Nonlinear Interaction Effects Research Articles

Nonlinear Source-Filter Coupling Due to the Addition of a Simplified Vocal Tract Model for Excised Larynx Experiments

Traditional excised larynx dissection and setup calls for the removal of all supraglottal structures, eliminating any source-filter interactions that measurably affect the acoustic properties of phonation. We introduce a simplified vocal tract model that can be used in the excised larynx experiments and tested the nonlinear source-filter interactions that are present with the addition of highly coupled, supraglottal structures. Aerodynamic and acoustic data were measured at phonation threshold pressure (PTP) and +25% PTP in 10 excised canine larynges using a modified dissection technique. PTP and phonation threshold flow (PTF) were defined as the pressure and flow at the phonation onset; phonation threshold power (PTW) is the product of these values. Data were recorded for four experimental conditions: PTP without vocal tract; +25% PTP without vocal tract; PTP with vocal tract; and +25% PTP with vocal tract. Differences in PTP, PTF, and PTW were evaluated. For trials conducted at +25% PTP, differences in airflow were evaluated. PTP (P=0.009) and PTW (P=0.002) were significantly reduced with the addition of the novel vocal tract. A reduction in PTF was also present with the vocal tract (P=0.021), but airflow was not significantly reduced in +25% PTP trials (P=0.196). The proposed vocal tract can be used with complete larynges when conducting excised larynx experiments. The effects of nonlinear source-filter interaction were observed during trials with the vocal tract, as evidenced by changes in threshold aerodynamic parameters.

ViSEN: Methodology and Software for Visualization of Statistical Epistasis Networks

The nonlinear interaction effect among multiple genetic factors, i.e. epistasis, has been recognized as a key component in understanding the underlying genetic basis of complex human diseases and phenotypic traits. Due to the statistical and computational complexity, most epistasis studies are limited to interactions with an order of two. We developed ViSEN to analyze and visualize epistatic interactions of both two-way and three-way. ViSEN not only identifies strong interactions among pairs or trios of genetic attributes, but also provides a global interaction map that shows neighborhood and clustering structures. This visualized information could be very helpful to infer the underlying genetic architecture of complex diseases and to generate plausible hypotheses for further biological validations. ViSEN is implemented in Java and freely available at https://sourceforge.net/projects/visen/.

Effect of nonlinear optical three-wave interaction on the lasing parameters of a dual-wavelength vertical-external-cavity surface-emitting laser

The influence of nonlinear optical interaction in a semiconductor dual-wavelength vertical-external-cavity surface-emitting laser on the main parameters of dual-wavelength radiation and lasing in the long-wavelength part of the mid-IR range, obtained in this laser as a result of nonlinear wave mixing, is investigated. An increase in the pump power leads to saturation of the short-wavelength lasing intensity and to a more rapid rise in the long-wavelength lasing intensity in comparison with the linear increase in lasing intensity in these regions in the absence of nonlinear interaction. Under the conditions of nonlinear interaction, the carrier concentration in the active layers is not stabilised near the lasing threshold but changes with an increase in the pump intensity and provides the corresponding gain in the laser active region, thus maintaining steady-state lasing. Some ways for modifying the laser active region in order to obtain the most efficient lasing in the mid-IR range are proposed.

A prototype for a tomography system using third-order acoustic nonlinear effects

A prototype of a tomography system for reconstructing the distributions of acoustic nonlinear parameters is developed and manufactured on the basis of the effect of nonlinear noncollinear interaction of three primary waves. Application of coded primary signals with further correlation processing of a detected combination signal makes it possible to reconstruct the complete image of an object as a result of a single experiment using a small number of transducers, i.e., three radiators and one receiver. A mirror system is proposed, consisting of two coaxial conical acoustic mirrors that make it possible to transform the front of a wave from a cylindrical transducer into a homogeneous quasi-plane beam with a large width close to the real medical diagnostics requirements. Results of physical experiments are given.

Quantum phase transition of a Bose-Einstein condensate in an optical cavity driven by a laser field

When an atomic ensemble is coupled with a cavity field governed by the well-known Dicke model , an important quantum phase transition (QPT) from the normal phase to the superradiant phase occurs, which was predicted more than 30 years ago. In this paper, both the atom-photon nonlinear interaction and the driving field are added to the Dicke's Hamiltonian. With the method of Holstein-Primafoff transformation, the ground state energy is given by the theoretical calculation, and the rich phase figures are presented. Meanwhile, these properties are observed experimentally. We mainly dicuss the effects of the atom-photon nonlinear interaction and the driving field on QPT.

