons move in a non-trivial Polyakov loop background. These models are successful candidates for explaining both critical behavior and the equation of state for the SU(3) gauge theory at finite temperature. Two sensitive lattice probes which can discriminate between models are the Polyakov loop P and e-3p.

On a Problem of the Theory of Smooth Loops

On a Problem of the Theory of Smooth Loops

Automorphism groups of simple Moufang loops over perfect fields

Let . The proof combines results and methods from geometrical loop theory, groups of Lie type and composition algebras; the result being an identification of the automorphism group of a Moufang loop with a subgroup of the automorphism group of the associated group with triality.

Modeling the polarization in ferroelectric materials: a novel analytical approach

We propose for the first time a fully analytical formulation of the polarization in ferroelectric materials that takes into account history effects. Our approach is based on the Preisach theory of the hysteresis loops. A symmetric exponential decay distribution of the dipoles thresholds has been introduced. Consequently, an exact analytical and continuous solution of the polarization could be derived, taking the electric field history into consideration. Experimental data on PZT capacitors show relevant agreement with the model for both saturated and minor loops. This confirms the validity of this approach, which consequently represents a very interesting candidate for efficient ferroelectric compact models to be used either in memory or in analog design applications.

Basal Ganglia Lesions and the Theory of Fronto-Subcortical Loops: Neuropsychological Findings in Two Patients with Left Caudate Lesions

Basal ganglia lesions have a high prevalence for associated behavioural impairments. However, the exact pattern of cognitive impairments and its relationship to individual basal ganglia lesion have rarely been investigated by means of a detailed neuropsychological and lesion study. Furthermore, different mechanisms have been proposed as relevant for the observed cognitive deficits; among these, the hypothesis of fronto-subcortical loops (Alexander et al., 1986) has made predictions regarding the relationship between the damage of particular striato-frontal circuits and the resulting behavioural impairment which await clinical confirmation. We present a study of two subjects who suffered a MRI-documented focal left basal ganglia hematoma. The two patients differed in their lesions; in one patient (PJ) large parts of the caudate nucleus were destroyed whereas in the other (AS) mainly the pallidum and putamen were lesioned and the caudate suffered only minor damage. In the acute phase, the behavioural and neuropsychological abnormalities were similar in both cases and included mainly abulia, an impairment of executive and attentional functions, and a severe amnestic syndrome. After several months many functions were restored in AS, whereas PJ’s abilities remained largely defective. Based on these data and on previous case studies several conclusions are drawn. Left caudate lesions induce marked and long-lasting behavioural and neuropsychological impairments comprising predominantly drive, executive control, attention, and memory. The extent of lesion in the head of the caudate nucleus is the critical factor regarding the severity and the outcome of the syndrome, whereas damage to the putamen and pallidum is less crucial for cognitive functions. A subset of behavioural alterations, among them abulia, attentional and frontal-executive dysfunctions, can well be attributed to lesions of the anterior cingulate circuit and the dorsolateral-frontal circuit at the basal ganglia level. Other impairments, most importantly the prominent amnestic syndrome, are more difficult to interpret on the grounds of this hypothesis and may be related to other pathomechanisms.