The Impact of Climate Change on Agriculture: Nonlinear Effects and Aggregation Bias in Ricardian Models of Farm Land Values

Ricardian (hedonic) analyses of the impact of climate change on farmland values typically assume additively separable effects of temperature and precipitation. Model estimation is implemented on data aggregated across counties or large regions. We investigate the potential bias induced by such approaches by using a large panel of farm-level data. Consistent with the literature on plant physiology, we observe significant non-linear interaction effects, with more abundant precipitation acting as a mitigating factor for increased heat stress. This interaction disappears when the same data is aggregated in the conventional manner, leading to predictions of climate change impacts which are significantly distorted.

PROPERTIES OF FREAK WAVES INDUCED BY TWO KINDS OF NONLINEAR MECHANISMS

We investigate the dynamic and kinematic characteristics of freak waves using a direct phase-resolved nonlinear numerical method. The focus is on the understanding of the effects of different nonlinear wave-wave interactions on freak waves development and characteristics in the evolution process of modulated Stokes wave trains. Long time simulations of modulated Stokes wave trains, with different parameters, are obtained. Based on these simulations, we find that there are different kinds of freak waves in different time scales due to two kinds of different nonlinear mechanisms. One is the modulation instability and another related to the wave group interaction. Both the dynamic and kinematic characteristics of the different kinds of freak waves are distinct. Occurrence of freak waves (especially of large height) is usually correlated with broadband wave spectra.

THE INTERACTION BETWEEN SHORT OCEAN SWELL AND TRANSIENT LONG WAVES: DISSIPATIVE AND NONLINEAR EFFECTS

The dissipation and nonlinear effects of random swell interaction with transient long waves are studied. Results from a laboratory experiment in which random swell was generated both with and without a co-existing transient long wave are analyzed. An instantaneous dissipation mechanism for estimating both instantaneous and bulk dissipation from data is used to determine the characteristics of dissipation for both cases. Fourier analysis of the free surface measurements and dissipation estimates reveals that the presence of the transient long wave does not have an appreciable impact on the known dissipation characteristics of random swell. However, the use of wavelet analysis, centered on the long wave in the time series, shows that the dissipation characteristics of the combined short-long wave signals deviate considerably from that of swell alone, indicating that smearing of the long wave signal by the Fourier analysis is sufficiently strong to affect dissipation estimates. A wavelet-based bispectral algorithm is used to determine the nonlinear wave-wave coupling in both swell and combined swell-long wave signals; the results indicate that there can be broader ranges of frequencies in which nonlinear coupling is present for the case of the combined short-long wave signal.

Interferometry using adiabatic passage in dilute-gas Bose-Einstein condensates

We theoretically examine three-well interferometry in Bose-Einstein condensates using adiabatic passage. Specifically, we demonstrate that a fractional coherent transport adiabatic passage protocol enables stable spatial splitting in the presence of nonlinear interactions. A reversal of this protocol produces a coherent recombination of the BEC with a phase-dependent population of the three wells. The effect of nonlinear interactions on the interferometric measurement is quantified and found to lead to an enhancement in sensitivity for moderate interaction strengths.

Effect of nonlinear soil-structure interaction on seismic response of low-rise SMRF buildings

The nonlinear behavior of a soil-foundation system may alter the seismic response of a structure by providing additional fl exibility to the system and dissipating hysteretic energy at the soil-foundation interface. However, the current design practice is still reluctant to consider the nonlinearity of the soil-foundation system, primarily due to lack of reliable modeling techniques. This study is motivated towards evaluating the effect of nonlinear soil-structure interaction (SSI) on the seismic responses of low-rise steel moment resisting frame (SMRF) structures. In order to achieve this, a Winklerbased approach is adopted, where the soil beneath the foundation is assumed to be a system of closely-spaced, independent, nonlinear spring elements. Static pushover analysis and nonlinear dynamic analyses are performed on a 3-story SMRF building and the performance of the structure is evaluated through a variety of force and displacement demand parameters. It is observed that incorporation of nonlinear SSI leads to an increase in story displacement demand and a significant reduction in base moment, base shear and inter-story drift demands, indicating the importance of its consideration towards achieving an economic, yet safe seismic design.

Criterial Analysis of Nonlinear Regimes of Transonic Flow Around the Airfoils with A Pulse-Periodic Source of Energy

The paper summarizes our data regarding the energy controlling of the transonic flow. The criterial analysis of the regimes of flow which is formed around the airfoils with an external pulse-periodic energy supply was performed. We selected four criteria, which belong to the class of criteria homochronicity. They are determined by the relations between the period of the energy supply, the rate of gas flow, the velocity of propagation of small disturbances and distances from the beginning or the end zone of energy supply to the position of the closing shock in the undisturbed flow, or the size of the zone of energy. It was shown that the conditions for the forming of the nonlinear regime can be described in terms of the entered criteria of homochronicity. We also obtained estimates for the minimum energy at which the effect of nonlinear interaction is possible, as well as the time of formation of the periodic mode. It was found that the nonlinear effect predominantly has gas-dynamic nature. It was shown that the results of numerical modeling are in agreement with the criterial estimates

An ultralow-energy negative cluster ion beam system and its application in preparation of few-layer graphene

We developed a cluster ion beam system that produces negative cluster beams of C1–C10 with ion current of 4.5 nA-50 μA at extraction voltages ranging from 6 to 20 kV. The system uses the injector of a tandetron accelerator and was established by inserting an electrostatic scanner on its ion-optical line and modifying its Faraday cup into a substrate holder. Utilization of clusters enables ultrashallow ion implantation at energies as low as 600 eV/atom without deceleration. Small carbon clusters C2 and C4 were implanted into Ni/SiO2/Si substrates and following post-thermal treatment graphene was obtained. Raman spectroscopy showed characteristic 2D peaks with G-to-2D peak ratios revealing formation of 2–3 layers of graphene. The Raman data reveals clear effect of nonlinear cluster-surface interaction in ion beam synthesis of two-dimensional nanomaterials.

Chaotic dynamics near steep transition states

Classical molecular motion near potential energy saddles can be more or less chaotic relative to motion near minima. The relative degree of chaos depends on the extent of coupling between the degrees of freedom and on the curvature of the potential energy landscape. Here, we explore these effects using constant energy molecular dynamics simulations and independent criteria associated with locally chaotic behavior – namely, the constancy of the local mode action and the magnitude of finite-time Lyapunov exponents. These criteria reconcile the chaotic basins and relatively ordered saddles of the Lennard-Jones trimer, with the chaotic saddles and ordered basins for reactive, all-atom H2O described by the Garofalini H2O potential. By modifying the Garofalini and Lennard-Jones models we separate the compounding effects of nonlinear three-body interactions and steep reaction path curvature on the local degree of chaos near saddles and minima.

Activity-dependent competition regulated by nonlinear interspike interaction in STDP: a model for visual cortical plasticity

The development of visual cortical circuits is strongly influenced by the sensory experience during a restricted critical period, as demonstrated by the loss of neural responses to the eye that has been briefly deprived of vision. It has been suggested that, to reflect the sensory experience into the synaptic pattern, the competition between different groups of correlated inputs to a postsynaptic cell is essential and that spike-timing-dependent plasticity (STDP) may provide the basis of this type of activity-dependent competition. To predict the consequences of competition by STDP in natural physiological conditions, I here investigate the effects of nonlinear interspike interactions in STDP which are experimentally observed in the visual cortical cells. The simulations using a biophysical STDP model show that the interspike interaction can prevent the induction of competition and counteract the effect of activity-dependent feedback (ADFB) modulation of STDP that facilitates competition. However, once the competition occurs, the level of competition is not affected by the interspike interaction. These results may suggest that the interspike interaction in STDP leads to a delay in the induction of experience-dependent plasticity through suppressing synaptic competition, thereby causing a delay in the onset of critical period in the visual cortex.

The science of risk models

An individual's overall cardiovascular risk should guide appropriate therapy and patient management. Several risk assessment scores are available; however, further development of risk algorithms is necessary to account for changes in available treatments and patient lifestyles, to make use of emerging risk factors and more accurate methods for measuring outcomes, and to provide more targeted measurement of risk for different patient subpopulations. When developing a risk model it is important to clearly define the outcome that the risk will predict, the period of follow up, the patient population, and the predictors to be used and how they will be combined. An appropriate statistical model is specified with the aim of finding the weighted combination of the candidate risk factors that best predicts the disease outcome. Stepwise regression is used to systematically search through candidate risk factors to produce a final model with an acceptable number of highly relevant variables. Possible non-linear effects of continuous variables and interactions between variables must be considered. However, the selection of variables requires not just statistical criteria but also clinical, biological and epidemiological judgement. In general, relatively simple, clinically reasonable and easy-to-use models that can be generalized to other settings are preferred to complex mathematical models that fit the sample data perfectly. There is a permanent need for updating cardiovascular risk scores to reflect advances in our clinical knowledge over time and changes in population risk. Development of a risk model requires both statistical expertise and a sound knowledge of the clinical and epidemiological aspects of cardiovascular disease.

Tunable exciton interactions in optical lattices with polar molecules

Rotational excitation of polar molecules trapped in an optical lattice gives rise to rotational excitons. Here we show that non-linear interactions of such excitons can be controlled by an electric field. The exciton--exciton interactions can be tuned to induce exciton pairing, leading to the formation of biexcitons. Tunable non-linear interactions between excitons can be used for many applications ranging from the controlled preparation of entangled quasiparticles to the study of polaron interactions and the effects of non-linear interactions on quantum energy transport in molecular aggregates.

Nonlinear analysis of an actuated seafloor-mounted carpet for a high-performance wave energy extraction

It is known that muddy seafloors can extract significant energy from overpassing surface waves via engaging them in strong interaction processes. If a synthetic seabed can respond to the action of surface gravity waves similar to the mud response, then it too can take out a lot of energy from surface waves. Analysis of the performance of a mud-resembling seabed carpet in harvesting ocean wave energy is the subject of this article. Specifically, and on the basis of the field measurements and observations of properties/responses of seafloor mud, we focus our attention on an artificial viscoelastic seabed carpet composed of (vertically acting) linear springs and generators. We show that the system of sea/synthetic-carpet admits two propagating wave solutions: the surface mode and the bottom mode. The damping of a surface-mode wave is proportional to its wavelength and hence is classic. However, the damping of a bottom-mode wave is larger for shorter waves, and is in general stronger than that of the surface-mode wave. To address the effect of (high-order) nonlinear interactions as well as to investigate the performance of our proposed carpet of wave energy conversion (CWEC) against a spectrum of waves, we formulate a direct simulation scheme based on a high-order spectral method. We show, by taking high-order nonlinear interactions into account, that the CWEC efficiency can be significantly higher for steeper waves. We further show that the bandwidth of high performance of the CWEC is broad, it yields minimal wave reflections and its theoretical efficiency asymptotically approaches unity within a finite and (relatively) short extent of deployment.

Nonlinear modal analysis of interaction between torsional modes and SVC controllers

This paper deals with the use of Modal Series (MS) method to study the nonlinear interaction between the torsional modes of a turbine-generator set and Static VAr Compensator (SVC) in the stressed power systems. The observations resulting from nonlinear simulations made incentive for suggesting the need for nonlinear analysis of torsional interaction phenomenon in stressed conditions. The obtained results from linear modal analysis were not consistent with those of nonlinear simulations and could not quantify the problem. While the results of nonlinear analysis MS method reveal that, the nonlinear interactions exist between shaft sections and SVC controllers. In the stressed conditions, these nonlinear interactions become more pronounced and it may be a warning for severe damage of shaft segments. By using the indices correspond to the MS method, the nonlinear interactions of torsional modes are evaluated for different conditions. To demonstrate the physical effects of nonlinear interaction of torsional modes with SVC controllers, the torsional torques imposed on shaft sections are provided using the nonlinear simulations. Finally, based on MS method a supplementary controller is designed for SVC to remedy the problem. The proposed approach is implemented on the IEEE 4-machine 11-bus test system.

Kolmogorov turbulence, Anderson localization and KAM integrability

The conditions for emergence of Kolmogorov turbulence, and related weak wave turbulence, in finite size systems are analyzed by analytical methods and numerical simulations of simple models. The analogy between Kolmogorov energy flow from large to small spacial scales and conductivity in disordered solid state systems is proposed. It is argued that the Anderson localization can stop such an energy flow. The effects of nonlinear wave interactions on such a localization are analyzed. The results obtained for finite size system models show the existence of an effective chaos border between the Kolmogorov-Arnold-Moser (KAM) integrability at weak nonlinearity, when energy does not flow to small scales, and developed chaos regime emerging above this border with the Kolmogorov turbulent energy flow from large to small scales.

Multistability and Loops-Coupled Hysteresis: Flight-Test Analysis on Error Detection of Inlet Start/Unstart

DOI: 10.2514/1.B34349Anerrordetectionofinletstart/unstarthasbeenreportedasasignificantflightaccidentintheCentralInstituteofAviation Motors/NASA Mach 6.5 scramjet flight test. It is believed that nonlinear effects that give rise to thecatastropheandhysteresisbehaviorsinthetransitionsofinletstart/unstartmaybetheessentialfactorsthatresultinthe flight accident. Starting from nonlinear interaction effects and dynamical system theories, evidence ofmultistabilityandloops-coupledhysteresisphenomenonexhibitedinthehypersonicinletisreported.Multistabilityof a dynamic system consists of the ability to express multiple stable states and to switch between these states inresponse to some external input. The loops-coupled hysteresis phenomenon, which appears as a generic feature ofmultistability systems, is characterized by the existence of at least one hysteresis loop that involves more than twostablestates.Thepresentstudyshowstheloops-coupledhysteresisphenomenonhasoccurredintheflighttest,andaneglect of the multistability and loops-coupled hysteresis phenomenon has given rise to the error detection of inletstart/unstart in the Central Institute of Aviation Motors/NASA Mach 6.5 scramjet flight test.